Recent Advances in Functional Fabric‐Based Wearable Supercapacitors

With the advent of wearable electronics, the urge to devise new and flexible energy storage devices to power up wearable systems has steadily risen over the past few decades. Wearable fabric‐based supercapacitors have emerged as a fantastic solution for powering up these systems. Functionalizing fabric surfaces with electroactive materials has proven to be the ideal way to fabricate high‐performance wearable supercapacitors. In this review, the recent progress in functional fabric‐based wearable supercapacitors is summarized. The article begins with the introduction of different fabric structures and outlining the functional materials implemented in wearable supercapacitors. The emphasis shifts toward summarizing the fabrication of functional fabric‐based electrodes according to different fabric architectures. Then, different novel fabric‐based supercapacitor configurations, the current state of integration, and the durability of such devices are analyzed. The review is concluded by emphasizing the existing drawbacks, envisaging potential applications, and, most importantly, the future perspective of the technology.


Introduction
6][7][8] The traditional textile form factors (fibers, yarns, fabrics) imbued with functional/smart nanomaterials are the most prevalent technique to achieve multifunctional e-textiles.By leveraging these DOI: 10.1002/admi.202300724form factors, scientists can develop an all-textile-supported smart apparel.[11] With its lightweight, conformable, and breathable features, e-textiles have been at the forefront of wearable technology research due to their prospective application in protective clothing, bio-signal monitoring, and defense industries. [12,13]evertheless, one key issue in realizing such wearable e-textile systems is the need for lightweight, conformable, and wearable energy storage devices. [14,15]onventional energy storage systems are incompatible with wearable e-textile systems.[18][19][20][21][22][23][24][25] Between the two, batteries offer reliable power output but suffer from low cycle life and declined power density.[28] However, SCs still suffer from poor energy density, which is also prevalent in wearable SCs.Fabricating wearable SCs, nevertheless, is difficult since flexible electrodes must exhibit outstanding structural integrity while maintaining capacitive performance.[31][32][33][34] Although plastics and metal meshes offer high flexibility, the wearability and comfort of such substrates are not satisfactory when compared with fabrics.With the advantage of being flexible, conformable, and biocompatible, fabric-based supercapacitors (FSCs) are more suitable to integrate into e-textile platforms than other substrate-based SCs. [35,36]Besides, an FSC is much more comfortable and can be readily integrated into garments being the same form factor.The unique interface and high surface area offered by fabrics are conducive to functional material deposition. [37,38]Such properties are highly desirable in wearable SC fabrication.For this reason, there is a recent surge in functional fabric-based wearable SC research and the energy density improvement of such devices.
A few comprehensive reviews on wearable SCs have been published in recent years.The review by Jost et al. [15] emphasized textile-based SCs and batteries with a concentration on their design strategies, form factors, compatibility, and current state of characterization.The recent reviews published in 2020 by Gao et al., [26] in 2021 by Ren et al., [27] and in 2022 by Islam et al. [29] provided in-depth commentary on the challenges, research trends, and commercialization prospects associated with wearable textile-based SCs and batteries.Additionally, the reviews specific to only fabric-based SCs are also reported by Khadem et al. [36] in 2022 and Lin et al. [35] in 2023.However, Khadem et al. [36] concentrated solely on the graphene-based fabric SCs, their fabrication, and their challenges without analyzing the role of fabric structure and other functional materials in the performance of wearable SCs.Lin et al. [35] only provided an issue-specific overview of the design, construction, and performance of fabric-based planar microsupercapacitors (MSCs), overlooking other most notable wearable SC constructions.Besides, the reviews by Chen et al. [39] in 2020, Cheng et al. [40] in 2021, and Guan et al. [28] in early 2023, concentrated solely on the 1D fiber-based wearable SCs without highlighting the current state-of-the-art of SCs based on two dimensional (2D) fabrics.In addition, none of the previous works emphasized, categorized, or summarized the development of wearable FSCs based on their inherent architectures and how such structures affect capacitive performance.In order to address this potential gap, this article comes in a timely fashion to shed light and build upon the previous works to holistically draw a roadmap for the development, characterization, and enhancement of the performance of wearable SCs based on 2D fabrics.This article elucidates the crucial design barriers faced by current FSC technology and attempts to address the gaps associated with previous studies.
This review concentrates exclusively on the contemporary research progress of wearable FSCs based on different fabric architectures (woven, knit, and nonwoven) and their performance characteristics.First, the article begins with a focus on the synopsis of different fabric architectures with their underlying manufacturing technologies and the functional materials utilized in wearable FSCs.Then, different functional fabric-based electrode architectures are outlined, emphasizing diverse novel fabrication strategies and comparative analysis among fabric-based electrodes.Second, the fabrication strategy for FSCs is summarized, concentrating on different state-of-the-art device configurations, integration, and durability against washing and bending.Third, the role of fabric architectures in SC performance is also analyzed critically.Finally, the review is concluded with a focus on future research direction and perspective of the field for functional fabric-based wearable SCs.While the recommendations do not presume an arbitrary view, the objective of this article is to equip the researchers with an understanding of the current status of wearable FSC technology and accelerate the development, manufacturing, and emergence of personalized FSC in the upcoming wearable electronics market.Figure 1 illustrates the concise outline of the article.

Materials for Functional Fabric-Based Wearable SCs 2.1. Fabric Manufacturing and Structure
The term "fabric" denotes a wide range of sheet-like, flexible, and 2D macrostructures typically consisting of fibers or yarns.However, fabrics can also be formed by combining two or more preexisting fabrics by stitching or adhesive bonding to realize a multilayered flexible structure. [41,42]Fibers and yarns are considered to be the fundamental building blocks of textile fabrics.Fabrics can be classified in different ways, but depending on the starting material used, fabrics can be divided into two categories, they are yarn-based fabrics and fiber-based fabrics. [43]Depending on the orientation and the mechanical manipulation of yarn in fabric structure, the yarn-based fabric can be divided into woven, knitted (warp/weft), braided, and multiaxial non crimp structures.The mechanical manipulation of yarn in yarn-based fabrics can occur in three possible ways such as straight (multi-non crimp structure), low undulation (woven structure, braided structure), and loop formation (knitted structures). [44,45]The relative deformation of yarns in fabric structures gives rise to varying textures and surface properties, which can influence the capacitive performance of FSCs.
The methods of constructing yarn-based fabrics can be achieved through interweaving, interlooping, intertwining, and laying of yarns.Woven and braided structures possess low undulation in their yarn geometry.Woven fabrics consist of two sets of yarns (warp and weft) interlacing in an orthogonal manner.The warp yarns run in a length-wise direction, typically wound in warp beams, and the weft yarns are inserted widthwise by a weft insertion system (shuttle, rapier, air-jet, or projectile) in a weaving machine (Figure 2A(i,ii)).Warp and weft yarns interweaving at right angles give the woven fabrics binding points, making the structure less flexible when compared to other fabric structures.Therefore, woven fabrics exhibit highly anisotropic behavior and are relatively less extensible in warp and weft directions. [46,47]Braided fabrics are constructed by intertwining three or more sets of yarn in a diagonal manner (Figure 2A(iii)).The braided structures are obtained in a braiding machine where the yarn carriers move with the help of horn gears (Figure 2A(iv)).50][51] Knitted fabrics, another yarn-based fabric, are constructed by simultaneous building up of loops through interlooping.The new row of loops is built up on top of the row immediately preceding it.For this reason, knitted fabrics can be easily stretched in all directions and exhibit inferior tensile properties than woven fabrics. [52]Knitted fabrics can be further divided into weftknitted (Figure 2B  (Figure 2B(iv)).Owing to the excellent versatility of warp knitting technology, 3D fabric structures can also be realized.Warp knitting machines are widely adopted for producing multi non crimp fabrics (Figure 2C(i)) or fully 3D-knitted fabric structures (Figure 2C(ii)).Raschel machines (Figure 2C(iii)) equipped with double-needle bars seamlessly produce fully 3D-knitted structures at high speed.However, for 3D fabrics with non crimp structures (no undulation), warp-knitting is only implemented for holding the multiple straight layers of yarns with a stitch, as evident from Figure 2C(i).
Nonwoven fabrics are the most prevalent fiber-based fabrics, commonly consisting of one or more fiber layers.The fiber layers are arranged in a constant or random manner and can be stabilized through mechanical, chemical, stitching action, or a combination of all.According to production processes, nonwoven fabrics can be manufactured by needle punching, meltblowing, and spunbonding technology.Figure 2D illustrates the inherent nonwoven structure, needle punching, meltblowing, and spunbonding technologies.The production of nonwovens is typically carried out in two stages.The first stage is web formation from fibrous sheets or polymer melts, which can be formed mechanically or thermally.The second stage is the consolidation of manufactured webs into final nonwoven fab-rics, which inserts the required mechanical strength into the nonwoven fabric.Since the process of spinning and winding is eliminated, nonwoven fabrics are inexpensive and have a high production rate. [55,56]While nonwoven fabrics are widely used in the construction, healthcare, packaging, and farming industries, they have poor strength and durability.Therefore, there is a scarcity of reports regarding nonwoven fabric-based SCs.
Woven, knitted, and nonwoven fabrics have distinct surface properties that stem from their unique structures and production processes.If fabrics are utilized as SC electrodes, it is important to choose the fabrics based on their architecture.Crucial physical properties such as yarn linear density, fabric structure, and the weight of fabrics play a vital role in determining the structural strength and flexibility of fabrics. [47,57]Therefore, fabric structure may affect the energy storage performance of wearable SCs, which will be focused in later chapters.

Functional Materials
The functional materials capable of energy storage are highly desirable for SC applications.Depending on the type of charge Interlacement of yarns at 90°produces woven structures (i) in shuttle weaving machines (ii); Diagonal intertwining of yarns produces braided structures (iii) in a braiding machine (iv).B) Interlooping of yarns construct stretchable weft-knitted structures (i) in flatbed knitting machines (ii).Through loop intermeshing, warp-knitted structures (iii) are formed in Tricot warp knitting machines (iv).C) 3D fabric structures of multi non-crimp (i) and 3D-knitted structures (ii).Reproduced with permission. [53]Copyright 2021, Elsevier Ltd.Reproduced with permission. [54]Copyright 2020, Elsevier B.V. The 3Dknitted fabric is produced in a double needle bar Raschel machine (iii) where two separate layers of fabric are produced and stitched together to render a 3D architecture.D) By directly manipulating fibers, nonwoven structures (i) are formed.The scheme demonstrates the basic nonwoven manufacturing processes, such as (ii) needle punching, (iii) melt-blowing, and (iv) spunbonding technologies.
storage mechanism, the functional materials used in wearable SCs can be divided into two types of materials.They are electric double-layer capacitance (EDLC) type and pseudocapacitance type functional materials. [58]EDLC-type materials form an oppositely charged double layer (also known as Helmholtz double layer) at the electrode-electrolyte interface.The energy is stored by charge separation, and the ions migrate from the electrolyte to the electrode-electrolyte interface constructing an electric double layer.Figure 3A(i) demonstrates the typical EDLC mechanism.The process is rapid, and thus, EDLC materials ensure high power density, good cyclic stability, and long cycle life.However, the energy density and capacitance of EDLC materials are not satisfactory. [59,60]Pseudocapacitive materials, on the other hand, outperform EDLC materials in terms of energy density and device capacitance.The pseudocapacitive materials store energy through battery-like Faradaic redox reactions.Therefore, pseudocapacitors have the potential to achieve high energy and power densities. [61,62]Figure 3A(ii) demonstrates the typical pseudocapacitance mechanism.Since the redox reactions occur at a faster rate than the EDLC, the pseudocapacitive materials open a gateway for achieving wearable SCs with high power densities.Despite such attractive attributes, the pseudocapacitive materials suffer from poor cyclic stability and subsequently shorten the lifetime of SCs.
Carbon-based materials are at the forefront of energy storage research owing to their high surface area, excellent conductivity, and high power density attributes. [63]Among the carbonaceous materials, carbon nanotubes (CNTs), graphene materials such as graphene oxide (GO) and reduced graphene oxide (rGO), and activated carbon (AC) are the most widely reported carbonaceous materials for fabricating fabric-based electrodes.Figure 3B lists some carbon-based materials.CNTs are a 1D allotrope of carbon typically produced by rolling single-layer graphene sheets (singlewalled carbon nanotube-SWCNT) or multilayer graphene sheets (multi-walled carbon nanotube-MWCNT).The high surface area and exceptional conductivity make CNTs attractive for wearable SC applications. [64]Graphene materials, such as GO/rGO, laserinduced graphene (LIG), and graphene aerogels (GAs) are also gaining popularity in fabricating wearable SCs due to their mechanical, electrical, and electrochemical properties.LIG has been widely investigated for wearable MSC devices owing to their rapid ink-less fabrication process and high conductivity. [65]GAs, on the other hand, offer high specific surface area and good electrical conductivity which makes them ideal for SC applications. [66]Besides, graphene materials create an effective bonding with fabric surfaces, making it lucrative for its usage in functional fabricbased SCs. [67]Therefore, there are a considerable amount of reports regarding graphene materials being employed in wearable SCs.Lastly, AC is utilized in SCs owing to its high stability, low cost, and environmentally friendly nature.Besides, its tunable pore size and high specific surface area deem it an outstanding electrode material for SCs. [68]ansition metal oxides (TMOs) are an attractive class of materials because of their high conductivity and pseudocapacitance, making them a strong candidate for wearable SCs.RuO 2 , MnO 2 , ZnO, Fe 2 O 3 , NiO, SnO 2, etc., are some of the most widely used TMOs used in SC applications. [69]Figure 3C illustrates the compound structures of some TMOs.However, the expensive synthesis process of TMOs makes them unsuitable for wide-scale application.In addition, metal nanoparticles/nanowires are also utilized in wearable SCs.Metal nanoparticles such as gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) and their consecutive nanowires (AuNWs, AgNWs) are widely employed for fabricating SC electrodes. [70]Like TMOs, the expensive nature and oxidation of metal NPs render them unsuitable for electrode fabrication at mass scale.Metal-organic frameworks (MOFs) are an exciting new class of materials that are widely studied for catalysis, phase separation, and biomedical applications.With their high specific surface area, porosity, and tunable crystal properties, MOFs have emerged as exciting new materials for fabricating SC electrodes. [71][74] Despite such progress, MOFs suffer from poor electrical conductivity, and their expensive, unsustainable processing restricts them from wide-scale applications.Figure 3D depicts the chemical structure of some MOFs.Besides, MOF-integrated electrodes require compounding with other nanomaterials to achieve desirable energy storage performance.
2D materials have attracted tremendous interest since the discovery of graphene in 2002. [75]Since then, many other 2D materials have been developed, such as hexagonal boron nitride (h-BN), transition metal dichalcogenides (TMDs), molybdenum disulfide (MoS 2 ), tungsten selenide (WSe 2 ), and transition metal carbides/nitrides/carbonitrides (MXenes) are systematically investigated for SC applications. [76]Figure 3E conscripts some chemical structures of 2D materials.However, when it comes to wearable fabric-based SCs, the reports on wearable SCs based on h-BN, TMDs, MoS 2 , and WSe 2 are scarce due to complex processing.MXenes, on the other hand, has emerged as an exciting new material for energy storage and conversion applications.MXenes offer outstanding conductivity, high capacitance, and tunable surface properties, making them ideal for wearable SC devices.There are a considerable amount of reports regarding the use of MXenes as wearable energy storage devices, more specifically, as SC electrodes. [77,78]To date, only Ti 3 C 2 T x MXene has been widely studied for wearable SC applications.Besides, the oxidation and low stability of such materials have restricted their wide-scale application in wearable electronics.
Intrinsically conductive polymers (ICPs) are a widely reported functional material class for SC applications.Among the conductive polymers, polyaniline (PANI), polypyrrole (PPy), and poly(3,4-ethylenedioxythiophene) (PEDOT) with its derivative poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PE-DOT: PSS) are the most scrutinized ICPs for SC fabrication. [79]igure 3F illustrates some of the ICPs used in wearable SCs.In the past two decades, the use of ICPs in wearable SCs has increased significantly due to their high reversibility, low cost, and high charge density capabilities.PANI offers a high rate of redox reactions, high conductivity, and flexibility.Yet, the hazardous by-products and instability make them unreliable in wearable SCs. [80]Therefore, when designing SC electrodes, other materials (carbon-based materials, metal oxides) must be combined with PANI to get better results.To mitigate the problems faced by PANI, PPy could be an alternative safe option for wearable SCs owing to its high stability, non-toxicity, low cost, outstanding conductivity, and biocompatibility.All these attributes make PPy an ideal choice for SC fabrication.Nevertheless, PPy's poor cyclic stability and rate performance inhibit its wide-scale application in wearable devices. [81]To counteract the drawbacks faced by both PANI and PPy, PEDOT can be a viable alternative due to its tunable conductivity in the oxidized state, low cost, and pseudocapacitance.However, PEDOT suffers from low stability and limited capacitance, which restricts its application at the industrial level.Nowadays, PEDOT doped with polystyrene sulfonate (PEDOT: PSS) is being widely investigated in SC applications, as its conductivity surpasses the pristine PEDOT polymer. [82,83]

Fabrication of Functional Fabric-Based Electrode Architectures
Due to a lack of electrical pathways, fabrics are not inherently conductive.In order to introduce electroactive functionality to fabric architectures, capacitive electrode materials must be applied at this level to convert nonfunctional fabrics into functional fabricbased electrodes (FEs) for SC applications.Functional nanomaterials such as carbon-based materials (carbon black, CNTs [84] ), conductive polymers [85] (PANI, PPy, PEDOT, PEDOT:PSS), metal oxides [86] (MnO 2 , Fe 2 O 3 , etc.), and 2D materials [31] (graphene, MXenes) have garnered popularity as an efficient electrode material for FFE fabrication.In order to functionalize the fabric surfaces with these functional nanomaterials, different fabrication strategies must be carried out.Depending on the three major fabric architectures, this chapter will narrate the fabrication strategies, electrochemical performance, and the underlying comparison among woven, knitted, and nonwoven fabric-based electrodes.Figure 4 summarizes all of the significant fabrication strategies to manufacture FEs.

Woven Fabric-Based Electrodes
To date, woven fabric-based electrodes (WFEs) are the most widely studied among FEs.Woven structures possess low porosity, high binding points, and have a firm construction compared to other fabric structures (knit, nonwoven).Therefore, woven structures are highly desirable for wearable SC electrode fabrication due to their robust interface.Coating remains the most prevalent technique to functionalize woven fabric surfaces for flexible electrode fabrication.While WFEs demonstrated exceptional supercapacitive performance with excellent cyclic stability, the functional materials, fabrication techniques, and fiber type strongly influence other SC attributes.Besides, a hierarchical microstructure with tunable surface properties can be realized since multiple functional materials can be decorated to the woven fabric surface.
Fabricating WFEs with binary/ternary functional materials is a popular strategy to achieve high-performance SC electrodes.For instance, a binary-structured cotton fabric-based WFE with PANI and MXene (Ti 3 C 2 T x ) as functional materials was fabricated by Ye et al. [87] They first grew a PANI layer on a cotton fabric surface and then coated it with MXene nanosheets to further enhance the conductivity (1 Ω sq −1 ). Figure 5A(i) illustrates the process.The MXene coating fully covered the PANI nanoparticles and synergistically increased the conductivity, as observed in Figure 5A(ii).The MXene/PANI-cotton WFE was lightweight and demonstrated a high areal capacitance of 1027.5 mF cm −2 at 1 mA cm −2 in aqueous H 2 SO 4 .Figure 5A(iii,iv) exhibits the cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) profiles of MXene/PANI-cotton WFEs.The electrode was also highly flexible, as shown in Figure 5A(v).Despite such high capacitive performance of WFEs, the electrode's capacitance retention was not satisfactory (only 61.7% after 10 000 cycles).This phenomenon could be attributed to PANI's volume change and MXene's gradual oxidation during the charge-discharge process. [87]A ternary WFE can be further fabricated by compounding EDLC and pseudocapacitive materials to improve cyclic stability.Kou et al. [88] pursued this idea and prepared conductive carbon oil/ink/PANIcotton (CCIP) WFEs using a simple dip coating technique.After the fabric was dip-coated simultaneously in conductive carbon oil and ink, in-situ polymerization of PANI was carried out, illustrated in Figure 5B(i).Figure 5B (ii,iii-v) exhibits the photograph and corresponding SEM images of such composite electrodes.The CCIP-based symmetric SC reached an areal capacitance of 323.3 mF cm −2 in PVA-H 2 SO 4 . [88]otton fabrics remain the most widely investigated substrate for fabricating WFEs.Nevertheless, in recent years, the functionalization of other natural and synthetic fibers for preparing SC electrodes has garnered considerable attention.Bonastre and co-workers, in 2023, developed a PPy/rGO-jute WFE by subsequent dip coating of rGO and electrochemical polymerization of PPy.This is one of the first reports on jute fabric-based SCs.The composite electrode achieved an ultralow sheet resistance of 6 Ω sq −1 .Besides, the electrode showed an ultrahigh areal capacitance of 5127 mF cm −2 in 0.1 m H 2 SO 4 . [89]Khairy et al., [90] in 2022, prepared and characterized PANI/GO-silk WFEs using vacuum filtration of GO solution and in situ polymerization of PANI.Such an electrode demonstrated a gravimetric capacitance of 450 F g −1 in 1 m Na 2 SO 4 .The functional electrode also demonstrated antibacterial, UV-blocking, and electrothermal properties. [90]Unlike natural fibers, synthetic fibers such as polyester (PET), nylon, viscose, and polypropylene (PP) are investigated for fabricating functional FEs.While there remains a plethora of synthetic fibers, PET fabrics are the most scrutinized for SC electrodes.For instance, Shao et al. [91] prepared PANI/rGO-PET WFE employing simple dip-coating followed by a GO reduction and an insitu polymerization to construct vertical PANI nanowire arrays.Figure 5C(i) illustrates such a fabrication process.The composite electrode reached an ultrahigh gravimetric capacitance of 1293 F g −1 in 1 m H 2 SO 4 .Figure 5C(ii,iii) demonstrates the CV and GCD profiles of such electrodes.Besides, its capacitance retention was maintained at 95% after 3000 charge-discharge cycles. [91]igure 5. Fabrication and electrochemical performance of woven fabric-based electrodes.A) (i) Schematic illustration of the fabrication of MXene/PANIcotton electrodes with its SEM image (ii).(iii,iv) show the CV and GCD curves of MXene/PANI-cotton electrodes.(v) Photograph of flexible MXene/PANIcotton electrode.Reproduced with permission. [87]Copyright 2023, Elsevier B.V. B) (i) Schematics of preparation of carbon oil/ink/PANI-cotton electrodes.(ii) Photograph of CCIP-cotton electrodes.(iii-v) SEM images of CCIP electrodes in different magnifications.Reproduced with permission. [88]opyright 2023, Elsevier B.V. C) (i) Preparation process of rGO/PANI-PET electrodes with their corresponding CV (ii) and GCD (iii) curves in 1 m H 2 SO 4 .Reproduced with permission. [91]Copyright 2016, Wiley-VCH Verlag GmbH.
In order to achieve uniform PPy thin films, tailoring the fabric surface with hydrophobic materials is an effective strategy.This is because surface hydrophobicity allows the uniform adsorption of oxidant species.Since the pyrrole monomers polymerize in-situ at the oxidant adsorbed sites, a uniform oxidant layer ensures a continuous and denser PPy film deposition than on an untreated substrate. [92,93]Such an approach was adopted by Lu et al. [94] to prepare a cotton WFE where the cotton fabric surface was first modified with hydrophobic polyurethane (PU).The PU coating rendered the fabric surface smooth and hydrophobic, which was conducive to PPy growth.After the interfacial polymerization of pyrrole, a uniform ultrathin layer (18 μm) of PPy was achieved with excellent adhesion to the fabric.The PPy/PU-cotton WFE reached an excellent sheet resistance of 220 Ω sq −1 with outstanding cyclic stability after 2000 cycles of charge-discharge (97% retention) in 1 m H 2 SO 4 . [94]While interface modification may ensure improved adhesion, the screen printing technique, even applicable today, remains the most versatile and facile technique to realize high-performance FEs.With the stencil technique, functional materials can be locally deposited on the fabric surface with minimal post-processing and excellent bonding.In 2022, Jiang et al. [95] fabricated an MWCNT-based cotton WFE by implementing screen printing where thermoplastic polyurethane (TPU) was used as a binder.The binder not only ensured effective conductive pathways but also firmly held the MWCNTs with the fabric surface.The MWCNT/TPU-cotton WFE demonstrated gravimetric and areal capacitances of 48.2 F g −1 and 29.0 mF cm −2 , respectively, in 2 m KOH aqueous electrolyte. [95]CPs implemented with other functional materials are popular for realizing high-performance WFEs.While ICPs remain the major players in WFE fabrication, modified copolymers can also be implemented.Such an approach was pursued by Chakraborty et al., [96] and for the first time, reported the use of copolymer in fabric architecture for SC application.They first prepared poly(ortho phenylenediamine-co-aniline) co-polymer (oPDA) using a microwave-assisted method.oPDA composited with acidfunctionalized MWCNT was coated onto the surface of PET fabric employing a dip coating technique.The symmetric SC fabricated from oPDA/MWCNT-PET electrode exhibited a gravimetric capacitance of 146.16 F g −1 in the PVA-KOH gel electrolyte.The fabricated device demonstrated enhanced biocompatibility yet achieved moderate cyclic stability (82% retention after 1000 cycles). [96]lended fabrics consisting of synthetic and natural fibers exhibited improved capacitance compared to pristine synthetic fabrics.Natural fibers are more prone to absorb functional material than synthetic fibers due to surface roughness, high surface area, and hydrophilicity.The hypothesis was confirmed in a 2022 study by Alzate et al., [97] where they compared WFEs based on pristine PET, PET-pineapple fiber (PF), and PET-water hyacinth Figure 6.Electrochemical properties and preparation protocols of different WFEs.A) (i) Fabrication scheme of MWCNT/rGO-cotton electrodes, (ii, iii) GCD and CV curves of composite electrodes in 5 m LiCl electrolyte.Reproduced with permission. [99]Copyright 2017, WILEY-VCH Verlag GmbH.B) (i) Protocol for preparing MXene/rGO-cotton electrodes.Highly flexible composite electrodes are demonstrated around the finger (ii) and elbow (iii).(iv) CV curve comparison between MXene-cotton and MXene/rGO-cotton with varying MXene loading.Reproduced with permission. [100]Copyright 2021, Elsevier Ltd. fiber (WHF) blended fabric.Both blended fabric substrates were subjected to an in situ polymerization reaction in which PPy was coated onto the fabric's surface.The PPy/PET-PF and PPy/PET-WHF electrodes exhibited higher areal capacitances (86.01 and 104.31 mF cm −2 , respectively) when compared to PPy-PET (51.53 mF cm −2 ), at 1 mA cm −2 in 1 m H 2 SO 4 .Such results demonstrated the outstanding attributes of both water hyacinth and pineapple fibers.This is because of the high specific surface area and strong bonding between PPy and natural fibers leading to more functional material loading and increasing the capacitance. [97]In a separate study, Padha and co-workers [98] fabricated PET-based electrodes using perovskite materials.The group produced NiSnO 3 and FeSnO 3 electrode materials following a facile sol-gel technique.The functional materials were deposited on PET fabric surfaces to achieve NiSnO 3 /PVA/graphite-PET and FeSnO 3 /PVA/graphite-PET electrodes.The NiSnO 3 /PVA/graphite-PET and FeSnO 3 /PVA/graphite-PET electrodes demonstrated gravimetric capacitances of 742 and 2853 F g −1 in 3 m KOH electrolyte, respectively.Such value is higher than any other perovskite-based materials used as SC electrodes.Both NiSnO 3 /PVA/graphite-PET and FeSnO 3 /PVA/graphite-PET electrodes exhibited outstanding cyclic stability of 100% after 10 000 charge-discharge cycles. [98]lthough many coating techniques are dominant in fabricating WFEs, they cannot achieve fabric electrodes with high mass loadings.Vacuum filtration can be implemented to achieve high mass-loading electrodes.Yang et al. [99] executed the idea and prepared MWCNT/rGO-cotton fabric-based electrodes with high mass loading utilizing an alternating vacuum filtration method.After the MWCNT solution was vacuum-filtered through Nicoated cotton fabric, the rGO solution was also vacuum-filtered through MWCNT/Ni-coated cotton fabric.Such alternative vac-uum filtration led to an ultrahigh mass-loading of 23.7 mg cm −2 .Figure 6A(i) illustrates such a fabrication process.Thus, a hierarchical composite MWCNT/rGO-cotton fabric electrode was fabricated, which demonstrated a record-breaking areal capacitance of 6200 mF cm −2 at a high current density of 20 mA cm −2 in aqueous LiCl (5.0 m) electrolyte.Such capacitance is higher than any other fabric-based electrode reported.Figure 6A(ii,iii) exhibits the GCD and CV curves of MWCNT/rGO-cotton electrodes. [99]The inherent low porosity and excellent support from the interlacement of yarns in woven fabric led to a high material loading.Besides, the cotton fibers in the fabric strongly locked graphene nanosheets and MWCNTs during the downward suction of the poured solution.Nevertheless, such a process cannot possibly be scaled up, restricting the mass production of WFEs.In contrast, spray-coating can potentially be implemented for scaling up WFE production.Zheng et al. [100] leveraged the spray-coating technique to enhance the overall conductivity.The group prepared rGO/Ti 3 C 2 T x -cotton fabric electrodes employing facile dipcoating and spray-coating techniques.After dip-coating and subsequent reduction of GO, Ti 3 C 2 T x MXene was spray-coated to achieve rGO/Ti 3 C 2 T x -cotton WFE.The synergy between rGO and Ti 3 C 2 T x significantly enhanced the conductivity of composite electrodes (34.9 ± 1.5 S m −1 after one cycle of spray coating).Figure 6B(i) illustrates such a process.The fabricated composite electrode was highly flexible, as shown in Figure 6B(ii,iii).In addition, the assembled device from such electrodes exhibited a high areal capacitance of 258 mF cm −2 in PVA-H 2 SO 4 .Figure 6B(iv) shows the CV curves of solid-state devices. [100]raphene aerogel (GA) has been gaining popularity as an efficient electrode material for SC electrode fabrication.However, reports regarding GA implemented in fabric SC are scarce.While there remains a wide range of natural and synthetic fabrics, carbon fiber fabric has been widely utilized Reproduced with permission. [103]Copyright 2022, Elsevier Ltd.B) Schematic illustration of Ni/ZnO-nylon fabric electrode preparation.Reproduced with permission. [105]Copyright 2022, Elsevier Ltd.
for GA-fabric-based wearable SCs.GA could be integrated into fabric architecture as a conductive element with a binder.For instance, Okhay et al. [101] screen-printed rGO aerogel and SWCNT materials on carbon fiber fabric for flexible SC electrodes where poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) worked as a binder.The screen-printed rGO/CNT/PVDF-HFP electrode exhibited a gravimetric and areal capacitance of 129 F g −1 and 232 mF cm −2 in 1 m Na 2 SO 4 . [101]Apart from being implemented as a functional element in printing inks, GAs can also be in-situ grown on fabric surfaces.Song et al. [102] adopted this approach to in situ grow rGO aerogel within the porous carbon fiber fabric through self-assembly of GO hydrogel, followed by freeze-drying.The GA-carbon fabric electrodes delivered a gravimetric capacitance of 391 F g −1 in 6 m KOH.Besides, the rGO aerogel-based carbon fabric was further fabricated into an all-solid-state symmetric SC which delivered a gravimetric capacitance of 245 F g −1 in PVA-KOH electrolyte.In addition, the wearable SC achieved an outstanding capacitance retention of 90% after 10 000 cycles. [102]

Knitted Fabric-Based Electrodes
Unlike woven fabrics, knitted fabrics have high porosity, good drapability, and excellent conformability.The highly ordered "open" structures of knitted fabrics are conducive to functional material growth, and the inherent structure can sustain large mechanical deformation.Therefore, knitted structures are highly desirable for fabricating highly flexible and stretchable SC electrodes.From a holistic point of view, knitted fabric-based elec-trodes (KFEs) exhibited outstanding stretchability while retaining capacitive performance.Like WFEs, variations of coating techniques are widely adopted for manufacturing KFEs.
KFEs based on synthetic fibers and their blends are favored for producing ultra-stretchable SC electrodes.While there remain many synthetic fibers, PET, nylon, and acrylic were dominant in producing KFEs.Using a 2 × 2 rib knitted PET fabric, Zheng et al. [103] decorated the fabric surface with PANI nanoarrays and MXene nanosheets.PANI nanoarrays were first deposited following a chemical polymerization method, after which MXene nanosheets were spray coated on the PANI layers to obtain PANI/MXene-PET fabric electrodes.Figure 7A illustrates such a process.Such electrodes exhibited a low sheet resistance of 2.1 ± 0.6 Ω sq −1 . [103]However, the conventional spray coating technique leads to poor functional material adhesion to the fiber surface.In order to improve the adhesion, a novel supersonic spraying technique has been proposed recently to construct KFEs with hierarchical architectures.For instance, Park et al. [104] prepared Cu/CNT/rGO-nylon fabric electrodes with multifunctional attributes using a supersonic cold spraying technique.The assembled coin-cell device from the Cu/CNT/rGO-nylon KFEs demonstrated an areal capacitance of 19.6 mF cm −2 .The capacitance retention was 89% after 2000 cycles of charge/discharge. [104]Such a method has a high industrial scalability potential.The same group later implemented an electrodeposition technique to assemble nickel nanocones and ZnO nanoflowers on nylon knitted fabric.Figure 7B shows such a technique.The obtained Ni/ZnO-nylon KFE exhibited a high areal capacitance of 510 mF cm −2 when assembled into a coin-cell device.Furthermore, the device also A) (i) Scheme depicting the fabrication process of PPy-knitted cotton/spandex fabric and its corresponding SEM images (ii-iv).Reproduced with permission. [107]Copyright 2021, Elsevier B.V. B) (i) Fabrication protocol for NiCu 2 Se 3 /Cu-Ni plated-cotton fabric electrodes with its photograph (ii).(iii-iv) illustrate the SEM images of NiCu 2 Se 3 /Cu-Ni plated-cotton at varying magnifications.CV (v) and GCD (vi) profiles of NiCu 2 Se 3 /Cu-Ni plated-cotton electrodes in 1 m KOH.Reproduced with permission. [109]Copyright 2023, American Chemical Society.C) (i) Fabrication protocol of NiCo 2 S 4 /CoS 2 -SSM electrode with its corresponding SEM images (ii-iii).(iv) CV curves of NiCo 2 S4/CoS 2 -SSM, NiCo 2 S 4 -SSM, and CoS 2 -SSM electrodes at 10 mV s −1 in 3 m KOH.Reproduced with permission. [110]Copyright 2020, WILEY-VCH Verlag GmbH.
exhibited a capacitance retention of ≈89% after 10 000 cycles of charge-discharge. [105]n knitwear manufacturing, elastomeric fibers are introduced into knitted structures to enhance the stretchability of the fabric.Therefore, KFEs constructed from elastomeric fiber blended knitted fabric are highly favored for their outstanding flexibility.For example, an acrylic/spandex (90/10) weft-knitted blended fabric was used by Zhou et al. [106] to assemble graphene nanoplatelets (GNPs) onto the fabric via a simple dipping and drying method.The resultant electrode was highly flexible and possessed dual functionality (energy storage and pressure sensing).The GNP-acrylic/spandex KFE achieved a gravimetric capacitance of 17.4 F g −1 in 1 m Na 2 SO 4 .Such an electrode also demonstrated reliable cyclic stability exhibiting 90% capacitance retention after 10 000 cycles of charge-discharge. [106]A similar approach was adopted by Lv et al. [107] to fabricate a multifunctional e-textile platform where knitted cotton/spandex blended fabric was introduced as a substrate.PPy was deposited using an optimized in situ polymerization reaction (Figure 8A(i)).Figure 8A(ii,iii,iv) illustrates the SEM images of PPy-knitted cotton/spandex fabric.Such an electrode was highly durable under varying deformations implying the superiority of elastomerblended knitted fabric.The resultant PPy-cotton/spandex electrode exhibited a high areal capacitance of 2599 mF cm −2 in 1 m Na 2 SO 4 electrolyte. [107]ince the screen-printing is so ubiquitous and cheap, it can also be implemented for KFE manufacturing.Like WFEs, screenprinted electrodes offer excellent conductive pathways for KFEs and can be bent seamlessly without any fluctuation in conductivity.For instance, Li et al. [108] employed screen printing to deposit PEDOT: PSS on a PET-knitted fabric.Then MnO 2 microspheres were electrochemically coated on the PEDOT: PSS layers to obtain the final PEDOT: PSS/MnO 2 -PET electrodes.The resultant electrode exhibited a slight reduction in conductivity after 2000 cycles of bending at 90°, indicating the suitability of screen-printed electrodes in long-term applications. [108]Metalizing fabric surfaces with nanoparticles is a popular method for constructing highly conductive current collectors on fabric surfaces.Since fabrics are insulative, a current collector layer could be introduced before functional material deposition.Gu et al., [109] in 2023, adopted this approach to prepare a metallicfabric electrode.They introduced functional ternary selenide microwire array materials (NiCu 2 Se 3 /Fe 2 CuSe 3 ) and a double network structure protocol.After the deposition of Cu-Ni alloy on knitted cotton fabric following an electroless plating technique, Cu(OH) 2 microwire arrays were grown on Cu-Ni alloy plated cotton fabric employing an oxidation etching.The Cu(OH) 2 arrays transformed into ternary selenide microwire arrays after a successive cation/anion exchange to achieve NiCu 2 Se 3 /Cu-Ni plated cotton fabric electrodes.Figure 8B(i,ii) illustrates such a process and the photograph of the functional electrode, respectively.The microarray structure was highly conducive to electrolyte intrusion, which resulted in better electrochemical performance.Figure 8B(iii,iv) demonstrates the FESEM images of such microarray architecture.The NiCu 2 Se 3 /Cu-Ni plated-cotton KFE achieved an areal capacitance of 1480.8 mF cm −2 in 1 m KOH electrolyte.Figure 8B(v,vi) depicts the CV and GCD curves of such electrodes. [109]hile weft-knitted structures are widely adopted for KFE fabrication, warp-knitted fabrics are primarily favored for fabricating ultra-stretchable electrodes.Warp-knitted structures are highly porous, lightweight, and stretchable in multiple directions compared to weft-knitted structures.In 2022, Su et al. [111] prepared a stretchable SC based on warp-knitted stainless steel fabric mesh (SSM).rGO and poly(3,4-ethylenedioxythiophene) (PE-DOT) coatings were grown on the SSM surface using a two-step electrodeposition technique in a three-electrode cell.rGO and PE-DOT simultaneously formed a 3D conductive network conducive to better electrolyte intrusion.The electrode was highly stretchable, stemming from the SSM substrate's excellent stretchability.The PEDOT/rGO-SSM showed gravimetric and areal capacitances of 77.09 F g −1 and 110.13 mF cm −2 , respectively, in 1 m H 3 PO 4 .The electrode also demonstrated a capacitance retention of 91% after 5000 cycles of charge-discharge. [111]In another work, Shao et al. [110] prepared a stretchable SS fiber-based warpknitted electrode decorated with NiCo 2 S 4 nanosheets and CoS 2 nanowires.NiCo 2 S 4 nanosheets wrapped by CoS 2 nanowires were assembled onto the warp-knitted SSM surface using a hydrothermal method followed by a sulfuration post-treatment.Figure 8C(i) illustrates such a process.Figure 8C(ii,iii) illustrates the corresponding SEM images of such electrodes.The NiCo 2 S 4 /CoS 2 -SSM electrode demonstrated a high gravimetric capacitance of 1212 F g −1 in 3 m KOH electrolyte.Figure 8C(iv) demonstrates the CV curves of such electrodes.Moreover, the electrode retained 80% of the initial capacitance even after 6000 charge/discharge cycles and could be stretched up to 40% without any distortion in its capacitive performance. [110]hough many fabrication techniques can be employed, knitting conductive yarns into a fabric structure is a scalable technique to realize conductive electrodes.Huang et al. [112] pursued this approach and fabricated a SWCNT-based weft knitted fabric from SWCNT-coated cellulose yarns.They first introduced a bobbin winding technique to continuously coat the yarns with SWCNT.The resultant yarns were subsequently machine-knitted into a fabric and electropolymerized to achieve PPy/SWCNTcellulose electrodes.The composite electrode showed stable electrochemical performance with multifunctional attributes. [112]his is one of the early reports for the scalable fabrication of KFEs.While the focus is primarily on functionalizing 2D weft/warp knitted structures, reports on 3D knitted SC electrodes are limited.A 2022 investigation led by Dou et al. [113] employed a 3D spacer fabric for SC electrodes where SWCNT and PPy were implemented as active materials.They first coated the 3D fabric with SWCNT using a simple dip-coating method.After that, the SWCNT-spacer fabric was subjected to in situ chemical polymerization reaction to obtain PPy/SWCNT-spacer fabric electrodes.Such an electrode exhibited a high areal capacitance of 1765.6 mF cm −2 .Besides, the electrode showed stable electrochemical performance at different pressure conditions. [113]

Nonwoven Fabric-Based Electrodes
With their tunable thickness, high surface area, low cost, and irregular porosity, nonwoven fabrics are an emerging new substrate for fabricating wearable SC electrodes.However, poor mechanical performance has barred its wide-scale implementation in flexible electrode fabrication.Besides, synthetic fiber-based nonwovens such as PP, viscose, and PET are predominant in fabricating nonwoven fabric-based electrodes (NFEs).Since nonwoven fabrics are produced based on the specific end-use, research progress on NFEs is slow, limited to only a handful of studies.Nevertheless, interest has been rising in functional NFE research and its potential use in wearable SCs over the last two years.A study published in 2022 by Zou et al. [114] reported the implementation of waste surgical masks (WSMs) to fabricate flexible SCs.The group experimented with the outer layer of WSM, which was composed of spunbonded nonwoven polypropylene (PP) fabric.First, gold nanoparticles (AuNPs) were deposited on PP nonwoven fabric to construct the current collectors.Then PPy microcones were deposited through an electropolymerization reaction to obtain PPy/AuNP-PP electrodes (Figure 9A(i)).The electropolymerization led to the formation of a 3D porous microstructure conducive to effective electrolyte intrusion.The electrode showed areal and volumetric capacitances of 1375.0 mF cm −2 and 48.1 F cm −3 , respectively, in 1 m H 2 SO 4 .Figure 9A(ii,iii) shows the GCD and CV profiles of such electrodes.Furthermore, the PPy/AuNP-PP electrodes demonstrated a capacitance retention of 81%. [114]However, the electrode exhibited poor bending durability.The poor mechanical attributes stem from the irregular and uneven bonding between fibers in the nonwoven structure.Therefore, nonwoven structures are less durable than woven or knitted structures.While the nonwoven can be strengthened through thermal and mechanical means, chemical modification can improve the overall mechanical durability.Such an approach was adopted by Zhang et al. [115] in 2022.The group prepared a quasi-solid state flexible SC based on crosslinked chitosan-viscose nonwoven fabric (c-CVF).They first deposited MWCNT by a simple dip-coating strategy followed by an in situ deposition of PPy through interfacial polymerization.Figure 9B(i) depicts the fabrication process and the gradual change in the appearance of c-CVF.The functional  [114] Copyright 2021, Elsevier B.V. B) (i) Fabrication process of PPy/MWCNT/c-CVF electrodes with its corresponding photographs after each step.CV (ii) and GCD (iii) curves of PPy/MWCNT/c-CVF electrodes.Reproduced with permission. [115]Copyright 2022, Elsevier Inc. materials simultaneously increased and reconstructed the surface of c-CVF-based NFEs.Through swelling, the chitosan component of the nonwoven fabric got the required flexibility, whereas the viscose fibers acted as a rigid frame, ensuring mechanical durability.The PPy/MWCNT/c-CVF electrode reached a high conductivity of 285.9 ± 1.2 S cm −1 .The electrode exhibited a high areal capacitance of 10 112.9 mF cm −2 in 1 m H 2 SO 4 .Figure 9B(ii,iii) exhibits the CV and GCD profiles of such electrodes.Furthermore, such electrodes exhibited a capacitance retention of 102.5% after 10 000 cycles of charge-discharge.Besides, PPy/MWCNT/c-CVF electrode was bent 200 times, retaining its original capacitance.Such mechanical performance can be attributed to the cross-linking modification of CVF. [115]ike WFEs, a ternary hierarchical microstructure can be constructed on nonwovens with enhanced electrochemical performance.In a step-by-step manner, Liu et al. [116] fabricated ternary CNT/PPy/rGO-PET nonwoven fabric electrodes.First, rGO was grown by thermal reduction of GO embedded on the surface of the PET nonwoven fabric.Then PPy was deposited through an in situ vapor polymerization reaction.Finally, the PPy/rGO-PET fabric was dipped in an MWCNT solution to further enhance the conductivity of composite electrodes.The group also claimed that the increase in MWCNT led to enhanced capacitive performance, whereas increasing PPy loading did not contribute to the overall capacitance enhancement.The CNT/PPy/rGO-PET electrode demonstrated a gravimetric capacitance of 319 F g −1 in 1 m KCL and a 94.5% capacitance retention after 1000 charge-discharge cycles. [116]In order to further improve the capacitance of NFEs, numerous coating strategies were imple-mented.A capillary-assisted assembly coating technique was introduced by Li et al. [117] to fabricate cellulosic nonwoven fabricbased electrodes with graphene and MnO 2 as functional materials.Figure 10A(i) depicts the fabrication process of MnO 2 /Gcellulosic NFE.An ultrathin layer of graphene was deposited onto the fabric substrate.Figure 10A(ii) exhibits the microstructure after graphene deposition.The MnO 2 particles were in situ grown on graphene nanosheets to achieve composite MnO 2 /Gcellulosic NFEs (Figure 10A(iii)).The MnO 2 /G-cellulosic NFE exhibited an areal capacitance of 368.2 mF cm −2 in a 6 m KOH electrolyte.After 5000 cycles of charge-discharge, 82.5% capacitance retention was observed.Figure 10A(iv) illustrates the CV curves of such electrodes. [117]Employing simple dip coating and a two-step electrodeposition method, Zhang et al. [118]   shows the corresponding cross-sections of rGO/Ni-nonwoven and rGO/Ni/Fe 2 O 3 -nonwoven, respectively. [118]hile variants of coating techniques are prevalent for fabricating WFEs and KFEs, the majority of the reports employ unconventional fabrication techniques for NFE manufacturing.A hydraulic press was used by Yu et al. [119] to incorporate graphene  [117] Copyright 2018, Elsevier B.V. B) (i) Fabrication protocol of rGO/Ni/Fe 2 O 3nonwoven electrodes.(ii) Photographs of pristine NW, rGO-NW, and rGO/Ni-NW.SEM images and their corresponding cross-sections of rGO/Ni-NW (iii) and rGO/Ni/Fe 2 O 3 -NW (iv).Reproduced with permission. [118]Copyright 2023, Elsevier B.V.
hydrogel materials (GHG) onto stainless steel nonwoven fabric (SSF).The prepared GHG was placed on top of SSF and converted into thin films after 30 MPa of pressure was applied for 30 min.The GHG-SSF electrode achieved an areal capacitance of 730.8 ± 8.7 mF cm −2 in 1 m H 2 SO 4 . [119]Stempien et al. [120] fabricated a PPy-based polypropylene (PP) NFE by reactive inkjet printing of PPy at sub-zero temperature.First, a gold electrode layer was placed on PP nonwoven fabric.Afterward, reactive inkjet printing of PPy was carried out at sub-zero temperatures to fabricate PPy/Au-PP electrodes.The PPy/Au-PP electrodes showed low sheet resistance of 13.4 ± 2.4 Ω sq −1 . [120]Pan et al. [121] developed a functional nylon-graphene nonwoven (NGN) fabric by melt-blowing nylon-6 into the nonwoven fabric and depositing GO onto the fabric surface.The GO-loaded fabric was then chemically reduced to rGO to offer outstanding electrical conductivity.Subsequently, a monolithic SC was fabricated by a CO 2 laser patterning technique on the nylon GO nonwoven composite.The laser irradiation converted the GO nanosheets into conductive rGO nanosheets.The monolithic SC demonstrated an areal capacitance of 10.37 mF cm −2 in PVA-H 2 SO 4 electrolyte, which was higher than reported MSCs. [121]Implementing a repeated vapor phase polymerization (VPP) process, Xu et al. [122] incorporated the conductive PEDOT polymer into a nanocomposite film composed of reduced graphene oxide/carbon nanotube (rGO/CNT) and prepared rGO/CNTs/PEDOT film on a flexible nonwoven fabric with hierarchical architecture.The rGO/CNTs/PEDOTnon woven fabric exhibited a gravimetric capacitance of 164 F g −1 in a 0.5 m Na 2 SO 4 electrolyte.The electrode also exhibited excellent cyclic stability of 93% after 1000 cycles of mechanical bending. [122]i et al. [123] employed an in-situ chemical oxidative polymerization to fabricate PEDOT nanowire-coated nonwoven (PE-DOT/NW) as the electrodes.The PEDOT nanowires immobilized on the nonwoven fabric surface constructed a highly conductive 3D flowerlike microstructure and mechanically robust electrode that could be directly used as an electrode without the need for organic binders or conductive additives.The asfabricated electrode exhibited a high gravimetric capacitance of 169 F g −1 in 1 m LiClO 4 electrolyte. [123]In another study, Wang et al. [124] fabricated an NFE by dip-coating bare nonwoven fabric in SWCNT ink and subsequent PANI nanowire deposition by in situ chemical polymerization.The assembled SC device achieved a gravimetric capacitance of 410 F g −1 in 1 m H 2 SO 4 electrolyte. [124]All these varying strategies confirm the versatility of nonwoven fabrics.Table 1 summarizes the electrical and electrochemical properties of functional fabric-based electrodes.

Comparison Among Fabric-Based Electrodes
The recent advances in fabrication, electrochemical properties, and different architectures of functional fabric-based electrodes are reviewed in this chapter.Overall, the functional fabric-based electrodes exhibited outstanding capacitive performance without any degradation in fabric architecture.Although woven, knitted, and nonwoven structured fabric-based electrodes excel in different areas, they perform poorly in some instances.

Design and Performance of Wearable SCs
The fabrication of FSCs is carried out in two distinct steps, and they are functional electrode preparation and assembly with gel electrolyte systems.The preparation of functional fabric-based electrodes is covered in the previous section (Chapter 3).This chapter will emphasize the configuration, integration, and durability aspects of functional fabric-based SCs and their performance characteristics.

Sandwiched
Sandwiched type and in-plane/planar type SCs are the two most predominant FSC configurations in the current literature.Between these two, the sandwiched configured SCs are widely implemented because of their ease of fabrication, flexibility, easy characterization, and better electrode material safety.For fabricating a typical sandwiched wearable SC, the FEs with the same area are cut and "sandwiched" with a gel electrolyte layer in between.
If the same electrode is employed, it is termed as "symmetric"; otherwise, sandwiched SC with different electrodes is coined as "asymmetric" SC.The sandwich configuration of FSCs has been repeatedly adopted by researchers in order to achieve the highest possible capacitive performance.FSCs based on WFEs demonstrate outstanding capacitive performance but lag in long-term durability.For instance, Ye et al. [87] fabricated a sandwiched structured sym-metric woven fabric-based SC (WFSC) employing MXene/PANIcotton WFEs with PVA-H 2 SO 4 as a gel electrolyte.The device achieved an areal capacitance of 479.2 mF cm −2 and demonstrated excellent flexibility.However, the device showed poor capacitance retention of 58.8% after only 1000 cycles of chargedischarge. [87]In order to improve the cyclic stability of polymeric WFEs, carbon-based electrode materials can be compounded with polymers.This strategy was pursued by Chakraborty et al. [96] to assemble a symmetric WFSC using oPDA/MWCNT-PET electrodes and PVA-KOH as gel electrolytes.The EDLC from MWCNTs and the pseudocapacitance from polymers significantly boosted the device's capacitance.The device reached a gravimetric capacitance of 147 F g −1 and an energy density of 6.62 Wh kg −1 at a power density of 205.10 kW kg −1 .A moderate capacitance retention of 82% was achieved after 1000 cycles of charge-discharge. [96]Increasing the functional material loading of WFEs can improve the overall capacitance of WFSCs tenfold.Such a case was observed in a report by Yang et al. [99] The group prepared a symmetric SC implementing MWCNT/rGOcotton WFE with high mass loading (23.7 mg cm −2 ) and PVA-LiCl as gel electrolytes.The SC achieved a record-breaking areal capacitance of 2675 mF cm −2 and the capacitance retention increased to 118% after 10 000 cycles of charge-discharge.The capacitance value was higher than any other FSCs based on KFEs or NFEs.The WFSC showed a volumetric capacitance of 20.45 F cm −3 and excellent flexibility (100% after 10 000 bending cycles). [99]SCs based on both weft-knitted and warp-knitted structures were implemented as sandwiched wearable SCs.128] Adv.Mater.Interfaces 2024, 11, 2300724 SC (KFSC) based on PPy-cotton/spandex KFEs and PVA-LiCl gel electrolyte.The device reached an areal capacitance of 978.9 mF cm −2 and a capacitance retention of 80% after 2000 cycles of charge-discharge. [107]However, the device's stretchability was not satisfactory.In order to achieve highly stretchable SC, the warp-knitted fabric can be ideal for functional material growth.For instance, Su et al. [111] fabricated a highly stretchable SC using PEDOT/rGO-SSM fabric electrode and PVA-H 3 PO 4 as a gel electrolyte.The highly stretchable SC achieved areal and gravimetric capacitances of 53 mF cm −2 and 18 F g −1 , respectively.The SC reached an energy density of 4.71 Wh cm −2 at a power density of 2 mW cm −2 .Furthermore, the capacitance decreased by only 3.2% and 5.3% under the flat state and at 90 o bending state for 100 cycles.Yet, operating window of such SC was ited to 0.8 V only.Such performance indicated the outstanding flexibility of SCs. [111]In another study, Zheng et al. [103] fabricated a symmetric SC using PANI/MXene-PET electrode and PVA-H 2 SO 4 as a gel electrolyte.Such a device achieved areal and gravimetric capacitances of 647 mF cm −2 and 54.8 F g −1 , respectively.The device demonstrated an energy density of 8.08 μWh cm −2 at a power density of 0.045 mW cm −2 .However, the device showed poor capacitive retention of 45.3%, and the operating voltage window was limited to only 0.6 V. [103] In order to boost the operating voltage window of FSCs, asymmetric device assemblies can be adopted.For example, Shao et al. [110] prepared a stretchable asymmetric SC where NiCo 2 S 4 /CoS 2 -SSM acted as a positive and activated carbon (AC)-SSM as a negative electrode.PVA-KOH was employed as a gel electrolyte.The asymmetric device reached a high working voltage of 1.6 V and a gravimetric capacitance of 169.4 F g −1 .The device achieved a high energy density of 60.2 Wh kg −1 at a power density of 800 W kg −1 and retained 75% of initial capacitance after 5500 cycles of charge-discharge. [110]achine knitting is an ingenious technique to realize wearable SCs in 3D-knitted architectures.With machine knitting, complex multidimensional textile structures can be realized with tunable structural properties.Wen et al. [54] adopted this approach and developed a 3D knitted structure with silver-plated nylon yarns and PET yarns employing an industrial computerized knitting machine (Shima Seiki's SVR123SP-14G).The 3D fabric (3DF) was subjected to electrodeposition to decorate a Ni layer with MnO 2 nanoparticles on one side and rGO nanosheets on the opposite side of the 3DF.The MnO 2 -3DF//rGO-3DF asymmetric device exhibited a high areal capacitance of 1.02 F cm −2 in the PVA-Na 2 SO 4 electrolyte.The device also achieved an energy density of 1.02 mWh cm −2 at a power density of 5.27 mW cm −2 . [54]Levitt et al. [127] prepared a 3D knitted wearable SC utilizing highly conductive Ti 3 C 2 T x MXene-coated cotton and nylon yarns.The fabricated device achieved an areal capacitance of 519 mF cm −2 in PVA-H 3 PO 4 electrolyte and showed excellent cyclic stability after 10 000 cycles of charge-discharge.Such a technique has potential in large-scale manufacturing of FEs. [127]lthough they are not scrutinized or widely investigated, the limited reports regarding NFEs demonstrated reliable energy storage performance when assembled into nonwoven fabricbased SCs (NFSCs).For instance, Zhang et al. [115] prepared a quasi-solid state flexible SC using PPy/MWCNT/c-CVF electrodes and PVA-H 2 SO 4 as a gel electrolyte.The symmetric device demonstrated an areal capacitance of 1748.0 mF cm −2 and an energy density of 155.4 Wh cm −2 at a power density of 0.88 mW cm −2 . [115]In 2021, Zou et al. [114] assembled a quasisolid state SC using PPy/AuNP-PP electrodes and PVA-H 2 SO 4 as a gel electrolyte.The symmetric SC reached an areal capacitance of 219.1 mF cm −2 and excellent capacitance retention of 92.1% after 10 000 charge-discharge cycles.Furthermore, the device exhibited excellent bending stability, where 88.3% initial capacitance was retained after 1 00 000 bending cycles (different bending cycles).Such outstanding bending performance was primarily owing to PP's excellent mechanical durability.Besides, the device achieved a maximum energy density of 19.48 μWh cm −2 (0.71 mWh cm −3 ) at a power density of 219.2 μW cm −2 (8.03 mW cm −3 ). [114]Yu et al. [119] prepared symmetric NFSC by sandwiching two GHG-SS fabrics and PVA-H 2 SO 4 as gel electrolytes.Figure 11A(i,ii) illustrates the fabrication process of sandwiched configured GHG-SS SC and photographs of SS fabric, GHG, and GHG-SS fabric electrodes.Figure 11A(iii) depicts the SEM image of such an electrode.The device demonstrated an areal capacitance of 180.4 ± 2.3 mF cm −2 and retained 96.8% of initial capacitance after 7500 chargedischarge cycles.Figure 11A(iv,v) demonstrates the GCD and CV curves of the wearable device.Moreover, the symmetric device reached a high energy density of 19.2 Wh cm −2 at a power density of 386.2 W cm −2 .Figure 11A(vi) exhibits the Ragone plot of solid-state devices.After 800 stretching bending cycles, the specific capacitance of the device was maintained at 96.4%, indicating outstanding flexibility. [119]All these reports clearly indicate the excellent performance of underexplored nonwoven fabrics in wearable SC applications.

Planar
Planar MSCs have garnered considerable attention owing to their thinner, lighter, and miniaturized nature. [129]The electrode materials are arranged within the same plane in a manner that a small gap is introduced, separating two electrodes and removing the possibility of a short circuit.The narrow interspaces between electrode arrays effectively shorten ion diffusion offering a high power output.In recent years, fabrics have been implemented to construct interdigitated electrodes, thereby fabricating planar MSCs.Variants of printing techniques were predominant in fabricating interdigitated electrodes onto fabric surfaces.A screen printing technique was employed by Jiang et al. [95] to fabricate a coplanar WFSC where MWCNT was printed on a cotton fabric surface.After coating the electrode materials with PVA-KOH gel electrolyte, the device delivered a gravimetric and areal capacitance of 26.4 F g −1 and 13.8 mF cm −2 , respectively.The device achieved capacitance retention of >90.0% after 2000 cycles of charging/discharging. [95] In 2023, Lin et al. [130] fabricated patterned micro-electrodes composed of acid-functionalized CNT and MnO 2 on cotton woven fabric employing the screen printing method.The CNT/MnO 2 -cotton fabric MSC achieved a maximum energy density of 0.228 mWh cm −2 at a power density of 0.587 mW cm −2 .The WFSC showed an areal capacitance of 8.479 mF cm −2 and excellent bending stability.Furthermore, the device achieved a capacitance retention of 72.94%, 79.87%, and 98.05% in stretching, folding, and bending, respectively.Such performance in dynamic deformations indicated the mechanical stability of MSCs based on woven fabrics. [130]Step-by-step process to fabricate GHG-SSF electrode and its corresponding SEM (iii).GCD (iv), CV (v), and Ragone plot (vi) profiles of assembled solid-state devices.Reproduced with permission. [119]Copyright 2016, American Chemical Society.B) Illustration depicting an in-plane type fabric-based SC with its performance parameters.(i, ii) Scheme of fabricating screen printed PEDOT: PSS/MnO 2 -PET MSC.(iii) SEM image of the cross-section of the electrode materials.GCD (iv), and CV (v) curves of PEDOT: PSS/MnO 2 -PET MSC.Reproduced with permission. [108]Copyright 2021, Wiley-VCH GmbH.
Like woven fabrics, knitted and nonwoven fabrics were also adopted for planar device fabrication.For instance, Li et al. [108] designed a PET-knitted fabric-based MSC in which PEDOT: PSS and MnO 2 -supported interdigitated electrodes were fabricated using a screen printing technique.Figure 11B(i,ii) depicts the schematic illustration and fabrication process of screen-printed planar SC. Figure 11B(iii) illustrates the cross-section of MnO 2deposited interdigitated electrodes.The MSC achieved an areal capacitance of 135.4 mF cm −2 in the PVA-LiCl gel electrolyte.Besides, the MSC achieved an energy density of 12.03 μWh cm −2 at a power density of 32 mW cm −2 and showed 93% capacitance retention after 3000 charge-discharge cycles.Figure 11B(iv,v) illustrates the GCD and CV profiles of wearable devices.Furthermore, the MSC retained ≈94% of its initial capacitance after 3000 cycles of bending. [108]In 2023, Zheng et al. [131] fabricated MXenesupported interdigitated electrodes that were screen printed on rayon nonwoven fabric and coated with PVA-H 2 SO 4 gel electrolyte to obtain MXene-based MSC.The device achieved an ultrahigh areal capacitance of 2390 mF cm −2 and an energy density of 119.5 μWh cm −2 at a power density of 0.36 mW cm −2 . [131]While printing techniques are favored for fabric-based MSCs, other methods were adopted to construct interdigitated electrodes.A thermal transfer printing method was adopted by Kwon et al. [132] to fabricate laser-induced graphene (LIG) on cotton fabric.The LIG-MSC delivered an energy density of .07-0.08 μWh cm −2 in the PVA-H 3 PO 4 electrolyte.The device obtained 93.6% capacitance retention after 5000 cycles of charge-discharge, implying outstanding stability. [132]Lu et al. [94] fabricated a planar MSC using PPy as a functional material.After the interfacial polymerization of pyrrole on the cotton fabric surface, the PPy layer was carefully etched by DMF in order to construct two separate electrodes on the fabric surface.After coating with PVA-H 2 SO 4 gel electrolyte, the assembled MSC demonstrated an areal capacitance of 2.64 mF cm −2 and retained 85% of initial capacitance after 3000 cycles of charge and discharge.Furthermore, the device achieved an energy density of 0.09 μWh cm −2 at a power density of 19.1 μW cm −2 . [94]ecently, LIG integrated fabric interfaces have gained tremendous attention for fabricating planar wearable MSCs.While there remain many fabric substrates for LIG fabrication, cotton, and Kevlar fabrics are utilized predominantly.For instance, Awasthi et al. [133] leveraged an optimized laser ablation technique to prepare LIG on phenolic resin-coated cotton fabric for wearable SC applications.The LIG-cotton electrode delivered an areal capacitance of 89.7 mF cm −2 in 1 m H 2 SO 4 . [133]In a recent study, Yang et al. [134] employed a femtosecond-direct-laser-writing technique to fabricate LIG electrodes on a Kevlar nonwoven fabric for wearable MSC applications.The planar LIG-Kevlar nonwoven MSC achieved an areal capacitance of 36.17 mF cm −2 in PVA-H 2 SO 4 and exhibited a 96.3% retention after 6000 cycles of charge-discharge. [134]These works demonstrate the excellent performance of LIG in fabric-based SC.
Introducing dopants into LIG could significantly boost the electrochemical performance of LIG-fabric-based MSCs.Rao et al. [135] adopted this approach and fabricated phosphorus (P)doped LIG by laser-scribing PVA/H 3 PO 4 -coated woven Kevlar fabric for wearable MSC applications.The P-doping optimized the micropores of LIG and the pseudocapacitance of P-dopant synergistically contributed to enhance the capacitive perfor-mance.Therefore, the flexible P-doped LIG-Kevlar fabric MSC achieved a high areal capacitance of 125.35 mF cm −2 in PVA-H 2 SO 4 and demonstrated an outstanding retention of over 88% after 10 000 cycles. [135]In another work, Lu et al. [136] leveraged a CO 2 laser scribing technique to produce Mn-doped LIG on carbonized cotton fabric.After carbonizing the cotton fabric at 300 °C, the carbonized cotton fabric was coated with Mn ioninduced hydrogel ink, followed by laser scribing to produce LIG.The Mn-doped LIG-carbonized cotton fabric was further fabricated into a bio-based MSC device which achieved an areal capacitance of 54.97 mF cm −2 in PVA/H 3 PO 4 electrolyte. [136]

All-in-One
A completely novel configuration of FSC was first reported by Jiang et al. [137] in early 2022.They proposed a unique woven fabric-based SC where the fabric acted both as a separator and firmly held the gel electrolyte system in place.First, the cotton woven fabric was coated with PVA-KOH electrolyte using a scalable dip-pad-dry method.Then they screen-printed MWCNT-based electrodes on both sides of the gel electrolyte-coated fabric to construct an all-in-one fabric-based SC. Figure 12A(i) depicts the fabrication process and structure of an all-in-one structured SC.The unique self-integrated SC demonstrated an areal capacitance of 4.83 mF cm −2 and an energy density of 6.7 μWh cm −2 at a power density of 0.48 mW cm −2 .Figure 12A(ii,iii) demonstrates the CV and GCD curves of such wearable SCs.The group further compared and analyzed the performance of all-in-one SCs with traditional flexible SC designs, such as in-plane and sandwich-type SCs employing screen printing.It was revealed that the all-in-one SC performed better than that of planar or sandwich-type design configurations. [137]In late 2022, the same group differentiated between all-in-one and sandwiched structure FSCs.Electrode materials were assembled by screen printing.The MWCNT-based all-in-one and sandwiched structured SC achieved areal capacitances of 4.16 and 4.17 mF cm −2 , respectively, in PVA/KOH electrolyte.Although in both configurations, the capacitance values were nearly the same, in long-term cyclic stability, the allin-one SC performed far better than the sandwiched SC. [138] Besides, the all-in-one SC exhibited superior bending stability.This is because, in sandwiched structure SC, the curved textile substrates and separator will exert a stretching force on the upper electrodes while exerting a compression force on the lower electrodes.Hence, both electrodes in the sandwiched supercapacitor would simultaneously endure compression and tensile force under bending deformation, resulting in electrode distortion and unstable electrochemical performance. [137,138]

Stacked
In early 2023, a report by Inman et al. [139] demonstrated an MXene-based woven cotton fabric SC adopting a unique stacked architecture.After depositing MXene (Ti 3 C 2 T x ) on fabric surfaces, multiple MXene-cotton electrodes were stacked alternately on top of each other with a gel electrolyte layer in between.Figure 12B depicts the construction schematics of a "stacked" configured fabric-based SC.The stacked configuration achieved All-in-one and stacked configurations of functional fabric-based wearable SCs.A) (i) The illustration indicates the fabrication process and structural schematics of novel all-in-one cotton fabric-based SC.CV (ii) and GCD (iii) curves of MWCNT-cotton all-in-one configured SC.Reproduced with permission. [137]Copyright 2022, Elsevier B.V. B) Schematic illustration depicting the structural breakdown of a stacked configuration of fabric-based SCs.
a maximum working voltage of 6 V in the PVA-LiCl electrolyte.Such a device reached an areal capacitance of 146 mF cm −2 and achieved an energy density of 0.401 mWh cm −2 with a power density of 0.248 mW cm 2 .The group further compared the novel stacked SC with different traditional fabric-based SC architectures, such as sandwiched and planar devices with interdigitated electrodes.It was revealed that the stacked design outperformed all other device configurations having the same footprint area of 25 cm 2 .Besides, the SC was able to power a temperature monitoring system with high current density requirements and carry out successful wireless data transmission to a receiver for 1.5 h. [139]This unique device architecture shows high prospects for the successful commercialization of wearable SC devices.Copyright 2021, Wiley-VCH GmbH.B) Interdigitated clothing applique is sewn into labcoats, providing power to a red LED.(i) Tree-shaped clothing applique SC. (ii) Interdigitated clothing applique SC.Reproduced with permission. [88]Copyright 2023, Elsevier B.V. C) (i) Scheme of elbow-fitted flexible fabric-based SC. (ii) Two NiCo 2 S 4 /CoS 2 -SSM//activated carbon-SSM asymmetric SC connected in series to light up an LED mounted on the elbow both in stretching (ii) and bending (iii) states.Reproduced with permission. [110]Copyright 2020, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.D) Wearable MWCNT-cotton symmetric SC attached to the jacket powered by a fabric-based triboelectric generator.Reproduced with permission. [140]Copyright 2017, AIP Publishing.E) MWCNT/rGO-cotton fabric SC sewn into a lab coat and lighting up and LED.Reproduced with permission. [99]Copyright 2017, WILEY-VCH Verlag GmbH.

Integration
Integration of FSCs at the apparel level is one of the most vital parameters dictating the fruitful commercialization of wearable SCs.While calculating the capacitance, energy density, and power density of FSCs are widely investigated, the integration of SCs for practical application remains underexplored, and in some cases, ignored.Therefore, studies regarding FSCs being directly integrated into apparel are scarce.For example, Li et al. [108] designed a PET-knitted fabric-based MSC in which PEDOT: PSS and MnO 2 microspheres were fabricated by screen printing and electrochemical coating.The planar device achieved a high energy density of 12.03 μWh cm −2 at a power density of 32 mW cm −2 .In order to demonstrate its practical application, the fabricated MSC was seamlessly integrated into a sweatshirt (Figure 14A(i,ii)).After 1000 m of running, the integrated MSC exhibited nearly similar performance (almost similar CV and GCD curves), which is evident from the CV and GCD curves in Figure 14A(iii,iv).The MSC showed stable electrochemical performance not only during running but also in water. [108]However, such MSC did not power any wearable system integrated into one single platform.There is a scarcity of reports where fully integrated intelligent apparel is powered by FSCs.In a 2023 report by Kou et al., [88] an interdigital clothing applique was prepared using CCIP electrode materials.The ready-to-use applique was capable of attaching to a lab coat using simple sewing op-erations, ensuring the wearability of fabric-based SC as both an attractive and functional element.The group designed two types of clothing applique, one with a tree shape (Figure 14B(i)) and the other with an interdigital pattern (Figure 14B(ii)).Both appliquetype wearable SCs were successful in powering up an LED. [88]uch customized FSCs show tremendous potential for mass fabrication.
In another work reported by Shao and co-workers, [110] NiCo 2 S 4 /CoS 2 -SSM//AC-SSM asymmetric SC was incorporated on an elbow to exhibit the outstanding flexibility of wearable fabric-based SC.The asymmetric SC was seamlessly attached to a sports sleeve.Such elbow-fitted fabric-based SC (Figure 14C(i-iii)) was capable of powering up an LED fitted on the sleeve.These demonstrations proved the wearability and integrability of knitted wearable SCs in existing apparel platforms. [110]Fabric-based SCs capable of self-charging are also being developed and implemented within apparel platforms.For instance, Song et al. [140] prepared all-fabric-based self-powered textiles with an integrated fabric-based triboelectric generator (TEG) and a fabric-based SC.The SWCNT-cotton symmetric SC achieved an areal capacitance of 16.76 mF cm −2 in the PVA-H 3 PO 4 gel electrolyte.The energy collected by TEG could charge the SC to nearly 100 mV after only walking for 6 min.Additionally, the SC and TEG were both embedded in commercial jackets, which is evident from Figure 14D. [140]In a separate study, Yang et al. [99] prepared a waterproof, high-performance wearable SC employing MWCNT/rGO-cotton electrodes.The whole device was secured in a PET film and later sewn into a lab coat.The symmetric MWCNT/rGO-cotton SC embedded in the lab coat successfully lit up an LED showing practical application in wearable electronics.Figure 14E demonstrates such a device powering up an LED. [99]In 2022, Selvam et al. [141] devised a self-charging fabric-based biocompatible SC that could be operated with both ionic liquid and sweat electrolyte modalities.GO, PEDOT, and CuO were employed as functional materials for bio-supercapacitors.The SC integrated on PET fabric could be mounted on the arm and was capable of self-charge while exercising.Such a unique result indicated the excellent integration of fabric-based SCs. [141]

Endurance
The long-term durability of FSCs depends on various aspects, such as bending performance, wearability, and, most importantly, washability of wearable FSCs.In order to boost the longterm working performance of FSCs, modified gel electrolyte systems can be employed.Li et al. [125] adopted this approach and proposed the use of a composite gel electrolyte system consisting of polyvinyl alcohol (PVA)/polyacrylamide (PAM) in order to adapt to a long-term working conditions.The device was also able to power up an electroluminescent device embedded in a lab coat (Figure 15A(i-vi)).They further compared FSCs based on PVA/PAM and only PVA electrolytes.The PANI/G-HF electrode-based symmetric device achieved a stable capacitance retention of 93.29% for the PVA/PAM electrolyte after 15 days, whereas it was only 43.2% when only PVA gel electrolyte was used (Figure 15A(vii)).Furthermore, the device could also perform impeccably underwater for 12 h, showing no decline in performance, which is evident from Figure 15A(viii). [125]Another key performance indicator for FSCs is the stability of the structural integrity of devices while maintaining stable capacitive performance.Overall, FSCs showed excellent flexibility at varying bending angles (0 o -180 o ).For example, the PEDOT: PSS/MnO 2 -PET MSC was subjected to different bending conditions to evaluate the performance under dynamic bending conditions (Figure 15B(i)).Even at different bending states, the CV curves remained nearly similar.The device retained 94% of initial capacitance after 3000 cycles of bending (Figure 15B(ii-iv)).Furthermore, the device could light up an LED even in bent and twisted conditions (Figure 15B(v,vi)). [108]It is apparent that warp-knitted structures offer higher flexibility and inherent stretchability than other functional fabric-based SCs.For instance, NiCo 2 S 4 /CoS 2 -SSM//AC-SSM asymmetric SC was constructed based on a warpknitted structure which rendered the device to be stretched at varying strains.After 1000 stretch-release cycles, the capacitance decreased by only 6.8%, 12.5%, and 23.6% for strains of 10%, 20%, and 30%, respectively (Figure 15C(i)).Additionally, the device was drawn, twisted, and bent, yet, the device still retained its initial capacitance implying outstanding stability under varying deformations (Figure 15C(ii-vi)). [110]an et al. [142] prepared 2D PPy-cotton WFE incorporated symmetric SC employing a salt-templated vapor phase polymerization reaction.The device was highly flexible at varying bending angles (0 o , 60 o , 90 o , and 180 o ).After 1000 bending cycles at varying angles, the device retained 94% of its initial capacitance of 60 o .Figure 15D depicts the photograph of the test procedure. [142]Kwon et al. [132] employed thermal transfer printing to fabricate interdigitated LIG film onto fabric surfaces.The LIG-supported fabric-based MSC exhibited stable electrochemical performance under varying bending angles.The MSC exhibited a high capacitance retention of 96% after 1000 cycles of bending, implying outstanding flexibility.Figure 15E demonstrates the bent states of LIG-MSC. [132]Yang et al. [99] fabricated MWCNT/rGO-cotton WFSC employing PVA-LiCl as a gel electrolyte.The device exhibited outstanding flexibility achieving no loss in capacitance retention (100%) after 10 000 cycles of bending (Figure 15F(i)).Furthermore, the device could be operated underwater, and after 1000 cycles, it exhibited 90.3% capacitance retention (Figure 15F(ii)). [99]With no practical decline in bending and operation underwater, the device is suitable for practical wearable applications.The electrochemical and mechanical properties of FSCs are summarized in Table 3.

Role of Fabric Architecture in Wearable SC Performance
In this review, FSCs based on different fabric architectures have been summarized.Since different fabric architectures possess different textures and surface properties, fabric architecture has the potential to influence the performance of FSCs.Such a hypothesis was pursued by Liu et al. [128] They investigated the role of cellulosic fabric structure on the performance of wearable SCs.The group subsequently coated knitted, woven, and nonwoven fabrics with PPy via an in situ chemical polymerization reaction.It was found that the PPy loading embedded on fabric surfaces depended on the porosity of the fabric.Optimum porosity of the fabric surfaces was vital in determining the PPy loading.The porosity of the nonwoven fabric was too big (>84%), and for the woven fabric, the porosity was less (68%).It was claimed that knitted fabric with its 84% porosity was ideal for achieving higher loading of PPy.The PPy-based knitted, woven, and nonwoven fabrics achieved areal capacitances of 4117, 2191, and 2905 mF cm −2 , respectively, in 1 m H 2 SO 4 .Such values proved that the structure of fabric had a crucial role in determining the supercapacitive performance of FSCs.The knitted structure was highly conducive to PPy growth, and its good bonding with fiber led to high mass loading.For the woven fabric, the pore size was too small to facilitate further pyrrole infiltration, and subsequent polymerization will occur in the solution instead of on the fibers.As for the nonwoven fabric, the pore size was too large, resulting in a lack of polymerization sites. [128]he fabrics with multidimensional fiber architectures exhibit a high surface area for functional materials to attach.Therefore, the hierarchical fiber architecture is more prone to higher active material loading, which in turn leads to enhanced electrochemical performance.For instance, Li et al. [143] compared cellulosic knit and hierarchical fabric (HF)-based SC with graphene (G) and PEDOT as functional materials.The G/PEDOT-knit SC (G/PKSC) and G/PEDOT-HF SC (G/PHSC) exhibited stable capacitive performance.However, due to the high surface area of fiber micro-arrays, active material loading was much higher than knit fabric substrates resulting in high reaction kinetics (Figure 16A).Therefore, the area-specific capacitance was     .Reproduced with permission. [125]Copyright 2021, American Chemical Society.B) (i) Flexibility of PEDOT: PSS/MnO 2 -PET MSC at varying angles.Capacitance retention with their corresponding CV curves of planar devices at different bending angles (ii) and bending cycles (iii).(iv) Capacitance retention after 3000 cycles of bending at 90 o .(v, vi) LED light demonstration in flat and twisted states.Reproduced with permission. [108]Copyright 2021, WILEY-VCH GmbH.C) (i) Capacitance retention of NiCo 2 S 4 /CoS 2 -SSM-based asymmetric SC at varying stretch-release cycles at dynamic strain (10-20%).The fabric SC can be normal (ii), stretched (iii), twisted (iv), or even bent (v).(vi) CV curves of SC in different conditions.Reproduced with permission. [110]Copyright 2020, WILEY-VCH Verlag GmbH.D) GCD curves of PPy-cotton fabric SC at various bending angles and the role of bending cycles (1000).Reproduced with permission. [142]Copyright 2022, Elsevier Ltd.E) LIG-MSC in various bending states (0 o -180 o ).Reproduced with permission. [132]Copyright 2020, Elsevier B.V. F) (i) Capacitance retention of MWCNT/rGO-cotton fabric SC after 10 000 bending cycles.(ii) Capacitance retention of fabric SC tested underwater with an inset photograph of a testing environment.Reproduced with permission. [99]Copyright 2017, WILEY-VCH Verlag GmbH.
245.5 mF cm −2 for G/PHSC, which is 5.9 times of G/PKSC.From Figure 16B,C, it is evident that the HF-based SC showed better capacitive performance than the knit fabric-based SC. [143] Such a result was expected since the fiber microarrays of HF expanded the effective surface area and shortened the ion transport pathways.Similar trends were also observed in other reports.In a separate study, Li et al. compared woven and nonwoven fabric-based SCs with graphene and MnO 2 as active materials.The group systematically investigated the influence of fabric structure and prepared graphene-woven fabric SC (GWF-SC), graphenenonwoven fabric SC (GNF-SC), and graphene/MnO 2 -nonwoven fabric SC (GMNF-SC) for performance comparison.Between the GWF-SC and GNF-SC, the GNF-SC showed the bigger CV and GCD curves, which is evident from Figure 17A(i,ii,iii).This is because the compact structure of woven fabrics inhibited graphene  [143] Copyright 2019, American Chemical Society.materials from emigrating into the inner part of the fabric and thus reduced the capacitive performance.Among the three solidstate SCs, the GMNF-SC outperformed all other SCs by showing the biggest CV and GCD curves and delivered a high areal capacitance of 138.8 mF cm −2 in PVA-H 2 SO 4 gel electrolyte.Due to high surface area and porosity, nonwoven structures were conducive to high material loading.Therefore, the GMNF-SC performed impeccably.Compared to nonwoven fabric substrates, the woven fabric substrate had fewer electroactive materials, thus reducing the electrochemical performance. [117]This result is in agreement with studies reported by Liu et al. [128] and Li et al. [143] The fabric structure also influences the flexibility of the assembled device.Among the woven, knitted, and nonwoven structures, knitted structures offer high stretchability and good recovery against mechanical deformations.In the majority of reports, the knitted structure integrated SCs exhibited highly stretchable SCs with nearly stable performance.For example, the PEDOT/rGO-SSM-based symmetric SC demonstrated high stretchability.The unique diamond structure of warp-knitted SSM allowed the device to function even at 10% strain and could be stretched up to 25% of its initial length.Additionally, the capacitance decreased by only 3.2% and 5.3% under the flat state and at the bending 90 o state for 100 cycles. [111]This excellent flexibil-ity was attributed to the amazing stretchability offered by warpknitted structures.However, the warp-knitted structure has drawbacks associated with the large voids created by millimeter-scale loops.Since high material loading on fabric substrates leads to the high capacitive performance of FSCs, the warp-knitted structures cannot achieve high material loading due to the large free space within the loops.For example, Shao et al. found that for warp-knitted SS fabric, the NiCo 2 S 4 /CoS 2 loading was comparatively lower than the previously reported studies.Yet, the fabric was occupying the same area.As a result, the areal capacitance was lower than expected. [110]This result also supports a study on warp-knitted fabric SCs reported by Su et al. [111] The fabrication technique of fabric electrodes can also affect the performance of FSCs.For instance, Stempien et al. [120] fabricated a PPy-based polypropylene (PP) nonwoven fabric SC by reactive inkjet printing of PPy at sub-zero temperature.The group also compared PPy-based SCs prepared at different temperatures and found that SCs fabricated at lower temperatures showed better supercapacitive performance.The capacitance retention after 2000 cycles of charge-discharge was 55.4% for the PPy layer prepared at −12 °C, while 14.8% capacitance retention was reported for the PPy layers prepared at 23 °C. [120]The nature of the current collecting techniques also affects the calculated/reported Reproduced with permission. [117]Copyright 2018, Elsevier B.V. B) Current collecting mechanism for knitted fabric-based electrodes.(i) Schematic diagram of center current collecting mechanism in fabric-based SC. (ii) Scheme depicting the multi-point current collecting mechanism in fabric-based SC.Reproduced with permission. [145]Copyright 2020, Elsevier B.V. capacitive performance.However, the positioning of current collectors is often absent or not mentioned in the majority of reports.An interesting study conducted by Wang et al. [145] investigated the phenomenon of current collection position on the capacitive performance of fabric electrodes.They prepared PPy-coated knitted cotton fabric-based electrodes using an in situ polymerization reaction.Interestingly, they found that the longer electrodes were massively underutilized despite having more functional materials on the fabric surface.However, when the current collection protocol was changed from end current collecting (ECC) to center current collecting (CCC), the capacitance increased by 46.8%. Figure 17B(i) depicts the ECC and CCC mechanisms.Based on CCC, the group further investigated the capacitive performance and proposed a unique multi-point current collecting system that boosted the capacitance from 5190 to 6950 mF. Figure 17B(ii) illustrates the multi-point current collecting mechanism.The assembled device also showed increased capacitive performance (3750-2900 mF) when a multi-point current collecting system was employed. [145]

Summary and Perspectives
In this article, the recent developments of functional fabric-based SCs are reviewed, from fabric-based electrode preparation strat-egy to device fabrication.Various fabric structures (woven, knit, nonwoven) influence the ultimate energy storage performance of wearable SCs.Numerous functional materials are used to fabricate functional fabric-based electrodes; however, conductive polymers were utilized repeatedly by different research groups.Among the fabric architectures, woven fabric-based electrodes and their SCs are the most widely studied.Despite this, the WFSCs exhibit relatively poor capacitive performance compared with other fabric structures (knit, nonwoven) incorporated SCs.Although there remain many fabrication techniques, coating (spray, dip) and printing (screen, inkjet) strategies were predominant and repeatedly implemented by different research groups for fabricating FSCs.The FSCs offer some unique device configurations and can be divided into four main types of configuration (sandwiched, planar, all-in-one, and stacked).Sandwiched and planar devices are the most widely studied and reported FSC configurations.Planar devices are typically fabricated as MSCs.[139] These configurations must be scrutinized and investigated meticulously for future endeavors in fabricating wearable fabric-based SCs.The performance of FSCs is highly dependent on the functional material, fabrication technique, fiber type, fabric structure, and configuration of the devices.While the flexibility of wearable SCs is investigated thoroughly with established testing protocols in the current literature, the wearability, integration, and safety features of FSCs are not explored thoroughly in the majority of studies.Besides, the current research progress only focuses on the laboratory-scale fabrication of wearable SCs since the wide-scale fabrication of such devices is very challenging to achieve. Figure 18 illustrates the potential applications of functional fabric-based wearable SCs.
Although functional fabric-based SCs show tremendous prospects in the future wearable electronics market, they face some major drawbacks for successful commercialization.Figure 18 conscripts some significant challenges faced by fabric SCs.Functional fabrics capable of energy storage are the first prerequisite for wearable SC fabrication.However, functionalization of fabric surfaces often requires sophisticated instrumentation, is very expensive, and in some cases, time-consuming to achieve.There is a scarcity of reports on the mass fabrication of wearable fabric-based SCs.Besides, the functionalization process is often not sustainable and has a high impact on the environment.Although the power density of current wearable SCs is great, the energy density of FSCs is not satisfactory.The poor energy density issue will render the device useless in long-term wearable applications.Additionally, the integration of wearable FSCs with other wearable electronic systems is not fully realized yet.Besides, the washability and wearability aspects of FSCs are still not up to the mark.In the majority of instances, the washability and wearability aspects are not mentioned in the reports and are often ig-nored.Lastly, the lack of standardized testing protocols fails to set a benchmark to compare different fabric-based SCs.Besides, device capacitance is often reported based on the active material weight and, in most cases, ignores the role of current collectors.Therefore, the current standard in the literature fails to report the realistic performance of wearable fabric SCs.In light of all the discussion above, the future research should be concentrated on-Testing Protocol: A sound and universal testing protocol is a way to analyze the realistic performance of wearable energy storage devices properly.Therefore, it is speculated that future research will focus on categorizing the fabric-based wearable SCs under a universal testing protocol carefully set up by both the electronics and textile industry.
Sustainable Synthesis: The majority of manufacturing strategies are not environmentally benign.It is anticipated that more studies will spring up focusing on the sustainable manufacturing of fabric-based electrodes and their SCs.
Microstructure Engineering: Highly porous and hierarchical microstructure of fabric electrodes is desirable for achieving high performance from SCs. Tuning reaction parameters is a way to control the microstructure of fabric electrodes.Future efforts should concentrate on tailoring the reaction parameters to achieve highly porous fabric electrodes.
Scaling up of Fabric-based SCs: Current research only exhibits the lab-scale fabrication of wearable SCs.It is extrapolated that the impending research will focus on the industrial scalability and cost-minimization strategies for the successful commercialization of functional fabric-based wearable SCs.
Safety and Comfortability: The majority of the reports do not investigate the safety and comfortability aspects of wearable SCs.Besides, the aesthetic aspects of FSCs are usually ignored.Since gel electrolyte systems are implemented, the possibility of leakage will render the device unsafe to use.Therefore, future efforts will most likely concentrate on the safety and comfortability of wearable SCs with a particular focus on electrolyte engineering.
Seamless Integration: Currently, the integration of FSCs into the garment level is very challenging to achieve.Additionally, the integration with other wearable systems is still not explored.It is anticipated that future endeavors will focus on overcoming the crucial design barriers that inhibit the seamless integration of wearable SCs in garment platforms.
(i)) and warp-knitted (Figure 2B(iii)) structures.Based on manufacturing techniques, weft knitting is advantageous as weft-knitted structures can be constructed from a single yarn.Industrially, weft-knitted fabrics are manufactured either in circular or flatbed knitting machines (Figure 2B(ii)).In contrast, for warp knitting, hundreds of yarns containing warp beams are necessary.2D warp-knitted open structures are predominantly produced in Tricot warp-knitting machines

Figure 1 .
Figure 1.Schematic illustration depicting the synopsis of the article.

Figure 2 .
Figure 2. Summary of fabric manufacturing technology and the distinct macro-architectures of woven, braided, knitted, 3D fabric, and nonwovens.A)Interlacement of yarns at 90°produces woven structures (i) in shuttle weaving machines (ii); Diagonal intertwining of yarns produces braided structures (iii) in a braiding machine (iv).B) Interlooping of yarns construct stretchable weft-knitted structures (i) in flatbed knitting machines (ii).Through loop intermeshing, warp-knitted structures (iii) are formed in Tricot warp knitting machines (iv).C) 3D fabric structures of multi non-crimp (i) and 3D-knitted structures (ii).Reproduced with permission.[53]Copyright 2021, Elsevier Ltd.Reproduced with permission.[54]Copyright 2020, Elsevier B.V. The 3Dknitted fabric is produced in a double needle bar Raschel machine (iii) where two separate layers of fabric are produced and stitched together to render a 3D architecture.D) By directly manipulating fibers, nonwoven structures (i) are formed.The scheme demonstrates the basic nonwoven manufacturing processes, such as (ii) needle punching, (iii) melt-blowing, and (iv) spunbonding technologies.

Figure 3 .
Figure 3. Charge storage mechanism and functional materials for SCs.A) Energy storage mechanisms of EDLC (i) and pseudocapacitive (ii) materials.B) Carbon-based materials.C) Transition metal oxides.D) Metal-organic frameworks.E) 2D materials.F) Conductive polymers.

Figure 4 .
Figure 4. Schematic illustrations of different fabrication techniques to produce functional fabric-based electrodes.A) Dip coating and drying; B) Screen printing; C) In-situ polymerization; D) Hydrothermal synthesis; E) Vacuum filtration; F) Electrodeposition; G) Conventional spray coating; H) Thermal transfer printing; I) Supersonic spray-coating; J) Melt-blowing; K) Reactive inkjet printing.
fabricated a lightweight PET-based NFE.The fabric was first dip-coated with rGO, followed by electrodeposition of a Ni layer and a Fe 2 O 3 layer to achieve an rGO/Ni/Fe 2 O 3 -PET electrode.Figure 10B(i,ii) illustrates the fabrication process and the photograph of NFE after each consecutive step.The electrode exhibited a high areal capacitance of 383.6 mF cm −2 in 1 m Na 2 SO 4 electrolyte.This is because the smooth surface created by the Ni layer prohibited the Fe 2 O 3 agglomeration and increased the effective surface area, which improved the overall capacitance.

•••
Able to retain hierarchical microstructure with multiple functional materials • Able to utilize the entire area of the electrode • Moderately flexible and not stretchable • Low material loading capability compared to knit and nonwoven fabric a) Developing ternary/quaternary composite electrodes • Functionalizing a wide variety of natural fibers (silk, jute, water hyacinth, pineapple) • Bonding enhancement between fabric and functional materials (Weft knitted) (Warp knitted) Knitted Fabric-based Electrodes • Highly stretchable and flexible • Highest material loading capability* • Excellent capacitance retention due to mechanical deformation • Poor capacitive performance compared to woven fabric electrodes • Poor cyclic stability • Unable to utilize the whole area of the electrode • Fabrication of stretchable electrodes with excellent recovery • Developing synthetic fiber-based (acrylic, PET, nylon, viscose) electrodes • Recent attempts to construct ternary/quaternary composite electrodes • Warp-knitted fabrics for highly stretchable electrodes Nonwoven FabricMaterial loading capability higher than woven fabric but lower than knit fabric a) • Improvement of mechanical durability • Enhancing capacitive performance • Unique fabrication techniques (capillary assisted coating, inkjet printing at sub-zero temperature, reactive inkjet printing) • Attempts to develop hierarchical microstructures a))

Figure 11 .
Figure 11.Sandwiched and in-plane configurations of functional fabric-based wearable SCs.A) Fabric SC assembly in sandwiched configuration.(i) Schematic illustration depicting GHG-SSF electrode-based sandwiched SC fabrication.(ii)Step-by-step process to fabricate GHG-SSF electrode and its corresponding SEM (iii).GCD (iv), CV (v), and Ragone plot (vi) profiles of assembled solid-state devices.Reproduced with permission.[119]Copyright 2016, American Chemical Society.B) Illustration depicting an in-plane type fabric-based SC with its performance parameters.(i, ii) Scheme of fabricating screen printed PEDOT: PSS/MnO 2 -PET MSC.(iii) SEM image of the cross-section of the electrode materials.GCD (iv), and CV (v) curves of PEDOT: PSS/MnO 2 -PET MSC.Reproduced with permission.[108]Copyright 2021, Wiley-VCH GmbH.

Figure 12 .
Figure 12.All-in-one and stacked configurations of functional fabric-based wearable SCs.A) (i) The illustration indicates the fabrication process and structural schematics of novel all-in-one cotton fabric-based SC.CV (ii) and GCD (iii) curves of MWCNT-cotton all-in-one configured SC.Reproduced with permission.[137]Copyright 2022, Elsevier B.V. B) Schematic illustration depicting the structural breakdown of a stacked configuration of fabric-based SCs.

Figure 13 .
Figure 13.Schematic depicting different novel configurations of functional fabric-based wearable SCs.A) Sandwiched configuration.B) Planar configuration.C) All-in-one configuration.D) Stacked configuration.

Figure 14 .
Figure 14.Integration of FSCs into clothing.A) (i, ii)The PEDOT: PSS/MnO 2 -PET MSC attached to a sweatshirt.CV (iii) and GCD (iv) curves of fabricbased wearable MSCs before and after 1000 m of running.Reproduced with permission.[108]Copyright 2021, Wiley-VCH GmbH.B) Interdigitated clothing applique is sewn into labcoats, providing power to a red LED.(i) Tree-shaped clothing applique SC. (ii) Interdigitated clothing applique SC.Reproduced with permission.[88]Copyright 2023, Elsevier B.V. C) (i) Scheme of elbow-fitted flexible fabric-based SC. (ii) Two NiCo 2 S 4 /CoS 2 -SSM//activated carbon-SSM asymmetric SC connected in series to light up an LED mounted on the elbow both in stretching (ii) and bending (iii) states.Reproduced with permission.[110]Copyright 2020, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.D) Wearable MWCNT-cotton symmetric SC attached to the jacket powered by a fabric-based triboelectric generator.Reproduced with permission.[140]Copyright 2017, AIP Publishing.E) MWCNT/rGO-cotton fabric SC sewn into a lab coat and lighting up and LED.Reproduced with permission.[99]Copyright 2017, WILEY-VCH Verlag GmbH.

Figure 15 .
Figure 15.The durability of functional fabric-based SCs.A) (i, ii) Three G/PANI-HF electrode-based SC operating underwater to power up an LED.(iii, iv) The same device was able to power an electroluminescent device with the QDU logo.(v, vi) A wearable electronic display showcasing "SOS" also powered by G/PANI-HF-based SC. (vii) Comparison of SCs based on gel electrolyte systems.(viii) GCD curve and photograph of fabric SC in water for 12 h.Reproduced with permission.[125]Copyright 2021, American Chemical Society.B) (i) Flexibility of PEDOT: PSS/MnO 2 -PET MSC at varying angles.Capacitance retention with their corresponding CV curves of planar devices at different bending angles (ii) and bending cycles (iii).(iv) Capacitance retention after 3000 cycles of bending at 90 o .(v, vi) LED light demonstration in flat and twisted states.Reproduced with permission.[108]Copyright 2021, WILEY-VCH GmbH.C) (i) Capacitance retention of NiCo 2 S 4 /CoS 2 -SSM-based asymmetric SC at varying stretch-release cycles at dynamic strain (10-20%).The fabric SC can be normal (ii), stretched (iii), twisted (iv), or even bent (v).(vi) CV curves of SC in different conditions.Reproduced with permission.[110]Copyright 2020, WILEY-VCH Verlag GmbH.D) GCD curves of PPy-cotton fabric SC at various bending angles and the role of bending cycles (1000).Reproduced with permission.[142]Copyright 2022, Elsevier Ltd.E) LIG-MSC in various bending states (0 o -180 o ).Reproduced with permission.[132]Copyright 2020, Elsevier B.V. F) (i) Capacitance retention of MWCNT/rGO-cotton fabric SC after 10 000 bending cycles.(ii) Capacitance retention of fabric SC tested underwater with an inset photograph of a testing environment.Reproduced with permission.[99]Copyright 2017, WILEY-VCH Verlag GmbH.

Figure 16 .
Figure 16.Role of fabric architecture in SC performance.A) Schematic illustration of the interface between gel electrolyte and fabric.B, C) Comparison of CV and GCD curves among Graphene/PEDOT-fabric-based SCs on different substrates.Reproduced with permission.[143]Copyright 2019, American Chemical Society.

Figure 17 .
Figure 17.Performance comparison among woven and nonwoven fabric-based SCs.A) CV (i), GCD (ii), and Nyquist (iii) curves comparison among G-WF, G-NF, and G/MnO 2 -NF based SC in PVA-H 2 SO 4 .Reproduced with permission.[117]Copyright 2018, Elsevier B.V. B) Current collecting mechanism for knitted fabric-based electrodes.(i) Schematic diagram of center current collecting mechanism in fabric-based SC. (ii) Scheme depicting the multi-point current collecting mechanism in fabric-based SC.Reproduced with permission.[145]Copyright 2020, Elsevier B.V.

Figure 18 .
Figure 18.Potential applications (left column) and challenges (right column) of functional fabric-based wearable SCs.Concept art of all-textile-based wearable electronics powered by functional fabric-based wearable SCs.

Table 2
compares the contemporary advantages, disadvantages, and recent research focus on woven, knitted, and nonwoven fabric-based electrodes.

Table 1 .
Electrical and electrochemical properties of functional fabric-based electrodes.

Table 2 .
A comparative analysis among woven, knitted, and nonwoven fabric-based electrodes.

Table 3 .
Electrochemical and mechanical performance of functional fabric-based wearable supercapacitors.