Li 1.3 Al 0.3 Ti 1.7 P 3 O 12 Activated PVDF Solid Electrolyte for 1 Advanced Lithium-Oxygen Batteries

： 14 Lithium-ion composite solid electrolyte membranes embedded with 15 Li 1.3 Al 0.3 Ti 1.7 P 3 O 12 and poly(vinylidene fluoride) are prepared using a facile casting 16 method. Furthermore, we added LiI as an active agent for decomposing the anode 17 product. The synergy resulted in a high conductivity of 7.4 mS cm -1 and lithium-ion 18 mobility of 0.59 and a reduction of the overpotential to 0.86 V for lithium-oxygen 19 batteries. The membrane has enhanced Young's modulus of 6.6 GPa that effectively 20 blocked the lithium dendrite growth during the battery operation and puncturing to the 21 membrane led to a significant LOB cycle life of 542 cycles. Meanwhile, Li|Li 22 symmetrical battery overpotential maintained at 42 mV after 470 hours of operation. 23


Introduction
Aprotic lithium oxygen batteries (LOBs) have attracted increasing attention as promising energy storage solutions due to their impressive theoretical energy density (approximately 3,600 Wh kg -1 ) [1][2][3][4][5][6] .However, several technical hurdles still impede their further development, such as the sluggish decomposition kinetics of lithium peroxide (Li2O2) [7][8][9] , electrode surface passivation resulting from the formation of thinfilm products, carbon cathode decomposition, electrolyte degradation, and various complications associated with the lithium anode [10][11][12][13][14][15][16] .Lithium metal (Li) exhibits an exceptionally high theoretical specific energy (3,860 mAh g -1 ) and a low oxygen reduction potential (-3.04 V vs. the standard hydrogen electrode), making it a good candidate for battery anodes [17,18] .In Li-O2 batteries, Li2O2 forms and decomposes at the cathode.Difficulty in decomposing the generated discharge product Li2O2 leads to poor round-trip efficiency and short cycle life of the battery.The discharge product causes the battery charging overpotential to increase dramatically, resulting in a high operating voltage, which reacts with the electrolyte and then causes the electrolyte to dry up therefore affecting the LOB's cycle life.Catalysts are commonly used to decompose Li2O2 by acting as electron and hole acceptors to reduce the charging overpotential of LOBs [19][20][21] .In the electrochemical step, the soluble redox mediator is oxidised (reaction (1)), then whereupon it undergoes a chemical reaction with Li2O2 (reaction (2)).
A key component affecting the performance of LOBs is the lithium metal anode.
Uneven mass and charge transfer within the non-uniform solid electrolyte interphase (SEI) layer leads to uncontrolled growth of lithium dendrites [32,33] .These dendrites can penetrate the SEI layer and continually deplete the electrolyte and lithium, facilitating reactions between the lithium metal and contaminant byproducts, ultimately leading to sudden short circuits and safety issues.Composite solid-state electrolyte membranes have been previously applied to LOBs, but mainly focused on enhancing ionic conductivity, neglecting the inhibition of lithium dendrite growth, whereas Young's modulus is a key factor in evaluating the inhibition of lithium dendrites.Ideal composite solid-state electrolyte membranes need to have the following conditions, the membrane's base polymer is supposed to have flexibility and mechanical strength, good contact with lithium metal, and produce uniform Li + transport channels.The polymer also has good compatibility with the electrolyte.The mixed solid electrolyte should also be uniformly distributed to avoid localised destruction of Li + , while the solid electrolyte should have good stability in air and water.Sodium superionic conductor (NASICON)type ceramic polymers, such as Li1.5A10.5Ti1.5(PO4)3(LATP), stand out as the most suitable choice for constructing composite solid electrolyte membranes due to their excellent air stability.However, LATP cannot be in direct contact with Li metal due to the reduction of Ti 4+ by Li [34,35] .Therefore, a polymer substrate is needed to form a stable interfacial layer with Li metal.Nonetheless, inherent characteristics of Li, including dendrite growth and volume changes during battery operation, pose significant challenges.These phenomena accelerate lithium consumption and elevate the battery's internal resistance, ultimately leading to premature failure.As Li2O2 is difficult to decompose, the battery generates excess charging overpotential, which impairs the performance of the battery, and the addition of a catalyst to the anode side of the battery can effectively decompose the discharge product.
LiI has been studied as a liquid redox mediator can effectively reduce the voltage during the charging process [28] .I3 -acts as an electron acceptor and a redox mediator.It showed the effect of the decomposition of discharge products on the performance of LOBs.However, during battery cycling, the production of I3 -can occur, and this makes it susceptible to reacting with the lithium anode.This reaction generates LiI3, which not only damages the lithium anode but also renders the I -ineffective.Conventional commercial glass fiber (GF) membrane has a porous structure with high conductivity, which can satisfy the environment where lithium ions are free to shuttle, but due to the porous structure of GF membranes, it causes I3 -to undergo the shuttling effect of redox mediators (RMs).Wu et al. prepared a protective separator with zeolite molecular sieves (4 Å) by adding zeolite to a poly (vinylidene fluoride-hexafluoropropylene)based membrane, to suppress the shuttle effect of TEMPO, the LOBs with this membrane had an extended cycle life up to 170 cycles at a current density of 250 mA g -1 [36] .Chen et al. used Nafion, PEO into a two-dimensional backbone structure to form a negative barrier for the purpose of blocking I3 -shuttling, and a of cycle life of 472 cycles which is 3.8 times improvement compare to GF was obtained at a current density of 500 mA g -1 [37] .Li et al. utilized a scalable and flexible membrane consisting of polytetrafluoro thylene@polystyrene (PTFE@PS), which possesses outstanding oxygen permeability and resistance to moisture.This membrane serves as an effective barrier, safeguarding both the lithium anode and the entire battery system against corrosion caused by moisture (H2O).Remarkably, when operated at a capacity of 500 mAh g -1 , the LOBs equipped with the PTFE@PS membrane exhibited a 5 times improvement in cycling performance compared to the LOBs lacking this membrane [38] .Sun et al. prepared polyetherketone nanofibrous membranes using chemically induced crystallisation, and LOBs using this prepared membrane had high cycling stability (194 cycles at 500 mAh g -1 ), and these polyetherketone nanofibrous membranes had a protective effect on the anode, as well as being able to regulate the Li + flux [39] .Yuan et al. coated lithium metal using an organic-inorganic interlayer-reinforced PVDF-HFP with a high Li + transfer number (0.62) and Young's modulus (6.17 GPa).The Li/Li symmetric battery could be operated stably for at least 2,190 hours and LOBs could be operated for 214 cycles, protecting the lithium metal anode and improving the ionic conductivity [40] .Protect the Li-metal anode from parasitic reactions caused by RMs and impurities diffusing from the cathode.LATP has gained our attention as a solid electrolyte membrane that exhibits better stability in air and water [41,42] , but conventional solid electrolyte membranes are difficult to be applied in practice due to the brittleness of their own ceramics, interfacial issues of electrode contact, and other reasons.
In this work, we reduced the charging overpotential of LOBs by adding LiI, blocked the shuttle effect of RMs using composite lithium-ion membranes, and retained I - effectively to play a role in the positive electrode while effectively protecting lithium metal.We prepared lithium-ion composite membranes by using PVDF as a base polymer and LATP solid electrolyte as an inorganic filler, which utilises the good compatibility of PVDF polymer with lithium surface, the formation of Li-F bonds to homogenise Li + , protects lithium metal from side reactions and provides highly stable lithium anode for LOBs.Compared with ordinary PVDF polymer membranes, lithiumion composite membranes have higher lithium-ion mobility (tLi + = 0.59), higher conductivity (7.4 mS cm -1 ), and LOBs obtained by using lithium-ion composite membranes can be operated for 542 cycles, which is much larger than that of the traditional commercial GF membranes (80 cycles).

Synthesis of LCM composite membranes
The LATP solid electrolyte was first mixed with DMF solvent using an ultrasonic sound bath at 25 o C for 30 min, PVDF pellets were added followed by further mixing for 4 h.Vacuum filtration was carried out for 4 h to remove any air bubbles.The obtained slurry was poured onto a glass plate and membranes with different thicknesses were cast using a doctor blade followed by drying in an oven at 60 °C for 4 h.The membranes were then sliced into d=16 mm for LOBs using a slicer and soaked in 1 M LiClO4/DMSO for at least 24 h before use.The ratio of PVDF pellets to DMF solvent was approximately 16%, and the LATP: PVDF mass ratios of 1:3, 1:2 and 1:1 were labelled LCM-1, LCM-2, and LCM-3 respectively.

Battery assembly and testing
10 mg of MWCNTs were uniformly dispersed in 30 ml of ethanol solution under ultrasound to form an ink-like slurry, which was subsequently sprayed onto carbon paper using a spray gun.The carbon paper was then cut to d=1 cm 2 (with loading of 0.1 mg MWCNTs) and dried in a vacuum drying oven at 80 °C for 12 h and placed in a vacuum chamber for use as a positive electrode.The batteries were assembled in the following order: negative electrode -PVDF/LCM -GF (injected electrolyte) -positive electrode, in a glove box filled with argon gas for the assembly of CR2032 type batteries with holes (Nanjing Jiumen Automation Technology Company), where the electrolyte added is 130 μL and 0.05 M LiI is 0.0065 mmol in the electrolyte.In which LCM-2 membrane possesses stable interfacial contact and excellent battery conductivity as the main research object.battery testing was carried out in a 99.9% pure oxygen atmosphere, the current density of the conventional battery cycle was 1 A g -1 , corresponding to a battery capacity of 1,000 mAh g -1 and the battery capacity is calculated based on the content of MWCNTs.A fixed capacity of 1,000 mAh g -1 was used to test the multiplier performance at 3 A g -1 , 5 A g -1 and full discharge performance was tested using 0.1 mA, 2 V as the abort test condition.
SSN|SSN symmetric battery was assembled, GF, PVDF, and LCM was used as a membrane, where a 1 M LiClO4 electrolyte was injected and assembled using a CR2032 non-porous battery case.SSN|SSN symmetric batteries were used to study the improvement of ionic conductivity by LCM membranes, and the Li|Li symmetrical battery testing was utilised to explore the influence of the LCM-2 membrane on the Li anode.

Characterisations
A field emission scanning electron microscope (Nova NanoSEM450) was used to study the morphology of the material surfaces and an X-ray diffractometer (Bruker D8A A25 X) to characterise the structural properties of the materials.Raman spectrometer (532 nm, DXR2, Thermo Scientific) is used for the discharge product analysis.An electrochemical workstation (CHI 760E, Shanghai Chenhua Instrument Co., Ltd.) was used for electrochemical performance testing, an X-ray spectrometer (Thermo Scientific K-Alpha+, X-ray source: Al Kα micro-focused monochromatic source) was used to characterise the elemental properties of the membranes, a Fourier Transform Infrared (FTIR) spectrometer (NICOLET IS 10) was used to characterise the functional groups of the membranes, and a Contact Angle Measuring Instrument (JC2000D1, Shanghai Zhongchen Digital Technology Equipment Co., Ltd.) was used to measure the hydrophilic nature of the membrane surface.Battery Performance Testing with Battery Tester (CT-4008T-5V10mA Neware Technology Limited).In order to demonstrate the puncture resistance of the membrane against lithium dendrites, the Young's modulus of the membrane was measured by AFM(SPM-9700HT).

Ionic conductivity
The electrochemical impedance spectroscopy (EIS) was carried out using a frequency range of 1 MHZ to 0.1 Hz, an AC voltage of 5 mV and a test temperature of 25 °C.The ionic conductivity can be calculated using equation (1)： where σ is the ionic conductivity, d is the thickness of the membrane, Rb is the solution resistance and A is the effective contact area of the SSN electrode.

Lithium-ion transfer number
The Lithium-ion transfer number (tLi + ) was obtained by using constant potential polarisation and electrochemical impedance mapping, tLi + can then be calculated by measuring the change in current before and after polarisation, combined with information from the impedance mapping EIS before and after polarisation, using equation ( 2): Where tLi + is the lithium-ion transfer number, Is and Ie are the initial and steady state currents for constant potential polarisation.ΔV is the constant potential polarisation voltage: mV, Rs and Re are the resistance of the diaphragm before and after constant potential polarisation.

I -permeation testing
An H-shaped apparatus was used to evaluate the permeability of I -by adding 7 mL of 0.05 M LiI containing 1 M LiClO4 electrolyte to the left side of the H-shaped electrolytic battery and 7 mL of 1 M LiClO4 electrolyte to the right side, with the septum in the middle.A solution of H2O2 with a mass fraction of 0.5% starch was prepared as the I -detector and 5 μL of the solution on the right side was aspirated and added to the detector during the test; if it turned blue, I -was present.

Electrolyte adsorption test
The electrolyte adsorption rate is used to measure the adsorption capacity of the membrane to the electrolyte.The liquid electrolyte absorption (δ) is assessed according to equation (3): Where, δ is the electrolyte adsorption rate and W0 and We represent the mass before and after adsorption of the electrolyte respectively.

Results and Discussion
The SEM image of the original PVDF membrane is shown in Fig. S2(a-b), where tiny cracks appeared on the surface, that is too big to block I3 -(0.514 nm) at the microscopic scale [43] , Fig. S2c shows the thickness of the PVDF membrane of about 60 μm, and the particles of the LATP are around 600 nm in Fig. S2d.The LATP particles can be added with different contents for varied ionic conductivity.negatively impacting the stability of the lithium anode.Consequently, we determined that a 33% LATP content in LCM-2 represented the optimal ratio, and SEM images showed that the surface filler particles of LCM-2 had good homogeneity and interfacial contact.Fig. 1a presents the SEM image of the LCM-2 membrane, predominantly composed of a blend of LATP particles and PVDF polymer.The membrane of LCM-2 exhibits a flat and dense structure, devoid of significant pores, which could hinder the infiltration of detrimental molecules/ions, preventing them from reacting with the lithium anode.Furthermore, the flat membrane structure promotes the even diffusion of Li + .The EDS surface (Fig. 1a) and cross-sectional (Fig. S3) images show that LATP particles are homogeneously mixed with PVDF, where C and F elements represent within the PVDF; P, Al and Ti represent on the LATP.
The peak of the PVDF membrane in the XRD in Fig. S2f appears at 20.5°.The XRD of Fig. S2f shows LATP particles corresponding to the PDF cards of LiTi2(PO4)3, and the XRD of the LCM-2 membrane shows the co-existence of the peaks of PVDF and LATP, which suggests that the crystalline phase of LATP was not disrupted during the preparation process and that the LATP particles were well-mixed with the PVDF polymer, while we found in Fig. 1b infrared spectroscopy (FTIR) that the normal PVDF-based membrane exhibits C-H bending (1,402 cm -1 ) and C-F bending (1,166 cm - 1 ).As the mass ratio of LATP increases, the C-F peak at 1,166 cm -1 of LCM-2 shifts to 982 cm -1 , because of the tightened interaction between LATP and PVDF.At the same time, the shift of the peaks illustrates the disruption of the crystallinity of PVDF membrane and the increase in the proportion of amorphous regions of the polymer due to the addition of LATP.Due to the addition of LATP, the tLi + of the LCM-2 membrane in Fig. 1c reached 0.59.Fig. 1d shows the improved ionic conductivity of the LCM membranes, which has been increased from 3.3 mS cm -1 of ordinary PVDF-based membranes to 4.6 mS cm -1 for the one with LCM-1 membrane, 7.4 mS cm -1 for the one with LCM-2 membrane and 8 mS cm -1 for the one with LCM-3 membrane.The addition of a small amount of solid electrolyte filler can effectively improve the lithium-ion mobility of the membrane, while the ionic conductivity shows a tendency to increase and then level off with the increase of the proportion of LATP.This may be because more vacant defects are provided with a small amount of active filler, making it easy for ions to jump continuously, and the solid electrolyte itself provides a large amount of Li + , increasing the concentration of Li + at the interface with the polymer.When the active filler content is higher than 40%, the active filler appears to pile up, at which point most of the ion transfer is concentrated between the filler-filler transfer, thus reducing the ionic conductivity, and we believe that LCM-2 membrane is the optimum ratio, shrinking the gap with the normal GF membrane of 17 mS cm -1 difference.

Characterisation of LCM membranes
We were able to prepare LCM membranes on a large scale by the solution casting method, and Fig. 2a shows the continuous and uniform membranes obtained under this method, and Fig. 2b shows the contact angle of LCM-2 membrane with the electrolyte (DMSO) of 13.5°, indicating that this membrane has good permeability towards the electrolyte which can provide a good internal ion channel environment.Fig. S4 The contact angles for the pristine PVDF membranes, (DMSO and water) were 11.2° and 87.2°, respectively.Fig. 2c indicates that the GF membrane has an electrolyte adsorption rate of 811.2%, which can withhold plenty of electrolyte to be consumed during battery cycling, therefore we chose GF membrane matrix material for the LCM membranes preparation.LCM membranes have an electrolyte adsorption rate of only 13.2%, the small amount of electrolyte helps to fill some pores of the membrane and facilitates the ions transfer.Compared to GF and PVDF membranes, LCM-2 membranes have lower porosity and enhanced I -blocking.The LiI catalyst was tested for I -transmission to show that the LiI catalyst was able to sustain the effect on the positive side, but not losing it to the negative side.An H-type device with 0.05 M LiI containing 1 M LiClO4 on the left side and 1 M LiClO4 on the right side was used to analyse the permeability of the membranes.As it can be seen in Fig. 2d, a minor amount of the I -ions permeated through the GF membranes at hour 6, the colour of the left size solution (H2O2 with 0.5% starch blue) changed to light blue, at the 12-hour time point, a substantial amount of I -ions transferred, leading to a pronounced dark blue colour.
Conversely, the LCM-2 membrane exhibited exceptional resistance to I -ion permeation throughout the 12-hour permeability test, showcasing its robust I -blocking properties.products.this difference is primarily attributed to the charging potential, as it can be that in Fig. 3a, the charging potential of LOBs after 20 cycles is only 3.78 V, whereas  (d-e) show that the discharge curves of GF and PVDF membranes are lower than the discharge voltage of 2.0 V, which indicates that the lithium anode has lost the ability to detach lithium ions, and both GF and PVDF membranes are unable to prevent harmful substances from attacking the lithium anode surface.The discharge potential of LOBs in Fig. 3c is kept at around 2.7 V within 113 cycles, but the charge potential reached 4.5 V, and the charging time was short.Fig. 3d shows that the addition of LiI into the LiClO4/DMSO electrolyte resulted in increased peak currents for the formation and decomposition of discharge products, suggesting that iodide accelerated the ORR and OER processes and that the two sets of peaks centred on 3.3 and 3.8 V vs. lithium voltages in the tests of LCM-2 membranes were attributed to the I3 -/I -and I2/I3 -redox couples, which experienced the equilibrium reactions of I3 -+ 2e -⇌ 3I -and I2 + I -+ e -⇌ I3 -, respectively [28] .It is shown that the LCM-2 membrane can retain LiI, at the positive electrode.We also compared the battery cycle performance of the LOBs with GF and LCM-2 membranes at 1A, 3A and 5A multipliers, Fig. 3e shows the cycle performance curves of LOB with LCM-2 membranes of 542, 201 and 144 cycles at 1A, 3A and 5A, respectively, and the performance of the one with GF membranes of 80, 53 and 35 cycles at 1A, 3A and 5A, respectively.The LCM-2 membranes were able to maintain their excellent battery performance at high charge/discharge rates.

Performance of lithium-oxygen batteries with LCM membranes
Fig. S5c shows the full discharge performance of the LOB using GF membranes at a full discharge capacity of 3,782 mAh.The full discharge performance of LOB with LCM-2 membranes showed a capacity of 43,755 mAh (Fig. 3f)., while the insertion of Fig. S5f indicates that the full discharge capacity in argon is only 68 mAh, indicating that the ORR contributes dramatically to such a high full discharge capacity.The LCM-2 membranes can effectively improve the stability of the battery during cycling, resulting in a significant improvement in cycling, multiplier, and full discharge capacity.

Mechanistic characterisation of membranes in the circulation
The elemental composition of the LCM-2 membrane after 80 LOB cycles were analysed using XPS.The XPS was calibrated using C at a binding energy of 284.8 eV.

Characterisation of LOBs Cathode
Fig. 5a shows the SEM image the morphology of multi-walled carbon nanotubes (MWCNTs) on the pristine cathode, showcasing their strong adhesion to the carbon paper.Fig. 5b shows the SEM of the GF membrane during discharge, where the cathode carbon paper is covered with discharge products, followed by their decomposition upon charging (as seen in Fig. 5c).After 80 cycles, the battery assembled with the GF membrane fails, as demonstrated in Fig. 5d, which illustrates a significant amount of deposit covering the cathode surface.Raman spectra in Fig. S9a indicates that the discharge products primarily consist of LiOH (460 cm -1 ) and Li2O2 (798 cm -1 ) [44,45] , with the intensity of LiOH peaks exceeding that of Li2O2, suggesting LiOH as the predominant product.For the LCM-2 membrane LOBs, Fig. 5e reveals that carbon nanotubes remain clearly visible after just one cycle, indicating that LiI accelerates the decomposition of discharge products and facilitates rapid product dissolution.In Fig. 5f, discharge products cover the carbon cathode surface after 542 cycles, appearing as small granular deposits.Raman spectra in Fig. S9b show that these granular products are primarily Li2O2, with a higher intensity of Li2O2 peaks compared to LiOH, signifying Li2O2 as the main product.Remarkably, the LCM-2 membrane LOB experiences failure not during discharge but during the charging process.Wide-ranging SEM mapping in Fig. S6 reveals that extensive granular products entirely cover the positive electrode.We posit that I -ions are continually consumed during the cycling process, as reflected in the battery's charging voltage reaching 4.3 V at 330 cycles.The ultimate failure of the LCM-2 membrane battery is attributed to insufficient charging time, resulting in an excess of challenging-to-decompose products on the positive electrode, confirming complete I -consumption.

Fig. 5 (a) SEM images of pristine MWCNTs; (b) SEM images of cathode products of
LOBs discharged once using GF membrane, (c) recharged once using GF membrane, (d) circulated for 80 cycles using GF membrane, (e) recharged once using LCM-2 membrane, (f) circulated for 542 cycles using LCM-2 membrane.

Characterisation of the Lithium Anodes
In Fig. S11a displays a smooth lithium surface, while Fig. S10a reveals that the thickness of the lithium sheet is 383 μm.As shown in Fig. 6a, after cycling the LCM-2 membrane LOB for 80 cycles, a relatively flat lithium surface under ordinary camera, while the SEM image provides a detailed microstructure view, revealing the appearance of small particles on the lithium surface.

Performance evaluation of Li + stripping and plating
solid polymer electrolytes with high mechanical modulus have been applied to control the generation of lithium dendrites during battery operation [46] , the Young's modulus of traditional polymers is below 1 GPa [47] , that is not able meet the requirements of lithium dendrite blocking, and the purpose of lithium dendrite blocking can be achieved by adding the optimal proportion of inorganic fillers to increase the Young's modulus [48][49][50] .Fig. 7a shows that the Young's modulus of t PVDF membrane is 640 MPa, Fig. S12a shows that due to the addition of LATP particles, the Young's modulus of LCM-1 membrane increases to 1.4 GPa, but it is not enough to meet the

Conclusion
Composite LCM membranes have been successfully synthesised by incorporating LATP solid electrolyte as an active filler into PVDF polymer.The charging overpotential of LOBs is reduced, the shuttle effect of RMs is blocked with the addition of LiI as an active catalyst, and the LCM-2 membrane's conductivity is significantly improved at 7.4 mS cm -1 compared to PVDF membranes with a conductivity of 3.3 mS cm -1 .Simultaneously, the addition of LATP led to a reduction in the porosity of the PVDF membrane and an enhancement in tLi + to 0.59.This improvement also contributed to a more effective blockage of I -.When applied in LOBs, the LCM-2 membrane demonstrated an impressive long cycle life of 542 cycles, along with a high specific capacity of 43,755 mAh.This underscores the efficacy of the solution casting method as a novel approach for the scalable production of durable LOBs membranes.

Fig. 3a shows
Fig.3ashows an extension of the cycle life of LOBs with LiI catalyst, achieving 542 cycles with an overpotential of 0.86 V when employing the LCM-2 membrane.Fig.S7(a-b) shows the cycle life testing result of LiI LOBs with LCM-1 and LCM-3 membranes are 417 and 392 cycles, respectively, indicating that the LCM-1 membrane is inadequate to form a "local blocking" effect, whereas the LCM-3 membrane, with an excess of solid electrolyte particles, may have contact with the lithium metal and potentially affect the battery's performance.In comparison, Fig.3bindicates the LOBs without LiI show only 113 cycles with the overpotential raised to 1.57 V with the same LCM-2 membrane is used.This outcome suggests that LiI successfully reduced the battery's charging potential and enhanced the efficient decomposition of cathode

Fig. 3
Fig. 3 LOB cycling performance using LCM-2 membranes at 0.05 M LiI in LiClO4/DMSO electrolyte (a) and LiClO4/DMSO electrolyte (b); Charge potential, discharge potential and charge capacity of LCM-2 membranes containing iodide ions and without iodide ions(c); GF and LCM-2 membranes tested using cyclic voltammetry with the addition of 0.05 M LiI to the LiClO4/DMSO electrolyte (d); rate performance (e) and full discharge capacity (f) with the GF and LCM-2 membranes.inFig.3b, it elevated to 4.3 V after the same number of cycles, leading to continued charging of the electrolyte under high-voltage conditions.The enhanced ionic conductivity of the LCM-2 membrane is attributed to the presence of the LATP solid electrolyte, while the Lewis acid-base interaction impedes anion mobility and results in the uniform deposition of lithium ions.For the GF membranes with LiI, the cycle life of the conventional GF membrane in Fig.S5aran only 80 cycles, and the LOB with the PVDF membrane ran only 131 cycles shown in Fig.S5b.This indicates that LiI does not play a role in the continuous decomposition of the anode product in the battery assembled with GF membrane and PVDF membrane.Figs.S5(d-e) show that the

Fig. 4a shows
Fig. 4a shows the C-C, C-O, and C-F bonds binding energies of 284.8 eV, 286.8 eV, and 290 eV, respectively, and the corresponding substances is (CH2CF2) n and Li2CO3.whereLi2CO3 may be produced due to the decomposition of the electrolyte.Fig.4b

Fig. 4
Fig. 4 LCM-2 membrane running 80 cycles at an etching depth of 100 nm (lithium side) (a) C 1s, (b) F 1s, (c) O 1s, (d) Li 1s, (e) Ti 2p, (f) Al 2p.shows that the binding energies of the Li-F and C-F bonds of element F are 684.8eV and 687.4 eV, respectively.Whereas the element F of the fresh LCM-2 membrane in Fig. S8b shows only the C-F peak at 286.6 eV, indicating that PVDF membrane and the lithium surface had more intimate contact with tight bonds after cycling and generated LiF which can homogenise the intercalation of lithium and prohibits the lithium dendrites growth.Fig. 4c shows the fine spectrum of O1s orbit with peaks at 528.5 eV, 531.6 eV, and 531.8 eV corresponding to Ti-O, Al-O, and Li-O, respectively.Which also confirms the presence of Li2CO3.Fig. 4d also shows the presence of Li-F, and the binding energy of Li at 55.7 eV.Fig. 4e shows that the binding energies of Ti 2p3/2 and Ti 2p1/2 are at 458.8 eV, 464.3 eV, and Fig. 4f shows that the binding energy of the Al-O bond of the element Al is located at 74.5 eV, and the presence of the elements Ti and Al shows that the LATP solid electrolyte is stable in the battery cycle, but their signals are is weaker than the other elements and can only be observed in the single element spectrum, which is not shown in the full spectrum of Fig. S8a.
Fig.6d's EDS image indicates that these particles primarily stem from trace amounts of LiOH, even though LiOH peaks were not detected in the XRD spectra in Fig.6e.The presence of elements C and F in Fig.6dsuggests that a minor amount of residual polymer remains on the lithium surface, confirming the close contact between the LCM membrane and the lithium sheet.In Fig.S10b, the LCM-2 membrane LOB results in a lithium sheet thickness of 353 μm after 80 cycles.However, Fig.6crevealed a completely pulverised lithium surface under an ordinary camera after cycled 80 cycles for the LOB with GF membrane.The XRD image in Fig.6ealso demonstrates that the lithium metal surface has undergone complete pulverisation, leading to the generation of LiOH.Additionally, Fig.S10dshows the SEM image that highlights the extent of lithium sheet pulverisation, leaving only a residual thickness of 161 μm.Unfortunately, this lithium sheet is non-functional due to the surface being covered by LiOH, which is the reason cause of the GF membrane's failure during battery cycling.Fig.6bshows the lithium surface of the LCM-2 membrane LOB after 542 cycles.Images in Fig.6bindicate that the lithium surface turned to a yellowish colour, likely originating from by-products deposited on the lithium surface resulting from electrolyte decomposition.The SEM image shows the development of a thin membrane on the lithium metal surface.In the XRD image of Fig.6e, lithium metal remains the dominant phase, with a small quantity of LiOH present.In Fig.S10c, the thickness of the lithium sheet is still 245 μm.The changes observed in the lithium flake's surface and thickness suggest that the LCM-2 membrane effectively protects the lithium anode.

Fig. 6
Fig. 6 Camera photographs and SEM of LOBs cycling process in lithium sheets (a) LCM-2 membrane cycling for 80 cycles, (b) LCM-2 membrane cycling for 542 cycles, (c) GF membrane cycling for 80 cycles.(d) SEM and EDS images after 80 cycles of cycling with lithium anode; (e) XRD images of 80 cycles of GF cycling, 80 cycles of LCM-2 cycling and 542 cycles.

Fig. 7
Fig. 7 (a) AFM topography surface images and young's modulus of PVDF membrane and LCM-2 membrane; (b) Li stripping/plating curves at 0.1 mA for Li|Li symmetric batteries with PVDF and LCM-2 membranes; (c) Protection mechanism of lithium anode by PVDF membrane vs.LCM-2 membrane; (d) Charge/discharge, full discharge, and multiplicity performance of LOBs are compared with previous literature.requirement of lithium dendrimer blocking, and by increasing the proportion of inorganic filler, Fig.7ashows that the Young's modulus of LCM-2 membrane reaches 6.6 GPa, which is more than 10 times of that of the PVDF membrane, and it achieves the goal of resisting lithium dendrimers.The AFM images of Fig.7aand Fig.S12 (a