A Self‐Healing Crease‐Free Supramolecular All‐Polymer Supercapacitor

Abstract While traditional three‐layer structure supercapacitors are under mechanical manipulations, the high‐stress region concentrates, inevitably causing persistent structural problems including interlayer slippage, crease formation, and delamination of the electrode–electrolyte interface. Toward this, an all‐polymeric, all‐elastic and non‐laminated supercapacitor with high mechanical reliability and excellent electrochemical performance is developed. Specifically, a polypyrrole electrode layer is in situ integrated into a silk fibroin‐based elastic supramolecular hydrogel film with extensive hydrogen and covalent bonds, where a non‐laminate device is realized with structural elasticity at the device level. The non‐laminate configuration can avoid slippage and delamination, while the elasticity can preclude crease formation. Furthermore, under more severe mechanical damage, the supercapacitors can restore the electrochemical performance through non‐autonomous self‐healing capabilities, where the supramolecular design of host–guest interactions in the hydrogel matrix results in a superior self‐healing efficiency approaching ≈95.8% even after 30 cutting/healing cycles. The all‐elastic supercapacitor delivers an areal capacitance of 0.37 F cm−2 and a volumetric energy density of 0.082 mW h cm−3, which can well‐maintain the specific capacitance even at −20 °C with over 85.2% retention after five cut/healing cycles.


Supporting Information
The regenerated SF was prepared according to previous report. [1] Briefly, the raw silk (produced in Zhejiang, China) was first boiled in 0.05 wt % Na 2 CO 3 (AR, Aladdin) for 90 min at 90 °C, and then thoroughly rinsed with deionized water and dried overnight at room temperature. Second, the degummed silk was dissolved in a solution containing CaCl 2 (AR, Aladdin), CH 3 CH 2 OH (AR, Aladdin) and H 2 O (1:2:8) at 60 °C for 2 h and subsequently centrifuged at 8000 rpm for 12 min to remove aggregates. After that, the supernatant was continuously dialyzed in deionized water by using a cellulose dialysis membrane (MWCO 12400 Da) over 3 days to remove residual salts and then lyophilized to finally achieve the regenerated SF.

Preparation of SF Conjugated with β-Cyclodextrin (SF-CD).
The SF-CD was obtained through Schiff base formation. [2] 2 g β-CD (99.999%, Adamas) was dissolved in 50 mL DMSO (AR, Aladdin), then adding 2 Equiv of Dess-Martin periodinane (DMP, Energy Chemical). The reaction mixture was magnetically stirred for 1 h at room temperature. After that, addition of 300 mL acetone and cooling at -10 °C facilitated the isolation of the crude product β-CD monoaldehyde (β-CD-CHO) followed by filtration.
The purification of β-CD-CHO was executed by repeating the dissolution of β-CD-CHO in DMSO and the precipitation with acetone to remove the periodinane byproduct. The acetone and DMSO was removed by dissolving β-CD-CHO in water, followed by stirring for 1 h and lyophilization. The as-prepared β-CD-CHO was dissolved and incubated in a given volume of regenerated SF solutions at 25 °C for 24 h to finally yield SF-CD.
The resultant product was then reprecipitated and washed with 200 ml ethanol. At last, the precipitate was dialyzed for 2 days with a dialytic tube, and lyophilized for 24 h to finally obtain the AA-β-CD.

Preparation of Supramolecular Hydrogels.
The designed supramolecular hydrogel was fabricated as follows: 10 mL 20 wt% SF-CD solution was first prepared with 0.5 M NaCl aqueous solution as solvent. 1 g PAA-β-CD, Subsequently, the hybrid solution was injected into a mold and radiated under UV radiation (360 nm) for 30 min. Finally, the hydrogels were washed thoroughly with deionized water to remove remaining reagents. For control group, PAA hydrogel was synthesized by replacing the dispersed monomer solution with equivalent acrylic acid.

In-situ Polymerization of PPy.
A piece of film materials (supramolecular hydrogel, common paper or cloth) with a typical area was soaked in 0.

Materials Characterization
Tensile tests of hydrogels were conducted by an HTSLLY9130A tensile machine

Electrochemical Measurements
To test the electrochemical performance, The PPy/supramolecular hydrogel film was cut into a sample (1 cm width × 3 cm length × 2 mm thickness). Cyclic voltammetry (CV) and galvanoststic charge/discharge (GCD) measurements of the supercapacitors were executed (1) where C A (mF cm -2 ) is the areal specific capacitance, C V (mF cm -3 ) is the volumetric specific capacitance, I (mA) is the discharge current, Δt (s) is the discharge time, A (cm -2 ) is the effective area of electrodes, i.e., the contact area between one electrode and the electrolyte, V (cm -3 ) is the total volume of the whole device, and ΔV (V) is the operating voltage which determined from the discharge curves excluding potential drop.
The volumetric energy densities and power densities were calculated according to the following equations: specific capacitance, ΔV (V) is the operating voltage excluding potential drop, P V (mW cm -3 ) is the volumetric power density, t (h) is discharging time.

Preparation and Characterization of the Photodetector Driven by the Supercapacitor
First, the interdigitated electrodes were prepared on a doped Si substrate with a 300 nm