Integrated supercapacitor with self-healing, arbitrary deformability and anti-freezing based on gradient interface structure from electrode to electrolyte

Flexible supercapacitors have attracted more and more attention because of their promising applications in wearable electronics, however, it is still important to harmonize their mechanical and electrochemical properties for practical applications. In the present work, a seamless transition between polyaniline (PANI) electrode and NH4VO3_FeSO4 dual redox-mediated gel polymer electrolyte (GPE) is presented through in situ formation of gradient interface structure. Multiple physical interactions make the GPE excellent mechanical and self-healing properties. Meanwhile, double role functions of Fe2+ ions greatly relieve the traditional contradiction between mechanical and electrochemical properties of GPE. Moreover, benefiting from the structure and reversible redox reactions of VO3- and Fe2+, the integrated supercapacitor delivers an exceptional specific capacitance of 441.8 mF/cm2, a high energy density of 63.1 μWh/cm2, remarkable cyclic stability. Simultaneously, the gradient structure from PANI electrode to GPE greatly improves the electrode/electrolyte interface compatibility and ion transport, which endows the supercapacitor with stable electrochemical performance. Furthermore, the supercapacitor well-maintains the specific capacitance even at -20 °C with over 89.19 % retention after 6 cutting/healing cycles. The gradient interface structure design will promote the development of high-performance supercapacitor.