In situ growth of submicron polypyrrole on NiTi alloy wire as electrodes for recoverable and flexible quasi-solid-state supercapacitors

Highlights: • A method for fabricating shape-memory supercapacitor was presented. • The quasi-solid-state SMSC device exhibited an energy density of 60.0 μWh cm⁻². • After 200 shape recovery cycles, the SMSC capacitance retention remained 92.3%. -- Abstract: In recent years, wearable and flexible supercapacitors have attracted extensive attention. High energy density supercapacitors based on shape-memory materials can meet the requirements of recoverability and fatigue resistance. We fabricate a symmetric wire-based shape-memory supercapacitor (SMSC) by depositing polypyrrole (PPy) on NiTi shape-memory alloy wire as electrodes. The SMSC exhibits high flexibility and excellent shape-memory performance, which can quickly recover to its original shape in a few seconds with almost constant capacitance when heated to the deformation temperature (approximately 60 °C) at arbitrary shapes of deformation. Furthermore, the SMSC displays an ultrahigh areal energy density of 60.0 μWh cm⁻² and represents excellent capacitance stability after multiple deformation/recovery processes. Considering its outstanding flexible ability and excellent electrochemical performance, the wire-based SMSC shows infinite potential in the application of flexible and wearable electronics.