In situ filling of a robust carbon sponge with hydrogel electrolyte: a type of omni-healable electrode for flexible supercapacitors

A sandwich-type supercapacitor consisting of self-healing layers and electrode layers can easily delaminate during deformation, thereby seriously affecting its reliability. In this work, a type of omni-healable electrode (denoted as CS@PANa–Fe3+–LiCl) is reported, which completely integrates a three-dimensional (3D) electrode material, a self-healing hydrogel and an electrolyte. Consequently, the ease of delamination and the large contact resistance due to the sandwich-type structure can be effectively overcome. Herein, the 3D porous carbon sponge (CS) serves both as an electroactive material and a carrier for the Fe3+-crosslinked sodium polyacrylate–LiCl (denoted as PANa–Fe3+–LiCl) hydrogel electrolyte. Combining the high electrical conductivity and good capacitance of the CS with the high ionic conductivity and excellent self-healability of the PANa–Fe3+–LiCl hydrogel electrolyte, the omnidirectionally integrated electrode exhibits good electrochemical and mechanical properties as well as excellent self-healing characteristics; furthermore, its capacity retention rate remains high (91.6%) even after five cutting/healing cycles. The as-fabricated CS@PA-SC device exhibits full self-healability, high energy density, good cycling stability, and integration characteristics. This investigation offers a facile and versatile strategy to integrate omni-healable electrodes that can be utilized to construct completely self-healable supercapacitors for wearable electronics.