A Stretchable and Healable Gelatin Hydrogel Assisted by Hofmeister Effect for All‐in‐One Flexible Supercapacitor

The all‐in‐one flexible supercapacitor holds great promise for wearable electronics due to its stable electrochemical performance under continuous strain. However, it is a challenge to achieve good mechanical strength, self‐healing performance, and high energy density for their potential applications. For this purpose, a stretchable and healable all‐in‐one supercapacitor consisting of gelatin hydrogel electrolytes and polypyrrole electrodes is constructed. The gelatin hydrogel is obtained by the hydrolysis of leather waste shavings and then physically cross‐linked by simply soaking in a sodium sulfate solution. Benefiting from the Hofmeister series, the kosmotropic sodium sulfate ions can significantly enhance the hydrophobic interactions and chain bundling, thus greatly improving the mechanical strength of gelatin hydrogel. As a result, the as‐prepared all‐in‐one supercapacitor exhibits an area‐specific capacitance of 219.0 mF cm −2 , a high energy density of 19.46 μWh cm −2 , and long cycling life. In particular, the all‐in‐one supercapacitor can be deformed under varied stress–strain via decross‐linking and dissociation, simultaneously delivers reliable self‐healing capability. This work presents a simple and green technology to prepare an all‐in‐one supercapacitor, which motivates the development of biomass wastes toward high‐performance electronics.