A high energy density supercapacitor fabricated with aqueous polymer electrolyte based on soybean protein isolate grafted by polyacrylic acid

Abstract

Soybean protein isolate (SPI) has good reactivity, hydrophilicity and film-forming properties, but its electrochemical performance is poor when used as a polymer electrolyte matrix. The graft-modification of the SPI using polyacrylic acid (PAA) allows the introduction of strong hydrophilic carboxyl groups into the SPI molecular chains. This enables the SPI to effectively absorb electrolytes in the subsequent electrolyte adsorption process, resulting in a modified polymer electrolyte. The resulting constructed supercapacitor can operate stably in a voltage window of 0–2 V and exhibit excellent electrochemical behavior with a high single electrode specific capacitance up to 293.08 F g−1 and an energy density of 38.76 W h kg−1 at a power density of 734.38 W kg−1, which is much better than SPI-based supercapacitor. This simple, low-cost and environmentally friendly approach has a great potential for the development of high-performance supercapacitor with high voltage window, high specific capacitance and high energy density.