One-pot synthesis of hydroxypropyl methylcellulose-based gel polymer electrolytes for high-performance supercapacitors

The electrolyte is a crucial component that significantly affects the electrochemical performance of supercapacitors. The hydroxypropyl methylcellulose (HPMC)-based gel polymer electrolyte (GPE) with high operating voltage was synthesized via an innovative “one-pot” method in this study, and the impacts of organic solvent/water ratio and LiNO₃ concentration on gelation and conductivity of the GPE were investigated systematically. Under the optimal condition with a DMF/water ratio of 10:0 and the incorporation of 7 % LiNO₃, the ionic conductivity reached 1.06 S m⁻¹. Integrated into symmetric supercapacitors, the HPMC-based GPE demonstrated an expanded electrochemical window of 2.7 V. It also possessed a specific capacitance of 115.8 F g⁻¹ at 1.0 A g⁻¹, an energy density of 29.31 Wh kg⁻¹, and outstanding cyclic stability, retaining 86 % of its initial capacitance after 2000 cycles. Through cyclic stability tests under pressure conditions, the assembled flexible supercapacitors were able to maintain capacitance retention of 60 % and coulombic efficiency of 97 %. This work offers a streamlined synthesis for HPMC-based GPE with superior electrochemical properties, which exhibits its potential in advancing supercapacitor technology for flexible electronics.