A flexible supercapacitor with high capacitance retention at an ultra-low temperature of-65.0 degrees C

A novel anti-freezing organo-hydrogel electrolyte is developed to improve capacitance retention of flexible supercapacitor at the ultra-low temperature. The electrolyte is composed of graphene/polyvinyl alcohol matrix and methyl sulfoxide/water/sulfuric acid mixture. It simultaneously possesses a high tensile strength of ca.2.58 MPa and a high ionic conductivity of ca.3.9 S/m. Furthermore, the electrolyte can still maintain high flexibility and high ionic conductivity (ca.1.0S/m) at-65 degrees C. In addition, a flexible supercapacitor with sandwich structure was assembled from the organo-hydrogel electrolyte and two polyaniline fiber/carbon cloth electrodes. The supercapacitor exhibits a high specific capacitance of 252.0F/g and excellent capacitance retention of 93% at-65 degrees C. The excellent capacitance retention is attributed to the synergistic effect of methyl sulfoxide, concentrated sulfuric acid and graphene nanosheets. This study provides a new way to design and prepare anti-freezing electrolyte with high-performance for application in the flexible solid-state electrochemical energy storage at ultra-low temperatures.