High toughness antifreeze conductive double network zwitterionic gel electrolyte for flexible supercapacitors

Abstract

AbstractFlexible wearable supercapacitors based on hydrogel electrolyte are considered as flexible energy storage device with great potential. However, polymer gel electrolytes contain a large number of water molecules, which can easily freeze at sub‐zero temperatures, thus severely inhibiting ion transport. The ionic conductivity, cyclic stability and mechanical properties of gel electrolytes decrease at low temperatures (below −25°C), which seriously hinders the application of flexible wearable supercapacitors. In order to improve the mechanical properties and ensure the excellent ionic conductivity of the electrolyte, a freezing‐resistant gel electrolyte constructed by supramolecular self‐assembly, which has a wide temperature range from 25 to −80°C, stable ionic conductivity and ultra‐high mechanical strength. Low‐temperature‐resistant gel electrolytes, called flexible supercapacitor‐SBMA‐co‐PVA‐AA/CaCl2 (FSAPC), have been designed and prepared by molecular‐scale supramolecular self‐assembly of rigid [2‐(methacryloyloxy)ethyl]dimethyl(3‐sulfopropyl) polymer chains and flexible poly(vinyl alcohol) polymer chains, and the test results showed that the gel electrolyte ‐SBMA‐co‐PVA‐AA/CaCl2 (PSAPC) has excellent conductivity of 34.07 mS cm−1 at 25°C, the flexible supercapacitor has a specific capacity of 8.57 Wh kg−1, and the capacity retention rate is 91.2% even after 5000 cycles at −25°C, excellent conductivity at −25°C for 31.88 mS cm−1 and at −80°C for 35.34 mS cm−1. The potential applications of the amphiphilic ionic gel electrolyte in the industrial development of low‐temperature resistant supercapacitors are noteworthy.