High Ion Conducting Dobule Network Crosslinked Gel Polymer Electrolytes for High‐Performance Supercapacitors

Abstract As the demand for electrical energy storage devices increases, various electrolytes are being studied. In particular, gel polymer electrolytes (GPEs) with excellent physical properties can improve safety and cycle life, so attempts are underway to replace organic liquid electrolytes facing fire or explosion issues. However, the intrinsic poor electrochemical properties of GPEs limit their commercialization in all‐solid‐state energy storage devices. In an attempt to solve this problem, epoxy/poly(ethylene glycol) (PEG)‐based double network electrolytes (DNEs) containing a mixture of bis(trifluoromethane)sulfonimide lithium salt (LiTFSI) and 1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIMTFSI) are designed to enhance the electrochemical properties of traditional single network electrolytes (SNEs). The synthesized epoxy/PEG‐based DNE has higher mechanical strength ( G ′ = 1.7 MPa) with outstanding ionic conductivity ( σ DC ≈ 5.8 × 10 −4 S cm −1 ) at room temperature, compared to the epoxy‐based SNE. Then, an all‐solid‐state supercapacitor based on the DNE and activated carbon electrodes exhibits higher specific capacitance (≈153 F g −1 ) and power density (833 W kg −1 ), compared to the SNE‐based supercapacitor.