Multifunctional, bicontinuous, flexible comb copolymer electrolyte for solid-state supercapacitors

Solid electrolytes with high safety, good flexibility, and wide potential windows have attracted significant interest as alternatives to conventional liquid electrolytes, which have the disadvantages of flammability and leakage. Herein, we report a high-performance polymer electrolyte comprising a poly(isobornyl methacrylate)-co-poly(ethylene glycol) methyl ether methacrylate (PIBMA-co-PEGMA) (PIBEG) amphiphilic comb copolymer for solid-state supercapacitors (SCs). The PIBEG comb copolymer was synthesized via facile, inexpensive, and scalable free radical polymerization, followed by the incorporation of an ionic liquid (IL) to fabricate an ion-conducting flexible polymer electrolyte. Owing to the microphase-separated structure, the PIBEG films showed homogeneity and good flexibility up to 85 wt% of IL loading. The PIBEG/IL electrolytes had a bicontinuous, worm-like nanostructure with an ionic conductivity of 4.35 mS cm⁻¹. The solid SC with PIBEG/IL electrolytes exhibited a specific capacitance of 48.6 F/g and an energy density of 37.12 Wh kg⁻¹ at a power density of 1174 W kg⁻¹, which are among the highest values reported for flexible solid SCs with conventional activated carbon electrodes. Furthermore, SCs could be fabricated without the use of separators or adhesives due to the multifunctional properties of PIBEG/IL electrolytes, including strong adhesion, high conductivity, and good mechanical strength.