Tuning Morphology and Properties of Epoxy-Based Solid-State Polymer Electrolytes by Molecular Interaction for Flexible All-Solid-State Supercapacitors

In the development of the next-generation safe solid-state supercapacitors with high energy density, durability, and flexibility, the synthesis of high ion conducting solid-state polymer electrolyte (SSPE) with electrochemical and mechanical stabilities is a great challenge. This study shows the promising potential of epoxy-based SSPEs containing oligoether, ionic liquid, and Li salt, where a microscopic fast ion-diffusing channel is bicontinuously interlaced with the macroscopic mechanical supporting cross-linked matrix via polymerization-induced microphase separation. Their ionic conductivities, mechanical, and dielectric properties are finely tuned through varying the Li salt concentration, thermodynamically leading to a change of the relative interactions of the two conducting and insulating phases, thereby creating variant morphologies (such as microscale, nanoscale, or less phase separation). The optimized SSPE, exhibiting an ionic conductivity of ∼10 –3 S/cm and elongation at break of 153% at 25 °C, is assembled with activated carbon electrodes, allowing us to fabricate a flexible all-solid-state supercapacitor. The device shows a broad potential window (3 V), high specific capacitance (178 F/g at 0.1 A/g), large energy and power density (56 Wh/kg at 99 W/kg and 3.5 kW/kg at 13 Wh/kg), and remarkable electrochemical and mechanical stabilities under mechanical deformation (80% capacitance retention under rolling condition for 2000 cycles).