Self-assembled block copolymer electrolyte membranes with silica network-derived nanochannels for all-solid-state supercapacitors

Abstract

Amphiphilic Block copolymer (BC) membranes, where the BC hydrophilic domain offers a continuous pathway for fast ion transport, while the BC hydrophobic domain provides a scaffold for high mechanical strength, are being widely studied as promising materials for energy storage applications due to their unique morphology with 3-dimensionally continuous macropores. We design silica network-derived poly(styrene)-b-poly(2-vinylpyridine) BC-based hierarchically porous membranes containing high-conducting ionic liquids (ILs) as solid-state electrolytes via nonsolvent-induced phase separation and nonhydrolytic sol–gel process. The introduction of a silica nanoparticle network within the self-assembled BC leads to micro- and nano-scale porous structures. This provides the functionalized BC/IL-based electrolytes (BCEs) with high IL uptake (87 wt%), high dielectric constant (123), low activation energy for ion conduction (6.8 kJ/mol), and high room temperature ionic conductivity (∼10-3 S/cm, comparable to pure IL). The optimized BCE is assembled with activated carbon electrodes, allowing us to fabricate an all-solid-state supercapacitor. The device delivers a broad voltage window (2.5 V), high specific capacitance (∼90 F/g at 0.2 A/g), large energy (E) and power (P) densities (a maximum of E=19 Wh/kg, observed at P=224 W/kg, and a maximum of P=1.3 kW/kg, observed at E=4 Wh/kg), and remarkable electrochemical stability (capacitance retention = 90% for 600 cycles and 76% for 1000 cycles and coulombic efficiency = 100% for 1000 cycles at 0.2 A/g). Therefore, the combination of self-assembly, phase inversion, and in-situ hybridization-derived hierarchical dual-pore construction, providing rapid ion migration, could be a new approach to powering next-generation energy storage devices.