Solid-State, Single-Anion-Conducting Networks for Flexible and Stable Supercapacitor Electrolytes

Supercapacitors are a complementary energy storage technology to batteries and will be important for next-generation applications such as wearable sensors, soft robotics, roll-up displays, and electric vehicles. Here, we report a flexible supercapacitor with an all solid-state, single-ion-conducting polymer network electrolyte. The electrodes are comprised of reduced graphene oxide held together with a neutral polymer network to stabilize the dispersion and lend flexibility to the overall supercapacitor. Due to the high thermal and electrochemical stability of the network polymerized ionic liquid electrolyte, the resulting device can be charged to high voltages (3 V) and operated at high temperatures (120 °C) with excellent cycling stability. A 300 F/g specific capacitance is achieved by charging the device at 0.57 A/g and 90 °C or at 1.8 A/g and 120 °C. Due to the flexible network, the device can bend up to 180° without a substantial change in capacitance. The electrode/electrolyte interface, network architecture, and single-ion-conducting nature of the electrolyte are shown to be critical for high capacitance through a series of control experiments with ionic liquid supercapacitors.