Structrual Carbon Fiber Composite Supercapacitors with a Dual-Phase Solid Electrolyte

Abstract

Structural composite supercapacitors that can carry mechanical loads and store electric energy hold great potential for lightweight electric mobility systems. Achieving the weight reduction requires mechanically-strong and stiff electrolytes with high ionic conductivity to reinforce high-capacity electrodes to carry mechanical loads. Herein, we present a systematical investigation of a dual-phase structural electrolyte featuring a bi-continuous network of epoxy and ionic liquid (IL), and its efficacy in fabricating carbon fiber-based composite supercapacitors. The results reveal that a dual-phase electrolyte containing 40 wt% IL and 60 wt% epoxy exhibits the highest multifuctional performance, measured by the product of stiffness and ionic conductivity. Composite supercapacitors fabricated with this electrolyte and high-performance carbon fibre electrodes grafted with MnO2 have been found to achieve a high areal capacitance of 11.1 mF/cm2, an energy density of 916 mWh/Kg and a maximum power density of 165.7 W/Kg based on the mass of the active material. Furthermore, such composite supercapacitors are capable of high tensile, compressive and flexural strength of 397, 41 and 104 MPa, respectively. These excellent mechanical and electrochemical properties make the carbon fiber supercapacitors a very promising solution for multifunctional energy storage devices in a wide range of applications.