A Flexible and Ultrahigh Energy Density Capacitor via Enhancing Surface/Interface of Carbon Cloth Supported Colloids

Abstract Pseudocapacitors are now reaching the energy density limits set by the surface redox reaction of their electrode materials, requiring new cation paradigms for a fast cation Faradaic reaction with high capacitance. In this work, a flexible and ultrahigh energy density capacitor is reported via enhancing surface/interface of active colloids and supported carbon cloth. A flexible asymmetrical capacitor assembled with Ni²⁺ colloidal cathode and Fe³⁺ colloidal anode displays a high energy density of 353 W h kg⁻¹ at the power density of 2250 W kg⁻¹, outperforming recent reported pseudocapacitors, and shows superior cycling stability after 10 000 charge–discharge cycles at current density of 30 A g⁻¹. This work demonstrates that the optimized surface/interface of carbon cloth and colloids can lead to the enhancement of both stability and activity of colloidal electrode.