Flexible Asymmetric Supercapacitor with Enhanced Energy Density Based on Surface-Modified Carbon Cloth Coupled with NiCoSe₂

Electrodes with excellent flexibility, wide voltage window and high capacity are the key to the performance of asymmetric supercapacitors (ASCs). Herein, a hybrid electrode based on modified nitrogen/alkali co-doped carbon cloth with NiCoSe₂ (NCSe/N-Na-ACC) was successfully synthesized and directly used as a positive electrode for ASCs. The surface-modified carbon cloth with N and Na ions effectively moderated the electronic conductivity and activity of the oxygen evolution reaction (OER), resulting in an enlarged overall voltage window, while NCSe provided high specific capacity. Therefore, the voltage of the NCSe/N-Na-ACC electrode increased to 1 V in aqueous electrolyte. As a result, the solid-state ASC assembled by the modified electrode delivered gratifying energy density of 139.5 W h kg^–1. Meanwhile, the excellent capacitance retention of 97.1% after 10,000 charge and discharge cycles implies that the ASC assembled with the NCSe/N-Na-ACC electrode has excellent cycling stability.