Design and regulation of FeCo2S4 nanoneedles deposited on carbon felt as binder-free electrodes for high-performance hybrid supercapacitor

Abstract

Hybrid supercapacitors have drawn much attention since they possess both high energy density and power density. Carbon felt (CF) is chosen as the substrate in this work due to its 3D porous structure, good conductivity, and excellent flexibility. FeCo2S4 nanoneedles are uniformly deposited on CF via hydrothermal, annealing and sulfidation processes, forming the binder-free FeCo2S4 @CF electrode. The morphology of FeCo2S4 deposited on the CF can be designed and regulated by controlling the hydrothermal reaction time. The electrode with unique features is beneficial to the exposure of electroactive sites and the rapid transport of electrons/ions, showing a high specific capacitance of 847.8 mF cm−2 and outstanding rate performance. The hybrid supercapacitor assembled by FeCo2S4 @CF electrode and activated carbon felt exhibits the maximum specific capacitance of 309.7 mF cm−2, energy density of 110.1 μWh cm−2 and power density of 562.4 μW cm−2. Besides, the capacitance retention of the device reaches 98.5% after 10,000 charge-discharge cycles and 87.2% after 3000 bending cycles respectively, revealing its great cycling stability and flexibility. Therefore, this work provides an effective and feasible strategy for the morphology regulation of binary transition metal sulfides with superior electrochemical performance for supercapacitors.