Ultrafast, Facile, and Scalable Microwave‐Assisted Synthesis Method to Prepare Nickel Sulfide Nanosheets for High Energy Density Hybrid Capacitors

Abstract A fast, easy, and scalable microwave‐assisted synthesis method is introduced to prepare NiS nanosheets (NiS NS). Two‐dimensional mesoporous NiS NS with high specific surface area of 210 m² g⁻¹ is capable of excellent electrochemical performance on carbon cloth. It possesses an excellent specific capacitance of 2241 F g⁻¹ (271 mA h g⁻¹) at a current density of 1 A g⁻¹ and retention of 88.3% at higher current density, indicating its remarkable rate capability. The hybrid asymmetric capacitor acquires an outstanding energy density of 73.1 Wh kg⁻¹ at a high power density of 800 Wk g⁻¹, and high energy density of 42.6 Wh kg⁻¹ is maintained at an extremely high power density of 12800 W kg⁻¹. Moreover, the assembled device shows stable performance for long‐term operation (retention of 75.2% after 10000 cycles). In addition, cyclic voltammetry (CV) and galvanostatic charge‐discharge(GCD) measurements are used to investigate the impact of the current collector on the electrochemical performance of the active material. This work may provide a pathway to synthesize low‐cost and efficient electrode materials by using the microwave for portable hybrid energy devices.