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

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.