Rational design of self-supported Ni3S2 nanoparticles as a battery type electrode material for high-voltage (1.8 V) symmetric supercapacitor applications

Abstract

Nickel sulfide (Ni₃S₂) has been widely known in the energy storage field, owing to the high theoretical capacitance, low cost, and environmental friendliness. We reported simple, low-cost hydrothermal synthesis of Ni₃S₂ nanoparticles as a remarkable electrode material for symmetric supercapacitor (SSC) in this paper. The structural characterization confirms the successful formation of the sample with a nanoparticle-like morphology with good crystallinity. The unique structure is composed of plenty of ion mobilization channels that exhibits superb electrochemical performance. When employed as an electrode material for supercapacitors, the fabricated Ni₃S₂ nanoparticles displayed the typical features of battery-type faradic electrodes showing an ultra-high specific capacitance of 2495 F g⁻¹ at 1 A g⁻¹ and excellent cycling stability (92.2% capacitance retention after 5000 consecutive CV cycles) within the potential frame of −0.2 to 0.6 V in a three-electrode system, which surpasses many previous literature reports. In the end, a SSC device was assembled exhibiting an optimized and stable potential window of 1.8 V with a high specific capacitance of 116.6 F g⁻¹ at 5 A g⁻¹. Moreover, the Ragone plot shows a high energy density of 52.4 W h kg⁻¹ and an ultra-high power density of 13 500.0 W kg⁻¹, indicating excellent cycling stability (95% retention after 7000 cycles). Additionally, we demonstrated a coin-type SSC that provides sufficient energy to turn on the red LED, which emits light over a certain period to open up possible realistic applications. These results show the great potential of Ni₃S₂ nanoparticles in the development of high-performance electrode materials for energy storage and conversion systems.