Microstructure and electrochemical performance of sulfur-containing nickel based composites for supercapacitors
摘要
Nickel based materials, including nickel hydroxides, oxides, and sulfides, typically have significantly larger theoretical specific capacitance but poor structural stability and sluggish reaction kinetics. To explore strategies for improving their electrochemical performance, this study focuses on the microstructure and electrochemical properties of sulfur-containing nickel based composites. NiS2/Ni(OH)2 composite with a porous structure formed by ultrathin nanosheets was firstly synthesized via a facile liquid-phase method. After subsequent thermal treatment at different temperatures (150 ℃, 300 ℃, 450 ℃ and 550 ℃), the structural phase, component and morphology of the composite underwent changes, resulting in NiS1.97/NiS/Ni(OH)2, Ni3S2/NiO and Ni3S2/NiO/Ni composites with different morphologies. Among the synthesized composites, NiS2/Ni(OH)2 has the largest specific capacitance, which is 1152 F g− 1 at a current density of 1 A g− 1, and still reaches 321 F g− 1 at 10 A g− 1. This is attributed to its relatively large specific surface area and low crystallinity, which can provide more active sites and reduced path for ion diffusion, thereby improving energy storage efficiency. Ni3S2/NiO/Ni has a smaller specific capacitance but better stability, with a capacitance retention of 149.8% after 10,000 cycles at 2 A g− 1. Furthermore, a fabricated hybrid supercapacitor device with NiS2/Ni(OH)2 composite as the positive electrode realizes an energy density of 12.1 Wh kg− 1 at 253.1 W kg− 1, and 7.6 Wh kg− 1 at a higher power density of 1277.8 W kg− 1. This work may provide a way to improve the energy storage of single metal materials.