Surface charge induced self-assembled nest-like Ni₃S₂/PNG composites for high-performance supercapacitors

The paper presents a self-assembly approach to synthesize Ni₃S₂/N, P co-doped graphene (PNG) composite electrode materials for supercapacitors with high energy storage performance and structural stability. Innovatively, the self-assembly approach is induced via the surface charge effect utilizing a two-step hydrothermal method. The doping of nitrogen (N) and phosphorus (P) atoms regulates the surface charge distribution on graphene nanosheets. Therefore, in the synthesized Ni₃S₂/PNG heterostructures, Ni₃S₂ nanowires are interwoven into nests and uniformly attached to PNG. The design of the electrode materials with such a special structure not only supports each other to improve the stability of the materials but also facilitates the rapid diffusion of electrolyte ions. Based on the advantages of composition and structure, Ni₃S₂/PNG has a high specific capacitance of 1117C g^-1 at a current density of 1 A/g and excellent rate performance. The asymmetric supercapacitors (ASC) assembled with Ni₃S₂/PNG and PNG as positive and negative materials respectively have a high energy density of 62 Wh kg^-1 at a power density of 158 W kg^-1.