Design and construction of hierarchical Ni3S2 @V-doped NiMn-LDH heterostructure on rGO/Ni foam as an advanced electrode for battery-supercapacitor hybrid devices

Transition metal dopant engineering and rational architecture design have been proven to be effective strategies to improve the electrochemical energy storage properties of electrodes. Herein, V-doped NiMn-layered double hydroxide composites were supported on reduced graphene oxide-coated Ni foam (NMV-L/rGO) by a hydrothermal method. The influences of V content on the electrochemical performances of NMV-L/rGO composites were investigated in detail. At an optimal content of V doping (15%), the NMV-L/rGO-15 reveals enhanced electrochemical properties, and it is subsequently applied as the substrate for the electrodeposition of Ni3S2 layer. Benefiting from the collaborative effect of NMV-L/rGO-15, Ni3S2, and rGO materials, as well as the unique hierarchical architecture, excellent electrochemical performance is obtained in the as-prepared Ni3S2 @NMV-L/rGO-15 composite, which exhibits a high specific capacity of 1412.0 C g−1 at 1 A g−1 as well as desirable long-term stability of 89% over 5000 cycles. Furthermore, the as-fabricated battery-supercapacitor hybrid device (BSH) based on Ni3S2 @NMV-L/rGO-15 and activated carbon (AC) electrodes displays a remarkable energy density of 60.0 W h kg−1 at the power density of 849.1 W kg−1 and superior capacity retention of 96% through 7000 cycles. Such excellent results indicate that the Ni3S2 @NMV-L/rGO-15 composite holds great potential as electrode material for high-performance BSHs.