Flower-like Heterogeneous Phosphorus-Doped Co₃S₄@Ni₃S₄ Nanoparticles as a Binder-free Electrode for Asymmetric All-Solid-State Supercapacitors

Through the hydrothermal method and the gas-phase phosphating method, the flower-like heterogeneous phosphorus-doped Co 3 S 4 @Ni 3 S 4 was synthesized in situ on a nickel foam substrate as the binder-free electrode material for supercapacitors. Phosphorus-doped Co 3 S 4 @Ni 3 S 4 electrode material combines the merits of transition metal sulfides and 3D porous network heterostructure, showing the excellent theoretical specific capacitance and the high specific surface area. The introduction of phosphorus atoms with an atomic radius larger than sulfur atoms can optimize the internal electronic structure and cause structural distortion. Therefore, the specific capacitance/specific capacity of this electrode can reach 3614 F g –1 (451 mAh g –1 ) at 1 A g –1 and still maintain the initial specific capacitance of 73% after 3000 cycles. The assembled P–Co 3 S 4 @Ni 3 S 4 -175//AC ASC device exhibits an ultra-high energy density of 72 Wh kg –1 at a power density of 800 W kg –1 . Meanwhile, it can show extraordinary cyclic stability, with a retention rate of 91% after 5000 cycles. This work provides a feasible synthesis method to prepare the composite electrode materials for supercapacitors.