Flower-like Spherical α-Ni(OH)2 Derived NiP2 as Superior Anode Material of Sodium-Ion Batteries

Transition metal phosphides (TMPs) are promising anode candidates for sodium-ion batteries, due to their high theoretical specific capacity and working potential. However, the low conductivity and excessive volume variation of TMPs during insertion/extraction of sodium ions results in a poor rate performance and long-term cycling stability, largely limiting their practical application. In this paper, the NiP 2 nanoparticles encapsulated in three-dimensional graphene (NiP 2 @rGO) were obtained from the flower-like sphericalα-Ni(OH) 2 by phosphating and carbon encapsulation processes. When used as a sodium-ion batteries anode material, NiP 2 @rGO composite shows excellent cycling performance (117 mA h g -1 at 10 A g -1 after 8000 cycles). The outstanding electrochemical performance of NiP 2 @rGO is ascribed to the synergistic effect of the rGO and NiP 2 core. The rGO wrapped on the NiP 2 nanoparticles build a conductive way, improving ionic and electronic conductivity. The effective combination of NiP 2 nanoparticles with graphene greatly reduces the NiP 2 nanoparticles aggregation and pulverization during the discharge/charge process. This paper may shed light on the construct of high-performance anode material for sodium ion batteries and to other electrode materials.