Monodispersed Ni2P nanodots embedded in N, P co-doped porous carbon as super stable anode material for potassium-ion batteries

Abstract Transition metal phosphides are considered as attractive anode materials of potassium-ion batteries owing to their high specific capacity and abundant reserves. However, the huge volume expansion and agglomeration of transition metal phosphides during the charge-discharge process always limit their practical application. In this work, we designed and prepared the composite of Ni2P and N, P co-doped porous carbon (Ni2P@NPC) by using biomass (gelatin) as raw material. Gelatin is rich in nitrogen element and has strong chelation with metal ions, resulting in uniform distribution of small Ni2P nanodots (5 nm in diameter) in N, P co-doped porous carbon. Moreover, the Ni2P@NPC composite was demonstrated to have large specific surface area and large carbon interlayer spacing, which could provide abundant reaction sites for K ions. The Ni2P@NPC has excellent electrochemical performance with a high capacity of 282 mAh g−1 at 100 mA g−1 after 100 cycles, and it still remains 212 mAh g−1 after 5000 cycles at 1 A g−1. In addition, the potassium-ion storage mechanism and the structure change of Ni2P@NPC during the charge-discharge cycles were investigated as well. This work provides a simple and environmentally friendly method to synthesize the high-performance anode materials for potassium-ion batteries.