Nickel Phosphide Nanosheets Supported on Reduced Graphene Oxide for Enhanced Aluminum-Ion Batteries

The electrochemical behavior of nickel phosphide nanosheets supported on reduced graphene oxide is first explored as cathode material for aluminum-ion batteries. Ni2P/rGO nanosheets are prepared through a hydrothermal method combined with a subsequent phosphorization process. Ni2P/rGO nanosheets deliver a high first discharge capacity of 274.5 mAh g–1 at 100 mA g–1, which remain at 73.0 mAh g–1 with a Coulombic efficiency of 93.5% after 500 cycles. And even at a higher current density of 200 mA g–1, the cathode still presents the favorable discharge capacity of 60.9 mAh g–1 and Coulombic efficiency of 94.5% over 3000 cycles. The higher discharge capacity and better cycling stability in comparison with these of the pure Ni2P verify that compositing reduced graphene oxide is an effective strategy to enhance the capacity and cycling stability of Ni2P for aluminum-ion batteries. Furthermore, the energy storage mechanism of Ni2P as cathode for aluminum-ion batteries is rigorously investigated, showing that the incorporation of Al3+ into Ni2P can generate AlmNinP and elemental Ni