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

Abstract

The\nelectrochemical behavior of nickel phosphide nanosheets supported\non reduced graphene oxide is first explored as cathode material for\naluminum-ion batteries. Ni₂P/rGO nanosheets are prepared\nthrough a hydrothermal method combined with a subsequent phosphorization\nprocess. Ni₂P/rGO nanosheets deliver a high first discharge\ncapacity of 274.5 mAh g^–1 at 100 mA g^–1, which remain at 73.0 mAh g^–1 with a Coulombic\nefficiency of 93.5% after 500 cycles. And even at a higher current\ndensity of 200 mA g^–1, the cathode still presents\nthe favorable discharge capacity of 60.9 mAh g^–1 and Coulombic efficiency of 94.5% over 3000 cycles. The higher discharge\ncapacity and better cycling stability in comparison with these of\nthe pure Ni₂P verify that compositing reduced graphene\noxide is an effective strategy to enhance the capacity and cycling\nstability of Ni₂P for aluminum-ion batteries. Furthermore,\nthe energy storage mechanism of Ni₂P as cathode for aluminum-ion\nbatteries is rigorously investigated, showing that the incorporation\nof Al³⁺ into Ni₂P can generate Al_<i>m</i>Ni_<i>n</i>P and elemental Ni.