Preparing a graphene/carbon nanotube coated hollow nickel phosphides microsphere anode with high stability for high-performance lithium/sodium battery

Transition metal phosphides as anode materials for energy storage batteries have attracted great attention due to their high specific capacity and safety. However, it is difficult to maintain the structural stability of the electrode material during the repeated Li⁺/Na⁺ insertion/ deintercalation process, especially at a high rate and long-life cycle. Herein, the graphene/carbon nanotubes coated Ni₂P (h-Ni₂P-G/CNTs) microspheres composite with hollow structure has been successfully prepared by one-step phosphorous heat treatment of Ni-MOF precursor microspheres and applied in the lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) anode. When the h-Ni₂P-G/CNTs is used as an anode for LIBs, it delivers high reversible capacities of 506 mAh/g after 200 cycles at 0.2 A/g. As an anode for SIBs, the electrode provides 430 mAh/g capacity at 0.1 A/g after 180 cycles. The excellent performances can be attributed to the synergistically structural and electronic modulations between h-Ni₂P, Ni, and G/CNTs, which provide more space to alleviate the volume effect on cycling and shortens the ion/charge diffusion path to speed up the reaction kinetics.