Enhanced rate capability of multi-layered ordered porous nickel phosphide film as anode for lithium ion batteries

Porous nickel phosphide films are fabricated by electrodeposition through self-assembled polystyrene sphere multi-layers as template. After the removal of the template, well-ordered and close-packed spherical pores are left in the films. The thin walls of the adjacent pores make up a three-dimensional network nanostructure in the triple-layer porous Ni3P film. The as-prepared triple-layer porous film delivers significantly enhanced rate capability over the single- and double-layer ones. After 50 cycles, the capacity of the triple-layer Ni3P porous film still sustains 557 mAh g−1 and 243 mAh g−1 at a charge–discharge rate of 0.2 C and 5 C (1 C = 388 mA g−1), respectively. According to the analysis of electrochemical impedance spectrum (EIS), the improved electrochemical performance of the triple-layer film can be attributed to the fast migration of Li+ through surface-passivating layer and the facilitated charge transfer into Ni3P three-dimensional network nanostructure.