Synergistic enhancement of Ni₂P anode for high lithium/sodium storage by N, P, S triply-doping and soft...

Transition metal phosphides have demonstrated excellent performance in the field of energy conversion and storage, where nickel phosphide is one of the most prominent type of phosphides. However, achieving long cycle life with higher specific capacity in the case of Ni₂P is still a great challenge. In this study, the composition and structure of Ni₂P composites are rationally and precisely adjusted by heteroatoms doping and micelle-assisted methods to attain high capacity for longer cycles at high rate. Among all studied combinations, nickel phosphide particles anchored to triple heteroatom (N, P, S) doped carbon network skeleton (Ni₂P@NPS) exhibited specific capacities of 727.3, 586.6, and 321.5 mA h g^-1 after 1000 cycles at 1, 2 and 6 A g^-1 for lithium-ion batteries (LIBs) and 230.1 mA h g^-1 at 1 A g^-1 for sodium-ion batteries (SIBs) after 560 cycles. The introduction of heteroatoms optimized the electronic structure of the electrode materials and promoted mass and charge transfer, while triple-heteroatom doped carbon substrates and uniformly dispersed spherical structures formed an active three-dimensional conductive network structure that provided a stronger driving force and richer channels for Li⁺/Na⁺ transport. Theoretical calculations showed that the high content of pyrrole nitrogen as well as the additional sulfur ensured improved electrical conductivity and enhanced ion adsorption performance. This study encourages further research into the synergistic effect of N, P, S co-doping materials for improving Li⁺/Na⁺ storage and the exploration of other heteroatom co-doping systems.