Mo-doped and vacancy-rich Ni₂P@NC anode: A dual-strategy approach to high-capacity and long cycle life sodium-ion...

The development of high-performance anode materials for sodium-ion batteries (SIBs) remains critical to overcome the limitations of lithium-ion technologies. In this work, Mo-doped Ni₂P encapsulated in nitrogen-doped carbon (Mo-Ni₂P@NC) SIB anodes with nanosheet-stacked porous architectures through a solvothermal and chemical vapor deposition (CVD) approach were synthesized. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses confirmed lattice expansion due to Mo substitution. Electrochemical evaluations revealed that Mo doping significantly enhanced the initial Coulombic efficiency (ICE) from 51.6 % (pristine Ni₂P) to 70.2 % and achieved a reversible specific capacity of 456 mAh g^-1 at 2.0 A g^-1 after 2000 cycles. Density functional theory (DFT) calculations demonstrated that Mo doping induced charge redistribution, lowered Na⁺ adsorption energy. Furthermore, vacancy defects produced by Mo-doping facilitate rapid ion transport and pseudocapacitive-dominated Na⁺ storage behavior minimized volume changes, ensuring long-term stability. Simultaneously, the optimized Mo-Ni₂P@NC-2||Na₃V₂(PO₄)₃/C full-cell delivered 143 mAh g^-1 after 200 cycles at 0.1 A g^-1, highlighting its practical application. This work elucidates the synergistic effects of heteroatom doping and vacancy in enhancing SIB anode performance, providing a strategy for designing high-ICE and durable energy storage materials.