W-Doping and NH ₃ Preintercalation Engineered VS ₂ with Interlayer N-Doped Carbon Confinement as a High-Conductivity Anode for Lithium-Ion Batteries

Two-dimensional (2D) layered VS2 is a promising lithium-ion batteries (LIB) anode for high capacity but is limited by low conductivity and severe volume expansion in cycling. By using the solvothermal method, this study presents a synergistic modification strategy: W6+ (1.37 Å) doping substitutes V4+ (1.31 Å) to induce lattice distortion and sulfur vacancies, reducing interfacial charge-transfer resistance (Rct) from 946.8 to 147.8 Ω. Simultaneously, NH3 preintercalation expands the interlayer spacing from 5.7 to 9.7 Å, enabling in situ pyrrole polymerization and Li+ diffusion. Annealing at 600 °C converts interlayer polypyrrole to N-doped carbon (60.7% pyrrolic N, 31.7% pyridinic N), forming a VS2 structure featuring rigid nitrogen-doped carbon (NC) interlayers, which enhance conductivity and buffer structural stress during cycling. The obtained VS2 after W-doping and NC intercalation (W-VS2@NC) demonstrates 705 mAh g–1 at 1 A g–1 (93% retention over 1000 cycles) and 526 mAh g–1 even at 5 A g–1. Mechanistic analyses confirm that W-doping introduces XPS-validated V3+/V2+ heterovalence for rapid electron transport, interlayer carbon layers (9.2 Å spacing) buffer volume changes via a “spring effect”, and N-doping (7.6% quaternary N) provides extra Li+ adsorption sites. This work presents a strategy for the synergistic optimization of conductivity and structural stability in layered sulfide anodes.