Stabilizing a Reversible Sodiation Pathway Through a Partial Conversion and Vacancy-Rich Host in Graphene-Confined...

Transition metal dichalcogenide (TMD) anodes for sodium-ion batteries (SIBs) are hindered by poor conductivity and destructive conversion reactions. Herein, the sodiation pathway in MoSe₂ is re-engineered via synergistic design. Heavy tellurium doping induces a partial conversion reaction, creating a stable, vacancy-rich Na_xMoSeTe intermediate for reversible Na⁺ storage. This engineered host is confined within a robust reduced graphene oxide framework, which acts as a conductive scaffold and mechanical buffer. This unique sodiation mechanism leverages an initial partial conversion to create a stable, vacancy-rich host, which then facilitates highly reversible sodium storage. Consequently, the resulting MoSeTe@rGO anode demonstrates exceptional performance: a high reversible capacity of 512 mAh g^-1 at 1 A g^-1, outstanding rate capability, and remarkable long-term stability, retaining over 97.99% of its capacity after 1000 cycles at 5 A g^-1. Ex situ studies and DFT calculations confirm this vacancy-mediated, reversible sodiation pathway. Furthermore, a full cell constructed with a Na₃V₂(PO₄)₃@C cathode delivers a stable capacity of 368 mAh g^-1 after 800 cycles at 5 A g^-1, showcasing its practical potential. This work presents a new paradigm for designing high-performance TMD anodes, shifting the focus from merely mitigating conversion reaction issues to proactively engineering more stable and efficient electrochemical pathways.