Unlocking high-voltage sodium ion batteries with MOF-derived Cr₂S₃@C anode materials

Extensive research on transition metal sulfide (TMS) materials highlights their potential as promising anode materials for sodium-ion batteries (SIBs). However, most TMS anodes exhibit average reaction potentials above 1.5 V vs. Na⁺/Na, resulting in full cell discharge plateaus below 2 V. Clearly, the inherently high reaction potentials associated with conversion reactions present a challenge in achieving high-voltage full cells. This not only significantly constrains the energy density utilization but also narrows the application scenarios for the final full cells. In this study, we present a cutting-edge MOF-derived Cr₂S₃@C composite as a promising anode material for SIBs, featuring a dual-mechanism charge storage process encompassing both conversion and alloying reactions. Remarkably, the conversion reactions occur at a low potential plateau and, in conjunction with alloying reactions, offer considerable promise for developing high-voltage full cells. The developed anode material exhibits an outstanding reversible specific capacity of 764 mAh g^-1, achieving a substantial energy density of 206 Wh kg^-1 at a cut-off voltage of 4.0 V when paired with a Na₃V₂(PO₄)₃ cathode. This study provides new insights into the rational selection of TMS anodes for SIBs and demonstrates the utility of Nernst-based theoretical screening for guiding nanocomposite anode design.