Electron Localization‐Stabilized Inherent Multivalence States Enable D ‐Band Center Upshift Promoting High Redox Activity for Sodium Storage in Cu‐Based VI‐Group Sulfides

ABSTRACT Multivalent transition metal sulfides (TMSs) with rapid electron transport capability and high redox activity hold significant research potential as sodium‐ion batteries (SIBs) anodes. Herein, layered TMSs Cu 2 MS 4 (M = Mo, W) were synthesized via a solvothermal method to compare their sodium storage properties. Compared to the relatively limited valence state changes in Cu 2 WS 4 , Cu 2 MoS 4 exhibits richer multivalent redox activity involving the synergistic interaction of Mo 4+ /Mo 5+ /Mo 6+ and Cu 2+ /Cu + . The material's inherent rich valence states enhance Na + adsorption by regulating the upward shift of the Mo d ‐band center in Cu 2 MoS 4 and optimizing the related electronic interactions, while also effectively improving redox reversibility and reactivity via synergistic multielectron pathways. Therefore, Cu 2 MoS 4 maintains an exceptional capacity retention of 531.2 mA h g −1 after 5500 cycles at 20 A g −1 , and retains 284.6 mA h g −1 even at an ultrahigh rate of 50 A g −1 , demonstrating outstanding rate capability. Theoretical calculations attribute these advantages to enhanced electron localization (post Na + incorporation), higher conductivity, lower ion diffusion barriers, and improved reaction reversibility versus Cu 2 WS 4 . This study establishes multivalent TMSs as a promising strategy for advanced sodium storage, facilitated by their enhanced electron localization effect.