Co-enabled electron reservoir and in situ catalytic reconstruction on MXene for kinetically enhanced room-temperature Na[sbnd]S batteries

Abstract

Room-temperature sodium‑sulfur (RT NaS) batteries hold great promise for next-generation energy storage, yet their practical deployment is hindered by the shuttle effect of polysulfides and sluggish reaction kinetics. Herein, an S@Co0.5Ni0.5Se2@MXene composite cathode is designed and an innovative strategy based on in-situ electrochemical reconstruction coupled with synergistic metal displacement is proposed. During cycling, Cu from the current collector dynamically transforms in situ into a highly catalytic Cu2S phase. Concurrently, Co and Ni species from the precursor are displaced and embedded into the electrode matrix as atomically/ionically dispersed species, with Co undergoing reversible valence changes that may contribute to enhanced charge transfer. DFT calculations confirm that the Ni/Co/Se-doped Cu2S exhibits an upshifted d-band center, optimizes polysulfide adsorption, and lowers energy barriers for both the rate-determining step (Na2S4 → Na2S2) and Na2S decomposition. This synergistic design enables the cathode to deliver a high capacity of 1441.4 mAh g−1 at 5.0 A g−1 and remarkable cycling stability, retaining 97.6% of its capacity after 1000 cycles at 2.0 A g−1 (0.0024% decay per cycle). This work provides a new paradigm for designing high-performance catalysts via in situ reconstruction for advanced RT NaS batteries.