Enhanced Sodium Polysulfide Adsorption by In Situ Construction of NiS ₂ /Cu ₂ S Heterointerfaces and Sulfur Vacancies Enabling High‐Performance Sodium Storage

Abstract Nickel disulfides have been actively investigated as sodium‐ion battery anode materials because of their relatively high capacity and relatively low cost. However, their practical application is severely hindered by overcharge failure in ether‐based electrolytes induced by the dissolution of sodium polysulfides. Herein, sulfur vacancy‐rich NiS ₂ /Cu ₂ S heterojunction nanoclusters anchored on Ti ₃ C ₂ T _x MXene nanosheets (NCMX) are synthesized through a facile solvothermal method. Density functional theory calculation combined with ex situ characterizations illustrates that sulfur vacancies significantly enhance the adsorption of sodium polysulfides, while the heterointerface‐induced built‐in electric field facilitates rapid Na⁺ adsorption and accordingly accelerates their efficient conversion to Na ₂ S. The synergistic effects endow the NCMX anode with exceptional sodium‐ion storage performances. It delivers remarkable reversible capacity (668 mAh g ⁻¹ at 0.1 A g ⁻¹ ), superb rate capability (482 mAh g ⁻¹ at 5 A g ⁻¹ ), and impressive cycling stability (543 mAh g ⁻¹ after 1000 cycles at 1 A g ⁻¹ with a negligible capacity decay of 0.0034% per cycle). Such a strategy of simultaneous construction of heterojunction and sulfur vacancies paves a new avenue to tackle the polysulfide shuttling to design advanced high‐performance transition metal disulfide anodes for sodium‐ion storage.