Defect Spinel Aluminum Molybdenum Sulfide: A Dual‐Function Catalyst for Polysulfide Conversion and Aluminum Intercalation in Aluminum–Sulfur Batteries

Aluminum-sulfur batteries (ASBs) are regarded as promising energy storage devices due to their cost-effectiveness and safety. However, ASBs suffer from problems of polysulfide shuttling and short lifetimes, which restrict their practical applications. In this work, defect spinel Aluminum molybdenum sulfide (AlMo₄S₈) embedded in carbon nanotubes synthesized via solid-state reaction is applied to ASBs. The carbon nanotube-connected spinel AlMo₄S₈ material effectively mitigates polysulfide shuttling while also contributing its own capacity in ASBs. Besides, AlMo₄S₈ serves as a "bi-directional catalyst" with bimetallic active sites to increase the ion transport pathway, effectively facilitating the reduction of polysulfides and the oxidation of Al₂S₃. The ASBs with AlMo₄S₈/CNTs@S cathode exhibit excellent electrochemical performance with high specific capacity (304.3 mAh g^-1 at 500 mA g^-1). The soft pack batteries fabricated with AlMo₄S₈/CNTs@S cathode (sulfur loading of 3.0 mg cm^-2) maintain a stable capacity for more than 50 cycles.