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

Abstract 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 (AlMo 4 S 8 ) embedded in carbon nanotubes synthesized via solid‐state reaction is applied to ASBs. The carbon nanotube‐connected spinel AlMo 4 S 8 material effectively mitigates polysulfide shuttling while also contributing its own capacity in ASBs. Besides, AlMo 4 S 8 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 Al 2 S 3 . The ASBs with AlMo 4 S 8 /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 AlMo 4 S 8 /CNTs@S cathode (sulfur loading of 3.0 mg cm −2 ) maintain a stable capacity for more than 50 cycles.