Unraveling the Anchoring Effect of MXene-Supported Single Atoms as Cathodes for Aluminum–Sulfur Batteries

As an alternative energy storage system, the stable cycle and high-rate performance of aluminum–sulfur (Al–S) batteries are increasingly affected by the dissolution of intermediate Al polysulfide (Al₂S_n) into the electrolyte. Introducing anchoring materials that can promote Al₂S_n conversion is an effective way to solve this problem. However, the lack of an interaction mechanism between Al₂S_n and anchoring materials hinders the design of anchoring materials. Here, we used single-atom-loaded MXene (SA@MXene) as a representative anchoring material to systematically investigate the binding strength between SA@MXene and Al₂S_n, the sulfur reduction process on MXene, and their geometric configurations, stabilities, and electronic structures. We evaluated the reaction activity of the various SA@MXene nanosheets and discovered four high-performance cathode candidates for Al–S batteries (SA = Y, Nb, Mo, Tc) with a minimum reaction energy barrier of 0.23 eV. Importantly, to unravel the interaction mechanism between Al₂S_n and the anchoring material, we proposed an activity volcano by consolidating the decisive S₈*, Al₂S₈*, and Al₂S₁₂* binding strengths, which provides a significant roadmap for designing cathodes for Al–S batteries. The proposed study of the Al–S conversion process will benefit the understanding of sulfur chemistry and provide valuable inspiration for the design of other catalytic reaction processes.