Boosting anionic redox of TiS4 via Se anion doping for high-performance Al-ion batteries

Aluminum-ion batteries (AIBs) are gaining attention for large-scale energy storage due to their low cost and high theoretical capacity. However, the existing cathode materials frequently encounter rapid capacity degradation and sluggish reaction kinetics due to the strong interaction with high-charge Al 3+ , which limits the utilization of AIBs. Here, the Se-doping strategy is proposed to facilitate the active participation of anions in charge compensation and enhance the anionic redox process of amorphous anion-rich TiS 4 . A refined amount of Se doping effectively improves reaction kinetics for Al-storage and stabilizes the structure of the material, preventing polysulfide dissolution under high dealumination states. As a result, amorphous TiS 3.5 Se 0.5 delivers unprecedented Al 3+ storage performance, with a stable capacity of 210 mAh g −1 at 500 mA g −1 over 400 cycles. Through detailed characterization, we reveal that a-TiS 3.5 Se 0.5 undergoes reversible Al 3+ insertion, accompanied by anionic redox processes involving S 2 2- and Se n- species, which lays the foundation for further development of anionic-redox-based cathodes for high-performance AIBs. An amorphous TiS 3.5 Se 0.5 cathode, with selenium atoms doped into the TiS 4 structure, has demonstrated enhanced redox activity, enabling faster Al 3+ insertion and improved reaction kinetics due to Se doping. This material has been successfully applied in rechargeable aluminum-ion batteries, offering long-term stability. • Developing a Se-doping synthesized strategy for boosting anionic redox process in TiS 4 for AIBs. • Se doping shifts the p -band center upwards improving both charge compensation and electrical conductivity of TiS 4 . • The increase in Se doping mitigates polysulfide dissolution during the anionic redox processes, thereby enabling highly reversible aluminum-ion storage. • Amorphous TiS 3.5 Se 0.5 demonstrates superior cycling stability for AIBs, maintaining a capacity of 210 mAh g −1 after 400 cycles.