Research progress on rechargeable aluminum sulfur (Al-S) batteries based on different electrolyte systems

Metal aluminum is inexpensive, pollution-free, safe to use, and abundant in resources. It has great potential in electrochemical energy storage, with a theoretical specific capacity of up to 2980 mAh g⁻¹. Sulfur not only has the advantages of abundant raw materials and low prices, but also has a theoretical capacity of 1675 mAh g⁻¹. The theoretical energy density of Al-S batteries can reach up to 1340 Wh kg⁻¹ when matched with metallic aluminum. However, the current research on Al-S batteries is still in its early stages, and the impact of differences in electrolyte systems on the electrochemical performance and working mechanism of Al-S batteries is not yet clear. The research on the electrochemical reaction mechanism, capacity degradation mechanism, and strategies to improve charge transfer kinetics of aluminum sulfur batteries is crucial for improving their electrochemical performance. From this perspective, this paper comprehensively summarizes the electrochemical performance, charging/discharging mechanisms, and battery level cost advantages of Al-S batteries with different electrolyte systems. The influence of the phase transition process of S and the shuttle effect of polysulfides on the electrochemical performance of Al-S batteries is elucidated based on different electrolyte systems. In addition, in response to the key issues currently existing in Al-S batteries, the next research directions are summarized and prospected.