Rechargeable alkali metal-chlorine batteries: advances, challenges, and future perspectives

The emergence of Li-SOCl₂ batteries in the 1970s as a high-energy-density battery system sparked considerable interest among researchers. However, limitations in the primary cell characteristics have restricted their potential for widespread adoption in today's sustainable society. Encouragingly, recent developments in alkali/alkaline-earth metal-Cl₂ (AM-Cl₂) batteries have shown impressive reversibility with high specific capacity and cycle performance, revitalizing the potential of SOCl₂ batteries and becoming a promising technology surpassing current lithium-ion batteries. In this review, the emerging AM-Cl₂ batteries are comprehensively summarized for the first time. The development history and advantages of Li-SOCl₂ batteries are traced, followed by the critical working mechanisms for achieving high rechargeability. The design concepts of electrodes and electrolytes for AM-Cl₂ batteries as well as key characterization techniques are also demonstrated. Furthermore, the current challenges and corresponding strategies, as well as future directions regarding the battery are systematically discussed. This review aims to deepen the understanding of the state-of-the-art AM-Cl₂ battery technology and accelerate the development of practical AM-Cl₂ batteries for next-generation high-energy storage systems.