Iodine conversion chemistry in aqueous batteries: Challenges, strategies, and perspectives

Aqueous batteries based on iodine conversion chemistry have emerged as appealing electrochemical energy storage technologies due to iodine's intrinsic advantages of fast conversion kinetics, ideal redox potential, and high specific capacity. However, active iodine suffers from several limitations, such as poor thermal stability, inferior electrical conductivity, and polyiodide shuttling, which must be overcome before a real breakthrough and wide application. Over the past decades, researchers worldwide have dedicated substantial effort to tackling the above obstacles. In this review, a systematic summary of recent advances in aqueous iodine-based static batteries (AISBs) is presented. It begins with an introduction to iodine's fundamental physicochemical properties, particularly focusing on the analysis of iodine conversion chemistry, and discussing the corresponding challenges by category. Furthermore, the coping strategies in terms of cathode host selection, electrolyte optimization, separator engineering, and suitable anodes are in-deeply discussed, and the key parameters and work principles are analyzed. The final section shares the thoughts on the potential research opportunities and future directions in advancing AISBs.