Advances and issues in developing metal-iodine batteries

Metal-iodine batteries (MIBs) hold practical promise for next-generation electrochemical energy storage systems because of the high electrochemical reversibility and low cost. Regardless of the considerable advancements in rechargeable MIBs, several challenges such as unsatisfied energy density and the inferior cycling stability still hinder their widespread applications. Over the past five years, researchers around the world have dedicated enormous resources to the study of battery chemistries and materials based on the progress of MIBs, but there is little systematic overview of these efforts yet. Here, a comprehensive overview related to the design of advanced electrode structures and battery models for MIBs is presented, beginning with the current understanding of the mechanisms and challenges, then methods such as various kinds of composite iodine cathodes, protective interlayers, and relevant solid-state battery systems. The review also underscores the key scientific issues of inhibiting iodine dissolution under reversible reaction conditions. Based on the works described and parallel recent studies in other systems, important and targeted guidelines for further research and development efforts in this field are provided. It is expected that this review will draw more attention to MIBs from both the academic and industrial communities. (C) 2020 Elsevier Ltd. All rights reserved.