Toward Sustainable Metal‐Iodine Batteries: Materials, Electrochemistry and Design Strategies

Abstract

Due to the natural abundance of iodine, cost‐effective, and sustainability, metal‐iodine batteries are competitive for the next‐generation energy storage systems with high energy density, and large power density. However, the inherent properties of iodine such as electronic insulation and shuttle behavior of soluble iodine species affect negatively rate performance, cyclability, and self‐discharge behavior of metal‐iodine batteries, while the dendrite growth and metal corrosion on the anode side brings potential safety hazards and inferior durability. These problems of metal‐iodine system still exist and need to be solved urgently. Herein, we summarize the research progress of metal‐iodine batteries in the past decades. Firstly, the classification, design strategy and reaction mechanism of iodine electrode are briefly outlined. Secondly, the current development and protection strategy of conventional metal anodes in metal‐iodine batteries are highlighted, and some potential anode materials and their design strategies are proposed. Thirdly, the key electrochemical parameters of state‐of‐art metal‐iodine batteries are compared and analyzed to solve critical issues for realizing next‐generation iodine‐based energy storage systems. Therefore, the aim of this review is to promote the development of metal‐iodine batteries and provide guidelines for their design.

Ionic Competition between Na+ and H+ in Aqueous Sodium-Ion Battery Electrolytes

“…Despite the noteworthy advantages of aqueous electrolytes, the electrolysis of water leads to the oxygen evolution reaction at the anode and the hydrogen evolution reaction at the cathode, resulting in a narrow electrochemical stability window of the electrolyte (1.23 V) . This limitation severely impacts the energy density and the choice of electrodes for aqueous batteries. − To enhance the overall performance of batteries, some research efforts have been focused on finding suitable high-capacity active materials or expanding the electrochemical stability window through additives. − Mukesh Kumar and his colleagues added sulfur to CoS 2 and introduced an ionic liquid to prepare S@CoS 2 –IL anode, where the synergistic effect between different substances effectively suppresses the dissolution of polysulfides and HS – . Wu et al obtained a Mg-based NASICON-structured material Na 3.4 Mn 1.2 Ti 0.8 (PO 4 ) 3 as a cathode using the sol–gel method. , In addition, some studies have focused on improving the electrolyte through additives: Liang et al introduced sodium ferrocyanide [Na 4 Fe­(CN) 6 ] into a high-concentration NaClO 4 -based aqueous electrolyte to fill the surface manganese vacancies in the Fe-doped Prussian blue Na 1.58 Fe 0.07 Mn 0.97 Fe­(CN) 6 ·2.65H 2 O cathode material formed during cycling; Sun et al prepared a mixed electrolyte with low concentration NaNO 3 and glycerol additive, then glycerol forms strong hydrogen bonds with water molecules, effectively expanding the electrochemical stability window of the mixed electrolyte to 2.7 V .…”