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　　New progress in research on high energy density and long life zinc-iodine flow batteries

　　Recently, a research team led by Li Xianfeng and Zhang Huamin, researchers at the Energy Storage Technology Research Department of the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, has made new progress in the research of high-energy-density, long-life zinc-iodine flow batteries. The research results were published online in "German Applied Chemistry" (Angew.Chem.Int.Ed.) as a VeryImportantpaper.

　　Large-scale energy storage technology is a key core technology for realizing the popularization and application of renewable energy. Flow batteries have good applications in the field of large-scale energy storage due to their high safety, large energy storage scale, high efficiency, and long life. prospect. Zinc-iodine flow batteries have good research and application prospects due to their good electrochemical activity, high electrolyte solubility, and high energy density (theoretical energy density can reach 250.59Wh/L). However, current zinc-iodine flow batteries have problems such as short cycle life and low power density.

　　In order to solve the above problems, the research team proposed to use cheap polyolefin porous membranes (US$15/m2) to replace expensive perfluorosulfonic acid ion exchange membranes, which greatly reduces battery costs. In addition, this system uses a mixed solution of KI and ZnBr2 as the positive and negative electrolytes of the battery, which greatly improves the conductivity and stability of the electrolyte in a neutral environment. Since the porous structure of the polyolefin porous membrane exhibits excellent ion conductivity in a neutral environment, the operating current density of the battery is greatly increased.

　　Experimental results show that when operating at 80mA/cm2, the energy efficiency of a single cell reaches 82%, which is 8 times higher than the previously reported zinc-iodine system, and the energy density reaches 80Wh/L; under the operating condition of 180mA/cm2, the energy efficiency of the battery More than 70%, showing good power characteristics. More importantly, the oxidized electrolyte I3- filled in the polyolefin porous structure can react with zinc dendrites, solving the problem of poor battery cycle life caused by zinc dendrites. Even if the battery is short-circuited due to zinc dendrites, the battery performance can be self-recovered through the dissolution of zinc dendrites by I3- in the membrane pores. The single cell of this system has been continuously operated for more than 1,000 cycles at 80mA/cm2, with no obvious performance degradation and showing good stability.

　　To further confirm the practicability of the system, the research team successfully integrated a kW-level stack, which operated stably for more than 300 cycles at 80 mA/cm2, with an energy efficiency of 80%, showing good reliability. This battery is still in the early stages of research, and its reliability under high current density needs to be further improved to promote its practicality and industrialization.

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