Dalian Institute of Materials Research has made new research on high energy density, long-life zinc-iodine flow battery

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Recently, Li Xianfeng and Zhang Huamin, research fellows of the Institute of Energy Storage Technology of the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, have made new progress in the study of high energy density, long-lived zinc-iodine flow batteries. The research results were published online as "Very Important Paper" in "Angew. Chem. Int. Ed."

Large-scale energy storage technology is a key core technology for achieving the universal application of renewable energy. Because of its high safety, large-scale energy storage, high efficiency, and long life, flow batteries have great applications in large-scale energy storage applications. prospect. Because of its good electrochemical activity, high electrolyte solubility and high energy density (theoretical energy density can reach 250.59Wh/L), zinc iodide flow batteries have good research and application prospects. However, current zinc-iodine flow batteries suffer from short cycle life and low power density.

To solve the above problems, the research team proposed to replace the expensive perfluorinated sulfonic acid ion exchange membranes with inexpensive polyolefin porous membranes (15 US dollars/m2), which greatly reduced the cost of the battery. In addition, the 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 the 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. The experimental results show that at 80mA/cm2, the energy efficiency of the single cell reaches 82%, which is 8 times higher than the previously reported zinc iodide system, and the energy density reaches 80Wh/L. Under the 180mA/cm2 operating condition, the energy efficiency of the battery More than 70% show excellent power characteristics. More importantly, the oxidized electrolyte solution I3-, which is filled in the polyolefin porous structure, can react with the zinc dendrite to solve the problem of poor cycling life of the battery due to zinc dendrite. Even if the battery is short-circuited due to zinc dendrite, the battery performance can also be self-healing through the dissolution of I3- to the zinc dendrites in the membrane pores. The system cell continuously operated at more than 1000 cycles at 80 mA/cm2, showing no significant degradation in performance and exhibiting good stability. To further confirm the practicability of the system, the research team successfully integrated a kW class reactor, which has a stable operation of more than 300 cycles at 80 mA/cm2 and an energy efficiency of 80%, showing excellent reliability. The battery is still in the initial stage of research, and it is necessary to further improve its reliability under high current density and promote its practical and industrialization.

The above work provides a good reference for the development of a new generation of high performance liquid flow battery systems, and also provides new ideas for the development of other zinc-based flow batteries.

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