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According to Sinochem New Network, recently, Yang Jiahui and his colleagues from the Energy Storage Technology Research Center at the Beijing Low-Carbon Clean Energy Research Institute of the Energy Group made a breakthrough in the field of long-duration energy storage. The team innovatively proposed phosphonic acid-based ligand complexes, which significantly improved the low-temperature frost resistance and electrochemical stability of the flow battery system. Flow batteries have attracted attention in the field of large-scale energy storage due to their inherent safety, but their insufficient low-temperature freezing resistance of the electrolyte limits their use in northern regions. Through innovative ligand engineering, the research team introduced a novel polyphosphonic acid ligand, diethylenetriaminepenta(methylenephosphonic acid), to form highly stable cage-like complexes, thereby achieving stable control over the complexation structure of the anode electrolyte in flow batteries. Furthermore, the research team also identified the molecular coordination environment and structural evolution patterns of the active substance during the electrochemical process. This technological achievement not only significantly reduces the problem of active substance transmembrane penetration due to the large molecular structure of the ligand, ensuring a Coulombic efficiency of nearly 100% throughout the nearly 7 days of testing, but also endows the electrolyte with ultra-low-temperature freezing resistance at -50.4°C as well as efficient and reversible electron transfer properties, thereby facilitating the use of flow batteries in low-temperature environments. This study proposes a completely new approach for developing phosphonic acid-based ligand complex electrolytes suitable for extreme low-temperature environments, providing material support for the creation of highly stable and long-lasting all-iron flow batteries for use in cold regions of the north and in outdoor energy storage applications in such low-temperature conditions. Furthermore, mechanism studies have further revealed the coordination between ligands and active substances as well as the structural evolution mechanisms during electrochemical processes, providing a basis for the rational design of electrolytes for future flow batteries and the optimization of their performance at low temperatures.