A highly stable phosphonate‐functionalized anthraquinone is introduced as the redox‐active material in a negative potential electrolyte (negolyte) for aqueous redox flow batteries operating at nearly neutral pH. The design and synthesis of 2,6‐DPPEAQ, (((9,10‐dioxo‐9,10‐dihydroanthracene‐2,6‐diyl)bis(oxy))bis(propane‐3,1‐diyl))bis(phosphonic acid), which has a high solubility at pH 9 and above, is described. Chemical stability studies demonstrate high stability at both pH 9 and 12. By pairing 2,6‐DPPEAQ with a potassium ferri/ferrocyanide positive electrolyte across an inexpensive, nonfluorinated permselective polymer membrane, this near‐neutral quinone flow battery exhibits an open‐circuit voltage of 1.0 V and a capacity fade rate of 0.00036% per cycle and 0.014% per day, which is the lowest ever reported for any flow battery in the absence of rebalancing processes. It is further demonstrated that the negolyte pH drifts upward upon atmospheric oxygen penetration but, when oxygen is excluded, oscillates reversibly between 9 and 12 during cycling. These results enhance the suitability of aqueous‐soluble redox‐active organics for use in large‐scale energy storage, potentially enabling massive penetration of intermittent renewable electricity.

中文翻译：

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接近中性pH值的具有膦酸酯功能的醌氧化还原液流电池，记录容量保持率

将高度稳定的膦酸酯官能化蒽醌作为负电势材料（负电解液）中的氧化还原活性材料引入，用于在接近中性pH值的水性氧化还原液流电池。2，（6-DPPEAQ）（（（（9,10-dioxo-9,10-dihydroanthracene-2,6-diyl）bis（oxy））bis（propane-3,1-diyl））bis（的设计与合成描述了在pH 9及以上具有高溶解度的膦酸。化学稳定性研究表明，在pH 9和12时都具有很高的稳定性。通过将2,6-DPPEAQ与亚铁酸钾/亚铁氰化钾正电解质配对在廉价的非氟化渗透选择性聚合物膜上，该接近中性的醌液流电池表现出开路电压为1.0 V，容量衰减率为每个周期0.00036％和每天0.014％，在没有重新平衡过程的情况下，这是所有液流电池中报告的最低值。进一步证明，当大气中氧气渗透时，电解质的pH值会向上漂移，但是当排除氧气时，在循环过程中会在9至12之间可逆振荡。这些结果增强了水溶性氧化还原活性有机物用于大规模储能的适用性，有可能使间歇性可再生电力得到大规模渗透。