The low aqueous solubility of 2,2,6,6-tetramethylpiperidinooxy (TEMPO) severely limits the capacity of aqueous organic redox flow batteries (AORFBs). Herein, a microemulsion solubilization strategy is developed to address this issue. By screening the co-solvent and the surfactant, a high aqueous solubility of 3.45 M is realized in the microemulsion consisting of acetonitrile and tetrabutylammonium chloride. Physicochemical characterizations reveal that the alkyl chains of tetrabutylammonium chloride are partitioned in the organic phase to realize the fusion and equilibrium of the organic and water phases, which realizes a superior stability, decent ionic conductivity and low viscosity. The AORFB fed with the 2.5 M electrolyte shows a capacity of 60.6 Ah L−1, which is one of the highest practical capacities among TEMPO-based AORFBs. This work manifests a facile and universal strategy by simply regulating the electrolytic solution to realize a high capacity in AORFBs, which shows advantages over the complicated molecule engineering strategy.

中文翻译：

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TEMPO 微乳剂可在水性有机氧化还原液流电池中实现极高容量的阴极


2,2,6,6-四甲基哌啶氧基 （TEMPO） 的水溶性低严重限制了水性有机氧化还原液流电池 （AORFB） 的容量。在此，开发了一种微乳溶解策略来解决这个问题。通过筛选助溶剂和表面活性剂，在由乙腈和四丁基氯化铵组成的微乳液中实现了 3.45 M 的高水溶性。物理化学表征表明，四丁基氯化铵的烷基链在有机相中分配，实现有机相和水相的熔融和平衡，从而实现了优异的稳定性、良好的离子电导率和低粘度。用 2.5 M 电解质进料的 AORFB 显示出 60.6 Ah L ⁻¹ 的容量，这是基于 TEMPO 的 AORFB 中最高的实用容量之一。这项工作通过简单地调节电解溶液来实现 AORFBs 中的高容量，展示了一种简单而通用的策略，显示出优于复杂分子工程策略的优势。