Low‐cost aqueous polysulfide (APS) chemistry has recently attracted intensive research as it is a promising candidate for redox flow batteries. However, the intrinsic properties, electrochemical stability, and compatibility with sodium super ionic conductor (NASICON) membrane have been rarely demonstrated to clarify the challenges on the road to practical application. Herein, a detailed study on the electrochemical reactions and failure mechanism of aqueous polysulfides is presented. Starting from investigating the intrinsic stability, the optimized concentration of NaOH is determined. Through constructing a hybrid Na‐APS cell to avoid the effect from the counterelectrode, the cycling behavior is found to be stable under the capacity cut‐off condition, while severe decay occurs after ≈80 cycles. Comprehensive analysis of the decay mechanism shows the decomposition and loss of active materials during the long‐term cycles. Meanwhile, the NASICON separator surface is found to be corrosive after electrochemical exposure with APS solution under a high‐pH environment. It is anticipated that the systematic study of the APSs’ electrochemical reactions and decay mechanism could be beneficial for their further application in redox flow batteries.

中文翻译：

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氧化还原液流电池中钠水多硫化物转化反应的电化学反应和失效机理研究

低成本含水多硫化物（APS）化学方法最近吸引了广泛的研究，因为它是氧化还原液流电池的有希望的候选者。但是，很少有内在特性，电化学稳定性以及与钠超离子导体（NASICON）膜的相容性来阐明在实际应用道路上的挑战。在此，对水性多硫化物的电化学反应和破坏机理进行了详细的研究。从研究内在稳定性开始，确定NaOH的最佳浓度。通过构建一个混合的Na‐APS电池以避免反电极的影响，发现在容量截止条件下循环行为是稳定的，而≈80次循环后会发生严重的衰减。对衰减机理的综合分析显示了长期循环中活性物质的分解和损失。同时，在高pH环境下，用APS溶液进行电化学暴露后，NASICON隔膜表面被发现具有腐蚀性。可以预期的是，对APS的电化学反应和衰减机理的系统研究可能有益于它们在氧化还原液流电池中的进一步应用。