Abstract Due to their preferential cation transport, dense cation exchange membranes like Nafion membranes are unsuitable for Zn/Br redox flow batteries which require bi-ionic transport of Zn2+ and Br- ions. This work shows that scaling the water cluster size of Nafion membranes by a pre-hydration treatment can achieve not only a high ionic conductivity but also a bi-ionic transport property. Small angle X-Ray scattering, diffusion cell, and electrochemical analysis verify that by increasing the pre-hydration temperature, the water clusters are expanded, resulting in an increase of water uptake, ionic conductivity and the anion transference number. The bi-ionic transport and low area specific resistance induced by the pretreatment enable the successful operation of a Zn/Br redox flow battery with a NRE-212 membrane. Compared with a conventional porous membrane, the properly treated Nafion membrane has an 11.3% higher energy efficiency indicating that the dense structured ion exchange membrane can be used for Zn/Br flow batteries by scaling the water cluster size.

中文翻译：

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缩放用于高性能锌/溴氧化还原液流电池的 Nafion 膜的水簇大小

摘要 由于其优先的阳离子传输，像 Nafion 膜这样的致密阳离子交换膜不适用于需要 Zn2+ 和 Br- 离子双离子传输的 Zn/Br 氧化还原液流电池。这项工作表明，通过预水化处理缩放 Nafion 膜的水簇大小不仅可以实现高离子电导率，还可以实现双离子传输特性。小角度X射线散射、扩散池和电化学分析证实，通过提高预水化温度，水团簇膨胀，导致吸水率、离子电导率和阴离子转移数增加。由预处理引起的双离子传输和低面积电阻率使具有 NRE-212 膜的 Zn/Br 氧化还原液流电池能够成功运行。