Flow batteries are an attractive technology for energy storage of grid-scale renewables. However, performance issues related to ion-exchange membrane (IEM) fouling and crossover of species have limited the success of flow batteries. In this work we propose the use of the solid-state sodium-ion conductor NaSICON as an IEM to fully eliminate active species crossover in room temperature, aqueous, neutral pH flow batteries. We measure the room temperature conductivity of NaSICON at 2.83–4.67 mS cm⁻¹ and demonstrate stability of NaSICON in an aqueous electrolyte with conductivity values remaining near 2.5 mS cm⁻¹ after 66 days of exposure. Charge and discharge of a full H-cell battery as well as symmetric cycling in a flow battery configuration using NaSICON as an IEM in both cases demonstrates the capability of the solid-state IEM. Extensive analysis of aged cells through electrochemical impedance spectroscopy (EIS) and UV–vis spectroscopy show no contaminant species having crossed over the NaSICON membrane after 83 days of exposure, yielding an upper limit to the permeability of NaSICON of 4 × 10⁻¹⁰ cm² min⁻¹. The demonstration of NaSICON as an IEM enables a wide new range of chemistries for application to flow batteries that would previously be impeded by species crossover and associated degradation.

液流电池是用于电网规模可再生能源存储的一种有吸引力的技术。但是，与离子交换膜（IEM）结垢和物质交叉有关的性能问题限制了液流电池的成功。在这项工作中，我们建议使用固态钠离子导体NaSICON作为IEM，以完全消除室温，水性，中性pH液流电池中的活性物质交叉。我们在2.83–4.67 mS cm ^-1下测量NaSICON的室温电导率，并证明NaSICON在水性电解质中的稳定性，电导率值保持在2.5 mS cm ^-1附近暴露66天后。在这两种情况下，使用NaSICON作为IEM的液流电池配置中，完整H电池的充电和放电以及对称循环都证明了固态IEM的能力。通过电化学阻抗谱（EIS）和紫外可见光谱对衰老的细胞进行的广泛分析显示，暴露83天后，没有污染物跨过NaSICON膜，因此NaSICON的渗透率上限为4×10 ^-10  cm ²  min ^-1。NaSICON作为IEM的演示使以前应用于物种的交叉和相关降解阻碍的液化电池应用领域有了新的变化。