Redox flow batteries (RFBs) based on lithium polysulfide (Li-PS) chemistry present great opportunities for large-scale energy storage and electric vehicles because of their use of abundant raw materials and their higher energy density compared with traditional flow batteries. However, to successfully implement Li-PS RFBs, issues related to the crossover of PS species through a membrane separator must be resolved. In this work, we demonstrate a facile method for fabricating a novel multifunctional electrochemical membrane (mECM) consisting of an organic ion exchange membrane reinforced with a porous carbon nanotube layer and a boron nitride layer. This rational design endows the membrane with remarkable ion selectivity and dimensional stability in organic electrolyte, leading to a greatly enhanced Li⁺/PS ion selectivity, which exceeds that of a commercial polyolefin separator (i.e., Celgard 2325) by three orders of magnitude. A Li-PS RFB with the mECM exhibited stable electrochemical performance (0.05% capacity decay per cycle after 40 cycles) with 78% capacity retention over 100 cycles at 0.75C, while a reference cell with a Celgard 2325 membrane rapidly lost its capacity (0.33% capacity decay per cycle and 33% capacity at 100 cycles). Our results strongly suggest that the mECM with its high Li⁺/PS ion selectivity is a promising membrane separator for developing high-performance Li-PS RFB systems.

基于多硫化锂 (Li-PS) 化学的氧化还原液流电池 (RFB) 为大规模储能和电动汽车提供了巨大的机会，因为与传统液流电池相比，它们使用了丰富的原材料和更高的能量密度。然而，要成功实施 Li-PS RFB，必须解决与 PS 物种通过膜分离器交叉相关的问题。在这项工作中，我们展示了一种制造新型多功能电化学膜 (mECM) 的简便方法，该膜由用多孔碳纳米管层和氮化硼层增强的有机离子交换膜组成。这种合理的设计使膜在有机电解质中具有显着的离子选择性和尺寸稳定性，从而大大提高了 Li ⁺/PS 离子选择性，超过商用聚烯烃隔膜（即 Celgard 2325）三个数量级。带有 mECM 的 Li-PS RFB 表现出稳定的电化学性能（40 次循环后每次循环容量衰减 0.05%），在 0.75C 下 100 次循环后容量保持率为 78%，而带有 Celgard 2325 膜的参考电池迅速失去其容量（0.33每个循环的容量衰减百分比和 100 次循环的容量衰减为 33%）。我们的结果强烈表明，具有高 Li ⁺ /PS 离子选择性的 mECM是开发高性能 Li-PS RFB 系统的有前途的膜分离器。