Hydrogen · Fuel Cell Research Center, Korea Institute of Science and Technology (KIST), Seoul, 02792, Korea.
Center for Energy Storage Research, Korea Institute of Science and Technology (KIST), Seoul, 02792, Korea.
Small. 2022 Dec;18(50):e2206284. doi: 10.1002/smll.202206284. Epub 2022 Nov 1.
Polybenzimidazole (PBI) membranes show excellent chemical stability and low vanadium crossover in vanadium redox flow batteries (VRFBs), but their high resistance is challenging. This work introduces a concept, membrane assemblies of a highly selective 2 µm thin PBI membrane between two 60 µm thick highly conductive PBI gel membranes, which act as soft protective layers against external mechanical forces and astray carbon fibers from the electrode. The soft layers are produced by casting phosphoric acid solutions of commercial PBI powder into membranes and exchanging the absorbed acid into sulfuric acid. A conductivity of 565 mS cm is achieved. A stability test indicates that gel mPBI and dense PBI-OO have higher stability than dense mPBI and dense py-PBI, and gel/PBI-OO/gel is successfully tested for 1070 cycles (ca. 1000 h) at 100 mA cm in the VRFB. The initial energy efficiency (EE) for the first 50 cycles is 90.5 ± 0.2%, and after a power outage stabilized at 86.3 ± 0.5% for the following 500 cycles. The initial EE is one of the highest published so far, and the materials cost for a membrane assembly is 12.35 U.S. dollars at a production volume of 5000 m , which makes these membranes very attractive for commercialization.
聚苯并咪唑（PBI）膜在钒氧化还原流电池（VRFB）中表现出优异的化学稳定性和低钒穿通，但它们的高电阻是一个挑战。本工作引入了一个概念，即在两个 60 µm 厚的高导电 PBI 凝胶膜之间组装高度选择性的 2 µm 厚的 PBI 膜，作为软保护层，防止外部机械力和电极上的碳纤维偏离。软层是通过将商业 PBI 粉末的磷酸溶液浇铸到膜中，并将吸收的酸交换成硫酸来制备的。实现了 565 mS cm 的电导率。稳定性测试表明，凝胶 mPBI 和致密 PBI-OO 比致密 mPBI 和致密 py-PBI 具有更高的稳定性，并且凝胶/PBI-OO/凝胶在 VRFB 中在 100 mA cm 下成功测试了 1070 个循环（约 1000 h）。前 50 个循环的初始能量效率（EE）为 90.5 ± 0.2%，停机后在接下来的 500 个循环中稳定在 86.3 ± 0.5%。初始 EE 是迄今为止发表的最高值之一，对于 5000 m 的产量，膜组件的材料成本为 12.35 美元，这使得这些膜非常有吸引力，有望商业化。
