Nibel Olga, Rojek Tomasz, Schmidt Thomas J, Gubler Lorenz
Electrochemistry Laboratory, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland.
Laboratory of Physical Chemistry, ETH Zürich, 8093, Zürich, Switzerland.
ChemSusChem. 2017 Jul 10;10(13):2767-2777. doi: 10.1002/cssc.201700610. Epub 2017 Jun 12.
All-vanadium redox flow batteries (VRBs) have attracted considerable interest as promising energy-storage devices that can allow the efficient utilization of renewable energy sources. The membrane, which separates the porous electrodes in a redox flow cell, is one of the key components in VRBs. High rates of crossover of vanadium ions and water through the membrane impair the efficiency and capacity of a VRB. Thus, membranes with low permeation rate of vanadium species and water are required, also characterized by low resistance and stability in the VRB environment. Here, we present a new design concept for amphoteric ion-exchange membranes, based on radiation-induced grafting of vinylpyridine into an ethylene tetrafluoroethylene base film and a two-step functionalization to introduce cationic and anionic exchange sites, respectively. During long-term cycling, redox flow cells containing these membranes showed higher efficiency, less pronounced electrolyte imbalance, and significantly reduced capacity decay compared to the cells with the benchmark material Nafion 117.
全钒氧化还原液流电池（VRB）作为一种有前景的储能装置，能够实现可再生能源的高效利用，因此引起了广泛关注。在氧化还原液流电池中，用于分隔多孔电极的膜是VRB的关键组件之一。钒离子和水通过膜的高渗透率会损害VRB的效率和容量。因此，需要具有低钒物种和水渗透率的膜，其特征还在于在VRB环境中具有低电阻和稳定性。在此，我们提出了一种两性离子交换膜的新设计概念，该概念基于将乙烯基吡啶辐射接枝到乙烯-四氟乙烯基膜中，并通过两步功能化分别引入阳离子和阴离子交换位点。在长期循环过程中，与使用基准材料Nafion 117的电池相比，包含这些膜的氧化还原液流电池显示出更高的效率、不太明显的电解质失衡以及显著降低的容量衰减。
