Lai Yiming, Wan Lei, Wang Baoguo
The state key laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China.
Membranes (Basel). 2019 Jul 19;9(7):89. doi: 10.3390/membranes9070089.
The development of chemically stable and high conductive membranes is one of the most important issues to improve the performance of vanadium flow batteries (VFBs). Herein, poly(vinylidene fluoride) (PVDF)/graphene composite nanoporous membranes were easily fabricated by manipulating crystallization processes. The graphene was used to enhance membrane selectivity and conductivity. In the nanoscale channels of the membranes, the graphene nanosheets reduced the apertures among the crystal grains, thus restraining vanadium ions crossover due to the size exclusion effect. Moreover, the oxygen groups on the graphene improved the surface hydrophilicity and formed hydrogen bonds with the PVDF polymer chains, which facilitated the proton transport. The composite membranes, with a 0.15 wt % graphene loading, showed a selectivity of 38.2 and conductivity of 37.1 mS/cm. The single cell exhibited a coulomb efficiency of 94.7%, a voltage efficiency of 88.5%, and an energy efficiency of 83.8%, which was 13% higher than that of the pristine PVDF membranes. The composite membranes showed excellent stability during 100 charge-discharge cycles. All these results indicate that the PVDF/graphene composite membrane is a promising candidate for VFB applications.
开发化学稳定且高导电的膜是提高钒液流电池（VFBs）性能的最重要问题之一。在此，通过控制结晶过程轻松制备了聚偏氟乙烯（PVDF）/石墨烯复合纳米多孔膜。石墨烯用于提高膜的选择性和导电性。在膜的纳米级通道中，石墨烯纳米片减小了晶粒间的孔径，从而由于尺寸排阻效应抑制了钒离子的交叉。此外，石墨烯上的氧基团改善了表面亲水性并与PVDF聚合物链形成氢键，这促进了质子传输。负载0.15 wt%石墨烯的复合膜显示出38.2的选择性和37.1 mS/cm的电导率。单电池表现出94.7%的库仑效率、88.5%的电压效率和83.8%的能量效率，比原始PVDF膜高13%。复合膜在100次充放电循环中表现出优异的稳定性。所有这些结果表明，PVDF/石墨烯复合膜是VFB应用的有前途的候选材料。
