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The vanadium redox flow battery (VRFB) is a promising sustainable energy storage system. In VRFB batteries, ion exchange membranes (IEM) are used to prevent the formation of cathode/anode short circuits and avoid electrolyte crossover and side reactions, while allowing proton conduction to maintain battery neutrality.

So far, perfluorosulfonic acid (PFSA) membrane is the most widely used IEM for VRFB. However, the severe vanadium ion penetration of the PFSA membrane will shorten the battery life and lead to unsatisfactory battery performance.

A research team led by Professor Li Huiyun, Professor Yu Shuhui and Dr. Ye Jiaye from Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences developed a hybrid film based on two-dimensional nano hybrid materials. Improve the performance of VRFB. 

The research was published on Advanced Functional Materials on November 9.

In the newly developed membrane, graphene oxide (GO) nanosheets are embedded in the PFSA matrix as a "barrier" to reduce the penetration of vanadium ions. Tungsten trioxide (WO3) nanoparticles grow in situ on the surface of GO nanosheets to overcome the electrostatic effect and enhance the hydrophilicity and dispersion of GO nanosheets.

"These hydrophilic tungsten trioxide nanoparticles on the surface of GO nanosheets act as proton active sites to promote proton transport," said Dr. Jiaye Ye, the first author of the study.

A thin layer of porous polytetrafluoroethylene (PTFE) is sandwiched between the membrane as a reinforcing layer to enhance the stability of the membrane.

Under the synergistic effect of WO3@GO and PTFE layer, the hybrid membrane exhibits high ion selectivity. Compared with commercial Nafion membranes, VRFB single cells with optimized hybrid membranes have higher coulombic and energy efficiency.

In their previous study published in the Journal of Chemical Engineering, the research team developed a sandwich structure composite film based on one-dimensional functionalized silicon carbide nanowires.

The researchers introduced functionalized silicon carbide nanowires into a perfluorosulfonic acid (PFSA) matrix and sandwiched between ultra-thin porous polytetrafluoroethylene layers.

This hybrid membrane not only maintains good proton conductivity, but also effectively reduces the penetration of vanadium ions, thereby improving the performance of the VRFB battery.

These studies provide a preparation strategy for high-performance IEMs designed for VRFB based on one-dimensional and two-dimensional modified materials, which can be extended to other fields including water treatment and fuel cells.

Tungsten trioxide nanoparticles grown in situ on graphene oxide nanosheets modulate ion selectivity of high-performance vanadium redox flow battery membranes

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Zhang Xiaomin Chinese Academy of Sciences xm.zhang@siat.ac.cn

Chinese Academy of Sciences Headquarters

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Copyright © 2021 American Association for the Advancement of Science (AAAS)