Ultrahigh Proton/Vanadium Selective and Durable Nafion/TiZrO4 Composite Membrane for High-Performance All-Vanadium Redox Flow Batteries

A single-phase TiZrO4 nanotube (TiZrO4NT)-incorporated Nafion composite membrane with ultrahigh ion selectivity is designed and fabricated for vanadium redox flow batteries (VFBs). A single cell of the VFB using the potential Nafion/ TiZrO4NT composite membrane shows high-capacity retention, low self-discharge rate, and high cycling efficiency. Furthermore, an excellent proton conductivity of 75.9 mS cm(-1) at room temperature and 23-fold higher H+/VO2+ selectivity (3.61 x 10(6) S min cm(-3)) are obtained for the Nafion/TiZrO4NT composite membrane compared with a state-of-the-art Nafion-212 membrane (55.4 mS cm(-1) and 0.168 x 10(6) S min cm(-3)). Subsequently, a high VFB performance is achieved with 1.7-fold higher discharge capacity and impressive cycling Coulombic efficiency (CE, 99.8%), voltage efficiency (VE, 84.1%), and energy efficiency (EE, 83.9%) using the Nafion/TiZrO4NT composite membrane than those of the Nafion-212 membrane (CE, 89.9%; VE, 81.2%; and EE, 72.9%). Moreover, the low area resistance of the membrane, high-rate capability, excellent battery durability of 300 charge-discharge cycles, and high self-discharge time ensure the incorporation of the TiZrO4NT filler into the Nafion matrix and improve the selectivity of the fabricated Nafion/TiZrO4NT composite membrane. Consequently, the Nafion/TiZrO4NT composite membrane with ultrahigh ion-selectivity and superior battery performance is considered a potential candidate for high-performance VFBs.

Automated summary

By incorporating TiZrO4 nanotubes into a Nafion composite membrane, a VFB with ultrahigh ion selectivity and superior performance is achieved, including high proton conductivity and increased discharge capacity.