Sulfonated polyimide/s-MoS2 composite membrane with high proton selectivity and good stability for vanadium redox flow battery

• DOI: 10.1016/j.memsci.2015.04.053
• Publication Date: 2015-05-08T03:00:17Z
• Authors: Jinchao Li; Yaping Zhang; Shuai Zhang; Xiaodong Huang
• Keywords: Flow battery; Nafion; Molybdenum disulfide

Abstract We report the fabrication and properties of high performance and inexpensive composite membranes of sulfonated polyimide (SPI) and sulfonated molybdenum disulfide (s-MoS 2 ) for the vanadium redox flow battery (VRFB) application. Scanning electron microscopy (SEM) images reveal the uniformity of SPI/s-MoS 2 membrane. Both EDS and XRD results verify the existence of s-MoS 2 in SPI/s-MoS 2 membrane and show the interaction between SPI and s-MoS 2 . The physico-chemical properties of as-prepared SPI/s-MoS 2 membrane, including water uptake and ion exchange capacity, etc. are evaluated and compared to those of SPI, SPI/MoS 2 and Nafion 117 membranes, respectively. The SPI/s-MoS 2 membrane possesses increased proton conductivity and reduced vanadium ion permeability than pure SPI membrane, and it has the highest proton selectivity (2.24×10 5 S min cm −3 ) among all membranes. The VRFB with SPI/s-MoS 2 membrane presents a higher coulombic efficiency ( CE ) and energy efficiency ( EE ) compared with Nafion 117 at the current density ranging from 20 to 80 mA cm −2 . The SPI/s-MoS 2 membrane shows a longer discharge time (193 h above 0.8 V) than Nafion 117 (72 h). Moreover, the SPI/s-MoS 2 membrane exhibits stable operation performance up to 500 cycles with no significant decline in CE and EE . All experimental results confirm that the SPI/s-MoS 2 membrane is suitable for use in VRFB.