Branched sulfonated polyimide/s-MWCNTs composite membranes for vanadium redox flow battery application

A novel sulfonated multi-wall carbon nanotubes (s-MWCNTs) filler is synthesized by ring opening reaction. And then, a series of branched sulfonated polyimide (bSPI)/s-MWCNTs composite membranes are also prepared for application in vanadium redox flow batteries (VRFBs). The optimized bSPI/s-MWCNTs-2% composite membrane has lower vanadium ion permeability (2.01 x 10(-7) cm(2) min(-1)) and higher proton selectivity (1.06 x 10(5) S min cm(-3)) compared to those of commercial Nafion 212 membrane. Moreover, the VRFB with bSPI/sMWCNTs-2% composite membrane exhibits higher coulombic efficiencies (CEs: 96.0-98.2%) and energy efficiencies (EEs: 79.7-69.5%) than that with Nafion 212 membrane (CEs: 86.5-92.5% and EEs: 78.5-67.6%) at 80-160 mA cm(-2). The VRFB with bSPI/s-MWCNTs-2% composite membrane has stable battery performance over 400 cycles at 100 mA cm(-2), whose EE value is in the top level among previously reported SPI-based composite membranes. The results show that the bSPI/s-MWCNTs-2% composite membrane has a great prospect in VRFB application. (c) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

A novel sulfonated multi-wall carbon nanotubes filler was synthesized and prepared for application in vanadium redox flow batteries. The optimized composite membrane showed improved barrier properties and selectivity, leading to higher coulombic and energy efficiencies compared to commercial Nafion 212 membrane.