Two-dimensional metal-organic framework nanosheets-modified porous separator for non-aqueous redox flow batteries

Abstract

Non-aqueous redox flow batteries (NARFBs) are promising for large-scale energy storage. However, the lack of high performance membrane is still impeding their further development. Two-dimensional (2D) metal-organic framework (MOF) nanosheets-modified porous separators are prepared by the filtration method. The NARFBs constructed with the 2D MOF nanosheets-modified separator exhibit substantially higher Coulombic efficiency (91.0% vs 82.9%) without obvious compromise on voltage efficiency (93.7% vs 94.2%), and larger average discharge capacity (1.30 vs 0.86 Ah L−1) compared with the pristine Celgard separator at 4 mA cm−2. Such performance is originated from the unique microstructure of 2D-MOF nanosheets. The interlayer spaces assembled by the nanosheet layers enable the fast transport of supporting electrolyte but impede the crossover of active materials and impose limited effect on the separator resistance. This work provides a facile and efficient strategy to mitigating the crossover effect in NARFB.