ABSTRACT

Non-aqueous redox flow batteries (NARFBs) hold potential application as an electricity energy storage for the intermittent renewable energy and can operate with high voltage and energy density. However, their further development is impeded by lacking proper membrane. Herein, a flexible free-standing anionic metal-organic framework (MOF) -based membrane is prepared through a solution casting method, with an anionic MOF (UiO-66-SO3Li) and polyvinylidene fluoride. The prepared membrane shows an impressive ionic selectivity (37.6) of Li+ to N-(ferrocenylmethyl)-N,N-dimethyl-N-ethylammonium (Fc1N112+) ions and high ionic conductivity. Benefitting from the unique micropore structure of MOF and the anionic transport channels of Li+ across the membrane, the resultant Li-based hybrid NARFB delivers a high-capacity retention (99.95% per cycle) over 500 cycles with a well-assembled stable interphase after long time lithium plating/stripping which decrease the voltage efficiency during the cycling. Calculations reveal that the membrane easily desolvates Li+ in the unique micropore structure of MOF before Li-deposition occurs, which suppresses parasitic reaction and accelerate Li uniform deposition. This work provides a viable method to design bifunctional NARFB membranes which achieve ion sieving and ion exchange functions.

Jiashu Yuan, Xiaotang Shi, Qianyuan Qiu, et al. Ion Selective Bifunctional Metal-Organic Framework-Based Membrane for Li Metal-Based Non-Aqueous Redox Flow Battery, ACS Applied Energy Materials. 2023, 6, 416−423