Membranes are a critical component of redox flow batteries (RFBs), and their major purpose is to keep the redox-active species in the two half cells separate and allow the passage of charge-balancing ions.
Indeed, preparing tailored membranes, i.e., membranes with well-controlled ionic channel sizes can result in a significant improvement of battery performance.
Once a clear understanding of the correlation between membrane apparent properties (such as conductivity, permselectivity and permeability) and cell capacity retention and performance is established through validated numerical models, development of a battery with optimized operating parameters will be made possible.
The first studies on the permeation of active species through the membrane in operating vanadium flow batteries were done by Xi et al. (2008) [ 99] and Sun et al. (2010) [ 100] and featured concentration monitoring of the reservoirs as a function of time using a dialysis cell.
P. Silambarasan, A.G. Ramu, M. Govarthanan, W. Kim, I.S. Moon. Cerium-polysulfide redox flow battery with possible high energy density enabled by MFI-Zeolite membrane working with acid-base electrolytes.
Modified Celgard membranes employed in Zn-based batteries: BMA:EBIH polymer ( a ), ( b) Zincate ions crossover through Celgard5550 and modified Celgard 5550, and power density of Celgard3501 and modified Celgard 3501-based Zn-slurry flow batteries ( c ). Reproduced with permission from [ 18, 19 ].