Recent development of membrane for vanadium redox flow battery applications: A review

Responding to rapid growth of the renewable energy applications, it is crucial to develop low cost and high efficient large-scale energy storage systems in order to smooth out the intermittency of the renewable energy resources. As one of the most promising large-scale energy storage systems, vanadium redox flow battery (VRFB) has attracted great attention in recent times. Membrane is one of the key components of VRFB which not only affects the whole cyclability performance but also determines the economic viability of the system. The membrane separates the positive and negative half-cells and prevents the cross-mixing of vanadium ions while providing required ionic conductivity. The ideal membrane should have good ionic exchange capacity; high ionic conductivity, low water uptake, swelling ratio, area electrical resistance and vanadium and other poly halide ions permeability; and good chemical stability, as well as low cost. Numerous efforts have been spent on the development of different types of membranes, including different functional groups ion exchange membrane and non-ionic porous membrane. This paper reviews the research on membranes in VRFB system, including the properties, development of traditional commercial membranes as well as recently developed membranes. It explores various methods of fabrication of the membrane products which have received relatively little attention. A detailed summary table of the new membranes with their properties, fabrication and costs is provided to serve as a reference guide for researchers and industrialists interested in VRFB system building and dynamic modelling set. Subsequently, the challenges and future directions of membrane research are examined.