Vanadium redox flow battery(VRB)

which is regarded as one of the most promising devices for massive electricity storage in renewable energy and energy-saving processes

has attracted much attention

because of its long life-time

simple configuration and independent power and capacity ratings.Proton conductive membrane

one of key materials in VRB

performs the role of conducting protons during charge/discharge recycle

and prevents vanadium ions from direct contact between the positive and negative electrolytes.To achieve high energy efficiency

long life and low cost of VRB stack

the membrane should meet the requirements of high conductivity

chemical and mechanical resistance

low permeability of vanadium ions and acceptable cost.So far

Nafion membranes are generally employed in VRB due to their both high conductivity and chemical stability

however

their extremely high cost and poor ion selectivity have become the main barrier of commercialization of VRB.In this review

a detailed introduction about recent progress in the field of proton conductive membranes for VRB is given

including three aspects:(i)post-treated Nafion membranes to improve selectivity;(ii)non-perfluorinated membranes from polymerization and sulfonation of monomers; and(iii)nano-porous membranes based on difference between ion stokes radius and its valence

which provides selectivity for protons towards vanadium ions.Finally

there is a highlight of the relationship between morphology and performance of the advanced proton conductive membranes for research and development in future.