UV-VIS spectrophotometer was employed to investigate the permeation behavior in transmembrane electrolyte ions for all-vanadium redox flow battery (VFB).Emphasis is placed on the impact on transmembrane osmosis of VO2+ ions with external factors such as concentration

temperature

state-of-charge (SOC)

electric field and osmotic pressure.It was helpful to explore the effects of ion diffusion and side reactions on the capacity loss for VFB by correlating the osmotic coefficient of different vanadium ions.The results indicate that it could increase the energy efficiency and reduce the transfer rate of VO2+ ions by improving the electrolyte concentration.Lowering the system temperature helps inhibit the cross-contamination during long term use and eliminating the side reactions.The osmotic coefficient of VO2+ ions decreased when increasing the SOC.As positive electric field was employed in electrolyte solution

VO2+ ions transmembrane diffusion would be accelerated within the aggravation of self-discharge; The osmotic pressure between the anode and cathode acclerates the permeation of VO2+

leading to a capacity loss for VFB.