Preparation And Modification Of PAN Nano-porous Membranes For All Vanadium Redox Flow Battery

All Vanadium Redox Flow Battery(VRB) is an efficient large-scale electrochemical energy storage technology, it has a fast start-up speed, high energy efficiency, long service life, flexible design, simple maintenance, low operating cost and it's safe and environmental friendly. Proton conducting membrane is a key part of VRB, nanofiltration membrane has just been applied to VRB over the years, it works by screening mechanism and has a high ion selectivity.Nano-porous membrane was prepared using polyacrylonitrile(PAN) as material with multi steps, so we focus on the influence of several key preparing factors on physical and electrochemical properties, also, Nano-porous membrane was modified in order to reduce the membrane resistance.Nano-porous membrane was prepared under different heat treatment temperatures, the effect on mechanical strength, water uptake, area resistance, V ion permeation, and charge-discharge properties were investigated. It indicated that as the heat treatment temperature rose, mechanical strength got better, water uptake and V ion permeation decreased. Membrane prepared under 130? had the lowest area resistance and the highest efficiency.Influence of heat treatment time and hydrolysis time were studied, too. It was found that long heat treatment time was good for improving mechanical strength and reducing permeation of V ion. Membrane heated for 7min had a lowest area resistance. The FTIR result showed that only part of the cyano-groups were hydrolyzed. When the hydrolysis time was over 24 hours, area resistance would increase rapidly.ZrP was precipitated in the surface of Nano-porous membranes, TGA result showed thermal decomposition temperature of modified membrane was a little bit lower than that of unmodified membrane, the more ZrP, the higher weight loss rate, but it's still over 400 ?, which indicated the thermostability of composite membrane was good. Charge-discharge properties indicated when the concentration of ZrOCl2 was 0.15mol/L, the modified membrane had the best cell performance. The energy efficiency increased by 6% after the modification while the coulombic efficiency was the same. Long-term operation showed a good stability.