Investigation On The Preparation And Performances Of Aromatic Thin Layer Composite Membrane For All Vanadium Redox Flow Battery

In recent years,countries around the world have been competing to develop wind energy and solar energy.However,solar and wind energy fluctuate greatly due to environmental and climate effects.Therefore,the development of large-scale energy storage devices to store these unstable green energy sources becomes the key to sustainable energy development.All-vanadium redox flow batteries have attracted much attention as a safe,efficient and environmentally friendly energy storage device.However,the price of commercialized All-vanadium redox flow batteries membrane has remained high,limiting the large-scale deployment of All-vanadium redox flow batteries.Therefore,the development of low-cost All-vanadium redox flow batteries membrane with excellent performance is of great significance for the development of green energy.The polyamide selective layer of the aromatic polyamide thin layer composite membrane?TFC?has a nano-sized pore size and can be sieved according to the size of the ions.Therefore,TFC membranes have been widely used in water treatment and electrodialysis.This paper attempts to apply TFC membranes to All-vanadium redox flow batteries,and has achieved good results,and on this basis it has been modified.In this paper,porous polyethersulfone membranes with low cost,hydrophilicity and mechanical properties are used as base membranes.Polytetramethylenediamine and trimesoyl chloride were used as monomers to interfacially polymerize polyamide on the surface of porous membrane to prepare TFC membrane.In the process of applying TFC membrane to All-vanadium redox flow batteries,the effects of polymerization times on the morphology,vanadium ion permeability,ion selectivity,area resistance and battery performance of TFC membrane were studied.The experimental results show that the surface of the TFC membrane is more dense,the penetration of vanadium ions is slowed down,and the sheet resistance and coulomb efficiency increase.At the current density of80 mA cm^-2,the coulomb efficiency of the once-polymerized TFC membrane was increased from 64.3%of the base membrane to 95.6%,and the coulomb efficiency of the TFC membrane was further increased to 98.4%after the second interfacial polymerization.In order to further improve the performance of TFC membrane,polyhydrodopamine was modified on the surface of TFC membrane by oxidative polymerization.The effects of surface modified polydopamine on the surface resistance,ion selectivity and battery performance of TFC membrane were studied.The results show that the surface resistance of the modified TFC membrane increases slightly,the ion selectivity increases greatly,up to 182.22,the stability of coulomb efficiency and energy efficiency is significantly improved,and the energy efficiency can remain about 80%after the 160 cycle.At the same time,the effects of base membrane with different thicknesses on the physicochemical properties and electrochemical properties of polydopamine modified TFC membrane were studied.The results show that reducing the thickness of the base membrane can increase the voltage efficiency and energy efficiency of the membrane to some extent.The voltage efficiency and energy efficiency of the modified TFC membrane with a base membrane thickness of 80?m at 80 mA cm^-2 were 85.83%and 84.03%,respectively.The paper finally estimated the price of TFC membrane and polydopamine-modified TFC membrane and compared the performance of different membrane.The results show that the prepared TFC membrane and polydopamine-modified TFC membrane are both more cost-effective than commercial Nafion 115 membrane.This is of great significance to the development of vanadium batteries.