Praparation Of Sulfonated Polyether Ether Ketone Membrane And Its Application In Vanadium Flow Battery And Ion Separation

Ion exchange membrane is a kind of polymer membrane which contains ion groups with selectived permeation to ions in solution.The first membrane was made in 1950,up to now,the materials of membrane is still developing vigorously.Ion exchange membranes has been used in all aspects of industrial society,in which energy is one of the most concerned areas.Ion exchange membranes are widely used in various fuel cells and energy storage systems.In this paper,SPEEK（sulfonated polyether ether ketone）membranes was prepared and a series of characterizations were carried out to proved that SPEEK membrane could be used in vanadium flow battery.We find that the SPEEK membrane with sulfonated degree of 61%had lower vanadium ion permeability than Nafion 117 membrane;While in the test of single battery,the SPEEK membrane with the thickness of 50μm has higher coulomb efficiency（CE）and energy efficiency（EE）.In the time of self-discharge test of vanadium flow battery,the time of self-discharge of SPEEK membrane is twice times as long as Nafion 117 membrane;In the cycle of single cell performance test,after 50 cycles of charging and discharging at current density of 60 mA/cm²,the coulomb efficiency of the vanadium batteries assembled by SPEEK membranes maintained at96%,the energy efficiency maintained at 85%.In addition,SPEEK membranes can be used in diffusion dialysis.The different selective permeation of Li⁺relative to Mg²⁺is realistically observed in the simulated diffusion dialysis tests with different thicknesses of SPEEK membranes.When the thickness of SPEEK membrane is 20μm,the selectivity between lithium ions and magnesium ions reaches 3.11.When the thickness of SPEEK membrane is 50μm,the selectivity between lithium ion and magnesium ion reaches 3.96.The amounts of lithium ions passing through the ion-exchange membranes will decline from 9.13%to 4.59%,while the amounts of magnesium ions passing through the ion-exchange membrane will decline from2.91%to 1.17%.In order to be more suitable for industrial production,simulated salt lake brine solutions and pure water were pumped through the DD dialyzer at different flow intensities.At low flow intensity(5.078 L h^-11 m^-2),we get the highest permeation of lithium ions.While at high intensity(26.889 L h^-11 m^-2),we get the highest selectivity.For the industrial applications,the appropriate flow intensity can be obtained through the investigation of the continuous diffusion dialysis tests.