For The Preparation Of Polyether Ether Ketone Ion Exchange Membrane And Alkyl Sulfonic Acid Anthraquinone Electrolyte And Its Application In Flow Battery

Flow battery（RFB）is a new type of electrochemical energy storage device,which has attracted wide attention due to its advantages of independent energy storage and power output,simple structure,large-scale energy storage,long cycle life and high safety.Electrolyte and ion exchange membrane are the key components of RFB.The electrolyte realizes the conversion of electrical energy and chemical energy through the oxidation-reduction reaction of the electrolyte to achieve the purpose of energy storage.The ion exchange membrane is mainly used to separate the positive and negative electrolytes and to transport ions between the positive and negative of RFB.At present,the most successful commercial flow battery is the all-vanadium flow battery,The all-vanadium flow battery that with vanadium ion electrolyte is the ripest in technique and most commercialized flow battery.However,the application of all-vanadium flow battery is limited by the which mainly uses vanadium ion electrolyte,but has the characteristics of high cost,highstrong acidity and high powerful oxidization,which seriously affects the service life of the flow battery.The most widely used ion exchange membrane is the Nafion membrane,but the the cost ofapplication of Nafion membrane is too high,and Nafion membrane as a proton exchange membrane also has the problem of excessivealso limited by its high cost and high vanadium ion permeability,which seriously affects its wide application.Therefore,the development of low-cost,high-performance electrolytes and ion exchange membranes is in great neededof great significance to the further development and application of flow batteries.In view of In order to solve the problems of electrolyte and ion exchange membrane,we used anthraquinone（AQ）with redox activitywas used as raw material to prepare organic anolyte for flow battery,and introduced sulfonic acid groups was introduced onto AQ to improve solubility of AQ anthraquinone molecules in water.Solubility of the ion exchange membrane,and thereby increasing the volume energy density of the battery,using poly ether ketone as the base materiawas usedl to prepare a new type of ion exchange membrane for flow batteries,and by sulfonating the polyether ether ketonethe conductivity of membranes increased by to increaseing their degree of sulfonationthe conductivity of the ion exchange membrane,In order to reduce vanadium ion permeability Permeability of vanadium ion of ion exchange membrane,amphoteric ion exchange membraneimidazole functionalized polyether ether ketone was prepared,by blending sulfonated polyether ether ketone and imidazoliumole functionalized polyether ether ketone were blended to obtain amphoteric ion exchange membrane.Donnan repulsion of imidazoliumions cation reduces the vanadium ion permeability of membranes permeability of vanadium ions.The main work and conclusions of this paper are as follows:（1）Methyl-containing polyether ether ketone（MPEEK）is synthesized from methylhydroquinone and 4,4’-difluorobenzophenone,adding K₂CO₃ to provide an alkaline environment,and reacting at 170 ^oC.Sulfonated polyether ether ketone membranes with different sulfonation degrees（SPEEK-x,x is the sulfonation degree of SPEEK）are synthesized by MPEEK sulfonation.The water absorption and water swelling of SPEEK-x increase with the increase of the degree of sulfonation in the membrane because SPEEK contains strong hydrophilic groups（sulfonic acid groups）.In addition,the permeability of vanadium ions will increase as the degree of sulfonation increases.At a current density of 60 m A cm^-2,the energy efficiency of VRFB assembled with SPEEK-75 film is the best,with an energy efficiency of64.7%.The output power density of VRFB assembled by SPEEK-100 is the largest,and its maximum power density is 300 m W cm^-2.The SPEEK membrane has a simple synthesis process and low cost,and has good fracture resistance.（2）MPEEK is synthesized from methylhydroquinone and 4,4’-difluorobenzophenone,adding K₂CO₃ to provide an alkaline environment,and reacting at 170 ^oC.Imidazole functionalized polyether ether ketone（Im PEEK）is synthesized by MPEEK and N-methylimidazole.Amphoteric ion exchange membrane（SPEEK/Im PEEK-x,x is the percentage of SPEEK to the total mass of the membrane）is made by blending SPEEK and Im PEEK.The performance of the amphoteric ion exchange membrane is affected by the ratio of sulfonated polyether ether ketone to imidazole-functionalized polyether ether ketone.The synthesis process is simple and the cost is low.The WU and SR of SPEEK/Im PEEK-x increased with the increase of SPEEK content in the membrane.The vanadium ion penetration of SPEEK/Im PEEK-25 and SPEEK/Im PEEK-50 is negligible,compared to Nafion 212 and SPEEK membranes.The amphoteric membrane effectively reduces cross-contamination between electrolytes and improves battery efficiency.At a current density of 60 m A cm^-2,the performance of the VRFB assembled by SPEEK/Im PEEK-90 is the best,with the coulombic efficiency,voltage efficiency and energy efficiency being 98.8%,75.6%and 74.5%,respectively.The maximum power density of the VRFB assembled by SPEEK/Im PEEK-90 is 150 m W cm^-2.These results indicate that the amphoteric ion exchange membrane with PEEK as the main chain has good application prospects in flow batteries.（3）Three kinds of alkyl sulfonate anthraquinones（1-hydroxy-2-oxopropane sulfonic acid anthraquinone（1,2-AQPSH₂）,2,6-dioxopropane sulfonic acid anthraquinone（2,6-AQDPSH₂）and1-hydroxy-2-oxopropane sulfonic acid anthraquinone（1,4-AQPSH₂））were synthesized from 1,2-dihydroxyanthraquinone,2,6-dihydroxyanthraquinone,and 1,4-dihydroxyanthracene with propane sultone,respectively.Their synthesis process is simple and easy to prepare.The solubility and oxidation-reduction property of the three alkylsulfonic acid anthraquinones in1 mol/L Na Cl aqueous solution under neutral conditions were studied in details.1,4-AQPSH₂,was chose and used as anodolyte,2,2,6,6-tetramethylpiperidinol（4-OH-TEMPO）used as catholyte,and Nafion 212was used as an ion exchange membrane to assemble a neutral water-based organic redox flow battery cell.The electrolyte effectively reduces the corrosion of the electrolyte to the battery and improves the battery life.The open circuit voltage of the flow battery was about 1.0 V,and at the current density of 60 m A cm^-2,the coulombic efficiency,energy efficiency and voltage efficiency of the cell were 97%,68%and 69%,respectively.There was no significant reduction of discharge capacity of the battery after 75charging and discharging g cycles at a current density of 60 m A cm^-2.These results indicate that 1,4-AQPSH₂ has a good application prospect as the anolyte of neutral water-based organic redox flow batteries.