Study On GMA-OE Based Solid Polymer Electrolyte

Electrolyte plays a very important part in lithium ion battery.Traditional orgaNic liquid electrolytes have great obstacles to the development of lithium-ion batteries because of their safety problems such as Volatility,leakage and flammability are the main disadvantages,which hinder the development of traditional organic liquid electrolytes.The solid polymer electrolyte has attracted great attention due to wide electrochemical window and no liquid leakage and it has been considered as a promising substitute for liquid electrolytes.In my work a copolymer of glycidyl methacrylate(GMA)and polyethylene glycol monomethyl ether methacrylate(OE)was prepared as a new polymer solid electrolyte.The structure of the copolymer was characterized by GPC,NMRmDSC and FT-IR.The conductivity,electrochemical stability window and lithium ion transference number of th e electrolyte membrane were analyzed and tested by electrochemical workstation.Compatibility of electrolyte membrane with lithium metal using battery testing system.The main results are as follows.,(1)Solid polymer electrolyte based on the random copolymer PGO-60,PGO-70.PGO-80 and PGO-90 from the monomers of glycidyl methacrylate(GMA)and oligo(ethylene oxide)methyl ether methacrylate(OE)was successfully synthesized.According to the results of NMR measurement,the actual ratio of polymer is very close to that of feed ratio,and the polymerization is ideal.The molecular weight of the polymer measured by GPC is between 32.2 k and 52.8 k.The Tg of the polymer measured by DSC increases with the increase of LiClO4 content.The electrochemical test results showed that the conductivity is 5.81×10-7 S/cm(PGO-90,LiClO4=50 wt%)at room temperature,and the maximum conductivity of 2.08×10-5 S/cm at 50 ?.(PGO-70).T he electrochemical stability window can reach 4.4 V(PGO-60,PGO-90),and the maximum lithium ion transference number(tLi+)is 0.549±0.054 for PGO-60.All electrolyte membranes have good compatibility with lithium metal.(2)Hydrolysis of the cpoxy group in PGO under acidic conditions gave birth to a ring-opening polymer HPGO.NMR test results showed that the hydrogen proton characteristic peak of the epoxy group disappeared.The FT-IR test found that HPGO had a stronger-O-H tensile vibration peak,and the absorption peak associated with the epoxy group at 910 cm-1 was weakened,indicating that the epoxy group was successfully opened.The electrochemical test results showed that the conductivity was 2.26×10-6 S/cm(HPGO-70,LiClO4=30 wt%)at room temperature,and the maximum conductivity of 2.71×10-5 S/cm at 50 ?(HPGO-60).The maximum tLi+=0.693±0.083 for HPGO-60 and electrochemical stability window of 4.4 V(HPGO-90).All electrolyte membranes had good compatibility with metallic lithium.Compared with PGO,HPGO had improved room temperature conductivity and lithium ion transference number,but the electrochemical stability window was slightly reduced.(3)Three different block polymers of PEO45-b-PGMA95,PEO53-b-PGM46 and PEO45-b-PGMA46 were prepared by RAFT polymerization.NMR test results confirmed all polymer chemical structures.The GPC test results showed that the PDI distribution of the polymer was between 1.13 and 1.22.The Tg of the polymer measured by DSC increased with the increase of LiClO4 content.The electrochemical test results showed that the conductivity of 6.00×10-7 S/cm(POE53-b-PGM46,LiClO4=50 wt%)at room temperature,and the conductivity is 4.50×10-6 S/cm at 50 0C.(POE45-b-PGMA95).Electrochemical stability window up to 4.5 V(POE45-b-PGMA46),the maximum tLi+=0.695 for POE45-b-PGMA95.Compared with PGO and HPGO,the electrochemical stability window of the block polymer was improved,and all electrolyte membranes had good compatibility with metallic lithium.