Study Of St-OE Based Solid Polymer Electrolyte

Lithium-ion battery is one of the most widely used secondary energy storage devices,due to its light weight,high energy density and excellent cycle stability.Traditional liquid lithium-ion batteries have safety problems such as liquid leakage and inflammability,while all-solid polymer lithium-ion batteries with higher saf'ety performance have become a research hotspot.Irn this paper,a series of polystyrele-co-polyethylene glycol monomethyl ether methacrylate random copolymer(PSO),polystyrene-b-polyethylene glycol monomethyl ether methacrylate block copolymer(bPSO),PSO random copolymer electrolyte,bPSO block copolymer electrolyte and bPSO/SIS blencded polymer electrolyte were prepared with polyethylene glycol monomethyl ether methacrylate(OE)and styrene(St)as monomers and styrene-isoprene-styrene block copolymer(SIS)as auxiliary material to study the eff'ects of polymer structues,OE and lithium salt content on the electrochemical performance of St-OE based solid polymer electrolytes.The results are as follows:1.PSO random copolymer was synthesized by solution polymerization,and PSO random copolymer electrolyte was prepared by doping lithium salt.It is manifested that the ionic conductivity of PSO rancdom copolymer electrolyte increases overall with the increase of OE con tent and lithium salt concentration.The highest ionic conductivities f'or the PSO copolymer electrolytes are 5.8×10-7 S/em at room temperature an d reach 6.75×10'6 S/cm at 60?,which are obtained at PSO-80 electrolyte with 50 wt%lithium salt.Moreover,the PSO electrolytes possess good compatibility with the lithium electrode and excellent electrochemical stability window.The PSO-70 and PSO-80 electrolyte are electrochemically stable Lup to 4.7 V(vs.Li-/Li).However,the lithium ion migration number of PSO electrolytes is low(about 0.3).2.bPSO block copolymer was synthesized by reversible addition-fragmentation chain transf'er(RAFT)polymerization,and bPSO block copolymer electrolyte was prepared by doping lithium salt.It is found that the iconic conductivity of bPSO block copolynmer electrolyte increases overall with the increase of OE and lithium salt content.The maximum ionic conductivity value of bPSO electrolytes is found to reach 5.97×10-7 S/cm at room temperature and 8.64×10-6 S/cm at 60 ?.The electrochemical stability of the bPSO electrolyte is around 4.5 V(vs.Li+/Li)and lithium ion migration number is relatively high.Finally,the bPSO electrolytes is highly stable in the lithium plating/stripping process in the Li/bPSO/Li battery.3.The bPSO/SIS polymer electrolyte membrane was prepared with bPSO-85 polymer as matrix by doping SIS elastomer.Compared with the bPSO electrolyte,SIS increases the elasticity of the electrolyte film,but slightly decreases its conductivity.The electrochemical stability and lithium ion mobility of the bPSO/SIS electrolyte are affected by doping a large amount of SIS.However,bPSO/SIS electrolyte with 5 wt%SIS elastomer not only retains the excellent electrochemical properties of the bPSO electrolyte,but also improves its conductivity at high temperature.The ionic conductivity of the bPSO/SIS-5 electrolyte is 2.8×10-7 S/cm at room temperature and 1.57×10-5 S/cm at 60 ?.The electrochemical stability is 4.5 V(vs.Li+/Li).