Synthesis Ofnew Polymer Solid Electrolyte And Research Of All Solid Lithium Metal Batteries

High-energy rechargeable lithium metal batteries are favored because of their high energy density and long service life.However,they have been hindered by dendrite growth and safety issues due to the use of liquid electrolytes.Solid polymer electrolyte(SPE)can effectively solve the above problems,but the traditional SPE has the disadvantages of low ionic conductivity at room temperature,large electrode/electrolyte interface impedance,and insufficient mechanical strength.These problems hinder the application of polymer solid-state lithium batteries.Therefore,designing a new SPE has become one of the hot topics of research in various countries today.The molecular design and film-forming structure of the material are the main factors affecting the performance of the polymer electrolyte.Based on these two points,this article creatively constructed a super-strong and super-tough polymer solid electrolyte-the solid polymer electrolyte(MS-PEGDA)formed by the 3D three-dimensional interpenetrating network structure adopts the metal organic framework(MOF),Tetrakis(3-mercaptopropionic acid)pentaerythritol(PETMP)and new polyethylene glycol diacrylate(PEGDA)are used as raw materials to synthesize ternary ordered co-polymer precursors under room temperature and UV pretreatment;The body slurry is cast on the surface of the positive and negative electrodes,and the film is formed by in-situ polymerization of light/heat.This polymer solid electrolyte has the characteristics of easy processing,high mechanical strength(stress 9.4MPa),super toughness(strain～500%)and high room temperature ion conductance(0.226 mS cm’1).Using in-situ polymerization,the formed electrolyte has good interface compatibility with the electrode surface and lower interface impedance(～550Ω).In addition,the new polymer electrolyte also has an electrochemical stability window of up to 5.4V,making it compatible with various high-voltage cathode materials to build high energy density lithium ion/lithium metal batteries.Solid polymer lithium metal batteries of lithium iron phosphate(LiFePO4,LFP),high nickel ternary cathode materials(LiNi0.8Co0.1Mn0.1O2,NCM811)and high pressure lithium cobaltate(LiCoO2,LCO)at room temperature and 0.2 C rate All of them can circulate stably for a long time.At 40℃,the Li ‖ LiFePO4 full battery is discharged at 0.1 and 0.5 C rates,and the discharge capacity of 163.3 and 141.1 mAh g-1 can be obtained respectively;after 500 cycles at 0.5 C,the discharge capacity of the full battery remains at 123.1 mAh g-1(retention rate is 85.6%),showing great practical application potential.Based on PEGDA,we designed and synthesized a polymer electrolyte membrane(SMA-g-PEGDA)with controllable hyperbranched,space-twisted double helix structure,achieving room temperature ion conductivity of up to 1.8 mS cm-1.At 0.1 C and 25℃,Li ‖ LiFePO4 full batteries assembled with SMA-g-PEGDA can provide a discharge capacity of 160.7 mAh g-1,which is still as high as 158.7 mAh g-1 after 130 cycles;at 25℃ and 0.5 C,the first-cycle discharge capacity of the battery can reach 148.4 mAh g-1,the discharge capacity retention rate after 160 cycles is 96.8%,and the average Coulomb efficiency is 98.6%.Compared with the aforementioned polymer solid electrolyte,this polymer electrolyte has more excellent electrochemical performance.In general,the two new polymer electrolytes are notable for their simple manufacturing and excellent performance,and at the same time lay the foundation for the industrialization of lithium metal batteries at room temperature.