Preparation And Application Of Composite Solid Electrolyte In An All-solid Battery

Conventional lithium-ion batteries with organic liquid electrolytes possess potential safety hazards such as flammability,leakage and explosion.The employment of polymer solid electrolytes can effectively solve the safety problems caused by the application of liquid electrolytes.The advantages of polymer electrolytes include higher mechanical strength,higher interface stability between electrode and electrolyte.However,existing problems such as low room temperature conductivity and narrow electrochemical window would hinder the application of polymer electrolytes.In order to improve the room temperature conductivity of the polymer solid electrolytes and the room temperature battery performance,polyethylene oxide(PEO)-based polymer electrolyte system has been studied and modified by reinforcing 3D framework and using succinonitrile as plasticizer.Also,both solution casting and in-situ polymerization processes have been applied during the modification process,and two new polymer solid electrolytes with high safety and stable electrochemical performance have been prepared.The specific research results are as follows:1.PEO,LiTFSI and succinonitrile(Succinonitrile,referred to as SN)were added into anhydrous acetonitrile and mixed thoroughly.Then the homogeneous solution was cast on the surface of thin glass fiber film and dried to obtain the composite electrolyte.By altering the amount of LiTFSI and SN,the optimum composition of the composite solid polymer electrolyte with the highest conductivity could be determined.A new composite solid polymer electrolyte PEO-SN₂₅-LiTFSI₁₀-GF with high ionic conductivity of 2.85×10^-4S cm^-1(25 ?)and good mechanical property has been successfully synthesized.Its electrochemical window exceeds 5.5V(vs.Li/Li⁺).In addition,it exhibits a tensile strength exceeding 8 MPa.The assembled LFP/PEO-SN₂₅-LiTFSI₁₀-GF/Libattery showed good cyclic performance.After 100cycles at 0.2C,the capacity retention maintained at 98.5%.Also,the battery showed favorable rate performance.In addition,The NCM811/PEO-SN₂₅-LiTFSI₁₀-GF/Libattery showed a capacity retention rate of 92.7%after cycling at 0.1C for 60 cycles at room temperature.2.Polyethylene glycol(diol)diacrylate(PEGDA),LiTFSI and SN were mixed and subjected to light curing polymerization.Consequently,a new type of solid polymer electrolyte with ultra-high room temperature conductivity has been successfully prepared.The obtained PEGDA-SN₈₀-LiTFSI₈electrolyte has an ionic conductivity of 4.02×10^-3S cm^-1at 25 ? and an electrochemical window of up to5.0V(vs.Li/Li⁺).The assembled LFP/PEGDA-SN₈₀-LiTFSI₈/Libattery showed good cyclic performance.After 200 cycles at 0.2C,the capacity retention maintained at89.5%.Also,the battery showed favorable rate performance.