Study On The Performance And Synthesis Of Polyether Containing Phosphorus Polymer For Lithium Ion Battery

The safety issue of lithium ion battery is a principal risk facing its application,the development of safe electrolyte has become a hot research topic.In this thesis,we carried out different application types of polyether safe electrolytes,the main research contents are as follows:?1?A facile method for preparing composite polymer electrolyte membrane with semi-interpenetrating network is reported.This polymer electrolyte is comprised of polyoxyethylene?PEO?and poly{Tri[3-?methyldimethoxysilyl?propyl]-terminated polypropylene glycol}?TSPPG?crosslinked network.It is important to note that crosslinked network can be self-formed at the assistance of LiBOB without any extra catalyst or additives.SEM images show that the surface of this membrane is homogenous and nonporous.The XRD and DSC results indicate the PEO crystallinity is deteriorated by the crosslinked process.Moreover,the resultant membrane added a small amount of heat-resistant solvent?PC?shows significantly higher ionic conductivity(10-3 S cm^-1),which can be comparable commercial liquid electrolyte,as well as the wider electrochemical window and superior battery performance of LiFePO₄/Li and LiFe_0.2Mn_0.8PO₄/Li cell at ambient temperature.Considering the properties mentioned above,this polymer electrolyte is eligible for lithium battery applications with improve safety and reliability.?2?The composite electrolyte?TSPPG-LLZO?is prepared by LLZO,TSPPG andLiBOB.After doping nano inorganic particles,the electrolyte modulus is improved,and the electrolyte membrane is flexible,which can be able to adapt to the change of lithium volume during charge-discharge process to restrain the growth of lithium dendrite.When the copper foil is modified by the composite electrolyte membrane,the deposition of lithium is more uniform.After adding LiPF6/EC:DMC,the ionic conductivity of gel electrolyte is 10-3S/cm,the cell with the composite electrolyte has super cell performance.?3?An ionic conducting ethyl phosphate-polyethylene glycol based copolymer?abbreviated as EPCP?as a promising flame retardant is synthesized by phosphate ester monomer with polyethylene glycol oligomer in this study.The structure of EPCP is characterized by Gel Permeation Chromatography?GPC?,FT-IR spectra and 1H NMR.The flammability tests demonstrate that the liquid electrolyte with 15 wt.% EPCP?abbreviated as EPCP15-LE?is totally nonflammable.More importantly,benefitted from the ionic transport capability of EPCP,the ionic conductivity of EPCP15-LE at room temperature is comparable with the liquid electrolyte?shorted as LE?.Moreover,the resultant electrolyte possessed wide electrochemical window?4.3 V?,which can be matched with relatively high voltage cathode materials.In addition,the cell using EPCP15-LE exhibits superior cycle performance and excellent rate capability.In a word,this flame retardant ionic conductor is a promising additive for safety-reinforced lithium battery.