Preparation Of Composite Polymer Electrolyte Membrane And Its Application In Lithium Batteries

Faced with the problems of global environmental pollution and energy crisis,it is crucial to seek efficient and clean energy storage and conversion systems.Lithium-ion batteries have the advantages of light weight,high energy density,and good cycle performance,and are currently one of the most widely used energy storage devices.First,the electrolyte is an important part of the lithium-ion battery,which has a very important impact on the performance of the battery.Traditional organic electrolytes have seriously hindered the development of lithium-ion batteries due to their shortcomings such as volatility,flammability,and easy leakage.The solid-state lithium battery has the advantages of high energy density,high safety,and shape plasticity,which has become a current research hotspot.However,at the same time,solid-state lithium-ion batteries have disadvantages such as low ionic conductivity at room temperature,poor interface compatibility with positive and negative electrodes,and large interface impedance between electrolyte/negative electrodes.Therefore,the key to the development of solid-state batteries is to prepare solid-state electrolyte materials with high electrical conductivity and high stability.In response to the above problems,different polymer materials have been prepared in this paper and a series of in-depth studies have been carried out.The specific work is as follows:（1）A novel single-ion solid-state polymer electrolyte P（AN-AMPSLi）was prepared by radical polymerization and solution casting methods.The final single-ion polymer electrolyte membrane was obtained by blending P（AN-AMPSLi）with PVDF-HFP with good film forming properties.The ionic conductivity,lithium ion migration number and electrochemical stability window of the solid polymer electrolyte were improved,and the interfacial compatibility between the electrolyte membrane and the electrode was improved.The interfacial impedance remained stable at 580Ωon the tenth day,and the end of 100 cycles The post-discharge capacity is 124.8 m Ah g^-1,and the capacity retention rate is 84.5%.It shows good cycle performance in the LFP-Li solid-state battery charge-discharge system,which provides the possibility for the application of solid-state lithium metal batteries.（2）In order to further improve the cycle performance of solid-state batteries and the interfacial compatibility between electrolyte membrane and lithium anode,sulfonated polyvinylidene fluoride-hexafluoropropylene（PVDF-HFP）and chlorosulfonic acid were used as raw materials to synthesize sulfonated polyvinylidene fluoride.A series of SPVDFLi-HFPx/PVDF-HFP composite electrolyte membranes were prepared by solution casting method.By comparison,it was found that when SPVDFLi-HFP and PVDF-HFP were mixed in a 1:1 mass ratio,the obtained polymer film had the best ionic conductivity and electrochemical window,and the lithium ion migration number increased from 0.34 to 0.81,and its LFP-The Li solid-state battery exhibits excellent cycling performance and rate capability,and the interfacial compatibility and interfacial impedance between the electrolyte membrane and the electrode are both more excellently improved compared to previous work..（3）A Polyethylene glycol methyl ether methacrylate-acrylonitrile（PPA）polyelectrolyte membrane with excellent toughness was prepared by a fast film-forming method of photo-induced cross-linking.By1-butyl-3-ethylimidazolium trifluoromethanesulfonimide salt（[EBIm][FSI]）and 1-butyl-2-methylpyrrolidine trifluoromethanesulfonimide salt([PYR₁₄][FSI])to modify the PPA polymer matrix.By comparison,it was found that the crystallinity of SPE based on the modification of[PYR₁₄][FSI]lowest,the glass transition temperature is lowest,and the ionic conductivity increases by an order of magnitude at 30°C.Li deposition/stripping curves demonstrate the good interfacial compatibility between the[PYR₁₄][FSI]-modified electrolyte membrane and the electrode,showing excellent cycling stability.Applying it to LFP-Li solid-state batteries,after cycling at different rates,the discharge capacity can still be recovered to 154m A cm^-2 after the density is drastically reduced to 0.1 C,After 150 cycles,the coulombic efficiency of the battery is still above 90%.It shows that the[PYR₁₄][FSI]modified polymer film has a strong application potential in lithium metal batteries.