Preparation And Performance Study Of PEO-based Polymer Electrolyte Modified For All-solid-state Lithium Batter

All solid-state lithium batteries have become a popular research direction due to their advantages such as high energy density,high safety performance,and simple structure.As a key material for all solid-state batteries,the selection of solid-state electrolytes will greatly affect the electrochemical performance and practical application of all solid-state batteries.At present,the mainstream solid-state electrolyte systems include polymers,oxides,and sulfides.Among them,polymer solid electrolytes are expected to be the first to achieve industrial application due to their advantages such as easy processing and good compatibility with electrodes.However,a single polymer solid electrolyte has problems such as low ion conductivity,narrow working voltage window,and low strength,which cannot meet the performance requirements of all solid-state lithium metal batteries.In order to improve the room temperature lithium ion conductivity of solid-state electrolytes and promote the development of all solid-state batteries,PEO based electrolytes were modified from two directions:composite metal organic framework fillers and polymer blends.Two new types of solid-state electrolytes with advantages such as high ion conductivity,high safety,strong mechanical properties,and stable electrochemical performance were designed and prepared.The chemical structure,morphology,thermal properties,mechanical and electrochemical properties of the electrolyte film were studied using characterization methods such as XRD,SEM,DSC,TGA,tensile testing,and AC impedance spectroscopy.Simultaneously,solid-state electrolytes were applied to all solid-state batteries and the performance of the batteries at different magnification rates was systematically studied.The specific research results are as follows:（1）MIL-101（Fe）nanomaterials with a size of 2～3μm were prepared by solvothermal method,and then composite with polyethylene oxide（PEO）polymer electrolyte to obtain a PEO-LITFSI-10wt.%MIL-101（Fe）composite solid electrolyte with uniform composition,high ionic conductivity,and stable electrochemical performance.The morphology,mechanical properties,thermal stability,ion mobility,electrochemical stability and lithium contact stability of PEO-LITFSI-10wt.%MIL-101（Fe）composite solid electrolyte were systematically studied.The morphology,mechanical properties,thermal stability,ion mobility,electrochemical stability and lithium contact stability of P composite solid electrolyte were systematically studied.Simultaneously assemble all solid-state batteries with PEO-LITFSI-MIL-101（Fe）composite solid electrolyte and study the performance of the batteries at different temperatures and rates.When EO:Li=16:1,the content of MIL-101（Fe）is 10wt.%,The conductivity reaches its maximum(3.64×10^-5 S·cm^-1 at 30℃),wide electrochemical window（5.25 V）,high lithium ion migration number（0.42）,good thermal stability and mechanical properties.The Li Fe PO₄|PLM10|Li all solid-state battery assembled with PLM10 electrolyte exhibits good rate and cycling performance at 50℃.The first discharge specific capacity at 0.1C,0.2C,0.3C,0.4C,0.5C,and 1C rates is 164.0,159.9,156.9,151.7,148.2,and 102.2 m Ah·g^-1,respectively;After 80 cycles at a rate of 0.1C,the capacity remains at 90.1%.The composite polymer electrolyte has good metal lithium contact stability and the ability to inhibit lithium dendrite growth.The assembled Li|PLM10|Li battery can stably cycle for 400 hours at 50℃and 0.1 m A·cm^-2 current density.（2）PEO/PVDF-HFP（SN）was prepared by blending PEO with PVDF-HFP as the matrix,composite solid plasticizer succinonitrile（SN）,and lithium bis（trifluoromethylsulfonyl）imine（Li TFSI）as the lithium salt.The proportions of each material component were optimized,with PEO/PVDF-HFP-5wt.%SN electrolyte exhibits the highest ionic conductivity(7.06×10^-5 S·cm^-1 at 30℃)and a wide electrochemical window（5.1 V）,high lithium ion migration number（0.59）,and high stability with Li|0.2PPHS-5wt.%SN|Li can stably cycle for over 1300 hours at a current density of0.1m A·cm^-2 at 50℃.The all solid-state lithium-ion battery Li Fe PO₄|0.2PPHS-5wt.%SN|Li assembled based on this composite solid electrolyte exhibits superior cycling performance.The first discharge specific capacity at 0.1C,0.2C,0.3C,0.4C,0.5C,and 1C rates at 50℃is 157.5,153.8,147.7,140.9,132.6,and 61.7m Ah·g^-1,respectively;After cycling at a rate of 0.1C for 200 cycles,the capacity remained at 89.2%.