Preparation And Electrochemical Performance Of Composite Electrolyte Based On Inorganic Fast Ionic Conductor LATP

Conventional liquid electrolytes for lithium ion batteries usually have irreversible decomposition and safety problems,while solid electrolytes are considered to be the key to improve the energy density and safety of lithium ion batteries.The combination of polymer electrolyte and inorganic solid electrolyte is considered as a feasible strategy to obtain high-performance solid composite electrolyte.Organic-inorganic composite electrolyte is usually composed of polymer matrix,inorganic inert ceramic filler or ceramic fast ionic conductor,which can integrate the advantages of polymer and inorganic electrolyte.Compared with polymer solid electrolyte and inorganic solid electrolyte,organic-inorganic composite electrolyte has excellent mechanical properties,high ionic conductivity and good interface stability.In this paper,the inorganic solid electrolyte LATP with NASICON structure is selected as the research object.The inorganic solid electrolyte LATP was successfully synthesized by sol-gel method and incorporated with PVDF/PMMA and PVDF/TPU polymer matrix,and the composite electrolyte was successfully prepared.The best synthesis conditions were selected by material characterization and electrochemical performance test.The test results are as follows:1. An inorganic solid electrolyte Li_1+xAl_xTi_2-x?PO₄?₃ was synthesized by sol-gel method.The effects of different synthetic conditions,such as Al content,calcination temperature and sintering time on LATP were investigated,respectively.The optimum synthesis conditions were found that the mole fraction of Al incorporation was x=0.3(Li_1.3Al_0.7Ti_1.7?PO₄?₃),calcination temperature was 900?and the sintering time was4 h.2. PVDF/PMMA was selected as polymer matrix,and the composite electrolyte was successfully prepared by adding LATP with different mass fraction.Through the related characterization and testing,the optimal amount of LATP incorporation was selected as 4wt%.The distribution of inorganic particles in the membrane was more uniform when 4wt%LATP was added into the composite electrolyte.After adding LATP,the thermal stability of the composite electrolyte was improved and the crystallinity was decreased.The composite electrolyte has a high liquid absorption rate.The conductivity was electrochemical window of the composite electrolyte film with LATP was more than 5 V,and the interface stability was good,which could meet the working requirements of all lithium-ion batteries on the market.At 0.1 C,LPP-4 showed the highest first discharge specific capacity of 147.5 m Ah g^-1.After 50 cycles,the discharge specific capacity was132.3 m Ah g^-1,the capacity retention rate was 89.6%,and the coulomb efficiency was close to 100%.3. PVDF/TPU was selected as polymer matrix,and the composite electrolyte was successfully prepared by adding LATP with different mass fraction.The optimal addition of LATP was 3%.The composite electrolyte with LATP has better thermal stability.The 4.23×10^-3 S cm^-1 at 80?.The electrochemical window of all composite electrolyte samples was higher than 5 V?vs.Li/Li⁺?.The first discharge specific capacity of LPT-3battery was 167.2 m Ah g^-1 at 0.1 C,and the coulomb efficiency was close to 100%.After50 cycles,the capacity retention rate was 78.6%.The results showed that the battery had good electrochemical performance at high charge-discharge rate.