Interface Regulation Of LATP Inorganic Electrolyte For All-solid-state Lithium Battery

In recent year,lithium-ion batteries are widely used in electronic equipment and electric vehicles.However,the organic electrolyte has the risk of leakage or even spontaneous combustion,which limits its further development.It is found that the all-solid-state lithium metal batteries with inorganic solid electrolyte have the advantages of high safety and energy density,and are considered as one of the best alternatives to lithium-ion batteries.The NASICON-type inorganic electrolyte Li_1.3Al_0.3Ti_1.7（PO₄）₃（LATP）is an ideal solid electrolyte material due to its high lithium-ion conductivity,wide electrochemical window and high environmental stability.However,Ti⁴⁺of LATP is easily reduced to Ti³⁺by lithium metal anode,resulting in electrolyte inactivation.The contact between LATP and electrode is poor and the interface impedance is high.In order to solve the above problems,we modified and regulated the structure of LATP inorganic electrolyte.Firstly,PVDF polymer electrolyte was used to modify the interface of LATP ceramic pellet to improve the interfacial compatibility of LATP/Li.Then,the multi-interface three-dimensional（3D）LATP was in-situ compounded with cross-linked polymer electrolyte to obtain the composite electrolyte with excellent electrochemical performance and solve the problem of electrolyte/electrode interface.The specific research contents are as follows:（1）Flexible PVDF polymer was used for double-sided modification of LATP ceramic pellet.The results show that the introduction of PVDF polymer layer effectively reduces the interface impedance（5789Ω→271Ω）,prevents the occurrence of side reactions between lithium anode and LATP,and ensures the stable operation of the battery.The Li/Li symmetric cell assembled by PVDF-modified LATP ceramic pellet exhibits stable cycling over 3000 h at a current density of 0.1 mAcm^-2and a small polarization（30 mV）.The all-solid-state LiFePO₄/Li cell exhibits superior cycling stability of capacity retention of 83.4%after 300cycles.（2）With an in-situ composite strategy,the polymer is used to fill and coat 3D LATP framework to form a 3D composite electrolyte.The results showed that the ionic conductivity of composite electrolyte is as high as7.97×10^-4 S cm^-1,and the electrochemical window is as wide as 5 V.The Li/Li symmetric cell,without any side reaction of LATP and Li,exhibits a low interfacial impedance of 116Ωand stable cycling of 500 h at 0.1mAcm^-2.The in-situ all-solid-state LiFePO₄/Li cell exhibits high discharge capacity of 166.1 mAhg^-1 and steady cycling performance of100 cycles at 0.5 C.