Study On The Modification And Interface Modification Of NASICON Solid Electrolyte Li_1.5Al_0.5Ti_1.5（PO₄）₃

With high power and high energy density,lithium-ion batteries（LIBs）are ideal energy storage systems for electronic products and electric vehicles.The use of organic liquid electrolyte in traditional Li-ion batteries has problems such as low ignition point,poor thermal stability and easy explosion,which restrict the application of LIBs.With the development of energy storage technology,higher requirements for energy density and safety of energy storage devices,etc.are put forward.The NASICON type Li_1.5Al_0.5Ti_1.5（PO₄）₃（LATP）electrolyte has the advantages of a wide electrochemical window（4.21 V）,a wide source of raw materials,good thermal stability and mechanical properties,but the NASICON type LATP solid-state electrolytes have problems such as high interfacial contact resistance,poor cycling performance,and low electrical conductivity that need to be addressed.In order to improve the overall performance of all-solid-state batteries,this study takes LATP as the research object and works on electrolyte modification and PVDF-HFP-PEO-SN（PPS）polymer layer modification of the interface between LATP and lithium metal to enhance LATP performance and reduce interfacial resistance,and assembles all-solid-state batteries to study the effects of LATP and PPS polymer layer on battery performance and explore the mechanism.The study and main findings are as follows:1.LATP powder was prepared by citric acid-assisted sol-gel method,mixed with LiBiO₃sintering aid,and sintered to form a high-performance solid electrolyte using low-pressure molding process production（18 MPa）;the microscopic morphology and phase composition of LATP samples were analyzed by XRD,SEM,XPS and EDS characterization techniques,and the sintering temperature and sintering time were investigated by AC impedance spectroscopy The effects of sintering temperature and sintering time on the electrochemical properties were investigated by AC impedance spectroscopy.The results show that the sintering process of LATP with the addition of sintering aid LiBiO₃ achieves an electrical conductivity of 2.9×10^-4 S·cm^-1,which is 5 times higher than that of LATP without the addition of sintering aid(5.28×10^-5 S·cm^-1),and meets the requirement of high energy storage battery at 700℃pre-sintering for 3 h,880℃sintering for 5 h,and 2 wt%of LiBiO₃ addition.2.The rigidity of LATP and its susceptibility to reduction by metallic Li resulted in poor contact with the electrode and high interfacial resistance.Therefore,this paper explores the polymer layer PVDF-HFP-PEO-SN（PPS）with good interfacial properties at room temperature to improve the interfacial properties of LATP;analyzes the physical phase composition of PPS and the microscopic interfacial morphology after coating on both sides of LATP by XRD,SEM,and EDS characterization;assembles Li||SSCEs||Li symmetric cells and Li||SSCEs||LFP solid-state lithium metal batteries were assembled,and the cycling performance of the batteries was investigated by using the blue power system and electrochemical workstation and the mechanism.The results show that:the Li symmetric cell cycles stably for 350 h at 0.1 m A·cm^-2 current density with good interfacial contact;the all-solid-state cell exhibits ideal initial discharge capacity(150 m Ah·g^-1)and good cycling performance at 25℃and 0.1 C multiplicity,and the discharge capacity remains92%after 50 cycles,and the Coulomb efficiency is close to 100%,meeting the all-solid-state cell operating requirements at room temperature.