Preparation Of Li_1.3Al_0.3Ti_1.7（PO₄）₃ Solid State Electrolyte And Interfacial Modification Of Li_1.3Al_0.3Ti_1.7（PO₄）₃–Type Solid-State Lithium-Ions

Lithium-ion batteries are used in electronic devices and energy storage devices because of environmental friendliness and high energy density.In recent years,lithium-ion batteries become more and more popular in daily life,where the news about combustion and explosion is reported.The design and development of solid-state electrolytes for the preparation of solid-state lithium-ion batteries with better safety performance is become a research hotspot nowadays,which NASICON solid-state electrolytes have become one of the research directions of solid-state electrolytes due to good environmental stability and excellent ionic conductivity.Therefore,this paper focuses on the NASICON type Li_1.3Al_0.3Ti_1.7（PO₄）₃（LATP）solid electrolyte and the solid-state lithium-ion batteries to optimize its performance of ionic conductivity and interfacial.The specific work is as follows:（1）LATP solid electrolyte powder are prepared by spray drying combined with O₂pressure-controlled calcination technology,and the influence of sintering pressure on the properties of LATP solid electrolyte is investigated.The results show that the morphology of LATP solid electrolyte becomes denser and denser with the increase of pressure,in which the sample when the sintering pressure is 0.5 MPa（LATP-5）has the highest compaction density that is2.748 gcm^-3.At that time,the sample grains are in close contact with each other and the porosity is low.Meanwhile,the ionic conductivity at 25°C is 8.452×10^-5 S cm^-1.In addition,the specific capacity of LiCoO₂/LATP-5/Li cell has 48.91 m Ah g^-1 at 0.5 C.Then,the LATP-5 solid electrolyte after the cycle is appeared adhesion phenomenon and grain boundary.（2）In order to further improve the structural stability and ionic conductivity of the solid electrolyte,pure phase Li_1.3Al_0.3Ti_1.7（PO₄）₃（LATP-5）materials with halogen（F^-,Cl^-and Br^-）substitution for O^2-are synthesized by pray drying combined with O₂pressure-controlled calcination technology.The results show that the ionic conductivity of solid electrolyte increased after doping F^-,Cl^-and Br^-,and LATP-F solid electrolyte has the best performance,in which the ionic conductivity reach 1.986×10^-4 S cm^-1 at 25°C.In addition,the Li/LATP-F/Li symmetric battery can charge/discharge cycle persistently to 1837 h.However,but the LiCoO₂/LATP-F/Li cell has no significant improvement in stability and long cycle performance at 0.5 C.Then,the morphology of the LATP-F electrolyte powder shows adhesion phenomenon but no micro-cracks,and XPS results show that about 42.24%of Ti⁴⁺is reduced to Ti³⁺after cycled.（3）In this section,InCl₃@LATP-F solid electrolyte is prepared by adding InCl₃between the interface of LATP-F solid electrolyte and the lithium metal by drip method,where the InCl₃ reacts with lithium metal to form a stable Li-In alloy that is greatly improving the Li/LATP interfacial contact problem during cycle.It is worth noting that the Li/InCl₃@LATP-F/Li symmetrical cell can be charge/discharged for 2500 h with a over-voltage of 0.2 V at 0.4 m A cm^-2.In addition,LiCoO₂/InCl₃@LATP-F/Li cell has126.4 m Ah g^-1 at 0.5 C after 100 cycles,and capacity retention rate reaches 95.42%.Meanwhile,the Li Fe PO₄/InCl₃@LATP-F/Li cell shows an excellent rate performance,in which discharge capacity has 93.7 m Ah g^-1 at 1.0 C after 200 cycles.The Ti³⁺content（only 13.72%）is significantly reduced after cycle,and SEM shows that the electrolyte is still uniform spheroid particles.