Influence Of LiBO₂ Addition And Surface Modification By AZO Coating On The Reparation And Properties Of Li_1.3Al_0.3Ti_1.7（PO₄）₃ Solid Electrolytes

Concerning the safety problems of conventional Li-ion batteries with organic electrolytes,it is crucial to develop reliable solid-state rechargeable lithium batteries with specific capacity,high energy density and high safety.In this study,we started from the preparation of the electrolytes materials,combined their advantages and disadvantages,improved their sinter quality and enhanced their density values,and designed the reliable all-solid-state lithium batteries.Li_1+xAl_xTi_2-x（PO₄）₃（LATP,x=0.3）is regarded as one of the most promising solid electrolytes due to its high ionic conductivity,excellent chemical stability to humidity and a wide electrochemical window.There are two problems restricting the application of NASICON-type LATP.One challenge is its poor sinterability;another challenge is its unstablity in contact with the Li metal anode,because the Ti⁴⁺will be easily reduced to Ti³⁺by the lithium-metal as anode.To address those problems,some efforts must be made in order to achieve acceptable density values and high chemical stability against the attack by lithium-metal.In this paper,we carried out our systematic research work based on the development of reliable all-solid-state lithium batteries,and the main achievements are as following:（1）Herein,a new strategy is proposed for improving the sintering behavior and enhancing the ionic conductivity of LATP by using LiBO₂ as the sintering aid via liquid phase sintering.The as-prepared samples LATP with homogeneous microstructure and high relative density of 97.1%were successfully synthesized,yielding high total ionic conductivity of 3.5×10^-4 S/cm and low activation energy of 0.39 eV at room temperature.It was found that the addition of LiBO₂ could effectively enhance the densification and increase the ionic conductivity of LATP electrolyte,proving an effective way to synthesis LATP ceramics by a simple and reliable route.（2）AZO film was prepared by magnetron sputtering on the surface of electrolyte LATP for the all-solid-state lithium battery.In addition,this is a surface modification method of AZO coating on the surface of electrolyte LATP to improve electrochemical stability of the LATP electrolyte against the attack by lithium-metal anode.The as-prepared AZO thin film is a kind of n-type semiconductor with a low resistivity,and the AZO layer remains a continuous and tight contact with the LATP sheet.The surface of AZO presents extremely smooth and rarely rough on a large scale,which is good for solid contacting in the following ASSLMBs.The AZO coating of the electrolyte LATP demonstrates high chemical stability and excellent lithium dendrite suppression performance,which is the candidate material used in the all-solid-state lithium battery.（3）The reliable all-solid-state lithium batteries with the AZO coating LATP as the electrolytes LATP were designed and prepared by using the mode of button cell.The AZO coating demonstrates a wide electrochemical potential ranges（>5 V）and an excellent performance of suppressing of lithium dendrites.An all-solid-state Li/LiFePO₄ battery with AZO-coated LATP as the solid electrolyte excellent capacity for suppressing the lithium dendrites and good capacity reversibility for 50charge/discharge cycles.The AZO coating LATP electrolytes also enabled the symmetric Li/AZO coated LATP/Li cell remaining stability for 960 hours,due to their excellent suppressing performance of lithium dendrites.