Research On Doping Modification Of Solid Lithium Ion Electrolyte Materials

The Li_1.3Al_0.3Ti_1.7（PO₄）₃solid-state lithium-ion conductor with a NASICON structure is expected to be used in all-solid-state lithium-ion batteries due to its high total ionic conductivity.In this paper,the solid-state method is used to prepare LATP electrolyte,and the LATP solid-state lithium ion conductor is doped and modified through a variety of methods.Firstly,the LATP lithium ion conductor is doped with the sintering aid Li₃BO₃.LATP lithium ion conductors doped with 1wt%,2wt%,3wt%,4wt%and 5wt%Li₃BO₃were synthesized by solid-state method.The effects of different doping amounts of Li₃BO₃on the structure and electrochemical performance of LATP lithium ion conductors were studied by XRD,SEM,AC impedance,and activation energy tests.The experimental results show that doping with a proper amount of Li₃BO₃can optimize the grain size,increase the LATP lattice volume,expand the lithium ion transport channel,increase the total ionic conductivity and reduce the activation energy,and the increase in the total ionic conductivity is mainly derived from the increase in grain boundary conductivity.The optimal doping amount of Li₃BO₃is 2wt%,and the total ionic conductivity is 3.72×10^-4S·cm^-1.Secondly,Zn was used to replace Li and Ti in LATP.The XRD,SEM,conductivity and activation energy of the samples were analyzed,and the effects of different doping amounts and different substitution positions of Zn on the structure and electrochemical performance of LATP lithium ion conductors were studied.The experimental results show that when Zn replaces Li,the total ionic conductivity of LATP is the highest(2.82×10^-4S·cm^-1)at the doping amount of 0.02,and the activation energy is the lowest（0.28e V）.When Zn replaces Ti,the total ionic conductivity of LATP lithium ion conductor is the highest(2.14×10^-4S·cm^-1)at the doping amount of 0.02,and the activation energy is the lowest（0.29e V）.LZATP and LATZP have better electrochemical performance when the doping amount is0.02,and the electrochemical performance of LZATP is better.Finally,based on Materials Studio simulation software,unit cell models of LiTi₂（PO₄）₃,Li_1.3Al_0.3Ti_1.7（PO₄）₃and Li_1.26Zn_0.02Al_0.3Ti_1.7（PO₄）₃were constructed,and the unit cells parameters related data were obtained.The effect of Zn doping on the electrochemical performance of LATP under ideal conditions were also studied.The simulation results show that the optimized geometric structure of 0.02-LZATP has a larger lattice volume than LATP,indicating that 0.02-LZATP reveals a more suitable lithium ion transport channel,which is beneficial to improve the ionic conductivity of the lithium ion conductor.