Study On The Preparation And Performance Improvement Of Li_1.3Al_0.3Ti_1.7?PO₄?₃ Solid Electrolyte

Lithium-ion batteries as storage devices for chemical energy and electric energy conversion are widely used in various fields,such as portable electronic products,electric and hybrid electric vehicles,and aerospace.However,current commercial lithium ion batteries using organic electrolytes are prone to safety problems such as liquid leakage,burning and explosion.All-solid-state lithium-ion batteries use solid electrolytes instead of flammable liquid electrolytes and separators not only overcome the safety problems of liquid electrolytes,obtain higher energy densities,but also simplify the battery structure and lower the cost.NASICON-type fast ion conductor Li1+xAlxTi1-x(PO4)3 has the characteristics of high safety,high ionic conductivity,negligible electronic conductivity,wide electrochemical window and chemical stability,which is one of the solid electrolytes with the most promising industrial applications.However,Li 1+xAlxTi1-x(PO4)3 solid electrolytes still exist some problems such as low conductivity,complicated preparation process and high energy consumption,which hinders its large-scale commercial application in lithium-ion batteries.In view of the above problems,this paper aims to optimize the preparation process and electrochemical performance of fast ion conductor LATP by doping with metal cations and improving the preparation process.The main research content is as follows:(1)Spherical LATP precursors were prepared by hydrothermal method.The effect of Al doping amount of 0.2.0.3.0.4 and 0.5 on the physicochemical properties of LATP was investigated.The morphology,structure and electrochemical performance of the LATP were tested and analyzed.The results show that the LATP particle size is uniform,about 0.1-1.0 ?m,and A1 doping is beneficial to improve the electrochemical performance of LATP.The prepared LATP electrolyte shows the highest ionic conductivity of 7.02×10-4 S cm-1,the relative density of 91.85%and the lowest activation energy of 0.28 eV when A1 doping amount is 0.3(Al0.3).(2)LATP electrolyte was prepared by low temperature solution-based method,and the preparation parameters such as calcining temperature and sintering temperature were optimized,and their structural and electrochemical properties were analyzed.The results show that the ionic conductivity of LATP electrolyte prepared by low temperature solution-based method has been greatly improved;LATP particles are uniform and have high phase purity.The electrolyte calcined at 700 0C and sintered at 900 ? show the best performance,the ionic conductivity can reach 1.09×1 O-3 S cm-1,relative density 93.52%and activation energy 0.26 eV.(3)A1 and Si co-doped highly conductive Li1+x+yAlxTi2-xSiyP3-yO12(x=0.3,y==0.2)ceramic electrolytes were prepared by low temperature solution-based method.The effect of Al/Si doping amount,calcining temperature and sintering temperature on the morphology,structure and ionic conductivity of the electrolytes were analyzed.The results show that the optimum doping amount of the Li1+x+yAlxTi2-xSiyP3-yO12 ceramic sample is Al0.3/Si0.4(Li1.7Alo.3Ti1.7Sio.4P2.6O12)-The Li1.7AlO.3Ti1.7Si0.4P2.6O12 ceramic electrolyte calcined at 650 ? and sintered at 1000 ? exhibit the highest ionic conductivity of 1.33× 10-3 S cm-1,the relative density of 94.32%and the activation energy of 0.25 eV.