Preparation And Doping Modification Of NASICON Solid State Lithium Ion Conductor

Due to Li_1.3Al_0.3Ti_1.7?PO₄?₃ solid lithium ion conductors with NASICON structure have the advantages of high mechanical strength,good hydrothermal stability,high ionic conductivity and low-priced raw materials,It are expected to be used in the next generation energy storage equipment-all-solid-state lithium-ion batteries which have high energy density.In this paper,through various parallel and comparative experiments,and through a number of characterizations,the preparation process and modification methods of solid-state lithium ion conductor LATP were systematically studied.Firstly,LATP lithium ion conductors were synthesized by solid-state reaction,sol-gel method,solution method and hydrothermal synthesis method.The effects of different preparation processes on the electrochemical performance of LATP lithium ion conductors were investigated by density test,XRD test,AC impedance and DC voltammetry data collection,It was found that the hydrothermal synthesis of LATP has the best electrochemical performance.Secondly,keep the preparation process unchanged,and prepare LATP lithium ion conductors with NH₄H₂PO₄ and H₃PO₄ as P sources,respectively.The effects of different P sources on the precursor solution,hydrothermal synthesis product,precursor powder and sintered pellet properties of LATP were studied by density,XRD,particle size distribution test,AC impedance and ion activation energy test.The results show that H₃PO₄ reacts more easily with other raw materials,and the prepared LATP lithium ion conductor has better performance.The sample sintered at 900°C for6 hours has the highest ionic conductivity of 4.33×10^-4 S/cm.Thirdly,The mesoporous material SBA-15 was initially doped into the LATP lithium ion conductor.LATP lithium ion conductors containing different percentages of SBA-15 were synthesized by solid-state reaction and sol-gel method respectively.The effects of different doping amounts of SBA-15 on the electrochemical performance of LATP were investigated by density,XRD,SEM,TEM and AC impedance test.The experimental results of the two preparations show that the proper doping amount of SBA-15 can improve the grain size,increase the total conductivity and reduce the activation energy,and find that the optimal doping amount of both methods is 3wt%.The total ionic conductivity is 2.83×10^-4 S/cm and 4.42×10^-4 S/cm,which is about twice that of LATP.The increase of total ionic conductivity mainly comes from the increase of grain boundary conductivity.Finally,the comparative experiment of LATP lithium ion conductor doped SiO₂by sol-gel method was carried out to analyzed the doping mechanism of mesoporous SBA-15 on LATP.The results show that the main reason for the increase of conductivity of SBA-15 on LATP doping is the nanoconfined effect of regular mesoporous structures on the grains of LATP.