Preparation Of Solid Electrolyte Li_1.3Al_0.3Ti_1.7(PO₄)₃ And Performance Research

Lithium-ion batteries are currently the most widely used batteries,which have broad application prospects in new energy vehicles,mobile phones and notebook computers.The traditional lithium-ion battery uses a liquid electrolyte to transport lithium ions,which is more difficult to encapsulate.The self-heating during operation can easily damage the internal separator of the battery.After the electrolyte leaks,the positive and negative electrodes directly contact and then burn.All-solid-state lithium-ion batteries use solid electrolytes,which effectively improves safety,energy density,battery capacity,and cycle stability.Li_1.3Al_0.3Ti_1.7?PO₄?3?LATP?is currently known as the solid electrolyte with the highest theoretical ion conductivity of 3×10-3S/cm,but due to its own decomposition reaction during sintering there are impurities in the LATP sample Phase and micro-cracks,the density decreases,resulting in ionic conductivity down to 10"4S/cm.In order to solve this problem,this article simulates the pure phase LATP grain growth process by Monte Carlo method,analyzes the microstructure change law of LATP during sintering process and makes predictions on its growth accordingly,by which we obtains the sample whose density exceeds the theoretical threshold of 96.7%.In order to further improve the performance of LATP,the microstructure of LATP samples was improved by adding sintering aids,the influence of sintering aids on the change of microstructure was analyzed,and the best sintering process parameters were determined according to the test results.The classical Monte Carlo method is used to simulate the grain growth during the pure phase LATP sintering process.The simulation results show that the classical Monte Carlo method can simulate the solid phase microstructure changes,but the material is not conserved during the simulation.Although the classic Monte Carlo method can show the mechanism of grain boundary diffusion and volume diffusion in LATP during sintering,it cannot show the mechanism of annihilation of pores.At the same time,the calculation of the transition probability in the simulation algorithm is not consistent with the actual situation.The Monte Carlo method is modified by algorithm improvement,and the modified Monte Carlo method is used to simulate the grain growth process during the LATP sintering process.The simulation results show that it can reflect the various sintering mechanisms in the LATP sintering process and can modify the microstructure of the system.The changes performed better.The accuracy of the simulation was tested using the Hillert model,and the test results showed that the simulation results were consistent with the classical grain growth kinetics.The sintering of LATP was carried out at 900? for 3h and 6h respectively.The corresponding relationship between simulated sintering time and actual sintering time was established through the test results,and the density and average grain size after sintering of pure phase LATP were predicted based on this.The prediction results determine that the sintering process parameters are sintering time 6h and sintering temperature above 900?.The pure phase LATP was sintered under different process parameters,and conduct SEM and XRD tests on the LATP sample.At the sintering temperature,LATP decomposes to produce LiTi?PO₄?O and AlPO₄ impurity phases.AlPO₄ diffuses to the grain boundary to hinder the growth of the grain,resulting in Micro-cracks were generated at the grain boundaries,which reduced the density of the sample.By adjusting the sintering time and sintering temperature,the sample obtained by sintering at 950? for 6 hours has the highest density of 96.47%,which is lower than the theoretical threshold.The modified LATP obtained by sintering after adding sintering aid B₂O₃ also contains LiTi?PO₄?O and AlPO₄ impurity phases.By adjusting the amount of sintering aid added,it can be known that as the content of sintering aid increases,the density of the modified sample rises first After high reduction,the comprehensive test results can be obtained when the sintering temperature is 950?,the sintering time is 6h,the B₂O₃ addition amount is lwt%,the modified LATP sample has the highest density of 98.87%,exceeding the theoretical threshold,which is the best Process parameters.