Preparation And Application Of LATP(Li_1.3Al_0.3Ti_1.7（PO₄）₃)in Composite Solid Electrolytes

In order to meet the growing demand for portable devices,electric vehicles,and large-scale energy storage,the research and development of lithium ion batteries has become an irresistible trend.However,there are many potential safety hazards in current lithium ion batteries using organic liquid electrolytes,and the development of solid electrolyte can effectively solve the above problems.The NASICON Li_1.3Al_0.3Ti_1.7（PO₄）₃（LATP）solid electrolyte is one of the most promising solid electrolytes with high ionic conductivity and good thermal stability.However,the interface contact of LATP electrolyte is poor.In order to solve this problem,organic-inorganic composite electrolyte membrane can be prepared by combining with polyethylene oxide（PEO）which has good flexibility,plasticity and good solubility to lithium salt.In addition,most of the current processes for preparing LATP are solid-phase ball milling,which results in low purity and crystallinity of the LATP electrolyte,many heterophases,and difficulty in controlling the grain size and morphology,leading to low electrical conductivity of the material.In this study,liquid phase co-precipitation method is used to prepare pure LATP,and at the same time,the crystallinity,morphology and particle size of the grains were regulated to further improve the ionic conductivity.Specific research contents are as follows:1.LATP solid electrolyte（LATP-CP）was prepared by liquid phase co-precipitation method,and the effects of reaction temperature,type of Ti source,type of precipitant,aging temperature and calcination temperature on the crystal phase of LATP were investigated.The optimal process conditions were optimized as follows:using Li O₃,Al（NO₃）₃,Ti-（OCH（CH₃）₂）₄,NH₄H₂PO₄as raw materials,ammonium hydroxide as precipitant,reaction temperature of 80℃,aging temperature of 120℃,calcination temperature of 800℃,and calcination duration of 6 h,pure phase LATP can be prepared.The influence of LATP content on the PEO-LATP composite electrolyte membrane was investigated.When the LATP content was 15%,the highest conductivity of the membrane at room temperature was0.78×10^-5S·cm^-1,and the ion activation energy was 0.204 e V.The conductivity of PEO-Li BOB-XLATP was investigated in the range of 20-50℃.When x=15,the conductivity of the composite electrolyte was the highest,reaching 4.45×10^-5S·cm^-1at 50℃.2.In order to further improve the density of the material and improve the electrical conductivity of the material,the GO hard template method was used to regulate the microstructure of LATP solid electrolyte（LATP-GO）.The effects of the amount of GO,the p H value of the solution,the calcination temperature and the duration of the calcination were investigated.The optimal process conditions are as follows:the molar ratio of GO to LATP is 1:1,the solution p H is 8.5,the calcination time is kept for 6 h,and the calcination temperature is 800℃.The two-dimensional sheet LATP can be prepared.The influence of different LATP content on the composite electrolyte membrane was investigated.When the LATP content was 15%,the highest conductivity of the membrane at room temperature was1.09×10^-5S·cm^-1,and the ion activation energy was 0.201 e V.The conductivity of PEO-Li BOB-XLATP was investigated in the range of 20-50℃.When x=15,the conductivity of the composite electrolyte was the highest and reached 6.55×10^-5S·cm^-1at 50℃.3.In order to further regulate the particle size,the nano-LATP solid electrolyte（LATP-MC）was prepared by microfluidic continuous co-precipitation method.The influences of feed flow rate,feed method,feed concentration and calcination temperature were explored,and a new feed method was developed on the basis of discussing the best process of co-precipitation method.The organic titanium insoluble in water is transferred to the ethanol system,and Lin O₃and Al（NO₃）₃are fed from the inletΙof the microreactor.NH₄H₂PO₄and the precipitant NH₄HCO₃are still in the water system,and enter the microreactor from the inlet.The particle size of LATP electrolyte prepared is about 100 nm.Latp prepared by microfluidic continuous co-precipitation has higher crystallinity and wider range of thermodynamic stability than the traditional co-precipitation method.The influence of the content of LATP on the composite electrolyte membrane was investigated.When the content of LATP was 15%,the highest conductivity of the membrane at room temperature was 1.23×10^-5S·cm^-1,and the ion activation energy was 0.11 e V.The conductivity of PEO-Li BOB-XLATP was investigated in the range of 20-50℃.When x=15,the conductivity of the composite electrolyte was the highest,reaching 7.41×10^-5S·cm^-1at 50℃.