Preparation Of Li_1.3Al_0.3Ti_1.7（PO₄）₃ Solid Electrolyte And Study On Interface Modification With Lithium Metal

The ceramic material Li1.3Al0.3Ti1.7(PO4)3(LATP)has a high ionic conductivity of 7×10-4 S cm-1,low cost of raw materials and high stability in the air.It is an ideal solid electrolyte material.In this paper,the effects of preparation parameters on the structure,morphology and ionic conductivity of LATP solid electrolyte were studied by solid-state sintering.Based on the fact that LATP and lithium metal anode are extremely unstable in thermodynamics,Ti4+is easily reduced to Ti3+ by lithium metal during the cycle,leading to the battery failure in the process of charging and discharging.Therefore,the key to solve this problem is to build a suitable interface layer between LATP and lithium anode.1.LATP was prepared by solid state method.The average density of the tablet is 2.65 g cm-3,which is more than 90%of the theoretical density,and the integrity of the slice is good.The ionic conductivity is 2.80×10-4 S cm-1,which is close to the theoretical ionic conductivity of 7×10-4 S cm-1.The results show that the tablet have a peak consistent with the standard XRD spectrum,indicating good crystallinity,no impurity phase,and the tablet have clean grains and tight grain gap.The LATP tablets after two sintering and three sintering processes were compared.It was found that the LATP tablets after three sintering had higher ionic conductivity,crystallinity and size uniformity.2.The amorphous LAGP(a-LAGP)films were sputtered on the quartz wafer,and annealed at different temperatures.Through XRD test,it is found that annealing at 900℃ can make a-LAGP crystallize.3.a-LAGP films were sputtered on both sides of LATP,annealed at different temperatures,and then the non annealed a-LAGP/LATP/a-LAGP electrolytes and the annealed LAGP/LATP/LAGP electrolytes were assembled into symmetrical cells.It was found that the symmetrical cell assembled by the non annealed electrolytes had a more stable galvanostatic cycle curve.The impedance of the symmetrical cell without a-LAGP film modification changes greatly before and after the cycle,while the impedance of the symmetrical cell with a-LAGP film modification does not change significantly.As the cycle goes on,cracks appear in the electrolyte tablet of symmetrical cells without a-LAGP film modification,while the micro morphology of the samples with a-LAGP film modification is basically the same before and after the cycle.In the Raman spectrum test,it is found that the annealing treatment of a-LAGP film not only makes the film crystallize,but also leads to the resintering of LATP,and finally leads to the similar Raman spectrum between the annealed electrolyte and the recycled electrolyte.4.By controlling the humidity during the preparation of LATP,the effects of different humidity of 50%RH,65%RH,80%RH on the morphology,phase structure and properties of LATP were investigated.The results show that humidity has a great influence on the morphology and structure of LATP after sintering,which further affects the ionic conductivity of LATP solid electrolyte.In the preparation of LATP,it is very important to control the environmental humidity for the synthesis of LATP solid electrolyte with ideal ionic conductivity.