利用固相反应法制备的石榴石结构的Li7La3Zr2O12粉体的形成机制

The formation mechanisms of garnet-like Li7La3Zr2O12 (LLZO) phase using LiOH?H2O as raw materials are investigated symmetrically by XRD and DTA/TG measurements. It was found that reaction mechanisms of the LLZO formation are as follows: 7Li2O 3La2O3 4ZrO2=2Li7La3Zr2O12 The production of LLZO phase takes place at about 680oC observed from the XRD patterns, in agreement with the thermic peak at 700oC in DTA/TG curves, which arises from the formation of LZZO phase. The stable existence temperature range of LLZO phase is wide, from 720 to 1000oC. However, LLZO is thermally unstable at the high temperatures (>1000oC) due to a serious loss of lithium element, and it discomposes into pyrochlore phase La2Zr2O7. And the amount of the decomposed products increased, and LLZO decreased gradually with the increase of the calcination temperature. When the reactant mixture was calcined at the low temperature, the produced phases were identified to be lanthanum compounds because La2O3 absorbs moisture and CO2 very easily. The chemical reactions at lower temperature are mainly related with the reactions among lanthanum compounds. LLZO powder was synthesized by solid state reaction at 800℃. It is found that the LLZO crystal belongs to the tetragonal symmetry. SEM observations show that the obtained LLZO powder was nano-sized.     

Li3PO4对Li0.5La0.5TiO3/Li3PO4复合固体电解质的电性能影响

利用复阻抗谱分析技术考察了复合Li3PO4的Li0.5La0.5TiO3 (LLTO) 固体电解质的离子电导率,同时还利用X射线衍射图谱、扫描电镜观测和相对致密度测量等实验手段研究了LLTO电解质中第二相的分散情况。结果发现,加入Li3PO4第二相后,尽管复合固体电解质LLTO拥有比较高的致密度,但是Li3PO4会导致离子电导率的降低。通过分析LLTO的晶体结构,晶界的微观结构和锂含量,阐明了LLTO离子电导率恶化的原因,往LLTO基质中分散的Li3PO4导致的锂含量和微观结构的变化是引起锂离子传导行为改变的主要原因。