尖晶石型LiMn_2O_4陶瓷的制备及其电导率

Preparation and conductivity of spinel LiMn_2O_4 ceramic

为研究尖晶石型LiMn2O4正极材料的导电性能,用无压、热压和等离子放电烧结的方法制备出了LiMn2O4陶瓷块体,用X射线衍射(XRD)、扫描电子显微镜(SEM)和交流阻抗谱研究了产物的物相、显微结构和电导率。结果发现,在高温或低氧浓度的烧结条件下LiMn2O4发生脱氧,分解生成LiMnO2和Mn3O4。通过埋粉工艺可以有效地抑制脱氧,提高LiMn2O4的烧结温度。等离子放电烧结可使坯体迅速达到致密,抑制晶格脱氧和晶粒长大。尖晶石型LiMn2O4的电导率由晶界电导控制,晶粒大小对电导率的影响很大。

Spinel LiMn2O4 ceramic was prepared by presureless sintering (PS), hot pressing (HP) and spark plasma sintering (SPS) in order to in investigate its conductivity. The phase, microstructure and conductivity of the product was studied by XRD, SEM and AC impedance analysis. The results show that lattice is deoxidized when LiMn2O4 is sintered at high temperature or oxygen deficient atmosphere, which finally results to the decomposition into LiMnO2 and Mn3O4. However, the deoxidation can be inhibited by imbedding the sample into LiMn2O4 powder during sintering process. SPS consolidates the sample quickly and inhibits the lattic deoxidation and grain growth. The conductivity of LiMn2O4 is controlled by grain boundary conductivity, and the effect of grain size on conductivity is great.