尖晶石LiMn_2O_4的结构性能与嵌脱锂动力学探讨

Study on structure performance and galvano-chemistry dynamics of spinel LiMn_2O_4

采用液相法混合得到的先驱体在不同的温度进行热处理可以合成尖晶石LiMn2O4正极材料;随热处理温度的提高,点阵参数a增大,晶格畸变减小,结晶完善程度提高,容量及循环性能提高,750～850℃温度范围处理的试样其结构可能存在如下相变过程:LiMn2O4(立方相)→LiMn2O4-δ(立方相)→LiMn2O4-δ(四方相);当温度高于850℃时发生的从立方相向四方相的转变使结晶有序度反而降低,性能下降;通过电化学嵌脱锂动力学研究发现随热处理温度升高,锂离子在电极材料中的扩散系数增大。

Spinel LiMn_2O_4 materials were prepared by liquid phase commixing and heat treatment at different temperatures. With the heat treatment temperature increasing, the lattice parameter a enlarges, capacity and cyclic performance enhance, the structure of samples within 750～850 ℃ treatment temperature may have several phase transitions:LiMn_2O_4 (cubic)→LiMn_2O_4-δ (cubic)→LiMn_2O_4-δ (tetragonal);when temperature is above 850 ℃,the degree of order of crystalline will decrease and performance become worse; also, study on galvano-chemistry dynamics of lithium insertion and extraction shows that coefficient of diffusion of lithium ions in electrodes materials enhance with the heat treatment temperature increasing.