多元稀土掺杂锂锰氧正极材料的结构及性能表征

Characterization of Structure and Properties of Lithium Manganese Oxygen Cathode Materials Doped with Rare Earth

采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、电池性能测试系统研究了多元稀土掺杂锂锰氧正极材料的相结构、形貌,并对其活化性能、循环稳定性能进行了表征。结果表明:采用Pechini法合成多元稀土掺杂LiMn2O4样品时,只有将掺杂元素的含量严格控制在一定范围内,所合成的LiMn2O4、LiLa0.03Mn1.97O4、LiLa0.012Ce0.012Mn1.976O4、LiLa0.012Nd0.012Mn1.976O4、LiCe0.012Nd0.012Mn1.976O4样品才具有纯尖晶石型LiMn2O4结构。当稀土掺杂元素含量较高时,所合成的LiLa0.015Ce0.015Mn1.97O4、LiLa0.015Nd0.015Mn1.97O4、LiCe0.015Nd0.015Mn1.97O4样品由LiMn2O4相及微量杂质相CeO2、Nd2O3、CeO2+Nd2O3组成。所有样品呈规则的近球形或球形,其粒径范围为0.5～2.8μm。适量的稀土元素掺杂将使LiMn2O4材料的初始容量减小、充放电效率及循环稳定性能增加,LiCe0.012Nd0.012Mn1.976O4样品具有较好的综合电化学性能,其初始容量为123.5mAh/g,经30次循环充放电后的容量为113.2mAh/g,为相同条件下LiMn2O4样品放电容量的1.27倍。

The phase structure, the morphology, activation performance and cycle stability of the rare-earth-doped lithium manganese oxygen cathode materials prepared by Pechini process were investigated by means of X-ray diffraction （XRD）, scanning electron microscope （SEM） and battery testing system. The results show that the prepared LiMn2O4、LiLa0.03Mn1.97O4、LiLa0.012Ce0.012Mn1.976O4、LiLa0.012Nd0.012Mn1.97604、LiCe0.012Nd0.012Mn1.976O4 samples are composed of single-phase spinel LiMnzO4 structure only when the content of rare earth is strictly controlled in a certain range. The LiLa0.015Ce0.015Mn1.97O4、LiLa0.015Nd0.015Mn1.97O4、LiCe0.015Nd0.015Mn1.97O4 and LiCe0.0l5Nd0.015Mn1.97O4 specimens consist of the LiMn2O4 and trace CeO2, Nd2O3, CeO2＋Nd2O3 phases when the content of the rare earth exceeds the range. The particles of all the specimens are regularly spheroid or near-sphere, and the size of the particles is 0.5-2.8 μm. The initial discharge capacity of the specimens would be decreased, and the ratio of discharge/charge capacity and cyclic stability of the specimens would be increased with the suitable rare earth element doping. The LiCe0.012Nd0.012Mnl.976O4 cathode materials has good comprehensive electrochemical performances whose initial discharge capacity is 123.5 mAh/g, and whose capacity is 113.2 mAh/g after the 30th cycle, 1.27 times as high as that of LiMn2O4 material.