多元稀土掺杂锂锰氧正极材料的结构及性能表征

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。

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

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 LiMn_2O_4, LiLa_(0.03)Mn_(1.97)O_4, LiLa0.012Ce0.012Mn_(1.976)O_4, LiLa0.012Nd_(0.012)Mn_(1.976)O_4 and LiCe_(0.012)Nd_(0.012)Mn_(1.976)O_4 samples are composed of single-phase spinel LiMn_2O_4 structure only when the content of rare earth is strictly controlled in a certain range. The LiLa_(0.015)Ce_(0.015)Mn1.97O4, LiLa_(0.015)Nd_(0.015)Mn1.97O4 and LiCe_(0.015)Nd_(0.015)Mn1.97O4 specimens consist of the LiMn_2O_4 and trace CeO_2, Nd_2O_3, CeO_2+Nd_2O_3 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 LiCe_(0.012)Nd_(0.012)Mn_(1.976)O_4 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 LiMn_2O_4 material.