Preparation, Modification And Performance Of Lithium-ion Battery Cathode Material Spinel Of Limn <sub> 2 </ Sub> The O <sub> 4 </ Sub>

Spinel phase LiMn₂O₄ is considered as the most promising cathode materials for lithium-ion battery due to its low cost, high capacity and environmental free. However, stoichiometric LiMn₂O₄ exhibits serious capacity fading upon cycling, especially at the high working environment (> 55 ℃). So some means were used to improve capability of LiMn₂O₄ and stability its crystal structure , such as doping metals (Co , Ni, Cr, Li), coating and new synthetic method.Two preparation technologies—metal-urea nitrate complexes precursors and half-solid state reaction method were reported to prepare LiMn₂O₄. The influence of synthesis conditions of metal-urea nitrate complexes precursors method on the structural and electrochemical properties of LiMn₂O₄ was investigated by TG/DTA, IR, X-ray diffraction, scanning electron microscopy and charge-discharge experiments. The production was well crystallized. The powders were a narrow particle size distribution and regular morphology about 60 run. Electrochemical performances indicated that LiMn₂O₄ delivered a high capacity of 176 mAh · g^-1 due to exhibiting 4V plateau and additional 3 V plateau. Materials prepared by half-solid state reaction method method exhibited an excellent reversibility, 94 mAh · g^-1 after 20^th cycle. Two preparation methods have some excellence, such as low cost, easily prepared and high practicality.The change of micro-structure is the real original reason of capacity decaying of LiMn₂O₄ with the charge—discharge. The doping or co-doping of LiMn₂O₄ spinel with elements of Li, Cr, Co, Ni can restrain the Jhan-Teller distortion and improve the stability of material. In our experiment, the result showed that co-doping was excellent stability and capacity than single-doping. Electrochemical performances indicated that Li_1.06Co_0.05Cr_0.1Mn_1.85O₄ delivered a high capacity of 198 mAh · g^-1 at 14^th cycle due to additional 3 V plateau, 145 mAh · g^-1 at 21^st cycle. The results show, there are two pairs of voltammetricwave (centered at 4 V) and a pairs of voltammetric wave (centered at 3 V), indicating materials an excellent reversibility. In our experiment, the doping F" (LiMn2C>3 95F0.05) exhibited the excellent capacity of 175mAh.g"' in the first cycle.The other major reason of capacity fading of LiMn2O4 spinel is the Mn dissolution into electrolyte. By surface coated with Ag, the high surface electronic conductivity can be obtained and material exhibited improved capacity and cycle life. By surface coated with SiC>2, LiMn2C>4 exhibited the excellent capacity of 114 mAh.g"1 in the fouth cycle.