高容量正极材料LiNi_(0.6)Co_(0.2)Mn_(0.2)O_2的制备及性能研究

Preparation and performance of LiNi_(0.6)Co_(0.2)Mn_(0.2)O_2 as high capacity cathode material

采用控制结晶法,预先合成出致密的球形前驱体Ni_(0.6)Co_(0.2)M n_(0.2)(OH)_2。前驱体与Li_2CO_3混合均匀后于高温条件下烧结,再进行复烧即可制备出表面光滑致密、振实密度高、容量高的正极材料Li Ni_(0.6)Co_(0.2)M n_(0.2)O_2。利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、X射线光电子能谱仪(XPS)及充电-放电测试对材料的结构和电学性能进行表征分析。研究了不同烧结及复烧温度对材料性能的影响,并分析了其影响机理。结果表明,通过优化烧结及复烧温度可以有效提高Li Ni_(0.6)Co_(0.2)M n_(0.2)O_2正极材料的电学性能。正极材料的中位粒径约为13μm,振实密度≥2.3 g/cm^3,比表面积为0.31 m^2/g,在3.0~4.3 V电位区间内,首次放电克比容量为178.51 m Ah/g,首次库伦效率为89.90%。

Firstly,the dense spherical precursor Ni0.6 Co0.2 Mn0.2(OH)2 was synthesized by controlled-crystallization process.Then,the precursor was blended with Li2 CO3 thoroughly.After sintering the mixture at high temperature,the LiNi0.6 Co0.2 Mn0.2 O2 cathode material with smooth and dense surface,high tap-density and capacity was prepared by re-sintering at low temperature.The structural and electrochemical properties were investigated by using scanning electron microscope(SEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and charge-discharge test.The influences of temperature of sintering and re-sintering on the materials characteristic and relevant mechanism were investigated.The resultes indicate that the performance of LiNi0.6 Co0.2 Mn0.2 O2 cathode material can be improved by optimizing the temperature of sintering and re-sintering.The mean diameter,tap density and BET of well-ordered spherical LiNi0.6 Co0.2 Mn0.2 O2 prepared under the best conditions are 13μm,2.3 g/cm3 and 0.31 m2/g,respectively.The initial discharge specific capacity of material prepared under the best conditions is 178.15 mAh/g at 3.0-4.3 V,and the coulombic efficiency is 89.90%for the first time.