纳米磷酸铁包覆锂离子电池正极材料LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2的制备及其电化学性能

为改善LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2正极材料的电化学性能,采用自制的磷酸铁纳米悬浮液,通过共沉淀法在LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2正极材料表面包覆纳米磷酸铁。应用XRD,TG-DTA,TEM等手段表征制备的磷酸铁的结构,形貌和液相状态;通过XRD,SEM,EDS,TEM,ICP,恒流充放电、循环伏安、交流阻抗表征制备的包覆材料的结构、形貌及电化学性能。研究烧结温度和包覆量对LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2正极材料电化学性能的影响。结果表明,热处理温度为400℃,2%(质量分数,下同)磷酸铁包覆能显著地改善LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2正极材料的循环性能和倍率性能。循环伏安和交流阻抗结果显示,包覆磷酸铁后改善了LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2正极材料的可逆性和动力学性能。ICP测试结果表明,磷酸铁包覆层能够有效地降低电解液对正极材料的溶解与侵蚀,稳定其层状结构,从而提高正极材料的电化学性能。

Fabrication and Electrochemical Performance of LiNi0.5Co0.2Mn0.3O2 Coated with Nano FePO4 as Cathode Material for Lithium-ion Batteries

Layered LiNi0.5Co0.2Mn0.3O2 coated with homogeneous nano FePO4 suspension was prepared by using co-precipitation method.XRD,TG-DTA and TEM were adopted to characterize the structure,morphology and liquid state of FePO4 prepared.The structure,morphology and electrochemical performance of the coated materials prepared were characterized by the means such as XRD,SEM,EDS,TEM,ICP,galvanostatic charge-discharge cycling,cyclic voltammetry (CV) and electrochemical impedance spectroscopy(EIS) tests.The effect of heat treatment temperature and coating quantity on the structure and electrochemical performance of coated LiNi0.5 Co0.2Mn0.3O2 by co-precipitation method was explored.The results show that 400℃ and 2％ (mass fraction,the same below) FePO4 coating can significantly improve cycle performance and rate capability of LiNi0.5Co0.2Mn0.3O2,CV and EIS testing results reveal that FePO4 coating can improve the reversibility and dynamic performance for LiNi0.5Co0.2Mn0.3O2.ICP results show that FePO4 coating layer can effectively reduce the electrolyte to dissolute and erode cathode materials,stabilize its layered structure,then improve the electrochemical performance of cathode materials.