氟化钠对Li_(1.3)Ni_(0.14)Mn_(0.68)Co_(0.07)O_2正极材料的电化学性能的影响

Electrochemical Performance of Li_(1.3)Ni_(0.14)Mn_(0.68)Co_(0.07)O_2 Cathode Treated by using a Sodium Fluoride Solution

采用不同浓度氟化钠溶液处理自制的Li_(1.3)Ni_(0.14)Mn_(0.68)Co_(0.07)O_2材料,制备了系列处理样.通过X射线衍射仪、扫描电镜、红外光谱、交流阻抗、循环伏安和充放电循环等方法研究了样品的物相结构及电化学性能.结果表明,Li_(1.3)Ni_(0.14)Mn_(0.68)Co_(0.07)O_2与氟化钠摩尔比为1 1.50条件下制备的处理样品的电化学性能最优.在2.5～4.6 V电压区间和1C倍率电流下,未处理和经处理样品第1循环的放电容量分别为71 mAh/g和128.6 mAh/g,第30循环的放电容量分别为173.9 mAh/g和193.3 mAh/g.处理样品的阻抗明显减小,样品表层价键有所增强,从而改善了样品的电化学性能.

A series of treated samples prepared by using the as-prepared Li1.3Ni0.14Mn0.68Co0.07O2 and sodium fluoride solution with various concentration.X-ray powder diffraction,scanning electron microscopy,infrared spectrum,Electrochemical impedance,cyclic voltammograms and charge-discharge tests were employed to investigate the structure and electrochemical performance of the treated samples.The results show that the treated optimal sample exhibits the best electrochemical performance among all samples while the molar ratio of Li1.3Ni0.14Mn0.68Co0.07O2 to sodium fluoride is 1:1.5.In the voltage range of 2.5 to 4.6 V and 1C rate,the discharge capacity of the untreated and treated optimal sample exhibits the 1st cycle capacity of 71 and 128.6 mAh/g,respectively;and the 30 th cycle capacity of 173.9 and 193.3 mAh/g.The charge-transfer resistance and polarization of the optimal sample significantly decreased,and the Ni-O,Co-O and Mn-O bond on the surface of the treated optimal sample enhanced,thereby the electrochemical performance of the sample improved.