Abstract: The Li[Li_0.2 Ni_0.2 Mn_0.6-X Ti_X]O₂(x =0. 00，0. 01,0. 02,0. 05 and 0. 10) cathode materials were pre- pared by uniformly mixing the carbonate precursor Mn_0.75 Ni_0.25CO₃ obtained by means of the co-precipitation meth- od,Li₂ CO₃ and different amounts of nano-TiO₂ and then sintering them under 900℃ for 10h.The ICP (Inductively Coupled Plasma) analysis indicates that the components of the prepared materials accord well with the initial de- sign.By means of XRD and SEM,it is found that,when the doping amount of Ti 4 + reaches up to a certain degree,the structure of the pristine material is changed and the micro particles are refined.The results of electrochemical tests show that,when the doping amount of Ti is 0. 02,the doped material exhibits an optimal electrochemical per- formance: specifically,the capacity still keeps constant and the mean voltage fading decreases to 0. 08 mV after 30 cycles at 0. 1C rate.In addition,the discharge capacities of the doped material at various rates increase by 7 ～ 13mAh/g in comparison with that of the material before the doping． EIS (Electrochemical Impedance Spectroscopy) tests demonstrate that the electrochemical performance improvement of the Li[Li_0.2 Ni_0.2 Mn_0.58 Ti_0.02 ]O₂ may be at- tributed to the improvement of the material structure stability by means of the Ti doping.

Key words: lithium ion battery, over-lithiuated oxide, Ti doping, electrochemical performance