Abstract: 5 V cathode materials LiNi0.5Mn1.5O4-xFx (x=0, 0.1) for lithium ion battery were synthesized via sol-gel method combined with high temperature treatment. The synthesized samples were characterized by X-ray diffractrometry (XRD), scanning electron microscopy (SEM) and specific surface area measurements (BET). Coin cells were assembled using these cathode materials, followed by storage at an elevated temperature (85 ℃) for 24 h, and then a series of electrochemical measurements were conducted to examine the changes of the electrochemical properties before and after cell storage at the elevated temperature. The experimental results showed that the open-circuit voltage of the cell declined quickly during high temperature storage because of self-discharge. The voltage retention was significantly influenced by specific surface area of the powder material and fluorine doping. The larger the specific surface area is, the shorter the voltage retention time becomes. Fluorine doping was favorable for stabilizing the cell voltage at elevated storage temperature and could improve the interfacial property between the electrode and electrolyte. Therefore, the charge and discharge performance was enhanced.

Key words: Fluorine doping, 5 V cathode material, High temperature storage, Secondary lithiumbattery