Structure and electrochemical performance of LiCoO2 cathode material in different voltage ranges

作者：Wang, Zhiguo; Wang, Zhixing^*; Peng, Wenjie; Guo, Huajun; Li, Xinhai; Wang, Jiexi; Qi, Ai

来源：Ionics, 2014, 20(11): 1525-1534.

DOI：10.1007/s11581-014-1098-z

• Lithium cobalt oxide
• Cathode material
• High voltage
• Phase transition
• Electrochemical performance

LiCoO2 sample prepared by high-temperature solid state calcination shows a typical hexagonal structure with a single phase and fine particle size distribution. The high-voltage electrolyte with additive fluoroethylene carbonate (FEC) has been used. Electrochemical results show that the initial discharge capacities of the prepared LiCoO2 cathode are 157.7, 169.5, 191.0, and 217.5 mAh g(-1) in the voltage ranges of 3.0-4.3, 3.0-4.4, 3.0-4.5, and 3.0-4.6 V, respectively. The capacity increases, while the initial coulombic efficiency and capacity retention decrease with increasing the charge cutoff voltage. The capacity retention is only 10.4 % after 200 cycles at 1C rate in the voltage range of 3.0-4.6 V. X-ray diffraction measurements confirm structural changes of the layered material in the different voltage ranges. A phase transition from the O3 to the H1-3 phase can be observed when LiCoO2 is charged above 4.5 V. The AC impedance analysis indicates that the resistances (R ((sf+b)), R (ct)) of the prepared LiCoO2 rapidly increase when the cell is charged to higher voltage. The amount of dissolved Co into the electrolyte also greatly increases with increasing the charge cutoff voltage.

• 出版日期2014-11
• 单位中南大学