Electrochemical Kinetics of the Li[Li0.23Co0.3Mn0.47]O2 Cathode Material Studied by GITT and EIS

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• 作者：Zhe Li ; Fei Du ; Xiaofei Bie ; Dong Zhang ; Yongmao Cai ; Xinran Cui ; Chunzhong Wang ; Gang Chen ; Yingjin Wei
• 刊名：Journal of Physical Chemistry C
• 出版年：2010
• 出版时间：December 30, 2010
• 年：2010
• 卷：114
• 期：51
• 页码：22751-22757
• 全文大小：311K
• 年卷期：v.114,no.51(December 30, 2010)
• ISSN：1932-7455

文摘

The Li[Li_0.23Co_0.3Mn_0.47]O₂ cathode material was prepared by a sol−gel method. Combinative X-ray diffraction (XRD) and Raman scattering studies showed that the material was a solid solution rather than a composite of nano Li₂MnO₃ and LiCoO₂. The material had a high discharge capacity of 250 mAh g⁻¹ in the voltage window of 2.0−4.8 V. However, the capacity retention was poor. The material showed different electrochemical mechanisms in the first charge and subsequent cycles. Galvanostatic intermittent titration technique (GITT) study showed that the Li⁺ diffusion coefficients during the first charge were as small as 10⁻¹⁹ cm² s⁻¹ because of the high kinetic barriers associated with the concurrent Li⁺ extraction, oxygen loss, and structural rearrangement. The Li⁺ diffusion coefficients increased to 10⁻¹⁴ cm² s⁻¹ after the first charge. However, they were still much smaller than those of typical layered materials such as LiCoO₂ and Li(Ni_1/3Co_1/3Mn_1/3)O₂. Electrochemical impedance spectroscopy (EIS) study showed that the large interface impedance at high potential seriously hindered the electrode performance of the material. A lower charge cutoff voltage of 4.6 V was the most suitable for this material considering that the correponding reversible capacity (200 mAh g⁻¹) was attractive for high energy density lithium ion batteries.