The kinetics of Li-ion deintercalation in the Li-rich layered Li1.12[Ni0.5Co0.2Mn0.3]0.89O2 studied by electrochemical impedance spectroscopy and galvanostatic intermittent titration technique

• DOI: 10.1016/j.electacta.2013.06.134
• Publication Date: 2013-07-08T06:02:45Z
• Authors: Yansong Bai; Xianyou Wang; Xiaoyan Zhang; Hongbo Shu; Xiukang Yang; Benan Hu; Qiliang Wei; Hao Wu; Yunfeng Song
• Keywords: Electrochemical kinetics; Double-layer capacitance; Open-circuit voltage

Abstract The kinetics of Li-ion deintercalation in Li 1.12 [Ni 0.5 Co 0.2 Mn 0.3 ] 0.89 O 2 samples is studied by electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT) during the first charge process. The impedance response of Li 1.12 [Ni 0.5 Co 0.2 Mn 0.3 ] 0.89 O 2 largely depends on the open-circuit voltage (OCV) of the cell, showing that the mechanism of electrode kinetics under different potentials is dominated by different electro-chemical reactions. Meanwhile, the equivalent circuit is proposed to simulate the EIS data, deducing the circuit elements ( R i and C i ) which are normally modeled as a multistep process of electro-chemical reactions. The change trend of R sf (the resistance of SEI film) and R ct (the charge-transfer resistance) in the first charge process are exactly similar. The C dl (double-layer capacitance) as a function of voltage gradually increases, particularly after 4.5 V. The maximum of C sf (the film capacitor) observed in the first charge process shows that the most intensive ionic fluxes will appear when the Li 1.12 [Ni 0.5 Co 0.2 Mn 0.3 ] 0.89 O 2 electrode reach to the transient equilibrium at different levels of deintercalation. To study the faster capacity fading of Li 1.12 [Ni 0.5 Co 0.2 Mn 0.3 ] 0.89 O 2 during the first charge process, the Li-ion diffusion coefficient ( D Li ) is also calculated based on the results of EIS and GITT.