The kinetics of Li-ion deintercalation in the Li-rich layered Li sub(1.12)[Ni sub(0.5)Co sub(0.2)Mn sub(0.3)] sub(0.89)O sub(2) studied by electrochemical impedance spectroscopy and galvanostatic intermittent titration technique

The kinetics of Li-ion deintercalation in Li sub(1.12)[Ni sub(0.5)Co sub(0.2)Mn sub(0.3)] sub(0.89)O sub(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 sub(1.12)[Ni sub(0.5)Co sub(0.2)Mn sub(0.3)] sub(0.89)O sub(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 sub(i) and C sub(i)) which are normally modeled as a multistep process of electro-chemical reactions. The change trend of R sub(sf) (the resistance of SEI film) and R sub(ct) (the charge-transfer resistance) in the first charge process are exactly similar. The C sub(dl) (double-layer capacitance) as a function of voltage gradually increases, particularly after 4.5 V. The maximum of C sub(sf) (the film capacitor) observed in the first charge process shows that the most intensive ionic fluxes will appear when the Li sub(1.12)[Ni sub(0.5)Co sub(0.2)Mn sub(0.3)] sub(0.89)O sub(2) electrode reach to the transient equilibrium at different levels of deintercalation. To study the faster capacity fading of Li sub(1.12)[Ni sub(0.5)Co sub(0.2)Mn sub(0.3)] sub(0.89)] sub(0.89)O sub(2) during the first charge process, the Li-ion diffusion coefficient (D sub(Li)) is also calculated based on the results of EIS and GITT.