Electrochemical deintercalation kinetics of 0.5Li2MnO3·0.5LiNi1/3Mn1/3Co1/3O2 studied by EIS and PITT

Abstract

The charge transfer resistances (Rct) and chemical diffusion coefficients of lithium ions (DLi+) in 0.5Li2MnO3·0.5LiNi1/3Mn1/3Co1/3O2 at various potentials in the first charge process were systematically tested by EIS and PITT. In the initial stage of the charging process, Rct gradually decreased to a minimum value of 68.5 Ω at 4.0 V. Then it sharply increased to 977.5 Ω at 4.8 V. The main reason was the activation of Li2MnO3 component started to decompose to Li2O and MnO2 at about 4.5 V. The DLi+ obtained from EIS and PITT was greatly dependent on the potential and it in the range of 10−16 to 10−12 cm2 s−1and 10−14 to 10−13 cm2 s−1, respectively. The DLi+ variation tendency with cell potential obtained from EIS and PITT was consistent with each other and with a maximum value at 4.0 V. The low Li+ diffusion coefficients was due to the high kinetic barrier associated with oxygen loss, surface and structural rearrangement. The results showed that the kinetic of 0.5Li2MnO3·0.5LiNi1/3Mn1/3Co1/3O2 was controlled by lithium-ion diffusion in the low voltage (<4.0 V) and controlled by charge transfer resistance in the high voltage (>4.3 V).