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

The charge transfer resistances (R-ct) and chemical diffusion coefficients of lithium ions (DLi+) in 0.5Li(2)MnO(3)center dot 0.5LiNi(1/3)Mn(1/3)Co(1/3)O(2) at various potentials in the first charge process were systematically tested by EIS and PITT. In the initial stage of the charging process, R-ct gradually decreased to a minimum value of 68.5 Omega at 4.0 V. Then it sharply increased to 977.5 Omega 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) cm(2) s(-1) and 10(-14) to 10(-13) cm(2) 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 0.5Li(2)MnO(3)center dot 0.5LiNi(1/3)Mn(1/3)Co(1/3)O(2) 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). (C) 2016 Elsevier B.V. All rights reserved.