Lithium-ion transfer at the interfaces between LiCoO2 and LiMn2O4 thin film electrodes and organic electrolytes

Interfacial reactions at positive electrodes and organic electrolytes interface for Li-ion batteries are studied by AC impedance methods. Thin film electrodes with flat and smooth surface are prepared by pulsed laser deposition, and the Li-ion transfer is investigated at structurally ordered interface. Charge transfer resistances attributed to Li-ion transfer at the interface are observed. The charge transfer resistances on LiMn2O4 thin film electrode are much smaller than those on c-axis orientated LiCoO2 thin film electrode, indicating that the charge transfer resistances are influenced by the number of active sites at the interface. Irrespective with positive electrode materials, activation energies evaluated from the temperature dependence of Li-ion transfer resistances are almost similar (about 50 kJ mol−1). These large activation energies suggest the existence of large energy barrier for Li-ion transfer at the interface between positive electrodes and organic electrolytes. After several charge-discharge cycles, some differences in the charge transfer resistances are observed; the increases in resistances on LiMn2O4 thin film electrode are smaller than those on LiCoO2 thin film electrode.