Electrochemical impedance spectroscopies of insertion and deinsertion of Li ion in spinel lithium manganese oxide with different contents of inserted lithium ions were studied by using a powder microelectrode. New equivalent circuits modeling the insertion and deinsertion were proposed to fit the experimental electrochemical impedance spectroscopies. The Warburg impedance describing the diffusion and the insertion capacitance describing the accumulation or consumption of Li ion in the oxide are in sequence when x ≤ 0.5, but in paralell when 0.5 < x≤ 1 in Li-x-MnO-4. The fitting results were in agreement with the experimental results. The capacitance and the resistance for the transfer of Li ions in the surface film on the oxide, the double capacitance and the resistance for the charge transfer of Li ion insertion or deinsertion, and the Warburg impedance and the insertion capacitance under different potentials were obtained by using the proposed models

Key words: SPINEL, MANGANESE OXIDE, LITHIUM OXIDE, LITHIUM ION, BATTERIES, EQUIVALENT CIRCUITS, DIFFUSION COEFFICIENTS