The electrochemical behavior of an LiMn2O4 electrode in organic electrolytes, consisting of mixed carbonate solvents with lithium (Li) salts, has been studied by constant current polarization and electrochemical impedance spectrometry. The discharge capacity and the impedance response of the electrode depended on the electrolyte composition. The state of charge, namely the Li content in the metal oxide, varied the impedance response. The interfacial resistance was more influenced by the electrolytic salt than the solvent. The apparent diffusion coefficient of Li in the oxide was evaluated from the impedance response. The relationship between the impedance response and the electrolyte composition is discussed.