Capacity Loss of Lithium Manganese Oxide Spinel in LiPF6 / Ethylene Carbonate‐Dimethyl Carbonate Electrolytes

The stability of lithium manganese oxide spinel in LiPF{sub 6}/EC:DMC (ethylene carbonate-dimethyl carbonate) based electrolytes has been investigated at different states of charge and at temperatures between 21 and 55 C. Reversible capacity loss due to reinsertion of lithium takes place at all states of charge and temperature. This reaction can proceed to the extent of inserting more than one Li per Mn{sub 2}O{sub 4} at 55 C resulting in the formation of tetragonal Li{sub 1+x}Mn{sub 2}O{sub 4}. The second process, irreversible capacity loss due to dissolution of the cathode, makes little contribution to capacity loss in highly charged electrodes, but has an effect comparable to reinsertion in discharged electrodes.