Lithium-ion rechargeable batteries find wide application in modern portable electronic devices. LiMn2O4 spinel is the most attractive cathode material for lithium-ion batteries due to its low cost, low toxicity and high energy density. An important problem prohibiting it from wider use as a cathode material is capacity fading during cycling. Jahn-Teller distortion and spinel solution are two main causes for the capacity loss. The charge ordering of Mn4+ and Mn3+ ions and Jahn-Teller distortion induces a phase transformation near the room temperature. The partial substitution of Li+ ions for manganese reduces the concentration of Mn3+ ions, suppresses the Jahn-Teller effect, and the cubic spinel phase can be retained at low temperature.
Small deviations in the preparation process can cause distinct structural changes. A slight lithium ions deficiency causes the tetragonal phase formation provided that the samples obtained at high temperature are rapidly quenched structure in the solid CO2. On the contrary, very small amount of excess lithium can influence the cubic to orthorhombic phase transition observed for stoichiometric LiMn2O4. Structure refinement by the Rietveld profile analysis, based on the laboratory and synchrotron radiation X-ray diffraction data, has been performed on the stoichiometric, Li-excess and Li-deficient lithium-manganese spinel oxide samples.
This work was supported by The Committee for Scientific Research (KBN) under the grant No 4T09A 164 23 (2002-2004).