The relationship between the structural changes and the capacity retention of oxygen-rich LiMn ₂O ₄ type cathode materials during cycling studied by in situ x-ray diffraction

Using in situ synchrotron x-ray diffraction during charge-discharge cycling, the relationship between the electrochemical performance and structural changes during cycling of a newly developed spinel cathode material was studied. This aluminum doped, lithium-rich new material, Li _1.07Al _0.15Mn ₁78O ₄, was jointly developed by Saga University and TOSOH Corporation in Japan. During the first charge from 3.0V to 4.8V, pseudo one-phase structural changes were observed. During the first discharge to 0.3V, tetragonal phase formation, which is normally observed in conventional LiMn ₂O ₄ spinel cathode after discharging below 3V, was suppressed at voltage as low as 0.3V. After multi-cycle cycling, the amount of inactive (dead) substance in this material is much less than that in oxygen deficient reference materials.