Structural fatigue in spinel electrodes in Li/Lix[Mn2]O4 cells

Evidence of structural fatigue has been detected at the surface of discharged Lix[Mn2]O4 spinel electrodes in Li/Lix[Mn2]O4 cells. Transmission electron microscopy has revealed a degradation of the structural integrity of Li[Mn2]O4 crystals in electrodes that were cycled between 3.3 and 2.2 V, where the transformation from cubic Li[Mn2]O4 to tetragonal Li2[Mn2]O4 is expected. It has also been observed in cells cycled at voltages above the 3 V plateau that domains of tetragonal Li2[Mn2]O4 coexist with cubic Li[Mn2]O4, even at 500 mV above the thermodynamic voltage expected for the onset of the tetragonal phase. It is proposed that the presence of Li2[Mn2]O4 on the particle surface may contribute to some of the capacity fade observed during cycling of Li/Lix[Mn2]O4 cells.