A ⁷Li NMR study of lithium insertion into lithium manganese oxide spinel

⁷Li magic angle spinning nuclear magnetic resonance was used to observe coexisting cubic and tetragonal phases in Li_1+xMn₂O₄. Cubic phase peaks are observed at 500-580 ppm vs. 1 M LiCL(aq); tetragonal phase peaks are observed around 100 ppm. Cycling Li_1+xMn₂O₄ on the 3 V plateau does not result in significant changes in the cubic phase. A small amount of residual tetragonal phase accounting for ∼3% of the ⁷Li NMR intensity, however, is observed in spinel deep discharged to x=1 then returned to x=0.