context: 7Li magic-angle spinning (MAS) ssNMR spectroscopy was performed to trace the local environment of Li. Fig. 2d and S4a† shows the 7Li projection magic-angle turning and phase-adjusted sideband separation (pjMATPASS) spectra for the pristine, two-cycled and treated LMO. The pristine LMO showed two isotropic peaks resulting from Li in the octahedral site (LiO6). The main peak with a shoulder at around 748 ppm comes from Li in the Li layer and the one at around 1500 ppm can be attributed to Li in the TM layer. For pristine LMO, the small peak at around 0 ppm was due to the residual Li2CO3. The main peaks at around 748 ppm and 1500 ppm remained in the two-cycled LMO samples (Fig. S4a†). The sharp signal with enhanced intensity at around 0 ppm was mainly due to the solid electrolyte interphase (SEI) components, such as Li2CO3 and LiF. The treated T-LMO sample exhibited that some Li-ions remained in the TM layer, as for LMO and two-cycled LMO. The remaining sidebands at around ±250 ppm in T-LMO came from a peak at around 0 ppm. Besides the similar peaks in LMO, a new peak appeared at around 529 ppm in T-LMO, which can be ascribed to Li in the tetrahedral site, like that in LiMn2O4. A broad peak at around 660 ppm corresponds well with that of the Li2Mn4O9 reference with Li in the tetrahedral site (Fig. S4b†). Although a small amount of disordered shells may exist in the T-LMO sample, their intensities are too low to be detected here, which might be overlapped by the strong NMR signal associated with Li contained in the crystalline core of the particles. The T-LMO curve was deconvoluted by the standard reference spectrum (black curve), which showed that T-LMO consists of 35.5% LMO, 16.9% LiMn2O4 and 47.6% Li2Mn4O9. The NMR spectra result provides direct evidence that new spinel phases appear in the T-LMO, which may be due to cation rearrangement.