context: EELS spectra are obtained from the thin edge of cycled LLOs as labelled by the orange lines in Fig. 4(a and d) to study oxygen vacancies and TM valence states. Detailed comparisons of O-K, Ni-L, Co-L and Mn-L spectra are presented in Fig. 4(g–j) and S7.† For O-K edges, the intensity of the prepeak (∼530 eV) is sensitive to the valence states of TM ions. The intensity of this prepeak decreases drastically from the interior of the particle to the surface and almost disappears at the surface of the cycled LLOs at the cut-off of 4.8 V (Fig. S7†), indicating a significant decrease of TM valence states. This matches well with the fine changes of Mn-L edges in Fig. 4(h), which show a chemical shift (∼2.5 eV) toward the lower binding energy on the surface (0–10 nm depth), as compared with the cycled bulk (≥30 nm depth). These signatures demonstrate that the majority of Mn ions start to shift to a lower valence at a depth of 20 nm beneath the surface of cycled LLOs at the cut-off of 4.8 V, while for the LLOs cycled at 4.5 V, the reduced valence of dominant Mn ions occurs in the top 10 nm layer beneath the surface (Fig. 4(j)). The valence decrease of Mn ions in LLOs is usually accompanied by Mn dissolution into the electrolyte during cycling, which is measured by ICP-OES as shown in Fig. S8.† The Mn concentration dissolved in the electrolyte at the cut-off of 4.8 V after 100 and 200 cycles reaches 139 and 267 ppm, respectively, which are much higher than the 56 and 97 ppm at 4.5 V. These results confirm the reduced Mn dissolution into the electrolyte for the LLOs cycled at the low cut-off of 4.5 V.