context: The anisotropic expansion of primary grains, especially at a high state of charge (SOC), results in microcracks in NCM-based secondary particles. The morphology changes of the LLO microspheres after 200 cycles at the cut-offs of 4.8 V and 4.5 V are studied by SEM in Fig. S3.† The LLO microspheres cycled at the cut-off of 4.8 V show some obvious cracks, especially for large particles. But for the LLO particles cycled at 4.5 V, there are no obvious cracks. The structural evolutions of the LLOs at the cut-offs of 4.8 V and 4.5 V are investigated by STEM and EELS, as shown in Fig. 4 and S4–S8.† The cross-sections of both cycled LLOs are shown in Fig. S8,† in which the porous structure can still be found. The elemental maps exhibit heterogeneous distribution of TM elements in both cycled LLOs (Fig. S5 and S6†). The intergranular space is mainly filled with F and C containing compounds while the surface is mainly coated with P containing compounds for both cycled LLOs. The low magnification HAADF-STEM image (Fig. 4(a)) shows some microcracks in the cycled LLOs at the cut-off of 4.8 V. The high resolution HAADF-STEM image with the FFT and inverse FFT patterns (Fig. 4(b and c)) confirms the entire transformation from layered to rock-salt phases on the surface of LLOs at the cut-off of 4.8 V. The LLOs at the cut-off of 4.5 V undergo transitions from layered to layered/rock-salt mixed and rock-salt phases over long-term cycling (Fig. 4(d–f)). These results confirm the mitigated phase transition for LLOs over long-term cycling at the low cut-off of 4.5 V, which is probably ascribed to the reduced side reaction on the electrode/electrolyte interface.