Electron beam damage from transmission electron microscopy of layered lithium transition-metal oxides is a threshold phenomenon that depends on the electron beam energy, which we demonstrate in this study by varying the accelerating voltage of a scanning transmission electron microscope. The electron beam irradiation experiment shows that Ni in LiNiO 2 has much lower threshold energy for displacement than Co in LiCoO 2 , which is supported by DFT calculations predicting that Ni has lower migration energy. The transition-metal ions are reduced from the oxidation state of +3 to +2 during migration from their original positions to the lithium sites, and Ni is more easily reduced than Co because of its electronic configuration. In addition, the high-energy electron beam induces oxygen release, which is another symptom of degradation of materials that occurs more strongly in Ni-containing materials with ion displacement.

The electrochemical properties of Li(NixCoyMnz)O2 (NCM) materials are decisively determined by the interplay of combined disordering of cations and the relevant chemical/electronic changes.

LiCoO2, one of the most popular cathode materials for lithium-ion batteries, is well known for undergoing insulator–metal transitions depending on the amount of lithium ions. In this study, we successfully visualize the change in the electrical conductivity of LiCoO2 without synthesizing large single crystals using conductive atomic force microscopy and high-resolution scanning electron microscopy. As expected, the anisotropic conductivity is observed only in the (003) plane. The electronic structures of LiCoO2, CoO2, and Li0.5CoO2 are studied from density functional theory calculation. This systematic calculation is in good agreement with the previously reported experimental finding that electron holes of hybrid orbitals of Co4+ (a1g) and oxygen (2p), which are produced by the lithium vacancy, contribute to the electrical conductivity of delithiated lithium cobalt oxides.