In Situ Observation of the Effect of Accelerating Voltage on Electron Beam Damage of Layered Cathode Materials for Lithium-Ion Batteries

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 LiNiO₂ has much lower threshold energy for displacement than Co in LiCoO₂, 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.