Structural origin of the high-voltage instability of lithium cobalt oxide

Layered lithium cobalt oxide (LiCoO2, LCO) is the most successful commercial cathode material in lithium-ion batteries. However, its notable structural instability at potentials higher than 4.35 V (versus Li/Li+) constitutes the major barrier to accessing its theoretical capacity of 274 mAh g(-1). Although a few high-voltage LCO (H-LCO) materials have been discovered and commercialized, the structural origin of their stability has remained difficult to identify. Here, using a three-dimensional continuous rotation electron diffraction method assisted by auxiliary high-resolution transmission electron microscopy, we investigate the structural differences at the atomistic level between two commercial LCO materials: a normal LCO (N-LCO) and a H-LCO. These powerful tools reveal that the curvature of the cobalt oxide layers occurring near the surface dictates the structural stability of the material at high potentials and, in turn, the electrochemical performances. Backed up by theoretical calculations, this atomistic understanding of the structure-performance relationship for layered LCO materials provides useful guidelines for future design of new cathode materials with superior structural stability at high voltages. A three-dimensional continuous rotation electron diffraction method allows atomistic characterization of the chemistry of curved layered cathode materials.

Automated summary

Layered lithium cobalt oxide is a successful commercial cathode material in lithium-ion batteries, but its structural instability at high potentials poses challenges. By using advanced electron diffraction methods and high-resolution transmission electron microscopy, researchers have identified that the curvature of cobalt oxide layers near the surface plays a crucial role in determining the structural stability and electrochemical performance of the material. This atomistic understanding of structure-performance relationships provides valuable insights for designing new cathode materials with superior stability at high voltages.