Discovery of a high-pressure phase of rutile-like CoO2 and its potential as a cathode material†
Due to the structural failure of layered CoO2, there has been considerable effort to improve the reversible capacity of commercial LiCoO2 cathode materials. Using a global structural search, we have discovered a rutile-like CoO2 phase as the ground state at 50 GPa. The material is thermally, mechanically and dynamically stable, even after removing the pressure. We show that, when lithiated, this LiCoO2 material can serve as an improved cathode material for Li-ion batteries. Its many advantages include good structural stability against transition metal migration and oxygen loss, one-dimensional channels for Li ion diffusion with variable energy barriers (0.36–0.86 eV), enhanced ionic mobility, and good intrinsic electronic conductivity brought about by its metallic band structure. Furthermore, with a voltage platform of 3.2–3.8 V, it provides better stability against conventional carbonate solvents than conventional layered cathode materials (>4.0 V). All these features demonstrate that the non-layered CoO2 phase synthesized at high pressure would be a promising cathode material, providing a performance beyond that of the currently used layered phase.
- This article is part of the themed collection: 2018 Journal of Materials Chemistry A HOT Papers