Comparison of Lattice Vibrations in Delithiated LCO and LNO

This application aims to map Ni/Co phonon modes in delithiated lithium-ion battery cathode materials, specifically delithiated LiCoO2 (LCO) and LiNiO2 (LNO), to determine which modes are responsible for transition metal mobility hence cathode instability. Lithium-ion batteries that have high energy densities are crucial for the shift to electric vehicles, but their capacity is approaching a ceiling. Increasing capacity involves substituting the Co content in the cathode for Ni. Recently published work from our group suggested that in the Ni-rich archetype LiNiO2 cathode, irreversible phase transitions happens due to transition metal migration upon delithiation. At 4.1V vs. Li+/Li, LNO undergoes a transition from an H2 to an H3 phase, leading to antisite disorder between the Li and Ni. At 4.3V and above, the Li in the structure will be extracted fully and anionic redox will dominate. Ni then migrates from the fully dense transition metal layer and accumulates at the surface of the particles, leaving vacancies on the transition metal site. This reduces the performance of LiNiO2. This is not observed with LiCoO2 which also has better battery cycling stability.
To investigate Ni's mobility compared to Co's, we propose using inelastic neutron scattering to observe Ni phonon modes across a wide temperature range. This study will address the lack of INS data on cathode materials and contribute foundational insights into layered cathode behaviour.