The layered lithium-ion cathode material LiNiO₂ (LNO) has attracted significant attention due to its high energy density, yet challenges related to structural stability and degradation during cycling have hindered its commercial adoption. Materials Chemistry Consortium Members at the University of Birmingham have advanced understanding of these issues by investigating the conditions under which molecular oxygen species form in nickel-rich cathodes at high states of charge.
Through a combination of atomistic modelling and a targeted redox-product structure search, the team identified two critical insights: (1) charged LiNiO₂ is kinetically stable and resists decomposition into molecular oxygen and reduced transition metal phases; and (2) structural defects can serve as nucleation points for oxygen formation. These findings help clarify previous inconsistencies in the literature regarding oxygen release in bulk LNO and related materials.
The project benefited from extensive benchmarking and method development work, made possible by access to large-scale compute resources on ARCHER2. This computational power was crucial for evaluating the stability of a wide range of potential redox products and for exploring the complex interplay between charge state, structure, and defect chemistry in LNO. The ability to perform high-throughput and large-scale calculations ensured that the methodological framework developed alongside the scientific investigation was both robust and scalable.
Outcomes:
- Demonstrated the kinetic stability of charged LiNiO₂ against decomposition into molecular oxygen and reduced Ni species.
- Identified structural defects as key sites for initiating molecular oxygen formation at high charge.
- Showed the critical role of defect chemistry in degradation mechanisms limiting cathode performance.
- Developed a scalable redox-product search approach, benchmarked extensively using ARCHER2.
- Provided insights to guide the design of more stable, high-energy-density lithium-ion cathode materials.
Funding
- This work was supported by the Faraday Institution (Grant No. FIRG017)
Contact for Further Information
- David Scanlon, Alex Squires, University of Birmingham