Strain-engineering and chemical doping of 3d transition metal oxides provide a rich playground for condensed matter physics, where phase transformations and new states of matter can be studied. At the heart of today’s Li-ion battery industry is the layered 3d metal oxide, Li_1-xCoO₂, which is used as the positive electrode. The reversible intercalation of Li ions from the lattice results in large lattice changes (>5%) and phase transformations induce heterogeneity at the atomic scale that ultimately limit the battery performance and lifetime. Although the full theoretical capacity of the LiCoO₂ is 274 mAh/g assuming full reversible Li extraction, the practical capacity is generally capped to half that i.e., voltage capped to avoid degradation due to phase transformations. To ultimately achieve energy density targets for the automotive industry of 500 Wh/Kg requires cathodes realizing > 250 mA/g. As a result, technological progress requires fundamental insight that a physics toolbox can provide regarding the evolution of LiCoO₂ derived cathode materials.

In this talk, I will summarize work employing a suite of Synchrotron-based techniques to bridge length scales in order to provide a complete description of the evolution of state-of-the-art Ni-rich cathode: Li_1-xNi_0.8Co_0.15Al_0.5O₂ (NCA) as we push towards full de-lithiation i.e., high voltages vs. Li⁺/Li⁰. Our recent studies have provided new insight into what is driving the surface degradation at high voltages and how it facilitates heterogeneity at the atomic scale limiting the battery performance.