Lithium-rich layered cathode materials, where excess lithium occupies transition metal (TM) sites in the TM layer, have shown capacities well beyond commercially available traditional layered cathodes. This is largely attributed to redox behavior of oxygen within the cathode, and has recently been examined computationally¹. However this increased capacity is accompanied by a high degree of irreversible capacity loss in first cycling, voltage decay, and low rate capability. This is partially attributed to an oxygen release mechanism, where oxygen vacancy formation accompanies delithiation, rather than the redox of TM ions². Numerous methods have been attempted to prevent the release of oxygen from the lattice, including TM substitution, morphology control, and surface coating. In this work, we employ density functional theory to calculate the oxygen vacancy formation energy in layered lithium-rich nickel manganese oxide with a variety of cation dopants. Computational results elucidate the impact of doping on the system, and provide rationale for these behaviors. These calculations further describe the impact of local TM bonding environment on specific oxygen sites, rationalizing their relative vacancy formation energies. Driven by these computational results, we experimentally introduce relevant dopants into our cathode materials and observe electrochemical cycling changes commensurate with the predicted changes. Characterization methods verify the predicted oxidation states and incorporation of the relevant dopants.

1. Seo, D. et al. "The structural and chemical origin of the oxygen redox activity in layered and cation-disordered Li-excess cathode materials." Nat. Chem.8, 1–6 (2016).

2. Hy, S. et al. "Performance and Design Considerations For The lithium Excess Layered Oxide Positive Electrode Materials For Lithium Ion Batteries." Energy Environ. Sci. 9, 1931–1954 (2016).