Title: Atomistic models of high-capacity layered metal oxide cathode materials
Abstract: New cathode materials with improved energy densities, longer cycle-life, and improved safety characteristics are needed for portable electronic devices, smart grid systems, and transportation technologies. The highest-energy-density cathode materials are based on transition-metal oxides, such as layered LiMO2 (M = Co, Ni, Mn). I will present two examples of current interest to the Li-ion battery research community.
The first example is on the promising layered Li(Ni1-x-yMnxCoy)O2 (NMC) oxides-based materials. These cathode materials are capable of addressing some of the challenges associated with next-generation energy storage devices. However, sufficient knowledge on the atomic-scale processes governing these metrics in working cells is still lacking.
The second example is on lithium and manganese-rich composite layered transition metal oxide (LMR-NMC) materials. These materials have the potential to double the capacity of the standard LiCoO2 electrodes. However they exhibit a slowly diminishing cell voltage with cycling known as voltage fade.
Herein, density functional theory is employed to predict the stability of several low-index surfaces of Li(Ni1/3Mn1/3Co1/3)O2 (NMC111) as a function of Li and O chemical potentials. Predicted particle shapes are compared with those of single crystal NMCs synthesized under different conditions. The reactivity of these surfaces toward electrolyte oxidation will also be presented. First-principles simulations are also performed on composite materials xLi2MnO3•(1-x)LiMO2 (with M = combinations Ni, Mn, and Co) to understand their behavior as cathode materials in Li-ion batteries. Attention is given to the structure of the pristine material, and to the destabilization of Mn and O ions with respect to migration that occurs during the first charge. Simulations have been applied to help interpret experimental x-ray (EXAFS and near-edge) and NMR spectroscopies.
Cm-Bio 3-9 Iddir