The Confi gurational Space of Rocksalt-Type Oxides for High-Capacity Lithium Battery Electrodes

be optimized. [ 7–12 ] In general, very little design guidelines are available to preselect high-capacity electrode materials, and the search for novel cathodes has been largely by trial and error. Here, we show that there is a welldefi ned relation between the composition, transition-metal ordering, and the diffusion kinetics of lithium intercalation. Mapping the confi gurational space of ordered and cation-disordered rocksalttype lithium metal oxides in terms of their diffusion kinetics leads to design guidelines for potential high-capacity cathode materials. Drawing a connection between the atomistic lithium hopping mechanism and macroscopic lithium diffusion allows us to determine the conditions under which fast lithium diffusion can be expected. Our methodology based on percolation theory is independent of the transition-metal species, and the results of our simulations therefore apply to any general rocksalt-type lithium metal oxide. In addition, it is straightforward to generalize the formalism to different classes of ion conductors, provided that the microscopic migration mechanism of the ions is known. In the second section, the structure of rocksalt-type lithium metal oxides and the current understanding of lithium migration are briefl y reviewed. A relationship between the microscopic hopping mechanism and macroscopic lithium diffusion is established. Percolation theory and the Monte–Carlo formalism used to predict lithium percolation properties are discussed in the third section. In sections 4 and 5, the results of the simulations are presented; we report critical compositions for the three most common ordered phases of lithium metal oxides, both, for the ideal crystal structures and as a function of gradual disordering. Finally, in section 6, we point out how the results of the percolation analyses can be used for engineering high-capacity cathode materials.