Ab Initio Exploration of Co-Free Layered Oxides as Cathode Materials in Li Ion Batteries

Layered oxides are promising cathode materials for lithium ion batteries because of their high capacity and voltage. Nearly all commercial layered-oxide cathodes are composed of cobalt (Co), such as LiCoO2, Li(Ni,Mn,Co)O2, and Li(Ni,Co,Al)O2. However, the cost and supply of Co have been a major concern on future extensive applications of lithium ion batteries. Therefore, Co-free layered-oxide cathodes with good stability at a high state of charge (SoC) for high practical capacity and simultaneously high voltage are desired. Here, we systematically investigated Co-free layered oxides using ab initio calculations based on density functional theory. The effects of transition metals and the main group metals (Ti, Zr, Mo, V, Mn, Ni, Cr, Fe, Al, Sb, and Sn) as well as compound effects of layered oxides with multiple elements on oxygen stability and voltage were examined. In addition, phase stability analyses of promising compounds were performed. Among the complex chemical interplays, Li(Ni,Mn,Fe)O2 was found to be a promising system with superior phase stability and high voltage. Furthermore, Li(Ni1/3Mn1/3Fe1/3)O2 shows a higher ion migration barrier against phase transformation and better oxygen stability at a 66% SoC than the commercial Li(Ni1/3Mn1/3Co1/3)O2 layered-oxide cathode. This work opens the door for the development of novel Co-free cathodes for lithium ion batteries.