Li-Ni-Mn-Co-Ti-O Voltage Profile

Abstract

The performance enhancements associated with Ti substitution of Co in the layered cathode material Li1(NixMnxCo1-2x)O2 were investigated using density functional theory calculations. Examining the structural and electronic changes at different lithium concentrations revealed that Ti substitution reduces the structural changes during delithiation due to the larger Ti cation and to the formation of an electron polaron on a Mn cation. The structural differences correlated with a decrease in the lithium intercalation voltage at lower lithium concentrations which should provide the additional capacity determined experimentally. Furthermore, we find that Ti addition suppresses the formation of the secondary rock salt phase associated with high voltage cycling, with the added stability attributed to stronger oxygen binding. Our results indicate how specific performance enhancement in electrode materials can be traced to distinct structural, electronic and thermodynamic changes resulting from controlled substitution.