Exploring Lithium Doping in the Layered Transition-Metal Oxides As Cathode Materials for Sodium-Ion Batteries

Layered transition metal oxides have been one of the most promising cathode materials in the lithium-ion as well as sodium-ion batteries. In the case of sodium-ion battery configuration, several transition metals elements are electrochemically active, leading to an extensive study on the composition and structure-property relationships. Particularly, substituting elements in the layered structure is one of the effective approaches to alter the composition, structure, and electrochemical properties. The substituted element could be positioned at either transition metal site or alkali site of the layered structure and plays different role depending on the position. In this talk, I will present the substitution of lithium on different sites within the layered oxides and its effect on the electrochemical performances. Lithium was substituted at (1) alkali site of O3-type layered structure and (2) transition metal site of P2-type layered structure as cathode materials for sodium-ion batteries. The substitution sites were identified by synchrotron and neutron powder diffraction patterns. Each type was compared with transition metal oxides that do not include lithium in order to understand the role of lithium in each substitution site.