Manganese based layered oxides with modulated electronic and thermodynamic properties for sodium ion batteries

Abstract

Manganese based layered oxides have received increasing attention as cathode materials for sodium ion batteries due to their high theoretical capacities and good sodium ion conductivities. However, the Jahn–Teller distortion arising from the manganese (III) centers destabilizes the host structure and deteriorates the cycling life. Herein, we report that zinc-doped Na _0.833[Li _0.25Mn _0.75]O ₂ can not only suppress the Jahn–Teller effect but also reduce the inherent phase separations. The reduction of manganese (III) amount in the zinc-doped sample, as predicted by first-principles calculations, has been confirmed by its high binding energies and the reduced octahedral structural variations. In the viewpoint of thermodynamics, the zinc-doped sample has lower formation energy, more stable ground states, and fewer spinodal decomposition regions than those of the undoped sample, all of which make it charge or discharge without any phase transition. Hence, the zinc-doped sample shows superior cycling performance, demonstrating that zinc doping is an effective strategy for developing high-performance layered cathode materials.

Abstract

Mn-based layered oxides are promising cathode materials for next generation sodium ion batteries. To address two existing issues facing the system, here the authors show that a simple zinc doping can suppress both Jahn–Teller distortion and phase separation, enabling enhanced cycling performance.