High capacity sodium-rich layered oxide cathode for sodium-ion batteries

摘要

Sodium-ion batteries have attracted significant recent attention currently considering the limited available lithium resource.However,the energy density of sodium-ion batteries is still insufficient compared to lithium-ion batteries,mainly because of the unavailability of high-energy cathode materials.In this work,a novel sodium-rich layered oxide material (Na2MnO3) is reported with a dynamical stability similar to that of the Li2MnO3 structure and a high capacity of 269.69 mA.h.g1,based on first-principles calculations.Sodium ion de-intercalation and anionic reaction processes are systematically investigated,in association with sodium ions migration phenomenon and structure stability during cycling of NaxMnO3 (1 ≤ x ≤ 2).In addition,the charge compensation during the initial charging process is mainly contributed by oxygen,where the small differences of the energy barriers of the paths 2c→4h,4h→2c,4h→4h,2c→2b,and 4h→2b indicate the reversible sodium ion occupancy in transitional metal and sodium layers.Moreover,the slow decrease of the elastic constants is a clear indication of the high cycle stability.These results provide a framework to exploit the potential of sodium-rich layered oxide,which may facilitate the development of high-performance electrode materials for sodium-ion batteries.