Investigation of structure and electrochemical properties of layered structure NaFexMn1-xO2

Layered oxides are promising electrode materials for sodium-ion batteries, the next generation of rechargeable batteries. The layered oxides with the tránition metallic manganese and iron have paid more attention due to its low-cost, eco-friendly, and facile preparation. In this work, the metallic sodium oxides with a layered structure based on Fe and Mn, NaFexMn1-xO2 (x = 1/3, 1/2 và 2/3) were synthesized via a solid-state reaction at 900 oC for 12–36 hours. All XRD patterns of NaFexMn1-xO2 pointed out the layered structure. In two ratio Fe:Mn = 1/3:2/3 and 1/2:1/2, the synthesized samples presented the P3-layered structure, while in ratio Fe:Mn = 2/3:1/3, the O3-structure was obtained. The lattice parameters were determined by Celref software. The lattice parameters and the volumic of unit cells depended on the ionic radius of cation Mn3+ and Fe3+. The Na-migration was studied by the cycling test with a constant current. The charge-discharge curves and the specific capacity depended on the ratio of Fe:Mn. The specific capacity was found out 120 mAh/g (1/2:1/2), 118 mAh/g (2/3:1/3), and 120 mAh/g (1/3:2/3). After 20 cycles, the capacity was maintained 77 mAh/g (1/2:1/2), 88 mAh/g (2/3:1/3), and 80 mAh/g (1/3:2/3).