Synthesis and Performance Elucidation of Ternary O3-Na0.8Fe0.4Mn0.3-Co0.2O2 Layered Positive Electrode for Sodium Ion Batteries

Abstract

We report here a combination of transition metal-based ternary sodium magnate layered cathodes with the compositions of Na_0.8Fe_0.4Mn_0.3Co_0.2O₂, Na_0.8Fe_0.4Mn_0.3Ni_0.2O₂, Na_0.8Fe_0.4Mn_0.3V_0.2O₂, Na_0.8Fe_0.4Mn_0.3Ti_0.2O₂, in order to elucidate the precise metal contents for the superb performing positive electrode. Based on their stoichiometry, the transition metal combination of Na_0.8Fe_0.4Mn_0.3Co_0.2O₂, O3-type crystal structure with R3m space group possess superior electrochemical behavior under the test of sodium-ion battery. When the charge-discharge capacities in the range of 2.0-4.2 V at 0.1 C are measured, it shows the comparatively higher performance of the first and second charge capacities of 162 mAhg^-1, 170 mAhg^-1 and discharge capacities of 157 mAhg^-1, 154 mAhg^-1, respectively. Moreover, it was remarkable to observe that the increasing/decreasing Co constituent substantially affects the performance and stability, but using the ternary combination in cathodes, a substantial reduction of Jahn-Teller distortion and increased biphasic characteristics were observed. The as-synthesized samples were characterized by FE-SEM, XRD, charge-discharge curve, EIS and cyclic voltammograms.