Exploring the Impact of Lanthanum on Sodium Manganese Oxide Cathodes: Insight into Electrochemical Performance

Abstract

This investigation focuses on nominally La-doped Na0.67MnO2, exploring its structural, electrochemical, and battery characteristics for Na-ion batteries. X-ray diffraction analysis reveals formation of composite materials containing three distinct phases: P2-Na0.67MnO2, NaM(n)8O(16), and LaMnO3. The bond structures of the powders undergo scrutiny through Fourier-transform infrared and Raman analyses, revealing dependencies on the Na-O, Mn-O, and La-O structures. X-ray photoelectron spectroscopy and energy-dispersive X-ray dot mapping analyses show that the La ions are unevenly dispersed within the samples, exhibiting a valence state of 3+. Half-cell tests unveil similarities in redox peaks between the cyclic voltammetry analysis of La-doped samples and P2-type Na0.67MnO2, with a reduction in peak intensities as La content increases. Electrochemical impedance spectroscopy model analysis indicates direct influences of La content on the half-cell's resistive elements values. The synergistic effect of composite material with multiple phases yields promising battery performances for both half and full cells. The highest initial capacity value of 208.7 mAh g(-1), with a 57% capacity fade, among others, is observed, and it diminishes with increasing La content. Full cells are constructed using an electrochemically presodiated hard carbon anode, yielding a promising capacity value of 184.5 mAh g(-1) for sodium-ion battery studies.