Synthesis and Characterization of Nanoporous NaMn2O4 electrode Material for Sodium-Ion Battery

Lithium is relative expensive and will be exhaust one day due to the limitation of lithium resources on the earth. In contrast to lithium, sodium is more abundant and lower cost of sodium-containing precursors, leading to sodium-ion battery is a promising energy storage device for large-scale systems. ^1-3

In the present work, we synthesized NaMn₂O₄ spheres with mesoporous structure via a revised microwave assisted high temperature solid-state reaction.  As shown in Fig. 1a, the powders consist of plurality of NaMn₂O₄ spheres, ranging from 2 um to 5 um. The high magnification SEM image shows that the materials possess mesopores with the diameter around 20 nm. The uniform mesoporous structure optimizes the sodium ion diffusion path, and facilitates the transportation of ions. The electrochemical performances of the nanoporous NaMn₂O₄were investigated as the electrodes for sodium-ion battery. The three cycles of consecutive cyclic voltammogram (CV) at a scan rate of 0.1 mV/s are shown in Fig. 1c. The CV curve reveals the materials have excellent reversibility. It has five cathodic redox peaks at around 2.4 V, 2.5 V, 2.85 V, 3.47 V and 4.17 V in the voltage range 2.0 V to 4.5V, respectively, indicating the multi-step insertion of the sodium ion into NaMn2O4 nanostructures.  Five anodic peaks were also observed at around 2.35 V, 2.6 V, 3.2 V, 3.5 V and 4.25 V are ascribed to the sodium ion deintercalation process, respectively. The five pairs of redox peaks demonstrate the excellent reverse capability of the materials. Furthermore, there are a bit of shifts with the increase of the cycles, leading to good cyclability.  

References

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3.    A. Darwiche, C. Marino, M. T. Sougrati, B. Fraisse, L. Stievano and L. Monconduit, Journal of the American Chemical Society, 2012, 134, 20805-20811.