Sodium ion batteries (SIBs) continue to receive a tremendous exposure due to its natural abundance (2.6 wt. %, compared to lithium (0.06%)), cost effective and similar chemical and electrochemical properties to the lithium ion batteries (LIBs). However SIBs are still suffering with low energy density and long cycle life which impedes the wide applications and its development of SIBs. These drawbacks such as higher redox potential (-2.71 V vs. SHE), higher atomic mass (23 g mol^-1) and large ionic radii (1.02 Å) of sodium metal facing a challenge for the choice of the electrode materials for the SIBs. Therefore, it’s necessary to use suitable cathode materials in order to occupy the sodium ions during insertion and de-insertion process [1-2].

In this case, numerous cathode materials have been investigated for SIBs such as layered transition metal oxides, fluoride-based sulfates and phosphates, olivins, and NASICONs [3-5]. However, their electrochemical performance (specific capacity, long-term cyclability and rate capability performance) as reported is not satisfactory. Thus, the finding of suitable electrode materials is a key challenge for the development of high-performance SIBs [6].

Manganese dioxide is known for large open tunnels, which can provide interstitial spaces for Na-ion storage and transport. Also, manganese dioxide is highly abundant, low cost and environmental benign. Therefore, in this work, α-MnO₂ nanoplatelets/OLC composite was explored as cathode material and has been synthesized by microwave irradiation method using electrolytic manganese oxide (EMD). The physical and chemical characterizations of materials reveal single phase, Mn valence state and its nanoplatelet morphology. The electrochemistry of the fabricated cells was examined by cyclic voltammetry, galvanostatic cycling and electrochemical impedance spectroscopy. The α-MnO₂ nanoplatelets/OLC composite exhibits highly stable and better capacity retention compared to pure α-MnO₂ nanoplatelets cathode materials. In this discussion, the explored detail of the material and its preparation, physical and electrochemical properties of α-MnO₂ nanoplatelets and its composite cathode materials for the application of Na-ion batteries will be presented.

References:

[1] D. Su, et al., J. Mater. Chem. A, 1, 4845-4850 (2013)

[2] J. Y. Hwang, et al. Chem. Soc. Rev., 46, 3529-3614 (2017)

[3] S. Guo, et al. Angew. Chem. Int. Ed., 54, 5894-5899 (2015)

[4] Funeka P. Nkosi, et al. J. Electrochem. Soc., 164 (13), A3362-A3370 (2017)

[5] F. Yang, et al., Small Methods, 1, 1700216 (2017)

[6] D. Su, et al., Npg Asia Materials, 5, e70 (2013)