Effect of Concentration on the Charge Storage Kinetics of Nanostructured MnO<sub>2</sub> Thin-Film Supercapacitors Synthesized by the Hydrothermal Method

oleh: Aviraj M. Teli, Sonali A. Beknalkar, Sachin A. Pawar, Deepak P. Dubal, Tukaram D. Dongale, Dipali S. Patil, Pramod S. Patil, Jae Cheol Shin

Format: Article
Diterbitkan: MDPI AG 2020-11-01

Deskripsi

In this study, amorphous manganese oxide (MnO<sub>2</sub>) nanostructured thin films were synthesized by a simple hydrothermal method. It is well known that the nanostructure plays a crucial role in energy storage applications. Herein, MnO<sub>2</sub> nanostructures ranging from plates to flakes were synthesized without the use of any hard or soft templates. The 4+ oxidation state of Mn was confirmed by X-ray photoelectron spectroscopy. The MnO<sub>2</sub> nanoflake structure has a specific surface area of 46 m<sup>2</sup>g<sup>−1</sup>, which provides it with an excellent rate capability and an exactly rectangular cyclic voltammogram (CV) curve. The MnO<sub>2</sub> nanoflake electrode has a high specific capacitance of about 433 Fg<sup>−1</sup>, an energy density of 60 Whkg<sup>−1</sup> at 0.5 mAcm<sup>−2</sup>, and an excellent cyclic stability of 95% over 1000 CV cycles in 1 M aq. Na<sub>2</sub>SO<sub>4</sub>. Kinetics analysis of the charge storage in the nanoflake MnO<sub>2</sub> sample shows a 55.6% diffusion-controlled contribution and 44.4% capacitive-controlled contribution to the total current calculated at a scan rate of 100 mVs<sup>−1</sup> from the CV curve.