Toward Low-Cost and Sustainable Supercapacitor Electrode Processing: Simultaneous Carbon Grafting and Coating of Mixed-Valence Metal Oxides by Fast Annealing.

Keyvan Malaie,Francesca Soavi,Mohammad Reza Ganjali

doi:10.3389/fchem.2019.00025

Keyvan Malaie, Francesca Soavi + Show 1 more

Open Access

https://doi.org/10.3389/fchem.2019.00025

Copy DOI

Abstract

There is a rapid market growth for supercapacitors and batteries based on new materials and production strategies that minimize their cost, end-of-life environmental impact, and waste management. Herein, mixed-valence iron oxide (FeOx) and manganese oxide (Mn3O4) and FeOx-carbon black (FeOx-CB) electrodes with excellent pseudocapacitive behavior in 1 M Na2SO4 are produced by a one-step thermal annealing. Due to the in situ grafted carbon black, the FeOx-CB shows a high pseudocapacitance of 408 mF cm−2 (or 128 F g−1), and Mn3O4 after activation shows high pseudocapacitance of 480 mF cm−2 (192 F g−1). The asymmetric supercapacitor based on FeOx-CB and activated-Mn3O4 shows a capacitance of 260 mF cm−2 at 100 mHz and a cycling stability of 97.4% over 800 cycles. Furthermore, due to its facile redox reactions, the supercapacitor can be voltammetrically cycled up to a high rate of 2,000 mV s−1 without a significant distortion of the voltammograms. Overall, our data indicate the feasibility of developing high-performance supercapacitors based on mixed-valence iron and manganese oxide electrodes in a single step.

Highlights

Supercapacitors are attracting increasing attention in today’s fast-growing electronics industry
For the first time, we report a novel synthesis approach to develop green supercapacitors based on binder-free, nonprecious metal oxides electrodes, that is, a fast thermal annealing (FTA) method for the preparation of pseudocapacitor electrodes based on amorphous iron oxide-carbon black (FeOx-CB) and Mn3O4x with high areal capacitances
We show that CB can be in situ composited with the metal oxides and simultaneously coated on the nickel foam without employing any binder, which improves the electrochemical performance of the pseudocapacitor substantially by reducing the electrical resistance and promoting charge transfer rate

Summary

INTRODUCTION

Supercapacitors are attracting increasing attention in today’s fast-growing electronics industry. Iron and manganese oxides have complementary working potential windows, making them appealing for developing high-voltage aqueous asymmetric supercapacitors Their only undesirable property is their low electrical conductivity that results in high IR drops at high charge/discharge rates. For the first time, we report a novel synthesis approach to develop green supercapacitors based on binder-free, nonprecious metal oxides electrodes, that is, a fast thermal annealing (FTA) method for the preparation of pseudocapacitor electrodes based on amorphous iron oxide-carbon black (FeOx-CB) and Mn3O4x with high areal capacitances. FTA is carried out at moderately low temperatures that reduces the energy cost of electrode production at large scale It requires a minimum amount of materials (i.e., only a metal nitrate in 5–10 ml of ethylene glycol as solvent) to prepare the electrodes; the waste produced during the electrode processing is very small. More details on the calculation of the supercapacitor parameters (Capacitance, and energy/power density) and their formulas can be found in section Preparation of Mn3O4/Ni Foam, Supplementary Material

RESULTS AND DISCUSSIONS

M Na2SO4 5 M LiCl

CONCLUSION