Low-cost flexible supercapacitors with high-energy density based on nanostructured MnO2 and Fe2O3 thin films directly fabricated onto stainless steel.

Girish S Gund,Jun Y Cho,Chandrakant D Lokhande,Chan Park,Pedro Gomez-Romero,Deepak P Dubal,Nilesh R Chodankar

doi:10.1038/srep12454

Abstract

The facile and economical electrochemical and successive ionic layer adsorption and reaction (SILAR) methods have been employed in order to prepare manganese oxide (MnO2) and iron oxide (Fe2O3) thin films, respectively with the fine optimized nanostructures on highly flexible stainless steel sheet. The symmetric and asymmetric flexible-solid-state supercapacitors (FSS-SCs) of nanostructured (nanosheets for MnO2 and nanoparticles for Fe2O3) electrodes with Na2SO4/Carboxymethyl cellulose (CMC) gel as a separator and electrolyte were assembled. MnO2 as positive and negative electrodes were used to fabricate symmetric SC, while the asymmetric SC was assembled by employing MnO2 as positive and Fe2O3 as negative electrode. Furthermore, the electrochemical features of symmetric and asymmetric SCs are systematically investigated. The results verify that the fabricated symmetric and asymmetric FSS-SCs present excellent reversibility (within the voltage window of 0–1 V and 0–2 V, respectively) and good cycling stability (83 and 91%, respectively for 3000 of CV cycles). Additionally, the asymmetric SC shows maximum specific capacitance of 92 Fg−1, about 2-fold of higher energy density (41.8 Wh kg−1) than symmetric SC and excellent mechanical flexibility. Furthermore, the “real-life” demonstration of fabricated SCs to the panel of SUK confirms that asymmetric SC has 2-fold higher energy density compare to symmetric SC.

Highlights

Screens and electronic newspapers, demand light weight, flexible and highly integrated electronic devices to be folded, rolled up, or even remolded into other structures and safely
In order to use our Flexible-solid-state supercapacitors (FSS-SCs) device for portable electronic application as a practical energy storage device, it should feature excellent mechanical flexibility along with high energy density and high power density
To investigate the efficiency of asymmetric FSS-SC device in energy storage capabilities in comparison with the symmetric device, we examined the energy density and power density at different current densities

Summary

Introduction

Screens and electronic newspapers, demand light weight, flexible and highly integrated electronic devices to be folded, rolled up, or even remolded into other structures and safely. Yang et al.[20] combined the same electrode materials, prepared by chemical methods on carbon fabric for the fabrication of asymmetric FSS-SC device and got specific capacitance (energy density) of 91.3 F g−1 (33.5 W h kg−1) with 1.6 V potential. Our efforts focused on getting a unique combination of optimal elements for the low-cost fabrication of thin and flexible MnO2-Fe2O3 supercapacitors, including cheap fabrication technology, use of polymer gel electrolyte, highly flexible stainless steel (SS) substrate and use of simple chemical methods (facile and eco-friendly routes allowing for the synthesis of large area electrodes). We report here the fabrication and testing of thin flexible solid state supercapacitors (FSS-SCs) based on MnO2 (electrodeposited) and Fe2O3 (SILAR method) electrodes, which allowed for the direct deposition in thin film form through facile, fast, cost-effective, additive and binder-free, and eco-friendly synthesis routes suitable to prepare large area electrodes. Symmetric (MnO2/MnO2) and asymmetric (MnO2//Fe2O3) FSS-SC devices were demonstrated and tested

Objectives

Methods

Results

Conclusion