Significant Performance Enhancement in Asymmetric Supercapacitors based on Metal Oxides, Carbon nanotubes and Neutral Aqueous Electrolyte.

Arvinder Singh,Amreesh Chandra

doi:10.1038/srep15551

Arvinder Singh, Amreesh Chandra

Open Access

https://doi.org/10.1038/srep15551

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Journal: Scientific reports	Publication Date: Oct 23, 2015
Citations: 114	License type: CC BY 4.0

Affiliation: Indian Institute of Technology Kharagpur

Abstract

Amongst the materials being investigated for supercapacitor electrodes, carbon based materials are most investigated. However, pure carbon materials suffer from inherent physical processes which limit the maximum specific energy and power that can be achieved in an energy storage device. Therefore, use of carbon-based composites with suitable nano-materials is attaining prominence. The synergistic effect between the pseudocapacitive nanomaterials (high specific energy) and carbon (high specific power) is expected to deliver the desired improvements. We report the fabrication of high capacitance asymmetric supercapacitor based on electrodes of composites of SnO2 and V2O5 with multiwall carbon nanotubes and neutral 0.5 M Li2SO4 aqueous electrolyte. The advantages of the fabricated asymmetric supercapacitors are compared with the results published in the literature. The widened operating voltage window is due to the higher over-potential of electrolyte decomposition and a large difference in the work functions of the used metal oxides. The charge balanced device returns the specific capacitance of ~198 F g−1 with corresponding specific energy of ~89 Wh kg−1 at 1 A g−1. The proposed composite systems have shown great potential in fabricating high performance supercapacitors.

Highlights

There is a growing demand to bring a step change in the specific power and energy delivered by supercapacitors
It is shown that the synergistic effect of Multiwall carbon nanotubes (MWCNTs) with electroactive materials SnO2 and V2O5 can lead to appreciable increase in the specific capacitance
From the transmission electron microscopy (TEM) micrographs, it can be seen that spherical SnO2 nanoparticles and layered V2O5 are uniformly dispersed in the MWCNTs (MW) matrix

Summary

Introduction

There is a growing demand to bring a step change in the specific power and energy delivered by supercapacitors Such increase, along with the intrinsic advantage of fast charging/discharging rates, long cycle life (> 10,000 cycles), and wide operational temperature range will allow the supercapacitors to compete with Li-ion batteries. The specific energy (E) of supercapacitors can be enhanced by increasing the operating voltage window (V) and/or capacitance (C) as E = 1⁄2CV2. Correctly charge-balanced electrodes endows ASCs with the advantage of an extended cell voltage and high specific energy. The charge balanced device assembled in 0.5 M Li2SO4 can be operated up to 1.8 V with no signature of gaseous evolution at upper bound of the potential This allows the device to reach the maximum specific capacitance of ~198 F g−1 and specific energy of ~89 Wh kg−1. The reasons contributing to the enhancement of specific energy are explained using the relevant theoretical models

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Conclusion