Supercapacitors have gained a lot of attention due to their unique features like high power, long cycle life and environment-friendly nature. They act as a link for energy-power difference between a traditional capacitor (having high power) and fuel cells/batteries (having high energy storage). In this perspective, a worldwide research has been reported to address this and rapid progress has been achieved in the advancement of fundamental as well as the applied aspects of supercapacitors. Here, a concise description of technologies and working principles of different materials utilized for supercapacitors has been provided. The main focus has been on materials like carbon-based nanomaterials, metal oxides, conducting polymers and their nanocomposites along with some novel materials like metal-organic frameworks, MXenes, metal nitrides, covalent organic frameworks and black phosphorus. The performance of nanocomposites has been analysed by parameters like energy, capacitance, power, cyclic performance and rate capability. Some of the latest supercapacitors such as electrochromic supercapacitor, battery-supercapacitor hybrid device, electrochemical flow capacitor, alternating current line filtering capacitor, micro-supercapacitor, photo-supercapacitor, thermally chargeable supercapacitor, self-healing supercapacitor, piezoelectric and shape memory supercapacitor have also been discussed. This review covers the up-to-date progress achieved in novel materials for supercapacitor electrodes. The latest fabricated symmetric/asymmetric supercapacitors have also been reported.

Review of supercapacitors: Materials and devices

Review of the use of transition-metal-oxide and conducting polymer-based fibres for high-performance supercapacitors

Supercapacitors have become the most significant energy conversion and storage system in recent renewable and sustainable nanotechnology. Due to its large energy capacity and supply with relatively short time and longer lifetime, supercapacitors breakthrough in advance energy applications. This review presents a comparative study of different materials, working principles, analysis, applications, advantages and disadvantages of various technologies available for supercapacitors. The aim of this article is to discuss the possibility of hybrid supercapacitor for the next generation of energy technology. The development of composite materials containing a wide range of active constituents (e.g., graphene, activated carbon, transition metals, metal oxides, perovskites and conducting polymers) by in-situ hybridization and ex-situ recombination is also discussed. This review consecrated largely the contribution of combining all materials (electrode and electrolyte) and their synthesis process and electrochemical performance. Enduringly, the potential issues and the perspectives for future research based on hybrid supercapacitors in energy applications are also presented.

Advanced materials and technologies for hybrid supercapacitors for energy storage – A review

Increased energy consumption stimulates the development of various energy types. As a result, the storage of these different types of energy becomes a key issue. Supercapacitors, as one important energy storage device, have gained much attention and owned a wide range of applications by taking advantages of micro-size, lightweight, high power density and long cycle life. From this perspective, numerous studies, especially on electrode materials, have been reported and great progress in the advancement in both the fundamental and applied fields of supercapacitor has been achieved. Herein, a review of recent progress in carbon materials for supercapacitor electrodes is presented. First, the two mechanisms of supercapacitors are briefly introduced. Then, research on carbon-based material electrodes for supercapacitor in recent years is summarized, including different dimensional carbon-based materials and biomass-derived carbon materials. The characteristics and fabrication methods of these materials and their performance as capacitor electrodes are discussed. On the basis of these materials, many supercapacitor devices have been developed. Therefore, in the third part, the supercapacitor devices based on these carbon materials are summarized. A brief overview of two types of conventional supercapacitor according to the charge storage mechanism is compiled, including their development process, the merits or withdraws, and the principle of expanding the potential range. Additionally, another fast-developed capacitor, hybrid ion capacitors as a good compromise between battery and supercapacitor are also discussed. Finally, the future aspects and challenges on the carbon-based materials as supercapacitor electrodes are proposed.

Recent progress in carbon-based materials for supercapacitor electrodes: a review

In this contribution, we report a facile preparation method of nickel cobalt oxide–reduced graphite oxide (NiCo2O4–rGO) composite material. A fast Faradic process has been realized by sodium dodecyl sulfate (SDS)-induced ultrasmall NiCo2O4 nanocrystals on rGO. As a result, this composite material gives a high specific capacitance of 1222 F g−1 at 0.5 A g−1 and 768 F g−1 at 40 A g−1, showing an outstanding rate capability. An asymmetric supercapacitor device with high energy and power densities has been successfully assembled based on NiCo2O4–rGO composite material and activated carbon. The optimized device shows a high energy density of 23.32 Wh kg−1 at a power density of 324.9 W kg−1. In addition, this asymmetric device shows good stability towards multistage current charge–discharge cycles.

Dodecyl Sulfate Induced Fast Faradic Process in Nickel Cobalt Oxide/Reduced Graphite Oxide Composite Material and Its Application for Asymmetric Supercapacitor Device

We have explored the effect of Cu dopant concentration on the electrical transport properties of Cu doped CdSe thin films at two concentrations of Cu (at 1 and 5 at.%). Structural, morphological and elemental analysis has been carried out by using X-ray Diffraction (XRD), Scanning electron microscopy (SEM) and Energy Dispersive X-ray analysis (EDX). XRD analysis reveals the hexagonal (wurtzite) structure of nc-CdSe:Cu 1% and nc-CdSe:Cu 5% thin films. EDX analysis determines the atomic weight percentage of Cu in these thin films. SEM studies reveal that the grains are uniformly distributed all over the surface of the substrates for nc-CdSe:Cu 1% and nc-CdSe:Cu 5% thin films. Dark conductivity measurements are made on nc-CdSe:Cu 1% and nc-CdSe:Cu 5% thin films in the temperature range 110–370 K in order to determine the effect of Cu concentration. The obtained results reveal that dark conductivity increases as the Cu dopant concentration increases as compared to undoped nc-CdSe thin films. Dark conductivity graphs show two distinct regions at high and low temperatures with decreasing activation energies. Low temperature data is analyzed using Mott’s variable-range hopping model which indicates hopping in localized states near the Fermi level. Various Mott parameters such as the density of localized states N(EF), characteristic temperature (To), hopping distance (R) and hopping energy (W) near the Fermi level are calculated. The concentration of charge carriers and carrier mobility are calculated for nc-CdSe:Cu 1% and nc-CdSe:Cu 5% thin films by using Hall measurements. Constant photocurrent measurement is also performed on Cu 1% and Cu 5% doped CdSe thin films to determine occupied density of states, Urbach parameter and density of defect states. Obtained results show that occupied density of states increases for nc-CdSe:Cu 5% as compared to nc-CdSe:Cu 1% thin films.

A comparative study of transport properties of copper doped cadmium selenide thin films at two dopant concentrations

https://iopscience.iop.org/article/10.1088/2053-1591/aae9c1/pdf

Characterization of nickel cobalt oxide: a potential material for supercapacitor

With increasing population and depleting natural resources there is a need for increasing agricultural productivity in sustainable and ecofriendly manner. The conventional agricultural practices utilize a lot of chemical fertilizers for increasing the productivity that pose a threat to agro-ecosystems like food chain contamination, soil quality degradation, water pollution etc. To overcome all these problems, there is need to shift towards sustainable agricultural practices like application of Plant Growth Promoting Microbes (PGPMs) instead of conventional chemical fertilizers restoring the agro-ecosystems. These microbes live in soil and are associated with rhizospheric region of plants, where they stimulate growth and productivity of their hosts by different direct and indirect mechanisms e.g. by phytohormones, siderophores, solubilization of minerals etc. Microbes used to make available soil nutrient to crops without compromising with the soil fertility in environmentally sustainable manner. Previous studies have shown positive effects of microbes on growth and yield of various crops in different climatic conditions, soil types also under biotic and abiotic stress conditions. Further, these microbes have also been used successfully as bio-control agents for various pathogens in the plants. Present review presents an overview of different mechanisms used by these microbes as growth promoter and role performed as bio-control agents for enhancing the productivity as well as the supportive role played for sustainable and ecofriendly agriculture without causing any negative effects on the environment and on living beings health. 

Plant Growth Promoting Microbes: Diverse Roles for Sustainable and Ecofriendly Agriculture

Metal-Organic frameworks are the advanced electrode materials for supercapacitors due to their controllable structures and large surface area. Here Ni-MOF has been prepared by hydrothermal method for their application as electrode material in supercapacitors. The prepared material is characterized with the help of X-ray diffraction and Fourier transforms infrared spectroscopy. The electrochemical performance of the prepared material has been studied in 1M LiOH aqueous electrolyte using cyclic voltammetry and galvanostatic charge-discharge methods. We get the different values of specific capacitance at different scan rates. The prepared Ni-MOF shows maximum specific capacitance of 309.05 Fg-1 at 5mVs-1 scan rate.

Poonam

Papers

Review of supercapacitors: Materials and devices

A comparative study of transport properties of copper doped cadmium selenide thin films at two dopant concentrations

Characterization of nickel cobalt oxide: a potential material for supercapacitor

Plant Growth Promoting Microbes: Diverse Roles for Sustainable and Ecofriendly Agriculture

Synthesis and characterization of Ni-BTC MOF for supercapacitor electrode