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Journal ArticleDOI

Vanadium Oxide Nanowire–Carbon Nanotube Binder‐Free Flexible Electrodes for Supercapacitors

01 Oct 2011-Advanced Energy Materials (WILEY‐VCH Verlag)-Vol. 1, Iss: 5, pp 936-945
TL;DR: In this paper, the authors developed a simple method for preparing freestanding carbon nanotube (CNT)-V2O5 nanowire (VNW) composite paper electrodes without using binders.
Abstract: Vanadium pentoxide (V2O5) layered nanostructures are known to have very stable crystal structures and high faradaic activity. The low electronic conductivity of V2O5 greatly limits the application of vanadium oxide as electrode materials and requires combining with conducting materials using binders. It is well known that the organic binders can degrade the overall performance of electrode materials and need carefully controlled compositions. In this study, we develop a simple method for preparing freestanding carbon nanotube (CNT)-V2O5 nanowire (VNW) composite paper electrodes without using binders. Coin cell type (CR2032) supercapacitors are assembled using the nanocomposite paper electrode as the anode and high surface area carbon fiber electrode (Spectracarb 2225) as the cathode. The supercapacitor with CNT-VNW composite paper electrode exhibits a power density of 5.26 kW Kg−1 and an energy density of 46.3 Wh Kg−1. (Li)VNWs and CNT composite paper electrodes can be fabricated in similar manner and show improved overall performance with a power density of 8.32 kW Kg−1 and an energy density of 65.9 Wh Kg−1. The power and energy density values suggest that such flexible hybrid nanocomposite paper electrodes may be useful for high performance electrochemical supercapacitors.
Citations
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Journal ArticleDOI
TL;DR: Flexible solid-state supercapacitors (SCs) have attracted increasing interest because they can provide substantially higher specific/volumetric energy density compared to conventional capacitors.
Abstract: Increasing power and energy demands for next-generation portable and flexible electronics such as roll-up displays, photovoltaic cells, and wearable devices have stimulated intensive efforts to explore flexible, lightweight and environmentally friendly energy storage devices. Flexible solid-state supercapacitors (SCs) have attracted increasing interest because they can provide substantially higher specific/volumetric energy density compared to conventional capacitors. Additionally, flexible solid-state SCs are typically small in size, highly reliable, light-weight, easy to handle, and have a wide range of operation temperatures. In this regard, solid-state SCs hold great promise as new energy storage devices for flexible and wearable electronics. In this article, we review recent achievements in the design, fabrication and characterization of flexible solid-state SCs. Moreover, we also discuss the current challenges and future opportunities for the development of high-performance flexible solid-state SCs.

1,105 citations

Journal ArticleDOI
TL;DR: In this paper, a concise description of technologies and working principles of different materials utilized for supercapacitors has been provided, where 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.
Abstract: 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.

1,030 citations

Journal ArticleDOI
TL;DR: This review article surveys the evolution of electrode materials, recent developments in 2D nanomaterials and their hybrid nanostructures with regulated electrical properties, and the new planar configurations of flexible supercapacitors.
Abstract: Flexible supercapacitors, as one of most promising emerging energy storage devices, are of great interest owing to their high power density with great mechanical compliance, making them very suitable as power back-ups for future stretchable electronics. Two-dimensional (2D) nanomaterials, including the quasi-2D graphene and inorganic graphene-like materials (IGMs), have been greatly explored to providing huge potential for the development of flexible supercapacitors with higher electrochemical performance. This review article is devoted to recent progresses in engineering 2D nanomaterials for flexible supercapacitors, which survey the evolution of electrode materials, recent developments in 2D nanomaterials and their hybrid nanostructures with regulated electrical properties, and the new planar configurations of flexible supercapacitors. Furthermore, a brief discussion on future directions, challenges and opportunities in this fascinating area is also provided.

912 citations

Journal ArticleDOI
TL;DR: In this article, the authors proposed pseudocapacitive transition-metal oxides and electronically conducting polymers based on faradic redox charge storage to achieve higher energy density than those of electrochemical double layer capacitive carbon materials.
Abstract: 1–4 ] However, super-capacitors deliver an unsatisfactory energy density. Intensive efforts have been devoted to the enhancement of their energy density to make it comparable to that of rechargeable batteries. Among the supercapacitor electrode materials, pseudocapacitive transition-metal oxides and electronically conducting polymers based on faradic redox charge storage have attracted signifi cant attention because of their higher energy density than those of electrochemical double-layer capacitive carbon materials.

479 citations

Journal ArticleDOI
TL;DR: A simple and scalable way of preparing a three-dimensional (3D) sub-5 nm hydrous ruthenium oxide (RuO2) anchored graphene and CNT hybrid foam (RGM) architecture for high-performance supercapacitor electrodes is reported.
Abstract: In real life applications, supercapacitors (SCs) often can only be used as part of a hybrid system together with other high energy storage devices due to their relatively lower energy density in comparison to other types of energy storage devices such as batteries and fuel cells. Increasing the energy density of SCs will have a huge impact on the development of future energy storage devices by broadening the area of application for SCs. Here, we report a simple and scalable way of preparing a three-dimensional (3D) sub-5 nm hydrous ruthenium oxide (RuO2) anchored graphene and CNT hybrid foam (RGM) architecture for high-performance supercapacitor electrodes. This RGM architecture demonstrates a novel graphene foam conformally covered with hybrid networks of RuO2 nanoparticles and anchored CNTs. SCs based on RGM show superior gravimetric and per-area capacitive performance (specific capacitance: 502.78 F g−1, areal capacitance: 1.11 F cm−2) which leads to an exceptionally high energy density of 39.28 Wh kg−1 and power density of 128.01 kW kg−1. The electrochemical stability, excellent capacitive performance, and the ease of preparation suggest this RGM system is promising for future energy storage applications.

460 citations

References
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Journal ArticleDOI
TL;DR: This work has shown that combination of pseudo-capacitive nanomaterials, including oxides, nitrides and polymers, with the latest generation of nanostructured lithium electrodes has brought the energy density of electrochemical capacitors closer to that of batteries.
Abstract: Electrochemical capacitors, also called supercapacitors, store energy using either ion adsorption (electrochemical double layer capacitors) or fast surface redox reactions (pseudo-capacitors). They can complement or replace batteries in electrical energy storage and harvesting applications, when high power delivery or uptake is needed. A notable improvement in performance has been achieved through recent advances in understanding charge storage mechanisms and the development of advanced nanostructured materials. The discovery that ion desolvation occurs in pores smaller than the solvated ions has led to higher capacitance for electrochemical double layer capacitors using carbon electrodes with subnanometre pores, and opened the door to designing high-energy density devices using a variety of electrolytes. Combination of pseudo-capacitive nanomaterials, including oxides, nitrides and polymers, with the latest generation of nanostructured lithium electrodes has brought the energy density of electrochemical capacitors closer to that of batteries. The use of carbon nanotubes has further advanced micro-electrochemical capacitors, enabling flexible and adaptable devices to be made. Mathematical modelling and simulation will be the key to success in designing tomorrow's high-energy and high-power devices.

14,213 citations

Journal ArticleDOI
TL;DR: This Review introduces several typical energy storage systems, including thermal, mechanical, electromagnetic, hydrogen, and electrochemical energy storage, and the current status of high-performance hydrogen storage materials for on-board applications and electrochemicals for lithium-ion batteries and supercapacitors.
Abstract: [Liu, Chang; Li, Feng; Ma, Lai-Peng; Cheng, Hui-Ming] Chinese Acad Sci, Inst Met Res, Shenyang Natl Lab Mat Sci, Shenyang 110016, Peoples R China.;Cheng, HM (reprint author), Chinese Acad Sci, Inst Met Res, Shenyang Natl Lab Mat Sci, 72 Wenhua Rd, Shenyang 110016, Peoples R China;cheng@imr.ac.cn

4,105 citations

Journal ArticleDOI
TL;DR: In-situ high-resolution transmission electron microscopy (HRTEM) studies of the structural transformations that occur during the synthesis of carbon-coated LiFePO4 and heat treatment to elevated temperatures were conducted in two different electron microscopes as discussed by the authors.

3,037 citations

Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate the importance and great potential of graphene-based composites in the development of high-performance energy-storage systems and demonstrate that the combined advantages of GSs and RuO 2 in such a unique structure are that the ROGSC-based supercapacitors exhibit high specifi c capacitance ( ∼ 570 F g − 1 for 38.3 wt% Ru loading), enhanced rate capability, excellent electrochemical stability ( ∼ 97.9% retention after 1000 cycles), and high energy density (20.1 Wh kg − 1 )
Abstract: Hydrous ruthenium oxide (RuO 2 )/graphene sheet composites (ROGSCs) with different loadings of Ru are prepared by combining sol–gel and low-temperature annealing processes. The graphene sheets (GSs) are well-separated by fi ne RuO 2 particles (5–20 nm) and, simultaneously, the RuO 2 particles are anchored by the richly oxygen-containing functional groups of reduced, chemically exfoliated GSs onto their surface. Benefi ts from the combined advantages of GSs and RuO 2 in such a unique structure are that the ROGSC-based supercapacitors exhibit high specifi c capacitance ( ∼ 570 F g − 1 for 38.3 wt% Ru loading), enhanced rate capability, excellent electrochemical stability ( ∼ 97.9% retention after 1000 cycles), and high energy density (20.1 Wh kg − 1 ) at low operation rate (100 mA g − 1 ) or high power density (10000 W kg − 1 ) at a reasonable energy density (4.3 Wh kg − 1 ). Interestingly, the total specifi c capacitance of ROGSCs is higher than the sum of specifi c capacitances of pure GSs and pure RuO 2 in their relative ratios, which is indicative of a positive synergistic effect of GSs and RuO 2 on the improvement of electrochemical performance. These fi ndings demonstrate the importance and great potential of graphenebased composites in the development of high-performance energy-storage systems.

1,102 citations

Journal ArticleDOI
TL;DR: In this article, the development of lower cost carbons appropriate for use in electrochemical capacitors is underway by several speciality carbon suppliers. The goal is to reduce the cost of the carbon to $10-15/kg.

923 citations