Carbon/carbon supercapacitors
TL;DR: In this article, the state-of-the-art on EDL capacitors is presented, with the objective to better understand their operating principles and to improve their performance, in particular for carbons having subnanometric pores where ions of the electrolyte are distorted and partly desolvated.
About: This article is published in Journal of Energy Chemistry.The article was published on 2013-03-01. It has received 265 citations till now. The article focuses on the topics: Electrolyte & Supercapacitor.
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TL;DR: Molecular dynamics simulations of realistic supercapacitors are performed and it is shown that both the desolvation and the local charge stored on the electrode increase with the degree of confinement.
Abstract: Liquids exhibit specific properties when they are adsorbed in nanoporous structures. This is particularly true in the context of supercapacitors, for which an anomalous increase in performance has been observed for nanoporous electrodes. This enhancement has been traditionally attributed in experimental studies to the effect of confinement of the ions from the electrolyte inside sub-nanometre pores, which is accompanied by their partial desolvation. Here we perform molecular dynamics simulations of realistic supercapacitors and show that this picture is correct at the microscopic scale. We provide a detailed analysis of the various environments experienced by the ions. We pick out four different adsorption types, and we, respectively, label them as edge, planar, hollow and pocket sites upon increase of the coordination of the molecular species by carbon atoms from the electrode. We show that both the desolvation and the local charge stored on the electrode increase with the degree of confinement.
585 citations
Peking University1, Pennsylvania State University2, Shinshu University3, Seoul National University4, Rensselaer Polytechnic Institute5, University of Toulouse6, Brown University7, Poznań University of Technology8, Tokyo Institute of Technology9, Nanyang Technological University10, University of Sydney11, Nankai University12, Centre national de la recherche scientifique13
TL;DR: Aqueous-two polymer phase separation has emerged as an easily accessible and versatile approach for sorting nanotubes which is promising for low-cost scalable production of high-purity SWCNTs.
262 citations
TL;DR: In this article, the authors summarized the progress on the applications of abundant biomaterials and materials derived from biomass in the field and critically evaluated a commercial potential of these materials upon ongoing trends in research & development of electrochemical capacitors.
218 citations
TL;DR: In this paper, polypyrrole-coated multiwalled carbon nanotubes (PPy-MWCNT) were used for the fabrication of activated carbon-coating MWCNT doped with nitrogen (N-AC-MWCLNT) electrodes with high mass loading in the range of 15-35 mg cm-2 and with a high active material to current collector mass ratio of 0.21-0.50.
Abstract: Polypyrrole-coated multiwalled carbon nanotubes (PPy-MWCNT) were used for the fabrication of activated carbon-coated MWCNT doped with nitrogen (N-AC-MWCNT). The conceptually new method for the fabrication of non-agglomerated PPy-MWCNT with good coating uniformity allowed the fabrication of uniform and well-dispersed N-AC-MWCNT with high surface area. The use of N-AC-MWCNT allowed the fabrication of supercapacitor electrodes with high mass loading in the range of 15–35 mg cm–2 and with a high active material to current collector mass ratio of 0.21–0.50. The N-AC-MWCNT electrodes showed excellent electrochemical performance in aqueous 0.5 M Na2SO4 electrolyte. The maximum specific capacitance of 3.6 F cm–2 (103.1 F g–1) was achieved for mass loading of 35 mg cm–2 at a scan rate of 2 mV s–1. The aqueous supercapacitor cells, based on N-AC-MWCNT electrodes, exhibited excellent performance with energy density of 16.1 mWh g–1, power density of 14.4 W g–1, and enlarged voltage window of 1.8 V. The individual ele...
200 citations
TL;DR: In this article, aqueous electrolyte/carbon-based supercapacitors were investigated and showed that short-term cycling leads to reversible gas evolution/consumption side-reactions giving negligible capacitance.
Abstract: High-voltage aqueous electrolyte based supercapacitors (U > 1.23 V) attract significant attention for next-generation high power, low cost and environmentally friendly energy storage applications. Cell ageing is however markedly pronounced at elevated voltages and results in accelerated overall performance fade and increased safety concerns. Online electrochemical mass spectrometry, combined with cell pressure analysis, is for the first time shown to provide a powerful means for in situ investigation of degradation mechanisms in aqueous electrolyte/carbon based supercapacitors. The activated carbon electrodes possess high specific surface area and oxygen-based surface functionalities (mainly phenol, lactone and anhydride groups), which are oxidized already at a cell voltage of 0.6 V to provoke the evolution of minor amounts of CO and CO2. Noticeable water decomposition starts at a high voltage of 1.6 V with the evolution of H2 on the negative electrode and carbon corrosion on the positive electrode with the generation of predominantly CO. In this paper we also report that short-term cycling leads to partly reversible gas evolution/consumption side-reactions giving negligible capacitance. On the other hand, long-term cycling causes irreversible side-reactions, deteriorates the electrochemical performance, and increases the internal pressure of the cell. Repeated cycling (U < 2 V) is confirmed as a more harmful technique for the electrode integrity compared to the voltage holding in a floating test. In situ gas analysis is shown to provide valuable insights into the electrochemical cell ageing aspects, such as the nature and potential onsets of side-reactions, hence paving the way for fundamental understanding and mitigating the performance and safety loss of high-energy aqueous supercapacitors.
192 citations
References
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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
TL;DR: This tutorial review provides a brief summary of recent research progress on carbon-based electrode materials forsupercapacitors, as well as the importance of electrolytes in the development of supercapacitor technology.
Abstract: This tutorial review provides a brief summary of recent research progress on carbon-based electrode materials for supercapacitors, as well as the importance of electrolytes in the development of supercapacitor technology. The basic principles of supercapacitors, the characteristics and performances of various nanostructured carbon-based electrode materials are discussed. Aqueous and non-aqueous electrolyte solutions used in supercapacitors are compared. The trend on future development of high-power and high-energy supercapacitors is analyzed.
6,057 citations
TL;DR: Electrochemical capacitors enable rapid storage and efficient delivery of electrical energy in heavy-duty applications and are being enabled by electrochemical capacitor technology.
Abstract: Rapid storage and efficient delivery of electrical energy in heavy-duty applications are being enabled by electrochemical capacitors.
4,177 citations
TL;DR: In this article, the fundamental principles, performance, characteristics, present and future applications of electrochemical capacitors are presented in this communication, and different applications demanding large ECs with high voltage and improved energy and power density are under discussion.
4,175 citations
TL;DR: In this article, different types of capacitors with a pure electrostatic attraction and/or pseudocapacitance effects are presented, and their performance in various electrolytes is studied taking into account the different range of operating voltage (1V for aqueous and 3 V for aprotic solutions).
4,091 citations