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"Brousse, Thierry"
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Supercapacitors based on carbon or pseudocapacitive materials
\"Electrochemical capacitors are electrochemical energy storage devices able to quickly deliver or store large quantities of energy. They have stimulated numerous innovations throughout the last 20 years and are now implemented in many fields. Supercapacitors Based on Carbon or Pseudocapacitive Materials provides the scientific basis for a better understanding of the characteristics and performance of electrochemical capacitors based on electrochemical double layer electrodes or pseudocapacitive materials, as well as providing information on the design and conception of new devices such as lithium-ion capacitors. This book details the various applications of supercapacitors, ranging from power electronics and stationary use, to transportation (hybrid vehicles, trams, planes, etc.). They are increasingly used in the automotive sector, especially as part of stop/start systems that have allowed for energy recovery through braking and reduced fuel consumption.\"--Publisher description.
Book
Microsupercapacitors as miniaturized energy-storage components for on-chip electronics
This Review discusses the technical challenges and performance metrics to integrate micro-supercapacitors into miniaturized electronic devices.
The push towards miniaturized electronics calls for the development of miniaturized energy-storage components that can enable sustained, autonomous operation of electronic devices for applications such as wearable gadgets and wireless sensor networks. Microsupercapacitors have been targeted as a viable route for this purpose, because, though storing less energy than microbatteries, they can be charged and discharged much more rapidly and have an almost unlimited lifetime. In this Review, we discuss the progress and the prospects of integrated miniaturized supercapacitors. In particular, we discuss their power performances and emphasize the need of a three-dimensional design to boost their energy-storage capacity. This is obtainable, for example, through self-supported nanostructured electrodes. We also critically evaluate the performance metrics currently used in the literature to characterize microsupercapacitors and offer general guidelines to benchmark performances towards prospective applications.
Journal Article
Capacitive tendency concept alongside supervised machine-learning toward classifying electrochemical behavior of battery and pseudocapacitor materials
In recent decades, more than 100,000 scientific articles have been devoted to the development of electrode materials for supercapacitors and batteries. However, there is still intense debate surrounding the criteria for determining the electrochemical behavior involved in Faradaic reactions, as the issue is often complicated by the electrochemical signals produced by various electrode materials and their different physicochemical properties. The difficulty lies in the inability to determine which electrode type (battery vs. pseudocapacitor) these materials belong to via simple binary classification. To overcome this difficulty, we apply supervised machine learning for image classification to electrochemical shape analysis (over 5500 Cyclic Voltammetry curves and 2900 Galvanostatic Charge-Discharge curves), with the predicted confidence percentage reflecting the shape trend of the curve and thus defined as a manufacturer. It’s called “capacitive tendency”. This predictor not only transcends the limitations of human-based classification but also provides statistical trends regarding electrochemical behavior. Of note, and of particular importance to the electrochemical energy storage community, which publishes over a hundred articles per week, we have created an online tool to easily categorize their data.
Analysis of capacitive behavior of electrode materials used in batteries and pseudocapacitors is challenging. Here, authors report an electrochemical signal analysis method available as an online tool to classify the charge storage behavior of a material as battery-like or a pseudocapacitor-like.
Journal Article
Ni(OH)2 and NiO Based Composites: Battery Type Electrode Materials for Hybrid Supercapacitor Devices
Nanocomposites of Ni(OH)2 or NiO have successfully been used in electrodes in the last five years, but they have been falsely presented as pseudocapacitive electrodes for electrochemical capacitors and hybrid devices. Indeed, these nickel oxide or hydroxide electrodes are pure battery-type electrodes which store charges through faradaic processes as can be shown by cyclic voltammograms or constant current galvanostatic charge/discharge plots. Despite this misunderstanding, such electrodes can be of interest as positive electrodes in hybrid supercapacitors operating under KOH electrolyte, together with an activated carbon-negative electrode. This study indicates the requirements for the implementation of Ni(OH)2-based electrodes in hybrid designs and the improvements that are necessary in order to increase the energy and power densities of such devices. Mass loading is the key parameter which must be above 10 mg·cm−2 to correctly evaluate the performance of Ni(OH)2 or NiO-based nanocomposite electrodes and provide gravimetric capacity values. With such loadings, rate capability, capacity, cycling ability, energy and power densities can be accurately evaluated. Among the 80 papers analyzed in this study, there are indications that such nanocomposite electrode can successfully improve the performance of standard Ni(OH)2 (+)//6 M KOH//activated carbon (−) hybrid supercapacitor.
Journal Article
Supercapacitors Based on Carbon or Pseudocapacitive Materials
Electrochemical capacitors are electrochemical energy storage devices able to quickly deliver or store large quantities of energy.They have stimulated numerous innovations throughout the last 20 years and are now implemented in many fields.
eBook
Asymmetric electrochemical capacitors—Stretching the limits of aqueous electrolytes
Ongoing technological advances in such disparate areas as consumer electronics, transportation, and energy generation and distribution are often hindered by the capabilities of current energy storage/conversion systems, thereby driving the search for high-performance power sources that are also economically viable, safe to operate, and have limited environmental impact. Electrochemical capacitors (ECs) are a class of energy-storage devices that fill the gap between the high specific energy of batteries and the high specific power of conventional electrostatic capacitors. The most widely available commercial EC, based on a symmetric configuration of two high-surface-area carbon electrodes and a nonaqueous electrolyte, delivers specific energies of up to ∼6 Whkg–1 with sub-second response times. Specific energy can be enhanced by moving to asymmetric configurations and selecting electrode materials (e.g., transition metal oxides) that store charge via rapid and reversible faradaic reactions. Asymmetric EC designs also circumvent the main limitation of aqueous electrolytes by extending their operating voltage window beyond the thermodynamic 1.2 V limit to operating voltages approaching ∼2 V, resulting in high-performance ECs that will satisfy the challenging power and energy demands of emerging technologies and in a more economically and environmentally friendly form than conventional symmetric ECs and batteries.
Journal Article
Interleaved Electroactive Molecules into LDH Working on Both Electrodes of an Aqueous Battery-Type Device
By selecting two electroactive species immobilized in a layered double hydroxide backbone (LDH) host, one able to act as a positive electrode material and the other as a negative one, it was possible to match their capacity to design an innovative energy storage device. Each electrode material is based on electroactive species, riboflavin phosphate (RF) on one side and ferrocene carboxylate (FCm) on the other, both interleaved into a layered double hydroxide (LDH) host structure to avoid any possible molecule migration and instability. The intercalation of the electroactive guest molecules is demonstrated by X-ray diffraction with the observation of an interlayer LDH spacing of about 2 nm in each case. When successfully hosted into LDH interlayer space, the electrochemical behavior of each hybrid assembly was scrutinized separately in aqueous electrolyte to characterize the redox reaction occurring upon cycling and found to be a rapid faradic type. Both electrode materials were placed face to face to achieve a new aqueous battery (16C rate) that provides a first cycle-capacity of about 7 mAh per gram of working electrode material LDH/FCm at 10 mV/s over a voltage window of 2.2 V in 1M sodium acetate, thus validating the hybrid LDH host approach on both electrode materials even if the cyclability of the assembly has not yet been met.
Journal Article
Energy from Garbage: Recycling Heavy Metal‐Containing Wastewater Adsorbents for Energy Storage
The global challenge of heavy metal contamination in wastewater necessitates efficient adsorbents, which, while they can effectively remove contaminants, ultimately become toxic waste themselves. Recycling wastewater adsorbents loaded with heavy metals is an alternative to their disposal as toxic garbage. This study presents a genuine recycling strategy for heavy metal‐loaded adsorbents, repurposing them as electrode materials for energy storage applications, that is, electrochemical capacitors, and thus synergistically tackles water purification and waste valorization. Graphene oxide was prepared via the improved Hummers’ method, and subsequently, a reduced graphene oxide (rGO) foam was hydrothermally synthesized. This rGO‐based foam adsorbed >95% of the Hg2+ ions in a 100 ppm solution, using a dose = 500 mg L−1, and up to 240 mg of Hg2+ ions/g on average at 25 °C, which are among the highest values reported so far. Electrochemically, the Hg‐loaded rGO (rGO/Hgads) exhibits mercury redox activity and a 15% increase in capacity as compared to pristine rGO in an aqueous cell. Overall, this demonstrates the potential of reprocessed wastewater adsorbents as efficient and sustainable electrodes for high‐power energy storage (time constant τ = 11 s), offering a compelling solution to add more value and extend the life cycle of waste materials. In the quest for sustainable development, the interlinking of waste management and energy storage represents a frontier in environmental science. Recycling spent carbon‐based wastewater adsorbents as electrode active materials for energy storage applications not only mitigates the environmental hazards associated with waste disposal but also contributes to the advancement of less expensive and broadly available energy storage solutions.
Journal Article
Electrode Design for MnO2-Based Aqueous Electrochemical Capacitors: Influence of Porosity and Mass Loading
The purpose of this study is to highlight the influence of some fabrication parameters, such as mass loading and porosity, which are not really elucidated and standardized during the realization of electrodes for supercapacitors, especially when using metal oxides as electrode materials. Electrode calendering, as one stage during the fabrication of electrodes, was carried out step-by-step on manganese dioxide electrodes to study the decreasing porosity effect on the electrochemical performance of a MnO2 symmetric device. One other crucial parameter, the mass loading, which has to be understood and well used for realistic supercapacitors, was investigated concurrently. Gravimetric, areal and volumetric capacitances are highlighted, varying the porosity for low-, medium- and large-mass loading. Low-loading leads to the best specific capacitances but is not credible for realistic supercapacitors, except for microdevices. Down 50% porosities after calendering, capacitances are increased and become stable faster, suggesting a faster wettability of the dense electrodes by the electrolyte, especially for high-mass loading. EIS experiments performed on electrodes without and with calendering lead to a significant decrease of the device’s time response, especially at high loading. A high-mass loading device seems to work as a power battery, whereas electrode calendaring, which allows decreasing the time response, leads to an electrical behavior closer to that expected for a supercapacitor.
Journal Article
Reactive sputtering of vanadium nitride thin films as pseudo-capacitor electrodes for high areal capacitance and cyclic stability
Vanadium nitride (VN) films with different thicknesses were deposited over polished silicon substrate using DC plasma reactive sputtering. These films were tested as electrodes for electrochemical capacitors in a 1 M KOH aqueous electrolyte solution. The electrodes show excellent specific capacitance with maximum areal capacitance value of 238.2 mF cm
−2
at 5 mV s
−1
scan rate, and 77.5% capacity retention after 2000 cycles. Moreover, the capacitance was found to increase with the VN deposit thickness. The XPS analyses of the electrodes confirm the presence of oxide and oxynitrides layers formed at the VN film surface, which could be responsible for the redox energy storage in this material. Such electrodes can compete with other pseudo-capacitive materials that deliver high energy density.
Journal Article