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.

https://hal.archives-ouvertes.fr/hal-02417326/document

Materials for electrochemical capacitors

In this critical review, metal oxides-based materials for electrochemical supercapacitor (ES) electrodes are reviewed in detail together with a brief review of carbon materials and conducting polymers. Their advantages, disadvantages, and performance in ES electrodes are discussed through extensive analysis of the literature, and new trends in material development are also reviewed. Two important future research directions are indicated and summarized, based on results published in the literature: the development of composite and nanostructured ES materials to overcome the major challenge posed by the low energy density of ES (476 references).

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A review of electrode materials for electrochemical supercapacitors

The surface area of a single graphene sheet is 2630 m2/g, substantially higher than values derived from BET surface area measurements of activated carbons used in current electrochemical double layer capacitors. Our group has pioneered a new carbon material that we call chemically modified graphene (CMG). CMG materials are made from 1-atom thick sheets of carbon, functionalized as needed, and here we demonstrate in an ultracapacitor cell their performance. Specific capacitances of 135 and 99 F/g in aqueous and organic electrolytes, respectively, have been measured. In addition, high electrical conductivity gives these materials consistently good performance over a wide range of voltage scan rates. These encouraging results illustrate the exciting potential for high performance, electrical energy storage devices based on this new class of carbon material.

Graphene-Based Ultracapacitors

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.

Carbon-based materials as supercapacitor electrodes

[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

Advanced Materials for Energy Storage

This paper is focused on neutral aqueous medium, i.e.lithium, sodium and potassium sulfate solutions in a wide range of concentrations (0.1–2.5 mol L−1) as promising electrolytes for electrochemical capacitors because they are cheap, non-corrosive and allow applying diverse current collectors. These properties make the capacitor assembling process much easier and cheaper. Additionally, such electrolytes are electrochemically stable and environmentally friendly. Electrochemical investigations carried out especially for 1 mol L−1Li2SO4 aqueous solution confirmed the possibility of efficient capacitor work in a wider voltage range, i.e. even at 2.2 V without any significant capacitance fade during 15 000 cycles. The physicochemical properties of ions (i.e. solvation, diffusion or mobility) and their influence on the capacitor electrochemical behaviour are considered.

Novel insight into neutral medium as electrolyte for high-voltage supercapacitors

This paper presents various applications of carbon nanotubes as components of electrode materials for such electrochemical use as electrochemical capacitors, fuel cells, hydrogen electrosorption and accumulators. Generally, carbon nanotubes give exceptional improvement of electrode performance due to their mesoporous and well conducting networks. The cell resistance is drastically reduced and the transport of ions is greatly enhanced. In addition to their good conductivity, carbon nanotubes can be flexible and stretchable which is crucial for cyclability of electrodes, especially if volumetric changes of electrode material occur during operation. Consequently, they serve as excellent support for conducting polymers (e.g. polyaniline, polypyrrole) and metal oxides (e.g. MnO2) giving attractive capacitor electrodes. The presence of nanotubes in carbon precursor rich in heteroatoms, e.g. nitrogen from melamine or oxygen, also supplies an interesting carbonized composite with a good charge propagation for supercapacitor use. Furthermore, carbon nanotubes have been tested for hydrogen electrosorption giving a very moderate hydrogen capacity (0.27 wt.%). However, modification of nanotubes can enhance hydrogen storage. On the other hand, carbon nanotubes can serve as an excellent additive to many electrode materials for improvement of conductivity and cell performance. They could be a good support of the catalytic particles for fuel cell application as well.

Carbon nanotubes and their composites in electrochemical applications

Electrochemical capacitors based on highly porous carbons prepared by KOH activation

http://digital.csic.es/bitstream/10261/100330/1/Templated_Centeno.pdf

Grzegorz Lota

Papers

Novel insight into neutral medium as electrolyte for high-voltage supercapacitors

Carbon nanotubes and their composites in electrochemical applications

Electrochemical capacitors based on highly porous carbons prepared by KOH activation

Templated Mesoporous Carbons for Supercapacitor Application

Effect of nitrogen in carbon electrode on the supercapacitor performance