Electrochemical supercapacitors for energy storage and delivery

Editorial

Electrochemical supercapacitors for energy storage and delivery:Advanced materials,technologies and applications

q

1.Introduction

In the effort to achieve a clean and sustainable world,energy storage and delivery have become one of today’s most important topics in globe research and development.In this regard,electro-chemical energy technologies such as batteries,fuel cells,and elec-trochemical supercapacitors have been recognized as the most important portion of the various energy storage and delivery tech-nologies.Among these technologies,supercapacitors,emerging as one of the most important energy storage and delivery devices for the 21st century,are particularly the most reliable and safe devices with extremely high power density and cycling stability in many applications including portable electronics,automobile vehicles,stationary power stations and energy storage devices,backup power supplies,etc.However,its challenges of low energy density as well as this low energy density induced high cost are the major drawbacks.To overcome these challenges,in recent years,there are tremendous efforts focusing on the development of new and cost-effective electrodes and electrolyte materials as well as electrode con?guration to improve the capacitance,the energy density of the next generation of supercapacitors.

In order to benchmark the state of research in this area at this time,Applied Energy organized a special issue dedicated to recent research development in Supercapacitors.The articles in this spe-cial issue cover the most recent progress of supercapacitor research and development in terms of both fundamentals and applications with focuses on cutting edge research on new materi-als for system designs and practical deployment investigations.2.Background of supercapacitors

Normally,the energy storage mechanism of supercapacitors is electrochemical in nature,but differs from that of batteries or fuel cells that rely on the coupling of Faradaic redox reactions.Instead,supercapacitors store and discharge energy dominantly through what is called electric double layer capacitance (EDLC).This occurs by employing two high surface area electrodes,that when charged,form a Helmholtz double layer at the interface between the con-ductive electrode materials and the electrolyte,as illustrated in

Fig.1.The electrodes have opposing charges,and in this fashion energy is stored by the electrostatic charge separation.As a result of this energy storage mechanism,supercapacitors can charge and discharge in a matter of seconds while delivering immense power densities (typically in the 10–1000KW/kg).Their operational life-times are also an attractive feature,boasting in excess of 100,000charge and discharge cycles before needing replacement (ref).Owing to these advanced properties,supercapacitors have gained commercial success in certain applications that include dynamic load levelling and uninterruptable power supplies.However,due to their low energy density,large untapped markets remain,including the use of supercapacitors in electric vehicles,large scale energy storage units (grid),and small scale portable electronics.For supercapacitors to effectively penetrate these markets,further technological advances,such as those reported in this special issue are required.

At the current state of research,a large body of research has been focused on increasing the energy density of supercapacitors by developing novel high surface area carbon materials,such as graphene,with unprecedented electric double layer capacitance.It is expected that the viability of supercapacitors could also be extended towards a wide range of applications if energy densities can be improved to more closely resemble those of batteries.To accomplish this,psuedocapacitors (or hybrid supercapacitors)are an emerging trend of research that includes compositing conven-tional EDLC electrodes with materials that contribute redox beha-viour during charge and discharge.These materials,with a high capacity to store energy must also be integrated into operational supercapacitor cell designs.These systems may then have their performance investigated and validated towards new,promising applications.

3.Research covered in this special issue

In this special issue,13papers have been included covering the areas of electric double layer capacitance materials,psuedocapac-itor material,system design and application deployment.3.1.New high surface area EDLC materials

Developing novel nano-structured electrode materials are one of the most active approaches in supercapacitors.For example,Article [1]reports the use of rice husks,a renewable resource,to prepare high surface area porous carbons that were used as EDLC

https://www.360docs.net/doc/0d3666400.html,/10.1016/j.apenergy.2015.05.0540306-2619/ó2015Published by Elsevier Ltd.

q

This paper is included in the Special Issue of Electrochemical Supercapacitors for Energy Storage and Conversion,Advanced Materials,Technologies and Applications edited by Dr.Jiujun Zhang,Dr.Lei Zhang,Dr.Radenka Maric,Dr.Zhongwei Chen,Dr.Aiping Yu and Prof.Yan.

materials for supercapacitor applications.Among different nano-materials,graphene,known for its high surface areas and charge mobility,are the most advanced ones being explored for superca-pacitor applications,such as in Article [2],with the impact of reducing agent used during graphene synthesis systematically investigated.In Article [3],carbon xerogels as EDLC materials are investigated,with the importance of tailoring their porous struc-tures clearly highlighted.

3.2.Psuedocapacitor material development

Article [4]discusses the development of alpha-phase MnO 2nanowire based psuedocapacitative electrodes for supercapacitor devices.Paper [5]reports the synthesis and application of new supercapacitor electrodes composed of nickel-manganese oxide deposited on a MWCNT/CFP composite substrate.Article [6]uses polypyrrole,a psuedocapacitative conductive polymer,doped with ?uorescent brightener CBS-X in what is deemed a smart electrode materials.Cobalt nicket silicate hollow spheres were prepared in Article [7]and were found to demonstrate very good stability for supercapacitor applications.New,three-component materials are developed and investigated in Article [8].This consisted of psuedo-capacitative RuO 2composited with carbon nanotubes and CMK-3,an ordered mesoporous carbon structure.3.3.Supercapacitor system designs

An all solid-state supercapacitor design is developed in Article [9],incorporating electrodes that are free-standing ?lms of the aforementioned polyaniline and high surface area carbon particles.A new asymmetric design,which refers to supercapacitors employ-ing two different electrodes is reported in Article [10].The elec-trodes used are consisted of polypyrrole coated carbon nanotubes.

3.4.Practical deployment

The feasibility from a techno-economic standpoint,along with the optimization of the energy storage unit chain is investigated in Article [11]towards the ?rst ever,quick charging plug-in ferry.Article [12]deals with the design and implementation of bi-direc-tional energy conversion systems on a DC motor drive.The integra-tion of supercapacitors to facilitate this is well characterized and reported.Article [13]hybridizes supercapacitors with batteries to prepare energy storage devices for remote area energy storage.This approach can be used to address the intermittency issues associated with renewable energy systems,such as wind and solar.References

[1]Gao Y,Li L,Jin Y,Wang Y,Yuan C,Wei Y,et al.Porous carbon made from rice

husk as electrode material for electrochemical double layer capacitor.Appl Energy 2015;153:41–7.

[2]Ramachandran R,Saranya M,Velmurugan V,Raghupathy BPC,Jeong SK,Grace

AN.Effect of reducing agent on graphene synthesis and its in?uence on charge storage towards supercapacitor applications.Appl Energy 2015;153:22–31.[3]Liu X,Li S,Mi R,Mei J,Liu L-M,Cao L,et al.Porous structure design of carbon

xerogels for advanced supercapacitor.Appl Energy 2015;153:32–40.

[4]Su X,Yu L,Cheng G,Zhang H,Sun M,Zhang X.High-performance a -MnO 2

nanowire electrode for supercapacitors.Appl Energy 2015;153:94–100.

[5]Li Y-H,Li Q-Y,Wang H-Q,Huang Y-G,Zhang X-H,Wu Q,et al.Synthesis and

electrochemical properties of nickel–manganese oxide on MWCNTs/CFP substrate as a supercapacitor electrode.Appl Energy 2015;153:78–86.

[6]Wang X,Deng J,Duan X,Liu D,Liu P.Fluorescent brightener CBS-X doped

polypyrrole as smart electrode material for supercapacitors.Appl Energy 2015;153:70–7.

[7]Rong Q,Long L-L,Zhang X,Huang Y-X,Yu https://www.360docs.net/doc/0d3666400.html,yered cobalt nickel silicate

hollow spheres as a highly-stable supercapacitor material.Appl Energy 2015;153:63–9.

[8]Lo A-Y,Jheng Y,Huang T-C,Tseng C-M.Study on RuO 2/CMK-3/CNTs

composites for high power and high energy density supercapacitor.Appl Energy 2015;153:15–21.

[9]Khosrozadeh A,Xing M,Wang Q.A high-capacitance solid-state supercapacitor

based on free-standing ?lm of polyaniline and carbon particles.Appl Energy 2015;153:87–93.

[10]Su Y,Zhitomirsky I.Asymmetric electrochemical supercapacitor,based on

polypyrrole coated carbon nanotube electrodes.Appl Energy 2015;153:48–55.[11]Trieste S,Hmam S,Olivier J-C,Bourguet S,Loron L.Techno-economic

optimization of a supercapacitor-based energy storage unit chain:application on the ?rst quick charge plug-in ferry.Appl Energy 2015;153:3–14.

[12]Sun L,Zhang N.Design,implementation and characterization of a novel bi-directional energy conversion system on DC motor drive using super-capacitors.Appl Energy 2015;153:101–11.

[13]Ma T,Yang H,Lu L.Development of hybrid battery-supercapacitor energy

storage for remote area renewable energy systems.Appl Energy 2015;153:56–62.

Guest Editors Aiping Yu a

Zhongwei Chen a Radenka Maric b

Lei Zhang c Jiujun Zhang c Jinyue Yan d

a

Chemical Engineering,University of Waterloo,Canada

b

Materials Science and Engineering,University of Connecticut,USA

c

National Research Council Canada,Canada

d

Royal Institute of Technology (KTH)and M?lardalen University,

Sweden

Fig.1.Schematic illustration of an EDLC.

153(2015)1–2