Advances in EC Capacitor Materials and Cell Design
This session, explored the latest advances in materials—including the development of advanced materials and processes to meet the pricing threshold of important markets—and in capacitor design—including
the development of advanced asymmetric ECs.
Session Chairman:
Katsuhiko Naoi, Professor of Chemistry, Institute of Symbiotic Science & Technology, Tokyo University of Agriculture & Technology
Prof. Katsuhiko Naoi is professor of chemistry at Tokyo University of Agriculture & Technology (TAT). He got his BS, MS and Ph.D. from Waseda University, Tokyo and post-doc at The University of Minnesota.
His major is energy chemistry, environmental, and materials science. His research interests are advanced supercapacitors, high-power Li-ion batteries, and fuel cells for automotive/stationary applications.
He serves as the chair of The Capacitor Technology Committee of The Electrochemical Society of Japan.
SESSION AGENDA
Cohesion of Supercapacitor and LIB Technologies for Future EES Katsuhiko Naoi, Professor of Chemistry, Institute of Symbiotic Science & Technology, Tokyo University
of Agriculture & Technology
Dynamic energy storage by supercapacitors is an important energy and environmental technology that is highly influential in advancing our future automotive and wireless society. Unlike batteries,
supercapacitors are efficient energy storage devices that exhibit high power capability, long cycle life, long calendar life, and wide operational temperature ranges. Figure 1 compares
many different characteristics of Li-ion battery and supercapacitor, showing that, except for the energy density, supercapacitors are superior in most of the items than Li-ion batteries.
Thus, the supercapacitor is regarded as a reliable, durable and safe technology with increasing effectiveness when utilized in smart mobility and wireless applications.
Characterization of the porous carbon / electrolyte interface in Double Layer Capacitors Patrice Simon, Professor, Université Paul Sabatier
The research on the design of Ionic Liquids (ILs) electrolytes for supercapacitor applications has seen a tremendous increase during the past few years. Differently from Li-batteries where
the electrolyte composition and stability must fit with several requirements (SEI formation, electrochemical kinetics), there is potentially more room for breakthroughs in supercapacitor
applications.
This talk will firstly present results about the experimental study of the ion confinement effect on the electrochemical characterizations of microporous carbons. We will show that ionic
liquids can be efficiently used as model electrolytes for pushing further our basic understanding of the electrolyte/carbon interactions in confined pores. In a second part, we will
present results showing that a careful design of the carbon structure in conjunction with the electrolyte is a way to go for designing high energy density supercapacitors with a large
operation temperature range.
Volumetric Energy Density of EDLCs: From Carbons to Oxides Thierry Brousse, Professor, Université de Nantes
This presentation is dedicated to the improvement of volumetric energy density of electrochemical double layer capacitors (EDLCs). Carbons are reaching a limitation in terms of pore size
distribution and specific surface area. Even if the recent progress in tuning pore size and size of ions from ionic liquids have led to interesting perspectives for enhancing double layer
capacitance, other ways must be found to drastically improve the volumetric energy density of EDLCs. Since the last 5 years, our group has developed a strategy aiming at synthesizing
new materials as alternative to carbons. Oxides and nitrides have been synthesized and investigated as potential candidates in symmetric or asymmetric supercapacitors (SCs). Based on
computer simulations of the theoretical volumetric energy density of oxide based devices, it seems that replacing carbon electrodes by oxides, even in an aqueous electrolyte, can lead
to surprising results. Indeed, volumetric energy density up to 5 times that of conventional carbon based EDLCs (7 Wh/L) can be estimated with adequate electrodes and geometry. Safer devices
operated at 1.5V maximum cell voltage in neutral or alkaline electrolytes can be designed.
This communication will focus on:
Calculations of volumetric energy density of oxides based SCs compared to carbon based EDLCs:
What are the main difficulties when implementing SC cells with oxides or nitrides in aqueous electrolyte?
Which parameters are important when changing carbon electrodes for oxides or nitrides based electrodes?
What is the level of volumetric energy density that can be achieved by replacing carbon electrodes by oxides or nitrides?
Practical examples:
Some example of architecture using different oxides or nitrides will be presented as well as their performance in terms of volumetric energy density
New materials and new composite electrodes will be proposed to increase volumetric energy density of SC
Electrochemical Capacitors Based on Aqueous Electrolytes Elżbieta Frąckowiak, Professor, Institute of Chemistry and Technical Electrochemistry, Poznan University of
Technology
The energy of electrochemical capacitors can significantly be increased by extension of the operating voltage as well as by introducing faradaic reactions (pseudocapacitance). Pseudocapacitance
can be originated from the electrode material or the electrolytic solution. The texture of the carbon material plays an important role, because of the ion size and character of faradaic
reactions which involve transport (diffusion) phenomena at the electrochemically available surface area. This presentation will be dedicated to various ways of enhancing energy of capacitors
based on aqueous medium. The following issues will be discussed:
Choice of the electrolytic solution concerning pH, corrosion;
Various salts for neutral medium;
Redox active species;
Voltage extension by special combination of anolyte and catholyte;
Estimation of capacitor cycle life by galvanostatic charge/discharge and floating.
Use of Sacrificial Oxide for Pre-lithiation of Graphitic Anode in Li-Ion Capacitors François Béguin, Professor, Institute of Chemistry and Technical Electrochemistry, Poznan University of Technology
In automotive applications, there is an important demand for electrochemical capacitors having much larger energy density than the traditional electrical double-layer systems. In this context,
Lithium-ion capacitors (LIC) have been proposed few years ago; they implement activated carbon and intercalated graphite as positive and negative electrodes, respectively. Hence, the
operation of this system requires an initial step to pre-lithiate graphite, either from an auxiliary lithium source[1] or directly from the electrolyte[2]. Since
both approaches are not completely satisfactory, research on alternative solutions is necessary. Another strategy consists in using sacrificial lithium oxide as lithium ions reservoir
added to the positive electrode[3]. In this presentation, we propose to use non-stoichiometric lithium nickel oxide Li1-xNi1+xO2, which is
no longer electrochemically active in the working voltage range from 2.0 to 4.3 V after the first lithium extraction. The presentation will discuss the key issues to develop a cell based
on lithium nickel oxide:
Synthesis and physico-chemical characterization of non-stoichiometric lithium nickel Li0.65Ni1.35O2;
Electrochemical characteristics of Li0.65Ni1.35O2 and optimisation of the composite positive electrode based on this oxide;
Selection of graphite and optimisation of the negative electrode;
Full cell assembling and determination of the optimized protocol to fabricate the lithium intercalation compound;
Performance of the optimized system;
Summary and perspectives for future developments
[1] Fuji Heavy Industry Patents:
N. Ando, S. Taguchi, Y. Hato, Organic electrolyte capacitor, EP1400996A1 (2002);
S. Tasaki, N. Ando, M. Nagai, A. Shirakami, K. Matsui, Y. Hato, Lithium ion capacitor, WO 2006/112068 (2006);
N. Ando, K. Kojima, S. Tasaki, H. Taguchi, T. Fujii, Y. Hato, C. Marumo, Organic electrolyte capacitor, US2007/0002524A1 (2007);
H. Tanizaki, N. Ando, Y. Hato, Lithium-ion capacitor, EP1914764A1 (2007).
[2] V. Khomenko, E. Raymundo-Piñero, F. Béguin, J. of Power Sources; 177 (2008) 643–651 [3] M.-S. Park, Y.-G. Lim, J.-H. Kim, Y.-J. Kim,
J. Cho and J.-S. Kim; Adv. Energy Mater.; 1 (2011) 1002–1006
