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Announcing the Successful Development
of a New Electric Double-Layer Capacitor with a High Energy
Density
( October 16, 2003 )
Asahi Glass Co., Ltd.
Asahi Glass Co., Ltd. has successfully developed a new electric
double-layer capacitor with an improved energy density, nearly
triple that of the conventional product (Asahi Glass is based
in Tokyo and its president is Shinya Ishizu.). The new capacitor
has a high capacitance density of 13F/cc per cell volume and
the world's highest operating voltage of 3.0V. These features
enable the new capacitor to resolve a weakness of capacitors,
namely the lack of energy compared with secondary batteries,
and provide a high energy density of 10 Wh/liter at a high
output range of 1000 W/liter. With this development, we expect
that the capacitor will find ready applications in industrial
fields, such as in the automotive industry.
In collaboration with ELNA Co., Ltd., an affiliated manufacturer
of capacitors, Asahi Glass started development of an electric
double-layer capacitor in 1985. The collaboration yielded
the successful development of a small, coin-shaped capacitor
used primarily for the back-up of IC memories and mass-production
commenced at ELNA Co., Ltd. in 1988.
Since that time, we have used the technology developed for
the mass production of the coin-shaped capacitor to try to
expand the technology for large capacitors in an effort to
increase the output power source. We have been independently
developing electrode and electrolyte solution to resolve the
problem of the shortage of energy density. The features of
the electrode and electrolyte that we have recently developed
are as follows:
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Electrode: A high-performance molded electrode
with high capacitance density and low electric resistance.
The main material is special high-purity, high-capacitance,
activated carbon, and the electrode is made using the
microfibril high-density molding method using fluorocarbon
resin PTFE made by Asahi Glass. |
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Electrolyte: High-performance organic electrolyte
maintaining a high operating voltage and high output,
made by combining asymmetrical quaternary ammonium salt,
one of our patented technologies, and low polar organic
solvent. |
To achieve good cost performance, we applied a cylindrical cell
structure of a rolled up electrode with good productivity and
developed a "Tabless structure" that does not require
a lead tab to be pulled out from the electrode, as with the
conventional type. The output is increased by improving the
volumetric capacitance density through the efficient packing
of the devices and by reducing the internal cell resistance.
The electric capacitance of a single cylindrical cell is approximately
500 to 2000 F. In addition, we have the technology to set single
cylindrical cells as a 14-V/42-V high-voltage module by connecting
them in series. In the course of these developments, we have
filed approximately 300 patent applications.
The current requirement for automobile application is a high-output
from a small-sized power source, so it is expected that there
will now be considerable demand for use in hybrid cars and
fuel cell cars. The market for hybrid cars in particular is
estimated to grow to approximately 2,200,000 units by 2010,
so we will be expanding our business by primarily targeting
the market for mini-hybrid cars that can maximize the performance
of the new capacitor.
Inquiries:
Shinichi Kawakami, Manager of Corporate Communications Division,
Asahi Glass Co., Ltd.
(Person in charge: Saito, Telephone: 03-3218-5509, E-mail:
info-pr@agc.co.jp)
Glossary
| 1. |
Electric double-layer capacitor
A capacitor that stores electricity in the electric double
layer formed at the interface between electrolyte solution
containing ions and electrode materials that have a large
surface area. With a very large electrostatic capacitance
compared with that of a normal capacitor, so it is used
as a means of power storage that is capable of charging
and discharging. Because of the physical phenomenon of
storing charge in the electric double layer, it is possible
to discharge a large amount of current and charge the
device quickly. There is very low deterioration in performance
after repeated charging and discharging, so the power
source can be used semi-permanently. |
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F (farad)
The unit of electrostatic capacitance of a capacitor.
When applying a DC voltage of V volts to a capacitor with
an electrostatic capacitance of C farads, the electric
charge, Q coulombs, stored in the capacitor is expressed
as Q = C x V. |
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Output density, energy density
When discharging a capacitor at an output of W watts,
if the duration of the discharge is represented in hours,
the amount of energy E generated at that time is expressed
as E = W x h. These values differ according to the size
of the capacitor. Therefore, to standardize the performance
for comparison, each value is divided by the volume of
the capacitor cell in liters and represented as W/liter
for output density and Wh/liter for energy density. |
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| 4. |
Microfibril high density molding method
When polytetrafluoroethylene (PTFE) is mechanically sheared,
it becomes just a few microns thick. The molding method
uses this property to immobilize activated carbon powders
into the micro fibrillated PTFE network. |
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Asymmetrical quaternary ammonium salt
Quaternary ammonium is a positive ion with four alkyl
groups attached to each nitrogen atom. Until now, symmetrical
quaternary ammonium consisting of the same four alkyl
groups has been used. The development of asymmetrical
ammonium that unites four different alkyl groups has enabled
us to significantly improve the solubility and the electrical
conductivity. |
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| 6. |
Cylindrical cell structure of rolled
up electrodes, series module
This is a cylindrical structure based on a device rolled
up with a separator between two long positive and negative
electrodes. When it is necessary to drive them at several
volts to a high voltage of several hundred volts, multiple
single cells are used in a module form, connecting them
in series. |
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