U.S. patent application number 11/917002 was filed with the patent office on 2009-01-29 for method for producing electrode for electrochemical elemetn and method for producing electrochemical element with the electrode.
This patent application is currently assigned to NIPPON CHEMI-CON CORPORATION. Invention is credited to Sam Kogan, Sergey A. Logvinov, Nikolay Shkolnik, Shunzo Suematsu, Kenji Tamamitsu, Alexander M. Timonov, Satoru Tsumeda, Hidenori Uchi.
Application Number | 20090026085 11/917002 |
Document ID | / |
Family ID | 37498203 |
Filed Date | 2009-01-29 |
United States Patent
Application |
20090026085 |
Kind Code |
A1 |
Uchi; Hidenori ; et
al. |
January 29, 2009 |
METHOD FOR PRODUCING ELECTRODE FOR ELECTROCHEMICAL ELEMETN AND
METHOD FOR PRODUCING ELECTROCHEMICAL ELEMENT WITH THE ELECTRODE
Abstract
A method for producing an electrode for an electrochemical
element absorbs monomers for polymerization on a surface having a
specific surface area of 100 to 3000 m.sup.2g.sup.-1 and having an
average pore diameter in the range of 0.4 to 100 nm, performing
electrolysis polymerization by applying pulse voltage, and forming
a conductive polymer layer on the surface of the conductive porous
material, forming a thin and uniform electrode film. In a method
for producing an electrochemical element, a conductive polymer
layer is formed on the conductive porous material by absorbing
monomers for polymerization on a surface of a conductive porous
material having a specific surface area and pore diameter as above
forming a electrochemical cell by using the conductive porous
material, the monomers are absorbed in the pores, putting the
electrochemical cell and the electrolyte solution in an outer
casing, and performing electrolysis polymerization of the monomers
in the electrolyte solution.
Inventors: |
Uchi; Hidenori; (Tokyo,
JP) ; Tamamitsu; Kenji; (Tokyo, JP) ;
Suematsu; Shunzo; (Tokyo, JP) ; Tsumeda; Satoru;
(Tokyo, JP) ; Timonov; Alexander M.; (Saint
Petersburg, RU) ; Logvinov; Sergey A.; (Lenningrad,
RU) ; Shkolnik; Nikolay; (West Hartford, CT) ;
Kogan; Sam; (Newton Center, MA) |
Correspondence
Address: |
YOUNG & THOMPSON
209 Madison Street, Suite 500
ALEXANDRIA
VA
22314
US
|
Assignee: |
NIPPON CHEMI-CON
CORPORATION
Tokyo
MA
GEN3 PARTNERS, INC.
Boston
|
Family ID: |
37498203 |
Appl. No.: |
11/917002 |
Filed: |
June 10, 2005 |
PCT Filed: |
June 10, 2005 |
PCT NO: |
PCT/JP2005/011085 |
371 Date: |
March 17, 2008 |
Current U.S.
Class: |
205/414 |
Current CPC
Class: |
Y02E 60/10 20130101;
H01M 4/0466 20130101; H01M 4/602 20130101; H01G 11/86 20130101;
H01M 4/60 20130101; H01M 4/0438 20130101; H01G 11/32 20130101; Y02T
10/70 20130101; H01G 11/28 20130101; H01M 10/052 20130101; H01M
4/606 20130101; Y02E 60/13 20130101; H01G 11/48 20130101; H01G
11/24 20130101; H01G 11/30 20130101; H01M 4/137 20130101; H01M
4/1399 20130101 |
Class at
Publication: |
205/414 |
International
Class: |
C25B 3/00 20060101
C25B003/00 |
Claims
1. A method for producing an electrode for an electrochemical
element, characterized by absorbing monomers for polymerization on
a surface of a conductive porous material having a specific surface
area of 100 to 3000 m.sup.2g.sup.-1 and having an average pore
diameter in the range of 0.4 to 100 nm, performing electrolysis
polymerization by applying pulse voltage using said conductive
porous material as an electrode in electrolyte solution to stack
said monomers for polymerization, and forming a conductive polymer
layer on the surface of the conductive porous material.
2. The method for producing the electrode according to claim 1,
characterized in that the monomers for polymerization are absorbed
on the surface of the conductive porous material by impregnating
said conductive porous material with solution of the monomers for
polymerization and subsequent removing solvent in the solution of
the monomers for polymerization.
3. The method for producing the electrode according to claim 1,
wherein the monomers for polymerization are in the form of complex
monomer solution of a transition metal having at least two
oxidation numbers, and wherein the conductive polymer formed by the
electrolysis polymerization is an energy storage redox polymer
layer including the polymer complex compound of the transition
metal so as to store energy through redox reaction.
4. The method for producing the electrode according to claim 3,
wherein polymer complex compound of said transition metal is a
polymer metal complex of tetra-dentate Schiff's base.
5. The method for producing the electrode according to claim 4,
wherein the polymer metal complex of said tetra-dentate Schiff's
base comprises the polymer complex compound represented by the
following graphical formula: ##STR00004## wherein Y is ##STR00005##
Me is transition metal, R is H or electron donating substituent, R'
is H or halogen, and, n is an integer number of 2 to 200000.
6. The method for producing the electrode according to claim 5,
wherein said transition metal Me is selected from a group
constituted of Ni, Pd, Co, Cu and Fe.
7. The method for producing the electrode according to claim 5,
wherein said R is selected from a group constituted of CH.sub.3O--,
C.sub.2H.sub.5O--, HO-- and CH.sub.3--.
8. A method for producing an electrochemical element, characterized
by forming a conductive polymer layer on the surface of the
conductive porous material within an outer casing by a step of
absorbing monomers for polymerization on a surface of a conductive
porous material having a specific surface area of 100 to 3000
m.sup.2g.sup.-1 and having an average pore diameter in the range of
0.4 to 100 nm forming a electrochemical cell by using the
conductive porous material wherein the monomers for polymerization
are absorbed in the pores, putting said electrochemical cell and
the electrolyte solution in an outer casing, and performing
electrolysis polymerization of the monomers for polymerization in
said electrolyte solution by applying pulse voltage from a external
electrode of the outer casing to stack said monomer for
polymerization.
9. The method for producing the electrochemical element according
to claim 8, characterized in that the monomers for polymerization
are absorbed on the surface of the conductive porous material by
impregnating said conductive porous material with solution of the
monomers for polymerization and subsequent removing solvent in the
solution of the monomers for polymerization.
10. The method for producing the electrochemical element according
to claim 8, wherein the monomers for polymerization are in the form
of complex monomer solution of a transition metal having at least
two oxidation numbers, and wherein the conductive polymer formed by
the electrolysis polymerization is an energy storage redox polymer
layer including the polymer complex compound of the transition
metal so as to store energy through redox reaction.
11. The method for producing the electrochemical element according
to claim 10, wherein the polymer complex compound of said
transition metal is a polymer metal complex of tetra-dentate
Schiff's base.
12. The method for producing the electrochemical element according
to claim 11, wherein the polymer metal complex of said
tetra-dentate Schiff's base comprises the polymer complex compound
represented by the following graphical formula: ##STR00006##
wherein Y is ##STR00007## Me is transition metal, R is H or
electron donating substituent, R' is H or halogen, and, n is an
integer number of 2 to 200000.
13. The method for producing the electrochemical element according
to claim 12, wherein said transition metal Me is selected from a
group constituted of Ni, Pd, Co, Cu and Fe.
14. The method for producing the electrochemical element according
to claim 12, wherein said R is selected from a group constituted of
CH.sub.3O--, C.sub.2H.sub.5O--, HO-- and CH.sub.3--.
15. The method for producing the electrode according to claim 2,
wherein the monomers for polymerization are in the form of complex
monomer solution of a transition metal having at least two
oxidation numbers, and wherein the conductive polymer formed by the
electrolysis polymerization is an energy storage redox polymer
layer including the polymer complex compound of the transition
metal so as to store energy through redox reaction.
16. The method for producing the electrochemical element according
to claim 9, wherein the monomers for polymerization are in the form
of complex monomer solution of a transition metal having at least
two oxidation numbers, and wherein the conductive polymer formed by
the electrolysis polymerization is an energy storage redox polymer
layer including the polymer complex compound of the transition
metal so as to store energy through redox reaction.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method for producing an
electrode for electrochemical element and a method for producing an
electrochemical element with the electrode, and for more detail,
relates to a method for producing an electrode for an
electrochemical element and a method for producing an
electrochemical element with the electrode in which energy density
is improved and which is excellent in output characteristics.
BACKGROUND OF THE INVENTION
[0002] In these years, an electric automobile and hybrid car have
been expected instead of a gasoline-powered vehicle and
diesel-powered vehicle which are engine-driven. In these electric
automobile and hybrid car, an electrochemical device having high
energy density and high output density properties are used as a
power source for driving a motor. A secondary battery and a double
electric layer capacitor are listed as this electrochemical
device.
[0003] As the secondary battery, a lead battery, nickel/cadmium
battery, nickel hydride battery, or proton battery and so on are
listed. These secondary battery uses acidic or alkaline aqueous
electrolyte solution which are high in ionic conductivity, thereby
to have excellent output characteristics that large electric
current is obtained when charging and discharging, however
electrolysis voltage of water is 1.23V, therefore higher voltage
may not be obtained. As a power source of the electric automobile,
a high voltage of approximately 200V is required, therefore many
batteries by just that much must be connected in series, resulting
in disadvantage for downsizing and trimming weight of the power
source.
[0004] As a secondary battery of high voltage type, a lithium ion
secondary battery using organic electrolyte solution is known. This
lithium ion secondary battery uses an organic solvent with high
decomposition voltage as an electrolytic solvent, therefore when
the lithium ion showing the lowest potential is an electric charge
relating to charge/discharge reaction, potential of 3V or more is
shown. The lithium ion secondary battery brings a battery using
carbon as a negative electrode occluding and releasing the lithium
ion and lithium cobalt oxide (LiCoO.sub.2) as a positive electrode
into mainstream. An electrolyte solution dissolving lithium salt
such as hexafluorophosphate lithium (LiPF.sub.6) into a solvent
such as ethylene carbonate and propylene carbonate is used.
[0005] However, this lithium ion secondary battery is high in
voltage and high in energy density to be excellent as a power
source, however charge reaction is occlusion and release of the
lithium ion of the electrode, therefore the secondary battery has a
problem to be inferior in output characteristics, which is a
disadvantage for the power source for the electric automobile
requiring large instantaneous current. Then, there is an approach
using derivative of polythiophene as a positive electrode for
improving the charge/discharge property at a high voltage (Japanese
Laid-Open Patent Publication No. 2003-297362).
[0006] An double electric layer capacitor uses a polarizable
electrode such as activated carbon as positive and negative
electrodes, and uses a solution dissolving quaternary ammonium salt
of boron tetrafluoride or phosphorus hexafluoride into an organic
solvent such as propylene carbonate. Thus, the double electric
layer capacitor regards an double electric layer generating at the
boundary surface between the surface of the electrode and the
electrolyte solution as an electric capacitance, and there is no
reaction involving ions such as a battery, thus the
charge/discharge property is high and deterioration in capacity due
to charge/discharge cycle is reduced. However, energy density due
to double layer capacity is low in the energy density compared to
the battery, that is significantly insufficient as a power source
of the electric automobile. At the same time, there is an approach
using polypyrrole as a positive electrode for the purpose of large
capacity (Japanese Laid-Open Patent Publication No. H6-104141).
[0007] Then, an electrochemical capacitor using conductive polymer
and metal oxide as an electrode material which is high in energy
density and high in output characteristics has been developed. An
electric charge storage mechanism of this electrochemical capacitor
is adsorption and desorption of anion and cation in the electrolyte
solution onto the electrode, and both energy density and output
characteristics are excellent. Particularly, an electrochemical
capacitor using conductive polymer such as polyaniline,
polypyrrole, polyacene, and polythiophene derivatives performs
charge and discharge by p-doping or n-doping of anion or cation in
non-aqueous electrolyte solution onto the conductive polymer. The
potential of this doping is low at a side of negative electrode and
high at a side of positive electrode, therefore high voltage
property is obtained (Japanese Laid-Open Patent Publication No.
2000-315527).
[0008] However, the capacitor using the above conductive polymer
was also desired to improved energy density and out put
characteristics. In order to comply with the above desire, an
energy storage device, such as a battery or super capacitor, is
developed that includes at least two electrodes, at least one of
the electrodes includes an electrically conducting substrate having
a layer of energy accumulating redox polymer complex compound of
transition metal having at least two different degrees of
oxidation, which polymer complex compound is formed of stacked
transition metal complex monomers. In the energy storage device,
the stacked transition metal complex monomers have a planar
structure with the deviation from the plane of no greater than 0.1
nm and a branched system of conjugated pi-bonds, the polymer
complex compound of transition metal can be formed as a polymer
metal complex with substituted tetra-dentate Schiff's base, and the
layer thickness of redox polymer is within the range 1 mm-20
micrometer (International Patent Publication No. WO03/065536).
Further, the above polymer complex compound may be used for both
positive and negative electrodes since it's central metal could be
reversibly oxidized-reduced. The capacitor using these electrodes
as the both electrodes allows to have a high operating voltage of
3V and a high energy density of 300 Jg.sup.-1, and a method for
producing it by which this energy density is obtained is also
described (International Patent Publication No. WO 04/030123).
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0009] However, demand for downsizing for the use of power source
of an electric automobile and so on is constant, therefore there is
a strong demand for enhanced energy density and enhanced output
characteristics. Then, an object of the present invention is to
provide a method for producing an electrode for an electrochemical
element and a method for producing an electrochemical element with
the electrode having a high energy density and excellent output
characteristics.
Means for Solving the Problems
[0010] The present invention has had discussions on a method for
producing electrode to solve the above problems. Consequently, the
present invention provides a method for forming a thin and uniform
electrode film more effectively through a method for producing an
electrode for an electrochemical element, characterized by
absorbing monomers for polymerization on a surface of a conductive
porous material having a specific surface area of 100 to 3000
m.sup.2g.sup.-1 and having an average pore diameter in the range of
0.4 to 100 nm, performing electrolysis polymerization by applying
pulse voltage using said conductive porous material as an electrode
in electrolyte solution to stack said monomers for polymerization,
and forming a conductive polymer layer on the surface of the
conductive porous material.
[0011] Further, through the method for producing an electrochemical
element, characterized by forming a conductive polymer layer on the
surface of the conductive porous material within an outer casing by
a step of absorbing monomers for polymerization on a surface of a
conductive porous material having a specific surface area of 100 to
3000 m.sup.2g.sup.-1 and having an average pore diameter in the
range of 0.4 to 100 nm, forming a electrochemical cell by using the
conductive porous material wherein the monomers for polymerization
are absorbed in the pores, putting said electrochemical cell and
the electrolyte solution in an outer casing, and performing
electrolysis polymerization of the monomers for polymerization in
said electrolyte solution by applying pulse voltage from a external
electrode of the outer casing to stack said monomer for
polymerization, the present invention makes it possible to produce
an electrochemical element with the said electrode for the
electrochemical element in the series of the steps through the
electrolysis polymerization by applying pulse voltage from the
external port of the electrochemical element after assembling the
structure of the electrochemical element, thereby reducing the
number of steps required for producing the electrochemical
element.
EFFECT OF THE INVENTION
[0012] The present invention enables more effectively thin and
uniform coating of the surface of an electrode structure of a
conductive porous material having a specific surface area of 100 to
3000 m.sup.2g.sup.-1 and having an average pore diameter in the
range of 0.4 to 100 nm with polymer complex compound of transition
metal, namely enables more effectively an increase of surface area
compared to film thickness, consequently the electrode prepared by
the present method increases ratio of doping and dedoping per unit
volume against films of anion and cation, and achieves improvement
of rate property and cycle property, resulting in an
electrochemical device use electrode having high power properties.
The electrode prepared as described above is also possible to form
the electrode film without blocking hole portions of porous
material, therefore surface area is increased and energy density is
improved. As a result, an electrochemical device use electrode
which is excellent in output characteristics and high energy
density can be obtained.
[0013] Also, because the double electric layer capacitor produced
by the method of the present invention is formed as the electrode
constituent of films in which polymer complex compound of
transition metal is formed on the surface of the conductive porous
material, such electrode can be used as a constituent element of
the device such as the battery or capacitor as it is. Accordingly,
it is possible to obtain in simplified and reduced steps the
electrode for the electrochemical element including polymer complex
compound of transition metal, which is excellent in output property
and enhanced in energy density.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1. is a schematic view showing a stacked state of
polymer metal complex (a--oxidized state, b--reduced state).
[0015] FIG. 2. a) is a schematic view showing polymer metal complex
in an oxidized state bonded on electrode surface by chemical
adsorption,
[0016] b) is a schematic view showing polymer metal complex in a
reduced state bonded on the electrode surface by the chemical
adsorption.
[0017] FIG. 3. a) is a schematic view when polymer metal complex is
in a neutral state,
[0018] b) is a schematic view when polymer metal complex is in an
oxidized state.
[0019] FIG. 4 is a cross sectional view of a double electric layer
capacitor produced by a method of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0020] First, the producing steps of the electrode for the
electrochemical element according to the present invention will be
explained.
[0021] As to the process for adsorbing monomers for polymerization
on the surface of the conductive porous material having a specific
surface area in the range of 100 to 3000 m.sup.2/g and having an
average pore diameter in the range of 0.4 to 100 nm, it is
preferable to employ a process for adsorbing monomers for
polymerization on the surface of the conductive porous material by
removing solvent in the solution of monomers for polymerization
after impregnating the conductive porous material with solution of
monomers for polymerization. Specifically, the process is performed
in such a way that the conductive porous material, for instance,
activated carbon fabric woven in the form of cloth is impregnated
with the solution of the monomers for polymerization, subsequently
pulled up, and then a solvent in the solution of monomers for
polymerization is removed by drying treatment, for instance.
Removal of the solvent allows the monomers for polymerization to
remain in the state of adhering so as not to easily desorb due to
adsorptive power of the activated carbon.
[0022] The conductive porous material used herein is preferable to
be conductive porous material having a specific surface area in the
range of 100 to 3000 m.sup.2/g and having an average pore diameter
in the range of 0.4 to 100 nm, specifically activated carbon, and
particularly preferable to be activated carbon fabric woven in the
form of cloth. As for the rest, the conductive porous material may
be molded in the form of disc, in which activated carbon powder,
acetylene black, and polytetrafluorethylene as binder are blended
respectively with 77:20:3 wt %.
[0023] In addition, the solution of the monomers for polymerization
used herein is preferable to be a complex monomer solution of a
transition metal having at least two different oxidation numbers,
and the conductive polymer formed by electrolysis polymerization is
preferable to be an energy storage redox polymer layer including a
polymer complex compound of a transition metal, which stores energy
through the redox reaction.
[0024] As to the process for performing electrolysis polymerization
by applying pulse voltage using said conductive porous material on
the surface of which monomers for polymerization are adsorbing as
an electrode in electrolyte solution to stack said monomers for
polymerization, and forming a conductive polymer layer on the
surface of the conductive porous material, as electrolysis
polymerization mode, for instance, potential sweep polymerization
method, constant potential polymerization method, constant current
polymerization method, and potential step method as well as
potential pulse method are listed. However, the potential pulse
method may be used in the present invention.
[0025] When electrolysis polymerization is performed under the
condition of impregnating conductive porous material having very
large specific surface area with the solution in which monomers for
polymerization are dissolved or dispersed, partial polymerization
reaction may develop on the conductive polymer stacked by the
electrolysis polymerization to form irregularity on the polymer
layer, thereby effecting uneven thickness. In addition, there is a
constraint that a time interval for the electrolysis polymerization
should be long in order to completely polymerize the monomers for
polymerization in the solution. As long as an average pore diameter
of the conductive porous material is in the range of 0.4 nm to 100
nm, the monomers of polymerization are adsorbed on the surface of
the conductive porous material due to the effects of taking the
monomers for polymerization in the pore as well as adsorbing power
of substance which the conductive porous material holds. In
particular, it is possible to thinly and uniformly adsorb monomers
for polymerization on the surface of the conductive porous material
by removing solvent in the solution of monomers for polymerization
after impregnating the conductive porous material with the solution
of monomers for polymerization. When the electrolysis
polymerization is performed in such condition, polymerization
reaction may develop remaining the state that the monomers of
polymerization are thinly and uniformly adsorbed on the surface of
the conductive porous material, thereby effecting conductive
polymer.
[0026] Conditions of the electrolysis polymerization in the method
for producing electrochemical elements according to the present
invention are as follows. In order to enhance the energy density of
the polymer complex compound of transition metal, it is necessary
to optimize a large variety of parameters relating to the
electrolysis polymerization. In particular, it is desired to
optimize the electrolysis time, the downtime and the polymerization
charge. In addition, as a result of study about a improvement in
the energy density of said electrode, not only these parameters but
also a specific surface area of the electrode substrate influences
on the enhancement of energy density. In the suitable
characteristics, the specific surface area of the electrode
substrate preferably may be 200 to 3000 m.sup.2g.sup.-1, more
preferably 1000 to 3000 m.sup.2g.sup.-1, further more preferably
1500 to 2500 m.sup.2g.sup.-1. Further, the electrolysis
polymerization on this substrate may be performed under the
following condition of the electrolysis time, the downtime, the
polymerization charge and the number of pulse. Namely, the
electrolysis time may be 0.1 to 60 second, preferably 0.5 to 10
second, more preferably 0.7 to 5 second. The downtime may be 10 to
300 second, preferably 10 to 60 second, more preferably 20 to 30
second. Accordingly, a pulse ratio, which defines as a proportion
of a pulse repetition time (the electrolysis time+the downtime) to
the electrolysis time, is less than 1500, preferably less than 60,
and less than 30. When the electrolysis polymerization is performed
to the electrode substrate having high-specific surface area
characteristics within these ranges, the optimal conditions for the
diffusion and the polymerization of the complex monomer oxidized
during the electrolytic times into the holes of the substrate or
the defects formed in the polymer could be obtained, thereby
forming a thin polymer film and as the result the electrode having
a high energy density could efficiently be produced. As to the
downtime, down-state means that value of the electric potential
becomes the value at which the polymerization of the monomer stops.
Such value of the electric potential may be -2 to +0.5 V,
preferably -1 to +0.3 V, more preferably -0.5 to 0 V.
[0027] In the present invention, pulse voltage condition may be
Ag/Ag+ of 0.5 to 1.0V, preferably Ag/Ag+ of 0.5 to 0.7V, more
preferably Ag/Ag+ of 0.5 to 0.6V If voltage is in this range, an
enough amount of complex monomer oxide is formed through an
electrochemical reaction, therefore the complex polymer compound of
transition metal is formed efficiently, and further the formed
complex polymer compound of transition metal is difficult to form
over-oxide, consequently complex polymer compound of high-capacity
density transition metal is formed.
[0028] In addition, in the electrolysis polymerization of the
present invention, polymerization is performed by immersing the
above electrode into the electrolyte solution and applying pulse
voltage, however not only such a double pole type but also triple
pole type may be used, polymerization of which is performed by
applying an constant potential to the reference electrode with
using a working electrode and a counter electrode as well as the
reference electrode or flowing oxidation current.
[0029] In the electrolysis polymerization of the present invention,
the number of cycle may be 100 to 10000 cycles, preferably 100 to
5000 cycles, more preferably 200 to 2000 cycles. If the number of
cycle is in this range, an amount of production of the complex
polymer compound of transition metal is enough, in addition, the
complex polymer compound of transition metal is not produced
excessively, therefore a thin film of the complex polymer compound
of transition metal is maintained.
[0030] The electrolyte solution used for the electrolysis
polymerization of the present invention is preferably non-aqueous
type using organic solvent, and a salt which is soluble in organic
solvent and which can ensure ions conductivity is preferably used
in the supporting electrolyte solution, and both the kind and
concentration are not limited.
[0031] Specifically, an organic solvent preferably contains one or
more substances selected from a group constituted of ethylene
carbonate, propylene carbonate, butylene carbonate, dimethyl
carbonate, ethylmethyl carbonate, diethyl carbonate, sulphorane,
acetonitrile, and dimethoxy ethane. As a solute, lithium salt
having the lithium ion, quaternary ammonium salt or quaternary
phosphonium salt having quaternary ammonium cation or quaternary
phosphonium cation respectively may be listed. As lithium salt,
LiPF.sub.6, LiBF.sub.4, LiClO.sub.4, LiN(CF.sub.3SO.sub.2).sub.2,
LiCF.sub.3SO.sub.3, LiC(SO.sub.2CF.sub.3).sub.3, LiAsF.sub.6 and
LiSbF.sub.6 and so on are listed. Also as quaternary ammonium salt
or quaternary phosphonium salt, a salt comprising cation expressed
by R1 R2 R3 R4N+ or R1 R2 R3 R4 P+ (where R1, R2, R3, R4 are alkyl
group with the number of carbon of 1 to 6), and anion consisting of
PF6-, BF4-, ClO4-, N(CF3SO2)2-, C3SO3-, C(SO2CF3)3-, AsF6- or SbF6-
is preferable. Specifically, PF6-, BF4-, ClO4- or N(CP3SO2)2- is
used as anion.
[0032] The most preferable electrolyte solution utilized in the
present electrolysis polymerization is propylene carbonate (PC)
dissolving (C.sub.2Hs).sub.4NBF.sub.4 in the density unit of
[mol/liter].
[0033] The conductive polymer layer formed by the present
electrolysis polymerization is the layer of an energy storage redox
polymer including a polymer complex compound of a transition metal,
which stores energy through the redox reaction. The polymer complex
compound of transition metal may be the polymer metal complex of
tetra-dentate Schiff's base, in particular, represented by the
following graphical formula:
##STR00001##
where Y is
##STR00002##
where Me is transition metal, R is H or electron donating
substituent, R' is H or halogen, and n is an integer number of 2 to
200000.] In particular, as preferable transition metal Me, Ni, Pd,
Co, Cu, and Fe are listed. As preferable R, CH.sub.3O--,
C.sub.2H.sub.5O--, HO--, and --C.sub.3 are listed.
[0034] According to the principles of the present invention a redox
polymer complex compound of transition metal is configured as
"unidirectional" or "stack" macromolecules.
[0035] Representatives of the group of polymer metal suitable for
the electrodes fall into the class of redox polymers, which provide
novice anisotropic electronic redox conduction. For more detail on
these polymer complexes, see Timonov A. M., Shagisultanova G. A.,
Popeko I. E. Polymeric Partially-Oxidized Complexes of Nickel,
Palladium and Platinum with Schiff Bases//Workshop on Platinum
Chemistry. Fundamental and Applied Aspects. Italy, Ferrara, 1991.
P. 28.
[0036] Formation of bonds between fragments can be considered, in
the first approximation, as a donor-acceptor intermolecular
interaction between a ligand of one molecule and the metal center
of another molecule. Formation of the so-called "unidimensional" or
"stack" macromolecules takes place as a result of said interaction.
Such a mechanism of the formation of "stack" structures of a
polymer currently is best achieved when using monomers of
square-planar spatial structure. Schematically this structure can
be presented as follows:
##STR00003##
[0037] Superficially a set of such macromolecules looks to the
unaided eye like a solid transparent film on an electrode surface.
The color of this film may vary depending on the nature of metal
and presence of substitutes in the ligand structure. But when
magnified, the stack structures become evident, see FIG. 1.
[0038] Polymer metal complexes are bonded with the inter-electrode
surface due to chemisorption.
[0039] Charge transfer in polymer metal complexes is effected due
to "electron hopping" between metal centers with different states
of charge. Charge transfer can be described mathematically with the
aid of a diffusion model. Oxidation or reduction of polymer metal
complexes, associated with the change in the states of charge of
metal centers and with directed charge transfer over polymer chain,
is accompanied, to maintain overall electrical neutrality of the
system, by penetration into a polymer of charge-compensating
counter-ions that are present in the electrolyte solution
surrounding the polymer or by the egress of charge-compensating
counter-ions from the polymer.
[0040] The existence of metal centers in different states of charge
in a polymer metal complex is the reason for calling them
"mixed-valence" complexes or "partially-oxidized" complexes.
[0041] The metal center in the exemplary polymer complex poly-[Ni
(CH3O-Salen)] may be in one of three states of charge:
[0042] Ni.sup.2+-neutral state;
[0043] Ni.sup.3+-oxidized state;
[0044] Ni.sup.+-reduced state.
[0045] When this polymer is in the neutral state (FIG. 3a), its
monomer fragments are not charged and the charge of the metal
center is compensated by the charge of the ligand environment. When
this polymer is in the oxidized state (FIG. 3b), its monomer
fragments have a positive charge, and when it is in the reduced
state, its monomer fragments have a negative charge. To neutralize
spatial (volume) charge of a polymer when the latter is in the
oxidized state, electrolyte anions are introduced into the polymer
structure. When this polymer is in the reduced state,
neutralization of the net charge results due to the introduction of
cations (see FIG. 2). The electrode of the present invention may
use polymer metal complex in an oxidized state as a charged state
of positive electrode and use a reduced state as a charged state of
negative electrode. Therefore, the electrode of the present
invention is allowed to be used for both positive and negative
electrodes.
[0046] The present invention more effectively enables thin and
uniform coating of the surface of an conductive porous material
with polymer complex compound of transition metal, namely more
effectively enables an increase of surface area compared to film
thickness, consequently the electrode prepared by the present
method increases ratio of doping and dedoping per unit volume
against films of anion and cation, and achieves improvement of rate
property and cycle property, resulting in an electrochemical device
use electrode having high power properties.
[0047] An electrochemical element provided with an electrode for
the electrochemical element produced by the method of the present
invention will be explained below.
(Secondary Battery)
[0048] A secondary battery may be prepared as following. In the
case of lithium secondary battery, a non-aqueous electrolyte
solution dissolving lithium salt as a solute is used as an
electrolyte solution. And, an electrode by a method of the present
invention is used as a positive electrode, and an electrode
occluding and releasing lithium such as lithium metal or carbon
capable of occluding and releasing lithium is used as a negative
electrode. The secondary battery may also be produced by using the
electrode of the present invention for the negative electrode, and
using lithium metal oxide such as LiCoO.sub.2 for the positive
electrode. In any cases, output characteristics and energy density
are improved.
[0049] When forming a proton battery, acid aqueous solution having
proton as an electrolyte solution is used. And an electrode of the
present invention is used as a positive electrode and the negative
electrode of the proton battery such as quinoxaline based polymer
is used as a negative electrode. The above proton battery is high
in energy density.
(Double Electric Layer Capacitor)
[0050] A double electric layer capacitor may be prepared as
following. The above non-aqueous type may be used as an electrolyte
solution. When using the electrode by the method of the present
invention for a positive electrode and using an electrode having
double electric layer capacity such as activated carbon for a
negative electrode, this double electric layer capacitor improves
in energy density. Also when using an electrode having the double
electric layer capacitor for a positive electrode and using the
negative electrode of the present invention as a negative
electrode, such as activated carbon for a negative electrode, this
double electric layer capacitor improves in energy density in the
same way.
(Electrochemical Capacitor)
[0051] An electrochemical capacitor may be prepared as following.
As an electrolyte solution, a non-aqueous electrolyte solution
dissolving lithium salt, quaternary ammonium salt or quaternary
phosphonium salt as a solute is used. When using the electrode by
the method of the present invention for a positive electrode and
using a conductive polymer such as polythiophene having
oxidation-reduction reaction responsiveness for a negative
electrode, or when using metal oxide such as the conductive polymer
or ruthenium oxide as the positive electrode and using the negative
electrode of the present invention as a negative electrode, energy
density improves. Further, the polymer complex electrode by the
method of the present invention may be used for both positive and
negative electrodes, therefore the electrode of the present
invention may be used for both electrodes, thereby that allows a
electrochemical capacitor having high energy density to be
obtained.
EXAMPLE
[0052] In the following, a manufacturing process of an
electrochemical element provided with an electrode for the
electrochemical element will be explained with regard to one
example of the present invention.
[0053] As illustrated in FIG. 4, the double electric layer
capacitor manufactured by the present invention is provided with a
metallic casing 1 in the form of a flat vessel and cover 2, an
activated carbon electrode 4, a separator 5 inserted between both
activated carbon electrodes 4 and a top sealing gasket 6 for
sealing surrounding area of the casing 1 and the cover 2. The
manufacturing process of such a double electric layer capacitor by
the present invention is as follow.
[0054] First, the activated carbon fabric woven in the form of
cloth is utilized as the activated carbon electrode 4. The
electrode 4 is impregnated with the solution of the monomers for
polymerization, subsequently pulled up, and then a solvent in the
solution of monomers for polymerization is removed by drying
treatment, for instance. Removal of the solvent allows the monomers
for polymerization to remain in the state of adhering so as not to
easily desorb due to adsorptive power of the activated carbon.
Then, the inside of the casing 1 is sealed by superimposing the
separator 5 on the activated carbon electrode 4, fitting the cover
2 on the casing 1 and caulking the casing 1 around the top sealing
gasket 6, after impregnating the activated carbon electrode 4 with
electrolyte solution by pouring thereon. Next, the electrolysis
polymerization of monomers for polymerization is performed by
applying pulse voltage from the external electrode of the
electrochemical element. By performing such electrolysis
polymerization, a conductive polymer is formed on the surface of
the activated carbon electrode. In the case, electric energy, which
has been applied during the electrolysis polymerization, is
efficiently consumed for the polymerization reaction because the
monomers for polymerization, which changes into a conductive
polymer, remain in the state of adhering to the surface of the
electrode. This enables to minimize the electric energy for forming
the conductive polymer with a desired thickness, and also to reduce
polymerization time.
[0055] The conditions regarding the conductive porous material, the
solution of monomers for polymerization, the electrolysis
polymerization, the electrolytic solution and the conductive
polymer layer which are utilized in the manufacturing process of
the electrochemical element according to the present invention are
equivalent to those in the manufacturing process of the electrode
for the electrochemical element described above.
[0056] In addition, as to the separator utilized in the
manufacturing process of the electrochemical element according to
the present invention, it is preferable to employ a micro porous
film or non woven fabric made of polyethylene or polypropylene in
the range of 0.05 to 0.1 mm in thickness
[0057] Thus, because the double electric layer capacitor produced
by the method of the present invention is formed as the electrode
constituent of films in which polymer complex compound of
transition metal is formed on the surface of the conductive porous
material, such electrode can be used as a constituent element of
the device such as the battery or capacitor as it is. Accordingly,
it is possible to obtain in simplified and reduced steps the
electrode for the electrochemical element including polymer complex
compound of transition metal, which is excellent in output property
and enhanced in energy density.
* * * * *