U.S. patent application number 13/562574 was filed with the patent office on 2013-05-09 for ion exchange membrane filling composition, method of preparing ion exchange membrane, ion exchange membrane, and redox flow battery.
This patent application is currently assigned to SAMSUNG ELECTRONICS CO., LTD.. The applicant listed for this patent is Myung-jin Lee, Jun-young Mun, Duk-jin Oh, Joung-won Park. Invention is credited to Myung-jin Lee, Jun-young Mun, Duk-jin Oh, Joung-won Park.
Application Number | 20130115504 13/562574 |
Document ID | / |
Family ID | 46690446 |
Filed Date | 2013-05-09 |
United States Patent
Application |
20130115504 |
Kind Code |
A1 |
Lee; Myung-jin ; et
al. |
May 9, 2013 |
ION EXCHANGE MEMBRANE FILLING COMPOSITION, METHOD OF PREPARING ION
EXCHANGE MEMBRANE, ION EXCHANGE MEMBRANE, AND REDOX FLOW
BATTERY
Abstract
A composition for filling an ion exchange membrane, a method of
preparing the ion exchange membrane, the filled ion exchange
membrane, and a redox flow battery using the filled ion exchange
membrane. The composition includes an ion conductive material and a
water soluble support.
Inventors: |
Lee; Myung-jin; (Seoul,
KR) ; Park; Joung-won; (Seongnam-si, KR) ;
Mun; Jun-young; (Seoul, KR) ; Oh; Duk-jin;
(Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Lee; Myung-jin
Park; Joung-won
Mun; Jun-young
Oh; Duk-jin |
Seoul
Seongnam-si
Seoul
Seoul |
|
KR
KR
KR
KR |
|
|
Assignee: |
SAMSUNG ELECTRONICS CO.,
LTD.
Suwon-si
KR
|
Family ID: |
46690446 |
Appl. No.: |
13/562574 |
Filed: |
July 31, 2012 |
Current U.S.
Class: |
429/101 ;
252/184; 429/247; 521/25; 521/27; 521/28 |
Current CPC
Class: |
H01M 4/36 20130101; H01M
8/20 20130101; H01M 8/1004 20130101; Y02E 60/10 20130101; H01M
8/1044 20130101; B01J 41/08 20130101; H01M 8/1053 20130101; Y02E
60/50 20130101; H01M 2300/0082 20130101; B01J 47/12 20130101; H01M
8/1058 20130101; C08J 5/22 20130101; H01M 4/881 20130101; B01J
41/00 20130101; H01M 4/8605 20130101; H01M 2/16 20130101; H01M
8/188 20130101; H01M 8/0289 20130101; H01M 4/8828 20130101 |
Class at
Publication: |
429/101 ;
429/247; 252/184; 521/28; 521/25; 521/27 |
International
Class: |
B01J 41/12 20060101
B01J041/12; C08J 5/22 20060101 C08J005/22; B01J 41/08 20060101
B01J041/08; H01M 2/16 20060101 H01M002/16; H01M 4/36 20060101
H01M004/36 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 3, 2011 |
KR |
10-2011-0114123 |
Claims
1. A composition for filling an ion exchange membrane, the
composition comprising: an ion conductive material; and a water
soluble support.
2. The composition of claim 1, wherein the ion conductive material
is at least one compound selected from the group consisting of an
ion conductive monomer and an ion conductive polymer.
3. The composition of claim 2, wherein the ion conductive monomer
comprises a quaternary ammonium salt.
4. The composition of claim 3, wherein the quaternary ammonium salt
is at least one compound selected from the group consisting of
compounds represented by Formulae 1 to 4 below: ##STR00011##
wherein in Formula 1, the ratio of x to y (x/y) is in a range of
about 0.1 to about 0.5. ##STR00012## wherein in Formula 4, n is an
integer of 100 to 10,000.
5. The composition of claim 2, wherein the ion conductive polymer
comprises at least one of poly(diallyldimethylammonium chloride),
poly(acrylamide-co-diallyldimethylammonium chloride), and
poly(dimethylamine-co-epichlorohydrin-co-ethylenediamine).
6. The composition of claim 1, wherein the water soluble support
comprises at least one of a water soluble monomer, and a water
soluble polymer.
7. The composition of claim 6, wherein the water soluble monomer
comprises at least one of vinyl alcohol, vinyl acetate,
acrylonitrile, and methyl methacrylate.
8. The composition of claim 6, wherein the water soluble polymer
comprises at least one of polyacrylamide, polyacrylic acid,
poly(acrylamide-co-acrylic acid), polyvinylalcohol, and poly(sodium
4-styrenesulfonate).
9. The composition of claim 1, wherein the weight ratio of the ion
conductive material to the water soluble support is in a range of
70:30 to 30:70.
10. The composition of claim 1, further comprising at least one
solvent.
11. The composition of claim 10, wherein the solvent comprises at
least one of water, methanol, ethanol, dimethylacetamide,
N-methyl-2-pyrrolidone, dimethylformamide, dimethyl sulfoxide, and
tetrahydrofuran.
12. The composition of claim 11, wherein the amount of the solvent
is in a range of about 0 to about 100 parts by weight based on a
total of 100 parts by weight of the ion conductive material and the
water soluble support.
13. The composition of claim 1, further comprising a thermal
polymerization initiator or a photopolymerization initiator.
14. A method of preparing an ion exchange membrane, the method
comprising: impregnating a porous substrate film having ion
exchanging properties with the composition of claim 1; and
polymerizing the impregnated composition.
15. The method of claim 14, wherein the porous substrate film
comprises at least one of a polyolefin, polytetrafluoroethylene
(PTFE), polyetheretherketone, a polysulfone, a polyimide, and a
polyamideimide.
16. An ion exchange membrane comprising a polymer product of the
composition of claim 1.
17. The ion exchange membrane of claim 16, wherein the ion exchange
membrane has an ion conductivity of 1.0 10.sup.-4 S/cm or more.
18. The ion exchange membrane of claim 16, wherein the ion exchange
membrane has a thickness of about 20 to about 100 .mu.m.
19. A redox flow battery comprising: a catholyte; an anolyte; and
the ion exchange membrane of claim 16 disposed between the
catholyte and the anolyte.
20. The redox flow battery of claim 19, wherein the ion exchange
membrane is an anion exchange membrane and at least one of the
catholyte and the anolyte is an organic electrolyte.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of Korean Patent
Application No. 10-2011-0114123, filed on Nov. 3, 2011 in the
Korean Intellectual Property Office, the disclosure of which is
incorporated herein in its entirety by reference.
BACKGROUND
[0002] 1. Field
[0003] Aspects of the present invention relate to ion exchange
membrane filling compositions, methods of manufacturing ion
exchange membranes, ion exchange membranes, and redox flow
batteries, and more particularly, to ion exchange membrane filling
compositions including ion conductive materials and water soluble
supports, methods of preparing ion exchange membranes by using the
ion exchange membrane filling compositions, ion exchange membranes
prepared by using the methods, and redox flow batteries including
the ion exchange membranes.
[0004] 2. Description of the Related Art
[0005] A typical secondary battery converts electric energy input
thereto by changing the electric energy into chemical energy and
then stores the chemical energy. Then, during discharging, the
battery converts the stored chemical energy into electric energy
and then outputs the electric energy.
[0006] Like the typical secondary battery, a redox flow battery
also converts electric energy input thereto by changing the
electric energy into chemical energy and then stores the chemical
energy. Then, during discharging, the redox flow battery converts
the stored chemical energy into electric energy and outputs the
electric energy. However, the redox flow battery is different from
the typical secondary battery in that because an electrode active
material retaining energy is present in a liquid state, not in a
solid state, a tank for storing the electrode active material is
needed.
[0007] In detail, in a redox flow battery, a catholyte and an
anolyte each function as an electrode active material, and a
typical example of these electrolytes is a transition metal oxide
solution. That is, in a redox flow battery, the catholyte and the
anolyte are stored in a tank in the form of a solution including a
redox transition metal in which the oxidation state is changed.
[0008] Also, in a redox flow battery, a cell for generating
electric energy has a structure of cathode/ion exchange
membrane/anode, and the catholyte and anolyte supplied to the cell
via a pump contact corresponding electrodes, respectively. At the
respective contact surfaces, transition metal ions included in the
respective electrolytes are oxidized or reduced. At this point, an
electromotive force corresponding to the Gibbs free energy is
generated. In this case, the electrodes do not directly participate
in the reactions and only aid oxidation/reduction of transition
metal ions included in the catholyte and the anolyte.
[0009] In a redox flow battery, the ion exchange membrane does not
participate in the reactions and performs (i) a function of quickly
transferring ions that constitute a charge carrier between the
catholyte and the anolyte, (ii) a function of preventing direct
contact between a cathode and an anode, and most importantly (iii)
a function of suppressing crossover of electrolyte active ions that
are dissolved in the catholyte and the anolyte and directly
participate in the reactions.
[0010] However, a conventional ion exchange membrane for a redox
flow battery is mainly used to selectively separate ions in an
aqueous system, and accordingly, ion mobility characteristics and
film properties in the aqueous solution are optimized. However, an
ion exchange membrane for a redox flow battery that has optimized
ion mobility characteristics and film properties in a non-aqueous
system, that is, an organic system, has not yet been sufficiently
studied.
SUMMARY
[0011] Aspects of the present invention provide ion exchange
membrane filling compositions including ion conductive materials
and water soluble supports.
[0012] Aspects of the present invention provide methods of
preparing ion exchange membranes by using the ion exchange membrane
filling compositions.
[0013] Aspects of the present invention provide ion exchange
membranes prepared by using the methods.
[0014] Aspects of the present invention provide redox flow
batteries including the ion exchange membranes.
[0015] According to an aspect of the present invention, a
composition for filling an ion exchange membrane includes: an ion
conductive material; and a water soluble support.
[0016] The ion conductive material may include at least one
compound selected from the group consisting of an ion conductive
monomer and an ion conductive polymer.
[0017] The ion conductive monomer may include a quaternary ammonium
salt.
[0018] The quaternary ammonium salt may include at least one of
poly(diallyldimethylammonium chloride),
poly(acrylamide-co-diallyldimethylammonium chloride), and
poly(dimethylamine-co-epichlorohydrin-co-ethylenediamine).
[0019] The water soluble support may include at least one of a
water soluble monomer and a water soluble polymer.
[0020] The water soluble monomer may include at least one of vinyl
alcohol, vinyl acetate, acrylonitrile, and methyl methacrylate.
[0021] The water soluble polymer may include at least one of
polyacrylamide, polyacrylic acid, poly(acrylamide-co-acrylic acid),
polyvinylalcohol, and poly(sodium 4-styrenesulfonate).
[0022] The weight ratio of the ion conductive material to the water
soluble support may be in a range of about 70:30 to about
30:70.
[0023] The composition may further include at least one
solvent.
[0024] The solvent may include at least one compound from water,
methanol, ethanol, dimethylacetamide, N-methyl-2-pyrrolidone,
dimethylformamide, dimethyl sulfoxide, and tetrahydrofuran.
[0025] The amount of the solvent may be in a range of about 0 to
about 100 parts by weight based on a total of 100 parts by weight
of the ion conductive material and the water soluble support.
[0026] The composition may further include a thermal polymerization
initiator or a photopolymerization initiator.
[0027] According to another aspect of the present invention, a
method of preparing an ion exchange membrane includes: impregnating
a porous substrate film having ion exchanging properties with the
composition; and polymerizing the impregnated composition.
[0028] The porous substrate film may include at least one compound
from a polyolefin, polytetrafluoroethylene (PTFE),
polyetheretherketone, a polysulfone, a polyimide, and a
polyamideimide.
[0029] According to another aspect of the present invention, an ion
exchange membrane includes a polymer product of the composition
described above.
[0030] The ion exchange membrane may have an ion conductivity of
1.0 10.sup.-4 S/cm or more.
[0031] The ion exchange membrane may have a thickness of about 20
to about 100 .mu.m.
[0032] The ion exchange membrane may be an anion exchange
membrane.
[0033] The anion exchange membrane may allow at least one anion
selected from the group consisting of BF.sub.4.sup.-,
PF.sub.6.sup.-, CF.sub.3SO.sub.3.sup.-, and
(CF.sub.3SO.sub.2).sub.2N.sup.- to permeate therethrough.
[0034] According to another aspect of the present invention, a
redox flow battery includes: a catholyte; an anolyte; and the ion
exchange membrane disposed between the catholyte and the
anolyte.
[0035] The ion exchange membrane may be an anion exchange membrane,
and at least one of the catholyte and the anolyte is an organic
electrolyte.
[0036] Additional aspects and/or advantages of the invention will
be set forth in part in the description which follows and, in part,
will be obvious from the description, or may be learned by practice
of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] These and/or other aspects and advantages of the invention
will become apparent and more readily appreciated from the
following description of the embodiments, taken in conjunction with
the accompanying drawings, of which:
[0038] FIG. 1 is a diagram to explain a method of preparing an ion
exchange membrane, according to an embodiment of the present
invention;
[0039] FIG. 2 is a schematic view of a redox flow battery according
to an embodiment of the present invention;
[0040] FIG. 3 shows impedance spectra showing cell resistance
characteristics of redox flow batteries manufactured according to
Example 1 and Comparative Example 2;
[0041] FIG. 4 is a graph of charging and discharging efficiency
(CE), voltage efficiency (VE), and energy efficiency (EE) of redox
flow batteries manufactured according to Example 3 and Comparative
Example 2 with respect to number of cycles of charging and
discharging;
[0042] FIG. 5 is a graph of a charging capacity and a discharging
capacity with respect to the number of cycles of charging and
discharging of a redox flow battery manufactured according to
Example 3;
[0043] FIG. 6 is a scanning electron microscope (SEM)
cross-sectional image of an ion exchange membrane (Comparative
Example 1) manufactured by using only an ion conductive material;
and
[0044] FIG. 7 is an SEM cross-sectional image of an ion exchange
membrane (Example 3) manufactured by using an ion conductive
material and a water soluble support.
DETAILED DESCRIPTION
[0045] Reference will now be made in detail to the present
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings, wherein like reference
numerals refer to the like elements throughout. The embodiments are
described below in order to explain the present invention by
referring to the figures. Expressions such as "at least one of,"
when preceding a list of elements, modify the entire list of
elements and do not modify the individual elements of the list.
[0046] Hereinafter, an ion exchange membrane filling composition
according to an embodiment of the present invention is described in
detail.
[0047] An ion exchange membrane filling composition according to an
embodiment of the present invention includes an ion conductive
material and a water soluble support. The term "ion exchange
membrane filling composition" used herein refers to "a composition
that is used to fill a porous substrate having ion exchanging
properties."
[0048] The ion conductive material is used in preparing an ion
exchange membrane, which will be described later, to increase
permeability of effective ions through the ion exchange membrane
and reduce crossover of electrolyte components other than the
effective ions. The term "effective ion" used herein refers to an
electrolyte component that permeates through the ion exchange
membrane to enable charging and discharging of a redox flow
battery. Examples of the effective ions are BF.sub.4.sup.-,
PF.sub.6.sup.-, CF.sub.3SO.sub.3.sup.-, and
(CF.sub.3SO.sub.2).sub.2N.sup.-.
[0049] The ion conductive material may include at least one
compound selected from the group consisting of an ion conductive
monomer and an ion conductive polymer.
[0050] The ion conductive monomer may include a quaternary ammonium
salt.
[0051] The quaternary ammonium salt may include at least one
compound selected from the group consisting of compounds
represented by Formulae 1 to 4 below:
##STR00001##
wherein in Formula 1, the ratio of x to y (x/y) may be in a range
of about 0.1 to about 0.5. Also, the weight average molecular
weight of the quaternary ammonium salt represented by Formula 1 may
be in a range of about 100,000 to about 500,000.
##STR00002##
wherein in Formula 4, n is an integer of 100 to 10,000.
[0052] The ion conductive polymer may include at least one of
poly(diallyldimethylammonium chloride),
poly(acrylamide-co-diallyldimethylammonium chloride), and
poly(dimethylamine-co-epichlorohydrin-co-ethylenediamine).
[0053] The water soluble support may compensate for hard and
brittle properties of the ion conductive material or a polymer
thereof to provide a flexible and tough ion exchange membrane.
[0054] The water soluble support may include at least one of a
water soluble monomer and a water soluble polymer.
[0055] The water soluble monomer may include at least of vinyl
alcohol, vinyl acetate, acrylonitrile, and methyl methacrylate.
[0056] The water soluble polymer may include at least of
polyacrylamide, a polyacrylic acid, poly(acrylamide-co-acrylic
acid), polyvinylalcohol, and poly(sodium 4-styrenesulfonate).
[0057] The ion exchange membrane filling composition may include a
combination of an ion conductive monomer and a water soluble
monomer, a combination of an ion conductive monomer and a water
soluble polymer, or a combination of an ion conductive polymer and
a water soluble monomer.
[0058] If the ion exchange membrane filling composition includes a
combination of an ion conductive monomer and a water soluble
monomer, the final ion exchange membrane may include a homopolymer
of the ion conductive monomer, a homopolymer of the water soluble
monomer, and/or a copolymer of the ion conductive monomer and the
water soluble monomer.
[0059] If the ion exchange membrane filling composition includes a
combination of an ion conductive monomer and a water soluble
polymer, the final ion exchange membrane may include a composite of
a homopolymer of the ion conductive monomer and the water soluble
polymer.
[0060] If the ion exchange membrane filling composition includes a
combination of an ion conductive polymer and a water soluble
monomer, the final ion exchange membrane may include a composite of
the ion conductive polymer and a homopolymer of the water soluble
monomer.
[0061] The weight ratio of the ion conductive material to the water
soluble support may be in a range of about 70:30 to about 30:70. If
the weight ratio of the ion conductive material to the water
soluble support is within the range described above, an ion
exchange membrane with a uniform composition and excellent ion
mobility characteristics and film properties may be obtained (see
FIG. 7).
[0062] The ion exchange membrane filling composition may
additionally include at least one solvent.
[0063] The solvent may include at least one of water, methanol,
ethanol, dimethylacetamide, N-methyl-2-pyrrolidone,
dimethylformamide, dimethyl sulfoxide, and tetrahydrofuran.
[0064] The amount of the solvent may be in a range of about 0 to
about 100 parts by weight based on a total of 100 parts by weight
of the ion conductive material and the water soluble support. If
the amount of the solvent is within the range described above, when
the ion exchange membrane filling composition is polymerized, the
drying time during a drying process may be reduced and a uniform
film property may be obtained.
[0065] The ion exchange membrane filling composition may
additionally include a thermal polymerization initiator or a
photopolymerization initiator.
[0066] The thermal polymerization initiator may include at least
one initiator selected from the group consisting of potassium
persulfate, ammonium persulfate, sodium persulfate, ammonium
bisulfate, sodium bisulfate, azobisisobutyronitrile,
1,1'-azobis(1-methylbutyronitrile-3-sodium sulfonate), and
4,4'-azobis(4-cyanovaleric acid).
[0067] The photopolymerization initiator may include at least one
initiator selected from the group consisting of
2,2-dimethoxy-2-phenylacetophenone, 2-oxoglutaric acid,
1-hydroxycyclohexylphenyl methanone, and
2-hydroxy-2-methylpropiophenone.
[0068] The amount of the thermal polymerization initiator may be in
a range of about 0.1 to about 0.5 wtppm based on a total weight of
the ion conductive material and the water soluble support. If the
amount of the thermal polymerization initiator is within the range
described above, a polymer (that is, an ion exchange membrane)
having a uniform composition may be obtained.
[0069] The amount of the photopolymerization initiator may be in a
range of about 0.1 to about 0.5 wtppm based on the total weight of
the ion conductive material and the water soluble support. If the
amount of the photopolymerization initiator is within the range
described above, a polymer (that is, an ion exchange membrane)
having a uniform composition may be obtained.
[0070] Hereinafter, a method of preparing an ion exchange membrane,
according to an embodiment of the present invention, is described
in detail with reference to FIG. 1. FIG. 1 is a diagram to explain
a method of preparing an ion exchange membrane, according to an
embodiment of the present invention.
[0071] Referring to FIG. 1, a method of preparing an ion exchange
membrane, according to the present embodiment of the present
invention, includes impregnating a porous substrate film 110 having
ion exchanging properties with an ion exchange membrane filling
composition including an ion conductive material 120 and a water
soluble support 130, and polymerizing the ion exchange membrane
filling composition that is impregnated into the porous substrate
film 110.
[0072] The thickness of the porous substrate film 110 may be 60
.mu.m or less. If the thickness of the porous substrate film 110 is
within the range described above, film resistance may be
reduced.
[0073] The porous substrate film 110 may include at least one of a
polyolefin, polytetrafluoroethylene (PTFE), polyetheretherketone, a
polysulfone a polyimide, and a polyamideimide. The porous substrate
film 110 may have a pore size of about 0.01 to about 0.1 .mu.m.
[0074] As an example of the polymerization, if the ion exchange
membrane filling composition is thermally polymerized, the
polymerization process may be performed at the temperature of about
40 to about 80.degree. C. for about 2 to about 10 hours. In this
case, during the polymerization process, a volatile material (for
example, an organic solvent) that may be included in the ion
exchange membrane filling composition may be removed.
[0075] As another example of the polymerizing, when the ion
exchange membrane filling composition is photopolymerized, the
polymerization process may be performed under irradiation of
ultraviolet rays at room temperature (for example, about 20 to
about 30.degree. C.) for about 30 minutes to about 1 hour. As
described above, when the ion exchange membrane filling composition
is photopolymerized, the method of preparing an ion exchange
membrane may further include drying after the polymerization. The
drying may be performed at the temperature of about 40 to about
80.degree. C. for 2 to 10 hours. In this case, during the drying, a
volatile material (for example, an organic solvent) that may be
included in the ion exchange membrane filling composition may be
removed.
[0076] The method of preparing an ion exchange membrane may further
include substituting a non-effective ion included in the ion
conductive material or a polymer thereof 120 with the effective ion
described above. The term "non-effective ion" used herein refers to
an ion (for example, Cr) that does not enter into the reactions of
the present invention. The substitution may be performed by using a
polycarbonate (PC)/triethylamine tetrafluoroborate (TEABF.sub.4)
solution, a polycarbonate (PC)/lithium
bis(trifluoromethanesulfonyl)imide (LiTFSI) solution, or the
like.
[0077] An ion exchange membrane prepared by using the method
described above may have more ion channels, which constitute ion
flow passages, than the porous substrate film 110.
[0078] Hereinafter, an ion exchange membrane according to an
embodiment of the present invention is described in detail.
[0079] The ion exchange membrane according to the present
embodiment includes a polymerization product of the ion exchange
membrane filling composition described above.
[0080] The ion exchange membrane may have an ionic conductivity of
1.0 10.sup.-4 S/cm or more (for example, about 2.0 10.sup.-4 to
about 5.0 10.sup.-4 S/cm).
[0081] The ion exchange membrane may have a thickness of about 20
to about 100 .mu.m.
[0082] The organic electrolyte may include a non-aqueous solvent, a
supporting electrolyte, and a metal-ligand coordination
compound.
[0083] The non-aqueous solvent may include at least one compound
selected from the group consisting of dimethyl acetamide, diethyl
carbonate, dimethyl carbonate, acetonitrile,
.gamma.-butyrolactone(GBL), propylene carbonate(PC), ethylene
carbonate(EC), N-methyl-2-pyrrolidone(NMP), fluoroethylene
carbonate, and N,N-dimethylacetamide.
[0084] The supporting electrolyte does not directly participate in
the reactions and maintains a charge balance between a catholyte
and an anolyte. The supporting electrolyte may include at least one
compound selected from the group consisting of LiBF.sub.4,
LiPF.sub.6, LiClO.sub.4, LiCF.sub.3SO.sub.3,
Li(CF.sub.3SO.sub.2).sub.2N, triethylamine tetrafluorborate
(TEABF.sub.4), 1-ethyl-2-methylpyrazolium tetrafluoroborate
(EMPBF.sub.4), spiro-(1,1')-bipyrrolidium tetrafluoroborate
(SBPBF.sub.4), piperidine-1-spiro-1'-pyrrolidinium
tetrafluoroborate (PSPBF.sub.4), tributylamine tetrafluoroborate
(TBABF.sub.4), and lithium bis(trifluoromethanesulfonyl)imide
(LiTFS1).
[0085] The metal included in the metal-ligand coordination compound
may include at least one metal selected from the group consisting
of iron (Fe), nickel (Ni), cobalt (Co), ruthenium (Ru), zinc (Zn),
manganese (Mn), yttrium (Y), zirconium (Zr), titanium (Ti),
chromium (Cr), magnesium (Mg), cerium (Ce), copper (Cu), lead (Pb),
and vanadium (V).
[0086] The ligand included in the metal-ligand coordination
compound may include at least one selected from the group
consisting of dipyridyl, terpyridyl, ethylenediamine,
propylenediamine, phenanthroline, and
2,6-bis(methylimidazole-2-ylidene)pyridine.
[0087] During oxidation and reduction, two or more electrons may
move from the metal-ligand coordination compound.
[0088] The metal-ligand coordination compound may include at least
one of compounds represented by the following formulae:
##STR00003## ##STR00004## ##STR00005## ##STR00006## ##STR00007##
##STR00008## ##STR00009## ##STR00010##
[0089] Hereinafter, a redox flow battery according to an embodiment
of the present invention will be described in detail with reference
to FIG. 2. FIG. 2 is a schematic view of a redox flow battery
according to an embodiment of the present invention.
[0090] Referring to FIG. 2, the redox flow battery according to the
present embodiment includes a cathode cell 1, an anode cell 2, an
ion exchange membrane 100 that separates the two cells 1 and 2, and
the tanks 21 and 22 each communicating with the cells 1 and 2.
[0091] The cathode cell 1 may include a cathode 13 and a catholyte
11.
[0092] The anode cell 2 may include an anode 14 and an anolyte
12.
[0093] Charging and discharging may occur due to a redox reaction
occurring at the cathode 13 and the anode 14.
[0094] Each of the cathode 13 and the anode 14 may include at least
one material selected from the group consisting of carbon felt,
carbon cloth, carbon paper, and metal foam.
[0095] At least one of the catholyte 11 and the anolyte 12 may be
the organic electrolyte described above.
[0096] The ion exchange membrane 100 may allow only the effective
ion (that is, a charge carrier ion of a supporting electrolyte) to
permeate therethrough and may prevent permeation of other
electrolyte components (that is, components other than the
effective ion) included in the catholyte 11 and the anolyte 12. The
ion exchange membrane 100 may be the ion exchange membrane
described above. Also, the ion exchange membrane 100 may be an
anion exchange membrane.
[0097] The cathode tank 21 stores the catholyte 11 and communicates
with the cathode cell 1 via a tube 41. Likewise, the anode tank 22
stores the anolyte 12 and communicates with the anode cell 2 via a
tube 42.
[0098] The catholyte 11 and the anolyte 12 circulate via pumps 31
and 32, respectively.
[0099] The operating principle of the redox flow battery is
disclosed in KR 2011-0088881. KR 2011-0088881 is incorporated
herein in its entirety by reference.
[0100] The redox flow battery may be used in, in addition to
existing mobile phones, mobile computers, or the like, an
application that requires high capacity and high power output, such
as an electric vehicle. Also, the redox flow battery may be
combined with an existing internal combustion engine, a fuel cell,
a super capacitor, or the like for use in a hybrid vehicle, or the
like. Also, the redox flow battery may be used in other
applications that require high power output and high voltage.
[0101] Hereinafter, the present invention will be described in
detail with reference to the following examples. However, the
present invention is not limited to the examples.
EXAMPLES
Examples 1 to 4 and Comparative Example 1
Preparation of Ion Exchange Membrane Filling Composition
[0102] An ion conductive material, a water soluble support, a
solvent (10 wt % N-methyl-2-pyrrolidone (NMP) aqueous solution),
and a thermal polymerization initiator (azobisisobutyronitrile
(AlBN)) were mixed at content ratios as shown in Table 1 below to
prepare ion exchange membrane filling compositions (or ion exchange
membrane forming compositions).
TABLE-US-00001 TABLE 1 Solvent Ion conductive Water soluble (NMP
Thermal material support aqueous polymerization Content Content
solution) initiator (parts by (parts by (parts by (AlBN) Type
weight) Type weight) weight) (wtppm*.sup.3) Example 1 VBTMAC*.sup.1
90 PVA*.sup.2 10 20 0.3 Example 2 VBTMAC 70 PVA 30 20 0.3 Example 3
VBTMAC 60 PVA 40 20 0.3 Example 4 VBTMAC 40 PVA 60 20 0.3
Comparative VBTMAC 100 Not used 20 10 Example 1
*.sup.1Vinylbenzyltrimethyl ammonium chloride (represented by
Formula 3) *.sup.2Polyvinyl alcohol *.sup.3Based on a total weight
of ion conductive material and water soluble support
Preparation of Ion Exchange Membrane
[0103] A porous substrate film (Fumatech Company, FAP4) was washed
with deionized water several times and then impregnated with a 2M
KOH solution to sufficiently substitute cr ions by OH.sup.- ions.
Then, the substituted porous substrate membrane was washed with
deionized water. Thereafter, water was removed from the washed
porous substrate film, followed by drying in a drying oven. Then,
the pre-treated and washed porous substrate film was placed on a
glass plate and then the ion exchange membrane filling compositions
were coated thereon to a thickness of 60 .mu.m. Then, the coated
porous substrate film was placed in an oven and then dried at the
temperature of 60.degree. C. for 7 hours. Thereafter, a
PC/TEABF.sub.4 solution (concentration of TEABF.sub.4: 0.5M) was
used to substitute OH.sup.- ions and cr ions included in the dried
porous substrate film with BF.sub.4Ions to complete the preparation
of ion exchange membranes. In Comparative Example 1, however, the
ion exchange membrane forming composition was directly coated on a
glass plate to a thickness of 60 .mu.m, and then drying and
substitution processes as described above were performed to obtain
an ion exchange membrane.
Preparation of Redox Flow Battery
[0104] A redox flow battery was manufactured as follows. As a
cathode and an anode, an electrode that was prepared by heat
treating carbon felt (Nippon Graphite, GF20-3, the thickness
thereof was 3 mm, and the size thereof was 5 cm 5 cm) in the
atmospheric condition at the temperature of 500.degree. C. for 5
hours was used.
[0105] As an ion exchange membrane, the ion exchange membranes
prepared above were used.
[0106] As a catholyte, 0.2M Fe
(2,2'-bipyridine).sub.3(BF.sub.4).sub.2 and 0.5M SBPBF.sub.4 salt
dissolved in a PC solvent were used, and as an anolyte, 0.1M
Ni(2,2'-bipyridine).sub.3BF.sub.4 and 0.5M SBPBF.sub.4 salt
dissolved in a PC solvent were used.
[0107] In detail, an insulating material (PTFE film), a current
collector (gold plate), and a bipolar plate (graphite) were stacked
on a nut-integrated end plate. The bipolar plate had a gas leak
hole. Thereafter, a square carbon felt electrode having a size of 5
cm.times.5 cm was cut in half to obtain two rectangular electrodes,
and then, one of the electrodes was inserted into a concave surface
of the bipolar plate to manufacture a cathode cell. Likewise, the
other electrode was used to manufacture an anode cell. Then, 3 ml
of the catholyte were injected into the cathode cell to complete
the manufacture of the cathode cell. Also, 3 ml of the anolyte were
injected into the anode cell to complete the manufacture of the
anode cell. Thereafter, the cathode cell and the anode cell were
arranged to face each other and then, four bolts into which
Belleville springs were inserted were inserted passing through the
two cells and then, the bolts were tightened in a diagonal sequence
by using a torque wrench until the torque reached 1.5 Nm. After
this assembling was completed, the remaining electrolytes were
inserted through liquid injection pores of the respective
electrodes, and then the pores were closed with a PTFE bolt,
thereby completing the manufacture of a redox flow battery.
Comparative Example 2
[0108] A redox flow battery was manufactured in the same manner as
in Examples 1 to 4 and Comparative Example 1, except that FAP4
manufactured by Fumatech Company was used as an ion exchange
membrane without any treatment.
Evaluation Example
Evaluation Example 1
Measurement of Ion Conductivity of Ion Exchange Membrane
[0109] Ion conductivities of the ion exchange membranes of Examples
1 to 4 and Comparative Examples 1 to 2 were measured and the
results are shown in Table 2 below. A SOLARTRON.RTM. 1260 impedance
spectroscope manufactured by Solartron Analytical Company of Lloyd
Instruments Group was used to measure the ion conductivity. Also,
the measurement frequency range was in a range of about 0.1 Hz to
about 1 MHz.
TABLE-US-00002 TABLE 2 Ex- Com- Com- Ex- Ex- Ex- am- parative
parative ample 1 ample 2 ample 3 ple 4 Example 1 Example 2 Ion 5.91
5.87 5.85 5.00 3.10 4.12 conductivity (10.sup.-4 S/cm)
[0110] Referring to Table 2, it was confirmed that the ion exchange
membranes prepared according to Examples 1 to 4 had higher ion
conductivity than the ion exchange membranes of Comparative
Examples 1 to 2.
Evaluation Example 2
Measurement of Cell Resistance of Redox Flow Battery
[0111] Impedance of the redox flow batteries prepared according to
Examples 1 to 4 and Comparative Examples 1 to 2 was measured, and
the results, that is, cell resistance are shown in Table 3 below.
Also, impedance spectra of the redox flow batteries manufactured
according to Example 1 and Comparative Example 2 are shown in FIG.
3. The impedance was measured by using the SOLARTRON.RTM. 1260
impedance spectroscope referenced above. Also, the measurement
frequency range was in a range of about 0.1 Hz to about 1 MHz. In
FIG. 3, Z.sub.1 is resistance and Z.sub.2 is impedance.
TABLE-US-00003 TABLE 3 Cell resistance (ohm, .OMEGA.) Example 1
0.90 Example 2 0.89 Example 3 0.92 Example 4 0.98 Comparative
Example 2 1.95 Comparative Example 2 1.17
[0112] Referring to Table 3 and FIG. 3, it was confirmed that the
redox flow batteries manufactured according to Examples 1 to 4 had
lower cell resistance than the redox flow batteries manufactured
according to Comparative Examples 1 to 2.
Evaluation Example 3
Charging and Discharging Test
[0113] Charging and discharging tests were performed at room
temperature (25.degree. C.) on the redox flow batteries
manufactured according to the Examples 1 to 4 and Comparative
Examples 1 to 2, and the results thereof are shown in Table 4,
below and FIGS. 4 and 5.
[0114] Charging and discharging conditions were as follows: the
redox flow batteries were charged with a constant current of 20 mA
until the voltage reached 2.5 V, and then discharged with a
constant current of 20 mA until the voltage decreased to 2.0 V. The
charging and discharging were repeatedly performed 10 times.
[0115] In Table 4 below and FIG. 4, the charging and discharging
efficiency (CE) refers to the percentage of the discharged charge
amount divided by the charged charge amount, the voltage efficiency
(VE) refers to the percentage of the average discharge voltage
divided by the average charge voltage, and the energy efficiency
(EE) refers to the product of the voltage efficiency and the
charging and discharging efficiency. Also, in Table 4 below, the
capacity reduction ratio refers to the percentage of the
discharging capacity, that is, the discharged charge amount in the
10.sup.th cycle divided by the discharged charge amount in the
first cycle.
TABLE-US-00004 TABLE 4 Ex- Com- Com- Ex- Ex- Ex- am- parative
parative ample 1 ample 2 ample 3 ple 4 Example 1 Example 2 Charging
81 83 92 85 -- 68 and discharging efficiency (CE) (%) Voltage 97 95
93 97 -- 91 efficiency (VE) (%) Energy 79 82 85 81 -- 60 efficiency
(EE) (%) Capacity 18 16 14 18 -- 3 reduction ratio (%)
[0116] Referring to Table 4, it was confirmed that the redox flow
batteries manufactured according to Examples 1 to 4 had higher
charging and discharging efficiency and, voltage efficiency and
energy efficiency, and lower capacity reduction ratio than the
redox flow batteries manufactured according to Comparative Examples
1 to 2. In the case of Comparative Example 1, however, physical
properties of the ion exchange membrane were degraded after cell
resistance was measured and thus, the charging and discharging test
was not performed thereon.
Evaluation Example 4
Evaluation of Electrolyte Component Crossover
[0117] Following the charging and discharging test, a concentration
of a non-effective ion (that is, Ni ion) passing through an ion
exchange membrane was measured by using inductively coupled plasma
(ICP), and the results thereof are shown in Table 5 below. In
detail, after the charging and discharging test was completed, a
concentration of a Ni ion present in the respective catholytes
(that is, concentration of permeated electrolyte) was measured to
evaluate the crossover of electrolyte components other than the
effective ion.
TABLE-US-00005 TABLE 5 Ex- Ex- Com- Com- Ex- Ex- am- am- parative
parative ample 1 ample 2 ple 3 ple 4 Example 1 Example 2
Concentration 13.5 13.0 12.6 12.6 -- 28.0 of Permeated Electrolyte
(wtppm)
[0118] Referring to Table 5, the crossover of electrolyte
components other than the effective ion in the redox flow batteries
manufactured according to Examples 1 to 4 was reduced relative to
that in the redox flow batteries manufactured according to
Comparative Examples 1 to 2.
Evaluation Example 5
Evaluation of Water Soluble Support Efficacy
[0119] The efficacy of a water soluble support on the formation of
an ion exchange membrane was evaluated by referring to FIG. 6, that
is, by evaluating an SEM cross-sectional image of the ion exchange
membrane (Example 1) in which the weight ratio of the water soluble
support/ion conductive material was 10/90, and by referring to FIG.
7, that is, by evaluating an SEM cross-sectional image of the ion
exchange membrane (Example 3) in which the weight ratio of the
water soluble support/ion conductive material was 40/60.
[0120] Referring to FIG. 6, it was confirmed that a polymer P of an
ion conductive material was formed on only one surface of porous
substrate film 10. On the other hand, referring to FIG. 7, the
composite of a polymer of an ion conductive material and a water
soluble support was uniformly formed in an ion exchange membrane.
From these results, it was confirmed that the water soluble support
improves impregnation properties of an ion exchange membrane
filling composition with respect to a porous substrate film to aid
formation of a redox flow battery having excellent film
properties.
[0121] As described above, the ion exchange membranes according to
the one or more of the above embodiments of the present invention
may have optimized ion mobility characteristics and film properties
in a non-aqueous system, that is, an organic system. Also, a redox
flow battery including the ion exchange membrane has high charging
and discharging efficiency, voltage efficiency and energy
efficiency and a low capacity reduction ratio.
[0122] It should be understood that the exemplary embodiments
described herein should be considered in a descriptive sense only
and not for purposes of limitation. Descriptions of features or
aspects within each embodiment should typically be considered as
available for other similar features or aspects in other
embodiments.
[0123] Although a few embodiments of the present invention have
been shown and described, it would be appreciated by those skilled
in the art that changes may be made in this embodiment without
departing from the principles and spirit of the invention, the
scope of which is defined in the claims and their equivalents.
* * * * *