U.S. patent application number 14/182453 was filed with the patent office on 2014-06-12 for battery electrode material formulation and manufacturing process.
This patent application is currently assigned to Lotte Chemical Corporation. The applicant listed for this patent is Lotte Chemical Corporation, ZBB Energy Corporation. Invention is credited to Nathan Coad, Peter Lex.
Application Number | 20140162104 14/182453 |
Document ID | / |
Family ID | 47746829 |
Filed Date | 2014-06-12 |
United States Patent
Application |
20140162104 |
Kind Code |
A1 |
Lex; Peter ; et al. |
June 12, 2014 |
Battery Electrode Material Formulation and Manufacturing
Process
Abstract
An improved chemical composition and manufacturing process for a
battery electrode are disclosed. This battery electrode may be
later arranged in flowing electrolyte battery cells. Battery
electrode material formulation may include a mixture of
polypropylene, carbon black, graphite, bonding additives and other
substances in different concentrations. The inclusion of graphite
may reduce the amount of carbon black in the mixture, thereby
reducing the swelling of the battery electrode in the presence of
bromine. Moreover, material formulation may reduce warpage caused
by the swelling of electrode material, and may additionally improve
the performance and properties of flowing electrolyte batteries. An
extrusion molding process may be employed in order to fabricate the
disclosed battery electrode.
Inventors: |
Lex; Peter; (Menomonee
Falls, WI) ; Coad; Nathan; (Bateman, AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Lotte Chemical Corporation
ZBB Energy Corporation |
Seoul
Menomonee Falls |
WI |
KR
US |
|
|
Assignee: |
Lotte Chemical Corporation
Seoul
WI
ZBB Energy Corporation
Menomonee Falls
|
Family ID: |
47746829 |
Appl. No.: |
14/182453 |
Filed: |
February 18, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13591802 |
Aug 22, 2012 |
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14182453 |
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Current U.S.
Class: |
429/101 ;
252/511; 264/105; 429/212 |
Current CPC
Class: |
H01M 8/188 20130101;
H01M 4/668 20130101; H02J 7/34 20130101; H01M 8/0213 20130101; H01M
4/0471 20130101; H01M 10/46 20130101; H01M 4/96 20130101; Y02E
60/50 20130101; H01M 4/8875 20130101; H01M 8/0221 20130101; H01M
8/0226 20130101; H01M 10/365 20130101; H01M 12/085 20130101; Y02E
60/10 20130101; H02J 1/10 20130101 |
Class at
Publication: |
429/101 ;
429/212; 252/511; 264/105 |
International
Class: |
H01M 4/66 20060101
H01M004/66; H01M 4/04 20060101 H01M004/04 |
Claims
1. An electrode for use in an electrolyte flow battery, the
electrode comprising: a. graphite; b. carbon black; and C.
polypropylene.
2. The electrode of claim 1 wherein the graphite is present in an
amount of between about 5% wt to about 15% wt.
3. The electrode of claim 1 wherein the carbon black is present in
an amount of between about 7% wt to about 20% wt.
4. The electrode of claim 1 wherein the polypropylene is a
combination of high melt flow index (MFI) polypropylene and low MFI
polypropylene.
5. The electrode of claim 4 wherein the high MA polypropylene is
present in an amount of between 5% wt to about 15% wt, and the low
MA polypropylene is present in an amount of between about 35% wt to
about 65% wt.
6. The electrode of claim 1 further comprising one or more of
carbon nanotubes, carbon nanofibers, graphene, micro-graphites,
insert molding adhesion promoters, glass beads, talc, mica,
coupling agents, stabilizing fillers, crystallinity promoters and
anti-oxidants.
7. The electrode of claim 1 further comprising a fibrous
component.
8. The electrode of claim 7 wherein the fibrous component is
selected from the groups consisting of glass fibers, carbon fibers
and mixtures thereof.
9. The electrode of claim 1 further comprising a polyolefin
elastomer.
10. The electrode of claim 9 wherein the polyolefin elastomer is
ethylene octene copolymer.
11. The electrode of claim 1 further comprising an activation
layer.
12. A method for forming an electrode for use in an electrolyte
flow battery, the method comprising the steps of: a. mixing
polypropylene and carbon black to form a first mixture; b. adding
graphite to the first mixture; c. extruding the first mixture into
pellets; and d. forming the electrode using the pellets.
13. The method of claim 12 further comprising the steps of: a.
extruding the pellets into a film after extruding the first mixture
into pellets; and b. cooling the film.
14. The method of claim 13 further comprising the step of cutting
the film into the desired configuration after cooling the film.
15. The method of claim 12 further comprising the step of placing
an activation layer on the electrode after forming the
electrode.
16. The method of claim 15 wherein the step of placing the
activation layer on the electrode comprises attaching the
activation layer to the electrode using an adhesive.
17. The method of claim 15 wherein the step of placing the
activation layer on the electrode comprises laminating the
activation layer onto the adhesive.
18. A battery cell stack for an electrolyte flow battery
comprising: a. a number of flow frames; and b. a number of
electrodes having the composition of claim 1 secured to the flow
frames.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority as a continuation-in-part
of U.S. Non-Provisional Patent Application Serial No. 13/591,802,
filed on Aug. 22, 2012, which in turn claims priority from U.S.
Provisional Patent Application Serial No. 61/526,145, filed on Aug.
22, 2011, the entirety of which are each expressly incorporated by
reference herein.
BACKGROUND
[0002] 1. Field
[0003] This invention relates generally to flowing electrolyte
battery systems, and more particularly, to material formulations
for battery electrodes employed in flowing electrolyte
batteries.
[0004] 2. Background Information
[0005] The performance of electrochemical storage devices involves
complex, interrelated physical and chemical processes between
electrode materials and electrolytes.
[0006] Flowing electrolyte batteries may include a stack of flow
frame assemblies where electrodes and separators are bonded to the
flow frames. There are flow channels in the frames designed to
direct electrolyte flow over the anode and cathode side of each
electrode. On one side of each electrode, a component of the
electrolyte is deposited and consumed during each cycle, while the
other side of the electrode may include a carbon felt to support
the catholyte evolution and consumption reactions.
[0007] There is a need for improvement in many aspects of the
design of flowing electrolyte batteries, including materials and
manufacturing processes. One of the key areas with room for
improvement relates to the formulation of electrodes.
[0008] Zinc-bromine batteries are an example of rechargeable
batteries. Rechargeable batteries may have their energy content
restored by being charged, however deterioration of the battery may
occur on each charge-discharge cycle. The deterioration may occur
due to the interaction between the electrolyte and the electrodes
within the battery cell. Electrolyte causes the electrode material
to degrade, thus decreasing the active surface of the electrode
while increasing internal resistance and diminishing battery
capacity.
[0009] Other limitations of existing battery electrodes is the
inefficient bond between the frame and the electrode, which causes
failures in battery performance. Another drawback is the fact that
solids content represents a considerable percentage of the
material's formulation. Some solids tend to absorb present
reagents; producing an expansion of the electrode in the frame,
thus creating warpage, which negatively affects battery
performance. By reducing the amount of solids in the formulation,
development of warpage may be decreased, while also improving the
bonding between the electrode and the frame. Moreover, larger
amounts of solids in the formulation may also cause the electrode
to be brittle, so it is necessary to add components capable of
increasing flexibility and tensile strength of the electrodes.
[0010] Therefore, battery electrodes currently employed in flow
batteries have performance and durability limitations. Electrodes
employed in flowing electrolyte batteries and other electrochemical
devices need to have low electrical resistivity, high chemical
stability, good mechanical properties, and for some applications
low weight and volume. Additionally, electrodes should be resistant
to deformation due to the presence of reagents, such as bromine, or
any other product employed during battery operation.
[0011] More efficient battery electrodes are key to the advancement
of energy storage technology, thus there is a need for material
formulations which may provide battery electrodes with good flex
strength, high conductivity, and resistance to expansion due to
reagent exposure.
BACKGROUND ART
[0012] U.S. Pat. No. 4,125,680 Shropshire et al., Bipolar
carbon-plastic electrode structure-containing multicell
electrochemical device and method of making same (Aug. 18,
1977)
[0013] Abstract A novel multicell electrochemical device having a
plurality of bipolar carbon-plastic electrode structures and a
novel method of making the device are described. A plurality of
bipolar carbon-plastic electrode structures are formed by first
molding thin conductive carbon-plastic sheets from heated mixtures
of specified carbon and plastic, and then establishing frames of
dielectric plastic material around the sheets and sealing the
frames to the sheets so as to render the resulting structures
liquid impermeable. A plurality of electrochemical cell elements in
addition to the electrode structures, e.g. separators, spacers and
the like, are also formed with dielectric plastic frames. The
frames of both the electrode structures and the additional elements
have projections on at least ne surface. The electrode structures
and the additional elements are stacked to form a group of items in
an electrochemically functional arrangement. The arrangement is
such that the projection of each frame contacts a frame surface of
the next item in the stack. The items in the stack are joined to
one another, e.g. by heat welding or ultrasonic welding, at these
areas of contact so as to form a multicell electrochemical device
capable of holding liquid therein.
[0014] U.S. Pat. No. 4,379,814 Tsien et al., Sheet electrode for
electrochemical systems (Apr. 12, 1983)
[0015] Abstract: An electrochemical cell construction features a
novel co-extruded plastic electrode in an interleaved construction
with a novel integral separator-spacer. Also featured is a leak and
impact resistant construction for preventing the spill of corrosive
materials in the event of rupture.
[0016] U.S. Pat. No. 4,496,637 Shimada et al., Electrode for
flowcell (Dec. 22, 1983)
[0017] Abstract: An electrode for an flowcell comprising electrode
material made of carbon fiber having average &It;002>
spacing of quasi-graphite crystalline structure of not more than
3.70 .ANG., and the average C-axis size of crystallite of not less
than 9.0 .ANG. and at least 3% by mole of oxygen atom bound to the
fiber surface based on carbon atom, whereby the electrode has
remarkable high electrical conductivity, current efficiency
handling characteristics and hydrodynamic characteristics, and is
adapted to flowcell.
[0018] U.S. Pat. No. 5,591,532 Eidler et al, Zinc-bromine battery
with non-flowing electrolyte (Jul. 7, 1995)
[0019] Abstract: A battery including a plurality of bipolar
electrodes and non-conductive separators, each having first and
second surfaces. A carbon coating is applied on the first surface
of each of the plurality of carbon plastic electrodes, and each
separator is disposed in spaced, sandwich relation with respect to
two of the plurality of electrodes. The electrodes and separators
define a plurality of electrochemical cells, including a plurality
of anodic half-cells, and a plurality of cathodic half-cells. A
high surface area carbon material is disposed in, and completely
fills, each cathodic half-cell, and an electrolyte is disposed in
each half-cell. A spacer is disposed in each anodic half-cell. The
spacer may be a mesh or screen made from polymeric material. The
spacer may also be an aggregated glass mat.
[0020] JP 07057740 Miyagawa et al., Electrode material of
zinc-bromine battery (Mar. 3, 1995)
[0021] Purpose: To provide an electrode material of zinc-bromine
battery, which can prevent increase in the internal resistance
while eliminating the warping caused by a swollen electrode
material, and which can improve the service life and the
reliability of the battery.
[0022] Constitution: An electrode material to be arranged in the
battery m in body of a zinc-bromine battery, comprises a
four-component sheet form molding consisting of kneaded material,
for which a predetermined composition ratio of carbon black,
graphite and ion trapping agent are added to a high density
polyethylene resin. The composition ratio of this electrode
material is 45-49 wt. % of high density polyethylene resin,
approximate 15 wt. % of carbon black, approximate 35 wt. % of
graphite, and 1-5 wt. % of ion trapping agent. The ion trapping
agent is of bismuth negative ion exchange type, and has acid
resistance and alkali resistance and an inorganic ion exchanger,
the form of which is selected among powder, paste and granular or
tape all having heat resistance of not lower than 400.degree.
C.
SUMMARY
[0023] According to various embodiments, a chemical composition and
manufacturing process are provided for fabricating battery
electrodes which may be used in flowing electrolyte batteries.
Flowing electrolyte batteries may be used as means to store and
transport energy. The disclosed chemical composition of battery
electrodes may include a mixture of polypropylene, glass fiber,
carbon fiber, graphite, carbon black, elastomer, among others. This
mixture may be later extruded to form electrode sheets.
[0024] According to an aspect of the present disclosure, the
invention addresses the deficiencies in the prior art by providing
a chemical composition of battery electrodes which may reduce
warpage and degradation that may be present when electrodes come in
contact with bromine. That is, by minimizing the amount of carbon
black in the chemical composition and adding graphite instead, the
swelling of the battery electrode in the presence of bromide may be
minimized. As a result, zinc-bromine batteries integrating the
disclosed battery electrodes may exhibit improved efficiency and
longer life span. In addition, by reducing warpage in the battery
electrode, the electrolyte flow distribution within the battery may
be also improved, therefore increasing battery performance and
stability.
[0025] Yet, according to another aspect of the present disclosure,
by employing the disclosed material formulation, nucleation of
battery electrodes may be reduced, thus diminishing dendrite
formation and branching between battery cells, which may translate
into separator failure and internal leakage within the flowing
electrolyte battery.
[0026] In other embodiments, chemical composition of battery
electrode may further include components such as, but not limited
to, carbon nanotubes, carbon nano-fibers, graphene,
micro-graphites, insert molding adhesion promoters, glass beads,
talc, mica, coupling agents, stabilizing fillers, crystallinity
promoters, anti-oxidants among others.
[0027] Numerous other aspects, features and advantages of the
present invention may be made apparent from the following detailed
description taken together with the drawing figures.
LIST OF FIGURES
[0028] Non-limiting embodiments of the present invention are
described by way of example with reference to the accompanying
figures which are schematic and are not intended to be drawn to
scale. Unless indicated as representing the background art, the
figures represent aspects of the invention.
[0029] FIG. 1 shows a flowchart of a manufacturing method for
battery electrodes, according to an embodiment.
[0030] FIG. 2 depicts an illustrative embodiment of a battery
electrode.
[0031] FIG. 3 illustrates an embodiment of second extrusion
process.
[0032] FIG. 4 represents an illustrative embodiment of a battery
cell stack.
DETAILED DESCRIPTION
[0033] Disclosed herein is a composition for electrodes that may be
employed in flowing electrolyte batteries, according to an
embodiment. The present disclosure is hereby described in detail
with reference to embodiments illustrated in the drawings, which
form a part hereof. In the drawings, which are not necessarily to
scale or to proportion, similar symbols typically identify similar
components, unless context dictates otherwise. Other embodiments
may be used and/or other changes may be made without departing from
the spirit or scope of the present disclosure. The illustrative
embodiments described in the detailed description are not meant to
be limiting of the subject matter presented herein.
Definitions
[0034] As used herein, "battery cell" may refer to an enclosure
provided with at least a pair of electrodes and at least one inlet
and one outlet configured to allow the flow of electrolyte through
the enclosure.
[0035] As used herein, "battery cell stack" may refer to one or
more battery cells, placed between a pair of terminal electrodes or
end caps, that share a common electrolyte path.
[0036] As used herein, "flow battery" or "flowing electrolyte
battery" may refer to an electrochemical device that includes at
least one battery cell stack and is capable of storing energy.
[0037] As used herein, "flow frame" may refer to a flow battery
component that forms at least a portion of the enclosure of a
battery cell, containing at least a portion of paths configured to
control the flow of electrolyte through a battery cell stack.
[0038] As used herein, "battery electrode" may refer to a structure
inside the battery through which electric current is passed.
[0039] As used herein "warpage" may refer to at least one
distortion in a battery component.
[0040] As used herein "bromine expansion" may refer to the
expansion suffered by an electrode due to exposure to bromine.
DESCRIPTION OF DRAWINGS
[0041] Disclosed herein is a material formulation and method for
producing battery electrodes which, according to an embodiment, may
be employed in the manufacturing of electrochemical devices such as
flowing electrolyte batteries.
[0042] FIG. 1 shows a flowchart of manufacturing method 100,
according to an embodiment. Manufacturing method 100 may start with
formulation components 102 which may include polypropylene, glass
fiber, graphite, carbon black, elastomers, and other additives.
Formulation components 102 may be compounded in first extrusion
process 104 to obtain pellets 106. Subsequently, pellets 106 may
pass through second extrusion process 108 in order to obtain
electrode film 110; where electrode film 110 may exhibit a uniform
thickness ranging from about 0.1 mm to about 4 mm, with 0.6 mm
being preferred. Afterwards, electrode film 110 may pass through
die cutting process 112 in order to form electrode sheets 114
within preferred dimensions.
[0043] Following the process in FIG. 1, electrode sheets 114 may be
coated with activation layer 116 which may include, in some
embodiments, carbon and adhesives. Activation layer 116 may be
pressed onto electrode sheet 114 to form a proper bond. Required
pressure to bond activation layer 116 onto electrode sheet 114 may
range from about 10 psi to about 200 psi, with 100 psi being
preferred. Finally, in order to obtain smooth plastic surface for
appropriate bonding with the flow frame of a flow battery,
electrode sheets 114 coated with activation layer 116 may pass
through edging process 118, where a rubber blade may remove the
carbon from all the perimeter of electrode sheet 114. and forming
battery electrode 120.
[0044] FIG. 2 depicts an illustrative embodiment of battery
electrode 120 obtained from manufacturing method 100. As seen in
FIG. 2, battery electrode 120 may include electrode sheet 114
coated with activation layer 116, along with edged perimeter 202
formed during edging process 118. Bonding between battery electrode
120 and frame may be improved by removing activation layer 116 as
edged perimeter 202 may have a good probability of achieving a
suitable bonding with the frame.
[0045] The dimensions of battery electrode 120 depicted in FIG. 2
may vary according to the size and application of the flowing
electrolyte battery that may integrate battery electrode 120.
[0046] Formulation Components 102
[0047] Chemical formulation of battery electrodes 120 may include
formulation components 102 such as polypropylene, glass fiber,
carbon fiber, graphite, carbon black, elastomers and other
additives. Two types of polypropylene compounds may be employed: 1)
polypropylene with low Melt Flow Index (MFI) and 2) polypropylene
with high MFI. Low MFI polypropylene is required to achieve an
extrusion grade material while improving the dispersion of carbon
fillers, which may increase the conductivity of battery electrode
120. High MFI polypropylene is employed in order to improve molding
process of battery electrode 120. Low MFI polypropylene may have a
MFI between 1 and 10 gm/10 min at 230.degree. C., 2.16 Kg, while
high MFI polypropylene may have a MFI between 10 and 130 gm/10 min
at 230.degree. C., 2.16 Kg. Suitable suppliers for high MFI
polypropylene and low MFI polypropylene may include Himont Inc.
[0048] Carbon black may be added in the mixture of formulation
components 102 in order to improve the electrical conductivity of
battery electrodes 120. Suitable suppliers for carbon black may
include Akzo Chemie America. Carbon black tends to swell in the
presence of bromine, producing an expansion of battery electrode
120. As such, in order to reduce the expansion in battery electrode
120, graphite may be used as one of the formulation components 102.
The addition of a suitable amount of graphite may allow a reduction
in the amount of carbon black needed in the formulation. Graphite
may also provide stability and conductivity to battery electrode
120. Graphite may be purchased from SGL and Timcal.
[0049] Carbon fiber may be also added to formulation components 102
to increase conductivity of battery electrode 120. Suitable
suppliers for carbon fiber may include Akzo Chemie America. To
enhance the strength of the resultant battery electrode 120,
formulation components 102 may also include glass fiber which may
add stability and resistance to bromine and thermal expansion.
Glass fiber may be purchase from Owens Corning.
[0050] Furthermore, bonding additives may be added to formulation
components 102 to enhance bonding properties and improve insert
molding process during the fabrication of flowing electrolyte
batteries that may integrate battery electrode 120. In some
embodiments, a polyolefin elastomer may be employed as bonding
additive. A suitable polyolefin elastomer may be ethylene octene
copolymer which may be provided by Dow Chemical. Ethylene octene
copolymer increases the mobility and miscibility of polypropylene
resulting in greater cohesion between battery electrode 120 and the
frame in which battery electrode 120 may be placed.
[0051] According to an embodiment formulation components 102 may
include low MFI polypropylene in concentrations ranging from about
35% wt to about 65% wt; high MFI polypropylene in concentrations
ranging from about 5% wt to about 1.5% wt; glass fiber in
concentrations from about 3% wt to about 10% wt; carbon fiber in
concentrations from about 2% wt to about 10% wt; graphite in
concentrations from about 5% wt to about 15% wt; carbon black in
concentrations from about 7% wt to about 20% wt; and polyolefin
elastomer in concentrations ranging from about 2% wt to about 10%
wt.
[0052] In other embodiments formulation components 102 may also
include carbon nanotubes, carbon nanofibers, graphene,
micro-graphites, insert molding adhesion promoter glass beads,
talc, mica, coupling agents, stabilizing fillers, crystallinity
promoters and anti-oxidants in varied concentrations.
[0053] Formation of Pellets 106
[0054] According to an embodiment, manufacturing method 100 for
battery electrodes 120 may include first extrusion process 104
where formulation components 102 such as, but not limited to, high
MFI polypropylene (PP), low MFI polypropylene and carbon black may
be mixed to form a first mixture. Subsequently, first mixture may
be blended in an internal mixer at a blade speed of about 200 rpm,
at a temperature ranging from about 300.degree. F. to about
500.degree. F. Graphite may be slowly added to first mixture with
the remaining formulation components 102 to obtain a pre-compounded
mixture. The resulting pre-compounded mixture may be extruded into
pellets 106. Suitable temperature for first extrusion process 104
of pellets 106 may vary from about 300.degree. F. to about
500.degree. F., while clamping pressure applied during first
extrusion process 104 molding may vary from about 20 psi to about
70 psi.
[0055] Second Extrusion Process 108
[0056] FIG. 3 illustrates an embodiment of second extrusion process
108 where pellets 106 may be supplied to hopper 302 and melted in
heated chamber 304 which contains rotating screw 306. Suitable
temperature for heated chamber 304 may range from about 300.degree.
F. to about 500.degree. F., with 400.degree. F. being preferred,
After heated chamber 304, melted pellets 308 are obtained.
Subsequently, melted pellets 308 may go through cooling chamber 310
which may operate at a temperature between 250.degree. F. and
450.degree. F., with 350.degree. F. being preferred. Subsequently,
melted pellets 308 may go through extruder 312 to obtain electrode
film 110 having a uniform thickness. Extruder 312 may exert a
pressure of about 50 psi.
[0057] After second extrusion process 108, electrode film 110 may
undergo die cutting process 112 in order to obtain rectangular
electrode sheets 114 of varied dimensions depending on the
specifications needed for the flowing electrolyte batteries.
[0058] Manufacturing Techniques for Coating Activation Layer 116
onto Electrode Sheet 114
[0059] There may be three techniques that can be employed for the
application of activation layer 116 onto electrode sheet 114.
[0060] In one embodiment, conductive glue may be applied onto one
surface of electrode sheet 114 by means of a porous roller.
Subsequently, electrode sheet 114 may be immediately immersed in a
fluidized bed of granular activated carbon. Afterwards, electrode
sheet 114 may be dried and then pressed at temperatures ranging
from about 290.degree. F. to about 400.degree. F., with 320.degree.
F. being preferred.
[0061] In other embodiment, activation layer 116 in sheet form may
be applied to electrode sheet 114 in a laminating process during
second extrusion process 108. Depending on the type of activation
layer 116 employed, the process may require a transfer sheet for
providing stability during the transfer process. Activation layers
116 in sheet form may include paper, felt, gas diffusion layers,
among others.
[0062] In another embodiment activation layer 116 may be placed or
glued, by means of a porous roller, on electrode sheet 114 and then
may be pressed under pressure and heat. Pressure may range from
about 10 psi to about 200 psi, with 100 psi being preferred; while
temperature may range from about 290.degree. F. to about
400.degree. F., 320.degree. F. being preferred. This process
partially submerges activation layer 116 into electrode sheet 114,
thus creating a permanent mechanical bond.
[0063] After coating process of activation layer 116, electrode
sheet 114 may undergo edging process 118 where a rubber blade may
be employed in order to remove activation layer /16 from the
perimeter of electrode sheet 114 and prepare electrode sheet 114
for bonding with the frame of a flowing electrolyte battery. The
amount of activation layer 116 removed from electrode sheet 114
during edging process 118 may depend on the surface dimensions and
bonding properties of the frame in which battery electrode 120 may
be bonded.
[0064] Battery Electrode 120 Properties
[0065] Battery electrodes 120 manufactured employing the disclosed
formulation components 102 and manufacturing method 100 may have a
melt flow index ranging from about 0 gm/10 min at 230.degree. C. 5
Kg to about 5 gm/10 min at 230.degree. C. 5 Kg.
[0066] Electrical performance of battery electrode 120 may include
a bulk resistivity ranging between 0 .OMEGA.cm and 5 .OMEGA.cm; and
a surface resistivity in ranges from 1 .OMEGA.cm.sup.2 to 15
.OMEGA.cm.sup.2.
[0067] Mechanical tests on battery electrode 120 may reveal a
tensile strength between 3500 psi and 6000 psi; a tensile modulus
between 500000 psi and 800000 psi; a tensile elongation ranging
from about 1.0% to about 5.0%; flexural strength of about 9000 psi;
a tensile strength reduction due to bromine exposure ranging from
about 0% to about 10%; a tensile modulus reduction due to bromine
exposure between 0% and 20%; a flexural modulus ranging from about
150000 psi to about 750000 psi; and a bromine expansion between
0.0% and 1.5%.
[0068] FIG. 4 represents an illustrative embodiment of battery cell
stack 400 for zinc-bromine batteries. Battery cell stack 400 may
include micro-porous separators 402, flow frames 404, half-cell
spacers 406 and battery electrodes 120. In order to assemble
battery cell stack 400, a pair of micro-porous separators 402 which
are previously bonded to flow frame 404 may be placed between two
flow frames 404 containing a pair of battery electrodes 120 each.
Subsequently, half-cell spacer 406 is placed between flow frames
404 containing micro-porous separators 402 and flow frames 404
containing battery electrodes 120. Half-cell spacers 406 may be
employed in order to maintain a constant cell gap and prevent the
contact between battery electrode 120 and micro-porous separator
402, thus allowing a constant electrolyte flow throughout the flow
channels (not shown in FIG. 4) of flow frames 404. Zinc-bromine
batteries are useful transportable means for energy storage, and
may include a series of battery cell stacks 400 depending on the
power capacity of the battery.
EXAMPLES
[0069] Example #1 is an embodiment of battery electrode 120 where
battery electrode 120 may exhibit the following properties: a melt
flow index of fess than 1 gm/10 min at 230.degree. C. 5 Kg, a bulk
resistivity of 0.8 .OMEGA.cm, a surface resistivity of 3.5
.OMEGA.cm.sup.2, a tensile strength of 4800 psi, a tensile modulus
of 660000 psi, a tensile elongation of 2.5%, a flexural strength of
9000 psi, a tensile strength reduction due to bromine exposure of
less than 5%, tensile modulus reduction due to bromine exposure of
less than 10%, a flexural modulus of 600000 psi, and a bromine
expansion of 0.5%. In order to obtain these properties, battery
electrode 120 may be manufactured using formulation components 102
containing 53% wt low MFI polypropylene, 10% wt high MFI
polypropylene, 5% wt glass fiber, 5% wt carbon fiber, 10% wt
graphite, 12% wt carbon black and 5% wt polyolefin elastomer.
[0070] Example #2 is an embodiment of battery electrode 120 where
battery electrode 120 may exhibit the following properties: a melt
flow index of than 1 gm/10 min at 230.degree. C. 5 Kg, a bulk
resistivity of 2.3 .OMEGA.cm, a surface resistivity of 10
.OMEGA.cm.sup.2, a tensile strength of 4300 psi, a tensile modulus
of 450000 psi, a tensile elongation of 2.2%, a flexural strength of
8600 psi, a tensile strength reduction due to bromine exposure of
less than 10%, tensile modulus reduction due to bromine exposure of
less than 10%, a flexural modulus of 450000 psi, and a bromine
expansion of 0.5%. In order to obtain these properties, battery
electrode 120 may be manufactured using formulation components 102
containing 50% wt low WWI polypropylene, 10% wt high MFI
polypropylene, 5% wt glass fiber, 5% wt carbon fiber, 13% wt
graphite, 10% wt carbon black and 7% wt polyolefin elastomer.
[0071] Example #3 is an embodiment of battery electrode 120 where
battery electrode 120 may exhibit the following properties: a melt
flow index of than 1 gm/10 min at 230.degree. C. 5 Kg, a bulk
resistivity of 1.5 .OMEGA.cm, a surface resistivity of 9
.OMEGA.cm.sup.2, a tensile strength of 4300 psi, a tensile modulus
of 480000 psi, a tensile elongation of 3.6%, a flexural strength of
8200 psi, a tensile strength reduction due to bromine exposure of
less than 10%, tensile modulus reduction due to bromine exposure of
less than 10%, a flexural modulus of 530000 psi, and a bromine
expansion of 0.5%. In order to obtain these properties, battery
electrode 120 may be manufactured using formulation components 102
containing 50% wt low MFI polypropylene, 10% wt high MFI
polypropylene, 5% wt glass fiber, 10% wt carbon fiber, 10% wt
graphite, 10% wt carbon black and 5% wt polyolefin elastomer.
[0072] While various aspects and embodiments have been disclosed
herein, other aspects and embodiments may be contemplated. The
various aspects and embodiments disclosed herein are for purposes
of illustration and are not intended to be limiting, with the true
scope and spirit being indicated by the following claims.
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