U.S. patent application number 11/141026 was filed with the patent office on 2005-10-06 for charge storage device.
Invention is credited to Keshishian, Sarkis, Mahon, Peter John, Paul, George Lange, Pynenburg, Rory Albert James.
Application Number | 20050219799 11/141026 |
Document ID | / |
Family ID | 3816702 |
Filed Date | 2005-10-06 |
United States Patent
Application |
20050219799 |
Kind Code |
A1 |
Paul, George Lange ; et
al. |
October 6, 2005 |
Charge storage device
Abstract
A charge storage device (1) includes a sealed prismatic housing
(2). Two opposed folded rectangular aluminium electrodes (3, 4) are
disposed within housing (2) and connected to the electrodes. A
porous, electronically insulating separator material, e.g.
Solupor.TM., sheet separator (7) is disposed intermediate
electrodes (3, 4) for maintaining those electrodes in a fixed
spaced apart configuration. An electrolyte (not shown) is also
disposed intermediate the electrodes. Collecting means in the form
of a scavenging agent is grafted to separator (7) for sequestering
one or more predetermined contaminants from the housing.
Inventors: |
Paul, George Lange;
(Chatswood West, AU) ; Pynenburg, Rory Albert James;
(Hillsboro, OR) ; Mahon, Peter John; (Narrabundah,
AU) ; Keshishian, Sarkis; (Ermington, AU) |
Correspondence
Address: |
KENYON & KENYON
1500 K STREET NW
SUITE 700
WASHINGTON
DC
20005
US
|
Family ID: |
3816702 |
Appl. No.: |
11/141026 |
Filed: |
June 1, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11141026 |
Jun 1, 2005 |
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10019393 |
Jun 3, 2002 |
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10019393 |
Jun 3, 2002 |
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PCT/AU00/01029 |
Aug 30, 2000 |
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Current U.S.
Class: |
361/512 |
Current CPC
Class: |
Y02E 60/50 20130101;
H01M 4/366 20130101; H01G 9/02 20130101; H01M 10/52 20130101; H01M
4/38 20130101; H01M 50/317 20210101; Y02E 60/13 20130101; H01M
4/621 20130101; H01M 50/409 20210101; H01M 50/463 20210101; H01M
4/96 20130101; H01G 9/08 20130101; Y02E 60/10 20130101; H01G 9/155
20130101; H01M 50/124 20210101 |
Class at
Publication: |
361/512 |
International
Class: |
H01G 009/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 30, 1999 |
AU |
PQ 2530 |
Claims
What is claimed is:
1. A charge storage device including: a housing; a first sheet
electrode disposed within the housing; a second sheet electrode
disposed within the housing adjacent to and opposed with the first
sheet electrode; a separator for enveloping substantially all of
the first electrode and for maintaining the electrodes in a spaced
apart configuration; an electrolyte disposed intermediate the
electrodes; and two terminals extending from the respective
electrodes and terminating outside the housing for allowing
external electrical connection to the electrodes.
2. A device according to claim 2 wherein the separator includes two
opposed separator sheets which are connected along at least one
common edge and the first electrode is disposed between the
separator sheets.
3. A charge storage device including: a housing; a first folded
sheet electrode disposed within the housing and having two opposite
faces; a second sheet electrode disposed within the housing and
having two opposed faces, wherein the second sheet electrode is
folded about the first sheet electrode such that each opposed face
is adjacent to and opposed with a respective opposite face; a
separator for enveloping substantially all of the first electrode
and for maintaining the electrodes in a spaced apart configuration;
an electrolyte disposed intermediate the electrodes; and two
terminals extending from the respective electrodes and terminating
outside the housing for allowing external electrical connection to
the electrodes.
4. A device according to claim 3 wherein the first electrode is
nested within the second electrode.
5. A device according to claim 3 wherein the separator is a sheet
that is nested between the first electrode and the second
electrode.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a charge storage
device.
[0002] The invention has been developed primarily for
supercapacitors and will be described hereinafter with reference to
that application. However, the invention is not limited to that
particular field of use and is also suitable for other charge
storage devices such as capacitors, batteries, fuel cells and the
like.
DISCUSSION OF THE PRIOR ART
[0003] Supercapacitors in the form of electric double layer
capacitors are known. These capacitors generally include a housing
for two aluminium electrodes each of which have a coating of
activated carbon or the like on at least one side. The electrodes
are typically wound or otherwise interleaved together with an
intermediate separator and wetted with an appropriate electrolyte.
The charge is stored in the electric double layer which is formed
between the carbon and the electrolyte. Due to the large surface
area per volume of the activated carbon the charge storage density
of these devices is high.
[0004] One limitation of these supercapacitors is that, due to the
nature of the known electrolytes, the housing must be sealed to
prevent both leakage of the electrolyte--comprising of salt and
solvents--from the housing and ingress of contaminants into the
housing. A failure to sufficiently guard against the latter causes
a degradation of the capacitor performance by reducing the maximum
achievable operating voltage, increasing the leakage current,
increasing the resistance and decreasing the available capacitance.
If the ingress is allowed to persist it will ultimately render the
capacitor unworkable.
[0005] Batteries are also known and also use electrolytes,
although, in distinction to supercapacitors, the energy is stored
electrochemically. In any event, batteries also require the secure
storage of the electrolyte within a housing to prevent its escape
to the environment and to maintain its purity.
[0006] As a partial solution to ensuring that the electrolyte is
maintained within the housing and free of contamination, much
effort has been expended in providing the housing with walls that
offer good barrier properties to the passage of fluids. An example
of such an arrangement for a battery is disclosed in U.S. Pat. No.
5,445,856. This battery housing includes a wall made from a
laminate having an oxygen scavenging agent either:
[0007] 1. Incorporated in one of the layers of the laminate; or
[0008] 2. Disposed between any two of the layers.
[0009] This feature is intended to increase the barrier properties
of the housing to the ingress of contaminants through the laminate.
While oxygen is the primary concern it is preferred that the agent
also inhibits the transport of water through the laminate.
[0010] Notwithstanding the additional complexity, cost and improved
barrier properties of this prior art housing, these types of charge
storage devices are still very much subject to electrolyte
contamination and degradation. Accordingly, over time, the
performance of the device progressively deteriorates and the
operation lifetime of the devices is compromised.
DISCLOSURE OF THE INVENTION
[0011] It is an object of the preset invention, at least in the
preferred embodiment, to overcome or substantially ameliorate one
or more of the disadvantages of the prior art, or at least to
provide a useful alternative.
[0012] According to one aspect of the invention there is provided a
charge storage device including:
[0013] a housing;
[0014] at least two opposed electrodes disposed within the
housing;
[0015] a separator disposed intermediate the electrodes;
[0016] an electrolyte disposed intermediate the electrodes; and
[0017] collecting means disposed within the housing for
sequestering one or more predetermined contaminants from the
housing.
[0018] Preferably, the electrodes each include a coating and the
collecting means is one component of at least one of the coatings.
More preferably, the coatings include an activated carbon and the
collecting means is incorporated into the at least one coating
prior to application to the electrodes. Even more preferably, the
at least one coating includes a binder and the collecting means is
contained within the binder.
[0019] Preferably also, the collecting means is activated to
sequester the one or more contaminants. More preferably, the
collecting means is included within the binder prior to that
activation. Even more preferably, the collecting means is activated
after assembly of the charge storage device. In still further
preferred embodiments, the activation is achieved by applying a
predetermined voltage across the electrodes. In other embodiments
the activation is achieved by electrochemical means.
[0020] In other embodiments, however, the collecting means is
activated prior to inclusion of the collecting means within the
binder. Moreover, in flier embodiments, the collecting means is
activated either prior to or during the assembly of the charge
storage device.
[0021] In some preferred embodiments the collecting means is
activated by exposure to predetermined wavelengths and intensities
of electromagnetic radiation such as ultraviolet radiation. In
other embodiments, the collecting means is exposed to an electron
beam.
[0022] In other embodiments, the collecting means is contained
within the electrolyte.
[0023] Preferably also, the collecting means sequesters oxygen from
the housing. More preferably, the collecting means is the compound
marked as ZERO 2 as sold and marketed by Southcorp Packaging. In
other embodiments, the collecting means sequesters water from the
electrolyte. In still further embodiments the collecting means
sequesters other substances such as bromine and chlorine.
[0024] In a preferred form the sequestering results in the
contaminants being isolated from the charge storage operation of
the device. In other embodiments the sequestering results in a
chemical change of the contaminants.
[0025] Preferably, where the collecting means is a component of the
electrolyte, the sequestering results in additional electrochemical
activity. More preferably, this additional activity improves the
overcharge performance of the device.
[0026] In some embodiments the collecting means is a scavenging
species. More preferably, the collecting means is grafted or
otherwise incorporated into the separator. As will be appreciated
by those skilled in the art, locating the collecting means with the
separator will allow optimum removal of contaminants from the
electrolyte.
[0027] Preferably also, the housing includes an interior surface
and an exterior surface, and the collecting means is disposed on
the interior surface.
[0028] According to a second aspect of the invention there is
provided a method for constructing a charge storage device having a
housing, the method including the step of providing collecting
means disposed within the housing for sequestering one or more
predetermined contaminants from the housing.
[0029] Preferably, the device includes two spaced apart electrodes,
a separator intermediate the electrodes and an electrolyte for
wetting the electrodes, the electrodes, separator and electrolyte
being disposed within the housing and the method including the
further step of grafting the collecting means to the housing. In
other embodiments the method includes the step of grafting the
collecting means to the separator. In still further embodiments the
collecting means is disposed within the electrolyte.
[0030] According to a third aspect of the invention there is
provided a charge storage device including:
[0031] a housing;
[0032] at least two opposed electrodes disposed within the
housing;
[0033] a separator disposed intermediate the electrodes;
[0034] an electrolyte disposed intermediate the electrodes; and
[0035] collecting means for allowing removal of one or more
predetermined contaminants from the housing.
[0036] Preferably, the collecting means includes a port in the
housing through which the one or more contaminants are selectively
drawn. More preferably, the device includes sealing means to
prevent ingress of contaminants through the port and into the
housing. Even more preferably, the sealing means is a one way
valve. In other embodiments, however, the sealing means is a septum
extending across the port.
[0037] In a preferred form the collecting means also sequesters the
one or more predetermined contaminants. Even more preferable, the
collecting means is activated to initialise the sequestering and
subsequently reactivated to:
[0038] effect release of the sequestered contaminants into the
housing; and then
[0039] once again commence the sequestering of the one or more
predetermined contaminants from the housing.
[0040] Preferably also, the collecting means includes a port in the
housing which is selectively subjected to an external negative
pressure to draw from the housing the contaminants released upon
reactivation of the collecting means.
[0041] In other embodiments, a scavenging agent is progressed
through the port and into the housing for sequestering the one or
more predetermined contaminants. More preferably, the scavenging
agent is removed from the housing via the port. Even more
preferably, the scavenging agent is activated for sequestering the
one or more contaminants prior to progression in to the housing. In
other embodiments, however, the activation occurs once the
scavenging agent is in the housing. More preferably, the activation
is achieved by exposure of the scavenging agent to predetermined
wavelengths of electromagnetic radiation. Even more preferably, the
housing includes a window which is at least partially transparent
to those predetermined wavelengths.
[0042] According to a fourth aspect of the invention there is
provided a method for removing one or more predetermined
contaminants from a charge storage device having a housing defining
a cavity, the method including the steps of:
[0043] providing a port in the housing for allowing selective
external fluidic communication with the cavity; and
[0044] applying an external negative pressure to the port to draw
the one or more contaminants from the cavity.
[0045] Preferably, the method includes the additional step of
providing a positive pressure to the cavity for directing the one
or more contaminants from the cavity and through the port. More
preferably, the port is a one way valve. In other embodiments,
however, the port is a self sealing septum and the method includes
the additional steps of:
[0046] providing an insertion device having a through passage which
extends between a first end and a second end;
[0047] applying a negative pressure to the first end; and
[0048] driving the second end through the septum to apply the
negative pressure to the cavity such that the one or more
contaminants are drawn into the through passage.
[0049] Preferably, the method includes the additional step of
providing collecting means in the cavity for sequestering the one
or more predetermined contaminants. Even more preferably, the
method includes the step of activating the collecting means to
initialise the sequestering. Even more preferably, the method
includes the step of reactivating the collecting means to effect
release of the sequestered contaminants into the housing and
thereafter applying the negative pressure to the first end. More
preferably, the reactivation also allows the collecting means to
recommence the sequestering of the one or more predetermined
contaminants from the housing.
[0050] According to a fifth aspect of the invention there is
provided a charge storage device including:
[0051] a housing;
[0052] a fist sheet electrode disposed within the housing;
[0053] a second sheet electrode disposed within the housing
adjacent to and opposed with the first sheet electrode;
[0054] a separator for enveloping substantially all of the first
electrode and for maintaining the electrodes in a spaced apart
configuration;
[0055] an electrolyte disposed intermediate the electrodes; and
[0056] two terminals extending from the respective electrodes and
terminating outside the housing for allowing external electrical
connection to the electrodes.
[0057] Preferably, the separator includes two opposed separator
sheets which are connected along at least one common edge and the
first electrode is disposed between the separator sheets. More
preferably, the separator sheets are integrally formed. Even more
preferably, the separator sheets are integrally formed along the
common edge.
[0058] Preferably also, each separator sheet includes a first edge
and a second edge spaced apart from the first, both of which extend
away from the common edge. More preferably, each separator sheet
also includes a third edge which extends between the first edge and
the second edge, wherein the first edges are opposed and joined
together and the second edges are opposed and joined together. Even
more preferably, the third edges are opposed.
[0059] In a preferred form, the first electrode includes a first
sub-sheet and a second sub-sheet which is opposed to the first.
More preferably, the fist and the second sub-sheets are opposed.
Even more preferably, each of the first and second sub-sheets are
joined along a common edge. Preferably also, the common edge
between the first and second sub-sheets is disposed adjacent to the
common edge between two opposed separator sheets.
[0060] According to another aspect of the invention there is
provided a method of constructing a charge storage device having a
housing, the method including the steps of:
[0061] disposing at least two opposed sheet electrodes within the
housing;
[0062] enveloping substantially all of a first one of the
electrodes with a separator for maintaining the electrodes in a
spaced apart configuration;
[0063] disposing an electrolyte intermediate the electrodes;
and
[0064] providing two ter extending from the respective electrodes
and terminating outside the housing for allowing external
electrical connection to the electrodes.
[0065] Preferably, the separator includes two opposed separator
sheets connected along at least one common edge and the method
includes the further step of disposing the first electrode between
the separator sheets. More preferably, the separator sheets are
integrally formed. Even more preferably, the separator sheets are
integrally formed along the common edge.
[0066] Preferably also, each separator sheet includes a first edge
and a second edge spaced apart from the first, both of which extend
away from the common edge. More preferably, each separator sheet
also includes a third edge which extends between the fist edge and
the second edge, wherein the method includes the further step of
joining together the first edges and joining together the second
edges. Even more preferably, the third edges are opposed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0067] Preferred embodiments of the invention will now be
described, by way of example only, with reference to the
accompanying drawings, in which:
[0068] FIG. 1 is a schematic cross section of a supercapacitor
according to the invention;
[0069] FIG. 2 is a plan view of a separator for the supercapacitor
of FIG. 1;
[0070] FIG. 3 is a schematic plan view of one of the electrodes of
the supercapacitor of FIG. 1;
[0071] FIG. 4 is a schematic perspective view of an electrode
assembly including the separator of FIG. 2 and the electrode of
FIG. 3;
[0072] FIG. 5 is a schematic perspective view of the assembly of
FIG. 4 nested within a like electrode to that shown in FIG. 3;
[0073] FIG. 6 is a schematic perspective view of an alternative
supercapacitor according to the invention; and
[0074] FIG. 7 is a schematic enlarged sectional view of the septum
included in the supercapacitor of FIG. 6.
PREFERRED EMBODIMENTS OF THE INVENTION
[0075] Referring to FIG. 1, a charge storage device 1 includes a
sealed prismatic housing 2. Two opposed folded rectangular
aluminium electrodes 3 and 4 are disposed within housing 2 and
connected to respective metal terminals 5 and 6 for allowing
external electrical connection to the electrodes. A Solupor.TM.
sheet separator 7 is disposed intermediate electrodes 3 and 4 for
maintaining those electrodes in a fixed spaced apart configuration.
An electrolyte (not shown) is also disposed intermediate the
electrodes. Collecting means in the form of a scavenging agent is
grafted to separator 7 for sequestering one or more predetermined
contaminants from the housing.
[0076] Separator 7 is formed in a "pocket" configuration, when it
is folded back upon itself and the transverse ends secured together
for providing an opening 8 between the transverse ends. For ease of
illustration, separator 7 is shown as having two fold lines. In
practice, however, a single fold line is used as the separator is
abutted directly against the opposed electrodes. The porous nature
of the separator allows the movement of ions in the electrolyte
between the electrodes.
[0077] Each electrode is formed from a single like aluminium sheet
having at least one tab 9 which is electrically engaged with the
respective terminals 5 and 6. The electrodes are folded into the
overlapping and nested configuration shown in the drawing. Again,
it will be appreciated that for ease of illustration electrode 4 is
shown with two fold lines. In practice, however, a single fold is
made as this electrode is abutted directly against separator 7.
[0078] Electrode 3 is received within opening 8 and enveloped by
separator 7 such that only tab 9 extends from the "pocket" or
pouch. This electrode and separator combination is then inserted
into the folded electrode 4 to complete a single capacitive cell.
While in this embodiment only a single cell is illustrated, in
other embodiments use is made of two or more such cells. The
electrode area of the electrodes is about 102 cm.sup.2 which
provides a nominal capacitance of about 28 Farads at 2.5 Volts.
[0079] Each of electrodes 3 and 4 includes a high surface area
coating 10 of activated carbon particles. This coating is of a
predetermined thickness and includes a binder to facilitate
intimate engagement between the carbon particles and the
electrodes.
[0080] In this embodiment the scavenging agent is the compound
marked as ZERO 2 as sold and marketed by Southcorp Packaging. About
25 mg of the compound is grafted to separator 7 during the
manufacture of the supercapacitor. More particularly, one of the
process steps of manufacture includes interleaving the separator
with the electrodes. Immediately prior to this step, the grafting
occurs, followed by activation of the scavenging agent by UV
radiation of a predetermined wavelength and intensity. The
separator with the activated scavenging agent is then interleaved
with the electrodes in the controlled manufacturing environment. As
would be understood by those skilled in the art, it is important to
conduct supercapacitor and other energy storage manufacture in
controlled conditions to minimize any contamination. Accordingly,
notwithstanding that the scavenging agent has been activated and
that it will almost immediately commence sequestering of
contaminants, the location of the still partially constructed
supercapacitor within the standard controlled environment minimises
exposure to those contaminants.
[0081] As terminals 5 and 6 extend from the inside to the outside
of housing 2 they are sealingly engaged intermediate their
respective ends with the housing. In this embodiment the sealing
engagement is effected by two rubber grommets 11 and 12. In other
embodiments use is made of grommets constructed from other
materials or combinations of materials. For example, some devices
make use of silicon sealing compounds and adhesives.
[0082] In any event, the commercially available sealing means are
not entirely effective and have a finite working lifespan as they
progressively degrade over time. Accordingly, with most if not all
sealing arrangements there will inevitably be some ingress of
contaminants into the housing over the operation life time of the
supercapacitor or other charge storage device.
[0083] The present embodiment provides a prolonged operational life
for supercapacitor 1 as any contaminants that do enter housing 2
will be preferentially rendered inert to the operation of the
supercapacitor by the scavenging agent that is grafted to separator
7. The quantity of scavenging agent used in this embodiment
sequesters up to about 0.2 cm.sup.3 of oxygen. In other embodiments
more or less of the scavenging agent is used. For example, in an
alternative embodiment utilising a plurality of the capacitive
cells, each pouch or pocket of the separator has about 20 mg of the
ZERO 2 compound grafted thereto.
[0084] As discussed below, the scavenging agent is, in other
embodiments, located other than on the separator. However, grafting
to the separator has a number of advantages, including the
disposition of the scavenging agent for the sequestering of
contaminants that are disposed between the electrodes. That is, the
ingress of contaminants into housing 2 adversely affects
performance if those contaminants enter the electrochemically
active region between the electrodes. Activity in this region can
physically, chemically or electrically interfere with the charge
storage ability of the supercapacitor. Consequently, in this
embodiment, any contaminant that is located within the active
region is increasingly likely to be sequestered.
[0085] As would be appreciated by those skilled in the art from the
teaching herein, notwithstanding the use of the invention,
manufacturing tolerances and raw material quality variations will
continue to ensure a variance of actual life span of
supercapacitors and other energy storage devices. The present
invention, however, when used with a given manufacturing technique,
provides an increase to the mean life span that would otherwise be
obtained.
[0086] In other embodiments of the invention (not shown) the
scavenging compound is grafted or otherwise incorporated into the
housing. That is, the housing defines an interior surface and an
exterior surface wherein the interior surface provides a site for
the scavenging agent.
[0087] The use of a scavenging agent within housing 2 allows the
level of detrimental contaminants to be reduced. Accordingly, for a
given manufacturing process, the failure rate for the
supercapacitors is reduced. An alternative is to vary the
manufacturing process. That is, the construction of supercapacitors
involves progressing the various constituents through a sequence of
carefully maintained environments to ensure sufficiently low levels
of contamination occur. These environments are expensive to provide
and consistently maintain. However, with the use of an internally
located scavenging agent some contamination is tolerable without
adversely affecting the failure rate of the supercapacitor
ultimately produced.
[0088] In embodiments where the scavenging agent is not exhausted
due to impurities or contaminants introduced in the manufacturing
process, it allows a continued removal of undesirable substances
from the housing and, in particular, from the electrolyte.
Accordingly, the ingress of contaminants into the housing will not,
during the useful life of the scavenging agent, compromise the
performance of the supercapacitor.
[0089] The prior art devices have been concerned with the barrier
properties of the walls of the respective housings. However, the
present inventor has discovered that the major concern is not the
walls themselves but the imperfect seal between a wall and the
protruding terminals, or between adjacent walls. To address this
issue, the preferred embodiments of the invention have the
sequestering agent disposed within the housing rather than within
the confines of a wall, as is the case with the device disclosed in
U.S. Pat. No. 5,445,856. That is, the preferred embodiments
described herein disposed the agent to capture not only specific
contaminants that are in transit through a wall, but also those
that gain entry to the housing via other paths.
[0090] Electrode 3 and 4 will now be described in more detail with
reference to FIGS. 2 to 4. More particularly, and as best shown in
FIG. 3, electrode 3 is substantially rectangular and includes two
rectangular sub-sheets 15 and 16. The sub-sheets are integrally
formed and symmetrical about a fold line 17 which defines a common
edge 18. Sheets 15 and 16 include respective integrally formed
rectangular sub-tabs 19 and 20 which, as shown in FIG. 4, abut to
collectively define tab 9.
[0091] Sheet 15 includes two spaced apart and parallel edges 21 and
22 which extend away normally from edge 18. A further edge 23
extends between edges 21 and 22. As also shown in FIG. 3, tab 19
extends from away from edge 23 adjacent to where that edge meets
with edge 22. Similarly, sheet 16 includes two spaced apart and
parallel edges 25 and 26 which extend away normally from edge 18. A
further edge 27 extends between edges 25 and 26. Similarly also,
tab 20 extends from away from edge 27 adjacent to where that edge
meets with edge 26.
[0092] Electrode 3 is coated on one side only with the activated
carbon and then folded about line 17 such that the coated side is
outwardly facing, as shown in FIG. 1.
[0093] Electrode 4 is the same as electrode 3 only that it is
interleaved in the opposite sense so that the respective tabs 9 are
spaced apart. This will be described in further detail below. For
convenience, corresponding features of the electrodes will be
designated with corresponding reference numerals.
[0094] Separator 7 is shown, not to scale, in plan in FIG. 2 and
includes two rectangular sub-sheets 31 and 32 which are integrally
formed along a common edge 33. This edge also defines a fold line
34. Sheet 31 also includes two spaced apart and parallel edges 35
and 36 which extend away normally from edge 33. A free edge 37
extends between edges 35 and 36. Similarly, sheet 32 includes two
spaced apart and parallel edges 39 and 40 which extend away
normally from edge 33. A free edge 41 extends between edges 39 and
40.
[0095] During manufacture, electrode 3 is folded about line 17 such
that the coated sides of sheets 15 and 16 are opposed and outwardly
facing. Additionally, tabs 19 and 20 are abutted. Separately,
separator 7 is folded about line 34 such that edges 35 and 39 are
parallel and abutted together, edges 36 and 40 are parallel abutted
together and edges 37 and 41 are parallel and adjacent to one
another. Thereafter, edges 35 and 39 are joined together and edges
35 and 39 are joined together. In some embodiments this is achieved
with adhesive, while in other embodiments heat welding or other
heat treatment is utilised. In still further embodiments the edges
are not joined.
[0096] As best illustrated in FIG. 4, electrode 3 is then nested
within the "pouch" or "pocket" formed by separator 7. As shown, the
separator envelopes substantially all of electrode 3 and, as will
be described below, maintains electrodes 3 and 4 in a spaced apart
configuration. Tab 9 extends outwardly beyond adjacent edges 37 and
41 to allow its electrical connection to terminal 5. For ease of
illustration, in FIG. 4 separator 7 is shown with edges 36 and 40
joined by way of heat welding, while edges 35 and 39 are adjacent,
although not yet joined.
[0097] Electrode 4 is then formed by folding a like coated sheet to
that which forms electrode 3. More particularly, the fold is made
along fold line 18 such that that the coated sides of sheets 15 and
16 are opposed and inwardly facing. Additionally, tabs 19 and 20
are adjacent to each other and opposed. The assembly of FIG. 4 is
then nested within electrode 4, as best illustrated in FIG. 5, such
that the respective tabs 9 of the electrodes are spaced apart. Tabs
19 and 20 of electrode 4 are then abutted and secured to terminal 6
to allow external electrical connection with the electrode.
[0098] The electrode assembly of FIG. 5 is referred to as a single
cell and, as would be appreciated by a skilled addressee from the
teaching herein, a plurality of the cells are able to be connected
in parallel to proportionally increase the capacitance of
supercapacitor 1. In other embodiments, a plurality of the cells
are stacked in parallel such that the respective tabs 9 for like
electrodes 3 and 4 form two spaced apart stacks of like tabs. The
tabs in each stack are then clamped together and the stacks
electrically connected to respective terminals 5 and 6.
[0099] Referring now to FIG. 6 and FIG. 7, where corresponding
features are denoted by corresponding reference numerals, there is
illustrated a supercapacitor 45. The supercapacitor housing 2 is
sealed and one sidewall 46 includes collecting means in the form of
a septum 47. As best shown in FIG. 7, wall 46 includes an inner
side 49, an outer side 50 and an aperture 51. Septum 47 includes an
annular mounting formation 53 which is sealingly engaged with side
50 of wall 46 and which surrounds aperture 51. A circular
self-sealing barrier membrane 54 extends across formation 53 and
creates a seal between the interior of the housing and
atmosphere.
[0100] Housing 2 also includes a sidewall 57 having a rectangular
window 58 of material which is at least partially transparent to
ultraviolet radiation. In other embodiments, window 58 is
differently shaped and which extends over a smaller portion of wall
57. In still further embodiments, window 58 is disposed in a
sidewall other than that of wall 57. Moreover, other embodiments
include window 58 in the base or top of housing 2.
[0101] Supercapacitor 45 includes a plurality of the capacitor
cells refereed to above which are connected in parallel. The like
electrodes are electrically connected to respective terminals 5 and
6.
[0102] Following the manufacture of supercapacitor 45, a collection
device (not shown) in the form of a needle is inserted through
membrane 54. The collection device also includes pressure means for
creating a negative pressure and a conduit for linking the pressure
means to the needle such that gases contained within housing 2 are
drawn through the needle and the conduit. That is, the collection
device allows the removal of gaseous contaminants from the hosing.
The removal occurs immediately following manufacture. In other
embodiments, however, the removal is performed at other times and,
as such, provides a reconditioning of the supercapacitor. In still
further embodiments both the initial removal and reconditioning is
performed. For example, in some cases, sensing circuitry is
connected in parallel with the supercapacitor to determine when the
time constant or other electrical property of the supercapacitor
varies by a predetermined percentage from the respective value
provided at the time of manufacture. When this variation is
detected it provides a warning signal to alert the user that
reconditioning is warranted.
[0103] Once sufficient gases have been withdrawn the pressure means
is deactivated and the needle withdrawn from the septum. The self
sealing effect of the septum will prevent the ingress of any gases
or moisture into the housing.
[0104] The other embodiments, once the pressure means is
deactivated, a scavenging agent is released into the conduit and
drawn into housing 2 due to the residual negative pressure. This
agent progresses into the electrolyte and is available, once
activated, for sequestering oxygen and/or other contaminants from
housing 2. Activation of the agent occurs by directing ultraviolet
radiation through window 58 and into housing 2. Other agents are
activated by radiation other than ultraviolet radiation and, in
these cases, window 58 is at least partially transparent to the
wavelength of the radiation required.
[0105] In other embodiments, such as where the scavenging agent is
grafted to the separator, supercapacitor 45 operates in the
following manner. After all the components are placed within
housing 2, and the housing sealed, the agent is activated by
directing the appropriate radiation through window 58. After a
given operational lifetime, or after testing shows that
contaminants have degraded the performance of the supercapacitor,
the agent is again activated. However, this subsequent activation
will cause the agent to release the sequestered contaminants into
housing 2. This being the case, the collection device referred to
above is then utilised to apply a negative pressure to the housing
such that the contaminants are drawn through the needle and conduit
away from the housing. Once the pressure means are deactivated the
needle is withdrawn from septum 47 and membrane 54 self seals.
Thereafter, the agent will continue to sequester contaminants that
subsequently enter housing 2. This process of reconditioning is
completed as required.
[0106] In other embodiments, septum 47 is replaced with a
mechanical one way valve.
[0107] Another embodiment of the invention, in the form of
supercapacitor 60, is illustrated in FIG. 8. This supercapacitor
includes a housing 61 formed from two like opposed flexible
laminate thermoformable sheets 63 and 64. The sheets are generally
rectangular and heat sealed about their common periphery 65.
[0108] The opposed sheets define an internal cavity in which is
disposed the other components (not shown) of supercapacitor 60. As
with the other embodiments of the invention, the components that
are internal to the cavity are two opposed sheet electrodes, a
porous separator disposed intermediate the electrodes, and an
electrolyte for allowing ionic conduction between the
electrodes.
[0109] Supercapacitor 60 also includes two terminals 69 and 70
which are electrically connected to the respective electrodes and
which extend from inside the cavity to outside the cavity for
allowing electrical connection of the supercapacitor to external
circuitry.
[0110] Terminals 69 and 70 are aluminium strips that are sealingly
engaged, intermediate their respective ends, with the periphery of
sheets 63 and 64. This sealing engagement is, however, imperfect
due to the very different and incompatible nature of the film and
the terminals. This places considerable reliance on the sealant
itself to adhere the two materials together.
[0111] In this embodiment the sealant is an adhesive sold under the
trade name Nucrel. While this provides good adhesive properties it
is sensitive the manufacturing process and susceptible to a loss of
adhesion during the lifetime of the capacitor. Moreover, while the
function of the sealant as an adhesive is adequate, its ability to
act as a barrier to ingress of contaminants is less effective. The
solution provided by this embodiment is the inclusion within the
separator of a collecting agent to sequester any oxygen that
penetrates the housing by way of the imperfect sealing of the
sealant against either or both of the aluminum terminals or the
sheets 63 and 64, or by progress of the contaminants through the
sealant itself.
[0112] The supercapacitors of the preferred embodiments provide a
longer operation lifetime than their predecessors. Alternatively,
the operation lifetime is maintained and the cost of manufacturing
reduced.
[0113] The preferred embodiments also offer a significant range of
possible dispositions of the collecting means. Accordingly a wide
variety of manufacturing processes can easily accommodate the
inclusion of this feature. That is, there is considerable design
flexibility in including the collecting means of the invention
within a supercapacitor. In most cases this is achieved with
minimal departure from existing manufacturing steps.
[0114] The preferred embodiments described above have arisen from
the understanding that there will always be some contamination of
the electrolyte either during the manufacturing process or over
time as contaminants penetrate the housing. On this basis, some
embodiments have the collecting means disposed within the housing
to sequester or otherwise chemically capture the contaminants that
are within the housing while, in other embodiments, the collecting
means allows removal of the contaminants from within the housing.
That is, these embodiments are concerned with addressing the issue
of contaminants within the housing, not providing a barrier to
those contaminants from getting there in the first place. That
barrier function is performed by the housing itself, both in the
form of the materials from which it is constructed and the manner
in which those materials are combined.
[0115] Although the invention has been described with reference to
specific examples, it will be appreciated by those skilled in the
art that it may be embodied in many other forms and in many other
technologies. More particularly, the invention is also applicable
to ultracapacitors, batteries such as Li ion batteries, fuel cells,
electrochemical catalysts, other ion specific electrodes and the
like.
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