U.S. patent application number 13/577877 was filed with the patent office on 2013-08-15 for component including a rechargeable battery.
This patent application is currently assigned to BAE SYSTEMS plc. The applicant listed for this patent is Michael Dunleavy, Sajad Haq, Martyn John Hucker. Invention is credited to Michael Dunleavy, Sajad Haq, Martyn John Hucker.
Application Number | 20130209839 13/577877 |
Document ID | / |
Family ID | 43828240 |
Filed Date | 2013-08-15 |
United States Patent
Application |
20130209839 |
Kind Code |
A1 |
Hucker; Martyn John ; et
al. |
August 15, 2013 |
COMPONENT INCLUDING A RECHARGEABLE BATTERY
Abstract
A component including a rechargeable battery and a method of
producing such a component are disclosed. The component uses one of
an acid and an alkaline chemistry and the battery has an anode
structure, a cathode structure, and a separator structure which
separates the anode from the cathode and contains an electrolyte.
The anode structure and the cathode structure are each formed from
a composite material which includes electrically conductive fibres
and electrochemically active material in a binder matrix and the
battery is formed to be structurally inseparable from the rest of
the component.
Inventors: |
Hucker; Martyn John;
(Woolaston, GB) ; Dunleavy; Michael; (Bishopston,
GB) ; Haq; Sajad; (Mansewood, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hucker; Martyn John
Dunleavy; Michael
Haq; Sajad |
Woolaston
Bishopston
Mansewood |
|
GB
GB
GB |
|
|
Assignee: |
BAE SYSTEMS plc
London
GB
|
Family ID: |
43828240 |
Appl. No.: |
13/577877 |
Filed: |
February 9, 2011 |
PCT Filed: |
February 9, 2011 |
PCT NO: |
PCT/GB11/50217 |
371 Date: |
September 19, 2012 |
Current U.S.
Class: |
429/9 ; 29/623.1;
429/213; 429/217; 429/218.1; 429/231.8; 429/246; 429/306 |
Current CPC
Class: |
H01M 2004/021 20130101;
H01M 10/32 20130101; H01M 10/30 20130101; H01M 2/1673 20130101;
H01M 4/622 20130101; Y02T 10/70 20130101; Y10T 29/49108 20150115;
H01M 4/74 20130101; H01M 10/465 20130101; B64C 3/26 20130101; H01M
4/0416 20130101; H01M 4/625 20130101; H01M 4/26 20130101; Y02E
60/10 20130101; H01M 10/0585 20130101; H01M 10/12 20130101; H01M
10/345 20130101; H01M 4/139 20130101; H01M 4/624 20130101; H01M
10/287 20130101; H01M 10/058 20130101; H01M 4/62 20130101; H01M
10/04 20130101; H01M 10/281 20130101; Y02P 70/50 20151101; H01M
2/1606 20130101; H01M 4/621 20130101; H01M 2/164 20130101 |
Class at
Publication: |
429/9 ; 429/246;
429/218.1; 429/231.8; 429/306; 429/213; 429/217; 29/623.1 |
International
Class: |
H01M 10/058 20060101
H01M010/058 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 9, 2010 |
GB |
1002040.2 |
Mar 17, 2010 |
GB |
1004474.1 |
Claims
1. A component comprising: a rechargeable battery having one of an
alkaline and acid based chemistry, the battery having an anode
structure, a cathode structure and a separator structure which
separates the anode structure from the cathode structure and
contains an electrolyte in which the anode structure and the
cathode structure are each formed from a composite material which
includes electrically conductive fibres and electrochemically
active material in a binder matrix and wherein the battery is
structurally inseparable from the rest of the component.
2. A component according to claim 1, in which the separator
structure is formed from a composite material which includes
electrically insulating fibres in a binder matrix.
3. A component according to claim 1, comprising: a battery using an
aqueous liquid or gel electrolyte.
4. A component according to claim 1, comprising: a nickel-zinc
rechargeable battery.
5. A component according to claim 1, comprising: a nickel-iron,
nickel-cadmium, nickel metal hydride or silver-zinc rechargeable
battery.
6. A component according to claim 1, comprising: a lead acid
battery.
7. A component according to claim 1, in which one or more of the
anode structure, the cathode structure and the separator structure
contains a porous additive which increases access of the
electrolyte into said structure.
8. A component according to claim 7, in which the porous additive
is one or more of a silica, a silica gel or carbon powder.
9. A component according to claim 1 in which at least one of the
anode structure and the cathode structure comprises: an
electrically conductive additive.
10. A component according to claim 9, in which the electrically
conductive additive is carbon powder.
11. A component according to claim 1, in which the electrolyte is a
solid polymer electrolyte.
12. A component according to claim 1, in which the electrically
conductive fibres of the anode and cathode structures are carbon or
metal fibres.
13. A component according to claim 1, in which the electrically
conductive fibres of the anode and cathode structures include
fibres having a conductive coating.
14. A component according to claim 13, in which the fibres having a
conductive coating include carbon fibres and/or electrically
insulating fibres.
15. A component according to claim 13, in which the fibres having a
conductive coating are metallised fibres.
16. A component according to claim 1, in which the electrically
conductive fibres of the anode and cathode structures are formed as
a woven fabric.
17. A component according to claim 1, in which the electrically
conductive fibres of the anode and cathode electrode structures are
formed as a non woven fabric.
18. A component according to claim 1, in which at least one of the
anode structure, the cathode structure and the separator structure
is formed from a composite material which includes an electrically
insulating polymer, ceramic or glass based binder matrix formed of
polymer, ceramic or glass.
19. A component according to claim 18, in which the electrically
insulating binder matrix is an epoxy resin.
20. A component according to claim 18, in which the electrically
insulating binder matrix is an elastomer.
21. A component according to claim 18, in which the electrically
insulating binder matrix is an open cell foam.
22. A component according to claim 1, in which at least one of the
anode structure, the cathode structure and the separator structure
is formed from a composite material which includes a solid polymer
electrolyte binder matrix.
23. A component according to claim 1, in combination with an
aircraft wing skin.
24. A component according to claim 23, in which the wing skin
includes a solar cell connected to the rechargeable battery.
25. A component according to claim 23, in combination with aircraft
structural health monitoring equipment in which the rechargeable
battery provides power to operate the structural health monitoring
equipment.
26. A component according to claim 1, in combination with vehicle
internal panelling.
27. A component according to claim 26, comprising: a spall liner
for a vehicle.
28. A component according to claim 26, comprising: a vehicle
instrument panel.
29. A component according to claim 1, comprising: mounting means
for electronic equipment.
30. A method of manufacturing a component including, and being
structurally inseparable from, a rechargeable battery having one of
an acid and alkaline based chemistry, the rechargeable battery
including an anode structure and a cathode structure having fibrous
reinforcing material and plastics matrix material and a separator
structure, the separator structure separating the anode from the
cathode structure and being adapted to contain an electrolyte, the
method comprising: laying up, on either side of the separator
structure, a layup of plies of electrically conductive fibrous
reinforcing material for the anode structure and the cathode
structure; introducing a binder matrix into at least the anode and
the cathode structures; and consolidating the layup of the cathode,
anode and separator structure into a single composite
component.
31. (canceled)
Description
BACKGROUND TO THE INVENTION
[0001] This invention relates to rechargeable batteries.
Rechargeable batteries are groups of one or more secondary cells. A
well known example of a rechargeable battery is the lithium ion
rechargeable battery, which is commonly used in consumer goods, and
in the automotive and aerospace industries. Lithium ion
rechargeable batteries offer a high energy density, which is a
significant factor in their popularity.
DESCRIPTION OF THE PRIOR ART
[0002] However, there are significant drawbacks attached to current
rechargeable battery design and to lithium ion battery technology
in particular. Current rechargeable batteries require housing in
protective casings. They also require structure and wiring, in the
equipment, to support them and to connect them to equipment remote
from them. For applications where space and weight are at a
premium, therefore, current rechargeable batteries have their
limitations. For lithium ion batteries, contact with certain common
substances, principally water, oxygen and carbon dioxide, are
deleterious to battery performance, and can represent a severe
hazard. As a result, a lithium ion battery is typically housed in a
hermetically sealed protective casing. The constituents of lithium
ion cells are typically toxic, and the battery can catch fire if
short circuited, punctured or otherwise compromised. Also, charge
and discharge rates need to be controlled carefully. In other
words, there are practical disadvantages which hinder the
exploitation of current rechargeable batteries and of lithium ion
batteries in particular.
[0003] The present inventors have realised that acid and alkaline
chemistries and in particular nickel-zinc rechargeable alkaline
batteries and certain related battery technologies have
considerable attractions. For example, nickel-zinc batteries
require virtually no charging circuitry, and have a low internal
resistance resulting in high charge/discharge rates. The
theoretical energy density of acid and alkaline chemistry batteries
is lower than lithium ion batteries, but in practice only a
fraction of the theoretical value is achieved, using lithium ion,
and nickel-zinc and other acid and alkaline chemistry batteries
offer the possibility of high efficiencies in this regard. In order
to encourage commercial use of nickel-zinc and other acid and
alkaline chemistry rechargeable batteries it is desirable to
provide structurally robust devices which are suited for `real
world` applications, and to enable convenient mass manufacture.
SUMMARY OF THE INVENTION
[0004] The present invention addresses the above described
drawbacks and desires, and/or provides improved battery gravimetric
or volumetric efficiency in terms of specific energy (Watt-hours
per kilogram) or energy density (Watt-hours per litre).
[0005] According to a first aspect of the invention there is
provided a component including a rechargeable battery using one of
an alkaline and acid based chemistry, the battery having an anode
structure, a cathode structure and a separator structure which
separates the anode from the cathode and contains an electrolyte,
in which the anode structure and the cathode structure are each
formed from a composite material which includes electrically
conductive fibres and electrochemically active material in a binder
matrix and wherein the battery is structurally inseparable from the
rest of the component.
[0006] In this way, it is possible to provide a component
comprising a `structural` rechargeable battery in which fibre
reinforced cell components provide a dual role by functioning as
active electrochemical or electrical elements and also as
structural features of the component, being integral therewith. The
battery may thus be entirely free of any border or barrier between
the cell or cells of the battery and any part of the component
which does not act as part of the battery. Thus, parts of the
component which are not part of the battery may simply comprise
composite material where the fibres or matrix are not electrically
conductive or electrochemically active.
[0007] This provides advantageous mechanical properties and/or
component performance properties. For example, conventional
batteries require additional support structures, such as casing,
packaging, separators, electrodes, current collectors and the like.
These, from a component operational point of view, are wholly
parasitic. The present inventors have recognised that these
additional support structures reduce the volumetric and/or
gravimetric efficiency of conventional batteries. In the present
invention, active electrochemical and electrical components are
multi-functional since they also perform a structural role as, for
example, load bearing, protective or otherwise physically robust
elements of the component.
[0008] Preferably, the separator structure is formed from a
composite material which includes electrically insulating fibres in
a binder matrix. The electrically insulating fibres may be glass,
polymer, ceramic or textile fibres, and may be selected depending
on the desired mechanical or physical properties of the component.
Examples of suitable electrically insulating fibres include E-glass
fabric, and silicon carbide fibres. Examples of textile fibres
include natural fibres such as cotton, and synthetic fibres which
are typically polymer fibres such as Nylon.RTM. and polyester.
[0009] In one preferred embodiment, the rechargeable battery is a
nickel-zinc rechargeable battery. The skilled reader will
appreciate that in such embodiments, the electrochemically active
materials may be nickel hydroxide and zinc oxide.
[0010] Alternatively, the rechargeable battery may be a
nickel-iron, nickel-cadmium, nickel metal hydride or silver-zinc
rechargeable battery.
[0011] Advantageously, one or more of the anode structure, cathode
structure and the separator structure may contain a porous additive
which increases access of the electrolyte into said structure. The
porous additive may be one or more of a silica, a silica gel or
carbon powder.
[0012] At least one of the anode structure and the cathode
structure may further include an electrically conductive additive
such as carbon powder. It will be apparent to the skilled reader
that carbon powder can perform a dual role as a porous additive and
an electrically conductive additive.
[0013] At least one of the anode structure and the cathode
structure may further include an ion conducting additive such as
polyethylene oxide (PEO).
[0014] When an aqueous electrolyte is employed, it is conveniently
removed for electrolyte replacement or battery storage purposes.
Aqueous electrolyte may be accommodated by partially bonding the
separator structure to the anode structure and/or cathode structure
to provide interstices. Alternatively, a porous additive as
mentioned above may be used to provide a more open cell structure
having channels for the electrolyte to promote circulation of the
electrolyte around the electrically active materials of the anode
and cathode.
[0015] Alternatively, the electrolyte may be a gel.
[0016] Further in the alternative, the electrolyte may be a solid
polymer electrolyte (SPE). The SPE may include polyvinyl alcohol
(PVA), polyethylene oxide (PEO), polyacrylic acid (PAA) or grafted
analogues or combinations thereof. Biphasic mixtures of SPE's may
be used. Additives may be present in the SPE to modify its
electrical, physical or chemical properties.
[0017] Advantageously, the electrically conductive fibres of the
anode and cathode structures are carbon or metal fibres. Carbon
fibres in particular will enable components of the invention to be
used where they are required to be strong and light such as in
structural applications for aircraft or satellites. A particular
application is seen as providing both structure and power in
unmanned aerial vehicles which are often required to stay in flight
for long periods, for example when carrying out surveillance
operations, and where a source of power which does not add
significantly to the weight of the aircraft will enable the
aircraft to stay in flight for longer than if conventional
batteries were used.
[0018] Batteries used in this way will work well with solar cells,
positioned say on the aircraft wings, which can be used to
re-charge the cells in flight. Equally, components according to the
invention, used for example as wing skins, can be used to provide
power for structural health monitoring of the aircraft when in
flight. The availability of such power, with low additional weight,
may enable longer flights to be planned in the knowledge that any
aircraft health issues which arise are likely to be notified early
and may be provided with more sophistication that was previously
possible because more monitoring systems can be provided for the
same weight, when compared with conventional batteries. Thus, more
accurate decision making about the flightworthiness of the aircraft
is likely to lead to greater mission availability.
[0019] The electrically conductive fibres of the anode and cathode
structures may include fibres having a conductive coating. The
fibres having a conductive coating may include carbon fibres and/or
electrically insulating fibres. Examples of electrically insulating
fibres include glass fibres, polymer fibres, ceramic fibres such as
silicon carbide fibres, and textile fibres. Examples of textile
fibres include natural fibres such as cotton and synthetic fibres
which are typically polymer fibres such as Nylon.RTM. and
polyester.
[0020] Preferably, where the electrically conductive fibres of the
anode and cathode structures include fibres having a conductive
coating, these fibres are metallised fibres, such as nickel coated
fibres. However, other conductive coatings might be utilised.
[0021] The electrically conductive fibres of the anode and cathode
structures may be in the form of a woven fabric or may be non
woven, for example in a non crimp fabric.
[0022] At least one of the anode structure, the cathode structure
and the separator may be formed from a composite material which
includes an electrically insulating polymer, ceramic or glass based
binder matrix. Preferably, the electrically insulating binder
matrix material is an epoxy resin. Other structural resins, such as
polyester resin, may be used.
[0023] Alternatively, the electrically insulating binder matrix
material may include or consist of an open cell foam, a geopolymer
or a SPE. In the latter case, the SPE may perform a dual role as
both binder and electrolyte.
[0024] An elastomeric binder matrix may be used. In this way, a
flexible rechargeable battery can be provided for inclusion in the
component or possibly an article of clothing or other textile
product, particularly if textile fibres are used in the manufacture
of the battery. Rechargeable batteries of this type may be
integrated into an item of clothing such as by sewing, vulcanising
or by being woven into the item of clothing.
[0025] Possible uses of such flexible batteries comprised in
clothing include power sources for hand held/hand operated items
such as lights, radios, recording devices, medical equipment,
heated clothing, etc., carried or worn by members of the emergency
services, police, armed forces and others. Equally, commonly
carried items such as cameras, mobile phones, PDAs and personal
computers may have primary or additional power supplied to them
from batteries incorporated into clothing, according to the
invention. Batteries in such clothing may be re-charged either by
connection to a mains electricity supply, when not in use, or by
employing photovoltaic cells, also carried in the clothing, to
charge the batteries.
[0026] The rechargeable battery may include a number [plurality] of
cells which may be interdigitated, multilayered or spatially
distributed within the component or article. For example, an
aircraft composite wing skin incorporating cells, according to the
invention, may have the cells distributed across a large area of
wing, either because the cells are connectable to solar cells
distributed on the wing skin or because the cells are connectible
to distributed power users such as lights, flight control surfaces,
valves or sensors for aircraft systems, etc., located in different
parts of the wing.
[0027] The thickness of the anode structure, cathode structure
and/or the separator structure may be conveniently varied in order
to provide desired mechanical and electrical properties. These
structures may be formed from one or more layers. Variation of the
number of layers is one way in which the thickness of these
structures may be varied.
[0028] The separator structure may include separator materials such
as microporous polymer films, which may be used instead of or in
combination with electrically insulating fibres in a binder matrix
to aid ion transport.
According to a second aspect of the invention there is provided a
method of manufacturing a component including, and being
structurally inseparable from, a rechargeable battery using one of
an acid and alkaline based chemistry, the rechargeable battery
including an anode structure and a cathode structure comprising
fibrous reinforcing material and plastics matrix material and a
separator structure, the separator structure separating the anode
from the cathode and being adapted to contain an electrolyte; the
method including the steps of laying up, either side of the
separator structure, a layup of plies of electrically conductive
fibrous reinforcing material for the anode structure and the
cathode structure, introducing a binder matrix into at least the
anode and the cathode structures and consolidating the layup of
cathode, anode and separator into a single composite component.
[0029] A composite component according to the invention may
conveniently be made by any known composite manufacturing processes
compatible with the cell chemistry concerned. For example, wet
layup; pre-pregging; resin infusion or resin transfer moulding or
vacuum assisted resin transfer moulding may all be used. Use of
such well known techniques allows great flexibility in form and
size of batteries incorporated into components made according to
the invention. One advantage of using these commonly used
techniques is that components of the invention may be employed to
replace already existing parts made by the same techniques but not
having the advantage of a battery formed integral therewith.
[0030] Components according to the invention may be used in new
designs or to replace worn, damaged or outdated parts of any items
which can be manufactured of composite material. For example,
vehicles, whether land, air, space or water born, may have parts
manufactured with integral cells, according to the invention.
Examples of such use may include wing skins on aircraft, and in
particular unmanned air vehicles, where components according to the
invention may be used to power structural monitoring equipment,
control surfaces, cameras, lights etc. Where the component may be
exposed to sunlight or be otherwise connectible to photovoltaic
equipment, the cell or cells may be charged using such equipment.
Owing to the ability of cells in composite components according to
the invention to be positioned anywhere in the component, where the
component is a wing skin the photovoltaic cells may be positioned
adjacent the cells of the invention to avoid unnecessary
wiring.
[0031] Further potential uses on vehicles may include body panels
on hybrid or electric drive vehicles where the components of the
invention can be used to save weight and bulk, compared to
conventional batteries. Such components may also find use on free
flooding hydrodynamic hulls of, say, submersible remotely operated
vehicles. The components would be especially useful on any vehicle
where weight or bulk was at a premium like an aircraft or a
satellite. On a satellite the saving in space and bulk of
components according to the invention which could be used to power
various systems would potentially be of great benefit and would
likely increase the payload capability of the satellite
substantially.
[0032] In buildings, components according to the invention may
comprise wall panels in portable or temporary buildings, room
dividers, suspended ceiling panels, doors or window frames. In all
these items the electrical power available from the battery would
replace or reduce the need for wiring and, once again, the cells
could be used in conjunction with photovoltaic equipment to
generate the power held in the cells of the components according to
the invention.
[0033] A further advantage of using cells incorporated into such
components is that the mass of the battery or batteries, where
desired, may be distributed evenly and integrally throughout the
various components. This can be very beneficial, for example, when
sudden shocks occur to the component. Such shocks might occur, for
example, for vehicles involved in collisions. For military or, say,
nuclear containment equipment, explosions or projectile impacts may
cause such shocks. Under such conditions the integral nature of the
batteries in the components of which they form part will prevent
their tending to act as uncontained missiles. Conventional
batteries, when used in military tanks or armoured carriers for
example, will be liable to act as uncontained missiles during an
explosion or under projectile impact. However, batteries integral
with the components according to the invention, because of the
inherent support for the cells provided by the structure of the
component, will not form separate detached objects and will avoid
this problem.
[0034] An example of a component according to the invention in
which rechargeable batteries are evenly distributed is internal
panelling for a vehicle which may be in the form of a spall liner,
as used in military vehicles. These vehicles are often used for
reconnaissance patrols during which they spend a considerable time
with their engines switched off on `silent watch`. In these
circumstances the batteries may be used to provide power for
sensors, communications, life support, air conditioning, etc. and
there must be enough residual battery power to restart the vehicle
engine. The spall liners will form part of the vehicle armour but
will also provide additional power without taking up any further
limited internal space and will not add further weight or bulk to
the vehicle. The extra weight of additional conventional batteries
would normally reduce manoeuvrability and speed of the vehicle.
Components according to the invention may also comprise external
vehicle armour as this is often manufactured from composite
material.
[0035] The distributed nature of the batteries in the components
also has the advantage of easing the design of an aircraft for the
correct weight distribution. There is no parasitic mass which has
to be positioned wherever space is available on the aircraft and
which forms a concentrated mass which must be balanced in order to
trim the aircraft and which must be wired to equipment to be
powered and also to a power source. The weight of supports and
packaging for the batteries will also be avoided as they will be
integral with the aircraft itself. The batteries may be positioned
closer to equipment to be powered as they form part of the aircraft
structure and do not need separate accommodation. Thus, for example
cabin interior lights may use a battery supply from cells
comprising cabin panelling in which the lighting is mounted and
wing lights or systems equipment may be supplied by power from
batteries according to the invention comprising part of the wing
structure. Instruments in the cockpit may be powered by batteries,
according to the invention, comprising the instrument panel
itself.
[0036] Of potential great importance would be the use of components
according to the invention in electrical or electronic equipment,
in particular portable equipment such as computers, personal
digital assistants (PDAs), cameras and telephones. Here mountings
for such equipment such as circuit boards, casings and the like
could be made according to the invention which would, again, assist
in cutting down the weight and bulk of such items enabling them to
be lighter, smaller and possibly cheaper, owing to the reduced part
count. Alternatively, for equipment carried on the user's person
such as cameras, PDAs and mobile phones, the power source for such
equipment could be comprised in items of clothing to be worn by the
user. In addition, the perennial problem of heat dissipation in
portable equipment powered by batteries could be alleviated by
incorporating the cells in, for example, the casing of a portable
computer where they could dissipate heat much more easily with the
possible avoidance of the need for cooling fans.
[0037] For energy capture, components such as wind turbine casings
or blades and solar array support structures could be made
according to the invention to cut down on wiring or on weight and
bulk.
[0038] When building structures are fabricated from such batteries
they may in addition be provided with solar panels, or other energy
generation means, so as to provide a readily portable structure
comprising both energy generation and energy storage means.
[0039] Whilst the invention has been described above, it extends to
any inventive combination of the features set out above, or in the
following description, drawings or claims.
DESCRIPTION OF THE DRAWINGS
[0040] Exemplary embodiments of the component in accordance with
the invention will now be described with reference to the
accompanying drawings in which:--
[0041] FIG. 1 shows a cross sectional side view of a component
integral with a nickel-zinc rechargeable electrochemical cell,
according to the invention, and
[0042] FIG. 2 shows a cross sectional side view of a component
integral with a rechargeable electrochemical cell according to the
invention and suitable for use with alternative cell
chemistries.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0043] The invention provides components comprising rechargeable
batteries using one of an acid or an alkaline chemistry and formed
at least in part from composite materials, thereby imparting
desired structural properties. FIG. 1 shows an example of a
component integral with an alkaline rechargeable battery of the
invention, depicted generally at 10, comprising an anode structure
12 which is spaced apart from a cathode structure 14 by a separator
structure 16. The anode and cathode structures 12, 14 may be
connected to suitable electrode contacts 18, 20 to permit charging
and discharging of the cell in the usual manner, although, as
explained in more detail below, the anode and cathode structures
12, 14 may act fully as current collectors.
[0044] Each of the anode and cathode structures 12, 14 and the
separator structure 16 are formed as a composite material
comprising suitable fibres in a binder matrix. The anode and
cathode structures 12, 14 comprise electrically conductive fibres
12a, 14a in respective binder matrices 12b, 14b. The separator
structure 16 comprises electrically insulating fibres 16a in a
binder matrix 16b.
[0045] A representative example of a component of the invention
integral with an alkaline battery in the form of a nickel-zinc
battery will now be described, in which epoxy resin is used as the
binder matrix throughout the device. The anode structure 12 is
formed from a plain weave carbon fibre fabric 12a embedded in an
epoxy resin binder 12b. The epoxy resin binder 12b also contains
porous carbon powder and nickel hydroxide (Ni(OH).sub.2) powder,
all of which is mixed thoroughly prior to use. The carbon fibre
fabric forms a convenient current collector.
[0046] The cathode structure 14 is formed from a plain weave carbon
fibre fabric 14a embedded in an epoxy resin binder 14b. The epoxy
resin binder 14b also contains porous carbon powder and zinc oxide
(ZnO) powder, all of which is mixed thoroughly prior to use.
Typically, the number of moles of zinc oxide used is approximately
half that of the nickel hydroxide, in view of the stoichiometry of
the electrochemical reaction. The electrochemistry of the nickel
zinc battery will be well known to the skilled reader, and
therefore further details are not provided herein. The carbon fibre
fabric forms a convenient current collector.
[0047] The active additives in the anode and cathode structures
(the nickel hydroxide, zinc oxide and carbon powder) are typically
present as fine powders having particle sizes in the range 1 to 10
.mu.m.
[0048] The separator structure 16 is formed from a plain weave
E-glass fabric 16a embedded in epoxy resin 16b. Other electrically
insulating fibres such as silicon carbide which provide suitable
structural reinforcement might be used instead. Other separators
such as microporous polymer films may be used either alone or in
combination with the glass fabric. The separator structure 16
contains an aqueous electrolyte consisting of 40% by weight
potassium hydroxide in deionised water. Zinc oxide is dissolved in
this solution until saturation or near saturation is achieved.
[0049] The electrolyte can be accommodated in a number of ways. The
separator structure may be partially bonded in order to provide
spaces which can be filled by the electrolyte. The electrolyte is
retained by capillary action between fibres. A 30 to 40% degree of
bonding is suitable for this purpose. A porous additive, such as a
silica or a silica gel, may be used to provide a more open cell
structure or a microporous polymer film may be employed. Vents may
be provided to control the release of gases during overcharge
conditions and fill/drain ports may be fitted to permit the
introduction and removal of the aqueous electrolyte for maintenance
or storage.
[0050] In other embodiments, one or more textile fibres may be used
to provide a more flexible device which might be incorporated, for
example, into an item of clothing. Textile fibres having a
conductive coating might be used in the anode and cathode
structures, and an elastomeric binder might be utilised to confer
further mechanical flexibility.
[0051] The component or article of the invention can be
manufactured in different ways. For example, it is possible to
fully manufacture each of the anode and cathode structures and the
separator structure separately and subsequently bond these
completed structures together. Alternatively, each structure may be
produced separately, but with partial cure of the epoxy resin
binder, so that the structures can be co-cured together. The entire
structure of the anode, cathode and separator structures may be
formed with a common binder, for example in a wet lay up process,
to provide a `monolithic` structure for the component.
[0052] Where silica, or a silica gel is used to provide an open
cell structure in the separator layer, the separator may be
pre-soaked in electrolyte prior to introduction of the epoxy binder
so that the epoxy does not penetrate into the open cells.
[0053] Porosity can be introduced into the binder material in order
to increase the utilisation of the active components of the
battery, by increasing the surface area available at which
electrochemical reactions can occur. Porosity can be achieved in
the electrode or separator structures by the addition of a porous
additive, such as silica gel as described above, or by the use of
sacrificial fillers. In one example, prior to curing, an electrode
material was sprinkled with a thick layer of common salt and
consolidated by rolling. The electrode material was then cured, and
the structure immersed in warm water to dissolve the salt. This
resulted in significantly higher performance of the resulting
structure in comparison to a control structure in which salt was
not used. Specifically, utilisation of the active materials present
increased by a factor of twenty. It will be appreciated that
numerous other sacrificial fillers, such as can be used in this
way. For example, commonly available materials such as sugar could
be used in the same manner. Enhanced porosity of a separator layer
may be achieved in the same manner.
[0054] There are numerous variations on the embodiment shown in
FIG. 1. Other alkaline batteries such as nickel-iron,
nickel-cadmium, nickel metal hydride (NiMH) and silver-zinc might
be produced in accordance with the invention. Alternatively, a lead
acid battery could be used with lead oxide being used as the active
material in the cathode and lead in the anode with sulphuric acid
acting as the electrolyte.
[0055] Alternative cell chemistries are now described in
conjunction with FIG. 2. Here, in an arrangement similar to that
shown in FIG. 1, the structure of a component in accordance with
the invention is shown in section in the form of a basic structural
cell. A separator 1, containing electrolyte is shown sandwiched
between an anode 2 and a cathode 3. The anode comprises active
material 4 and a current collector 5 and the cathode 3 comprises
active material 6 and a current collector 7. Table 1, below, shows
alternative chemistries for the positive active material, the
negative active material and the electrolyte. Active material may
be intimately mixed with current collector binder, eg. epoxy resin,
and/or applied as a surface coating on the inner faces 8, 9
adjacent the separator. Choice of active materials and electrolyte
set the cell chemistry; chemistry substitution is simply a matter
of blending the appropriate electrically active materials.
TABLE-US-00001 TABLE 1 +ve active -ve active Cell type material
material Electrolyte Nickel- Nickel hydroxide Zinc oxide 40% KOH
solution zinc (aqueous) Nickel- Nickel hydroxide Iron oxide 40% KOH
solution iron (aqueous) Lead-acid Lead oxide Lead 4.2M Sulphuric
acid (aqueous)
[0056] Features and techniques which are known in the art of
alkaline rechargeable batteries may be used in conjunction with the
present invention. For example, nickel-zinc battery technology
developed by PowerGenix Corp, of San Diego, Calif. 92131-1109, USA
may be incorporated into the present invention.
[0057] Other electrolyte systems may be used. For example, a porous
separator structure may be produced by using a geopolymer or an
open cell foam. A gel electrolyte may be produced by adding gelling
agents to an aqueous electrolyte solution. In an alternative
approach, a solid polymer electrolyte (SPE) or a SPE blend may be
used in the separator structure, for example to act as a binder and
an electrolyte. The SPE or SPE blend may also bind the anode and
the cathode structures, or at least bind the anode and cathode
structures to the separator structure. This will increase the
access of the electrolyte into the anode and cathode structures.
Multiphase electrolytes, comprising SPE blended with a mechanically
stiff matrix material can also be used. For example, SPE materials
such as polyethylene oxide (PEO) and polyvinyl alcohol (PVA) can be
used. Suitable mechanically-stiff matrix materials for blending
include epoxies, polyesters, or polyimides.
[0058] The anode, cathode and separator structures are not
necessarily planar. Non-planar configurations may be employed, for
example, to provide a curved or even a generally tubular battery
structure. The composite structures of the invention are well
suited for such configurations. The battery may comprise a number
of electrodes and secondary electrochemical cells, each cell
comprising anode, cathode and separator structures.
* * * * *