U.S. patent application number 16/530716 was filed with the patent office on 2019-12-12 for apparatus and associated methods.
This patent application is currently assigned to LytEn, Inc.. The applicant listed for this patent is LytEn, Inc.. Invention is credited to Piers ANDREW, Andrew Peter MATTHEWS, Teuvo Tapani RYHANEN, Di WEI.
Application Number | 20190378663 16/530716 |
Document ID | / |
Family ID | 49292548 |
Filed Date | 2019-12-12 |
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United States Patent
Application |
20190378663 |
Kind Code |
A1 |
RYHANEN; Teuvo Tapani ; et
al. |
December 12, 2019 |
Apparatus and Associated Methods
Abstract
An apparatus including an open interconnected wall structure
having one or more pores, the open interconnected wall structure
including a first electrode material, the pores including an
electrolyte and a second electrode material, wherein the
electrolyte and second electrode material are supported on the
first electrode material within the pores such that the first
electrode material is separated from the second electrode material
by the electrolyte to enable the generation and/or storage of
electrical energy using the apparatus.
Inventors: |
RYHANEN; Teuvo Tapani;
(Helsinki, FI) ; WEI; Di; (Cambridge, GB) ;
ANDREW; Piers; (Cambridge, GB) ; MATTHEWS; Andrew
Peter; (Cambridge, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LytEn, Inc. |
Sunnyvale |
CA |
US |
|
|
Assignee: |
LytEn, Inc.
Sunnyvale
CA
|
Family ID: |
49292548 |
Appl. No.: |
16/530716 |
Filed: |
August 2, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13482377 |
May 29, 2012 |
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16530716 |
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13439371 |
Apr 4, 2012 |
9324995 |
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13482377 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 10/052 20130101;
H01G 11/26 20130101; H01G 2009/0412 20130101; H01G 11/56 20130101;
H01M 12/08 20130101; Y02E 60/10 20130101; Y02E 60/128 20130101;
H01M 4/70 20130101; Y02E 60/13 20130101; H01G 11/70 20130101; H01G
9/025 20130101; H01G 9/048 20130101; H01M 10/058 20130101; H01M
4/04 20130101; H01G 11/06 20130101; H01M 10/04 20130101 |
International
Class: |
H01G 11/70 20060101
H01G011/70 |
Claims
1. A method of making an apparatus, the method comprising:
depositing an electrolyte and a second electrode material into two
or more pores of a substrate having an open interconnected wall
structure comprising a first electrode material, the pores
comprising the electrolyte and the second electrode material in a
first of the two or more pores and a different second electrode
material in a second of the two or more pores, wherein the
electrolyte and each of the second electrode materials are
supported on the first electrode material within the two or more
pores such that: the first electrode material is separated from the
second electrode material in the first of the two or more pores by
the electrolyte to form a battery structure for generation of
electrical energy from the first of the two or more pores; and the
first electrode material is separated from the second electrode
material in the second of the two pores by the electrolyte to form
a capacitor structure for storage of electrical energy in the
second of the two or more pores.
2. The method of claim 1, wherein the method comprises forming the
open interconnected wall structure before deposition of the
electrolyte and second electrode material.
3. The method of claim 2, wherein forming the open interconnected
wall structure comprises: depositing the first electrode material
in the interconnected spaces between and defined by a plurality of
particles of a lattice to create an interconnected wall structure
comprising the first electrode material; and removing the plurality
of particles to create two or more pores in the interconnected wall
structure to create an open interconnected wall structure
comprising the first electrode material.
4. The method of claim 2, wherein forming the open interconnected
wall structure comprises coating the surfaces of a plurality of
particles of a lattice, a block-copolymer, a sponge, or a base
substrate with the first electrode material, wherein: the lattice,
the block co-polymer, the sponge, or the base substrate has an open
interconnected wall structure comprising two or more pores; and the
coating provides an open interconnected wall structure comprising
the first electrode material.
5. A computer program, recorded on a carrier, the computer program
comprising computer code configured to control the method of claim
1.
6. The method of claim 1, wherein the first electrode material and
the second electrode material each comprise a first active material
and a second active material respectively, wherein at least one of
the first active material and the second active material comprises
an electrically insulating lithium-based compound configured for
use in generation and/or storage of electrons.
7. The method of claim 6, wherein each of the first active material
and the second active material are deposited using one or more of:
atomic layer deposition, chemical vapor deposition, and
electrochemical deposition.
8. The method of claim 1, wherein the first and/or second electrode
material comprises a charge collection material in physical contact
with an active material of the first and/or second electrode
material.
9. The method of claim 1, wherein the electrolyte is a lithium
salt.
10. The method of claim 2, wherein the open interconnected wall
structure has a gyroid structure defined by a configuration of
spherical particles that form a lattice and wherein the gyroid
structure is trigonometrically approximated by the equation cos
xsin y+cos ysin z+cos zsin x=0.
11. The method of claim 10, wherein the gyroid structure comprises
a block copolymer comprising polyfluorostyrene and a
polylactide.
12. The method of claim 10, wherein the gyroid structure comprises
a cubic bicontinuous double gyroid phase of
poly(4-fluorostyrene)-b-poly(D,L-lactide).
13. The method of claim 3 further comprising: etching the first
electrode material before and/or after removing the plurality of
particles.
14. The method of claim 3 further comprising: etching the base
substrate to produce the two or more pores.
15. The method of claim 3, wherein removing the plurality of
particles comprises one or more of: etching, melting, and
dissolving the plurality of particles.
16. The method of claim 4, wherein forming the open interconnected
wall structure further comprises removing the plurality of
particles of the lattice, the block co-polymer, the sponge or the
base substrate.
17. The method of claim 16, wherein removing the plurality of
particles of the lattice, the block co-polymer, the sponge or the
base substrate comprises one or more of: etching, melting, and
dissolving the plurality of particles of the lattice, the block
co-polymer, the sponge or the base substrate.
18. The method of claim 16 further comprising: etching the first
electrode material before and/or after removing the plurality of
particles of the lattice, the block co-polymer, the sponge or the
base substrate.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This patent application is a Divisional of U.S. patent
application Ser. No. 13/482,377 filed May 29, 2012, which is a
Continuation-in-part of patent application Ser. No. 13/439,371,
filed Apr. 4, 2012, the entireties of which are incorporated by
reference herein.
TECHNICAL FIELD
[0002] The present disclosure relates to the field of electrical
storage cells, associated methods and apparatus, and in particular
concerns a high surface area electrode on which an electrolyte and
second electrode are deposited to form an electrical storage cell
(battery, capacitor or battery-capacitor hybrid) with a compact
structure and increased storage density and capacity. The cell may
form part of an electronic device, in particular, so-called
hand-portable electronic devices which may be hand-held in use
(although they may be placed in a cradle in use). Such
hand-portable electronic devices include mobile phones and
so-called Personal Digital Assistants (PDAs).
[0003] The portable electronic devices may provide one or more
audio/text/video communication functions (e.g. tele-communication,
video-communication, and/or text transmission, Short Message
Service (SMS)/Multimedia Message Service (MMS)/emailing functions,
interactive/non-interactive viewing functions (e.g. web-browsing,
navigation, TV/program viewing functions), music recording/playing
functions (e.g. MP3 or other format and/or (FM/AM) radio broadcast
recording/playing), downloading/sending of data functions, image
capture function (e.g. using a (e.g. in-built) digital camera), and
gaming functions.
BACKGROUND
[0004] Energy storage density and capacity are important parameters
of any electrical storage apparatus. As portable electronic devices
become ever more power hungry, greater demands are being placed on
the storage density and capacity of the batteries and capacitors
which power these devices. Various high surface area materials have
been considered for forming the electrodes of next generation
storage cells. Examples include activated carbon, carbon nanotubes,
and metal/semiconductor nanowires. High surface area materials
increase the electrical storage density/capacity by increasing the
area of the electrode which is in contact with the electrolyte,
thereby facilitating the generation and/or storage of electrical
energy. One problem associated with such materials, however, is
their particulate form, which reduces the structural integrity of
the electrode and requires the use of additional binders. Such
binders increase the cost and complexity of the fabrication
process, and may also increase the electrical resistance of the
electrode.
[0005] The apparatus and methods disclosed herein may or may not
address this issue.
[0006] The listing or discussion of a prior-published document or
any background in this specification should not necessarily be
taken as an acknowledgement that the document or background is part
of the state of the art or is common general knowledge. One or more
aspects/embodiments of the present disclosure may or may not
address one or more of the background issues.
SUMMARY
[0007] According to a first aspect, there is provided an apparatus
comprising an open interconnected wall structure having one or more
pores, the open interconnected wall structure comprising a first
electrode material, the pores comprising an electrolyte and a
second electrode material, wherein the electrolyte and second
electrode material are supported on the first electrode material
within the pores such that the first electrode material is
separated from the second electrode material by the electrolyte to
enable the generation and/or storage of electrical energy using the
apparatus.
[0008] The term "open" in reference to the open interconnected wall
structure may be taken to mean that one or more of the pores on the
exterior allow access to the internal surface area of the
structure. The term "interconnected" in reference to the open
interconnected wall structure may be taken to mean that at least
some of the walls of the structure are physically connected to one
another (i.e. they form a continuous structure).
[0009] The electrolyte may form a coating on the open
interconnected wall structure. The second electrode material may
substantially fill the remaining volume of the pores. The
electrolyte may be a solid electrolyte or gel electrolyte (e.g. an
electrolyte comprising one or more of lithium phosphorous
oxynitride, poly(ethylene oxide) derivatives, borate ester groups,
and titanium dioxide).
[0010] The first and second electrode materials may each comprise
an active material. The first and/or second electrode material may
comprise a charge collection material. The active material may in
physical contact with the charge collection material.
[0011] The term "active material" may be taken to mean an electrode
material which takes part in the charging/discharging mechanism of
the apparatus. In a battery, for example, the active material may
be an electrode material which participates in an electrochemical
reaction or intercalation mechanism. In a supercapacitor, on the
other hand, the active material may be an electrode material which
participates in the formation of an electric double layer.
[0012] The charge collection material may comprise one or more of a
metal and a semiconductor. The metal may comprise one or more of
gold, silver, nickel and copper.
[0013] The first electrode material may form the open
interconnected wall structure. The open interconnected wall
structure may comprise a substrate on which the first electrode
material is supported.
[0014] The open interconnected wall structure may have a gyroid
structure. The gyroid structure may be trigonometrically
approximated by:
cos xsin y+cos ysin z+cos zsin x=0 Equation 1 [0015] (where x, y
and z are the three spatial directions)
[0016] Some or all of the pores may be interconnecting. Some or all
of the pores may form through channels within the open
interconnected wall structure. Some or all of the pores may form
blind channels within the open interconnected wall structures. Some
or all of the pores may be arranged periodically. Some or all of
the pores may have a diameter of less than 2 nm (i.e. microporous).
Some or all of the pores may have a diameter of between 2 nm and 50
nm inclusive (i.e. mesoporous). Some or all of the pores may have a
diameter of greater than 50 nm (i.e. macroporous).
[0017] The first electrode material, electrolyte and/or second
electrode material within one pore may be different from the first
electrode material, electrolyte and/or second electrode material
within another pore.
[0018] The apparatus may comprise a plurality of the open
interconnected wall structures electrically connected to one
another. The first electrode material, electrolyte and/or second
electrode material of one open interconnected wall structure may be
different from the first electrode material, electrolyte and/or
second electrode material of another open interconnected wall
structure.
[0019] The expression "generation of electrical energy" may be
taken to encompass the redox reactions and intercalation mechanisms
associated with batteries and battery-capacitor hybrids, whilst the
expression "storage of electrical energy" may be taken to encompass
the charge separation associated with capacitors and
battery-capacitor hybrids.
[0020] The apparatus may be an electrical storage apparatus. The
apparatus may be one or more of a battery (primary or secondary
battery), a capacitor (electrostatic, electrolytic, or
supercapacitor), and a battery-capacitor hybrid. The battery may be
one or more of a lithium-sulphur battery and a lithium-air
battery.
[0021] According to a further aspect, there is provided a device
comprising any apparatus described herein. The device may be an
electronic device, a portable electronic device, a portable
telecommunications device, and a module for any of the
aforementioned devices.
[0022] The device may comprise a solar cell configured to convert
energy from electromagnetic radiation incident upon the solar cell
into electrical energy. The apparatus may be configured to store
said electrical energy. The solar cell may form a coating on the
external surface of the apparatus.
[0023] According to a further aspect, there is provided a method of
making an apparatus, the method comprising depositing an
electrolyte and a second electrode material into one or more pores
of an open interconnected wall structure comprising a first
electrode material, the pores comprising the electrolyte and the
second electrode material, wherein the electrolyte and second
electrode material are supported on the first electrode material
within the pores such that the first electrode material is
separated from the second electrode material by the electrolyte to
enable the generation and/or storage of electrical energy using the
apparatus.
[0024] The method may comprise forming the open interconnected wall
structure before deposition of the electrolyte and second electrode
material.
[0025] Forming the open interconnected wall structure may comprise:
depositing the first electrode material in the interconnected
spaces between and defined by a plurality of particles of a lattice
to create an interconnected wall structure comprising the first
electrode material; and removing the particles to create one or
more pores in the interconnected wall structure to create an open
interconnected wall structure comprising the first electrode
material. Removing the particles may comprise one or more of
etching, melting and dissolving the particles. Forming the open
interconnected wall structure may further comprise etching the
first electrode material before removing the particles (e.g. to
allow access to the particles).
[0026] Forming the open interconnected wall structure may further
comprise etching the first electrode material after removing the
particles (e.g. to increase the surface area of the open
interconnected wall structure).
[0027] Forming the open interconnected wall structure may comprise
coating the surfaces of a plurality of particles of a lattice, a
block-copolymer, a sponge, or a base substrate with the first
electrode material, the lattice, the block co-polymer, the sponge,
or the base substrate having an open interconnected wall structure
comprising one or more pores, the coating providing an open
interconnected wall structure comprising the first electrode
material.
[0028] Forming the open interconnected wall structure may further
comprise etching the base substrate to produce the one or more
pores. Forming the open interconnected wall structure may further
comprise removing the particles, the sponge, or the base substrate
after coating the surfaces (e.g. to reduce the weight of the
apparatus andior to increase the surface area of the open
interconnected wall structure). Removing the particles, the sponge,
or the base substrate may comprise one or more of etching, melting
and dissolving the particles, the sponge, or the base substrate.
Forming the open interconnected wall structure may further comprise
etching the first electrode material before removing the particles,
the sponge, or the base substrate (e.g. to allow access to the
particles, the sponge, or the base substrate). Forming the open
interconnected wall structure may comprise etching the first
electrode material after removing the particles, the sponge, or the
base substrate (e.g. to increase the surface area of the open
interconnected wall structure).
[0029] To form a porous structure using a block copolymer one can
cast a thin film (e.g. 100's nm to micrometers in thickness) of the
block copolymer which then phase separates into the desired
morphology consisting of two or more phases on the nanoscale. You
can then remove one of the polymer phases (chemical etch, UV
exposure depending on the polymer) to leave a porous scaffold. This
can then be filled with the desired material or materials (e.g. by
Atomic Layer Deposition or electrochemical deposition). The
remaining polymer scaffold may then itself be removed and the
resulting volume possibliy filled with another desired material in
similar fashion. In the case of energy storage devices, one could
deposit the block copolymer film on a (metallic) charge collector
layer and proceed from there.
[0030] The particles of the lattice may or may not be spherical
particles.
[0031] The first electrode material may be deposited using one or
more of atomic layer deposition, chemical vapour deposition, and
electrochemical deposition.
[0032] According to a further aspect, there is provided an
apparatus comprising means for acting as a support with one or more
pores, the means for acting as a support comprising means for
acting as a first electrode, the one or more pores comprising means
for acting as an electrolyte and a means for acting as a second
electrode material, wherein the means for acting as an electrolyte
and means for acting as a second electrode material are supported
on the means for acting as a first electrode material within the
pores such that the means for acting as a first electrode material
is separated from the means for acting as a second electrode
material by the means for acting as an electrolyte to enable the
generation and/or storage of electrical energy using the
apparatus.
[0033] According to a further aspect, there is provided an
apparatus comprising a substrate and an active material, the
substrate comprising an open interconnected wall structure of
electrically conductive material having one or more pores, the open
interconnected wall structure providing the substrate upon which
the active material is supported, wherein the active material
comprises an electrically insulating lithium-based compound
configured for use in generating and/or storing electrons, and
wherein the open interconnected wall structure is configured to act
as a charge collector for the generated and/or stored electrons
through which an electrical path for the electrons is provided.
[0034] The term "electrically insulating" in reference to the
lithium-based compound may be taken to mean that the lithium-based
compound exhibits zero or a relatively low electrical conductivity.
The term "open" in reference to the open interconnected wall
structure may be taken to mean that one or more of the pores on the
exterior allow access to the internal surface area of the
structure. The term "interconnected" in reference to the open
interconnected wall structure may be taken to mean that at least
some of the walls of the structure are in physical (and therefore
electrical) contact with one another.
[0035] The substrate may be formed from an open interconnected wall
structure of electrically conductive material. On the other hand,
the substrate may comprise an open interconnected wall structure
upon which a coating of electrically conducting material is
deposited. In such a case, the open interconnected wall structure
may not itself be electrically conductive, but the coating is.
Either way, the substrate comprising the open interconnected wall
structure can be used to support the active material and may act as
a charge collector to provide an electrical path for the generated
electrons.
[0036] The open interconnected wall structure may have a gyroid
structure. The gyroid structure may be trigonometrically
approximated by:
cos xsin y+cos ysin z+cos zsin x=0 Equation 1 [0037] (where x, y
and z are the three spatial directions)
[0038] Some or all of the pores may be interconnecting. Some or all
of the pores may form through channels within the substrate. Some
or all of the pores may form blind channels within the substrate.
Some or all of the pores may have a diameter of less than 2 nm
(i.e. microporous). Some or all of the pores may have a diameter of
between 2 nm and 50 nm inclusive (i.e. mesoporous). Some or all of
the pores may have a diameter of greater than 50 nm (i.e.
macroporous). Some or all of the pores may be arranged
periodically.
[0039] The insulating lithium-based compound may comprise one or
more of lithium sulphide and lithium oxide.
[0040] The active material may form a coating on the open
interconnected wall structure of electrically conductive material.
The term "active material" may be taken to mean an electrode
material which takes part in the charging/discharging mechanism of
the apparatus. In a battery, for example, the active material may
be an electrode material which participates in an electrochemical
reaction or intercalation mechanism. In a supercapacitor, on the
other hand, the active material may be an electrode material which
participates in the formation of an electric double layer.
[0041] The electrically conductive material may comprise one or
more of a metal and a semiconductor. The metal may comprise one or
more of gold, silver, nickel, aluminium and copper.
[0042] The apparatus may be configured for the generation and/or
storage of electrons. The expression "generation of electrons" may
be taken to encompass the redox reactions and intercalation
mechanisms associated with batteries and battery-capacitor hybrids,
whilst the expression "storage of electrons" may be taken to
encompass the charge separation associated with capacitors and
battery-capacitor hybrids. The apparatus may be one or more of an
electrical storage apparatus and an electrode for an electrical
storage apparatus. The electrical storage apparatus may be one or
more of a battery (primary or secondary battery), a capacitor
(electrostatic, electrolytic, or supercapacitor), and a
battery-capacitor hybrid. The electrical storage apparatus may be
one or more of a lithium-sulphur battery and a lithium-air
battery.
[0043] According to a further aspect, there is provided a device
comprising any apparatus described herein. The device may be an
electronic device, a portable electronic device, a portable
telecommunications device, and a module for any of the
aforementioned devices.
[0044] According to a further aspect, there is provided a method of
making an apparatus, the method comprising depositing an active
material on top of a substrate comprising an open interconnected
wall structure of electrically conductive material having one or
more pores, wherein the active material comprises an electrically
insulating lithium-based compound configured for use in generating
and/or storing electrons, and wherein the open interconnected wall
structure is configured to act as a charge collector for the
generated and/or stored electrons through which an electrical path
for the electrons is provided.
[0045] The method may comprise forming the substrate before
deposition of the active material.
[0046] Forming the substrate may comprise: depositing an
electrically conductive material in the interconnected spaces
between and defined by a plurality of particles of a lattice to
create an interconnected wall structure of electrically conductive
material; and removing the particles to create one or more pores in
the interconnected wall structure to provide an open interconnected
wall structure of electrically conductive material. Removing the
particles may comprise one or more of etching, melting and
dissolving the particles. Forming the substrate may comprise
etching the electrically conductive material before removing the
particles (e.g. to allow access to the particles). Forming the
substrate may comprise etching the electrically conductive material
after removing the particles (e.g. to increase the surface area of
the open interconnected wall structure).
[0047] Forming the substrate may comprise coating the surfaces of a
plurality of particles of a lattice, a block-copolymer, a sponge,
or a base substrate with an electrically conductive material, the
lattice, the block co-polymer, the sponge, or the base substrate
having an open interconnected wall structure comprising one or more
pores, the coating providing an open interconnected wall structure
of electrically conductive material. Forming the substrate may
comprise etching the base substrate to produce the one or more
pores. Forming the substrate may comprise removing the particles,
the block-copolymer, the sponge, or the base substrate after
coating the surfaces (e.g. to reduce the weight of the apparatus
and/or to increase the surface area of the open interconnected wall
structure). Removing the particles, the block-copolymer, the
sponge, or the base substrate may comprise one or more of etching,
melting and dissolving the particles, the block-copolymer, the
sponge, or the base substrate. Forming the substrate may comprise
etching the electrically conductive material before removing the
particles, the block-copolymer, the sponge, or the base substrate
(e.g. to allow access to the particles, the block-copolymer, the
sponge, or the base substrate). Forming the substrate may comprise
etching the electrically conductive material after removing the
particles, the block-copolymer, the sponge, or the base substrate
(e.g. to increase the surface area of the open interconnected wall
structure).
[0048] The particles of the lattice may or may not be spherical
particles.
[0049] The active material may be deposited using one or more of
atomic layer deposition, chemical vapour deposition, and
electrochemical deposition.
[0050] The steps of any method disclosed herein do not have to be
performed in the exact order disclosed, unless explicitly stated or
understood by the skilled person.
[0051] According to a further aspect, there is provided a computer
program (which may or may not be recorded on a carrier), the
computer program comprising computer code configured to perform any
method described herein.
[0052] The apparatus may comprise a processor configured to process
the code of the computer program. The processor may be a
microprocessor, including an Application Specific Integrated
Circuit (ASIC).
[0053] The present disclosure includes one or more corresponding
aspects, example embodiments or features in isolation or in various
combinations whether or not specifically stated (including claimed)
in that combination or in isolation. Corresponding means and
corresponding functional units (e.g. supporter) for performing one
or more of the discussed functions are also within the present
disclosure.
[0054] The above summary is intended to be merely exemplary and
non-limiting.
BRIEF DESCRIPTION OF THE FIGURES
[0055] A description is now given, by way of example only, with
reference to the accompanying drawings, in which:
[0056] FIG. 1a illustrates schematically the discharge process of a
conventional battery;
[0057] FIG. 1b illustrates schematically the charging process of a
conventional battery;
[0058] FIG. 2a illustrates schematically the discharge process of a
lithium-ion battery;
[0059] FIG. 2b illustrates schematically the charging process of a
lithium-ion battery;
[0060] FIG. 3a illustrates schematically the charging process of a
supercapacitor;
[0061] FIG. 3b illustrates schematically the discharge process of a
supercapacitor;
[0062] FIG. 4a illustrates schematically the charging process of a
lithium-ion capacitor;
[0063] FIG. 4b illustrates schematically the discharge process of a
lithium-ion capacitor;
[0064] FIG. 5 illustrates schematically one embodiment of an
electrical storage apparatus;
[0065] FIG. 6 illustrates schematically another embodiment of an
electrical storage apparatus;
[0066] FIG. 7 illustrates schematically one method of forming an
open interconnected wall structure using a lattice of spherical
particles;
[0067] FIG. 8 illustrates schematically another method of forming
an open interconnected wall structure using a lattice of spherical
particles;
[0068] FIG. 9 illustrates schematically one method of forming an
open interconnected wall structure using a block co-polymer
comprising one or more pores;
[0069] FIG. 10 illustrates schematically one method of forming an
open interconnected wall structure using a sponge comprising one or
more pores;
[0070] FIG. 11 illustrates schematically one method of forming an
open interconnected wall structure using a base substrate
comprising one or more pores;
[0071] FIG. 12 illustrates schematically removal of the support
material after deposition of the first electrode material;
[0072] FIG. 13a illustrates schematically the layered structure of
an electrical storage apparatus according to a first
embodiment;
[0073] FIG. 13b illustrates schematically the layered structure of
an electrical storage apparatus according to a second
embodiment;
[0074] FIG. 13c illustrates schematically the layered structure of
an electrical storage apparatus according to a third
embodiment;
[0075] FIG. 13d illustrates schematically the layered structure of
an electrical storage apparatus according to a fourth
embodiment;
[0076] FIG. 14 illustrates schematically a plurality of electrical
storage cells connected in series;
[0077] FIG. 15 illustrates schematically a plurality of electrical
storage cells connected in parallel;
[0078] FIG. 16 illustrates schematically two electrical storage
cells formed within the same open interconnected wall
structure;
[0079] FIG. 17 illustrates schematically an electronic device
comprising the apparatus described herein;
[0080] FIG. 18 illustrates schematically an electrical storage
apparatus comprising a solar cell formed thereon:
[0081] FIG. 19 illustrates schematically a method of making the
apparatus described herein; and
[0082] FIG. 20 illustrates schematically a computer readable medium
providing a program for controlling the method of FIG. 19.
DESCRIPTION OF SPECIFIC ASPECTS/EMBODIMENTS
[0083] In electrical circuits, batteries and capacitors are used to
provide other components with electrical power. These power
supplies operate in different ways, however.
[0084] Batteries use electrochemical reactions to generate
electricity. The discharge process of a conventional battery is
shown in FIG. 1a. Batteries comprise two electrical terminals
(electrodes 102, 103) separated by an electrolyte 101. A battery
may also contain a separator 110 to prevent direct physical contact
between the electrodes, which is particularly important when liquid
electrolytes are used. At the negative electrode (the anode 102),
an oxidation reaction takes place which produces electrons. These
electrons flow round an external circuit 105 (indicated by the
arrows 104) from the anode 102 to the positive electrode (the
cathode 103) causing a reduction reaction to take place at the
cathode 103. The flow of electrons can be used to power one or more
electrical components 106 in the external circuit 105. The
oxidation and reduction reactions may continue until the reactants
are completely converted. Importantly though, unless electrons are
able to flow from the anode 102 to the cathode 103 via the external
circuit 105, the electrochemical reactions cannot take place. This
allows batteries to store electricity for long periods of time. As
the electrons flow round the external circuit from the anode 102 to
the cathode 103, a negative charge cloud develops in the
electrolyte 101 around the cathode 103, and a positive charge cloud
develops in the electrolyte 101 around the anode 102. Positive 107
and negative 108 ions in the electrolyte 101 move to neutralise
these charge clouds, allowing the reactions, and the flow of
electrons, to continue. Without the ions 107, 108 from the
electrolyte 101, the charge clouds around each electrode 102, 103
would inhibit the generation of electricity.
[0085] A primary cell is any kind of battery in which the
electrochemical reaction is irreversible. These are used as
disposable batteries. With secondary batteries, on the other hand,
the electrochemical reaction is reversible, meaning that the
chemical reactants can be restored to their original states. These
are used as rechargeable batteries. The charging process of a
conventional rechargeable battery is shown in FIG. 1b. To charge
the battery, a potential difference is applied between the anode
102 and cathode 103. The positive terminal of the charger 109
strips electrons from the cathode 103 and returns them to the anode
102 (indicated by the arrows 111), inducing chemical reactions at
the electrode-electrolyte interface. Again, to compensate for the
transfer of charge, positive 107 and negative 108 ions in the
electrolyte 101 move between the electrodes 102, 103 in opposite
directions to before.
[0086] The current and voltage generated by a battery is directly
related to the materials used for the electrodes and electrolyte.
The ability of a material to lose or gain electrons with respect to
another material is known as its electrode potential. The strengths
of oxidising and reducing agents are indicated by their standard
electrode potentials. Materials with a positive electrode potential
are used to form the anode, whilst those with a negative electrode
potential are used to form the cathode. The greater the difference
between the anode and cathode potentials, the greater the amount of
electrical energy that can be produced by the cell.
[0087] Lithium appears at the top of the electrochemical series
(large negative electrode potential), indicating that it is the
strongest reducing agent. Likewise, fluorine appears at the bottom
of the electrochemical series (large positive electrode potential),
indicating that it is the strongest oxidising agent. As a result of
lithium's high electrode potential, lithium batteries are capable
of producing voltages of nearly 4V, over twice the voltage of a
zinc-carbon or alkaline battery. Depending on the choice of
materials for the anode, cathode and electrolyte, the current,
voltage, capacity, life and safety of a lithium battery can change
dramatically.
[0088] A lithium-ion battery is a different type of rechargeable
battery which uses a lithium ion "intercalation" mechanism rather
than traditional redox reactions. This involves the insertion of
lithium ions into and out of the crystal structure of the
electrodes as the ions pass back and forth between the electrodes
during charging and discharging. To achieve this, the electrodes
require open crystal structures which allow the insertion and
extraction of lithium ions, and the ability to accept compensating
electrons at the same time. Such electrodes are called
"intercalation hosts". Lithium-ion batteries are currently one of
the most popular types of battery for portable electronics because
they exhibit one of the best energy-to-weight ratios, no memory
effect, and a slow loss of charge when not in use.
[0089] In a typical lithium-ion battery, the anode is made from
carbon, the cathode is a metal oxide, and the electrolyte is a
lithium salt in an organic solvent. Commercially, the most popular
anode material is graphite, and the cathode is generally one of
three materials: a layered oxide (such as lithium cobalt oxide),
one based on a polyanion (such as lithium iron phosphate), or a
spinel (such as lithium manganese oxide). The electrolyte is
typically a mixture of organic carbonates such as ethylene
carbonate or diethyl carbonate containing complexes of lithium
ions. These non-aqueous electrolytes often comprise
non-coordinating anion salts such as lithium hexafluorophosphate
(LiPFe), lithium hexafluoroarsenate monohydrate (LiAsFe), lithium
perchlorate (LiClO.sub.4), lithium tetrafluoroborate (LiBF.sub.4),
and lithium triflate (LiCF.sub.3SO.sub.3).
[0090] FIGS. 2a and 2b illustrate schematically the discharge and
charging processes of a lithium-ion battery, respectively. As shown
in the figures, the anode 202 and cathode 203 each comprise an
open-crystal intercalation material 235 deposited on top of a
charge-collecting substrate 236. During discharge, lithium ions 234
are extracted from the anode 202, migrate across the electrolyte
201, and are inserted into the crystal structure of the cathode
203. At the same time, compensating electrons travel in the
external circuit (in a direction indicated by the arrows 204) and
are accepted by the cathode 203 to balance the reaction. This
process is reversible. During charging, an external electrical
power source (the charger 209) applies a potential difference
between the electrodes 202, 203 forcing the electrons to travel in
the opposite direction (indicated by the arrows 211). The lithium
ions 234 are then extracted from the cathode 203, migrate across
the electrolyte 201, and are inserted back into the crystal
structure of the anode 202.
[0091] In a lithium-ion battery, the lithium ions are transported
to and from the cathode and anode, with the transition metal,
cobalt (Co), in Li.sub.xCoO.sub.2 being oxidised from Co.sup.3+ to
Co.sup.4+ during charging, and reduced from Co.sup.4+ to Co.sup.3+
during discharge. The anode and cathode half-reactions for a
lithium-ion battery comprising a graphite anode and a lithium
cobalt oxide cathode are as follows:
Anode xLi.sup.++xe.sup.-+6CLi.sub.xC.sub.6 Equation 2
Cathode LiCoO.sub.2Li.sub.1-xCoO.sub.2+xLi.sup.++xe.sup.- Equation
3
[0092] The overall reaction has its limits, however.
Overdischarging the lithium-ion battery can supersaturate the
lithium cobalt oxide, leading to the production of lithium oxide,
by the following irreversible reaction:
Li.sup.++LiCoO.sub.2.fwdarw.Li.sub.2O+CoO Equation 4
[0093] whilst overcharging the lithium-ion battery can lead to the
synthesis of Co.sup.4+ by the following irreversible reaction:
LiCoO.sub.2.fwdarw.Li.sup.++CoO.sub.2 Equation 5
[0094] In contrast to batteries, capacitors store charge
electrostaticaliy, and are not capable of generating electricity. A
relatively new type of capacitor known as a "supercapacitor" (also
known as an electric double layer capacitor, an ultracapacitor, a
pseudocapacitor, and an electrochemical double layer capacitor)
offers greater energy storage than a conventional or electrolytic
capacitor, and is becoming increasingly popular for portable
electronic applications.
[0095] FIGS. 3a and 3b illustrate schematically the charging and
discharge processes of a supercapacitor, respectively.
Supercapacitors have a cathode 303 and an anode 302, each
comprising an electrically conducting plate 336 (charge collector),
which are separated by an electrolyte 301. When a liquid
electrolyte is used, the supercapacitor may also comprise a
separator 310 to prevent direct physical contact between the
cathode and anode. The plates 336 are coated in a porous material
337 (such as powdered carbon) to increase their surface area for
greater charge storage. When a power supply (charger) applies a
potential difference between the electrodes 302, 303, the
electrolyte 301 becomes polarised. The potential on the cathode 303
attracts negative ions 308 in the electrolye 301, and the potential
on the anode 302 attracts positive ions 307.
[0096] Unlike batteries, the applied potential is kept below the
breakdown voltage of the electrolyte 301 to prevent electrochemical
reactions from taking place at the surface of the electrodes 302,
303. For this reason, supercapacitors cannot generate electricity
like electrochemical cells. Also, without electrochemical reactions
taking place, no electrons are generated. As a result, no
significant current can flow between the electrolyte 301 and the
electrodes 302, 303. Instead, the ions 307, 308 in solution arrange
themselves at the surfaces of the electrodes 302, 303 to mirror the
surface charge 338 and form an insulating "electric double layer".
In an electric double layer (i.e. a layer of surface charge 338 and
a layer of ions 307, 308), the separation of the surface charge 338
and ions 307, 308 is on the order of nanometers. The combination of
the electric double layer and the use of a high surface area
material 337 on the surface of the plates 336 allow a huge number
of charge carriers to be stored at the electrode-electrolyte
interface.
[0097] To discharge the supercapacitor, an electrical connection
305 is made between the charged electrodes 302, 303, causing
electrons to flow from the anode to the cathode via the external
circuit (as indicated by the arrows 304). This flow of charge can
be used to power one or more electrical components 306 in the
external circuit 305.
[0098] Supercapacitors have several advantages over batteries, and
as a result, have been tipped to replace batteries in many
applications. They function by supplying large bursts of current to
power a device and then quickly recharging themselves. Their low
internal resistance, or equivalent series resistance (ESR), permits
them to deliver and absorb these large currents, whereas the higher
internal resistance of a traditional chemical battery may cause the
battery voltage to collapse. Also, whilst a battery generally
demands a long recharging period, supercapacitors can recharge very
quickly, usually within a matter of minutes. They also retain their
ability to hold a charge much longer than batteries, even after
multiple chargings. When combined with a battery, a supercapacitor
can remove the instantaneous energy demands that would normally be
placed on the battery, thereby lengthening the battery
lifetime.
[0099] Whereas batteries often require maintenance and can only
function well within a small temperature range, supercapacitors are
maintenance-free and perform well over a broad temperature range.
Supercapacitors also have longer lives than batteries, and are
built to last until at least the lifetime of the electronic devices
they are used to power. Batteries, on the other hand, typically
need to be replaced several times during the lifetime of a
device.
[0100] Supercapacitors are not without their drawbacks, however.
Despite being able to store a greater amount of energy than
conventional and electrolytic capacitors, the energy stored by a
supercapacitor per unit weight is considerably lower than that of
an electrochemical battery. In addition, the working voltage of a
supercapacitor is limited by the electrolyte breakdown voltage,
which is not as issue with batteries.
[0101] Lithium-ion batteries have the highest energy density of all
systems, whilst supercapacitors have the highest power density and
lifetime. Recently, a new hybrid storage device called a
lithium-ion capacitor has been developed which aims to integrate
the advantages of lithium-ion batteries and supercapacitors. The
cathode of a lithium-ion capacitor employs activated carbon at
which charges are stored as an electric double layer at the
interface between the carbon and the electrolyte, similar to a
supercapacitor. The anode, on the other hand, is made of a
nanostructured intercalation material pre-doped with lithium ions,
similar to a lithium-ion battery. This pre-doping process lowers
the anode potential and results in a high cell output voltage.
Typically, output voltages for lithium-ion capacitors are in the
range of 3.8V to 4V. As a consequence, lithium-ion capacitors have
a high energy density.
[0102] Furthermore, the capacity of the anode is several orders of
magnitude greater than the capacity of the cathode. As a result,
the change in anode potential during charging and discharging is
far smaller than the change in cathode potential. The intercalation
anode can also be coupled with an intercalation cathode, such as
LiCoO.sub.2 or LiMn.sub.2O.sub.4, to increase the power of the
lithium-ion capacitor. The electrolyte used in a lithium-ion
capacitor is typically a lithium-ion salt solution, and a separator
may be used to prevent direct physical contact between the anode
and cathode.
[0103] FIGS. 4a and 4b illustrate schematically the charging and
discharge processes of a lithium-ion capacitor, respectively. The
behaviour of a lithium-ion capacitor is much the same as that of a
supercapacitor, and therefore the reference numerals of FIGS. 4a
and 4b correspond to similar features in FIGS. 3a and 3b. The main
difference between the two systems, however, is that instead of
positive ions in the electrolyte 401 arranging themselves at the
electrode-electrolyte interface to form an electric double layer
when the device charges, lithium ions 434 insert themselves
(intercalation) into the crystal structure 435 of the anode 402.
Like a lithium-ion battery, therefore, lithium-ion capacitors
undergo fast electrochemical reactions and do not simply rely on
the formation of an electric double layer to store electrical
charge.
[0104] As stated in the background section, many of the high
surface area electrode materials which have been considered for
next generation storage cells suffer from low structural integrity
and/or high resistance as a result of their particulate form. There
will now be described an apparatus and associated methods that may
provide a solution to this problem.
[0105] The present apparatus (as shown in FIG. 5) comprises a high
surface area electrode (anode or cathode) on which the electrolyte
and second electrode (cathode or anode, respectively) are deposited
to form an electrical storage cell 525 (battery, capacitor or
battery-capacitor hybrid). Unlike the particulate materials
mentioned above, the high surface area electrode takes the form of
an open interconnected wall structure 515 having one or more pores
517. The open interconnected wall structure 515 comprises a first
electrode material 514 and serves as the first electrode (anode or
cathode) of the storage cell 525. An electrolyte 522 and second
electrode material 523 (cathode or anode, respectively) are
deposited on top of the first electrode material 514 within the
pores 517 of the open interconnected wall structure 515 such that
the first electrode material 514 is separated from the second
electrode material 523 by the electrolyte 522 to enable the
generation and/or storage of electrical energy.
[0106] Since the open interconnected wall structure 515 is formed
(at least in part) from the first electrode material 514, and the
electrolyte 522 and second electrode material 523 are deposited on
top of the first electrode material 514, the use of an open
interconnected wall structure 515 increases the surface area of
both electrodes and maximises the degree of interaction between the
electrolyte 522 and the anode/cathode materials 514, 523.
[0107] In one embodiment (as shown in FIG. 5), the electrolyte 522
forms a coating on the open interconnected wall structure 515 and
the second electrode material 523 fills the remaining volume of the
pores 517 to form a closed, non-porous cell. Filling the pores 517
of the structure 515 with the second electrode material 523
prevents contaminant materials from entering the pores 517, but
also increases the weight of the cell without any corresponding
increase in storage density/capacity. In another embodiment (as
shown in FIG. 6), the electrolyte 622 and second electrode material
623 form consecutive coatings on the open interconnected wall
structure 615 without filling the entire volume of the pores
617.
[0108] A number of different interconnected wall structures 615 can
be used provided that the structure 615 is open (via external pores
617). The open nature of the structure 615 allows the electrolyte
622 and second electrode material 623 to be deposited within the
pores 617 of the structure 615.
[0109] One example of an open interconnected wall structure 715 can
be fabricated (as illustrated in FIG. 7) by arranging a plurality
of spherical particles 712 (e.g. polystyrene particles) to form a
lattice 713, and depositing the first electrode material 714 (e.g.
by evaporation, sputtering, chemical vapour deposition (CVD),
atomic layer deposition (ALD) or electrochemical deposition (ECD))
between the spherical particles 712. An open interconnected gyroid
structure can be formed from using a block copolymer phase
separation process.
[0110] CVD, ALD and ECD are particularly useful here because the
deposition is independent on the orientation of the target surface.
With evaporation and sputtering techniques, on the other hand, the
target surface needs to be in the line-of-sight of the material
source. Nevertheless, this issue can be addressed by using multiple
material sources arranged to face different surfaces of the target
structure, or by using a single material source and multiple
deposition steps (and rotating the structure or material source
between each deposition). Even if evaporation or sputtering are
used to provide a complete coating, however, the coating is
unlikely to have a uniform thickness due to the overlap from each
deposition step. In this sense, CVD, ALD and ECD are preferable.
ALD also has the advantage that it can produce pinhole free films.
This factor is useful for forming an electrode of an electrical
storage cell because pinholes in the first electrode material 714
can increase the electrical resistance of the cell. Pinholes in
insulating layers can compromise the insulating behaviour of
insulating layer.
[0111] Once the first electrode material 714 has been deposited,
the spherical particles 712 can be removed (e.g. by etching,
melting or dissolving the particles) to create pores in the
structure. If the first electrode material 714 has completely
coated the external surfaces of the particles 712, some or all of
the coating may need to be removed (e.g. by wet or dry etching such
as galvanostatic or potentiostat etching) to allow access to, and
removal of, the spherical particles 712. The resulting structure
715 (albeit shown in cross-section in FIG. 7) is a
three-dimensional arrangement of interconnecting walls 716 with
channels 717 (pores) therebetween.
[0112] At this stage, however, the pores 717 of the structure 715
are not necessarily interconnected (although the walls would be
interconnected to provide mechanical/structural integrity). As a
result, some of the internal pores 717 may be inaccessible to the
electrolyte and second electrode material, which reduces the useful
surface area of the structure 715. This can be addressed (for
example) by immersing the structure 715 in a bath of liquid (wet)
etchant for a predetermined period of time. As the etching time
increases, the number of interconnections 735 (and therefore the
internal surface area of the material) increases, but the
structural integrity decreases. The optimum etching time is
therefore chosen to provide a sufficient surface area without
compromising the rigidity of the structure 715, and will vary
depending on the specific electrode material 714 and etchant
used.
[0113] FIG. 8 illustrates an alternative method of fabricating the
open interconnected wall (e.g. gyroid) structure. This time,
instead of filling the spaces between the spherical particles 812
of the lattice 813, the first electrode material 814 is deposited
as a coating on the particles 812. This may be performed simply by
depositing a smaller amount of the first electrode material 814 so
as to leave spaces between the particles 812. Since the spheres 812
are already packed together in the form of a lattice 813, the first
electrode material 814 on the surface of one particle is in
physical and electrical contact with the first electrode material
on the surface of an adjacent particle. In this way, the resulting
structure comprises a continuous layer of the first electrode
material 814 and a plurality of interconnecting channels 817. The
first electrode material 814 also serves to bind the particles
together, thereby improving the structural integrity.
[0114] Whilst the above-mentioned fabrication processes refer to
"spherical" particles, these techniques may also be performed using
any appropriately shaped/sized particles (not necessarily all the
same shapesize) provided that they are able to form a lattice
comprising one or more pores or channels.
[0115] FIG. 9 illustrates another method of fabricating the open
interconnected wall (e.g. gyroid) structure. Instead of coating a
lattice of spherical particles as shown in FIG. 8, however, the
first electrode material 914 is deposited onto a block co-polymer
918. Block co-polymers 918 comprise two or more chemically distinct
polymers (e.g. polystyrene and PMMA, polystyrene and polyimide, or
polyfluorostyrene and polylactic for gyroids or double gyroids)
linked together by a covalent bond at one end, and have the ability
to self-assemble into a variety of ordered porous nanostructures.
Depending upon the volume fraction of the components, block
co-polymer nanoscopic domains (e.g. body-centred cubic spheres,
hexagonally packed cylinders, lamellae, or bicontinuous gyroids)
can be prepared under certain conditions. The molecular weight of
the block co-polymer 918 and the individual blocks can be varied to
control the size and separation distance of these nanoscopic
domains.
[0116] Block copolymers 918 may comprise two or more homopolymer
blocks. Block copolymers 918 with two or three distinct blocks are
called diblock copolymers and triblock copolymers, respectively.
Suitable diblock copolymers include
poly(4-fluorostyrene)-b-poly(D,L-lactide) and
poly(ethylene)-poly(ethylenepropylene), whilst a suitable triblock
copolymer includes
poly(1,4-isoprene)-block-polystyrene-block-poly(2-vinylpyridine).
The cubic bicontinuous double gyroid phase of
poly(4-fluorostyrene)-b-poly(D,L-lactide) allows the formation of
an open interconnected wall structure in which the pores are fully
interconnected.
[0117] The block co-polymer 918 in FIG. 9 comprises a plurality of
ordered pores 917. When a layer of the first electrode material 914
is deposited onto the block co-polymer (preferably using CVD, ALD
or ECD), it coats the external surface of the polymer 918 as well
as the internal surfaces of the pores 917. The resulting structure
therefore comprises a continuous layer of the first electrode
material 914. The arrangement of the pores 917 within the structure
will depend on the specific polymers and the fabrication
conditions. In some cases the pores 917 may be interconnected, but
in other cases they may not be. Interconnection of the pores 917 is
not absolutely necessary, but it increases the surface area of the
electrodes and therefore improves the storage density and capacity
of the electrical storage apparatus. It will be appreciated that
the block copolymer needs to have one of the polymer phases/blocks
removed to make the porous structure. This can then be filled with
the desired materials.
[0118] Rather than depositing the first electrode material onto a
block co-polymer, it may be deposited on top of a sponge 1019
(natural or synthetic) as shown in FIG. 10. Sponges 1019 typically
comprise a plurality of (interconnecting) pores 1017 and have an
inherently high surface area. The external and internal surfaces of
the sponge 1019 can therefore be coated with the first electrode
material 1014 to create an open interconnected wall structure which
is suitable for use as an electrode. As with the block co-polymer,
it is not essential that the pores 1017 are connected to one
another, but interconnected pores are beneficial.
[0119] Another alternative is to deposit the first electrode
material 1114 onto a substrate 1120 (referred to herein as the base
substrate) comprising one or more preformed holes 1117 (pores), as
shown in FIG. 11. The pores 1117 may be formed in the substrate
1120 using a variety of techniques (e.g. drilling or etching
through an etch-resistance mask). In this way, the number, density,
diameter, depth and shape of the pores 1117 can be controlled. It
is also possible to control whether the pores 1117 interconnect
with one another or not. By coating the external and internal
surfaces of the base substrate 1120, an open interconnected wall
structure may be produced which is suitable for use as an
electrode.
[0120] The pores in the open interconnected wall structure may form
through channels (i.e. from one side of the material to the other,
as denoted by reference numeral 1033) or blind channels (i.e. open
at one side of the material but terminating inside the material, as
denoted by reference numeral 917). In addition, the pores may (e.g.
pores 917) or may not (e.g. pores 1017) be arranged periodically,
and may have a diameter of less than 2 nm (microporous), between 2
nm and 50 nm inclusive (mesoporous), or greater than 50 nm
(macroporous).
[0121] In each of the fabrication processes illustrated in FIGS. 8,
10 and 11, there is no need to remove the support material
(spherical particles, sponge or base substrate) upon which the
first electrode material is deposited. However, removal of the
support material can be useful for two reasons. First of all, it
can reduce the overall weight of the electrical storage device
(which is an important factor given that storage cells are often
characterised by their energy-to-weight ratio). Secondly, removal
of the support material increases the surface area of the
structure.
[0122] This aspect is illustrated in FIG. 12 which shows the base
substrate 1220 of FIG. 11 after being coated by the first electrode
material 1214. To remove the support material 1220 (base substrate
in this case), part of the first electrode material 1214 may need
to be removed to provide access to the underlying material 1220.
This step may be performed by etching. In the figure shown, the
first electrode material 1214 at the lower surface 1221 of the base
substrate 1220 has been removed. Once the substrate material 1220
is exposed, a wet etch (or an alternative technique) can be used to
remove the substrate material 1220. It is important, however, that
the first electrode material 1214 is more resistant to the etchant
than the substrate material 1220, otherwise this step could
partially or completely remove (or damage) the first electrode
material. An alternative option may be to use an etch resistant
mask to prevent interaction between the etchant and the first
electrode material 1214. Removal of the substrate material 1220
results in an interconnected wall structure of first electrode
material 1214 which is lightweight, open and porous, with a high
surface area. The block copolymer fabrication process would apply a
corresponding technique.
[0123] Nevertheless, the support material 1220 can provide
mechanical support for the electrode and electrolyte materials. The
decision on whether or not to remove the support material 1220
after deposition of the first electrode material 1214 will
therefore depend partly on the mechanical strength of the first
electrode material 1214. If the first electrode material 1214 is
unable to support the electrolyte and second electrode materials on
its own without mechanical deformation, the underlying support
material 1220 may also be required.
[0124] Once the open interconnected wall structure has been formed,
the electrolyte and second electrode material can be deposited onto
the first electrode material to form the storage cell. As with
deposition of the first electrode material onto the support
material (e.g. base substrate), CVD, ALD and ECD are particularly
useful because they can be used to coat surfaces which are not in
the line-of-sight of the material source in an evaporation or
sputtering system. It is not necessary to coat the entire surface
area of the open interconnected wall structure with the electrolyte
and second electrode material, but doing so maximises the
generation and/or storage of electrons because the first electrode
material is able to interact with a greater amount of electrolyte.
Electrochemical deposition has the advantage that the material
deposited has to be electrically connected to the base substrate
for deposition to occur. This might not be the case for ALD or
CVD.
[0125] FIG. 13 shows three, four, five and six-layer configurations
of storage cell which can be formed using the open interconnected
wall structure described herein. In the three-layer configuration
(FIG. 13a), the support material 1320 (spherical particles, block
co-polymer, sponge or base substrate) has been removed after
deposition of the first electrode material 1314, and the first 1314
and second 1323 electrode materials (which are separated by the
electrolyte 1322) each comprise an active material. The active
material is the electrode material which takes part in the
charging/discharging mechanism of the cell. If the electrical
storage apparatus is a battery, the active material is an electrode
material which participates in an electrochemical reaction or
intercalation mechanism. On the other hand, if the electrical
storage apparatus is a supercapacitor, the active material is an
electrode material which participates in the formation of an
electric double layer. As described above, removal of the support
material 1320 increases the surface area of the first 1314 and
second 1323 electrodes and reduces the overall weight of the
electrical storage apparatus.
[0126] In the four-layer configuration (FIG. 13b), however, the
support material 1320 has been retained after deposition of the
first electrode material 1314. The support material 1320 may be
required if the mechanical strength of the first electrode material
1314 on its own is insufficient to support the overlying
electrolyte 1322 and second electrode material 1323.
[0127] In the five-layer configuration (FIG. 13c), the support
material 1320 has been removed after deposition of the first
electrode material 1314, as per the configuration of FIG. 13a. This
time, however, the first 1314 and second 1323 electrode materials
each comprise a charge collection material 1324 as well as the
active material. The charge collection material provides an
electrical path between the active material of each electrode and
the external circuitry of the storage cell to enable a flow of
electrons, and may be required if the active material exhibits zero
or a relatively low electrical conductivity. In some cases, the
active material of one electrode may have a higher electrical
conductivity than the active material of the other electrode. In
this scenario, a charge collection material 1324 may only be
required in the less conductive electrode. The material used to
form the charge collector 1324 should be highly conductive.
Suitable examples include metals such as gold, silver, nickel,
copper, or an alloy comprising two or more of these metals.
Nevertheless, a semiconducting material may be used instead.
[0128] The six-layer configuration (FIG. 13d) is the same as the
five-layer configuration of FIG. 13c, except that the support
material 1320 has been retained after deposition of the first
electrode material 1314.
[0129] The first 1314 and second 1323 electrode materials are not
limited to any specific active materials, and may comprise a
variety of different elements and compounds. The same is true of
the electrolyte 1322, although the material used to form the
electrolyte 1322 will depend largely on the chemistry of the active
electrode materials.
[0130] In one embodiment, the electrical storage apparatus is a
lithium sulphur battery in which the active material of the first
electrode (anode) comprises lithium sulphide and the active
material of the second electrode (cathode) comprises sulphur. Given
that the electrical conductivity of sulphur is relatively low, it
may need to be deposited on top of a charge collection material.
The electrolyte may be a solid electrolyte such as lithium
phosphorous oxynitride (LiPON), a polymer electrolyte containing
poly(ethylene oxide) derivatives, or a polymer electrolyte
containing borate ester groups.
[0131] During discharge of a lithium-sulphur battery, the lithium
sulphide at the anode is split into lithium ions and sulphur,
releasing electrons in the process. The lithium ions then migrate
through the electrolyte to the sulphur cathode where they form
lithium sulphide. During charging, on the other hand, the lithium
sulphide at the cathode is converted back into sulphur and lithium
ions, and the lithium ions migrate back through the electrolyte to
the anode to produce lithium sulphide.
[0132] In another embodiment, the electrical storage apparatus is a
lithium-air battery in which the active material of the first
electrode (anode) comprises lithium oxide and the active material
of the second electrode (cathode) comprises porous carbon and a
metal catalyst (such as manganese, cobalt, ruthenium, platinum,
silver, or a mixture of cobalt and manganese). The electrolyte in
this embodiment may be an organic electrolyte (such as LiPF.sub.3,
LiAsFe, LiN(SO.sub.2CF.sub.3).sub.2, or LiSO.sub.3CF.sub.3), an
aqueous electrolyte (comprising a lithium salt dissolved in water),
or a combination of an organic electrolyte and an aqueous
electrolyte separated by a lithium-conducting membrane.
[0133] During discharge of the lithium-air battery, the lithium
oxide at the anode is split into lithium ions and oxygen, releasing
electrons in the process. The lithium ions then migrate through the
electrolyte to the carbon cathode where they form lithium oxide.
During charging, on the other hand, the lithium oxide at the
cathode is converted back into oxygen and lithium ions, and the
lithium ions migrate back through the electrolyte to the anode to
produce lithium oxide.
[0134] In a further embodiment, the electrical storage apparatus is
a lithium-ion battery. In this embodiment, the active material of
the first electrode (cathode) could, for example, comprise lithium
cobalt oxide, lithium iron phosphate or lithium manganese oxide;
the active material of the second electrode (anode) could comprise
graphite; and the electrolyte could comprise a lithium salt (such
as lithium hexafluorophosphate, lithium hexafluoroarsenate
monohydrate, lithium perchlorate, lithium tetrafluoroborate, or
lithium triflate) in an organic solvent (such as ethylene carbonate
or diethyl carbonate).
[0135] In yet another embodiment, the electrical storage apparatus
is a lithium-ion capacitor. In this embodiment, the active material
of the first electrode (anode) could, for example, comprise lithium
cobalt oxide, lithium iron phosphate or lithium manganese oxide;
the active material of the second electrode (cathode) could
comprise activated carbon; and the electrolyte could comprise a
lithium salt (such as lithium hexafluorophosphate, lithium
hexafluoroarsenate monohydrate, lithium perchlorate, lithium
tetrafluoroborate, or lithium triflate) in an organic solvent (such
as ethylene carbonate or diethyl carbonate).
[0136] Given that electrical storage cells (battery, capacitor or
batter-capacitor hybrid) are used to power other electronic
components in a device, the electrical characteristics (e.g.
operating current, voltage, resistance, capacitance, etc) of the
cell are an important consideration. In general, the maximum
operating voltage of a supercapacitor is limited by the breakdown
voltage of the electrolyte (1.1V for aqueous electrolytes and 2.3V
for organic electrolytes), whilst the maximum operating voltage of
a battery is limited by the active materials used in the
electrochemical reactions. In order to increase the operating
voltage, however, several cells 1425 may be connected in series
(e.g. as a stack of storage cells). As shown in FIG. 14, this may
be achieved by electrically connecting the open interconnected wall
structures to one another. The total voltage for three storage
cells connected in series is given by
V.sub.total=V.sub.1+V.sub.2+V.sub.3, where V.sub.n is the operating
voltages of the respective cells. When connected in series, the
total current is given by I.sub.total=I.sub.1=I.sub.2=I.sub.3, the
total resistance is given by R.sub.total=R.sub.1+R.sub.2+R.sub.3,
and the total capacitance (relevant for supercapacitors) is given
by C.sub.total=1C.sub.1+1/C.sub.2+1/C.sub.3, where I.sub.n, R.sub.n
and C.sub.n are the operating current, resistance and capacitance
of the respective cells.
[0137] On the other hand, several cells 1425 could be connected in
parallel (e.g. as a stack of storage cells). Again, this may be
achieved by electrically connecting the open interconnected wall
structures to one another, as shown in FIG. 15. In this
configuration, the total voltage is given by
V.sub.total=V.sub.1=V.sub.2=V.sub.3, the total current is given by
I.sub.total=I.sub.1+I.sub.2+I.sub.3, the total resistance is given
by R.sub.total=1/R.sub.1+1/R.sub.2+1/R.sub.3, and the total
capacitance (relevant for supercapacitors) is given by
C.sub.total=C.sub.1+C.sub.2+C.sub.3.
[0138] In the configurations of FIGS. 14 and 15, the individual
cells may or may not have identical chemistries. For example, in
one embodiment, each cell may be a battery or a supercapacitor,
whilst in another embodiment, one cell may be a battery and another
cell may be a supercapacitor. In the latter embodiment, the
supercapacitor may be used to provide fast bursts of power, and the
battery may be configured to charge the supercapacitor after each
discharge operation. In situations where the chemistry of one cell
is different from the chemistry of another cell, only part of the
structure may be different (i.e. the first electrode material,
electrolyte and/or second electrode material of one cell may be
different from the first electrode material, electrolyte and/or
second electrode material of another cell).
[0139] Rather than connecting the open interconnected wall
structure of one cell to the open interconnected wall structure of
another cell to form a stack of electrical storage cells, multiple
cells may be formed from a single open interconnected wall
structure (as shown in FIG. 16). This may be achieved by depositing
the first electrode material 1614, electrolyte 1622 and second
electrode material 1623 of one cell within a first pore 1639 of the
structure, and depositing the first electrode material 1614,
electrolyte 1622 and second electrode material 1623 of another cell
within a second pore 1640 of the structure. As with the
configurations of FIGS. 14 and 15, the first electrode material,
electrolyte and/or second electrode material of one cell may or may
not be the same as the first electrode material, electrolyte and/or
second electrode material of another cell. As a result, a battery
and a supercapacitor may be formed within the same open
interconnected wall structure (for example).
[0140] It will be appreciated that techniques for forming the open
interconnected wall structure have been disclosed; a block polymer
route (in particular for producing gyroid structures) and a
nanosphere lithography route. The latter route will create an opal,
or inverse opal structure. The opal, or inverse opal structures
will also achieve the end goal of a high-surface area electrode
which has electrical connectivity to a current-collector substrate.
In summary,
(1) Block Copolymer Route
[0141] The gyroid or double gyroid morphologies are typically
(only) created by the phase separation of block copolymers. In this
process a solution of the block copolymer is cast or coated onto a
substrate, and in the present case, that substrate is likely to be
a metal, and thus become the current collector of an energy storage
device. As the solvent evaporates, the block copolymer forms a
phase-separated film on the substrate. The phases are constituted
of regions of the different immiscible polymer blocks, and note
that a number of different phase-separation morphologies are
possible, depending on the relative block lengths. Many of these
morphologies (gyroid, double gyroid, hexagonal pillar array,
vertically-oriented lamellae) are likely to be useful in the
present application, namely those which have a continuous pathway
to the substrate (and thus can create structures with electrically
conducting pathways to the substrate).
[0142] Note that, at this point, the film is entirely solid (bar a
residue of solvent). In order to use the polymer structure
so-formed, removal of one of the polymer phases would be required
to leave behind the necessary porous structure. This can be
achieved by wet chemical etch, UV exposure, or a mixture of the two
depending on the polymer to be removed. This process leaves behind
a polymer scaffold, which can be used to template the materials of
interest. The methods previously discussed can be used to coat the
polymer scaffold--ALD, CVD or electrochemical deposition. The
latter technique is especially useful, since if the current
collector substrate is used as one of the deposition electrodes, it
can be assured that the deposited material is electrically
continuous to the substrate as needed. The possible disadvantage of
this method is that it may totally fill the pores, so a multilayer
coating may not so feasible.
[0143] Two strategies are now possible. The polymer scaffold
remaining can either be used as a permanent feature, or it may be
sacrificial. We can employ both approaches, but leaving the polymer
scaffold behind is not as an attractive a strategy since it is
functionally inactive and takes up useful space that might be
filled with active material. If the scaffold is to remain, it is
possible to build up layers of materials (electrode 1, solid
electrolyte, electrode 2, etc) to create the desired structure.
This approach may not be very easy if the pore diameter is very
small.
[0144] Alternatively, and advantageously, one can totally fill the
pores with an (electrode) material using one of the methods above,
then remove the scaffold to leave the electrode material, which is
in a wire-like network--the pore network. Subsequent materials
(electrolyte, second electrode, etc) may then be back filled into
the "inverse" scaffold using ALD, CVD or electrochemical
deposition.
(2) Opal Route.
[0145] As mentioned above, self-assembled crystals of polymer micro
or nanospheres are created and used to template the deposition of
the battery materials. In this case, the structure formed is a type
of opal (face-centred cubic crystal).
[0146] FIG. 17 illustrates schematically a device 1726 comprising
the electrical storage apparatus 1725 described herein. The device
1726 also comprises a processor 1727 and a storage medium 1728,
which are electrically connected to one another by a data bus 1729.
The device 1726 may be an electronic device, a portable electronic
device, a portable telecommunications device, or a module for any
of the aforementioned devices. With regard to FIGS. 5, 6, 14, 17
and 18, it will be appreciated that these show respective schematic
illustrations of an electrical storage apparatus. It will be
further appreciated that the respective anode and cathode layers
are electrically separated to avoid short-circuiting which would
occur if, for example, wires were used from the anode through the
cathode, or vice versa.
[0147] The electrical storage apparatus 1725 is configured to
generate and/or store electrical energy, which may be used to power
one or more components of the device 1726. The processor 1727 is
configured for general operation of the device 1726 by providing
signalling to, and receiving signalling from, the other device
components to manage their operation. The storage medium 1728 is
configured to store computer program code configured to perform,
control or enable operation of the electrical storage apparatus
1725. The storage medium 1728 may also be configured to store
settings for the other device components. The processor 1727 may
access the storage medium 1728 to retrieve the component settings
in order to manage operation of the device components. In
particular, the storage medium 1728 may comprise voltage settings
for charging the electrical storage apparatus 1725. The internal
connections 1729 between the processor 1727 and storage medium 1728
can be understood to provide active coupling between the processor
1727 and storage medium 1728 to allow the processor 1727 to access
the computer program code stored on the storage medium 1728. The
storage medium 1728 may be a temporary storage medium such as a
volatile random access memory. On the other hand, the storage
medium 1728 may be a permanent storage medium such as a hard disk
drive, a flash memory, or a non-volatile random access memory.
[0148] The device 1726 may also comprise a solar cell 1833
configured to convert energy from electromagnetic radiation 1841
incident upon the solar cell 1833 into electrical energy. The
electrical storage apparatus 1825 described herein may be
configured to store this energy for subsequent use. In one
embodiment, as shown in FIG. 18, the solar cell 1833 forms a
coating on the external surface of the electrical storage apparatus
1825. This configuration ensures that electromagnetic radiation
1841 incident from any angle may be converted into electrical
energy and therefore provides greater design freedom for the
arrangement of components inside the device 1726. When the
electrical storage apparatus 1825 has the configuration shown in
FIG. 6, encasing the electrical storage apparatus 1825 within the
solar cell 1833 also helps to prevent contaminant materials from
entering the pores of the open interconnected wall structure.
[0149] The main steps 1930-1931 of the method used to make the
electrical storage apparatus 1725 are illustrated schematically in
FIG. 19.
[0150] FIG. 20 illustrates schematically a computer/processor
readable medium 2032 providing a computer program according to one
embodiment. In this example, the computer/processor readable medium
2032 is a disc such as a digital versatile disc (DVD) or a compact
disc (CD). In other embodiments, the computer/processor readable
medium 2032 may be any medium that has been programmed in such a
way as to carry out an inventive function. The computer/processor
readable medium 2032 may be a removable memory device such as a
memory stick or memory card (SD, mini SD or micro SD).
[0151] The computer program may comprise computer code configured
to perform, control or enable deposition of an electrolyte and a
second electrode material into one or more pores of an open
interconnected wall structure to provide an open interconnected
wall structure comprising a first electrode material, the pores
comprising the electrolyte and the second electrode material,
wherein the electrolyte and second electrode material are supported
on the first electrode material within the pores such that the
first electrode material is separated from the second electrode
material by the electrolyte to enable the generation and/or storage
of electrical energy using the apparatus.
[0152] Other embodiments depicted in the figures have been provided
with reference numerals that correspond to similar features of
earlier described embodiments. For example, feature number 1 can
also correspond to numbers 101, 201, 301 etc. These numbered
features may appear in the figures but may not have been directly
referred to within the description of these particular embodiments.
These have still been provided in the figures to aid understanding
of the further embodiments, particularly in relation to the
features of similar earlier described embodiments.
[0153] It will be appreciated to the skilled reader that any
mentioned apparatus/device and/or other features of particular
mentioned apparatus/device/server may be provided by apparatus
arranged such that they become configured to carry out the desired
operations only when enabled, e.g. switched on, or the like. In
such cases, they may not necessarily have the appropriate software
loaded into the active memory in the non-enabled (e.g. switched off
state) and only load the appropriate software in the enabled (e.g.
on state). The apparatus may comprise hardware circuitry and/or
firmware. The apparatus may comprise software loaded onto memory.
Such software/computer programs may be recorded on the same
memory/processor/functional units and/or on one or more
memories/processors/functional units.
[0154] In some embodiments, a particular mentioned apparatus/device
may be pre-programmed with the appropriate software to carry out
desired operations, and wherein the appropriate software can be
enabled for use by a user downloading a "key", for example, to
unlock/enable the software and its associated functionality.
Advantages associated with such embodiments can include a reduced
requirement to download data when further functionality is required
for a device, and this can be useful in examples where a device is
perceived to have sufficient capacity to store such pre-programmed
software for functionality that may not be enabled by a user.
[0155] It will be appreciated that any mentioned
apparatus/circuitry/elements/processor may have other functions in
addition to the mentioned functions, and that these functions may
be performed by the same apparatus/circuitry/elements/processor.
One or more disclosed aspects may encompass the electronic
distribution of associated computer programs and computer programs
(which may be source/transport encoded) recorded on an appropriate
carrier (e.g. memory, signal).
[0156] It will be appreciated that any "computer" described herein
can comprise a collection of one or more individual
processors/processing elements that may or may not be located on
the same circuit board, or the same region/position of a circuit
board or even the same device. In some embodiments one or more of
any mentioned processors may be distributed over a plurality of
devices. The same or different processor/processing elements may
perform one or more functions described herein.
[0157] It will be appreciated that the term "signalling" may refer
to one or more signals transmitted as a series of transmitted
and/or received signals. The series of signals may comprise one,
two, three, four or even more individual signal components or
distinct signals to make up said signalling. Some or all of these
individual signals may be transmitted/received simultaneously, in
sequence, and/or such that they temporally overlap one another.
[0158] With reference to any discussion of any mentioned computer
and/or processor and memory (e.g. including ROM, CD-ROM etc), these
may comprise a computer processor, Application Specific Integrated
Circuit (ASIC), field-programmable gate array (FPGA), and/or other
hardware components that have been programmed in such a way to
carry out the inventive function.
[0159] The applicant hereby discloses in isolation each individual
feature described herein and any combination of two or more such
features, to the extent that such features or combinations are
capable of being carried out based on the present specification as
a whole, in the light of the common general knowledge of a person
skilled in the art, irrespective of whether such features or
combinations of features solve any problems disclosed herein, and
without limitation to the scope of the claims. The applicant
indicates that the disclosed aspects/embodiments may consist of any
such individual feature or combination of features. In view of the
foregoing description it will be evident to a person skilled in the
art that various modifications may be made within the scope of the
disclosure.
[0160] While there have been shown and described and pointed out
fundamental novel features as applied to different embodiments
thereof, it will be understood that various omissions and
substitutions and changes in the form and details of the devices
and methods described may be made by those skilled in the art
without departing from the spirit of the invention. For example, it
is expressly intended that all combinations of those elements
and/or method steps which perform substantially the same function
in substantially the same way to achieve the same results are
within the scope of the invention. Moreover, it should be
recognized that structures and/or elements and/or method steps
shown and/or described in connection with any disclosed form or
embodiment may be incorporated in any other disclosed or described
or suggested form or embodiment as a general matter of design
choice. Furthermore, in the claims means-plus-function clauses are
intended to cover the structures described herein as performing the
recited function and not only structural equivalents, but also
equivalent structures. Thus although a nail and a screw may not be
structural equivalents in that a nail employs a cylindrical surface
to secure wooden parts together, whereas a screw employs a helical
surface, in the environment of fastening wooden parts, a nail and a
screw may be equivalent structures.
* * * * *