U.S. patent application number 14/679393 was filed with the patent office on 2015-10-01 for high power and high energy electrodes using carbon nanotubes.
This patent application is currently assigned to FASTCAP SYSTEMS CORPORATION. The applicant listed for this patent is Nicolo Michele Brambilla, Fabrizio Martini, Riccardo Signorelli. Invention is credited to Nicolo Michele Brambilla, Fabrizio Martini, Riccardo Signorelli.
Application Number | 20150279578 14/679393 |
Document ID | / |
Family ID | 47712489 |
Filed Date | 2015-10-01 |
United States Patent
Application |
20150279578 |
Kind Code |
A1 |
Martini; Fabrizio ; et
al. |
October 1, 2015 |
High Power and High Energy Electrodes Using Carbon Nanotubes
Abstract
An electrode useful in an energy storage system, such as a
capacitor, includes an electrode that includes at least one to a
plurality of layers of compressed carbon nanotube aggregate.
Methods of fabrication are provided. The resulting electrode
exhibits superior electrical performance in terms of gravimetric
and volumetric power density.
Inventors: |
Martini; Fabrizio; (Boston,
MA) ; Brambilla; Nicolo Michele; (Brookline, MA)
; Signorelli; Riccardo; (Cambridge, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Martini; Fabrizio
Brambilla; Nicolo Michele
Signorelli; Riccardo |
Boston
Brookline
Cambridge |
MA
MA
MA |
US
US
US |
|
|
Assignee: |
FASTCAP SYSTEMS CORPORATION
Boston
MA
|
Family ID: |
47712489 |
Appl. No.: |
14/679393 |
Filed: |
April 6, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13587037 |
Aug 16, 2012 |
9001495 |
|
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14679393 |
|
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61524071 |
Aug 16, 2011 |
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Current U.S.
Class: |
361/502 ;
156/230; 156/276; 29/25.03 |
Current CPC
Class: |
H01G 11/70 20130101;
B32B 37/025 20130101; H01G 11/68 20130101; H01G 11/86 20130101;
H01G 11/28 20130101; B82Y 30/00 20130101; H01G 11/36 20130101; Y02E
60/13 20130101 |
International
Class: |
H01G 11/86 20060101
H01G011/86; H01G 11/28 20060101 H01G011/28; H01G 11/36 20060101
H01G011/36; H01G 11/68 20060101 H01G011/68 |
Goverment Interests
STATEMENT OF FEDERALLY SPONSORED RESEARCH
[0001] This invention was made with government support under grant
DE-AR0000035/0001 awarded by the Unites States Department of Energy
(ARPA-E). The United States government has certain rights in the
invention.
Claims
1-11. (canceled)
12. A method for fabricating an aligned carbon nanotube aggregate
for an electrode, the method comprising: selecting a substrate;
growing the aligned carbon nanotube aggregate onto the substrate;
and disposing a bonding layer onto the aligned carbon nanotube
aggregate following the growth thereof, wherein the bonding layer
is adapted for bonding with a current collector of the
electrode.
13. The method as in claim 12, further comprising compressing the
aligned carbon nanotubes aggregate to provide a compressed carbon
nanotube aggregate.
14. The method as in claim 12, wherein the bonding layer comprises
at least one of a combination of iron, chromium and nickel;
aluminum; gold; silver; palladium; tin; platinum and a combination
of any of the foregoing materials.
15. The method as in claim 12, further comprising treating the
aligned carbon nanotube aggregate to facilitate removal from the
substrate.
16. The method as in claim 15, wherein the treating comprises
oxidizing the carbon nanotube aggregate.
17. An ultracapacitor comprising: at least one electrode comprising
a current collector comprising at least one layer of compressed
carbon nanotubes disposed thereon.
18. The ultracapacitor as in claim 17, wherein the electrode
comprises a bonding layer disposed between the current collector
and the compressed carbon nanotubes.
19. A method for fabricating an ultracapacitor, the method
comprising: selecting an electrode comprising at least one layer of
compressed carbon nanotubes disposed thereon; and including the
electrode in the ultracapacitor.
20. The method as in claim 19, further comprising incorporating an
electrolyte in the ultracapacitor.
Description
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to producing aligned
carbon-nanotube aggregates and, in particular, to methods and
apparatus for producing carbon-nanotube aggregates.
[0004] 2. Description of the Related Art
[0005] Carbon nanotubes (hereinafter referred to also as "CNTs")
are carbon structures that exhibit a variety of properties. Many of
the properties suggest opportunities for improvements in a variety
of technology areas. These technology areas include electronic
device materials, optical materials as well as conducting and other
materials. For example, CNTs are proving to be useful for energy
storage in capacitors.
[0006] However, effective transfer of the CNTs onto a current
collector for a capacitor has proven to be challenging. Further,
techniques have not enabled transfer of CNTs in a form that will
provide for desired power capabilities.
[0007] Thus, what are needed are methods and apparatus for
production of a high power electrode based on carbon nanotubes.
Preferably, the methods and apparatus are simple to perform and
thus offer reduced cost of manufacture, as well as an improved rate
of production.
BRIEF SUMMARY OF THE INVENTION
[0008] In one embodiment, an electrode is provided. The electrode
includes a current collector that has at least one layer of
compressed carbon nanotubes disposed thereon.
[0009] In another embodiment, a method for fabricating an electrode
is provided. The method includes selecting a current collector that
has a bonding layer disposed thereon; and bonding to the bonding
layer another bonding layer including a layer of aligned carbon
nanotubes disposed thereon.
[0010] In yet another embodiment, a method for fabricating an
aligned carbon nanotube aggregate for an electrode is provided. The
method includes selecting a substrate; growing the aligned carbon
nanotube aggregate onto the substrate; and disposing a bonding
layer onto the aligned carbon nanotube aggregate following the
growth thereof, wherein the bonding layer is adapted for bonding
with a current collector of the electrode.
[0011] In a further embodiment, an ultracapacitor is provided. The
ultracapacitor includes at least one electrode comprising a current
collector that has at least one layer of compressed carbon
nanotubes disposed thereon.
[0012] In yet another embodiment, a method for fabricating an
ultracapacitor is provided. The method includes selecting an
electrode having at least one layer of compressed carbon nanotubes
disposed thereon and including the electrode in the
ultracapacitor.
BRIEF DESCRIPTION OF DRAWINGS
[0013] The foregoing and other features and advantages of the
invention are apparent from the following detailed description
taken in conjunction with the accompanying drawings in which:
[0014] FIG. 1 is a block diagram depicting a current collector and
a substrate onto which a plurality of carbon nanotubes (CNT) have
been formed;
[0015] FIG. 2 is a block diagram depicting loading the CNT of FIG.
1 onto the current collector;
[0016] FIG. 3 is a block diagram depicting the loaded current
collector of FIG. 2, as well as another substrate prepared for
transfer of additional CNT onto the loaded current collector;
[0017] FIG. 4 is a block diagram depicting loading of additional
CNT onto the loaded current collector; and
[0018] FIG. 5 is a block diagram depicting a high-power electrode
resulting from multiple transfers of CNT onto the current collector
of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0019] Disclosed are methods and apparatus for providing a
high-power electrode, where the electrode includes at least one
layer of carbon nanotube aggregate (CNT). Advantageously, the
electrode may be fabricated from mass-produced CNT and exhibits,
among other things, higher gravimetric power density (power as a
function of weight) and volumetric power density (power as a
function of volume) than previously achievable. Further, the
high-power electrode exhibits a low internal resistance and can be
fabricated to provide high voltages (of about four or more
volts).
[0020] In order to provide some context for the teachings herein,
reference is first made to U.S. Pat. No. 7,897,209, entitled
"Apparatus and Method for Producing Aligned Carbon Nanotube
Aggregate." This patent is incorporated herein by reference, in its
entirety.
[0021] The foregoing patent (the "'209 patent") teaches a process
for producing aligned carbon nanotube aggregate." Accordingly, the
teachings of the '209 patent, which are but one example of
techniques for producing aligned carbon nanotube aggregate, may be
used to produce carbon nanotube aggregate (CNT) referred to
herein.
[0022] One example of a device incorporating an electrode as
provided herein is provided in U.S. Patent Application Publication
No. 2007-0258192, entitled "Engineered Structure for Charge Storage
and Method of Making," also incorporated herein by reference, in
its entirety. In general, methods and apparatus disclosed herein
may be used to enhance an energy storage system, such as the
embodiments disclosed in this publication. One embodiment of such
energy storage is referred to as an "ultracapacitor." However, it
should be recognized that the teachings herein may be applicable to
other embodiments of energy storage and are therefore not limited
to practice with an ultracapacitor.
[0023] Referring now to FIG. 1, there is a shown a first component,
a current collector 2. Generally, the current collector 2 includes
a conductor layer 3, and may include a bonding layer 4. The
conductor layer 3 may be fabricated from any material suited for
conducting charge in the intended application. An exemplary
material includes aluminum. The conductor layer 3 may be presented
as a foil, a mesh, a plurality of wires or in other forms.
Generally, the conductor layer 3 is selected for properties such as
conductivity and being electrochemically inert.
[0024] In some embodiments, the conductor layer 3 is prepared by
removing an oxide layer thereon. The oxide may be removed by, for
example, etching the conductor layer 3 with KOH.
[0025] In some embodiments, a bonding layer 4 is disposed on the
conducting layer 3. The bonding layer 4 may appear as a thin layer,
such as layer that is applied by sputtering, e-beam or through
another suitable technique. In various embodiments, the bonding
layer 4 is between about 1 nm to about 100 nm. Generally, the
bonding layer 4 is selected for its properties such as
conductivity, being electrochemically inert and compatibility with
the material of the conductor layer 3. Some exemplary materials
include aluminum, gold, silver, palladium, titanium, tin and
platinum as well as alloys or in combinations of materials, such as
Fe--Cr--Ni.
[0026] A second component includes a substrate 8 that is host to
the carbon nanotube aggregate (CNT) 10. Some exemplary techniques
for providing the CNT 10 are provided in the '209 patent. In the
embodiment shown in FIG. 1, the substrate 8 includes a base
material 6 with a thin layer of a catalyst 7 disposed thereon.
[0027] In general, the substrate 8 is at least somewhat flexible
(i.e., the substrate 8 is not brittle), and is fabricated from
components that can withstand environments for deposition of the
CNT 10 (e.g., a high-temperature environment of between about 400
degrees Celsius to about 1,100 degrees Celsius).
[0028] Once the CNT 10 have been fabricated, another bonding layer
4 is disposed thereon. In some embodiments, the another bonding
layer 4 is between about 10 nm to 1,000 nm thick. Subsequently, the
bonding layer 4 of the current collector 2 is mated with the
another bonding layer 4 disposed over the CNT 10, as shown in FIG.
2.
[0029] FIG. 2 illustrates aspects of mating the CNT 10 with the
current collector 2. As implied by the downward arrows, pressure is
applied onto the base material 6. The application of the CNT 10 may
be accompanied by heating of the components. As an example, when
platinum is used in the bonding layers 4, heating to between about
200 degrees Celsius to about 250 degrees Celsius is generally
adequate. Subsequently, the CNT 10 and the catalyst 7 are
separated, with a resulting layer of CNT 10 disposed onto the
current collector 2.
[0030] Various post-manufacture processes may be completed to
encourage separation of the CNT 10 from the catalyst 7. For
example, following completion of deposition, the substrate 8
including the CNT 10 thereon may be exposed to (e.g., heated in) an
environment of room air, carbon dioxide or another oxidative
environment. Generally, the post-manufacture treatment of the CNT
10 includes slowly ramping the CNT 10 to an elevated temperature,
and then maintaining the CNT 10 at temperature for a few hours at a
reduced pressure (i.e., below 1 atmosphere).
[0031] As shown in FIG. 3, the process of transferring the CNT 10
onto the current collector 2 with the addition of pressure results
in a layer of compressed CNT 12. The compressed CNT 12, which now
include physical defects, such as windows and cracks, generally
provide more surface area for charge storage, while in a smaller
volume than the uncompressed CNT 10. Also shown in FIG. 3, is the
addition of another layer of CNT 10.
[0032] As shown in FIG. 4, the another layer of CNT 10 may be
applied over the compressed CNT 12. In some embodiments, this
process involves applying a nominal amount of pressure (such as by
hand). Generally, it is considered that the another layer of CNT 10
is transferred to (i.e., adheres to) the compressed CNT 12 by the
Van der Waals forces between the carbon nanotubes. Advantageously,
this results in another layer of compressed CNT 12 (i.e., another
thickness of compressed CNT 12) on the current collector 2.
[0033] The process may be repeated to provide a plurality of
thicknesses of compressed CNT 12 on the current collector 2. In
general, however, it is expected that certain practical limitations
will be realized. That is, for example, compounding defects in
transfer of each layer may result in a layer of compressed CNT 12
that does not exhibit desired performance for charge storage.
However, it is also expected that as transfer protocols continue to
improve, that the addition of an ever greater number of layers will
be possible.
[0034] Accordingly, the current collector 2 with at least one layer
of compressed CNT 12 to a plurality of layers of compressed CNT 12
disposed thereon may be used as a charge storage device (i.e., a
high-power electrode). Generally, such embodiments of the
high-power electrode are particularly well adapted for use in a
capacitor, or an ultracapacitor. In addition to some of the
foregoing mentioned advantages (higher gravimetric and volumetric
power densities, low internal resistance and high voltage
delivery), less electrolyte is required. Thus, users are provided
with an improved performance energy storage that is less expensive
to manufacture.
[0035] In other embodiments, consideration may be given to the
particular properties of the base material 6, the catalyst 7, the
conductor layer 3 and the bonding layers 4. That is, for example,
if the foregoing fabrication is completed in a substantially
oxygen-free environment, it is expected that other materials and
processes may be used (or omitted) to provide for the current
collector 2 with at least one layer of compressed CNT 12 to a
plurality of layers of compressed CNT 12. Accordingly, these and
other embodiments as may be devised by one skilled in the art are
within the ambit of the invention and the teachings herein.
[0036] In further embodiments, at least one other layer may be
included. For example, an ohmic contact layer may be included, and
provided to enhance ohmic contact between the another bonding layer
4, the compressed CNT 12 (which also may be referred to as an
"energy storage layer," an "active layer" and by other similar
terms) or another layer. In another example, an adhesion layer may
be included, and provided to enhance adhesion between the another
bonding layer 4 and the compressed CNT 12, or another layer.
Materials in the additional or optional layers may be chosen
according to at least one property, such as electrical
conductivity, compatibility and the like.
[0037] With regard to the ohmic contact layer, the ohmic contact
layer may be useful for achieving an ohmic contact with the
carbonaceous layer. If the ohmic contact layer will be exposed to
the electrolyte in which the electrode will ultimately be immersed
(such as through a porous carbonaceous layer), the ohmic contact
layer material should be chosen for good electric compliance,
usually a suitably low reaction rate, with that particular
embodiment of electrolyte. The ohmic contact layer may be deposited
onto the carbonaceous layer using magnetron sputtering, thermal
evaporation, or a similar process. Exemplary materials that may be
used in the ohmic contact layer are aluminum (Al), tantalum (Ta),
and platinum (Pt). In general, a thickness of this ohmic contact
layer varies in the range of from about 1 nm to about 10 .mu.m.
[0038] With regard to the "adhesion layer," this layer may be used
to improve adhesion between the current collector 2 and another
layer. The adhesion layer may be deposited onto the current
collector 2 using magnetron sputtering or a similar process.
Typical materials included in the adhesion layer are titanium (Ti),
chromium (Cr), titanium-tungsten (Ti--W) or a combination of those
materials. If the conductivity of the material making up the
adhesion layer is relatively low, then its thickness should be
limited to achieve suitable current handling performance. In
general, a thickness of this adhesion layer varies between about 1
nanometer (nm) and about 100 (nm).
[0039] Having disclosed aspects of embodiments of the production
apparatus and techniques for fabricating aggregates of carbon
nanotubes, it should be recognized that a variety of embodiments
may be realized. Further a variety of techniques of fabrication may
be practiced. For example, steps of fabrication may be adjusted, as
well as techniques for joining, materials and chemicals used and
the like.
[0040] As a matter of convention, it should be considered that the
terms "may" as used herein is to be construed as optional;
"includes," "has" and "having" are to be construed as not excluding
other options (i.e., steps, materials, components, compositions,
etc., . . . ); "should" does not imply a requirement, rather merely
an occasional or situational preference. Other similar terminology
is likewise used in a generally conventional manner.
[0041] While the invention has been described with reference to
exemplary embodiments, it will be understood that various changes
may be made and equivalents may be substituted for elements thereof
without departing from the scope of the invention. For example, in
some embodiments, one of the foregoing layers may include a
plurality of layers there within. In addition, many modifications
will be appreciated to adapt a particular instrument, situation or
material to the teachings of the invention without departing from
the essential scope thereof. Therefore, it is intended that the
invention not be limited to the particular embodiment disclosed as
the best mode contemplated for carrying out this invention, but
that the invention will include all embodiments falling within the
scope of the appended claims.
* * * * *