Carbon nanotube (CNT)-metal composite product and production method thereof

Abstract

The present invention provides carbon nanotube (CNT)-polymer-metal composite substrate products, each of which includes a first current collector comprising at least one carbon nanotube (CNT) mat and a highly conductive metal element electrically connected to a first terminal tab, the highly conductive metal element being bonded to at least one carbon nanotube mat, and optionally including a second current collector comprising a metal conductive element electrically connected to a second terminal tab, an insulating material separating the first and second current collectors, an electrolyte solution disposed between the first and second current collectors, and a housing configured to accommodate the first current collector, the second current collector, the insulating material, the electrolyte solution, and an active material.

Description

Technical Field

[0001] The present invention relates generally to carbon nanotube-metal composite products and methods of producing the same, and more particularly to methods and apparatus for efficiently collecting electrical current using CNT-metal composite substrates. Background Art

[0002] Many designs of power devices are inefficient in terms of electrode weight and energy supply per unit weight.

[0003] Efforts have been made to improve the design of power sources such as batteries, capacitors, and fuel cells, as well as non-energy storage devices such as electrochemical synthesis cells, electronic shielding units, heating elements, and lightning rods. However, many commercially available systems remain inefficient.

[0004] Thus, there remains an unmet need for improved efficiency of power sources and non-energy storage devices. Summary of the Invention

[0005] An object of the present invention is to provide an improved carbon nanotube (CNT)-metal composite substrate.

[0006] In some other embodiments of the present invention, improved products comprising CNT-metal composite substrates are provided.

[0007] In other embodiments of the present invention, weight-reduced products comprising a CNT-metal composite substrate are provided.

[0008] In some additional embodiments of the present invention, improved products comprising CNT-metal composite substrates for current collection are provided.

[0009] In yet other embodiments of the present invention, improved products are provided that include composite materials of lightweight, electrically conductive, thin substrates having relatively high tensile strength.

[0010] In some additional embodiments of the present invention, reduced weight products including CNT-metal composite substrates for current collection are provided.

[0011] In some additional embodiments of the present invention, improved methods for producing products comprising CNT-metal composite substrates are provided.

[0012] In some additional embodiments of the present invention, improved methods for producing products comprising CNT metal composite substrates for current collection are provided.

[0013] It is an object of some aspects of the present invention to provide methods and apparatus with efficient current collection.

[0014] In some embodiments of the present invention, improved methods and apparatus are provided for reducing weight and performing efficient current collection.

[0015] In other embodiments of the present invention, methods and systems for providing efficient current collection are described.

[0016] In further embodiments of the present invention, methods and apparatus for low weight, high efficiency current collection are provided.

[0017] The present invention provides an apparatus and method for providing power, the apparatus comprising: a first current collector comprising at least one carbon nanotube (CNT) mat; and a highly conductive metal element electrically connected to the first terminal tab, the highly conductive metal element being bonded to the at least one carbon nanotube mat; a second current collector comprising a metal conductive element electrically connected to the second terminal tab, an insulating material separating the first current collector and the second current collector, an electrolyte solution disposed between the first current collector and the second current collector, and a housing configured to accommodate the first current collector, the second current collector, the insulating material, and the electrolyte solution.

[0018] The present invention further provides carbon nanotube (CNT) metal composite substrate products, each product including a first current collector, the first current collector including at least one carbon nanotube (CNT) mat, a first active material, and a highly conductive metal element electrically connected to a first terminal tab, the highly conductive metal element being combined with at least one carbon nanotube mat, and optionally including a second current collector, the second current collector including a metal conductive element electrically connected to a second terminal tab, an insulating material separating the first current collector and the second current collector, an electrolyte solution disposed between the first current collector and the second current collector, and a shell configured to accommodate the first current collector, the second current collector, the insulating material, the electrolyte solution, and the active material.

[0019] According to some embodiments of the present invention, the apparatus is a non-energy storage device selected from the group consisting of an electrochemical synthesis cell, an electronic shielding unit, an EMI (electromagnetic interference) device or apparatus, a heating element, and a lightning rod.

[0020] According to some further embodiments of the present invention, the CNT metal products of the present invention are used as termination elements for electrically connecting a device to an external electrical component.

[0021] According to other embodiments of the present invention, the CNT-metal products of the present invention can be used in many practical applications. One non-limiting example is use in CNT-metal joining techniques such as brazing, welding, soldering, and other joining methods.

[0022] Therefore, according to an embodiment of the present invention, there is provided an apparatus for providing power, the apparatus comprising:

[0023] a first current collector having a resistivity between 1-20mohm / sq, the first current collector comprising;

[0024] i. at least one carbon nanotube (CNT) mat; and

[0025] ii. a highly conductive metal element comprising at least a first metal electrically connected to a first tab, the highly conductive metal element being combined with the at least one carbon nanotube mat;

[0026] b. a second current collector comprising a metal conductive element comprising a second metal electrically connected to a second terminal tab;

[0027] c. a separator material separated between the first current collector and the second current collector;

[0028] d. an electrolyte solution disposed between the first current collector and the second current collector; and

[0029] e. A housing configured to accommodate the first current collector, the second current collector, a separator, and an electrolyte solution.

[0030] Therefore, according to another embodiment of the present invention, there is provided an apparatus for providing power, the apparatus comprising:

[0031] a first current collector having a resistivity between 1 -20mohm / sq, the first current collector comprising;

[0032] i. at least one carbon nanotube (CNT) mat;

[0033] ii. A highly conductive metal element having a density of at least 4 g / cm2 electrically connected to at least the first terminal. 3 a first metal of a highly conductive metal element bonded to at least one carbon nanotube mat;

[0034] iii. a first active material;

[0035] b. a second current collector comprising a metal conductive element comprising a second metal electrically connected to a second tab and a second active material;

[0036] c. a separator material separated between the first current collector and the second current collector;

[0037] d. an electrolyte solution disposed between the first current collector and the second current collector; and

[0038] e. A housing configured to house the first current collector, the second current collector, a separator, and an electrolyte solution.

[0039] Therefore, according to an embodiment of the present invention, there is provided an apparatus for providing power, the apparatus comprising:

[0040] a first current collector having a resistivity between 1-20mohm / sq, the first current collector comprising;

[0041] i. at least one carbon nanotube (CNT) mat; and

[0042] ii. A highly conductive metal element having a density greater than 4 g / cm2 and electrically connected to at least the first terminal. 3 a first metal, said highly conductive metal element being bonded to at least one carbon nanotube mat;

[0043] b. A second current collector comprising a metal conductive element having a density of less than 4 g / cm2 and electrically connected to at least the second terminal tab. 3 the second metal;

[0044] c. a separator material separated between the first current collector and the second current collector;

[0045] d. an electrolyte solution disposed between the first current collector and the second current collector; and

[0046] e. A housing configured to house the first current collector, the second current collector, a separator, and an electrolyte solution.

[0047] In addition, according to an embodiment of the present invention, the average weight per unit area of ​​the first current collector is 1 to 4 mg / cm 2 .

[0048] Furthermore, according to embodiments of the present invention, the highly conductive metal element comprises copper. Alternatively or alternatively, it may comprise nickel. In other devices other than LIBs and other battery types, the anode may be other metals.

[0049] Furthermore, according to an embodiment of the present invention, the copper is in the form of a perforated foil.

[0050] Furthermore, according to an embodiment of the present invention, the at least one carbon nanotube (CNT) mat includes two carbon nanotube (CNT) mats.

[0051] Still further, according to embodiments of the present invention, a highly conductive metal element is sandwiched between two carbon nanotube (CNT) mats or combined with only one CNT mat.

[0052] Additionally, according to an embodiment of the present invention, the device further comprises an active material coated / applied to at least one of the mats.

[0053] Furthermore, according to an embodiment of the present invention, the device is a power source selected from a battery, a capacitor, and a fuel cell.

[0054] According to some embodiments of the invention, the battery is a lithium-ion battery.

[0055] Furthermore, according to an embodiment of the present invention, the second current collector includes at least one of aluminum, graphite, silicon, phosphate, lithium, oxide, and a combination thereof.

[0056] Additionally, according to embodiments of the present invention, the device is configured to provide energy per unit weight of about 50 Wh / kg to 150 Wh / kg or up to 800 Wh / kg.

[0057] Furthermore, according to an embodiment of the present invention, the apparatus is configured to provide a power per unit weight of about 200 W / kg to 5 kW / kg.

[0058] Therefore, according to another embodiment of the present invention, there is provided an apparatus for providing power, the apparatus comprising:

[0059] a first current collector having a resistivity between 1 -20mohm / sq, the first current collector comprising;

[0060] i. at least one carbon nanotube (CNT) mat or substrate; and

[0061] ii. A highly conductive metal element having a density greater than 4 g / cm2 and electrically connected to at least the first terminal. 3 a first metal, said highly conductive metal element being bonded to at least one carbon nanotube mat;

[0062] b. A second current collector having a resistivity in the range of 1 to 20 mohm / sq, wherein the first current collector comprises:

[0063] i. at least one carbon nanotube (CNT) mat or substrate; and

[0064] ii. A highly conductive metal element having a density of at least 4 g / cm2 electrically connected to the first terminal. 3 a second metal of the highly conductive metal element, the highly conductive metal element being bonded to at least one carbon nanotube mat;

[0065] c. a separator material separated between the first current collector and the second current collector;

[0066] d. an electrolyte solution disposed between the first current collector and the second current collector; and

[0067] e. A housing configured to house the first current collector, the second current collector, a separator, and an electrolyte solution.

[0068] Therefore, according to another embodiment of the present invention, there is provided a method for manufacturing an apparatus for providing at least one of power and energy, the method comprising:

[0069] a. Forming a first current collector having a resistivity between 1 and 20 mohm / sq, comprising:

[0070] 1. combining at least one carbon nanotube (CNT) mat with a highly conductive metal element electrically connected to a first tab;

[0071] 2. coating / applying at least one carbon nanotube (CNT) mat with an active material;

[0072] b. Preparing a second current collector comprising a metal conductive element electrically connected to a second tab and coating the second current collector with an active material;

[0073] c. A separator disposed between the first current collector and the second current collector.

[0074] d. introducing the first current collector, the second current collector and the insulating material into the housing; and

[0075] e. Adding an electrolyte solution between the first current collector and the second current collector to form the device.

[0076] Additionally, according to an embodiment of the present invention, the forming step is selected from a sandwich method and a physical vapor deposition (PVD) method.

[0077] Additionally, according to one embodiment of the present invention, the bonding step includes methods such as, but not limited to, physical methods, chemical methods, gluing, electrical methods, and non-electrical methods.

[0078] Furthermore, according to an embodiment of the present invention, the apparatus is a non-energy storage device selected from the group consisting of an electrochemical synthesis cell, an electronic shielding unit, a heating element, and a lightning rod.

[0079] Importantly, according to embodiments of the present invention, the method further comprises treating at least one of the carbon nanotube (CNT) mat to reduce at least one of its porosity or wettability, or to increase its oleophobicity (oil repellency).

[0080] Additionally, according to an embodiment of the present invention, the method further comprises treating at least one carbon nanotube (CNT) mat with a polymer impregnation to reduce its porosity.

[0081] Additionally, according to one embodiment of the present invention, the method further comprises treating at least one carbon nanotube (CNT) mat by impregnation with a polymer to improve its physical properties.

[0082] Additionally, according to an embodiment of the present invention, the method further comprises treating at least one carbon nanotube (CNT) mat by impregnation with a polymer to electrically insulate the carbon nanotube mat.

[0083] Additionally, according to one embodiment of the present invention, the treating step comprises heating at least one carbon nanotube (CNT) mat or substrate to a temperature above 300° C. for at least 30 minutes in air, or to at least 400° C. in air or any other suitable oxidizing environment.

[0084] Furthermore, according to one embodiment of the present invention, the heating in air step comprises heating the at least one carbon nanotube (CNT) mat to a temperature of about 450° C. for about one hour.

[0085] Still further, according to an embodiment of the present invention, a highly conductive metal element is disposed between two carbon nanotube (CNT) mats.

[0086] Furthermore, according to an embodiment of the present invention, there is provided an electromagnetic interference (EMI) shielding apparatus including at least one current collector and at least one conductive metal element.

[0087] The present invention can be more fully understood through the following detailed description of the preferred embodiments in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] The present invention will now be described in conjunction with certain preferred embodiments with reference to the following illustrative drawings so that it may be more fully understood.

[0089] With specific reference now to the drawings, it is emphasized that the details shown are exemplary only and are presented only for the purpose of illustrative discussion of the preferred embodiments of the invention and for the purpose of providing what is believed to be the most useful and easily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a basic understanding of the invention, and the description taken in conjunction with the drawings will make it apparent to those skilled in the art as to how the invention may be embodied in several forms in practice.

[0090] In the figure:

[0091] Figure 1A is a simplified diagram of a typical weight distribution of components of a prior art energy battery;

[0092] Figure 1B is a simplified diagram of a typical weight distribution of components of a prior art power battery;

[0093] Figure 2A is prepared according to an embodiment of the present invention Figure 5A A simplified flow chart of the main steps in the method of carbon nanotube-copper composite sandwich current collector;

[0094] Figure 2B is prepared according to an embodiment of the present invention Figure 5BA simplified flow chart of the main steps in the method of carbon nanotube-copper PVD coated current collector;

[0095] Figure 3A is a simplified schematic diagram of an electrode according to an embodiment of the present invention;

[0096] Figure 3B is an image of a carbon nanotube (CNT) mat according to an embodiment of the present invention;

[0097] Figure 4 A-4D are simplified schematic diagrams of carbon nanotube (CNT) mats according to some embodiments of the present invention - (a) CNT mat (raw); (b) 3D polymer-impregnated CNT mat; (c) skinned CNT mat impregnated with polymer; (d) CNT mat with skin;

[0098] Figure 5A and 5B are simplified schematic diagrams of two methods for making current collectors according to embodiments of the present invention;

[0099] Figure 6A An image showing a perforated thin copper foil of a current collector according to an embodiment of the present invention;

[0100] Figure 6B shows a CNT mat strip bonded to a perforated copper foil of an electrode according to an embodiment of the present invention;

[0101] Figure 6C The negative electrode active material coated with the electrode according to the embodiment of the present invention is shown. Figure 7 strips;

[0102] Figure 7 A plurality of anodes according to an embodiment of the present invention are shown, each anode having a Figure 6B The lugs cut from the strips;

[0103] Figure 8 shows a PVD-copper coated CNT mat of an electrode according to an embodiment of the present invention;

[0104] Figure 9 Graph showing the forming capability of CNTs impregnated with a polymer current collector compared to pristine CNTs and Cu foil-based current collectors according to embodiments of the present invention;

[0105] Figure 10A is a simplified schematic diagram of a device having at least one CNT element ultrasonically welded to a copper foil termination support along one side of an electrode in accordance with an embodiment of the present invention;

[0106] Figure 10Bis a simplified diagram of a device having at least one CNT element ultrasonically welded to copper foil termination legs in accordance with an embodiment of the present invention; and

[0107] Figure 11 is a simplified graph comparing the attenuation of electromagnetic fields as a function of electromagnetic frequency for an EMI shielding device of the present invention according to an embodiment of the present invention compared to a standard prior art device.

[0108] Like reference numerals refer to like parts throughout the drawings. DETAILED DESCRIPTION

[0109] In the detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, those skilled in the art will appreciate that these are specific embodiments and that the present invention may be practiced in various ways that embody the features of the present invention described and claimed herein.

[0110] In some other embodiments of the present invention, improved products comprising CNT-based substrates are provided.

[0111] In some other embodiments of the present invention, weight-reduced products comprising CNT-based substrates are provided.

[0112] In some additional embodiments of the present invention, improved products comprising CNT-based substrates for current collection are provided.

[0113] In some additional embodiments of the present invention, reduced weight products comprising CNT-based substrates for current collection are provided.

[0114] In some additional embodiments of the present invention, improved methods for producing products comprising CNT-based substrates are provided.

[0115] The present invention discloses a novel current collector based on a CNT (carbon nanotube) mat, which is suitable for use in power sources such as batteries, capacitors, and fuel cells, as well as in non-energy storage devices such as electrochemical synthesis cells, electronic shielding units, heating elements, and lightning rods. For example, in battery systems, the novel current collector can reduce weight and cost compared to conventional systems, and it is noted that reducing weight directly increases energy per unit weight.

[0116] Although not intended to be limiting, the present invention is described with reference to primary and / or rechargeable lithium ion batteries (LIB or LB), and the present invention can be applied to other battery / electrode types or any of the above devices. A typical lithium ion battery includes a lithium negative electrode (anode) and a positive electrode (cathode), typically an oxide or phosphate. The negative electrode (anode) is composed of graphite, silicon or other lithium-based intercalation active materials or metallic lithium, supported on a copper current collector, typically a foil or mesh. The positive electrode (cathode) is typically composed of an oxide or phosphate-based active material supported on an aluminum current collector.

[0117] Active materials are materials deposited on the current collector that provide chemical energy and discharge (other materials are inert).

[0118] For the anode, the active material can be lithium, graphite, Si or any other anode material. The cathode active material can be a metal oxide or phosphate.

[0119] The negative and positive electrodes are wrapped with a separator, wound or layered into a jelly roll or stack, and then inserted into a container, such as a cylindrical, prismatic, or pouch-shaped container. Typically, the electrodes are tabbed to provide external contacts, and the electrolyte is added to the cell and electrochemically formed. The cell is then sealed.

[0120] For energy or power optimization of a battery, the current sinking capability of the current collector is crucial. For electric vehicle / hybrid applications using, for example, lithium-iron phosphate chemistry, the energy cell will have a high energy per unit weight of approximately 150 Wh / kg and a power per unit weight of only 200 W / kg.

[0121] In contrast, a power cell of this type with the same chemistry would achieve a power level of 5kW / kg, but would only have an energy per unit weight of 50Wh / kg. In practice, with this type of power cell, the active material is often a thick layer on a supporting foil, whereas in a power cell, the active material is a thin layer on a supporting foil. The figure below provides a weight breakdown for power cells and power cells.

[0122] Now refer to Figure 1A , which is a diagram of typical weight distribution of components of a prior art energy cell. It can be seen that in an energy cell, the copper (anode) current collector only accounts for 7% of the cell weight, which is an acceptable figure.

[0123] Go to Figure 1B , a graph showing the typical weight distribution of components in a conventional power battery. It can be seen that the copper current collector (anode) accounts for as much as 23% of the battery's weight, a figure that is excessively high and also affects product cost. Typical copper current collector thickness in conventional batteries is 8-20 microns.

[0124] Figure 2A is prepared according to an embodiment of the present invention Figure 5A A simplified flow chart 200 of the main steps in a method for preparing a carbon nanotube-copper composite sandwich current collector.

[0125] In step 202 of producing one or more carbon nanotube (CNT) mats, several gaseous components are injected into a reactor. The reactor is in a furnace within a temperature range of 900-1200 degrees Celsius. The pressure range in the ceramic tube reactor is between 0.5-1 bar gauge. The gaseous component includes a carbon source, which is gaseous under the above conditions, such as, but not limited to, gases such as methane, ethane, propane, butane, saturated and unsaturated hydrocarbons and combinations thereof. Another gaseous component is a catalyst or catalyst precursor, such as ferrocene. Carrier gases such as helium, hydrogen, nitrogen and combinations thereof are typically used. In some cases, this process is defined as a floating catalyst CVD (chemical vapor deposition) process.

[0126] Without being bound by any particular theory, the catalyst lowers the activation energy for extracting carbon atoms from the gas, and carbon nanotubes begin to nucleate on top of the catalyst, which may be in the form of nanoparticles. Further into the tubular reactor, the CNTs are elongated and this process continues until a critical mass forms in the form of an aerogel-like substance, which is discharged from the reactor. The aerogel-like substance is collected on a rotating drum that moves from side to side. The rotation speed of the drum, as well as other process conditions and duration, determine the final thickness and properties of the carbon nanotube mat. Typical thicknesses of CNT mats range from 10 to 150 microns.

[0127] At least one thermoplastic organic polymer is used in the step 204 of impregnating the CNT mat with a polymer. Some non-limiting examples of these polymers are sodium carboxymethylcellulose (NaCMC), polyvinylidene fluoride (PVDF), PVA, PVP, and combinations thereof.

[0128] The impregnation step can be performed by one or more methods known in the art, such as, but not limited to, polymer deposition, polymer dip coating, polymerization on a CNT mat, polymer formation, or any other method known in the art. The impregnation step typically deposits an additional 1-50 microns, 3-30 microns, or 4-15 microns of polymer. This polymer increases the tensile strength of the CNTs (see Table 4 below).

[0129] In step 206 of preparing perforated copper foil, a copper foil having a thickness of 5-30 microns, 6-25 microns, or 8-20 microns is obtained. The perforations are typically circular. The perforations may be formed by any one or more methods known in the art, such as, but not limited to, stamping, laser cutting, chemical or physical etching, etc. The percentage of area removed is typically between 10-90%, 20-80%, 30-70%, or 40-60%. The perforations may have other shapes and forms, such as rectangular, square, triangular, irregular, and combinations thereof. In some cases, one or more edges of the perforated copper foil are not perforated, sometimes for overlapping purposes, see Figure 6A .

[0130] During the process of forming the sandwich of two CNT-polymer mats and perforated copper foil between step 208, the perforated copper foil is placed between the two CNT-polymer mats with the border / edge of the remaining copper foil being (606, 608, Figure 6A ) protrudes beyond the coverage of the CNT polymer mat ( Figure 5A ). These layers can be pressed, bonded, or glued together by any suitable method known in the art.

[0131] Now refer to Figure 2B , Figure 2B is prepared according to an embodiment of the present invention Figure 5B A simplified flow chart 250 of the major steps in a method of producing a carbon nanotube-copper PVD coated current collector.

[0132] In step 252 of producing one or more carbon nanotube (CNT) mats, several gaseous components are injected into a reactor. The reactor is in a furnace within a temperature range of 900-1200 degrees Celsius. The pressure range in the ceramic tube reactor is between 0.5-1 bar gauge. The gaseous component includes a carbon source, which is gaseous under the above conditions, such as, but not limited to, gases such as methane, ethane, propane, butane, saturated and unsaturated hydrocarbons and combinations thereof. Another gaseous component is a catalyst or catalyst precursor, such as ferrocene. Carrier gases such as helium, hydrogen, nitrogen and combinations thereof are typically used. In some cases, this process is defined as a floating catalyst CVD (chemical vapor deposition) process.

[0133] Without being bound by any particular theory, the catalyst lowers the activation energy for extracting carbon atoms from the gas, and carbon nanotubes begin to nucleate on top of the catalyst, which can be in the form of nanoparticles. Further into the tubular reactor, the CNTs are elongated and continue to elongate until a critical mass forms in the form of an aerogel-like substance, which exits the reactor. The aerogel-like substance is collected on a rotating drum that moves from side to side. The rotation speed of the drum, as well as other process conditions and duration, determine the final thickness and properties of the carbon nanotube mat. Typical thicknesses of CNT mats range from 10 to 150 microns.

[0134] At least one thermoplastic organic polymer is used in the step 254 of impregnating the CNT mat with a polymer. Some non-limiting examples of these polymers are sodium carboxymethylcellulose (NaCMC), polyvinylidene fluoride (PVDF), PVA, PVP, and combinations thereof.

[0135] The impregnation step can be performed by one or more methods known in the art, such as, but not limited to, polymer deposition, polymer deep coating, polymerization on the CNT mat, polymer formation, or any other method known in the art. The impregnation step typically deposits an additional 1-50 micron, 3-30 micron, or 4-15 micron of polymer. This polymer improves the tensile strength of the CNTs (see Table 4 below).

[0136] In the CNT-polymer mat metallization step 256, the CNT mat receives copper deposition on both sides or one side by any one or more suitable methods known in the art, such as PVD, CVD, electrolytic coating, electroless plating, and the like, and combinations thereof. The thickness of the deposited copper is typically in the range of 10 nm to 50 microns, 30 nm to 30 microns, 40 nm to 15 microns, or 100 nm to 10 microns.

[0137] According to some embodiments of the present invention, polymers are impregnated into the CNT mat to reduce or eliminate parasitic reactions between the electrolyte and the high surface area of ​​the CNT fibers.

[0138] Apply polymer to CNTs before metal coating / application:

[0139] 1. The application of polymer can be done in a variety of ways, including impregnation, step polymerization, dip coating, lamination, etc. The purpose of these application techniques is to form electrical insulation between the CNT mat and the coating metal to reduce parasitic reactions during battery function, including, for example, electrolyte reduction.

[0140] The following development steps can be performed in two ways:

[0141] (a) Impregnation of polymer into 3D CNT mat (before metallization) to eliminate electrolyte penetration and contact with CNTs

[0142] (b) Formation of a "perfect" polymer "skin" on the outer surface of the CNTs. This skin should eliminate any electrical contact between the metal layer deposited on the skin and the CNTs. In this case, the electrolyte will penetrate into the CNT mat, but since the CNTs are electrically insulating, no electrolyte reduction process will occur on the CNTs. Both methods are Figure 4 This is schematically illustrated in A-4D.

[0143] It should be understood that these flowcharts and figures are illustrative and should not be considered limiting. The order of some steps may be changed. Some steps may not be performed. Figure 2A and 2B Some or all of may be combined in various combinations and permutations.

[0144] Now refer to Figure 3A , which is a simplified schematic diagram of an electrode 300 according to an embodiment of the present invention.

[0145] The inventors have discovered that CNT woven or nonwoven mat fiber agglomerates, the subject of U.S. Patent 7,323,157, provide the basis for an improved negative electrode current collector (anode) 300. This CNT mat is strong and freestanding, comprising aggregates of interlocking fine CNT fibers 5-7 nm in diameter and typically at least several hundred microns in length, produced in a high temperature continuous fiber web process without a binder material. The lack of a binder material is important to ensure purity and electrochemical stability. The mat is typically 10-20 microns thick and has a density of 5-10 gr / m 2 , porosity is 75%. Thickness and porosity can be adjusted according to process conditions.

[0146] An electrode substrate current collector 304 is provided between the two CNT mats 302 and 306 .

[0147] Figure 3B is an image 350 of a carbon nanotube (CNT) mat according to an embodiment of the present invention.

[0148] However, experiments based on building and testing the current-voltage characteristics of batteries have shown that if a CNT mat current collector is used alone to support the negative electrode active material, its resistance is too high to compete with a standard copper foil current collector in terms of current-drawing capability. It should be noted that for some applications, such as very long-duration discharge batteries (low-rate discharge batteries) or electronic shielding, a CNT mat alone is sufficient (with a high resistivity value).

[0149] There is also the technical problem of bonding to the mat since common, convenient techniques such as spot welding or ultrasonic welding to metal contacts are not applicable to individual CNTs.

[0150] Now refer to Figure 4 A-4D, Figure 4 A-4D are simplified schematic diagrams of carbon nanotube (CNT) mats according to some embodiments of the present invention - (a) CNT mat without polymer (original) 410; (b) three-dimensional (3D) polymer-impregnated CNT mat (no skin), 420; (c) CNT mat 430 having (one or more) skins 432 and impregnated with 3D polymer, and (d) CNT mat 440 having only polymer skin 442.

[0151] Impregnation of CNTs with polymers creates a CNT-polymer composite, making it easier to handle the CNT mat and increasing the tensile strength of the CNT CC. Following impregnation, a thin copper coating is applied to the CNT composite. This coating can be applied by PVD, electroless plating, or electrolytic copper deposition. Another option is to create a CNT-perforated copper foil-CNT sandwich.

[0152] Process conditions and raw materials determine the Figure 4 In some cases, due to physical / chemical limitations, increasing the molecular weight of the polymer and / or changing other properties of the polymer will prevent it from entering the CNT mat, resulting in the formation of a CNT mat with a polymer skin ( Figure 4 D) without the polymer penetrating the CNT mat in 3D.

[0153] Table 1 shows a simplified comparison of energy batteries and power batteries of the prior art with energy batteries and power batteries of the present invention. In the present invention, the copper electrode (anode) of the prior art is replaced with a carbon nanotube-copper electrode.

[0154]

[0155] Table 1. Comparison of energy and power batteries of the prior art (copper current collector, CuCC) with batteries of the present invention having carbon nanotube current collectors (CNT-CC)

[0156] *Weight includes all battery components and does not include battery case / pouch

[0157] The present invention provides an improved cost-effective current collector with reduced weight properties that replaces conventional prior art negative electrode (copper) current collectors.While the cost effectiveness may be questionable, the benefits of reduced weight are clear.

[0158] According to some embodiments of the present invention, the electrodes of the present invention provide current draw characteristics that are maintained relative to prior art versions, as well as a significant increase and improvement in energy output per unit weight, particularly for power batteries.

[0159] For the positive electrode, this issue is less critical because the current collector used is lightweight aluminum (with a density of only 2.7 gm / cc, making it difficult to suggest an alternative material) compared to copper (with a density of 8.9 gm / cc). The same principles can still be applied through perforated aluminum foil or aluminum-PVD.

[0160] Now refer to Figure 5A and 5B , Figure 5A and 5B are simplified schematic diagrams of two respective methods 500, 550 for making current collectors according to embodiments of the present invention.

[0161] The inventors have overcome the aforementioned limitations using two main strategies.

[0162] In the first method (sandwich method 500), the current collector is made of a composite of two CNT mats 502, 506 sandwiched between them and bonded to a thin (8-20 micron) perforated copper foil 504. This is more efficient than other supports (such as woven or expanded copper mesh). The edges of the foil are not perforated and are free of CNT mats and active material to provide a lap area. The CNT mats are bonded by a method selected from physical, chemical, electrical, non-electrical methods, and combinations thereof to bond the CNTs to the metal.

[0163] According to an embodiment of the present invention, a CNT mat is first bonded to a copper foil by etching the foil with acid, then physically connecting the CNTs to the copper and the foil on both sides of the perforated copper foil or just one side by using (isopropyl alcohol) IPA or other liquid contact to enhance the van der Waals forces between the CNTs and the copper and the CNTs. On this substrate, the active material is applied by applying a slurry on both sides. If only one CNT mat is used for the current collector, the active material loading on each side should be adjusted to ensure balanced capacity on both sides of the electrode.

[0164] In the second method (PVD method, 550), a thin layer (typically 0.1-1 micron) of copper 552, 556 is applied to both sides of the CNT mat 554 using PVD (physical vapor deposition). The active material is applied as usual and simply bonded by any suitable welding method (for example, but not limited to, any suitable bonding method known in the art, such as ultrasonic welding, laser welding, etc.). In one embodiment, the tab contact 558 is ultrasonically welded to the weld 560 directly onto the PVD copper layer.

[0165] The PVD method can include any suitable form of CNT mat metallization known in the art. The process can be varied so that for certain cell types, only one side of the CNT mat can carry copper. Similarly, instead of depositing copper by PVD, electroplating or electroless plating, magnetron sputtering, electron beam coating, seeding, physical deposition, or chemical deposition by, for example, thermal reduction treatment can be used. For other cell types or device types, other metals besides copper, such as nickel, can be deposited on the CNT mat. Both methods are schematically illustrated in Figure 5.

[0166] Go to Figure 6A , an image of a perforated thin copper foil 602 of an electrode 600 is seen, according to an embodiment of the present invention, which includes a plurality of perforations 604. The perforated thin copper foil (8-20 microns thick), for example, is used in the sandwich method of FIG5. Various perforation designs are possible (for example, the shape and coverage percentage of the perforations can be varied to reduce the weight of the foil while optimizing conductivity).

[0167] 6, a corresponding non-perforated edge 606, 608 is provided on each side 605, 607 of the perforated region 610 to allow for overlapping. Typically, the CNT mat(s) 502, 506 and active material are positioned to cover only the perforated region.

[0168] Figure 6B An image is shown that includes a strip of CNT mat 632 bonded to a perforated copper foil 634 of an electrode 630, in accordance with an embodiment of the present invention.

[0169] Figure 6C shows an embodiment according to the present invention Figure 6B The strip is coated with a negative active material 652 (such as but not limited to graphite) of the electrode 650.

[0170] Figure 7 An image 700 shows a plurality of anodes 702, 704, 706, 708, 710, and 712, each of which has a Figure 6C The corresponding tabs 703, 705, 707, 709, 711 and 713 are cut from the strips.

[0171] Figure 8 A PVD-copper coated CNT mat 802 of an electrode 800 according to an embodiment of the present invention is shown. Figure 8 A photograph of a PVD copper coated CNT mat 802 is shown in . The PVD current collector 800 is coated with active material and can be bonded by soldering copper tape directly on the PVD copper surface (see FIG. 10 ).

[0172]

[0173]

[0174] Table 2 - Experimental sheet resistance measurement results - CNT-Cu (perforated)-CNT sandwich and PVD-CNT

[0175] *Due to the 75%-80% porosity of CNTs, the actual thickness depends on the measurement technique.

[0176] **Experimental results, including two terminations to substrate. Sheet resistance of 10 micron copper is 1.7 mohm / sq.

[0177] In Table 2, the interlayer 500 ( Figure 5A ) and PVD coated pad 550 ( Figure 5B ) method were compared with the values ​​of CNT mat alone and copper foil alone.

[0178] Table 2 provides the sheet resistance measured at two points, including termination welding (ultrasonic). Since termination is a challenge with CNT-based mats, and the current invention provides a technique to address this challenge, it is more practical to include the termination technique and the corresponding resistivity.

[0179] The first column lists the various current collectors, including key parameters and construction details. The second column gives the "nominal" thickness of the current collector in microns, the third column gives its weight per unit area (mg / sq cm), and the fourth column gives the weight gain of each current collector compared to copper foil. The last column gives the sheet resistance measured by two probes in mohm / sq.

[0180] As can be seen in Table 2, the minimum resistivity for 10 micron non-porous copper is 4 mohm / sq (which sets the performance standard for typical lithium-ion power batteries), which only increases to 5 mohm / sq if the foil is 60% perforated.

[0181] In contrast, a CNT mat just 10 microns thick cannot achieve a high sheet resistance of approximately 2,000 mohms / sq. However, a sandwich approach in various configurations can equal the performance of copper alone at a reduced weight (-60%), while a PVD approach at 10-20 mohms / sq shows promise in achieving the performance of copper alone at similar, or even greater, weight reduction.

[0182] Li-ion batteries initially fabricated using the new current collectors from the interlayer or PVD method showed significant irreversible capacity loss upon formation and regular cycling compared to standard batteries using ordinary copper foil current collectors. The capacity loss was shown to be caused by electrolyte interactions, as the internal surface area of ​​the carbon nanotube mat is much larger than that of ordinary copper foil. Irreversible capacity loss upon formation is well known for all prior art FIBs. By limiting the access of electrolyte to the interior of the CNT mat (according to Figure 4 A-4D and Table 3), this problem is addressed in the present invention. This is achieved by treating the CNT mat to reduce wetting of the mat by the organic electrolyte located inside the battery. In one embodiment, this treatment involves heating the CNT mat in an oven at 450°C in air for one hour. Several other techniques can be implemented to prevent / minimize wetting of the CNT mat by organic solvents.

[0183] Another approach is to pre-lithiate the CNT-based electrodes, thereby forming a solid electrolyte interphase (SEI) directly on the graphite and CNT surfaces immediately after the cell is filled with electrolyte.

[0184] A third approach is to impregnate the polymer into the void spaces of the CNT mat. After impregnation, but before evaporating the solvent carrying the impregnated polymer, the mat is rolled up, thereby "squeezing" the polymer.

[0185] Rolling / calendering has a triple function:

[0186] a. Thinning the CNT mat;

[0187] b. Minimizing the weight of polymer contained / impregnated into the CNT pores; and

[0188] c. A thin polymer "skin" is formed on top of both sides of the CNT mat. This polymer "skin" makes the CNT mat more reliable and easier to metallize. Furthermore, the skin provides electrical insulation between the metal coating and the CNT fibers. This isolation helps eliminate electrochemical reactions of the solvent / electrolyte on the CNT fibers.

[0189] Figure 9 Shown is a graph of Formability versus Li for various current collector configurations according to embodiments of the present invention; CNTs impregnated with a polymer current collector compared to pristine CNT current collector and pure copper foil current collector (prior art).

[0190] The polymer-impregnated CNTs showed encouraging results, where the polymer-impregnated CNTs provided a formation capacity of about 0.2 mAh / cm 2 Compared with CNT, this is a lower formation capacity (-1.2mAh / cm 2). This indicates that the polymer is indeed impregnated into most of the CNTs and covers the CNT surface, which leads to electrical insulation between the CNTs and the electrolyte and causes a decrease in the irreversible capacity.

[0191] Despite the encouraging results, the obtained values ​​of CNT formation ability are still far from the target values ​​for copper (-10 μA / cm 2 ).

[0192] After process and instrument optimization, better (smaller) formability values ​​were obtained, resulting in values ​​for CNT-Cu products similar to the state-of-the-art values ​​for Cu foils – as shown in Table 3.

[0193]

[0194] Table 3 - Full cell formation capabilities of 2nd generation CNTs (impregnated with polymer-based anodes) and Cu foil-based anodes

[0195] In Table 3, the formation capacities of complete cells consisting of impregnated CNT-based anodes after 3 polarization cycles are shown, with values ​​of formation capacities very close to those of Cu foil – making impregnated CNTs a viable solution for current collectors, which could replace Cu foil.

[0196] The mechanical properties of polymer-impregnated CNT mats compared to metal foil and polymer foil are as follows:

[0197]

[0198] Table 4 - Mechanical properties of pristine CNTs, polymer-impregnated CNTs, and other alternatives

[0199] The above results shown in Table 4 clearly demonstrate that impregnation of polymer into the CNT mat increases the strength of the CNTs while reducing their strain.

[0200] When the mechanical properties of CNTs are compared to their possible replacement alternatives (see Table 4), which include: a) copper foil b) polymer films, it can be seen that the strength of the impregnated CNTs is comparable to that of copper foil, but with an increased failure strain, while providing a lightweight solution. This indicates that after polymer impregnation, the CNTs have the ability to withstand a roll-to-roll battery assembly process with similar forces as those on Cu foil compared to (SOTA) lithium-ion batteries (LIBs) and still provide higher energy density. Additionally, when the impregnated CNTs are compared to polymer films, it can be seen that even though polymers provide a lightweight solution, they are still very weak (i.e., exhibit relatively low failure stresses) and therefore face handling issues when faced with the roll-to-roll battery assembly process.

[0201] refer to Figure 10A , which is a simplified diagram of an apparatus 1000 having at least one CNT element 1002 ultrasonically welded to a copper foil leg, according to an embodiment of the present invention.

[0202] The process steps involved in the splicing process include Figure 10A A copper foil termination bracket 1006 is prepared in the shape described in (but not limited to a specific design) and termination legs 1004 are cut out of it. In addition, the termination bracket is placed closely next to the Cu PVDCNT current collector (CNT element) 1002 and ultrasonically welded along the termination bracket with a weld 1008. This type of termination (tab) has a low electrical contact resistance and is capable of absorbing large currents.

[0203] refer to Figure 10B , which is a simplified diagram of an apparatus having at least one CNT element 1030 ultrasonically welded to a copper foil leg 1034, in accordance with an embodiment of the present invention.

[0204] The process steps involved in the tabbing process include cutting the Cu PVD CNT current collector into shapes 1032 (in Figure 5B 550 ), the termination legs 1034 are then cut from the Cu foil, and finally the two parts are ultrasonically welded together via weld 1036 .

[0205] This type of termination (tab) has a higher contact resistance (compared to Figure 10A ) and is therefore more suitable for applications requiring lower current consumption. However, this type of termination saves considerable weight, thus retaining the higher specific energy of the device.

[0206] It will be appreciated that the CNT metal products of the present invention may be used in a variety of practical applications. One non-limiting example is use in CNT-metal joining techniques such as brazing, welding, soldering, and other joining methods.

[0207] Figure 11 is a simplified graph showing the attenuation of an EMI shielding material versus electromagnetic frequency. The graph illustrates the attenuation of an EMI shielding device according to an embodiment of the present invention compared to a standard commercial metallized prior art device.

[0208] like Figure 11As seen in Figure 2, the copper-coated CNT device of the present invention exhibits 75 dB of attenuation across the entire frequency range, compared to commercial prior art devices that exhibit lower attenuation across the entire frequency range. Furthermore, the copper-coated CNT device has an areal density of only 19 gr / sqm (gsm), compared to heavier commercial prior art devices that have an areal density greater than 70 gr / sqm (gsm). When considering both performance and weight, the copper-coated CNT device offers superior performance at a fraction of the weight compared to prior art devices.

[0209] The references cited herein teach many principles applicable to the present invention. Therefore, where appropriate, the entire contents of these publications are incorporated herein by reference to teach additional or alternative details, features and / or technical background.

[0210] It should be understood that the application of the present invention is not limited to the details set forth in the description contained herein or shown in the accompanying drawings. The present invention can have other embodiments and can be practiced and executed in various ways. It will be readily understood by those skilled in the art that various modifications and changes may be applied to the embodiments of the present invention as described above without departing from the scope of the present invention, the scope of the present invention being defined in and by the appended claims.

Claims

1. A device comprising at least one carbon nanotube (CNT)-based substrate, the device comprising a first current collector having a resistivity between 1 and 20 mohm / sq, the first current collector comprising at least one polymer-impregnated carbon nanotube (CNT) substrate and a conductive metal element attached to the at least one substrate, the CNT substrate having an average weight per unit area of ​​1 to 4 mg / cm 2 The tensile strength is greater than 200 MPa within the range, wherein polymer impregnation is used to eliminate electrolyte penetration and contact with CNTs and to form a polymer skin on the outer surface of CNTs, wherein the polymer is impregnated into the void space of the CNT mat, and then the CNT mat is rolled up to squeeze the polymer, and then the solvent with the impregnated polymer is evaporated.

2. The device of claim 1, wherein the device is selected from the group consisting of a chemical synthesis cell, an electronic shielding unit, an EMI electromagnetic interference device or apparatus, a heating element, and a lightning rod.

3. The device according to claim 1, wherein The at least one polymer-impregnated carbon nanotube (CNT) substrate includes at least one thermoplastic organic polymer.

4. The device according to claim 3, wherein The at least one thermoplastic organic polymer is selected from the group consisting of sodium carboxymethylcellulose (NaCMC), polyvinylidene fluoride (PVDF), PVA, PVP, and combinations thereof.

5. The apparatus according to claim 2, comprising: The first current collector and the conductive metal element include copper foil.

6. A device comprising at least one carbon nanotube (CNT)-based substrate for providing at least one of power and energy, the device comprising: a resistivity of 1-20mohm / sq between the first current collector, the first current collector comprising: i. at least one polymer-impregnated carbon nanotube (CNT) mat or substrate having an average weight per unit area of ​​1 to 4 mg / cm 2 forming a polymer skin on the outer surface of the CNT, wherein the polymer is impregnated into the void space of the CNT mat, and then the CNT mat is rolled up to squeeze the polymer, and then the solvent with the impregnated polymer is evaporated; and ii. a highly conductive metal element electrically connected to the first tab, the highly conductive metal element being bonded to the at least one carbon nanotube mat; b. a second current collector comprising a metallic conductive element electrically connected to a second tab; c. an isolating material separated between the first current collector and the second current collector; d. an electrolyte disposed between the first current collector and the second current collector; and e. A housing configured to house the first current collector, the second current collector, a separator, and an electrolyte solution.

7. The device according to claim 6, wherein The first current collector comprises a polymer having a thickness of 1 to 50 microns.

8. The device according to claim 6, wherein The highly conductive metal element includes copper.

9. The device according to claim 8, wherein The copper is in the form of perforated foil.

10. The device according to claim 6, wherein The at least one polymer-impregnated carbon nanotube (CNT) mat includes two polymer-impregnated carbon nanotube (CNT) mats.

11. The device according to claim 10, wherein The highly conductive metal element is sandwiched between the two polymer-impregnated carbon nanotube (CNT) mats.

12. The device of claim 6, further comprising an active material coated on the at least one pad.

13. The device according to claim 6, wherein The means is a power source selected from a battery and a capacitor.

14. The device according to claim 6, wherein The second current collector includes at least one of aluminum, graphite, silicon, phosphate, lithium, oxide, and combinations thereof.

15. The device of claim 6, configured to provide 50 Wh / kg to 800 Wh / kg of energy per unit weight.

16. The apparatus of claim 6, configured to provide a power per unit weight of 200 W / kg to 5 kW / kg.

17. A method for fabricating a device comprising at least one carbon nanotube (CNT)-based substrate for providing at least one of power and energy, the method comprising: a. Forming a first current collector having a resistivity between 1 and 20 mohm / sq, comprising: i. impregnating a carbon nanotube (CNT) mat or substrate with at least one polymer to form at least one polymer-impregnated carbon nanotube (CNT) mat or substrate, thereby eliminating electrolyte penetration and contact with the CNTs, forming a polymer skin on the outer surface of the CNTs, and enhancing the tensile strength of the polymer-impregnated carbon nanotube (CNT) mat or substrate to greater than 200 MPa; wherein the polymer is impregnated into the void space of the CNT mat, and the CNT mat is then rolled up to squeeze the polymer, and then the solvent with the impregnated polymer is evaporated; ii. The average weight per unit area is 1-4 mg / cm 2 The at least one polymer-impregnated carbon nanotube (CNT) mat or substrate within the range is combined with a highly conductive metal element electrically connected to the first tab; and iii. Coating the at least one polymer-impregnated carbon nanotube (CNT) mat or substrate with an active material.

18. The method according to claim 17, further comprising: b. Preparing a second current collector comprising a metal conductive element electrically connected to a second tab and coating the second current collector with an active material: c. providing an isolation material between the first current collector and the second current collector; d. introducing the first current collector, the second current collector and the insulating material into the housing; and e. Adding an electrolyte solution between the first current collector and the second current collector to form the device.

19. The method according to claim 17, wherein The forming step is selected from electroplating or chemical plating, magnetron sputtering, electron beam coating, seeding, physical deposition, and chemical deposition.

20. The method according to claim 17, wherein The means is a power source selected from a battery and a capacitor.

21. The method according to claim 20, wherein The battery is a lithium-ion battery.

22. The method according to claim 17, wherein The device is a non-energy storage device selected from the group consisting of an electrochemical synthesis battery, an electronic shielding unit, a heating element, and a lightning rod.

23. The method of claim 17, further comprising treating the at least one carbon nanotube (CNT) mat to at least one of reduce its porosity and wettability or increase its oleophobicity.

24. The method according to claim 23, wherein The treating step includes heating the at least one carbon nanotube (CNT) mat to a temperature greater than 300° C. for at least 30 minutes.

25. The method according to claim 24, wherein The heating step includes heating the at least one carbon nanotube (CNT) mat to a temperature of 450° C. for one hour.

26. The method according to claim 17, wherein The highly conductive metal element is disposed between two carbon nanotube (CNT) mats.

27. The method according to claim 17, wherein The step of impregnating with at least one polymer limits the penetration of electrolyte into the interior of the CNT mat to 1-6 μA / cm 2 The range is up to 10 hours, thus reducing the irreversible capacity.

28. The method according to claim 17, wherein The highly conductive metal element is a copper foil termination standoff, and the bonding step further comprises ultrasonically welding the copper foil termination standoff to the at least one polymer impregnated carbon nanotube (CNT) mat or substrate.

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