Composite electrode

Abstract

The present invention provides an energy storage device that is used in an ultracapacitor and has a high-performance electrode structure that has high operating voltage, high operating temperature, high energy density, high power density, low equivalent series resistance, and the like. The electrode (100) for use in an energy storage device such as an ultracapacitor or battery includes a conductive layer (102), an adhesive layer (104), and an active layer (106). The active layer functions as an energy storage medium by providing a surface interface to an electrolyte in the form of an electric double layer, and is thicker than the adhesive layer, and may be 1.5, 2.0, 5.0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 500, 1000 times thicker or even thicker than the adhesive layer.

Description

Technical Field

[0001] This application claims the benefit of U.S. Provisional Patent Application 62 / 429,727, filed December 2, 2016, entitled "Composite Electrode," and incorporates by reference all of its specifications herein.

Background Art

[0002] Carbon nanotubes (hereinafter also referred to as CNTs) are carbon structures that exhibit various properties. Many of these properties suggest opportunities for improvement in various technical fields. These technical fields include electronic device materials, optical materials, and conductive and other materials. For example, CNTs have been shown to be useful for energy storage in capacitors.

[0003] However, CNTs are usually expensive to produce and pose special challenges in electrode manufacturing. Therefore, while CNTs exhibit advantageous properties, there is a need for electrode materials that reduce the amount of CNTs contained in the material, for example, less than 10% by weight.

Summary of the Invention

[0004] The applicant has developed a composite electrode structure that exhibits advantageous properties. In some embodiments, the electrode exhibits the advantageous properties of CNTs while reducing the amount of CNTs contained in the material, for example, less than 10% by weight.

[0005] The electrodes of the type described herein can be used in ultracapacitors to provide high performance (e.g., high operating voltage, high operating temperature, high energy density, high power density, low equivalent series resistance, etc.).

[0006] In one aspect, an apparatus is disclosed that includes an active storage layer that includes a network of carbon nanotubes that defines a space and a carbonaceous material disposed in the space and coupled by the network of carbon nanotubes, the active layer being configured to provide energy storage.

[0007] In some embodiments, the active layer is substantially binder-free. In some embodiments, the active layer consists essentially or otherwise of a carbonaceous material. In some embodiments, the active layer is electrostatically bonded between carbon nanotubes and the carbonaceous material. In some embodiments, the carbonaceous material includes activated carbon.

[0008] In some embodiments, the carbonaceous material includes carbon in a nano-form other than carbon nanotubes.

[0009] In some embodiments, the network of carbon nanotubes constitutes less than 50% of the weight of the active layer, less than 10% of the weight of the active layer, less than 5% of the weight of the active layer, or less than 1% of the weight of the active layer.

[0010] Some embodiments include an adhesive layer, such as a layer consisting essentially or otherwise of carbon nanotubes. In some embodiments, the adhesive layer is disposed between the active layer and the conductive layer.

[0011] In some embodiments, the surface of the conductive layer facing the adhesive layer includes rough or textured portions. In some embodiments, the surface of the conductive layer facing the adhesive layer includes nanostructured portions. In some embodiments, the nanostructured portions include carbide nanowhiskers. These nanowhiskers are thin, elongated structures (e.g., nanorods) that generally extend from the surface of the conductive layer 102. The nanowhiskers have a radius thickness in the range of 100 nm, 50 nm, 25 nm, 10 nm or less, e.g., from 1 nm to 100 nm or any partial range thereof. The nanowhiskers have a longitudinal length several times their radius thickness, e.g., 20 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 1 μm, 5 μm, 10 μm or greater, e.g., in the range of 20 nm to 100 μm or any partial range thereof.

[0012] In some embodiments, the active layer is annealed to reduce the presence of impurities.

[0013] In some embodiments, the active layer is compressed to deform at least a portion of the carbon nanotube network and the carbonaceous material.

[0014] Some embodiments include an electrode including the active layer. Some embodiments include an ultracapacitor including the electrode. In some embodiments, the ultracapacitor has an operating voltage of 1.0V, 2.0V, 2.5V, 3.0V, 3.1V, 3.2V, 3.5V, 4.0V or greater.

[0015] In some embodiments, the ultracapacitor has a maximum operating temperature of at least 250°C, an operating voltage of at least 1.0V, and a lifespan of at least 1000 hours. In some embodiments, the ultracapacitor has a maximum operating temperature of at least 250°C, an operating voltage of at least 2.0V, and a lifespan of at least 1000 hours. In some embodiments, the ultracapacitor has a maximum operating temperature of at least 250°C, an operating voltage of at least 3.0V, and a lifespan of at least 1000 hours. In some embodiments, the ultracapacitor has a maximum operating temperature of at least 250°C, an operating voltage of at least 4.0V, and a lifespan of at least 1000 hours. In some embodiments, the ultracapacitor has a maximum operating temperature of at least 300°C, an operating voltage of at least 1.0V, and a lifespan of at least 1000 hours. In some embodiments, the ultracapacitor has a maximum operating temperature of at least 300°C, an operating voltage of at least 2.0V, and a lifespan of at least 1000 hours. In some embodiments, the ultracapacitor has a maximum operating temperature of at least 300°C, an operating voltage of at least 3.0V, and a lifespan of at least 1000 hours. In some embodiments, the ultracapacitor has a maximum operating temperature of at least 300°C, an operating voltage of at least 4.0V, and a lifespan of at least 1000 hours.

[0016] In another aspect, a method includes dispersing carbon nanotubes in a solvent to form a dispersion, mixing the dispersion with a carbonaceous material to form a slurry, applying the slurry to a layer, drying the slurry to substantially remove the solvent, and forming an active layer comprising a network of carbon nanotubes defining spaces and a carbonaceous material disposed in the spaces and bonded by the network of carbon nanotubes. Some embodiments include forming or applying a layer of carbon nanotubes and providing an adhesive layer on a conductive layer.

[0017] In some embodiments, the applying step includes applying the slurry on an adhesive layer.

[0018] Various embodiments can include any of the elements or features described herein, or any element or feature described herein alone or optionally appropriately combined.

Brief Description of the Drawings

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Best Mode for Carrying Out the Invention

[0020] Referring to FIG. 1, a typical embodiment of the electrode 100 is disclosed for use in an energy storage device such as, for example, an ultracapacitor or a battery. The electrode includes a conductive layer 102 (also referred to herein as a current collector), an adhesive layer 104, and an active layer 106. When used in an ultracapacitor of the type described herein, the active layer 106 functions as an energy storage medium by providing a surface interface to an electrolyte (not shown), for example, in the form of an electrical double layer (commonly referred to in the art as a Helmholtz layer). In some embodiments, the adhesive layer 104 can be omitted, for example, if the active layer 106 exhibits good adhesion to the conductive layer 102.

[0021] In some embodiments, the active layer 106 is thicker than the adhesive layer 104, for example, 1.5, 2.0, 5.0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 500, 1000 times or even greater than the thickness of the adhesive layer 104. For example, in some embodiments, the thickness of the active layer 106 ranges from 1.5 to 1000 times (or any partial range thereof, such as, for example, 5 to 100 times) the thickness of the adhesive layer 104. For example, in some embodiments, the active layer 106 has a thickness in the range of 0.5 to 2500 μm or any partial range thereof, such as, for example, 5 μm to 150 μm. In some embodiments, the adhesive layer 104 has a thickness in the range of 0.5 μm to 50 μm or any partial range thereof, such as, for example, 1 μm to 5 μm.

[0022] Referring to FIG. 2, in some embodiments, the active layer 106 consists of a carbonaceous material 108 (e.g., activated carbon) bonded by a matrix 110 of CNTs 112 (e.g., a web or network formed of CNTs). In some embodiments, for example when the length of the CNTs is longer than the thickness of the active layer 106, the CNTs 112 forming the matrix 110 mainly lie horizontally parallel to the main surface of the active layer 106. As shown, the CNTs 112 form straight segments, but in some embodiments, when long CNTs are used, some or all of the CNTs have a bent, snake-like shape instead. For example, when the carbonaceous material 108 includes lumps of activated carbon, the CNTs 112 can bend between and wrap around the lumps.

[0023] In some embodiments, the active layer is substantially free of other binding materials such as, for example, polymer materials, adhesives, etc. In other words, in such embodiments, the active layer is substantially free of any material other than carbon. For example, in some embodiments, the active layer is, by mass, at least about 90 wt%, 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt%, 99.5 wt%, 99.9 wt%, 99.99 wt%, 99.999 wt% or more elemental carbon. Nevertheless, the matrix 110 operates in combination with the carbonaceous material 108 to maintain the structural integrity of the active layer 106, for example, without peeling off, delaminating, powdering, etc.

[0024] Substantially any Non It has been found that using an active layer substantially free of carbon impurities increases the performance of the active layer such that a high voltage difference, high temperature, or both are present. Without wishing to be bound by theory, it is believed that the absence of impurities prevents the occurrence of unwanted chemical side reactions that are promoted under other high temperature or high voltage conditions.

[0025] As described above, in some embodiments, the matrix 110 of carbon nanotubes provides a structural backbone for the active layer 106, comprising a carbonaceous material 108 that fills the space between the CNTs 112 of the matrix 110. In some embodiments, the electrostatic forces (e.g., van der Waals forces) between the CNTs 112 within the matrix 110 and between the matrix 112 and other carbonaceous materials 108 provide substantially all of the binding forces that maintain the structural integrity of the layer.

[0026] In some embodiments, the CNTs 112 can include single-walled nanotubes (SWNTs), double-walled nanotubes (DWNTs), or multi-walled nanotubes (MWNTs), or mixtures thereof. Although an individual matrix 110 of CNTs 112 is shown, in some embodiments, the matrix can include interconnected bundles, clusters, or aggregates of CNTs. For example, in some embodiments where the CNTs are initially formed standing vertically side by side, the matrix is composed of at least a portion of a brush-like bundle of CNTs arranged in a row.

[0027] To provide some background for the teachings herein, reference is first made to U.S. Patent No. 7,897,209, entitled "Apparatus and Method for Manufacturing an Aligned Carbon Nanotube Aggregate." The aforementioned patent (the " '209 patent") teaches a process for manufacturing an aligned carbon nanotube aggregate. Thus, the teachings of the '209 patent, which is one example of a technique for manufacturing CNTs in the form of an aligned carbon nanotube aggregate, can be used to collect the CNTs referred to herein. Advantageously, the teachings of the '209 patent can be used to obtain long CNTs with high purity. In other embodiments, other suitable methods known in the art for manufacturing CNTs can be used.

[0028] In some embodiments, the active layer 106 can be formed next. A first solution (also referred to herein as a slurry) is provided that includes a solvent and a dispersion of carbon nanotubes, such as carbon nanotubes arranged in a vertical row. A second solution (also referred to herein as a slurry) is provided that includes a solvent with carbon dispersed therein. This carbon additive includes at least one form of a material consisting essentially of carbon. Typical forms of the carbon additive include, for example, at least one of activated carbon, carbon powder, carbon fiber, rayon, graphene, aerogel, nanohorn, carbon nanotubes, etc. In some embodiments, the carbon additive is formed substantially of carbon, while in alternative embodiments, it is recognized that the carbon additive may include at least some impurities, such as additives included by design.

[0029] In some embodiments, the step of forming the first and / or second solution includes introducing mechanical energy to mix the solvent and the carbon material, for example using an ultrasonic crusher (sometimes referred to as a sonifier) or other suitable mixing device (such as a high shear mixer). In some embodiments, the mechanical energy introduced per kilogram of the mixture into the mixture is at least 0.4 kWh / kg, 0.5 kWh / kg, 0.6 kWh / kg, 0.7 kWh / kg, 0.8 kWh / kg, 0.9 kWh / kg, 1.0 kWh / kg or greater. For example, the mechanical energy introduced per kilogram of the mixture into the mixture is in the range of 0.4 kWh / kg to 1.0 kWh / kg or any partial range thereof, such as 0.4 kWh / kg to 0.6 kWh / kg.

[0030] In some embodiments, the solvent used includes an anhydrous solvent. For example, the solvent includes at least one of ethanol, methanol, isopropyl alcohol, dimethyl sulfoxide, dimethylformamide, acetone, acetonitrile, etc.

[0031] As described above, the two solutions are subject to "sonolysis" (a physical effect realized in an ultrasonic field). For the first solution, sonolysis is generally carried out for a period suitable for unraveling, standing up, or otherwise analyzing carbon nanotubes. For the second solution, sonolysis is generally carried out for a period suitable for ensuring good dispersion or mixing of the carbonaceous additives in the solvent. In some embodiments, other techniques for imparting mechanical energy to the mixture are used in addition to or instead of sonolysis, such as physical mixing using stirring or impellers.

[0032] As soon as one or both of the first solution and the second solution are suitably sonolyzed, they are then mixed to provide a combined solution, which is again sonolyzed. Generally, the combined mixture is sonolyzed for a period suitable for ensuring good mixing of the carbon nanotubes with the carbonaceous additives. This second mixing (followed by appropriate coating and drying steps as described below) results in the form of an active layer 106 comprising a matrix 110 of CNTs 112 with carbonaceous additives that provide a carbonaceous material 108 filling the space of the matrix 110.

[0033] In some embodiments, mechanical energy is introduced into the combined mixture using an ultrasonic crusher (sometimes referred to as a sonifier) or other suitable mixing device (such as a high-shear mixer). In some embodiments, the mechanical energy introduced into the mixture per kilogram of the mixture is at least 0.4 kWh / kg, 0.5 kWh / kg, 0.6 kWh / kg, 0.7 kWh / kg, 0.8 kWh / kg, 0.9 kWh / kg, 1.0 kWh / kg or greater. For example, the mechanical energy introduced into the mixture per kilogram of the mixture is in the range of 0.4 kWh / kg to 1.0 kWh / kg or any partial range thereof, such as 0.4 kWh / kg to 0.6 kWh / kg.

[0034] In some embodiments, the mixed slurry is wet-formed directly on the adhesive layer 104 or the conductive layer 102 and dried (e.g., by applying heat or vacuum or both) until substantially all of the solvent and other liquids are removed, thereby forming the active layer 106. In some such embodiments, it is desirable to protect various portions of the underlying layer (e.g., the underside of the conductive layer 102 when the current collector is targeted for two-sided operation) from the solvent, for example, by masking an area or providing a drain path to guide the solvent.

[0035] In other embodiments, the mixed slurry is dried elsewhere and then transferred onto the adhesive layer 104 or the conductive layer 102 to form the active layer 106 using other suitable techniques (e.g., roll-to-roll layer coating). In some embodiments, the non-dried mixed slurry is placed on a suitable surface and dried to form the active layer 106. Any material considered suitable is used on the surface, but typical materials include PTFE since subsequent removal from the surface is facilitated by its properties. In some embodiments, the active layer 106 is formed by pressing to provide a layer having a desired thickness, area, and density.

[0036] In some embodiments, the average length of the CNTs 112 forming the matrix 110 is at least 0.1 μm, 0.5 μm, 1 μm, 5 μm, 10 μm, 50 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 1000 μm or greater. For example, in some embodiments, the average length of the CNTs 112 forming the matrix 110 is in the range from 1 μm to 1000 μm, or any partial range thereof, such as from 1 μm to 600 μm for example. In some embodiments, 50%, 60%, 70%, 80%, 90%, 95%, 99% or more of the CNTs 112 are within 10% of the average length of the CNTs 112 constituting the matrix 110.

[0037] In various embodiments, the other carbonaceous material 108 can include various forms of carbon, including activated carbon, carbon black, graphite, and the like. The carbonaceous material can include, for example, carbon particles including nanoparticles in the form of nanotubes, nanorods, sheet-like graphene, flakes, or bent flake forms, and / or in the form of cones, rods, spherical (C60 structured molecules), and the like.

[0038] The applicant has found the unexpected result that an active layer of the type described herein can provide typical performance (e.g., high conductivity, low resistance, high voltage performance, and high energy and power density) even when the percentage of the mass of CNTs in the layer is quite low. For example, in some embodiments, the active layer is elemental carbon in a form other than CNTs (e.g., activated carbon) at least about 50 wt%, 60 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt%, 99.5 wt% or even more. In particular, in one application including high-performance ultracapacitors, an active layer 106 that is 95 wt% to 99 wt% activated carbon (with the remaining CNTs 112) has been shown to exhibit excellent performance.

[0039] In some embodiments, the matrix 110 of CNT112 forms an interconnected network of highly conductive paths for current (e.g., ion conduction) through the active layer 106. For example, in some embodiments, the highly conductive contacts occur at points where the CNTs 112 of the matrix 110 cross each other, or where they are close enough that quantum tunneling of charge carriers (e.g., ions) is possible from one CNT to the next. The active layer is composed of a relatively low mass fraction of CNT112 (e.g., 10 wt%, 5 wt%, 4 wt%, 3 wt%, 2 wt%, 1 wt% or less, e.g., in the range of 0.5 wt% to 10 wt%, or any partial range thereof such as, for example, 1 wt% to 5.0 wt%), while the interconnected network of highly conductive paths formed by the matrix 110 can provide long conductive paths (e.g., conductive paths on the order of the thickness of the active layer 106) that facilitate current within and through the active layer 106.

[0040] For example, in some embodiments, the matrix 110 includes one or more structures of interconnected CNTs, and the structures have an overall length along one or more dimensions greater than 2, 3, 4, 5, 10, 20, 50, 100, 500, 1000, 10000 times or greater than the average length of the component CNTs that make up the structure. For example, in some embodiments, the matrix 110 includes one or more structures of interconnected CNTs, and the structures have an overall length from 2 to 10000 times (or any partial range thereof) the average length of the component CNTs that make up the structure. For example, in some embodiments, the matrix 110 can include highly conductive paths having a length in the range of 100 μm, 500 μm, 1000 μm, 10000 μm or greater, e.g., 100 μm - 10000 μm, and any partial range thereof.

[0041] As used herein, the term "highly conductive path" should be understood as a path formed by interconnected CNTs having a conductivity higher than that of other carbonaceous materials 108 (e.g., activated carbon) surrounding the matrix 110 of the CNT112.

[0042] Although not wishing to be bound by theory, in some embodiments, the matrix 110 can be characterized as a conductive interconnect network of CNTs that exhibits connectivity higher than the percolation threshold. The percolation threshold is a mathematical concept related to percolation theory, which is a form of long-range connectivity in a random arrangement. While there are no so-called "giant" connected components of the order of the system size below the threshold, there are giant components of the order of the system size above it.

[0043] In some embodiments, the percolation threshold is determined by measuring the conductivity of the layer while increasing the mass fraction of the CNTs 112 in the active layer 106 and holding all other properties of the layer constant. In some such cases, the threshold is identified at the mass fraction at which the conductivity of the layer shows a sharp increase and / or at a larger mass fraction at which the conductivity of the layer increases only slowly with further addition of CNTs. Such behavior indicates crossing the threshold required for a form of interconnected CNT structure that provides a conductive path on the order of the length of the active layer 106.

[0044] Returning to FIG. 1, in some embodiments, one or both of the active layer 106 and the adhesive layer 104 are processed by applying heat to remove impurities (e.g., functional groups of CNTs and, for example, moisture, oxides, halides, etc.). For example, in some embodiments, one or both of the layers can be heated to at least 100°C, 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C or higher, for at least 1 minute, 5 minutes, 10 minutes, 30 minutes, 1 hour, 2 hours, 3 hours, 12 hours, 24 hours, or longer. For example, in some embodiments, the layer is processed to reduce the moisture in the layer to less than 1000 ppm, 500 ppm, 100 ppm, 10 ppm, 1 ppm, 0.1 ppm or less.

[0045] Returning to FIG. 1, in some embodiments, the adhesive layer 104 is formed having carbon nanotubes. For example, in some embodiments, the adhesive layer 104 is at least about 50 wt%, 75 wt%, 80 wt%, 90 wt%, 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt%, 99.5 wt%, 99.9 wt%, 99.99 wt%, 99.999 wt% CNT. In some embodiments, the CNTs are grown directly on the conductive layer 102 using, for example, the chemical vapor deposition techniques described in U.S. Patent Publication No. 20150210548, entitled "Inline Manufacture of Carbon Nanotubes," published July 30, 2015. In some embodiments, the CNTs are transferred onto the conductive layer 102 using, for example, the wet or dry transfer processes of the type described in U.S. Patent Publication No. 20150279578, entitled "High Power and High Energy Electrodes Using Carbon Nanotubes," published October 1, 2015. In some embodiments, the adhesive layer 104 adheres to the upper active layer 106 using only substantially electrostatic forces (e.g., van der Waals forces) between the CNTs of the adhesive layer 104, the carbon material, and the CNTs of the active layer 106.

[0046] In some embodiments, the CNTs of the adhesive layer 104 can include single-walled nanotubes (SWNTs), double-walled nanotubes (DWNTs), or multi-walled nanotubes (MWNTs), or mixtures thereof. In some embodiments, the CNTs are aligned vertically in a row. In one particular embodiment, the CNTs of the adhesive layer 104 are primarily or all SWNTs and / or DWNTs, while the CNTs of the active layer 106 are primarily or all MWNTs. For example, in some embodiments, the CNTs of the adhesive layer 104 are at least 75%, at least 90%, at least 95%, at least 99% or more SWNTs or at least 75%, at least 90%, at least 95%, at least 99% or more DWNTs. In some embodiments, the CNTs of the active layer 106 are at least 75%, at least 90%, at least 95%, at least 99% or more MWNTs.

[0047] In some embodiments, the adhesive layer 104 is formed by applying pressure to a layer of carbonaceous material. In some embodiments, this compression process changes the structure of the adhesive layer 104 in a way that promotes adhesion to the active layer 106. For example, in some embodiments, pressure is applied to a layer comprising an array of CNTs aligned vertically in a row or an aggregate of CNTs aligned vertically in a row, thereby deforming or breaking the CNTs.

[0048] In some embodiments, the adhesive layer is formed by shaping a wet slurry of CNTs (with or without additional carbon) mixed in a solvent onto the conductive layer 102. In various embodiments, similar techniques as described above are used to form the active layer 106 from the wet slurry.

[0049] In some embodiments, mechanical energy is introduced into the wet slurry using an ultrasonic disrupter (sometimes referred to as a sonifier) or other suitable mixing device (e.g., a high shear mixer). In some embodiments, the mechanical energy introduced into the mixture per kilogram of the mixture is at least 0.4 kWh / kg, 0.5 kWh / kg, 0.6 kWh / kg, 0.7 kWh / kg, 0.8 kWh / kg, 0.9 kWh / kg, 1.0 kWh / kg or greater. For example, the mechanical energy introduced into the mixture per kilogram of the mixture is in the range of 0.4 kWh / kg to 1.0 kWh / kg or any partial range thereof such as, for example, 0.4 kWh / kg to 0.6 kWh / kg.

[0050] In some embodiments, the proportion of solid carbon in the wet slurry is less than 10 wt%, 5 wt%, 4 wt%, 3 wt%, 2 wt%, 1 wt%, 0.5 wt%, 0.1 wt% or less, for example, in the range of 0.1 wt% to 10 wt% or any partial range thereof such as, for example, 0.1 wt% to 2 wt%.

[0051] In various embodiments, the conductive layer 102 is made of a suitable conductive material such as, for example, a metal foil (e.g., an aluminum foil). In some embodiments, the surface of the conductive layer 102 is roughened, patterned, or otherwise textured, for example, to promote adhesion to the adhesive layer 104 and to promote good conductivity from the active layer 106. For example, in some embodiments, the conductive layer is etched (e.g., mechanically or chemically). In some embodiments, the conductive layer 102 has a thickness in the range of 1 μm to 1000 μm, or any partial range thereof, for example, 5 μm to 50 μm.

[0052] In some embodiments, the conductive layer 102 includes a nanostructured surface. For example, as described in International Patent Publication No. WO 2016 / 057983, entitled "Nanostructured Electrodes in Energy Storage Devices," published on April 14, 2016, the conductive layer has an upper surface that includes nanoscale features, such as whiskers (e.g., carbide whiskers), that promote adhesion to the adhesive layer 104 and good conductivity from the active layer 106. A typical current collector is a commercially available current collector from Toyo Aluminum Co., Ltd. under the trade name TOYAL-CARBO.

[0053] In some embodiments, one or both of the active layer 106 and the adhesive layer 104 are treated by applying heat and / or vacuum to remove impurities (e.g., impurities such as functional groups of CNTs, moisture, oxides, halides).

[0054] In some embodiments, one or both of the active layer 106 and the adhesive layer 104 are compressed, for example, to break a portion of the constituent CNTs or other carbonaceous materials to increase the surface area of each layer. In some embodiments, this compression treatment increases the adhesion between one or more of the layers, the ion transport rate within the layer, and the surface area of the layer. In various embodiments, the compression can be applied before or after each layer is coated and formed on the electrode 100.

[0055] In some embodiments, the adhesive layer 104 may be removed so that the active layer 106 is disposed directly on the conductive layer 102.

[0056] Referring to FIG. 3, in some embodiments, the electrode 100 may be double-sided and include an adhesive layer 104 and an active layer 106 formed on each of two opposite major surfaces of the conductive layer 102. In some embodiments, the adhesive layer 104 may be removed on one or both sides of the two-sided electrode 100.

[0057] Referring to FIG. 4, a typical embodiment of a method 200 for making the active layer 106 of the electrode 100 is described. In step 201, the CNTs are dispersed in a solvent to form a dispersion of the CNTs. In some embodiments, the dispersion can be formed using any of the techniques described in U.S. Patent Publication No. 20150279578, entitled “High Power and High Energy Electrodes Using Carbon Nanotubes,” published on Oct. 1, 2015, including agitation, sonication, or a combination of the two. In various embodiments, any suitable solvent can be used, including, for example, ethanol, methanol, isopropyl alcohol, dimethyl sulfoxide, dimethylformamide, acetone, acetonitrile, and the like. Generally, it is advantageous to select a solvent that is substantially removed in the drying step 204 described below, using, for example, heating and / or vacuum drying techniques.

[0058] In some embodiments, the mixture of CNTs and solvent is passed through a filter, such as an array of microchannels (e.g., having channels with diameters on the order of the radius of the CNTs), to physically separate the CNTs and help promote the dispersion.

[0059] In some embodiments, the CNT dispersion can be formed without adding surfactants, for example, to avoid the presence of impurities derived from these surfactants at the completion of method 200.

[0060] In step 202, the CNT dispersion is mixed with a carbonaceous material (e.g., activated carbon) to form a slurry. In some embodiments, the slurry can be formed using any of the techniques described in U.S. Patent Publication No. 2015 / 0279578, published on October 1, 2015, including stirring, sonication, or a combination of the two. In some embodiments, the slurry has a solid carbon proportion of 20 wt%, 15 wt%, 10 wt%, 5 wt%, 2 wt%, less than 1 wt% or even less, for example, in the range of 1 wt% to 20 wt%, or for example, any partial range of 4% to 6%. The mass ratio of CNTs to other carbonaceous materials in the slurry is less than 1:5, 1:10, 1:15, 1:20, 1:50, 1:100 or less, in the range of 1:10 to 1:20, or any partial range thereof.

[0061] In step 203, the slurry is applied to the adhesive layer 104 or, if the adhesive layer 104 is removed, to the conductive layer 102 of the electrode 100. In some embodiments, the slurry is formed into a sheet and covers the electrode. For example, in some embodiments, the slurry is applied by a slot die to control the thickness of the applied layer. In other embodiments, the slurry is applied to the conductive layer 102 and then leveled to a desired thickness using, for example, a doctor blade.

[0062] In some embodiments, the slurry is compressed (e.g., using a calendaring device) before or after being applied to the electrode 100. In some embodiments, the slurry is partially or completely dried during this step 203 (e.g., by applying heat, vacuum, or a combination thereof).

[0063] In step 204, if the slurry is not dried or is only partially dried during step 203, the slurry applied to the electrode is completely dried (e.g., by applying heat, vacuum, or a combination thereof). In some embodiments, substantially all of the solvent (and other non-carbonaceous materials such as, for example, the dispersing substance) is removed from the active layer 106. In some embodiments, if impurities remain after the drying step, an additional step of heating the layer (e.g., baking or annealing) is performed. For example, in some embodiments, one or both of the active layer 106 and the adhesive layer 104 are treated by applying heat to remove impurities (e.g., functional groups of CNTs and impurities such as, for example, moisture, oxides, halides).

[0064] Referring to FIG. 5, a typical embodiment of a method 300 for making the adhesive layer 104 of the electrode 100 is described. In step 301, the CNTs are dispersed in a solvent to form a dispersion of the CNTs. In some embodiments, the dispersion can be formed using any of the techniques described in U.S. Patent Publication No. 2015 / 0279578, published Oct. 1, 2015, including agitation, sonication, or a combination of the two. In various embodiments, any suitable solvent is used, including organic solvents such as, for example, isopropyl alcohol, acetonitrile, propylene carbonate. Generally, it is advantageous to choose a solvent that is substantially removed in the drying step 304 described below.

[0065] In some embodiments, the mixture of CNTs and solvent is passed through a filter, such as an array of microchannels (e.g., having channels with diameters on the order of the radius of the CNTs), to physically separate the CNTs and help promote the dispersion.

[0066] In some embodiments, the CNT dispersion can be formed without adding surfactants, for example, to avoid the presence of impurities derived from these surfactants at the completion of method 300.

[0067] In step 302, the CNT dispersion is optionally mixed with an additional carbonaceous material (such as activated carbon) to form a slurry. In some embodiments, the additional carbonaceous material is removed so that the slurry consists of CNTs dispersed in a solvent. In some embodiments, the slurry has a solids percentage of less than 5 wt%, 4 wt%, 3 wt%, 2 wt%, 1 wt%, 0.5 wt%, 0.1 wt% or less, or ranges from 0.1 to 5 wt% or any sub-range thereof.

[0068] In step 303, the slurry is applied to the conductive layer 102 of the electrode 100. In some embodiments, the slurry coats the electrode. For example, in some embodiments, the slurry is applied by a slot die to control the thickness of the applied layer. In other embodiments, the slurry is applied to the conductive layer 102 and then leveled to a desired thickness, for example using a doctor blade.

[0069] In some embodiments, the slurry is compressed (e.g., using a calendaring device) before or after being applied to the electrode 100. In some embodiments, the slurry is partially or completely dried during this step 303 (e.g., by applying heat, vacuum, or a combination thereof).

[0070] In step 304, if the slurry is not dried or is only partially dried during step 203, the slurry applied to the electrode is completely dried (e.g., by applying heat, vacuum, or a combination thereof). In some embodiments, substantially all of the solvent (and other non-carbonaceous materials such as, for example, the dispersing substance) is removed from the active layer 106. In some embodiments, if impurities remain after the drying step, an additional step of heating the layer (e.g., baking or annealing) is performed. For example, in some embodiments, one or both of the active layer 106 and the adhesive layer 104 are treated by applying heat to remove impurities (e.g., functional groups of CNTs and impurities such as, for example, moisture, oxides, halides).

[0071] In some embodiments, method 300 for forming the adhesive layer 104 and method 200 for forming the active layer 106 are performed in sequence such that the upper active layer 106 is subsequently formed after the adhesive layer 104. In some embodiments, the foregoing methods can be repeated, for example, to form two-sided electrodes of the type described herein.

[0072] Advantageously, in some embodiments, method 300 for forming the adhesive layer 104 and / or method 200 for forming the active layer 106 can be implemented as a roll-to-roll process so as to enable mass production of electrode sheets having a length of, for example, several tens of meters or more.

[0073] FIG. 6 shows a typical mixing device 400 for implementing method 300 for forming the adhesive layer 104 and / or method 200 for forming the active layer 106. For the sake of brevity, device 400 is described as being used when forming the active layer 106 using method 200. However, as will be apparent to those skilled in the art, device 400 can be readily configured to implement method 300 for forming the adhesive layer 104.

[0074] Apparatus 400 includes a mixing vessel 401. The mixing vessel receives a slurry composed of a solvent, carbon nanotubes, and (optionally) additional carbonaceous materials of the type described above. In some embodiments, this slurry (or its components) is first formed in the mixing vessel 401. In other embodiments, the slurry is formed elsewhere and then transferred to the mixing vessel 401.

[0075] In some embodiments, the mixing vessel 401 includes one or more mechanisms for mixing the slurry, such as, for example, an impeller or a high-shear mixer. In some embodiments, a mixing mechanism is provided that can stir the slurry at a controlled rate, for example, up to 1000 revolutions per minute (RPM) or more. In some embodiments, the mixing vessel can include one or more devices for imparting mechanical energy to the slurry, such as, for example, an ultrasonic disrupter, a mixer (such as a high-shear mixer), a homogenizer, or other known suitable devices. In some embodiments, the mixing vessel is temperature-controlled using one or more heating and / or cooling elements, such as, for example, an electric heater, a tube for circulating cooling water, or other such devices known in the art.

[0076] The slurry in the mixing vessel 401 is circulated through a flow line 402, such as a pipe or a tube, using, for example, a pump 403. The pump 403 is of any suitable form, such as, for example, a positive displacement pump. A flow meter 404 is provided to measure the flow rate of the slurry through the flow line 402. A filter 405 is provided to filter the slurry flowing through the flow line 402, for example, to remove agglomerates of solid material having a size larger than a desired threshold.

[0077] In some embodiments, for example when the mixing vessel 401 does not include an ultrasonic crusher, the in-line ultrasonic crusher 406 is provided to decompose the slurry flowing through the flow line 402 by ultrasonic waves. For example, in some embodiments, a flow through an ultrasonic crusher such as the Branson Digital SFX-450 ultrasonic crusher commercially available from Thomas Scientific, Swedesboro, NJ 08085, High Hill Road 1654, USA is used.

[0078] In some embodiments, a temperature control device 407, such as a heat exchanger arranged in a sleeve around the flow line 402 for example, is provided to control the temperature of the slurry flowing through the flow line 402.

[0079] In some embodiments, the valve 408 is selectively controlled to direct a first portion of the slurry flowing through the flow line 402 that is recirculated back to the mixing vessel 401, while a second portion is provided to be output externally, for example to a coating device 500 or the like. In some embodiments, a sensor 409, such as a pressure sensor or a flow sensor for example, is provided to sense one or more aspects of the output portion of the slurry.

[0080] In various embodiments, any or all of the elements of the device 400 are operably connected to one or more computer devices to provide automatic monitoring and / or control of the mixing device 400. For example, the ultrasonic crusher 406 includes digital control to control its operating parameters, such as power and duty cycle for example.

[0081] In various embodiments, the coating apparatus 500 is of any suitable type known in the art. For example, FIG. 7A depicts a typical embodiment of a coating apparatus 500 featuring a slot die 501 that distributes the received slurry from a source such as a mixing device 400 through a dispensing channel 502 over a substrate 503 (e.g., a conductive layer 102 that is bare or already coated with an adhesive layer 104) moving over a roller 504. By setting the height of the slot die over the substrate 503 on the roller 504 and controlling the flow rate and pressure of the slurry in the channel 502, the thickness and density of the applied coating can be controlled. In some embodiments, the channel 502 may include one or more reservoirs to help ensure a constant flow of the slurry to provide a uniform coating during operation.

[0082] FIG. 7B shows a typical embodiment of a coating apparatus 500 featuring a doctor blade 601 that levels the received slurry from a source such as a mixing device 400 applied by one or more applicators 602 (one is shown) over a substrate 603 (e.g., a conductive layer 102 that is bare or already coated with an adhesive layer 104) moving over a roller 604. The direction of movement of the substrate 603 is indicated by the thick black arrow. By setting the height of the doctor blade 601 over the substrate 603 on the roller 604 and controlling the flow rate and pressure of the slurry by the applicator 602, the thickness and density of the applied coating can be controlled. Although a single doctor blade 601 is shown, multiple blades can be used, e.g., a first blade to set a rough thickness of the coating and a second blade disposed downward from the first blade to provide a finely smooth coating.

[0083] Furthermore, capacitors incorporating electrodes that provide improved performance over a wide temperature range to a user are disclosed herein. Such ultracapacitors include an energy storage cell and an electrolyte system hermetically sealed within a housing, the cell being electrically connected to a positive contact and a negative contact, and the ultracapacitor being configured to operate at temperatures in a temperature range of from about -100°C to about 300°C or more, or any partial range thereof, such as from -40°C to 200°C, from -40°C to 250°C, from -40°C to 300°C, from 0°C to 200°C, from 0°C to 250°C, from 0°C to 300°C. In some embodiments, such ultracapacitors can operate at voltages of 1.0V, 2.0V, 3.0V, 3.2V, 3.5V, 4.0V or more with a lifetime exceeding 1000 hours.

[0084] As shown in FIGS. 8A and 8B, exemplary embodiments of the capacitor are shown. In each case, the capacitor is an ultracapacitor 10. The difference between FIGS. 8A and 8B is that the exemplary ultracapacitor 10 of FIG. 8A includes a separator. The concepts disclosed herein generally apply equally to any exemplary ultracapacitor 10. The electrolyte of one embodiment is optimal for constructing an exemplary ultracapacitor 10 without a separator. Unless otherwise specified, the discussion herein applies equally to any ultracapacitor 10 whether or not it has a separator.

[0085] A typical ultracapacitor 10 is an electric double layer capacitor (EDLC). The EDLC includes at least one set of electrodes 3 (the electrodes 3 can simply be referred to as the negative electrode 3 and the positive electrode 3 for reference purposes in this specification). When assembled into the ultracapacitor 10, each of the electrodes 3 (each being an electrode 100 of the type shown in FIG. 1 above) has a double layer of charge present at the electrolyte interface. In some embodiments, a plurality of electrodes 3 are included (for example, in some embodiments, at least two sets of electrodes 3 are included). However, for the purpose of discussion, only one set of electrodes 3 is shown. As a convention in this specification, it is assumed that at least one of the electrodes 3 uses a carbon-based energy storage medium 1 (such as the active layer 106 of the electrode 100 shown in FIG. 1), and each of the electrodes includes the carbon-based energy storage medium 1. It should be noted that electrolytic capacitors are different from ultracapacitors because metal electrodes are significantly different (at least on the order of magnitude) in surface area.

[0086] Each of the electrodes 3 includes a respective current collector 2 (also referred to as a current collecting device), which is the conductive layer 102 of the electrode 100 shown in FIG. 1. In some embodiments, the electrodes 3 are separated by a separator 5. Generally, the separator 5 is a thin structural material (usually a sheet) used to separate the positive electrode 3 from the negative electrode 3. The separator 5 also serves to separate the sets of electrodes 3. As soon as they are assembled, the electrodes 3 and the separator 5 provide a storage cell 12. It should be noted that in some embodiments, the carbon-based energy storage medium 1 is not included in one or both of the electrodes 3. That is, in some embodiments, each of the electrodes 3 consists only of the current collector 2. The material used to provide the current collector 2 can be roughened, anodized, etc. to increase its surface area. In these embodiments, the current collector 2 acts alone as the electrode 3. Considering this, however, as used in this specification, the term "electrode 3" generally refers to a combination of the energy storage medium 1 and the current collector 2 (which is not limited at least for the aforementioned reasons).

[0087] At least one form of the electrolyte 6 is included in the ultracapacitor 10. The electrolyte 6 fills the space between the electrode 3 and the separator 5. Generally, the electrolyte 6 is a substance not related to charged ions. A solvent for dissolving the substance is appropriately included in some embodiments of the electrolyte 6. The electrolyte 6 conducts electricity by ion transport.

[0088] In some embodiments, the electrolyte 6 is in a gel or solid form (e.g., a polymer layer impregnated with an ionic liquid). Examples of such electrolytes are provided in International Patent Publication No. WO 2015 / 102716, published on July 9, 2015, entitled "Advanced Electrolytes in High-Temperature Energy Storage Devices".

[0089] In other embodiments, the electrolyte 6 is in a non-aqueous liquid form, such as an ionic liquid, of a type suitable for high-temperature applications, for example. Examples of such electrolytes are provided in International Patent Publication No. WO 2015 / 102716, published on July 9, 2015, entitled "Advanced Electrolytes in High-Temperature Energy Storage Devices".

[0090] In some embodiments, the storage cell 12 is formed in one of a wound form or a prismatic form that is then packaged in a cylindrical or prismatic housing 7. As soon as the electrolyte 6 is included, the housing 7 is hermetically sealed. In various examples, the package is hermetically sealed by techniques using laser, ultrasonic, and / or welding techniques. In addition to providing robust physical protection for the storage cell 12, the housing 7 constitutes an external contact to provide electrical transmission to each terminal 8 within the housing 7. Each of the terminals 8 then provides electrical access to the energy stored in the energy storage medium 1 through an electrical lead that is generally connected to the energy storage medium 1.

[0091] As discussed herein, "hermetic" refers to a seal where the quality (i.e., leak rate) is defined in units of "atm-cc / second" which means gas (e.g., helium) of 1 cubic centimeter per second at the pressure and temperature of the ambient atmosphere. This is equivalent to the unit expression of "standard He-cc / sec". Further, 1 atm-cc / sec is recognized to be equal to 1.01325 mbar-liter / sec. Generally, the ultracapacitor 10 disclosed herein can provide a hermetic seal having a leak rate of about 5.0×10 -6 atm-cc / sec or less and can exhibit a leak rate of about 5.0×10 -10 atm-cc / sec or less. Also, the performance of a successful hermetic seal should appropriately be determined by the user, designer or manufacturer, and "hermetic" is considered to include the meaning of a standard that should ultimately be defined by the user, designer, manufacturer or other stakeholders.

[0092] Leak detection is done, for example, by the use of a tracer gas. Using a tracer gas such as helium for leak testing, for example, is advantageous because it is a dry, fast, accurate and non-destructive method. In one example of this technique, the ultracapacitor 10 is placed in an environment of helium. The ultracapacitor 10 is subjected to pressurized helium. The ultracapacitor 10 is then placed in a vacuum chamber connected to a detector (e.g., an atomic absorption unit) that can monitor the presence of helium. With knowledge of the pressurization time, pressure and internal volume, the leak rate of the ultracapacitor 10 is determined.

[0093] In some embodiments, at least one lead (also referred to herein as a tab) is electrically connected to each one of the current collectors 2. A plurality of leads are grouped together and connected to respective terminals 8 (depending on the polarity of the ultracapacitor 10). The terminals 8 are then connected to electrical accesses, referred to as “contacts” (e.g., one of the housing 7 and an external electrode (also conventionally referred to herein as a “feedthrough” or a “pin”). A suitable exemplary design is provided in International Patent Publication No. WO 2015 / 102716, published on Jul. 9, 2015, entitled “Advances in Electrolytes for High Temperature Energy Storage Devices”.

[0094] The various forms of the ultracapacitor 10 are coupled. The various forms are coupled using known techniques, such as, for example, by using at least one mechanical connector, by electrically contacting the contacts with each other, such as by welding the contacts. A plurality of ultracapacitors 10 are electrically connected in at least one of parallel and series manners.

[0095] As used herein, the symbol “wt%” means weight percent. For example, when referring to the weight percent of a solute in a solvent, “wt%” refers to the proportion of the total mass of the mixture of the solute and the solvent constituted by the solute.

[0096] The entire contents of each of the above-mentioned published publications and patent applications are incorporated herein by reference. In the event of any conflict between the cited documents and the present disclosure, the present disclosure shall govern.

[0097] While the present 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 present invention. For example, in some embodiments, one of the aforementioned layers may include a plurality of layers therein. Further, it will be understood that many modifications may be made to adapt a particular apparatus, situation or material to the teachings of the present invention without departing from its essential scope. Therefore, the present invention is not limited to the particular embodiments disclosed as the best mode contemplated for carrying out this invention, and it is intended that the present invention will include all embodiments falling within the scope of the appended claims.

Claims

1. a network of carbon nanotubes defining a space; a carbonaceous material arranged in space and fixed by a network of carbon nanotubes; a binder-free active storage layer comprising the active storage layer is a heat treated layer configured to provide energy storage and free of non-carbon impurities; The length of the carbon nanotube is longer than the thickness of the active storage layer. The active storage layer is made of carbon nanotubes and carbonaceous material that are electrostatically bonded together. the carbon nanotube network is present in the active storage layer in an amount ranging from 0.5% to 4% by weight based on the weight of the active storage layer; A device, wherein an adhesion layer is disposed between the active layer and the conductive layer, the adhesion layer comprising at least 50% by weight of carbon nanotubes.

2. 10. The apparatus of claim 1, wherein the active storage layer consists essentially of a carbonaceous material.

3. The apparatus of claim 1 , wherein the carbonaceous material comprises activated carbon.

4. The apparatus of claim 1 , wherein the carbonaceous material comprises a nanoform of carbon other than carbon nanotubes.

5. The device of claim 1 , wherein the network of carbon nanotubes comprises less than 1% by weight of the active storage layer.

6. The device of claim 1, wherein the adhesion layer consists essentially of carbon nanotubes disposed between the active storage layer and the conductive layer.

7. The device of claim 6 , wherein the surface of the conductive layer facing the adhesive layer comprises a rough or textured portion.

8. The device of claim 6 , wherein the surface of the conductive layer facing the adhesion layer comprises nanostructured portions.

9. The apparatus of claim 8 , wherein the nanostructured portion comprises a carbide nanowhisker.

10. The device of claim 1 , wherein the active storage layer is annealed to reduce the presence of impurities.

11. The device of claim 1 , wherein the active storage layer is compressed to deform at least a portion of the carbon nanotube network and the carbonaceous material.

12. The device of claim 1 further comprising an electrode comprising an active reservoir layer.

13. 13. The device of claim 12, further comprising: the electrode being a two-sided electrode comprising a second active storage layer.

14. The apparatus of claim 12 , further comprising an ultracapacitor comprising an electrode.

15. 15. The apparatus of claim 14, wherein the ultracapacitor has an operating voltage greater than 3.0V.

16. 15. The apparatus of claim 14, wherein the ultracapacitor has an operating voltage greater than 3.2V.

17. 15. The apparatus of claim 14, wherein the ultracapacitor has an operating voltage greater than 3.5V.

18. 15. The apparatus of claim 14, wherein the ultracapacitor has an operating voltage greater than 4.0V.

19. 15. The apparatus of claim 14, wherein the ultracapacitor has a lifetime of at least 1000 hours at a maximum operating temperature of at least 250°C and an operating voltage of at least 1.0V.

20. 15. The apparatus of claim 14, wherein the ultracapacitor has a lifetime of at least 1000 hours at a maximum operating temperature of at least 250°C and an operating voltage of at least 2.0V.

21. 15. The apparatus of claim 14, wherein the ultracapacitor has a life span of at least 1000 hours at a maximum operating temperature of at least 250°C and an operating voltage of at least 3.0V.

22. 15. The apparatus of claim 14, wherein the ultracapacitor has a life span of at least 1000 hours at a maximum operating temperature of at least 250°C and an operating voltage of at least 4.0V.

23. 15. The apparatus of claim 14, wherein the ultracapacitor has a lifetime of at least 1000 hours at a maximum operating temperature of at least 300°C and an operating voltage of at least 1.0V.

24. 15. The apparatus of claim 14, wherein the ultracapacitor has a lifetime of at least 1000 hours at a maximum operating temperature of at least 300°C and an operating voltage of at least 2.0V.

25. 15. The apparatus of claim 14, wherein the ultracapacitor has a lifetime of at least 1000 hours at a maximum operating temperature of at least 300°C and an operating voltage of at least 3.0V.

26. 15. The apparatus of claim 14, wherein the ultracapacitor has a life span of at least 1000 hours at a maximum operating temperature of at least 300°C and an operating voltage of at least 4.0V.

27. dispersing carbon nanotubes in a solvent to form a dispersion; mixing the carbonaceous material and the dispersion to form a slurry; applying a slurry to the layer; drying the slurry to substantially remove the solvent to form an active storage layer comprising a network of carbon nanotubes defining void spaces and a carbonaceous material disposed in the void spaces and bound by the network of carbon nanotubes; The length of the carbon nanotube is longer than the thickness of the active storage layer. the carbon nanotube network is present in the active storage layer in an amount ranging from 0.5% to 4% by weight based on the weight of the active storage layer; an adhesive layer disposed between the active layer and the conductive layer, the adhesive layer comprising at least 50% by weight of carbon nanotubes; The method, wherein the active storage layer is a heat treated layer that is free of non-carbon impurities.

28. The method of claim 27, comprising applying a slurry onto the adhesive layer.

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