Capacitor structure and method for fabricating the same

Abstract

This application discloses a capacitor structure and its fabrication method. The capacitor structure includes: a first electrode comprising a carbon nanotube; a second electrode comprising graphene and vanadium oxide; a separating membrane separating the first electrode and the second electrode; and a first-type electrolyte surrounding the first electrode, the second electrode, and the separating membrane.

Description

[Technical Field]

[0001] This application claims priority to U.S. Patent Application No. 18 / 903,246 (i.e., priority date "October 1, 2024"), the contents of which are incorporated herein by reference in their entirety.

[0002] This disclosure relates to a capacitor structure and a method for manufacturing the same, and more specifically, to an asymmetric supercapacitor and a method for manufacturing the same. [Previous Technology]

[0003] While conventional capacitors are practical in many applications, they cannot meet the needs of electric vehicles (EVs) and renewable energy systems. These capacitors typically have low energy density, meaning they can only store a limited amount of energy relative to their weight and size, a critical limitation for applications requiring rapid energy storage and discharge. For example, in electric vehicles, conventional capacitors cannot provide the high power output needed for rapid acceleration or effectively manage regenerative braking. Furthermore, their limited lifespan and charge-discharge cycle life make them less suitable for applications requiring durability and reliability. With the growing demand for more efficient and sustainable energy solutions, the need for supercapacitors is also increasing, as they offer higher energy and power density, faster charging times, and longer cycle life. These characteristics make supercapacitors ideal for integration with conventional battery systems, improving performance, and expanding the operation of modern electric vehicles and other energy-intensive applications.

[0004] The discussion in the preceding technical paragraphs is for background information only. The statements in the discussion in the preceding technical paragraphs are not an admission that the content disclosed in this paragraph constitutes the prior art of this disclosure, and nothing in the discussion in the preceding technical paragraphs shall be used as an admission that any part of this application, including the parts in the discussion in the preceding technical paragraphs, constitutes the prior art of this disclosure. [Summary of the Invention]

[0005] One aspect of this disclosure provides a capacitor structure, including: a first electrode including a carbon nanotube; a second electrode including graphene and vanadium oxide; a separator separating the first electrode and the second electrode; and a first type electrolyte surrounding the first electrode, the second electrode and the separator.

[0006] Another aspect of this disclosure provides a capacitor structure, including: a first electrode comprising a carbon nanotube; a second electrode comprising graphene and vanadium oxide; and a second type electrolyte located between the first electrode and the second electrode; wherein the second type electrolyte is a solid electrolyte. Both the first electrode and the second electrode are in contact with the second type electrolyte.

[0007] Another aspect of this disclosure provides a method for manufacturing a capacitor structure, comprising: forming a first electrode on a first conductive collector; forming a second electrode on a second conductive collector; and encapsulating the first electrode, the first conductive collector, the second electrode, the second conductive collector together with an insulating membrane separating the first electrode and the second electrode in a housing, and filling the housing with a first type electrolyte; wherein the first electrode comprises a carbon nanotube. The second electrode comprises graphene and vanadium oxide.

[0008] Due to the design of the capacitor structure disclosed herein, the first electrode employs a carbon nanotube, thereby making the dispersion more uniform and enhancing charge transport. Furthermore, the graphene in the second electrode provides a larger surface area for distributing vanadium oxide, further improving the conductivity of the second electrode. Therefore, the overall performance of the capacitor structure can be improved. Moreover, the use of a second type of electrolyte enhances the safety, mechanical stability, and operating voltage window of the capacitor structure, while also reducing self-discharge.

[0009] The technical features and advantages of this disclosure have been summarized quite extensively above to provide a better understanding of the detailed description of this disclosure below. Other technical features and advantages constituting the subject matter of the claims of this disclosure will be described below. Those skilled in the art to which this disclosure pertains will understand that the concepts and specific embodiments disclosed below can be readily used to modify or design other structures or processes to achieve the same purpose as this disclosure. Those skilled in the art to which this disclosure pertains will also understand that such equivalent constructions cannot depart from the spirit and scope of this disclosure as defined in the appended claims.

Implementation Method

[0011] This disclosure provides numerous different embodiments or examples for implementing various features of the provided subject matter. Specific examples of components and configurations described below are provided to simplify this disclosure. Of course, these are merely illustrative and not intended to be limiting. For example, in the following description, forming a first feature on or above a second feature may include embodiments in which the first and second features are formed in direct contact, or embodiments in which an additional feature is formed between the first and second features such that the first and second features may not be in direct contact. Furthermore, element symbols and / or letters may be repeated in various examples in this disclosure. Such repetition is for simplicity and clarity and is not in itself a limitation on the relationship between the various embodiments and / or configurations discussed.

[0012] Furthermore, for ease of description, spatially related terms may be used herein, such as "below," "under," "lower part," "above," "upper part," or other similar terms, to describe the relative relationship between one element or feature depicted in the diagram and another element or feature. In addition to the orientations depicted in the diagram, spatially related terms are intended to cover different orientations of the element in use or operation. The element may be oriented in other ways (rotated 90 degrees or otherwise), and the spatially relative descriptors used herein may be interpreted accordingly.

[0013] It should be understood that when a component or layer is referred to as being "connected to" or "coupled to" another component or layer, it may be directly connected to or coupled to another component or layer, or there may be intermediate components or intermediate layers.

[0014] It should be understood that although various elements may be described herein using the terms first, second, etc., these elements should not be limited by these terms. Unless otherwise stated, these terms are used only to distinguish one component from another. Thus, for example, the first component, first member, or first part discussed below may be referred to as the second component, second member, or second part without departing from the teachings of this disclosure.

[0015] Unless the context otherwise indicates, terms such as “identical,” “equal,” “plane,” or “coplanar” as used herein do not necessarily mean exactly the same orientation, layout, location, shape, size, quantity, or other measure when referring to orientation, layout, location, shape, size, quantity, or other measure, but are intended to cover substantially identical orientations, layouts, locations, shapes, sizes, quantities, or other measures within an acceptable range of possible variations (e.g., due to manufacturing processes). The term “substantially” may be used herein to reflect this meaning. For example, articles described as “substantially identical,” “substantially equal,” or “substantially coplanar” may be exactly the same, equal, or coplanar, or may be substantially identical, equal, or coplanar within an acceptable range of possible variations (e.g., due to manufacturing processes).

[0016] It should be noted that in the description disclosed herein, "above" (or "up") corresponds to the direction of the arrow in the Z direction, and "below" (or "down") corresponds to the opposite direction of the arrow in the Z direction.

[0017] It should be noted that the term "about," which modifies the amount of ingredients, components, or reactants disclosed herein, refers, for example, to numerical variations that may occur through typical measurement and liquid handling procedures used to prepare concentrates or solutions. Furthermore, variations may occur due to unintentional errors in the measurement procedures, differences in the manufacture, source, or purity of the ingredients used to prepare the composition or to carry out the method, etc. On one hand, the term "about" means within 10% of the reported value. On another hand, the term "about" means within 5% of the reported value. And yet another hand, the term "about" means within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1% of the reported value.

[0018] Figure 1 is a cross-sectional view illustrating a capacitor structure 100A according to an embodiment of the present disclosure. Figure 2 illustrates a graphene strip according to an embodiment of the present disclosure. Figure 3 illustrates a cylindrical graphene strip according to an embodiment of the present disclosure. Figure 4 illustrates a cross-section of a multi-walled carbon nanotube according to some embodiments of the present disclosure.

[0019] Referring to Figure 1, the capacitor structure 100A may include a first electrode 110, a second electrode 210, a first conductive collector 120, a second conductive collector 220, a separator 310, a first-type electrolyte 410, and a housing 610. The first electrode 110 may be disposed on the first conductive collector 120 and electrically connected to the first conductive collector 120. The second electrode 210 may be disposed on the second conductive collector 220 and electrically connected to the second conductive collector 220. The first electrode 110 and the second electrode 210 may be opposite each other with the separator 310 between them. The first electrode 110, the first conductive collector 120, the second electrode 210, the second conductive collector 220, and the separator 310 may be immersed in the first-type electrolyte 410 and encapsulated in the housing 610. In other words, the housing 610 may be filled with the first-type electrolyte 410. The first type electrolyte 410 may surround the first electrode 110, the first conductive collector 120, the second electrode 210, the second conductive collector 220, and the separator 310.

[0020] Referring to FIG1, in some embodiments, the size D1 of the first electrode 110 and the size D2 of the first conductive collector 120 may be substantially the same. In some embodiments, the size D1 of the first electrode 110 may be smaller than the size D2 of the first conductive collector 120. In some embodiments, the size D3 of the second electrode 210 and the size D4 of the second conductive collector 220 may be substantially the same. In some embodiments, the size D3 of the second electrode 210 may be smaller than the size D4 of the second conductive collector 220. In some embodiments, the size D5 of the insulating film 310 may be larger than the size D1 of the first electrode 110, the size D2 of the first conductive collector 120, the size D3 of the second electrode 210, or the size D4 of the second conductive collector 220.

[0021] Referring to Figure 1, in some embodiments, the first electrode 110 may include a carbon nanotube. In some embodiments, the first electrode 110 may include nitrogen atoms. In some embodiments, the first electrode 110 may include nitrogen atoms bonded to the carbon nanotube. In some embodiments, the first electrode 110 may include a nitrogen-doped carbon nanotube. In some embodiments, the carbon nanotube may be a single-walled nanotube, a multi-walled nanotube, or a combination thereof. The carbon nanotube can be considered as a graphene ribbon rolled into a tubular or cylindrical shape (as shown in Figure 2).

[0022] Referring to Figure 2, in some embodiments, the graphene ribbon comprises a plurality of sp 2-hybridized carbon atoms 176 interconnected to form an atomically thick sheet 178. In some embodiments, the graphene ribbon may have one or more corrugations conforming to the sheet 178. In some embodiments, the corrugations may have an amplitude of at least less than about 25 nanometers (nm), preferably about 1 nm. In some embodiments, the amplitudes of the one or more corrugations may be different. That is, one corrugation may have an amplitude α, while another corrugation may have an amplitude δ, where α and δ may be different. In some embodiments, the graphene ribbon may have an electron mobility of at least about 5,000 cm²V⁻¹s⁻¹. In some embodiments, the electron mobility of the graphene ribbon may be at least about 10,000 cm²V⁻¹s⁻¹, or at least about 15,000 cm²V⁻¹s⁻¹. The high electron mobility of graphene bands can support charge transport capabilities.

[0023] A plurality of sp2 mixed carbon atoms 176 may be interconnected in groups. In some embodiments, at least a majority of the sp2 mixed carbon atoms in the graphene strip are interconnected in groups of six carbon atoms, wherein each group of six carbon atoms forms a substantially flat regular hexagon 132. In some embodiments, at least about 95% of the sp2 mixed carbon atoms 176 in the graphene strip may be interconnected in groups of six carbon atoms to form a plurality of regular hexagons 132. In some embodiments, at least about 99% of the sp2 mixed carbon atoms 176 in the graphene strip may be interconnected to form a plurality of regular hexagons 132. In some embodiments, at least about 99.99% of the sp2 mixed carbon atoms 176 in the graphene strip may be interconnected to form a plurality of regular hexagons 132.

[0024] In some embodiments, each side 134 of the regular hexagon 132 may have a carbon-carbon bond length from about 0.075 nm to about 0.35 nm. In some embodiments, each side 134 of the regular hexagon 132 has a carbon-carbon bond length from about 0.1 nm to about 0.2 nm or from about 0.13 nm to about 0.16 nm. In some embodiments, the graphene ribbon may include a large aromatic molecule, wherein the large aromatic molecule contains a plurality of sp2 mixed carbon atoms 176.

[0025] In some embodiments, at least some of the sp2 mixed carbon atoms 176 of the graphene strip can be interconnected in one or more groups of four, five, seven, eight, and nine carbon atoms. These one or more groups of four, five, seven, eight, and nine carbon atoms can be interconnected with one or more groups of regular hexagons 132 of the sp2 mixed carbon atoms 176 of the graphene strip. In some embodiments, at least some of the sp2 mixed carbon atoms 176 of the graphene strip can be interconnected in groups of five carbon atoms, wherein each group of five carbon atoms forms a substantially regular pentagon. In some embodiments, at least some of the sp2 mixed carbon atoms 176 of the graphene strip can be interconnected in groups of seven carbon atoms, wherein each group of seven carbon atoms forms a substantially regular heptagon.

[0026] Referring to Figure 3, each single-walled nanotube may include a single graphene strip configured as a nanotube. In some embodiments, each single-walled nanotube may include a seamless hollow tube, wherein the seamless hollow tube has an atomically thick graphene wall and a chiral vector. In some embodiments, the chiral vector may include a pair of indices (n, m), which represent unit vectors along two directions of the graphene strip lattice. In some embodiments, the single-walled nanotube may have a chiral vector, wherein one of the following is true: a) n = m; and b) (nm) / 3 is an integer.

[0027] In some embodiments, the diameter of each single-walled nanotube may be between about 1 Å and about 200 nm, between about 3 nm and about 50 nm, or between about 10 nm and about 20 nm. In some embodiments, the length 122 of each single-walled nanotube may be between about 1,000 nm and about 10 cm, between about 200 micrometers (µm) and about 1,000 µm, or between about 500 µm and about 600 µm. In some embodiments, each single-walled nanotube may include a first end 144 and a second end 146. The first end 144 and the second end 146 may be opposite each other. In some embodiments, the first end 144 and the second end 146 may be turned on or off. In some embodiments, the first end 144 may be located on a first conductive collector 120.

[0028] Referring to Figure 4, each multi-walled nanotube may include one or more graphene ribbons 132 (as shown in Figure 2) wound around a single-walled nanotube core. These graphene ribbons 132 form multiple graphene walls 118. The multi-walled nanotube may have a concentric cylindrical structure (labeled 126 in Figure 4) or a helical structure (labeled 128 in Figure 4). The interlayer distance 130 between the graphene ribbons, which is the annular space between the inner and outer graphene walls 118 or the difference between the diameter of the outer graphene ribbon and the diameter of the inner graphene ribbon, may be between about 1 Å and about 10 Å, or between about 2 Å and about 4 Å.

[0029] In some embodiments, carbon nanotubes can be formed by various methods, including: epitaxial growth, silicon carbide reduction, hydrazine reduction, sodium reduction of ethanol, chemical vapor deposition, high-temperature and high-pressure carbon monoxide vapor phase synthesis, catalytic vapor deposition using carbon-containing raw materials and metal catalyst particles, laser ablation, arc method, template synthesis, template-free synthesis, or self-assembly synthesis. In some embodiments, carbon nanotubes can be formed by chemical vapor deposition or plasma-enhanced chemical vapor deposition. Chemical vapor deposition can be used to grow random carbon nanotubes, while plasma-enhanced chemical vapor deposition can produce aligned carbon nanotubes on various conductive or semiconductive substrates. In some embodiments, nitrogen gas may be included during plasma-enhanced chemical vapor deposition. In some embodiments, carbon nanotubes can be used in a synthetic form or in a form modified with metals such as group VIB and group VIIIB elements. These metals can serve as catalysts or substrates for the synthesis of carbon nanotubes.

[0030] As an example, a thin layer of aluminum (e.g., 10 nm thick) can be coated on a conductive substrate (e.g., nickel foil), followed by a 3 nm thick iron film as a catalyst for carbon nanotube growth. This substrate can then be heated in a quartz tube furnace (at approximately 750°C) and exposed to a mixed gas containing approximately 48% argon, approximately 28% hydrogen, and approximately 24% ethylene for a duration ranging from approximately 10 to approximately 20 minutes. This process can produce carbon nanotubes whose length can be controlled by adjusting the gas pressure and exposure time.

[0031] As another example, template-free synthesis can be provided to mass-produce well-aligned carbon nanotubes. In this embodiment, iron(III) phthalocyanine can be pyrolyzed onto a quartz substrate at a temperature from about 800°C to about 1100°C to form a film of oriented carbon nanotubes, followed by sputtering a metal layer (e.g., aluminum with a thickness ranging from 5 μm to 100 μm) onto this film of oriented carbon nanotubes. The carbon nanotubes can then be peeled off in a dry state using double-sided conductive tape.

[0032] In both examples, the length of the carbon nanotubes can be controlled by controlling the pressure of the gas mixture and the duration of exposure of the heated substrate to the gas mixture. In both examples, the carbon nanotubes can be grown in a highly oriented manner, wherein the individual carbon nanotubes are substantially parallel to each other and perpendicular to the substrate (e.g., the first conductive collector 120). In some embodiments, the spacing between the carbon nanotubes can be between about 1 nm and about 1,000 nm, or between about 10 nm and about 250 nm.

[0033] In some embodiments, plasma etching (or other forms of etching or milling) may be performed to remove the ends or tips of the carbon nanotubes and open the interior of the carbon nanotubes, thereby effectively doubling the electrolyte-accessible surface area of ​​the carbon nanotubes. In some embodiments, etching may also purify the carbon nanotubes by removing residual catalyst.

[0034] In some embodiments, etching may be oxygen plasma etching. Oxygen plasma etching can substantially remove any surface contamination and / or amorphous carbon on the carbon nanotubes. Oxygen plasma etching can be performed by operating a radio frequency generator at 250 kHz, 30 W, and 0.62 Torr for 20 minutes. Oxygen plasma etching can increase the spacing between carbon nanotubes.

[0035] Referring again to FIG. 1, a first electrode 110 may be disposed on the first conductive collector 120. In some embodiments, the carbon nanotube of the first electrode 110 may be substantially perpendicular to the first conductive collector 120. In some embodiments, the first conductive collector 120 may be any highly conductive and / or superconducting material. Examples may include, but are not limited to: conductive metal (e.g., copper, aluminum, nickel, and stainless steel) foil, conductive metal mesh, conductive polymer, conductive polymer composite material, graphite, superconducting ceramics, and other similar materials. In some embodiments, the first conductive collector 120 may be porous or non-porous. In some embodiments, the first conductive collector 120 may be nickel foil. In some embodiments, the thickness of the first conductive collector 120 may be sufficient to provide current collection for the first electrode 110. In some embodiments, the thickness of the first conductive collector 120 may be between about 10 µm and about 75 µm.

[0036] Referring to FIG. 1, the second electrode 210 may include graphene. In some embodiments, the second electrode 210 may include nitrogen atoms. In some embodiments, the second electrode 210 may include nitrogen atoms bonded to graphene. In some embodiments, the second electrode 210 may include nitrogen-doped graphene. In some embodiments, the second electrode 210 may include vanadium oxide (e.g., V₂O₅). It should be noted that in this disclosure, graphene and graphene sheets are used interchangeably.

[0037] In some embodiments, the graphene of the second electrode 210 can be formed by the reduction of graphene oxide. Graphene oxide can be formed by the exfoliation of graphene oxide. Graphene oxide can be formed by the chemical oxidation of graphite using any suitable known oxidant.

[0038] In some embodiments, purified graphene oxide can be exfoliated by liquid dispersion using ultrasonic treatment or mechanical shearing to form graphene oxide. In some embodiments, the majority of the dried graphene oxide is subjected to rapid thermal treatment, resulting in partial or complete exfoliation due to the volatilization of bonded oxygen groups (epoxy, carboxyl, hydroxyl) and any incorporated substances (e.g., water, other solvents, residual acids, or intentionally incorporated substances).

[0039] In some embodiments, the purified and exfoliated graphene oxide (in the form of graphene oxide) may then be reduced. The reduction may be a chemical reduction, which involves adding a reducing agent to the graphene oxide to convert it into reduced graphene oxide or graphene. In some embodiments, the purified and exfoliated graphene oxide may be dispersed in water before reduction. In some embodiments, the concentration of the graphene oxide dispersed in water (i.e., the purified and exfoliated graphene oxide) may be less than 0.05% by weight.

[0040] In some embodiments, the reducing agent may include inorganic reducing agents (e.g., hydrazine or sodium borohydride) and organic reducing agents (e.g., hydroquinone, dimethylhydrazine, or N,N'-diethylhydroxylamine). In some embodiments, the reducing agent may be hydrazine. When the reducing agent is hydrazine, the amount added may be 1.0 to 7.0 grams of 35% hydrazine per gram of graphite oxide, 1.5 to 5.0 grams of 35% hydrazine per gram of graphite oxide, or 1.5 to 2.5 grams of 35% hydrazine per gram of graphite oxide. In some embodiments, the reducing agent may include a wide range of liquid and gaseous chemicals, such as ascorbic acid, sulfur-based reducing agents (e.g., sodium sulfite, sodium bisulfite, sodium thiosulfate, sodium sulfide, thiocyanate, sulfur dioxide), dipotassium hydrogen phosphate, oxalate, hydroxide, hydroquinone, indole, sugar, iodide, protein, metal hydride, hydrogen, carbon monoxide, urea, and ammonia. In some embodiments, graphene oxide can also be reduced by heat and light.

[0041] In some embodiments, the pH value during graphene oxide reduction may be greater than 6 or between 9 and 11. The pH value during graphene oxide reduction can be adjusted by adding an alkali. In some embodiments, the alkali may include ammonia, sodium hydroxide, potassium hydroxide, or a water-soluble organic alkali, such as methylamine, ethanolamine, dimethylamine, and trimethylamine. In some embodiments, the alkali may be a volatile alkali, such as ammonia, which may be removed after the graphene is processed into a solid film or composite material. When the alkali is ammonia, the amount added may be 7 to 20 grams of 28% ammonia per gram of graphene oxide, 8 to 16 grams of 28% ammonia per gram of graphene oxide, or 10 to 13 grams of 28% ammonia per gram of graphene oxide.

[0042] In some embodiments, graphene can be formed on the second conductive collector 220 by drop casting, evaporation, coating, precipitation, spraying (e.g., air spraying) or other suitable techniques of diluting graphene dispersion.

[0043] In some embodiments, heat treatment, such as annealing, may be performed to improve the rigidity and strength of the graphene in the second electrode 210. In some embodiments, the heat treatment process temperature may be about 220°C. The enhanced mechanical properties can be attributed to the better orderliness of the graphene stack resulting from the heat treatment, thereby enhancing the interlayer contact interactions of the graphene sheets.

[0044] In some embodiments, graphene may be dispersed in water or a solvent containing a binder to form a mixture. The weight ratio of graphene to binder may be between 25:75 and 99:1, or between 90:10 and 98:2. In some embodiments, the binder may include cellulose materials, rubber, and fluorinated resins. In some embodiments, graphene may be dispersed in water or a solvent containing a binder and spacers to form a mixture. In some embodiments, graphene may be dispersed in water or a solvent containing spacers to form a mixture. The spacers may prevent or reduce the recombination of graphene sheets. This mixture may then be dried on the second conductive collector 220. In some embodiments, graphene and spacers may be co-precipitated on the second conductive collector 220. In some embodiments, the co-precipitation of graphene and spacers may be induced by adding salt, changing the pH value, or the concentration.

[0045] In some embodiments, the spacer may include surface modification of the graphene sheet, such as surface deformation or attachment of polymers or particles. In some embodiments, the spacer may include a polymer added between the graphene sheets. In some embodiments, this polymer may be conductive to further improve the conductivity of the second electrode 210.

[0046] In some embodiments, the spacer may include particles of a primarily chemically inert material, such as carbon black, activated carbon, carbon nanotubes, carbon nano-onions, carbon nanofibers, and other carbon allotropes or other forms of carbon. In some embodiments, the spacer may include inert particles, wherein the inert particles include oxides (e.g., alumina, zirconium oxide, or silicon oxide) and non-oxides (silicon, carbides, or nitrides).

[0047] In some embodiments, the spacers may include molecules that will remain between the graphene sheets during operation of the second electrode 210. For example, large organic salts may be spatially locked in place by the re-aggregation of graphene, but prevented from re-stacking and maintain a high accessible surface area by other electrolytes, including other more mobile ionic liquids. The spacer molecules may include adhesives, polyionic liquid polymers, ionic polymers, and ionic liquids, etc.

[0048] In some embodiments, the spacers can be bonded to graphene by reduction of the graphene oxide dispersion in the presence of spacers. For example, reduction of graphene oxide in the presence of cationic polyethyleneimine can produce water-soluble PEI-modified graphene sheets. As another example, graphene oxide in a dispersion containing carbon black is reduced to form a composite material, wherein the carbon black separates the basal surfaces of the graphene.

[0049] An exemplary example of forming the graphene in the second electrode 210 can be described as follows. Graphite oxide can be synthesized from graphite by purifying the product using the Hummers method and an additional dialysis step. The synthesized graphite oxide is suspended in water to obtain a brown dispersion, which can be dialyzed to completely remove residual salts and acids. The purified graphite oxide suspension can then be dispersed in water to form a 0.05% by weight dispersion. By ultrasonically treating the dispersion for 30 minutes, the graphite oxide can be exfoliated into graphene oxide. The resulting brown dispersion can then be centrifuged at 3000 RPM for 30 minutes to remove any unexfoliated graphite oxide (typically present in very small amounts). To achieve the chemical conversion of graphene oxide to graphene, the resulting homogeneous dispersion (5.0 mL) was mixed with 5.0 mL of water, 5.0 μL of hydrazine solution (35% by weight aqueous solution), and 35.0 μL of ammonia solution (28% by weight aqueous solution) in a 20 mL glass vial. After vigorous shaking or stirring for several minutes, the vial was placed in a water bath at 95°C for 1 hour. Excess hydrazine in the reaction mixture could be removed by dialysis with diluted ammonia solution.

[0050] In some embodiments, the second electrode 210 may be a layered structure. For example, the second electrode 210 may include: a bottom layer containing graphene (or nitrogen-doped graphene), and a top layer disposed on the bottom layer and containing vanadium oxide. The bottom layer of the second electrode 210 may be disposed on the second conductive collector 220. In some embodiments, the top layer containing vanadium oxide may be formed by, for example, electrochemical deposition, chemical vapor deposition, physical vapor deposition, sputtering, or reactive deposition. In some embodiments, the thickness of the top layer containing vanadium oxide may be between about 1 nm and about 100 nm. In some embodiments, vanadium oxide may be dispersed in the spaces between the graphene sheets.

[0051] Referring to FIG. 1, a second electrode 210 may be disposed on the second conductive collector 220. In some embodiments, the second conductive collector 220 and the first conductive collector 120 may be formed of the same material. In some embodiments, the second conductive collector 220 and the first conductive collector 120 may be formed of different materials. In some embodiments, the second conductive collector 220 may be any highly conductive and / or superconducting material. Examples may include, but are not limited to: conductive metal (e.g., copper, aluminum, nickel, and stainless steel) foil, conductive metal mesh, conductive polymer, conductive polymer composite material, graphite, superconducting ceramics, and other similar materials. In some embodiments, the second conductive collector 220 may be porous or non-porous. In some embodiments, the second conductive collector 220 may be nickel foil. In some embodiments, the thickness of the second conductive collector 220 may be sufficient to provide current collection for the second electrode 210. In some embodiments, the thickness of the second conductive collector 220 may be between about 10 µm and about 75 µm.

[0052] Referring to FIG1, an isolation membrane 310 may be disposed between the first electrode 110 and the second electrode 210. In some embodiments, the isolation membrane 310 may comprise a thin, non-conductive, and porous material. The porosity of the isolation membrane 310 may be between about 40% and about 87%, or between about 65% and about 85%. The thickness of the isolation membrane 310 may be between about 25 μm and about 75 μm.

[0053] Referring to Figure 1, the first type electrolyte 410 can be liquid. The first electrode 110, the first conductive collector 120, the second electrode 210, the second conductive collector 220, and the separator 310 can be immersed in the first type electrolyte 410. In some embodiments, the first type electrolyte 410 may include an aqueous electrolyte, an organic electrolyte, or an ionic liquid. In some embodiments, the aqueous electrolyte may include sulfuric acid, potassium hydroxide, sodium sulfate, or sodium chloride. In some embodiments, the organic electrolyte may include tetraethylammonium tetrafluoroborate or propylene carbonate and lithium salt. In some embodiments, the ionic liquid may include 1-butyl-3-methylimidazolium tetrafluoroborate or 1-ethyl-3-methylimidazolium ethyl sulfate.

[0054] Referring to Figure 1, the first electrolyte 410, the first electrode 110, the first conductive collector 120, the second electrode 210, the second conductive collector 220, and the separator 310 can be encapsulated in the housing 610. In some embodiments, the housing 610 can be formed of materials such as aluminum, titanium, stainless steel, or polymer materials (e.g., polypropylene or polyvinyl chloride).

[0055] By using carbon nanotubes as the first electrode 110, the dispersion can be made more uniform, and charge transfer can be enhanced. Furthermore, the graphene in the second electrode 210 can provide a larger surface area for the distribution of vanadium oxide, thereby further improving the conductivity of the second electrode. In this way, the overall performance of the capacitor structure 100A can be improved.

[0056] FIG5 is a cross-sectional view illustrating a capacitor structure 100B according to another embodiment of the present disclosure.

[0057] Referring to Figure 5, the capacitor structure 100B may include a first electrode 110, a second electrode 210, a first conductive collector 120, a second conductive collector 220, a second type electrolyte 510, and a housing 610. The first electrode 110 may be disposed on the first conductive collector 120 and electrically connected to the first conductive collector 120. The second electrode 210 may be disposed on the second conductive collector 220 and electrically connected to the second conductive collector 220. The first electrode 110 and the second electrode 210 may be opposite each other with the second type electrolyte 510 in between. Both the first electrode 110 and the second electrode 210 may be in contact with the second type electrolyte 510. The first electrode 110, the first conductive collector 120, the second electrode 210, the second conductive collector 220, and the second type electrolyte 510 may be encapsulated in the housing 610.

[0058] Referring to FIG5, in some embodiments, the size D1 of the first electrode 110 and the size D2 of the first conductive collector 120 may be substantially the same. In some embodiments, the size D1 of the first electrode 110 may be smaller than the size D2 of the first conductive collector 120. In some embodiments, the size D3 of the second electrode 210 and the size D4 of the second conductive collector 220 may be substantially the same. In some embodiments, the size D3 of the second electrode 210 may be smaller than the size D4 of the second conductive collector 220. In some embodiments, the size D6 of the second type electrolyte 510 may be larger than the size D1 of the first electrode 110, the size D2 of the first conductive collector 120, the size D3 of the second electrode 210, or the size D4 of the second conductive collector 220.

[0059] Referring to Figure 5, the first electrode 110, the first conductive collector 120, the second electrode 210, the second conductive collector 220 and the housing 610 can be formed using the same or similar materials and steps as those in Figure 1, and will not be described again here.

[0060] Referring to Figure 5, the second type electrolyte 510 may be a solid electrolyte. In some embodiments, the second type electrolyte 510 may include an ion-conducting polymer, or a combination of an ion-conducting polymer and an ionic compound. In some embodiments, the thickness of the second type electrolyte 510 may be between about 0.5 μm and about 50 μm. In some examples, the ion-conducting polymer may include polyetheretherketone, sulfonated polyetheretherketone, polystyrene, poly(ether ketone ketone), polyethylene oxide, perfluorosulfonic acid polymer, polyvinyl alcohol, polytetrafluoroethylene, polypyrrole, polyvinylidene fluoride, polyvinyl dioxythiophene, polyaniline, or combinations thereof. In some embodiments, the ionic compound may include lithium hydroxide, lithium nitrate, lithium trifluoromethyl sulfur trioxide, or combinations thereof. In some embodiments, the ionic compound may include lithium salts, sodium salts, potassium salts, magnesium salts, ammonium salts, imidazolium-based salts, and / or pyridinium-based salts. In some embodiments, the lithium salt may include lithium hexafluorophosphate or lithium perchlorate. In some embodiments, the potassium salt may include potassium hydroxide. In some embodiments, the sodium salt may include sodium sulfate or sodium nitrate. In some embodiments, the ammonium salt may include ammonium perchlorate. In some embodiments, the magnesium salt may include magnesium perchlorate. In some embodiments, the imidazole salt may include 1-ethyl-3-methylimidazolium tetrafluoroborate or 1-butyl-3-methylimidazolium tetrafluoroborate. In some embodiments, the pyridine salt may include 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imidine or 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imidine.

[0061] By using the second type electrolyte 510, the safety, mechanical stability, operating voltage window and miniaturization potential of the capacitor structure 100B can be improved, and the self-discharge of the capacitor structure 100B can be reduced.

[0062] Figure 6 is a flowchart illustrating a method 10 for manufacturing a capacitor structure 100A according to an embodiment of the present disclosure.

[0063] Referring to FIG6, in step S11, a first electrode 110 may be formed on the first conductive collector 120. In some embodiments, the first electrode 110 may include a carbon nanotube and may be formed using various methods, including: epitaxial growth, silicon carbide reduction, hydrazine reduction, sodium reduction of ethanol, chemical vapor deposition, high-temperature and high-pressure carbon monoxide vapor phase synthesis, catalytic vapor deposition using carbon-containing raw materials and metal catalyst particles, laser ablation, arc method, template synthesis, template-free synthesis, or self-assembly synthesis. In some embodiments, the first electrode 110 may be grown directly on the first conductive collector 120 using a catalyst, or the first electrode 110 may be formed separately and then transferred to the collector.

[0064] Referring to FIG6, in step S13, a second electrode 210 may be formed on the second conductive collector 220. In some embodiments, the second electrode 210 may include graphene and vanadium oxide. Graphene may be formed by the reduction of graphene oxide. In some embodiments, graphene may be formed on the second conductive collector 220 by drop casting, evaporation, coating, precipitation, spraying (e.g., spray gun spraying) or other suitable techniques of diluted graphene dispersion. Vanadium oxide may be formed by, for example, electrochemical deposition, chemical vapor deposition, physical vapor deposition, sputtering or reactive deposition.

[0065] Referring to Figure 6, in step S15, the first electrode 110, the first conductive collector 120, the second electrode 210 and the second conductive collector 220, together with the separating membrane 310 separating the first electrode 110 and the second electrode 210, can be encapsulated in the housing 610 and filled with the first type electrolyte 410.

[0066] The first electrode 110, the first conductive collector 120, the second electrode 210, the second conductive collector 220, the separator 310, the first electrolyte 410 and the shell 610 together constitute the capacitor structure 100A.

[0067] One aspect of this disclosure provides a capacitor structure, including: a first electrode including a carbon nanotube; a second electrode including graphene and vanadium oxide; a separator separating the first electrode and the second electrode; and a first type electrolyte surrounding the first electrode, the second electrode and the separator.

[0068] Another aspect of this disclosure provides a capacitor structure, including: a first electrode comprising a carbon nanotube; a second electrode comprising graphene and vanadium oxide; and a second type electrolyte located between the first electrode and the second electrode; wherein the second type electrolyte is a solid electrolyte. Both the first electrode and the second electrode are in contact with the second type electrolyte.

[0069] Another aspect of this disclosure provides a method for manufacturing a capacitor structure, comprising: forming a first electrode on a first conductive collector; forming a second electrode on a second conductive collector; and encapsulating the first electrode, the first conductive collector, the second electrode, and the second conductive collector together with a separating membrane separating the first electrode and the second electrode in a housing, and filling the housing with a first type electrolyte; wherein the first electrode comprises a carbon nanotube. The second electrode comprises graphene and vanadium oxide.

[0070] Due to the design of the capacitor structure disclosed herein, the first electrode 110 employs a carbon nanotube, thereby making the dispersion more uniform and enhancing charge transport. Furthermore, the graphene in the second electrode 210 provides a larger surface area for distributing vanadium oxide, further improving the conductivity of the second electrode 210. Therefore, the overall performance of the capacitor structure 100A can be improved. Moreover, the use of a second-type electrolyte 510 can enhance the safety, mechanical stability, and operating voltage window of the capacitor structure 100B, while also reducing self-discharge.

[0071] Although the present disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions and replacements can be made without departing from the spirit and scope of the present disclosure as defined in the claims. For example, many of the above-described processes can be implemented using different methods, and other processes or combinations thereof can be substituted for many of the above-described processes.

[0072] Furthermore, the scope of this application is not limited to the specific embodiments of the processes, machinery, manufacturing, material composition, means, methods, and steps described in the specification. Those skilled in the art can understand from the disclosure herein that existing or future processes, machinery, manufacturing, material composition, means, methods, or steps that have the same function or achieve substantially the same results as the corresponding embodiments described herein can be used based on this disclosure. Therefore, such processes, machinery, manufacturing, material composition, means, methods, or steps are included within the scope of the patent application of this application. [Simplified Explanation of the Diagram]

[0010] A more comprehensive understanding of the disclosure of this application can be obtained by referring to the drawings that combine the embodiments and the scope of the claim. It should be noted that, in accordance with industry standard practice, the features are not drawn to scale. In fact, for clarity of discussion, the dimensions of various features can be arbitrarily increased or decreased. Figure 1 is a cross-sectional view illustrating a capacitor structure according to an embodiment of this disclosure; Figure 2 illustrates a graphene strip according to an embodiment of this disclosure; Figure 3 illustrates a cylindrical graphene strip according to an embodiment of this disclosure; Figure 4 illustrates a cross-section of a multi-walled carbon nanotube according to some embodiments of this disclosure; Figure 5 is a cross-sectional view illustrating a capacitor structure according to another embodiment of this disclosure; and Figure 6 is a flowchart illustrating a method for manufacturing a capacitor structure according to an embodiment of this disclosure.

Claims

1. A capacitor structure, comprising: First conductive collector; A second conductive collector; A first electrode, comprising a carbon nanotube, and electrically connected to the first conductive collector; A second electrode, comprising graphene and vanadium oxide, and electrically connected to the second conductive collector; An insulating membrane separates the first electrode from the second electrode; And a first type electrolyte surrounding the first electrode, the second electrode and the separator; wherein the second electrode is a layered structure comprising: a bottom layer containing the graphene; and a top layer containing the vanadium oxide and located on the bottom layer.

2. The capacitor structure as claimed in claim 1, wherein a dimension of the first electrode is equal to or smaller than a dimension of the first conductive collector.

3. The capacitor structure as claimed in claim 1, wherein a dimension of the second electrode is equal to or smaller than a dimension of the second conductive collector.

4. The capacitor structure as claimed in claim 1, wherein a dimension of the isolation membrane is larger than a dimension of the first electrode.

5. The capacitor structure as claimed in claim 4, wherein the carbon nanotubes of the first electrode are nitrogen-doped.

6. The capacitor structure as claimed in claim 4, wherein the graphene of the second electrode is nitrogen-doped.

7. The capacitor structure as claimed in claim 1, wherein the thickness of the top layer is between about 1 nm and about 100 nm.

8. The capacitor structure as claimed in claim 4, wherein the thickness of the isolation film is between about 25 μm and about 75 μm.

9. The capacitor structure as claimed in claim 4, wherein the porosity of the separator is between about 40% and about 87%.

10. The capacitor structure as claimed in claim 4, wherein the first type electrolyte includes an aqueous electrolyte, an organic electrolyte, or an ionic liquid.

11. The capacitor structure as claimed in claim 4, wherein the first conductive collector comprises a metal foil.

12. The capacitor structure as described in claim 4, further comprising: A housing encapsulates the first electrode, the first conductive collector, the second electrode, the second conductive collector, the separator, and the first type electrolyte.

13. A capacitor structure, comprising: First conductive collector; A second conductive collector; A first electrode, comprising a carbon nanotube, and electrically connected to the first conductive collector; A second electrode comprising graphene and vanadium oxide and electrically connected to the second conductive collector; and a second type electrolyte located between the first electrode and the second electrode, wherein the second type electrolyte is a solid electrolyte, wherein both the first electrode and the second electrode are in contact with the second type electrolyte; wherein the second type electrolyte comprises a combination of an ion-conducting polymer and an ion compound; and wherein the thickness of the second type electrolyte is between about 0.5 μm and about 50 μm.

14. The capacitor structure as claimed in claim 13, wherein a dimension of the first electrode is equal to or smaller than a dimension of the first conductive collector.

15. The capacitor structure as claimed in claim 13, wherein a dimension of the second electrode is equal to or smaller than a dimension of the second conductive collector.

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