Supercapacitor electrode coating material comprising active composite particles and conductive carbon-containing particles

Abstract

A coating for use as a supercapacitor electrode is disclosed. The coating comprises active composite particles including activated metal oxide particles and carbon-containing support particles, and conductive carbon-containing particles.

Description

[Technical Field]

[0001] government contracts This disclosure was made with government support under Government Contract No. 2021039-142041 awarded by the United States Army Ground Vehicle Systems Center. The U.S. Government has certain rights in this disclosure.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 378,886, filed October 10, 2022, which is incorporated herein by reference.

[0003] A coating for use in a supercapacitor electrode is disclosed that includes active composite particles and conductive carbon-containing particles. [Background technology]

[0004] There is a great demand for high-power energy resources for use in various products, such as portable electronic devices and electric vehicles. Supercapacitors offer a promising alternative to conventional capacitors and can replace or be used in conjunction with batteries for such uses. Compared to conventional capacitors, the specific energy of supercapacitors can be several orders of magnitude higher. In addition, supercapacitors can store energy and provide power at rates relatively higher than those available with batteries. Summary of the Invention

[0005] Disclosed herein is a coating for use as a supercapacitor electrode, the coating comprising active composite particles including activated metal oxide particles and carbon-containing support particles, and conductive carbon-containing particles.

[0006] Disclosed herein are active composite particles for use in supercapacitor electrode coatings. The active composite particles include activated metal oxide particles and carbon-containing support particles.

[0007] Disclosed herein is a method of making active composite particles for use in supercapacitor electrode coatings, the method comprising spray-drying an aqueous solution comprising activated metal oxide particles and carbon-containing support particles, and recovering active composite particles comprising the activated metal oxide particles and the carbon-containing support particles.

[0008] Disclosed herein is a supercapacitor electrode comprising a current collector substrate, active composite particles comprising activated metal oxide particles and carbon-containing support particles, and an electrode coating comprising conductive carbon-containing particles. [Brief explanation of the drawings]

[0009] [Figure 1] 1 includes rheological profiles of various aqueous graphene dispersions. [Figure 2] 1 includes viscosity measurements of aqueous dispersions containing various amounts of graphene. [Figure 3] 1 includes the instability index of various aqueous graphene dispersions. [Figure 4] Contains rheological data for dispersions containing MnO2, graphene, conductive carbon, and a binder. [Figure 5] 1 is a cross-sectional scanning electron microscope image of a MnO2+GNP cathode coating on a carbon-coated Ni foil. [Figure 6] Cross-sectional scanning electron microscopy-electron dispersive spectroscopy (SEM-EDS) mapping of MnO2+GNP cathode coating on carbon-coated Ni foil. [Figure 7] 10 is a cross-sectional scanning electron microscope image of a MnO2|GNP cathode coating on a carbon-coated Ni foil. [Figure 8]Cross-sectional scanning electron microscopy-electron dispersive spectroscopy (SEM-EDS) mapping of MnO2|GNP cathode coating on carbon-coated Ni foil. [Figure 9] 10 is a cross-sectional scanning electron microscope image of a spray-dried MnO2|GNP cathode coating on a carbon-coated Ni foil. [Figure 10] Cross-sectional scanning electron microscopy-electron dispersive spectroscopy (SEM-EDS) mapping of spray-dried MnO2|GNP cathode coatings on carbon-coated Ni foils. [Figure 11] 1 includes capacitance versus current density (j) plots for electrodes with an 80 / 10 / 10 active / carbon black / binder coating. [Figure 12] 1 includes capacitance vs. current density (j) plots for electrodes with 88 / 2 / 10 active / carbon black / binder coatings. [Figure 13] 1 includes capacitance versus current density (j) plots for electrodes with an 80 / 10 / 10 active / carbon black / binder coating. [Figure 14] 1 includes capacitance versus current density (j) plots for electrodes with an 80 / 10 / 10 active / carbon black / binder coating. [Figure 15] This involves full-cell cyclic voltammetry using an 80 / 10 / 10 active / carbon black / binder electrode composition. [Figure 16] 1 includes capacitance versus current density (j) plots for electrodes with an 80 / 10 / 10 active / carbon black / binder coating. [Figure 17] Includes composite and interfacial resistivity measurements of supercapacitor cathode coatings on foil with an active / carbon black / binder blend of 88 / 2 / 10. DETAILED DESCRIPTION OF THE INVENTION

[0010] The supercapacitor electrode coating includes active composite particles and conductive carbon-containing particles. The supercapacitor electrode coating may also include a binder. The active composite particles may include activated metal oxide particles and graphene-based carbon nanoparticles. As used herein, the term "activated," when referring to metal oxide particles, means that the material undergoes physical, thermal, and / or chemical processes to accumulate ionic charge and / or generate electrochemical interactions or reactions with other components during use.

[0011] The electrode coatings can be used in various types of supercapacitors, including asymmetric supercapacitors, symmetric supercapacitors, Li-ion capacitors, Na-ion capacitors, etc. For example, as known to those skilled in the art, an asymmetric supercapacitor or asymmetric pseudocapacitor comprises two electrodes of different materials, i.e., a cathode and an anode, separated by an ion-conducting, electrically insulating electrolyte and a separator contained within a cell. The electrodes of different compositions store electrical energy through the adsorption of oppositely charged ions to their respective surfaces.

[0012] The electrode coatings can be used to produce supercapacitor cathodes and / or supercapacitor anodes. Although supercapacitor cathodes are primarily described herein, it should be understood that the present supercapacitor coatings can also be used as supercapacitor anodes.

[0013] The supercapacitor electrode coating may typically comprise at least 50 weight percent, or at least 60 weight percent, or at least 70 weight percent of the active composite particles, based on the total weight of the coating. The supercapacitor electrode coating may typically comprise up to 99 weight percent, or up to 98 weight percent, or up to 95 weight percent of the active composite particles. The supercapacitor electrode coating may typically comprise 50 to 99 weight percent, e.g., 60 to 98 weight percent, or 70 to 95 weight percent, of the active composite particles.

[0014] Supercapacitor electrode coatings typically contain at least 0.5 weight percent, or at least 1 weight percent, or at least 2 weight percent, or at least 4 weight percent, or at least 5 weight percent, or at least 8 weight percent of conductive carbon-containing particles, based on the total weight of the coating. Supercapacitor electrode coatings typically contain up to 50 weight percent, or up to 30 weight percent, or up to 20 weight percent, or up to 15 weight percent, or up to 12 weight percent of conductive carbon-containing particles. Supercapacitor electrode coatings typically contain 0.5 to 50 weight percent conductive carbon-containing particles, for example, 1 to 30 weight percent, or 2 to 20 weight percent, or 5 to 15 weight percent, or 8 to 12 weight percent conductive carbon-containing particles. The conductive carbon-containing particles may include carbon black or graphite.

[0015] Supercapacitor electrode coatings may typically include a binder, such as at least 0.01 weight percent binder, or at least 0.1 weight percent, or at least 1 weight percent, or at least 2 weight percent binder, based on the total weight of the coating. Supercapacitor electrode coatings may typically include up to 20 weight percent binder, or up to 15 weight percent, or up to 10 weight percent binder. Supercapacitor electrode coatings may typically include 0 to 20 weight percent binder, such as 1 to 15 weight percent, or 2 to 10 weight percent.

[0016] The active composite particles typically contain at least 1 weight percent activated metal oxide particles, e.g., at least 50 weight percent or at least 70 weight percent activated metal oxide particles. The active composite particles may contain up to 99 weight percent activated metal oxide particles, e.g., up to 95 weight percent or up to 90 weight percent activated metal oxide particles.

[0017] The active composite particles typically include at least 1 weight percent of carbon-containing support particles, e.g., at least 5 weight percent, or at least 10 weight percent of carbon-containing support particles. The active composite particles may include up to 99 weight percent of carbon-containing support particles, e.g., up to 50 weight percent, or up to 30 weight percent of carbon-containing support particles.

[0018] The active composite particles can typically comprise 1 to 99 weight percent activated metal oxide particles and 1 to 99 weight percent carbon-containing support particles, for example, 50 to 95 weight percent activated metal oxide particles and 5 to 50 weight percent carbon-containing support particles, or 70 to 90 weight percent activated metal oxide particles and 10 to 30 weight percent carbon-containing support particles.

[0019] The active composite particles may contain a composite binder that can help bind the activated metal oxide particles and graphene-based carbon nanoparticles together and / or particles, including activated metal particles, grown or deposited on the graphene-based carbon nanoparticles. Suitable composite binders include polyacrylic acid, polyvinylpyrrolidone, poly(maleic acid), poly(4-styrenesulfonic acid) sodium salt, poly(4-styrenesulfonic acid-co-maleic acid) sodium salt, and the like. The composite binder can also be crosslinked with a carbodiimide crosslinker, such as Carbodilite V-02-L2 or melamine. The composite binder can comprise 0 to 10 weight percent, 0.01 to 5 weight percent, or 0.1 to 2 weight percent of the active composite particles.

[0020] Dispersants may be present in the active composite particles and / or in powders containing the active composite particles at 0 to 5 or 10 weight percent. For example, suitable dispersants in or mixed with the active composite particles may include polyacrylic acid, polyvinylpyrrolidone, poly(maleic acid), poly(4-styrenesulfonic acid) sodium salt, poly(4-styrenesulfonic acid-co-maleic acid) sodium salt, and the like. For example, the dispersant may be an acrylic polymer containing acrylic acid that is neutralized using sodium hydroxide or potassium hydroxide. The dispersant may also be crosslinked with a carbodiimide crosslinker, such as Carbodilite V-02-L2.

[0021] The active composite particles may have an average particle size of 100 nanometers to 100 microns, or 1 to 20 microns, or 2 to 10 microns, as measured by standard scanning electron microscope (SEM) testing. The composite particles may be dispersed onto a segment of carbon tape attached to an aluminum stub and coated with Au / Pd for 20 seconds. The sample may then be analyzed in a Quanta 250FEG SEM under high vacuum. The accelerating voltage may be set to 20.00 kV, and the spot size may be 3.0. Thirty particles from three different areas may be measured to provide the average particle size for each sample.

[0022] The activated metal oxide particles may include manganese oxide, potassium manganese oxide, sodium manganese oxide, lithium manganese oxide, nickel manganese oxide, iron manganese oxide, ruthenium oxide, cobalt oxide, cobalt manganese oxide, iron oxide, nickel oxide, nickel hydroxide, titanium oxide, iron cobalt oxide, vanadium oxide, etc. When the activated metal oxide is manganese oxide, it may be provided as stoichiometric MnO2 or as sub-stoichiometric or super-stoichiometric manganese oxide. Manganese oxide has the chemical structure A x MnO y Manganese oxide can be activated by including alkaline cations and water within its structure, which can be written as nHO, where "A" is an alkali metal such as lithium, sodium, or potassium, "x" is the number of alkali metals in the reduced chemical formula, "y" is the number of oxygen atoms contained within the metal oxide structure, where y is typically less than or equal to 2, and "n" is the number of water molecules within the reduced chemical structure of the activated metal oxide. Manganese oxide can be further activated by electrochemical reduction with an applied voltage or by reducing the oxidation state from 7+ to 4+, 3+, 2+, or neutral through chemical reducing agents such as ethanol, isopropanol, ethylene glycol, benzyl alcohol, 2-pyridinemethanol, furfuryl alcohol, poly(ethylene glycol), sodium thiosulfate, manganese(II) acetate, manganese(II) chloride, or manganese(II) sulfate. The other metal oxides listed above can be activated in a similar manner.

[0023] The carbon-containing support particles of the active composite particles may provide an electrically conductive support structure on which the activated metal oxide particles may be grown or deposited. As used herein, the term "grown on," when referring to activated metal oxide particles and carbon-containing support particles, means that the activated metal oxide particles may be deposited on preformed carbon-containing support particles, including directly on the surface of such carbon-containing support particles, on other activated metal oxide particles previously deposited on the carbon-containing support particles, grown in solution in the presence of the carbon-containing support particles, and combinations thereof. Thus, physical and / or chemical interactions between the activated metal oxide particles and the carbon-containing support particles may occur. For example, the activated metal oxide particles may be grown or deposited on the carbon-containing support particles before or during a spray drying process in which an aqueous solution or slurry containing the particles is spray-dried, as described in more detail below. The carbon-containing support particles may include graphene-based carbon nanoparticles, such as thermally produced graphene-based carbon nanoparticles, exfoliated graphite-graphene nanoparticles, carbon nanotubes, reduced graphene oxide, graphene oxide, and fullerenes.

[0024] The carbon-containing support particles can include activated carbon, which can be used instead of or in addition to the graphene-based carbon nanoparticles. The activated carbon support particles can be activated by heat treatment or exposure to reactive metal oxide precursor materials such as potassium permanganate, manganese acetate, nickel acetate, nickel acetylacetonate, iron acetate, iron acetylacetonate, cobalt acetate, cobalt acetylacetonate, titanium chloride, titanium oxysulfate, vanadium chloride, vanadium oxychloride, vanadium acetylacetonate, ruthenium chloride, (1,5-cyclooctadiene)ruthenium chloride, and ruthenium acetylacetonate. The activated carbon support particles can also be activated by the use of alkaline hydroxide salts such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide.

[0025] When the carbon-containing support particles comprise graphene-based carbon nanoparticles, such nanoparticles may comprise exfoliated graphite graphene, which may be obtained from commercial sources, such as Angstron, XG Sciences, and other commercial sources.

[0026] Heat-treated grapheme-based carbon nanoparticles can be thermally produced according to the methods and apparatus described in U.S. Patent Nos. 8,486,363, 8,486,364, and 9,221,688, which are incorporated herein by reference. Such thermally produced grapheme-based carbon nanoparticles are commercially available from Raymor. Other carbon-containing materials, such as activated carbon, can be used in combination with or in place of the grapheme-based carbon nanoparticles.

[0027] As used herein, the term "graphene-based carbon particles" refers to particles of sp 2 "Graphene-based carbon nanoparticles" refers to carbon particles having a structure comprising one or more one-atom-thick planar sheets of bonded carbon atoms. The average number of stacked layers can be less than 100, e.g., less than 50. The average number of stacked layers can be less than 30, e.g., less than 20, less than 10, or less than 5, in some cases less than 5. The average number of stacked layers can be greater than 2, e.g., greater than 3, or greater than 4. At least a portion of the graphene-based carbon particles can be in the form of substantially curved, curled, creased, or folded platelets. The graphene-based carbon nanoparticles can be turbostatic, i.e., adjacent stacked atomic layers do not exhibit the ordered AB Bernal stacking associated with conventional exfoliated graphene, but rather exhibit disordered or non-ABABAB stacking. Alternatively, the graphene-based carbon particles can be in the form of nanotubes. The particles typically do not have a spherical or equiaxed morphology.

[0028] The grapheme carbon nanoparticles can have a thickness measured perpendicular to the carbon atom layers of 10 nanometers or less, 5 nanometers or less, or 4, 3, 2, or 1 nanometers or less, such as 3.6 nanometers or less. The grapheme carbon particles can be from 1 atomic layer up to 3, 6, 9, 12, 20, or 30 atomic layers, or more, thick. The grapheme carbon particles present in the composition can have widths and lengths measured parallel to the carbon atom layers of at least 50 nanometers, such as greater than 100 nanometers, and in some cases, greater than 100 nanometers up to 500 nanometers, or greater than 100 nanometers up to 200 nanometers. The grapheme carbon particles can be provided in the form of ultra-thin flakes, platelets, or sheets with a relatively high aspect ratio of greater than 3:1, such as greater than 10:1 (the aspect ratio is defined as the ratio of the longest dimension of the particle to the shortest dimension of the particle). Alternatively, when the graphene carbon particles are in the form of nanotubes, they may have outer diameters ranging from 0.3 to 100 nanometers, or 0.4 to 40 nanometers, lengths ranging from 0.3 nanometers to 50 centimeters, or 500 nanometers to 500 microns, and length:diameter aspect ratios ranging from 1:1 to 100,000,000:1, or 10:1 to 10,000:1.

[0029] Grapheme carbon particles can have a relatively low oxygen content. For example, grapheme carbon particles can have an oxygen content of 2 atomic weight percent or less, such as 1.5 or 1 atomic weight percent or less, or 0.6 atomic weight percent or less, such as about 0.5 atomic weight percent or less, even when the grapheme carbon particles have a thickness of 5 nanometers or less, or 2 nanometers or less. The oxygen content of grapheme carbon particles can be determined using X-ray photoelectron spectroscopy, as described in D.R. Reyer et al., Chem. Soc. Rev. 39, 228-240 (2010).

[0030] The graphene carbon particles may have a BET specific surface area of ​​at least 50 square meters per gram, for example, 70 to 1000 square meters per gram, or in some cases, 200 to 1000 square meters per gram or 200 to 400 square meters per gram. As used herein, the term "BET specific surface area" refers to the specific surface area determined by nitrogen adsorption according to ASTM D3663-78 standard, based on the Brunauer-Emmett-Teller method described in the periodical "The Journal of the American Chemical Society," 60, 309 (1938).

[0031] The grapheme carbon particles may have a Raman spectroscopy 2D / G peak ratio of at least 0.9:1, or 0.95:1, or 1:1, such as at least 1.2:1 or 1.3:1. As used herein, the term "2D / G peak ratio" refers to a Raman spectroscopy 2D / G peak ratio at 2692 cm -1 The intensity of the 2D peak at 1,580 cm -1 Such a 2D / G peak ratio may exist in grapheme carbon nanoparticles having an average number of stacked layers greater than two, such as three or more than three stacked layers.

[0032] The grapheme carbon particles may have a relatively low bulk density. For example, the grapheme carbon particles may have a bulk density of 0.1 g / cm 3 0.2g / cm 3 The bulk density of the crushed grapheme carbon particles can be characterized by having a bulk density (tapped density) of less than 0.4 grams. The bulk density of the crushed grapheme carbon particles can be determined by placing 0.4 grams of grapheme carbon particles into a glass graduated cylinder with readable graduations. The cylinder is raised approximately 1 inch and tapped 100 times by tapping the base of the cylinder against a hard surface to allow the grapheme carbon particles to settle into the cylinder. The volume of the particles is then measured and the bulk density is calculated by dividing 0.4 grams by the measured volume, where the bulk density is expressed in g / cm.3 It is expressed in units of:

[0033] The grapheme carbon particles may have a compaction density and density factor less than those of graphite powder and certain types of substantially flat grapheme carbon particles. Lower compaction densities and lower density factors, respectively, are currently believed to contribute to better dispersion and / or rheological properties than grapheme carbon particles exhibiting higher compaction densities and higher density factors. The compaction density of the grapheme carbon particles may be 0.9 or less, such as less than 0.8, less than 0.7, 0.6-0.7, etc. The density factor of the grapheme carbon particles may be less than 40%, such as less than 30%, 25-30%, etc.

[0034] The packed density of grapheme carbon particles can be calculated from the measured thickness of a given mass of particles after compaction. Specifically, the measured thickness is determined by subjecting 0.1 grams of grapheme carbon particles to a cold press in a 1.3 centimeter mold for 45 minutes at a force of 15,000 pounds, with a contact pressure of 500 MPa. The packed density of the grapheme carbon particles is then calculated from this measured thickness according to the following equation:

number

[0035] The density factor of the grapheme carbon particles is then the calculated compressed density of the grapheme carbon particles, as determined above, plus the density of graphite, 2.2 g / cm 3 It is determined as the ratio of

[0036] The grapheme carbon particles may have a measured bulk liquid conductivity of at least 100 microsiemens immediately after mixing and at subsequent time points, such as 10 minutes, 20 minutes, 30 minutes, or 40 minutes, e.g., at least 120 microsiemens, at least 140 microsiemens, etc. The bulk liquid conductivity of the grapheme carbon particles may be determined as follows: First, a sample containing a 0.5% solution of grapheme carbon particles in butyl cellosolve is sonicated for 30 minutes with a bath sonicator. Immediately after sonication, the sample is placed in a standard calibrated electrolytic conductivity cell (K=1). A Fisher Scientific AB30 conductivity meter is introduced to the sample to measure the conductivity of the sample. The conductivity is plotted over the course of approximately 40 minutes.

[0037] The grapheme carbon particles may be substantially free of undesirable or harmful materials. For example, the grapheme carbon particles may contain zero or only trace amounts of polycyclic aromatic hydrocarbons (PAHs), e.g., less than 2 weight percent PAHs, less than 1 weight percent PAHs, or zero PAHs.

[0038] Grapheme-based carbon nanoparticles can be produced, for example, by a thermal treatment process. Thermally produced grapheme-based carbon particles can be made from a carbon-containing precursor material that is heated to high temperatures in a thermal treatment zone, such as a plasma. A carbon-containing precursor, such as a hydrocarbon, provided in gaseous or liquid form is heated in the thermal treatment zone to produce grapheme-based carbon particles in or downstream of the thermal treatment zone. For example, thermally produced grapheme-based carbon particles can be produced by the systems and methods disclosed in U.S. Patent Nos. 8,486,363, 8,486,364, and 9,221,688.

[0039] Graphene carbon particles can be made by using the apparatus and method described in U.S. Pat. No. 8,486,363, in which (i) one or more hydrocarbon precursor materials capable of forming two-carbon fragment species (such as n-propanol, ethane, ethylene, acetylene, vinyl chloride, 1,2-dichloroethane, allyl alcohol, propionaldehyde, and / or vinyl bromide) are introduced into a thermal treatment zone (such as a plasma), and (ii) the hydrocarbon is heated to a temperature of at least 1,000° C. in the thermal treatment zone to form graphene carbon particles. Graphene carbon particles can be made by using the apparatus and method described in U.S. Pat. No. 8,486,364, in which (i) a methane precursor material (such as a material comprising at least 50 percent methane, or in some cases, gaseous or liquid methane of at least 95 or 99 percent purity or higher) is introduced into a thermal treatment zone (such as a plasma), and (ii) the methane precursor is heated in the thermal treatment zone to form graphene carbon particles. Such methods can produce grapheme carbon particles having at least some, and in some cases all, of the above characteristics.

[0040] During the production of graphene carbon particles by the above-described thermal production method, a carbon-containing precursor is provided as a feedstock that can be contacted with an inert carrier gas. The carbon-containing precursor material can be heated in a heat-treatment zone by a plasma system, such as a DC plasma, RF plasma, or microwave plasma. The precursor material can be heated to temperatures ranging from greater than 2,000°C to 20,000°C or greater, e.g., 3,000°C to 15,000°C. For example, the temperature of the heat-treatment zone can be in the range of 3,500°C to 12,000°C, e.g., 4,000°C to 10,000°C. While the heat-treatment zone can be generated by a plasma system, it should be understood that any other suitable heating system can be used to create the heat-treatment zone, such as various types of furnaces, including electrically heated tube furnaces.

[0041] The gas stream may be contacted with one or more quench streams injected into the plasma chamber through at least one quench stream inlet. The quench stream may cool the gas stream to promote the formation of grapheme carbon particles or control their size or morphology. After contacting the gas product stream with the quench stream, the ultrafine particles may pass through a focusing element. After the grapheme carbon particles exit the plasma system, they may be collected. Any suitable means may be used to separate the grapheme carbon particles from the gas stream, such as a bag filter, a cyclone separator, or deposition on a substrate.

[0042] Without being bound by any theory, it is currently believed that the aforementioned methods for producing grapheme-based carbon nanoparticles are particularly well-suited for producing grapheme-based carbon nanoparticles having a relatively low thickness and a relatively high aspect ratio, as combined with a relatively low oxygen content, as discussed above. Furthermore, such methods are currently believed to produce a significant amount of grapheme-based carbon nanoparticles having a substantially curved, rolled, folded, or folded morphology (referred to herein as a "3D" morphology), as opposed to producing particles having a substantially two-dimensional (or flat) morphology. This characteristic is believed to be reflected in the aforementioned packed density characteristics, and is currently believed to be beneficial when a significant portion of the grapheme-based carbon particles have a 3D morphology, as this may promote "edge-to-edge" and "edge-to-edge" contact between the grapheme-based carbon particles within the composition. This is believed to be because particles having a 3D morphology are less likely to aggregate in the composition (due to lower van der Waals forces) than particles having a two-dimensional morphology. It is also currently believed that even in the case of "face-to-face" contact between particles having 3D morphology, the particles may have two or more face planes, so that the entire particle surface is not involved in a single "face-to-face" interaction with another single particle, but instead can participate in interactions with other particles, including other "face-to-face" interactions in other planes. As a result, graphene-based carbon particles having 3D morphology may provide good electrical and / or thermal conductive paths in active composite particles and may be useful for achieving electrical and / or thermal conductive characteristics in coatings.

[0043] Binders that can be used in supercapacitor electrode coatings include polymers such as poly(vinyl esters), poly(vinyl alcohols), poly(vinyl acetals), poly(vinyl ethers), poly(N-vinylamides), poly(N-vinyl lactams), poly(N-vinylamines), and copolymers thereof. Examples of poly(vinyl esters) include poly(vinyl acetate), poly(vinyl benzoate), poly(vinyl propionate), poly(vinyl pivalate), poly(vinyl 2-ethylhexanoate), poly(vinyl neodecanoate), poly(vinyl neononanoate), and copolymers thereof. Examples of poly(vinyl ethers) include poly(methyl vinyl ether), poly(ethyl vinyl ether), poly(butyl vinyl ether), poly(isobutyl vinyl ether), poly(cyclohexyl vinyl ether), poly(phenyl vinyl ether), and poly(benzyl vinyl ether), and copolymers thereof. Examples of poly(N-vinylamides) and poly(N-vinyllactams) include poly(N-vinylformamide), poly(N-vinylacetamide), poly(N-vinyl-N-methylacetamide), poly(N-vinylphthalimide), poly(N-vinylsuccinimide), poly(N-vinylpyrrolidone), poly(N-vinylpiperidone), and poly(N-vinylcaprolactam), as well as copolymers thereof. Examples of poly(N-vinylamines) include poly(N-vinylimidazole) and poly(N-vinylcarbazole), as well as copolymers thereof. In addition to these vinyl monomers, other comonomers can be used, such as acrylate esters, methacrylate esters, unsaturated acids (acrylic acid, methacrylic acid), maleic anhydride, styrene and other vinyl aromatic monomers, acrylonitrile, methacrylonitrile, and olefins such as ethylene, propylene, butylene, and long-chain alpha-olefins. Poly(vinyl alcohol) can be produced by saponification of poly(vinyl esters) such as poly(vinyl acetate) and copolymers of poly(vinyl acetate).Poly(vinyl alcohol) groups can be further reacted with different aldehydes and ketones to produce poly(vinyl acetals), such as poly(vinyl butyral). Aldehydes that can be used include formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, isobutyraldehyde, pivaldehyde, glyoxylic acid, and benzaldehyde. Poly(vinyl butyral) is often a telopolymer containing residues of vinyl acetate, vinyl alcohol, and cyclic butyral groups. Characteristics of poly(vinyl butyral) and related poly(vinyl acetals) include the degree of acetalization, residual hydroxyl content, residual acetate content, and molecular weight. Additionally, other polymers can include polysaccharides such as chitosan, chitin, sodium carboxymethylcellulose, cellulose acetate, and sodium alginate. For example, the binder may include poly(vinyl butyral) or similar types of binders such as other poly(vinyl acetals), such as poly(vinyl formaldehyde), poly(vinyl acetaldehyde), poly(vinyl benzaldehyde), and the like, and may optionally include any of the comonomers described above. When poly(vinyl butyral) or similar compositions are used as binders, they may be optionally functionalized.

[0044] Functionalized poly(vinyl butyral) binder materials can be made by processes such as the reaction between the residual hydroxyl functionality of poly(vinyl butyral) and an electrophile, such as a carboxylic acid, anhydride, or isocyanate-functional material. In the case of the reaction between the residual hydroxyl and a cyclic anhydride, a pendant carboxylic acid can be formed. Reactions such as these can be carried out in solution and catalyzed using an appropriate catalyst.

[0045] Functionalized poly(vinyl butyral) can possess properties and characteristics that can be controlled by the reacted components. Due to the functionalization process, the base poly(vinyl butyral) polymer can be modified to increase the molecular weight of the polymer. Additionally, modifying the functionality can alter the thermal transitions of the material, such as the glass transition temperature. Due to the functionalization process, the hydroxyl equivalent weight often decreases, while the acid number can increase. As a result, the functionalized poly(vinyl butyral) can also be more or less hydrophobic compared to the initial material, depending on the added functionality. Additionally, due to added functional groups such as carboxylic acid, the functionalized poly(vinyl butyral) can provide ionic interactions with other coating components.

[0046] When used in supercapacitor electrode coatings, functionalized poly(vinyl butyral) binders may offer benefits including increased adhesion to activated metal oxide / activated carbon particles, carbon within the coating, and / or current collector, increased dispersibility of materials within the coating during slurry preparation, and increased hydrophilicity.

[0047] Supercapacitor electrode coatings can be produced by combining or mixing separately produced metal oxide particles and carbon particles, or by producing one type of particle followed by the other. For example, as described in more detail below, carbon particles such as grapheme-based carbon nanoparticles can be first provided in an aqueous dispersion, followed by producing metal oxide particles such as manganese oxide in an aqueous dispersion containing the preformed grapheme-based carbon nanoparticles. The active composite particles and / or coatings can be produced using spray drying techniques. Spray drying involves forcing a solution or slurry through a small nozzle, aerosolizing the solution or slurry through hot gas. The hot gas rapidly dries the individual aerosolized particles at high temperatures with minimal residence time, removing the volatile solvent and creating dry, spherical particles of solid material composed of non-volatile material from the original solution or slurry. The final dried particles are then collected. The slurry of activated metal oxide particle composites with a carbon-based support and polymeric material can be passed through a spray drying nozzle, aerosolized from the nozzle, rapidly dried by hot air, and collected. After completing the spray drying of the slurry, the final active material powder can be collected for further processing into an electrode coating. Spray drying allows for the formation of a relatively uniform particle size consisting of a substantially uniform mixture of activated metal oxide, carbon-based support, and polymer material, preventing the formation of activated metal oxide aggregates typically observed with conventional oven drying. The lack of formation of large aggregates of activated metal oxide particles can be attributed to the rapid drying nature of spray drying, which limits the time typically required for metal oxide aggregates to form and forces them to dry as a uniform mixture with the carbon support and polymer material. For example, an aqueous solution containing activated metal oxide particles and carbon-containing support particles can be spray dried to produce active composite particles.

[0048] Supercapacitor electrode coatings can be deposited on various types of substrates used in supercapacitors. For example, the coating can be deposited on current collector plates, foils, meshes, foams, etc. Suitable current collector substrates can be made from metals such as nickel, stainless steel (e.g., 316 stainless steel, 304 stainless steel), aluminum, copper, and titanium, as well as other electrically conductive materials such as graphite and carbon fiber. Any suitable type of coating process can be used, such as spraying, rolling, brushing, additive manufacturing, etc.

[0049] If the coating is formed by an additive manufacturing process, such a process may include any suitable process, such as material jetting, binder jetting, directed energy deposition, material extrusion, sheet lamination, powder bed fusion, liquid bath photopolymerization, etc. Material jetting is an additive manufacturing process in which droplets of feedstock material are selectively deposited. The feedstock material may be deposited layer by layer until a coating of the desired thickness is formed. Binder jetting is an additive manufacturing process in which a liquid adhesive is selectively deposited to bond the powder material. The powder material may be spread in a thin layer on the printing plate. Droplets of binder may be deposited into the powder bed to bond the powder at the locations of the droplets. After one layer is completed, the printing plate may be lowered and another layer of powder material may be spread over the printing plate. This process is repeated until the coating is complete.

[0050] Supercapacitor electrode coatings can have controlled thicknesses, for example, greater than 20 microns, or greater than 50 microns, or greater than 70 microns. Electrode coatings can have thicknesses up to 500 microns, e.g., up to 350 microns, or up to 200 microns. Typical electrode coating thicknesses can range from 20 to 500 microns, e.g., 50 to 350 microns, or 70 to 200 microns.

[0051] The thickness of a supercapacitor electrode coating can also be measured by weight per unit surface area. The thickness of an electrode coating is typically less than 1 mg / cm. 2 Super, e.g., 3 mg / cm 2> or 5 mg / cm 2 The electrode coating thickness can be up to 50 mg / cm 2 , e.g., up to 20 mg / cm 2 , or up to 10 mg / cm 2 The thickness of the electrode coating is typically 1 to 50 mg / cm 2 , or 3 to 20 mg / cm 2 , or 5-10 mg / cm 2 The range may be:

[0052] Supercapacitor electrode coatings can have controlled porosity, such as at least 20 volume percent, at least 40 volume percent, or at least 60 volume percent. Porosities of up to 90 volume percent, up to 80 volume percent, or up to 75 volume percent can be provided. The porosity of electrode coatings can typically range from 20 to 90 volume percent, e.g., 50 to 80 volume percent, or 60 to 75 volume percent. Porosity can be measured by standard techniques known to those skilled in the art. For example, the relative densities of all components of the coating can be calculated, the total volume of the components can be determined by conventional imaging techniques using commercially available software, and the total volume of the coating can be determined by measuring the thickness and other dimensions of the film coating, from which the porosity in volume percent can be calculated.

[0053] Supercapacitor electrode coatings can have a controlled microstructure through controlled aggregation of activated metal oxide particles, activated carbon particles, and polymer dispersants, so that material and microstructural uniformity can also be achieved. Access to the electrolyte on the particle surface can be attributed to the spaces between the MnO2|GNPs, binder, and CNTs within the particle, which may exist because the MnO2|GNPs are prevented from agglomerating with each other in a way that blocks surface access to the electrolyte. If MnO2|GNPs are bonded to other MnO2|GNP particles through agglomeration, the surface in direct contact with another particle may be inaccessible to electrolyte, reducing capacitance. The surfaces of MnO2|GNP particles can be prevented from bonding with each other through spray drying, and instead, they can be fixed in a position that makes the surfaces of primary particles more exposed to the electrolyte within secondary particles, allowing these surfaces greater access to the electrolyte.

[0054] The supercapacitor electrode coating can include, for example, a substantially uniform distribution of the active composite particles and / or conductive carbon-containing particles throughout the thickness of the coating. Alternatively, the active composite particles and / or conductive carbon-containing particles can be distributed non-uniformly throughout the thickness of the coating in a graded structure. For example, the active composite particles and / or conductive carbon-containing particles can be provided in a higher concentration or loading on or near the surface of the electrode coating, or conductive carbon-containing particles, such as carbon black, can be provided in a higher concentration on or near the bottom of the coating near the conductive substrate.

[0055] Before depositing a supercapacitor electrode coating on a substrate, the substrate can be pretreated. For example, in the case of cathode coating, the current collector substrate can be pretreated by processes such as acid treatment to remove the oxide layer and application of an organic coating to improve supercapacitor electrode coating adhesion and prevent oxidation or reduction electrochemical reactions from occurring on the current collector surface. The native oxide present on the metal current collector can be removed by immersion in an acidic solution, such as hydrochloric acid, hydrofluoric acid, or oxalic acid. The pH value of these solutions can range from 0 to 4. Removal of the current collector oxide layer can be accelerated through the application of an electrochemical bias. For example, an electrochemical potential of 5 V can be applied across a substrate immersed in an acidic solution for 2 minutes.

[0056] After deoxidation of the metal substrate surface, an organic coating can be applied to the surface using a wet application method such as doctor blade drawdown. The organic coating formulation can contain a carbon material, such as carbon black, graphite, or a combination of the two, blended with a fluoropolymer binder, such as polyvinylidene difluoride, an acrylic polymer, and a melamine crosslinker, dispersed in an organic solvent. For example, the binder can include a fluoropolymer and an addition polymer, as described in U.S. Patent Application Publication No. 2020 / 0176777, paragraphs

[0020] -

[0023] ,

[0037] -

[0049] ,

[0166] , and

[0173] . The carbon content typically ranges from 70 to 95 weight percent of the solids, with the remainder being polyvinylidene difluoride and 0.5 to 2 weight percent melamine. These films can then be cured at 120°C for 4 minutes. When applied to a deoxidized current collector, the pretreatment coating is typically 0.2-0.6 mg / cm 2 and can be used without further processing.

[0057] When activated metal oxide particles and activated carbon particles are combined together in a rapid drying process, a slurry or suspension of activated metal oxide particles and activated carbon particles in a liquid carrier can be provided, which is rapidly dried to form a powder containing composite particles of activated metal oxide and activated carbon. For example, each composite particle can include a combination of activated metal oxide particles and graphene-based carbon nanosheets, where the activated metal oxide particles contact each other to form a continuous or interconnected network of activated metal oxide particles and the graphene-based carbon nanosheets are distributed throughout the composite particle. Alternatively, the graphene-based carbon nanosheets can contact each other to form a continuous or interconnected network of graphene-based carbon within the composite particle. Thus, each composite particle can include multiple activated metal oxide particles and multiple graphene-based carbon nanosheets adjacent, bonded, or aggregated together to form the composite particle. In such aggregated composite particles, the activated metal oxide particles and graphene-based carbon nanosheets can be uniformly or non-uniformly distributed throughout each particle.

[0058] The following examples are for illustrative purposes, however, should not be construed as limiting. [Example]

[0059] Formulation of aqueous graphene dispersions A 1500 g aqueous dispersion of grapheme-based carbon particles is prepared using a 14 / 1 pigment-to-dispersant ratio at a total solids loading of 3-6 weight percent, depending on the formulation. The grapheme-based carbon source included thermally generated grapheme-based carbon nanoparticles sold under the names Raymor PureWave Graphene Nanoplatelets and XG Sciences M25 Exfoliated Graphene Nanoplatelets. The dispersant is typically polyvinylpyrrolidone with a molecular weight of around 1.3 MDa. The dispersion is first mixed in an appropriate amount of water with a Coles blade at 500-1000 rpm for approximately 60 minutes, then transferred to an Eiger mill with a milling chamber volume of 250 mL. The milling media size used during the milling step is approximately 1.0 mm (Zirmil Y), and is added to the milling chamber to occupy approximately 80% of the total volume. The dispersion is milled at 2000 rpm with a 15-minute residence time. [Table 1]

[0060] Rheological profiles of the dispersions listed in Table 1 are provided in Figure 1. Figure 1 includes rheological profiles of (●) Raymor PureWave graphene, (+) XG Sciences M25 graphene, (■) 3 weight percent aqueous graphene dispersions of 1:1 and (▲) 1:3 weight ratios of Raymor PureWave graphene and XG Sciences M25 graphene, and (◆) 6 weight percent aqueous dispersion of 1:3 Raymor PureWave graphene and XG Sciences M25 graphene.

[0061] Viscosity measurements of the dispersions listed in Table 1 are provided in Figure 2. Figure 2 includes viscosity measurements of aqueous dispersions containing various amounts of XG Sciences M25 exfoliated graphite graphene-based carbon, Raymor PureWave graphene-based carbon, and dispersant at either 3 weight percent or 6 weight percent total solids.

[0062] The rheological profile shown in Figure 1 and the viscosity measurements shown in Figure 2 are measured by standard procedures using an Anton Paar MCR302 and CP50-1TG female cone. Viscosity measurements at a shear rate of 10 Hz can be used for comparison of dispersion rheology.

[0063] Instability index plots for the dispersions listed in Table 1 are provided in Figure 3. The instability index characteristics are measured as described above. Figure 3 includes the instability index for (●) Raymor PureWave graphene, (+) XG Sciences M25 graphene, (■) a 3 weight percent aqueous graphene dispersion containing a 1:1 and (▲) 1:3 weight ratio blend of Raymor PureWave graphene and XG Sciences M25 graphene, and (◆) a 6 weight percent aqueous dispersion of 1:3 Raymor PureWave graphene and XG Sciences M25 graphene. The instability index is measured by the following procedure.

[0064] Instability index analysis can be used for accelerated evaluation of long-term stability, measuring dispersion sedimentation at a specified centrifugation speed and temperature. Unless otherwise indicated in the specification or claims, the "instability index" is measured as follows: a dispersion sample is loaded into a centrifuge and pulsed near-IR light at 865 nm is transmitted through the sample. During centrifugation, the near-IR light transmitted through the sample is measured using a dispersion analyzer sold by LuM GmbH under the name LUMiSizer Model 611. Measurements are made at a relative centrifugal acceleration (RCA) of 2202, 25°C, and a centrifugation speed of 4000 rpm during approximately 20-35 minutes of centrifugation. The instability index is calculated by comparing the transmission level at the start of centrifugation with the transmission level after 20 minutes and normalizing the recorded change in transmission level. The reported instability index is a dimensionless number between 0 and 1, with "0" meaning no change in particle concentration and "1" meaning the dispersion is completely phase separated. A relatively unstable dispersion will exhibit a higher increase in permeability due to significant phase separation of the graphene-based carbon nanoparticles and the solvent, while a relatively stable dispersion will exhibit a lower increase in permeability due to less phase separation. The instability index can be calculated using the SEPView® software tool. A description of how the SEPView® software tool determines the instability index is provided in the article entitled "Instability Index" (T. Detloff, T. Sobisch, D. Lerche, Instability Index, Dispersion Letters Technical, T4 (2013) 1-4, Update 2014), which is incorporated herein by reference. The instability index of an aqueous dispersion of graphene-based carbon nanoparticles can typically be less than 0.7, for example, less than 0.6, or less than 0.5, or less than 0.4, or less than 0.3, or less than 0.1.

[0065] 1-3 demonstrate the rheological changes observed when expanded graphite-graphene particles or exfoliated graphite-graphene particles are dispersed with turbostratic, thermally produced grapheme-based carbon particles, and the resulting increased stability of grapheme-based carbon in solution achieved when a 1:1 w / w ratio of expanded graphite-graphene and turbostratic, thermally produced grapheme-based carbon particles is used in solution prior to using the particles as a conductive support for the growth of activated metal oxides, such as manganese dioxide.

[0066] Synthesis of MnO2|GNPs Potassium permanganate (182.7 g, 1.16 mol) was dissolved in 2818 g of deionized water. Separately, benzyl alcohol (375.1 g, 3.47 mol) was added to a 500 mL addition funnel attached to a 5 L multi-neck flask. The aqueous graphene dispersion (3 weight percent graphene, total graphene / polyvinylpyrrolidone dispersant ratio was 14:1) was charged to a 5 L multi-neck round-bottom flask (374 g total dispersion, 11.97 g total solid material) and stirred with a Teflon® stir blade mounted on an air motor rotating at 100-500 rpm. The stir blade speed can be adjusted as needed during the reaction from 100-1000 rpm to maintain proper cooling and dispersion of the material. The flask was then placed in an ice bath, and benzyl alcohol addition was initiated at a rate of approximately 6 mL / min for 5 minutes. The addition of potassium permanganate is then initiated at a rate of approximately 50 mL / min using a peristaltic pump and silicone tubing. Nitrogen gas is charged to the reaction flask throughout the experiment to aid in cooling and remove oxygen from the reaction atmosphere. The reaction temperature is maintained at approximately 15-25°C throughout the reaction. Complete addition of the reagents to the flask takes approximately one hour, after which the reaction is continued to stir at approximately room temperature for another hour to ensure complete reaction. The final reaction is then filtered and washed with deionized water and isopropanol, followed by a final rinse with deionized water, after which the hydrated product is recovered. The powder is measured for total solids content to determine the level of hydration. In some instances, the intermediate powder is dried under vacuum at 100°C for at least 4-6 hours.

[0067] After recovery of the product of potassium permanganate reduction, a portion of the powder is resuspended in an aqueous solution containing poly(acrylic acid) (Sigma Aldrich, 450 kg / mol) and neutralized to pH 7 with potassium hydroxide (denoted as KPAA) and carbon nanotubes (C-Nano LB217-54, denoted as CNT) to obtain a dispersion with approximately 34 weight percent total solids. This weight percent can be adjusted as needed to accommodate viscosity changes and ensure proper mixing of the 5-40 weight percent materials. This solution of KPAA and CNT is prepared prior to the addition of the powders. For example, 11.6 g of a 13 weight percent KPAA solution is loaded into a small plastic container with a lid along with 20.0 g of a 6.25 weight percent CNT dispersion containing 5 weight percent CNT (1.25 weight percent dispersant). The solution is thoroughly mixed in a small planetary THINKY mixer at 2000 rpm for approximately 2-5 minutes. This solution is then transferred to a larger plastic container equipped with an appropriately sized Coles blade mixer and incorporated with 264 g of MnO2|GNP hydrated powder (the powder was measured to be 37 weight percent solids and 63% water). If necessary, additional deionized water is added and stirred at 1000-1500 rpm to ensure a shear-thinning, relatively thick slurry. When diluting the solution with 704 g of deionized water, the solution is mixed for 1 hour, after which the stirring speed is reduced to 250-750 rpm. The solution is stirred for an additional hour at 250-750 rpm. If necessary, apply horn sonication (Branson Sonifier® 550) to the dispersion at 80% power for 1 hour and then cool in an ice bath. Before the next step, prepare 0.4 g of carbodiimide crosslinker solution (40 weight percent, Carbodilite V-02-L2) and stir for at least 10-20 minutes.

[0068] The solution is then spray dried in a small spray dryer (Büchi) with an inlet temperature set at 220° C., aspirator set at 60%, and pump speed set at 18-26%, controlling the outlet temperature to approximately 90-95° C. In some instances, the resulting powder is further dried under vacuum at 150° C. for at least 4-6 hours.

[0069] Figure 4 contains rheological data measured as described above for dispersions containing approximately equal concentrations of MnO, graphene, conductive carbon, and binder. These data include: (O) commercially available activated MnO physically mixed with PureWave graphene and M25 graphene in a 1:1 w / w ratio; (Δ) MnO synthetically grown in the presence of PureWave graphene and M25 graphene in a 1:1 w / w ratio and dried under vacuum at 100 °C for at least 4 hours; and (□) MnO synthetically grown in the presence of PureWave graphene and M25 graphene in a 1:1 w / w ratio and compounded with an acrylic binder and carbon nanotubes before spray drying. All samples contain approximately 69–71 weight percent MnO, 7–8 weight percent graphene, 10–11 weight percent binder consisting of PVBA and PVP in a 4:1 w / w ratio, and approximately 10–12 weight percent conductive carbon black, such as Super P. The solvent was butyl cellosolve and all slurries had a total solids content of 33.5 weight percent.

[0070] Figure 5 shows a cross-sectional scanning electron microscope image of a MnO2 + GNP cathode coating on a carbon-coated Ni foil. The carbon coating contains both Super P and graphite at the Ni interface.

[0071] Figure 6 shows a cross-sectional scanning electron microscopy-electron dispersive spectroscopy (SEM-EDS) mapping of the MnO2+GNP cathode coating on a carbon-coated Ni foil, highlighting the heterogeneous distribution of (top left) carbon, (top right) oxygen, (bottom left) manganese, and (bottom right) nickel.

[0072] Figure 7 is a cross-sectional scanning electron microscope image of a MnO2|GNP (non-spray dried) cathode coating on a carbon-coated Ni foil. The carbon coating contains both Super P and graphite at the Ni interface.

[0073] Figure 8 shows a cross-sectional scanning electron microscopy electron dispersive spectroscopy (SEM-EDS) mapping of the MnO2|GNP (non-spray dried) cathode coating on carbon-coated Ni foil, highlighting the dispersion of (top left) carbon, (top center) oxygen, (top right) potassium, (bottom left) manganese, and (bottom right) nickel.

[0074] Figure 9 shows a cross-sectional scanning electron microscope image of a spray-dried MnO2|GNP cathode coating on a carbon-coated Ni foil. The carbon coating contains both Super P and graphite at the Ni interface.

[0075] Figure 10 shows a cross-sectional scanning electron microscopy electron dispersive spectroscopy (SEM-EDS) mapping of the spray-dried MnO2|GNP cathode coating on a carbon-coated Ni foil, highlighting the uniform distribution of (top left) nickel, (top right) carbon, (bottom left) potassium, (bottom center) manganese, and (bottom right) oxygen. [Table 2]

[0076] Cathode Binder No.1 A four-neck round-bottom flask was charged with 120 grams of poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) [MW 90,000-120,000] [88 weight percent butyral, 11 weight percent hydroxyl, 1 weight percent acetate], 360 grams of 2-butoxyethanol acetate, 27 grams of succinic anhydride, and 0.15 grams of 1,4-diazabicyclo[2.2.2]octane. The flask was equipped with a mechanical stirrer blade, thermocouple, and reflux condenser. Under a nitrogen atmosphere, the flask was heated to a set point of 100°C. The reaction was then held at 100°C for four hours. The reaction temperature was then increased to 120°C and maintained for four hours. After this hold, the reaction was cooled and poured into a suitable container. The final measured solids content of the resin was determined to be 30.4% solids.

[0077] Cathode Binder No.2 A four-neck round-bottom flask is charged with 104 grams of Mowital B30-T, 312.5 grams of 2-butoxyethanol acetate, 30 grams of succinic anhydride, and 0.13 grams of 1,4-diazabicyclo[2.2.2]octane. The flask is equipped with a mechanical stirrer blade, thermocouple, and reflux condenser. Under a nitrogen atmosphere, the flask is heated to a set point of 120°C. The reaction is then held at 120°C for 8 hours. The reaction temperature is then reduced to 90°C, and 223 grams of 2-butoxyethanol is added to the flask. The reaction mixture is stirred for 2 hours. After this hold, the reaction is cooled and poured into a suitable container. The final measured solids content of the resin is determined to be 18.4% solids.

[0078] Cathode Binder No.3 A four-neck round-bottom flask is charged with 92.4 grams of Mowital B30-T, 462 grams of 2-butoxyethanol acetate, 48 grams of succinic anhydride, and 0.12 grams of 1,4-diazabicyclo[2.2.2]octane. The flask is equipped with a mechanical stirrer blade, thermocouple, and reflux condenser. Under a nitrogen atmosphere, the flask is heated to a set point of 100°C. The reaction is then held at 100°C for 6 hours. The reaction temperature is then reduced to 90°C, and 224 grams of 2-butoxyethanol is added to the flask. The reaction mixture is stirred for 30 minutes. After this hold, the reaction is cooled and poured into a suitable container. The final measured solids content of the resin is determined to be 16.5% solids.

[0079] Cathode Binder No.4 A four-neck round-bottom flask was charged with 120 grams of poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) [MW 90,000-120,000] [88 weight percent butyral, 11 weight percent hydroxyl, 1 weight percent acetate], 360 grams of 2-butoxyethanol acetate, 27 grams of succinic anhydride, and 0.15 grams of 1,4-diazabicyclo[2.2.2]octane. The flask was equipped with a mechanical stirrer blade, thermocouple, and reflux condenser under a nitrogen atmosphere. The reaction mixture was then held at 100°C for 8 hours. 81.5 grams of 2-butoxyethanol was then added to the flask. The reaction mixture was stirred for 15 minutes. After this hold, the reaction mixture was cooled and poured into a suitable container. The final measured solids content of the resin was determined to be 24.6% solids.

[0080] Carbon Pretreatment Compound 5.2 g of Timcal graphite and Carbon Super P conductive carbon black (MTI) were added to 37.15 g of triethyl phosphate solution containing 2 weight percent of a mixture of PVDF and acrylic copolymer. The dispersion was mixed by hand for 30 seconds and then mixed in a centrifugal mixer at 2000 rpm in 2-minute intervals for a total of 6 minutes. After the carbon was fully dispersed, 0.4 g of triethyl phosphate solution containing 10 weight percent of melamine formaldehyde crosslinker was added and mixed in a centrifugal mixer at 2000 rpm for 15 seconds. The carbon dispersion was coated onto Ni foil using a 5-mil drawdown bar and subsequently cured at 150 °C for 10 minutes, yielding a coating density of 0.7 mg cm. -2 Apply a load of .

[0081] MnO2|GNP Cathode Electrode Formulation - 80 / 10 / 10 "Active" / Conductive Carbon / Binder For samples without spray-dried MnO2|GNPs, fifteen 5 mm yttrium-infused zirconia grinding beads were added to the mixer to ensure proper particle disintegration. 0.67 g of Carbon Super P conductive carbon black (MTI) was added to 5.26 g of butyl cellosolve and 1.26 g of a butyl cellosolve solution containing 11 weight percent polyvinylpyrrolidone (1.3 MDa, Aldrich). This dispersion was mixed in a centrifugal mixer at 2000 rpm for a total of 4 minutes, or in 2-minute intervals until completely dispersed. After mixing, the black dispersion was diluted with 5.26 g of the black dispersion and mixed in a centrifugal mixer at 2000 rpm for 2 minutes. After dilution, 2.18 g of a butyl cellosolve acetate / butyl cellosolve solution containing 25 weight percent acid-functionalized polyvinyl butyral copolymer resin (PVBA) was added and mixed in a centrifugal mixer at 2000 rpm for 2 minutes. Once fully dispersed, 5.36 g of MnO2|GNPs are added and the final slurry is mixed in a centrifugal mixer at 2000 rpm in 2-minute intervals for a total of 6 minutes, or until fully dispersed. For non-spray-dried commercial MnO2 or synthetic MnO2|GNPs, the milling time is stopped after a total of 12 minutes of milling. The final dispersion is then applied to a carbon-pretreated Ni foil (0.7 mg cm) using a drawdown bar thickness range of 5-10 mil, preferably 6-8 mil. -2 The film is coated onto a 25 μm thick Ni foil with a pre-treated carbon layer approximately 15-20 μm thick at load, followed by curing at 55°C and 120°C for 2 minutes each. The final cured film is then calendered to the desired porosity, typically 60-75 volume percent.

[0082] Figure 11 shows the results of a 1.27 cm2 sample containing (○) commercial manganese(IV) oxide mixed with a 1:1 w / w blend of PureWave and XG Sciences graphene at a 9:1 MnO2:graphene weight ratio, (Δ) MnO2|GNP raw powder that was not blended with CNTs or KPAA or spray dried, and (□) MnO2|GNPs spray dried with CNTs and KPAA. 2The figure includes a capacitance vs. current density (j) plot for the active material electrode. The coating formulation was 80 / 10 / 10 "active":carbon black:binder. The binder in this system was PVBA / PVP in a 4:1 w / w ratio, and the carbon black source was Super P. The final film porosity after calendering was measured to be approximately 73 volume percent. Each electrochemical cell was cycled from 0 to 1.25 V vs. Ag / AgCl, with a Pt mesh counter electrode and an Ag / AgCl (saturated KCl) reference electrode.

[0083] Figure 12 shows the 1.27 cm of MnO2|GNP with a blend of 88 / 2 / 10 active / carbon black / binder. 2 Included are capacitance vs. current density (j) plots for the electrodes, where the graphene used for the active material was estimated to be a 9:1 w / w ratio of MnO and a graphene source of either PureWave graphene, XG Sciences M25 graphene, or a 1:1 w / w ratio of PureWave and M25 graphene. The binder in this system was PVBA / PVP in a 4:1 w / w ratio, and the carbon black source was Super P. Each electrochemical cell was cycled from 0 to 1.25 V vs. Ag / AgCl with a Pt mesh counter electrode and an Ag / AgCl (saturated KCl) reference electrode.

[0084] Figure 13 shows 1.27 cm of MnO2|GNPs synthesized using (black open circles) benzyl alcohol, (dark gray triangles) ethylene glycol, or (light gray squares) manganese(II) acetate as reducing agents to potassium permanganate in solution, followed by spray drying with potassium-ionized poly(acrylic acid) and carbon nanotubes. 3 Included is a capacitance vs. current density (j) plot of the electrode. The coating is made with an 80 / 10 / 10 active / carbon black / binder blend using Super P as the carbon black source and PVBA / PVP (4:1 w / w) as the binder.

[0085] Figure 14 shows the 1.27 cm of MnO2|GNP with an 80 / 10 / 10 active / carbon black / binder blend. 2 Included are capacitance vs. current density (j) plots for the electrodes, where the graphene used for the active material was estimated to be a 4:1 w / w ratio of MnO and a graphene source from PureWave Graphene. The binder in this system was PVBA / PVP in a 4:1 w / w ratio, and the carbon black source was Super P. Each electrochemical cell was cycled from 0 to 1.25 V vs. Ag / AgCl, with a Pt mesh counter electrode and an Ag / AgCl (saturated KCl) reference electrode.

[0086] The data shown in Figures 11-14 were generated by testing the coating in a half-cell format with an Ag / AgCl (saturated KCl) reference electrode and a Pt mesh counter electrode in a 7 mM NaClO acetonitrile / brine (AWiS) electrolyte. The cell was charged at a constant current of 1-10 A / g, then allowed to rest for 1 minute before being symmetrically discharged to the charge rate and allowed to rest for 10 minutes. The charge passed during discharge was divided by the change in voltage of the discharge.

[0087] Figure 15 contains cyclic voltammetry of full cells using an 80 / 10 / 10 active material / carbon black / binder formulation with (dark gray dashed line) a YP-80F activated carbon symmetric electrode on Al foil using PVDF as a binder in 1 M TEABF in acetonitrile, (light gray dotted line) a YP-80F activated carbon symmetric electrode in 7 molar NaClO acetonitrile / brine electrolyte on bare Ni foil using chitosan as a binder at the anode and on carbon-coated Ni foil using a PVBA / PVB (4:1 w / w) binder at the cathode, and (black solid line) a YP-80F / MnO|GNP asymmetric electrode in 7 molar NaClO acetonitrile / brine (AWiS) electrolyte on bare Ni foil using YP-80F activated carbon as the active material and chitosan as a binder at the anode and on carbon-coated Ni foil using MnO|GNP as the active material and a PVBA binder at the cathode. All systems use Super P as the conductive carbon black source. The data shown in Figure 15 are generated by first assembling the relevant charge-balanced anode and cathode electrodes into 2032 stainless steel coin cells with a polyolefin-based separator and the appropriate electrolyte (1 M tetraethylammonium tetrafluoroborate in anhydrous acetonitrile or 7 M sodium perchlorate in acetonitrile / brine electrolyte). For cells tested using 1 M TEABF4 in acetonitrile, all cells are properly dried and assembled under Ar atmosphere in a glovebox. For cells tested with acetonitrile / brine electrolyte, the electrolyte contains a 2:3 acetonitrile / water molar ratio, and the cells are prepared under ambient conditions. The voltages of these cells are then scanned through cyclic voltammetry at a rate of 1 mV / s until the desired voltage is reached using a Bio-Logic VSP potentiostat.

[0088] Figure 16 shows the 1.27 cm of MnO2|GNP with an 80 / 10 / 10 active / carbon black / binder blend. 2Included are capacitance vs. current density (j) plots for the electrodes, where the graphene used in the active material is estimated to be a 4:1 w / w ratio of MnO2 and PureWave graphene as the graphene source. The binder in this system is PVBA / PVP in a 4:1 w / w ratio, and the carbon black source is Super P. Each electrochemical cell is cycled from 0 to 1.25 V vs. Ag / AgCl, with a Pt mesh counter electrode and an Ag / AgCl (saturated KCl) reference electrode. The data shown in Figure 16 and Figures 11-14 were generated by applying galvanostatic charge and discharge at various current densities to the working electrodes in flooded half-cell electrochemical cells using a Bio-Logic VSP potentiostat. In all cases of half-cell testing described herein, the reference electrode is Ag / AgCl (saturated KCl), and the counter electrode is Pt. The electrolyte used is a 7 molar sodium perchlorate acetonitrile / brine electrolyte, AWiS, where the acetonitrile / water molar ratio is 2:3.

[0089] Devices incorporating the present electrode coatings can achieve a capacitance of at least 100 F / g, e.g., at least 140 F / g, or at least 150 F / g. The capacitance can range from 100 to 300 F / g, or 140 to 250 F / g, or 150 to 200 F / g. The current density can range from 0.1 to 30 A / g, or 0.5 to 20 A / g, or 1 to 10 A / g, where mass in grams refers to the mass of active material on the electrode.

[0090] Figure 17 includes (left) composite resistivity measurements and (right) interfacial resistivity measurements of a supercapacitor cathode coating on Ni foil in an 88 / 2 / 10 formulation of MnO2|GNP / Super P / binder (modified polyvinyl butyral). The resistivity of the electrode coating was measured using a HIOKI electrode resistance meter (HIOKI RM26111). The composite volume resistivity and interfacial contact resistivity were measured after calibrating the instrument with gold-coated (short) and bare plastic (open) plates provided by the manufacturer and inputting the known resistivity of the metal current collector. Resistivity data were collected at three different regions of the electrode and averaged for accuracy. Film resistivity can affect charge transport within the coating; higher resistivity means poor conductivity, i.e., slower charge transport, and vice versa for lower resistivity. Better charge transport (lower resistivity) in the electrode coating enables the electrode's power performance (fast charge / discharge).

[0091] For purposes of detailed description, it should be understood that the present disclosure may contemplate various alternative modifications and step sequences unless expressly stated to the contrary. Moreover, other than in any operating examples, or unless otherwise indicated, all numbers expressing values, amounts, percentages, ranges, subranges, and fractions, etc., may be read as if preceded by the word "about," even if the term does not explicitly appear. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and appended claims are approximations that may vary depending upon the desired properties obtained by the present disclosure. At the very least, and without intending to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should be construed in light of at least the number of reported significant digits and by applying ordinary rounding techniques. Where closed or open-ended numerical ranges are recited herein, all numbers, values, amounts, percentages, subranges, and fractions within or subsumed within the numerical ranges are to be considered specifically included in and belonging to the original disclosure of this application, as if those numbers, values, amounts, percentages, subranges, and fractions were expressly written out in their entirety.

[0092] Notwithstanding that the numerical ranges and parameters setting forth broad ranges are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible. However, any numerical value inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0093] It should also be understood that any numerical range recited herein is intended to include all subranges subsumed therein. For example, a range of "1 to 10" is intended to include all subranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, i.e., all subranges having minimum values ​​equal to or greater than 1 and maximum values ​​equal to or less than 10.

[0094] As used herein, unless expressly stated otherwise, plural terms can include their singular counterparts, and vice versa, unless expressly stated otherwise. Additionally, in this application, although "and / or" may be expressly used in certain instances, the use of "or" means "and / or" unless expressly stated otherwise.

[0095] As used herein, "including," "containing," and similar terms are understood to be synonymous with "comprising" within the context of this application and, therefore, are open-ended and do not exclude the presence of additional, unstated or undescribed elements, materials, components, or method steps. As used herein, "consisting of" is understood within the context of this application to exclude the presence of any unspecified element, component, or method step. As used herein, "consisting essentially of" is understood within the context of this application to include the specified elements, materials, components, or method steps, and "those that do not materially affect the basic and novel characteristics."

[0096] As used herein, the terms "on," "onto," "applied on," "applied onto," "formed on," "deposited on," and "deposited onto" mean formed on, superimposed on, deposited on, or provided on, but not necessarily in contact with, a surface. For example, an electrodepositable coating composition "deposited on" a substrate does not exclude the presence of one or more other intervening coating layers of the same or different composition located between the electrodepositable coating composition and the substrate.

[0097] Although particular examples of the present disclosure have been described above for purposes of illustration, it will be obvious to those skilled in the art that many changes can be made to the details of the present disclosure without departing from the scope of the appended claims.

Claims

1. 1. A coating for use as a supercapacitor electrode, comprising: active composite particles comprising activated metal oxide particles and carbon-containing support particles; and conductive carbon-containing particles.

2. The coating of claim 1 , wherein the activated metal oxide particles are grown on the carbon-containing support particles.

3. 10. The coating of claim 1, wherein the activated metal oxide particles comprise manganese oxide, potassium manganese oxide, sodium manganese oxide, lithium manganese oxide, or a combination thereof.

4. The coating of claim 1 , wherein the activated metal oxide particles comprise stoichiometric manganese oxide.

5. The coating of any one of claims 1 to 4, wherein the carbon-containing support particles comprise graphene-based carbon nanoparticles.

6. 6. The coating of claim 5, wherein the grapheme carbon nanoparticles comprise thermally produced grapheme carbon nanoparticles.

7. 7. The coating of claim 6, wherein the grapheme carbon nanoparticles comprise exfoliated graphitic graphene nanoparticles.

8. The coating of any one of claims 5 to 7, wherein the graphene-based carbon nanoparticles comprise carbon nanotubes.

9. The coating of any one of claims 1 to 8, wherein the activated metal oxide particles comprise at least 1 weight percent, or at least 50 weight percent, or at least 70 weight percent of the active composite particles.

10. The coating of any one of claims 1 to 9, wherein the activated metal oxide particles comprise up to 99 weight percent, or up to 95 weight percent, or up to 90 weight percent of the active composite particles.

11. 11. The coating of any one of claims 1 to 10, wherein the activated metal oxide particles comprise 1 to 99 weight percent, or 50 to 95 weight percent, or 70 to 90 weight percent of the active composite particles.

12. The coating of any one of claims 1 to 11, wherein the carbon-containing support particles comprise at least 1 weight percent, or at least 5 weight percent, or at least 10 weight percent of the active composite particles.

13. The coating of any one of claims 1 to 12, wherein the carbon-containing support particles comprise up to 99 weight percent, or up to 50 weight percent, or up to 30 weight percent of the active composite particles.

14. The coating of any one of claims 1 to 13, wherein the carbon-containing support particles comprise from 1 to 99 weight percent, or from 5 to 50 weight percent, or from 10 to 30 weight percent of the active composite particles.

15. 15. The coating of any one of claims 1 to 14, wherein the conductive carbon-containing particles comprise carbon black, graphite, carbon nanotubes, graphene, activated carbon, or a combination thereof.

16. The coating of any one of claims 1 to 15, wherein the conductive carbon-containing particles comprise carbon black.

17. The coating of any one of claims 1 to 16, wherein the conductive carbon-containing particles are activated.

18. The coating of claim 1 , wherein the active composite particles further comprise a composite binder.

19. 20. The coating of claim 18, wherein the composite binder comprises polyacrylic acid neutralized with potassium hydroxide.

20. 20. The coating of claim 18 or 19, wherein the composite binder comprises up to 10 weight percent, or up to 5 weight percent, or up to 2 weight percent, and / or at least 0.01 weight percent, or at least 0.1 weight percent of the active composite particles.

21. The coating of any one of claims 1 to 20, wherein the active composite particles comprise at least 50 weight percent, or at least 60 weight percent, or at least 70 weight percent of the coating.

22. The coating of any one of claims 1 to 21, wherein the active composite particles comprise up to 99 weight percent, or up to 98 weight percent, or up to 95 weight percent of the coating.

23. The coating of any one of claims 1 to 22, wherein the active composite particles comprise 50 to 99 weight percent, or 60 to 98 weight percent, or 70 to 98 weight percent of the coating.

24. The coating of any one of claims 1 to 23, wherein the active composite particles have an average particle size of at least 100 nanometers, or at least 1 micron, or at least 2 microns.

25. The coating of any one of claims 1 to 24, wherein the active composite particles have an average particle size of at most 100 microns, or at most 20 microns, or at most 10 microns.

26. The coating of any one of the preceding claims, wherein the active composite particles have an average particle size of from 100 nanometers to 100 microns, or from 1 to 20 microns, or from 2 to 10 microns.

27. 27. The coating of any one of the preceding claims, wherein the conductive carbon-containing particles comprise at least 0.5 weight percent, or at least 1 weight percent, or at least 2 weight percent, or at least 4 weight percent, or at least 5 weight percent, or at least 8 weight percent of the coating.

28. 28. The coating of any one of the preceding claims, wherein the conductive carbon-containing particles comprise up to 50 weight percent, or up to 30 weight percent, or up to 20 weight percent, or up to 15 weight percent, or up to 12 weight percent of the coating.

29. 29. The coating of any one of the preceding claims, wherein the conductive carbon-containing particles comprise 0.5 to 50 weight percent, or 1 to 30 weight percent, or 2 to 20 weight percent, or 5 to 15 weight percent, or 8 to 12 weight percent of the coating.

30. The coating of any one of claims 1 to 29, wherein the coating further comprises a binder.

31. 31. The coating of claim 30, wherein the binder comprises poly(vinyl esters), poly(vinyl alcohols), poly(vinyl acetals), poly(vinyl ethers), poly(N-vinylamides), poly(N-vinyl lactams), poly(N-vinylamines), and copolymers thereof, acrylate esters, methacrylate esters, unsaturated acids (acrylic acid, methacrylic acid), maleic anhydride, styrene, and other vinyl aromatic monomers, acrylonitrile, methacrylonitrile, and olefins, polysaccharides, and combinations thereof.

32. 32. The coating of claim 30 or 31, wherein the binder comprises poly(vinyl butyral).

33. 33. The coating of claim 32, wherein the poly(vinyl butyral) is functionalized.

34. 34. The coating of claim 33, wherein the poly(vinyl butyral) is functionalized with a cyclic acid anhydride.

35. 35. The coating of any one of claims 30 to 34, wherein the binder comprises at least 0.01 weight percent, or at least 0.1 weight percent, or at least 1 weight percent, or at least 2 weight percent of the coating.

36. The coating of any one of claims 30 to 35, wherein the binder comprises up to 20 weight percent, or up to 15 weight percent, or up to 10 weight percent of the coating.

37. 37. The coating of any one of claims 30 to 36, wherein the binder comprises 0.01 to 20 weight percent, or 0.1 to 20 weight percent, or 1 to 15 weight percent, or 2 to 10 weight percent of the coating.

38. The coating of any one of claims 1 to 37, wherein the conductive carbon-containing particles form an interconnected network in the coating.

39. The coating of any one of claims 1 to 38, wherein at least a portion of the active composite particles are separated from one another in the coating.

40. The coating of any one of claims 1 to 39, wherein at least a portion of the active composite particles are separated from one another by the conductive carbon-containing particles.

41. The coating of any one of claims 1 to 40, wherein the coating has a thickness of at least 20 microns, or at least 50 microns, or at least 70 microns.

42. The coating of any one of the preceding claims, wherein the coating has a thickness of up to 500 microns, or up to 350 microns, or up to 200 microns.

43. 43. The coating of any one of the preceding claims, wherein the coating has a thickness of from 20 to 500 microns, or from 50 to 350 microns, or from 70 to 200 microns.

44. The coating has a thickness of at least 1 mg / cm ２ , or at least 3 mg / cm ２ , or at least 5 mg / cm ２ 44. The coating of any one of claims 1 to 43, having a thickness of

45. The coating has a thickness of up to 50 mg / cm ２ , or up to 20 mg / cm ２ , or up to 10 mg / cm ２ 45. The coating of any one of claims 1 to 44, having a thickness of

46. The coating has a thickness of 1 to 50 mg / cm ２ , or 3 to 20 mg / cm ２ , or 5 to 10 mg / cm ２ 46. ​​The coating of any one of claims 1 to 45, having a thickness of

47. The coating of any one of the preceding claims, wherein the coating has a porosity of at least 20 volume percent, or at least 40 volume percent, or at least 60 volume percent.

48. The coating of any one of the preceding claims, wherein the coating has a porosity of up to 90 volume percent, or up to 80 volume percent, or up to 75 volume percent.

49. 49. The coating of any one of the preceding claims, wherein the coating has a porosity of 20 to 90 volume percent, or 40 to 80 volume percent, or 60 to 75 volume percent.

50. 1. An active composite particle for use in a supercapacitor electrode coating, comprising: Activated metal oxide particles; and a carbon-containing support particle.

51. 51. The active composite particle of claim 50, wherein the activated metal oxide particles are grown on the carbon-containing support particles.

52. 51. The active composite particle of claim 50, wherein the activated metal oxide particles comprise manganese oxide, potassium manganese oxide, sodium manganese oxide, lithium manganese oxide, or a combination thereof.

53. 51. The active composite particle of claim 50, wherein the activated metal oxide particle comprises manganese oxide.

54. The manganese oxide is MnO ２ 54. The active composite particle of claim 53, comprising:

55. 55. The active composite particle of any one of claims 50 to 54, wherein the carbon-containing support particles comprise graphene-based carbon nanoparticles.

56. 56. The active composite particle of any one of claims 50 to 55, wherein the grapheme-based carbon nanoparticles comprise thermally produced grapheme-based carbon nanoparticles.

57. 57. The active composite particle of any one of claims 50 to 56, wherein the graphene carbon nanoparticles comprise exfoliated graphite nanoparticles.

58. 58. The active composite particle of any one of claims 50 to 57, wherein the graphene-based carbon nanoparticles comprise carbon nanotubes.

59. 59. The active composite particle of any one of claims 50-58, wherein the activated metal oxide particles comprise at least 1 weight percent, or at least 50 weight percent, or at least 70 weight percent of the active composite particle.

60. 60. The active composite particle of any one of claims 50 to 59, wherein the activated metal oxide particles comprise up to 99 weight percent, or up to 95 weight percent, or up to 90 weight percent of the active composite particles.

61. 61. The active composite particle of any one of claims 50 to 60, wherein the activated metal oxide particles comprise 1 to 99 weight percent, or 50 to 95 weight percent, or 70 to 90 weight percent of the active composite particle.

62. 62. The active composite particle of any one of claims 50-61, wherein the grapheme carbon nanoparticles comprise at least 1 weight percent, or at least 5 weight percent, or at least 10 weight percent of the active composite particle.

63. 63. The active composite particle of any one of claims 50 to 62, wherein the grapheme carbon nanoparticles comprise up to 99 weight percent, or up to 50 weight percent, or up to 30 weight percent of the active composite particle.

64. 64. The active composite particle of any one of claims 50 to 63, wherein the grapheme carbon nanoparticles comprise 1 to 99 weight percent, or 5 to 50 weight percent, or 10 to 30 weight percent of the active composite particle.

65. The active composite particle of any one of claims 50 to 64, wherein the active composite particle further comprises a composite binder or dispersant.

66. 66. The active composite particle of claim 65, wherein the composite binder or dispersant comprises polyacrylic acid neutralized with potassium hydroxide or polyvinylpyrrolidone.

67. 67. The active composite particle of claim 65 or 66, wherein the composite binder comprises up to 10 weight percent, or up to 5 weight percent, or up to 2 weight percent, and / or at least 0.01 weight percent, or at least 0.1 weight percent of the active composite particle.

68. 68. The active composite particle of any one of claims 50 to 67, wherein the active composite particle has an average particle size of at least 100 nanometers, or at least 1 micron, or at least 2 microns.

69. 69. The active composite particle of any one of claims 50 to 68, wherein the active composite particle has an average particle size of at most 100 microns, or at most 20 microns, or at most 10 microns.

70. 70. The active composite particle of any one of claims 50 to 69, wherein the active composite particle has an average particle size of from 100 nanometers to 100 microns, or from 1 to 20 microns, or from 2 to 10 microns.

71. The active composite particles of any one of claims 50 to 70, wherein the active composite particles are spray dried.

72. 1. A method of making active composite particles for use in supercapacitor electrode coatings, comprising: spray drying an aqueous solution comprising activated metal oxide particles and carbon-containing support particles; and recovering the activated composite particles comprising the activated metal oxide particles and the carbon-containing support particles.

73. A supercapacitor electrode, a current collector substrate; Electrode coating, Active composite particles comprising activated metal oxide particles and carbon-containing support particles; and an electrode coating comprising conductive carbon-containing particles.

74. 74. The supercapacitor electrode of claim 73, wherein the supercapacitor electrode comprises a cathode.

75. 75. The supercapacitor electrode of claim 74, wherein the cathode is pretreated.

76. 76. The supercapacitor electrode of claim 75, wherein the pretreated cathode comprises a surface layer comprising conductive carbon particles.

77. 77. A supercapacitor electrode according to claim 75 or 76, wherein the surface layer further comprises a binder.

78. 78. The supercapacitor electrode of claim 77, wherein the binder comprises an acrylic copolymer crosslinked with poly(vinylene difluoride) and melamine.

79. 79. The supercapacitor electrode of any one of claims 73-78, wherein the current collector substrate comprises nickel, stainless steel, 316 stainless steel, 304 stainless steel, aluminum, copper, titanium, zirconium, graphite foil, carbon paper, or a combination thereof.

80. 80. A supercapacitor comprising a supercapacitor electrode according to any one of claims 73 to 79, wherein the supercapacitor has a capacitance of at least 100 F / g, or at least 140 F / g, or at least 150 F / g.

81. 80. A supercapacitor comprising the supercapacitor electrode of any one of claims 73 to 79, wherein the supercapacitor has a capacitance of 100 to 300 F / g, or 140 to 250 F / g, or 150 to 200 F / g.

82. 82. The supercapacitor of claim 80 or 81, wherein the capacitance is measured at a current density of 1 to 10 A / g.

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