Supercapacitor module with matched supercapacitors

Abstract

To provide a supercapacitor module which eliminates the need for a balancing circuit, prevents overvoltages from occurring within the module, effectively eliminates the need for a balancing circuit entirely, and allows a simple passive balancing circuit to be used instead of an active balancing circuit.SOLUTION: A supercapacitor module 100 includes: a first supercapacitor 102 having a first parameter value for a capacitor parameter under a first test condition; and a second supercapacitor having a second parameter value for the capacitor parameter under the first test condition. A ratio of the second parameter value to the first parameter value is from about 0.8 to about 1.2. The supercapacitor module prevents overvoltages across the first and second supercapacitors, so that the supercapacitor module satisfactorily operates without a balancing circuit.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 62 / 555,098, filed September 7, 2017, which is incorporated herein by reference in its entirety. [Background technology]

[0002] Electrical energy storage cells are widely used to power electronic, electromechanical, electrochemical, and other useful devices. For example, double-layer supercapacitors can use a pair of polarizable electrodes containing carbon particles (e.g., activated carbon) impregnated with a liquid electrolyte. Due to the effective surface area of ​​the particles and the small spacing between the electrodes, large capacitance values ​​can be achieved. Individual double-layer capacitors can be combined together to form modules with increased output voltages and increased energy capacities.

[0003] The performance and lifespan of a supercapacitor module depend on the voltage across each supercapacitor in the module. For example, a voltage exceeding the rated voltage of a supercapacitor, referred to as "overvoltage," can reduce the performance and / or lifespan of the module. To prevent overvoltage, a supercapacitor module typically includes a balancing circuit that regulates the voltage across the supercapacitors in the module. For example, the balancing circuit may be designed to maintain approximately equal voltages across each of the supercapacitors in the module. Summary of the Invention [Problem to be solved by the invention]

[0004] However, the use of balancing circuits in a supercapacitor module may undesirably increase the size, cost, and / or complexity of the module. The balancing circuits may also undesirably generate heat, which may require cooling of the module, further adding to the cost and / or complexity of the module and increasing the likelihood of heat-induced failure damage. [Means for solving the problem]

[0005] According to one embodiment, a capacitor module is disclosed that includes a first supercapacitor having a first parameter value for a capacitor parameter at a first test condition. The capacitor module includes a second supercapacitor having a second parameter value for the capacitor parameter at about the first test condition. The ratio of the second parameter value to the first parameter value may be between 0.8 and 1.2.

[0006] Other features and aspects of the disclosure are described in more detail below. A full and enabling disclosure of the present disclosure, including the best mode thereof, directed to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, in which reference is made to the accompanying figures. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is an exploded view of one embodiment of a module housing that may be used to house a module of the present invention. [Figure 2] FIG. 1 is a perspective view of a supercapacitor module according to one embodiment of the present invention. [Figure 3] 1 is a schematic diagram of one embodiment of a supercapacitor, in accordance with aspects of the present invention; [Figure 4a] FIG. 1 is a diagram illustrating the relationship between temperature and capacitance. [Figure 4b] FIG. 1 is a diagram illustrating the relationship between temperature and leakage current. [Figure 4c]FIG. 1 is a diagram illustrating the relationship between temperature and equivalent series resistance. [Figure 5] FIG. 1 shows a hypothetical example of selecting a supercapacitor based on leakage current measurements. [Figure 6] FIG. 1 illustrates a hypothetical example of selecting a supercapacitor using a clustering algorithm and / or a machine learning algorithm. [Figure 7a] 1 is a plot of experimental test data. [Figure 7b] 1 is a plot of experimental test data. [Figure 8a] 10 is a plot of experimental test data for one embodiment of a supercapacitor module under a second set of test conditions. [Figure 8b] 10 is a plot of experimental test data for one embodiment of a supercapacitor module under a second set of test conditions. DETAILED DESCRIPTION OF THE INVENTION

[0008] Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present disclosure. Those skilled in the art will appreciate that the discussion of the present invention is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the present disclosure as embodied in the exemplary configurations.

[0009] As mentioned above, a supercapacitor module typically includes a balancing circuit that controls the respective voltage across each supercapacitor of the module to prevent overvoltage. Some balancing circuits may be active, such as an integrated circuit. Other balancing circuits may be passive, such as one or more passive components, such as resistors, capacitors, etc., that connect the terminals of the supercapacitors.

[0010] Matching supercapacitors as described herein can eliminate the need for balancing circuits. For example, by selecting supercapacitors with similar properties as described herein, the module can operate with corresponding approximately equal voltages across each supercapacitor. In some embodiments, this can prevent overvoltages from occurring within the module, effectively eliminating the need for balancing circuits altogether. In other embodiments, a simple passive balancing circuit may be used in place of an active balancing circuit.

[0011] Eliminating balancing circuitry from a module results in a smaller, cheaper, less costly, and / or less complex module. Additionally, eliminating the need for balancing circuitry can reduce the amount of heat generated by the module during operation. This, in turn, can eliminate the need for a cooling system, generally resulting in a more robust and reliable module that is less susceptible to damage or failure due to overheating.

[0012] I. Supercapacitor module configuration 1, in one embodiment, module housing 10 may include a top surface 12, a bottom surface 14, and a side surface 16 extending between top surface 12 and bottom surface 14. In this regard, a supercapacitor (shown in FIG. 2) may be housed between top surface 14 and bottom surface 14 of module housing 10. Additionally, module housing 30 may include external terminals or connections (not shown) for use and connection to a device.

[0013] 2, a capacitor module 100 may include multiple supercapacitors 102 disposed within a module housing 10. As shown herein, it should be understood that the module 100 may include more than two supercapacitors. For example, a module may include two supercapacitors, and in some embodiments may include more than two, such as four or more, such as six or more, such as eight or more supercapacitors, and in some embodiments may include between eight and thirty individual supercapacitors. For example, in one embodiment, a module may include 15 supercapacitors as shown in FIG. 2.

[0014] The module may include a support structure 104 configured to secure the supercapacitors within the housing 10. It should be understood that the module configurations illustrated herein are merely examples. Any suitable module configuration may be used. For example, in some embodiments, the supercapacitors may be stacked end-to-end. In some embodiments, instead of the housing 10 shown in FIG. 2, the housing comprises, for example, a thin packaging material.

[0015] II. Supercapacitor Configuration Any of a variety of different individual supercapacitors may generally be used in the modules of the present invention. However, in general, a supercapacitor includes an electrode assembly and an electrolyte contained within a housing and optionally hermetically sealed. The electrode assembly may include, for example, a first electrode containing a first carbonaceous coating (e.g., activated carbon particles) electrically coupled to a first current collector, and a second electrode containing a second carbonaceous coating (e.g., activated carbon particles) electrically coupled to a second current collector. It should be understood that additional current collectors may be used if desired, particularly when the supercapacitor includes multiple energy storage cells. The current collectors may be formed from the same or different materials. Nevertheless, each current collector is typically formed from a substrate comprising a conductive metal, such as aluminum, stainless steel, nickel, silver, palladium, and alloys thereof. Aluminum and aluminum alloys are particularly suitable for use in the present invention. The substrate may take the form of a foil, sheet, plate, mesh, or the like. The substrate may have a relatively thin thickness, for example, a thickness of about 200 micrometers or less, in some embodiments, from about 1 to about 100 micrometers, in some embodiments, from about 5 to about 80 micrometers, and in some embodiments, from about 10 to about 50 micrometers. Although not required, the surface of the substrate may optionally be roughened by cleaning, etching, blasting, etc. When the term "about" is used in conjunction with a numerical value, it refers to within 20% of the stated amount.

[0016] The first and second carbonaceous coatings may be electrically coupled to the first and second current collectors, respectively. They may be formed of the same or different types of materials and may include one or more layers, but each carbonaceous coating generally includes at least one layer containing activated particles. In certain embodiments, for example, the activated carbon layer may be positioned directly on the current collector, and optionally may be the only layer of the carbonaceous coating. Examples of suitable activated carbon particles include coconut shell-based activated carbon, petroleum coke-based activated carbon, pitch-based activated carbon, polyvinylidene chloride-based activated carbon, phenolic resin-based activated carbon, polyacrylonitrile-based activated carbon, and activated carbon obtained from natural sources such as coal, charcoal, or other natural organic sources.

[0017] In certain embodiments, it may be desirable to selectively control certain aspects of the activated carbon particles, such as their particle size distribution, surface area, and pore size distribution, to help improve ion mobility for certain types of electrolytes after being subjected to one or more charge / discharge cycles. For example, at least 50% by volume of the particles (D50 size) may be in the range of about 0.01 to about 30 micrometers, in some embodiments about 0.1 to about 20 micrometers, and in some embodiments about 0.5 to about 10 micrometers. At least 90% by volume of the particles (D90 size) may also have a size ranging from about 2 to about 40 micrometers, in some embodiments from about 5 to about 30 micrometers, and in some embodiments, from about 6 to about 15 micrometers. The BET surface may have a size ranging from about 900 micrometers. 2 / g to approximately 3,000m 2 / g, in some embodiments, about 1,000 m 2 / g to approximately 2,500m 2 / g, and in some embodiments, about 1,100 m 2 / g to approximately 1,800m 2 / g.

[0018] In addition to having a certain size and surface area, activated carbon particles may contain pores having a certain size distribution. For example, the amount of pores less than about 2 nanometers in size (i.e., "micropores") may provide a pore volume of about 50 vol.% or less, in some embodiments about 30 vol.% or less, and in some embodiments, 0.1 vol.% to 15 vol.% of the total pore volume. The amount of pores between about 2 nanometers and about 50 nanometers in size (i.e., "mesopores") may similarly range from about 20 vol.% to about 80 vol.%, in some embodiments about 25 vol.% to about 75 vol.%, and in some embodiments, about 35 vol.% to about 65 vol.%. Finally, the amount of pores greater than about 50 nanometers in size (i.e., "macropores") may be about 1 vol.% to about 50 vol.%, in some embodiments about 5 vol.% to about 40 vol.%, and in some embodiments, about 10 vol.% to about 35 vol.%. The total pore volume of a carbon particle may be about 0.2 cm.sup.2 or less. 3 / g to about 1.5cm 3 / g, in some embodiments, about 0.4 cm 3 / g to approximately 1.0 cm 3 / g, with a median pore width of about 8 nanometers or less, in some embodiments from about 1 to about 5 nanometers, and in some embodiments, from about 2 to 4 nanometers. Pore size and total pore volume may be measured using nitrogen adsorption or analyzed by the Barrett-Joyner-Halenda ("BJH") technique, as is well known in the art.

[0019] If desired, the binder may be present in the first and / or second carbonaceous coating in an amount of about 60 parts or less, in some embodiments, about 40 parts or less, and in some embodiments, about 1 to about 25 parts per 100 parts of carbon. The binder may, for example, constitute about 15 wt. % or less, in some embodiments, about 10 wt. % or less, and in some embodiments, about 0.5 wt. % to about 5 wt. % of the total weight of the carbonaceous coating. Any of a variety of suitable binders can be used in the electrode. For example, water-insoluble organic binders such as styrene-butadiene copolymers, polyvinyl acetate homopolymers, vinyl-acetate ethylene copolymers, vinyl-acetate acrylic copolymers, ethylene-vinyl chloride copolymers, ethylene-vinyl chloride-vinyl acetate terpolymers, acrylic polyvinyl chloride polymers, acrylic polymers, nitrile polymers, fluoropolymers such as polytetrafluoroethylene or polyvinylidene fluoride, polyolefins, and the like, as well as mixtures thereof, may be used in certain embodiments. Water-soluble organic binders may include polysaccharides and their derivatives. In certain embodiments, the polysaccharide may be a nonionic cellulose ether, such as an alkyl cellulose ether (e.g., methyl cellulose and ethyl cellulose); a hydroxyalkyl cellulose ether (e.g., hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl hydroxybutyl cellulose, hydroxyethyl hydroxypropyl cellulose, hydroxyethyl hydroxybutyl cellulose, hydroxyethyl hydroxypropyl hydroxybutyl cellulose, etc.); an alkyl hydroxyalkyl cellulose ether (e.g., methyl hydroxyethyl cellulose, methyl hydroxypropyl cellulose, ethyl hydroxyethyl cellulose, ethyl hydroxypropyl cellulose, methyl ethyl hydroxyethyl cellulose, and methyl ethyl hydroxypropyl cellulose); a carboxyalkyl cellulose ether (e.g., carboxymethyl cellulose); and the like, as well as protonated salts of any of the foregoing, such as sodium carbonate. It may also be carboxymethyl cellulose.

[0020] Other materials may be used in the activated carbon layer of the first and / or second carbonaceous coating and / or in other layers of the first and / or second carbonaceous coating. For example, in certain embodiments, a conductivity promoter may be used to further increase electrical conductivity. Exemplary conductivity promoters include, for example, carbon black, graphite (natural or synthetic), graphite, carbon nanotubes, nanowires or nanotubes, metal fibers, graphene, and the like, as well as mixtures thereof. Carbon black is particularly preferred. When used, the conductivity promoter typically comprises about 60 parts or less, in some embodiments 40 parts or less, and in some embodiments, from about 1 to about 25 parts per 100 parts of activated carbon particles of the carbonaceous coating. The conductivity promoter may comprise, for example, about 15 wt. % or less, in some embodiments about 10 wt. % or less, and in some embodiments, from about 0.5 wt. % to about 5 wt. % of the total weight of the carbonaceous coating. The activated carbon particles likewise typically constitute 85% or more by weight of the carbonaceous coating, in some embodiments, about 90% or more by weight, and in some embodiments, about 95% to about 99.5% by weight.

[0021] The specific technique for applying the carbonaceous coating to the current collector may vary, as is known to those skilled in the art, including printing (e.g., rotogravure), spraying, slot-die coating, drop coating, dip coating, and the like. Regardless of the application technique, the resulting electrode is typically dried to remove moisture from the coating, e.g., at temperatures above about 100°C, in some embodiments above about 200°C, and in some embodiments, from about 300°C to about 500°C. The electrode may be compressed (e.g., calendered) to optimize the volumetric efficiency of the supercapacitor. After any optional compression, the thickness of each carbonaceous coating may generally vary based on the desired electrical performance and operating range of the supercapacitor. However, typically, the thickness of the coating is from about 20 to about 200 micrometers, from 30 to about 150 micrometers, and in some embodiments, from about 40 to about 100 micrometers. The coating may be present on one or both sides of the current collector. Nevertheless, the thickness of the entire electrode (including the current collector and carbonaceous coating(s) after optional compression) is typically in the range of about 20 to about 350 micrometers, in some embodiments in the range of about 30 to about 300 micrometers, and in some embodiments in the range of about 50 to about 250 micrometers.

[0022] The electrode assembly typically also includes a separator positioned between the first and second electrodes. Other separators may be used in the electrode assembly if desired. For example, one or more separators may be positioned on the first electrode, the second electrode, or both. A separator can electrically isolate one electrode from another, helping to prevent electrical shorting while still allowing ions to transport between the two electrodes. In certain embodiments, separators may be used that include, for example, cellulosic fibrous materials (e.g., airlaid paper webs, wetlaid paper webs, etc.), nonwoven materials (e.g., polyolefin nonwoven fabrics), woven fabrics, films (e.g., polyolefin films), etc. Cellulosic fibrous materials are particularly suitable for use in supercapacitors that contain natural fibers, synthetic fibers, etc. Specific examples of cellulose fibers suitable for use in separators include hardwood pulp fibers, softwood pulp fibers, rayon fibers, regenerated cellulose fibers, etc. Regardless of the particular material used, the separator typically has a thickness of from about 5 to about 150 micrometers, in some embodiments from about 10 to about 100 micrometers, and in some embodiments, from about 20 to about 80 micrometers.

[0023] The manner in which the components of the electrode assembly are assembled together is as known in the art. For example, the electrodes and separator may first be folded, wrapped, or otherwise contacted together to form an electrode assembly. In certain embodiments, the electrodes, separator, and optional electrolyte may be rolled into an electrode assembly having a "jelly roll" configuration.

[0024] To form a supercapacitor, an electrolyte is placed in ionic contact with the first and second electrodes before, during, and / or after the electrodes and separator are combined together to form an electrode assembly. The electrolyte is generally non-aqueous in nature and therefore contains at least one non-aqueous solvent. To help extend the operating temperature range of the supercapacitor, it is typically desirable for the non-aqueous solvent to have a relatively high boiling temperature, e.g., above about 150°C, in some embodiments above about 200°C, and in some embodiments, from about 220°C to about 300°C. Particularly suitable high-boiling solvents include cyclic carbonate solvents such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate. Of course, other non-aqueous solvents may be used alone or in combination with the cyclic carbonate solvent. Examples of such solvents include open-chain carbonates (e.g., dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, etc.), aliphatic monocarboxylates (e.g., methyl acetate, ethyl propionate, etc.), lactone solvents (e.g., butyrolactone, valerolactone, etc.), nitriles (e.g., acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile, etc.), amides (e.g., N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidinone), alkanes (e.g., nitromethane, nitroethane, etc.), sulfur compounds (e.g., sulfolane, dimethyl sulfoxide, etc.); and the like.

[0025] The electrolyte may contain at least one ionic liquid dissolved in a non-aqueous solvent. The concentration of the ionic liquid can vary, but it is typically desirable for the ionic liquid to be present at a relatively high concentration. For example, the ionic liquid may be present in an amount of about 0.8 moles (M) per liter of electrolyte or greater, in some embodiments about 1.0 M or greater, in some embodiments about 1.2 M or greater, and in some embodiments about 1.3 to about 1.8 M.

[0026] Ionic liquids are generally salts having relatively low melting temperatures, for example, about 400°C or less, in some embodiments about 350°C or less, in some embodiments about 1°C to about 100°C, and in some embodiments about 5°C to about 50°C. The salts contain a cationic species and a counterion. The cationic species contains a compound having at least one heteroatom (e.g., nitrogen or phosphorus) as the "cationic center." Examples of such heteroatom compounds can include, for example, unsubstituted or substituted organic quaternary ammonium compounds, such as ammonium (e.g., trimethylammonium, tetramethylammonium, etc.), pyridinium, pyridazinium, pyramidinium, pyrazinium, imidazolium, pyrazolium, oxazolium, triazolium, thiazolium, quinolinium, piperazinium, pyrrolidinium, quaternary ammonium spiro compounds in which two or more rings are connected together by a spiro atom (e.g., carbon, heteroatom, etc.), quaternary ammonium fused ring structures (e.g., quinolinium, isoquinolinium, etc.), and the like. In certain embodiments, for example, the cationic species can be an N-spirobicyclic compound, such as a symmetric or asymmetric N-spirobicyclic compound having a cyclic ring. An example of such a compound has the following structure:

[0027] [ka]

[0028] wherein m and n are independently a number from 3 to 7, and in some embodiments, 4 to 5 (e.g., pyrrolidinium or piperidinium). It has.

[0029] Similarly, suitable counterions for the cationic species include halogens (e.g., chloride, bromide, iodide, etc.); sulfates or sulfonates (e.g., methyl sulfate, ethyl sulfate, butyl sulfate, hexyl sulfate, octyl sulfate, hydrogen sulfate, methane sulfonate, dodecylbenzene sulfonate, dodecyl sulfate, trifluoromethane sulfonate, heptadecafluorooctanesulfonate, sodium dodecylethoxy sulfate, etc.); sulfosuccinates; amides (e.g., dicyanamide); imides (e.g., bis(pentafluoroethylsulfonyl)imide, bis(trifluoromethylsulfonyl)imide, bis(trifluoromethyl)imide, etc.); borates (e.g., tetrafluoroborate, tetrachloroborate, tetrachloromethane, etc.); anoborates, bis[oxalato]borates, bis[salicylate]borates, and the like; phosphates or phosphinates (e.g., hexafluorophosphate, diethylphosphate, bis(pentafluoroethyl)phosphinate, tris(pentafluoroethyl)-trifluorophosphate, tris(nonafluorobutyl)trifluorophosphate, and the like); antimonates (e.g., hexafluoroantimonate); aluminates (e.g., tetrachloroaluminate); fatty acid carboxylates (e.g., oleate, isostearate, pentadecafluorooctanoate, and the like); cyanates; acetates; and the like, as well as combinations of any of the foregoing.

[0030] Some examples of suitable ionic liquids can include, for example, spiro-(1,1')-bipyrrolidinium tetrafluoroborate, triethylmethylammonium tetrafluoroborate, tetraethylammonium tetrafluoroborate, spiro-(1,1')-bipyrrolidinium iodide, triethylmethylammonium iodide, tetraethylammonium iodide, methyltriethylammonium tetrafluoroborate, tetrabutylammonium tetrafluoroborate, tetraethylammonium hexafluorophosphate, and the like.

[0031] As mentioned above, the supercapacitor also includes a housing in which the electrode assembly and electrolyte are held and optionally hermetically sealed. The properties of the housing may be varied as desired. In one embodiment, for example, the housing may include a metal container ("can") formed from tantalum, niobium, aluminum, nickel, hafnium, titanium, copper, silver, steel (e.g., stainless steel), alloys thereof, composites thereof (e.g., metals coated with conductive oxides), and the like. Aluminum is particularly suitable for use in the present invention. The metal container may have any of a variety of different shapes, such as cylindrical, D-shaped, etc. Cylindrical containers are particularly suitable.

[0032] The electrode assembly may be sealed within the cylindrical housing using a variety of different techniques. Referring to FIG. 3 , one embodiment of a supercapacitor 2000 is shown that includes an electrode assembly 2108 that includes layers 2106 wound together in a jellyroll configuration. In this particular embodiment, the supercapacitor includes a first collector disc 2114 that includes a disk-shaped portion 2134, a stud portion 2136, and a fastener 2138 (e.g., a screw). The collector disc 2114 is aligned with a first end of a hollow core 2160 formed in the center of the electrode assembly, and then the stud portion 2136 is inserted into an opening in the core so that the disk-shaped portion 2134 seats against the first end of the electrode assembly 2108 at the first contact edge 2110. A lid 2118 is welded (e.g., laser welded) to the first terminal 2116, and a socket, which may be threaded, for example, is coupled to the fastener 2138. The supercapacitor also includes a second collector disk 2120 including a disk-shaped portion 2142, a stud portion 2140, and a second terminal 2144. The second collector disk 2120 is aligned with the second end of the hollow core 2160, and then the stud portion 2140 is inserted into the opening in the core so that the collector disk portion 2142 rests against the second end of the electrode assembly 2108.

[0033] The metal container 2122 (e.g., a cylindrical can) is then slid onto the electrode assembly 2108 so that the second collector disk 2120 enters the container 2122 first, passes through the first insulating washer 2124, passes through the axial hole in the end of the container 2122, and then passes through the second insulating washer 2126. The second collector disk 2120 also passes through a plain washer 2128 and a spring washer 2130. A lock nut 2132 is tightened onto the spring washer 2130, compressing the spring washer 2130 against the plain washer 2128, which in turn compresses the spring washer 2130 against the second insulating washer 2126. The second insulating washer 2126 is pressed against the outer periphery of the axial bore of the metal can 2122, and as the second collector disk 2120 is pulled out due to this compression force against the bore, the first insulating washer 2124 is pressed between the second collector disk 2120 and the inner periphery of the axial bore of the can 2122. A flange on the first insulating washer 2124 prevents electrical contact between the second collector disk 2120 and the rim of the axial bore. Simultaneously, the lid 2118 is pulled into the opening of the can 2122 until the rim of the lid 2118 is seated just inside the lip of the opening of the can 2122. The rim of the lid 2118 is then welded to the lip of the opening of the can 2122.

[0034] When the lock nut 2132 is tightened against the spring washer 2130, a hermetic seal may be formed between the axial bore, the first insulating washer 2124, the second insulating washer 2126, and the second collector disk 2120. Similarly, welding of the lid 2118 to the lip of the container 2122 and the first terminal 2116 may form another hermetic seal. A hole 2146 in the lid 2118 may be left open to serve as an inlet for the electrolyte described above. Once the electrolyte enters the can (i.e., is drawn into the can in a vacuum as described above), a bushing 2148 is inserted into the hole 2146 and seats against a flange 2150 at the inner edge of the hole 2146. The bushing 2148 may be a hollow cylinder whose shape is adapted to receive, for example, a plug 2152. Plug 2152, which is cylindrical in shape, is pressed into the center of bushing 2148, thereby forcing bushing 2148 inside hole 2146 and forming an airtight seal between hole 2146, bushing 2148, and plug 2152. Plug 2152 and bushing 2148 may be selected to be removed when a predetermined level of pressure is reached within the supercapacitor, thereby forming an overpressure safety mechanism.

[0035] The above embodiments generally refer to the use of a single electrochemical cell in a capacitor. However, it should be understood that the capacitors of the present invention may also include two or more electrochemical cells. In one such embodiment, for example, the capacitors may include two or more electrochemical cells, whether the same or different. The electrochemical cell may comprise a stack of two or more electrochemical cells.

[0036] The resulting supercapacitor can exhibit excellent electrical properties. For example, the supercapacitor exhibits a capacitance of approximately 6 farads per cubic centimeter (F / cm) when measured at a temperature of 23°C, a frequency of 120 Hz, and no applied voltage. 3 ") or more, in some embodiments, about 8 F / cm 3 or more, in some embodiments from about 9 to about 100 F / cm 3 , and in some embodiments, from about 10 to about 80 F / cm 3The supercapacitor may have a low equivalent series resistance (ESR), such as about 150 milliohms or less, in some embodiments about 125 milliohms or less, in some embodiments about 0.01 to about 100 milliohms, and in some embodiments about 0.05 to about 70 milliohms, as determined at a temperature of 23° C., a frequency of 100 kHz, and no applied voltage.

[0037] In particular, supercapacitors can exhibit excellent electrical properties when exposed to high temperatures. For example, a supercapacitor may be placed in contact with an atmosphere having a temperature of about 80°C or higher, in some embodiments, about 100°C to about 150°C, and in some embodiments, about 105°C to about 130°C (e.g., 85°C or 105°C). The capacitance and ESR values ​​can remain stable at such temperatures for a significant period of time, such as about 100 hours or more, in some embodiments, about 300 hours to about 5000 hours, and in some embodiments, about 600 hours to about 4500 hours (e.g., 168, 336, 504, 672, 840, 1008, 1512, 2040, 3024, or 4032 hours).

[0038] In one embodiment, for example, the ratio of the capacitance value of a supercapacitor after exposure to a high temperature atmosphere (e.g., 85°C or 105°C) for 1008 hours to the capacitance value of the supercapacitor when initially exposed to the high temperature atmosphere is about 0.75 or greater, in some embodiments, about 0.8 to 1.0, and in some embodiments, about 0.85 to 1.0. Such high capacitance values ​​can also be maintained under various extreme conditions, such as when a voltage is applied and / or when in a humid atmosphere. For example, the ratio of the capacitance value of a supercapacitor after exposure to a high temperature atmosphere (e.g., 85°C or 105°C) and an applied voltage to the initial capacitance value of the supercapacitor when exposed to the high temperature atmosphere but before a voltage is applied may be about 0.60 or greater, in some embodiments, about 0.65 to 1.0, and in some embodiments, about 0.7 to 1.0. The voltage may be, for example, about 1 volt or greater, in some embodiments about 1.5 volts or greater, and in some embodiments, about 2 to about 10 volts (e.g., 2.1 volts). In one embodiment, for example, the above-mentioned ratio may be maintained for 1008 hours or more. The supercapacitor may maintain the above-mentioned capacitance value when exposed to a high humidity level, for example, when placed in contact with an atmosphere having a relative humidity of about 40% or more, in some embodiments, about 45% or more, in some embodiments, about 50% or more, and in some embodiments, about 70% or more (e.g., about 85% to 100%). The relative humidity may be determined, for example, according to ASTM E337-02, Method A (2007). For example, the ratio of the capacitance value of the supercapacitor after exposure to a high temperature atmosphere (e.g., 85°C or 105°C) and high humidity (e.g., 85%) to the initial capacitance value of the supercapacitor when exposed to the high temperature atmosphere but before exposure to the high humidity may be about 0.7 or more, in some embodiments, about 0.75 to 1.0, and in some embodiments, about 0.80 to 1.0. In one embodiment, for example, this ratio may be maintained for 1008 hours or more.

[0039] The ESR can remain stable at such temperatures for a significant period of time, as discussed above. In one embodiment, for example, the ESR of a supercapacitor after 1008 hours of exposure to a high temperature atmosphere (e.g., 85°C or 105°C) is compared to the ESR of a supercapacitor after first exposure to a high temperature atmosphere. The ratio of the ESR of the supercapacitor after exposure to a high temperature atmosphere (e.g., 85°C or 105°C) and an applied voltage to the initial ESR of the supercapacitor when exposed to the high temperature atmosphere but before the voltage is applied may be about 1.8 or less, in some embodiments about 1.7 or less, and in some embodiments about 0.2 to about 1.6. In one embodiment, for example, the above-mentioned ratio may be maintained for 1008 hours or more. The supercapacitor may maintain the above-mentioned ESR values ​​when exposed to high humidity levels. For example, the ratio of the ESR of a supercapacitor after exposure to a high temperature atmosphere (e.g., 85°C or 105°C) and high humidity (e.g., 85%) to the initial capacitance value of the supercapacitor when exposed to the high temperature atmosphere but before exposure to the high humidity may be about 1.5 or less, in some embodiments about 1.4 or less, and in some embodiments, from about 0.2 to about 1.2. In one embodiment, for example, this ratio may be maintained for 1008 hours or more.

[0040] III. Supercapacitor Matching In some embodiments, a supercapacitor module may include multiple supercapacitors. The supercapacitors may be matched such that a balancing circuit is not required to control the respective voltages across each of the supercapacitors. In some embodiments, the supercapacitors may be matched based on one or more characteristics, such as direct current leakage (DCL), equivalent series resistance (ESL), capacitance, and / or any other suitable characteristic, as described in more detail below.

[0041] In one embodiment, the capacitor module may include a first supercapacitor having a first parameter value for a capacitor parameter at a first test condition. The capacitor may include a second supercapacitor having a second parameter value for the capacitor parameter at about the first test condition. The first test condition may include various test condition parameters, such as temperature, humidity, direct current (DC) voltage, alternating current (AC) voltage, time before use, and / or the like, as described in more detail below. As described above, the capacitor parameters may include DC current leakage, equivalent series resistance, and / or capacitance. DC current leakage, also referred to as "leakage current," is the amount of current flowing through a capacitor at a given DC voltage, e.g., the rated DC voltage of the supercapacitor. Additionally, any suitable characteristic of a capacitor may be a capacitor parameter.

[0042] In some embodiments, the ratio of the second parameter value to the first parameter value may be from about 0.8 to about 1.2, in some embodiments, the ratio may be from about 0.85 to about 1.15, and in some embodiments, from about 0.9 to about 1.1, and in some embodiments, from about 0.95 to about 1.05, and in some embodiments, from about 0.975 to about 1.025, and in some embodiments, from 0.99 to 1.01, and in some embodiments, from 0.995 to 1.005.

[0043] In some embodiments, matching the supercapacitors can eliminate the need for a voltage balancing circuit. As described above, the balancing circuit can control the respective voltages across each supercapacitor to prevent overvoltages. The balancing circuit can be active, such as an integrated circuit, or passive, such as one or more passive components (e.g., resistors) that connect to the terminals of the supercapacitors. By matching the supercapacitors described herein, the module can operate with approximately equal voltages across each supercapacitor. This can prevent overvoltages from occurring. , thus eliminating the need for balancing circuits in some embodiments.

[0044] In some embodiments, the first capacitor may be connected in series with the second supercapacitor without an active or passive balancing circuit. In some embodiments, a simple passive balancing circuit may be used, while the active balancing circuit may be eliminated. In other embodiments, the first supercapacitor may be connected in series with the second supercapacitor using a simplified active balancing circuit. For example, the simplified active balancing circuit may include fewer components, consume less energy, cost less to produce, and / or generate less heat than a standard active balancing circuit.

[0045] Although described above with reference to two supercapacitors, as noted above, a module may include any suitable number of supercapacitors. In some embodiments, additional supercapacitors beyond the first and second supercapacitors may be selected based on a comparison with the first supercapacitor using the methods described herein. For example, each of the additional supercapacitors may have a respective parameter value for the capacitor parameter at the first test conditions that is approximately equal to the first parameter value for the capacitor parameter at the first test conditions. Each of the additional supercapacitors may be selected based on a ratio of the capacitor parameter value at the first test conditions for each additional supercapacitor that is about 0.8 to about 1.2 times the capacitor parameter value for the first capacitor parameter at the first test conditions. In other embodiments, the ratio falls within any of the other ratio ranges discussed herein.

[0046] In some embodiments, each supercapacitor may be compared only to the supercapacitor to which it is directly connected. For example, each nth supercapacitor may be compared to n-1, n+1, or both supercapacitors. In some embodiments, each supercapacitor may be selected such that the module is assembled based on the last supercapacitor added to the module, i.e., supercapacitor n-1). In some embodiments, capacitor parameters for each of the nth supercapacitors may be compared to nominal target capacitor parameters. In other embodiments, the supercapacitors may be selected using any statistical analysis technique, machine learning algorithm, and / or optimization algorithm. For example, in one embodiment, the supercapacitors may be selected such that the standard deviation(s) of one or more capacitor parameters are within one or more respective predetermined standard deviation ranges.

[0047] In some embodiments, empirical analysis may be combined with other methods described herein to match supercapacitors. For example, a test voltage may be applied across a first supercapacitor. Several supercapacitors may then be "auditioned" to determine which supercapacitor should be added to the module as the second supercapacitor. This may involve connecting each "auditioned" supercapacitor, one at a time, in series with the first supercapacitor. While a voltage is applied across the supercapacitors in series, the voltage across the first supercapacitor and the voltage across the auditioned supercapacitor may be measured and the mathematical difference calculated. The "auditioned" supercapacitor that results in the smallest mathematical difference between the voltage across the first supercapacitor and the voltage across the "auditioned" supercapacitor may then be selected as the second supercapacitor. The process may then be repeated to select a third supercapacitor, a fourth supercapacitor, and so on. Furthermore, the above process may assist in determining the optimal order for connecting supercapacitors within a module.

[0048] In other embodiments, any suitable optimization algorithm may be used to optimize the potential for the module. The selection and / or connection sequence of the potential supercapacitors may be theoretically determined. For example, the empirical selection procedure described above may be theoretically simulated using known characteristics of potential supercapacitors and theoretical or empirical relationships between the supercapacitor characteristics, relevant test conditions, and the voltages obtained across the supercapacitors when connected to a module. In other embodiments, given a possible pool of potential supercapacitors, each possible combination and / or sequence of supercapacitors can be theoretically modeled to determine the most suitable combination and connection sequence to minimize voltage differences and / or overvoltages in the module.

[0049] In other embodiments, when selecting multiple supercapacitors for a module, several capacitor parameters may be measured for each supercapacitor. The supercapacitors may then be ranked based on the capacitor parameters. For example, in some embodiments, the supercapacitors may be ranked first by the capacitor parameter determined to be most predictive of the interaction of the supercapacitors in the module. The supercapacitors may then be ranked second by the next most predictable capacitor parameter, and so on. In other embodiments, each capacitor parameter may be assigned a weight, and the supercapacitors may then be ranked according to a weighted average of the capacitor parameters. The weight may be based on how determinative the respective capacitor parameter is of the voltage across the supercapacitors once connected in the module. The selection and / or connection order of the supercapacitors may be selected based on the resulting rankings.

[0050] IV. Selection Based on Direct Current Leakage (DCL) In some embodiments, supercapacitors may be selected based on their DCL. For example, a first supercapacitor may have a DCL of 25 microamperes (μA) at first test conditions. In some embodiments, the first test conditions may include temperature, relative humidity, applied DC voltage, and / or applied AC voltage at a constant frequency. For example, the first test conditions may include an applied DC voltage of 5 volts (no AC voltage component) at a temperature of 25°C. A second supercapacitor may be selected based on having a DCL at the first test conditions that is approximately 0.9 to 1.1 times the DCL of the first supercapacitor. Thus, in this example, the second supercapacitor may have a DCL of 22.5 μA to 27.5 μA at an applied DC voltage of 5 volts (no AC voltage component) and a temperature of 25°C. For example, supercapacitors may be selected based on DCL testing using one of the test methods described in the following sections.

[0051] In another embodiment, a first supercapacitor may be selected as described above, and a second supercapacitor may be selected based on having a DCL that is about 0.95 to about 1.05 times the DCL of the first supercapacitor at about the same voltage and about the same temperature. Thus, in this example, the second supercapacitor may have a DC of about 23.75 μA to about 26.25 μA at about 5 volts and about 25° C.

[0052] In another embodiment, a first supercapacitor may be selected as described above, and a second supercapacitor may be selected based on having a DCL that is about 0.975 to about 1.025 times the DCL of the first supercapacitor at about the same voltage and about the same temperature. Thus, in this example, the second supercapacitor may have a DCL of between about 24.375 μA and about 25.625 μA at about 5 volts and about 25° C.

[0053] In another embodiment, the first supercapacitor may be selected as described above, and the second The second supercapacitor may be selected based on having a DCL that is about 0.99 to about 1.01 times the DCL of the first supercapacitor at about the same voltage and about the same temperature. Thus, in this example, the second supercapacitor may have a current of about 24.75 μA to about 25.25 μA at about 5 volts and about 25° C.

[0054] V. Selection Based on Equivalent Series Resistance (ESR) In some embodiments, the supercapacitor may be selected based on its ESR. In some embodiments, the ESR is determined by the resistance to AC current (ESR AC ), and in other embodiments, the ESR may be related to the DC current (ESR DC For example, supercapacitors may be selected based on ESR testing using the test methods described in the following section.

[0055] For example, the first supercapacitor had an ESR of 65 milliohms under the first test condition. AC In some embodiments, the first test conditions may include a temperature, a relative humidity, an applied DC voltage, and / or an applied AC voltage at a constant frequency. For example, the first test conditions may include an AC voltage of 10 millivolts (mV) at 1 kHz (DC bias voltage of 0.0 volts) and a temperature of 25°C. In other embodiments, the DC bias voltage may be, for example, 1.1 volts or 2.1 volts. The second supercapacitor may have an ESR of approximately the same as that of the first supercapacitor at the first test conditions. AC ESR of about 0.9 to 1.1 times AC Thus, in this example, the second supercapacitor may be selected based on having an ESR of about 58.5 milliohms to about 71.5 milliohms at about 10 mV, about 1 kHz (DC bias is 0.0 volts), and a temperature of about 25° C. AC may have

[0056] In another embodiment, a first supercapacitor may be selected as described above, and a second supercapacitor may be selected to have an ESR of approximately the first supercapacitor at first test conditions. AC ESR of approximately 0.95 to 1.05 times AC Thus, in this example, the second supercapacitor may be selected based on having an ESR of about 61.75 milliohms to about 68.25 milliohms at about 10 mA (DC bias at 0.0 volts), about 1000 Hz, and about 25° C. AC may have

[0057] In another embodiment, a first supercapacitor may be selected as described above, and a second supercapacitor is selected to have an ESR of about the first supercapacitor at first test conditions. AC ESR of approximately 0.975 to 1.025 times ACThus, in this example, the second supercapacitor may be selected based on having an ESR of about 63.375 milliohms to about 66.625 milliohms at about 10 mV (DC bias is 0.0 volts), about 1000 Hz, and about 25° C. AC may have

[0058] In another embodiment, a first supercapacitor may be selected as described above, and a second supercapacitor is selected to have an ESR of about the first supercapacitor at first test conditions. AC ESR of approximately 0.99 to 1.01 times AC Thus, in this example, the second supercapacitor may have a capacitance of about 64.350 milliohms to about 65.650 milliohms at about 10 mV (DC bias at 0.0 volts), about 1000 Hz, and about 25°C.

[0059] VI. Capacitance-Based Selection In some embodiments, the supercapacitors may be selected based on capacitance. For example, a first supercapacitor may have a capacitance of 5 Farads (F) under first test conditions. In some embodiments, the first test conditions may include temperature, relative humidity, applied DC voltage, and / or applied AC voltage at a constant frequency. For example, the first test conditions may include a temperature of about 25° C. The second supercapacitor may be selected based on having a capacitance at about the first test conditions that is about 0.9 to about 1.1 times the capacitance of the first supercapacitor. Thus, in this example, the second supercapacitor may have a capacitance of about 4.5 F to about 5.5 F at a temperature of about 25° C. The supercapacitor may be selected based on capacitance testing using the test method described in the following section.

[0060] In another embodiment, the first supercapacitor may be selected as described above, and the second supercapacitor may be selected based on having a capacitance at about the first test condition that is about 0.95 to about 1.05 times the capacitance of the first supercapacitor. Thus, in this example, the second supercapacitor may have a capacitance of about 4.75 F to about 5.25 F at about 25° C.

[0061] In another embodiment, the first supercapacitor may be selected as described above, and the second supercapacitor may be based on having a capacitance at about the first test condition that is about 0.975 to about 1.025 times the capacitance of the first supercapacitor. Thus, in this example, the second supercapacitor may have a capacitance of about 4.875 F to about 5.125 F at about 25° C.

[0062] In another embodiment, the first supercapacitor may be selected as described above, and the second supercapacitor may be selected based on having a capacitance at about the first test condition that is about 0.99 to about 1.01 times the capacitance of the first supercapacitor. Thus, in this example, the second supercapacitor may have a capacitance of about 4.95 F to about 5.05 F at about 25° C.

[0063] VII. Selection Based on Multiple Parameters In some embodiments, a supercapacitor may be selected based on a combination of two or more of the above parameters. For example, in one embodiment, a first supercapacitor may have (1) a DCL of 25 microamperes (μA) at an applied voltage of 5 volts (DC) (no AC voltage component) and a temperature of 25° C., and (2) an ESR of 65 milliohms at 10 millivolts (mV), 1000 Hz (no DC voltage bias), and a temperature of 25° C. A second supercapacitor may be selected based on (1) a ratio of the DCL of the second supercapacitor at a first test condition to the DCL of the first supercapacitor within a first ratio range (e.g., from about 0.8 to about 1.2), and (2) a second ratio of the ESR of the second supercapacitor at a second test condition to the ESR of the first supercapacitor within a second ratio range (e.g., from about 0.95 to about 1.05). In some embodiments, the first ratio range may be equal to the second ratio range. For example, in one embodiment, each of the first and second ranges may be from about 0.99 to about 1.01. In other embodiments, the first ratio range for DCL may be different from the second ratio range for ESR. For example, in one embodiment, the first ratio range for DCL may be from about 0.99 to about 1.01, and the second ratio range for ESR may be from about 0.95 to about 1.05.

[0064] It should be understood that any suitable combination of ratio ranges and parameters may be used. In some embodiments, the supercapacitors may be selected based on all three parameters (DCL, ESR, and capacitance). In other embodiments, additional parameters may be used, such as peak current, maximum energy, energy density, etc. Furthermore, as described above, any suitable statistical analysis technique, machine learning algorithm, and / or optimization algorithm may be used. Although described as having two supercapacitors, the module may include any suitable number of supercapacitors, as described above. It should be understood that the second supercapacitor may have a different capacitance than the first supercapacitor. Furthermore, the above discussion of selecting a second supercapacitor based on a first supercapacitor is equally applicable to selecting a third supercapacitor based on the second supercapacitor, and so on.

[0065] 4a-4c, the leakage current and equivalent series resistance may each vary with temperature. The relationship between each capacitor parameter and temperature can be determined empirically or theoretically. These relationships may be used to select a supercapacitor, as described in more detail below.

[0066] For example, FIG. 5 shows a hypothetical example of testing and matching supercapacitors. In this hypothetical example, a target range of about 0.8 to about 1.2 is used for the ratio of capacitor parameter values. FIG. 5 shows leakage current versus temperature for five supercapacitors 4002, 4004, 4006, 4008, and 4010. The leakage current of each supercapacitor may be measured at 25° C. (indicated by the vertical dotted line at 25° C.). A ratio of the leakage current for each supercapacitor may be formed for one of the supercapacitors. For example, a ratio may be calculated for supercapacitor 4010 because supercapacitor 4010 has the lowest leakage current at 25° C. The ratio of the leakage current at 25° C. for supercapacitor 4008 to the leakage current at 25° C. for supercapacitor 4010 is about 1.1, which is within the target range of 0.8 to 1.2. Thus, in this hypothetical example, supercapacitors 4008 and 4010 may be matched to form a module. FIG. 5 shows that the ratio of leakage currents for these supercapacitors 4008, 4010 is predicted to remain within the above range for all temperatures within the range of −40° C. to 80° C. This matching can provide a module in which the leakage currents of the supercapacitors are approximately equal regardless of changes in temperature. In other words, this can automatically control the respective voltages across each supercapacitor so that overvoltages do not occur. FIG. 5 also shows that another module can be formed using supercapacitors 4004, 4006. It should be understood that this hypothetical example is applicable to forming modules having more than just supercapacitors.

[0067] In some embodiments, a relationship between a capacitor parameter (e.g., leakage current) and a test condition (e.g., temperature) is used to match supercapacitors. For example, in some embodiments, supercapacitors may be matched based on measurements taken under various test conditions. For example, the leakage current of a second supercapacitor may be tested at a different temperature than a first supercapacitor, which is tested under a first test condition. The known relationship between the capacitor parameter and temperature may be used to estimate a second parameter value for the second supercapacitor at approximately the first test condition so that the second supercapacitor can be matched to the first supercapacitor based on available data.

[0068] For example, referring to Figure 5, the leakage current of supercapacitor 4008 may be known to be at 80°C, and the leakage current of supercapacitor 4010 may be known at 25°C. Using the relationship between leakage current and temperature shown in Figure 5, the leakage current for supercapacitor 4008 may be estimated at 25°C. This estimate may then be used to determine whether a second supercapacitor is a suitable match for the first supercapacitor.

[0069] Similarly, in some embodiments, relationships between different capacitor parameters can be determined such that supercapacitors can be matched based on capacitor parameter values ​​for different capacitor parameters. For example, leakage current can be determined empirically or theoretically. The ESR may be correlated to the equivalent series resistance, which may be used to match a first supercapacitor with a known leakage current at a first condition to a second supercapacitor with a known ESR at a second condition.

[0070] In some embodiments, supercapacitors may be matched using two or more capacitor parameters using statistical analysis and / or machine learning. For example, referring to FIG. 6 , in one embodiment, data for multiple supercapacitors, any suitable clustering algorithm, or machine learning model may be used to locate groups of supercapacitors with similar capacitor parameters. For example, in FIG. 6 , “capacitor parameter 1” may be capacitance measured at a first test condition, and “capacitor parameter 2” may be leakage current measured at approximately the first test condition. The algorithm may group the supercapacitors into groups containing similar supercapacitors. While illustrated with respect to two capacitor parameters, in some embodiments, the clustering algorithm may be configured to create clusters of supercapacitors based on three or more capacitor parameters. Example inputs for the clustering algorithm include the ratios of capacitor parameter values ​​discussed herein, the desired number of supercapacitors per module, and the desired overall properties of the module (e.g., total capacitance, ESR, and DCL).

[0071] As mentioned above, in some embodiments, a machine learning model may be used to match supercapacitors. For example, the model may be trained using the example data shown in FIG. 6 and configured to predict and optimize the respective voltages obtained across the individual supercapacitors of a theoretical module. For example, a training set of data may be created by monitoring the respective voltages across the individual supercapacitors in various modules of different sizes, capacitances, etc. These monitored voltages, combined with known capacitor parameter values ​​for each supercapacitor in the module, may be used as a training data set such that the machine learning model may be configured to minimize voltage discrepancies and / or overvoltages when clustering or grouping supercapacitors based on capacitor parameter values.

[0072] The invention will be better understood with reference to the following examples. Test Method The following sections provide exemplary methods for testing supercapacitors to determine various capacitor parameters. However, capacitor parameters may be tested using any suitable method. Additionally, some capacitor parameters may change from when the supercapacitor was first formed. Therefore, capacitor parameters may be measured after an initial test period. For example, in some embodiments, testing may be performed after an initial test period of 20 to 150 hours, in some embodiments, 40 to 130 hours, and in some embodiments, 50 to 110 hours, e.g., 72 hours.

[0073] Additionally, testing may be performed at various temperatures and relative humidity levels, for example, the temperature may be room temperature (approximately 23°C), 25°C, 85°C, or 105°C, and the relative humidity may be 25% or 85%.

[0074] I. Direct Current Leakage (DCL) DC current leakage may be measured across the resistor using a Keithley 2400, 2602, or 3330 precision LCZ meter. DC current leakage of a supercapacitor is measured by charging the supercapacitor to 5 volts for 72 hours at 25°C and 25% humidity. The DCL may then be measured by: The supercapacitor may then be connected in series with a resistor having a known resistance of 1000 ohms. The current flowing from the supercapacitor through the resistor may be allowed to stabilize for 10 minutes, and then the voltage across the resistor may be measured. Ohm's law may then be used to calculate the DCL as the voltage across the resistor divided by the known resistance of the resistor.

[0075] II. Equivalent Series Resistance (ESR) Equivalent series resistance (ESR) for AC current AC ) may be measured using a Keithley 2400, 2602, or 3330 precision LCZ meter with a DC bias of 0.0 volts, 1.1 volts, or 2.1 volts (0.5 volt peak-to-peak sinusoidal signal). The operating frequency is 1 kHz.

[0076] DC equivalent series resistance (ESR) DC The ESR may be measured by cyclically charging and discharging the supercapacitor at a constant current between (1) the rated voltage of the supercapacitor and (2) half the rated voltage of the supercapacitor. The equivalent series resistance may then be calculated for each of these charge and discharge steps based on the respective current flow and voltage associated with each step. DC The value may be calculated by averaging the resistance values ​​calculated in the previous step.

[0077] III. Capacitance The capacitance of the supercapacitor may be measured using a Keithley 2400, 2602, or 3330 precision LCZ meter at a DC bias of 0.0 volts, 1.1 volts, or 2.1 volts (0.5 volt peak-to-peak sinusoidal signal). The operating frequency is 120 Hz. The temperature is room temperature (approximately 23°C) and the relative humidity is 25%.

[0078] Alternatively, the supercapacitor may be charged to its rated voltage using a power source at a known temperature and humidity. For example, the supercapacitor may be charged to its rated voltage at room temperature and 25% relative humidity. The supercapacitor may then be removed from the power source and discharged at a constant current while the time required to discharge the supercapacitor from a first voltage to a second voltage is measured. The capacitance may then be calculated based on the first voltage, the second voltage, and the elapsed time.

[0079] Example The ability to form matched supercapacitor modules that operate satisfactorily without the use of balancing circuits was demonstrated: pairs of supercapacitors were matched based on similar DCL values ​​and connected in series to form modules.

[0080] The resulting module has a rated voltage of 5.0 volts, a rated capacitance of 5F at room temperature, and a rated ESR of 1000hz and 10mV (0.0DC bias voltage). AC The modules had a resistance of 65 milliohms. The modules were tested at 100%, 90%, 80%, and 70% of the rated voltage of the modules, corresponding to 5.0 volts, 4.5 volts, 4.0 volts, and 3.5 volts, respectively. Testing was performed at an operating temperature of 85°C. Each group of modules was cycled between their respective test voltages as described above and half of their respective test voltages under constant current at 85°C.

[0081] Satisfactory operating limits were defined for both capacitance and ESR, specifically requiring that (1) the capacitance remain greater than or equal to 70% of the rated capacitance at 85°C, and (2) the ESR remain less than or equal to 300% of the rated ESR at 85°C.

[0082] Test results showed that the module satisfactorily remained within the above operating limits for over 3,000 hours at 4 volts and for over 4,000 hours at 3.5 volts without the use of any balancing circuitry.

[0083] Figures 7a and 7b show that modules tested at 4 volts and 85°C successfully met operational limits for over 3,000 hours without the use of a balancing circuit. Specifically, referring to Figure 7a, the average capacitance of the modules was rated capacitance (CAP SPEC ) remained above 70% of the rated ESR. However, at approximately 3,500 hours, the capacitance dropped below the 70% threshold. Referring to Figure 7b, the average ESR of the module remained well below 300% of the rated ESR (ESR0) throughout the test period.

[0084] Figures 8a and 8b show that modules tested at 3.5 volts and 85°C remained at satisfactory operating limits for 4,000 hours without the use of a balancing circuit. In particular, referring to Figure 8a, the average capacitance of the modules remained above 70% of the rated capacitance for 4,000 hours. Referring further to Figure 8b, the average ESR of the modules remained well below 300% of the rated ESR for 4,000 hours.

[0085] These and other modifications and variations of the present invention may be practiced by those skilled in the art without departing from the spirit and scope of the present invention. Additionally, it should be understood that aspects of the various embodiments may be interchanged both in whole and in part. Furthermore, those skilled in the art will appreciate that the foregoing description is by way of example only and does not limit the invention as further set forth in the appended claims. (1) According to a first aspect of the present invention, a supercapacitor module includes a first supercapacitor having a first parameter value for a capacitor parameter at a first test condition and a second supercapacitor having a second parameter value for the capacitor parameter at approximately the first test condition, wherein a ratio of the second parameter value to the first parameter value is from about 0.8 to about 1.2. (2) According to the second aspect of the present invention, in the first aspect, the ratio of the second parameter value to the first parameter value is from about 0.85 to about 1.15. (3) According to a third aspect of the present invention, in the first aspect, the ratio of the second parameter value to the first parameter value is from about 0.9 to about 1.1. (4) According to a fourth aspect of the present invention, in the first aspect, the supercapacitor module does not include a voltage balancing circuit. (5) According to a fifth aspect of the present invention, in the first aspect, the capacitor parameter is leakage current. (6) According to a sixth aspect of the present invention, in the fifth aspect, the leakage current is greater than about 23.75 microamperes and less than about 26.25 microamperes at an applied DC voltage of about 5 volts and a temperature of about 25°C. (7) According to a seventh aspect of the present invention, in the first aspect, the capacitor parameter is an equivalent series resistance. (8) According to an eighth aspect of the present invention, in the seventh aspect, the equivalent series resistance is greater than about 61.75 milliohms and less than about 68.25 milliohms at an applied AC voltage of about 10 mV at a frequency of about 1000 Hz and a temperature of about 25°C. (9) According to a ninth aspect of the present invention, in the first aspect, the capacitor parameter is capacitance. (10) According to a tenth aspect of the present invention, in the ninth aspect, the capacitance is greater than about 4.75F and less than about 5.25F at a temperature of about 25°C. (11) According to an eleventh aspect of the present invention, in the first aspect, the first test condition includes a test voltage. (12) According to the twelfth aspect of the present invention, in the first aspect, the first test conditions include a test temperature. (13) According to a thirteenth aspect of the present invention, in the first aspect, the first supercapacitor is connected in series with the second supercapacitor. (14) According to a fourteenth aspect of the present invention, in the first aspect, the first supercapacitor has a third parameter value with respect to a second capacitor parameter at a second test condition, the second supercapacitor has a fourth parameter with respect to the second capacitor parameter at approximately the second test condition, and a second ratio of the fourth parameter value to the third parameter value is from about 0.8 to about 1.2. (15) A fifteenth aspect of the present invention is a method for manufacturing a supercapacitor module from a first supercapacitor having a first parameter value for a capacitor parameter under first test conditions and a second supercapacitor, comprising selecting the second supercapacitor based on the second capacitor having a second parameter value for the capacitor parameter under the first test conditions, approximately, wherein a ratio of the second parameter value to the first parameter value is from about 0.8 to about 1.2. (16) According to a sixteenth aspect of the present invention, in the fifteenth aspect, the capacitor parameter is leakage current. (17) According to a seventeenth aspect of the present invention, in the fifteenth aspect, the capacitor parameter is an equivalent series resistance. (18) According to an eighteenth aspect of the present invention, in the fifteenth aspect, the capacitor parameter is capacitance. (19) According to a nineteenth aspect of the present invention, in the fifteenth aspect, the method further includes the step of housing the first and second supercapacitors in a housing without a balancing circuit. (20) According to a twentieth aspect of the present invention, in the fifteenth aspect, the voltage across the first capacitor is not adjusted using a balancing circuit. (21) According to a twenty-first aspect of the present invention, in the fifteenth aspect, the method further includes connecting the first supercapacitor in series with the second supercapacitor without a balancing circuit. (22) According to the 22nd aspect of the present invention, in the 15th aspect, the second ratio of the second parameter value to the first parameter value is from about 0.9 to about 1.1. (23) According to the 23rd aspect of the present invention, in the 15th aspect, the second ratio of the second parameter value to the first parameter value is from about 0.95 to about 1.05. (24) According to a 24th aspect of the present invention, in the 15th aspect, the first supercapacitor has a third parameter value for a second capacitor parameter under second test conditions, and the second supercapacitor has a fourth parameter value for the second capacitor parameter under approximately the second test conditions, and the step of selecting the second supercapacitor is further based on a second ratio of the fourth parameter value to the third parameter value being from about 0.8 to about 1.2.

Claims

1. conducting a first test of a plurality of supercapacitors, measuring a first capacitor parameter at first test conditions including a test temperature, wherein the first capacitor parameter is an equivalent series resistance or a capacitance; selecting, from the plurality of supercapacitors, a first supercapacitor having a first parameter value and a second supercapacitor having a second parameter value based on a result of the first test and a relationship between the first capacitor parameter and temperature, wherein a first ratio of the second parameter value to the first parameter value is between 0.8 and 1.2; electrically connecting the first supercapacitor and the second supercapacitor in series; A method for fabricating a supercapacitor module comprising:

2. The method of claim 1 , wherein the first ratio is from 0.85 to 1.

15.

3. The method of claim 1 , wherein the first ratio is from 0.9 to 1.

1.

4. The method of claim 1 , wherein the supercapacitor module does not include a voltage balancing circuit.

5. The method of claim 1 , wherein the first capacitor parameter is an equivalent series resistance.

6. 6. The method of claim 5, wherein the equivalent series resistance is greater than 61.75 milliohms and less than 68.25 milliohms at an applied AC voltage of 10 mV at a frequency of 1000 Hz and a temperature of 25°C.

7. The method of claim 1 , wherein the first capacitor parameter is capacitance.

8. 8. The method of claim 7, wherein the capacitance is greater than 4.75F and less than 5.25F at a temperature of 25°C.

9. The method of claim 1 , wherein the first test condition comprises a test voltage.

10. conducting a second test of the plurality of supercapacitors, measuring a second capacitor parameter under second test conditions; selecting the first supercapacitor having a third parameter value and the second supercapacitor having a fourth parameter value from the plurality of supercapacitors, wherein a second ratio of the fourth parameter value to the third parameter value is between 0.8 and 1.2; The method of claim 1 further comprising:

11. The method of claim 10 , wherein the second capacitor parameter is an equivalent series resistance, a capacitance, or a leakage current.

12. The method of claim 10, wherein the second ratio is from 0.9 to 1.

1.

13. The method of claim 10, wherein the second ratio is from 0.95 to 1.05.

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