Electrode assembly for ultracapacitor

Abstract

To provide an ultracapacitor that solves the problem of increased equivalent series resistance at high temperatures.SOLUTION: An electrode assembly 10 for an ultracapacitor contains: a first electrode 12 comprising a first current collector 20 electrically coupled to first carbonaceous coatings 22, 24; a second electrode 14 comprising a second current collector 40 electrically coupled to second carbonaceous coatings 42, 44, and a separator 60 positioned between the first electrode and the second electrode. At least a portion of the first current collector projects beyond a first longitudinal edge to define a first projecting portion, where the offset ratio of the first projecting portion is from about 0.02 to about 0.3.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This application claims the benefit of the filing of U.S. Provisional Patent Application No. 62 / 527,278, filed Jun. 30, 2017, which is hereby incorporated by reference in its entirety.

Background Art

[0002] Electrical energy storage cells are widely used to power electronic devices, electromechanical devices, electrochemical devices, and other useful devices. For example, an electric double layer ultracapacitor generally uses a pair of polarized electrodes containing carbon particles (e.g., activated carbon) impregnated with an electrolyte. Due to the effective surface area of the particles and the small spacing between the electrodes, a large capacitance value can be achieved. However, problems remain. For example, many conventional ultracapacitors are sensitive to high temperatures, which can result in increased equivalent series resistance (ESR). Accordingly, there is a current need for an ultracapacitor having improved electrical characteristics.

Summary of the Invention

[0003] According to one embodiment of the present invention, an electrode assembly for an ultracapacitor defining a length between opposing first and second longitudinal edges is disclosed. The electrode assembly includes a first electrode including a first current collector electrically coupled to a first carbonaceous coating, a second electrode including a second current collector electrically coupled to a second carbonaceous coating, and a separator disposed between the first electrode and the second electrode. At least a portion of the first current collector projects beyond the first longitudinal edge to define a first protruding portion. The offset ratio of the first protruding portion is from about 0.02 to about 0.3.

[0004] Other features and aspects of the present invention are set forth in greater detail below. A complete and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in more detail in the remainder of the specification, which makes reference to the accompanying drawings.

Brief Description of the Drawings

[0005]

Figure 1

Figure 2

Figure 3

Figure 4

DETAILED DESCRIPTION OF THE INVENTION

[0006] The repeated use of reference numerals in this specification and the drawings is intended to represent the same or similar features or elements of the present invention. Those skilled in the art should understand that this discussion is merely an explanation of exemplary embodiments and is not intended to limit the broader aspects of the present invention, which are embodied in the exemplary configurations.

[0007] Generally speaking, the present invention relates to an electrode assembly for use in an ultracapacitor. The electrode assembly includes a first electrode including a first carbonaceous coating (e.g., activated carbon particles) electrically coupled to a first current collector, and a second electrode including a second carbonaceous coating (e.g., activated carbon particles) electrically coupled to a second current collector. Also, a separator is disposed between the first electrode and the second electrode. The electrode assembly is formed by combining the electrodes and the separator together, for example, by stacking them, winding them spirally, or the like.

[0008] Regardless of the technology used, at least one of the current collectors (the first and / or second current collectors) protrudes beyond the longitudinal edge of the electrode assembly. The protruding portion of the current collector can provide an increased surface area for contacting the terminals within the housing, thereby reducing the ESR. For example, the resulting ultracapacitor can have an ESR of about 100 milliohms or less, in some embodiments less than about 80 milliohms, in some embodiments about 0.01 to about 50 milliohms, and in some embodiments about 0.05 to about 20 milliohms, as determined without an applied voltage at a frequency of 100 kHz and a temperature of 25°C. The ESR can also be stably maintained at various different temperatures. For example, the ultracapacitor can be disposed 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). Even at such high temperatures, the ESR can generally be maintained within the above ranges 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). For example, in one embodiment, the ratio of the ESR of the ultracapacitor after 1008 hours of exposure to a high temperature atmosphere (e.g., 85°C or 105°C) to the ESR of the ultracapacitor at the time of first exposure to the high temperature atmosphere is about 1.3 or less, in some embodiments about 1.2 or less, and in some embodiments about 0.2 to about 1.

[0009] Such a low ESR value can be maintained even when a high voltage is applied and / or under various extreme conditions such as in a high humidity atmosphere. For example, the ratio of the ESR of an ultra-capacitor after being exposed to a high temperature atmosphere (e.g., 85 °C or 105 °C) and an applied voltage to the initial ESR of the ultra-capacitor before being exposed to the high temperature atmosphere but before the voltage is applied can be about 1.8 or less, about 1.7 or less in some embodiments, and about 0.2 to about 1.6 in some embodiments. The voltage can be, for example, about 1 volt or more, about 1.5 volts or more in some embodiments, and about 2 to about 10 volts (e.g., 2.1 volts) in some embodiments. For example, in one embodiment, the above ratio can be maintained for 1008 hours or more. The ultra-capacitor can also maintain the above-described ESR value when exposed to a high humidity level. For example, the ratio of the ESR of an ultra-capacitor after being exposed 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 ultra-capacitor before being exposed to the high temperature atmosphere but before being exposed to the high humidity atmosphere can be about 1.5 or less, about 1.4 or less in some embodiments, and about 0.2 to about 1.2 in some embodiments. For example, in one embodiment, this ratio can be maintained for 1008 hours or more.

[0010] The "offset ratio" of the protruding current collector, which is obtained by dividing the length of the protruding portion of the current collector by the length of the electrode assembly, is generally controlled within a range of about 0.02 to about 0.3, in some embodiments about 0.04 to about 0.2, and in some embodiments about 0.05 to about 0.1. For example, the length of the protruding portion of the current collector can be about 1 to about 20 millimeters, in some embodiments about 2 to about 16 millimeters, and in some embodiments about 5 to about 15 millimeters. Also, the length of the electrode assembly can be about 5 to about 100 millimeters, in some embodiments about 8 to about 60 millimeters, and in some embodiments about 10 to about 25 millimeters. The inventors have found that by selectively controlling the electrode offset ratio and relative length of the protruding portion and the electrode assembly, the resulting ultracapacitor can achieve not only a reduced ESR but also a high capacitance value. The ultracapacitor can exhibit, for example, a capacitance value of about 6 farads per square centimeter (F / cm ) or more when measured without an applied voltage at a frequency of 12 2 0 Hz and a temperature of 25°C, in some embodiments about 8 F / cm 2 or more, in some embodiments about 9 to about 100 F / cm 2 , and in some embodiments about 10 to about 80 F / cm 2 .

[0011] The capacitance can also be stably maintained at the above high temperature 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). For example, in one embodiment, the ratio of the capacitance value of the ultracapacitor after being exposed to a high-temperature atmosphere (e.g., 85°C or 105°C) for 1008 hours to the capacitance value of the ultracapacitor at the time of first being exposed to the high-temperature atmosphere is about 0.75 or more, in some embodiments about 0.8 to 1.0, and in some embodiments about 0.85 to 1.0. Also, the high capacitance value can be maintained when a voltage is applied and / or in a high-humidity atmosphere. For example, the ratio of the capacitance value of the ultracapacitor after being exposed to a high-temperature atmosphere (e.g., 85°C or 105°C) and an applied voltage to the initial capacitance value of the ultracapacitor that has been exposed to the high-temperature atmosphere but before the voltage is applied can be about 0.60 or more, in some embodiments about 0.65 to 1.0, and in some embodiments about 0.7 to 1.0. The voltage can be, for example, about 1 volt or more, in some embodiments about 1.5 volts or more, and in some embodiments about 2 to about 10 volts (e.g., 2.1 volts). For example, in one embodiment, the above ratio can be maintained for 1008 hours or more. The ultracapacitor can also maintain the above-described capacitance value when exposed to a high humidity level, such as 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 can be determined, for example, in accordance with ASTM-E337-02, Method A (2007).For example, the ratio of the capacitance value of the ultracapacitor after being exposed 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 ultracapacitor that has been exposed to the high-temperature atmosphere but not to the high humidity can be about 0.7 or more, about 0.75 to 1.0 in some embodiments, and about 0.80 to 1.0 in some embodiments. For example, in one embodiment, this ratio can be maintained for 1008 hours or more.

[0012] Here, various embodiments of the present invention will be described in more detail. I. Electrode Assembly: A. Electrodes: As shown above, the electrode assembly includes first and second electrodes, each of which includes a first and a second current collector. It should be understood that additional current collectors can also be used if desired, particularly when the ultracapacitor includes multiple energy storage cells. The current collectors can be formed from the same or different materials. However, each current collector is typically formed from a conductive metal such as aluminum, stainless steel, nickel, silver, palladium, etc., and alloys thereof, including a substrate. Aluminum and aluminum alloys are particularly suitable for use in the present invention. The substrate can be in the form of foil, sheet, plate, mesh, etc. The substrate can also have a relatively small thickness such as about 200 micrometers or less, about 1 to about 100 micrometers in some embodiments, about 5 to about 80 micrometers in some embodiments, and about 10 to about 50 micrometers in some embodiments. Although not essential by any means, the surface of the substrate can optionally be roughened by washing, etching, blasting, etc.

[0013] The first and second carbonaceous coatings are also electrically coupled to the first and second current collectors, respectively. They can be formed from the same or different types of materials and may include one or more layers, but each of the carbonaceous coatings generally includes at least one layer containing activated particles. For example, in some embodiments, an activated carbon layer can be disposed directly on the current collector, and in some cases, this may be the only layer of the carbonaceous coating. Examples of suitable activated carbon particles include, for example, coconut shell-based activated carbon, petroleum coke-based activated carbon, pitch-based activated carbon, polyvinylidene chloride-based activated carbon, phenol resin-based activated carbon, polyacrylonitrile-based activated carbon, and activated carbon from natural sources such as coal, charcoal, or other natural organic sources.

[0014] In some embodiments, it may be desirable to selectively control some characteristics of the activated carbon particles, such as their particle size distribution, surface area, and pore size distribution, to help improve the ion mobility with respect to some types of electrolytes after one or more charge-discharge cycles. For example, at least 50 volume% of the particles may have a dimension (D50 diameter) 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. Also, at least 90 volume% of the particles may have a dimension (D90 diameter) in the range of about 2 to about 40 micrometers, in some embodiments about 5 to about 30 micrometers, and in some embodiments about 6 to about 15 micrometers. Also, the BET surface area may be from about 900 m 2 / g to about 3,000 m 2 / g, in some embodiments from about 1,000 m 2 / g to about 2,500 m 2 / g, and in some embodiments from about 1,100 m 2 / g to about 1,800 m 2 / g.

[0015] In addition to having specific dimensions and surface area, the activated carbon particles may also contain pores having a specific pore size distribution. For example, the amount of pores with a diameter of less than about 2 nanometers (i.e., micropores) can provide a pore volume of about 50% by volume or less of the total pore volume, about 30% by volume or less in some embodiments, and a pore volume of 0.1% to 15% by volume in some embodiments. Also, the amount of pores with a diameter between about 2 nanometers and about 50 nanometers (i.e., mesopores) can be about 20% to about 80% by volume, about 25% to about 75% by volume in some embodiments, and about 35% to about 65% by volume in some embodiments. Finally, the amount of pores with a diameter greater than about 50 nanometers (i.e., macropores) can be about 1% to about 50% by volume, about 5% to about 40% by volume in some embodiments, and about 10% to about 35% by volume in some embodiments. The total pore volume of the carbon particles is about 0.2 cm 3 / g to about 1.5 cm 3 / g, about 0.4 cm 3 / g to about 1.0 cm 3 / g, and the median pore width can be about 8 nanometers or less, about 1 to about 5 nanometers in some embodiments, and about 2 to about 4 nanometers in some embodiments. The pore diameter and total pore volume can be measured using nitrogen adsorption and can be analyzed by the Barrett-Joyner-Halenda (BJH) method as is well known in the art.

[0016] If desired, a binder can be present in an amount of about 60 parts or less per 100 parts of carbon in the first and / or second carbonaceous coating, in some embodiments 40 parts or less, and in some embodiments about 1 to about 25 parts. The binder can constitute, for example, about 15 wt% or less of the total weight of the carbonaceous coating, in some embodiments about 10 wt% or less, and in some embodiments about 0.5 wt% to about 5 wt%. Any of a variety of suitable binders can be used in the electrode. For example, in some embodiments, styrene-butadiene copolymer, polyvinyl acetate homopolymer, vinyl acetate-ethylene copolymer, vinyl acetate-acrylic copolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl chloride-vinyl acetate terpolymer, acrylic polyvinyl chloride polymer, acrylic polymer, nitrile polymer, polytetrafluoroethylene or polyvinylidene fluoride such as fluoropolymers, polyolefins, etc., and water-insoluble organic binders such as mixtures thereof can be used. Also, water-soluble organic binders such as polysaccharides and their derivatives can be used. In one particular embodiment, the polysaccharide is an alkyl cellulose ether (e.g., methyl cellulose and ethyl cellulose); hydroxyalkyl cellulose ether (e.g., hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl hydroxybutyl cellulose, hydroxyethyl hydroxypropyl cellulose, hydroxyethyl hydroxybutyl cellulose, hydroxyethyl hydroxypropyl hydroxybutyl cellulose, etc.); 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); carboxyalkyl cellulose ether (e.g., carboxymethyl cellulose); etc., such as non-ionic cellulose ethers, and can be any of the above protonated salts such as sodium carboxymethyl cellulose.

[0017] Other materials can also be used within the activated carbon layer of the first and / or second carbonaceous coatings and / or within other layers of the first and / or second carbonaceous coatings. For example, in some embodiments, a conductivity promoter can be used to further increase conductivity. Representative conductivity promoters include, for example, carbon black, graphite (natural or artificial), graphite, carbon nanotubes, nanowires or nanotubes, metal fibers, graphene, etc., as well as mixtures thereof. Carbon black is particularly preferred. When used, the conductivity promoter usually constitutes about 60 parts or less per 100 parts of activated carbon particles in the carbonaceous coating, in some embodiments 40 parts or less, and in some embodiments about 1 to about 25 parts. The conductivity promoter can, for example, constitute about 15 wt% or less of the total weight of the carbonaceous coating, in some embodiments about 10 wt% or less, and in some embodiments about 0.5 wt% to about 5 wt%. Also, the activated carbon particles usually constitute 85 wt% or more of the carbonaceous coating, in some embodiments about 90 wt% or more, and in some embodiments about 95 wt% to about 99.5 wt%.

[0018] The specific method of applying the carbonaceous coating to the current collector can be varied as is well known to those skilled in the art, such as printing (e.g., rotogravure), spraying, slot die coating, drop coating, dip coating, etc. Regardless of the method of applying it, the resulting electrode is usually dried at a temperature of about 100°C or higher, in some embodiments about 200°C or higher, and in some embodiments about 300°C to about 500°C in order to remove moisture from the coating. The electrode can also be compressed (e.g., calendared) to optimize the volumetric efficiency of the ultracapacitor. After any optional compression, the thickness of each carbonaceous coating can generally be varied based on the desired electrical performance and operating range of the ultracapacitor. However, usually the thickness of the coating is about 20 to about 200 micrometers, 30 to about 150 micrometers, and in some embodiments about 40 to about 100 micrometers. The coating can be present on one or both surfaces of the current collector. However, the thickness of the entire electrode (including the current collector and the carbonaceous coating after optional compression) is typically in the range of about 20 to about 350 micrometers, in some embodiments about 30 to about 300 micrometers, and in some embodiments about 50 to about 250 micrometers.

[0019] B. Separator: A separator is also disposed between the first electrode and the second electrode. If desired, other separators can also be used in the electrode assembly. For example, one or more separators can be disposed on the first electrode, the second electrode, or both. The separator helps to electrically insulate one electrode from the other to prevent electrical short circuits, yet still enables the transport of ions between the two electrodes. For example, in some embodiments, separators can be used that include cellulose fiber materials (such as airlaid paper webs, wetlaid paper webs, etc.), non-woven fiber materials (such as polyolefin non-woven webs), woven fabrics, films (such as polyolefin films), etc. Cellulose fiber materials such as those containing natural fibers, synthetic fibers, etc. are particularly suitable for use in ultracapacitors. Specific examples of cellulose fibers suitable for use in the separator can include, for example, hardwood pulp fibers, softwood pulp fibers, rayon fibers, regenerated cellulose fibers, etc. Regardless of the specific material used, the separator typically has a thickness of about 5 to about 150 micrometers, in some embodiments about 10 to about 100 micrometers, and in some embodiments about 20 to about 80 micrometers.

[0020] The method of assembling the components of the electrode assembly can be varied as is known in the art. For example, the electrodes and the separator can be first folded, wound, or otherwise brought into contact together to form the electrode assembly. In one particular embodiment, the electrodes, separator, and optionally the electrolyte can be wound to form an electrode assembly having a "jelly roll" structure. For example, referring to FIGS. 1-2, an embodiment of an electrode assembly 10 is shown that includes a first electrode 12, a second electrode 14, and a separator 60 disposed between the electrodes 12 and 14. In this particular embodiment, the electrode assembly 10 also includes another separator 70 disposed on the second electrode 14. In this way, each of the two coated surfaces of the electrodes is separated by the separator, thereby maximizing the surface area and capacitance per unit volume. The first electrode 12 includes carbonaceous coatings 22 and 24 disposed on opposite surfaces of a first current collector 20, while the second electrode 14 includes carbonaceous coatings 42 and 44 disposed on opposite surfaces of a second current collector 40. Of course, it should be understood that it is not necessary for both surfaces of the current collector to include carbonaceous coatings.

[0021] As shown in FIG. 2, the electrodes 12 and 14 and the separators 60 and 70 are wound together such that the assembly 10 extends longitudinally between the longitudinal edges 41 and 21 to define a length “L”. For example, in the illustrated embodiment, the separators 60 and 70 are shown as having equal values and lengths greater than the corresponding lengths of the carbonaceous coatings. Thus, the length “L” of the assembly 10 in this embodiment is effectively the distance between the outermost edges of the separators. For example, the length “L” may be from about 5 to about 100 millimeters, in some embodiments from about 8 to about 60 millimeters, and in some embodiments from about 10 to about 25 millimeters. The first current collector 20 is arranged to have a first protruding portion 64 that protrudes beyond the longitudinal edge 21 of the assembly 10. Similarly, the second current collector 40 is arranged to have a second protruding portion 62 that protrudes beyond the longitudinal edge 41 of the assembly 10. For example, the length “L1” of the first protruding portion 64, the length “L2” of the second protruding portion 62, or both may be from about 1 to about 20 millimeters, in some embodiments from about 2 to about 16 millimeters, and in some embodiments from about 5 to about 15 millimeters. In the illustrated embodiment, the protrusion of the current collector is achieved by using a current collector having a length greater than the corresponding carbonaceous coating. However, alternatively, the protrusion of the current collector can also be achieved by simply displacing the current collector relative to other components of the assembly.

[0022] II. Non-aqueous electrolyte: To form an ultracapacitor, the electrolyte is placed in ionic contact with the first and second electrodes before, during, and / or after assembling the electrodes and separators to form an electrode assembly. The electrolyte is generally non-aqueous and thus contains at least one non-aqueous solvent. To help extend the operating temperature range of the ultracapacitor, typically the non-aqueous solvent has a boiling point of about 150° C. or higher, in some embodiments about 200° C. or higher, and in some In one embodiment, it is desirable to have a relatively high boiling point such as about 220°C to about 300°C. Particularly suitable high-boiling solvents include, for example, cyclic carbonate solvents such as ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, etc. Of course, other non-aqueous solvents can also be used alone or in combination with cyclic carbonate solvents. Examples of such solvents include, for example, open-chain carbonates (e.g., dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, etc.), aliphatic monocarboxylates (e.g., methyl acetate, methyl 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-diethylacetamide, N-methylpyrrolidinone), alkanes (e.g., nitromethane, nitroethane, etc.), sulfur compounds (e.g., sulfolane, dimethyl sulfoxide, etc.), and the like.

[0023] The electrolyte can also include at least one ionic liquid dissolved in a non-aqueous solvent. The concentration of the ionic liquid can be varied, but generally, it is desirable to have the ionic liquid present at a relatively high concentration. For example, the ionic liquid can be present in an amount of about 0.8 mol (M) or more per liter of electrolyte, in some embodiments about 1.0 M or more, in some embodiments about 1.2 M or more, and in some embodiments about 1.3 to about 1.8 M.

[0024] Ionic liquids are generally salts having a relatively low melting point such as 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 salt contains a cationic species and a counter ion. The cationic species includes compounds having at least one heteroatom (e.g., nitrogen or phosphorus) as a "cationic center". Examples of such heteroatom compounds include, for example, Ammonium (e.g., trimethylammonium, tetraethylammonium, etc.), pyridinium, pyridazinium, pyrimidinium, pyrazinium, imidazolium, pyrazolium, oxazolium, triazolium, thiazolium, quinolinium, piperidinium, pyrrolidinium, quaternary ammonium spiro compounds (two or more rings are joined together by a spiro atom (e.g., carbon, heteroatom, etc.)), quaternary ammonium condensed ring structures (e.g., quinolinium, isoquinolinium, etc.), and other unsubstituted or substituted organic quaternary ammonium compounds can be mentioned. For example, in one specific embodiment, the cationic species may be an N-spiro bicyclic compound such as a symmetric or asymmetric N-spiro bicyclic compound having a cyclic ring. An example of such a compound is the following structure:

[0025] [Chemical formula]

[0026] (wherein m and n are independently numbers from 3 to 7, and in some embodiments are numbers from 4 to 5) having (e.g., pyrrolidinium or piperidinium).

[0027] Also, suitable counterions for the cationic species include halogens (e.g., chloride, bromide, iodide, etc.); sulfate or sulfonate (e.g., methyl sulfate, ethyl sulfate, Butyl sulfate, hexyl sulfate, octyl sulfate, hydrogen sulfate, methanesulfonate, dodecylbenzenesulfonate, dodecyl sulfate, trifluoromethanesulfonate, heptadecafluorooctanesulfonate, sodium dodecylethoxysulfate, etc.); sulfosuccinate; amide (e.g., dicyanamide); imide (e.g., bis(pentafluoroethylsulfonyl)imide, bis(trifluoromethylsulfonyl)imide, bis(trifluoromethyl)imide, etc.); borate (e.g., tetrafluoroborate, tetracyano borate, bis[oxalato]borate, bis[salicylato]borate, etc.); phosphate or phosphinate (e.g., hexafluorophosphate, diethyl phosphate, bis(pentafluoroethyl)phosphinate, tris(pentafluoroethyl)trifluorophosphate, tris(nonafluorobutyl)trifluorophosphate, etc.); antimonate (e.g., hexafluoroantimonate); aluminate (e.g., tetrachloroaluminate); fatty acid carboxylate (e.g., oleate, isostearate, pentadecafluorooctanoate, etc.); cyanate, acetate, etc., and any combination of the above can be mentioned.

[0028] Some examples of suitable ionic liquids 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, etc.

[0029] III. Housing: An ultracapacitor can also include a housing in which an electrode assembly and an electrolyte are held and which is optionally hermetically sealed. The nature of the housing can be varied as desired. For example, in one embodiment, the housing can include a metal container (can) formed from tantalum, niobium, aluminum, nickel, hafnium, titanium, copper, silver, steel (e.g., stainless), alloys thereof, composites thereof (e.g., a metal coated with a conductive oxide), and the like. Aluminum is particularly suitable for use in the present invention. The metal container can have any of a variety of different shapes such as cylindrical, D-shaped, etc. A cylindrical container is particularly preferred.

[0030] Referring to FIGS. 3 to 4, one embodiment of a housing that can be used in an ultracapacitor is shown in more detail. In this particular embodiment, the housing includes a metal container 2122 (e.g., a cylindrical can) that defines a base 3000 and an open end 3200. A lid 2118 is disposed over the open end 3200 and attached (e.g., welded) to the container 2122 to seal the housing. In one particular embodiment, as shown in FIG. 4, the lid 2118 can include a first current collector disk 2114 that includes a disk-shaped portion 2134, a stud portion 2136, and a fastener 2138 (e.g., a screw). Align the current collector disk 2114 with a first end of a hollow core 2160 formed at the center of the electrode assembly 10, and then insert the stud portion 2136 into the opening of the core such that the first current collector disk 2114 (e.g., the disk-shaped portion 2134 and / or the stud portion 2136) contacts a second protruding portion 62 of the second current collector 40. In this way, the second current collector 40 is disposed in electrical contact with the lid 2118. The fastener 2138 may also be coupled (e.g., screwed) to the first terminal 2116. Further, the metal container 2122 can include a second current collector disk 2120 that includes a disk-shaped portion 2142, a stud portion 2140, and a second terminal 2144. Align the second current collector disk 2120 with a second end of the hollow core 2160, and then insert the stud portion 2140 into the opening of the core such that the second current collector disk 2120 (e.g., the disk-shaped portion 2142 and / or the stud portion 2140) contacts a first protruding portion 64 of the first current collector 20. In this way, the first current collector 20 is disposed in electrical contact with the base 3000. Although not specifically shown in FIGS. 3 to 4, the length of the protruding portion 62 and / or 64 can be folded or deformed in other forms when contacting the current collector disk.

[0031] Test method: Equivalent series resistance (ESR): The equivalent series resistance can be measured using a Keithley 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 sine wave signal). The operating frequency is 100 kHz. Various temperature and relative humidity levels can be tested. For example, the temperature can be 25°C, 85°C, or 105°C, and the relative humidity can be 25% or 85%.

[0032] Capacitance: The capacitance can be measured using a Keithley 3330 Precision LCZ meter with a DC bias of 0.0 volts, 1. 1 volt, or 2.1 volts (0.5 volt peak-to-peak sine wave signal). The operating frequency is 120 Hz. Various temperature and relative humidity levels can be tested. For example, the temperature can be 25°C, 85°C, or 105°C, and the relative humidity can be 25% or 85%.

[0033] These and other modifications and variations of the present invention can be made by those skilled in the art without departing from the spirit and scope of the present invention. Further, it should be understood that the various aspects of the various embodiments can be exchanged in whole or in part. Further, those skilled in the art will understand that the above description is by way of example only and is not intended to limit the present invention as further described in the appended claims.

Claims

1. An electrode assembly for an ultracapacitor defining a length between a first longitudinal edge and a second longitudinal edge facing each other, the electrode assembly comprising: a first electrode including a first current collector electrically coupled to a first carbonaceous coating, at least a portion of the first current collector protruding beyond the first longitudinal edge to define a first protruding portion, the offset ratio of the first protruding portion being from about 0.02 to about 0.3; a second electrode including a second current collector electrically coupled to a second carbonaceous coating; and a separator disposed between the first electrode and the second electrode; The electrode assembly comprising the above.

2. The electrode assembly according to claim 1, wherein at least a portion of the second current collector protrudes beyond the second longitudinal edge to define a second protruding portion, and the offset ratio of the second protruding portion is from about 0.02 to about 0.

3.

3. The electrode assembly according to claim 1 or 2, wherein the length of the first protruding portion, the second protruding portion, or both is from about 1 to about 20 millimeters.

4. The electrode assembly according to claim 1, wherein the length of the electrode assembly is from about 5 to about 100 millimeters.

5. The electrode assembly according to claim 1, wherein the electrode assembly has a jelly roll structure.

6. The electrode assembly according to claim 1, wherein the first current collector and the second current collector each comprise a substrate containing a conductive metal.

7. The electrode assembly according to claim 6, wherein the conductive metal is aluminum or an alloy thereof.

8. The electrode assembly according to claim 1, wherein the first carbonaceous coating, the second carbonaceous coating, or both contain activated carbon particles.

9. The electrode assembly according to claim 1, wherein the separator contains a cellulose fiber material.

10. An ultracapacitor comprising the electrode assembly according to any one of claims 1 to 9, and a non-aqueous electrolyte in ionic contact with the first electrode and the second electrode.

11. The ultracapacitor according to claim 10, wherein the non-aqueous electrolyte contains an ionic liquid dissolved in a non-aqueous solvent, and the ionic liquid contains cationic species and counterions.

12. The ultracapacitor according to claim 11, wherein the non-aqueous solvent contains propylene carbonate, nitrile, or a combination thereof.

13. The ultra-capacitor according to claim 11, wherein the cationic species includes an organic quaternary ammonium compound.

14. The organic quaternary ammonium compound has the following structure: 【Chemical 1】 (wherein m and n are independently numbers from 3 to 7) The ultra-capacitor according to claim 13, which has the structure.

15. The ultra-capacitor according to claim 11, wherein the ionic liquid is present at a concentration of about 1.0 M or more.

16. The ultra-capacitor according to claim 10, which shows an ESR of about 100 milliohms or less when determined at a frequency of 100 kHz and a temperature of 25°C.

17. The ultra-capacitor according to claim 10, which shows a capacitance value of about 6 farads per square centimeter or more when determined at a frequency of 120 Hz and a temperature of 25°C.

18. The ultra-capacitor according to claim 10, which includes a housing that includes a container having a base and an open end, a lid is disposed adjacent to the open end, and further, the electrode assembly is disposed in the housing such that the first protruding portion is in a position in electrical contact with the base or the lid.

19. At least a part of the second current collector protrudes beyond the second longitudinal edge to define a second protruding portion, and the offset ratio of the second protruding portion is about 0.02 to about 0.

3. The ultra-capacitor according to claim 18.

20. The ultra-capacitor according to claim 19, wherein the first protruding portion is in electrical contact with the base, and the second protruding portion is in electrical contact with the lid.

21. The ultra-capacitor according to claim 18, wherein the container is formed of metal.

22. The ultra-capacitor according to claim 18, wherein the container has a cylindrical shape.

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