HK1169512B - Volumetrically efficient wet electrolytic capacitor - Google Patents

Description

Wet electrolytic capacitor with high volume efficiency

Technical Field

The present invention relates to a wet electrolytic capacitor, and more particularly, to a wet electrolytic capacitor having a high volume efficiency.

Background

Electrolytic capacitors are increasingly used in circuit design due to their volumetric efficiency (volumetric efficiency), reliability and process compatibility. In general, electrolytic capacitors have a greater capacitance per unit volume than other types of capacitors, making them very useful in circuits with relatively high currents and relatively low frequencies. One type of capacitor that has been developed is a wet electrolytic capacitor comprising an anode, a cathode and a liquid or "wet" working electrolyte. The wet electrolytic capacitor combines the features of high capacitance and low leakage current. In some cases, wet electrolytic capacitors are preferred over solid electrolytic capacitors. For example, in some cases, wet electrolytic capacitors may be used at higher operating voltages than solid electrolytic capacitors. Further, for example, the size of a wet electrolytic capacitor is much larger than that of a solid electrolytic capacitor, and therefore, the capacitance of such a large wet electrolytic capacitor is larger.

In a conventional wet electrolytic capacitor, the anode may be a metal foil (e.g., aluminum foil). Since the electrostatic capacitance of the capacitor is proportional to the electrode area thereof, the surface of the metal foil may be roughened or chemically converted to increase the effective area thereof before the dielectric film is formed. This roughening step of the metal foil surface is called etching. Etching is generally carried out by a method of immersing in a hydrochloric acid solution (chemical etching) or a method of electrolysis in an aqueous hydrochloric acid solution (electrochemical etching). The capacitance of the electrolytic capacitor depends on the coarsening degree (surface area) of the anode foil, the thickness of the oxide film, and the dielectric constant. Attempts have been made to use porous sintered bodies (also known as "bricks") in wet electrolytic capacitors due to the limited surface area that can be provided by etching the metal foil. For example, tantalum pellets in powder form are mixed with a suitable binder/lubricant to form a tantalum block (tantalum slug) to ensure that the tantalum pellets adhere to each other when pressed to form an anode. The powdery tantalum is pressed around a tantalum wire under the high-pressure condition and sintered at high temperature under the vacuum condition to form a spongy structure. This structure is a highly porous structure that provides a relatively large internal surface area.

Although the above methods have certain advantages, the capacitors cannot achieve high energy density (energy/volume) and high volumetric efficiency (capacitance voltage/volume). One method of increasing the energy density and capacitance of a capacitor includes, for example, increasing the size of the anode. However, a larger volume is generally required to accommodate the insulation, liquid seal, etc., which reduces volumetric efficiency. Since they are easily bent and deformed during sintering, they are generally bent and deformed in any case

It is difficult to form a large-sized anode block.

Therefore, there is a need for a volume efficient (volumetric efficiency) wet electrolytic capacitor having a high energy density.

Disclosure of Invention

According to one embodiment of the present invention, a wet electrolytic capacitor is disclosed that includes a metal can including a first edge portion and an opposing second edge portion extending longitudinally from an end portion to define an interior space. An electrochemically active cathode material is deposited on at least a portion of the inner surface of the metal can. The capacitor also includes an anode formed of an anodized, sintered porous body. The anode includes an upper end and a lower end, wherein a first edge portion and an opposing second edge portion extend longitudinally between the upper end and the lower end defining a length of the anode. The distance between the first edge portion and the second edge portion of the anode also defines the width of the anode. The ratio of the width of the anode to the width of the interior space is about 0.80-1.00. The anode is located in the interior space defined by the metal housing and occupies about 70vol% or more of the interior space. The capacitor also includes a liquid electrolyte in electrical contact with the anode and the electrochemically active material.

In another embodiment of the present invention, a method of forming a wet electrolytic capacitor is disclosed. The method includes pressing a powder including tantalum, niobium, or a conductive oxide thereof to form a porous body, wherein an anode lead is drawn from the porous body. The porous body is sintered in a heat treatment apparatus without physical contact of the surface of the porous body with the outer surface. The sintered porous body is anodized to form an anode having a length of about 1 to 60 mm and a width of about 1 to 40 mm. The anode is inserted into the interior space of the metal housing, wherein at least a portion of the interior surface of the metal housing is coated with an electrochemically active material. The anode and electrochemically active material are in contact with a liquid electrolyte.

Other features and aspects of the present invention will be described in more detail below.

Drawings

A full and enabling description of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the detailed description, which follows, when taken in conjunction with the accompanying figures and wherein like reference numerals identify identical or similar elements. Wherein:

FIG. 1 is a cross-sectional view of an anode used in one embodiment of a wet electrolytic capacitor of the present invention, wherein the anode is surrounded by a separator;

FIG. 2 is a cross-sectional view of one embodiment of a housing for use in the present invention, wherein the housing is coated with an electrochemically active cathode material;

FIG. 3 shows the anode of FIG. 1 positioned in the housing shown in FIG. 2;

FIG. 4 is a cross-sectional view of the anode/housing assembly of FIG. 3 with a liquid seal;

FIG. 5 is a cross-sectional view of one embodiment of a seal cover assembly for use in the present invention;

FIG. 6 illustrates the closure assembly of FIG. 5 positioned on the shell of FIG. 4;

FIG. 7 is a cross-sectional view of one embodiment of a wet electrolytic capacitor of the present invention;

FIG. 8 is a cross-sectional view of a sintered anode body used in one embodiment of the present invention;

fig. 9-10 schematically illustrate one embodiment of a sintering method used in the present invention.

Detailed Description

For those skilled in the art, the following description is only provided as a specific embodiment of the present invention, and is not intended to limit the scope of the present invention.

The present invention relates generally to a wet electrolytic capacitor including an anode disposed in an interior space of a metal can. The anode and metal housing are dimensioned: the anode occupies a majority of the internal spatial volume. More specifically, the anode occupies about 70vol% or more of the interior space, in some embodiments about 75vol% or more, in some embodiments about 80vol% to about 98vol%, and in some embodiments, about 85vol% to about 97 vol%. Among other advantages, the use of an anode that occupies a large portion of the internal space may increase the volumetric efficiency (capacitance vs. voltage/volume) of the resulting capacitor. For example, the volumetric efficiency range is approximately 10,000 μ F V/cm³-150,000µF*V/cm³In some embodiments, about 15,000 μ F V/cm³-100,000 µF*V/cm³In some embodiments, about 20,000 μ F V/cm³-95,000µF*V/cm³. The volumetric efficiency is obtained by multiplying the voltage rating of the component by its capacitance and then dividing the resulting product by the component volume. For example, a component has a capacitance of 1800 μ F and a nominal voltage of 50 volts, the product of which is 90,000 μ F V. If the volume occupied by the component is about 2 cm³The volume efficiency is then about 45,000. mu.F V/cm³。

By optimizing the dimensional stability of the anode, it is easier to use an anode that is large enough in size to occupy most of the internal space of the metal can. More specifically, the present inventors have discovered that selective control of the materials and methods of making the anode can maintain dimensional stability even after sintering. For example, the anode comprises a porous anode body made of valve metal powder. Of powdersThe specific charge may vary, from about 2,000 μ F V/g to about 80,000 mF V/g, in some embodiments about 5,000 μ F V/g to about 40,000 μ F V/g or higher, and in some embodiments about 10,000-. The valve metal composition comprises a valve metal (i.e., a metal capable of oxidation) or a valve metal-based compound such as tantalum, niobium, aluminum, hafnium, titanium and alloys thereof, oxides thereof, nitrides thereof, and the like. For example, the valve metal composition may comprise a conductive oxide of niobium, such as an oxide of niobium having an atomic ratio of niobium to oxygen of 1:1.0 ± 1.0, in some embodiments, an atomic ratio of niobium to oxygen of 1:1.0 ± 0.3, in some embodiments, an atomic ratio of niobium to oxygen of 1:1.0 ± 0.1, and in some embodiments, an atomic ratio of niobium to oxygen of 1:1.0 ± 0.05. For example, the oxide of niobium may be NbO_0.7、NbO_1.0、NbO_1.1And NbO₂. Examples of such valve metal oxides are described in Fife patent No. 6,322,912, Fife et al patent Nos. 6,391,275, 6,416,730, Fife patent No. 6,527,937, Kimmel et al patent No. 6,576,099, Fife et al patent No. 6,592,740, Kimmel et al U.S. patent Nos. 6,639,787, 7,220,397, and Schnitter application publication No. 2005/0019581, Schnitter et al application publication No. 2005/0103638, and Thomas et al U.S. patent application publication No. 2005/0013765, which are incorporated herein by reference in their entirety.

The particles may be, for example, platelets, horns, nodules, and mixtures or variations thereof. The particles have a sieve size distribution of at least about 60 mesh, in some embodiments about 60 mesh to about 325 mesh, and in some embodiments about 100 mesh to about 200 mesh. Further, the specific surface area is about 0.1 to 10.0 m²A/g, in some embodiments about 0.5 to about 5.0m²A/g, in some embodiments about 1.0 to about 2.0 m²(ii) in terms of/g. The term specific surface area refers to the surface area as measured by physical gas adsorption (B.E.T.) published by Brunauer, Emmet and Teller, Inc., journal of the American Chemical Society, 60, pp.309, 1938, and the adsorbed gas is nitrogen. Likewise, volume (or Scott) densityTypically about 0.1 to 5.0 g/cm³And in some embodiments, about 0.2 to about 4.0 g/cm³And in some embodiments about 0.5 to about 3.0 g/cm³。

Other components may also be added to the powder to promote the structure of the anode body. For example, a binder (binder) and/or lubricant may be used to ensure that the particles properly bind to each other when pressed into an anode body. Suitable binders include camphor, stearic acid and other soap fatty acids, polyethylene glycol (Carbowax) (united states carbide), glyphosate (glyphosate) (united states general electric), polyvinyl alcohol, naphthalene, vegetable waxes, and microcrystalline waxes (refined paraffin waxes). The binder is soluble and dispersible in the solvent. Examples of the solvent include water, alcohol and the like. When used, the binder and/or lubricant may be present in an amount of about 0.1% to about 8% by weight. However, it should be understood that the present invention does not necessarily require the use of binders and lubricants.

The resulting powder may be compacted using any conventional powder press. For example, the die may be a single station die employing a single die and one or more punches. Alternatively, an anvil die using only a single die and a single lower punch may also be used. There are several basic types of single station presses, such as cam presses, toggle presses/toggle presses and eccentric presses/crank presses with different production capacities, which may be, for example, single-action, double-action, floating-bed presses, movable-bed presses, opposed-ram presses, screw presses, impact presses, hot-pressing presses, impression presses or finishing presses. After pressing, the resulting anode body may be cut into any desired shape, such as square, rectangular, circular, oval, triangular, hexagonal, octagonal, heptagonal, pentagonal, and the like. The anode body may also have a "slot" shape that includes one or more grooves, flutes, depressions or depressions therein to increase the surface area to volume ratio, minimize ESR and extend the frequency response of the capacitor. The anode body will then undergo a heating step to remove most, if not all, of the binder/lubricant. For example, the anode body is typically heated using an oven at a temperature of about 150 ℃ to 500 ℃. Alternatively, the particles may be contacted with an aqueous solution to remove the binder/lubricant, as described in U.S. patent 6,197,252 to Bishop et al.

Once formed, the anode body is sintered. The sintering temperature, atmosphere and time depend on various factors such as anode type, anode size, etc. Generally, sintering is carried out at a temperature of about 800 ℃ to about 1900 ℃, in some embodiments about 1000 ℃ to about 1500 ℃, and in some embodiments about 1100 ℃ to about 1400 ℃; the sintering time may be from about 5 minutes to about 100 minutes, and in some embodiments, from about 30 minutes to about 60 minutes. If desired, sintering may be carried out in an atmosphere that limits the transfer of oxygen atoms to the anode. For example, sintering may be performed in a reducing atmosphere, such as in a vacuum, inert gas, hydrogen, or the like. The pressure of the reducing atmosphere is about 10 torr to about 2000 torr (1 torr corresponds to about 1 mm hg), in some embodiments about 100 torr to about 1000 torr, and in some embodiments, about 100 torr to about 930 torr. Mixtures of hydrogen and other gases (e.g., argon or nitrogen) may also be used.

Sintering typically results in large shrinkage due to the specific charge of the powder used to form the anode body. This shrinkage can cause the anode structure to bend significantly as the size of the anode body increases. Without being bound by theory, it is believed that the bowing increases when the anode body is in physical contact with an external hard surface (e.g., the surface of a sintered disk). More specifically, such a hard surface may limit the shrinkage (sometimes referred to as "pinning") of the anode body where physical contact exists, thereby resulting in less shrinkage of the area of physical contact than other portions of the anode body. This differential shrinkage in turn causes the anode body to bend, forming a curved shape (e.g., a crescent). To minimize such bowing, the inventors have found that sintering can be carried out in such a way that the surface of the anode body does not come into physical contact with an outer surface (e.g., the surface of a sintered disk).

For example, referring to fig. 9-10, one embodiment of such a sintering technique is shown in which one or more anodes 20 are connected to a crossbar 200 by anode leads 42. The anode lead 42 may be attached to the rail 200 using any known method, such as welding, swaging, etc. In this manner, the anode 20 can "hang" on the rail 200 without physically contacting the outer surface. Thus, the resulting anode assembly 201 is positioned on a surface 221, which is then passed through a heat treatment apparatus or furnace 220 (FIG. 10). When the anodes 20 are heated in the heating furnace 220, they are able to shrink freely and are not physically constrained. It should also be understood that sintering may take on various other configurations and is not limited to such configurations. For example, in another embodiment, the suspended anode may be placed vertically in a furnace and then lifted out after the sintering process is complete.

Despite its relatively large dimensions, the resulting anode remains dimensionally stable, with only minor, if any, bending. Dimensional stability may be characterized by the orientation of the anode relative to a longitudinal inboard plane extending through the anode terminal. For example, referring to FIG. 8, one embodiment of an anode 20 is shown, the anode 20 extending in the direction of the longitudinal axis 3. The anode 20 has an upper end 17 and a lower end 19, with a first edge portion 7 and a second edge portion 9 opposite the first edge portion 7 extending between the upper end 17 and the lower end 19. The inner longitudinal plane 13 passes through the upper end 17 in a direction parallel to the longitudinal axis 3. Due to its dimensional stability, the anode 20 only undergoes minor, if any, changes in surface between the inner flat surface 13 and the edge portions 7 and 9. That is, the difference "W" between the pitch "a" (the distance between the inner flat surface 13 and the edge portion 7) and the pitch "b" (the distance between the inner flat surface 13 and the edge portion 9), also referred to as "warp", is generally small in the length direction of the anode 20. For example, the difference W (or "warp") may be about 0.25 mm or less, in some embodiments about 0.20 mm or less, in some embodiments about 0.15 mm or less, and in some embodiments about 0-0.10 mm, along the length of the anode 20, such as the center of the anode as shown in fig. 8.

Also can adopt andthe curvature is inversely proportional to the radius of curvature to define the dimensional stability of the anode 20. A radius of curvature may be specified that represents the general shape orientation of the anode 20, such as the orientation of the medial transverse plane 14 perpendicular to the medial longitudinal plane 13. More specifically, the radius of curvature is represented by "R" in fig. 8, and can be calculated using the following formula: radius = W/2 + L²(ii)/8W, wherein W is the "warp" as described above,Lis the length. In certain embodiments, the radius of curvature in the direction of medial transverse plane 14 is about 25 centimeters or greater, in some embodiments about 50 centimeters or greater, and in some embodiments about 100 centimeters or greater.

The anode may also be coated with a medium, as described above. The medium may be formed by: the sintered anode is anodized ("anodizing") to form a dielectric layer on and/or within the anode. For example, a tantalum (Ta) anode may be anodized to tantalum pentoxide (Ta)₂O₅). Generally, anodization begins by applying a solution to the anode, such as by dipping the anode into an electrolyte. A solvent, such as water (e.g., deionized water), is typically employed. In order to enhance the ion conductivity, a compound that can be dissociated in a solvent to form ions may be used. Examples of such compounds include, for example, acids, as described in the electrolyte section below. For example, the acid (e.g., phosphoric acid) may be present in the anodizing solution in an amount of about 0.01wt% to about 5wt%, in some embodiments about 0.05wt% to about 0.8wt%, and in some embodiments, about 0.1wt% to about 0.5 wt%. Mixtures of acids may also be employed if desired.

A current is passed through the anodizing solution to form a dielectric layer. The forming voltage value determines the thickness of the dielectric layer. For example, the power supply is initially established in a constant current mode until the desired voltage is reached. The power supply can then be switched to a constant potential mode to ensure that the desired dielectric layer thickness is formed over the entire surface of the anode. Of course, other methods known to those skilled in the art, such as pulsed or step potentiostatic methods, may be used. The voltage at which anodization occurs is generally about 4-250V, in some embodiments about 9-200V, and in some embodiments about 20-150V. During anodization, the anodization solution is maintained at an elevated temperature, for example, about 30 ℃ or higher, in some embodiments about 40 ℃ to 200 ℃, and in some embodiments, about 50 ℃ to 100 ℃. The anodization may also be performed at room temperature or lower. The resulting dielectric layer may be formed on the surface of the anode or within the anode hole.

The anodes of the present invention as described above are generally applicable to wet electrolytic capacitors made by any technique known in the art. Thus, fig. 1-6 illustrate one particular embodiment of a method of forming the capacitor 10 of the present invention.

For example, referring to FIG. 1, one embodiment of an anode 20 for use with the present invention is shown. As described above, the anode 20 is formed of a sintered porous body coated with a dielectric layer (not shown). The anode 20 can be any desired shape, such as cylindrical, D-shaped, rectangular, triangular, prismatic, etc. An anode lead 42 (e.g., wire, tab, etc.) is electrically connected to the anode 20. Electrical contact to anode 20 can be made by various means, such as by resistance or laser welding to lead 42. Alternatively, the lead 42 may be embedded within the anode body during its formation (e.g., prior to sintering). Regardless, the leads 42 are generally fabricated from any conductive material, such as tantalum, niobium, nickel, aluminum, hafnium, titanium, etc., and oxides and/or nitrides thereof.

If desired, the anode 20 is impregnated with an electrolyte (not shown) prior to placement inside the housing. During the latter stages of production, electrolyte is also added to the capacitor. The electrolyte is a material that provides a connection path between the anode and the cathode. Various suitable electrolytes are described in U.S. patent nos. 5,369,547 and 6,594,140 to Evans et al, which are incorporated herein by reference in their entirety. In general, the electrolyte is ionically conductive, having an ionic conductivity of about 0.5 to about 100 milliSiemens per centimeter ("mS/cm"), in some embodiments about 1 to about 80 mS/cm, in some embodiments about 5 mS/cm to about 60 mS/cm, and in some embodiments about 10 to about 40 mS/cm, as measured using any known conductivity meter, such as Oakton Con Series 11, at a temperature of 25 ℃. It is believed that within the above range, the ionic conductivity of the electrolyte extends the electric field into the electrolyte for a length (debye length) sufficient to result in significant charge separation. This extends the potential energy of the dielectric to the electrolyte, and therefore the resulting capacitor stores a higher potential energy than predicted from the dielectric thickness. In other words, the capacitor chargeable voltage exceeds the formation voltage of the dielectric. The ratio of the capacitor chargeable voltage to the formation voltage may be, for example, about 1.0-2.0, in some embodiments about 1.1-1.8, and in some embodiments, about 1.2-1.6. For example, the capacitor charging voltage may be about 200-350V, in some embodiments about 220-320V, and in some embodiments about 250-300V.

The electrolyte is typically in liquid form, such as a solution (e.g., aqueous or non-aqueous), dispersion, colloid, and the like. For example, the working electrolyte may be an aqueous acid solution (e.g., sulfuric, phosphoric, or nitric acid), an aqueous base solution (e.g., potassium hydroxide), or an aqueous salt solution (e.g., an ammonium salt such as a nitrate salt) and any other suitable electrolyte known in the art, such as a salt dissolved in an organic solvent (e.g., an ammonium salt dissolved in a glycol-based solution). Various suitable electrolytes are described in U.S. patent nos. 5,369,547 and 6,594,140 to Evans et al, which are incorporated herein by reference in their entirety.

By selecting a range of ionic compounds (e.g., acids, bases, salts, etc.) within a certain concentration range, the desired ionic conductivity can be achieved. In one particular embodiment, the weak organic acid salt is effective in achieving the desired electrolyte conductivity. The cation of the salt may comprise a monoatomic cation, such as an alkali metal (e.g., Li)⁺、Na⁺、K⁺、Rb⁺Or Cs⁺) Alkaline earth metals (e.g. Be)²⁺、Mg²⁺、Ca²⁺、Sr²⁺Or Ba²⁺) Transition metal (e.g., Ag)⁺、Fe²⁺、Fe³⁺Etc.) and polyatomic cations, such as NH₄ ⁺. Monovalent ammonium (NH)₄ ⁺) Sodium, sodium (Na)⁺) Lithium (Li)⁺) Are particularly suitable cations for the present invention. The organic acid used to form the anion of the salt is a "weak acid" having a first acid dissociation constant (pK) measured at 25 ℃_a1) Generally from about 0 to about 11, in some embodiments from about 1 to about 10, and in some embodiments, from about 2 to about 10. Any suitable weak organic acid may be used in the present invention, such as carboxylic acids, e.g., acrylic acid, methacrylic acid, malonic acid, succinic acid, salicylic acid, sulfosalicylic acid, adipic acid, maleic acid, malic acid, oleic acid, gallic acid, tartaric acids (e.g., d-tartaric acid, meso-tartaric acid, etc.), citric acid, formic acid, acetic acid, glycolic acid, oxalic acid, propionic acid, phthalic acid, isophthalic acid, glutaric acid, gluconic acid, lactic acid, aspartic acid, glutamic acid, itaconic acid, trifluoroacetic acid, barbituric acid, cinnamic acid, benzoic acid, 4-hydroxybenzoic acid, aminobenzoic acid, and the like; and mixtures of the above acids, and the like. In the case of salts, polybasic acids (e.g., dibasic, tribasic, etc.) are particularly desirable, such as adipic acid (pK)_a1A pK of 4.43_a25.41), alpha-tartaric acid (pK)_a1Has a pK of 2.98_a24.34), meso-tartaric acid (pK)_a1Is 3.22 and pK_a24.82), oxalic acid (pK)_a11.23 and pK_a24.19), lactic acid (pK)_a1A pK of 3.13_a2Has a pK of 4.76_a36.40), etc.

The actual amount used may vary depending on the particular salt used, its solubility in the solvent used for the electrolyte, and the other components present, such weak organic acid salts being present in the electrolyte in an amount of about 0.1 to about 25 weight percent, in some embodiments about 0.2 to about 20 weight percent, in some embodiments about 0.3 to about 15 weight percent, and in some embodiments about 0.5 to about 5 weight percent.

The electrolyte is typically an aqueous solution because it contains an aqueous phase solvent, such as water (e.g., deionized water). For example, the electrolyte may contain water (e.g., deionized water) in an amount of about 20wt% to about 95wt%, in some embodiments about 30wt% to about 90wt%, and in some embodiments, about 40wt% to about 85 wt%. A second solvent may also be used to form a solvent mixture. Suitable second solvents may include, for example, glycols (e.g., ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, hexylene glycol, polyethylene glycol, ethoxydiglycol, dipropylene glycol, and the like); glycol ethers (e.g., methyl glycol ether, ethyl glycol ether, isopropyl glycol ether, etc.); alcohols (e.g., methanol, ethanol, n-propanol, isopropanol, and butanol); ketones (e.g., acetone, methyl ethyl ketone, and methyl isobutyl ketone); esters (e.g., ethyl acetate, butyl acetate, diethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, ethylene carbonate, propylene carbonate, etc.); amides (e.g., dimethylformamide, dimethylacetamide, dimethyloctyl/decyl fatty acid amide, and N-alkylpyrrolidone); sulfoxides or sulfones (e.g., dimethyl sulfoxide (DMSO) and sulfolane), and the like. Such solvent mixtures typically contain from about 40wt% to about 80wt% water, in some embodiments from about 50wt% to about 75wt% water, in some embodiments from about 55wt% to about 70wt% water, and the second solvent content is from about 20wt% to about 60wt%, in some examples from about 25wt% to about 50wt%, and in some embodiments, from about 30wt% to about 45 wt%. For example, the second solvent may comprise from about 5wt% to about 45wt%, in some embodiments from about 10wt% to about 40wt%, and in some embodiments, from about 15wt% to about 35wt% of the electrolyte.

If desired, the electrolyte may be relatively neutral, having a pH of about 4.5 to about 7.0, in some embodiments about 5.0 to about 6.5, and in some embodiments, about 5.5 to about 6.0. To help achieve the desired pH, one or more pH adjusting agents (e.g., acids, bases, etc.) may be used. In one embodiment, an acid is used to reduce the pH to the desired range. Suitable acids include, for example, inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, polyphosphoric acid, boric acid, and the like; organic acids including carboxylic acids such as acrylic acid, methacrylic acid, malonic acid, succinic acid, salicylic acid, sulfosalicylic acid, adipic acid, maleic acid, malic acid, oleic acid, gallic acid, tartaric acid, citric acid, formic acid, acetic acid, glycolic acid, oxalic acid, propionic acid, phthalic acid, isophthalic acid, glutaric acid, gluconic acid, lactic acid, aspartic acid, glutamic acid, itaconic acid, trifluoroacetic acid, barbituric acid, cinnamic acid, benzoic acid, 4-hydroxybenzoic acid, aminobenzoic acid, and the like; sulfonic acids such as methanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid, trifluoromethanesulfonic acid, styrenesulfonic acid, naphthalenedisulfonic acid, hydroxybenzenesulfonic acid, and the like; high molecular acids, such as poly (acrylic acid) or poly (methacrylic acid) and copolymers thereof (e.g., maleic acid-acrylic acid copolymer, sulfonic acid-acrylic acid copolymer, styrene-acrylic acid copolymer), carrageenan, carboxymethyl cellulose, alginic acid, and the like. Although the total concentration of the pH adjusting agents may vary, they comprise from about 0.01wt% to about 10wt%, in some embodiments from about 0.05wt% to about 5wt%, and in some embodiments, from about 0.1wt% to about 2wt% of the electrolyte.

The electrolyte may also contain other components that help improve the electrical performance of the capacitor. For example, depolarizers may be used in the electrolyte to help suppress the generation of hydrogen gas at the cathode of the electrolytic capacitor, which can cause the capacitor to swell and ultimately cause failure. Where a depolarizer is used, the amount of depolarizer in the electrolyte is about 1 to 500 ppm, in some embodiments about 10 to 200 ppm, and in some embodiments about 20 to 150 ppm. Suitable depolarizers can include nitroaromatic compounds such as 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, 2-nitrobenzoic acid, 3-nitrobenzoic acid, 4-nitrobenzoic acid, 2-nitroacetophenone, 3-nitroacetophenone, 4-nitroacetophenone, 2-nitroanisole, 3-nitroanisole, 4-nitroanisole, 2-nitrobenzaldehyde, 3-nitrobenzaldehyde, 4-nitrobenzaldehyde, 2-nitrobenzyl alcohol, 3-nitrobenzyl alcohol, 4-nitrobenzyl alcohol, 2-nitrophthalic acid, 3-nitrophthalic acid, 4-nitrophthalic acid, and the like. Nitroaromatic depolarizers particularly suitable for use in the present invention are nitrobenzoic acids substituted with one or more alkyl groups (e.g., methyl, ethyl, propyl, butyl, etc.) and the anhydrides or salts thereof. Specific examples of such alkyl-substituted nitrobenzoic acid compounds include, for example, 2-methyl-3-nitrobenzoic acid; 2-methyl-6-nitrobenzoic acid; 3-methyl-2-nitrobenzoic acid; 3-methyl-4-nitrobenzoic acid; 3-methyl-6-nitrobenzoic acid; 4-methyl-3-nitrobenzoic acid; and anhydrides or salts thereof.

If desired, a separator (separator) 92 may also be provided adjacent the anode 20 to inhibit direct contact between the anode and cathode, while still allowing ionic current flow from the electrolyte to the electrodes. Examples of suitable materials suitable for such use include, for example, porous polymeric materials (e.g., polypropylene, polyethylene, polycarbonate, etc.), porous inorganic materials (e.g., glass fiber mats, porous glass sandpaper, etc.), ion exchange resin materials, and the like. Specific examples include ionic perfluorosulfonic acid polymer membranes (e.g., Nafion. of e.i. DuPont de Nemeours & co.), sulfonated fluorocarbon polymer membranes, Polybenzimidazole (PBI) membranes, and Polyetheretherketone (PEEK) membranes. To optimize the volumetric efficiency of the capacitor, it is generally desirable that the thickness of the isolation layer 92 be relatively small. For example, when a spacer layer is used, the thickness of spacer layer 92 is typically about 5-250 microns, in some embodiments about 10-150 microns, and in some embodiments, about 15-100 microns.

For example, referring to fig. 2-3, the anode 20 and optionally the separator 92 can be located in the interior space of the metal housing 12. The metal housing 12 is typically made of a metal such as tantalum, niobium, aluminum, nickel, hafnium, titanium, copper, silver, steel (e.g., stainless steel), alloys thereof (e.g., conductive oxides), composites thereof (e.g., metal coated with conductive oxides), and the like. The metal housing 12 may be any desired shape, such as cylindrical, D-shaped, rectangular, triangular, prismatic, etc. For example, in one embodiment, the metal shell 12 includes a generally cylindrical sidewall. Multiple sidewalls may also be employed if desired. Generally, the housing 12 and the anode 20 have the same or similar shape so that the anode 20 can be easily placed into the interior space 11 of the housing. For example, in the illustrated embodiment, the anode 20 and the metal can 12 are each generally cylindrical.

To achieve the desired volumetric efficiency, the difference between the width (e.g., diameter) of the anode and the width (e.g., diameter) of the interior space 11 defined by the metal housing 12 is relatively small. For example, the width of the anode 20 is defined by the distance between the first edge portion 7 and the second edge portion 9, and the width of the interior space is defined by the distance between the inner surface of the first edge portion 77 and the inner surface of the second edge portion 79. Generally, the ratio of the anode width to the interior space width ranges from about 0.80 to about 1.00, in some embodiments from about 0.85 to about 0.99, in some embodiments from about 0.90 to about 0.99, and in some embodiments, from about 0.94 to about 0.98. The width of anode 20 may range, for example, from about 0.5 mm to about 50 mm, in some embodiments from about 1 mm to about 40 mm, and in some embodiments, from about 4 mm to about 30 mm. Similarly, the width of the interior space 11 may range from about 0.5 mm to about 60 mm, in some embodiments from about 1 mm to about 50 mm, and in some embodiments, from about 4 mm to about 35 mm. The overall diameter of the metal shell 12 may also vary, for example, from about 1 mm to about 70 mm, in some embodiments from about 2 mm to about 60 mm, and in some embodiments, from about 5 mm to about 50 mm.

Although not required, the length ratio is typically slightly less than the width ratio so that the metal housing can accommodate one or more optional liquid seals, as will be described in more detail below. For example, the length of anode 20 is defined by the distance between opposing ends 17 and 19, and the length of interior space 11 is defined by the distance between lower end 88 and upper edge 87 of edge portions 77 and 79. Generally, the ratio of the anode length to the internal space length ranges from about 0.5 to about 1.00, in some embodiments from about 0.6 to about 0.98, and in some embodiments, from about 0.65 to about 0.95. The length of anode 20 is, for example, about 0.5 to about 100 mm, in some embodiments about 1 to about 60 mm, and in some embodiments, about 5 to about 30 mm. Likewise, the length of the interior space 11 is about 1-200 mm, in some embodiments about 5-100 mm, and in some embodiments about 10-50 mm.

If desired, the interior surfaces (e.g., sidewalls and/or ends) of the metal shell may optionally be roughened to increase surface area. Surface roughening may be performed by various methods such as mechanical methods (e.g., sandpaper, grit blasting, etc.), chemical etching, and spark anodization as described in U.S. patent application 12/330,943 to Dreissig et al and U.S. patent application 12/209,588 to Ning et al, among others. In any manner, the housing 12 is internallyAt least a portion of the surface is coated with an electrochemically active cathode material (not shown) to increase the effective surface area. For example, the cathode material may be deposited on the inner surface of the metal housing 12. One suitable cathode material is a conductive polymer, such as those that are pi-conjugated and are electrically conductive after oxidation or reduction (conductivity after oxidation is at least about 1 μ S-cm)^-1). Examples of such pi-conjugated conductive polymers include, for example, polyheterocycles (e.g., polypyrrole; polythiophene, polyaniline, and the like), polyacetylene, poly-p-phenylene, polyphenolates, and the like. Suitable polythiophenes include, for example, polythiophene and derivatives thereof, such as poly (3, 4-ethylenedioxythiophene) ("PEDT"). In one embodiment, polythiophene derivatives having repeating units of formula (i) or formula (ii) or formula (i) and formula (ii) are used:

in the formula:

a is optional C₁-C₅Olefinic substituents (e.g., methylene, vinyl, n-propenyl, n-butenyl, n-pentenyl, and the like);

r is linear or branched optional C₁-C₁₈Alkyl substituents (e.g., methyl, ethyl, n-or isopropyl, n-butyl, isobutyl, sec-or tert-butyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1-ethylpropyl, 1-dimethylpropyl, 1, 2-dimethylpropyl, 2-dimethylpropyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl, n-octadecyl, etc.); optionally C₅-C₁₂Cycloalkyl substituents (e.g., cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, etc.); optionally C₆-C₁₄Aryl substituents (e.g., phenyl, naphthyl, and the like); optionally C₇-C₁₈Aralkyl substituents (e.g., benzyl, o, m, p-tolyl, 2,3-, 2,4-, 2,5-, 2,6, 3,4-, 3, 5-xylyl, trimethylphenyl, and the like); optionally C₁-C₄A hydroxyalkyl substituent or a hydroxy substituent; and

x is an integer from 0 to 8, in some embodiments from 0 to 2, and in some embodiments, 0. Examples of substituents for "a" or "R" include, for example, alkyl, cycloalkyl, aryl, aralkyl, alkoxy, halo, ether, thioether, disulfide, sulfoxide, sulfone, sulfonate, amino, aldehyde, ketone, carboxylate, carboxylic acid, carbonate, carboxylate, cyano, alkylsilane, and alkoxysilyl, carboxamide groups and the like.

The total number of repeating units of formula (I) or formula (II) or formulae (I) and (II) is generally from 2 to 2000, and in some embodiments from 2 to 100.

Particularly suitable polythiophene derivatives are those in which A is optionally C₂-C₃A derivative of an olefinic substituent and x is 0 or 1. In one embodiment, the polythiophene derivative is PEDT, having a repeating unit of formula (ii) wherein "a" is CH₂-CH₂And "x" is 0. Methods of forming such polythiophene derivatives are known in the art and are described, for example, in U.S. patent 6,987,663 to Merker et al. This patent is incorporated in its entirety into this patent. For example, polythiophene derivatives can be formed from monomeric precursors, such as optionally substituted thiophenes. Particularly suitable monomeric precursors are substituted 3, 4-alkylenedioxythiophenes having the general formulae (III), (IV) or mixtures of thiophenes of the general formulae (III) and (IV):

wherein A, R and X are as defined above.

Examples of such monomeric precursors include, for example, optionally substituted 3, 4-vinyldioxythiophene. Derivatives of these monomer precursors, such as dimers or trimers of the above monomer precursors, may also be employed. Higher molecular weight derivatives such as tetramers, pentamers, etc. of the monomer precursors are suitable for use in the present invention. The derivatives may be composed of the same or different monomer units and may be used in pure form as well as in a mixture with another derivative and/or monomer precursor. Oxidized or reduced forms of these monomeric precursors may also be used.

To obtain the desired conductive polymer, the monomer precursors as described above typically require oxidative polymerization in the presence of an oxidizing agent. The oxidizing agent can be a transition metal salt, such as an inorganic or organic acid salt containing an iron (III), copper (II), chromium (VI), cerium (IV), manganese (VII) or ruthenium (III) cation. Particularly suitable transition metal salts include iron (III) cations, such as iron (III) halides (e.g., FeCl)₃) Or iron (III) salts of other mineral acids, e.g. Fe (ClO)₄)₃Or Fe₂(SO₄)₃And Iron (III) salts of organic acids and of inorganic acids containing organic groups. Examples of iron (III) salts of inorganic acids having organic groups include, for example, C_1-C₂₀Iron (iii) salts of sulfuric monoesters of alkanols (e.g., iron (iii) lauryl sulfate). Also, examples of the iron (III) salt of an organic acid include, for example, C₁-C₂₀Iron (iii) alkylsulfonate (e.g., methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, butanesulfonic acid, or dodecylsulfonic acid); an iron (iii) salt of an aliphatic perfluorosulfonic acid (such as trifluoromethanesulfonic acid, perfluorobutanesulfonic acid, or perfluorooctanesulfonic acid); aliphatic C₁-C₂₀Iron (III) carboxylates (e.g., 2-ethylhexylcarboxylic acid); an iron (iii) salt of an aliphatic perfluorocarboxylic acid (such as trifluoroacetic acid or perfluorooctanoic acid); optionally is covered with C₁-C₂₀An iron (iii) salt of an alkyl-substituted aromatic sulfonic acid (e.g., benzenesulfonic acid, o-toluenesulfonic acid, p-toluenesulfonic acid, or dodecylbenzenesulfonic acid); and iron (iii) cycloalkanesulfonate salts (e.g., camphorsulfonic acid), and the like. Mixtures of the above-mentioned iron (III) salts can also be used. Iron (III) p-toluenesulfonate, iron (III) o-toluenesulfonate and mixtures thereof, especially suitableThe invention is also disclosed.

In some cases, the morphology of the conductive polymer material may be a dispersion of particles of relatively small size, for example, having an average particle size of about 1 to about 500 nanometers, in some embodiments about 5 to about 400 nanometers, and in some embodiments, about 10 to about 300 nanometers. D of the particles₉₀Value (particle size less than or equal to D)₉₀The particle volume of the value is 90% of the total volume of all solid particles) is about 15 microns or less, in some embodiments about 10 microns or less, and in some embodiments, about 1nm to about 8 microns. The diameter of the particles can be determined by known methods, such as ultracentrifugation, laser diffraction, and the like.

The charged conducting polymer (e.g., polythiophene) is typically neutralized with a separate counter ion to facilitate the formation of the conducting polymer into a particulate form. That is, the charge on the backbone of the conductive polymer (e.g., polythiophene or derivative thereof) used in the coating is typically neutral or positive (cationic). Polythiophene derivatives, for example, typically carry a positive charge on the main polymer chain. In some cases, the polymer may have positive and negative charges in the structural unit, the positive charge being located on the backbone and the negative charge optionally being located on an "R" substituent, such as a sulfonate or carboxylate group. The positive charge of the backbone may be partially or fully neutralized by the optional presence of anionic groups on the "R" substituent. Viewed as a whole, in these cases, the polythiophene can be cationic, neutral or even anionic. However, because the polythiophene backbone is positively charged, they are all considered cationic polythiophenes.

The counter ion may be a monomeric anion or a polymeric anion. The polymeric anion can be, for example, a polycarboxylic acid (e.g., polyacrylic acid, polymethacrylic acid, polymaleic acid, etc.) anion; polysulfonate anions (e.g., polystyrene sulfonic acid ("PSS"), polyvinylsulfonic acid), and the like. The acid may also be a copolymer, such as copolymers of vinyl carboxylic and vinyl sulfonic acids with other polymerizable monomers, such as acrylates and styrene. Likewise, suitable monomeric anions includeE.g. C₁-C₂₀Alkyl sulfonic acid (e.g., dodecyl sulfonic acid) anions; aliphatic perfluorosulfonic acid (such as trifluoromethanesulfonic acid, perfluorobutanesulfonic acid, or perfluorooctanesulfonic acid) anion; aliphatic C₁-C₂₀Carboxylic acid (2-ethylhexyl carboxylic acid) anion; aliphatic perfluorocarboxylic acid (such as trifluoroacetic acid or perfluorooctanoic acid) anions; optionally is covered with C₁-C₂₀Alkyl-substituted aromatic sulfonic acid (e.g., benzenesulfonic acid, o-toluenesulfonic acid, p-toluenesulfonic acid, or dodecylbenzenesulfonic acid) anion; cycloalkanesulfonic acid (e.g., camphorsulfonic acid or tetrafluoroborate, hexafluorophosphate, perchlorate, hexafluoroantimonate, hexafluoroarsenate or hexachloroantimonate) anions, and the like. Particularly suitable counterions are polymeric anions such as polycarboxylic acids or polysulfonic acids (e.g., polystyrene sulfonic acid ("PSS")). The molecular weight of such polymeric anions is generally about 1,000-2,000,000, and in some embodiments, about 2,000-500,000.

When used, the weight ratio of such counterions to the conductive polymer in a given coating is generally from about 0.5:1 to about 50:1, in some embodiments from about 1:1 to about 30:1, and in some embodiments, from about 2:1 to about 20: 1. The weight of the conductive polymer mentioned in the above weight ratio refers to the weight of the monomer portion used (assuming that the monomer is completely converted during polymerization).

In addition to the conductive polymer, the electrochemically active cathode material may be replaced with metal particles formed from metals such as ruthenium, iridium, nickel, rhodium, rhenium, cobalt, tungsten, manganese, tantalum, niobium, molybdenum, lead, titanium, platinum, palladium, and osmium, as well as combinations of these metals. For example, in one particular embodiment, the electrochemically active material comprises palladium particles. Non-insulated oxide particles may also be used with the present invention. Suitable oxides include a metal selected from the group consisting of ruthenium, iridium, nickel, rhodium, rhenium, cobalt, tungsten, manganese, tantalum, niobium, molybdenum, lead, titanium, platinum, palladium, and osmium, as well as combinations of these metals. Particularly suitable metal oxides include ruthenium dioxide, niobium oxide, niobium dioxide, iridium oxide, and manganese dioxide. Carbonaceous particles having a desired conductivity, such as activated carbon, carbon black, graphite, and the like, may also be used. Some suitable forms of activated carbon and methods for making the same are described in U.S. patent 5,726,118 to Ivey, U.S. patent 5,858,911 to Wellen et al, and U.S. patent application publication No. 2003/0158342 to Shinozaki et al. The above patents are incorporated by reference into this patent in their entirety.

The cathode material can be applied to the housing 12 by a variety of known methods, such as dipping, spin coating, dipping, pouring, dripping, injecting, spraying, doctor blading, brushing, or printing (e.g., ink jet, screen, or pad printing). Although the viscosity of the dispersion varies depending on the coating technique employed, the viscosity is generally about 0.1 to 100,000 mPas (at a shear rate of 100 s)^-1Measured), in some embodiments from about 1 to about 10,000 mPas, in some embodiments from about 10 to about 1,500 mPas, and in some embodiments, about 100 to about 1000 mPas. Once coated, the layer can be dried and cleaned. Drying may be carried out at a temperature of about-10 ℃ to about 250 ℃, and in some embodiments, about 0 ℃ to about 200 ℃. The thickness of the resulting dried coating is approximately 0.2 microns ("μm") -100 μm, in some embodiments approximately 1 μm-40 μm, and in some embodiments, approximately 3 μm-10 μm. It should be understood that the coating thickness need not be the same at all locations of the housing 12.

In order to suppress leakage of the electrolyte from the capacitor, a cap assembly, for example, connected to the metal can by welding, is generally used. The cap assembly may include one or more seals, fluid seals, and the like. For example, referring to FIG. 5, one embodiment of a seal cap assembly 50 is shown including a cap 52 having an upper planar surface 60 spaced from a lower planar surface 62. The lid 52 is typically made of a metal, such as tantalum, niobium, aluminum, nickel, hafnium, titanium, copper, silver, steel (e.g., stainless steel), alloys thereof (e.g., conductive oxides), composites thereof (e.g., metal coated with conductive oxides), and the like. Desirably, the housing 12 and the cover 52 are made of the same material, such as titanium or an alloy thereof. In the illustrated embodiment, the cap 52 has a generally cylindrical cross-section. However, it should be understood that the present invention may take any geometric configuration, such as D-shaped, rectangular, triangular, prismatic, etc. Between the flats 60 and 62, the cap 52 has an outer diameter 68 from which is stepped an inner diameter portion 69.

The lid 52 defines an interior aperture 59. The internal bore may be cylindrical and have a substantially constant internal diameter. In the illustrated embodiment, the bore 59 is defined by a cylindrical sidewall 57 spaced inwardly from an inner diameter portion 69. The side wall 57 may be integrally formed with the lid or may be formed by a separate hoop component attached to the lid 52. Regardless, the conductive tube 56 extends through the aperture 59. The conductive tube 56 is generally hollow and is sized and shaped to receive an anode lead. The conductive tube 56 is typically fabricated from a metal such as tantalum, niobium, aluminum, nickel, hafnium, titanium, copper, silver, steel (e.g., stainless steel), alloys thereof (e.g., conductive oxides), composites thereof (e.g., metal coated with conductive oxides), and the like. An insulating material (e.g., glass) is also disposed in the bore 59 to form a seal 54 (e.g., a glass-to-metal seal) between the conductive tube 56 and the sidewall 57.

The cap assembly 50 may also include a fluid seal 70 made of a substantially insulating sealing material having, for example, a resistance of about 1 × 10 measured at 20 deg.C²Ohm-meters or greater, and in some embodiments about 1 × 10⁵Ohm-meters or greater, and in some embodiments about 1 × 10¹⁵-1×10²⁵Ohm-meter. A liquid seal 70 covers at least a portion of the lower surface 62 of the lid 52 to limit contact with electrolyte that may leak from the housing. This may allow the lid 52 to be omitted from the circuit, helping to increase leakage current. Thus, the liquid seal 70 sometimes covers a substantial portion of the lower surface 62 of the lid 52 and the lower surface of the seal 54. By "substantially" is meant sealing 80% or more of the surface, in some embodiments covering about 90% or more, and in some embodiments covering about 100% of the surface. As shown in FIG. 5, the liquid seal 70 also generally covers at least a portion of the conductive tube 56, such as the sidewall 53.

To help achieve the desired surface coverage,for example, capacitors may sometimes have a rated operating temperature of up to about 250 ℃. in this case, the sealing material may become flowable at about a temperature of greater than 250 ℃, in some embodiments about 275 ℃ to 350 ℃, and in some embodiments about 285 ℃ to 325 ℃. "flowable" is generally understood to mean that the material has a viscosity of about 10 × 10⁵-10×10⁷Centipoise. Such flowable materials may be crystalline or semi-crystalline (polymeric) materials that melt or soften at the appropriate temperature, or they may simply be amorphous materials with a glass transition temperature low enough to flow at the appropriate temperature. For example, a glass material, e.g. containing CaO, Al, may be used₂O₃、B₂O₃、SrO、BaO、La₂O₃、SiO₂、TiO₂And Na₂O or combinations thereof. Comprising boron oxide (B)₂O₃) Barium oxide (BaO), lanthanum oxide (La)₂O₃) And optionally at least one other oxide are particularly suitable. Such compositions are described in more detail in U.S. patent nos. 5,648,302 and 5,104,738, which are incorporated herein by reference in their entirety.

Another example of a suitable crystalline or semi-crystalline sealing material for use in the wet seal 70 is a fluoropolymer. The term "fluoropolymer" refers to a hydrocarbon backbone polymer in which some or all of the hydrogen atoms are replaced with fluorine atoms. The backbone polymer is typically a polyolefin and is formed from fluorine substituted unsaturated olefin monomers. The fluoropolymer may be a homopolymer of a fluorine-substituted monomer or a copolymer of a mixture of a fluorine-substituted monomer and a non-fluorine-substituted monomer. Together with the fluorine atom, the fluoropolymer may also be substituted with other halogen atoms, such as chlorine and bromine atoms. Representative monomers suitable for forming fluoropolymers of the present invention are tetrafluoroethylene ("TFE"), vinylidene fluoride ("VF 2"), hexafluoropropylene ("HFP"), chlorotrifluoroethylene ("CTFE"), perfluoroethyl vinyl ether ("PEVE"), perfluoromethyl vinyl ether ("PMVE"), perfluoropropyl vinyl ether ("PPVE"), and the like, and mixtures thereof. Specific examples of suitable fluoropolymers include polytetrafluoroethylene ("PTFE"), perfluoroalkyl vinyl ether ("PVE"), poly (tetrafluoroethylene-co-perfluoroalkyl vinyl ether) ("PFA"), fluorinated ethylene propylene copolymer ("FEP"), ethylene-tetrafluoroethylene copolymer ("ETFE"), polyvinylidene fluoride ("PVDF"), polychlorotrifluoroethylene ("PCTFE"), and copolymers of TFE with VF2 and/or HFP, and mixtures of the above fluoropolymers. A particularly suitable fluoropolymer is poly (tetrafluoroethylene-co-perfluoroalkyl vinyl ether) ("PFA").

If desired, the liquid seal 70 may be a laminate structure including layers having different flow characteristics. For example, the liquid seal 70 may include a sealing layer that flows readily at the temperatures indicated above and a hard layer that does not generally flow or only flows at temperatures above the sealing layer temperature. For example, typically the hard layer may become flowable at a temperature that is 5 ℃ or more, in some embodiments about 10 ℃ or more, in some embodiments about 20 ℃ or more, higher than the temperature at which the seal layer can flow. For example, in one embodiment, the sealing layer is made of poly (tetrafluoroethylene-co-perfluoroalkylvinylether) ("PFA") having a melting point typically of about 305 ℃, and the hard layer is made of poly (tetrafluoroethylene) ("PTFE") having a melting point typically of about 327 ℃. Among other advantages, the hard layer generally reduces the likelihood that the sealing layer will flow to places in the capacitor where it is not desired to do so when heated, and maintains surface coverage of the inner surface of the lid.

For example, the sealing material 70 may be a laminate structure (e.g., sealing layer/hard layer) comprising two layers, wherein the sealing layer is directly adjacent to the lid 52. In this way the sealing layer flows easily and coats the lower surface of the cover and seal, but the hard layer may limit the possibility of the sealing layer entering the housing. In another embodiment, the sealing material 70 may be a laminate structure (e.g., sealing layer/hard layer/sealing layer) comprising three layers, wherein the sealing layer is adjacent to the lid 52 and the anode. Among other advantages, this configuration allows the sealing material 70 to be easily applied to the lid 52 and/or anode during capacitor manufacture.

In addition to the fluid seal 70 discussed above, the capacitor of the present invention may also include one or more second fluid seals. Referring again to fig. 4, for example, a gasket 89 is shown positioned adjacent the upper end 17 of the anode 20. The gasket 89 is generally cylindrical and includes a hole coaxial with the gasket through which the anode lead 42 extends. The gasket 89 may be made of any of the types of insulating materials described above, such as PTFE. An elastomeric ring 94 may also be used as an additional fluid seal. If desired, an elastomeric ring 94 may be located adjacent the edge portions 77 and 79 of the housing 12 to help inhibit electrolyte from leaking therefrom. The elastomeric ring 94 may be made of an elastomer that is resistant to electrolyte corrosion and has a dielectric strength sufficient to withstand the highest voltages generated by the capacitor. In one embodiment, the elastomer can operate at temperatures of about-55 ℃ to 200 ℃ without degradation or loss of elasticity. Examples of elastomers that may be used include butyl rubber, chlorobutyl rubber, ethylene-propylene rubber (EPR), ethylene-propylene-diene monomer rubber (EPDM), fluoroelastomers such as VITON ™ cells, polytetrafluoroethylene, chloroprene rubber, butadiene rubber, nitrile rubber, isoprene rubber, silicone rubber and styrene-butadiene rubber.

Fig. 6 illustrates one embodiment of attaching the cap assembly 50 to the shell 12. As shown, the cap assembly 50 is positioned: the liquid seal 70 is adjacent the elastomeric ring 94. Once in the desired position, pressure may be applied to the assembly 50 to compress the resilient ring 94 and establish a second fluid seal. For example, the elastomeric ring may be compressed to about 30% -85% of its original thickness. The cover 52 is then welded to the housing 12. Referring to fig. 7, the anode lead 42 extends through the contact tube 56 and is sealed at the outer end thereof by a weld 104. An outer anode lead 100, preferably made of nickel, may also be welded at weld 104. Also, an outer cathode lead 102 is welded to the bottom of the can 12.

Hair brushThe obtained capacitor has excellent electrical performance. For example, capacitors also have a relatively high energy density, making them suitable for high pulse applications. Energy density is generally according to the formula E =1/2 CV²Where C is the capacitance in farads (F) and V is the capacitor operating voltage in volts (V). For example, capacitance can be measured using a capacitance meter (e.g., a Keithley 3330 precision LCZ meter with Kelvin leads, 2 volt bias and 1 volt signal) at an operating frequency of 10-120 Hz and a temperature of 25 ℃. For example, the energy density of the capacitor is about 2.0 joules per cubic centimeter (J/cm)³) Or higher, and in some embodiments about 3.0J/cm³And in some embodiments about 4.0J/cm³-10.0J/cm³And in some embodiments about 4.5-8.0J/cm³. Also, the capacitance is about 1 millifarad per square centimeter ("mF/cm)²") or higher, and in some embodiments about 2 mF/cm²Or higher, and in some embodiments, from about 5 to about 50 mF/cm²And in some embodiments about 8-20 mF/cm²。

Equivalent series resistance ("ESR") is the degree to which a capacitor acts as a resistance when the capacitor is charged and discharged in an electronic circuit. ESR may be less than about 15,000 milliohms, in some embodiments less than about 10,000 milliohms, in some embodiments less than about 5,000 milliohms, and in some embodiments, between about 1 milliohm and about 1000 milliohms when measured at a frequency of 1000 Hz, a bias voltage of 2 volts, and a signal of 1 volt. In addition, leakage current, which generally refers to current flowing from one conductor to an adjacent conductor through an insulator, can also be kept at a relatively low level. For example, the value of the standard leakage current of the capacitor of the invention is in some embodiments approximately below 1 μ A/μ F V, in some embodiments approximately below 0.5 μ A/μ F V, and in some embodiments approximately below 0.1 μ A/μ F V, wherein μ A is microampere and μ F V is the product of the capacitance and the rated voltage. The Leakage current is measured using a Leakage current tester (e.g., MC 190 Leakage test, mantrocour Electronics LTD, UK) at a temperature of 25 ℃, a certain rated voltage, and after charging for about 60-300 seconds. The above ESR and standard leakage current can be maintained even after aging at high temperature for a long time. For example, these values may be maintained for about 100 hours or more, in some embodiments for 300 hours to 2500 hours, and in some embodiments for 400 hours to 1500 hours (e.g., 500 hours, 600 hours, 700 hours, 800 hours, 900 hours, 1000 hours, 1100 hours, or 1200 hours) at a temperature of about 100 ℃ to 250 ℃, and in some embodiments, at about 100 ℃ to 200 ℃ (e.g., 100 ℃, 125 ℃, 150 ℃, 175 ℃, or 200 ℃).

The electrolytic capacitors of the present invention may be used in a variety of applications, including, but not limited to, medical devices, such as implantable defibrillators, pacemakers, cardioverters, neurostimulators, drug delivery devices, and the like; automotive applications; military applications, such as radar systems; consumer electronics such as radios, televisions, and the like. In one embodiment, for example, the capacitor may be used in an implantable medical device to provide high voltage therapy (e.g., about 500 volts to 850 volts, or, if desired, about 600 volts to 900 volts) to a patient. The apparatus may comprise a fully sealed and biologically inert container or housing. One or more leads are used to electrically connect the device to the patient's heart intravenously. Cardiac electrodes are provided to sense cardiac activity and/or to provide voltage to the heart. At least a portion of the lead (e.g., the lead tip) is provided adjacent to, or in contact with, one or more ventricles and atrium of the heart. The instrument also includes a capacitor bank, which typically includes two or more capacitors connected in series and connected to a battery internal or external to the instrument to provide power to the capacitor bank. Partly because of the higher conductivity, the capacitor of the present invention has excellent electrical properties, and is therefore suitable for use in capacitor banks for implantable medical devices.

While the preferred embodiments of the present invention have been illustrated and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (24)

1. A wet electrolytic capacitor comprising:

a metal shell including a first edge portion and an opposing second edge portion extending longitudinally from a first end to define an interior space;

an electrochemically active cathode material deposited on at least a portion of the inner surface of the metal housing, wherein the electrochemically active cathode material comprises a dispersion of particles having an average diameter of from 1nm to 500 nm;

an anode formed of an anodized, sintered porous body, the anode comprising an upper end and a lower end, wherein a first edge portion of the anode and an opposing second edge portion extend longitudinally between the upper end and the lower end defining a length of the anode, wherein a medial longitudinal plane extends through the upper end of the anode in a direction parallel to the longitudinal direction, wherein a distance between the medial longitudinal plane along the length of the anode and each edge portion of the anode remains substantially constant, the distance between the first edge portion and the second edge portion of the anode further defining a width of the anode, wherein a ratio of the anode width to an interior space width is from 0.80 to 1.00, and further wherein the anode is positioned within the interior space defined by the metal housing and occupies 70 vol.% or more of the interior space; and

a liquid electrolyte in electrical contact with the anode and the electrochemically active material.

2. The wet electrolytic capacitor as claimed in claim 1, wherein the anode occupies 80 vol.% to 98 vol.% of the internal space.

3. The wet electrolytic capacitor as claimed in claim 1, wherein a difference between a spacing between the intermediate longitudinal plane and the anode first edge portion and a spacing between the intermediate longitudinal plane and the anode second edge portion in a length direction of the anode is 0.20 mm or less.

4. The wet electrolytic capacitor as claimed in claim 1, wherein a radius of curvature of the anode in a medial transverse plane direction perpendicular to the medial longitudinal plane is 25 cm or more.

5. The wet electrolytic capacitor as claimed in claim 1, wherein a ratio of the length of the anode to the length of the internal space is 0.70 to 1.00.

6. The wet electrolytic capacitor as claimed in claim 1, wherein the anode length is 1 to 60 mm.

7. The wet electrolytic capacitor as claimed in claim 1, wherein a ratio of the anode width to the internal space width is 0.90 to 0.99.

8. The wet electrolytic capacitor of claim 1 wherein the width of the anode is 1-40 millimeters.

9. The wet electrolytic capacitor of claim 1 further comprising an isolation layer surrounding at least a portion of the first edge portion of the anode, the second edge portion of the anode, the upper end portion of the anode, the lower end portion of the anode, or a combination thereof.

10. The wet electrolytic capacitor as claimed in claim 1, further comprising a lead wire which is led out from the anode porous body in a longitudinal direction.

11. The wet electrolytic capacitor of claim 1 wherein the electrochemically active cathode material comprises a conductive polymer.

12. The wet electrolytic capacitor as claimed in claim 11, wherein the conductive polymer is poly (3, 4-ethylenedioxythiophene).

13. The wet electrolytic capacitor as claimed in claim 1, wherein the porous body comprises a conductive oxide of tantalum, niobium or both.

14. The wet electrolytic capacitor as claimed in claim 1, wherein the liquid electrolyte is an aqueous solution.

15. The wet electrolytic capacitor of claim 1 wherein the metal can and anode are substantially cylindrical.

16. The wet electrolytic capacitor as claimed in claim 1, wherein the metal case is made of titanium, tantalum or a combination thereof.

17. The wet electrolytic capacitor of claim 1 wherein the metal can defines an opening at a second end opposite the first end of the metal can, the capacitor further comprising a cover sealing the opening.

18. A method of manufacturing a wet electrolytic capacitor, the method comprising:

pressing a powder comprising tantalum, niobium or their conductive oxides to form a porous body, wherein an anode lead is drawn from the porous body; sintering the porous body in a heat treatment apparatus without physical contact of the surface of the porous body with the outer surface;

anodizing the sintered porous body to form an anode, wherein the anode has a length of 1 to 60 mm and a width of 1 to 40 mm, and further, wherein the anode comprises an upper end and a lower end, wherein a first edge portion of the anode and an opposing second edge portion extend longitudinally between the upper end and the lower end defining a length of the anode, wherein the intermediate longitudinal plane extends through the upper end portion of the anode in a direction parallel to the longitudinal direction, wherein the distance between the intermediate longitudinal plane and each edge portion of the anode in the direction of the length of the anode remains substantially constant, the distance between the first edge portion and the second edge portion of the anode further defining the width of the anode, wherein the ratio of the width of the anode to the width of the interior space is from 0.80 to 1.00, and further wherein the anode is disposed within the interior space defined by the metal can and occupies 70 vol.% or more of the interior space;

inserting the anode into the interior space of a metal housing, wherein at least a portion of the interior surface of the metal housing is coated with an electrochemically active material, wherein the electrochemically active material comprises a dispersion of particles having an average diameter of 1nm to 500 nm; and

the anode and electrochemically active material are contacted with a liquid electrolyte.

19. The method of claim 18, wherein the sintering is performed at a temperature of 1000 ℃ to 1500 ℃.

20. The method of claim 18, wherein the porous body is suspended from the rail by an anode lead during sintering.

21. The method of claim 18, wherein the electrochemically active cathode material comprises poly (3, 4-ethylenedioxythiophene).

22. The method of claim 18, wherein the liquid electrolyte is an aqueous solution.

23. The method of claim 18, wherein the metal housing and anode are substantially cylindrical.

24. The method of claim 18, wherein the metal housing is made of titanium, tantalum, or a combination thereof.