Electrode, capacitor element, and capacitor

Abstract

According to applications, an electrode is provided having a substrate and a sintered body on a first major surface of the substrate. The substrate includes a first valve metal. The sintered body includes fused or sintered particles comprising a second valve metal. The first major surface of the substrate is surface-modified.

Description

Technical Field

[0001] This application relates to electrodes, electrolytes, capacitor elements, capacitors, and methods for forming, modifying, or impregnating electrodes. Background Technology

[0002] This application relates to electrodes, electrolytes, capacitor elements, capacitors, and methods for forming, modifying, or impregnating electrodes.

[0003] Overall, improving capacitors, especially electrolytic capacitors, can be challenging. Specifically, attempts to improve the volumetric efficiency of capacitors may introduce secondary problems.

[0004] For example, the inventors of this application have discovered that at least some capacitors with high volumetric efficiency are prone to problems. Specifically, one of these problems may be a shortened lifespan under the same operating conditions as capacitors with lower volumetric efficiency.

[0005] In particular, when sintered anodes or similar materials are used in capacitors, other challenges may arise. Summary of the Invention

[0006] Therefore, one object of this application is to provide an electrode or capacitor that at least partially solves the above-mentioned problems or one of the following problems.

[0007] The electrode, electrolyte, capacitor, or capacitive element or method in the independent claim each at least partially solves the problem addressed above or below. Advantageous embodiments are provided in the dependent claims.

[0008] Several features are disclosed below, which, when used individually, can provide the benefits described above or other benefits as described below. However, synergistic effects and additional benefits can be achieved, especially when combined.

[0009] A sintered electrode is described according to a first embodiment, which is applicable to all other embodiments described below, but not necessarily to all other embodiments.

[0010] In the most general sense, a sintered electrode is an electrode having a sintered body. Sintered electrodes can be used in capacitors, preferably in electrolytic capacitors. Preferably, the sintered electrode includes a valve element. This means that it can include one or more valve elements.

[0011] One or more different types of particles, comprising or composed of valve metal, are sintered or fused together in a sintered body. "Fusing" here means that the particles in the sintered body are not loose but incorporated into a solid, and preferably a porous, particle structure, where these particles are partially fused together with other particles. Such sintered bodies of fused particles can generally be achieved by any method. Specifically, it can be achieved by sintering valve metal particles, i.e., by a heating or annealing step of fusing or fusion of the particles. This means that the term "sintered body" is not limited to an actual sintered particle body. Although, for example, no heat treatment is used, any other technique that results in similar fusion of particles can form a sintered body. However, sintering is the most preferred technique.

[0012] The inventors of this application have discovered that sintering electrodes, particularly when used as anodes, can help improve the volumetric efficiency of capacitors. Specifically, the volumetric efficiency can be improved compared to etched electrodes. The electrodes, especially those used as anodes, are preferably passivated with an oxide layer.

[0013] The term "valve metal" as used herein and hereinafter should be understood in its general technical sense and without any other limitations. For example, valve metals include at least aluminum, titanium, tantalum, niobium, tungsten, chromium, zirconium, hafnium, zinc, vanadium, bismuth, or antimony. Aluminum, tantalum, and vanadium are particularly preferred. The most preferred valve metal for the electrodes used in the embodiments disclosed herein is aluminum.

[0014] According to one embodiment, the electrode can be a sintered block anode, in which case this means that most of the anode's volume can consist of a sintered body or sintered material. In this case, the block of sintered material can be contacted via lead terminals or the like.

[0015] According to a preferred embodiment compared to other embodiments described herein, the sintered anode may have a substrate. In principle, the substrate may substantially comprise or consist of any conductive material (e.g., a metal or alloy). Preferably, the substrate also comprises or consists of a valve metal, which may be referred to herein as a first valve metal. In this case, the valve metal of the sintered body particles may be referred to as a second valve metal. In both cases, the first and second valve metals may be selected individually from the valve metals listed above. Most preferably, they are the same. Even more preferably, both are aluminum.

[0016] The sintered body can be disposed on the main surface of the substrate. For example, and preferably, the substrate can be a sheet or foil, and the sintered body can be a sintered layer disposed on the main surface of the foil. Even more preferably, the two opposing main surfaces of the substrate foil can be covered by a sintered layer. For example, such an arrangement can achieve a higher specific capacitance than that achievable by etching an anode.

[0017] The inventors of this application have discovered, as described above, that electrodes having a substrate in a sintered body may, in some cases, lack adhesion between the sintered body and the surface. In such cases, the sintered body may delaminate from the substrate. This can occur, for example, during the processing of electrode foils, such as slitting, winding, and cold soldering processes, and during capacitor operation. Besides affecting the quality of the electrode and the capacitor made therefrom, the delaminated portion may also generate gas during capacitor storage or operation. Delamination may leave exposed metal, which can be oxidized by the electrolyte, for example, thereby generating gas. This gas can cause pressure buildup within the capacitor, potentially damaging it.

[0018] To at least partially overcome this problem, the inventors surprisingly discovered that by surface modification of the first main surface of the substrate, the sintered body disposed on said main surface can have improved adhesion. Therefore, delamination can be better prevented.

[0019] According to one embodiment, surface modification can increase the surface area or roughness of the first primary surface of the substrate. The comparison point can be the unmodified substrate surface. The inventors believe that increasing surface area can contribute to increased adhesion.

[0020] According to one embodiment, surface modification may include protrusions. The protrusions can be any portion of the modified surface resulting from the surface modification that is above the average level. According to a preferred variation of this embodiment, some protrusions may be pointed and / or edge-shaped. Generally, the protrusions may have a smaller thickness along at least one direction at the point facing furthest from the substrate than at points more towards the substrate.

[0021] According to one embodiment, surface modification may include indentations recessed into the substrate. For example, the indentations may have a concave shape. Specifically, it is preferable that these portions recessed into the substrate have a crater-like shape.

[0022] According to the above implementation scheme and the modification of the implementation scheme (the surface of the implementation scheme includes the crater), the protruding part can be the edge part or the tip part of the crater-shaped crater.

[0023] The inventors have discovered that adhesion can be improved by having some or all of the aforementioned surface morphology characteristics. For example, indentations may help to accommodate particles. Protrusions can provide portions of the modified substrate surface that are heated to the sintering temperature more quickly during sintering, which can simplify the sintering of the sintered body onto the main surface.

[0024] Therefore, in general, the surface-modified portion is configured to improve adhesion during the sintering process, which is also one embodiment of this specification.

[0025] The formation of the surface modification is not limited to any specific structure in the most general sense. Furthermore, it is not limited to any type of method for producing the structure. Specifically, the technique may include, for example, a photolithography step.

[0026] According to a preferred embodiment, surface modification is achieved through chemical or electrochemical surface etching. Specifically, in surfaces containing valve metals, and most preferably aluminum-containing surfaces, indentations can be easily etched therein by chemical or electrochemical methods. The edge portions of the indentations can form protrusions. Thus, a simple method for achieving surface modification can be realized.

[0027] Overall, surface modification, and especially etching, can be advantageous because it can at least partially remove naturally occurring oxides or impurities that have formed on the substrate surface.

[0028] According to one implementation scheme, the surface roughness R of the surface-modified host substrate is... a It can be on the same order of magnitude as the particles in the sintered body. It can also be smaller. The term "on the same order of magnitude" can be understood according to the general technical meaning of the word. For example, this could refer to the average size of the structure on the surface (surface roughness R). a The surface roughness can be 0.1 to 10 times the average particle size used. Alternatively or additionally, the surface roughness can be 0.01 to 50 μm. More preferably, it can be 0.1 to 50 μm, 0.5 to 10 μm, or even 0.7 to 7 μm or 0.5 to 5 μm.

[0029] The inventors of this application have discovered that adhesion is better when the size of the surface structure is similar to the size of the particles used for sintering.

[0030] According to one embodiment, the particles of the sintered body have an average size between 0.5 μm and 10 μm, for example, 1 μm to 5 μm.

[0031] The inventors have discovered that this particle size of the sintered body contributes to improving the volumetric efficiency of the electrode. Furthermore, the inventors have found that particles of this size can adhere well using the methods described above. In particular, the structure produced by etching and / or the aforementioned surface roughness conditions provides excellent adhesion for particles of this size.

[0032] According to a further embodiment, the valve metal content in the substrate can be 98% by weight or more, for example 99% by weight or more, or even more preferably 99.7% by weight or more, or even more preferably 99.9% by weight or more. These values ​​are particularly relevant for the valve metal aluminum. Previously, high-purity valve metal substrates were typically required to produce sintered electrodes. These substrates were more expensive to manufacture compared to the lower-purity substrates mentioned above. Furthermore, the inventors have found that lower purity of the substrate can facilitate surface modification of the substrate.

[0033] According to one embodiment, for the reasons stated above, the purity of the valve metal in the substrate can be less than 99.99% by weight, and more preferably less than 99.9% by weight. Therefore, for example, a range of 98% by weight to 99.90% or 99.99% by weight can be used. Alternatively, the above values ​​can replace "98%" within this range. In particular, for a range of 99.7% by weight to 99.99% by weight, or especially 99.7% by weight to 99.90% by weight, the inventors have found that the impurity level is beneficial for surface modification without being too high, and other disadvantages of impurities are also reduced.

[0034] The next embodiment is also preferably used for electrodes having a sintered body as described above. However, this method can also be applied to any other type of electrode that can be used in electrolytic capacitors. Electrodes may have defects or crack sites for a variety of reasons. Among these defects or crack sites, the oxide layer preferably formed on the electrode surface may be partially missing.

[0035] The inventors have discovered that the sintered body described above is particularly prone to the formation of the aforementioned cracks. For example, cracks may form as a result of the electrode manufacturing process. For instance, for foil electrodes having a foil substrate and a sintered body, cracks or partial delamination of the sintered body may occur during process steps such as slitting, winding, and cold soldering, as well as during subsequent capacitor operation.

[0036] According to this embodiment, any site of such cracks or at least partially lacking an oxide layer can be at least partially passivated using a passivation compound.

[0037] If not passivated quickly, gases may form at these sites during operation or passive storage due to chemical reactions with exposed metal. This can lead to unwanted excess gas buildup in the capacitor, potentially damaging it. Ventilation systems can be used to accommodate such gas formation. Therefore, passivating these sites helps reduce gas generation and can also help avoid complex gas compensation devices.

[0038] Previously, the high energy density or capacitance density of sintered anode foil, combined with numerous surface cracks, led to high energy consumption or leakage current until the damaged electrode had sufficient passivation oxide. Typically, for state-of-the-art electrodes, multiple repairs were required during the capacitor's lifespan, and the large amounts of hydrogen generated limited the applicability of this technology. These drawbacks can be mitigated by using passivation compounds.

[0039] As described in more detail below, the substances may be applied directly to the anode or capacitor elements (e.g., winding elements) before assembling the capacitor, or they may be applied as a component of the electrolyte itself.

[0040] The inventors have discovered that passivating compounds can reduce gas generation in liquid electrolytes before and during the formation of oxides. This means that, in addition to the passivation effect of the compounds themselves, they can also promote site closure through the combination of the passivating compound and the formed oxide.

[0041] Passivating compounds are generally unrestricted and can be applied in the form of molecules, particulate compounds, or composite materials.

[0042] According to one implementation, a phosphorus-containing compound or a silicon-containing compound may be used as the aforementioned partial passivation compound.

[0043] For example, according to one embodiment, the silicon-containing compound can be provided in the form of particles. For example, such particles can contain silicon oxide.

[0044] According to one embodiment, the application of a passivation compound can also reduce the requirement for a high purity level of the valve metal in the electrode. This is applicable to both the substrate and the sintered body when the sintered electrode has a substrate and a sintered body. For example, the passivation compound can be useful when using a valve metal purity of 99.7% or 99.8% by weight or higher, such as 99.7% to 99.99% by weight or 99.7% to 99.0% by weight. The inventors have found that the passivation component, combined with reduced purity, can help reduce leakage current. This applies to both the substrate and the sintered body. In both cases, this effect is particularly pronounced for Al.

[0045] According to one implementation scheme, surface modification and passivation can be preferably combined, as they can help reduce the free metal surface area in a complementary manner. These two methods can also help to use less pure metal.

[0046] Furthermore, the inventors have discovered that by using passivation compounds in capacitor devices, the thickness of the separator can be reduced through better passivation. This can improve volumetric efficiency. For example, this can help reduce the thickness of the separator to 44 μm or less, or 40 μm or less, or even 35 μm or less. These values ​​can be the total thickness of the separator between the anode and cathode foils. The term "separator" as used herein and in this specification can refer to the functional unit that separates the cathode and anode. It is not limited to a single-layer separator, but can also include separator structures with two or more layers.

[0047] According to a further embodiment, an electrode having an impregnation on at least a portion of its surface is described. Again, the electrode is preferably an electrode with an impregnated sintered portion. However, it is not limited to such a sintered electrode. The impregnation is configured to increase the wettability of the electrolyte to the electrode or the impregnated portion. The inventors have found that the wettability of the electrolyte to the electrode becomes increasingly important by increasing the surface area of ​​the electrode, for example, and particularly by having a sintered body.

[0048] The inventors have discovered that the high density and compactness of sintered electrodes and the oxides grown on them can make electrolytes difficult to wet, especially for electrolytes with high viscosity. This is improved by impregnation compounds.

[0049] According to one embodiment, silanes can act as impregnating agents that improve wettability. They are also suitable for polyethylene oxide, sulfonates, or anionic surfactants. Silanes, polyethylene oxide, sulfonates, or anionic surfactants can be used alone, or a mixture of one or two of them.

[0050] The above-mentioned methods for increasing wettability can also be preferably applied to the above-mentioned surface modification and to reduce non-passivated sites in a complementary manner.

[0051] Furthermore, an electrolyte for electrolytic capacitors is described as a further embodiment.

[0052] According to a first embodiment, an electrolyte is described comprising a compound configured to adsorb onto crack sites or electrode sites at least partially lacking an oxide layer. The compound is configured to at least partially passivate said sites. Electrolytes that can be used in electrolytic capacitors may include the aforementioned at least partially passivating compound.

[0053] The advantages mentioned above also apply here.

[0054] According to one embodiment, the passivation compound can be a phosphorus-containing compound or a silicon-containing compound with a molecular or particulate structure as described above. In the latter case, this can be an emulsion comprising the particles in the electrolyte. For example, particles containing silicon oxide at a concentration ranging from 0.1 to 5 wt%, such as 0.5 to 1.5 wt%, can be used.

[0055] For example, the electrolyte can be combined with the aforementioned electrodes in a capacitor, and preferably with a sintered electrode. Therefore, the partially passivated electrode can be formed in situ using the electrolyte. In many cases, even after adsorption onto the electrode, some passivation compounds may still be present in the electrolyte.

[0056] According to a further embodiment, an electrolyte for an electrolytic capacitor is described, having an impregnation compound configured to impregnate part of an electrode surface. The impregnation compound is configured to increase the wettability of the electrolyte to the electrode surface. It is further configured to adsorb onto the electrode surface. For example, it can be the silane, polyethylene oxide, sulfonate, and / or anionic surfactant described above and added to the electrolyte.

[0057] According to one embodiment, the concentration of the impregnation compound in the electrolyte can be from 10 to 200 ppm by weight, for example, from 15 to 50 ppm by weight. Generally, and particularly for the examples of the listed impregnation compounds, the inventors have found that the wettability of the electrolyte can be significantly improved within this concentration range.

[0058] For example, the electrolyte can be combined with the aforementioned electrodes in a capacitor, and preferably with a sintered electrode. Therefore, the aforementioned impregnated electrode can be formed in situ using an electrolyte. In many cases, even after adsorption onto the electrode, some of the impregnating compound may still remain in the electrolyte.

[0059] Impregnation compounds and passivation compounds can be added together to the electrolyte.

[0060] According to a further embodiment, which can be used independently of but also advantageously combined with the other embodiments described above, an electrolyte for an electrolytic capacitor is described, having a conductivity of 660 μS / cm or less at a temperature of 30°C before wetting the insulating element or winding element. The inventors of this application have found that a conductivity of 660 μS / cm or less can be advantageous for sintering electrodes and can help reduce the thickness of the insulating element impregnated with the electrolyte.

[0061] Having lower electrical conductivity can reduce the generation of localized heat during the self-healing process, or reduce the need for the passivation process of the damaged sintered body as described above. Until this application, highly conductive electrolytes were typically used, in which the surface repair process generates high-density localized heat, resulting in very high leakage current.

[0062] According to a variation of the above-described embodiment, the electrolyte may have a water content of 1% to 10%. The inventors of this application have discovered that such a high water content in the electrolyte can help reduce the thickness of the separator paper.

[0063] According to a further embodiment, a capacitor element is described. The capacitor element can be configured to store charge during capacitor operation. For example, the capacitor element can be configured to charge and discharge during capacitor operation. For example, the capacitor element may include a cathode and an anode. The cathode and anode can be electrically contacted via conductive elements (e.g., wires or leads). Typically, the cathode and anode are not limited. Preferably, the anode can have the characteristics of the electrodes described above.

[0064] According to one embodiment that is superior to other embodiments, the capacitor element can be a winding element in which the anode and cathode are wound. For example, the winding element can be a cylindrical winding element or a flat winding element.

[0065] According to one embodiment, which is superior to other embodiments, the winding element can be configured as an electrolytic capacitor. In this case, the electrolyte is arranged between the anode and the cathode. For example, an insulating element soaked or impregnated with the electrolyte can be arranged between the anode and the cathode. There are no limitations on the insulating element, except that it should be configured to be impregnated or wetted with the electrolyte and it should not be conductive. The insulating element may comprise a cellulose-based material such as paper or be composed of it. In the electrolytic capacitor, it is preferable that the anode has an oxide on its surface to provide at least partial chemical and electrical isolation between the anode and the electrolyte.

[0066] There are generally no restrictions on the electrolyte. However, the electrolyte described above may possess the characteristics of the electrolyte described above, thereby producing the advantages described.

[0067] According to one embodiment, a capacitor element can be described in which an insulating element is impregnated with an electrolyte having a maximum conductivity of 660 μS / cm and preferably additionally having a water content of 1% to 10%. In this case, the thickness of the insulating element can be 44 μm or less. For example, the thickness of the insulating element can even be 40 μm or less, and even 35 μm or less.

[0068] According to a further embodiment, a capacitor having a capacitive element is provided. The capacitive element may be one of the capacitive elements described above, or may have a combination of their features. Alternatively or additionally, the capacitor may have any of the above-described electrodes as an anode. Alternatively or additionally, the capacitor may have any electrolyte, but preferably one of the above-described electrolytes.

[0069] According to a further embodiment, a method for manufacturing or processing an electrode is described below. Where applicable, this method may have the features explained above for the electrode or electrolyte.

[0070] According to one embodiment, a method for manufacturing an electrode is described. First, a substrate is provided. The substrate used herein comprises or is composed of a first valve metal. For example, it may comprise or be primarily composed of aluminum. For example, it may have the purity level described above for the substrate. In a further step, the main surface of the substrate is modified to obtain a surface-modified main surface of the substrate. For example, as described above, the surface modification may be the formation of protrusions and / or indentations, and may also increase surface roughness, and preferably increase adhesion to the sintered body. As a next step of the method, a sintered body is formed on the surface-modified main surface. The sintered body comprises or is composed of fused particles, which comprise or are composed of a second valve metal. There are no limitations on the methods for forming the sintered body, and any suitable method may be used. For example, the formation of the sintered body may include sintering the particles at a temperature of 400 to 660°C. For example, the particles may include aluminum as a main component. For example, forming the sintered body may also include applying a slurry containing the particles. The slurry may then be sintered. The particles typically comprise a second valve metal and preferably aluminum.

[0071] As mentioned above, surface modification can be achieved by any suitable method, such as photolithography or any type of etching. Most preferably, chemical or electrochemical etching is used.

[0072] According to a further embodiment, a method is described in which at least a portion of a sintered body is modified by adsorbing a compound onto crack sites or at least sites that are at least partially lacking an oxide layer. The compound is configured to at least partially passivate said sites. The properties of such a compound described above can also be applied here. This method can be carried out on the formed electrode, or by adding at least a partially passivating compound to an electrolyte, or a combination of both.

[0073] According to a further embodiment, a method is described for impregnating, and preferably sintering, at least a portion of, an electrode. The impregnation can be performed by applying an impregnation compound, which can be an impregnation compound as described above. The impregnation compound is configured to increase the wettability of the electrolyte to the electrode surface. Furthermore, the method can be performed before the electrode is fitted into a capacitor, or by immersing the impregnation compound in the electrolyte, or a combination of both.

[0074] This application discloses the following scheme:

[0075] Option 1. An electrode having a substrate and a sintered body on a first main surface of the substrate, wherein

[0076] The substrate comprises or is composed of a first valve metal.

[0077] The sintered body comprises or is composed of fused or sintered particles, wherein the fused or sintered particles contain or are composed of a second valve metal.

[0078] The first main surface is surface modified.

[0079] Option 2. The electrode according to Option 1, wherein the surface modification is an increase in surface area and / or surface roughness compared to the unmodified substrate surface.

[0080] Option 3. The electrode according to Option 1, wherein the surface modification is configured to increase the adhesion of the sintered body or the particles of the sintered body to the surface compared to the unmodified substrate surface.

[0081] Option 4. The electrode according to Option 1, wherein the surface modification includes a protruding portion.

[0082] Option 5. The electrode according to Option 1, wherein the surface modification is chemical or electrochemical surface etching.

[0083] Option 6. The electrode according to Option 1, wherein the surface modification includes indentations recessed into the substrate.

[0084] Option 7. The electrode according to Option 1, wherein the surface roughness R generated by surface modification a The average particle size of the particles is on the same order of magnitude as or smaller than the average particle size of the sintered body.

[0085] Option 8. The electrode according to Option 1, wherein the particles of the sintered body have an average size of 0.5 μm to 20 μm.

[0086] Option 9. The electrode according to Option 1, wherein the content of valve metal in the substrate is 98% by weight or more, preferably 99.7% by weight or more.

[0087] Option 10. The electrode according to Option 1, wherein the content of valve metal in the substrate is 99.99% by weight or less.

[0088] Option 11. Includes electrodes of a sintered body, wherein

[0089] The sintered body comprises or is composed of fused or sintered particles, wherein the fused or sintered particles contain or are composed of valve metal.

[0090] The compound is adsorbed onto crack sites of the sintered body or sites of the sintered body that are at least partially lacking an oxide layer, and the compound is configured to at least partially passivate the sites.

[0091] Option 12. Includes electrodes of a sintered body, wherein

[0092] The sintered body comprises or is composed of fused or sintered particles, wherein the fused or sintered particles contain or are composed of valve metal.

[0093] Phosphorus-containing or silicon-containing compounds are adsorbed onto crack sites of the sintered body or sites of the sintered body that are at least partially lacking an oxide layer.

[0094] Option 13. The electrode according to Option 11 or 12, wherein the compound adsorbed to the crack site comprises molecular and / or particulate compounds and / or composite materials.

[0095] Scheme 14. An electrode having a combination of features of at least one of Schemes 11 to 12 and Scheme 1.

[0096] Option 15. An electrode having an impregnation on at least a portion of its surface, wherein the impregnation is configured to increase the wettability of the electrolyte.

[0097] Option 16. The electrode according to Option 15, wherein the impregnating material comprises polyethylene oxide, sulfonate and / or anionic surfactant.

[0098] Scheme 17. An electrode having the combined features of Scheme 15 and Scheme 1.

[0099] Scheme 18. An electrode having a combination of features of Scheme 15 and at least one of Scheme 11 or 12.

[0100] Option 19. An electrolytic capacitor having an anode, a cathode, and an isolator, the anode having a sintered body, the isolator being impregnated with an electrolyte, the electrolyte comprising a compound configured to adsorb onto crack sites of an electrode or sites of an electrode at least partially lacking an oxide layer, and the compound being configured to at least partially passivate the sites.

[0101] The sintered body comprises or is composed of fused or sintered particles, wherein the fused or sintered particles contain or are composed of valve metal, and

[0102] The compounds present in the electrolyte are adsorbed onto crack sites of the sintered body or sites of the sintered body that are at least partially lacking an oxide layer, and the compounds are configured to at least partially passivate the sites.

[0103] Option 20. An electrolytic capacitor having an anode, a cathode, and an isolator, the anode having a sintered body, the isolator being impregnated with an electrolyte comprising a phosphorus-containing compound or a silicon-containing compound, and

[0104] The sintered body comprises or is composed of fused or sintered particles, wherein the fused or sintered particles contain or are composed of valve metal, and

[0105] The compounds present in the electrolyte are adsorbed onto crack sites of the sintered body or sites of the sintered body that are at least partially lacking an oxide layer, and the compounds are configured to at least partially passivate the sites.

[0106] Option 21. An electrolytic capacitor having an anode, a cathode, and an isolator, the anode having a sintered body, the isolator being impregnated with an electrolyte, the electrolyte comprising an impregnation compound configured to impregnate a portion of an electrode surface, and the impregnation compound being configured to increase the wettability of the electrolyte to the electrode surface when adsorbed onto the electrode surface.

[0107] The sintered body comprises or is composed of fused or sintered particles, wherein the fused or sintered particles contain or are composed of valve metal, and

[0108] The impregnation compound present in the electrolyte is adsorbed onto at least a portion of the surface of the anode, wherein the impregnation is configured to increase the wettability of the electrolyte.

[0109] Option 22. The electrolytic capacitor according to Option 21, wherein the concentration of the impregnation compound in the electrolyte is 10 to 200 ppm by weight.

[0110] Option 23. An electrolytic capacitor having an anode, a cathode, and an isolator, the anode having a sintered body, the isolator being impregnated with an electrolyte, the electrolyte having a conductivity of 660 μS / cm or less at a temperature of 30°C before wetting the isolator or winding elements.

[0111] The sintered body comprises or is composed of fused or sintered particles, wherein the fused or sintered particles contain or are composed of valve metal.

[0112] Option 24. The electrolytic capacitor according to Option 23, having a water content of 1% to 10%.

[0113] Option 25. An electrolytic capacitor according to options 19, 20, 22, 21 or 23, wherein an electrolyte-impregnated separator is disposed between the cathode and the anode, and wherein the total thickness of the separator is 44 μm or less.

[0114] Option 26. A capacitor element comprising an electrode as an anode according to at least one of options 1, 11, 12 or 15.

[0115] Option 27. A capacitor comprising a capacitor element according to Option 26 disposed in a housing.

[0116] Further advantageous embodiments and further embodiments of electrodes or capacitors, and methods of producing such electrodes or capacitors, will become apparent from the exemplary embodiments described below in conjunction with the accompanying drawings. However, it should be noted that this application is not limited to the exemplary embodiments described. Furthermore, the exemplary embodiments are shown at least in part in the accompanying drawings as realistic schematic diagrams. These schematic diagrams are not drawn to scale, and absolute and relative dimensions may be depicted in a distorted manner. Instead, individual elements may be exaggerated for better representation or understanding. Therefore, absolute or relative dimensions cannot be derived from the schematic diagrams unless otherwise stated. Elements that are identical, similar, or have the same effect in the drawings are indicated by the same reference numerals. Attached Figure Description

[0117] Figure 1 A schematic diagram of the surface modification method is shown;

[0118] Figure 2 A schematic cross-section of a first embodiment of the electrode is shown;

[0119] Figure 3 An embodiment of the electrode with a fractured surface is shown;

[0120] Figure 4 The intermediate stage of at least partially passivating the electrode is shown;

[0121] Figure 5 An embodiment with at least partial passivation of the electrodes is shown;

[0122] Figure 6 The wetting behavior of the unimpregnated electrode is schematically illustrated;

[0123] Figure 7 The wetting behavior of the impregnated electrode is shown;

[0124] Figure 8 An exemplary implementation of a capacitor is shown. Detailed Implementation

[0125] exist Figure 1 A schematic cross-section of a method for forming a surface-modified substrate is shown in the figure. A substrate 1 having a first main surface 2 and a second main surface 3 is shown on the left side of the figure. The substrate 1 is composed of a material containing 99.7% by weight or more aluminum. It is then subjected to chemical or electrochemical etching. Specifically, electrochemical etching can be performed using a method similar to the formation of the cathode in the formation of an electrolytic capacitor. Thus, a modified first main surface 2' is formed from the first main surface 2. A modified second main surface 3' is formed from the second main surface 3. The formed structures include pointed or edge-shaped protrusions, and concave surfaces or bowl-shaped recesses embedded in the substrate.

[0126] Chemical etching can be performed in HCl or NaOH solution. The concentration can be from 0.5 mol / L to 4 mol / L, preferably 1 mol / L. Etching can be performed at a temperature of, for example, 60°C, but other temperatures are also possible. Electrochemical etching can be performed under substantially the same conditions, and at 100 mA / cm². 2 Up to 3A / cm 2 The process is carried out at a specific current density. Conditions can be selected or adjusted to produce the described structure.

[0127] In further steps, the results are as follows Figure 2 As shown, a first sintered body 4 and a second sintered body 5 can be formed on a first modified main surface 2' and a second modified main surface 3'. Sintered bodies 4 and 5 are formed from aluminum particles provided in a slurry. The slurry is deposited onto the modified substrate surface 2' and the modified substrate surface 3'. Subsequently, the slurry can be debound and sintered. Sintering is performed at a temperature of 400 to 660°C. The particles within sintered bodies 4 and 5 become fused together through sintering. The particles are aluminum-based particles with an aluminum content of 99% by weight or higher. Not explicitly described here, the aluminum sintered body can be passivated by oxidation, thereby forming an insulating surface oxide.

[0128] By performing the aforementioned surface modification, the adhesion between the sintered body and the surface can be improved. The inventors attribute this to the increase in surface roughness, and may also attribute it to the removal of natural oxides and potential impurities on the substrate. Furthermore, the inventors found that the lower substrate purity simplifies the formation of the surface modification.

[0129] exist Figures 3 to 5 The method for passivating crack sites is shown in the figure. Figure 3 A substrate 1 with a surface-modified main surface 2' is shown, as described above for... Figure 1 and Figure 2As explained. A sintered body 4 is formed on substrate 1. The sintered body consists of fused particles 6. Surface oxides 7 are explicitly depicted here. The sintered body may be damaged during capacitor manufacturing steps such as slitting, winding, and cold soldering. This can lead to the formation of crack sites 8. Figure 4 As shown, the component configured to at least partially passivate these crack sites 8 can adsorb onto these crack sites 8. This can be done in the electrolyte of the capacitor, or alternatively, before the addition of the electrolyte. Here, the passivation compound 9 is formed of silicon oxide particles. These can be present in an electrolyte-like emulsion or applied via a separate emulsion before capacitor potting. This silicon oxide, or alternatively, a phosphorus-containing compound or particles, adheres to the crack sites and forms modified crack sites 8', as... Figure 4 As shown in the diagram. This has partially provided passivation for these crack sites. This can reduce the gas generated by the reaction of the electrolyte in the assembled capacitor.

[0130] like Figure 5 As shown, when a suitable solution or, in particular, an electrolyte containing some water, is applied, a partial oxide 10, indicated by dashed lines, can be formed in addition to the silicon particles 9. This oxide can at least partially and additionally passivate the crack sites. The inventors have found that crack sites can be better passivated by using at least partially passivating compounds (e.g., silicon oxide), by passivation of newly formed oxides in the electrolyte, or by another separate technique. Crack sites here are indicated by reference numeral 8”, signifying an increased degree of passivation.

[0131] exist Figure 6 The image depicts a sintered electrode immersed in an electrolyte. In this case, the electrolyte 11 has a problem in adequately wetting the entire sintered body.

[0132] To overcome this problem, such as Figure 7 As shown, the inventors discovered that the impregnation compound 12 can adsorb onto the particles 6 of the sintered body. This can be done before potting the capacitor, or by adding this compound to the electrolyte. In the case of the electrolyte, the concentration of the impregnation compound can be from 10 to 200 ppm by weight. As shown, the wettability of the electrolyte is improved, thus allowing a larger portion of the capacitor to be used for capacitive interaction.

[0133] exist Figure 8In the diagram, capacitor 13 is shown in schematic cross-section. Capacitor 13 has a housing 14 enclosed by a cover 15. Within this housing formed by the housing 14 and the cover 15, a winding element 16 is assembled. Although not explicitly described, the winding element includes a cathode, which is not limited to this. Furthermore, it also includes an anode, which can be any of the aforementioned anodes. Additionally, two lead contacts 17 are provided to contact the anode and cathode. Furthermore, the anode and cathode in the winding element are separated by a spacer paper. The spacer paper is impregnated in an electrolyte. Optionally, the electrolyte may contain the aforementioned substances for passivating cracks and increasing wettability. Furthermore, the electrolyte used herein preferably has a conductivity of 660 μS / cm or less and a water content of 1 to 10%. Therefore, the thickness of the spacer paper can be reduced to 40 μm or even less.

[0134] List of reference numerals

[0135] 1. Substrate

[0136] 2 First primary surface

[0137] 2' Modified first primary surface

[0138] 3 Second Main Surface

[0139] 3' Modified second primary surface

[0140] 4 First sintered body

[0141] 5 Second sintered body

[0142] 6 particles

[0143] 7 Oxides

[0144] 8 Crack sites

[0145] 9. Passivation compounds

[0146] 10 Partial Oxides

[0147] 11 Electrolytes

[0148] 12 Impregnation compounds

[0149] 13 Capacitors

[0150] 14. Shell

[0151] 15 Covers

[0152] 16 Winding elements

[0153] 17 Lead Contacts

Claims

1. An electrode having a substrate and a sintered body on a first main surface of the substrate, wherein The substrate comprises or is composed of a first valve metal. The sintered body comprises or is composed of fused or sintered particles, wherein the fused or sintered particles contain or are composed of a second valve metal. The first main surface is surface modified.

2. The electrode according to claim 1, wherein the surface modification is an increase in surface area and / or surface roughness compared to the unmodified substrate surface.

3. The electrode according to claim 1, wherein the surface modification is configured to increase the adhesion of the sintered body or the particles of the sintered body to the surface compared to the unmodified substrate surface.

4. The electrode according to claim 1, wherein the surface modification includes a protruding portion.

5. The electrode according to claim 1, wherein the surface modification is chemical or electrochemical surface etching.

6. The electrode of claim 1, wherein the surface modification includes indentations recessed into the substrate.

7. The electrode according to claim 1, wherein the surface roughness R produced by surface modification a The average particle size of the particles is on the same order of magnitude as or smaller than the average particle size of the sintered body.

8. The electrode according to claim 1, wherein the particles of the sintered body have an average size of 0.5 μm to 20 μm.

9. A capacitor element comprising the electrode as an anode according to claim 1.

10. A capacitor comprising a capacitive element as claimed in claim 9 disposed in a housing.

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