Cathode, electrolytic capacitor containing it, and process for forming the cathode

Abstract

An electrode for an electrolytic capacitor, preferably a wound electrolytic capacitor, is provided, the electrode comprising a carrier substrate and a first metallization on a first side of the carrier substrate.

Description

Field of Invention 【0001】 This specification relates to electrodes and electrolytic capacitors equipped with electrodes. Related technology description. 【0002】 Electrolytic capacitors, especially wound electrolytic capacitors, are extremely important in various technologies for short-term storage of electrical energy or other applications. 【0003】 There is a continuing demand for improved volumetric efficiency in electrolytic capacitors. This means that capacitors need to be smaller while maintaining the same capacitance; in other words, this demand means that capacitors can achieve increased capacitance while maintaining their size. 【0004】 However, in the case of conventional wound electrolytic capacitors with etched aluminum cathodes and anodes, and a separator between the cathodes and anodes, possible improvements are hindered by physical constraints related to both the manufacturing process and functional requirements of wound electrolytic capacitors. 【0005】 U.S. Patent No. 7,990,681 and U.S. Patent Application Publication No. 2004 / 0100756 describe electrolytic capacitors with cathode thicknesses ranging from 15 to 60 μm, or even up to 80 μm. 【0006】 The problem to be solved by the present invention is to improve upon capacitors known from the prior art and to disclose a cathode suitable for the improved capacitor. 【0007】 The above problems can be at least partially solved by the electrode described in claim 1, or a capacitor equipped with such an electrode. 【0008】 In a first embodiment, electrodes for an electrolytic capacitor, preferably a wound electrolytic capacitor, are described. The electrodes comprise a carrier substrate and a first metallization on a first side of the carrier substrate. It is particularly preferable that the first metallization is formed on the first side of the carrier substrate. Therefore, it is also particularly preferable that the first metallization is attached to or bonded to the first side of the carrier substrate. 【0009】 The electrode structure according to the first embodiment is preferably applied to the cathode of a wound electrolytic capacitor. The electrode is most preferably a cathode. This means that the principle described below is particularly relevant to the cathode. However, the principle described herein can also be similarly applied to the anode of a wound electrolytic capacitor. 【0010】 The electrodes may be in the form of foil. In particular, the electrodes may be electrode foil. As a result, it is preferable that the metal-coated carrier substrate is also in the form of foil. The carrier substrate may also be a carrier substrate foil. 【0011】 The electrodes described above enable the manufacture of electrolytic capacitors with higher volumetric efficiency, especially when the electrode is the cathode. 【0012】 The inventors have found that thin metal coatings in the thickness range of 0.01 to 1 μm can be sufficient to replace the function of conventional cathodes, so the teachings of the present invention are suitably applicable to cathodes. On the other hand, in the case of conventional anodes, thicker metal coatings would be more advantageous in order to enable the formation of deep etched structures or oxide layers. 【0013】 The inventors found that conventional electrodes, particularly conventional aluminum cathodes for wound electrolytic capacitors, require a relatively thick, unetched core to provide sufficient stability and tensile strength for handling in state-of-the-art roll-to-roll processes. Otherwise, the correspondingly constructed electrodes can crack or break. Therefore, conventional etched aluminum cathodes are virtually impossible to make thinner than 15 μm for handling in state-of-the-art roll-to-roll processes. 【0014】 The inventors of this invention thoroughly analyzed the cathode structure, taking into account production in a roll-to-roll process and the electrical function in a wound electrolytic capacitor. Because the manufacturing process applies longitudinal stress to the cathode, the cathode requires sufficient stability, particularly sufficient tensile strength, to withstand this stress. In a wound electrolytic capacitor, the cathode must provide at least a conductive surface that provides capacitance. Furthermore, to provide sufficient capacitance, it is highly preferable that the conductive surface is also surface-hardened. In conventional cathodes, the entire cathode is composed of aluminum, a similar metal, or an alloy, where the metal provides both tensile strength and conductivity, thus both functions intersect. However, this structure requires a certain minimum thickness. Considering this, the inventors separated the electrical function portion from the function portion that provides stability or tensile strength. The latter function is provided by the carrier substrate, while the electrical function is provided by the metal coating. Thus, the metal coating formed on the surface of the carrier substrate can provide the conductivity and other electrical functions required for a coiled electrolytic capacitor, while the carrier substrate can prevent the electrodes from cracking or breaking during the roll-to-roll process. The carrier substrate has a first metal coating on its first side, which may not itself provide electrical function, while the metal coating provides electrical function. The carrier substrate may be nonmetallic, nonconductive, or insulating. In this case, since the density of the nonmetallic material may be lower than that of the metal, it is also possible to reduce the weight of the cathode, and therefore the weight of the wound electrolytic capacitor. 【0015】 The inventors have recognized that by providing a carrier substrate, it is possible to reduce the thickness of the electrical functional portion, which is a metal coating, to 0.01 to 1 μm. Furthermore, the entire electrode can also be thinner than conventional electrodes. Alternatively, the combination of the electrode with a separator according to the first embodiment can be made thinner in a wound capacitor than conventional electrodes with a separator, as will be described in more detail below. In either case, the volumetric efficiency of the capacitor can be increased accordingly. 【0016】 The cathode according to the present invention can be thinner than conventional cathodes. This, in particular, can improve volumetric efficiency. A thinner cathode allows wound electrolytic capacitors to be made smaller while maintaining a constant capacitance. Alternatively, if it is possible to thin one layer, such as the cathode, the area of ​​the layer in the wound capacitor coil can be increased. The free volume obtained by the reduction in thickness makes it possible to increase the area of ​​all components in the coil of the wound electrolytic capacitor. This area can be increased by providing longer electrodes in the wound electrolytic capacitor coil. 【0017】 The metal coating preferably comprises aluminum. In particular, the metal coating is preferably made of aluminum. The metal coating may consist of aluminum and aluminum-derived compounds such as aluminum oxides and hydroxides. Aluminum has high conductivity, can be advantageously processed using thin-film techniques, and can form metal coatings with a thickness range of 0.01 to 1 μm. In addition, aluminum can be easily surface-hardened or etched. 【0018】 Furthermore, in the electrode, it is preferable that the carrier substrate has a higher tensile strength than the first metal coating. 【0019】 In particular, the carrier substrate material preferably has a higher tensile strength than the metal coating along at least one spatial direction. 【0020】 In particular, it is preferable that the tensile strength of the carrier substrate in the winding direction, i.e., the long extension direction (longitudinal direction) of the electrodes of a wound electrolytic capacitor, be higher than the tensile strength of the metal coating. This makes it possible to make the electrodes thinner than when the electrodes are made of pure or mainly metal coating material. 【0021】 Therefore, in the case of an aluminum metal coating on a carrier substrate having higher tensile strength than aluminum, the electrode can be made thinner, as in the case where the electrode is made of pure aluminum. Nevertheless, the thinner electrode can still cope with the tensile stress of the roll-to-roll process. 【0022】 In a further embodiment, the carrier substrate may have a second metal coating on its second side. In particular, it is preferable that the carrier substrate has a second metal coating formed on its second side. 【0023】 In the case of an insulating, non-conductive substrate into which the electrolyte of a wound electrolytic capacitor cannot penetrate, the electrolyte can come into contact with the metal surface on both sides of the substrate. Therefore, a second metal coating allows the capacitance to be utilized on both sides of the substrate, thereby maximizing the capacitance. This also allows both sides of the electrodes to come into contact with the electrolyte in a stack of conventional wound electrolytic capacitors. Thus, the electrodes can completely replace conventional electrodes, and electrodes that are entirely metallic can also have electrode-electrolyte interfaces on both sides. 【0024】 Furthermore, the carrier substrate also provides tensile strength to the second metal coating. Therefore, in a carrier substrate configuration having first and second metal coatings on both sides, the carrier substrate provides mechanical or tensile strength, while electrical functions are fulfilled by the first and second metal coatings. In particular, it is preferable that the carrier substrate has higher tensile strength than the second metal coating. Furthermore, it is preferable that the materials of the first and second metal coatings are the same. 【0025】 In particular, the carrier substrate is more preferably a continuous or non-porous substrate, or a substrate that is not penetrated by the electrolyte in a wound electrolytic capacitor. The continuous or non-porous carrier substrate allows for a smooth metal coating that can be accessed by non-sophisticated surface enhancement techniques. 【0026】 The carrier substrate particularly preferably contains a polymer material. 【0027】 The inventors of the present invention have found that by using a polymer material for the carrier substrate and two metal coatings on both sides of the polymer substrate, the electrodes can have a thickness in the range of 4 to 7 μm while being able to cope with the stress of the roll-to-roll process. In particular, such electrodes can have a size less than half that of a conventional aluminum cathode, while functionally being able to completely replace the aluminum cathode. The polymer as the carrier substrate material has a lower density than both metals and can provide an excellent weight reduction effect because it allows for thinner electrodes. 【0028】 According to a further aspect, the carrier substrate can at least partially serve as an electrolyte-containing separator or an electrolyte-retaining separator for an electrolytic capacitor. Furthermore, the second side of the carrier substrate in this aspect has no metal coating or remains without a metal coating. 【0029】 This means that this aspect relates to a configuration in which only one metal coating is present on a carrier substrate that can at least partially serve as an electrolyte-containing separator or an electrolyte-retaining separator. 【0030】 In a conventional capacitor configuration, a separator always exists between the anode and the cathode, and the separator itself has a necessary thickness for electrical engineering requirements such as providing sufficient insulation and a sufficient distance between the cathode and the anode. 【0031】 If the carrier substrate material is similar to that of a separator, or can at least partially perform the role of a separator in a wound electrolytic capacitor, and only one side is metal-coated, then the electrolyte can penetrate or immerse itself in the carrier substrate, thereby allowing access to the metal coating from both sides. This allows for a simpler production process since only one side needs to be metal-coated, while also creating a second anode / cathode gap that can increase capacitance. 【0032】 Furthermore, the inventors have found that, in terms of volume or function, the carrier substrate can at least partially replace the separator in a wound electrolytic capacitor configuration. In particular, since the carrier substrate can perform at least a portion of the separation function, the thickness of the separator can be reduced. For example, the thickness of the separator may be reduced to approximately the same extent as the thickness of the carrier substrate. As will be described in more detail below, even a carrier substrate thick enough to completely replace the separator is possible. 【0033】 This means that, in this embodiment, the total thickness of the carrier substrate, which can partially perform the role of a separator, and the separator (which may or may not be present) can be thinner than the total thickness of a conventional electrode and a conventional separator. 【0034】 It is particularly preferable that the carrier substrate can be permeated or immersed by the electrolyte, at least partially. In particular, it is preferable that the material of the carrier substrate can be permeated or immersed by the electrolyte of the electrolytic capacitor. This has the advantages described above. 【0035】 In particular, to achieve this, the carrier substrate may be porous. The carrier substrate may also be sponge-like. 【0036】 Alternatively, the carrier substrate may be a fibrous carrier substrate. This means that the material of the carrier substrate comprises fibers. The fibers may be natural fibers or artificial fibers. Natural fibers are more preferred because they are more readily wetted by the electrolyte. An example of a natural fiber that can be suitably used and included in the substrate is cellulose fiber, which exhibits favorable wetting behavior with the electrolyte. 【0037】 If the carrier substrate is fibrous, it may be preferable that the fibers are woven together such that a macroscopically interwoven superpattern is formed. However, the fibers may also be nonwoven, which does not rule out the possibility of some degree of order existing at the micro or mesoscopic level. In this case, the fibers may be loose, naturally clumped together, or compressed, matted, or felted. For paper-like substrates, it is most preferable to compress the substrate by calendering to increase its tensile strength. Therefore, paper-like substrates are preferably calendered. Alternatively, increased tensile strength may be provided by having a woven substrate. Woven fabrics can increase tensile strength in all spatial directions. Nonwoven substrates may be more advantageous than woven substrates in that they are more easily immersed in electrolytes. 【0038】 In particular, the carrier substrate may be a separator material. The material is preferably paper or contains paper. 【0039】 The fibrous or porous materials described above may offer even higher tensile strength than metal coatings. 【0040】 This allows the carrier substrate to fulfill two roles: firstly, it can hold the metal coating, and secondly, it can at least partially function as a separator. 【0041】 In another embodiment, the carrier substrate may have a thickness of less than 15 μm. Furthermore, the metal coating may have a thickness in the range of 0.01 to 1 μm. It is even more preferable that the entire electrode has a thickness of less than 15 μm. 【0042】 Furthermore, the metal coating can be surface-strengthened, thereby achieving a density of at least 5 μF / cm². 2 A surface capacitance of at least 20 μF / cm² is provided for the metal coating. 2 It is even more preferable to provide the surface capacitance. 【0043】 Surface hardening can be achieved by various methods. This may include applying a metal coating to a rough surface of the carrier substrate, thereby roughening even a thin metal coating. Furthermore, post-deposition treatments such as lithography, etching, or electrochemical etching may be applied. 【0044】 Surface strengthening of electrodes can improve the capacitance of wound electrolytic capacitors, especially when applied as the cathode in such capacitors. 【0045】 In a further embodiment, the carrier substrate provides a tensile strength of at least 10 N / cm to the electrode. Such tensile strength enables handling in a roll-to-roll process. 【0046】 In a further embodiment, the metal coating may comprise multiple layers. Several methods for forming the metal coating on a carrier substrate, as described below, can result in a very thin metal film as the metal coating. 【0047】 Providing multiple layers by stacking them one by one on top of the previous layer is advantageous because it allows for achieving the desired thickness. Sufficient thickness enables deeper three-dimensional structures, which can, for example, allow for improved surface strengthening through post-treatment. 【0048】 In particular, when the metal coating is layered or comprises multiple layers, it is preferable that each layer of the metal coating be ribbon-shaped or strip-shaped. These can then be arranged vertically in a mesh pattern, forming raised and recessed portions, thereby increasing the surface area of ​​the metal coating. 【0049】 In another embodiment, a wound electrolytic capacitor is described. The capacitor according to this embodiment comprises an anode and a cathode, the cathode having the characteristics of an electrode in which only one side of the carrier substrate is metal-coated, and the carrier substrate may partially act as a separator. All preferred embodiments described for this type of electrode or cathode are also applicable to this wound electrolytic capacitor. 【0050】 In this wound electrolytic capacitor, a separator is placed between the metal-coated first side of the carrier substrate and the anode side of the carrier substrate facing this metal-coated first side. Furthermore, the first separator and the carrier substrate, which can at least partially function as an electrolyte-containing separator or electrolyte-retaining separator, are immersed in an electrolyte. 【0051】 In this configuration, the carrier substrate can at least partially act as a separator for the gap between the cathode and anode, which does not have a first separator. In other words, the carrier substrate can at least partially function as a separator between the inside of the first metal coating and the anode side facing the second side of the carrier substrate. 【0052】 It may be preferable that there be no additional separator in the gap formed between the second side of the carrier substrate that is not metal-coated and the anode side of the carrier substrate that faces this second side. 【0053】 In this case, the role of the separator is entirely fulfilled by the carrier substrate. 【0054】 However, according to another alternative embodiment, an additional second separator can be placed between the second side of the carrier substrate, which is the side that is not metal-coated, and the anode side of the carrier substrate facing the second side. 【0055】 In this case, it is possible to have a thinner second separator, such as when the substrate cannot perform the role of a separator at least partially. 【0056】 Therefore, even in such configurations, and in configurations without a second separator, it is possible to improve the volumetric efficiency of the wound electrolytic capacitor by having a thinner thickness by combining the cathode with an optional second separator. Note that the optional second separator can be replaced entirely or at least partially by the cathode. 【0057】 In another embodiment, a wound electrolytic capacitor is described having an anode and a cathode which is an electrode having a carrier substrate with metal coatings on both sides, wherein in the coil of the wound electrolytic capacitor, two separators are arranged between the metal-coated sides of the cathode and the anode side facing the cathode. 【0058】 As described above, the tensile strength of the carrier substrate can be less than the tensile strength of a portion of a conventional electrode made solely of metal, so the cathode can be thinner than a conventional cathode. 【0059】 Lead tabs, assembled on the surface of the electrode and wound into the wound electrolytic capacitor, can make contact with the anode or cathode in the wound electrolytic capacitor. In particular, lead tabs can be applied to cathodes that are metal-coated on both sides. Applying lead tabs is technically straightforward when the substrate is homogeneous and solid. For this reason, it is particularly preferable for the substrate to be non-porous or non-fibrous for the application of lead tabs. This is preferably achieved for substrates that are metal-coated on both sides and therefore do not need to be fibrous or porous. The lead tabs may be applied to the electrode, for example, by cold pressing. 【0060】 In the case of a cathode where the carrier substrate can at least partially act as a separator, the application of lead tabs is technically more difficult because the morphology of the carrier substrate material is often more irregular. Particularly in this case, and also in the case of a cathode with metal coatings on both sides, the following configuration is preferable: In a wound electrolytic capacitor, it is preferable that at least a portion of the cathode extends the anode toward one side of the capacitor coil, and the extended portion of the cathode has a metal cover that covers at least a portion of the side, allowing external contact. 【0061】 If the cathode extends towards the bottom or top of the capacitor coil, this side can be covered with a metal cover to connect the extended cathode winding. In this way, at least some individual windings are connected in parallel by the metal cover, thus reducing the equivalent series resistance (ESR). In particular, this type of connection can be more advantageous than lead tabs. 【0062】 In a wound electrolytic capacitor configuration, the metal cover can serve as an external contact for the cathode, or negative terminal. External contacts for the anode can be provided via lead tabs. 【0063】 In all of the above-described wound electrolytic capacitors having the electrode defined above as the cathode, reducing the thickness allows for the lengthening of all components of the wound capacitor. That is, in a fixed-size capacitor, the cathode, anode, and separator can be lengthened because the volume required by the cathode within the coil is reduced. For example, if the cathode is thin, the length of the anode can be increased by 7% to 20%, and so can the other components, potentially increasing the capacitance by 7% to 15% compared to conventional volume or external-size capacitors. 【0064】 In another embodiment, the use of the above-described electrodes as cathodes in wound electrolytic capacitors is described. The advantageous characteristics and benefits of the electrodes, and the details given with respect to wound electrolytic capacitors, are also applicable to the use of the electrodes as cathodes in wound electrolytic capacitors. 【0065】 Furthermore, a process for forming electrodes for a wound electrolytic capacitor in a roll-to-roll process is described, wherein a carrier substrate is continuously wound from a first roll, a metal coating is continuously applied to at least a portion of the first side of the carrier substrate, and the metal-coated portion of the carrier substrate is continuously wound onto a second roll. 【0066】 The carrier substrate may have the characteristics defined above. In particular, the electrodes may provide sufficient tensile strength to be processed in a roll-to-roll process. This is suitable for the present roll-to-roll process, but also for roll-to-roll applications for forming wound electrolytic capacitor coils. 【0067】 Furthermore, a second metal coating may be applied to the second side of the carrier substrate. 【0068】 In this process, the metal coating may be applied to the carrier substrate, i.e., the first side and / or second side, by physical vapor deposition, atomic layer deposition, chemical vapor deposition, or galvanic current application. Physical vapor deposition may be, for example, thermal deposition, electron beam deposition, sputtering, or pulsed laser deposition. These techniques can produce thin or ultrathin metal coatings with thicknesses ranging from 0.01 to 1 μm. 【0069】 In a further embodiment, the formed metal coating may be post-treated by plasma etching, electrolytic etching, or lithography. This makes it possible to achieve the surface strengthening described above. 【0070】 In a further embodiment, the metal coating may be formed as a layer in a subsequent roll-to-roll process step, or in a single roll-to-roll process step in which the metal coating sublayer is applied from several sources. 【0071】 Having a multilayer metal coating may offer the advantages mentioned above. 【0072】 In particular, a sublayer may be formed in a subsequent deposition step, or a subsequent roll-to-roll step, or a single roll-to-roll step using several deposition sources, having the form of a ribbon or strip and applicable to form a mesh pattern. 【0073】 This strengthens the surface, which means that a larger surface area can be formed. 【0074】 Furthermore, a process is described for forming a capacitor including the above-described electrodes, that is, a process including the above-described process, which includes winding the electrodes in a roll-to-roll process, wherein the cathode is such an electrode, accompanied by the anode and the separator described in the above embodiments, and further includes impregnation or immersion with an electrolyte. 【0075】 Furthermore, lead tabs, or several lead tabs, may be applied to the cathode and / or anode, for example, by welding. This can be particularly suitable for cathodes having metal coatings on both sides. In addition, or alternatively, a metal cover may be provided for wound electrolytic capacitors having a cathode extending toward one side of the wound electrolytic capacitor. For example, the metal cover may be applied by metal spraying, which may be a thermal spraying process. Examples of thermal spraying processes or techniques include arc, flame, plasma, high-speed oxygen fuel, or other spray layer deposition methods. Alternatively, a combination of these may be applied to one or more metals to form a metal cover. [Brief explanation of the drawing] 【0076】 The present invention will be described in more detail below by examples of embodiments and with reference to the figures. The figures include both embodiments and process-related information. Note that in schematic diagrams or representations, components are not shown to scale. In these, the size, length, or ratio of the components may be distorted. Such ratios may not be obtained from the schematic diagrams. [Figure 1] Figure 1 shows an electron microscope image of an aluminum cathode etched using a conventional method. [Figure 2] Figure 2 is an electron microscope image of an aluminum cathode etched with alternating current (AC). [Figure 3] Figure 3 shows a cross-sectional electron image of a conventional electrode made of a perfect metal. [Figure 4] Figure 4 is a schematic diagram of the first embodiment of the cathode. [Figure 5] Figure 5 is a schematic diagram of a second embodiment of the cathode. [Figure 6] Figure 6 is a schematic diagram of a third embodiment of the cathode. [Figure 7] Figure 7 is a schematic diagram of a first embodiment of the process for forming a cathode. [Figure 8] Figure 8 shows a second embodiment of the process for forming a cathode. [Figure 9] Figure 9 shows a wound electrolytic capacitor. [Figure 10] Figure 10 is a schematic diagram of a first embodiment for stacking wound electrolytic capacitors. [Figure 11] Figure 11 is a schematic diagram of a second embodiment of stacking in wound electrolytic capacitors. 【0077】 Figure 1 shows a secondary electron image recorded by a scanning electron microscope of a common cathode made of alumina, etched using a simple electrochemical etching process. Surface strengthening can be achieved in this way. As can be seen from Figure 1, the surface strengthening, or the three-dimensional structure of the surface, is irregular. 【0078】 Similar etching can also be applied to electrodes or cathodes according to the present invention. 【0079】 Figure 2 shows a secondary electron image recorded by a scanning electron microscope of an aluminum-based cathode foil etched using a sophisticated alternating current (AC) etching method. This allows for the production of more regular and orderly structures than the less sophisticated electrochemical etching shown in Figure 1. 【0080】 Therefore, as can be seen from Figure 2, AC etching yields a more regular surface structure, resulting in better efficiency in terms of capacitance and capacitance increase relative to weight loss. 【0081】 Figure 3 shows a cross-sectional electron microscope image of a conventional cathode. It was found that the conventional cathode is relatively thick, with a thickness of approximately 40 μm. Conventionally, the thickness of such cathodes has been in the range of 15 to 60 μm. In particular, the roll-to-roll process used in the production of wound electrolytic capacitors needs to meet a certain tensile strength of at least approximately 10 N / cm. To achieve this, the unetched areas (the areas sandwiched between the two brighter regions in Figure 3) must not be too thin. 【0082】 The inventors of the present invention have recognized that by separating the parts that provide mechanical strength from the technically relevant parts, which are metal or conductive surfaces, it is generally possible to reduce the thickness of the electrodes, particularly the cathode, thereby reducing the volume of the wound electrolytic capacitor or increasing the length or area of ​​all the components wound around the wound electrolytic capacitor to increase the capacitance in a given volume. 【0083】 Figure 4 shows a schematic diagram of a first embodiment of cathode 1 as an example for electrodes. Cathode 1 is in the form of a film or is a cathode film. Cathode 1 comprises a carrier substrate 2. The carrier substrate 2 is non-conductive or non-metallic. A metal coating 3 is assembled on a first surface of the carrier substrate 2. The metal coating 3 can be formed on the first surface of the substrate 2. Cathode 1 is suitable for incorporation into a wound electrolytic capacitor. 【0084】 It should be noted that the principles described here and below for the cathode can also be applied to the anode of a wound electrolytic capacitor, insofar as they are technically applicable. 【0085】 The carrier substrate 2 has a higher tensile strength than the metal coating 3. In particular, the carrier substrate 2 can provide the electrode with a tensile strength of at least 10 N / cm. 【0086】 A metal coating is a thin metal film that can be applied by various techniques, as described below. The metal coating must have a density of at least 5 μF / cm². 2 The surface may be hardened to provide a specific capacitance. The metal coating 3 has a thickness of 0.01 to 1 μm. The metal coating may consist of or be composed of any suitable metal or alloy. However, the metal coating is most preferably made of aluminum. The electrode preferably has aluminum as its main component. The electrode may be made of aluminum. 【0087】 The metal coating 3 can perform the electrical functions of a conventional metal electrode. However, since stability and tensile strength are provided by the carrier substrate 2, the metal coating 3 can be much thinner than a conventional electrode. 【0088】 In particular, the carrier substrate 2 may be a polymer substrate with a thickness of less than 15 μm. In this case, a second metal coating is preferred, as described below. 【0089】 Alternatively, the carrier substrate 2 can at least partially perform the role of an electrolyte-containing separator or electrolyte-retaining separator for an electrolytic capacitor. In particular, the carrier substrate 2 may be permeable to or immersed in the electrolyte of the electrolytic capacitor. For this purpose, the carrier substrate 2 may be porous or fibrous. The fibers may be of any properties, but cellulose fibers are most preferred. In particular, the substrate can be made of a paper-like material similar to the material of the separator in an electrolytic capacitor. Alternatively, woven or nonwoven fibers may also be used. Due to these properties, the cathode 2 shown in Figure 4 is most suitable when the carrier substrate 2 has only the first metal coating 3 and no further metal coatings. In this case, the thickness of the carrier substrate can be less than 15 μm. However, if the carrier substrate is intended to completely replace the separator in a wound electrolytic capacitor, the thickness can be greater. 【0090】 Figure 5 shows a schematic diagram of a second embodiment of cathode 1. Cathode 1 may have the same properties as those described for the first embodiment shown in Figure 4. However, in the case of the cathode according to Figure 5, the carrier substrate 2 cannot be permeated by the electrolyte. The carrier substrate 2 is most preferably comprising or composed of a polymer. Suitable polymer examples are polypropylene (PP) or polyethylene terephthalate (PET). In the second embodiment, a first metal coating 3 and a second metal coating 4 are formed on the carrier substrate 2. The metal coatings 3 and 4 may be identical in terms of their properties and structure. 【0091】 In the case of a non-penetrating substrate, cathode 1 can completely replace all the electrical functions of the conventional cathode. 【0092】 In this case, the overall thickness may be less than 16 μm. Specifically, the carrier substrate may have a thickness of less than 15 μm, and the metal coatings 3 and 4 each have a thickness of 0.01 to 1 μm. It is more preferable that the electrodes have a thickness of less than 10 μm. The polymer substrate may have a thickness in the range of 1 to 7 μm, while it is even more preferable that the metal coatings have the thickness defined above. Overall, this allows the cathode to have a thickness in the range of 3 to 7 μm, which is most preferable. Therefore, using the electrodes of Figure 4, a considerable reduction in thickness can be achieved compared to conventional cathodes. Thus, the thickness can be reduced by more than 50% compared to conventional cathodes. 【0093】 Figure 6 shows a schematic diagram of a third embodiment of cathode 1. The cathode 1 of the third embodiment is identical in characteristics to the cathode of the second embodiment, as shown in Figure 5. However, the metal coatings 3 and 4 each include sub-layers 3' and 4', respectively. The metal coatings are layered. 【0094】 By having multiple layers, it is possible to achieve the desired film thickness by depositing several layers on other layers using various thin-film deposition techniques. In this way, the desired thickness for post-deposition treatment of the metal coating may be formed. 【0095】 Furthermore, it is also possible to have discontinuous layers, such as layers in the form of ribbons or strips arranged rectangularly to form a mesh pattern. This mesh pattern forms depressions and ridges on the surface, thereby reinforcing the active surface. 【0096】 Figure 7 shows a schematic diagram of a first embodiment of a roll-to-roll process. In a roll-to-roll process for forming the cathode of a wound electrolytic capacitor, a carrier substrate 2 is provided on a first roll 5. The carrier substrate 2 is continuously unwound from the first roll 5. The carrier substrate 2 may pass through one or more guide rolls 6 that guide or redirect the carrier substrate 2. The carrier substrate 2 is continuously unwound onto a second roll 9. Between the first roll 5 and the second roll 9, at least one side of the carrier substrate 2 is metal-coated by a first metallizer 7. In particular, the metallizer 7 may be any device capable of applying or forming the first metal coating on the first side of the carrier substrate 2. In particular, the metal coating is preferably performed by a physical deposition technique (PVD technique) such as thermal deposition, electron beam deposition, sputtering, or pulsed laser deposition. Alternatively, atomic layer deposition or chemical deposition may be applied. The metallizer 7 can be placed in any technically appropriate location. In the depiction in Figure 7, the metallizer 7 is positioned facing the guide roll 6, which ensures that the passing film is in a stable position relative to the metallizer 7. 【0097】 Using the configuration shown in Figure 7, it is possible to coat one side of the carrier substrate 2 in a single run to achieve the configuration shown in Figure 4. In particular, this is suitable for cathodes that can at least partially perform the role of an electrolyte-containing separator or electrolyte-retaining separator for electrolytic capacitors. 【0098】 In the case of polymer substrates or similar substrates, a second metal coating can be applied in a similar manner by applying a metal coating to the second side of the carrier substrate 2 in a second roll-to-roll process. 【0099】 After the described roll-to-roll process, the metal coating may be surface-hardened. In particular, plasma etching, electrolytic etching, or lithography can be applied. 【0100】 Alternatively, or in addition to the above, it is also possible to obtain a layered structure as shown in Figure 6 by performing multiple layers of metal coating deposition on the surface. This makes it possible to apply partial layers, such as ribbons or strips, in a mesh pattern to form a surface-reinforced metal coating. 【0101】 Figure 8 shows a schematic diagram of a second embodiment of the process for forming the cathode. 【0102】 The principle is similar to that described for the first embodiment of the process shown in Figure 7. In particular, the carrier substrate 2 is continuously unwound from the first roll 5 and continuously wound onto the second roll 9. Between the first roll 5 and the second roll 9, the carrier substrate passes through several guide rolls 6. The guide rolls help to expose two different sides of the carrier substrate 2 at different points. 【0103】 The carrier substrate 2 first passes through a first metallizer 7 that metal-coates the first side of the carrier substrate 2. After being re-guided by several guide rolls 6, the carrier substrate 2 passes through a second metallizer 8 that metal-coates the other side (second side) of the carrier substrate 2. Both the first and second metallizers are positioned facing the guide rolls 6 for the reasons explained in Figure 7. 【0104】 For example, an alternative configuration is possible in which the second metallizer is positioned so as to face the second side of the carrier substrate 2, thereby eliminating the need for guidance by guide rolls. 【0105】 This configuration allows both sides of the capacitor to be metal-coated within a single roll-to-roll process to form the structure shown in Figure 5. 【0106】 It is also possible to form a layered metal coating by using several evaporators for one side in a single configuration, by having multiple roll-to-roll processes in sequence, or by having a special metallizer. 【0107】 Figure 9 shows a wound electrolytic capacitor 10 with all coil components (invisible) inside the capacitor. The wound electrolytic capacitor 10 is equipped with a side cover 11 that can protect the internal coil from physical shock. 【0108】 Furthermore, a metal cover 13 is provided at the bottom of the wound electrolytic capacitor 10. In this particular case, the metal cover 13 may allow external contact of the cathode, as described below. The anode may be in contact via several lead tabs 12 included in the wound capacitor coil. For example, the metal cover may be applied by metal spraying, which may be a thermal spraying process. Examples of thermal spraying processes or techniques include arc, flame, plasma, high-speed oxygen fuel, or other spray layer deposition methods. Alternatively, a combination of these may be applied to one or more metals to form the metal cover. 【0109】 Figure 10 shows a schematic diagram of the capacitor coil of a wound electrolytic capacitor. The coil is partially unfolded to show the stacking of layers. The wound electrolytic capacitor comprises an anode 16 in the form of an anode film and a cathode 1. The anode 16 may be a conventional anode having a thickness in the range of 110 to 130 μm. The cathode 1 may have the above characteristics and may, in particular, be a cathode having a carrier substrate that can at least partially perform the role of an electrolyte-containing separator or an electrolyte-retaining separator. In particular, the description given for Figure 4 may fit the cathode 1. Furthermore, as can be seen from the enlarged view on the right, the cathode 1 is metal-coated on only one side (the first side) of the carrier substrate 2. The first metal coating 3 faces inward and thereby faces the surface facing one side of the anode 16. A first separator 14 is incorporated between this side of the anode 16 and the first side of the substrate 2 on which the metal coating 3 is located. The first separator 14 may have a thickness of 30 to 50 μm. The first separator 14 electrically and spatially separates the cathode 1 and the anode 16 in this gap. Furthermore, the anode 16 is in contact via lead tabs 12 wound around a wound electrolytic capacitor. 【0110】 Both the first separator 14 and the carrier substrate 2, once assembled into the capacitor, are immersed or moistened by the electrolyte of the electrolytic capacitor. 【0111】 In this description, no additional separator is provided in the gap between the second side of the carrier substrate 2, which is the side without the metal coating, and the side of the anode 16 facing this side in the wound electrolytic capacitor coil. In this case, the carrier substrate 2 can fully perform the role of the second separator. In particular, the carrier substrate 2 can contain or be immersed in an electrolyte. This allows for the diffusion of the electrolyte. This spatially and electrically isolates the first metal coating 3 from the anode 16 toward the second side of the carrier substrate 2. 【0112】 However, alternatively, the second separator may be arranged in a similar manner, as illustrated in Figure 11. However, in the case of the depiction in Figure 10, the thickness of the second separator can be reduced to almost the thickness of the carrier substrate. This is due to the fact that the carrier substrate can at least partially perform the role of a separator. 【0113】 The overall thickness of the combination of cathode 1 and a potential second separator (which is not present at all in Figure 10) can be less than the sum of the thicknesses of a conventional cathode and an adjacent conventional separator. In the case of a conventional separator, the cathode may have a thickness of more than 15 μm, and the separator may have a thickness in the range of more than 30 μm. In the present invention, the entire cathode, with a substrate that can at least partially perform the role of a separator, can have a thickness of 3 to 7 μm. In this case, the additional separator (which is not the first separator) may have a thickness in the range of 15 to 25 μm. Thus, a thickness reduction of at least 28% can be achieved. 【0114】 Furthermore, the cathode 1 has a width that extends toward the bottom side of the capacitor coil. The width is extended relative to the size of the anode 16 in the coil. A metal cover 13 is applied to the bottom (the side of the capacitor coil) which contacts each individual winding of the cathode 1. This allows external contact of the cathode, and a low equivalent series resistance (ESR) is achieved by the parallel circuit formed by the metal covering. Contact of the anode is made via lead tabs. 【0115】 Alternatively, lead tabs for the cathode could be provided, but this is not preferable for the reasons mentioned above. In addition, if the thin metal film is provided on a porous or fibrous substrate, it is technically difficult to attach the lead tabs to the thin metal film. 【0116】 Figure 11 shows a schematic diagram of a second embodiment of the coil of a wound electrolytic capacitor. Generally, the characteristics of the second coil may be the same as those of the first coil shown in Figure 10. However, in this case, the cathode 1 is a cathode having two metal coatings 3 and 4 on both sides of the carrier substrate 2, as shown in Figure 5. 【0117】 Cathode 1 may have a thickness in the range of 3 to 7 μm, which is at least half that of a conventional aluminum cathode. 【0118】 The anode 16 may have a thickness in the range of 110 to 130 μm. Furthermore, again, the first separator 14 is assembled between the first side of the cathode 1 and the side of the anode 16 facing this first side of the cathode. Furthermore, the second separator 15 is assembled between the second side of the cathode and the other side of the anode facing the second side of the cathode. Both separators may have a thickness in the range of 30 to 50 μm. 【0119】 Overall, the thickness reduction described above allows for a 7-20% increase in the length of the anode, cathode, and separator compared to conventional wound electrolytic capacitors with a pure aluminum cathode. This enables a 7-15% increase in capacitance. 【0120】 External electrical contacts can be made as described above with respect to Figure 10. However, it should be noted that polymer foil with metal coatings on both sides is more suitable when cathode 1 is also provided with lead tabs for external electrical contacts. 【0121】 However, even with this configuration, the equivalent series resistance can still be reduced by the cathode contact through the metal cover 13. 【0122】 Tables 1 and 2 show an experimental series of 10 capacitors (Cap1 to Cap10) with a size of 30 × 60 mm, according to the embodiment shown in Figure 11. In particular, the capacitors have a double-sided metal-coated polymer film as the cathode. 【0123】 As can be seen from Table 1, a capacitance of 640 to approximately 765 μF was achieved at a frequency of 100 Hz. At a frequency of 100 Hz, the equivalent series resistance was between 590 and 670 mΩ. The impedance measured at this frequency was between 2179 and 2557 mΩ. 【0124】 Similar values ​​were achieved at a frequency of 120 Hz. Specifically, the capacitance was between 634 and 746 μF. The equivalent series resistance was between 567 and 634 mΩ. Furthermore, the impedance was between 1867 and 2177 mΩ. 【0125】 10 4 At Hz, the capacitance is in the range of over 305 μF to 329 μF. The equivalent series resistance is between 247 mΩ and 266 mΩ. The impedance is between 252 mΩ and 271 mΩ. 【0126】 10 5 At Hz, the capacitance is between 103 μF and 119 μF. The equivalent series resistance is between 234 and 252 mΩ. The impedance is between 235 and 252 mΩ. 【0127】 From the frequency dependence in Table 1, the extinction coefficient tan δ between 29 and 34 can be calculated. [Table 1] 【0128】 Furthermore, Table 2 shows that the self-discharge is good. In particular, the current value (LC) after 1 minute of charge loss due to leakage current is... 1 min The leakage current (LC) generated after 2 minutes has been shown to be in the range of 218-260 μA. 2 min The current was between 116 and 150 μA, and the leakage current (LC) generated after 5 minutes was between 116 and 150 μA. 5 min The current is between 61 and 80 μA. 【0129】 Furthermore, Figure 2 shows that a fairly lightweight wound electrolytic capacitor with a size of 30 × 60 mm can be formed using a cathode equipped with a polymer carrier substrate. The weight of the electrolytic capacitor was between 76.9 and 77.5 g. In particular, a weight of less than 77.5 g can be achieved when using a double-sided metal-clad polymer film cathode in a 30 × 60 mm size. [Table 2] [Explanation of symbols] 【0130】 1 cathode 2 Carrier board 3. First metal coating 4. Second metal coating 5. The first roll 6 Guide Roll 7. The First Metalizer 8. The Second Metalizer 9. Second role 10-winding electrolytic capacitor 11 Side cover 12 Lead Tabs 13 Metal cover 14. First separator 15. Second separator 16 Anode [Item of the invention] [Item 1] An electrode for an electrolytic capacitor (10), comprising a carrier substrate (2) and a first metal coating (3) formed on the first side of the carrier substrate (2). [Item 2] The electrode according to item 1, wherein the carrier substrate (2) has a higher tensile strength than the metal coating (3). [Item 3] The electrode according to item 1 or 2, wherein the carrier substrate (2) has a second metal coating (4) formed on the second side of the carrier substrate (2). [Item 4] The electrode according to item 3, wherein the carrier substrate (2) includes a polymer material. [Item 5] The electrode according to item 1 or 2, wherein the carrier substrate (2) can at least partially perform the role of an electrolyte-containing separator or electrolyte-retaining separator for an electrolytic capacitor, and the second side of the carrier substrate (2) is free of a metal coating. [Item 6] The electrode according to item 5, wherein the carrier substrate (2) can be permeated or immersed by the electrolyte of the electrolytic capacitor. [Item 7] The electrode according to item 5 or 6, wherein the carrier substrate (2) is porous. [Item 8] The electrode according to item 5 or 6, wherein the carrier substrate (2) is a fibrous carrier substrate (2). [Item 9] The electrode according to item 8, wherein the carrier substrate (2) contains cellulose fibers. [Item 10] The electrode according to any one of items 1 to 9, wherein the carrier substrate (2) has a thickness of less than 15 μm and the metal coating (3) has a thickness of 0.01 to 1 μm. [Item 11] The metal coating (2) is surface-hardened, thereby providing at least 5 μF / cm 2 An electrode according to any one of items 1 to 10, wherein the specific capacitance is provided. [Item 12] The electrode according to any one of items 1 to 11, wherein the carrier substrate (2) provides the electrode with a tensile strength of at least 10 N / cm. [Item 13] The electrode according to any one of items 1 to 12, wherein the metal coating (3) comprises multiple layers. [Item 14] The electrode according to item 13, wherein the layer of the metal coating (3) is a ribbon, and the layer is arranged such that a mesh pattern is formed by the ribbon. [Item 15] A wound electrolytic capacitor (10) comprising an anode (16), a cathode (1) which is an electrode described in any one of items 5 to 9, and a first separator (14), The first separator (14) is positioned between the metal-coated first side of the carrier substrate (2) and the anode (16) side of the carrier substrate (2) facing the metal-coated first side. A wound electrolytic capacitor (10) in which the first separator (14) and the carrier substrate (2) are immersed in the electrolyte. [Item 16] A wound electrolytic capacitor (10) according to item 15, wherein no additional separator is provided in the gap formed by the second side of the carrier substrate (2) and the anode (16) side of the carrier substrate (2) facing this second side. [Item 17] A wound electrolytic capacitor (10) according to item 15, wherein an additional second separator (15) is disposed between the second side of the carrier substrate (2) and the side of the anode (16) facing this second side of the carrier substrate (2). [Item 18] A wound electrolytic capacitor (10) comprising an anode (16), a cathode (1) which is an electrode as described in item 3 or 4, and two separators (14, 15), A wound electrolytic capacitor (10) in which the two separators (14, 15) are positioned between the metal-coated sides of the cathode (1) and the sides of the anode (16) facing these sides of the cathode (1). [Item 19] A wound electrolytic capacitor (10) according to any one of items 15 to 18, wherein at least a portion of the cathode (1) extends the anode (16) toward one side of the capacitor coil, and the extended portion of the cathode (1) has a metal cover (13) that covers at least a portion of this side, allowing external contact. [Item 20] A process for forming electrodes for wound electrolytic capacitors using a roll-to-roll process, The carrier substrate (2) is continuously unwound from the first roll (5), A metal coating is continuously applied to at least a portion of the first side of the carrier substrate (2), A process in which the metal-coated portion of the carrier substrate (2) is continuously wound onto a second roll (9).

Claims

[Claim 1] A cathode for an electrolytic capacitor (10), The device comprises a carrier substrate (2) and a first metal coating (3) formed on the first side of the carrier substrate (2), The first metal coating (3) comprises a plurality of ribbons arranged in a mesh pattern, The cathode comprises a carrier substrate (2) containing a polymer material, a porous material, or a fibrous material. [Claim 2] The cathode according to claim 1, wherein the carrier substrate (2) has a higher tensile strength than the first metal coating (3). [Claim 3] The cathode according to claim 1, wherein the carrier substrate (2) has a second metal coating (4) formed on the second side of the carrier substrate (2). [Claim 4] A cathode for an electrolytic capacitor (10), The device comprises a carrier substrate (2) and a first metal coating (3) formed on the first side of the carrier substrate (2), The first metal coating (3) comprises a plurality of ribbons arranged in a mesh pattern, The carrier substrate (2) can at least partially perform the role of an electrolyte-containing separator or electrolyte-retaining separator for an electrolytic capacitor. The second side of the carrier substrate (2) is a cathode without a metal coating. [Claim 5] The cathode according to claim 4, wherein the carrier substrate (2) can be permeated or immersed by the electrolyte of the electrolytic capacitor. [Claim 6] The cathode according to claim 4, wherein the carrier substrate (2) is porous. [Claim 7] The cathode according to claim 4, wherein the carrier substrate (2) is a fibrous carrier substrate (2). [Claim 8] The cathode according to claim 7, wherein the carrier substrate (2) includes cellulose fibers. [Claim 9] The cathode according to claim 1, wherein the carrier substrate (2) has a thickness of less than 15 μm, and the first metal coating (3) has a thickness of 0.01 to 1 μm. [Claim 10] The carrier substrate (2) has a load of at least 10 N / cm². ２ The cathode according to claim 1, which provides the cathode with the tensile strength. [Claim 11] A wound electrolytic capacitor (10) comprising an anode (16), a cathode (1) as described in claim 4, and a first separator (14), The first separator (14) is positioned between the metal-coated first side of the carrier substrate (2) and the anode (16) side of the carrier substrate (2) facing the metal-coated first side. A wound electrolytic capacitor (10) in which the first separator (14) and the carrier substrate (2) are immersed in an electrolyte. [Claim 12] The wound electrolytic capacitor (10) according to claim 11, wherein no additional separator is provided in the gap formed by the second side of the carrier substrate (2) and the anode (16) side of the carrier substrate (2) facing this second side. [Claim 13] The wound electrolytic capacitor (10) according to claim 11, wherein an additional second separator (15) is disposed between the second side of the carrier substrate (2) and the side of the anode (16) facing this second side of the carrier substrate (2). [Claim 14] A wound electrolytic capacitor (10) comprising an anode (16), a cathode (1) as described in claim 3, and two separators (14, 15), A wound electrolytic capacitor (10) in which the two separators (14, 15) are arranged between the metal-coated sides of the cathode (1) and the anode (16) facing these sides of the cathode (1). [Claim 15] The wound electrolytic capacitor (10) according to claim 11 or 14, wherein at least a portion of the cathode (1) extends the anode (16) toward one side of the capacitor coil, and the extended portion of the cathode (1) has a metal cover (13) that covers at least a portion of this side, allowing external contact. [Claim 16] A process for forming a cathode for a wound electrolytic capacitor according to claim 1 using a roll-to-roll process, The carrier substrate (2) is continuously unwound from the first roll (5), A metal coating is continuously applied to at least a portion of the first side of the carrier substrate (2), A process in which the metal-coated portion of the carrier substrate (2) is continuously wound onto a second roll (9).

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