The present invention relates to an electrode material, in particular to a cathode foil for an electrolytic capacitor, which can be used in electrolytic capacitors such as a solid electrolytic capacitor and a hybrid capacitor, as well as an electrolytic capacitor.
Examples of functions and properties required in cathodes of hybrid capacitors include:
It can be said that, except for the compatibility with the electrolytic solution in the above (ii) and (iii), these are very important functions and properties also in cathodes for solid electrolytic capacitors.
In relation to this, for a foil provided with a smooth titanium layer on a smooth foil, and further a smooth carbon layer thereon, for example, the adhesion is insufficient with a dispersion of the solid electrolyte of (i) in which an aqueous solution in particular is used as a dispersion medium; the retentivity of the electrolytic solution of (ii) is also poor. Particularly for a solid electrolyte consisting of an electroconductive polymer, it becomes difficult to maintain a good-doped state, and it becomes highly resistant when made into an element. Size reduction of an etched and formed cathode foil is difficult because of its large thickness, hence when combining this with an anode to configure a capacitor, a synthetic capacitance is generated, which ends up lowering the capacitance acquisition rate of the anode. Moreover, there is a problem such that the ESR (Equivalent Series Resistance) is low on the high-frequency side for example of 100 kHz, while the ESR is remarkably high on the low frequency side for example of 120 Hz, resulting in a narrow frequency range for the low-ESR. A contact resistance with the solid electrolyte becomes large, and the portion not coated with the solid electrolyte is dependent on the electrolytic solution, and hence low temperature properties are also a concern.
Furthermore, the cathode foil may also end up being subject to formation locally in the aging anodic oxidation step after element formation, and thus there is also concern of a decrease in capacitance and an increase in resistance. For example, a formation film layer provided to an aluminum base material has a certain protective function against the electrolytic solution. However, for a solid electrolyte consisting of an electroconductive polymer, it is difficult to completely suppress chemical reactions with an acidic electrolytic solution for maintaining a doped state of a chemical polymerizing solution and a solid electrolyte, as well as chemical reactions between a base material and slightly remaining moisture, for example. Moreover, on the other hand, if a natural oxide film and a formation film are in direct contact with the solid electrolyte in the state as-is, there is a problem such that a contact resistance ends up becoming high because a depletion layer is generated at the contact interface.
The thickness of an etched and formed foil provided with an intermediate layer (titanium layer) and a carbon layer is thin, and this foil can retain an electroconductive polymer and an electrolytic solution in an etched layer. However, it is difficult to completely coat the titanium layer and carbon layer provided on the etched layer all the way to the inside of the etched layer, and hence an aluminum oxide layer is necessary (for example, a formation film of approximately several voltages is necessary) to protect a foil from the electrolytic solution, solid electrolyte and chemical polymerizing solution. Although this formation film layer also has a function to protect a foil from the electrolytic solution similarly to that above, because it would act as an insulator as-is, it is highly likely to be a cause of high resistance. Most of these problems can be said to also apply to a solid electrolytic capacitor whose electrolyte consists solely of a solid electrolyte, with no electrolytic solution interposed.
A variety of conventional cathode foils used in electrolytic capacitors such as a solid electrolytic capacitor and a hybrid capacitor have been developed. Patent Literature 1 and Patent Literature 3 describe electrolytic capacitors with an inorganic-based conductive layer formed at the surface of a cathode foil roughened by etching (surface expansion rate of 1.5 to 500-fold). However, these cathode foils have problems such as the following.
Moreover, Patent Literature 4 describes a cathode foil for an aluminum electrolytic capacitor, characterized by: a first layer consisting of at least one kind of a metal, nitride thereof, carbide thereof, carbonitride thereof and oxide thereof formed on an aluminum foil surface; and a second layer consisting of at least one kind of a metal, nitride thereof, carbide thereof, carbonitride thereof and oxide thereof formed on the first layer, where the first layer has a denser structure than that of the second layer. However, the main purpose of the invention according to Patent Literature 4 is to improve the hydration resistance in a cathode for a capacitor which uses only a water-containing electrolytic solution as an electrolyte, and there is room for improvement for further low resistance and durability of a cathode which can be used in an electrolytic capacitor such as a hybrid capacitor and a solid electrolytic capacitor.
Patent Literature 2 describes a cathode foil for a hybrid capacitor using a smooth base material on which a carbon layer is formed. Moreover, Patent Literature 5 describes a cathode foil for a solid electrolytic capacitor which uses a smooth base material, where carbon is present on a metal layer. However, because there is no uneven portion on the surface layer side of these cathode foils, it is considered that there is room for further improvement in ESR and in durability. Moreover, because there is no uneven portion on the surface layer side of the cathode foil, the friction force with a separator paper (isolating paper) is weak, and during the extraction of a winding core jig in the element winding step of the electrolytic capacitor, the cathode foil flies out towards the extraction direction of the winding core jig, and hence a winding deviation malfunction easily occurs.
Patent Literature 9 describes an electrolytic capacitor utilizing a cathode containing a plurality of metal particles having a median diameter of from approximately 20 to 500 micrometers, where the particles are arranged on the surface of a substrate and are sintered and bonded. However, there is room for improvement because this is too large at the micron unit size and a geometrical structure necessary to retain a solid electrolyte and an electrolytic solution cannot be obtained. In addition, Patent Literature 6 to Patent Literature 8, and Patent Literature 10 to Patent Literature 24 can be mentioned as conventional techniques; however, it is considered that there is room for improvement in the function and performance in all of these.
In consideration of the above, the object of the present invention is to provide an electrode material which can be used for example in a cathode foil an electrolytic capacitor having at least one advantage of the below (1) to (7), and an electrolytic capacitor having a cathode foil using such an electrode material:
To solve the aforementioned problem, the present invention provides an electrode material having an oxide layer on a smooth base material and further having an inorganic conductive layer on the oxide layer, in which the inorganic conductive layer has a first conductive layer containing a metal and/or a metal compound, and a second conductive layer containing carbon, the first conductive layer has an uneven portion on the surface layer side thereof, and the second conductive layer is positioned at the outermost layer of the inorganic conductive layer. The ‘smooth base material’ here, in one example, is a base material of which no roughening treatment such as etching was performed; however, it is not necessary for the base material surface to be completely flat. A smooth base material also includes that of which micro coarseness and undulations exist on a surface due to unavoidable slight rolling stripes, scars etc. which occur in a foil base manufacturing process such as rolling processing for example (of course, the base material surface may also be completely smooth). Moreover, the ‘oxide layer’ may also be an oxide layer formed without performing any special treatment such as in a natural oxide film or may also be an oxide layer intentionally formed by treatment such as a formation treatment. The oxide layer may completely or partially coat the smooth base material, and the smooth base material and the first conductive layer may also be in direct contact for example by means of the dense layer material in the first conductive layer penetrating the oxide layer portion (forming a dense layer by the arc ion plating (AIP) method for example, as mentioned below). Furthermore, when the second conductive layer is formed on the uneven portion of the first conductive layer, there are cases where the second conductive layer is divided into multiple portions due to the shape of this uneven portion (see
The smooth base material and the first conductive layer may be composed of substances which differ from each other.
The second conductive layer may be a layer substantially consisting of carbon.
The phrases ‘substantially consisting of carbon’ or ‘consisting of carbon’ in the above description does not necessarily mean that components other than carbon are not contained whatsoever as substances constituting this second conductive layer. The actual component constituents can be variously changed, e.g., in accordance with the limits on manufacture technology in relation to controls of component purity in the layer and mixing of impurities in the layer, and in accordance with the degree of resistance as a tolerable error in the aforementioned electrode material in other separate products (components other than carbon may also be contained in the second conductive layer, within the range that the function of the electrode material is maintained to an allowable extent). This point also applies to descriptions such as ‘substantially consisting of XX’, ‘consisting of XX’, ‘substantially containing only XX’, and ‘containing only XX’.
The inorganic conductive layer may further have a dense layer in which the metal and/or the metal compound is densely present, and the dense layer may be formed between the oxide layer and the first conductive layer. The term ‘is densely present’ here means that (the metal and/or the metal compound) exists densely compared to that in the aforementioned ‘uneven portion’.
In the inorganic conductive layer, both the first conductive layer and the second conductive layer, or at least the first conductive layer may be a layer consisting of a particle deposition layer. The first conductive layer may be a layer containing at least one kind from amongst titanium, aluminum, a nitride thereof, an oxide thereof, an oxynitride thereof, a carbide thereof, and a carbonitride thereof. The substances which can be used in the first conductive layer are not limited to these; however, when using an aluminum base material as the base material, from the viewpoints of energy efficiency and adhesion with the aluminum base material, it is preferable to use a metal such as titanium (Ti) and aluminum (Al) in particular (metals containing a plurality of components such as alloys may also be used to the extent that the adhesion with the base material and electroconductivity in the first conductive layer are not lost).
The oxide layer may be a phosphorous-containing oxide layer.
The smooth base material may be a base material containing aluminum or an aluminum alloy. Materials which can be used as the base material are not limited to aluminum, but any other materials which are valve action metals such as tantalum (Ta), titanium (Ti), niobium (Nb), hafnium (Hf), zirconium (Zr), zinc (Zn) and tungsten (W), any other materials, or aluminum alloys in which any of these materials are added to aluminum can also be used.
The maximum value of an electric current value of a cyclic voltammogram obtained by means of the cyclic voltammetry method, under the conditions of a sweep range being ±0.3 V vs Pt, a sweep rate being 500 mV/sec, an electrolytic solution at 30° C., Pt as a reference electrode, stainless steel as a counter electrode, and the electrode material as a working electrode, may be 6.5 times or more of the maximum value of an electric current value of a cyclic voltammogram under the same conditions except for using the smooth base material as a working electrode.
A mixed layer in which substances constituting the first conductive layer and substances constituting the second conductive layer are present in a mixed state is formed between the first conductive layer and the second conductive layer. The components of the mixed layer may be constituted so as to change from components substantially containing only the substances constituting the first conductive layer to components substantially containing only the substances constituting the second conductive layer, upon heading from the first conductive layer towards the second conductive layer. Similarly to that already mentioned, the phrases ‘substantially containing only the substances constituting the first conductive layer’ and ‘containing only the substances constituting the first conductive layer’ do not necessarily mean that components other than the ‘substances constituting the first conductive layer’ are not contained whatsoever. Moreover, the phrases ‘substantially containing only the substances constituting the second conductive layer’ and ‘containing only the substances constituting the second conductive layer’ do not necessarily mean that components other than the ‘substances constituting the second conductive layer’ are not contained whatsoever (other components may also be contained within the range in which the function of the electrode material is maintained to an allowable extent).
Moreover, in the above description, the phrase ‘so as to change from components substantially containing only substances constituting the first conductive layer to components substantially containing only substances constituting the second conductive layer, upon heading from the first conductive layer towards the second conductive layer’ does not necessarily mean that the content of the substances constituting the second conductive layer in the mixed layer monotonically increases in the direction from the first conductive layer towards the second conductive layer. The actual components in each position in the mixed layer can undergo a variety of changes in accordance with fluctuations etc. in each of the component concentrations arising due to limits on manufacture technology. However, a mixed layer is preferably formed so that the content of the substances constituting the second conductive layer increases continuously whilst heading from the first conductive layer towards the second conductive layer.
A mixed layer in which substances constituting the first conductive layer and substances constituting the second conductive layer are present in a mixed state is formed between the first conductive layer and the second conductive layer, and components of the mixed layer are constituted so as to change from components substantially containing only substances constituting the first conductive layer to components substantially containing only substances constituting the second conductive layer, upon heading from the first conductive layer towards the second conductive layer, and when the amount of each C bond state present is analyzed by means of XPS (X-ray photoelectron spectroscopy) with respect to the depth direction from the surface layer of the second conductive layer, the ratio of the amount of present bonds between metal elemental atoms and carbon atoms constituting the first conductive layer may be 5% or more, with respect to the total amount of said each C bond state present by means of the C1s spectrum.
For a half width of a G band peak obtained by peak separation in a Raman spectrum by means of Raman spectroscopy, the half width of carbon contained in the second conductive layer may be 3.8 times or more with respect to the half width of graphite crystals.
The substances constituting the first conductive layer and the substances constituting the second conductive layer may differ from each other.
The BET specific surface area obtained using krypton (Kr) as an adsorption gas may be 1.5 times or more of said BET specific surface area of the smooth base material.
The mean diameter of a projecting part of an uneven portion on the surface layer side of the inorganic conductive layer may be 210 nm or less.
The carbon may be a graphite-like carbon.
Although there are no particular limitations on the kind of material to employ as the carbon, the use of a graphite-like carbon which has particularly excellent electric conductivity amongst the carbon materials is preferable for reducing the ESR of the electrolytic capacitor; and is moreover preferable also in terms of manufacturing costs. Here, graphite-like carbon means that, of the carbon which has an amorphous structure with mixed bonds of both diamond bonds (sp3 hybrid orbital bonds of the carbons) and graphite bonds (sp2 hybrid orbital bonds of the carbons), the ratio of graphite bonds is more than 50% (the number of graphite bond is higher than the number of diamond bonds). However, besides an amorphous structure, also included are those having a phase consisting of a crystal structure (namely, hexagonal-based crystal structure consisting of sp2 hybrid orbital bonds) which consists of a partially graphite structure. The ratio of sp3 bond and sp2 bond states in the carbon can be analyzed by methods such as Raman spectroscopy and XPS (X-ray photoelectron spectroscopy (also known as ESCA)).
In the electrode material of an embodiment of the present invention, a static friction coefficient and a dynamic friction coefficient of a surface on the surface layer side with respect to a separator paper may be respectively higher than a static friction coefficient and a dynamic friction coefficient of a surface on a surface layer side of an electrode material with respect to a separator paper, the electrode material comprising a conductive layer consisting of carbon, which is the outermost layer on the surface layer side, and comprising no uneven portion on the surface layer side.
The present invention moreover provides a cathode foil for an electrolytic capacitor, using the aforementioned electrode material of the present invention.
The aforementioned cathode foil for an electrolytic capacitor may be a cathode foil for an electrolytic capacitor, in which at least a solid electrolyte is interposed between an anode foil and a cathode foil.
The present invention also provides an electrolytic capacitor in which at least a solid electrolyte is interposed between an anode foil and a cathode foil, the electrolytic capacitor having the aforementioned cathode foil of the present invention. In one example, a solid electrolyte capacitor is provided.
The aforementioned electrolytic capacitor may be an electrolytic capacitor in which an electrolytic solution is further interposed between the anode foil and the cathode foil. In one example, a hybrid capacitor is provided.
The present invention provides an electrode material that can be used for example in a cathode foil for an electrolytic capacitor, having at least one advantage of the aforementioned (1) to (7) mentioned in relation to the ‘Technical Problem’, and an electrolytic capacitor having a cathode foil using such an electrode material. Specifically, these are as follows, for example.
a) is a SEM (Scanning Electron Microscopy) photograph (surface image) of the same cathode foil as that of
a) is a graph showing the amounts of each element present in the depth direction, of the same cathode foil as that of
A cathode foil for an electrolytic capacitor using an electrode material, and an electrolytic capacitor using the cathode foil will be explained below as an embodiment of the present invention. However, as already mentioned, the aluminum foil used as a base material in the below explanation, and the titanium (Ti) or aluminum (Al) for forming the first conductive layer may be substituted with other materials. For example, materials for forming the first conductive layer may include any of the following: tantalum (Ta), titanium (Ti), chromium (Cr), aluminum (Al), niobium (Nb), vanadium (V), tungsten (W), hafnium (Hf), copper (Cu), zirconium (Zr), zinc (Zn), as well as nitrides of these metals, oxides of these metals, oxynitrides of these metals, carbides of these metals, and carbonitrides of these metals (the first conductive layer may contain any other material besides these, and the same also applies to the other layers). Moreover, the carbon is not limited to graphite-like carbon but may be any carbon material. Furthermore, the applications of the electrode material of the present invention are also not limited to a cathode foil for an electrolytic capacitor such as a solid electrolytic capacitor or a hybrid capacitor, but also an electrode (such as a cathode, an anode, a positive electrode and a negative electrode) of any other electrical storage element such as a secondary battery, an electric double layer capacitor and a lithium ion capacitor. The electrolytic capacitor of the present invention is not limited to the winding type electrolytic capacitor mentioned below, but may be any type such as e.g. a laminated type and a chip type. The uneven part of the first conductive layer shown in
The aforementioned deterioration resistance with respect to a solid electrolyte, a chemical polymerizing solution, an electrolytic solution and moisture can be further improved by doing the following.
A commercially available high-purity aluminum sheet can be used as the smooth aluminum foil 2. Although there is no particular limitation on the thickness of the aluminum sheet, a thickness of 10 μm or more and 50 μm or less is preferable for the aluminum sheet used as a cathode foil for a winding type electrolytic capacitor (such as a solid electrolytic capacitor and a hybrid capacitor).
The oxide layer 3 is an oxide layer such as a natural oxide film, or an oxide film intentionally formed for example by a formation treatment such as a phosphorous-containing anodic oxidation or an immersion treatment. The oxide film is formed, e.g., by exposing the smooth aluminum foil 2 in air, or by performing an anodic oxidation treatment with an ammonium dihydrogen phosphate solution, or by a heat treatment after immersion in an aqueous phosphoric acid solution or in an aluminum biphosphate aqueous solution.
In one example, the first conductive layer 4 is formed by: arranging in a vacuum chamber, a smooth aluminum foil 2 on which an oxide layer 3 is formed, or when a dense layer 6 described later is formed though it is not a requirement, a smooth aluminum foil 2 having an oxide layer 3 on which a dense layer 6 is further formed by a method such as an arc ion plating method in the vacuum chamber, and Ti or Al that is an evaporation source metal material; and evaporating the metal material to make the evaporated metal material adhere onto the oxide layer 3 (or when the dense layer 6 is formed, onto the dense layer 6) (vapor deposition method). As the vapor deposition method, methods such as the chemical vapor phase deposition (CVD) method and the sputtering method can be used; however, among the vacuum deposition methods, the electron beam vapor deposition method is well-suited in terms of control of the geometrical structure. The electron beam vapor deposition method is a method of irradiating an accelerated electron beam at a vapor deposition substance to heat and vaporize this, thereby depositing this substance on the base material. The granularity of the unevenness in the first conductive layer can be controlled, for example, by adjusting the particle diameter of the metallic material made to adhere. The particle diameter of the metal material can be suitably controlled in the vapor deposition by, e.g., adjusting the conditions such as the type of gas to be introduced, the degree of vacuum and the temperature of the base material. In a mode in which a first conductive layer 4 consisting of a nitride, an oxide or a carbide of a metal such as Ti or Al is formed on the smooth aluminum foil 2 on which the oxide layer 3 is formed, or when the dense layer 6 is formed, the smooth aluminum foil 2 on which the dense layer 6 is further formed on the oxide layer 3, the first conductive layer 4 may be formed by performing the aforementioned method for example in an atmosphere of nitrogen gas, oxygen gas, or a hydrocarbon gas such as acetylene gas and methane gas. Moreover, in the mode of forming a first conductive layer 4 consisting of an oxynitride or a carbonitride of a metal such as Ti or Al, the first conductive layer 4 may be formed in an atmosphere for example of nitrogen gas and oxygen gas, or of nitrogen gas and a hydrocarbon gas such as acetylene gas and methane gas.
The second conductive layer 5 is not formed by dispersing carbon particles in a binder such as a resin binder and then applying this, for example, but is preferably formed for example by employing a vapor deposition method such as the ion plating method. This is because in a layer of carbon particles formed by kneading with a binder, the occupation rate of carbon substantially decreases by the quantity of the binder to be mixed in, the contact between the material of the first conductive layer and carbon particles is a point contact, the formation of a mixed layer is also difficult, moreover, it is difficult to increase the electric conductivity at the interface by the aforementioned application method, the interface resistance increases while adhesion also worsens, and a thin and uniform coating is difficult. The second conductive layer 5 is preferably formed as a smooth and dense GLC (Graphite-Like Carbon) film. Moreover, the degree of the non-crystallinity is high to the extent that the half width, obtained by measuring the carbon by Raman spectroscopy and separating the G band peak (sp2 bonding portion), is large, and properties such as the density, hardness and Young's modulus increase in general. Thus, it is preferable to determine the half width of the carbon used in the second conductive layer 5 so as to be 3.8 times or more of the half width of a crystal graphite. Thereby, the second conductive layer 5 has a higher degree of non-crystallinity to be a film with excellent deterioration resistance (chemical resistance and durability) with respect to a solid electrolyte, a chemical polymerizing solution, an electrolytic solution and moisture. When the second conductive layer 5 is formed on the uneven portion of the first conductive layer 4, since the shape of the second conductive layer 5 is dependent on the shape of the uneven portion of the first conductive layer 4, the second conductive layer 5 does not necessarily need to be uneven (the thickness thereof is substantially constant) and may be a smooth and dense film. As shown in
The second conductive layer 5 is obtained by a method similar to that of the dense layer 6; however, among these, an ion plating method such as the arc ion plating method which has a particularly high ionization rate and adhering energy of the film forming material is one of the preferred means because of the ease of forming a mutual diffusion state with the first conductive layer and the high lowering effect of the interface resistance. Specifically, the second conductive layer 5 is formed by: arranging a laminate body in which the oxide layer 3 and the first conductive layer 4 are formed on the smooth aluminum foil 2 (when forming the dense layer 6, the dense layer 6 is further formed between the oxide layer 3 and the first conductive layer 4), and a carbon material as an evaporating source (graphite material as one example, when forming the second conductive layer 5 as a GLC film) in a vacuum chamber; then evaporating and ionizing the carbon material by generating a vacuum arc discharge between an anode and a cathode that is the evaporating source target; and guiding the carbon cations thereby generated towards the laminate body. The arc ion plating method is well-suited for the formation of a high melting point compound film such as a carbide or nitride, because a high Joule heat by the arc current can be locally generated on a target, and because the ionization rate of the evaporated film forming substance can be increased due to the high plasma density. Here, a negative bias voltage may also be applied to the laminate body to accelerate the carbon cations heading towards this laminate body. When providing an uneven geometric shape to second conductive layer 5, the carbon material (a graphite material as one example, when forming the second conductive layer 5 as a GLC film) may be guided by employing the same electron beam vapor deposition method as that employed to form the uneven portion of first conductive layer 4. Although the second conductive layer 5 may also contain any component besides carbon, when forming a second conductive layer 5 containing a component other than carbon, any other material in addition to the carbon material may be prepared as an evaporating source, and not only carbon material but this other material may also be similarly evaporated and ionized and guided towards the laminate body.
The dense layer 6 is formed by: arranging a smooth aluminum foil 2 on which the oxide layer 3 is formed, and a Ti or Al metallic material as an evaporating source in a vacuum chamber; then evaporating and ionizing the Ti or Al by means of an electron beam and plasma generating electrode etc.; and guiding the metal cations ionized by the arc discharge and thereby generated, towards the smooth aluminum foil 2. Here, a negative bias voltage may also be applied to the smooth aluminum foil 2 to accelerate the metal cations heading towards this smooth aluminum foil 2. Thus, the Ti or Al ions penetrate the oxide layer 3 formed on the surface of the smooth aluminum foil 2, and rigidly adhere to the smooth aluminum foil 2. However, it is not a requirement for the material of the first conductive layer 4 to penetrate the oxide layer 3 and adhere to the smooth aluminum foil 2. An oxide layer 3 such as a natural oxide film, or an oxide film formed by means of a phosphorous-containing anodic oxidation treatment may also be present without having pores etc. between the first conductive layer 4 and the smooth aluminum foil 2. In the mode of forming a dense layer 6 consisting of a nitride, an oxide or a carbide of a metal such as Ti or Al, on the smooth aluminum foil 2 on which the oxide layer 3 is formed, the dense layer 6 may be formed by performing the aforementioned method in e.g. an atmosphere of nitrogen gas, oxygen gas, or a hydrocarbon gas such as acetylene gas and methane gas. Moreover, in the mode of forming a dense layer 6 consisting of an oxynitride or carbonitride of a metal such as Ti or Al, the dense layer 6 may be formed in an atmosphere of e.g., nitrogen gas and oxygen gas, or nitrogen gas and a hydrocarbon gas such as acetylene gas and methane gas.
Moreover, in addition to ion plating methods such as the arc ion plating method, as other methods for forming the dense layer 6, the vacuum deposition method, chemical vapor phase deposition method, sputtering method, atom layer deposition method, sol-gel method, plating method, coating method, and printing method etc. can also be employed. In one example, the ion plating method can be used from the perspective of suppressing the ESR of the capacitor lower due to the dense layer 6 and smooth aluminum foil 2 penetrating and firmly adhering to the oxide layer 3, and from the perspective of easily forming a smooth metal film.
In one example, the mixed layer 7 can be formed by performing the step of forming the first conductive layer 4 by means of a vapor deposition method such as the aforementioned vacuum deposition method, and the step of forming the second conductive layer 5 by the arc ion plating method, such that the time arises for both these steps to take place simultaneously, without completely time-separating the forming step of the first conductive layer 4 and the forming step of the second conductive layer 5. By introducing such a mixed layer 7, the adhesion and chemical stability of the substance constituting the first conductive layer 4 (a metal, or any substance containing the nitride, oxide, oxynitride, carbide or carbonitride of the metal, as mentioned above) and a substance constituting the second conductive layer 5 (carbon such as GLC, and when the second conductive layer 5 also includes a material other than carbon, any other substance contained in the second conductive layer 5) are increased, and a change in quality due to the chemical reaction of metal is prevented.
The mixed layer 7 is preferably constituted so as to substantially contain only the substances constituting the first conductive layer 4 in the boundary region with the first conductive layer 4 and substantially contain only the substances constituting the second conductive layer 5 in the boundary region with the second conductive layer 5, and such that the content of the substances constituting the second conductive layer 5 is continuously increased particularly upon heading from first conductive layer 4 towards second conductive layer 5. Such a mixed layer 7 can be formed, as one example, by:
Moreover, (i) to (iii) are processes mainly suited to the single wafer treatment of a batch method; however, as another alternative a mixed layer can also be formed by the roll-to-roll method, in which a continuous film forming treatment is performed in the order of from the first conductive layer to the second conductive layer whilst conveying a foil, in a chamber where the material target constituting the first conductive layer and then the material target constituting the second conductive layer are arranged in this order. A mixed layer is formed by arranging each of the first and second vapor deposition source targets next to each other such that the vapor and ions of each vapor deposition material conically radiated from each of the first and second evaporating source targets towards the base material have an overlap with (contact with) each other prior to arriving at the base material. By suitably controlling each of the distances of each of these vapor deposition source targets, and the distances of each vapor deposition source target and base material, the mixing and the diffusion state and bond state etc. of the mixed layer are adjusted to the optimal states. In this case, the aforementioned increase/decrease adjustment of the electron beam irradiation amount does not take place, each may be always constant, and hence this process can be said to be more suited for mass production. Moreover, regardless of the distance of each of the vapor deposition source targets and the distance of each vapor deposition source target and base material, a mixed layer may also be obtained by heating the base material temperature to about several hundred ° C. for example.
As already mentioned, it is not a requirement to laminate each layer on both surface sides of the base material 2 as shown in
It is sufficient for each of the thicknesses of the oxide layer 3, dense layer 6, first conductive layer 4, mixed layer 7 and second conductive layer 5 to be approximately 0.005 μm or more and 1 μm or less. When the total thickness of each layer excluding the base material 2 is 0.05 μm or more on one surface side of the base material 2, a cathode foil with good properties is obtained. However, each layer may be formed to be thicker or thinner. The thickness of each of the layers of
Defining the actual surface area of the electrode material 1 by the BET specific surface area method of adsorbing nitrogen gas or krypton gas is crucial as an index of the retentivity of the solid electrolyte and electrolytic solution. In an embodiment of the present invention, taking precedence of this, evaluation was performed by the cyclic voltammetry method in order to obtain an electrochemically effective surface area together with the ease of electricity flow such as an interfacial resistance which is crucial when being made into an actual capacitor. An index relating to the electrochemically effective surface area was obtained by: performing a linear sweep on the voltage under the conditions of 1M of tetraethyl ammonium hexafluorophosphate using a solvent of propylene carbonate as the electrolytic solution, a Pt electrode as a reference electrode, stainless steel as a counter electrode, an electrolytic solution at a temperature of 30° C., a sweep range being ±0.3 V vs Pt electrode, and a sweep rate being 500 mV/sec; and comparing the maximum value of an electric current value of a cyclic voltammogram measured when the electrode material in an embodiment of the present invention was used as the working electrode, with the maximum value of an electric current value measured when the smooth base material was used as the working electrode. Moreover, when the electrode material in an embodiment of the present invention is used as the working electrode, it is preferable to determine the maximum value of an electric current value to be 6.5 times or more of the maximum value of an electric current value when the smooth base material is used as the working electrode. By means of the electrode material used as the working electrode, exhibiting the maximum value being 6.5 times of that of the smooth material used as the working electrode, an ESR reducing effect can be obtained due to the improved retention power of the solid electrolyte and the electrolytic solution.
As the evaluation method in relation to the bonds of metal elemental atoms and carbon atoms constituting the first conductive layer, analysis on the amounts of each element present in the depth direction, as well as the bond states can be performed by means of XPS. By repeating etching and measurement for every several nm, the ratio of the amount of bonds present of metal elemental atoms and carbon atoms constituting the first conductive layer can be analyzed with respect to the total amount of all bonds present of which detected carbon atoms are involved. Thus, a low resistance conductor is obtained when this ratio is 5% or more and an ESR reducing effect can be obtained, and hence the ratio of the amount of bonds present of metal elemental atoms and carbon atoms constituting the first conductive layer is preferably 5% or more, with respect to the total amount of all bonds present of which detected carbon atoms are involved.
Moreover, when an electrode material in an embodiment of the present invention using a valve action metal as the base material 2, is used as a cathode foil of an electrolytic capacitor, when an electric current flows by electrochemical polarization within a range of an electric current density of a leakage current of an electrolytic capacitor, a potential corresponding to this electric current may be on a higher side than a natural immersion potential of a reference cathode foil having a purity of 99.99% or more and with the same type of valve action metal used in the base material 2. Moreover, the natural immersion potential when immersed in an electrolytic solution may be on a higher side than a natural immersion potential when a reference cathode foil having a purity of 99.99% or more with the same type of valve action metal used in base material 2 was immersed in the same electrolytic solution (Patent Literature 26 and Patent Literature 27). Thereby, when a dielectric material oxide film formed at an anode foil is repaired by a leakage current, the generation of hydrogen gas at the cathode side can be suppressed. To further explain this point, a natural oxide film is formed at the aforementioned reference cathode foil, which has a natural immersion potential in which the cathode reaction which reduces the hydrogen ions dominantly occurs. Moreover, the cathode foil in an embodiment of the present invention has a natural immersion potential on the higher side than the aforementioned reference cathode foil. Thus, when the cathode foil in an embodiment of the present invention is incorporated in an electrolytic capacitor and a leakage current also occurs, the potential of the cathode foil in an embodiment of the present invention can be maintained on a higher side than the natural immersion potential of the aforementioned reference cathode foil. Thus, the potential in a cathode foil in an embodiment of the present invention when a leakage current occurs in an electrolytic capacitor, is within the range of the potential in which the cathode reaction which reduces dissolved oxygen dominantly occurs, and a cathode reaction which reduces hydrogen ions is suppressed. As a result, the raising of the inner pressure of the electrolytic capacitor caused by the generation of hydrogen gas can be suppressed, and hence the risk that a case which houses the capacitor element expands, can be reduced.
As mentioned above, the BET specific surface area method of adsorbing nitrogen gas or krypton gas can be mentioned as a method to obtain the actual surface area required in order for an inorganic conductive layer, containing the first conductive layer and the second conductive layer and having an uneven portion on the surface layer side, to retain a solid electrolyte and an electrolytic solution. Within this, when krypton gas with a saturated vapor pressure lower than that of nitrogen gas is use as the adsorption gas, a high precision measurement is enabled even in a region with a small specific surface area. The surface expansion magnification calculated from a BET specific surface area using krypton gas as the adsorption gas (BET specific surface area of the electrode material/BET specific surface area of the smooth base material) is preferably determined to be 1.5 or more. By determining this surface expansion magnification to be 1.5 times or more, the retentivity of a solid electrolyte and an electrolytic solution is further improved, and a further ESR reducing effect can be obtained. The surface area may be further increased by further thickening the first conductive layer; however, making this to be too thick will result in the reduced volume efficiency of the capacitor, and increased manufacturing costs. Thus, it is more preferable to determine the surface expansion magnification calculated from a BET specific surface area obtained using krypton gas as the adsorption gas to be 1.5 times or more and 200 times or less.
a) to d) are scanning electron microscope (SEM) surface photographs in relation to the cathode foils of Examples 2, 4, 5 and 6. Here, images that look like particulate shapes are observed in the SEM photographs, these are projecting parts in an uneven portion on a surface on the surface layer side, namely on a surface layer side of an inorganic conductive layer, of the electrode material. As mentioned above, the electrode material 1 has the oxide layer 3, the first conductive layer 4, the mixed layer 7 and the second conductive layer 5 formed in this order on the smooth base material 2, in which there is an uneven portion on the surface layer side of the first conductive layer 4. Moreover, in Examples 2, 4, 5 and 6, the first conductive layer is a particle deposition layer formed by vapor deposition, and thereon the mixed layer and the second conductive layer are formed; however, both the mixed layer and the second conductive layer are thin. Thus, when observing the surface of the cathode foil of each of the Examples by SEM, it seems as if a sample is observed where only the first conductive layer which is a particle deposition layer is formed, as in
A solid electrolytic capacitor and a hybrid capacitor will be explained below as examples of an electrolytic capacitor which can be prepared using the cathode foil of the present invention. Here, the case in which the cathode foil 1 having the layer structure of
A solid electrolyte layer may also be formed using a polypyrrole-based or polyaniline-based, polyacene-based, polyparaphenylene vinylene-based or polyisothianaphthene-based etc. electroconductive polymer, or using manganese dioxide (MnO2), TCNQ (tetracyanoquinodimethane) complex salt, etc.
The hybrid capacitor, after performing the steps (i) and (ii) similarly to the case of preparing the solid electrolytic capacitor 8, is prepared by a method including the following.
A solid electrolyte layer may also be formed using a polypyrrole-based or polyaniline-based, polyacene-based, polyparaphenylene vinylene-based, polyisothianaphthene-based etc. electroconductive polymer, or using manganese dioxide (MnO2), TCNQ (tetracyanoquinodimethane) complex salt, etc.
A variety of cathode foils prepared as examples of the present invention, electrolytic capacitor structures, analytical results, performance test results etc. will be explained below.
Such cathode foils have the following advantages.
In addition,
a) is a graph showing the ratio of atoms present in the depth direction of the sample prepared under the same conditions as those for the sample shown in
Each of the cathode foils of Examples 1 to 11 was prepared as a cathode foil in an embodiment of the present invention, and each of the cathode foils of Comparative Examples 1 to 3 was prepared as a cathode foil of the comparative example. Hybrid capacitors of Examples 1 to 11 were each prepared utilizing the cathode foils of Examples 1 to 11, and hybrid capacitors of Comparative Examples 1 to 3 were each prepared utilizing the cathode foil of Comparative Examples 1 to 3, and a performance test (ESR measurement) took place for each prepared hybrid capacitor. The preparation conditions and ESR measurement conditions of each hybrid capacitor were as follows.
Example 1: Ar gas was introduced into a chamber vessel which was vacuumed until 0.003 Pa. A first target consisting of Ti material and a second target consisting of a graphite material were arranged next to each other in the order of the first target and the second target as seen from the unwinding portion of the base material. In doing so, the first and second targets were arranged next to each other so that the vapor and ions of each vapor deposition material conically radiated from each of the first and second targets towards the base material have an overlap with (contact with) each other prior to arriving at the base material. A smooth foil of aluminum was conveyed in this order into a process with such targets arranged. An uneven Ti layer of 200 nm was provided by means of electron beam vapor deposition; and then a carbon film was formed by means of arc ion plating. By means of this continuous film forming by the roll-to-roll method, a mixed layer was respectively obtained at the interface between the oxide layer on the smooth base material and the first conductive layer, and at the interface between the first conductive layer and the second conductive layer (the mixed layer formed at the interface between the oxide layer and the first conductive layer was a mixed layer in which substances constituting the oxide layer and substances constituting the first conductive layer were present in a mixed state, and differed from the mixed layer in which the substances constituting the first conductive layer and the substances constituting the second conductive layer were present in a mixed state). Using the thus-obtained foil as a cathode, this was combined with an anode foil (an etched and formed aluminum foil anodically oxidized at 53 V) to prepare a hybrid capacitor. The initial ESR (100 kHz) was measured and left for 2000 hr (1 hr means 60 minutes) at 125° C., after which the ESR (100 kHz) was measured. A hybrid capacitor was prepared as follows. That is, an anode foil and the cathode foil prepared as described above were first overlapped via a separator paper in between, and then an anode terminal was connected to the anode foil and a cathode terminal was connected to the cathode foil. This was then wound to prepare a capacitor element. Next, a solid electrolyte layer was formed by immersing a capacitor element in a polymer dispersion solution of an aqueous solvent, in a vessel vacuumed until about 7000 Pa, and then drying it under an atmospheric environment of 150° C. for 30 minutes. An electrolytic solution containing ethylene glycol as a solvent was further impregnated in the capacitor element, in a vessel vacuumed to about 5000 Pa. Finally, the capacitor element was housed in an aluminum case and sealed with a sealing rubber.
Example 2: Ar gas of the same amount as that of Example 1 was introduced into a chamber vessel vacuumed to 0.003 Pa, a smooth foil of aluminum was conveyed, and a Ti film of 10 nm was formed by means of arc ion plating. Afterwards, an aluminum foil in which the Ti layer was formed by arc ion plating was conveyed in the same film forming process as that of Example 1, an uneven Ti layer of 200 nm was provided by means of vapor deposition, and a carbon film was formed by means of arc ion plating. The process thereafter was the same as that of Example 1.
Example 3: Other than using a smooth base material subjected to an anodic oxidation treatment in an ammonium dihydrogen phosphate solution at an applied voltage being 5V, a treatment similar to that of Example 2 was performed.
Example 4: Other than introducing two types of gas (Ar and N2), the same as described in Example 2 was performed.
Example 5: Other than employing the uneven Ti layer provided by means of vapor deposition having a thickness of 70 nm, the same as described in Example 2 was performed.
Example 6: Other than forming a film of Al instead of Ti by means of arc ion plating, and afterwards providing an uneven Al layer instead of an uneven Ti layer by means of vapor deposition, the conditions were the same as those of Example 2.
Example 7: The conditions were the same as those of Example 2, except that the amount of Ar gas introduced was 1/40 of that in Example 2.
Example 8: The conditions were the same as those of Example 6, except that the amount of Ar gas introduced was 1/10 of that in Example 6.
Example 9: Other than the uneven Ti layer provided by means of vapor deposition being configured as 30 nm, the conditions were the same as those of Example 2.
Example 10: Other than providing an Al layer instead of an uneven Ti layer by means of vapor deposition, the conditions were the same as those of Example 1.
Example 11: Other than gas introduced being N2 gas only, the conditions were the same as those of Example 2.
Comparative Example 1: A smooth base material was used, the same amount of Ar gas as that of Examples 1 to 3 was introduced, a Ti film was formed by means of arc ion plating, then a carbon film was formed by arc ion plating, and this was utilized as a cathode. Otherwise, the conditions were the same as that of Example 1.
Comparative Example 2: An etched foil whose base material underwent anodic oxidation treatment at 2 V was utilized, the same amount of Ar gas as that of Examples 1 to 3 was introduced, a Ti film was formed by means of arc ion plating, then a carbon film was formed by arc ion plating, and this was utilized as a cathode. Otherwise, the conditions were the same as that of Example 1.
Comparative Example 3: No gas was introduced, a (dense) Ti layer was formed by vacuum vapor deposition on a smooth base material, then N2 gas was introduced until the pressure in the vessel was equivalent to that of Examples 1 to 3, an (uneven) Ti layer was formed by means of vacuum vapor deposition, and this was utilized as a cathode. Otherwise, the conditions were the same as that of Example 1. The film constituents of the cathode foil of Comparative Example 3 were similar to those disclosed in JP 2014-022707 A.
In the cathode foils of Examples 1 to 11 and Comparative Examples 1 and 2 in which a carbon conductive layer was formed, a mixed layer was formed under the carbon conductive layer. Carbon and substances constituting the layer under the mixed layer were mixed and were present in the mixed layer. Moreover, the carbon layer in Examples 1 to 11, and Comparative Examples 1 and 2 contained GLC.
The electric current values of the cathode foils of the Examples and Comparative Examples were measured by means of the cyclic voltammetry method. The measurements took place under a nitrogen atmosphere employing a glove box. As the measuring liquid, 1M of tetraethyl ammonium hexafluorophosphate was prepared using propylene carbonate as a solvent. The three-electrode technique was employed in the measurement, using stainless steel as the counter electrode, Pt electrode as the reference electrode, and the cathode foils of the Examples and Comparative Examples as the working electrodes. The measurement conditions of the cyclic voltammetry were determined: a measuring liquid temperature being 30° C., sweep range being ±0.3 V, and sweep rate being 500 mV/sec. The electric currents and voltages from 1 to 5 cycles were recorded, the maximum values of the electric currents of each cycle were calculated, and the mean values thereof were regarded as the maximum electric current values of the cathode foils of the Examples and Comparative Examples. Similarly, the maximum electric current value for the smooth base material alone was also measured and using the thus-obtained maximum electric current value as 1, the maximum electric current values of the cathode foils of the Examples and Comparative Examples were indicated.
For the cathode foils of the Examples and Comparative Examples, etching and measurement were repeated by means of XPS in 2.5 nm units by SiO2 conversion, and the bond states in the depth direction were observed. JPS-9010TR manufactured by JEOL Ltd., was employed as the XPS apparatus, and measurement was performed under the below conditions.
The integral values were calculated for the curves drawn when the horizontal axis expressed SiO2 conversion depth, and the longitudinal axis expressed the peak areas of each C bond state, and this was regarded as the amount of C bond states present. The value resulting from dividing the amount of TiC bond states (in the vicinity of 282 eV) or Al4C3 bond states (in the vicinity of 282.4 eV) present by the total amount of C bond states present, was regarded as the ratio of bonds of metal elemental atoms and carbon atoms present in the cathode foils of Examples and Comparative Examples.
The half width of the sp2 band (G band) peaks obtainable by separating the peak caused by the C—C bonds as measured by Raman spectroscopy was measured for the cathode foils of Examples and Comparative Examples. As one example,
Moreover,
For Examples 1 to 8, 10 and 11, initially, the ESR of the hybrid capacitor of Example 10 was substantially equivalent to the ESRs of the hybrid capacitors of Examples 1 to 8 and 11; however, after the 2000-hr deterioration, the ESR of the hybrid capacitor of Example 10 was higher than the ESRs of the hybrid capacitors of Examples 1 to 8 and 11. On this point, the ratio of metal carbide obtained by means of XPS was 5% or more with the cathode foils of Examples 1 to 8 and 11, whereas it was only 3% with the cathode foil of Example 10. Thus, in Example 10, compared to the other examples, the interfacial resistance increase due to the rapid changes of the component constituents of the electrode material in between a metal-containing first conductive layer and a carbon-containing second conductive layer could not be suppressed, and a sufficiently low resistance conductor could not be obtained; hence the ESR after the 2000-hr deterioration was higher with Example 10. Moreover, metal carbides detected by means of XPS also include those in the mixed layer. Therefore, it is more preferable that the magnification of the maximum electric current value by the cyclic voltammetry method is 6.5 times or more, and additionally that a mixed layer is further formed between the first conductive layer and the second conductive layer, and that the ratio of metal carbide obtained by XPS is 5% or more.
In Examples 1 to 8 and 11, initially, the ESR of the hybrid capacitor of Example 11 was nearly equivalent to the ESRs of the hybrid capacitors of Examples 1 to 8; however, after the 2000-hr deterioration, the ESR of the hybrid capacitor of Example 11 was higher than the ESRs of the hybrid capacitors of Examples 1 to 8. On this point, the magnification of the half width of the G band peak obtained by Raman spectroscopy was 3.8 times or more with the cathode foils of Examples 1 to 8, whereas it was only 3.5 times with the cathode foil of Example 11. Thus, in Example 11, compared to the other examples, the degree of the non-crystallinity of carbon was reduced and the deterioration resistance was worse, and the ESR after the 2000-hr deterioration was higher. Therefore, it is furthermore preferable that the magnification of the maximum electric current value obtained by the cyclic voltammetry method is 6.5 times or more, a mixed layer is formed between the first conductive layer and the second conductive layer, the ratio of metal carbide obtained by XPS is 5% or more, and in addition, the magnification of the half width of the G band peak obtained by Raman spectroscopy is 3.8 times or more.
The below each relate to samples of ultra-thin pieces in the thickness direction of the entire film portion including the base material portion near the film.
In addition, the solid electrolytic capacitors of Examples 1 to 11 and Comparative Examples 1 to 3 were each prepared using the cathode foils of the aforementioned Examples 1 to 11 and Comparative Examples 1 to 3 (compared to the preparation method of the hybrid capacitors of Examples 1 to 11 and Comparative Examples 1 to 3, these were prepared by a preparation method which was different only in that the treatment of impregnating an electrolytic solution in the capacitor element after forming the solid electrolyte layer was not performed). A performance test (ESR measurement) took place for each prepared solid electrolytic capacitor.
The adhering mechanism of the solid electrolyte and cathode foil was that of the sticky tape type, and
In the recent hybrid capacitors, from the viewpoints such as heat resistance, electroconductivity, voltage resistance performance and manufacturing costs, it is often the case that a solid electrolyte layer is formed by: immersion into an aqueous PEDOT/PSS dispersion solution mixed with polystyrene sulfonic acid (PSS) in order to disperse the polyethylene dioxythiophene (PEDOT) in the aqueous solution; and then drying after impregnation. It is considered that the adhesion and retentivity of the solid electrolyte is also dependent on the wettability and surface free energy of the cathode foil.
In a coil former element where a capacitor element is made by pinch winding and rolling a separator paper between each of the strip-shaped electrode foil pieces of the anode side and the cathode side, the type where winding begins with a winding axis pinching a cathode foil may be especially prone to the occurrence of winding deviation. This is because when there is a small friction coefficient between the cathode foil in the vicinity of the winding axis and the separator paper contacting therewith, the cathode foil in contact with the winding axis ends up moving towards the extracting direction of the winding axis when extracting the winding axis after the coil former element formation, with insufficient grip force (friction force) of the cathode foil with the separator paper.
The present disclosure discloses configurations as follows.
Electrode material comprising an oxide layer on a base material and further comprising an inorganic conductive layer on the oxide layer, wherein
Electrode material according to configuration 1, wherein the smooth base material and the first conductive layer are constituted from substances which differ from each other.
Electrode material according to configuration 1 or 2, wherein the second conductive layer consists substantially of carbon.
Electrode material according to any one of configurations 1 to 3, wherein the inorganic conductive layer further comprises a dense layer in which the metal and/or the metal compound is densely present, and the dense layer is formed between the oxide layer and the first conductive layer.
Electrode material according to any one of configurations 1 to 4, wherein in the inorganic conductive layer, both the first conductive layer and the second conductive layer, or at least the first conductive layer consists of a particle deposition layer, and wherein the first conductive layer contains at least one kind of titanium, aluminum, a nitride thereof, an oxide thereof, an oxynitride thereof, a carbide thereof, and a carbonitride thereof.
Electrode material according to any one of configurations 1 to 5, wherein the oxide layer is a phosphorous-containing oxide layer.
Electrode material according to any one of configurations 1 to 6, wherein the smooth base material contains aluminum or an aluminum alloy.
Electrode material according to any one of configurations 1 to 7, wherein a maximum value of an electric current value of a cyclic voltammogram obtained by means of the cyclic voltammetry method, under the conditions of a sweep range being ±0.3 V vs Pt, a sweep rate being 500 mV/sec, an electrolytic solution at 30° C., Pt as a reference electrode, stainless steel as a counter electrode, and the electrode material as a working electrode, is 6.5 times or more of the maximum value of an electric current value of a cyclic voltammogram under the same conditions except for using the smooth base material as a working electrode.
Electrode material according to any one of configurations 1 to 8, wherein a mixed layer in which substances constituting the first conductive layer and substances constituting the second conductive layer are present in a mixed state is formed between the first conductive layer and the second conductive layer, and wherein components of the mixed layer are constituted so as to change from components substantially containing only substances constituting the first conductive layer to components substantially containing only substances constituting the second conductive layer, upon heading from the first conductive layer towards the second conductive layer.
Electrode material according to configuration 8, wherein a mixed layer in which substances constituting the first conductive layer and substances constituting the second conductive layer are present in a mixed state is formed between the first conductive layer and the second conductive layer, and wherein components of the mixed layer are constituted so as to change from components substantially containing only substances constituting the first conductive layer to components substantially containing only substances constituting the second conductive layer, upon heading from the first conductive layer towards the second conductive layer, and wherein, when the amount of each C bond state present is analyzed by means of XPS (X-ray photoelectron spectroscopy) with respect to the depth direction from the surface layer of the second conductive layer, the ratio of the amount of present bonds between metal elemental atoms and carbon atoms constituting the first conductive layer is 5% or more, with respect to the total amount of said each C bond state present by means of the C1s spectrum.
Electrode material according to configuration 10, wherein for a half width of a G band peak obtained by peak separation in a Raman spectrum by means of Raman spectroscopy, the half width of carbon contained in the second conductive layer is 3.8 times or more with respect to the half width of graphite crystals.
Electrode material according to configuration 11, wherein substances constituting the first conductive layer and substances constituting the second conductive layer differ from each other.
Electrode material according to configuration 11 or 12, wherein a BET specific surface area obtained using krypton (Kr) as an adsorption gas is 1.5 times or more of said BET specific surface area of the smooth base material.
Electrode material according to configuration 13, wherein the mean diameter of a projecting part of an uneven portion on the surface layer side of the inorganic conductive layer is 210 nm or less.
Electrode material according to any one of configurations 1 to 14, wherein the carbon is a graphite-like carbon.
Electrode material according to any one of configurations 1 to 15, wherein a static friction coefficient and a dynamic friction coefficient of a surface on a surface layer side of the electrode material with respect to a separator paper are respectively higher than a static friction coefficient and a dynamic friction coefficient, with respect to a separator paper, of a surface on a surface layer side of an electrode material comprising a conductive layer consisting of carbon, which is the outermost layer on the surface layer side, and comprising no uneven portion on the surface layer side.
Cathode foil for an electrolytic capacitor using the electrode material according to any one of configurations 1 to 16.
Cathode foil for an electrolytic capacitor according to configuration 17, wherein at least a solid electrolyte is interposed between an anode foil and a cathode foil.
Electrolytic capacitor wherein at least a solid electrolyte is interposed between an anode foil and a cathode foil, the electrolytic capacitor having the cathode foil according to configuration 18.
Electrolytic capacitor according to configuration 19, wherein an electrolytic solution is further interposed between the anode foil and the cathode foil.
The electrode material of the present invention can be utilized as a cathode foil of an electrolytic capacitor such as a hybrid capacitor, solid electrolytic capacitor and the like. The electrode material of the present invention can be further used in a variety of capacitors, as well as in a variety of electrical storage devices such as electric double layer capacitor, lithium ion capacitor, lithium ion battery, and in a variety of electric generating elements such as a fuel cell battery, a solar battery, a thermoelectric generating element and vibration electric generating element.
Number | Date | Country | Kind |
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2022-116595 | Jul 2022 | JP | national |
2023-116068 | Jul 2023 | JP | national |
This application is a Continuation-in-Part of International Patent Application No. 10 PCT/JP2023/026574, filed on Jul. 20, 2023, which claims the benefit of priority to Japanese Patent Application Nos. 1) 2022-116595, filed on Jul. 21, 2022; and 2) 2023-116068, filed on Jul. 14, 2023, the entire contents of which are incorporated herein by reference.
Number | Date | Country | |
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Parent | PCT/JP2023/026574 | Jul 2023 | WO |
Child | 19026059 | US |