JP2017216090A - Coating material for underlying layer and electrode for electrochemical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating material for an underlying layer which can ensure a high level of adhesion between a current collector and an active material layer and which enables the formation of an underlying layer reduced in contact resistance in a thickness direction.SOLUTION: A coating material for an underlying layer is designed for forming an underlying layer to be disposed between a current collector and an active material layer in an electrode for an electrochemical device, which includes the current collector and the active material layer formed on the current collector. The coating material for an underlying layer comprises: a conducting agent; a binding agent; and a liquid component. The conducting agent includes carbon black. The carbon black is 500 m/g or less in specific surface area according to BET method. In the coating material for an underlying layer, the concentration of solid components is 15-30 mass%; and the solid components have an average particle diameter of 1.5 μm or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrode for an electrochemical element excellent in conductivity and a coating for an underlayer for forming this electrode. For example, a capacitor such as an electric double layer capacitor (EDLC) or a pseudo capacitor (P-EDLC), The present invention relates to an electrode used for a lithium ion battery or the like and a coating for an underlayer.

  In recent years, from the viewpoints of energy saving, environmental protection, and use of alternative energy for petroleum, technological development using electrochemical elements such as secondary batteries and EDLC has been progressing mainly in automobiles. Hybrid vehicles (HEV) and PEVs (electric vehicles) Development is accelerating. Further, high-performance secondary batteries and EDLC are also being used in SSD (Solid state drive) type hard disks.

  The electrode for electrochemical devices generally has a current collector and an active material layer formed on the surface thereof. However, when the active material layer is formed directly on the surface of the current collector, the electrode resistance may increase or the current collector may be oxidized. Thus, it has been proposed to form a conductive underlayer on the surface of the current collector and to form an active material layer on the surface (Patent Documents 1 and 2).

International Publication No. 2012/108212 Pamphlet JP 2009-272454 A

  When a conductive underlayer is formed, the interface resistance between the current collector and the active material layer is expected to be low. In particular, the underlayer is required to ensure adhesion between the current collector and the active material layer in addition to low contact resistance in the thickness direction.

One aspect of the present invention is an electrode for an electrochemical element including a current collector and an active material layer formed on the current collector, and is disposed between the current collector and the active material layer. A coating for a foundation layer for forming the foundation layer,
Including a conductive agent, a binder, and a liquid component;
The conductive agent includes carbon black,
The carbon black has a specific surface area of 500 m ² / g or less by the BET method,
The concentration of the solid content in the paint for the underlayer is 15 to 30% by mass,
It is related with the coating material for base layers whose average particle diameter of the said solid content is 1.5 micrometers or less.

Another aspect of the present invention provides a current collector,
An underlayer formed on the surface of the current collector;
An active material layer formed on the surface of the underlayer,
The underlayer includes a conductive agent and a binder,
The conductive agent includes carbon black,
The carbon black has a specific surface area of 500 m ² / g or less by the BET method,
The said binder is related with the electrode for electrochemical elements containing a polyamidoimide resin and a cellulose derivative.

  According to the undercoat paint according to the present invention, it is possible to ensure high adhesion between the current collector and the active material layer, and to form an underlayer with reduced contact resistance in the thickness direction. it can. Therefore, in the electrode for electrochemical devices, the interface resistance between the current collector and the active material layer can be reduced.

It is a schematic longitudinal cross-sectional view which shows an example of the electrode for electrochemical elements which concerns on this invention. 2 is a Raman spectrum of the underlayer of Example 1. It is a graph which shows the normalization contact resistance in the base layer of Examples 1-3 and Comparative Examples 1-3. It is a graph which shows the volume resistivity in the base layer of Examples 1-3 and Comparative Examples 1-3. It is a graph which shows the adhesive strength (peeling strength) of the base layer of Examples 1-3 and Comparative Examples 1-3. It is a graph which shows the normalized contact resistance in the base layer of Examples 4-7. It is a graph which shows the volume resistivity in the base layer of Examples 4-7. It is a graph which shows the adhesive strength of the base layer of Examples 4-7. It is a graph which shows the normalization contact resistance in the base layer of Example 2 and 8-11. It is a graph which shows the volume resistivity in the base layer of Example 2 and 8-11. It is a graph which shows the adhesive strength of the foundation layer of Example 2 and 8-11. 6 is a graph showing changes with time in adhesion strength of the underlayers of Examples 1 and 12.

[Underlayer paint]
An undercoat paint according to an embodiment of the present invention is an electrode for an electrochemical device including a current collector and an active material layer formed on the current collector, and is provided between the current collector and the active material layer. It is the coating material for base layers for forming the base layer distribute | arranged to. The base layer coating material includes a conductive agent, a binder, and a liquid component. The conductive agent includes carbon black, and the carbon black has a specific surface area (BET specific surface area) of 500 m ² / g or less according to the BET method. The concentration of the solid content in the coating for the underlayer is 15 to 30% by mass, and the average particle size of the solid content is 1.5 μm or less.

  In order to increase the conductivity by interposing between the current collector and the active material layer, it is important to reduce the contact resistance particularly in the thickness direction. However, depending on the type and physical properties of the conductive agent used, the contact resistance in the thickness direction may not be sufficiently reduced. Moreover, when the solid content concentration of the coating material for a base layer containing a conductive agent or a binder is low, the coating film tends to be thin, and it is difficult to ensure sufficient adhesion between the current collector and the active material layer. Even when sufficient adhesion can be secured, the resistance of the underlayer tends to increase. On the other hand, when the solid content concentration is increased, it is difficult to obtain a uniform coating film, and the resistance of the underlying layer may increase. In some cases, the adhesion may be reduced.

In this embodiment, since a conductive agent containing carbon black having a BET specific surface area of 500 m ² / g or less is used, the solid content concentration in the undercoat paint, the average particle size of the solid content, the viscosity of the undercoat paint, etc. Easy to adjust. Therefore, the solid content concentration can be increased to 15% by mass or more. Moreover, the average particle diameter of solid content can be reduced to 1.5 micrometers or less. Therefore, an excessive increase in viscosity is suppressed, and a coating film can be easily formed. Furthermore, since the uniformity of a coating film and a foundation layer can be improved, the resistance of the foundation layer can be reduced. In addition, high adhesion between the current collector and the active material layer can be ensured. By using carbon black having a BET specific surface area of 500 m ² / g or less, the contact resistance in the thickness direction of the underlayer can be reduced. As a result, since the interface resistance between the current collector and the active material layer can be reduced, high output of the electrode can be expected.

(Conductive agent)
The conductive agent contained in the base layer coating material contains carbon black (first carbon black) having a BET specific surface area of 500 m ² / g or less. By using carbon black having such a small BET specific surface area, even if the solid content concentration in the paint is increased, the average particle diameter of the solid content can be reduced, and a uniform coating film can be easily formed.

The BET specific surface area of the first carbon black may be 500 m ² / g or less, preferably 300 m ² / g or less, and may be 150 m ² / g or less. The BET specific surface area of the first carbon black is, for example, 30 m ² / g or more, and preferably 45 m ² / g or more. These upper limit value and lower limit value can be arbitrarily combined. The BET specific surface area of the first carbon black may be, for example, 30 to 500 m ² / g, 45 to 500 m ² / g, or 45 to 300 m ² / g.

As 1st carbon black, what has said BET specific surface area can be especially used without a restriction | limiting. Specific examples of the first carbon black include furnace black, acetylene black, channel black, lamp black, and disk black. These carbon blacks may be used alone or in combination of two or more. In particular, when the conductive agent contains furnace black having a BET specific surface area of 500 m ² / g or less, the reason is not clear, but it is easy to reduce the contact resistance in the thickness direction of the underlayer.

Furnace black can be easily distinguished from acetylene black by Raman spectrum, for example. More specifically, the Raman spectrum of a carbon material such as carbon black generally has a D-band peak in the vicinity of 1330 cm ⁻¹ (for example, 1320 to 1360 cm ⁻¹ ), and near 1580 cm ⁻¹ (for example, 1560). ˜1590 cm ⁻¹ ) with a G band peak. In the Raman spectrum of carbon black with the Raman shift as the x-axis and the Raman intensity as the y-axis, a straight line passing through the lowest point that is a valley between the D band and the G band based on carbon black and parallel to the x axis is a straight line A And At this time, the Raman shift (cm ⁻¹ ) between the intersection of the curve indicating the Raman spectrum of each of the D band and the G band and the straight line A and the lowest point is defined as a. Further, the Raman intensity between the respective peaks of the D band and the G band and the intersection of the perpendicular drawn from these peaks and the straight line A is defined as b. At this time, acetylene black has a b / a ratio exceeding 3.0 for each band, whereas furnace black has a smaller b / a ratio than acetylene black. When the first carbon black includes furnace black, the b / a ratio is, for example, 3.0 or less, and preferably 2.7 or less or 1.8 or less.

  When the conductive agent (or carbon black) includes carbon black having a relatively large specific surface area, the Raman intensity b (D (b)) at the D band peak with respect to the Raman intensity b (G (b)) at the G band peak. ) Ratio: D (b) / G (b) tends to increase. Further, acetylene black and ketjen black tend to have a larger D (b) / G (b) ratio than furnace black. In a preferred embodiment, the D (b) / G (b) ratio is, for example, less than 1.10, preferably 1.05 or less, and more preferably 1.00 or less.

  The carbon black preferably contains furnace black. When the ratio of furnace black in carbon black increases, the D (b) / G (b) ratio tends to decrease. In this case, the D (b) / G (b) ratio is, for example, 1.05 or less, preferably 1.00 or less, and more preferably 0.90 or less.

In one embodiment of the present invention, it is important to use a conductive agent contained in the base layer coating material containing carbon black having a BET specific surface area of 500 m ² / g or less. However, the same effect can be obtained even when carbon black having a D (b) / G (b) ratio within the above range is used as the conductive agent contained in the coating for the underlayer. The present invention also includes an embodiment using a conductive agent containing carbon black having a D (b) / G (b) ratio in a specific range.

  The b / a ratio and the D (b) / G (b) ratio can be obtained based on the Raman spectrum of the thin film containing carbon black, respectively. More specifically, the b / a ratio is calculated for each of the D band and G band of the Raman spectrum measured for a thin film (underlayer to be described later) formed using the underlayer coating material. The D (b) / G (b) ratio may be calculated by obtaining the Raman intensity b for each of the D band and G band of the Raman spectrum measured in the same manner. In the electrode for electrochemical devices, the active material layer is peeled off to expose the underlayer, and in this state, the Raman spectrum is measured to obtain the b / a ratio and the D (b) / G (b) ratio. be able to. Since the Raman spectrum is measured in the vicinity of the surface layer of the thin film (underlayer), the b / a ratio and the D (b) / G (b) ratio hardly depend on the thickness of the thin film (underlayer). Therefore, the thickness of the thin film (underlying layer) at the time of measuring the Raman spectrum may be appropriately determined within a range that does not hinder the measurement.

  The Raman spectrum can be measured based on, for example, JIS K0137 (2010) “General Rules for Raman Spectroscopic Analysis”. The measurement can be performed, for example, at a temperature of 15 to 25 ° C. and a humidity of 60 to 70% RH.

  Carbon black is composed of secondary particles in which a plurality of primary particles are three-dimensionally connected. The average particle size of the primary particles of the first carbon black is not particularly limited, but is preferably 10 to 50 nm, and preferably 20 to 50 nm or 20 to 45 nm, from the viewpoint of easily reducing the resistance of the underlayer. Further preferred. The average particle size of carbon black can be measured by, for example, a dynamic light scattering method.

  The conductive agent may include a conductive component other than the first carbon black. As long as the conductive agent contains the first carbon black, an effect corresponding to the amount added can be obtained, but the ratio of the first carbon black to the conductive agent is preferably 10% by mass or more, for example. It may be not less than 50% by mass or not less than 50% by mass. The ratio of the first carbon black in the conductive agent is 100% by mass or less.

The conductive agent can further include an amorphous granular carbon material. As an index of the degree of development of the graphite-type crystal structure in the carbon material, an average interplanar spacing _d002 of (002) plane measured by an X-ray diffraction (XRD) spectrum is used. The average spacing d ₀₀₂ of the graphite and a small typically less than 0.337 nm, the average spacing d ₀₀₂ of amorphous particulate carbonaceous material, for example, not less than 0.337 nm. Mean spacing d ₀₀₂ of the particulate carbonaceous material may be at least 0.37 nm, it may be 0.37~0.42nm or 0.38～0.40Nm.

  The granular carbon material, for example, generates particles formed of a phenol resin by reacting an aldehyde compound with a phenol compound in the presence of an acid catalyst and a protective colloid agent, and cures the phenol resin by heating the particles. To obtain cured particles and carbonize the cured particles. The temperature for carbonization is preferably a temperature at which crystallization does not proceed, for example, 500 to 1200 ° C, and preferably 550 to 1000 ° C or 550 to 900 ° C. By carbonizing at such a temperature, an amorphous carbon material can be obtained while ensuring conductivity. JP, 2009-49236, A can be referred to for the manufacturing method of a granular carbon material, for example.

The average particle diameter of the granular carbon material is, for example, 50 nm to 20 μm, and may be 1 to 20 μm or 1 to 10 μm. The average particle diameter of the granular carbon material may be as small as 50 nm to 5 μm or 0.1 to 2 μm, for example. When a granular carbon material having a small average particle diameter is used, it is easy to reduce the thickness of the underlayer. Here, the average particle diameter means the median diameter (D ₅₀ ) in the volume-based particle size distribution.

  The average aspect ratio of the granular carbon material is, for example, 1 to 1.7, and preferably 1 to 1.5. In addition, it can be said that the granular carbon material which has such an average aspect-ratio is substantially spherical shape, and includes the granular carbon material of a spherical shape or an elliptical sphere, or a shape close | similar to these.

The average aspect ratio is a scanning electron micrograph (SEM) of the particulate carbonaceous material, a plurality of arbitrarily selected (e.g., 10) for particles of, perpendicular to each other, and the maximum diameter D _m, the maximum diameter D _m to measure the direction of the diameter (maximum diameter) D _p, determine the aspect ratio of each particle by dividing D _m in D _p, it can be calculated by further averaging.

The BET specific surface area of a granular carbon material can be suitably selected from the range of 1-2500 m < ² > / g, for example. Especially, it is preferable to use what is 1-100 m < ² > / g or 1-50 m < ² > / g.
The single particle ratio of the granular carbon material is preferably 0.7 or more, and may be 0.8 or more. The single particle ratio is a mass ratio of primary particles (single particles) in the entire granular carbon material, where 1 is the mass of the entire granular carbon material.

  When the conductive agent includes the first carbon black and the granular carbon material, the ratio of the first carbon black to the conductive agent is, for example, 10% by mass or more, and preferably 10 to 80% by mass. It may be ˜50% by mass. Even when the ratio of the first carbon black is within such a range, the effect of reducing the contact resistance in the thickness direction of the underlayer can be sufficiently obtained.

The conductive agent may include carbon black (second carbon black) having a BET specific surface area exceeding 500 m ² / g. However, when the second carbon black is used, the solid content concentration, viscosity, and solid content of the coating for the underlayer are used. It becomes difficult to adjust the average particle size. Therefore, the ratio of the second carbon black to the conductive agent is preferably 5% by mass or less or 1% by mass or less, and particularly preferably the conductive agent does not contain the second carbon black.

  Examples of conductive components other than these include conductive carbon materials other than the above, such as graphite and carbon fiber, conductive metal components (metals, alloys, metal compounds, etc.), and conductive polymers.

(Binder)
Examples of the binder (first binder) contained in the coating for the underlayer include, for example, an olefin resin, an acrylate resin, a polyimide resin, a polyamideimide resin, a fluororesin, a cellulose derivative (for example, carboxymethylcellulose (CMC) or Examples thereof include salts thereof (such as Na salt and ammonium salt of CMC) and synthetic rubbers (such as styrene butadiene rubber (SBR)). Examples of fluororesins include polytetrafluoroethylene (PTFE), copolymers containing tetrafluoroethylene (TFE) units, polyvinylidene fluoride (PVDF), copolymers containing vinylidene fluoride (VDF) units (VDF- Hexafluoropropylene (HFP) copolymer, VDF-HFP-acrylic copolymer, etc.). A 1st binder can be used individually by 1 type or in combination of 2 or more types.

  An acrylate resin, a polyamideimide resin, a fluororesin, and a cellulose derivative are preferable from the viewpoint that a high binding force can be obtained with a small amount. The acrylate resin is a general term for resins containing units of acrylic acid or its alkyl ester or methacrylic acid or its alkyl ester.

  From the viewpoint of heat resistance and withstand voltage, among the first binder, a resin having no carbon-carbon double bond and having a melting point of 160 ° C. or higher, a thermosetting resin having a Tg of 260 ° C. or higher, etc. Is preferred. Examples of such a resin include an addition type thermosetting imide (polyimide resin) having an allyl group at both ends and a polyamide imide (PAI) resin. From the viewpoint of heat resistance, a PAI resin is particularly preferable.

  When the PAI resin is used, when the electrode is manufactured, it can be dried at a high temperature, so that water can be prevented from remaining on the electrode. Since water is electrolyzed and gasified in the electrochemical element, it is considered as a deterioration factor. When a PAI resin is used as the first binder, such remaining of water can be suppressed, so that the durability of the electrode and thus the electrochemical element can be improved.

  As the first binder, those that can be used in a state dispersed in an aqueous medium (for example, fluororesin, synthetic rubber, PAI resin, cellulose derivative, acrylate resin, etc.) are also preferable. Among these, fluororesin, synthetic rubber, and PAI resin are preferable. It is preferable to use at least one selected from the group (particularly PAI resin) and a cellulose derivative.

  The amount of the first binder contained in the base layer coating is, for example, 1 to 70 parts by weight, preferably 1 to 60 parts by weight, based on 100 parts by weight of the conductive agent contained in the base layer coating. 3-40 mass parts may be sufficient. If the specific surface area of the first carbon black is large, it is necessary to use a large number of first binders in order to ensure sufficient film formability. In the present embodiment, even when the amount of the first binder is in such a range, sufficient film forming property and high binding force between the current collector and the active material layer can be ensured, The resistance of the underlayer can be suppressed low.

  Among the first binders, the cellulose derivative also functions as a dispersant for dispersing the solid content in the coating for the underlayer. By using a cellulose derivative, it becomes easy to disperse | distribute solid content containing 1st carbon black more uniformly, and the average particle diameter of solid content can be made smaller. The amount of the cellulose derivative contained in the base layer coating is, for example, 0.1 to 50 parts by weight, preferably 1 to 20 parts by weight, with respect to 100 parts by weight of the conductive agent contained in the base layer coating. More preferably, it is 10 mass parts.

(Liquid component)
The liquid component of each slurry may be appropriately selected from water, an organic medium, a mixture thereof, and the like according to the type of the binder. Examples of the organic medium include alcohols, dimethylformamide, amides such as N-methyl-2-pyrrolidone (NMP), ethers such as tetrahydrofuran, and esters such as ethyl acetate. For example, when using a fluororesin such as acrylate resin, cellulose derivative, PAI resin, PTFE, VDF copolymer, or synthetic rubber as a binder, water or a mixture of water and an organic medium is used as a liquid component. The Moreover, when using fluororesins, such as PVDF and a VDF copolymer, you may use organic media like NMP.

From the viewpoint of ensuring a safe working environment, it is preferable to use a liquid component containing water. Examples of such a liquid component include water and a mixed medium of water and a water-soluble organic medium such as alcohol (such as an aliphatic alcohol having 1 to 4 carbon atoms such as ethanol and isopropanol).
The ratio of the water which occupies in a liquid component is 70-100 mass%, for example, and 80-100 mass% or 90-100 mass% is preferable.

  When preparing the slurry, the binder may be used in the form of an emulsion or dispersion as necessary. In addition to a stabilizer for stabilizing the slurry, a known additive such as a surfactant or an antifoaming agent may be added to each slurry as necessary.

  In the present embodiment, since the first carbon black having a relatively low BET specific surface area is used, the viscosity of the coating for the underlayer can be maintained in an appropriate range even if the solid content concentration is increased. Therefore, the solid content concentration of the coating material for the underlayer can be increased to, for example, 15 to 30% by mass or 20 to 30% by mass. The solid content concentration can be adjusted by adjusting the BET specific surface area of the first carbon black, the type and amount of the conductive agent, the type and molecular weight of the first binder, and the like. From the viewpoint of easily adjusting the solid content concentration, it is preferable to use at least a cellulose derivative such as CMC or a salt thereof as the first binder.

The base layer coating material is a slurry in which a solid component such as a conductive agent is dispersed in a liquid component. The binder may be dispersed in the liquid component or may be dissolved. In the present embodiment, since the first carbon black having a relatively low BET specific surface area is used, the average particle size of the solid content contained in the underlayer coating material can be reduced to 1.5 μm or less. It can suppress that the viscosity of this increases too much. The average particle size of the solid content in the coating for the underlayer is preferably 0.5 μm or less, and more preferably 0.4 μm or less or 0.3 μm or less.
The average particle size of the solid, for example, a median diameter (D ₅₀₎ in volume-based particle size distribution measured by laser diffraction particle size distribution measuring apparatus. In the measurement, the paint may be diluted with a dispersion medium as necessary. As the dispersion medium, a liquid that does not dissolve the solid content is used.

  The viscosity of the base layer coating material is, for example, 50 to 1500 mPa · s, and preferably 50 to 700 mPa · s. The viscosity is measured at 25 ° C. using, for example, a commercially available spindle type B-type viscometer. In order to reduce the viscosity while maintaining a high solid content concentration, it is also advantageous to use an amorphous granular carbon material in combination with the first carbon black as a conductive agent.

  Since the base layer coating material has the above composition, it is possible to form a base layer with reduced contact resistance in the thickness direction. Since the underlayer is disposed between the current collector and the active material layer, the underlayer coating material is useful for reducing the interface resistance between the current collector and the active material layer. In addition, the base layer can ensure high adhesion between the current collector and the active material layer. The coating for the underlayer is easy to adjust the thickness of the underlayer, has a high film forming property, and even when the thickness of the underlayer is large, it is easy to obtain a uniform underlayer with high adhesion.

[Electrodes for electrochemical devices]
The present invention also includes an electrode for an electrochemical device including a current collector, a base layer formed on the surface of the current collector, and an active material layer formed on the surface of the base layer. The underlayer can be formed using the above-mentioned underlayer paint. The electrochemical element mainly means a capacitor or a battery, and includes, for example, EDLC, P-EDLC, lithium ion battery and the like. The structure of the capacitor or battery is not particularly limited, and includes a coin type, a wound type, a laminated type, and the like.

Hereinafter, the structure of the electrode for an electrochemical element according to the present invention will be described with reference to schematic longitudinal sectional views of the electrode.
FIG. 1 is a longitudinal sectional view schematically showing an example of the structure of an electrode according to the present invention. Here, a case where the active material layer 2 is provided on one surface of the current collector 1 will be described. However, the electrode according to the present invention is not limited to the form of FIG. 1, and the active material layer and the base layer (or conductive layer) are provided on one side of the current collector, and the active material layer and the both sides of the current collector are provided. The case where an underlayer is provided is included. Further, if necessary, the active material layer and the base layer may be formed on one main surface of the current collector, and the active material layer may be directly formed on the other main surface.

  In FIG. 1, the base layer 3 is formed on one main surface of the current collector 1, and the active material layer 2 is formed on the surface of the base layer 3. When the underlayer 3 contains the conductive agent and the binder, the contact resistance in the thickness direction can be greatly reduced while keeping the volume resistivity in the surface direction low to some extent.

Next, each component of the electrode for electrochemical devices according to the present invention will be described in more detail.
(Current collector)
The current collector is usually in the form of a sheet. A metal foil is preferably used for the current collector. The thickness of the metal foil is, for example, 8 to 60 μm, preferably 20 to 40 μm. Examples of the material of the metal foil include metals such as Al, Ni, Cu, Fe, Cr, and Mo or alloys containing at least one selected from these metals (for example, Al alloys, Ni alloys, Cu alloys, and stainless steels). It is done. Aluminum foil is preferably used for the capacitor electrode and the positive electrode of the lithium ion battery. Also, copper foil is preferably used for the negative electrode of the lithium ion battery. The metal foil may be a plain foil that has not been subjected to an etching treatment, or may be an etching foil. The plain foil can be expected to have high withstand voltage characteristics. The etching foil is excellent in adhesion with the base layer. The current collector may have a three-dimensionally processed structure. For example, a punching foil or a lath wire mesh current collector may be used.

(Underlayer)
The underlayer is formed using an underlayer paint. The thickness of the underlayer varies depending on the type of electrode, but for example, a range of 0.5 to 40 μm can be selected. In the case of EDLC, it is 1-20 micrometers, for example, and in the case of a lithium ion secondary battery, it is 10-40 micrometers, for example. Even in the case where the thickness of the underlayer is large (for example, 5 μm or more), in the present invention, the contact resistance in the thickness direction can be reduced, so that high output can be achieved. The thickness of the underlayer may be 0.5 to 15 μm or 1 to 10 μm.

In the present invention, the contact resistance in the thickness direction of the underlayer is, for example, 10Ω / mm or less, and can be further reduced to 6Ω / mm or less or 5Ω / mm or less.
The contact resistance in the thickness direction of the underlayer is the contact resistance (Ω) (normalized contact resistance (Ω / mm)) of the underlayer per unit thickness (1 mm) of the underlayer. Normalized contact resistance was prepared by providing two current collectors on which an underlayer was formed, and overlaid with a conductive plate (stainless steel (SUS) plate) with the underlayer facing each other, and applying a predetermined load. In this state, the resistance (Ω) between the two underlayers is obtained, converted per sheet, and divided by the thickness (mm) of the underlayer.

In general, it is difficult to keep the volume resistivity in the plane direction low while keeping the contact resistance in the thickness direction of the underlayer low. In the present invention, the volume resistivity in the surface direction can be lowered while reducing the contact resistance in the thickness direction of the underlayer as described above. The volume resistivity in the surface direction of the underlayer is, for example, 1.0 Ω · cm or less, and may be 0.1 to 0.5 Ω · cm.
The volume resistivity (Ω · cm) in the surface direction of the underlayer is determined by forming the underlayer on the surface of the resin film and measuring the surface resistivity (Ω / □) of the underlayer. It can be obtained by multiplying (cm).

(Active material layer)
An active material layer is formed on the surface of the base layer.
The active material layer includes an active material, and may further include a binder (second binder) and / or a conductive agent (carbon black or the like) as necessary.
As the active material, for example, activated carbon, graphite, hard carbon, soft carbon, transition metal compound, silicon, silicon compound, or the like can be used depending on the type of electrochemical element. These active materials may be used alone or in combination of two or more as necessary.

  In the case of an electrode for an electric double layer capacitor, activated carbon is used as an active material. In this case, the positive electrode (anode) and the negative electrode (cathode) both contain activated carbon as an active material. On the other hand, in the case of a pseudo capacitor, various materials are used as the active material. For example, activated carbon is used for the positive electrode, and graphite, soft carbon, hard carbon, or the like is used for the negative electrode.

Also in the case of an electrode for a lithium ion battery, various materials are used as the active material. A transition metal compound or the like is used for the positive electrode. As the transition metal compound, a lithium-containing transition metal oxide containing at least one selected from the group consisting of Co, Ni and Mn and an olivic acid (LiFePO ₄ ) type compound are preferably used. For the negative electrode, graphite, soft carbon, hard carbon, silicon, silicon compounds (silicon carbide, silicon oxide, etc.) and the like are used.

  The present invention can be applied to any of these electrodes, but is most effective when applied to electrodes for electric double layer capacitors and pseudocapacitors.

  In the active material layer, it is preferable to use the material shown as the first binder for the second binder. The second binder may be a different material from the first binder, but the same material may be used from the viewpoint of improving the adhesion between the base layer and the active material layer. For example, when a PAI resin is used as the first binder, a PAI resin may also be used as the second binder.

  In the active material layer, the amount of the second binder varies depending on the type of the electrode. For example, in the case of an electric double layer capacitor or a pseudo capacitor, 3 to 10 parts by mass with respect to 100 parts by mass of the active material (activated carbon or graphite). Furthermore, 4-6 mass parts is suitable. When the amount of the second binder is increased, the adhesion between the underlayer and the active material layer is improved, but the direct current resistance and the alternating current resistance (ESR) tend to increase. When there is too little 2nd binder amount, there exists a tendency for the adhesiveness of active material particles to fall.

  The thickness of the active material layer varies depending on the type of electrode, but is, for example, 50 to 200 μm in the case of an electric double layer capacitor. In the case of a coin-type electrochemical device, the thickness of the active material layer is 400 to 700 μm.

  The electrode is applied to the surface of the current collector with a base layer paint (specifically, a slurry for the base layer (first slurry)) and dried to form the base layer. On the surface of the base layer, The active material layer slurry (second slurry) can be applied and dried to form an active material layer. Alternatively, the electrode may be formed by forming a coating film of the first slurry and a coating film of the second slurry on the surface of the current collector and drying. If necessary, the electrode precursor on which the electrode and the base layer are formed may be compressed in the thickness direction by a roller or the like. In addition, it does not restrict | limit especially as a coating method of the coating material for base layers, Various methods, such as a gravure coat, a die coat, a kiss coat, can be used. From the viewpoint of easily forming a thin film, gravure coating is preferred.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example and a comparative example, this invention is not limited to a following example.

Example 1
A paint for the underlayer (first slurry) was prepared by the following procedure, and an undercoat layer was formed using the prepared paint. For the underlayer, the resistance in the thickness direction (contact resistance) and the resistance in the surface direction (volume resistivity) were measured.

(1) Preparation of first slurry CMC ammonium salt was added and dissolved in an aqueous isopropyl alcohol solution (concentration: 4.1 mass%) with stirring. Under stirring, carbon black (furnace black, BET specific surface area: 50 m ² / g, average primary particle size: 38 nm) was added to the resulting mixture and dispersed using a bead mill. Next, a first slurry was prepared by adding PAI resin and stirring. The amount of CMC ammonium salt was 3 parts by mass and the amount of PAI resin was 16 parts by mass with respect to 100 parts by mass of carbon black. The solid content concentration in the first slurry was 22.5% by mass, and the viscosity was 223 mPa · s. It was 0.3 micrometer when the average particle diameter of solid content in a 1st slurry was measured in the above-mentioned procedure.

(2) Evaluation (a) Resistance in the thickness direction (contact resistance)
The first slurry is applied with a wire bar to one surface of a current collector (etched aluminum foil (arithmetic mean roughness Ra: 0.112 μm), length 40 cm × width 15 cm, thickness 30 μm) A film was formed. At this time, the coating film was applied so that an uncoated part was formed around it. And the base layer was formed by drying a coating film. The thickness of the underlayer was 6.8 μm. A current collector having an underlayer was cut into a 10 cm long by 5 cm wide rectangle to prepare a sample. At this time, it cut so that it might have an uncoated part in the one end part of a longitudinal direction. A total of six similar samples were prepared.

Two samples are sandwiched between SUS plates (diameter 30 mm, thickness 5 mm) with the base layers facing each other, and two SUS plates (length 40 mm x width 40 mm, thickness 5 mm) from both sides of the current collector I caught it. Place the obtained laminate on a table so that the two SUS plates are up and down, apply a load of 34 kgf / cm ² (≈3.3 MPa) from above, and measure the resistance of the uncoated part of each sample. Device (Digital Hitester 3239, manufactured by Hioki Electric Co., Ltd.). In this state, the resistance between two samples (contact resistance) is measured, converted to one sample, and further divided by the thickness (mm) of the underlayer to normalize the contact resistance (Ω / mm )
The same measurement was performed using the remaining samples, and the result was obtained as an average of three times.

(B) Plane direction resistance (volume resistivity)
The first slurry was applied to one surface of a polyethylene terephthalate film (thickness: 100 μm) with a wire bar, a coating film was formed, and the base layer was formed by drying. The thickness of the underlayer was 7.9 μm. A sample having a base layer was cut into a size of 8 cm long × 5 cm wide to prepare a sample. A total of four similar samples were prepared.

  One sample was set in a resistance measuring instrument (Loresta GP MCP-T610 type), and the surface resistivity (Ω / □) was measured. The volume resistivity (Ω · cm) was determined by multiplying the surface resistivity by the thickness (cm) of the underlayer. Each sample was measured in the same manner, and the result was obtained as an average value of four samples.

(C) Adhesion strength (peel strength)
Using the first slurry, a base layer was formed on one surface of the current collector in the same manner as in the evaluation of contact resistance. The peel strength (initial peel strength) of the sample thus prepared was determined. Note that the peel strength is measured by applying an adhesive tape (25 mm wide) to the surface of the underlayer, lifting one end of the adhesive tape and pulling it in the opposite direction 180 degrees, and then measuring the peel strength with a spring weight. did.

(D) b / a ratio Using the first slurry, a base layer was formed on one surface of the current collector in the same manner as in the evaluation of contact resistance. Based on JIS K0137 (2010) “Raman spectroscopic analysis rules”, the Raman spectrum of the underlayer produced in this way was measured at a temperature of 20 ± 2 ° C. and a humidity of 65 ± 2% RH. RAMANtouch (registered trademark): manufactured by nanophoton. At this time, the measurement was performed under the conditions of an excitation wavelength of 532 nm, an exposure time of 15 seconds, an integration number of 5, an excitation output of 1.6 mW, a diffraction grating of 600 gr / mm, an objective lens of 50 times, and a numerical aperture (NA) of 0.60. For each of the D band and G band, the b / a ratio and the D (b) / G (b) ratio from the Raman intensity b of the D band and G band were determined by the procedure described above. For each band, the b / a ratio and the D (b) / G (b) ratio were measured at any four locations of the underlayer, and the average value was calculated. The b / a ratio of the D band was 0.8. The b / a ratio of the G band was 1.2, and the D (b) / G (b) ratio was 0.8.
FIG. 2 shows the Raman spectrum measured at any one location of the underlayer of Example 1.

Example 2
As carbon black, acetylene black (BET specific surface area: 133 m ² / g, average primary particle size: 26 nm) was used instead of furnace black. The amount of CMC ammonium salt was 5 parts by mass with respect to 100 parts by mass of carbon black. Except for these, a first slurry was prepared in the same manner as in Example 1. The solid content concentration in the first slurry was 22.9% by mass, the viscosity was 516 mPa · s, and the average particle size of the solid content in the first slurry was 0.4 μm. Evaluation was performed in the same manner as in Example 1 except that the obtained first slurry was used. The thickness of the underlayer was 9.2 μm, the b / a ratio was D band 3.2 and G band 3.6, and the D (b) / G (b) ratio was 1.0. .

Example 3
As carbon black, furnace black (BET specific surface area: 225 m ² / g, average primary particle size: 25 nm) was used in place of the furnace black used in Example 1. Further, in order to obtain a uniform slurry while keeping the solid content concentration substantially the same as in Example 1, the amounts of CMC ammonium salt and PAI resin with respect to 100 parts by mass of carbon black were changed to 7 parts by mass and 52 parts by mass, respectively. did. Moreover, the density | concentration of the isopropyl alcohol aqueous solution was 3.3 mass%, and the usage-amount of the aqueous solution was adjusted suitably. Except for these, a first slurry was prepared in the same manner as in Example 1. The solid content concentration in the first slurry was 21.4% by mass, the viscosity was 1216 mPa · s, and the average particle size of the solid content in the first slurry was 0.2 μm. Evaluation was performed in the same manner as in Example 1 except that the obtained first slurry was used. The thickness of the underlayer was 7.8 μm, the b / a ratio was D band 1.2 and G band 1.6, and the D (b) / G (b) ratio was 0.9. .

Comparative Example 1
As carbon black, ketjen black (BET specific surface area: 800 m ² / g, average primary particle size: 39.5 nm) was used instead of the furnace black used in Example 1. In order to make the solid content concentration as high as possible and to obtain a uniform slurry, the amounts of CMC ammonium salt and PAI resin with respect to 100 parts by mass of carbon black were 50 parts by mass and 80 parts by mass, respectively. Moreover, the density | concentration of the isopropyl alcohol aqueous solution was 5.9 mass%, and the usage-amount of aqueous solution was adjusted suitably. Except for these, a first slurry was prepared in the same manner as in Example 1. The solid content concentration in the first slurry was 13.4% by mass, the viscosity was 4200 mPa · s, and the average particle size of the solid content in the first slurry was 0.8 μm. Evaluation was performed in the same manner as in Example 1 except that the obtained first slurry was used. The thickness of the underlayer was 6.6 μm, the b / a ratio was D band 2.0 and G band 2.2, and the D (b) / G (b) ratio was 1.2. .

Comparative Example 2
As carbon black, ketjen black (BET specific surface area: 1270 m ² / g, average primary particle size: 30 nm) was used in place of the furnace black used in Example 1. Further, in order to make the solid content concentration as high as possible and to obtain a uniform slurry, the amounts of CMC ammonium salt and PAI resin with respect to 100 parts by mass of carbon black were 30 parts by mass and 32 parts by mass, respectively. Further, the concentration of the aqueous isopropyl alcohol solution was adjusted to 0.9% by mass, and the amount of the aqueous solution used was appropriately adjusted. Except for these, a first slurry was prepared in the same manner as in Example 1. The solid content concentration in the first slurry was 8.1% by mass, the viscosity was 1840 mPa · s, and the average particle size of the solid content in the first slurry was 2.9 μm. Evaluation was performed in the same manner as in Example 1 except that the obtained first slurry was used. In addition, the thickness of the underlayer was 4.0 μm, the b / a ratio was D band 3.7 and G band 3.9, and the D (b) / G (b) ratio was 1.4. .

Comparative Example 3
As carbon black, furnace black (BET specific surface area: 1500 m ² / g, average primary particle size: 12 nm) was used in place of the furnace black used in Example 1. Further, in order to make the solid content concentration as high as possible and to obtain a uniform slurry, the amounts of CMC ammonium salt and PAI resin with respect to 100 parts by mass of carbon black were changed to 19 parts by mass and 52 parts by mass, respectively. Moreover, the density | concentration of the isopropyl alcohol aqueous solution was 1.3 mass%, and the usage-amount of aqueous solution was adjusted suitably. Except for these, a first slurry was prepared in the same manner as in Example 1. The solid content concentration in the first slurry was 11.6% by mass, the viscosity was 544 mPa · s, and the average particle size of the solid content in the first slurry was 2.7 μm. Evaluation was performed in the same manner as in Example 1 except that the obtained first slurry was used. The thickness of the underlayer was 6.6 μm, the b / a ratio was D band 1.3 and G band 1.7, and the D (b) / G (b) ratio was 1.1. .

  The results of normalized contact resistance of Examples 1 to 3 and Comparative Examples 1 to 3 are shown in FIG. 3, the results of volume resistivity are shown in FIG. 4, and the results of adhesion strength (peel strength) are shown in FIG. 3 to 5, “Ex.” Is attached to the examples, and “ComEx.” Is attached to the comparative examples.

In the comparative example using carbon black having a BET specific surface area of more than 500 m ² / g, the volume resistivity in the plane direction is not much different from that in the example, but the contact resistance in the thickness direction is significantly higher than that in the example. . In these comparative examples, the D (b) / G (b) ratio was 1.1 or more.

Moreover, in the comparative example, even if it tried to raise solid content concentration of a 1st slurry like an Example, it could raise only to 8.1 to 13.4%. In the comparative example, a large amount of CMC salt is required to disperse carbon black, and a large amount of PAI resin needs to be added in order to ensure a certain degree of film formability. The CMC salt of the dispersant functions as a first binder together with the PAI resin. Therefore, it is considered that a large amount of the first binder is contained in the underlayer, and it is difficult to form a uniform coating film and the contact resistance is increased.
On the other hand, in Examples using carbon black having a BET specific surface area of 500 m ² / g or less (or D (b) / G (b) ratio is less than 1.1), the normalized contact resistance in the thickness direction is 4.7Ω. / Mm or less, and the volume resistance in the surface direction is also low. Also, high adhesion strength can be secured.

Example 4
CMC Na salt and CMC ammonium salt were added and dissolved in an aqueous isopropyl alcohol solution (concentration: 4.2 mass%) with stirring. Under stirring, the resulting mixture is mixed with a granular carbon material, CNT (multi-walled carbon nanotube, average fiber diameter 150 nm, fiber length 10 to 20 μm, aspect ratio 67 to 133), and carbon black (furnace black, BET specific surface area: 33 m ² / g, average primary particle size: 55 nm) was added and dispersed using a bead mill. A first slurry was prepared by adding PAI resin and stirring. The mass ratio of the granular carbon material, CNT, and carbon black was 80: 2: 18. The amount of Na salt of CMC is 0.5 parts by mass, the amount of ammonium salt of CMC is 2.5 parts by mass, and the amount of PAI resin is 4 parts by mass with respect to 100 parts by mass of the total amount of granular carbon material, CNT and carbon black. The part. The solid content concentration in the first slurry was 22.8% by mass, and the viscosity was 80 mPa · s. When the average particle size of the solid content in the first slurry was measured by the procedure described above, it was 1.3 μm. Evaluation was performed in the same manner as in Example 1 except that the obtained first slurry was used. The thickness of the underlayer was 8.2 μm, the b / a ratio was D band 0.6, the G band 1.1, and the D (b) / G (b) ratio was 0.8. .

In addition, the used granular carbon material was synthesize | combined in the following procedures.
CMC Na salt (protective colloid agent) aqueous solution (CMCNa salt concentration 2 mass%) 0.4 mass with respect to 100 mass parts of an aqueous solution containing formaldehyde and hydrochloric acid (formaldehyde concentration 10 mass%, hydrochloric acid concentration 16 mass%) Was added and stirred. The temperature of the obtained aqueous solution was adjusted to 20 ° C., and 3.5 parts by mass of 30 ° C. phenol (purity 95% by mass) was added and mixed with stirring. The mixture was stirred until it became light pink from the cloudy state (temperature of the reaction mixture: about 30 ° C.). The reaction mixture was heated to 80 ° C. with stirring and held at 80 ° C. for about 30 minutes. The obtained mixture was filtered to recover the solid content, and the solid content was washed with water, suspended in 5% by mass ammonia water, and stirred at 40 ° C. for 1 hour to neutralize. The suspension was filtered to recover the solid content, washed with water, and dried to obtain a granular phenol resin.

The phenol resin was placed in an electric furnace, heated to 950 ° C. at a rate of 100 ° C./hour in a nitrogen gas atmosphere, and carbonized by firing at 950 ° C. for 3 hours. In this way, a granular carbon material was synthesized.
When the average aspect ratio and the average particle diameter were determined from the SEM image of the obtained granular carbon material by the procedure described above, the average aspect ratio was 1.0 and the average particle diameter was 2 μm. The obtained granular carbon material was almost spherical. Mean spacing d ₀₀₂ of the particulate carbonaceous material is not less than 0.337 nm, it was amorphous.

Example 5
A first slurry was prepared in the same manner as in Example 4 except that furnace black (BET specific surface area: 50 m ² / g, average primary particle size: 38 nm) was used instead of furnace black used in Example 4. did. The solid content concentration in the first slurry was 22.8% by mass, the viscosity was 80 mPa · s, and the average particle size of the solid content in the first slurry was 1.1 μm. Evaluation was performed in the same manner as in Example 1 except that the obtained first slurry was used. The underlayer had a thickness of 7.5 μm. The b / a ratio was D band 0.8 and G band 1.2, and the D (b) / G (b) ratio was 0.8.

Example 6
A first slurry was prepared in the same manner as in Example 4 except that acetylene black (BET specific surface area: 133 m ² / g, average primary particle size: 26 nm) was used instead of the furnace black used in Example 4. did. The solid content concentration in the first slurry was 22.8% by mass, the viscosity was 204 mPa · s, and the average particle size of the solid content in the first slurry was 1.4 μm. Evaluation was performed in the same manner as in Example 1 except that the obtained first slurry was used. Note that the thickness of the underlayer was 8.5 μm. The b / a ratio was D band 3.2 and G band 3.6, and the D (b) / G (b) ratio was 1.0.

Example 7
A first slurry was prepared in the same manner as in Example 4 except that furnace black (BET specific surface area: 225 m ² / g, average primary particle size: 25 nm) was used instead of furnace black used in Example 4. did. The solid content concentration in the first slurry was 22.8% by mass, the viscosity was 148 mPa · s, and the average particle size of the solid content in the first slurry was 1.4 μm. Evaluation was performed in the same manner as in Example 1 except that the obtained first slurry was used. The base layer had a thickness of 7.0 μm. The b / a ratio was D band 1.2 and G band 1.6, and the D (b) / G (b) ratio was 0.9.

The results of normalized contact resistance in Examples 4 to 7 are shown in FIG. 6, the results of volume resistivity are shown in FIG. 7, and the results of adhesion strength (peel strength) are shown in FIG. 6 to 8, Examples 4 to 7 are referred to as Ex. 4 to Ex. This is shown in FIG.
In Examples 4 to 7 using carbon black having a BET specific surface area of 500 m ² / g or less (or a D (b) / G (b) ratio of less than 1.1), while securing a low volume resistivity, The normalized contact resistance is reduced to an extent comparable to Examples 1-3. In Examples 4 to 7, high adhesion strength was obtained.

Examples 8-11
As carbon black, instead of the acetylene black of Example 2, both the same furnace black as used in Example 1 and the same acetylene black as used in Example 2 were used in the following mass ratio. . Except for this, a first slurry was prepared in the same manner as in Example 2. In Example 11, the first slurry was prepared in the same manner as in Example 1 except that the concentration of the isopropyl alcohol aqueous solution and the amount of ammonium salt of CMC relative to 100 parts by mass of carbon black were the same as in Example 2. . Evaluation was performed in the same manner as in Example 1 except that the obtained first slurry was used.
Furnace Black: Acetylene Black =
100: 0 (Example 11, underlayer thickness: 8.2 μm, b / a ratio: D band 0.9, G band 1.3, D (b) / G (b) ratio: 0.8)
75: 25 (Example 8, thickness of base layer: 9.7 μm, b / a ratio: D band 1.5, G band 1.8, D (b) / G (b) ratio: 0.9)
50: 50 (Example 9, underlayer thickness: 10.8 μm, b / a ratio: D band 2.2, G band 2.5, D (b) / G (b) ratio: 1.0)
25: 75 (Example 10, thickness of base layer: 10.0 μm, b / a ratio: D band 2.5, G band 2.7, D (b) / G (b) ratio: 1.0)
0: 100 (Example 2, underlayer thickness: 9.2 μm, b / a ratio: D band 3.2, G band 3.6, D (b) / G (b) ratio: 1.0)

The results of normalized contact resistance of Examples 8 to 11 are shown in FIG. 9, the results of volume resistivity are shown in FIG. 10, and the results of adhesion strength (peel strength) are shown in FIG. 9 to 11 also show the results of Example 2. 9 to 11, Examples 2 and 8 to 11 are referred to as Ex. 2, and Ex. 8-Ex. 11.
In Examples 8 to 11 using carbon black having a BET specific surface area of 500 m ² / g or less (or a D (b) / G (b) ratio of less than 1.1), while securing a low volume resistivity, The normalized contact resistance has been reduced to a value comparable to or smaller than Examples 1-3. In Examples 8 to 11, high adhesion strength was obtained.

Example 12
A first slurry was prepared in the same manner as in Example 1 except that an acrylate resin (Tg: −40 ° C.) was used instead of the PAI resin as a binder. Using the obtained first slurry, a base layer was formed on one surface of the current collector in the same manner as in the evaluation of contact resistance. The peel strength (initial peel strength) of the sample thus prepared was determined in the same manner as in Example 1.
Subsequently, it was put into a 150 ° C. hot air drying furnace to evaluate the change in peel strength with time (peel strength after 1, 2 and 7 days). Example 1 also taught the change in peel strength over time.
The measurement results are shown in FIG. In FIG. 12, the acrylate resin is represented by AC.

  As shown in FIG. 12, the initial peel strength was high when any of the binders was used, and there was no significant difference between the two. However, after 1 day at 150 ° C., Example 1 using PAI resin had a high value of 488 gf / 25 mm (≈4.8 N / 25 mm), whereas Example 12 using acrylate resin had 75 gf. / 25 mm (≈0.74 N / 25 mm). In Example 1 using PAI resin, peel strength comparable to the initial peel strength was obtained even after 7 days, whereas in Example 12 using acrylate resin, 44 gf / 25 mm (≈0.41 N). / 25 mm).

Example 13
(1) Production of electrode An EDLC electrode was produced by the following procedure.
A first slurry was prepared in the same manner as in Example 1.
Activated carbon (average particle size 8 μm) as an active material, acetylene black (average particle size of primary particles 0.03 μm) as a conductive agent, SBR as a binder, and a predetermined amount of water are mixed in a mixer. Thus, a second slurry was prepared.

  The first slurry is applied to one surface of an etched aluminum foil having a thickness of 30 μm (arithmetic average roughness Ra: 0.112 μm) to form a coating film having a thickness of about 20 μm, and then dried. A stratum was formed. The active material layer was formed by apply | coating a 2nd slurry to the surface of a base layer, forming a coating film with a thickness of 270 micrometers, and drying. The total thickness of the base layer and the active material layer after drying was 88 μm. Thereafter, it was compressed to 80 μm by a roll press apparatus. In this way, an electrode for EDLC was produced.

(2) ESR measurement A 2032 coin cell type EDLC was prepared using an electrode, and an ESR at a frequency of 1 kHz was measured using an LCR meter “4284A” manufactured by Agilent, and it was 3.9Ω.

Comparative Example 4
An electrode was prepared and ESR was measured in the same manner as in Example 13 except that the active material layer was directly formed on one surface of the aluminum foil as a current collector without forming the base layer. As a result, the ESR was 5.5Ω.
It can be seen that ESR is lower in Example 13 than in Comparative Example 4, and the resistance at the electrode is lower.

  In addition, although the said Example demonstrated the electrode for EDLC, it can manufacture by the same or similar method as the above also about the electrode of a pseudo capacitor or a secondary battery.

  The underlayer coating composition according to the present invention can form a low resistance underlayer and can increase the output, and thus can be applied to various electrodes for electrochemical devices. In particular, it is effective in large-sized electrochemical elements (capacitors such as EDLC) applied to large-scale industrial machines such as construction machines such as automobiles and cranes.

1 Current collector 2 Active material layer 3 Underlayer

Claims (11)

In an electrode for an electrochemical device including a current collector and an active material layer formed on the current collector, an underlayer disposed between the current collector and the active material layer is formed. A coating for the underlayer,
Including a conductive agent, a binder, and a liquid component;
The conductive agent includes carbon black,
The carbon black has a specific surface area of 500 m ² / g or less by the BET method,
The concentration of the solid content in the paint for the underlayer is 15 to 30% by mass,
An undercoat paint having an average particle size of the solid content of 1.5 µm or less.   The paint for base layers according to claim 1, having a viscosity of 50 to 1500 mPa · s.   The paint for an underlayer according to claim 1 or 2, wherein the liquid component contains water.   The said binder is a base layer coating material of Claim 3 containing at least 1 type selected from the group which consists of a fluororesin, synthetic rubber, and a polyamideimide resin, and a cellulose derivative.   The paint for base layers according to claim 1, wherein a ratio of the carbon black in the conductive agent is 10% by mass or more.   The paint for an underlayer according to any one of claims 1 to 5, wherein the conductive agent further contains an amorphous granular carbon material.   The undercoat paint according to any one of claims 1 to 6, wherein the carbon black includes furnace black. The said specific surface area is the coating material for base layers of any one of Claims 1-7 which is 45-300 m < ² > / g.   The amount of the said binder is a coating material for base layers of any one of Claims 1-8 which is 1-70 mass parts with respect to 100 mass parts of said electrically conductive agents. A current collector,
An underlayer formed on the surface of the current collector;
An active material layer formed on the surface of the underlayer,
The underlayer includes a conductive agent and a binder,
The conductive agent includes carbon black,
The carbon black has a specific surface area of 500 m ² / g or less by the BET method,
The said binder is an electrode for electrochemical elements containing a polyamidoimide resin and a cellulose derivative. The electrode for an electrochemical element according to claim 10, wherein the specific surface area is 45 to 300 m ² / g.

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