JP5600576B2 - Current collector, electrode structure, non-aqueous electrolyte battery, and power storage component - Google Patents

Description

  The present invention relates to a current collector, an electrode structure, a nonaqueous electrolyte battery, and a power storage component. More particularly, the present invention relates to a current collector suitable for use in electrodes of nonaqueous electrolyte batteries, electric double layer capacitors, and lithium ion capacitors.

  Conventionally, non-aqueous electrolyte batteries typified by lithium ion batteries have been required to shorten the charging time, and for this purpose, they must be charged at a high current density. In particular, non-aqueous electrolyte batteries for automobiles are required to be able to discharge at a high current density in order to obtain sufficient acceleration performance. Thus, in order to improve the characteristic (high rate characteristic) in which the battery capacity does not decrease when charging / discharging at a large current density, it is important to reduce the internal resistance of the battery. The internal resistance includes interfacial resistance between constituent elements and resistance to movement of ions as charged particles in the electrolyte, and these must be reduced. Of these, one of the important internal resistances is the interface resistance, and it is known that improving the adhesion between the components is effective as one of the methods for reducing the interface resistance.

  For example, as a method for improving the adhesion between the current collector and the active material layer, a method of covering a metal foil with a conductive resin as a current collector has been proposed, and the following patent documents are coated with an acrylic resin. Techniques to do this are disclosed. In Patent Document 1, as a method for producing a positive electrode having excellent adhesion, a conductive material containing polyacrylic acid or a copolymer of acrylic acid and an acrylic ester as a main binder and carbon powder as a conductive filler is used as a metal foil. A method for producing a positive electrode is disclosed in which a conductive medium is applied, a positive electrode mixture layer is formed on the conductive resin layer, and then dried and integrated. In Patent Document 2, a negative electrode material layer is formed on a negative electrode current collector, and the negative electrode material layer includes a carbon powder capable of occluding and releasing lithium ions and a binder made of PVDF (polyvinylidene fluoride). In the negative electrode plate for a lithium secondary battery containing lithium, a binder layer made of an acrylic copolymer in which a conductive material is mixed between the negative electrode current collector and the negative electrode material layer is formed. A negative electrode plate for a secondary battery is disclosed. Patent Document 3 discloses that an electrode structure having excellent binding properties and excellent cycle characteristics can be obtained. A current collector comprising a metal foil coated with a resin layer comprising an ionomer of an ethylene-methacrylic acid copolymer and a conductive filler. Is disclosed.

Japanese Patent Laid-Open No. 62-160656 JP-A-9-35707 Japanese Patent Laid-Open No. 11-144737

  However, these techniques may not always provide sufficient high rate characteristics. When the current collector is covered with a conductive resin on a conductive substrate such as aluminum or copper, and the interface resistance between the current collector and the active material layer is reduced, the conductive resin layer and the active material layer It is important that the adhesiveness is high and the volume resistivity of the conductive resin layer itself is low. The adhesion mentioned here affects the interfacial resistance between the conductive resin layer and the active material layer, and means that there is no peeling even when the electrolyte is infiltrated, and that the adhesion is strong. Furthermore, since the volume of the active material layer changes due to charge / discharge in nonaqueous electrolyte batteries, the active material layer and the current collector are likely to peel off, and the volume change of the active material is rapid during high-rate charge / discharge. Strong adhesion is required. In the conventional technique, it is estimated that the reduction in the adhesion between the conductive resin layer and the active material layer and the volume resistivity of the conductive resin layer itself are not necessarily sufficient. In addition, when the current collector is covered with a conductive resin layer, the interface resistance due to the adhesion between the conductive substrate and the conductive resin layer is thought to affect the discharge rate. However, most of the proposals for the adhesion between the current collector and the active material layer were not considered together with the adhesion between the conductive substrate and the conductive resin layer.

  The object of the present invention is to reduce the internal resistance of a non-aqueous electrolyte battery, and can be suitably used for non-aqueous electrolyte batteries such as lithium ion secondary batteries, electric double layer capacitors, lithium ion capacitors and other power storage components. An object of the present invention is to provide a current collector capable of improving characteristics. The current collector of the present invention can provide an electrode structure having a low interface resistance with the active material layer or the electrode material layer by forming the active material layer or the electrode material layer. In addition, a nonaqueous electrolyte battery using an electrode structure in which an active material layer is formed on a current collector of the present invention is a non-aqueous electrolyte battery that has a current collector having the above characteristics and has reduced internal resistance and improved high rate characteristics. A water electrolyte battery can be provided. Furthermore, the present invention provides a power storage component such as an electric double layer capacitor or a lithium ion capacitor that is required for charging and discharging with a large current used in a copying machine or an automobile.

  By using the following current collector, it is possible to obtain a non-aqueous electrolyte battery excellent in high-rate characteristics, a charged component such as an electric double layer capacitor or a lithium ion capacitor.

  That is, according to the present invention, a current collector in which an acrylic resin layer having conductivity is formed on at least one surface of a conductive substrate, the acrylic resin layer includes an acrylic resin and conductive particles, A current collector having a water contact angle of 30 degrees or more and 110 degrees or less measured in a constant temperature room of 23 ° C. on the surface of the acrylic resin layer by the θ / 2 method, and an electrode provided with the current collector A structure, a nonaqueous electrolyte battery, and a power storage component (eg, an electric double layer capacitor or a lithium ion capacitor) are provided.

  When the present inventors diligently studied to improve the high rate characteristics of a non-aqueous electrolyte battery or the like, it was found that the water contact angle on the surface of the acrylic resin layer strongly correlates with the high rate characteristics. And when the water contact angle was 30 degrees or more and 110 degrees or less, it discovered that a high rate characteristic was very excellent and came to completion of this invention.

  The present invention is based on two findings. The first finding is that the high rate characteristic is good when the water contact angle is 110 degrees or less. The contact angle is one of indexes indicating whether different materials are likely to adhere to each other. The smaller the contact angle, the higher the adhesion between different materials. Therefore, when the contact angle is 110 degrees or less, the adhesiveness between the conductive substrate and the acrylic resin layer, and between the acrylic resin layer and the active material layer is increased, and the high rate characteristics are improved.

  Another finding is that the high rate characteristics are good when the water contact angle is 30 degrees or more. As described above, the contact angle is one of the indexes indicating whether different materials are likely to adhere to each other. Therefore, the smaller the contact angle, the higher the adhesion between different materials. The inventors initially thought that there is no lower limit to the range of preferred water contact angles, and that the smaller the water contact angle, the better the adhesion between different materials and the higher the high rate characteristics. However, it was surprisingly found that the high rate characteristics deteriorate when the water contact angle is less than 30 degrees. The reason why such a result was obtained is currently under investigation and is not necessarily clear, but if the water contact angle is too small, the adhesion between the conductive substrate and the acrylic resin layer may deteriorate. I guess that is the cause.

  By the way, the water contact angle of the acrylic resin layer is not uniquely determined by the material composition of the acrylic resin layer, and greatly changes when the method of forming the acrylic resin layer changes. When the inventors actually conducted an experiment, even with resin materials having the same composition, the water contact angle of the acrylic resin layer was greatly changed by changing the drying temperature, drying time, and drying method, For example, even if the resin composition and the drying temperature are known, the water contact angle changes only by changing the production conditions such as the drying time. Therefore, it has been found that the determination of the water contact angle is extremely important in the present invention.

FIG. 1 is a cross-sectional view illustrating a configuration of a current collector according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a configuration of an electrode structure formed using the current collector of one embodiment of the present invention.

Hereinafter, the current collector of one embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 1, a current collector 1 of the present invention is a current collector 1 in which an acrylic resin layer (current collector resin layer) 5 having conductivity is formed on at least one surface of a conductive substrate 3. Yes, the acrylic resin layer 5 contains an acrylic resin and conductive particles, and the water contact angle measured by the θ / 2 method in a temperature-controlled room at 23 ° C. on the surface of the acrylic resin layer 5 is not less than 30 degrees and not more than 110 degrees. .
Further, as shown in FIG. 2, by forming an active material layer or an electrode material layer 9 on the acrylic resin layer 5 of the current collector 1, it can be used for a non-aqueous electrolyte battery, an electric double layer capacitor, or a lithium ion. An electrode structure 7 suitable for a capacitor can be formed.
Hereinafter, each component will be described in detail.

(1) Conductive base material As the conductive base material of the present invention, various metal foils can be used. As the metal foil, aluminum foil, aluminum alloy foil for positive electrode or negative electrode, copper foil, stainless steel foil, nickel foil or the like for negative electrode can be used. Among these, aluminum foil, aluminum alloy foil, and copper foil are preferable from the viewpoint of balance between high conductivity and cost. When an aluminum foil is used as the positive electrode, the present invention aims at improving high rate characteristics, and therefore, it is preferable to use a pure aluminum system such as JIS A1085 having high conductivity. The thickness of the foil is preferably 5 μm or more and 50 μm or less. If the thickness is less than 5 μm, the strength of the foil may be insufficient and it may be difficult to form an acrylic resin layer or the like. On the other hand, if it exceeds 50 μm, other components, particularly the active material layer or the electrode material layer, must be thinned. Especially, non-aqueous electrolyte batteries, electric double layer capacitors, lithium ion capacitors and other power storage components In such a case, a sufficient capacity may not be obtained.

(2) Acrylic resin layer In this invention, the acrylic resin layer which added the electroconductive particle on the electroconductive base material is formed. The forming method is not particularly limited, but it is preferable to apply an acrylic resin solution or dispersion onto the conductive substrate. As a coating method, a roll coater, a gravure coater, a slit die coater or the like can be used. The resin used in the present invention must be acrylic. As a result of investigating the volume resistivity of the resin layer by adding conductive particles to various resins, it is based on the inventor's knowledge that sufficiently low resistance can be obtained by using an acrylic resin with a specified water contact angle It is. Note that this difference in resistance is presumed to be because the distribution state in the resin layer differs depending on the resin even if the same conductive particles are added, and the resistance is different from the regulation of the water contact angle described later.

The acrylic resin used in the present invention is a resin formed from a monomer mainly composed of acrylic acid or methacrylic acid, or a derivative thereof. The ratio of the acrylic component in the monomer of the acrylic resin is, for example, 50% by mass or more, and preferably 80% by mass or more. The upper limit is not particularly defined, and the monomer of the acrylic resin may be substantially composed of only the acrylic component. In addition, the acrylic resin monomer may contain one or more acrylic components alone.
Among acrylic resins, an acrylic copolymer containing at least one of methacrylic acid or a derivative thereof and a polar group-containing acrylic compound as a monomer is preferable. This is because the high rate characteristics are further improved by using an acrylic copolymer containing these monomers. Examples of methacrylic acid or derivatives thereof include methacrylic acid, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate and the like. Examples of the polar group-containing acrylic compound include acrylonitrile, methacrylonitrile, acrylamide, and methacrylamide. Further, among the polar group-containing acrylic compounds, an acrylic compound having an amide group is preferable. Examples of the acrylic compound having an amide group include acrylamide, N-methylol acrylamide, and diacetone acrylamide.
The weight average molecular weight of the acrylic resin is not particularly limited, but is preferably 30,000 or more and 200,000 or less. If the molecular weight is too small, the flexibility of the resin layer is low, and if the current collector is wound with a small radius of curvature, the resin layer may crack and the capacity of the battery may decrease, and if the molecular weight is too large, This is because the adhesion tends to be low. The weight average molecular weight can be measured using GPC (gel exclusion chromatography) in a resin solution before addition of a conductive material.

  Since the current collector serves as a passage for electrons moving from the electrode to the counter electrode, the surface of the current collector must also have electronic conductivity. Since acrylic resin is an insulator, conductive particles must be added to impart electronic conductivity. As the conductive particles used in the present invention, carbon powder, metal powder, and the like can be used. Among them, carbon powder is preferable. As the carbon powder, acetylene black, ketjen black, furnace black, carbon nanotubes and the like can be used. In addition, carbon fibers and carbon nanotubes can be used as long as they are conductive. Among these, it is preferable to use acetylene black which has a relatively long aggregate and can easily improve conductivity with a relatively small addition amount. By reducing the amount added, the increase in the water contact angle on the surface of the acrylic resin layer can be suppressed, the desired water contact angle described later can be achieved, and the adhesion with the active material layer or the electrode material layer is reduced. Can be suppressed. The addition amount of the conductive particles is preferably 20 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the resin in the resin layer. If the amount is less than 20 parts by mass, the resistance of the acrylic resin layer increases. If the amount exceeds 80 parts by mass, the water contact angle on the surface of the resin layer increases, and the adhesion to the active material layer or the electrode material layer may decrease. It is. The conductive material can be dispersed in the resin liquid by using a planetary mixer, a ball mill, a homogenizer, or the like.

  The water contact angle on the surface of the acrylic resin layer of the present invention needs to be 30 degrees or more and 110 degrees or less. Even if conductive particles are simply added to an acrylic resin to form an acrylic resin layer, the interface between the conductive substrate and the acrylic resin layer, the interface between the acrylic resin layer and the active material layer, or the acrylic resin layer In some cases, sufficient adhesion cannot be obtained at the interface of the electrode material layer. This is because even the acrylic resin changes the state of the resin layer depending on the type and forming conditions of the resin. In particular, there is a contact angle indicating wettability of liquid as a surface property that has a great influence on adhesion, and by measuring the contact angle of water with relatively large surface tension, the current collector and the active material layer formed on it The adhesion of the electrode material layer can be evaluated. In this case, it seems that the acrylic resin layer and the water contact angle seem to improve the adhesion and the discharge rate as the water contact angle is small, but if the contact angle is too small, In the present invention, it is necessary to define the water contact angle because it may adversely affect the adhesion and discharge rate characteristics. This point will be described later.

  In the present specification, the water contact angle means a value obtained by measuring by a θ / 2 method in a constant temperature room at 23 ° C. The water contact angle can be measured using a contact angle meter. After the resin layer is formed on the current collector, a contact angle is measured by adhering several μl of pure water to pure water on the surface. Since the surface tension of water changes with temperature, the water contact angle is measured in a thermostatic chamber at 23 ° C.

As a result of forming an acrylic resin layer under various conditions and measuring the water contact angle, it was found that if it was 110 degrees or less, sufficient adhesion to the active material layer and the electrode material layer was obtained. More preferably, it is 95 degrees or less, More preferably, it is 80 degrees or less. In addition, as a result of forming an acrylic resin layer having a different water contact angle and investigating the adhesive relationship between the conductive substrate and the acrylic resin layer, the water contact angle on the surface of the acrylic resin layer was less than 30 degrees. It was found that the high rate characteristic was inferior when it was. Although the cause is not clear, it is presumed that a subtle difference in adhesion between the conductive substrate and the acrylic resin layer is detected. Therefore, the water contact angle needs to be 30 degrees or more. In particular, the water contact angle is preferably 65 degrees or more. This is based on knowledge based on numerous experiments by the present inventors. When the water contact angle is 65 degrees or more, the adhesion between the conductive substrate and the acrylic resin layer is particularly good. As described above, the regulation of the water contact angle of the present invention considers not only the adhesion between the acrylic resin and the active material layer or the electrode material layer, but also the adhesion between the conductive substrate and the acrylic resin layer. Thus, the current collector of the present invention in which the water contact angle is defined as described above can give high rate characteristics satisfactorily when used in a battery or a charged part as an electrode structure.

In order to obtain the current collector of the present invention, an acrylic resin layer can be formed on at least one surface of the conductive substrate such as the aluminum foil described above by a known method. It is necessary to have. For example, when an acrylic resin layer is formed by coating, the baking temperature and baking time affect the water contact angle. The baking temperature is preferably 100 to 200 ° C. as the temperature reached by the conductive substrate, and the baking time is preferably 10 to 60 seconds. This is because when the acrylic resin layer is formed under such conditions, the water contact angle on the surface contributes to adjustment within the range of 30 degrees or more and 110 degrees or less. However, since the water contact angle is comprehensively determined by various factors such as the resin composition, the resin concentration in the resin liquid, the baking temperature, the baking time, and the baking method, the baking temperature and baking time are within the above range. Even within, the water contact angle may be less than 30 degrees or may exceed 110 degrees. Conversely, even if the baking temperature and baking time are outside the above ranges, the water contact angle may be within the range of 30 to 110 degrees.
In general, the higher the baking temperature and the longer the baking time, the greater the water contact angle. Therefore, in order to set the water contact angle to 30 degrees or more and 110 degrees or less, first, an acrylic resin layer is formed under a certain condition, the water contact angle is measured in the formed acrylic resin layer, and the measured water If the contact angle is lower than 30 degrees, adjustment is required to increase the baking temperature or increase the baking time, and if the measured water contact angle is larger than 110 degrees, the baking temperature is decreased or the baking time is shortened. It is. Therefore, the value of the water contact angle is not determined only by the composition of the acrylic resin and the baking temperature, but if the above method is used, the water contact angle can be set to a desired value with only a few trials and errors. Is possible.

  When the current collector of the present invention is used, even when an active material layer or an electrode material layer is formed and the electrolyte is infiltrated, it is sufficient for the interface between the acrylic resin layer and the active material layer or the acrylic resin layer and the electrode material layer. In addition to ensuring sufficient adhesion, it is also possible to ensure sufficient adhesion at the interface with the conductive substrate. Further, even after repeated charge and discharge, no large peeling is observed, and sufficient adhesion and excellent discharge rate characteristics can be obtained.

  The thickness of the acrylic resin layer is preferably 0.1 μm or more and 5 μm or less. If the thickness is less than 0.1 μm, a portion that cannot be completely coated is generated, and sufficient battery characteristics may not be obtained. If the thickness exceeds 5 μm, when the battery or power storage component described later is used, the active material layer or the electrode material layer may have to be thinned, so that a sufficient capacity density may not be obtained. In addition, when used in a prismatic battery such as a lithium ion secondary battery, when the electrode structure is wound in combination with a separator, a relatively hard acrylic resin layer is cracked in the innermost winding portion having a very small radius of curvature. In some cases, a part that peels off from the active material layer or the like is generated. More preferably, it is 0.3 to 3 μm.

  The method for producing the current collector of the present invention is not particularly limited. However, when the acrylic resin layer is formed on the conductive substrate, the conductive group is improved so that the adhesion of the surface of the conductive substrate is improved. It is also effective to perform a known pretreatment on the material. In particular, when a metal foil produced by rolling is used, rolling oil or wear powder may remain, and adhesion can be improved by removing it by degreasing or the like. The adhesion can also be improved by a dry activation treatment such as a corona discharge treatment.

3. Electrode Structure The electrode structure of the present invention can be obtained by forming an active material layer or an electrode material layer on at least one surface of the current collector of the present invention. The electrode structure for an electrical storage component in which the electrode material layer is formed will be described later. First, in the case of an electrode structure in which an active material layer is formed, a nonaqueous electrolyte battery can be manufactured using this electrode structure, a separator, a nonaqueous electrolyte, and the like. In the electrode structure for a nonaqueous electrolyte battery and the nonaqueous electrolyte battery of the present invention, a member other than the current collector can be a known nonaqueous battery member.
The active material layer formed in the present invention may be one that has been conventionally proposed for non-aqueous electrolyte batteries. For example, the current collector of the present invention using an aluminum foil as a positive electrode, LiCoO ₂ , LiMnO ₂ , LiNiO ₂ or the like as an active material, carbon black such as acetylene black as a conductive material, and these are binders By applying a paste dispersed in PVDF, the positive electrode structure of the present invention can be obtained.
As the negative electrode, for example, graphite, graphite, mesocarbon microbeads or the like are used as the active material for the current collector of the present invention using copper foil as the conductive base material, and these are dispersed in CMC as a thickener, and then the binder. The negative electrode structure of the present invention can be obtained by applying a paste mixed with SBR.

4). Nonaqueous electrolyte battery The nonaqueous electrolyte battery of the present invention can be constituted by sandwiching a separator impregnated with an electrolyte for a nonaqueous electrolyte battery having a nonaqueous electrolyte between the positive electrode structure and the negative electrode structure. . As the nonaqueous electrolyte and the separator, those used for known nonaqueous electrolyte batteries can be used. As the electrolytic solution, carbonates or lactones can be used as a solvent. For example, a solution obtained by dissolving LiPF ₆ or LiBF ₄ as an electrolyte in a mixed solution of EC (ethylene carbonate) and EMC (ethyl methyl carbonate) is used. Can do. As the separator, for example, a film having a microporous made of polyolefin can be used.

5. Power storage components (electric double layer capacitors, lithium ion capacitors, etc.)
The current collector of the present invention can also be applied to power storage components such as an electric double layer capacitor and a lithium ion capacitor that require discharging at a large current density. The electrode structure for a power storage component of the present invention is obtained by forming an electrode material layer on the current collector of the present invention. By using this electrode structure and a separator, an electrolytic solution, etc., an electric double layer capacitor, a lithium ion capacitor, etc. A power storage component can be manufactured. In the electrode structure and power storage component of the present invention, members other than the current collector can be members for known electric double layer capacitors or lithium ion capacitors.

  The electrode material layer is composed of an electrode material, a conductive material, and a binder for both the positive electrode and the negative electrode. In the present invention, an electrode structure can be obtained by forming the electrode material layer on at least one side of the current collector of the present invention. Here, as the electrode material, those conventionally used as electrode materials for electric double layer capacitors and lithium ion capacitors can be used. For example, carbon powder or carbon fiber such as activated carbon or graphite can be used. As the conductive material, carbon black such as acetylene black can be used. As the binder, for example, PVDF (polyvinylidene fluoride) or SBR (styrene butadiene rubber) can be used. In addition, the electric storage component of the present invention can constitute an electric double layer capacitor or a lithium ion capacitor by fixing the electrode structure of the present invention with a separator interposed therebetween and allowing the electrolyte to penetrate into the separator. As the separator, for example, a polyolefin microporous film, an electric double layer capacitor nonwoven fabric, or the like can be used. For example, carbonates and lactones can be used as the solvent in the electrolyte, and the electrolyte includes tetraethylammonium salt and triethylmethylammonium salt as the cation, and hexafluorophosphate and tetrafluoroborate as the anion. Can be used. A lithium ion capacitor is a combination of a negative electrode of a lithium ion battery and a positive electrode of an electric double layer capacitor. These production methods can be carried out according to known methods, except that the current collector of the present invention is used, and are not particularly limited.

(1) Lithium ion battery An example in which the current collector of the present invention is applied to a lithium ion battery will be described below.

(Example 1) An acrylic copolymer containing acrylic acid, butyl acrylate and methyl acrylate as monomers is polymerized at a blending ratio of 5:45:50 so that the weight average molecular weight falls within the range of 90000-120000, and a surfactant. 60% by mass of acetylene black based on the solid content of the resin was added to the resin liquid dispersed in water using a varnish and dispersed for 8 hours in a ball mill to obtain a paint. This paint was applied to one side of a 20 μm thick aluminum foil (JIS A1085) with a bar coater and heated for 30 seconds so that the substrate temperature reached 120 ° C. to prepare a current collector. The film thickness after baking was 2 μm. This heating was performed in a thermostatic bath.
For the positive electrode, a paste in which LiCoO _{2 as an} active material and acetylene black as a conductive material were dispersed in PVDF (polyvinylidene fluoride) as a binder was applied to the current collector at a thickness of 70 μm to obtain a positive electrode structure. The negative electrode is obtained by dispersing active material graphite in CMC (carboxymethylcellulose) and then applying a paste mixed with SBR (styrene butadiene rubber) as a binder to a copper foil having a thickness of 20 μm at a thickness of 70 μm. did. A coin battery was manufactured by sandwiching a polypropylene microporous separator between these electrode structures in a battery case. As the electrolytic solution, an electrolytic solution obtained by adding 1M LiPF ₆ to a mixed solution of EC (ethylene carbonate) and EMC (ethyl methyl carbonate) was used.

Example 2 A coin battery was fabricated in the same manner as in Example 1 using an acrylic copolymer containing acrylic acid, butyl acrylate, and acrylamide as a monomer at a blending ratio of 5:30:65.
(Example 3) A coin battery was fabricated in the same manner as in Example 1 by using an acrylic copolymer containing ethyl methacrylate, butyl acrylate, and methyl methacrylate in a blending ratio of 10:70:20 as a monomer.
(Example 4) A coin battery was fabricated in the same manner as in Example 1 using an acrylic copolymer containing methacrylic acid, butyl methacrylate, and acrylonitrile in a blending ratio of 5:70:15 as a monomer.
(Example 5) Using an acrylic copolymer containing methacrylic acid, butyl acrylate, and acrylamide as a monomer at a blending ratio of 5:30:65, the film thickness after baking is 0.5 μm, and other conditions are as in Example 1. A coin battery was prepared in the same manner as described above.
(Example 6) Using an acrylic copolymer containing methacrylic acid, butyl acrylate, and acrylamide as a monomer at a blending ratio of 5:30:65, the film thickness after baking is 4 μm, and other conditions are the same as in Example 1 A coin battery was prepared.
(Example 7) A resin solution in which an acrylic copolymer containing acrylic acid, butyl acrylate, and methyl acrylate as a monomer in a mixing ratio of 5:45:50 is dispersed in water for 60 seconds so that the substrate temperature reaches 90 ° C. A current collector was produced by heating. The film thickness after baking was 2 μm. Other conditions were the same as in Example 1 to produce a coin battery.

(Comparative example 1) 60% of acetylene black is added to a resin solution obtained by dissolving an epoxy resin and a melamine resin in MEK at a blending ratio of 95: 5, and dispersed by a ball mill for 8 hours. It was. This paint was applied to one side of a 20 μm thick aluminum foil (JIS A1085) with a bar coater, and heated for 15 seconds so that the substrate temperature reached 240 ° C. The film thickness after baking was 2 μm. Other conditions were the same as in Example 1 to produce a coin battery.
(Comparative Example 2) A resin solution in which an acrylic copolymer containing acrylic acid, butyl acrylate, and methyl acrylate as a monomer in a blending ratio of 5:40:55 is dispersed in water for 70 seconds so that the substrate temperature reaches 220 ° C. A current collector was produced by heating. The film thickness after baking was 2 μm. Other conditions were the same as in Example 1 to produce a coin battery.
(Comparative Example 3) A resin solution in which an acrylic copolymer containing acrylic acid, butyl acrylate, and methyl acrylate as a monomer in a blending ratio of 5:40:55 is dispersed in water for 60 seconds so that the substrate temperature reaches 50 ° C. A current collector was produced by heating. The film thickness after baking was 2 μm. Other conditions were the same as in Example 1 to produce a coin battery.
(Comparative Example 4) A resin liquid in which an acrylic copolymer containing acrylic acid, butyl acrylate, and methyl acrylate as a monomer in a mixing ratio of 5:40:55 is dispersed in water is applied on a base material, and then on a hot plate at 60 ° C. Was heated for 10 minutes to prepare a current collector. The film thickness after baking was 2 μm. Other conditions were the same as in Example 1 to produce a coin battery.

  Results of investigating the water contact angle of the conductive resin layer formed on these current collectors, the adhesion between the base material and the acrylic resin layer, the adhesion between the acrylic resin layer and the active material layer, and the discharge rate characteristics of the coin battery Is shown in Table 1. The water contact angle was measured using a contact angle meter (Drop Master DM-500, manufactured by Kyowa Interface Science Co., Ltd.) in a thermostatic chamber at 23 ° C., with 1 μl of water droplets attached to the resin layer surface, and the contact angle after 2 seconds was θ / It was measured by 2 methods. Adhesiveness was evaluated by visually checking the peeled state when the Nichiban cellophane tape was applied to the surface of the resin layer and pressed sufficiently, and then peeled off at once. The evaluation criteria were ○ for no peel, Δ if the peel area was within 90%, and x if the peel area exceeded 90%. Discharge rate characteristics are: discharge upper limit voltage 4.2V, charge current 0.2C, discharge end voltage 2.8V, temperature 25 ° C, discharge current 1C, 5C, 10C, 20C discharge capacity (0.2C reference, unit%) Was measured. (1C is the current value (A) when the current capacity (Ah) of the battery is taken out in one hour (h). At 20C, the current capacity of the battery can be taken out in 1 / 20h = 3 min. can do.)

  Each of Examples 1 to 6 has a discharge rate characteristic at 20C of 80% or more, which indicates that the high rate characteristic is excellent. In Example 7, the discharge rate characteristic at 20 C was 79%, which was slightly low. This result is considered to be because in Example 7, the adhesion between the base material and the acrylic resin layer was slightly inferior to those in Examples 1 to 6. On the other hand, since Comparative Example 1 is an epoxy resin, the high rate property is inferior in spite of sufficient adhesion, and Comparative Example 2 is an acrylic resin layer, although the resin system is acrylic. Since the water contact angle was larger than 110 degrees and the adhesion was poor, the interface resistance was increased, resulting in poor high rate characteristics. In Comparative Example 3, the water contact angle was low, but the adhesion between the base material and the acrylic resin layer was low, and the high rate characteristics were inferior. In Comparative Example 4, unlike the other Examples and Comparative Examples, the resin liquid layer was dried by heating on a hot plate. Although the temperature of the hot plate was relatively low, the water contact angle was a relatively large value of 125 degrees, and the high rate characteristics were also poor.

(2) Electric Double Layer Capacitor An example where the current collector of the present invention is applied to an electric double layer capacitor will be described below.

(Example 8) An acrylic copolymer containing acrylic acid, butyl acrylate, and methyl acrylate as monomers is polymerized so that the weight average molecular weight falls within the range of 90000-120000 at a blending ratio of 5:45:50, and a surfactant is obtained. The resin liquid used and dispersed in water was added with 60% by mass of acetylene black based on the solid content of the resin, and dispersed in a ball mill for 8 hours to obtain a paint. This paint was applied to one side of a 20 μm thick aluminum foil (JIS A1085) with a bar coater and heated for 30 seconds so that the substrate temperature reached 120 ° C. to prepare a current collector. The film thickness after baking was 2 μm. This heating was performed in a thermostatic bath.
A paste obtained by dispersing activated carbon as an electrode material and ketjen black as a conductive material in PVDF as a binder was applied to the current collector at a thickness of 80 μm to obtain an electrode structure. The electrode structure was fixed with a non-woven fabric for an electric double layer capacitor impregnated with an electrolytic solution in between, thereby constituting an electric double layer capacitor. The electrolytic solution used was propylene carbonate, which is a solvent, with 1.5 M TEMA (triethylmethylammonium) and tetrafluoroboric acid added.

Example 9 An electric double layer capacitor was produced in the same manner as in Example 8 using an acrylic copolymer containing acrylic acid, butyl acrylate, and acrylamide as a monomer at a blending ratio of 5:30:65.
Example 10 An electric double layer capacitor was produced in the same manner as in Example 8 using an acrylic copolymer containing ethyl methacrylate, butyl acrylate, and methyl methacrylate as a monomer in a blending ratio of 10:70:20.
Example 11 An electric double layer capacitor was produced in the same manner as in Example 8 using an acrylic copolymer containing methacrylic acid, butyl methacrylate, and acrylonitrile in a blending ratio of 5:70:15 as a monomer.
(Example 12) Using an acrylic copolymer containing methacrylic acid, butyl acrylate, and acrylamide as a monomer at a blending ratio of 5:30:65, the film thickness after baking is 0.5 μm, and other conditions are as in Example 8. An electric double layer capacitor was fabricated in the same manner as described above.
(Example 13) Using an acrylic copolymer containing methacrylic acid, butyl acrylate, and acrylamide as a monomer in a blending ratio of 5:30:65, the film thickness after baking was 4 μm, and other conditions were the same as in Example 8. An electric double layer capacitor was prepared.
(Example 14) A resin solution in which an acrylic copolymer containing acrylic acid, butyl acrylate, and methyl acrylate as a monomer in a mixing ratio of 5:45:50 is dispersed in water is used for 60 seconds so that the substrate temperature reaches 90 ° C. A current collector was produced by heating. The film thickness after baking was 2 μm. Other conditions were the same as in Example 8 to produce an electric double layer capacitor.

(Comparative Example 5) 60% acetylene black with respect to the solid content of the resin was added to a resin solution obtained by dissolving an epoxy resin and a melamine resin in MEK at a blending ratio of 95: 5, and dispersed by a ball mill for 8 hours. It was. This paint was applied to one side of a 20 μm thick aluminum foil (JIS A1085) with a bar coater, and heated for 15 seconds so that the substrate temperature reached 240 ° C. The film thickness after baking was 2 μm. Other conditions were the same as in Example 8, and an electric double layer capacitor was produced.
(Comparative Example 6) A resin solution in which an acrylic copolymer containing acrylic acid, butyl acrylate, and methyl acrylate as a monomer in a mixing ratio of 5:40:55 is dispersed in water is 70 seconds so that the substrate temperature reaches 220 ° C. A current collector was produced by heating. The film thickness after baking was 2 μm. Other conditions were the same as in Example 8, and an electric double layer capacitor was produced.
(Comparative Example 7) A resin solution in which an acrylic copolymer containing acrylic acid, butyl acrylate, and methyl acrylate as a monomer in a blending ratio of 5:40:55 is dispersed in water for 60 seconds so that the substrate temperature reaches 50 ° C. A current collector was produced by heating. The film thickness after baking was 2 μm. Other conditions were the same as in Example 8, and an electric double layer capacitor was produced.
(Comparative Example 8) A resin liquid in which an acrylic copolymer containing acrylic acid, butyl acrylate, and methyl acrylate as a monomer at a blending ratio of 5:40:55 is dispersed in water is applied on a base material, and then on a hot plate for 10 minutes. The resin liquid layer was dried by heating to produce a current collector. The film thickness after baking was 2 μm. Other conditions were the same as in Example 8, and an electric double layer capacitor was produced.

  Table 2 shows the results of investigating the water contact angle of these current collectors, the adhesion between the substrate and the acrylic resin layer, the adhesion between the acrylic resin layer and the electrode material layer, and the discharge rate characteristics of the electric double layer capacitor. . The water contact angle and adhesion evaluation methods are the same as in the case of the lithium ion battery. As for the discharge rate characteristics, the discharge capacity (1 C reference, unit%) was measured at a charge upper limit voltage of 2.8 V, a charge rate of 1 C, a charge end condition of 2 h, a discharge end voltage of 0 V, a temperature of 25 ° C., and discharge rates of 100 C, 300 C, and 500 C. .

  It can be seen that all of Examples 8 to 13 have an excellent discharge rate characteristic at 500 C of 80% or more and are excellent in the high rate characteristic. In Example 14, the discharge rate characteristic at 500 C was 79%, which was slightly low. This result is considered to be because in Example 14, the adhesion between the base material and the acrylic resin layer was slightly inferior to those in Examples 8 to 13. On the other hand, Comparative Example 5 is inferior in high-rate characteristics because the resin system is an epoxy system, and Comparative Example 6 is an acrylic resin system, but the water contact angle on the surface of the acrylic resin layer is larger than 110 degrees, and adhesion As a result, the interfacial resistance is increased due to inferior properties, resulting in poor high rate characteristics. In Comparative Example 7, the water contact angle was low, but the adhesion between the substrate and the acrylic resin layer was low, and the high-rate characteristics were inferior. In Comparative Example 8, unlike the other Examples and Comparative Examples, the resin liquid layer was dried by heating with a hot plate. Although the temperature of the hot plate was relatively low, the water contact angle was a relatively large value of 125 degrees, and the high rate characteristics were also poor.

1: Current collector
3: Conductive substrate
5: Acrylic resin layer (resin layer for current collector)
7: Electrode structure 9: Active material layer or electrode material layer

Claims (4)

A current collector in which an acrylic resin layer having conductivity is formed on at least one surface of a conductive substrate, the acrylic resin layer including an acrylic resin and conductive particles, A current collector having a water contact angle of 30 ° to 110 ° measured in a constant temperature room at 0 ° C. by the θ / 2 method. An electrode structure comprising an active material layer or an electrode material layer formed on the current collector of claim 1. A non-aqueous electrolyte battery using an electrode structure in which an active material layer is formed on the current collector of claim 1. A power storage component comprising an electrode structure in which an electrode material layer is formed on the current collector of claim 1.