JP5780871B2 - 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 (such as an electric double layer capacitor and a lithium ion capacitor) suitable for charging and discharging at a large current density.

  Conventionally, a non-aqueous electrolyte battery represented by a lithium ion battery has been required to shorten the charging time. For this purpose, it is necessary to be able to be charged at a high current density and at a high speed. Further, non-aqueous electrolyte batteries for automobiles are required to be capable of high-output discharge with a large current density in order to obtain sufficient automobile acceleration performance. In this way, when charging / discharging at a large current density, it is important to reduce the internal resistance of the battery in order to improve the characteristics (high rate characteristics) in which the battery capacity does not decrease. The same applies to other nonaqueous electrolyte batteries such as electric double layer capacitors and lithium ion capacitors and charged parts.

  In general, the causes of internal resistance include electrical resistance of constituent materials, interfacial resistance between constituent elements, conduction resistance of ions that are charged particles in the electrolyte, electrode reaction resistance, etc. There is a need to reduce. One of the most important internal resistances among these is the interfacial resistance generated between the conductive base material made of metal foil such as aluminum foil and copper foil and the active material layer, and one of the methods for reducing this interfacial resistance. It is known that it is effective to improve the adhesion at the interface.

  As a method for improving the adhesion between the current collector and the active material layer, for example, it has been conventionally proposed to coat the current collector with a conductive resin and apply a paste for forming the active material layer thereon. . Patent Document 1 discloses a technique for forming a conductive coating film by applying a conductive paint containing a conductive filler, vinyl butyral as a binder, and dibutyl phthalate as a plasticizer to a positive electrode current collector. Patent Document 2 discloses a technique for forming a conductive coating film containing polyacrylic acid or a copolymer of acrylic acid and an acrylate ester as a main binder and carbon powder as a conductive filler on a positive electrode current collector. It is disclosed.

JP-A-2-109256 Japanese Patent Laid-Open No. 62-160656

  However, these techniques do not always provide sufficient high-rate characteristics and do not satisfy the electrode life. When reducing the interfacial resistance between the current collector and the active material layer comprising the conductive base material and the conductive resin, not only the high adhesion between the conductive resin layer and the active material layer of the current collector but also the conductivity It is also important that the volume resistivity of the resin layer itself is low. The adhesion mentioned here is directly related to the interfacial resistance and electrode life between the conductive resin layer and the active material layer. Even when the electrolyte is infiltrated into this interface, there is no peeling and the property of adhering firmly. means. Furthermore, in the positive and negative electrodes of non-aqueous electrolyte batteries and lithium ion capacitors, the volume of the active material in the active material layer changes due to charge / discharge, so that the active material is easily peeled off from the active material layer, and further adheres to the active material layer. Peeling tends to occur at the interface with the current collector. In particular, since the volume change of the active material is abrupt in high rate charge / discharge, the conductive resin layer and the active material layer of the current collector require particularly strong adhesion. The adhesion between the layer and the active material layer is low, which is not satisfactory in battery life, and the volume resistivity of the conductive resin layer itself is not always sufficiently reduced.

  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. It is an object of the present invention to provide a current collector that can improve characteristics and extend battery life. By further forming an active material layer or an electrode material layer, the current collector of the present invention can be an electrode structure having good adhesion to the active material layer or the electrode material layer. Moreover, since the nonaqueous electrolyte battery using the electrode structure in which the active material layer is formed on the current collector of the present invention has the current collector having the above characteristics, the internal resistance is reduced and the high rate characteristics are improved. Can do. 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 high-speed, high-speed charge / discharge, such as used in a copy 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,
(1) A current collector having a conductive resin layer on at least one side of a conductive substrate, the resin layer containing a nitrified cotton-based resin and a conductive material, and in a constant temperature room at 23 ° C. on the surface of the resin layer A current collector having a contact angle of 20 degrees or more and 80 degrees or less measured by the θ / 2 method at
(2) A current collector having a conductive resin layer on at least one side of a conductive substrate, the resin layer containing a nitrified cotton-based resin and a conductive material, and in a constant temperature room at 23 ° C. on the surface of the resin layer A current collector measured by the θ / 2 method at a contact angle of 80 degrees or more and 120 degrees or less,
(3) A current collector having a conductive resin layer on at least one surface of a conductive substrate, the resin layer containing a nitrified cotton-based resin and a conductive material, and in a constant temperature room at 23 ° C. on the surface of the resin layer The contact angle of the solvent-based model active material paste measured by the θ / 2 method is 20 ° to 80 ° and the contact angle of the aqueous model active material paste is 80 ° to 120 °. An electric body, an electrode structure including the current collector, a nonaqueous electrolyte battery, and a power storage component (eg, an electric double layer capacitor or a lithium ion capacitor) are provided.

The present invention is characterized in that the state of the resin layer is defined by the contact angle of the model active material paste (hereinafter referred to as “paste contact angle”). The “model active material paste” is a model of an active material paste used when an active material layer is actually formed. There are two types of active material pastes: a solvent-based active material paste in which an active material is pasted using a solvent and a water-based active material paste in which an active material is pasted using water. There are active material paste and water-based model active material paste. Solvent-based model active material paste, specifically, "LiMn ₂ O ₄ powder (Yu n nan Yuxihuilong Ltd. technology) 17.9 parts by mass, 1.1 mass PVDF (Kishida Chemical Ltd. # 1100) in the binder resin Parts (as solids), 1.0 parts by weight of acetylene black (Denka Black HS-100 manufactured by Denki Kagaku) as the conductive material, 20 parts by weight of NMP as the solvent, and 3 minutes stirring with a defoaming stirrer It is defined as “the obtained paste”. Aqueous Model active material paste, specifically, "24 parts by mass of LiMn ₂ O ₄ powder (manufactured by Yu n nan Yuxihuilong technology) to the active material, the binder resin aqueous dispersion-type PTFE (the Daikin Polyflon D-1E) 0.28 parts by mass (as solid content), 2.5 parts by mass of acetylene black (Denka Black HS-100 manufactured by Electrochemical Co., Ltd.) and 33 parts by mass of water after stirring at 2000 rpm for 1 minute in a disperser , A paste obtained by stirring for 30 seconds with a stirrer (Primix Filmmix 40-40, peripheral speed 30 m / s).

  The inventors of the present invention have found that the paste contact angle on the surface of the resin layer is strongly correlated with the high-rate characteristics when intensive studies were conducted to improve the high-rate characteristics of nonaqueous electrolyte batteries and the like. It has also been found that whether the high-rate characteristics are improved depends on whether the active material paste used is solvent-based or water-based. If the paste contact angle of the solvent-based active material paste (hereinafter referred to as “solvent-based paste contact angle”) is 20 degrees or more and 80 degrees or less, the high rate is obtained when the active material paste used is solvent-based. If the properties are good and the paste contact angle of the aqueous active material paste (hereinafter referred to as “aqueous paste contact angle”) is 80 degrees or more and 120 degrees or less, the active material paste used is aqueous. It has been found that the high rate characteristics are improved. In addition, based on this finding, when both the solvent-based paste contact angle and the water-based paste contact angle are within the above range, it is excellent regardless of whether the active material paste actually used is solvent-based or water-based. It was found that the high rate characteristics were improved. Conventionally, it has been difficult to form a resin layer that exhibits excellent characteristics regardless of whether the active material paste is solvent-based or water-based. It has become possible to form a resin layer capable of improving the characteristics.

  The present invention is based on two findings. The first finding is that the high rate characteristic is good when the paste contact angle is below a specific upper limit value. 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 less than or equal to the above upper limit value, the adhesiveness between the conductive substrate and the resin layer, and between the resin layer and the active material layer is increased, and the high rate characteristic is improved.

  Another finding is that the high rate characteristics are good when the paste contact angle is greater than or equal to a specific lower limit. 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 was no lower limit to the range of the preferred paste contact angle, and that the smaller the paste 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 paste contact angle is less than the lower limit. The reason why such a result was obtained is currently under investigation and is not necessarily clear, but if the paste contact angle is too small, the adhesion between the conductive substrate and the resin layer is deteriorated. I guess that.

  By the way, the paste contact angle of the resin layer is not uniquely determined by the material composition of the resin layer, and changes greatly when the method of forming the resin layer changes. When the inventors actually conducted an experiment, even when the resin material has the same composition, the paste contact angle of the resin layer changes greatly by changing the drying temperature, drying time, and drying method. Even if the composition and the drying temperature are known, the paste contact angle changes only by changing the production conditions such as the drying time. Therefore, it was found that it is extremely important to determine the paste contact angle 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 having a conductive resin layer (current collector resin layer) 5 on at least one surface of a conductive base material 3. The conductive resin layer 5 includes a nitrified cotton-based resin and a conductive material, and a solvent-based paste contact angle measured by the θ / 2 method in a constant temperature room at 23 ° C. on the surface of the resin layer 5 is 20 degrees or more and 80 degrees or less, and / Or The contact angle of the aqueous model active material paste is 80 degrees or more and 120 degrees or less.
Further, as shown in FIG. 2, by forming an active material layer or an electrode material layer 9 on the resin layer 5 of the current collector 1, it is used for a non-aqueous electrolyte battery, an electric double layer capacitor, or a lithium ion capacitor. As a result, a suitable electrode structure 7 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 for non-aqueous electrolyte batteries, electric double layer capacitors, or lithium ion capacitors can be used. Specifically, aluminum, aluminum alloy, copper, stainless steel, nickel, etc. can be used for the negative electrode. Among these, aluminum, an aluminum alloy, and copper are preferable from the 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 conductive substrate is not particularly limited, but is preferably 0.5 μm or more and 50 μm or less. If the thickness is less than 0.5 μm, the strength of the foil is insufficient and it may be difficult to form a 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) Conductive resin layer In this invention, the resin layer which added the electrically conductive material on the conductive base material is formed. Although the formation method of a conductive resin layer is not specifically limited, It is preferable to apply | coat the solution, dispersion liquid, paste, etc. of resin on the said conductive base material. As a coating method, a roll coater, a gravure coater, a slit die coater or the like can be used, but is not particularly limited. The conductive resin layer used in the present invention must be a nitrified cotton-based resin. Here, the nitrified cotton-based resin refers to a resin that necessarily contains nitrified cotton as a resin component, and includes a case where all of the resin components are nitrified cotton. As a result of investigating the volume resistivity of the resin layer by adding a conductive material to various resins, the inventors have surprisingly found that a sufficiently low resistance can be obtained by using these resins with a defined paste contact angle. Based on knowledge. 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 material is added, and the resistance is different in combination with the specification of the paste contact angle described later.

<Nitrated cotton-based resin>
In the present invention, as described above, the nitrified cotton-based resin is a resin containing nitrified cotton as a resin component, and may be composed only of nitrified cotton, or contains nitrified cotton and another resin. May be. Nitrified cotton is a cellulose having a nitro group. However, compared to other celluloses such as carboxymethyl cellulose (CMC), there are proposals for optimization even though it may be exemplified as an application for an electrode. There has been no optimization for active use.

  The present inventors obtain a nitrified cotton-based resin composition by dispersing a conductive material in the nitrified cotton, and form a conductive resin layer containing the nitrified cotton-based resin and the conductive material on the conductive substrate. As a result, it was found that the high rate characteristics of the nonaqueous electrolyte battery can be dramatically improved. The nitrogen concentration of the nitrified cotton used in the present invention is preferably 10 to 13%, particularly preferably 10.5 to 12.5%. If the nitrogen concentration is too low, it may not be sufficiently dispersed depending on the type of conductive material. If the nitrogen concentration is too high, the nitrified cotton becomes chemically unstable and dangerous for use in batteries. Since the nitrogen concentration depends on the number of nitro groups, the nitrogen concentration can be adjusted by adjusting the number of nitro groups. The viscosity of the nitrified cotton is usually 1 to 6.5 seconds, particularly 1.0 to 6 seconds, and the acid content is 0.006% or less, particularly 0.005% or less, as measured according to JIS K-6703. It is recommended that When deviating from these ranges, the dispersibility of the conductive material and the battery characteristics may deteriorate.

  When the entire resin component is 100% by mass, the nitrified cotton-based resin of the present invention can use 100% by mass of nitrified cotton, but it can also be used in combination with other resin components. It is preferable to contain nitrified cotton in an amount of usually 40% by mass or more, preferably 50% by mass or more and 90% by mass or less, particularly 80% by mass or less, based on all resin components. The ratio of nitrified cotton is specifically, for example, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90% by mass, and is within the range of any two numerical values exemplified here. It may be. As a result of investigating the internal resistance of conductive resin layers manufactured by adding conductive materials to various resins, the resistance of the resin layer can be drastically reduced when it contains 50% by mass or more of nitrified cotton, and sufficient high-rate characteristics are obtained. In addition to being obtained, it was found that the adhesiveness was excellent and the life could be extended. On the other hand, if the blending amount of nitrified cotton is too small, the improvement effect by blending nitrified cotton with respect to the dispersion of the conductive material may not be obtained. It is estimated that it can be lowered.

  Various resins can be added to the nitrified cotton-based resin of the present invention in combination with the above-described nitrified cotton. In the present invention, as a result of investigating battery performance (including capacitor performance; the same applies hereinafter), it is preferable to add melamine resin, acrylic resin, polyacetal resin, and epoxy resin together, and nitrify as a resin component. The battery performance can be improved in the same manner or more than when 100% by mass of cotton is used. Each resin component will be described below.

  Since the melamine-based resin causes a curing reaction with nitrified cotton, the curability of the resin is improved, and the adhesion with the conductive base material is also improved, so that the battery performance is estimated to be improved. The ratio of the addition amount is 5 to 200% by mass, more preferably 10 to 150% by mass when the nitrified cotton as the resin component is 100% by mass. If it is less than 5% by mass, the effect of addition is low, and if it exceeds 200% by mass, the curing proceeds too much, the resin layer becomes too hard, and it is easy to peel off during battery production, and the discharge rate characteristics may deteriorate. As the melamine-based resin, for example, butylated melamine, isobutylated melamine, methylated melamine and the like can be suitably used. The number average molecular weight of the melamine resin is, for example, 500 to 50,000, specifically, for example, 500, 1000, 2000, 2500, 3000, 4000, 5000, 10,000, 20,000, and 50,000, It may be within a range between any two of the exemplified numerical values. The number average molecular weight means that measured by GPC (gel exclusion chromatograph).

  Since the acrylic resin is excellent in adhesion to a conductive substrate, particularly aluminum and copper, the addition of the acrylic resin to the conductive substrate of the nitrified cotton-based resin can be further improved. The added amount is preferably 5 to 200% by mass, particularly preferably 10 to 150% by mass, based on 100% by mass of nitrified cotton. If it is less than 5% by mass, the effect of addition is low, and if it exceeds 200% by mass, the dispersion of the conductive material may be adversely affected and the discharge rate characteristics may deteriorate. As the acrylic resin, a resin mainly composed of acrylic acid or methacrylic acid and derivatives thereof, and an acrylic copolymer containing these monomers can be suitably used. Specifically, methyl acrylate, ethyl acrylate, methyl methacrylate, isopropyl methacrylate and the like and copolymers thereof. Further, polar group-containing acrylic compounds such as acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, and copolymers thereof can also be suitably used. The weight average molecular weight of the acrylic resin is, for example, 30,000 to 1,000,000, specifically, for example, 30,000, 40,000, 50,000, 60,000, 80,000, 90,000, 100,000, 150,000. , 200,000, 300,000, 400,000, 500,000, 700,000, 800,000, 900,000, 1 million, and may be in the range between any two of the numerical values exemplified here. The weight average molecular weight means that measured by GPC (gel exclusion chromatograph).

  Since the polyacetal-based resin is excellent in flexibility and compatibility with nitrified cotton, it imparts appropriate flexibility to the resin layer and improves adhesion to the active material layer. The added amount is preferably 5 to 200% by mass, particularly preferably 20 to 150% by mass, based on 100% by mass of nitrified cotton. If it is less than 5% by mass, the effect of addition is low, and if it exceeds 200% by mass, the dispersion of the conductive material may be adversely affected and the discharge rate characteristics may deteriorate. As the polyacetal resin, polyvinyl butyral, polyacetoacetal, polyvinyl acetoacetal and the like can be suitably used. The weight average molecular weight of the polyacetal resin is, for example, 10,000 to 500,000. Specifically, for example, 10,000, 20,000, 30,000, 40,000, 50,000, 60,000, 70,000, 90,000, 90,000 , 100,000, 150,000, 200,000, 500,000, and may be within a range between any two of the numerical values exemplified here. The weight average molecular weight means that measured by GPC (gel exclusion chromatograph).

  Since the said epoxy resin is excellent in adhesiveness with an electroconductive base material, adhesiveness with an electroconductive base material improves further by adding. The added amount is preferably 5 to 200% by mass, particularly preferably 10 to 150% by mass, based on 100% by mass of nitrified cotton. If it is less than 5% by mass, the effect of addition is low, and if it exceeds 200% by mass, the dispersion of the conductive material may be adversely affected and the discharge rate characteristics may deteriorate. As the epoxy resin, glycidyl ether type resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, and tetramethylbiphenyl type are preferable. The weight average molecular weight of the epoxy resin is, for example, 300 to 50,000, specifically, for example, 300,500,1000,2000,3000,4000,5000,10,000,20,000,50,000, It may be within a range between any two of the exemplified numerical values. The weight average molecular weight means that measured by GPC (gel exclusion chromatograph).

In the present invention, the nitrified cotton-based resin may contain 100% nitrified cotton as a resin component as described above, but at least one of the above-described acrylic resin and polyacetal-based resin, and a melamine-based resin And nitrified cotton are more preferable. This is because in such a combination, the discharge rate characteristic and the battery life extension characteristic are particularly good.
In the present invention, when the total of acrylic resin, polyacetal resin, melamine resin, and nitrified cotton is 100% by mass, melamine resin is 5 to 55% by mass, and nitrified cotton is 40 to 90%. More preferably, it is mass%. The balance obtained by subtracting the blending amount of the melamine resin and the nitrified cotton from 100% by mass is the blending amount of the acrylic resin or the polyacetal resin. This is because in this case, the discharge rate characteristics and the battery life extension characteristics are further improved. Specifically, the content of the melamine-based resin is, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55 mass%, and between any two of the numerical values exemplified here. It may be within the range. The content of nitrified cotton is 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90% by mass, and is within the range between any two of the numerical values exemplified here. Also good.

<Conductive material>
The conductive resin layer of the present invention is provided between the conductive base material and the active material layer or the electrode material layer, and serves as a passage for electrons moving between them. Therefore, the resin layer also needs to have electronic conductivity. is there. Since the resin is highly insulating, a conductive material must be blended in order to impart electronic conductivity. As the conductive material used in the present invention, known 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. 30-100 mass% is preferable with respect to 100 mass% of resin components of a resin layer, and, as for the addition amount of a electrically conductive material, 40-80 mass% is further more preferable, and 50-70 mass% is more preferable. If the amount is less than 30% by mass, the volume resistivity of the resin layer is increased, and if it exceeds 100% by mass, the adhesion to the conductive substrate is lowered. A known method can be used for dispersing the conductive material in the resin component liquid. For example, the conductive material can be dispersed by using a planetary mixer, a ball mill, a homogenizer, or the like.

<Contact angle>
The paste contact angle on the surface of the resin layer of the present invention is such that the solvent-based paste contact angle is 20 degrees or more and 80 degrees or less, and / or the contact angle of the aqueous model active material paste is 80 degrees or more and 120 degrees or less. is necessary. Even if a resin layer is formed simply by adding a conductive material to the resin, sufficient adhesion is obtained at the interface between the conductive base material and the resin layer, the interface between the resin layer and the active material layer, or the interface between the resin layer and the electrode material layer. It may not be obtained. This is because even the nitrified cotton-based 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 that indicates wettability of the liquid as a surface property that has a large effect on adhesion, and the contact angle of a model active material paste that models the active material paste that is actually used when forming the active material layer is measured. By doing so, the adhesiveness between the current collector and the active material layer or electrode material layer formed thereon can be evaluated. In this case, it seems that the resin layer and the paste contact angle seem to improve the adhesion as the paste contact angle is small and the discharge rate can be improved, but if the contact angle is too small, the adhesion to the conductive substrate In the present invention, it is necessary to define the paste contact angle. This point will be described later.

  In this specification, the paste contact angle means a value obtained by measurement by the θ / 2 method in a constant temperature room at 23 ° C. The paste contact angle can be measured using a contact angle meter. After forming a resin layer on the current collector, several μl of model active material paste is adhered to the surface and the contact angle is measured. Since the surface tension of the model active material paste varies depending on the temperature, the paste contact angle is measured in a thermostatic chamber at 23 ° C.

  As a result of forming the resin layer under various conditions and measuring the paste contact angle, it was found that sufficient adhesion to the active material layer and the electrode material layer can be obtained if it is not more than the above upper limit value. In addition, as a result of forming a resin layer having a different paste contact angle and investigating the adhesive relationship between the conductive substrate and the resin layer, the high rate characteristic is obtained when the paste contact angle on the surface of the resin layer is less than the lower limit. I found it inferior. Although the cause is not clear, it is presumed that a subtle difference in adhesion between the conductive substrate and the resin layer is detected. Therefore, the paste contact angle needs to be equal to or greater than the lower limit.

  Thus, the regulation of the paste contact angle of the present invention is not only about the adhesion between the resin and the active material layer or the electrode material layer, but also considering the adhesion between the conductive substrate and the resin layer, As described above, the current collector of the present invention in which the contact angle of paste is defined can give a high rate characteristic satisfactorily when used for a battery or a charged part as an electrode structure.

  In order to obtain the current collector of the present invention, a resin layer can be obtained by a known method on at least one surface of the conductive base material such as the aluminum foil described above, but the paste contact angle described above is obtained. It is necessary to. For example, when a resin layer is formed by coating, the baking temperature and baking time affect the paste contact angle. The baking temperature is preferably 100 to 250 ° C. as the temperature reached by the conductive substrate, and the baking time is preferably 10 to 60 seconds. This is because when the resin layer is formed under such conditions, it contributes to adjusting the paste contact angle on the surface within the above range. Moreover, if it is less than 100 degreeC, nitrified cotton-type resin will not fully harden | cure, and if it exceeds 250 degreeC, adhesiveness with an active material layer may fall. However, since the paste 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 range, the paste contact angle may reach the lower limit or exceed the upper limit. Conversely, even if the baking temperature and baking time are outside the above ranges, the paste contact angle may be within the above ranges.

  In general, the higher the baking temperature and the longer the baking time, the larger the paste contact angle. Therefore, in order to make the paste contact angle below the above range, first, a resin layer is formed under a certain condition, the paste contact angle is measured in the formed resin layer, and the measured paste contact angle must be smaller than the above lower limit value. For example, if the baking temperature is increased or the baking time is increased, and the measured paste contact angle is larger than the upper limit value, it is necessary to adjust the baking temperature or shorten the baking time. Therefore, the value of the paste contact angle is not determined only by the resin composition or baking temperature. However, if the above method is used, the paste contact angle can be set to a desired value with only a few trials and errors. It is.

  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 solution is infiltrated, sufficient adhesion is provided at the interface between the resin layer and the active material layer or the resin layer and the electrode material layer. In addition to ensuring, sufficient adhesion can also be secured 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 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 resin layer is cracked at the innermost winding portion with a very small radius of curvature. In some cases, a part peeled off from the active material layer or the like may occur. More preferably, it is 0.3 to 3 μm.

  Although the manufacturing method of the current collector of the present invention is not particularly limited, when the resin layer is formed on the conductive substrate, the conductive substrate is improved so that the adhesion of the surface of the conductive substrate is improved. It is also effective to perform a known pretreatment. 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.

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, an electrode structure (battery component) for a non-aqueous electrolyte battery, for example, a lithium ion secondary battery, using the electrode structure, a separator, a non-aqueous electrolyte solution, etc. Can be manufactured). 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.
Here, the active material layer formed as an electrode structure in the present invention may be conventionally proposed for non-aqueous electrolyte batteries. For example, the current collector of the present invention using aluminum as the positive electrode, LiCoO ₂ , LiMnO ₂ , LiNiO ₂ or the like as the active material, carbon black such as acetylene black as the conductive material, and PVDF as a binder Alternatively, the positive electrode structure of the present invention can be obtained by applying and drying a paste dispersed in water-dispersed PTFE.
When the negative electrode structure is used, 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 as the conductive base material, and these are used as a thickener CMC. After the dispersion, the paste mixed with SBR as a binder is applied and dried as an active material layer forming material, whereby the negative electrode structure of the present invention can be obtained.

Nonaqueous electrolyte battery The present invention may be a nonaqueous electrolyte battery. In this case, there is no particular limitation other than using the current collector of the present invention. For example, the non-aqueous electrolyte battery of the present invention is sandwiched between separators impregnated with an electrolyte for a non-aqueous electrolyte battery having a non-aqueous electrolyte between the positive electrode structure and the negative electrode structure having the current collector of the present invention as a constituent element. A water electrolyte battery can be constructed. 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.

Power storage components (electric double layer capacitors, lithium ion capacitors, etc.)
The electric double layer capacitor, lithium ion capacitor, etc. of the present invention can also be applied to power storage components such as electric double layer capacitors and lithium ion capacitors that require high-speed charge / discharge at a large current density. is there. 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 can be made of an electrode material, a conductive material, and a binder for both the positive electrode and the negative electrode. In the present invention, an electricity storage component can be obtained after forming the electrode material layer on at least one side of the current collector of the present invention to form an electrode structure. 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), SBR (styrene butadiene rubber), water-dispersed PTFE, or the like 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.

  EXAMPLES Hereinafter, although the Example and comparative example of this invention are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

<1. Evaluation of current collector>
<Preparation of current collector>
In Examples 1 to 29 and Comparative Examples 1 to 4, acetylene black was mixed in a blending amount shown in Table 1 in a resin solution obtained by dissolving various resins shown in Table 1 in MEK (methyl ethyl ketone), and dispersed for 8 hours in a ball mill. And made a paint. This paint was applied to one side of a 20 μm thick aluminum foil (JIS A1085) with a bar coater and baked under the conditions shown in Table 1 to produce a current collector. The temperatures in Table 1 are all substrate arrival temperatures.
In Comparative Examples 5 to 8, current collectors were prepared in the same manner as described above except that various resins shown in Table 1 were dissolved in NMP (N methyl 2-pyrrolidone) to prepare resin solutions.
In Table 1, the weight of nitrified cotton is the weight of solid content. Table 2 shows the details of the resin abbreviated in Table 1.

<Measurement of resin layer thickness>
The thickness of the resin layer is calculated using the film thickness measuring instrument Keitaro G (manufactured by Seiko em) from the difference in thickness between the resin layer forming part and the unformed part (aluminum foil only part). did.

<Electric resistance of resin layer>
A cubic copper block with a side of 20 mm was placed on the resin layer (the surface in contact with the resin was mirror-finished), and a load of 700 gf was applied to measure the electrical resistance between the aluminum foil and the copper block.

<Adhesion between aluminum foil and resin layer>
The cellophane tape was affixed to the surface of the resin layer, and evaluation was performed based on the state of peeling of the resin layer when it was peeled off at a stroke.
A: No peeling B: About 1/4 peeling C: About 1/2 peeling D: About 3/4 peeling E: Whole surface peeling

<Measurement of paste contact angle>
Use a contact angle meter (Dropmaster DM-500, manufactured by Kyowa Interface Science Co., Ltd.) for the solvent or aqueous paste contact angle, and attach 2 μL of solvent or aqueous model active material paste to the resin layer surface in a constant temperature room at 23 ° C. The contact angle after 2 seconds was measured by the θ / 2 method.

<2. Lithium-ion battery discharge rate characteristics evaluation, electrode life evaluation>
As shown below, discharge rate characteristic evaluation and electrode life evaluation of a lithium ion battery formed by forming an active material layer using a solvent-based active material paste were measured.

<Method for producing lithium ion battery>
As the positive electrode, a paste obtained by dispersing a paste in which PVD (polyvinylidene fluoride) as a binder was dispersed in an active material of LiCoO ₂ and a conductive material of acetylene black at a thickness of 70 μm was used. For the negative electrode, an active material graphite dispersed in CMC (carboxymethylcellulose) and then a paste mixed with a binder SBR (styrene butadiene rubber) was applied to a 20 μm thick copper foil at a thickness of 70 μm. It was. 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.

<Discharge rate characteristics evaluation method>
The discharge capacities of these lithium ion batteries (0,0,5, 10 and 20 C) at a charge upper limit voltage of 4.2 V, a charge current of 0.2 C, a discharge end voltage of 2.8 V and a temperature of 25 ° C. 2C standard, unit%). (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.)

<Evaluation method of electrode life>
After charging at an electrolyte temperature of 40 ° C. with an upper limit voltage of 4.2 V and a charging current of 20 C, the battery was discharged at an end voltage of 2.8 V and a discharging current of 20 C, and the discharge capacity was 60 with respect to the discharge capacity of the first cycle. The number of times of less than% (up to 500 times) was measured and evaluated according to the following criteria.
A: 500 times or more B: 450 times or more and less than 500 times C: 400 times or more and less than 450 times D: Less than 400 times

<3. Evaluation of discharge rate characteristics and electrode life of electric double layer capacitors>
As shown below, discharge rate characteristic evaluation and electrode life evaluation of an electric double layer capacitor formed by forming an active material layer using a solvent-based electrode material paste were measured.

<Method of manufacturing electric double layer capacitor>
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 electrode at a thickness of 80 μm to form the same electrode structure for both the positive electrode and the negative electrode. The two electrode structures were fixed with an electric double layer capacitor non-woven fabric impregnated with an electrolytic solution therebetween, 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.

<Discharge rate characteristics evaluation method>
Under the conditions of an upper limit charging voltage of 2.8 V, a charging current of 1 C, a charging end condition of 2 h, a discharge end voltage of 0 V, a temperature of 25 ° C., a discharge current rate of 100 C, 300 C, and 500 C, the discharge capacity of these electric double layer capacitors (1 C reference, Unit%) was measured.

<Evaluation method of electrode life>
After charging at an electrolyte temperature of 40 ° C. with an upper limit voltage of 2.8 V and a charging current of 500 C, the battery is discharged to a final voltage of 0 V with a discharging current of 500 C, and the discharging capacity is less than 80% with respect to the discharging capacity of the first cycle. Was measured (maximum 5000 times) and evaluated according to the following criteria.
A: 5000 times or more B: 4500 times or more and less than 5000 times C: 4000 times or more and less than 4500 times D: Less than 4000 times

The evaluation results are shown in Table 1. In Table 1, the weight of nitrified cotton is the weight of solid content. Table 2 shows the details of the resin abbreviated in Table 1.
According to Table 1, in all examples in which the resin of the resin layer is a nitrified cotton-based resin and the solvent-based paste contact angle on the surface of the resin layer is 20 degrees or more and 80 degrees or less, the resin layer was prepared using a solvent-based paste. Both lithium ion batteries and electric double layer capacitors showed excellent high-rate characteristics and battery life. On the other hand, the high rate characteristics were not good in Comparative Examples 3 to 10 using ethyl cellulose as the resin of the resin layer. Further, even in Comparative Example 1 where the solvent-based paste contact angle is too large and Comparative Example 2 which is too small, the high rate characteristics were not good.

  Further, according to the results in Table 1, even when the contact angle of the aqueous model active material paste is 80 degrees or more and 120 degrees or less, in the lithium ion battery or the electric double layer capacitor manufactured using the solvent-based paste, the discharge rate The characteristics may not be good. However, according to the results of preliminary experiments by the present inventors, when the contact angle of the aqueous model active material paste is 80 degrees or more and 120 degrees or less, a lithium ion battery or an electric double layer capacitor produced using the aqueous paste Especially good results have been obtained. In addition, when both the solvent-based paste contact angle and the water-based model active material paste contact angle are within the above ranges, even if the paste used for producing the lithium ion battery or the electric double layer capacitor is a solvent-based paste, Even so, good results were obtained.

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

Claims (2)

An active material layer or an electrode material layer is provided on the resin layer of the current collector having a conductive resin layer on at least one surface of the conductive substrate, and any of the following conditions (1) to (3) is satisfied An electrode structure.
(1) In the current collector, the resin layer contains a nitrified cotton-based resin and a conductive material, and the contact angle of the solvent-based model active material paste measured by the θ / 2 method in a thermostatic chamber at 23 ° C. on the surface of the resin layer. Is a current collector in which the nitrogen concentration of the nitrified cotton contained in the nitrified cotton-based resin is 10 to 13%, and the active material layer or the electrode material layer has an NMP solvent. It is formed with a solvent-based active material paste.
(2) In the current collector, the resin layer contains a nitrified cotton-based resin and a conductive material, and the contact angle of the aqueous model active material paste measured by the θ / 2 method in a 23 ° C. constant temperature room on the surface of the resin layer is 80 to 120 degrees, and the current collector or electrode material layer is a water-based active material paste, wherein the nitrogen concentration of the nitrified cotton contained in the nitrified cotton-based resin is 10 to 13%. Formed with.
(3) In the current collector, the resin layer contains a nitrified cotton-based resin and a conductive material, and the contact angle of the solvent-based model active material paste measured by the θ / 2 method in a thermostatic chamber at 23 ° C. on the surface of the resin layer. Is 20 degrees or more and 80 degrees or less, the contact angle of the water-based model active material paste is 80 degrees or more and 120 degrees or less, and the nitrogen concentration of the nitrified cotton contained in the nitrified cotton-based resin is 10 to 13% The active material layer or the electrode material layer is formed of a solvent-based active material paste or a water-based active material paste whose solvent is NMP. A nonaqueous electrolyte battery or a power storage component comprising the electrode structure according to claim 1 .