JP2012072396A - Coating liquid, current collector, and method for manufacturing current collector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an undercoat layer of a current collector excellent in penetration resistance and the moisture resistance, using an aqueous solvent.SOLUTION: A coating liquid includes as essential components (A) water or a mixed solvent of water and organic solvent, (B) a conductive material, and (C) at least one selected from the group consisting of polysaccharides and derivatives thereof, and as required, (D) at least one selected from the group consisting of di- or more valent organic acids and derivatives thereof, wherein the masses W, Wand Wof the components (B), (C) and (D) contained in the coating liquid satisfy expression (1): 0.5≤W/(W+W)≤5.

Description

  The present invention relates to a coating liquid. More specifically, the present invention relates to a coating liquid for producing a current collector used for an electrochemical element such as a secondary battery or an electric double layer capacitor, a solar battery, a touch panel or the like.

  As electrochemical devices, secondary batteries such as lithium ion secondary batteries and nickel metal hydride batteries, and capacitors such as electric double layer capacitors and hybrid capacitors are known.

  The electrode of an electrochemical element generally comprises a current collector and an electrode active material layer. The electrode is usually produced by applying a coating liquid containing an electrode active material, a binder, and a solvent to a current collector and drying it. Further, in order to reduce the internal resistance or impedance of the secondary battery or electric double layer capacitor, it has been proposed to interpose an undercoat layer on the current collector surface.

  By the way, a film obtained with a coating liquid containing a polysaccharide such as chitosan has high ion permeability or ion mobility, and can reduce the internal resistance or impedance of a lithium ion secondary battery or an electric double layer capacitor. It is said (for example, Patent Document 4).

  Then, as a coating liquid for forming an undercoat layer, for example, in Patent Document 1, a coating liquid containing hydroxyalkyl chitosan and an organic acid or a derivative thereof is applied on a current collector and dried. It has been proposed to produce an electrode active material layer or an undercoat layer, and Patent Document 2 discloses a coating solution for forming an undercoat layer containing a hydroxyl group-containing resin such as cyanoethylated dihydroxypropyl chitosan and an organic acid or a derivative thereof. Is described.

  Patent Document 3 describes a paste containing an ion-permeable compound obtained by crosslinking chitosan, chitin or the like with pyromellitic anhydride, conductive carbon fine particles such as acetylene black, and a solvent such as water. ing.

JP 2008-060060 A International Publication No. WO2009 / 147789 International Publication No. WO2007 / 043515 Pamphlet JP 2006-286344 A

  In the coating liquid for forming the undercoat layer, a case where a nitrogen-containing aprotic polar solvent such as N-methylpyrrolidone or a sulfur-containing aprotic polar solvent such as dimethyl sulfoxide is used as a dispersion medium, or an aqueous solvent is used. Sometimes it is used.

  Nitrogen-containing aprotic polar solvents and sulfur-containing aprotic polar solvents have a high boiling point, require high-temperature drying or drying for a long time, and require drying equipment that responds to the odor and toxicity of solvent vapors From the viewpoint of cost reduction and environmental impact reduction, there is a demand for conversion to an aqueous solvent.

  On the other hand, in the case where the undercoat layer is formed using an aqueous solvent, when the obtained current collector is stored under humidity conditions, a lithium ion secondary battery or an electric double layer capacitor manufactured using the current collector is used. In some cases, the internal resistance or impedance significantly increased as compared with the case where an undercoat layer was formed using an aprotic polar solvent.

  Accordingly, an object of the present invention is to form a current collector undercoat layer excellent in penetration resistance value and moisture resistance using an aqueous solvent, and to provide a coating liquid used for the production thereof.

The present invention relates to a coating solution, a current collector and a method for producing the current collector shown in the following [1] to [14].
[1]
(A) water or a mixed solvent of water and an organic solvent;
(B) a conductive material;
(C) One or more selected from the group consisting of polysaccharides and polysaccharide derivatives is included as an essential component, and (D) a divalent or higher valent organic acid and a divalent or higher organic acid derivative as required. A coating liquid containing at least one selected from the group, wherein the mass of each component (B), (C), (D) contained in the coating liquid is W _B , W _C , and W _D , respectively. _{, W} B, _W C, coating _{solution W D} satisfies the following equation (1).
0.5 ≦ W _B / (W _C + W _D ) ≦ 5 (1)
[2] The coating solution according to [1], wherein the organic solvent contains a primary or secondary monofunctional alcohol having 1 to 4 carbon atoms.
[3] The polysaccharide is one or more selected from the group consisting of chitin, chitosan, and cellulose, and the polysaccharide derivative is one or more selected from the group consisting of a cellulose derivative and a chitosan derivative. Or the coating liquid as described in [2].
[4] The coating solution according to any one of [1] to [3], wherein the polysaccharide derivative is a hydroxyalkylated polysaccharide.
[5] Any of [1] to [4], wherein the divalent or higher organic acid is a trivalent or higher organic acid, and the divalent or higher organic acid derivative is a trivalent or higher organic acid derivative. The coating liquid according to claim 1.
[6] In any one of [1] to [5], the divalent or higher organic acid is an aromatic carboxylic acid, and the divalent or higher organic acid derivative is an aromatic carboxylic acid derivative. The coating liquid as described.
[7] The coating solution according to any one of [1] to [5], wherein the derivative of the divalent or higher organic acid is an acid anhydride.
[8] The coating liquid according to any one of [1] to [7], wherein the conductive material is a carbonaceous material.
[9] A current collector, wherein the coating liquid according to any one of [1] to [8] is applied on a conductive substrate and heated at a temperature of 100 ° C. or higher and 300 ° C. or lower. Body manufacturing method.
[10] A current collector in which an undercoat layer is formed by applying the coating liquid according to any one of [1] to [8] to one side or both sides of a conductive substrate.
[11] The current collector according to [10], wherein the conductive substrate is aluminum or copper.
[12] An electrode in which an electrode active material layer is formed on the undercoat layer of the current collector of any one of [10] or [11].
[13] An electrochemical device having the electrode according to [12].
[14] A power supply system having the electrochemical element according to [13].

  The current collector according to the present invention can be produced at low cost using an aqueous solvent, and is excellent in penetration resistance value and moisture resistance.

The coating liquid according to the present invention is
(A) water or a mixed solvent of water and an organic solvent;
(B) Conductive material (C) One or more selected from the group consisting of polysaccharides and polysaccharide derivatives as essential components, and (D) divalent or higher organic acids and divalent or higher organics as necessary One or more selected from the group consisting of acid derivatives may be included.

((A) Water or a mixed solvent of water and an organic solvent)
The organic solvent used as the component (A) is preferably one that mixes with water and has a low environmental load because the evaporation rate during heating is close to that of water. Specifically, for example, methanol, ethanol, isopropyl alcohol, n-butanol, isobutanol, etc., primary or secondary monofunctional alcohol having 1 to 4 carbon atoms, methoxyethanol, dimethoxyethane, tetrahydrofuran, 1, 4 -C3-C4 ethers such as dioxane and the like, ethers having 3 or 4 carbon atoms, acetone, methyl ethyl ketone, etc., preferably primary or secondary monofunctional alcohols having 1 to 4 carbon atoms, more preferably Is isopropyl alcohol. These organic solvents can be used alone or in combination of two or more.

  The amount of the organic solvent used is preferably 50% by mass or less, more preferably 40% by mass or less, and most preferably 30% by mass or less in a mixed solvent of water and organic solvent.

((B) Conductive material)
The conductive material which is the component (B) of the coating liquid according to the present invention is preferably a carbonaceous material containing carbon as a main component. As the carbonaceous material, acetylene black, ketjen black, carbon fiber, carbon nanotube, carbon nanofiber, graphite and the like are suitable. These conductive carbon materials can be used singly or in combination of two or more.

  Examples of conductive materials other than carbonaceous materials include powders of metals such as gold, silver, copper, nickel, and aluminum.

  The conductive material may be particles having a spherical shape or an indefinite shape, or may have an anisotropic shape such as a needle shape or a rod shape.

  The particulate conductive material is not particularly limited by the particle size, but preferably has a volume-based average primary particle size of 10 nm to 50 μm, more preferably 10 nm to 100 nm. The average particle diameter of the conductive material is obtained by measuring the particle diameter of a predetermined number of conductive material particles using an electron microscope and averaging the measured particle diameters.

  An anisotropically shaped conductive material has a large surface area per weight and a large contact area with the current collector and electrode active material, etc., so even if a small amount is added, it is between the current collector and electrode active material or between electrode active materials. The conductivity between them can be increased. Particularly effective anisotropic conductivity imparting materials include carbon nanotubes and carbon nanofibers. Carbon nanotubes and carbon nanofibers have a fiber diameter of usually 0.001 to 0.5 μm, preferably 0.003 to 0.2 μm, and a fiber length of usually 1 to 100 μm, preferably 1 to 30 μm. It is suitable for improvement.

The conductive material preferably has a powder electrical resistance of 5.0 × 10 ⁻¹ Ω · cm or less measured in accordance with JIS K1469.

((C) polysaccharides and polysaccharide derivatives)
The polysaccharide and the polysaccharide derivative, which are the component (C) of the coating liquid according to the present invention, are high molecular compounds obtained by polymerizing a number of monosaccharides or their derivatives through glycosidic bonds. A polymer obtained by polymerizing 10 or more monosaccharides or derivatives thereof is usually called a polysaccharide, but even a polymer obtained by polymerizing less than 10 monosaccharides can be used. The monosaccharide constituting the polysaccharide may be a normal monosaccharide such as glucose having only a hydroxyl group as a basic skeleton, a uronic acid having a carboxyl group, or an amino sugar having an amino group or an acetylamino group. . The molecular weight of the polysaccharide or derivative thereof is preferably 1.0 × 10 ^{4 to} 2.0 × 10 ⁵ , more preferably 5.0 × 10 ^{4 to} 2.0 × 10 ⁵ in terms of weight average molecular weight. When the molecular weight is within this range, the dispersibility of the conductive material is good, and the coating property of the coating solution and the strength of the undercoat layer obtained by applying the coating solution are excellent. The molecular weight can be determined as a value converted to a standard sample such as pullulan using gel permeation chromatography. The polysaccharide may be either a homopolysaccharide or a heteropolysaccharide.

  Examples of polysaccharide derivatives include those in which polysaccharides are hydroxyalkylated, carboxyalkylated, and sulfated. Hydroxyalkylated polysaccharides are particularly preferred because they can increase the solubility in water. The hydroxyalkylated polysaccharide can be produced by a known method.

  Specific examples of polysaccharides include agarose, amylose, amylopectin, alginic acid, inulin, carrageenan, chitin, glycogen, glucomannan, keratan sulfate, colominic acid, chondroitin sulfate, cellulose, dextran, starch, hyaluronic acid, pectin, pectic acid, Examples include heparan sulfate, levan, lentinan, chitosan, pullulan, curdlan and derivatives thereof.

  Of these, chitin, chitosan, and cellulose are preferable because of their high ion permeability. Hydroxyalkylated hydroxyalkylchitin, hydroxyalkylchitosan, and hydroxyalkylcellulose are more preferable, and hydroxyalkylchitosan, particularly hydroxyalkyl groups are glyceryl groups. Certain glycerylated chitosans are most preferred.

((D) Bivalent or higher valent organic acids and derivatives of divalent or higher organic acids)
It is preferable that the coating liquid which concerns on this invention contains 1 or more types chosen from the group which consists of a divalent or higher valent organic acid and a divalent or higher valent organic acid derivative as (D) component. The divalent or higher valent organic acid and the divalent or higher valent organic acid derivative are not particularly limited as long as the polysaccharide can be cross-linked, but those capable of cross-linking the polysaccharide by a thermal reaction are preferable. The organic acid having a valence of 2 or more and the derivative of an organic acid having a valence of 2 or more preferably have a temperature at which a crosslinking reaction occurs at 100 to 300 ° C. If the temperature is less than 100 ° C., the crosslinking reaction is too fast and difficult to handle. If it exceeds 300 ° C., the polysaccharide contained in the coating solution may be decomposed. The divalent or higher valent organic acid is a trivalent or higher valent organic acid, and the divalent or higher valent organic acid derivative is preferably a trivalent or higher valent organic acid derivative from the viewpoint of high crosslinking effect. Aromatic carboxylic acids and alicyclic carboxylic acids are preferred because they are excellent in thermal stability of the undercoat layer obtained by applying the coating liquid according to the present invention, and aromatic carboxylic acids are particularly preferred. Examples of the derivatives of divalent or higher organic acids include esters of divalent or higher organic acids, acid anhydrides, and the like, and acid anhydrides are preferable because the crosslinking reaction easily proceeds and there are few by-products.

  Examples of the aromatic carboxylic acid include phthalic acid, isophthalic acid, terephthalic acid as the divalent aromatic carboxylic acid, and trimellitic acid and pyromellitic acid as the trivalent or higher valent aromatic carboxylic acid. Examples of the aromatic carboxylic acid derivative include divalent aromatic carboxylic acid derivatives such as dimethyl phthalate, diethyl phthalate, dimethyl isophthalate, dimethyl terephthalate, diethyl terephthalate, and phthalic anhydride. As derivatives of aromatic carboxylic acids, trimethyl trimellitic acid, trimellitic acid anhydride, pyromellitic acid anhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic acid anhydride, 3,3 ′, 4,4 And '-benzophenone tetracarboxylic anhydride.

  Examples of the alicyclic carboxylic acid include tetrahydrophthalic acid and hexahydrophthalic acid as the divalent alicyclic carboxylic acid, and cyclohexane 1,2,4-tricarboxylic acid and cyclohexane as the trivalent or higher alicyclic carboxylic acid. 1,2,4,5-tetracarboxylic acid. As the derivative of the alicyclic carboxylic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic acid anhydride, Hydrogenated methyl nadic acid anhydride, trialkyltetrahydrophthalic anhydride, 1,2,4-cyclohexane tricarboxylic acid anhydride, 1,2,4,5-cyclohexane as acid anhydride of trivalent or higher alicyclic carboxylic acid Examples thereof include tetracarboxylic acid anhydride.

  Of these divalent or higher organic acids or derivatives of divalent or higher organic acids, trimellitic anhydride or pyromellitic anhydride is preferably used, and pyromellitic anhydride is particularly preferably used.

  These divalent or higher valent organic acids and divalent or higher valent organic acid derivatives can be used singly or in combination of two or more.

(Coating fluid)
The coating liquid according to the present invention includes (B) a conductive material, (C) one or more selected from the group consisting of polysaccharides and polysaccharide derivatives, (D) a divalent or higher valent organic acid and a divalent or higher valent derivative. The blending amount (mass basis) in the coating liquid of one or more components selected from the group consisting of W _B , W _C , and W _D is satisfied with the following formula (1),
0.5 ≦ W _B / (W _C + W _D ) ≦ 5 (1)
Preferably the following formula (2) is satisfied,
0.6 ≦ W _B / (W _C + W _D ) ≦ 3 (2)
More preferably, the following formula (3) is satisfied.
0.9 ≦ W _B / (W _C + W _D ) ≦ 2 (3)

By making W _B / (W _C + W _D ) in the above range, the dispersion of the conductive material in the coating liquid becomes uniform, and the current collection obtained by applying and heating the coating liquid to the conductive substrate A current collector having good penetration resistance and moisture resistance can be obtained without causing the conductive agent and undercoat layer to fall off the body. However, _{W D} may be zero.

Further, when the coating liquid contains one or more selected from the group consisting of (D) a divalent or higher valent organic acid and a divalent or higher valent organic acid derivative, the blending mass W _C of the (C) component and the (D) component mass W _D of the formulation, preferably the following formula (4), satisfies more preferably the following formula (5), most preferably the following formula (6).
0.8 ≦ W _C / W _D ≦ 5 (4)
1 ≦ W _C / W _D ≦ 3 (5)
1.1 ≦ W _C / W _D ≦ 2.5 (6)

By the W C _/ W _D to this value, to improve the polysaccharide dispersion in a coating solution, coating the coating liquid on the conductive substrate, the undercoat layer obtained by drying Mechanical strength, moisture resistance, and electrolytic solution resistance can be improved.

  The amount of component (A) used in the coating solution is preferably 20 to 99% by mass, more preferably 50 to 98% by mass, and 80 to 95% by mass of the entire coating solution. Most preferred. (A) By making the usage-amount of a component into such a value, a coating liquid becomes moderate viscosity, it is excellent in workability | operativity, such as application | coating, Application | coating of an undercoat layer obtained by apply | coating and drying a coating liquid The amount can be suitable.

  The viscosity of the coating solution is preferably 100 to 50000 mPa · s, more preferably 100 to 10000 mPa · s, and still more preferably 100 to 5000 mPa · s at normal temperature. Viscosity is measured using a B-type viscometer by selecting a rotor and rotation speed suitable for the viscosity range to be measured. For example, when measuring the viscosity of a coating solution of several hundred mPa · s, the rotor No. 2, 60 rpm.

  In addition to the components (A) to (D) described above, the coating liquid of the present invention includes a dispersion stabilizer, a thickener, an anti-settling agent, an anti-skinning agent, an antifoaming agent, an electrostatic coating property improving agent, Additives such as an anti-sagging agent, a leveling agent, a crosslinking catalyst, and a repellency inhibitor may be included. Any known additive can be used as the additive, and the amount of the additive is preferably 10 parts by mass or less with respect to the total of 100 parts by mass of (B) to (D). .

  The coating liquid comprises (A) to (C) each component and, if necessary, (D) one or more selected from the group consisting of divalent or higher organic acids and derivatives of divalent or higher organic acids, and the above additives. Can be mixed using a mixer. Examples of the mixer include a ball mill, a sand mill, a pigment disperser, a pulverizer, an ultrasonic disperser, a homogenizer, a planetary mixer, and a Hobart mixer. At this time, it is preferable to add a liquid prepared by previously mixing the components (A), (C), and (D) and additives to the conductive material (B) and mix them, so that a uniform coating liquid can be easily obtained.

(Current collector)
The current collector is obtained by applying a coating liquid containing a conductive material on a conductive substrate and then drying to form an undercoat layer.

  The conductive substrate includes not only a substrate having no holes but also a substrate having holes such as a punching metal foil or a net. The surface of the conductive substrate may be smooth, but a surface roughened by an electrical or chemical etching process, that is, an etching foil is also suitable.

  The conductive substrate is not particularly limited depending on the thickness, but usually 5 μm to 200 μm is preferable. With such a thickness, the ratio of the current collector in the predetermined volume of the electrochemical element or the like is suppressed to a certain level, the performance of the electrochemical element or the like per volume is improved, and the conductive base material or the current collector is increased. Sufficient strength can be secured for handling the body and electrodes.

  As the material of the conductive base material, known materials can be used as the electrode base material of the electrochemical element, and examples thereof include a metal foil and a conductive resin film. Specifically, an aluminum foil, a copper foil, etc. are mentioned as a preferable thing. As the aluminum foil, a pure aluminum-based A1085 material, A3003 material or the like is usually used, and as the copper foil, a rolled copper foil or an electrolytic copper foil is usually used.

  The method for applying the coating liquid to the conductive substrate is not particularly limited, and a known coating method used in the production of an undercoat layer used for a lithium ion battery, an electric double layer capacitor, or the like can be employed as it is.

  Specific examples include a casting method, a bar coater method, a dip method, and a printing method. Among these, from the point that it is easy to control the thickness of the coating film, bar coat, gravure coat, gravure reverse coat, roll coat, Meyer bar coat, blade coat, knife coat, air knife coat, comma coat, slot diamond coat, A slide die coat and a dip coat are preferred.

  Application | coating may be performed to a part of electroconductive base material, and may be performed to the whole surface. When applying to a part of the conductive substrate, leave only the edge of the conductive substrate and apply a solid coating to the remaining part, or apply it in a pattern such as a grid, grid, or dot Good. Moreover, you may perform application | coating to the single side | surface or both surfaces of an electroconductive base material. In the case of applying to both sides, the application operation may be performed on each side, or the application operation may be performed on both sides simultaneously.

The coating amount of the coating liquid on the conductive substrate is preferably 0.2 to 5 g / m ² , more preferably 0.5 to 3 g / m ² , and most preferably 1 to ² g / m in terms of weight after drying. ² . By setting it as such a coating amount, it is effective for reduction of internal resistance and impedance.

  Although the drying method of a coating liquid is not restrict | limited in particular, Preferably it heats for 10 second to 10 minutes within the temperature range of 100-300 degreeC, More preferably, 120-250 degreeC. By heating under such conditions, water remains in the undercoat layer obtained by drying the coating liquid while maintaining productivity, or the crosslinking reaction does not proceed sufficiently. It is possible to reduce the risk of decomposition of the organic components therein, and to reduce the roughness of the surface of the undercoat layer.

  The thickness of the undercoat layer is preferably 0.01 μm or more and 50 μm or less, more preferably 0.1 μm or more and 10 μm or less. With such a thickness, the internal resistance and impedance can be reduced with a thin current collector that is advantageous for miniaturization of an electrochemical element or the like.

The penetration resistance value of the current collector can be measured as follows. Two current collectors provided with an undercoat layer are cut into strips having a predetermined size, and the undercoat layers are joined together and fixed so that the contact surface has a predetermined area and shape. Each end where the current collectors are not in contact with each other is coupled to an AC milliohm meter, and the penetration resistance value of the current collector is measured.
The penetration resistance value of the current collector is preferably 100 mΩ or less at 25 ° C.

  The moisture resistance of the current collector can be evaluated, for example, as follows. First, for the current collector before the start of the moisture resistance test (preferably after production, the exposure to the environment with a relative humidity of 10% or more is less than 60 minutes), the penetration resistance value was measured by the above-described method, and this was determined as the initial resistance. Value. The current collector after measurement is immediately placed in a constant temperature and humidity chamber at 25 ° C. and 50% relative humidity in an air atmosphere. After the elapse of 300 hours, the current collector is taken out and the penetration resistance value is measured immediately and compared with the initial resistance value. The penetration resistance value after 300 hours is preferably 150% or less, with the initial resistance value being 100%.

(electrode)
An electrode of a lithium ion secondary battery or an electric double layer capacitor is obtained by forming an electrode active material layer on an undercoat layer of a current collector. There are no particular limitations on the material used for the electrode active material layer and the method for forming the electrode active material layer, and known materials and methods used in the manufacture of lithium ion secondary batteries, electric double layer capacitors, and hybrid capacitors are employed. be able to.

  The current collector may be used for an electrode of an electrochemical element other than the above, or may be used for an electrode of a solar cell or a touch panel.

(Electrochemical element)
The electrochemical element has the above-described electrode, and usually has a separator and an electrolyte. As the electrode in the electrochemical device, both the positive electrode and the negative electrode may be the electrode according to the present invention, or one of them may be the electrode according to the present invention, and the other may be a known electrode. In the lithium ion battery, at least the positive electrode is preferably the electrode according to the present invention. The separator is not particularly limited as long as it is used in a secondary battery such as a lithium ion battery, an electric double layer capacitor, a hybrid capacitor, or the like, and may be omitted when a solid electrolyte is used as an electrolyte. The electrolyte is not particularly limited as long as it is used in a secondary battery such as a lithium ion battery, an electric double layer capacitor, a hybrid capacitor, etc., and is not limited, and may be an electrolytic solution, a gel electrolyte, a polymer electrolyte, an inorganic solid electrolyte, or a molten salt. Any of electrolytes may be used.

  The electrochemical element can be applied to a power supply system. And this power supply system includes automobiles; transport equipment such as railways, ships and airplanes; portable equipment such as mobile phones, personal digital assistants and portable electronic computers; office equipment; solar power generation systems, wind power generation systems, fuel cell systems, etc. It can be applied to the power generation system.

  Next, the present invention will be described more specifically with reference to examples and comparative examples. The scope of the present invention is not limited by this embodiment. The coating liquid, current collector, electrode, electrochemical element, and power supply system according to the present invention can be appropriately modified and implemented without departing from the scope of the present invention.

(Manufacture of coating liquid)
(Examples 1-4)
The raw materials shown in Table 1 were dispersed for 10 minutes at a rotation speed of 300 rpm using a dissolver type stirrer to obtain coating liquids 1 to 4.
(Comparative Examples 1-3)
Comparative coating liquids 1 to 3 were produced by dispersing the raw materials shown in Table 1 in the same manner as in Examples 1 to 4.

(Manufacture of current collector)
(Examples 5 to 8)
An aluminum foil having a thickness of 30 μm made of A1085 material washed with alkali was prepared. Using an applicator, the coating liquids 1 to 4 prepared in Examples 1 to 4 were coated on both surfaces of an aluminum foil by a casting method so that the coating amount after drying was 0.5 m ² / g. Then, it heat-dried at 180 degreeC for 3 minute (s), and obtained the collectors 1-4.
(Comparative Examples 4-6)
Comparative collectors 1 to 3 were produced in the same manner as in Examples 5 to 8, except that the coating liquids 1 to 4 were the comparative coating liquids 1 to 3 manufactured in Comparative Examples 1 to 3, respectively.
Among the obtained comparative current collectors, in the comparative current collector 3, the conductive material was peeled off from the aluminum foil, and could not be put to practical use.

(Measurement of penetration resistance value and moisture resistance test)
Two current collectors 1 to 4 obtained in Examples 5 to 8 and comparative current collectors 1 to 3 obtained in Comparative Examples 4 to 6 were cut out in a size of 20 mm in width and 100 mm in length. The two coated surfaces cut out were put together, and the contact surface was adjusted to 20 mm × 20 mm and placed on a vinyl chloride plate. The contact portion was fixed by applying a load to the portion where the two sheets were in contact with each other so as to be 1 kg / cm ² . Each end where the current collectors were not in contact with each other was coupled to an AC milliohm meter, and the penetration resistance value of the current collector was measured. In addition, the penetration resistance value measured immediately after coating and heat drying was used as the initial value.

  The current collector for which the initial resistance value was measured was immediately stored in a constant temperature and humidity chamber at 25 ° C. and a relative humidity of 50% for 300 hours in an air atmosphere. The current collector after storage was taken out and the penetration resistance value was measured immediately, and the penetration resistance value after 300 hours was calculated and recorded when the initial resistance value was 100%.

  Table 2 shows the results of measurement of the penetration resistance value of the current collector and the moisture resistance test. The current collector obtained using the coating liquid of the present invention is excellent in initial resistance value and moisture resistance, and has an initial penetration resistance value as compared with the comparative current collector 2 produced using a non-aqueous coating liquid. It was shown that the moisture resistance is not inferior.

(Manufacture and evaluation of lithium-ion batteries)
(Examples 9 to 12)
The current collectors 1 to 4 produced in Examples 5 to 8 were each cut into a size of 10 cm × 10 cm. 95 parts by mass of lithium cobalt oxide (Nippon Kagaku Kogyo Co., Ltd., trade name Cellseed C), 2 parts by mass of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name Denka Black (powder product)), polyvinylidene fluoride ( Made by Kureha Co., Ltd., trade name KF polymer # 1120) 3 parts by mass, N-methyl-2-pyrrolidone (industrial grade) 95 parts by mass slurry was applied to each of the current collectors 1-4 and dried The positive electrode was formed by pressing to form a positive electrode active material layer having a thickness of 50 μm on one side.

  On the other hand, artificial graphite (made by Showa Denko KK, trade name SCMG-AR) 94 parts by mass, acetylene black (manufactured by Electrochemical Industry Co., Ltd., trade name DENKA BLACK (powder) Product)) 1 mass part, polyvinylidene fluoride (manufactured by Kureha Co., Ltd., trade name KF polymer # 9130), 5 mass parts, and N-methyl-2-pyrrolidone (industrial grade) 94 mass parts were mixed and applied. The negative electrode was formed by drying, pressing, and forming a negative electrode active material layer having a thickness of 55 μm on one side.

A separator (made by POLYPORE International, Inc., trade name Celgard 2500) is incorporated between the positive electrode and the negative electrode, and the required number of sheets is alternately stacked for a design capacity of 1 Ah. Installed with a welder. These are put in a bag-shaped aluminum laminate packaging material, and after removing moisture with a vacuum dryer at 60 ° C., a LiPF ₆ solution (manufactured by Kishida Chemical) is injected as an organic electrolyte, and impregnated in a vacuum atmosphere for 24 hours. The opening of the laminate packaging material was sealed with a vacuum sealer to produce a lithium ion secondary battery.

  The lithium ion secondary battery is manufactured using a current collector whose exposure time to an environment having a relative humidity of 10% or more is less than 30 minutes (referred to as “current collector immediately after manufacture”), Two types were prepared using what was stored for 300 hours in a constant temperature and humidity chamber at 25 ° C. and a relative humidity of 50% (referred to as a “current collector after 300 hours storage”).

(Comparative Examples 7 and 8)
Lithium ion secondary batteries were produced in the same manner as in Examples 9 to 12 except that the current collectors were the comparative current collectors 1 and 2 produced in Comparative Examples 4 and 5.

  The internal resistance of the obtained lithium ion secondary battery was measured by an AC impedance method using an impedance meter at a measurement frequency of 1 kHz. The results are shown in Table 3. Table 3 shows that the lithium ion secondary battery manufactured using the current collector of the present invention has low internal resistance and excellent moisture resistance.

  Regarding the lithium ion secondary batteries manufactured in Examples 9 to 12 and Comparative Examples 7 and 8, the cycle characteristics of the lithium ion secondary batteries were measured. The measurement was performed using a charge / discharge device (manufactured by Toyo System Co., Ltd.), changing the current rate to 0.2C, 2C, and 20C, and setting the initial capacity maintenance rate after 200 cycles to 100% as the capacity maintenance rate for 0.2C. displayed. The cut voltage was 2.7 to 4.2 V, and the SOC was 100%.

  The results are shown in Table 4. From Table 4, it was shown that the current collector of the present invention was excellent in cycle characteristics and moisture resistance, and was not inferior to the current collector produced with a non-aqueous coating solution.

(Manufacture and evaluation of electric double layer capacitors)
(Examples 13 to 16)
In each of the current collectors 1 to 4 produced in Examples 5 to 8, 100 parts by mass of activated carbon (Kuraray Chemical Co., Ltd., trade name YP-50F), acetylene black (Electrochemical Industry Co., Ltd., trade name) Denka Black (powdered product) 5 parts by mass, Styrene Butadiene Rubber (Nippon A & L Co., Ltd., trade name Nalstar SR-103) 7.5 parts by mass, Carboxymethylcellulose (Daicel Finechem Co., Ltd., trade name CMC DN) -10L) A paste composed of 2 parts by mass and 200 parts by mass of pure water was applied, dried and pressed to form an electrode layer having a single-sided thickness of 80 μm, thereby obtaining an electrode for an electric double layer capacitor.

  Next, two electric double layer capacitor electrodes were punched out with a diameter of 20 mmφ. Two electrodes are stacked on top of each other with a separator (made by Nippon Kogyo Paper Industries Co., Ltd., trade name TF40) in between, and placed in an evaluation capacitor container. P / EAFIN (1 mol / liter)) was poured into the container, electrodes and the like were immersed therein, and finally the container was covered to prepare an electric double layer capacitor for evaluation.

  In addition, electric double layer capacitors are manufactured using current collectors that have been exposed to an environment with a relative humidity of 10% or higher for less than 30 minutes (referred to as “current collectors immediately after manufacture”), and air Two types were prepared, one that was stored in a constant temperature and humidity chamber at 25 ° C. and 50% relative humidity for 300 hours (referred to as “current collector after 300 hours storage”).

(Comparative Examples 9 and 10)
In Examples 13 to 16, an electric double layer capacitor was produced and evaluated in the same manner except that the comparative current collectors 1 and 2 produced in Comparative Examples 4 and 5 were used as the current collector.

The impedance and electric capacity of the electric double layer capacitors obtained in Examples 13 to 16 and Comparative Examples 4 and 5 were measured. The impedance was measured using an impedance measuring instrument (Kikusui Electronics Co., Ltd., trade name PAN110-5AM) under the condition of 1 kHz. The electric capacity was measured by charging and discharging at 0 to 2.5 V at a current density of 1.59 mA / cm ² using a charge / discharge test apparatus (Hokuto Denko Co., Ltd., trade name HJ-101SM6). The electric capacity (F / cell) per cell of the electric double layer capacitor was calculated from the discharge curve measured at the second constant current discharge. The capacity retention rate (%) was calculated as (electric capacity at the 50th cycle) / (electric capacity at the second cycle) × 100.

  The results are shown in Table 5. From Table 5, the electric double layer capacitor produced using the current collector of the present invention has low impedance, excellent cycle characteristics, and non-aqueous coating solution as a product produced using the aqueous coating solution. It was shown that there was no inferiority compared to the one produced by using it.

Claims (14)

(A) water or a mixed solvent of water and an organic solvent;
(B) a conductive material;
(C) One or more selected from the group consisting of polysaccharides and polysaccharide derivatives is included as an essential component, and if necessary, (D) a divalent or higher organic acid and a divalent or higher organic acid derivative. A coating liquid containing at least one selected from the group, wherein the mass of each component (B), (C), (D) contained in the coating liquid is W _B , W _C , and W _D , respectively. _{, W} B, _W C, coating _{solution W D} satisfies the following equation (1).
0.5 ≦ W _B / (W _C + W _D ) ≦ 5 (1)   The coating liquid according to claim 1, wherein the organic solvent contains a primary or secondary monofunctional alcohol having 1 to 4 carbon atoms.   3. The polysaccharide according to claim 1 or 2, wherein the polysaccharide is at least one selected from the group consisting of chitin, chitosan and cellulose, and the polysaccharide derivative is at least one selected from the group consisting of a cellulose derivative and a chitosan derivative. Coating liquid.   The coating solution according to claim 1, wherein the polysaccharide derivative is a hydroxyalkylated polysaccharide.   5. The divalent or higher valent organic acid is a trivalent or higher valent organic acid, and the divalent or higher valent organic acid derivative is a trivalent or higher valent organic acid derivative. 6. Coating liquid.   The coating liquid according to claim 1, wherein the divalent or higher organic acid is an aromatic carboxylic acid, and the divalent or higher organic acid derivative is an aromatic carboxylic acid derivative.   The coating liquid according to claim 1, wherein the divalent or higher-valent organic acid derivative is an acid anhydride.   The coating liquid according to claim 1, wherein the conductive material is a carbonaceous material.   The manufacturing method of the electrical power collector characterized by apply | coating the coating liquid of any one of Claims 1-8 on an electroconductive base material, and heating at the temperature of 100 to 300 degreeC.   The electrical power collector by which the coating liquid of any one of Claims 1-8 was apply | coated to the single side | surface or both surfaces of an electroconductive base material, and the undercoat layer was formed.   The current collector according to claim 10, wherein the conductive substrate is aluminum or copper.   The electrode by which the electrode active material layer was formed on the undercoat layer of the electrical power collector of Claim 10 or 11.   An electrochemical device having the electrode according to claim 12.   A power supply system comprising the electrochemical device according to claim 13.