JP2004103314A - Collector and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a collector allowing active material layers to be correctly stacked on and integrated with both its front and back surfaces, and of preventing the active material from falling off in manufacturing a secondary battery or in using it. <P>SOLUTION: In this collector A, front and back conductive resin layers 2 and 3 are stacked on and integrated with both front and back surfaces of metal foil 1; multiple through-holes A1 penetrating to the back surface of the metal foil 1 from the front surface of the resin layer 2 are formed; the active material layers can be stacked and integrated in separate processes on the one-side surface basis because the back-side openings of the through-holes A1 are closed by the resin layer 3; and thereby, the active material layers can simply and surely be stacked on and integrated with both the front and back surfaces of the collector by using a simple facility while correctly adjusting the thicknesses of the active material layers. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a current collector used for a secondary battery and a capacitor, particularly a lithium secondary battery, and a method for manufacturing the same.
[0002]
[Prior art]
A secondary battery is basically composed of a positive electrode, a negative electrode, a separator for insulating the positive electrode and the negative electrode, and an electrolytic solution for allowing ions to move between the positive electrode and the negative electrode. The positive electrode and the negative electrode are simultaneously coated with various active materials on both surfaces of a current collector made of a metal foil having a large number of through-holes as described in Patent Document 1, and laminated and integrated. Being manufactured.
[0003]
However, as described above, simultaneously applying an active material to both surfaces of a current collector made of a metal foil having a large number of through holes penetrates is very difficult to adjust the thickness of the active material and requires complicated equipment. There was a problem.
[0004]
The positive electrode and the negative electrode are housed in a secondary battery body in a spirally wound state when a secondary battery is manufactured. When the positive electrode and the negative electrode are wound, the active material is removed from the surface of the current collector. If the active material falls off the surface of the current collector during use of the secondary battery, a problem occurs such that a secondary battery having a desired electric capacity cannot be obtained. There has been a problem that the capacity gradually decreases, and there has been a demand for a current collector in which the active material laminated and integrated on the surface does not fall off during the production or use of the secondary battery.
[0005]
[Patent Document 1]
JP-A-11-67217 (Claims)
[0006]
[Problems to be solved by the invention]
The present invention provides a current collector and a current collector in which an active material layer can be accurately laminated and integrated on the front and back surfaces by a simple operation, and the active material does not fall off during production or use of a secondary battery. Provided is a method for manufacturing a current collector.
[0007]
[Means to solve the problem]
The current collector according to claim 1, wherein the front and back conductive resin layers are laminated and integrated on the front and back surfaces of the metal foil, and a large number of through holes penetrating from the front surface of the front side conductive resin layer to the back surface of the metal foil are provided. And a back opening of the through hole is closed by a back conductive resin layer.
[0008]
According to a second aspect of the present invention, in the current collector of the first aspect, the front and back conductive resin layers are formed by dispersing conductive particles in a synthetic resin.
[0009]
The method of manufacturing a current collector according to claim 3, wherein the front side conductive resin layer having a large number of through holes formed on the surface of the metal foil is laminated and integrated, and the back side conductive resin layer is formed on the back surface of the metal foil. After the layers are laminated and integrated to produce a laminated sheet, the metal foil is etched through the through-holes of the front-side conductive resin layer in the laminated sheet, and the metal foil is passed through the through-holes reaching the back-side conductive resin layer. It is characterized in that it is installed.
[0010]
[Action]
Since the through-hole in the current collector of the present invention has a state in which the back side opening is closed by the back side conductive resin layer, the active material layer is integrally laminated on the front and back surfaces of the current collector of the present invention. It is not necessary to simultaneously laminate and integrate the active material layers on the front and back surfaces as in the case of a conventional current collector, but simply and reliably laminate the active material layers in a separate process for each side of the current collector. Can be changed.
[0011]
Further, as described above, since the active material layers are laminated and integrated on each side of the current collector, the thickness accuracy of the active material layers can be improved, and a uniform secondary battery or capacitor can be obtained.
[0012]
Further, the active material layer laminated and integrated on the front and back surfaces of the current collector is surely laminated and integrated on the front and back conductive resin layers, and in particular, the active material layer laminated and integrated on the front conductive resin layer The active material layer, part of which enters and penetrates the through-hole and is locked and integrated on both sides of the current collector, is unpredictable when the current collector is wound or used. There is no such thing as falling off.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
An example of the current collector of the present invention will be described with reference to the drawings. As the metal foil 1 of the current collector A, the same metal foil as that conventionally used for current collectors of secondary batteries and capacitors is used. For example, aluminum foil, aluminum alloy foil, copper foil, copper alloy Foil and the like. The copper foil may be either a rolled copper foil manufactured by a rolling method or an electrolytic copper foil manufactured by an electrolytic method.
[0014]
The thickness of the metal foil 1 is generally 8 to 30 μm. When used for a lithium secondary battery, the thickness is 15 to 25 μm for an aluminum foil and 10 to 25 μm for a copper foil. It is preferably 20 μm.
[0015]
Further, as shown in FIG. 1, a front side conductive resin layer 2 is laminated and integrated on the surface of the metal foil 1, and a non-porous back side conductive resin layer 3 is formed on the back side of the metal foil 1. Are laminated and integrated. The non-porous shape means that a through hole similar to the through hole A1 described below is not provided, and a fine hole such as a pinhole may be formed.
[0016]
The front and back conductive resin layers 2 and 3 are formed by dispersing conductive particles in a synthetic resin. As the synthetic resin constituting the front and back conductive resin layers 2 and 3, the metal foil 1 does not deteriorate due to the etching treatment of the metal foil 1 to be described later or does not cause cracks or holes in the front and back conductive resin layers 2 and 3. It is sufficient that the front and back conductive resin layers 2 and 3 can be laminated and integrated on the front and back surfaces. Preferably, the compatibility with the synthetic resin used for the active material layer laminated and integrated on both surfaces of the current collector A is obtained. Good to have, for example, polyamide-imide resin, epoxy resin, melamine resin, phenolic resin, thermosetting resin such as urethane resin; fluorine resin, polyolefin resin, acrylic resin, thermoplastic resin such as polyester resin and the like, Thermosetting resins are preferred, and polyamideimide resins are more preferred.
[0017]
Examples of the conductive particles include, for example, carbon-based particles such as Ketjen black, carbon black, acetylene black, graphite, and carbon nanotubes; and metal-based particles such as silver, nickel, copper, zinc, and aluminum. Carbon-based particles are preferred, Ketjen Black, carbon black, and graphite are more preferred, and Ketjen Black, carbon black and graphite are particularly preferred. The conductive particles may be used alone or in combination of two or more.
[0018]
When the scattered amount of the conductive particles in the front and back conductive resin layers 2 and 3 is large, the adhesion between the metal foil 1 and the front and back conductive resin layers 2 and 3 may be reduced. Since the conductivity of the front and back conductive resin layers 2 and 3 may be reduced, it is preferably 20 to 80 parts by weight based on 100 parts by weight of the synthetic resin.
[0019]
If the thickness of the front and back conductive resin layers 2 and 3 is large, the thickness of the active material layer D laminated and integrated on the front side conductive resin layer 2 may be non-uniform or thin. In this case, the mechanical strength of the back-side conductive resin layer 3 is reduced, and the back-side conductive resin layer 3 may fall off during the production of the current collector A.
[0020]
In the above-mentioned front and back conductive resin layers 2 and 3, silane coupling agents, leveling agents, defoamers, dispersants, inorganic particles such as silica, pigments, polyfunctional isocyanates, etc., as long as the physical properties are not impaired. May be added.
[0021]
Further, as shown in FIGS. 1 and 2, a large number of through-holes A1 penetrating from the front surface of the front-side conductive resin layer 2 to the back surface of the metal foil 1 are entirely formed to form the current collector A. In addition, all of the back-side openings of the through-hole A <b> 1 are closed by the back-side conductive resin layer 3.
[0022]
The planar shape of the through-hole A1 is not particularly limited, and examples thereof include, in addition to a circle, a polygon such as a triangle, a quadrangle, a pentagon, and a hexagon, and the like, preferably a circle and a regular polygon, and a circle. Is more preferred.
[0023]
The form of forming the through-hole A1 is not particularly limited, but it is preferable that the through-holes A1 having the same shape and the same size are penetrated with a substantially uniform density. B) As shown in FIGS. 2 and 3, circular through-holes A10 having the same diameter are provided in a grid pattern at predetermined intervals in front, rear, left and right, and through holes A10 adjacent to each other in front, rear, left and right. A10. A form in which a through-hole A11 having the same diameter as the through-hole A10 is penetrated in a state where the center matches the center of gravity of a virtual square obtained by connecting the centers of A10... B) FIGS. As shown in FIG. 5, circular through holes A10 having the same diameter are pierced in a grid pattern at predetermined intervals in front, rear, left and right, and the centers of the through holes A10, A10,. Virtual obtained by connecting Form obtained by penetrated through holes A11 having the same diameter as the through-hole A10 in a state of being matched with the center square of the center of gravity thereof. In the penetrating form b), the distance between the through-holes A10, A10 adjacent in the left-right direction is longer than the distance between the through-holes A10, A10 adjacent in the front-rear direction. The distance between the holes A10, A10 is preferably at least twice the diameter of the through-hole A10 (A11) so that the through-hole A11 does not enter the space between the through-holes A10, A10 adjacent in the front-rear direction. .
[0024]
If the diameter of the through hole A1 is large, the mechanical strength of the current collector A may be reduced. If the diameter is small, the active material layer D cannot enter and be locked in the through hole A1. Since the adhesion between the front-side conductive resin layer 2 and the active material layer D may decrease, the thickness is preferably 0.1 to 3 mm. Note that the diameter of the through hole A1 refers to the diameter of the smallest virtual perfect circle that can surround the through hole A1 when the through hole A1 is non-circular.
[0025]
Furthermore, if the distance between the through holes A1 and A1 is large, the degree of the active material layer D entering and locking into the through hole A1 decreases, and the distance between the front conductive resin layer 2 and the active material layer D decreases. May be reduced, and if the width is too narrow, the mechanical strength of the current collector A may be reduced. The distance between the through holes A1 and A1 means an average distance between the centers of the adjacent through holes A1 and A1 when the through hole A1 is circular, and the through hole is non-circular. In this case, it refers to the average distance between the centers of adjacent perfect circles in the smallest virtual perfect circle that can surround the through hole A1.
[0026]
If the penetration density of the through-hole A1 is large, the mechanical strength of the current collector A may be reduced. If the penetration density is small, the active material layer D enters and locks in the through-hole A1. The degree is reduced, and the adhesion between the front-side conductive resin layer 2 and the active material layer D may be reduced. Therefore, the number is preferably 1 to 400 / cm ² .
[0027]
Next, a method for manufacturing the current collector will be described. First, as shown in FIG. 6, a long metal foil 1 'in a state where no through-hole is formed is unwound and supplied to the rotary printing press 4, and the unwound metal foil 1' After the front side conductive paint is continuously applied to the entire surface of the surface except for both ends in the width direction at a constant thickness, the metal foil 1 ′ having the front side conductive paint applied to the surface is continuously applied to the heating device 5. And heats the front-side conductive paint to continuously produce a first laminated sheet B in which the front-side conductive resin layer 2 is laminated and integrated over substantially the entire surface of the metal foil 1 '. The front side conductive paint is obtained by dispersing conductive particles in a synthetic resin serving as a binder.
[0028]
As shown in FIGS. 4 and 5, the front conductive resin layer 2 has circular through-holes 21a having the same diameter in a grid pattern at predetermined intervals in front, rear, left and right. Are provided so as to penetrate between the two surfaces of the through-hole 21a, and the center of the virtual rectangle obtained by connecting the centers of the through-holes 21a, 21a,. A through-hole 21 b having the same diameter as 21 a is formed through both surfaces of the front-side conductive resin layer 2.
[0029]
The distance between the through-holes 21a, 21a adjacent in the left-right direction is longer than the distance between the through-holes 21a, 21a adjacent in the front-rear direction, and the distance between the through-holes 21a, 21a adjacent in the left-right direction is increased. The diameter of the through hole 21a (21b) is set to be twice or more the diameter of the through hole 21a, so that the through hole 21b does not enter between the through holes 21a, 21a adjacent in the front-rear direction. Here, the front-back direction refers to the unwinding direction of the metal foil 1 ', and the left-right direction refers to the direction orthogonal to the front-back direction along the surface of the metal foil 1'.
[0030]
Further, in order to prevent the metal foil after etching, which will be described later, from cracking in the length direction during transportation, each of the both ends in the width direction of the front side conductive resin layer 2 has a predetermined width. A non-porous portion 22 in which the through holes 21a and 21b are not formed is formed.
[0031]
Subsequently, the first laminated sheet B is continuously supplied to the rotary printing press 6 so that the entire surface of the back surface of the metal foil 1 ′ of the first laminated sheet B except for both ends in the width direction is electrically connected to the back side. After the paint is continuously applied with a constant thickness, the paint is continuously supplied to the heating device 7 to heat the back-side conductive paint. A second laminated sheet C formed by laminating and integrating the back conductive resin layer 3 in a shape is manufactured. Subsequently, the second laminated sheet C is formed over the entire surface of the back conductive resin layer 2 of the second laminated sheet C. For the purpose of preventing cracks in the vertical direction, the masking film C 'is continuously laminated in a releasable manner and then continuously wound in a coil shape (see FIGS. 6 and 7). In addition, it is preferable to use the same conductive paint as the front conductive paint in which conductive particles are dispersed in a synthetic resin serving as a binder.
[0032]
Next, the second laminated sheet C wound up in a coil shape is continuously unwound, and after cutting both edges in the width direction of the second laminated sheet C, the second laminated sheet C is placed in an acid bath. The metal foil 1 ′ is supplied continuously, and the metal foil 1 ′ exposed through the many through holes 21 a and 21 b of the front conductive resin layer 2 in the second laminated sheet C is etched. 2 through holes 21 reaching the back conductive resin layer 3 in a state conforming to the pattern of the through holes 21, that is, through holes A 1, A 1 reaching (penetrating) from the surface of the front conductive resin layer 2 to the back surface of the metal foil 1 ′. Are provided to manufacture the current collector A, and the current collector A is continuously wound into a coil shape (see FIG. 8). The backside openings of the through holes A1 of the current collector A are all closed by the backside conductive resin layer 3. The current collector A is wound in a coil shape with the masking film C 'laminated on the back surface.
[0033]
As shown in FIG. 8, the current collector A thus obtained has the front and back conductive resin layers 2 and 3 laminated and integrated on the entire front and back surfaces of the metal foil 1, and also has the front side conductive resin. A large number of through-holes A1, A1,... Penetrating from the surface of the layer 2 to the back of the metal foil 1 are formed, and the entire back-side opening of the through-hole A1 is closed by the back-side conductive resin layer 3.
[0034]
Then, as shown in FIG. 9, the coil-shaped current collector A is continuously unwound, the active material is continuously applied to the surface of the current collector A, and then supplied to the heating device 8 to be collected. The active material layer D is laminated and integrated on the surface of the conductor A, and a single-sided active material laminated sheet E (see FIG. 10) is manufactured and continuously wound into a coil.
[0035]
As described above, since the current collector A has a state in which the other end opening of the entire through hole A1 is completely closed by the back-side conductive resin layer 3, only one surface of the current collector A is provided. The active material layer D can be applied to the surface of the current collector A, and the active material layer D can be easily integrated while accurately adjusting the thickness of the active material layer D. And reliably.
[0036]
Moreover, since a part of the active material layer D laminated and integrated on the surface of the current collector A enters and is locked in the through-hole A1, the active material layer D is A is firmly and reliably laminated and integrated on the surface of A.
[0037]
Next, as shown in FIG. 11, after unwinding the single-sided active material laminated sheet E continuously, and continuously peeling off the masking film C ′ laminated on the back surface of the single-sided active material laminated sheet E, The active material is continuously applied onto the back side conductive resin layer 3 of the single-sided active material laminated sheet E and then supplied to the drying device 9 to laminate and integrate the active material layer F on the back surface of the single-sided active material laminated sheet E. Thus, the double-sided active material laminated sheet G (see FIG. 12) can be manufactured continuously.
[0038]
The active material applied and laminated on the front and back conductive resin layers 2 and 3 is not particularly limited as long as it is conventionally used for an electrode or a capacitor. And a synthetic resin as a binder mixed with such conductive particles.
[0039]
In this manner, the active material can be applied to only the back surface of the single-sided active material laminated sheet E, and the active material layer F can be laminated and integrated. It is possible to integrate the layers while adjusting them accurately.
[0040]
Moreover, the active material layers D and F of the double-sided active material laminated sheet G are composed of the synthetic resin in the active material layers D and F and the front and back conductive resin layers 2 and 3 on the front and back conductive resin layers 2 and 3. The active material layers D and F are firmly and reliably laminated and integrated on both sides of the current collector A because the synthetic resin and the synthetic resin to be thermally fused are integrated. Even if A is wound in a coil shape, it does not fall off unexpectedly.
[0041]
Further, the active material layer D laminated and integrated on the front side conductive resin layer 2 of the current collector A enters the through hole A1 and reaches the back side conductive resin layer 3, and the active material layer D And the synthetic resin constituting the back-side conductive resin layer 3 are heat-sealed and integrated, so that the active material layer D of the double-sided active material laminated sheet G is more firmly attached to the surface of the current collector A. It is laminated and integrated.
[0042]
【The invention's effect】
The current collector according to claim 1, wherein the front and back conductive resin layers are laminated and integrated on the front and back surfaces of the metal foil, and a large number of through holes penetrating from the front surface of the front side conductive resin layer to the back surface of the metal foil are provided. The active material layer can be stacked and integrated in a separate step for each side of the current collector, since the formed, and the back opening of the through hole is closed by the back conductive resin layer. Therefore, the lamination and integration of the active material layers on both surfaces of the current collector can be easily and reliably performed using simple equipment while accurately adjusting the thickness of the active material layers.
[0043]
In addition, a part of the active material layer to be laminated and integrated on the surface of the current collector can enter and lock into the through hole, and the active material layer can be reliably laminated and integrated on the current collector. .
[0044]
The current collector according to claim 2 is the current collector according to claim 1, wherein the front and back conductive resin layers are formed by dispersing conductive particles in a synthetic resin. The synthetic resin in the active material to be laminated and integrated on both sides of the body and the synthetic resin constituting the front and back conductive resin layers are heat-sealed and integrated to form an active material layer on the front and back surfaces (both surfaces) of the current collector. Can be more firmly and reliably laminated and integrated.
[0045]
In the method for manufacturing a current collector according to claim 3, a front-side conductive resin layer having a large number of through-holes formed on a surface of a metal foil is laminated and integrated, and a back-side conductive resin layer is formed on a back surface of the metal foil. After laminating and integrating to produce a laminated sheet, the metal foil is etched through the through hole of the front side conductive resin layer in the laminated sheet, and a through hole reaching the back side conductive resin layer is formed in the metal foil. Since the front conductive resin layer with a large number of through holes formed on the surface of the metal foil and the back conductive resin layer on the back surface are integrated and laminated, the etching process of the metal foil is performed The current collector can be manufactured by a simple operation such as performing through the through hole of the conductive resin layer, and a masking film for etching treatment is formed on the front and back surfaces of the metal foil as in the conventional method of manufacturing the current collector. Peelable stack , Without performing complicated operations such as peeling off the masking film after the etching treatment, it is possible to efficiently manufacture the current collector.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a current collector of the present invention.
FIG. 2 is a plan view of the current collector of FIG.
FIG. 3 is a partially enlarged view of FIG. 2;
FIG. 4 is a plan view showing another example of the current collector of the present invention.
FIG. 5 is a partially enlarged view of FIG. 4;
FIG. 6 is a schematic side view showing a part of a manufacturing apparatus used in the current collector manufacturing method of the present invention.
FIG. 7 is a longitudinal sectional view showing a second laminated sheet in a state where a masking film is laminated on the back surface.
FIG. 8 is a longitudinal sectional view showing the current collector in a state where a masking film is laminated on the back surface.
FIG. 9 is a schematic side view showing an apparatus for laminating and integrating an active material layer on the surface of a current collector.
FIG. 10 is a longitudinal sectional view showing a single-sided active material laminated sheet.
FIG. 11 is a schematic side view showing an apparatus for laminating and integrating an active material layer on the back surface of a current collector.
FIG. 12 is a longitudinal sectional view showing a double-sided active material laminated sheet.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 metal foil A1 through hole 2 front conductive resin layer 21 (21a, 21b) through hole 3 back conductive resin layer A current collector D, F active material layer

Claims (3)

The front and back conductive resin layers are laminated and integrated on the front and back surfaces of the metal foil, and a large number of through-holes are formed from the surface of the front-side conductive resin layer to the back surface of the metal foil. A current collector closed by a backside conductive resin layer. The current collector according to claim 1, wherein the front and back conductive resin layers are formed by dispersing conductive particles in a synthetic resin. After laminating and integrating the front-side conductive resin layer having a large number of through holes formed on the surface of the metal foil, and laminating and integrating the back-side conductive resin layer on the back surface of the metal foil, the laminated sheet is manufactured. 3. The method for producing a current collector according to claim 1, wherein said metal foil is etched through a through hole of said front conductive resin layer, and a through hole reaching said back conductive resin layer is formed in said metal foil.

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