JP5950757B2 - Metal plate material, resin coating method on metal plate surface and use thereof - Google Patents

Description

  The present invention relates to a metal plate material in which a resin coating layer is formed on the surface of a metal plate material such as copper foil, and a selective resin coating method on the surface of the metal plate material.

  Conventionally, a negative electrode for a lithium ion secondary battery is formed by applying a slurry containing active material particles, a conductive additive, a binder and the like on a current collector such as a copper foil to form a negative electrode active material layer. It was produced (for example, refer to Patent Document 1).

JP 2008-027664 A

  However, although the active material particles and the conductive auxiliary agent are fixed to the copper foil surface through the binder, the binder such as a mixture of styrene butadiene rubber and carboxymethyl cellulose that is usually used is the surface of the copper foil. There is a problem in that the active material layer easily peels off from the current collector.

  The present invention has been made in view of the above-described problems, and the object of the present invention is to selectively coat the resin with excellent adhesion to the resin while maintaining the conductivity of the metal surface as a current collector. It is to obtain the metal plate material which performed.

In order to achieve the above-mentioned object, the following invention is provided.
(1) A metal plate material whose surface is resin-coated, wherein the metal plate material includes any one metal selected from the group consisting of aluminum, copper, gold, and silver, and the concave portion on the surface of the metal plate material A metal plate material, wherein a resin coating layer is selectively formed with resin fine particles, and a resin coating layer with resin fine particles is not formed on a convex portion of the surface of the metal plate material.
(2) The metal plate according to (1), wherein the resin coating layer contains a metal nanostructure and / or conductive carbon.
(3) The resin fine particles forming the resin coating layer are resin fine particles containing at least one resin selected from the group consisting of styrene butadiene rubber, acrylic rubber, acrylonitrile butadiene rubber, isoprene rubber, and butadiene rubber. The metal plate material according to (1) or (2).
(4) The metal plate material according to any one of (1) to (3), wherein the metal plate material is a copper foil having a thickness of 50 μm or less.
(5) The resin coating layer is selectively formed on the resin-coated surface recesses of the metal plate material, and the resin coating layer is not formed on the resin-coated surface projections of the metal plate material, A negative electrode comprising a negative electrode active material layer on the metal plate and the resin coating layer, wherein the resin coating layer improves adhesion of the negative electrode active material layer.
(6) A fine particle liquid in which resin fine particles having an average particle size of 10 to 1000 nm are dispersed in a dispersion medium at a solid content concentration of 3 to 20 wt% is applied to the surface of the metal plate, and then the metal plate is dried to obtain a resin. The fine particles are moved from the convex portion of the metal plate material to the concave portion, and a resin coating layer is selectively formed on the concave portion of the surface of the metal plate material by resin fine particles, and the convex portion on the surface of the metal plate material is formed of resin fine particles A resin coating method on the surface of a metal plate, wherein a resin coating layer is not formed.
(7) The resin coating method on the surface of a metal plate according to (6), wherein the fine particles of the resin have metal nanostructures and / or conductive carbon attached to the surface.
(8) The ten-point average roughness Rz of the surface to be coated of the metal plate before the surface is coated with the resin is 0.5 μm or more and 10 μm or less, and Rz is at least twice the average particle size of the resin fine particles. (6) or (7), the method for coating a resin on the surface of a metal plate.

  By this invention, the metal plate material which is excellent in adhesiveness with resin can be obtained, maintaining the electroconductivity of a metal surface.

The figure which shows the cross section of the metal plate material 1 by which the surface was resin-coated based on embodiment of this invention. (A)-(c) The figure which shows the resin coating method of the metal plate material surface based on embodiment of this invention. The figure which shows the cross section of the negative electrode 13 which concerns on embodiment of this invention. The graph which shows the relationship between the density | concentration of the organic fine particle liquid used for resin coating of the copper foil surface, and the surface resistance of copper foil by which the surface was resin-coated. (A) The photograph which shows the surface of the copper foil by which the surface was resin-coated, (b) An enlarged photograph, (c) The further enlarged photograph. (A) Photograph showing a cross section of a copper foil whose surface is resin-coated, (b) Inclined cross-sectional photograph of a copper foil whose surface is resin-coated, (c) Inclination of another region of the copper foil whose surface is resin-coated Cross section photo. The graph which shows the relationship between the density | concentration of the organic fine particle liquid used for resin coating on the copper foil surface, and the resistance value of the active material layer surface. The graph which shows the relationship between the density | concentration of the organic fine particle liquid used for resin coating of the copper foil surface, and the adhesive force with the active material layer apply | coated to the surface of the copper foil by which the surface was resin-coated.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Configuration of metal plate with resin-coated surface)
Hereinafter, an embodiment of the present invention will be described taking a metal foil as an example of a metal plate material. FIG. 1 is a view showing a cross section of a metal plate 1 having a resin-coated surface according to an embodiment of the present invention. The metal plate 1 whose surface is coated with resin has the resin coating layer 3 in the concave portion 4 of the metal plate 1, but does not have the resin coating layer 3 on the convex portion 6 of the metal plate 1.

  The resin coating layer 3 made of organic fine particles preferably contains at least one resin selected from the group consisting of styrene butadiene rubber, acrylic rubber, acrylonitrile, acrylonitrile butadiene rubber, isoprene rubber, and butadiene rubber, and particularly styrene butadiene rubber. Is preferable, and further contains a hydroxyl group or a carboxyl functional group in the molecule. Since these materials can easily obtain a suspension using water as a dispersion medium, they are suitable for the resin coating method according to this embodiment.

  The metal plate 5 preferably contains at least one metal selected from the group consisting of aluminum, copper, gold, and silver. The metal plate 5 containing these metals can be easily obtained by rolling or electrolysis, and even when water is applied with a suspension of a dispersion medium, the surface of the metal plate 5 is rusted. Will not cause any damage.

  In particular, it is preferable to use a copper foil having a thickness of 50 μm or less as the metal plate material 5. This is because such a thin copper foil is widely used as a current collector for a negative electrode for a lithium ion secondary battery.

  Furthermore, it is preferable that the resin coating layer 3 contains a metal nanostructure and / or conductive carbon. As the metal nanostructure, nanoparticles such as gold, silver, and copper, nanowires, and nanosheets can be used. As the conductive carbon, graphite, carbon nanotube (CNT), fullerene (C60), activated carbon, carbon nanohorn (conical carbon nanotube) and the like can be used. By including these, conductivity is generated in the resin coating layer 3 itself, and the surface resistance of the metal plate 1 whose surface is resin-coated is improved.

(Resin coating method on metal plate surface)
A resin coating method on the surface of the metal plate will be described with reference to FIG.
First, as shown in FIG. 2A, the fine particle liquid 7 is supplied to the surface of the metal plate 5, and the coater bar 11 is moved in the A direction and applied. The fine particle liquid 7 is a liquid in which resin fine particles 9 and the like are dispersed in a water dispersion medium. As a coating method, it is preferable to use a coating method such as bar coating or blade coating in which the fine particle liquid 7 stays on the surface of the metal plate 5 to some extent and requires a certain amount of time for drying. Drying is preferred. In the drying process described later, since the resin fine particles 9 need to be attracted to the concave portion 4 on the surface of the metal plate 5 by water having a strong surface tension, the resin coating is selectively applied to the concave portion 4 when there is a certain amount of drying time. This is because the layer 3 is easily formed. On the other hand, in a coating method such as spin coating where droplets are blown in an instant, the resin coating layer 3 is formed on the entire surface of the metal plate 5 and the conductivity of the surface of the metal plate is deteriorated.

  The fine particle liquid 7 is a liquid in which resin fine particles 9 are dispersed in water. An organic solvent may be added to the fine particle liquid 7. Here, an organic solvent can be used as the dispersion liquid instead of water. Moreover, it is preferable that the solid content concentration of the fine particle liquid 7 to apply | coat is 3-20 wt%, and it is more preferable that it is 5-20 wt%. If the solid content concentration is too thin, the amount of the resin coating layer 3 formed in the recess 4 is reduced, there is almost no effect of forming the resin coating layer 3, and the adhesion of the metal plate material on the surface side of the coating resin is insufficient. On the other hand, if the solid content concentration is too high, the resin coating layer 3 covers the entire surface of the metal plate 5 and the electrical resistance becomes too high.

  Then, as shown in FIG.2 (b), the surface of the metal plate material 5 is dried. Since the resin fine particles 9 are attracted to the concave portions 4 on the surface of the metal plate material 5 by the water having a strong surface tension, the resin fine particles 9 gather in the concave portions 4 of the metal plate material 5.

  Then, as shown in FIG. 2C and FIG. 1, the resin coating layer 3 is formed in the concave portion 4 of the metal plate 5, and the resin coating layer 3 is not formed on the convex portion 6. A plate 1 is obtained.

  The average particle diameter of the resin fine particles 9 contained in the fine particle liquid 7 is preferably 10 to 1000 nm. As will be described later, since the ten-point average roughness of the surface of the metal plate 5 before resin coating on the surface is 10 μm or less, the size may be such that the resin fine particles enter the recesses 4 on the surface of the metal plate 5. This is because it is preferable.

The ten-point average roughness Rz of the surface to be coated of the metal plate 5 before the surface is coated with the resin is not particularly limited, but is preferably 0.5 μm or more and 10 μm or less. Here, the Rz is set to 0.5 μm or more. When the Rz is 0.5 μm or less, the uneven shape necessary for the movement of the resin fine particles on the surface of the metal plate material is not sufficiently formed, and the concave portions due to the resin fine particles are not formed. This is because selective coating cannot be performed stably. Furthermore, when Rz is 2.0 μm or more, unevenness for the resin fine particles to move in the fine particle liquid is more stably formed. Therefore, Rz is more preferably 2.0 μm or more.
On the other hand, if Rz exceeds 10 μm, the unevenness of the surface of the metal plate material is too large, and the adhesion by the resin selectively coated on the recesses cannot be ensured.
Although resin fine particles 9 having an average particle diameter of 10 to 1000 nm are used, the ten-point average roughness of the surface of the metal plate 5 before resin coating on the surface is preferably 5 times or more the average particle diameter of the resin fine particles 9. More desirably, it is 10 times or more. In realizing the effect of the present invention, the convexity of the metal surface is preferably 5 times or more, more preferably 10 times or more the average particle diameter of the fine particles.

  The resin fine particles 9 preferably have a metal nanostructure and / or conductive carbon attached to the surface. If these conductive materials adhere to the surface of the resin fine particles 9, these conductive materials are also added to the formed resin coating layer 3, and the conductivity of the resin coating layer 3 is improved. is there.

(Electrode using metal plate with resin-coated surface)
The metal plate 1 having a resin-coated surface according to the present embodiment can be used as a negative electrode current collector. FIG. 3 is a view showing a cross section of the negative electrode 13 according to the embodiment of the present invention. As shown in FIG. 3, here, the negative electrode 13 has the resin coating layer 3 in the concave portion 4 of the metal plate material 5 and the surface of the metal plate material 1 in which the convex portion 6 does not have the resin coating layer 3 is resin-coated. A negative electrode active material layer 15 is formed on the surface. The negative electrode active material layer 15 is obtained by applying and drying a slurry containing a negative electrode active material, a conductive agent, a binder, and the like on the surface of the metal plate 5 coated with a resin and firing it as necessary. . The negative electrode 13 can be used as a negative electrode for a lithium ion secondary battery.

  Similarly to the negative electrode, a positive electrode active material layer can be formed on the metal plate 5 to obtain a positive electrode for a lithium ion secondary battery. The positive electrode active material layer is obtained by applying a slurry containing a positive electrode active material, a conductive agent, a binder, and the like. Here, various metal plate materials can be used as the metal plate material 5, but it is desirable to use copper foil or aluminum foil. If copper foil or aluminum foil is used as a current collector for a negative electrode or a positive electrode for a lithium ion secondary battery, a suitable negative electrode or positive electrode excellent in cost and performance can be obtained.

(Effect of this embodiment)
In the metal plate 1 with the resin-coated surface according to the present embodiment, the resin coating layer 3 is not formed on the convex portion 6 on the surface, so that the surface resistance of the surface of the metal plate 5 is small. Therefore, even if the negative electrode active material layer 15 is formed on the surface, electrical connection can be formed between the metal plate 5 (current collector) and the negative electrode active material layer 15.

  Moreover, since the resin coating layer 3 is formed in the recessed part 4 of the surface, the metal plate material 1 by which the surface which concerns on this embodiment was resin-coated has high adhesiveness with the resin material. For this reason, when the negative electrode active material layer 15 is formed on the surface, the adhesion between the metal plate 5 (current collector) and the negative electrode active material layer 15 is high.

  Further, even when a positive electrode for a lithium ion secondary battery in which a positive electrode active material layer is formed on a metal plate material 5 is obtained, a good electrical connection is similarly made between the metal plate material 5 and the positive electrode active material layer. Obtained and highly adhesive.

Hereinafter, the present invention will be specifically described with reference to examples.
[Example]
A dispersion of styrene butadiene rubber latex (BM-400B, average particle size 100 nm) manufactured by Nippon Zeon Co., Ltd. on copper foil NC-WS (Furukawa Electric Co., Ltd., 10-point average roughness Rz = 1.5 μm) 10 wt%) was applied by blade coating, and the surface of the copper foil was coated with a resin. From application to drying, about 20 minutes were required at room temperature in the atmosphere. By diluting the stock solution of styrene-butadiene rubber latex, other latex dispersions with different solid content concentrations (0.625 wt%, 1.25 wt%, 2.5 wt%, 5 wt%, 20 wt%) were prepared. Similarly, resin coating was performed on the surface of the copper foil.

[Comparative example]
A copper foil with no resin coating on the surface was used as a comparative example. In addition, by diluting the stock solution of styrene butadiene rubber latex, other latex dispersions having solid content concentrations of 30 wt% and 40 wt% were prepared and coated on the surface of the copper foil in the same manner as in the above examples. .

[Measurement of surface resistance]
The surface resistance of the materials of Examples and Comparative Examples was measured with a resistivity meter (Loresta GP MCP-T610 type, 4-terminal 4-probe method) manufactured by Mitsubishi Chemical Analytech.

  FIG. 4 shows the relationship between the concentration of the organic fine particle liquid used for resin coating on the copper foil surface and the surface resistance of the copper foil. FIG. 4 shows that there is no significant change in the surface resistance of the copper foil even when the surface is coated with resin. Note that when the solid content concentration exceeds 30 wt%, the area of the selectively covered recesses increases, and the fine particles remain not only in the recesses but also in the protrusions, which is a characteristic structure of the present invention. Resin fine particles gathered only in a certain concave portion, and the resin coating layer was not selectively formed in the concave portion, but was also present in the convex portion. Further, the copper foil coated with the fine particle liquid having a solid content concentration of 40 wt% was not only observed in the same structure but also could not be measured because the surface resistance was too high.

  Here, although the photograph is omitted, when a fine particle liquid having a solid content concentration of 40 wt% was applied, the fine coating was selectively coated so as to be understood from the state of the copper foil surface having a solid content concentration of 10 wt% described later. Since the area ratio of the concave portion of the resin portion is rapidly increased, the area ratio of the convex portion is rapidly decreased, so that the electrical resistance is rapidly increased and the surface resistance cannot be measured.

  The copper foil (fine particle liquid concentration 10 wt%) according to the example was observed with a scanning electron microscope (SEM). FIG. 5A is a photograph showing the surface of a copper foil whose surface is resin-coated, with the white portion in the upper half being an untreated portion and the black portion in the lower half being a resin-coated surface. Further, FIG. 5B is an enlarged photograph of a portion whose surface is coated with resin, and FIG. 5C is an enlarged photograph of FIG. 5B. The part that appears white is the part where copper is exposed, and the part that appears black is the part covered with resin. As described above, even when the concentration of the fine particle liquid is 10 wt%, the convex portions not coated with the resin are distributed in the shape of islands in the shape of elongated bamboo leaves on the copper foil surface, and from the area of the concave portion selectively coated with the resin Clearly, there are few.

  6A is a photograph showing a cross-section of a copper foil whose surface is coated with a resin, and FIGS. 6B and 6C are cross-sectional photographs observed at an angle of 20 ° with respect to the vertical. It is observed that resin is accumulated in the concave and convex recesses on the surface of the copper foil and a resin coating layer is formed.

[Preparation of negative electrode slurry containing active material and production of negative electrode]
After putting natural graphite (SMG-N) manufactured by Hitachi Chemical as a negative electrode active material into a mixer, a 40 wt% styrene butadiene rubber latex emulsion (manufactured by Nippon Zeon Co., Ltd., BM-400B), slurry as a binder A 1 wt% solution of sodium carboxymethylcellulose (manufactured by Daicel Chemical Industries, Ltd., # 2200) as a thickener for adjusting the viscosity of the slurry was prepared. The composition of the slurry was 96% by weight of the negative electrode active material, 2% by weight of the binder (converted to solid content), and 2% by weight of the thickener (converted to solid content). The slurry was applied and dried on a copper foil as a metal plate, and baked to obtain a negative electrode. As the copper foil, a copper foil not coated with a resin and a copper foil coated with a resin using a latex dispersion having a solid content concentration of 10 wt%, 20 wt%, or 40 wt% were used.

  FIG. 7 is a graph showing the relationship between the concentration of the organic fine particle liquid used for resin coating on the copper foil surface and the resistance value on the active material layer surface. The surface resistance of the active material layer was measured by the same measurement method as that of the copper foil. From FIG. 7, even when the concentration of the organic fine particle liquid used for resin coating of the copper foil is increased, the resistance value on the surface of the active material layer is not particularly changed.

[Measurement of adhesion]
Using the doctor blade of an automatic coating apparatus, the copper slurry of Examples and Comparative Examples was coated on an electrolytic copper foil for current collector having a thickness of 10 μm (Furukawa Electric Co., Ltd., NC-WS). The negative electrode was manufactured by coating with a thickness of 15 μm and drying at 70 ° C. for 10 minutes. The adhesion between the active material layer and the copper foil was measured by a 90 ° peel test (crosshead speed = 10 mm / min) using an autograph (AG-10 kN) manufactured by Shimadzu Corporation.

  FIG. 8 shows the relationship between the concentration of the organic fine particle liquid used for resin coating on the copper foil surface and the adhesive force between the active material layer applied on the copper foil surface as described above. It can be seen that the adhesion between the active material layer and the copper foil is increased by performing the above. This is because the binder resin contained in the active material layer closely adheres to the resin coating layer on the copper foil surface. In particular, when the concentration of the fine particle liquid is 1 wt% or 2 wt%, there is no significant difference from the comparative example, but when the concentration exceeds 3 wt%, the adhesion is rapidly improved, and when the concentration is 5 wt% or more, the adhesion is gradually saturated. There is no big change and it is stable.

[Battery characteristics evaluation]
Negative electrode for test electrode, lithium for counter electrode and reference electrode, microporous membrane made of polyolefin for separator, ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl containing 1.3 mol / L LiPF ₆ in electrolyte An evaluation cell was constructed using an electrolytic solution obtained by adding 1% by weight of vinylene carbonate (VC) to a mixed solution of carbonate (DMC), and the charge / discharge characteristics were examined. The charge / discharge characteristics were evaluated by measuring the initial discharge capacity and the discharge capacity after 30 cycles of charge / discharge, and determining the ratio of the discharge capacity after charge / discharge of 30 cycles to the initial discharge capacity as a percentage. The maintenance rate.

As a result of confirming the battery characteristics under the above conditions, when untreated copper foil was used, the capacity was confirmed to be reduced to 25% at the 30th cycle with respect to the initial battery capacity (= 360 mAh / g). On the other hand, when using a copper foil whose surface was coated with a 2.5 wt% styrene-butadiene latex dispersion, a 15% capacity reduction was confirmed with respect to the initial battery capacity (= 350 mAh / g). Good charge / discharge cycle characteristics were obtained by using a copper foil coated with resin. Further, 10.7 ppm of carbon nanotubes (NT-7K manufactured by Hodogaya Chemical Co., Ltd.) was added as a conductive carbon to a 2.5 wt% latex dispersion, and the same copper foil surface coating treatment as described above was performed. = 355 mAh / g), a 6% capacity reduction was confirmed, and very good charge / discharge cycle characteristics were obtained.
[Industrial applicability]

  The metal foil having a resin-coated surface according to the present invention can be used as a current collector for an electrode of a lithium ion secondary battery. In addition, a high-frequency substrate in which a resin insulating layer and a metal foil are laminated with high adhesion can be obtained by sticking a metal foil having a resin-coated surface according to the present invention to the surface of the insulating layer.

  In addition, the metal foil having a resin-coated surface according to the present invention can be used for a terminal having a connection interface between aluminum and copper. In other words, if aluminum and copper are bonded after the resin coating according to the present invention is applied to the surface of aluminum or copper, the recesses on the surface of aluminum and copper are filled with resin fine particles, so that a gap is hardly generated at the interface. Capillary phenomenon makes it difficult for water to enter the interface. Therefore, it is possible to prevent water from entering the interface and causing corrosion of aluminum.

  In order to improve the adhesion between the insulating resin and the metal, the resin coating can be applied to the surface of the metal foil according to the present invention on the surface of the metal that requires partial insulation before the resin coating. In particular, in the F-coating (registered trademark) of the resin-coated alloy strip, when the resin is coated on the alloy strip, the resin coating is peeled off by applying the resin coating method to the surface of the metal foil according to the present invention. Difficult alloy strips can be obtained.

  In the flexible printed circuit board, when a metal foil having a resin-coated surface according to the present invention is used, the adhesion between the insulator and the metal foil can be improved. Therefore, the metal foil does not peel from the insulator during bending, and the bending characteristics are improved.

The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the technical idea disclosed in the present application, and these are naturally within the technical scope of the present invention. Understood.
In particular, the present invention is not limited to metal foils but includes all metal plate materials having a metal surface including metal sheet materials.

DESCRIPTION OF SYMBOLS 1 ......... Metal plate material by which resin coating was carried out on the surface 3 ......... Resin coating layer 4 ......... Concave part 5 ......... Metal plate material 6 ......... Convex part 7 ......... Particulate liquid 9 ......... Resin fine particle 11 ... ...... Coater stick

Claims (6)

A metal plate whose surface is coated with resin,
The metal plate material includes any one metal selected from the group consisting of aluminum, copper, gold, and silver,
In the concave portion of the surface of the metal plate material, a resin coating layer is selectively formed by resin fine particles,
The metal plate material is characterized in that a resin coating layer made of resin fine particles is not formed on the convex portion of the surface of the metal plate material ,
A metal plate material comprising a metal nanostructure and / or conductive carbon in the resin coating layer. Claims wherein the resin fine particles to form a resin coating layer is a styrene-butadiene rubber, and wherein the acrylic rubber, a resin fine particles containing the acrylonitrile butadiene rubber, isoprene rubber, at least one resin selected from the group consisting of butadiene rubber Item 2. The metal plate material according to Item 1 . The metal plate material according to claim 1 , wherein the metal plate material is a copper foil having a thickness of 50 μm or less. After a fine particle liquid in which resin fine particles having an average particle size of 10 to 1000 nm are dispersed in a dispersion medium at a solid content concentration of 3 to 20 wt% is applied to the surface of the metal plate material, the metal plate material is dried to convert the resin fine particles into metal A resin coating layer is selectively formed with resin fine particles in the concave portions on the surface of the metal plate material, and the resin coating layer with resin fine particles is formed on the convex portions on the surface of the metal plate material. A resin coating method on the surface of a metal plate material, characterized in that it is not formed. 5. The resin coating method for the surface of a metal plate according to claim 4, wherein the fine particles of the resin have metal nanostructures and / or conductive carbon attached to the surface. The ten-point average roughness Rz of the surface to be coated of the metal plate before the surface is coated with the resin is 0.5 μm or more and 10 μm or less, and Rz is at least twice the average particle size of the resin fine particles. The resin coating method on the surface of a metal plate according to claim 4 or 5 .