JP2008173590A - Coating apparatus and method of manufacturing electrode foil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique to make the thickness of a coating layer including edge parts uniform in a coating apparatus for applying a coating liquid (a liquid containing an electrode active material) on a sheet like base material (a metallic foil). <P>SOLUTION: The coating apparatus 10 is provided with a coating backup roller 13 on which the sheet like material 9 is wound and a die coater 12 for applying the coating liquid L on the sheet like based material 9 carried on the coating backup roller 13. In the coating backup roller 13, the peripheral surface of a part (a prescribed part W<SB>1</SB>) of the coating backup roller where the coating liquid is applied on the wound sheet like base material 9 in a prescribed width by the die coater 12 is formed cylindrical and the peripheral surface of a part (a liquid flowing part W<SB>2</SB>) of the coating backup roller where the applied coating liquid flows to be spread to the end part side is formed to have a circular conical surface which has nearly the same axis as the cylindrical surface and in which the diameter is gradually reduced toward the end part of the coating backup roller 13. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an electrode foil constituting a secondary battery, and a coating apparatus used for manufacturing the electrode foil.

Conventionally, an electrode foil in which an active material layer is formed on the surface of a metal foil is used as a battery electrode. For example, in a lithium ion battery, an active material layer containing graphite (carbon) is formed on a copper foil, with an electrode foil formed by forming an active material layer containing lithium cobalt oxide (LiCoO ₂ ) on both sides of an aluminum foil as a positive electrode. The resulting electrode foil is used as a negative electrode, and these electrode foils are stacked in a plurality of layers.

The positive electrode is formed by applying a positive electrode active material such as lithium cobaltate and a binder dissolved on a both sides of an aluminum foil with a solvent, drying, and pressing.
Similarly to the positive electrode, the negative electrode is obtained by applying a copper foil with a negative electrode active material such as a carbon material and a binder dissolved in a solvent, drying, and pressing.

In manufacturing the electrode foil, a coating apparatus is used to apply a liquid (pasted) electrode active material or binder to the metal foil. For example, the technique described in Patent Document 1.
For example, as shown in FIG. 7, the coating apparatus includes a coating backup roller 13 for continuously feeding out a sheet-like base material 9 wound up in a roll shape, and a sheet-like base on the coating backup roller 13. A die coater 12 for applying a coating liquid containing an electrode active material to the material 9 is provided.

  The electrode foil having the electrode active material layer formed on the surface thereof by applying and drying the liquid containing the electrode active material in the coating apparatus increases the packing density of the electrode active material and makes it uniform. An electrode foil is obtained through a step of pressing with a rolling device (roll press device). The electrode foil is used after being cut into a predetermined size.

By the way, when the liquid containing the electrode active material is applied to the metal foil, the liquid tends to flow and spread in the width direction on the metal foil. The formed coating layer 11 tends to have rounded edges in the width direction. As a result, the edge of the electrode active material layer formed on the electrode foil is rounded, the thickness of the layer becomes non-uniform, and it becomes a part that is cut off wastefully, or in order to reduce electrode performance even if left behind There is a problem that it is a useless part that is not used.
JP 11-288708 A

  In view of the above prior art, the present invention proposes a technique for making the thickness of the coating layer formed on the sheet substrate uniform, including the edges, in the coating apparatus for applying the coating liquid to the sheet substrate. To do. In addition, when the sheet base material is a metal foil, the coating liquid is a liquid containing an electrode active material, and the electrode foil is manufactured, the thickness of the electrode active material layer formed on the electrode foil is uniform including the edges. Propose technology to do.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

  That is, in claim 1, a coating backup roller around which a sheet-like base material is wound, and a coating device comprising at least a die coater for applying a coating liquid to the sheet-like base material conveyed on the coating backup roller. A coating apparatus, wherein the coating backup roller includes a portion where a coating liquid applied with a prescribed width on the wound sheet-like base material flows and spreads toward the end side on the wound sheet-like base material. It is characterized in that the diameter gradually decreases toward the end of the backup roller.

  In claim 2, a coating apparatus comprising at least a coating backup roller around which a sheet-like base material is wound, and a die coater for applying a coating liquid to the sheet-like base material passing over the coating backup roller. In the coating backup roller, the peripheral surface of the portion where the coating liquid applied with a specified width by the die coater on the wound sheet-like base material flows to the end side and spreads, is applied to the coating surface. It is characterized in that it is formed with a conical surface that gradually decreases in diameter toward the end of the backup roller.

  The coating apparatus according to claim 3, comprising at least a coating backup roller around which the sheet-like base material is wound, and a die coater for applying a coating liquid to the sheet-like base material conveyed on the coating backup roller. In the coating backup roller, the peripheral surface of the portion where the coating liquid is applied with a specified width by the die coater on the wound sheet-like base material is formed as a cylindrical surface, and the same is applied. The peripheral surface of the portion where the coating liquid flows and spreads toward the end side is formed by a conical surface that is substantially coaxial with the cylindrical surface and gradually decreases in diameter toward the end of the coating backup roller. It is.

  In Claim 4, in the said coating apparatus using the manufacturing system of the electrode foil which comprises the coating apparatus of any one of Claims 1-3, and a rolling apparatus, in sheet form A step of applying a coating liquid containing an electrode active material to a metal foil as a base material and then drying it to form an electrode active material layer on the metal foil; And a step of pressing the metal foil on which the layer is formed.

  According to the present invention, the electrode active material layer formed on the sheet-like base material is forcedly formed with raised portions at both edges in the width direction. Therefore, when this sheet-like base material is pressed, the material of the raised shape portion moves to a thin portion existing outside the raised shape portion, and an electrode foil having a substantially uniform thickness of the electrode active material layer is obtained. be able to.

Next, embodiments of the invention will be described.
1 is a schematic configuration diagram of an electrode foil manufacturing system including a coating apparatus according to an embodiment of the present invention, FIG. 2 is a diagram of a coating unit of the coating apparatus, FIG. 3 is a diagram of a coating backup roller, FIG. 4 is a view of a coating backup roller of another form, FIG. 5 is a cross-sectional view of a sheet-like substrate on which an electrode active material layer is formed, and FIG. 6 is a cross-sectional view of the manufactured electrode foil.
FIG. 7 is a view of a coating portion of a conventional coating apparatus, and FIG. 8 is a cross-sectional view of a sheet-like substrate on which an electrode active material layer is formed by the conventional coating apparatus.

  A coating apparatus 10 according to an embodiment of the present invention is an apparatus for forming a coating layer 11 on a sheet-like substrate 9 that is used for manufacturing an electrode foil used as an electrode of a secondary battery or the like. . As shown in FIG. 1, the electrode foil manufacturing system includes the coating device 10 and a rolling device 22.

The “sheet-like base material 9” serves as a substrate on which the coating layer 11 is formed. In this embodiment for producing an electrode foil, an aluminum foil, a copper foil, etc. Any metal foil depending on the type and application.
Further, the “coating liquid L containing an electrode active material” is a slurry in which an electrode active material (positive electrode active material or negative electrode active material) dissolved in a solvent is mixed with a binder in this embodiment for producing an electrode foil. It is a fluid. The positive electrode active material or the negative electrode active material is an arbitrary electrode active material according to the type and application of the electrode foil to be produced. For example, lithium cobaltate, lithium nickelate, or lithium manganate is used as the positive electrode active material. In addition, graphite, carbon, lithium aluminum alloy, tin oxide and the like can be used as the negative electrode active material.
Furthermore, the “coating layer 11” is an electrode active material layer in this embodiment for producing an electrode foil.

The coating apparatus 10 according to the present embodiment includes a coating unit 20 having a function of applying the coating liquid L to the sheet-like substrate 9 and a drying unit 21 having a function of drying the coating liquid L. The drying unit 21 can be, for example, a drying furnace or a blower, and the coating liquid L is forcibly dried while passing through the drying unit 21.
In the present embodiment, the coating apparatus 10 includes the coating unit 20 and the drying unit 21. However, the drying unit 21 may be configured separately.

In the coating apparatus 10, the sheet-like substrate 9 wound in a roll shape is continuously drawn out and conveyed to the coating unit 20, and the coating liquid L is applied to one surface (surface) of the sheet-like substrate 9. After being transported to the drying unit 21 and forcedly dried, it is wound into a roll again.
The coating layer 11 is formed on one surface of the sheet-like base material 9 by a series of processes by the coating apparatus 10. In this embodiment for manufacturing the electrode foil, an electrode active material layer is formed on the metal foil by a series of treatments by the coating apparatus 10.
In addition, when forming the coating layer 11 on both surfaces of the sheet-like base material 9, the process similar to the above is given to the other surface (back surface) of the sheet-like base material 9, and the other surface ( A coating layer can be formed on the back surface.

Subsequently, in the rolling device 22, the sheet-like base material 9 wound in a roll shape is continuously drawn out, is conducted between the rolling rolls, and is taken up again in a roll shape. By the press treatment by the rolling device 22, the filling density of the coating layer 11 formed on the sheet-like substrate 9 is increased.
In the present embodiment for producing the electrode foil, the metal foil on which the electrode active material layer is formed is pressed in the rolling device 22 to increase the packing density of the electrode active material in the electrode active material layer, Moreover, it is equalized and becomes electrode foil.

Here, the structure of the coating part 20 of the said coating apparatus 10 is demonstrated.
As shown in FIGS. 2 and 3, the coating unit 20 of the coating apparatus 10 includes a coating backup roller 13 around which the sheet-like base material 9 is wound, and a sheet that passes over the coating backup roller 13. And a die coater 12 for applying the coating liquid L to the substrate 9.
Hereinafter, the width direction of the sheet-like substrate 9 is referred to as “width direction”. Therefore, the direction substantially parallel to the axis of the coating backup roller 13 around which the sheet-like substrate 9 is wound is the width direction.

  In addition to the coating backup roller 13, the coating apparatus 10 includes one or a plurality of guide rollers 14, and the sheet-like base material 9 is wound with tension. By rotating these rollers 13 and 14, the sheet-like base material 9 wound up in a roll shape is continuously fed out to the coating unit 20 at a predetermined speed, and further conveyed to the drying unit 21, and then again. It is wound up into a roll.

The die coater 12 causes the coating liquid L supplied from the coating liquid tank 15 (FIG. 1) to flow out from the slit 12 a opened in the beak-shaped nozzle and onto the sheet-like substrate 9 on the coating backup roller 13. It is to be painted. The slit 12a of the nozzle of the die coater 12 is long in the width direction of the sheet-like base material 9, and the prescribed width in which the coating liquid L is applied to the sheet-like base material 9 is determined by the opening width of the slit 12a. .
The die coater 12 is not limited to the configuration of the present embodiment, and widely used existing die coaters can be widely used.

  The coating backup roller 13 winds the sheet-like base material 9 on which the coating liquid L is applied by the die coater 12, and receives the coating pressure from the die coater 12. The coating backup roller 13 in this embodiment is rotated by receiving the tension of the sheet-like substrate 9 that is conveyed when the guide roller 14 disposed upstream or downstream of the coating backup roller 13 is rotationally driven. This is a driven roller.

In the above configuration, the slit 12a of the die coater 12 is brought close to the sheet-like substrate 9 wound around the coating backup roller 13, and the coating liquid L is applied with a specified width (opening width of the slit 12a of the die coater 12). the site to be a "defining portion W ₁ of the sheet-like substrate 9 '. Furthermore, among the coating backup roller 13, a portion defining part W ₁ of the sheet-like base material 9 is wound, a "defining portion W ₁ of the coating backup roller 13".
Therefore, the width of the defining portion W ₁ of the coating backup roller 13 and the defining portion W ₁ of the sheet-like base material 9 is substantially equal to the opening width of the slit 12 a of the die coater 12.

Further, the both sides of the defining portion W ₁ of the sheet-like base material 9 was applied to the specified portions W ₁ coating liquid L is present sites extending flow to the end side. This portion is referred to as “liquid flow portion W ₂ · W _{2 of} sheet-like base material 9”. Further, a portion of the coating backup roller 13 around which the liquid flow portion W ₂ · W ₂ of the sheet-like base material 9 is wound is referred to as “liquid flow portion W ₂ · W _{2 of the} coating backup roller 13”. In this case, the coating layer 11 is formed in a width (W shown in FIG. 3) of the sheet-like base material 9 extending between the defining portion W ₁ and the liquid flow portions W ₂ and W ₂ .

The coating backup roller 13 is provided with a shape for forcibly forming raised portions at both edges in the width direction of the coating layer 11 formed on the sheet-like substrate 9.
That is, the defining portion W ₁ of the coating backup roller 13 has a cylindrical shape, at least the liquid flow section W ₂ · _{W 2} of the coating backup roller 13 is directed from the said defined portion W ₁ in the width direction end portion side gradually reduced The shape is a diameter. That is, a portion of the coating backup roller 13 where the coating liquid L applied with a specified width on the wound sheet-like base material 9 by the die coater 12 flows toward the end side and spreads is the coating coating roller 13. The diameter gradually decreases toward the end of the backup roller 13.

In other words, the coating backup roller 13, defining portion peripheral surface of the W ₁ is formed by a cylindrical surface, at least the peripheral surface of the liquid flow portion W ₂ · _{W 2} is the cylindrical surface substantially coaxial conical surface or substantially hemispherical It will be formed on the surface. In other words, the peripheral surface of the coating backup roller 13 on which the coating liquid L is applied with a specified width by the die coater 12 on the wound sheet-like base material 9 is formed as a cylindrical surface, The peripheral surface of the portion where the applied coating liquid L flows and spreads toward the end side is formed by a conical surface that is substantially coaxial with the cylindrical surface and gradually decreases in diameter toward the end of the coating backup roller 13.

  In the coating backup roller 13 according to the present embodiment, the peripheral surface of the coating portion 32 is a cylindrical surface, and includes the liquid flow portions 33 and 33, and the peripheral surface on the axial end portion side of the coating portion 32. Is a conical surface substantially coaxial with the cylindrical surface. The coating backup roller 13 has a so-called drum-shaped outer shape in which truncated cones are integrally formed at both ends of a cylinder.

However, the switching positions of the shapes of the defining portion W ₁ and the liquid flow portions W ₂ and W ₂ of the coating backup roller 13 may be slightly shifted inward in the width direction. That is, the coating backup roller 13 can be gradually reduced in diameter to shape from a widthwise end portion of the defining portion W _1. It is desirable to appropriately adjust the switching position of the shape between the defining portion W ₁ and the liquid flow portions W ₂ and W ₂ of the coating backup roller 13 according to the viscosity of the coating liquid L and the coating amount.

The coating backup roller 13 only needs to have a shape in which the diameters of the liquid flow portions W ₂ and W ₂ are gradually reduced. For example, in the coating backup roller 13, as shown in FIG. the peripheral surface of the defining portion W ₁ and both end portions to form a cylindrical surface, the remaining peripheral surface including a liquid flow portion W ₂ · _{W 2} can be formed by a conical surface.
Further, for example, as shown in FIG. 4B, in the coating backup roller 13, the peripheral surface of the defining portion W ₁ is formed as a cylindrical surface, and from the defining portion W ₁ to the end of the coating backup roller 13. The peripheral surface can be formed of a substantially hemispherical surface.

Since the sheet-like base material 9 wound around the coating backup roller 13 is under tension, it is elastically deformed following the shape of the peripheral surface of the coating backup roller 13.
As a result, in the sheet-like base material 9 wound around the coating backup roller 13, the liquid flow portions W ₂ and W ₂ are more spaced apart from the slits 12 a of the nozzles of the die coater 12 than the defining portion W _1. Compared with the case where the peripheral surfaces of the liquid flow portions W ₂ , W ₂ of the coating backup roller 13 are formed by cylindrical surfaces having the same diameter as the defining portion W ₁ , the coating liquid L is present at both ends of the slit 12 a. Since the flow resistance when flowing out to the sheet-like base material 9 becomes small, a larger amount of the coating liquid L is placed on the coating surface.

As shown in FIG. 5, the coating layer 11 formed on the sheet-like base material 9 by the coating apparatus 10 having the above-described configuration has raised shape portions 11 a and 11 a at both edges in the width direction, and the thin portion 11 b. -11b is formed in the width direction edge part side further than the said protruding shape part 11a * 11a.
The “protrusion-shaped portion 11 a” is formed due to the shape of the liquid flow portions W ₂ and W ₂ of the coating backup roller 13. Further, the “thin portion 11b” indicates an end portion having a thickness smaller than that of the other portion of the coating layer 11 at the end portion in the width direction of the liquid flow portions W ₂ and W ₂ .

And when the sheet-like base material 9 in which the coating layer 11 is formed as described above is pressed by the rolling device 22, the coating layer 11 spreads from the center in the width direction toward the end, and the central portion or the raised shape is formed. The material of the portions 11a and 11a moves to the thin portions 11b and 11b, and the thickness of the coating layer 11 becomes substantially uniform as shown in FIG.
That is, an electrode foil in which the thickness of the electrode active material layer formed on the metal foil is substantially uniform can be obtained. Since the electrode foil does not require a treatment such as cutting off the end in the width direction in order to make the thickness of the electrode active material layer substantially uniform, use the end in the width direction of the metal foil on which the electrode active material layer is not formed. Electrode can be connected.

Incidentally, the coating backup roller 13 of the liquid flow portion W ₂ · _{W 2} of width (axial length) and location, as well as the inclination angle θ of the conical surface forming the liquid flow portion W ₂ · _{W 2,} the coating liquid It is appropriately adjusted according to the viscosity of L, and is determined so that the thickness of the coating layer 11 becomes substantially uniform when pressed by the rolling device 22. Liquid flow portion W ₂ · _{W 2} of width of these coating backup roller 13 (axial length) and location, as well as the inclination angle θ of the conical surface forming the liquid flow portion W ₂ · _{W 2,} through experiments, or It can be obtained by simulation.

The schematic block diagram of the manufacturing system of the electrode foil containing the coating apparatus which concerns on one Example of this invention. The figure of the coating part of a coating device. Illustration of coating backup roller. The figure of the coating backup roller of another form. Sectional drawing of the sheet-like base material in which the electrode active material layer was formed. Sectional drawing of the manufactured electrode foil. The figure of the coating part of the conventional coating apparatus. Sectional drawing of the sheet-like base material in which the electrode active material layer was formed with the conventional coating apparatus.

Explanation of symbols

9 Sheet-like substrate (metal foil)
10 Coating equipment 11 Coating layer (electrode active material layer)
12 Die Coater 13 Coating Backup Roller W ₁ Regulation Part W ₂ Liquid Flow Part

Claims (4)

A coating apparatus comprising at least a coating backup roller around which a sheet-like substrate is wound, and a die coater for applying a coating liquid to the sheet-like substrate conveyed on the coating backup roller,
Of the coating backup roller, on the end of the coating backup roller, a portion where the coating liquid applied with a specified width by the die coater flows and spreads toward the end on the wound sheet-like substrate. To make the shape gradually reduce the diameter,
Feature coating equipment. A coating apparatus comprising at least a coating backup roller around which a sheet-like base material is wound, and a die coater for applying a coating liquid to the sheet-like base material passing over the coating backup roller,
Among the coating backup rollers, the peripheral surface of the part where the coating liquid applied with a specified width on the wound sheet-like base material by the die coater flows toward the end side and spreads, Forming a conical surface that gradually decreases in diameter toward the end,
Feature coating equipment. A coating apparatus comprising at least a coating backup roller around which a sheet-like substrate is wound, and a die coater for applying a coating liquid to the sheet-like substrate conveyed on the coating backup roller,
Of the coating backup roller, on the wound sheet-like substrate, the peripheral surface of the portion where the coating liquid is applied with a specified width by the die coater is formed as a cylindrical surface, and the coated coating liquid is also the end Forming the peripheral surface of the portion that flows and expands toward the part side with a conical surface that is substantially coaxial with the cylindrical surface and gradually decreases in diameter toward the end of the coating backup roller,
Feature coating equipment. Using the electrode foil manufacturing system comprising the coating apparatus according to any one of claims 1 to 3 and a rolling apparatus,
In the coating apparatus, after applying a coating liquid containing an electrode active material to a metal foil as a sheet-like substrate, drying it, and forming an electrode active material layer on the metal foil;
A step of pressing the metal foil on which the electrode active material layer is formed in the rolling device,
A method for producing an electrode foil, comprising:

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