Rolling device for electrode plate

Abstract

The invention relates to an electrode plate rolling device. Disclosed is a rolling device for an electrode sheet, which is not susceptible to contamination even if a DLC film on a rolling roller is peeled off. A rolling device (10) is disposed in a conveyance path for conveying an electrode sheet (1) of a power storage device, and is provided with a pair of rolling rollers (31). Each of the pair of rolling rollers (31) has: a base material (32); a base layer (33) that is formed at least in a rolled region (32a) in which the electrode sheet (1) is rolled in the outer peripheral surface of the base material (32); and a diamond-like carbon (DLC) coating film (34) formed on the outer peripheral surface of the underlayer (33). The base layer (33) is harder than the base material (32).

Description

Technical Field

[0001] The invention relates to a rolling device for an electrode sheet. Background Art

[0002] For example, in the Japanese Patent Application Publication No. 2018-190681, a method for manufacturing an electrode material is disclosed, which includes a process for stamping an electrode material coated with an active material slurry layer and a ceramic slurry layer on a strip metal foil in the thickness direction. The ceramic slurry layer contains ceramic particles. In the method described in the Japanese Patent Application Publication No. 2018-190681, while conveying the electrode material, the outer peripheral surface of the roller body is stamped using a stamping roller covered with a wear-resistant layer of diamond-like carbon (DLC). According to the Japanese Patent Application Publication No. 2018-190681, the direct sliding contact between the roller body and the ceramic particles disappears through the wear-resistant layer, and the wear of the roller body is suppressed.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-190681 Summary of the invention

[0006] Problems to be solved by the invention

[0007] As described in Japanese Patent Application Publication No. 2018-190681, a DLC coating with high hardness is formed on the surface of the rolling roller of the electrode sheet of the rolling storage device, thereby improving the wear resistance of the rolling roller. However, the toughness of the DLC coating is weak and sometimes peels off from the substrate of the rolling roller. When the DLC coating peels off, the substrate wears rapidly. When the substrate wears rapidly, the microparticles of the substrate generated by the wear become contamination, which may affect the quality of the electrode sheet.

[0008] Therefore, a rolling device for an electrode sheet that is unlikely to be contaminated even if the DLC coating of the rolling roll peels off is proposed here.

[0009] Means for solving problems

[0010] The electrode sheet rolling device disclosed herein is a rolling device arranged in a conveying path of the electrode sheet of the power storage device, and the rolling device comprises a pair of rolling rollers. The pair of rolling rollers respectively comprises: a substrate; a base layer formed at least in a rolling area of ​​the outer peripheral surface of the substrate where the electrode sheet is rolled; and a diamond-like carbon (DLC) coating formed on the outer peripheral surface of the base layer. The base layer is harder than the substrate.

[0011] According to the rolling device of the above-mentioned electrode sheet, there is a base layer harder than the base material between the base material and the DLC coating. Even if the DLC coating of the rolling roller is peeled off, the base material does not contact the electrode sheet due to the base layer. Therefore, the wear of the base material is prevented. In addition, the base layer is harder than the base material and is difficult to wear. As a result, pollution can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic side view of a rolling device for an electrode sheet.

[0013] Figure 2 It is a schematic plan view of a rolling device for an electrode sheet.

[0014] Figure 3 is a schematic cross-sectional view of a rolling roll.

[0015] (Explanation of Reference Numerals)

[0016] 1: electrode sheet; 2: electrode foil; 3: active material layer; 4: protective layer; 10: rolling device; 20: unwinding device; 30: punching device; 31: rolling roller; 31D: lower rolling roller; 31U: upper rolling roller; 32: substrate; 32a: rolling area; 33: base layer; 34: DLC coating; 35: film thickness sensor; 40: winding device. DETAILED DESCRIPTION

[0017] Hereinafter, an embodiment of a rolling device for an electrode sheet of an electrical storage device will be described. In addition, the embodiment described here is of course not intended to limit the present invention in particular. In addition, each of the drawings is a schematic diagram and does not necessarily faithfully reflect the actual implementation.

[0018] [Structure of rolling device]

[0019] Figure 1 1 is a schematic side view of an electrode sheet rolling device 10 according to one embodiment. Figure 2 1 is a schematic plan view of a rolling device 10 for an electrode sheet. Here, the rolling device 10 rolls an electrode sheet 1 for a lithium-ion secondary battery. However, the electrode sheet 1 is not limited to an electrode sheet for a lithium-ion secondary battery, and may be an electrode sheet for various known power storage devices. Power storage devices are terms indicating all devices that can extract electrical energy, including so-called storage batteries (chemical batteries) such as lithium-ion secondary batteries and nickel-metal hydride batteries, and capacitors (physical batteries) such as double-layer capacitors.

[0020] The electrode sheet 1 includes a strip-shaped electrode foil 2 and an active material layer 3 formed on the electrode foil 2. The positive electrode sheet is a component in which a positive electrode active material layer 3 containing a positive electrode active material is formed on the surface of a strip-shaped electrode foil 2 (for example, aluminum foil) of a predetermined width and thickness. The positive electrode active material is a material that can release lithium ions during charging and absorb lithium ions during discharge, such as a lithium transition metal composite material in a lithium ion secondary battery. The negative electrode sheet is a component in which a negative electrode active material layer 3 containing a negative electrode active material is formed on the surface of a strip-shaped electrode foil 2 (for example, copper foil) of a predetermined width and thickness. The negative electrode active material is a material that can absorb lithium ions during charging and release the lithium ions absorbed during discharge, such as natural graphite in a lithium ion secondary battery. Regarding the positive electrode active material and the negative electrode active material, there are various proposals other than the above-mentioned materials, and no particular limitation is made.

[0021] The positive electrode sheet also includes a protective layer 4 that protects the active material layer 3 and prevents it from reacting with the electrolyte. Here, the protective layer 4 is a passive layer containing a metal oxide (ceramic). The protective layer 4 contains, for example, aluminum oxide (alumina). However, there are various proposals for the protective layer 4 other than the above-mentioned materials, and no particular limitation is made. The protective layer 4 is formed in an overlapping manner on the upper layer of the active material layer 3 of the positive electrode. Figure 1 and Figure 2 In the figure, a positive electrode sheet including a protective layer 4 is shown as an electrode sheet 1. In addition, the following description assumes that the electrode sheet 1 includes a protective layer 4 unless otherwise specified.

[0022] The raw material of the active material layer 3 is set in a slurry state and applied to the electrode foil 2. The raw material of the active material layer 3 can be applied to one side of the electrode foil 2 or to both sides. In the case of the positive electrode sheet, the material of the protective layer 4 is set in a slurry state and applied to the active material layer 3 in an overlapping manner. The electrode sheet 1 is formed with a portion coated with the active material layer 3 and the protective layer 4 and an uncoated portion where the active material layer 3 and the protective layer 4 are not formed. The applied slurry-like raw materials of the active material layer 3 and the protective layer 4 are dried by a drying process. Then, the rolling device 10 continuously punches the electrode sheet 1 while conveying the electrode sheet 1 in the long side direction, adjusts the thickness of the active material layer 3 and the protective layer 4 to a thickness within a specified range, and densifies the active material in the active material layer 3.

[0023] like Figure 1 As shown, the rolling device 10 is arranged on the conveying path of the electrode sheet 1 of the power storage device. Figure 1As shown, the rolling device 10 itself may also have a mechanism for conveying the electrode sheet 1. In the present embodiment, the rolling device 10 includes a roll-out device 20, a punching device 30, and a winding device 40. The electrode sheet 1 after the active material layer 3 and the protective layer 4 are dried is provided to the roll-out device 20 through a roller. The winding device 40 winds up the electrode sheet 1 sent out from the roll-out device 20 and rolled by the punching device 30. However, the rolling device 10 may also be provided on the conveying path of the electrode sheet 1 of other conveying devices.

[0024] The rolling device 10 (more specifically, the punching device 30) includes a pair of rolling rollers 31U and 31D. The upper rolling roller 31U and the lower rolling roller 31D are opposite to each other up and down across the conveying path of the electrode sheet 1. When rolling the electrode sheet 1, the upper rolling roller 31U is lowered by a driving device not shown in the figure, and punches the electrode sheet 1 together with the lower rolling roller 31D. The thickness of the active material layer 3 and the protective layer 4 after rolling is measured by the film thickness sensor 35. The position of the upper rolling roller 31U in the up-down direction or the punching pressure is feedback-controlled based on the thickness of the active material layer 3 and the protective layer 4 measured by the film thickness sensor 35. In addition, in the following, without distinguishing between the upper rolling roller 31U and the lower rolling roller 31D, the reference numeral 31 is sometimes used and referred to as the rolling roller 31, a pair of rolling rollers 31, etc.

[0025] The punching force of the rolling device 10 is not particularly limited, and sometimes can reach a linear pressure of 40,000 N / cm. The length of the electrode sheet 1 in the width direction of the rolling rollers 31U and 31D can sometimes reach 100 cm. The conveying speed of the electrode sheet 1 during rolling is also not particularly limited, and sometimes can reach 100 m / min. The linear pressure of the rolling device 10 is high, the conveying speed of the electrode sheet 1 is fast, and the protective layer 4 is hard, thereby applying a large friction force to a pair of rolling rollers 31U and 31D. The Vickers hardness of the ceramic part of the protective layer 4 is, for example, 1400 HV to 1800 HV. In addition, the conveying speed of the electrode sheet 1 is fast, and thus the amount of wear of the rolling roller 31 per hour also increases.

[0026] Figure 3 31 is a schematic cross-sectional view of the rolling roller 31. Figure 3As shown, the rolling roller 31 has a substrate 32, a base layer 33 and a diamond-like carbon (DLC) coating 34. The substrate 32 is a base of the rolling roller 31 formed into a cylindrical shape. The substrate 32 is, for example, a high-carbon bearing steel material (SUJ material), and is preferably formed of, for example, SUJ2 with high versatility. However, the material of the substrate 32 is not limited to SUJ material. The substrate 32 may also be composed of, for example, chrome steel, chrome-molybdenum steel, stainless steel, etc. As the material of the substrate 32, it is preferred that the material has the strength to withstand the stamping pressure of the rolling roller 31 and is excellent in availability, processability, cost, etc. The hardness of the substrate 32 does not need to be so high in this embodiment. The Vickers hardness of the preferred material for the substrate 32 is, for example, above 600HV and below 900HV.

[0027] The base layer 33 is a layer harder than the base material 32 and is formed on the surface of the base material 32. The base layer 33 is formed at least in the rolling area 32a (see FIG. 1 ) where the electrode sheet 1 is rolled on the outer peripheral surface of the base material 32. Figure 2 ).like Figure 2 As shown, the rolling area 32a is the area that contacts the electrode sheet 1 during rolling. The width of the rolling area 32a of the electrode sheet 1 related to the width direction is equal to the width of the electrode sheet 1. The base layer 33 can also be formed in a portion of the outer peripheral surface of the substrate 32 that includes the rolling area 32a and is wider than the rolling area 32a. For example, the base layer 33 can be formed on the entire outer peripheral surface of the substrate 32.

[0028] In the present embodiment, the base layer 33 is formed of a superhard alloy. In more detail, the base layer 33 is formed by a spray coating of a superhard alloy. Superhard alloy is a material formed by sintering tungsten carbide with metals such as cobalt and nickel. In superhard alloy, the metal that combines the particles of tungsten carbide is not limited to cobalt and nickel. The spray coating is a coating formed by spraying a material in a molten state or a state close to a molten state on a substrate. The spray coating of superhard metal is formed, for example, by a high-speed flame spraying method. However, the base layer 33 may also be a spray coating of a material other than a superhard alloy, for example, a spray coating of a material (so-called cermet) containing a metal oxide (ceramic) and a metal. Alternatively, the base layer 33 may also be formed by a method other than spraying. For example, the base layer 33 may be formed by hard chrome plating.

[0029] The base layer 33 is formed of a material at least harder than the base material 32. The Vickers hardness of the base layer 33 is preferably 900 HV or more. The Vickers hardness of the base layer 33 is more preferably 1200 HV or more. The Vickers hardness of superhard metal is about 1100 HV to 1500 HV. The Vickers hardness of hard chrome plating is about 750 HV to 1000 HV.

[0030] The base layer 33 is preferably formed thickly. Spraying is suitable as a method for forming the base layer 33 thickly. The base layer 33 is preferably formed to have an average thickness of 50 μm or more. More preferably, the base layer 33 is formed to have an average thickness of 100 μm or more.

[0031] like Figure 3 As shown, the DLC coating 34 is formed on the outer peripheral surface of the base layer 33. The DLC coating 34 is a carbon coating having a carbon bond structure of both diamond and graphite. The DLC coating 34 is formed, for example, by a plasma CVD (chemical vapor deposition) method in which bicarbonate gas is plasmatized and evaporated, or by sputtering using graphite as a raw material. The Vickers hardness of the DLC coating 34 is, for example, greater than 1600 HV and less than 2500 HV. The Vickers hardness of the DLC coating 34 is greater than the Vickers hardness of the base layer 33. The average thickness of the DLC coating 34 is, for example, 2 μm to 3 μm. The achievable thickness of the DLC coating 34 is less than several μm. The average thickness of the base layer 33 is thicker than the average thickness of the DLC coating 34. The average thickness of the base layer 33 is preferably more than 10 times the average thickness of the DLC coating 34.

[0032] [Effects of the Embodiments]

[0033] Hereinafter, the effects that can be achieved by the rolling device 10 for the electrode sheet 1 according to the present embodiment will be described.

[0034] The rolling device 10 of the electrode sheet 1 of the present embodiment is a rolling device arranged in a conveying path of the electrode sheet 1 of the electric storage device, and is provided with a pair of rolling rollers 31. The pair of rolling rollers 31 respectively have: a substrate 32; a base layer 33 formed at least in a rolling region 32a where the electrode sheet 1 is rolled among the outer peripheral surface of the substrate 32; and a DLC coating 34 formed on the outer peripheral surface of the base layer 33. The base layer 33 is harder than the substrate 32.

[0035] The DLC coating 34 has weak toughness and sometimes peels off from the substrate 32. For example, if the rolling roller 31 bites into a foreign object, the DLC coating 34 is likely to peel off. In the past, the rolling rollers that rolled the electrode sheets 1 of the power storage device formed a DLC coating on the outer peripheral surface of the substrate. Therefore, in the previous rolling rollers, if the DLC coating peeled off, the substrate wore out rapidly. The electrode sheet 1, especially the protective layer 4, is very hard. Furthermore, the punching pressure is large, and the conveying speed of the electrode sheet 1 is fast, so the substrate wears out rapidly. When the substrate wears out rapidly, the microparticles of the substrate generated by the wear become contamination, which may affect the quality of the electrode sheet 1.

[0036] In this regard, in the rolling device 10 of the present embodiment, there is a base layer 33 that is harder than the base layer 32 between the base material 32 and the DLC coating 34. Even if the DLC coating 34 of the rolling roller 31 is peeled off, the base material 32 does not contact the electrode sheet 1 due to the base layer 33. Therefore, the wear of the base material 32 is prevented. In addition, the base layer 33 is harder than the base material 32 and is difficult to wear. As a result, contamination can be suppressed.

[0037] In addition, in the conventional rolling roller, the DLC coating wears due to long-term use, and when part or all of it disappears, the substrate wears rapidly. Therefore, the substrate wears during the period from when the DLC coating wears or peels off until the wear or peeling of the DLC coating is detected and the rolling roller is replaced. As a result, the life of the rolling roller is shortened. In addition, during the period when the substrate is usable, the DLC coating is formed again on the substrate and reused.

[0038] In contrast, in the rolling device 10 of the present embodiment, after the DLC coating 34 is worn or peeled off, it is the base layer 33 that contacts and wears the electrode sheet 1. The base layer 33 is harder than the base material 32, and the amount of wear is less than that of the base material 32. Therefore, the rolling roller 31 can be maintained in a reusable state for a long period of time, and the DLC coating 34 can be formed again more times than before. As a result, the life of the rolling roller 31 can be extended than before.

[0039] In the present embodiment, the base layer 33 is formed of a cemented carbide. According to this structure, the base layer 33 formed of a cemented carbide has high hardness, so the wear amount of the rolling roll 31 can be further reduced.

[0040] In the present embodiment, the average thickness of the base layer 33 is thicker than the average thickness of the DLC coating 34. According to this structure, since the base layer 33 is thick, the life of the rolling roller 31 can be further extended.

[0041] In the present embodiment, the average thickness of the base layer 33 is 50 μm or more. According to this structure, the base layer 33 is thick, so the life of the rolling roller 31 can be further extended. According to the trial production of the inventors of the present application, the life of the rolling roller 31 with an average thickness of the base layer 33 of 50 μm or more is several times longer than that of the conventional rolling roller (the material of the base material is SUJ2) in which the DLC coating is formed on the surface of the base material.

[0042] In this embodiment, the base layer 33 is formed by thermal spraying. According to this structure, the material of the base layer 33 has a high degree of freedom. Thermal spraying has few restrictions on the material that can form the coating. In addition, thermal spraying can easily form the base layer 33 thickly.

[0043] [Other embodiments]

[0044] An embodiment of the electrode sheet rolling device proposed herein is described above. However, the above embodiment is only an example and can be implemented in other ways. For example, in the above embodiment, the rolling roller 31 is a three-layer structure of a substrate 32, a base layer 33 and a DLC coating 34, but it is not limited to this. The rolling roller can also have a layer structure of more than four layers in which the substrate is arranged at the innermost side in the radial direction, the DLC coating is arranged at the outermost side in the radial direction, and the base layer is arranged between the two.

[0045] In addition, unless otherwise specified, the above-mentioned embodiments do not limit the present invention. In addition, the technology disclosed herein can be modified in various ways, and each component and each process mentioned herein can be appropriately omitted or appropriately combined as long as no special problems are caused.

[0046] This specification contains the disclosure as described in the following items.

[0047] Item 1. A rolling device for an electrode sheet,

[0048] The rolling device is arranged on a conveying path for conveying an electrode sheet of an electric storage device and includes a pair of rolling rollers.

[0049] The pair of rolling rollers respectively have:

[0050] Base material;

[0051] A base layer formed at least in a rolling region where the electrode sheet is rolled in the outer peripheral surface of the substrate; and

[0052] A diamond-like carbon (DLC) coating is formed on the outer peripheral surface of the base layer.

[0053] The base layer is harder than the substrate.

[0054] Item 2. A rolling device for an electrode sheet as described in Item 1,

[0055] The base layer is formed of a superhard alloy.

[0056] Item 3. A rolling device for an electrode sheet as described in Item 1 or 2,

[0057] The average thickness of the base layer is thicker than the average thickness of the DLC film.

[0058] Item 4. An electrode sheet rolling device as described in any one of Items 1 to 3,

[0059] The average thickness of the base layer is 50 μm or more.

[0060] Item 5. An electrode sheet rolling device as described in any one of Items 1 to 4,

[0061] The base layer is formed by spray coating.

Claims

1. A rolling device for an electrode sheet, the rolling device being arranged in a conveying path for conveying an electrode sheet of an electrical storage device, wherein: The rolling device includes a pair of rolling rolls. The pair of rolling rollers respectively have: Base material; A base layer formed at least in a rolling region where the electrode sheet is rolled in the outer peripheral surface of the substrate; and A diamond-like carbon coating, i.e., a DLC coating, is formed on the outer peripheral surface of the base layer. The base layer is harder than the substrate.

2. The electrode sheet rolling device according to claim 1, The base layer is formed of a superhard alloy.

3. The electrode sheet rolling device according to claim 1, The average thickness of the base layer is thicker than the average thickness of the DLC film.

4. The electrode sheet rolling device according to claim 1, The average thickness of the base layer is 50 μm or more.

5. The electrode sheet rolling device according to claim 1, The base layer is formed by spray coating.

Images