Method and device of manufacturing electrode sheet

Abstract

To provide a method of manufacturing an electrode sheet capable of suppressing reduction in peel strength between an electrode layer and a power collection sheet while suppressing increase in drying time.SOLUTION: A method of manufacturing an electrode sheet includes: a preparation step of preparing a coating sheet having a coating part applied with an electrode material, on a first surface of a power collection sheet that has a longitudinal direction in a first direction; and a drying step of drying the coating part to obtain an electrode sheet by irradiating the coating sheet with a laser light from a plurality of laser heads arranged side by side in the first direction while transporting the coating sheet in the first direction. At the drying step, hot wind whose temperature is 50°C to 140°C and whose wind speed is equal to or more than 5 m / s is supplied to a laser irradiation part irradiated with the laser light from each laser head on the coating sheet to be transported, until the next laser irradiation.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method and an apparatus for manufacturing an electrode sheet. [Background technology]

[0002] A known technique for manufacturing an electrode sheet used in the manufacture of batteries such as lithium-ion secondary batteries is to apply an electrode material to a conveyed current collector sheet to form a coated portion, and then dry the coated portion to obtain an electrode layer.

[0003] For example, Patent Document 1 discloses a method for manufacturing an electrode, which includes a coating process in which an active material mixture is applied to a long metal foil being transported to form a coated portion of the active material mixture; a first irradiation process that is performed before the coating process and in which a laser is irradiated to an irradiation position on the long metal foil that is located upstream in the transport direction of the long metal foil from both ends of the mixture application location along the short side of the long metal foil; a second irradiation process that is performed after the first irradiation process and in which a laser is irradiated to both short side edges of the coated portion formed by the coating process; and a drying process that is performed after the second irradiation process and in which the coated portion is dried. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-029256 Summary of the Invention [Problem to be solved by the invention]

[0005] A technique for drying coated sheets having a coated portion coated with an electrode material has been proposed, which uses laser light as a heat source. In this case, the temperature of the current collecting sheet tends to become high in areas of the coated sheet where the electrode material is not present. As a result, the temperature of the current collecting sheet near the edge of the coated portion becomes high, which tends to reduce the peel strength between the electrode layer and the current collecting sheet. On the other hand, weakening the laser irradiation conditions is also an option, but this increases the drying time.

[0006] The present disclosure has been made in consideration of the above-mentioned circumstances, and has as its main object to provide a method for manufacturing an electrode sheet that can suppress an increase in drying time while suppressing a decrease in peel strength between the electrode layer and the current collecting sheet. [Means for solving the problem]

[0007] [1] a preparation step of preparing a coated sheet having a coated portion coated with an electrode material on a first surface of a current collecting sheet having a longitudinal direction in a first direction; a drying step of irradiating the coated sheet with laser light from a plurality of laser heads arranged side by side in the first direction while conveying the coated sheet in the first direction, thereby drying the coated portion to obtain an electrode sheet, The drying step is a method for manufacturing an electrode sheet, in which hot air having a temperature of 50°C or higher and 140°C or lower and a wind speed of 5 m / s or higher is supplied to the laser irradiation section of the coated sheet being conveyed, which has been irradiated with laser light from each laser head, until the next laser irradiation.

[0008] [2] The method for manufacturing an electrode sheet according to [1], wherein the hot air is blown out from a plurality of hot air outlets arranged alternately with the plurality of laser heads in the first direction.

[0009] [3] An electrode sheet manufacturing device for manufacturing an electrode sheet by drying a coated sheet having a coated portion coated with an electrode material disposed on a first surface of a current collecting sheet having a longitudinal direction in a first direction, a conveyor for conveying the coated sheet in the first direction; an electrode sheet manufacturing device comprising: a laser light irradiator having a plurality of laser heads that irradiate the coated sheet with laser light; and a hot air supplying machine having a plurality of hot air outlets that blow hot air onto the coated sheet and a control unit that controls the temperature of the hot air blown out from the hot air outlets to be 50°C or higher and 140°C or lower, and the air speed to be 5 m / s or higher.

[0010] [4] The electrode sheet manufacturing apparatus according to [3], wherein the plurality of hot air outlets and the plurality of laser heads are arranged alternately in the first direction. [Effects of the Invention]

[0011] According to the electrode sheet manufacturing method of the present disclosure, it is possible to manufacture an electrode sheet in which an increase in drying time is suppressed while a decrease in peel strength between the electrode layer and the current collector sheet is suppressed. [Brief explanation of the drawings]

[0012] [Figure 1] 1A and 1B are a schematic plan view and a schematic cross-sectional view illustrating a coated sheet according to the present disclosure. [Figure 2] FIG. 2 is a schematic diagram illustrating a drying step in the present disclosure. [Figure 3] FIG. 10 is a schematic perspective view illustrating laser irradiation. [Figure 4] 1 is a schematic cross-sectional view illustrating an electrode sheet according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0013] The electrode sheet manufacturing method and electrode sheet manufacturing apparatus of the present disclosure will be described in detail below with reference to the drawings. The following drawings are schematic, and the size and shape of each part are appropriately exaggerated for ease of understanding. Furthermore, in this specification, when describing the arrangement of another member relative to a certain member, the term "above" or "below" simply refers to both the case where another member is arranged directly above or below the certain member so as to be in contact with the certain member, and the case where another member is arranged above or below the certain member via another member, unless otherwise specified.

[0014] A. Electrode sheet manufacturing method Fig. 1(a) is a schematic plan view illustrating a coated sheet prepared in a preparation step according to the present disclosure, and Fig. 1(b) is a cross-sectional view taken along line AA of Fig. 1(a). As shown in Figs. 1(a) and 1(b), coated sheet 10 has coated portions 2 coated with an electrode material on a first surface S1 of current collector sheet 1, the longitudinal direction of which is in a first direction D1. The coated sheet may also include uncoated portions 3 and intermittent portions 4 that are not coated with the electrode material.

[0015] Fig. 2 is a schematic diagram illustrating the drying step in the present disclosure. As shown in Fig. 2, in the drying step, while the coated sheet 10 is conveyed in a first direction D1, laser light is irradiated onto the coated sheet 10 from multiple laser heads L1 to L5 arranged side by side in the first direction D1, and the coated portion is dried to obtain an electrode sheet 20.

[0016] Figure 3 is a schematic perspective view illustrating laser irradiation. When a coated sheet is continuously irradiated with a laser, the current collecting sheet 1 tends to reach high temperatures in areas where no coated section 2 exists (e.g., uncoated sections 3 and intermittent sections 4). This can cause the current collecting sheet to reach high temperatures near the edges of the coated sections, reducing the peel strength between the electrode layer and the current collecting sheet and potentially causing the electrode layer to peel off, resulting in deterioration of the quality of the electrode layer edges. Furthermore, the current collecting sheet can be oxidized, resulting in a decrease in battery performance.

[0017] The present disclosure is characterized in that in the drying step, hot air at a predetermined temperature and at a predetermined air speed is supplied to laser irradiation sections X1 to X5, which have been irradiated with laser light from each of the laser heads L1 to L5, on the conveyed coated sheet 10. For example, to laser irradiation section X1, which has been irradiated with laser light from laser head L1, hot air at a predetermined temperature and at a predetermined air speed is supplied from hot air outlet H2 until the next laser irradiation from laser head L2.

[0018] According to the present disclosure, in the drying process of a coated sheet, hot air at a predetermined temperature and speed is supplied to the laser irradiation section X between laser irradiations, allowing the laser irradiation section to be adequately cooled at a hot air temperature that is not too low. Furthermore, exposure to hot air also improves the drying effect of the coated section. Therefore, without extending the drying time, the temperature rise of the current collecting sheet due to continuous laser irradiation can be suppressed, and an electrode sheet can be produced in which the decrease in peel strength between the electrode layer and the current collecting sheet is suppressed.

[0019] 1. Preparation process The preparation process in the present disclosure is a process of preparing a coated sheet 10 having a coated portion 2 coated with an electrode material on a first surface S1 of a current collecting sheet having a longitudinal direction in a first direction D1, as shown in Figure 1.

[0020] The current collecting sheet has a longitudinal direction in the first direction. The current collecting sheet has a first surface S1 which is one surface in the thickness direction, and a second surface S2 which is the reverse side of the first surface S1. The current collecting sheet is preferably used as a current collector such as a negative electrode current collector, a positive electrode current collector, or a bipolar current collector. For example, a metal foil such as aluminum, copper, SUS, or nickel is used as the current collecting sheet. The thickness of the current collecting sheet is, for example, 0.1 μm or more, and may be 1 μm or more. On the other hand, the thickness of the current collecting sheet is, for example, 1 mm or less, and may be 100 μm or less.

[0021] The electrode material may be a negative electrode material (a material for a negative electrode active material layer). The negative electrode material includes, for example, a negative electrode active material, a conductive material, a binder, and a solvent. The electrode material may also be a positive electrode material (a material for a positive electrode active material layer). The positive electrode material includes, for example, a positive electrode active material, a conductive material, a binder, and a solvent. These materials are not particularly limited, and known materials may be used.

[0022] As shown in Figure 1, coated sheet 10 may have uncoated sections 3 that are not coated with electrode material. For example, a coated section may be formed in the central section in the lateral direction of the current collecting sheet, and uncoated sections may be formed on both ends of the current collecting sheet in the lateral direction, sandwiching the coated section. Coated sheet 10 may also have intermittent sections 4 that are not coated with electrode material.

[0023] The method for preparing the coated sheet is not particularly limited, but for example, the coated sheet can be produced by conveying the current collecting sheet in a first direction with a conveyor while applying the electrode material to the first surface of the current collecting sheet with a coater to form a coated portion. In this case, the electrode material may be applied continuously or intermittently.

[0024] As shown in FIG. 2, the coating machine 40 is preferably positioned upstream in the conveying direction of a laser light irradiator equipped with laser heads L1 to L5 and a hot air supplying machine equipped with hot air outlets H1 to H6, which will be described later, and this process and a drying process, which will be described later, are preferably performed consecutively.

[0025] 2.Drying process The drying process in the present disclosure is a process of irradiating laser light from multiple laser heads onto the coated sheet while conveying the coated sheet in a first direction, thereby drying the coated portion and obtaining an electrode sheet. In this process, hot air having a temperature of 50°C to 140°C and a wind speed of 5 m / s or more is supplied to the laser-irradiated portion of the conveyed coated sheet that has been irradiated with laser light from each laser head until the next laser irradiation.

[0026] In the drying process, the coated sheet is transported in a first direction, i.e., in the longitudinal direction of the coated sheet. For example, in FIG. 2, the coated sheet is transported from the left side of the drawing to the right side by transport rolls 30. The transport speed of the coated sheet is, for example, constant. As the coated sheet 10 is transported and passes below multiple laser heads L1 to L5, laser light from each of the laser heads L1 to L5 is irradiated onto the coated sheet 10.

[0027] The multiple laser heads are preferably arranged side by side at intervals along the first direction above the conveyed coated sheet. The intervals (the distance between adjacent laser heads) may be the same or different. The laser head typically incorporates an optical lens (not shown) having a predetermined curvature. The laser head irradiates laser light oscillated by a laser oscillator (not shown) through the optical lens toward the coated sheet.

[0028] In this process, hot air at a predetermined temperature and speed is supplied to the laser irradiation section (for example, laser irradiation section X1 irradiated with laser light from laser head L1) irradiated with laser light from each of the laser heads L1 to L5 until the next laser irradiation (laser irradiation from laser head L2).

[0029] The temperature of the hot air is 50°C or higher, and may be 60°C or higher, or 70°C or higher. If the hot air temperature is too low, the coated area will be cooled and the drying time will be longer. On the other hand, the temperature of the hot air is 140°C or lower, and may be 110°C or lower, or may be 90°C or lower. If the hot air temperature is too high, excessive drying will occur and the peel strength will be reduced. In this way, by cooling appropriately at a hot air temperature that is not too low, it is possible to prevent the current collecting sheet from becoming too hot due to laser irradiation without extending the drying time, and good peel strength can be obtained.

[0030] The hot air velocity is 5 m / s or more, and may be 10 m / s or more. If the hot air velocity is low, the cooling effect will be low. This will result in excessive drying and a decrease in peel strength. On the other hand, the hot air velocity may be 60 m / s or less, and may be 30 m / s or less.

[0031] The hot air is preferably blown out from a plurality of hot air outlets H1 to H6 arranged at intervals along the first direction, as shown in Fig. 2. Each of the hot air outlets H1 to H6 blows hot air from above toward the surface of the coated sheet 10 being conveyed. As shown in Fig. 2, the plurality of hot air outlets H1 to H6 are preferably arranged alternately with the plurality of laser heads L1 to L5 in the first direction D1.

[0032] The energy density of the laser light irradiated from the laser head onto the coated sheet is, for example, 0.1 W / cm 2 or more, and 0.2 W / cm 2 On the other hand, the energy density may be, for example, 1.0 W / cm 2 less than 0.5W / cm 2 It may be the following:

[0033] The coated portion is dried in the drying step to obtain the electrode sheet 20. As shown in Fig. 2, the electrode sheet 20 is taken up by a take-up roll 31, for example.

[0034] 3. Other processes The electrode sheet manufacturing method according to the present disclosure may include a coating step of forming a coated portion on the second surface of the current collecting sheet, where the electrode material is coated. In this case, it is preferable that the coated portion on the second surface be formed at a position that overlaps the coated portion on the first surface in a plan view. Furthermore, after the coating step, it may include a drying step of drying the coated portion on the second surface. In this case, it is preferable that the second surface of the current collecting sheet is also irradiated with laser light and blown with hot air, similar to the first surface.

[0035] The method for producing an electrode sheet according to the present disclosure may include a pressurizing step of pressing the electrode sheet in a thickness direction, whereby the electrode layer is pressed against the current collector sheet.

[0036] 4. Electrode sheet FIG. 4 is a schematic cross-sectional view showing an example of an electrode sheet manufactured in the present disclosure. As shown in FIG. 4(a), an electrode sheet 20 has a current collector sheet 1 and an electrode layer 5 formed on a first surface S1 of the current collector sheet 1. In FIG. 4(a), the electrode layer is formed intermittently. As shown in FIG. 4(b), the electrode sheet 20 may also have an electrode layer 6 on a second surface S2 of the current collector sheet 1. In FIG. 4(b), the electrode layer 6 is formed intermittently. That is, as shown in FIG. 4(b), the electrode sheet may have electrode layers 5 and 6 on both the first and second surfaces of the current collector sheet.

[0037] Such an electrode sheet is used in the manufacture of a battery and may be a positive electrode sheet or a negative electrode sheet. When the electrode sheet in the present disclosure is a positive electrode sheet, it is combined with a negative electrode sheet and a separator to form an electrode assembly. Similarly, when the electrode sheet in the present disclosure is a negative electrode sheet, it is combined with a positive electrode sheet and a separator to form an electrode assembly. Furthermore, the electrode layer 5 shown in FIG. 4(a) may be a positive electrode active material layer or a negative electrode active material layer. The electrode layer 5 and the electrode layer 6 shown in FIG. 4(b) may both be positive electrode active material layers or both be negative electrode active material layers, or one may be a positive electrode active material layer and the other a negative electrode active material layer.

[0038] The type of battery in which the electrode body is used is not particularly limited, and examples thereof include lithium-ion secondary batteries. Examples of uses of the battery include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric vehicles (BEVs), gasoline-powered vehicles, and diesel-powered vehicles. In particular, the battery is preferably used as a driving power source for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or electric vehicles (BEVs). The battery may also be used as a power source for mobile objects other than vehicles (for example, trains, ships, and aircraft), or as a power source for electrical appliances such as information processing devices.

[0039] B. Electrode sheet manufacturing equipment The electrode sheet manufacturing apparatus of the present disclosure is an electrode sheet manufacturing apparatus that produces an electrode sheet by drying a coated sheet having a coated portion coated with an electrode material arranged on a first surface of a current collecting sheet having a longitudinal direction in a first direction, and is provided with: a conveying machine for conveying the coated sheet in the first direction; a laser light irradiator having a plurality of laser heads that irradiate the coated sheet with laser light; and a hot air supplying machine having a plurality of hot air outlets that blow hot air onto the coated sheet and a control unit that controls the temperature of the hot air blown out of the hot air outlets to be not less than 50°C and not more than 140°C, and the air speed to be not less than 5 m / s.

[0040] According to the electrode sheet manufacturing device of the present disclosure, it is possible to manufacture an electrode sheet that can suppress a decrease in the peel strength between the electrode layer and the current collector sheet while suppressing an increase in drying time.

[0041] The conveying device in the present disclosure is not particularly limited as long as it is capable of conveying a coated sheet, and examples thereof include conveying rollers. The laser light irradiator includes a plurality of the above-described laser heads. The number of laser heads included in the laser light irradiator may be, for example, two or more, five or more, or ten or more. The laser light irradiator may further include a laser oscillator. The hot air supplying device has a control unit that controls multiple hot air outlets and the temperature and air speed of the hot air. The control unit controls the temperature of the hot air blown out from the hot air outlets to between 50°C and 140°C and the air speed to 5 m / s or more. Note that if the distance between the hot air outlets and the coated sheet is sufficiently short, the temperature of the hot air blown out from the hot air outlet and the temperature of the hot air supplied to the coated sheet will be approximately the same. The distance between the hot air outlet and the coated sheet is, for example, 20 cm or less, and may be 19 cm or less. Alternatively, it may be, for example, 0.1 cm or more, or 0.2 cm or more. The number of hot air outlets included in the hot air supplier may be, for example, two or more, five or more, or ten or more. [Example]

[0042] The present disclosure will be further described below with reference to examples and comparative examples.

[0043] (Examples 1 to 11, Comparative Examples 1 to 4) (Coating sheet preparation process) A negative electrode material containing a negative electrode active material (graphite), a binder (styrene butadiene rubber), a conductive material (carbon nanotubes), and a thickener (carboxymethyl cellulose) was intermittently coated on a first surface of a copper foil sheet having a longitudinal direction in a first direction, along the first direction, to prepare a coated sheet on the first surface of the copper foil sheet in which coated areas coated with the negative electrode material and intermittent areas not coated with the negative electrode material were alternately arranged along the first direction.

[0044] (drying process) Next, the coated sheet was transported and passed under multiple laser heads and multiple hot air outlets arranged alternately, whereby it was irradiated with laser light (energy density 0.5 W / cm2 The coated area was dried by blowing hot air onto the coated sheet. The temperature and speed of the hot air supplied to the coated sheet were controlled as shown in Table 1.

[0045] [evaluation] (Peel strength measurement) Using the electrode sheet obtained above, the peel strength when the electrode layer was peeled from the copper foil sheet was measured according to the method of "JIS K 6854-1 (Adhesives - Peel Adhesion Strength Test Method - Part 1: 90 degree peel)". A value of 0.12 N / cm or more was evaluated as OK, and a value of less than 0.12 N / cm was evaluated as NG.

[0046] (Measurement of temperature of current collector sheet) The temperature of the current collector sheet of the electrode sheet obtained above was measured, and it was evaluated as NG when it was 150° C. or higher, and OK when it was less than 150° C. The results are shown in Table 1.

[0047] [Table 1]

[0048] As shown in Table 1, it was confirmed that, when the temperature of the hot air is 50°C or higher and 140°C or lower and the air speed is 5 m / s or higher, an electrode sheet can be produced in which an increase in drying time is suppressed while a decrease in peel strength between the electrode layer and the current collecting sheet is suppressed (Examples 1 to 11).

[0049] On the other hand, in Comparative Example 1, the hot air temperature was too low, which cooled the coated area and increased the drying time. In Comparative Example 2, the hot air temperature was too high, which resulted in over-drying and a decrease in peel strength. In Comparative Examples 3 and 4, the cooling effect was low due to the low air velocity, resulting in a decrease in peel strength.

[0050] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure. [Explanation of symbols]

[0051] 1... Current collecting sheet 2... Coating department 3...Uncoated area 4...Intermittent section 5,6...electrode layer 10...Coated sheet 20...Electrode sheet

Claims

1. a preparation step of preparing a coated sheet having a coated portion coated with an electrode material on a first surface of a current collecting sheet having a longitudinal direction in a first direction; a drying step of irradiating the coated portion with laser light from a plurality of laser heads arranged side by side in the first direction while transporting the coated sheet in the first direction, thereby drying the coated portion to obtain an electrode sheet, the drying step includes supplying hot air having a temperature of 50°C or higher and 140°C or lower and a wind speed of 5 m / s or higher to a laser irradiation section of the coated sheet being conveyed, the laser irradiation section being irradiated with laser light from each laser head, until the next laser irradiation; In the drying step, drying by irradiation with the laser light and drying by the hot air are performed, and the drying by the hot air is drying that cools the laser irradiated portion, the coated sheet has an intermittent portion between adjacent coated portions in the first direction, where no coated portion is present, In the drying step, the adjacent coated portions as well as the intermittent portions are heated by continuous laser irradiation.

2. The method for manufacturing an electrode sheet according to claim 1 , wherein the hot air is blown out from a plurality of hot air outlets arranged alternately with the plurality of laser heads in the first direction.

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