Manufacturing method for electrode

Abstract

To provide a manufacturing method for an electrode, in which a binder can be removed from a surface of a coating part efficiently in a short time in a drying step.SOLUTION: A manufacturing method for an electrode in the present disclosure includes: a preparing step of preparing a coating sheet including a current collector sheet with a longitudinal direction and a coating part disposed on a first surface of the current collector sheet and containing an electrode material including an active material and a binder; a drying step of drying the coating part while conveying the coating sheet in the longitudinal direction; and a removing step of removing the binder from a surface of the coating part by irradiating the coating part after the drying step with a laser. In the removing step, the laser has a wavelength of 353 nm or less and the laser has an energy density of 0.05 J / cm2 or more.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] 2. Description of the Related Art Known technology relating to a manufacturing method of an electrode sheet used in manufacturing batteries such as lithium-ion secondary batteries is a method in which an electrode material is applied to a conveyed current collector sheet to form a coated portion, and the coated portion is dried to obtain an electrode layer.

[0003] For example, Patent Document 1 discloses a technique for removing the binder from the surface of an electrode layer by irradiating the electrode layer with a CW laser after drying. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-171020 A Summary of the Invention [Problem to be solved by the invention]

[0005] From the viewpoint of reducing input and output resistance and improving battery performance, it is preferable that the binder is removed from the surface of the electrode layer (the surface opposite to the current collector sheet). Also, from the viewpoint of manufacturing efficiency, it is preferable that the binder can be removed efficiently in a short 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 that can efficiently remove a binder from the surface of a coated portion in a short period of time. [Means for solving the problem]

[0007] [1] The present invention has a preparation step of preparing a coated sheet having a current collecting sheet having a longitudinal direction and a coated portion disposed on a first surface of the current collecting sheet and containing an electrode material including an active material and a binder; a drying step of drying the coated portion while conveying the coated sheet in the longitudinal direction; and a removal step of irradiating the coated portion after the drying step with a laser to remove the binder from a surface of the coated portion, wherein the wavelength of the laser in the removal step is 353 nm or less and the energy density of the laser is 0.05 J / cm. 2 This completes the method for producing an electrode. Effect of the Invention

[0008] The present disclosure has the effect of being able to efficiently remove the binder from the surface of the coated portion in a short period of time. [Brief description of the drawings]

[0009] [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. [Diagram 2] FIG. 2 is a schematic side view illustrating a drying process in the present disclosure. [Diagram 3] 1 is a schematic cross-sectional view illustrating an electrode according to the present disclosure. [Figure 4] 1 shows cross-sectional SEM images showing the results of an example and a reference example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The electrode manufacturing method according to the present disclosure will be described in detail below with reference to the drawings. Each of the drawings shown below is a schematic illustration, and the size and shape of each part are appropriately exaggerated for ease of understanding.

[0011] Fig. 1(a) is a schematic plan view illustrating a coated sheet prepared in the preparation step, and Fig. 1(b) is a cross-sectional view taken along line AA in Fig. 1(a) Fig. 2 is a schematic side view showing the drying step as viewed from the short side direction.

[0012] As shown in FIGS. 1(a) and (b), in the method for producing an electrode according to the present disclosure, first, a coated sheet 10 is prepared, which includes a current collecting sheet 1 having a longitudinal direction D1 and a coated portion 2 arranged on a first surface S1 of the current collecting sheet 1 (preparation step). The coated portion 2 contains an electrode material including an active material and a binder. Next, the coated portion 2 is dried while the coated sheet 10 is transported in the longitudinal direction D1 (drying step). Then, a laser is irradiated onto the coated portion 2 after the drying step to remove the binder from the surface of the coated portion 2 (removal step). In the removal step, the wavelength of the laser is 353 nm or less, and the energy density of the laser is 0.05 J / cm. 2 That's all.

[0013] According to the present disclosure, a laser having a predetermined wavelength and energy density is irradiated onto the dried coated portion, so that the binder on the surface of the coated portion can be decomposed and removed efficiently in a short period of time.

[0014] Since the binder in the electrode layer is a material for suppressing peeling from the current collector sheet, the binder located on the surface of the electrode layer (the surface opposite to the current collector sheet) does not contribute to suppressing peeling from the current collector sheet and also causes an increase in resistance. According to the present disclosure, by irradiating such a binder with a laser of a predetermined wavelength and energy density, the molecular bonds of the binder can be cut efficiently in a short time, and the binder can be modified and removed. As a result, an electrode that can suppress the battery resistance when used in a battery can be manufactured. In addition, by removing the binder, a groove that can contact the electrolyte can be formed on the surface of the electrode layer, so that the contact area between the electrolyte and the electrode layer can be increased, resulting in an electrode that can suppress the resistance more when used in a battery. The same applies when the coating portion contains a thickener.

[0015] Furthermore, if the coated area contains a conductive material, the conductive material on the surface of the coated area, which has a low contribution to the formation of an electronic conduction path, can also be modified and removed by irradiating it with a laser.

[0016] By using a specific laser, the area of ​​the laser irradiation can be increased, so that the binder can be decomposed efficiently in a short time. As a result, the manufacturing process time of the electrode can be shortened, and the electrode can be manufactured with high productivity.

[0017] 1. Preparation process The preparing step in the present disclosure is a step of preparing a coated sheet having a current collecting sheet with a longitudinal direction and a coated portion disposed on a first surface of the current collecting sheet.

[0018] As shown in FIG. 1(a), the current collector sheet 1 has a longitudinal direction D1. The current collector sheet 1 usually has a lateral direction D2. As shown in FIG. 1(b), the current collector sheet 1 has a first surface S1 which is one surface in the thickness direction, and usually has a second surface S2 which is the reverse side of the first surface S1. The material of the current collector sheet is preferably a material used as a current collector such as a negative electrode current collector, a positive electrode current collector, or a bipolar current collector. Examples of the material of the current collector sheet include metals such as aluminum, copper, SUS, and nickel. The thickness of the current collector sheet is, for example, 0.1 μm or more and 100 μm or less.

[0019] The coated portion is disposed on the first surface of the current collecting sheet, and contains an electrode material including an active material and a binder. The electrode material may also contain at least one of a conductive material, an electrolyte, and a thickener. The coated portion is a portion that becomes an electrode layer, which will be described later. The coated portion may be disposed only on the first surface of the current collecting sheet, or may be disposed on both the first surface and the second surface of the current collecting sheet.

[0020] The active material may be a positive electrode active material. Examples of the positive electrode active material include oxide active materials. Examples of the oxide active material include LiCoO2, LiMnO2, LiNiO2, LiVO2, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc., rock salt layered active materials, LiMn2O4, Li(Ni 0.5 Mn 1.5)O4 and the like; and olivine type active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCuPO4.

[0021] The active material may be a negative electrode active material. Examples of the negative electrode active material include carbon active materials, oxide active materials, and metal active materials. Examples of the carbon active material include mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon. Examples of the oxide active material include Nb2O5, Li4Ti5O 12 and SiO. Metal active materials include, for example, In, Al, Si, and Sn.

[0022] Examples of the binder include fluorine-containing binders such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), rubber-based binders such as butadiene rubber, and acrylic-based binders.

[0023] Examples of conductive materials include carbon materials, metal particles, and conductive polymers. Examples of carbon materials include particulate carbon materials such as acetylene black (AB) and ketjen black (KB); and fibrous carbon materials such as carbon fiber, carbon nanotubes (CNT), and carbon nanofibers (CNF). Examples of thickeners include polysaccharides such as carboxymethylcellulose and methylcellulose.

[0024] Examples of the electrolyte include inorganic solid electrolytes such as sulfide solid electrolytes and oxide solid electrolytes. Examples of the sulfide solid electrolyte include solid electrolytes containing Li, X (X is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and S. The sulfide solid electrolyte may further contain at least one of O and halogen elements. Examples of the halogen elements include F, Cl, Br, and I.

[0025] Examples of oxide solid electrolytes include Li2O-B2O3-P2O5, Li2O-SiO2, Li2O-B2O3, Li 1.3 Al 0.3 Ti 0.7 (PO4)3, Li5La3Ta2O 12 , Li7La3Zr2O 12 , Li6BaLa2Ta2O 12 , Li 3.6 S 0.6 P 0.4 O4, Li4SiO4, Li3PO4, Li3PO 4-3 / 2x N x (x≦1).

[0026] Moreover, the coated sheet usually has an uncoated portion that is disposed on the first surface of the current collecting sheet and does not contain an electrode material. The uncoated portion can be regarded as a portion of the coated sheet where the current collecting sheet is exposed. As shown in FIG. 1(a), the uncoated portion 3 is disposed at the ends (both ends) of the coated portion 2 in the short direction D2 of the current collecting sheet 1. As shown in FIGS. 1(a) and 1(b), when the coated portion 2 is disposed intermittently in the longitudinal direction D1, the uncoated portion 3 is also disposed at the ends (both ends) of the coated portion 2 in the longitudinal direction D1. In other words, the uncoated portion 3 is disposed around the entire outer edge of the coated portion 2.

[0027] The coated sheet can be prepared by mixing the above-mentioned electrode materials together with a solvent such as water to prepare an electrode slurry, and applying the electrode slurry to the first surface of a current collector sheet.

[0028] 2.Drying process The drying step in the present disclosure is a step of drying the coated portion while transporting the coated sheet in the longitudinal direction.

[0029] As shown in Fig. 2, in the drying step, a drying device 20 is usually used to dry the coated part 2. The drying device may be a conventionally known device capable of drying the coated part, such as a hot air device or a laser device. The drying method and drying conditions are not particularly limited and may be set appropriately.

[0030] 3.Removal process The removing step in the present disclosure is a step of irradiating the coated portion after the drying step with a laser to remove the binder from the surface of the coated portion.

[0031] In the drying process, the wavelength of the irradiated laser is 353 nm or less. The wavelength of the laser may be 350 nm or less, 300 nm or less, or 250 nm or less. On the other hand, the laser wavelength may be, for example, 193 nm or more, or 200 nm or more.

[0032] In the drying process, the energy density of the irradiated laser is 0.05 J / cm 2 That's it. The energy density of the laser is 0.1 J / cm 2 It may be 0.3 J / cm or more. 2 It may be more than 0.5 J / cm 2 It may be 0.7 J / cm or more. 2 On the other hand, the energy density of the laser may be, for example, 2 J / cm 2 Less than or equal to 1.5 J / cm 2 It may be less than or equal to 1.2 J / cm 2 It may be the following.

[0033] 3. Electrode Fig. 3 is a schematic cross-sectional view showing an example of an electrode manufactured in the present disclosure. As shown in Fig. 3, the electrode has a current collecting sheet 101 and an electrode layer 102 formed on a first surface S1 of the current collecting sheet 101. In Fig. 3, the electrode layer 102 is formed intermittently. Although not particularly shown, the electrode layer 102 may be formed on the first surface S1 and the second surface S2 of the current collecting sheet. In addition, the shape of the electrode is usually a sheet having a longitudinal direction and a lateral direction.

[0034] Such an electrode (electrode sheet) is usually used in the manufacture of a battery. The electrode sheet 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 body. 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 body. Also, the electrode layer 102 shown in FIG. 3 may be a positive electrode active material layer or a negative electrode active material layer.

[0035] The electrode layer contains at least one of a positive electrode active material and a negative electrode active material, a conductive material, and a binder, and may further contain an electrolyte. These materials are as described above.

[0036] The type of battery in which the electrode is used is not particularly limited, and may be, for example, a lithium ion secondary battery. 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 automobiles, and diesel automobiles. 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 moving objects other than vehicles (for example, railways, ships, and aircraft), and may also be used as a power source for electrical appliances such as information processing devices.

[0037] The present disclosure is not limited to the above-described embodiment. The above-described embodiment is merely an example, and any configuration that is substantially the same as the technical idea described in the claims of the present disclosure and that exhibits similar effects is included in the technical scope of the present disclosure. EXAMPLES

[0038] [Example 1] A negative electrode active material (artificial graphite), a thickener (carboxymethyl cellulose: CMC), and a binder (styrene butadiene rubber: SBR) were added to water and mixed to obtain a negative electrode slurry. The obtained negative electrode slurry was applied to a current collector sheet (copper foil) having a longitudinal direction to obtain a current collector sheet and a coated sheet having a coated portion.

[0039] The coated sheet was conveyed in the longitudinal direction while the coated portion was laser-dried. After that, a laser (excimer laser) with a wavelength of 248 nm was irradiated on the dried coated portion at 1 J / cm. 2 The irradiation was performed at an energy density of 100 nm to 150 nm. As a result, an electrode having a current collecting sheet and an electrode layer (negative electrode layer) was produced.

[0040] [Examples 2 to 4, Comparative Examples 1 and 2] An electrode was produced in the same manner as in Example 1, except that the wavelength and energy density of the laser irradiated to the coated portion after drying were changed as shown in Table 1.

[0041] [evaluation] For each electrode obtained, a cross-sectional SEM image of the negative electrode layer was obtained to confirm whether the binder had been removed from the coated surface (negative electrode layer surface). The results are shown in Table 1. When the binder was sufficiently removed in a short time, it was marked with a circle, and otherwise it was marked with an X. Also, cross-sectional SEM images of Examples 1, 3, and 4 are shown in FIG. 4 together with a cross-sectional SEM image of a reference example (Ref) in which an electrode was prepared in the same manner as Example 1 except that laser removal was not performed. In FIG. 4, the darkened areas represent the binder (residual binder).

[0042] [Table 1]

[0043] As shown in Table 1 and Figure 4, it was confirmed that the binder can be removed from the surface of the coated part in a short time by irradiating a laser with a specified wavelength and a specified energy density. Even when the time was extended under the same conditions as in Comparative Example 2, the binder could not be removed. This is thought to be because the energy density was too low. [Explanation of symbols]

[0044] 1...Current collecting sheet 2 … Coating section 3 … Uncoated area 10...Coated sheet 20...Drying equipment

Claims

[Claim 1] a preparation step of preparing a coated sheet having a current collecting sheet having a longitudinal direction and a coated portion disposed on a first surface of the current collecting sheet and containing an electrode material including an active material and a binder; a drying step of drying the coated portion while transporting the coated sheet in the longitudinal direction; a removing step of irradiating the coated portion after the drying step with a laser to remove the binder from a surface of the coated portion, In the removal step, the wavelength of the laser is 353 nm or less, and the energy density of the laser is 0.05 J / cm ２ This completes the method for producing an electrode.

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