Electrode active material layer, electrode stack, and method for manufacturing an electrode stack

Abstract

This disclosure aims to provide an electrode active material layer having different mechanical properties in each portion. [Solution] An electrode active material layer 100 having an electrode active material and a binder 110, wherein in the peripheral region of the electrode active material layer 100, when the cross-section in the thickness direction of the electrode active material layer 100 is divided into five equal parts from a first peripheral portion to a fifth peripheral portion from one surface to the other surface, the area ratio of the binder 110 in the fifth peripheral portion and the area ratio of the binder 110 in the first peripheral portion satisfy a predetermined relationship, and in the central region of the electrode active material layer 100, when the cross-section in the thickness direction of the electrode active material layer 100 is divided into five equal parts from a first central portion to a fifth central portion from one surface to the other surface, the area ratio of the binder 110 in the fifth central portion and the area ratio of the binder 110 in the first central portion satisfy a predetermined relationship.

Description

[Technical Field]

[0001] This disclosure relates to an electrode active material layer, an electrode stack, and a method for manufacturing an electrode stack. [Background technology]

[0002] Various proposals have been made to improve the physical properties of the electrode active material layer by adjusting the distribution of the binder present within the electrode active material layer and the shape of the electrode active material layer.

[0003] Patent Document 1 discloses a method for manufacturing an electrode, comprising the steps of forming an active material layer containing an active material and a binder, and removing the binder from the surface of the active material layer by irradiating the surface of the active material layer with a pulse laser having a pulse width of 100 ns or less. Patent Document 1 states that, according to the disclosure in Patent Document 1, electrodes with reduced resistance can be manufactured.

[0004] Patent Document 2 discloses a storage battery comprising a positive electrode having a positive electrode layer containing a positive electrode active material on a positive electrode current collector foil, and a negative electrode having a negative electrode layer containing a negative electrode active material on a negative electrode current collector foil, stacked with these electrodes sandwiched between separators; a battery container housing the electrode group; and an electrolyte filled in the battery container, wherein the positive electrode active material and the negative electrode active material are distributed substantially equally within the positive and negative electrode layers, and regions with different ratios of the electrolyte and the positive and negative electrode active materials are provided within the positive and negative electrode layers where the positive and negative electrode active materials are distributed substantially equally. Patent Document 2 states that, according to the disclosure in Patent Document 2, the amount of heat generated can be adjusted without reducing the energy density.

[0005] Patent Document 3 discloses an electrode shape control method that includes a molding step in which a laser is irradiated onto at least a portion of an electrode sheet coated with electrode slurry, and the electrode slurry in the laser-irradiated area is moved to an adjacent area to shape the electrode slurry. Patent Document 3 states that, according to the disclosure in Patent Document 3, it is possible to provide an electrode shape control method and an electrode manufacturing method that can control the shape of the electrode after electrode coating while minimizing capacitance loss.

[0006] On the other hand, laser drying is known as a method for drying electrode slurries coated on current collector layers. Compared to hot air drying, laser drying has the advantage of consuming less energy and having a lower environmental impact.

[0007] Patent Document 4 discloses an electrode manufacturing method comprising: a transport step of transporting an electrode body coated with at least one electrode material by a transport unit; and a drying step of drying the electrode material while transporting the electrode body by the transport unit, wherein the drying step includes an irradiation step of drying the electrode material by irradiating it with a laser when the electrode body is transported to at least one first position in the transport direction of the transport unit; and a recovery step of recovering the vapor generated as a result of the laser irradiation of the electrode material by a vapor recovery unit provided at least one second position adjacent to the first position in the transport direction. Patent Document 4 states that, according to the disclosure in Patent Document 4, it is possible to suppress a decrease in drying efficiency when drying the electrode material with a laser. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2023-161721 [Patent Document 2] Japanese Patent Publication No. 2013-020802 [Patent Document 3] Special Publication 2024-518633 [Patent Document 4] JP-A-2023-169591

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] In order to provide good performance as a battery, the electrode active material layer is required to have various mechanical properties such as the adhesion to the current collector layer and its own flexibility. These required mechanical properties may vary for each part of the electrode active material layer.

[0010] Therefore, an object of the present disclosure is to provide an electrode active material layer having different mechanical properties for each part.

MEANS FOR SOLVING THE PROBLEMS

[0011] The present disclosure achieves the above object by the following means. <Aspect 1> An electrode active material layer having an electrode active material and a binder, the electrode active material layer satisfying the following relationship: (B 5p / B 1p ) / (B 5c / B 1c )≥1.50 B 5p ≥B 1p B 5p : In the peripheral region of the electrode active material layer, when the cross-section in the thickness direction of the electrode active material layer is divided into five equal parts from one surface to the other surface into the first peripheral part to the fifth peripheral part, the area ratio of the binder in the fifth peripheral part, B 1p : The area ratio of the binder in the first peripheral part, B 5c : In the central region of the electrode active material layer, when the cross-section in the thickness direction of the electrode active material layer is divided into five equal parts from one surface to the other surface into the first central part to the fifth central part, the area ratio of the binder in the fifth central part, B 1c : The area ratio of the binder in the first central part. <Aspect 2> The electrode active material layer according to Embodiment 1 that satisfies the following relationship: B 5p / B 5c ≥1.20. <Aspect 3> The electrode active material layer according to embodiment 1 or 2, satisfying the following relationship: B 1p / B 1c ≤0.80. <Aspect 4> The electrode active material layer according to any one of embodiments 1 to 3, wherein the content of the binder is 0.5% by mass or more relative to the electrode active material layer. <Aspect 5> The electrode active material layer according to any one of embodiments 1 to 4, wherein the thickness of the electrode active material layer is 2.0 mm or less. <Pattern 6> To provide an electrode mixture slurry layer containing the above-mentioned electrode active material, the above-mentioned binder, and dispersion medium. Dry the electrode mixture slurry layer mentioned above. including and In the above drying process, the drying rate in the peripheral region of the electrode mixture slurry layer is different from the drying rate in the central region of the electrode mixture slurry layer. A method for producing an electrode active material layer according to any one of embodiments 1 to 5. <Aspect 7> An electrode laminate having a current collector layer and an electrode active material layer according to any one of embodiments 1 to 5 laminated on the current collector layer. <Aspect 8> The electrode laminate according to embodiment 7, wherein the peel strength between the current collector layer and the electrode active material layer in the central region of the electrode active material layer is 0.06 N / cm or more. <Pattern 9> To provide a current collector layer having a conductive layer and a carbon coating layer on the conductive layer, To provide an electrode mixture slurry layer containing the electrode active material, the binder, and the dispersion medium on at least a portion of the carbon coating layer, and The electrode mixture slurry layer and the adjacent region adjacent to the electrode mixture slurry layer and having the carbon coating layer are irradiated with laser light to dry the electrode mixture slurry layer. A method for manufacturing an electrode laminate according to embodiment 7 or 8, including the method described in embodiment 7 or 8. <Aspect 10> The method according to embodiment 9, wherein the laser light absorption rate of the carbon coating layer with respect to the above-mentioned laser light is 0.2 or more. <Aspect 11> The method according to embodiment 9 or 10, wherein the thermal conductivity of the conductive layer is 50 W / m·K or more. [Effects of the Invention]

[0012] According to this disclosure, it is possible to provide an electrode active material layer having different mechanical properties in each part. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a front cross-sectional view illustrating the electrode active material layer of this disclosure. [Figure 2] Figure 2 is a top view and a bottom view illustrating the electrode active material layer of this disclosure. [Figure 3] Figure 3 is a schematic diagram illustrating the method for manufacturing the electrode stack according to this disclosure. [Figure 4] Figure 4 is a schematic diagram illustrating the examples and comparative examples. [Figure 5] Figure 5 is a schematic diagram illustrating the examples and comparative examples. [Modes for carrying out the invention]

[0014] 《Electrode active material layer》 The electrode active material layer of this disclosure is An electrode active material layer having an electrode active material and a binder, satisfying the following relationship: (B 5p / B 1p ) / (B 5c / B 1c)≧1.50 B 5p ≥B 1p B 5p : In the peripheral region of the electrode active material layer, when the cross-section in the thickness direction of the electrode active material layer is divided into five equal parts from one surface to the other, from the first peripheral portion to the fifth peripheral portion, the area ratio of the binder in the fifth peripheral portion, B 1p : Area ratio of the binder in the first peripheral portion mentioned above, B 5c : In the central region of the electrode active material layer, when the cross-section in the thickness direction of the electrode active material layer is divided into five equal parts from one surface to the other, from the first central part to the fifth central part, the area ratio of the binder in the fifth central part, B 1c : The area ratio of the binder in the first central portion mentioned above.

[0015] The electrode active material layer of this disclosure can provide different mechanical properties in each part.

[0016] Specifically, for example, as shown in Figure 1, the electrode active material layer 100 of this disclosure has an electrode active material (not shown) and a binder 110. The degree of binder segregation in the peripheral region 300 is greater than the degree of binder segregation in the central region 400. The degree of binder segregation in the peripheral region 300 is "B 5p / B 1p It is expressed as ", and the degree of binder segregation in the central region 400 is "B 5c / B 1c This is represented as follows: Due to the difference in the degree of segregation of the binder between the peripheral region 300 and the central region 400, the peripheral region 300 and the central region 400 have different mechanical properties.

[0017] Here, the cross-section in the thickness direction of the electrode active material layer 100 is virtually divided equally into five parts (101-105), and the binder area ratio in the first to fifth parts (101-105) of the peripheral region 300 is "B 1p ~B 5pThe binder area ratio in the first to fifth parts (101 to 105) of the central region 400 is "B 1c ~B 5c "

[0018] The embodiments of this disclosure will be described in detail below. However, this disclosure is not limited to the embodiments described below and can be implemented in various ways within the scope of the gist of this disclosure.

[0019] The electrode active material layer of this disclosure satisfies the following relationship: (B 5p / B 1p ) / (B 5c / B 1c )≧1.50 B 5p ≥B 1p B 5p : In the peripheral region of the electrode active material layer, when the cross-section in the thickness direction of the electrode active material layer is divided into five equal parts from one surface to the other, from the first peripheral portion to the fifth peripheral portion, the area ratio of the binder in the fifth peripheral portion, B 1p : Area ratio of the binder in the first peripheral portion mentioned above, B 5c : In the central region of the electrode active material layer, when the cross-section in the thickness direction of the electrode active material layer is divided into five equal parts from one surface to the other, from the first central part to the fifth central part, the area ratio of the binder in the fifth central part, B 1c : The area ratio of the binder in the first central portion mentioned above.

[0020] In this specification, the term "peripheral region" refers to the region within the electrode active material layer that is included in the longitudinal and widthwise directions of the electrode active material layer, from the edge to 20%, 10%, or 5% of the total length, respectively, as shown in Figures 1 and 2.

[0021] In this specification, the term "central region" refers to the region within the electrode active material layer that is included in the longitudinal and widthwise directions of the electrode active material layer, from the center to 20%, 10%, or 5% of the total length, respectively, as shown in Figures 1 and 2.

[0022] One of the above surfaces is B 5p ≥B 1p This is the surface. This identifies the first peripheral portion to the fifth peripheral portion, and the first central portion to the fifth central portion.

[0023] (B 5p / B 1p ) / (B 5c / B 1c Since (B) ≥ 1.50, the peripheral region and the central region have sufficiently different degrees of binder segregation, resulting in different mechanical properties for each. 5p / B 1p ) / (B 5c / B 1c ) ≥ 1.60, 1.70, 1.80, 1.90, or 2.00, (B 5p / B 1p ) / (B 5c / B 1c ) ≤ 10.00, 8.00, 6.00, 5.00, 4.00, or 3.00.

[0024] The area ratio of the binder can be obtained by calculating the area occupied by the binder in the first peripheral region to the fifth peripheral region and the first central region to the fifth central region of the cross-section in the thickness direction of the electrode active material layer, using scanning electron microscope (SEM) images. For example, when SBR is used as the binder, staining the SBR with the Os staining method, which adds osmium (Os) to the double bond portion of the SBR, provides a bright contrast and makes calculation easier.

[0025] In the electrode active material layer of this disclosure, B 5p / B 5c It may be ≥1.20, 1.22, 1.24, 1.26, 1.28, 1.30, or 1.32. In addition, in the electrode active material layer of this disclosure, B 1p / B 1cIt may be ≤0.80, 0.75, 0.70, or 0.65.

[0026] When bending stress is applied to the electrode active material layer, the edges on the surface side of the electrode active material layer are particularly susceptible to stress and cracking. Therefore, high flexibility on the surface side is required in the peripheral region of the electrode active material layer. In contrast, in the electrode active material layer of this disclosure as described above, when the first portion (first peripheral portion and first central portion) is arranged in contact with the current collector layer, the high binder content on the surface side (fifth peripheral portion) of the peripheral region of the electrode active material layer can suppress cracking at the edges on the surface side of the electrode active material layer.

[0027] On the other hand, a high bonding force with the current collector layer is required in the central region of the electrode active material layer. In response to this, in the electrode active material layer of the present disclosure as described above, when the first portion (first peripheral portion and first central portion) is arranged in contact with the current collector layer, the high binder content in the current collector layer side (first central portion) of the central region of the electrode active material layer allows the electrode active material layer to have a high bonding force with the current collector layer, thereby preventing delamination.

[0028] Specifically, for example, as shown in Figure 2(a), on one side (top surface) in the thickness direction of the electrode active material layer 100 of this disclosure, the binder content is higher in the peripheral region 300 than in the central region 400, and as shown in Figure 2(b), on the opposite side (bottom surface) of the top surface, the binder content is higher in the central region 400 than in the peripheral region 300. By arranging the bottom surface of the electrode active material layer 100 having such a binder distribution in contact with the current collector layer, an electrode laminate can be obtained in which the electrode active material layer 100 and the current collector layer have high bonding strength and high flexibility.

[0029] In the electrode active material layer of this disclosure, B 5p / B 5c It may be ≤2.00, 1.80, 1.60, or 1.40. Furthermore, in the electrode active material layer of this disclosure, B 1p / B 1c It may be ≥0.50, 0.55, or 0.60.

[0030] The binder content is not particularly limited. For example, with the entire electrode active material layer (total solid content) as 100% by mass, the binder content may be 0.5% by mass or more, 1.0% by mass or more, or 2.0% by mass or more, and may be 10.0% by mass or less, 7.0% by mass or less, 5.0% by mass or less, 4.5% by mass or less, or 4.0% by mass or less.

[0031] The material of the binder is not particularly limited. The binder may be, for example, polyvinylidene fluoride (PVdF), butadiene rubber (BR), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), etc., but is not limited to these. The binder is not particularly limited, and may be used alone or in combination of two or more types.

[0032] The shape of the electrode active material layer is not particularly limited, but may be, for example, a sheet with a substantially flat surface. The thickness of the electrode active material layer is not particularly limited, but may be, for example, 0.1 μm or more, 1 μm or more, or 10 μm or more, or 2.0 mm or less, 1.0 mm or less, or 0.5 mm or less.

[0033] The electrode active material layer of this disclosure is an electrode active material layer having an electrode active material and a binder. The electrode active material layer of this disclosure may be a positive electrode active material layer or a negative electrode active material layer.

[0034] <Cathode active material layer> When the electrode active material layer of this disclosure is a positive electrode active material layer, this positive electrode active material layer comprises at least a positive electrode active material and a binder, and may further optionally contain a solid electrolyte and a conductive additive. The positive electrode active material layer may also contain various other additives. The respective contents of the positive electrode active material, solid electrolyte, conductive additive, etc. in the positive electrode active material layer should be appropriately determined according to the desired battery performance.

[0035] (Cathode active material) The material of the positive electrode active material is not particularly limited as long as it is capable of intercalating and releasing lithium ions. Examples of positive electrode active materials include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), and nickel-cobalt-manganese oxide (NCM:LiCO2). 1 / 3 Ni 1 / 3 Mn 1 / 3 O2), lithium nickel-cobalt aluminum oxide (LiNi 0.8 (CoAl) 0.2 O2), Li 1+x Mn 2-x-y M y This may include, but is not limited to, heteroatom-substituted Li-Mn spinel with a composition represented by O4 (where M is one or more metallic elements selected from Al, Mg, Co, Fe, Ni, and Zn).

[0036] The positive electrode active material is not particularly limited, but may have a coating layer. The coating layer is a layer containing a material that has lithium ion conductivity, low reactivity with the positive electrode active material and solid electrolyte, and can maintain a coating layer form that does not flow even when in contact with the active material and solid electrolyte. Specific examples of materials constituting the coating layer include LiNbO3 and Li4Ti5O3. 12 Examples include Li3PO4, but are not limited to these.

[0037] The shape of the positive electrode active material is not particularly limited, as long as it is a shape common for positive electrode active materials in batteries. The positive electrode active material may be, for example, particulate. The positive electrode active material may be primary particles or secondary particles formed by the aggregation of multiple primary particles. The average particle diameter D of the positive electrode active material 50 For example, it may be 1 nm or more, 5 nm or more, or 10 nm or more, and it may also be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less. Note that the average particle diameter D 50 This is the particle diameter (median diameter) at 50% of the integrated value in the volume-based particle size distribution determined by laser diffraction and scattering.

[0038] (solid electrolyte) The material of the solid electrolyte is not particularly limited and may be, for example, a sulfide solid electrolyte, an oxide solid electrolyte, a polymer electrolyte, or the like.

[0039] Examples of sulfide solid electrolytes include, but are not limited to, sulfide-based amorphous solid electrolytes, sulfide-based crystalline solid electrolytes, or argyrodite-type solid electrolytes. Specific examples of sulfide solid electrolytes include Li2S-P2S5 systems (Li7P3S 11 , Li3PS4, Li8P2S9, etc.), Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-LiBr-Li2S-P2S5, Li2S-P2S5-GeS2 (Li 13 GeP3S 16 , Li 10 GeP2S 12 , etc.), LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li 7-x PS 6-x Cl x , etc.; or combinations thereof can be cited, but are not limited thereto.

[0040] Examples of oxide solid electrolytes include Li7La3Zr2O 12 , Li 7-x La3Zr 1-x Nb x O 12 , Li 7-3x La3Zr2Al x O 12 , Li 3x La 2 / 3-x TiO3, Li 1+x Al x Ti 2-x (PO4)3, Li 1+x Al x Ge 2-x (PO4)3, Li3PO4, or Li 3+x PO 4-x N x (LiPON), etc.; or combinations thereof can be cited, but are not limited thereto.

[0041] The sulfide solid electrolyte and oxide solid electrolyte may be glass or crystallized glass (glass ceramics).

[0042] Examples of polymer electrolytes include, but are not limited to, polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof.

[0043] (Conductive additive) The conductive additive is not particularly limited. Examples of conductive additives include, but are not limited to, vapor-grown carbon fibers (VGCF), acetylene black (AB), Ketjenblack (KB), carbon nanotubes (CNT), and carbon nanofibers (CNF). The conductive additive may be particulate or fibrous, and its size is not particularly limited. While the conductive additive is not particularly limited, it may be used alone or in combination of two or more types.

[0044] <Negative electrode active material layer> When the electrode active material layer of this disclosure is a negative electrode active material layer, this negative electrode active material layer comprises at least a negative electrode active material and a binder, and may further optionally contain a solid electrolyte and a conductive additive. The negative electrode active material layer may also contain various other additives. For the binder, solid electrolyte and conductive additive, refer to the description of the positive electrode active material layer above. The respective contents of the negative electrode active material, solid electrolyte and conductive additive in the negative electrode active material layer may be appropriately determined according to the desired battery performance.

[0045] (Negative electrode active material) As the negative electrode active material, various materials can be used whose potential for intercalating and releasing lithium ions (charge / discharge potential) is lower than that of the positive electrode active material described above. The material of the negative electrode active material is not particularly limited and may be metallic lithium, or any material capable of intercalating and releasing metallic ions such as lithium ions. Examples of materials capable of intercalating and releasing metallic ions such as lithium ions include alloy-based negative electrode active materials, carbon materials, or lithium titanate (Li4Ti5O4). 12Examples include, but are not limited to, those listed above.

[0046] The alloy-based anode active material is not particularly limited and includes, for example, Si alloy-based anode active materials or Sn alloy-based anode active materials. Si alloy-based anode active materials include silicon, silicon oxide, silicon carbide, silicon nitride, or solid solutions thereof. Si alloy-based anode active materials may also contain metallic elements other than silicon, such as Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Sn, Ti, etc. Sn alloy-based anode active materials include tin, tin oxide, tin nitride, or solid solutions thereof. Sn alloy-based anode active materials may also contain metallic elements other than tin, such as Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Ti, Si, etc.

[0047] The carbon material is not particularly limited and examples include hard carbon, soft carbon, and graphite.

[0048] The shape of the negative electrode active material is not particularly limited, but any shape common for negative electrode active materials in batteries is acceptable. The negative electrode active material may be in the form of parts or sheets, for example.

[0049] Method for manufacturing electrode active material layer The method for manufacturing the electrode active material layer in this disclosure is: To provide an electrode composite layer containing an electrode active material, a binder, and a dispersion medium. Dry the electrode mixture slurry layer mentioned above. including and In the above drying process, the drying rate in the peripheral region of the electrode mixture slurry layer is different from the drying rate in the central region of the electrode mixture slurry layer.

[0050] According to this disclosure, it is possible to provide a method for manufacturing an electrode active material layer having different mechanical properties in each part.

[0051] The electrode active material layer is generally formed by coating an electrode mixture slurry onto, for example, a current collector layer to form an electrode mixture slurry layer, and then drying the electrode mixture slurry layer.

[0052] During the drying process described above, so-called binder migration occurs, in which the binder moves in the direction of volatilization of the dispersion medium. The amount of binder migration increases as the volatilization rate of the dispersion medium, i.e., the drying rate of the electrode mixture slurry layer, increases.

[0053] Therefore, by changing the drying rate in the peripheral region and the central region of the electrode mixture slurry layer, the amount of binder migration differs between the peripheral and central regions. This makes it possible to manufacture an electrode active material layer in which the degree of binder segregation differs between the peripheral and central regions.

[0054] The method for manufacturing an electrode active material layer according to this disclosure includes providing an electrode mixture slurry layer containing an electrode active material, a binder, and a dispersion medium. For details regarding the electrode active material layer, electrode active material, and binder, refer to the above description of the electrode active material layer.

[0055] In this disclosure, “electrode mixture” means a composition that can constitute an electrode active material layer, either as is or by further containing other components. In this disclosure, “electrode mixture slurry” means a slurry that includes a dispersion medium in addition to the “electrode mixture,” and thereby can be applied and dried to form an electrode active material layer.

[0056] The dispersion medium is not particularly limited and may be, for example, a nonpolar solvent such as heptane, xylene, and toluene, as well as a polar solvent such as a tertiary amine solvent, an ether solvent, a thiol solvent, a ketone solvent (e.g., diisobutyl ketone), and an ester solvent (e.g., butyl butyrate).

[0057] The content of the dispersion medium is not particularly limited, and may be such that the solid content of the electrode mixture slurry is 30% or more, 35% or more, 40% or more, 45% or more, or 50% or more, or it may be such that it is 80% or less, 75% or less, 70% or less, 65% or less, or 60% or less.

[0058] The coating method for the electrode mixture slurry is not particularly limited and may include the doctor blade method, die coating method, gravure coating method, spray coating method, electrostatic coating method, bar coating method, etc.

[0059] The method for producing the electrode active material layer according to this disclosure includes drying the electrode mixture slurry layer.

[0060] The drying method is not particularly limited and may include, for example, laser drying, hot air drying, hot air drying, reduced pressure drying, dielectric heating drying, etc.

[0061] The drying temperature is not particularly limited and may be 50°C or higher, 70°C or higher, 90°C or higher, 100°C or higher, 110°C or higher, or 120°C or higher, and may be 300°C or lower, 250°C or lower, 200°C or lower, 180°C or lower, 160°C or lower, 150°C or lower, or 140°C or lower.

[0062] In the drying process, the drying rate in the peripheral region of the electrode mixture slurry layer differs from the drying rate in the central region of the electrode mixture slurry layer.

[0063] Here, the central and peripheral regions of the electrode mixture slurry layer can be referred to by replacing "electrode active material layer" with "electrode mixture slurry layer" in the above description of the central and peripheral regions of the electrode active material layer.

[0064] The method for adjusting the drying rate is not particularly limited; for example, it may be adjusted so that the drying temperature of the peripheral region and the drying temperature of the central region are different.

[0065] Electrode Stack The electrode laminate of the present disclosure comprises a current collector layer and an electrode active material layer of the present disclosure laminated on the current collector layer.

[0066] According to this disclosure, it is possible to provide an electrode laminate having different mechanical properties in each part.

[0067] The electrode laminate of this disclosure comprises a current collector layer and an electrode active material layer of this disclosure laminated on the current collector layer. The electrode laminate may also be a bipolar electrode laminate having a positive electrode active material layer and a negative electrode active material layer. For details regarding the electrode active material layer, positive electrode active material layer, and negative electrode active material layer, please refer to the description of the electrode active material layer above.

[0068] The peel strength between the current collector layer and the electrode active material layer in the central region of the electrode active material layer is not particularly limited and may be, for example, 0.06 N / cm or more, 0.07 N / cm or more, or 0.08 N / cm or more, and may be 0.5 N / cm or less, 0.4 N / cm or less, 0.3 N / cm or less, or 0.2 N / cm or less.

[0069] The peel strength between the current collector layer and the electrode active material layer can be calculated according to JIS-K-6854-1. This is achieved by fixing the test material of the current collector layer, on which the electrode active material layer is laminated, to a hard base member with double-sided tape or adhesive, peeling off one end of the electrode active material layer, fixing the aforementioned end to a 90° peel test machine, and peeling off the electrode active material layer while pulling it in a direction that is 90° to the unpeeled portion of the test material, and measuring the tensile strength with a load cell or the like.

[0070] The flexibility of the electrode stack is not particularly limited and may be determined as appropriate based on the required performance of the active material layer, etc. The flexibility can be determined, for example, by a cylindrical mandrel test in which the electrode stack obtained by stacking the electrode active material layer on the current collector layer is wound around a cylinder, and the diameter of the cylinder at which cracks begin to appear in the electrode active material layer may be 30 mm or less, 28 mm or less, 26 mm or less, 24 mm or less, 22 mm or less, or 20 mm or less, and may also be 5 mm or more, 7 mm or more, or 9 mm or more.

[0071] The current collector layer may be a positive electrode current collector layer or a negative electrode current collector layer. When the current collector layer is a positive electrode current collector layer, a positive electrode active material layer is laminated on the current collector layer. When the current collector layer is a negative electrode current collector layer, a negative electrode active material layer is laminated on the current collector layer. For details on the positive electrode active material layer and the negative electrode active material layer, refer to the description of the electrode active material layer above.

[0072] <Positive electrode current collector layer> When the current collector layer of this disclosure is a positive electrode current collector layer, the material of the conductive layer having a current collector layer is not particularly limited, but a conductor that is common as a positive electrode of a battery can be appropriately adopted. Examples of conductive layer materials include, but are not limited to, Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, etc. The positive electrode current collector layer may also have a carbon coating layer on its surface. The positive electrode current collector layer may also be a metal foil or a substrate on which the above metals are plated or vapor-deposited.

[0073] The shape of the positive electrode current collector layer is not particularly limited, but examples include foil-like, plate-like, or mesh-like shapes. Among these, a foil-like shape is preferred.

[0074] The thickness of the positive electrode current collector layer is not particularly limited, but may be 0.1 μm or more, or 1 μm or more, or 1 mm or less, or 100 μm or less.

[0075] <Negative electrode current collector layer> When the current collector layer of this disclosure is a positive electrode current collector layer, the material of the conductive layer having a current collector layer is not particularly limited, but a conductor commonly used for the negative electrode of a battery can be appropriately adopted. Examples of materials used for the conductive layer include, but are not limited to, Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, or carbon sheets. The negative electrode current collector layer may have a carbon coating layer on its surface.

[0076] The shape of the negative electrode current collector layer is not particularly limited, but examples include foil-like, plate-like, or mesh-like shapes. Among these, a foil-like shape is preferred.

[0077] The thickness of the negative electrode current collector layer is not particularly limited, but may be 0.1 μm or more, or 1 μm or more, or 1 mm or less, or 100 μm or less.

[0078] Method for manufacturing electrode stacks The method for manufacturing the electrode laminate disclosed herein is: To provide a current collector layer having a conductive layer and a carbon coating layer on the conductive layer, To provide an electrode mixture slurry layer containing the electrode active material, the binder, and the dispersion medium on at least a portion of the carbon coating layer, and The electrode mixture slurry layer and the adjacent region adjacent to the electrode mixture slurry layer and having the carbon coating layer are irradiated with laser light to dry the electrode mixture slurry layer. Includes.

[0079] According to this disclosure, it is possible to provide a method for manufacturing an electrode laminate having different mechanical properties in each part.

[0080] The electrode active material layer in the electrode laminate is particularly prone to cracking in the peripheral region; therefore, from the viewpoint of improving flexibility, it is preferable that a large amount of binder is distributed on the surface side in the peripheral region. In other words, it is preferable that binder migration occurs when the electrode mixture slurry layer dries.

[0081] On the other hand, the bonding force between the electrode active material layer and the current collector layer in the electrode laminate largely depends on the bonding force between the electrode active material layer and the current collector layer in the central region; therefore, it is desirable for a large amount of binder to remain on the bonding surface. In other words, the occurrence of binder migration during the drying of the electrode composite slurry layer is undesirable.

[0082] In contrast, by applying an electrode mixture slurry layer to at least a portion of the carbon coating layer in a current collector layer having a carbon coating layer, and drying the electrode mixture slurry layer and adjacent regions adjacent to the electrode mixture slurry layer by irradiating them with laser light, it is possible to generate more binder migration in the peripheral regions of the electrode mixture slurry layer compared to the central region of the electrode mixture slurry layer. Therefore, the degree of binder segregation in the peripheral regions becomes greater than the degree of binder segregation in the central region.

[0083] Although not limited to theory, carbon coatings have a high laser light absorption rate, so current collector layers with carbon coatings tend to absorb laser light easily and become hot. Therefore, when laser light is irradiated onto the carbon coating surface of an adjacent current collector layer, the current collector layer in that adjacent region becomes hot. This heat is then transferred to the peripheral region of the electrode mixture slurry layer, causing the peripheral region of the electrode mixture slurry layer to also become hot and promoting binder migration. On the other hand, the central region of the electrode mixture slurry layer does not experience increased binder migration because it receives less heat from the adjacent region.

[0084] Therefore, it is possible to manufacture an electrode laminate that has high flexibility in the peripheral region and high bonding strength between the electrode active material layer and the current collector layer in the central region, and the electrode laminate as a whole also has high flexibility and high bonding strength between the electrode active material layer and the current collector layer.

[0085] The method for manufacturing an electrode laminate according to this disclosure includes providing a current collector layer having a conductive layer and a carbon coating layer on the conductive layer. The conductive layer can be described in the above-described description of the electrode laminate. The carbon coating layer may be laminated over the entire surface of the conductive layer, or on a portion of the surface of the conductive layer.

[0086] (Carbon coating layer) The laser light absorption rate of the carbon coating layer with respect to the above-mentioned laser light is not particularly limited and may be, for example, 0.20 or higher, 0.30 or higher, 0.40 or higher, or 0.50 or higher. A high laser light absorption rate of the carbon coating layer can promote migration of the edges of the electrode active material layer. Alternatively, the laser light absorption rate of the carbon coating layer may be 1.00 or lower, 0.90 or lower, 0.80 or lower, or 0.60 or lower.

[0087] The laser light absorptivity (-) was measured using a spectrophotometer to obtain the laser light reflectivity (-). The laser light absorptivity (-) was calculated from 1 - [laser light reflectivity].

[0088] The carbon coating layer may have its laser light absorption rate adjusted by rubbing its surface with a nonwoven fabric or the like.

[0089] The carbon coating layer may contain at least carbon particles and may also contain a binder, dispersant, etc. For the binder, refer to the description of the electrode active material layer above. Examples of dispersants include carboxyethyl cellulose. The content of carbon particles, binder, dispersant, etc., may be appropriately determined depending on the performance required of the carbon coating layer.

[0090] The shape of the carbon coating layer is not particularly limited and may be, for example, a sheet. The thickness of the carbon coating layer is not particularly limited and may be, for example, 0.1 μm or more, 0.2 μm or more, 0.3 μm or more, or 0.5 μm or more, or 5.0 μm or less, 3.0 μm or less, 2.0 μm or less, or 1.0 μm or less.

[0091] The thermal conductivity of the current collector layer is not particularly limited and may be, for example, 50 W / m·K or higher, 70 W / m·K or higher, 100 W / m·K or higher, 150 W / m·K or higher, or 200 W / m·K or higher. A high thermal conductivity of the current collector foil layer can promote migration in the peripheral region of the electrode active material layer. The thermal conductivity of the current collector foil may also be 400 W / m·K or lower, 350 W / m·K or lower, or 300 W / m·K or lower.

[0092] The method for manufacturing an electrode laminate according to this disclosure includes providing an electrode mixture slurry layer containing an electrode active material, a binder, and a dispersion medium in at least a portion of a carbon coat layer. For the electrode active material and binder, refer to the above-described description of the electrode active material layer, and for the dispersion medium and electrode mixture slurry layer, refer to the above-described description of the method for manufacturing the electrode active material layer.

[0093] From the viewpoint of heating the electrode mixture slurry layer to a high temperature, it is preferable that a carbon coating layer be present in the region adjacent to the electrode mixture slurry layer.

[0094] The coating method is not particularly limited and may include the doctor blade method, die coating method, gravure coating method, spray coating method, electrostatic coating method, bar coating method, etc.

[0095] The method for manufacturing the electrode laminate according to the present disclosure includes drying the electrode slurry layer by irradiating the electrode slurry layer and adjacent regions adjacent to the electrode slurry layer with laser light.

[0096] Here, the central and peripheral regions of the electrode mixture slurry layer can be referred to by replacing "electrode active material layer" with "electrode mixture slurry layer" in the above description of the central and peripheral regions of the electrode active material layer.

[0097] In this specification, "adjacent region" means a region outside the electrode active material layer that is included in the longitudinal and widthwise (not shown) directions of the electrode composite slurry layer 106, from the edge to 10%, 15%, or 20% of the total length, and that is adjacent to the peripheral region, as shown in Figure 3.

[0098] The laser light source is not particularly limited and may be, for example, a YAG laser, a carbon dioxide laser, etc. The wavelength of the laser light may be 0.5 μm or more, 0.6 μm or more, 0.7 μm or more, 0.8 μm or more, or 0.9 μm or more, and may be 1.5 μm or less, 1.4 μm or less, 1.3 μm or less, 1.2 μm or less, or 1.1 μm or less.

[0099] The output power of the laser light source is not particularly limited and may be appropriately determined by the laser light irradiation area, laser light irradiation time, etc. The output power of the laser light source may be, for example, 0.1 kW or more, 1 kW or more, 5 kW or more, 10 kW or more, 15 kW or more, 20 kW or more, or 30 kW or more, and may be 100 kW or less, or 50 kW or less.

[0100] The irradiation time of the laser beam is not particularly limited, and may be extended, for example, until the reduction drying period of the electrode mixture slurry layer is reached. The irradiation time of the laser beam may be, for example, 30 seconds or more, 1 minute or more, or 2 minutes or more, and may be 30 minutes or less, 20 minutes or less, or 10 minutes or less. [Examples]

[0101] The present invention will be specifically described by examples and comparative examples, but the present invention is not limited thereto.

[0102] Fabrication of electrode active material layer Lithium cobalt oxide (LiCoO2) as the electrode active material and styrene-butadiene copolymer (SBR) as the binder were weighed in seconds at a mass ratio of 97.5:2.5 and mixed with ion-exchanged water to prepare an electrode mixture slurry with a solid content of 55%.

[0103] As shown in Figure 4(a), a current collector layer was prepared for Example 1, in which a carbon coating layer A was laminated over the entire surface of a square-shaped aluminum foil with a side length of 200 mm, which served as the conductive layer.

[0104] As shown in Figure 4(b), a current collector layer was prepared for Example 2, in which a carbon coating layer A was laminated in a square shape with sides of 180 mm in the center of a square aluminum foil surface with sides of 200 mm, which served as the conductive layer.

[0105] As shown in Figure 4(c), a current collector layer was prepared for the fabrication of Example 3, in which a carbon coating layer A was laminated in a square shape with sides of 150 mm in the center of a square aluminum foil surface with sides of 200 mm, which served as the conductive layer.

[0106] Furthermore, by rubbing the carbon coating layer A, which is located in a square region with a side length of 150 mm in the central part of the surface of the current collector layer used for Example 1, with a nonwoven fabric, a carbon coating layer B was formed in which the laser light absorption rate of carbon coating layer A in the rubbed area was reduced, and a current collector layer for Example 4 was fabricated as shown in Figure 4(d). The laser light absorption rate of carbon coating layer A was 0.5, and the laser light absorption rate of carbon coating layer B was 0.4.

[0107] Next, a current collector layer for Example 5 was fabricated in the same manner as the current collector layer for Example 4, except that carbon coat layer A was rubbed with a nonwoven fabric to form carbon coat layer C, as shown in Table 1 and Figure 4(e). The laser light absorption rate of carbon coat layer C was 0.2.

[0108] Furthermore, a square-shaped aluminum foil current collector with a side length of 200 mm and no carbon coating layer was prepared as a current collector layer for creating Comparative Example 1. The laser light absorption rate of the aluminum foil current collector was 0.05.

[0109] The electrode slurry described above was applied to the center of the surface of each current collector layer in a square shape with sides of 100 mm and a thickness of 400 μm to form an electrode slurry layer. Then, a laser beam was irradiated onto the square area with sides of 200 mm where the current collector was located and on the side where the electrode slurry layer was stacked, and the electrode slurry layer was dried until the electrode slurry layer reached its decay drying period, thereby creating electrode active material layers for Examples 1 to 5 and Comparative Example 1 as shown in Table 1 on the current collector layer.

[0110] Here, Figure 5(a) corresponds to the electrode stack having an electrode active material layer of Example 1, Figure 5(b) corresponds to the electrode stack having an electrode active material layer of Example 2, Figure 5(c) corresponds to the electrode stack having an electrode active material layer of Example 3, Figure 5(d) corresponds to the electrode stack having an electrode active material layer of Example 4, Figure 5(e) corresponds to the electrode stack having an electrode active material layer of Example 5, and Figure 5(f) corresponds to the electrode stack having an electrode active material layer of Comparative Example 1.

[0111] Measurement of binder content From the cross-sectional view in the thickness direction of the electrode active material layer of Examples 1-5 and Comparative Example 1, B 1p ~B 5p and B 1p ~B 5p The values ​​were calculated using scanning electron microscope (SEM) images. The measurement results are shown in Table 1. Note that the first layer is in contact with the current collector layer.

[0112] Evaluation of the flexibility of the electrode active material layer In a cylindrical mandrel test, electrode stacks containing the electrode active material layers of Examples 1-5 and Comparative Example 1 were wound around a cylinder, and the cylinder diameter at which cracks began to appear in the electrode active material layer was measured to evaluate flexibility. A smaller cylinder diameter indicates greater flexibility.

[0113] Evaluation of the binding force between the electrode active material layer and the current collector layer. Using electrode laminates having electrode active material layers from Examples 1-5 and Comparative Example 1, the adhesion strength between the electrode active material layer and the current collector layer was evaluated by measuring the peel strength between the electrode active material layer and the current collector layer in Examples 1-5 and Comparative Example 1.

[0114] The results of each evaluation are shown in Table 1.

[0115] [Table 1]

[0116] From Examples 1-5 and Comparative Example 1 in Table 1, it can be seen that binder migration is promoted in the peripheral region of the electrode active material layer, and the degree of binder segregation in the peripheral region is significantly higher than in the central region, resulting in improved flexibility of the electrode active material layer. On the other hand, migration is not promoted in the central region, the electrode active material layer and the current collector layer have sufficient peel strength, and the electrode active material layer has high bonding strength with the current collector layer. Therefore, the electrode active material layer has different mechanical properties in the peripheral region and the central region. [Explanation of Symbols]

[0117] 100 Electrode active material layer 101 Part 1 102 Part 2 103 Part 3 104 Part 4 105 Part 5 106 Electrode mixture slurry layer 110 Binder 200 Current collector layer 201 Current collector layer (uncoated section of carbon coating layer) 202 Current collector layer (carbon coating layer A laminated section) 203 Current collector layer (carbon coating layer B laminated section) 204 Current collector layer (carbon coated layer C laminated section) 210 Carbon coating layer 300 Peripheral region 400 central area 500 adjacent regions

Claims

1. An electrode active material layer having an electrode active material and a binder, wherein the electrode active material layer satisfies the following relationship: (B ５ｐ / B １ｐ ) / (B ５ｃ / B １ｃ )≧1.50 B ５ｐ ≧B １ｐ B ５ｐ : In the peripheral region of the electrode active material layer, when the cross-section in the thickness direction of the electrode active material layer is divided into five equal parts from one surface to the other, from the first peripheral portion to the fifth peripheral portion, the area ratio of the binder in the fifth peripheral portion, B １ｐ : Area ratio of the binder in the first peripheral portion, B ５ｃ : When the cross-section in the thickness direction of the electrode active material layer in the central region of the electrode active material layer is equally divided into a first central portion to a fifth central portion from one surface to the other surface, the area ratio of the binder in the fifth central portion B １ｃ : Area ratio of the binder in the first central portion.

2. The electrode active material layer according to claim 1, satisfying the following relationship: B ５ｐ / B ５ｃ ≧1.20。

3. The electrode active material layer according to claim 1 or 2, satisfying the following relationship: B １ｐ / B １ｃ ≦0.80。

4. The electrode active material layer according to claim 1 or 2, wherein the content of the binder is 0.5% by mass or more relative to the electrode active material layer.

5. The electrode active material layer according to claim 1 or 2, wherein the thickness of the electrode active material layer is 2.0 mm or less.

6. To provide an electrode mixture slurry layer containing the electrode active material, the binder, and the dispersion medium. Drying the electrode mixture slurry layer, including and In the drying process described above, the drying rate in the peripheral region of the electrode mixture slurry layer is different from the drying rate in the central region of the electrode mixture slurry layer. A method for producing an electrode active material layer according to claim 1 or 2.

7. An electrode laminate having a current collector layer and an electrode active material layer according to claim 1 or 2 laminated on the current collector layer.

8. The electrode laminate according to claim 7, wherein the peel strength between the current collector layer and the electrode active material layer in the central region of the electrode active material layer is 0.06 N / cm or more.

9. To provide a current collector layer having a conductive layer and a carbon coating layer on the conductive layer, To provide an electrode mixture slurry layer containing the electrode active material, the binder, and the dispersion medium on at least a portion of the carbon coating layer, and The electrode mixture slurry layer and the adjacent region adjacent to the electrode mixture slurry layer and having the carbon coating layer are irradiated with laser light to dry the electrode mixture slurry layer. A method for manufacturing the electrode laminate according to claim 7, including the following:

10. The method according to claim 9, wherein the laser light absorption rate of the carbon coating layer with respect to the laser light is 0.2 or more.

11. The method according to claim 9 or 10, wherein the thermal conductivity of the conductive layer is 50 W / m·K or more.

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