Method for manufacturing electrode sheets for non-aqueous secondary batteries and method for manufacturing non-aqueous secondary batteries

Abstract

The present invention provides a method for manufacturing electrode sheets for non-aqueous secondary batteries that suppresses an increase in the battery's installation area, and a method for manufacturing a non-aqueous secondary battery. [Solution] A method for manufacturing an electrode sheet for a non-aqueous secondary battery includes: a first coating step of applying a first electrode mixture paste, obtained by kneading a first solvent and a first electrode mixture, to the first surface 31A of an electrode substrate 31; a first drying step of drying the first electrode mixture paste applied to the first surface 31A of the electrode substrate 31; a second coating step of applying a second electrode mixture paste, obtained by kneading a second solvent and a second electrode mixture, to the second surface 31B of the electrode substrate 31 after the first drying step; and a second drying step of drying the second electrode mixture paste applied to the second surface 31B of the electrode substrate 31. In the first drying step, vapors due to the evaporation of the first solvent are discharged from through holes 32; and in the second drying step, vapors due to the evaporation of the second solvent are discharged from through holes 32.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an electrode sheet of a non-aqueous secondary battery and a method for manufacturing a non-aqueous secondary battery.

Background Art

[0002] In a method for manufacturing an electrode sheet of a non-aqueous secondary battery, when drying an electrode mixture paste coated on an electrode substrate, a solvent is evaporated from the pores of the electrode substrate. At this time, the vapor is discharged so that the amount of vapor discharged is larger on the interface side with the electrode substrate than on the surface side of the electrode mixture paste. As a result, the electrode binder contained in the electrode mixture paste moves from the surface side to the interface side of the electrode mixture paste. Then, the electrode binder segregated on the interface side in the electrode mixture paste enhances the bonding force between the electrode substrate and the electrode active material (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the other hand, in the above-described method for manufacturing an electrode sheet, one electrode sheet is manufactured by bonding electrode substrates that support the electrode mixture paste. In a non-aqueous secondary battery including such an electrode sheet, it is desirable to suppress an increase in the installation area of the battery due to an increase in the thickness of the electrode sheet caused by bonding the electrode substrates.

Means for Solving the Problems

[0005] In a method for manufacturing an electrode sheet for a non-aqueous secondary battery to solve the above problems, the electrode mixture constituting the electrode sheet includes an electrode active material and an electrode binder, and the electrode substrate constituting the electrode sheet has a plurality of through holes penetrating from a first surface to a second surface. This manufacturing method includes a first coating step of coating the first surface with a first electrode mixture paste obtained by kneading a first solvent and a first electrode mixture; a first drying step of drying the first electrode mixture paste coated on the first surface; a second coating step of coating the second surface after the first drying step with a second electrode mixture paste obtained by kneading a second solvent and a second electrode mixture; and a second drying step of drying the second electrode mixture paste coated on the second surface. In the first drying step, vapors due to the evaporation of the first solvent are discharged from the through holes, and in the second drying step, vapors due to the evaporation of the second solvent are discharged from the through holes.

[0006] According to the above method, since electrode composite paste is applied to the first and second surfaces of the electrode substrate, the number of electrode substrates in one electrode sheet can be reduced to one. Furthermore, in both the first and second drying steps, vapors resulting from the evaporation of the solvent are discharged through the through-holes of the electrode substrate, allowing the electrode binder to segregate closer to the electrode substrate compared to a case where vapors are not discharged through the through-holes. As a result, when the amount of electrode binder is equal, the bonding strength between the electrode substrate and the electrode active material can be increased on both the first and second surfaces. Also, if sufficient bonding strength is obtained between the electrode substrate and the electrode active material, the amount of electrode binder can be reduced.

[0007] In the above method, in the second drying step, the electrode substrate may be inverted so that the second surface is positioned vertically below the first surface, and the second surface may be heated from vertically below the second surface to discharge the steam from the through-hole.

[0008] According to the above method, in the second drying step, the second surface is positioned vertically below the first surface, and the second surface is heated from vertically below. Therefore, by utilizing the vapor flow due to the temperature difference, the vapor accompanying the evaporation of the second solvent can be discharged from the through-holes in the electrode substrate.

[0009] In the above method, the second electrode mixture paste may have a lower viscosity than the first electrode mixture paste so that the second electrode mixture paste is connected to the dried first electrode mixture paste through the through-hole.

[0010] According to the above method, the coated second electrode composite paste connects the first and second surfaces through through-holes. As a result, the connection between the electrode active materials by the electrode binder through the through-holes, combined with the segregation of the electrode binder, can enhance the bonding strength between the electrode substrate and the electrode active material on both the first and second surfaces. Furthermore, in the first coating step, it becomes possible to apply a high viscosity to the first electrode composite paste that does not reach the second surface through the through-holes, thereby shortening the time required for the first drying step and improving the accuracy of the thickness of the first electrode composite paste after drying.

[0011] In the above method, the opening of the through hole may be such that the first electrode mixture paste does not reach the second surface through the through hole in the first coating step, and the second electrode mixture paste connects to the dried first electrode mixture paste through the through hole.

[0012] According to the above method, the coated second electrode composite paste connects the first and second surfaces through the through-holes. As a result, the connection between the electrode active materials by the electrode binder through the through-holes, combined with the segregation of the electrode binder, can enhance the bonding strength between the electrode substrate and the electrode active material on both the first and second surfaces. Furthermore, since the diameter of the through-holes is large enough to allow the second electrode composite paste to flow in, the drying time required in the first and second drying processes can be shortened.

[0013] In a method for manufacturing an electrode sheet for a non-aqueous secondary battery to solve the above problems, the electrode mixture constituting the electrode sheet includes an electrode active material and an electrode binder, and the electrode substrate constituting the electrode sheet has a plurality of through holes penetrating from a first surface to a second surface. This manufacturing method includes a first coating step of coating the first surface with a first electrode mixture paste obtained by kneading a first solvent and a first electrode mixture; a first drying step of drying the first electrode mixture paste coated on the first surface; a second coating step of coating the second surface after the first drying step with a second electrode mixture paste obtained by kneading a second solvent and a second electrode mixture; and a second drying step of drying the second electrode mixture paste coated on the second surface. In the first drying step, vapors due to the evaporation of the first solvent are discharged from the through holes, and the second electrode mixture paste may have a lower viscosity than the first electrode mixture paste so that the second electrode mixture paste connects to the dried first electrode mixture paste through the through holes.

[0014] According to the above method, since electrode composite paste is applied to the first and second surfaces of the electrode substrate, the number of electrode substrates in one electrode sheet can be reduced to one. Furthermore, in the first drying step, compared to the case where steam is not discharged from the through holes, the bonding strength between the first surface and the electrode active material can be increased by segregating the electrode binder closer to the electrode substrate. In addition, since the first electrode composite paste dries more easily than the second electrode composite paste, the time required for the first drying step can be shortened. Then, in the second drying step, the bonding strength between the second surface and the electrode active material can be increased by connecting the electrode active materials with the electrode binder through the through holes. Furthermore, if sufficient bonding strength is obtained between the electrode substrate and the electrode active material, the amount of electrode binder can be reduced.

[0015] In a method for manufacturing an electrode sheet for a non-aqueous secondary battery to solve the above problems, the electrode mixture constituting the electrode sheet includes an electrode active material and an electrode binder, and the electrode substrate constituting the electrode sheet has a plurality of through holes penetrating from a first surface to a second surface. This manufacturing method includes a first coating step of coating a first electrode mixture paste, obtained by kneading a first solvent and a first electrode mixture, onto the first surface; a first drying step of drying the first electrode mixture paste coated onto the first surface; a second coating step of coating a second electrode mixture paste, obtained by kneading a second solvent and a second electrode mixture, onto the second surface after the first drying step; and a second drying step of drying the second electrode mixture paste coated onto the second surface. In the first drying step, vapors resulting from the evaporation of the first solvent are discharged from the through-holes, and the opening of the through-holes is such that the first electrode mixture paste does not reach the second surface through the through-holes in the first coating step, and is such that the second electrode mixture paste connects to the dried first electrode mixture paste through the through-holes.

[0016] According to the above method, since electrode composite paste is applied to the first and second surfaces of the electrode substrate, the number of electrode substrates in one electrode sheet can be reduced to one. Furthermore, in the first drying step, compared to the case where steam is not discharged from the through-holes, the bonding strength between the first surface and the electrode active material can be increased by segregating the electrode binder closer to the electrode substrate. Then, in the second drying step, the bonding strength between the second surface and the electrode active material can be increased by connecting the electrode active material through the electrode binder via the through-holes. In addition, if sufficient bonding strength is obtained between the electrode substrate and the electrode active material, the amount of electrode binder can be reduced. Moreover, since the diameter of the through-holes is large enough to allow the second electrode composite paste to flow in, the drying time required in the first and second drying steps can be shortened.

[0017] In the above method, in the first drying step, the drying atmosphere facing the first electrode composite paste and the drying atmosphere facing the second surface may be made different from each other so that the steam flow is formed from the first surface through the through hole to the second surface.

[0018] According to the above method, regardless of the position of the first surface in the vertical direction with respect to the second surface, by discharging the vapor accompanying the evaporation of the solvent from the through-holes of the electrode substrate on the first surface of the electrode substrate, the electrode binder can be segregated closer to the electrode substrate, thereby enhancing the bonding strength between the electrode substrate and the electrode active material.

[0019] A method for manufacturing a non-aqueous secondary battery for solving the above problems is a method for manufacturing a non-aqueous secondary battery including an electrode sheet and a non-aqueous electrolyte, and includes manufacturing the electrode sheet using the method for manufacturing the electrode sheet of the non-aqueous secondary battery.

Effect of the Invention

[0020] According to the present invention, since the number of electrode substrates included in one electrode sheet can be reduced to one, an increase in the installation area due to the bonding of the electrode substrates can be suppressed. <(

Brief Description of the Drawings

[0021] [Figure 1] It is a perspective view showing a schematic configuration of a non-aqueous secondary battery of the first embodiment. [Figure 2] It is a diagram showing a developed part of the electrode body of the same embodiment. [Figure 3] It is a plan view showing an electrode substrate of an electrode sheet of a non-aqueous secondary battery of the same embodiment. [Figure 4] (a) is a plan view showing through-holes provided in an electrode substrate of an electrode sheet of a non-aqueous secondary battery of the same embodiment, and (b) is a cross-sectional view showing the through-holes provided in the electrode substrate. [Figure 5] It is a cross-sectional view showing a state where an electrode mixture paste is applied to an electrode substrate of an electrode sheet of a non-aqueous secondary battery of the same embodiment. [Figure 6] It is a cross-sectional view showing a state where an electrode mixture paste is applied to an electrode substrate of an electrode sheet of a non-aqueous secondary battery of the same embodiment. [Figure 7] It is a cross-sectional view showing a state where a first electrode mixture paste is applied to a first surface of an electrode substrate of an electrode sheet of a non-aqueous secondary battery of the same embodiment. [Figure 8]This is a cross-sectional view showing the state in which the first electrode composite paste, which is coated on the first surface of the electrode substrate of the electrode sheet of the non-aqueous secondary battery of the same embodiment, is being heated. [Figure 9] This is a cross-sectional view showing the state in which the first electrode composite paste, which is coated on the first surface of the electrode substrate of the electrode sheet of the non-aqueous secondary battery of the same embodiment, is being heated. [Figure 10] This is a cross-sectional view showing the state after heating of the first electrode composite paste coated on the first surface of the electrode substrate of the electrode sheet of the non-aqueous secondary battery of the same embodiment. [Figure 11] This is a cross-sectional view showing the state in which the second electrode composite paste is applied to the second surface of the electrode substrate of the electrode sheet of the non-aqueous secondary battery of the same embodiment. [Figure 12] This is a cross-sectional view showing the state in which the second electrode composite paste, which is coated on the second surface of the electrode substrate of the electrode sheet of the non-aqueous secondary battery of the same embodiment, is being heated. [Figure 13] This is a cross-sectional view showing the state after heating of the second electrode composite paste coated on the second surface of the electrode substrate of the electrode sheet of the non-aqueous secondary battery of the same embodiment. [Figure 14] This is a cross-sectional view showing the state in which the second electrode composite paste is applied to the second surface of the electrode substrate of the electrode sheet of the non-aqueous secondary battery of the second embodiment. [Figure 15] This is a cross-sectional view showing the state in which the second electrode composite paste, which is coated on the second surface of the electrode substrate of the electrode sheet of the non-aqueous secondary battery of the same embodiment, is being heated. [Figure 16] This is a cross-sectional view showing the state after heating of the second electrode composite paste coated on the second surface of the electrode substrate of the electrode sheet of the non-aqueous secondary battery of the same embodiment. [Modes for carrying out the invention]

[0022] [First Embodiment] The first embodiment of the method for manufacturing an electrode sheet for a non-aqueous secondary battery and the method for manufacturing a non-aqueous secondary battery will be described below with reference to Figures 1 to 13. A lithium-ion secondary battery will be described as an example of a non-aqueous secondary battery.

[0023] [Lithium-ion rechargeable battery 10] As shown in Figure 1, the lithium-ion secondary battery 10, which is a non-aqueous secondary battery, is a cell battery that forms a battery pack when multiple lithium-ion secondary batteries 10 are combined and enclosed in a resin or metal case. The battery pack is used in hybrid vehicles and electric vehicles.

[0024] The lithium-ion secondary battery 10 comprises a battery case 11 and a cover 12. The battery case 11 is rectangular in shape with an opening on its upper side. The cover 12 seals the opening of the battery case 11. The battery case 11 and the cover 12 are made of a metal such as aluminum or an aluminum alloy. The lithium-ion secondary battery 10 is formed as a sealed battery case by attaching the cover 12 to the battery case 11.

[0025] The cover 12 is provided with two positive external terminals 13A and a negative external terminal 13B. The positive external terminal 13A and the negative external terminal 13B are used for charging and discharging power. Multiple wound bodies 20 are housed inside the battery case 11. The wound bodies 20 are electrode bodies. The positive electrode side current collector portion 20A, which is the positive electrode end of the wound body 20, is electrically connected to the positive external terminal 13A via the positive electrode side current collector member 14A. The negative electrode side current collector portion 20B, which is the negative electrode end of the wound body 20, is electrically connected to the negative external terminal 13B via the negative electrode side current collector member 14B. In addition, a non-aqueous electrolyte is injected into the battery case 11 through an injection hole (not shown). Note that the shapes of the positive external terminal 13A and the negative external terminal 13B are not limited to the shapes shown in Figure 1, but may be any shape.

[0026] [Wound body 20] As shown in Figure 2, the wound body 20 is a flat electrode body formed by winding a laminate in which a long positive electrode sheet 21 and a negative electrode sheet 24 are laminated with a separator 27 in between. The positive electrode sheet 21, the negative electrode sheet 24, and the separator 27 are laminated so that their respective longitudinal directions coincide with the longitudinal direction D1. Before winding, the laminate is laminated in the order of positive electrode sheet 21, separator 27, negative electrode sheet 24, separator 27. The positive electrode sheet 21 and the negative electrode sheet 24 are electrode sheets.

[0027] [Positive electrode sheet 21] The positive electrode sheet 21 comprises a positive electrode current collector 22 and a positive electrode composite layer 23. The positive electrode current collector 22 is a foil-shaped positive electrode substrate formed in an elongated shape. The positive electrode composite layer 23 is provided on each of two opposing surfaces of the positive electrode current collector 22. The positive electrode current collector 22 has an uncoated positive electrode side portion 22A at one end in the width direction D2 where the positive electrode composite layer 23 is not formed and the positive electrode current collector 22 is exposed.

[0028] The positive electrode current collector 22 is made of a metal foil composed of aluminum or an alloy mainly composed of aluminum. The positive electrode current collector 22 functions as a current collector at the positive electrode. The unpainted positive electrode side portion 22A of the positive electrode current collector 22 is pressed against each other by opposing surfaces in the state of the wound body 20, forming the positive electrode side current collector portion 20A.

[0029] The positive electrode composite layer 23 is a cured form of a liquid positive electrode composite paste. The positive electrode composite paste contains a positive electrode active material, a positive electrode solvent, a positive electrode conductive material, and a positive electrode binder. The positive electrode composite layer 23 is formed when the positive electrode composite paste dries and the positive electrode solvent vaporizes. Therefore, the positive electrode composite layer 23 contains a positive electrode active material, a positive electrode conductive material, and a positive electrode binder.

[0030] The positive electrode active material is a lithium-containing composite oxide capable of intercalating and releasing lithium ions, which are charge carriers in the lithium-ion secondary battery 10. The lithium-containing composite oxide is an oxide containing lithium and other metallic elements other than lithium. The other metallic elements other than lithium are, for example, at least one selected from the group consisting of nickel, cobalt, manganese, vanadium, magnesium, molybdenum, niobium, titanium, tungsten, aluminum, and iron contained as iron phosphate in the lithium-containing composite oxide.

[0031] For example, lithium-containing composite oxides include lithium cobaltate (LiCoO2), lithium nickelate (LiNiO2), and lithium manganate (LiMn2O4). Another example is lithium-containing composite oxide, a ternary lithium-containing composite oxide containing nickel, cobalt, and manganese, which is lithium nickel-cobalt-manganate (LiNiCoMnO2). Yet another example is lithium iron phosphate (LiFePO4).

[0032] The positive electrode solvent is an NMP (N-methyl-2-pyrrolidone) solution, which is an example of an organic solvent. Examples of positive electrode conductive materials include carbon black such as acetylene black and Ketjenblack, carbon fibers such as carbon nanotubes and carbon nanofibers, and graphite. The positive electrode binder is an example of a resin component contained in the positive electrode paste. Examples of positive electrode binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), and styrene-butadiene rubber (SBR).

[0033] The positive electrode sheet 21 may have an insulating layer at the boundary between the uncoated portion 22A on the positive electrode side and the positive electrode composite layer 23. The insulating layer contains an inorganic component having insulating properties and a resin component that functions as a binder. The inorganic component is at least one selected from the group consisting of powdered boehmite, titania, and alumina. The resin component is at least one selected from the group consisting of PVDF, PVA, and acrylic.

[0034] [Negative electrode sheet 24] The negative electrode sheet 24 comprises a negative electrode current collector 25 and a negative electrode composite layer 26. The negative electrode current collector 25 is a foil-shaped negative electrode substrate formed in an elongated shape. The negative electrode composite layer 26 is provided on each of two opposing surfaces of the negative electrode current collector 25. The negative electrode current collector 25 has a negative electrode side unpainted portion 25A at one end in the width direction D2, which is located opposite the positive electrode side unpainted portion 22A, where the negative electrode composite layer 26 is not formed and the negative electrode current collector 25 is exposed.

[0035] The negative electrode current collector 25 is made of metal foil composed of copper or an alloy mainly composed of copper. The negative electrode current collector 25 functions as a current collector at the negative electrode. In the state of the wound body 20, the unpainted negative electrode side portion 25A has opposing surfaces pressed against each other to form the negative electrode side current collector portion 20B.

[0036] The negative electrode composite layer 26 is a cured body of a liquid negative electrode composite paste. The negative electrode composite paste contains a negative electrode active material, a lithium salt, a negative electrode solvent, a negative electrode thickener, and a negative electrode binder. The negative electrode composite layer 26 is formed when the negative electrode composite paste dries and the negative electrode solvent vaporizes. Therefore, the negative electrode composite layer 26 contains the negative electrode active material, a lithium salt, and further, as additives, a negative electrode thickener and a negative electrode binder. The negative electrode composite layer 26 may further contain additives such as a conductive material.

[0037] The negative electrode active material is a material capable of intercalating and releasing lithium ions. Examples of negative electrode active materials include carbon materials such as graphite, poorly graphitizable carbon, and easily graphitizable carbon. The negative electrode solvent is, for example, water. The lithium salt can be one or more lithium compounds (lithium salts) selected from LiPF6, LiBF4, LiClO4, LiAsF6, LiCF3SO3, LiC4F9SO3, LiN(CF3SO2)2, LiC(CF3SO2)3, LiI, LiBOB (lithium bisoxalate borate), etc. As an example of a negative electrode thickener, CMC (carboxymethylcellulose) can be used as a thickener containing a sodium salt. The negative electrode binder can be the same as that used for the positive electrode binder. As an example of a negative electrode binder, SAR (styrene-acrylic acid copolymer) can be used as a binder containing a sodium salt.

[0038] [Separator 27] The separator 27 prevents contact between the positive electrode sheet 21 and the negative electrode sheet 24, and holds the non-aqueous electrolyte between the positive electrode sheet 21 and the negative electrode sheet 24. When the wound body 20 is immersed in the non-aqueous electrolyte, the non-aqueous electrolyte penetrates from the ends in the width direction D2 of the separator 27 toward the center.

[0039] The separator 27 is a nonwoven fabric made of polypropylene or the like. As the separator 27, for example, porous polymer membranes such as porous polyethylene membranes, porous polyolefin membranes, and porous polyvinyl chloride membranes, and ion-conductive polymer electrolyte membranes can be used.

[0040] [Nonaqueous electrolyte] A non-aqueous electrolyte is a composition containing a supporting salt in a non-aqueous solvent. As the non-aqueous solvent, one or more materials selected from the group consisting of propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, etc., can be used. As the supporting salt, one or more lithium compounds (lithium salts) selected from LiPF6, LiBF4, LiClO4, LiAsF6, LiCF3SO3, LiC4F9SO3, LiN(CF3SO2)2, LiC(CF3SO2)3, LiI, etc., can be used.

[0041] [Electrode sheet 30] As shown in Figure 3, the electrode sheet 30 is either a positive electrode sheet 21 or a negative electrode sheet 24. The electrode substrate 31 constituting the electrode sheet 30 has a plurality of through holes 32. The through holes 32 penetrate from a first surface to a second surface opposite the first surface. If the through holes 32 are circular, the size of the opening of the through hole 32 is the diameter of the opening. If the through holes 32 are elliptical or rectangular, the size of the opening of the through hole 32 is the diameter of the circle circumscribing the opening.

[0042] As shown in Figures 4(a) and 4(b), the size of the opening of the through-hole 32 can be changed depending on the properties of the electrode composite paste and the drying method of the electrode composite paste. For example, compare the first through-hole 32A, the second through-hole 32B, and the third through-hole 32C, which have different opening sizes. The opening sizes decrease in the order of the first through-hole 32A, the second through-hole 32B, and the third through-hole 32C. For example, the diameter of the opening of the first through-hole 32A is 50 [μm], and the diameter of the opening of the third through-hole 32C is 20 [μm].

[0043] As shown in Figure 5, when the viscosity of the electrode composite paste 33 is low, for example between 1000 [mPa·s] and 3000 [mPa·s], the electrode composite paste 33 applied to the first surface 31A of the electrode substrate 31 will drip into the through hole 32. In other words, the larger the opening of the through hole 32, the greater the amount of electrode composite paste 33 that drips. The electrode composite paste 33 that drips into the first through hole 32A reaches the opposite second surface 31B.

[0044] As shown in Figure 6, when the viscosity of the electrode composite paste 33 is high, for example, 7000 [mPa·s] or higher, the amount of electrode composite paste 33 that drips into the through hole 32 from the first surface 31A of the electrode substrate 31 is less compared to low viscosity. In other words, the higher the viscosity of the electrode composite paste 33, the greater the amount of electrode composite paste 33 that drips.

[0045] [Manufacturing method for electrode sheet 30] Next, the manufacturing method of the electrode sheet 30 will be described with reference to Figures 7 to 13. The manufacturing method of the electrode sheet 30 includes a first coating step, a first drying step, a second coating step, and a second drying step.

[0046] The manufacturing method for the electrode sheet 30 is applicable to the manufacture of either the positive electrode sheet 21 or the negative electrode sheet 24. The electrode substrate 31 is the positive electrode substrate when the electrode sheet 30 is the positive electrode sheet 21, and the negative electrode substrate when the electrode sheet 30 is the negative electrode sheet 24. The electrode composite paste 33 is the positive electrode composite paste when the electrode sheet 30 is the positive electrode sheet 21, and the negative electrode composite paste when the electrode sheet 30 is the negative electrode sheet 24. The electrode composite constituting the electrode sheet 30 includes an electrode active material 34 and an electrode binder 35. The electrode active material 34 is the positive electrode active material when the electrode sheet 30 is the positive electrode sheet 21, and the negative electrode active material when the electrode sheet 30 is the negative electrode sheet 24. The electrode binder 35 is the positive electrode binder when the electrode sheet 30 is the positive electrode sheet 21, and the negative electrode binder when the electrode sheet 30 is the negative electrode sheet 24.

[0047] The electrode mixture paste 33 applied to the first surface 31A of the electrode substrate 31 is the first electrode mixture paste 33A. The first electrode mixture paste 33A is made by kneading a first solvent and a first electrode mixture. The electrode mixture paste 33 applied to the second surface 31B of the electrode substrate 31 is the second electrode mixture paste 33B. The second electrode mixture paste 33B is made by kneading a second solvent and a second electrode mixture. The second electrode mixture paste 33B has a lower viscosity than the first electrode mixture paste 33A so that the second electrode mixture paste 33B is connected to the first electrode mixture layer 36A, which is the first electrode mixture paste 33A after drying, via the through holes 32. The viscosity of the first electrode mixture paste 33A may be adjusted by changing the amount of the first solvent relative to the amount of the first electrode mixture, or the amount of electrode binder 35 contained in the first electrode mixture. The viscosity of the first electrode mixture paste 33A may be adjusted by the type of first solvent and the blending of the mixed solvent. The viscosity of the first electrode mixture paste 33A is the viscosity at the temperature of the electrode sheet 30 during the drying process of the first electrode mixture paste 33A. The viscosity of the second electrode mixture paste 33B may be adjusted by changing the amount of second solvent relative to the amount of second electrode mixture and the amount of electrode binder 35 contained in the second electrode mixture. The viscosity of the second electrode mixture paste 33B may be adjusted by the type of second solvent and the blending of the mixed solvent. The viscosity of the second electrode mixture paste 33B is the viscosity at the temperature of the electrode sheet 30 during the drying process of the second electrode mixture paste 33B.

[0048] The opening of the through-hole 32 in the electrode substrate 31 is such that the first electrode composite paste 33A, applied to the first surface 31A of the electrode substrate 31, does not reach the second surface 31B of the electrode substrate 31 through the through-hole 32. The opening of the through-hole 32 is such that the second electrode composite paste 33B, applied to the second surface 31B of the electrode substrate 31, connects to the first electrode composite layer 36A, which is the dried first electrode composite paste 33A, through the through-hole 32.

[0049] [First coating process] As shown in Figure 7, the first coating step involves coating the first electrode composite paste 33A onto the first surface 31A of the electrode substrate 31. In the first coating step, the electrode substrate 31 is positioned so that the first surface 31A is vertically upward, and the coating is performed. The first electrode composite paste 33A coated onto the first surface 31A of the electrode substrate 31 does not reach the second surface 31B of the electrode substrate 31 through the through holes 32. The electrode active material 34 and electrode binder 35 contained in the coated first electrode composite paste 33A are dispersed without bias.

[0050] [First drying process] As shown in Figure 8, the first drying step dries the first electrode composite paste 33A coated on the first surface 31A of the electrode substrate 31. In the first drying step, the electrode substrate 31 is inverted so that the first surface 31A of the electrode substrate 31 is positioned vertically downward. The first surface 31A of the electrode substrate 31 is then heated from vertically downward to release the vapor 37 produced by the evaporation of the first solvent through the through-hole 32. The vapor 37 passes through the through-hole 32 and moves from the first surface 31A to the second surface 31B of the electrode substrate 31. At this time, the electrode binder 35 contained in the coated first electrode composite paste 33A moves towards the electrode substrate 31 as the vapor 37 moves.

[0051] As shown in Figure 9, in the first drying step, the electrode substrate 31 may be positioned so that its first surface 31A is vertically upward, and the first electrode composite paste 33A coated on the first surface 31A of the electrode substrate 31 may be heated from vertically upward. In this case, the drying atmosphere facing the first electrode composite paste 33A and the drying atmosphere facing the second surface 31B of the electrode substrate 31 are made to be different from each other so that a flow of vapor 37 is formed from the first surface 31A of the electrode substrate 31 through the through hole 32 to the second surface 31B of the electrode substrate 31. The drying atmosphere includes the temperature, pressure, and gas flow velocity of each space partitioned by the electrode substrate 31 in the drying step, and includes elements that determine the partial pressure of the solvent in each space facing the electrode substrate 31. For example, the pressure of the drying atmosphere facing the second surface 31B of the electrode substrate 31 is set to a negative pressure, which is lower than the pressure of the drying atmosphere facing the first electrode composite paste 33A. Alternatively, the pressure of the dry atmosphere facing the first electrode mixture paste 33A is set to a positive pressure, which is higher than the pressure of the dry atmosphere facing the second surface 31B of the electrode substrate 31. In this way, the steam 37 moves from the first surface 31A of the electrode substrate 31 through the through hole 32 to the second surface 31B of the electrode substrate 31. At this time, the electrode binder 35 contained in the coated first electrode mixture paste 33A moves towards the electrode substrate 31 as the steam 37 moves.

[0052] As shown in Figure 10, when the first electrode composite paste 33A coated on the first surface 31A of the electrode substrate 31 is dried, the solvent evaporates and it becomes the first electrode composite layer 36A. The electrode binder 35 contained in the first electrode composite layer 36A moves toward the electrode substrate 31 as the vapor 37 moves, and segregates toward the electrode substrate 31.

[0053] [Second coating process] As shown in Figure 11, the second coating step involves coating the second electrode composite paste 33B onto the second surface 31B of the electrode substrate 31 after the first drying step. In the second coating step, the electrode substrate 31 is positioned so that its second surface 31B is vertically upward, and the coating is performed. The second electrode composite paste 33B coated onto the second surface 31B of the electrode substrate 31 connects to the first electrode composite layer 36A via the through-holes 32. The electrode active material 34 and electrode binder 35 contained in the coated second electrode composite paste 33B are dispersed without bias.

[0054] [Second drying process] As shown in Figure 12, the second drying step dries the second electrode composite paste 33B coated on the second surface 31B of the electrode substrate 31. In the second drying step, the electrode substrate 31 is inverted so that the second surface 31B is positioned vertically downward. The second surface 31B of the electrode substrate 31 is then heated from vertically downward to release the vapor 37 produced by the evaporation of the second solvent through the through-hole 32. The vapor 37 passes through the through-hole 32 and moves from the second surface 31B to the first surface 31A of the electrode substrate 31. At this time, the electrode binder 35 contained in the coated second electrode composite paste 33B moves towards the electrode substrate 31 as the vapor 37 moves.

[0055] As shown in Figure 13, when the second electrode composite paste 33B coated on the second surface 31B of the electrode substrate 31 is dried, the solvent evaporates and it becomes the second electrode composite layer 36B. The electrode binder 35 contained in the second electrode composite layer 36B moves toward the electrode substrate 31 as the vapor 37 moves, and segregates toward the electrode substrate 31.

[0056] With this method of manufacturing the electrode sheet 30, the first electrode composite paste 33A coated on the first surface 31A of the electrode substrate 31 can enhance the bonding force between the electrode substrate 31 and the electrode active material 34 due to the electrode binder 35 that segregates towards the electrode substrate 31. Similarly, the second electrode composite paste 33B coated on the second surface 31B of the electrode substrate 31 can enhance the bonding force between the electrode substrate 31 and the electrode active material 34 due to the electrode binder 35 that segregates towards the electrode substrate 31. Furthermore, since the second electrode composite paste 33B coated on the second surface 31B of the electrode substrate 31 connects to the first electrode composite layer 36A via the through-hole 32, the bonding force between the first electrode composite layer 36A and the second electrode composite layer 36B to the electrode substrate 31 can be enhanced.

[0057] [Effects of the First Embodiment] Next, the effects of the first embodiment will be described. (1-1) Since electrode composite pastes 33A and 33B are applied to the first surface 31A and the second surface 31B of the electrode substrate 31, the number of electrode substrates 31 in one electrode sheet 30 can be reduced to one. In addition, in both the first drying step and the second drying step, vapor 37 due to the evaporation of the solvent is discharged from the through holes 32 of the electrode substrate 31, so the electrode binder 35 can be segregated closer to the electrode substrate 31 compared to when vapor 37 is not discharged from the through holes 32. As a result, when the amount of electrode binder 35 is the same, the bonding strength between the electrode substrate 31 and the electrode active material 34 can be increased on both the first surface 31A and the second surface 31B. Also, when sufficient bonding strength between the electrode substrate 31 and the electrode active material 34 is obtained, the amount of electrode binder 35 can be reduced.

[0058] (1-2) In the second drying step, the second surface 31B is positioned vertically below the first surface 31A, and the second surface 31B is heated from vertically below. Therefore, by utilizing the vapor flow due to the temperature difference, the vapor 37 accompanying the evaporation of the second solvent can be discharged from the through-hole 32 of the electrode substrate 31.

[0059] (1-3) The coated second electrode composite paste 33B connects the first surface 31A and the second surface 31B through the through holes 32. As a result, the connection between the electrode active materials 34 by the electrode binder 35 through the through holes 32, combined with the segregation of the electrode binder 35, can increase the bonding force between the electrode substrate 31 and the electrode active material 34 on both the first surface 31A and the second surface 31B. Furthermore, in the first coating process, it is possible to apply a high viscosity to the first electrode composite paste 33A that does not reach the second surface 31B through the through holes 32, which makes it possible to shorten the time required for the first drying process and to improve the accuracy of the thickness of the first electrode composite paste 33A after drying.

[0060] (1-4) The coated second electrode composite paste 33B connects the first surface 31A and the second surface 31B through the through holes 32. As a result, the connection between the electrode active materials 34 by the electrode binder 35 through the through holes 32, combined with the segregation of the electrode binder 35, can increase the bonding force between the electrode substrate 31 and the electrode active material 34 on both the first surface 31A and the second surface 31B. Furthermore, since the diameter of the through holes 32 is large enough to allow the second electrode composite paste 33B to flow in, it is possible to shorten the drying time in the first and second drying processes.

[0061] (1-5) Regardless of the vertical position of the first surface 31A relative to the second surface 31B, the vapor 37 resulting from the evaporation of the solvent on the first surface 31A of the electrode substrate 31 is discharged from the through-hole 32 of the electrode substrate 31, thereby segregating the electrode binder 35 closer to the electrode substrate 31 and increasing the bonding force between the electrode substrate 31 and the electrode active material 34.

[0062] [Second Embodiment] The method for manufacturing an electrode sheet for a non-aqueous secondary battery and a second embodiment of the method for manufacturing a non-aqueous secondary battery will be described below with reference to Figures 14 to 16. The method for manufacturing the electrode sheet 30 of the lithium-ion secondary battery 10 in this embodiment differs from the first embodiment in that the vapor 37 resulting from the evaporation of the second solvent of the second electrode composite paste 33B coated on the second surface 31B of the electrode substrate 31 is not discharged from the through-hole 32. The differences from the first embodiment will be described below.

[0063] [Manufacturing method for electrode sheet 30] A method for manufacturing the electrode sheet 30 will be described. The manufacturing method of the second embodiment involves the same process as the manufacturing method of the first embodiment from the first coating step to the first drying step.

[0064] The second electrode mixture paste 33B also has a lower viscosity than the first electrode mixture paste 33A, similar to the manufacturing method of the first embodiment, so that it is connected to the first electrode mixture layer 36A, which is the dried first electrode mixture paste 33A, via the through-holes 32.

[0065] The opening of the through-hole 32 in the electrode substrate 31 is also the same as in the manufacturing method of the first embodiment, such that the first electrode composite paste 33A does not reach the second surface 31B through the through-hole 32 during the first coating step. The opening of the through-hole 32 is such that the second electrode composite paste 33B connects to the first electrode composite layer 36A, which is the dried first electrode composite paste 33A, through the through-hole 32.

[0066] [Second coating process] As shown in Figure 14, the second coating step involves coating the second electrode composite paste 33B onto the second surface 31B of the electrode substrate 31 after the first drying step. In the second coating step, the electrode substrate 31 is positioned so that its second surface 31B is vertically upward, and the coating is performed. The second electrode composite paste 33B coated onto the second surface 31B of the electrode substrate 31 is connected to the first electrode composite layer 36A via the through-holes 32. The electrode active material 34 and electrode binder 35 contained in the coated second electrode composite paste 33B are dispersed without bias.

[0067] [Second drying process] As shown in Figure 15, the second drying step dries the second electrode composite paste 33B coated on the second surface 31B of the electrode substrate 31. In the second drying step, the electrode substrate 31 is positioned so that the second surface 31B of the electrode substrate 31 is vertically upward, and the second electrode composite paste 33B coated on the second surface 31B of the electrode substrate 31 is heated from vertically upward. The vapor 37 produced by the evaporation of the second solvent is discharged from the surface of the second electrode composite paste 33B coated on the second surface 31B of the electrode substrate 31. At this time, the electrode binder 35 contained in the coated second electrode composite paste 33B moves towards the surface as the vapor 37 moves.

[0068] As shown in Figure 16, when the second electrode composite paste 33B coated on the second surface 31B of the electrode substrate 31 is dried, the solvent evaporates and it becomes the second electrode composite layer 36B. The electrode binder 35 contained in the second electrode composite layer 36B moves toward the surface as the vapor 37 moves, and segregates toward the surface.

[0069] With this method of manufacturing the electrode sheet 30, the first electrode composite paste 33A coated on the first surface 31A of the electrode substrate 31 can enhance the bonding force between the electrode substrate 31 and the electrode active material 34 due to the electrode binder 35 that segregates towards the electrode substrate 31. On the other hand, the second electrode composite paste 33B coated on the second surface 31B of the electrode substrate 31 connects to the first electrode composite layer 36A via the through-holes 32, thereby enhancing the bonding force between the first electrode composite layer 36A and the second electrode composite layer 36B to the electrode substrate 31.

[0070] [Effects of the second embodiment] Next, the effects of the second embodiment will be described. (2-1) Since electrode composite pastes 33A and 33B are applied to the first surface 31A and the second surface 31B of the electrode substrate 31, the number of electrode substrates 31 in one electrode sheet 30 can be reduced to one. In addition, in the first drying step, compared to the case where steam 37 is not discharged from the through hole 32, the bonding strength between the first surface 31A and the electrode active material 34 can be increased by segregating the electrode binder 35 closer to the electrode substrate 31. Furthermore, since the first electrode composite paste 33A dries more easily than the second electrode composite paste 33B, the time required for the first drying step can be shortened. Then, in the second drying step, the bonding strength between the second surface 31B and the electrode active material 34 can be increased by connecting the electrode active material 34s with the electrode binder 35 through the through hole 32. In addition, if sufficient bonding strength is obtained between the electrode substrate 31 and the electrode active material 34, the amount of electrode binder 35 can be reduced.

[0071] (2-2) Since the diameter of the through-hole 32 is large enough to allow the second electrode composite paste 33B to flow in, it is possible to shorten the drying time in the first drying process and the second drying process.

[0072] [Other embodiments] Each of the above embodiments can be implemented with the following modifications. Each of the above embodiments and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0073] In the first embodiment described above, in the first drying step, the electrode substrate 31 is positioned so that its first surface 31A and second surface 31B are vertically aligned, and the drying atmosphere facing the first electrode mixture paste 33A and the drying atmosphere facing the second surface 31B are made to be different from each other so that a flow of steam 37 is formed from the first surface 31A through the through hole 32 to the second surface 31B. However, as long as a flow of steam 37 is formed from the first surface 31A through the through hole 32 to the second surface 31B, the electrode substrate 31 may be positioned so that its first surface 31A and second surface 31B are not vertically aligned. According to the above method, regardless of the vertical position of the first surface relative to the second surface, the vapor 37 resulting from the evaporation of the solvent on the first surface 31A of the electrode substrate 31 is discharged from the through-hole 32 of the electrode substrate 31, thereby segregating the electrode binder 35 closer to the electrode substrate 31 and increasing the bonding strength between the electrode substrate 31 and the electrode active material 34.

[0074] In the first embodiment described above, the second electrode composite paste 33B has a lower viscosity than the first electrode composite paste 33A. This can be changed so that the composition and composition ratio of the first electrode composite paste 33A and the composition and composition ratio of the second electrode composite paste 33B are the same, or the viscosity of the first electrode composite paste 33A and the viscosity of the second electrode composite paste 33B are the same. In this case, the second electrode composite paste 33B applied to the second surface 31B may or may not reach the first surface 31A of the electrode substrate 31 through the through holes 32. Even if the second electrode composite paste 33B does not reach the first surface 31A, the electrode binder 35 of the second electrode composite layer 36B is segregated closer to the electrode substrate 31, thereby increasing the bonding force between the second surface 31B and the electrode active material 34.

[0075] In the first embodiment described above, the opening of the through-hole 32 was sized such that the second electrode composite paste 33B coated on the second surface 31B of the electrode substrate 31 could connect to the first electrode composite layer 36A, which is the first electrode composite paste 33A after drying, through the through-hole 32. Alternatively, the opening of the through-hole 32 could be sized such that the second electrode composite paste 33B coated on the second surface 31B of the electrode substrate 31 could not connect to the first electrode composite layer 36A, which is the first electrode composite paste 33A after drying, through the through-hole 32. In this case, the second electrode composite paste 33B coated on the second surface 31B would not reach the first surface 31A of the electrode substrate 31 through the through-hole 32. Furthermore, since the electrode binder 35 of the second electrode composite layer 36B is segregated closer to the electrode substrate 31, the bonding force between the second surface 31B and the electrode active material 34 can be increased.

[0076] The lithium-ion secondary battery 10 may be installed in automated transport machines, special vehicles for cargo handling, electric vehicles, hybrid vehicles, etc., as well as in computers and other electronic devices, or it may constitute a system other than those mentioned above. For example, it may be installed in mobile objects such as ships and aircraft, or it may be part of a power supply system that supplies electricity from a power plant to buildings and homes where the secondary battery is installed via a substation or the like. [Explanation of Symbols]

[0077] 10…Lithium-ion rechargeable battery 11…Battery case 12... Lid 13A... Positive external terminal 13B…Negative external terminal 14A... Positive electrode current collector 14B... Negative electrode current collector 20...Wound body 20A... Positive electrode current collector 20B... Negative electrode current collector 21…Positive electrode sheet 22...Positive electrode current collector 22A...Unpainted area on the positive electrode side 23…Positive electrode composite layer 24... Negative electrode sheet 25...Negative electrode current collector 25A...Unpainted area on the negative electrode side 26…Negative electrode composite material layer 27... Separator 30… Electrode sheet 31...electrode base material 31A…Side 1 31B…Second side 32…Through hole 33A...First electrode composite paste 33B...Second electrode composite paste 34...electrode active material 35… Electrode binder 36A...First electrode composite layer 36B…Second electrode composite material layer 37... Steam

Claims

1. A method for manufacturing electrode sheets for non-aqueous secondary batteries, The electrode composite material constituting the electrode sheet includes an electrode active material and an electrode binder. The electrode substrate constituting the electrode sheet has a plurality of through holes that penetrate from the first surface to the second surface, A first coating step involves applying a first electrode mixture paste, obtained by kneading a first solvent and a first electrode mixture, to the first surface. A first drying step of drying the first electrode composite paste coated on the first surface, A second coating step involves applying a second electrode mixture paste, obtained by kneading a second solvent and a second electrode mixture, to the second surface after the first drying step. The process includes a second drying step of drying the second electrode composite paste applied to the second surface, In the first drying step, vapors generated by the evaporation of the first solvent are discharged from the through-holes. In the second drying step, vapors resulting from the evaporation of the second solvent are discharged through the through-holes. A method for manufacturing electrode sheets for non-aqueous secondary batteries, characterized by the following features.

2. In the second drying step, the electrode substrate is inverted so that the second surface is positioned vertically below the first surface, and the second surface is heated from vertically below the second surface to discharge the steam through the through hole. A method for manufacturing an electrode sheet for a non-aqueous secondary battery according to claim 1.

3. The second electrode mixture paste has a lower viscosity than the first electrode mixture paste, so that the second electrode mixture paste is connected to the dried first electrode mixture paste through the through-holes. A method for manufacturing an electrode sheet for a non-aqueous secondary battery according to claim 1.

4. The opening of the through-hole is such that, in the first coating step, the first electrode mixture paste does not reach the second surface through the through-hole, and the second electrode mixture paste connects to the dried first electrode mixture paste through the through-hole. A method for manufacturing an electrode sheet for a non-aqueous secondary battery according to claim 1.

5. A method for manufacturing electrode sheets for non-aqueous secondary batteries, The electrode composite material constituting the electrode sheet includes an electrode active material and an electrode binder. The electrode substrate constituting the electrode sheet has a plurality of through holes that penetrate from the first surface to the second surface, A first coating step involves applying a first electrode mixture paste, obtained by kneading a first solvent and a first electrode mixture, to the first surface. A first drying step of drying the first electrode composite paste coated on the first surface, A second coating step involves applying a second electrode mixture paste, obtained by kneading a second solvent and a second electrode mixture, to the second surface after the first drying step. The process includes a second drying step of drying the second electrode composite paste applied to the second surface, In the first drying step, vapors generated by the evaporation of the first solvent are discharged from the through-holes. The second electrode mixture paste has a lower viscosity than the first electrode mixture paste, so that the second electrode mixture paste is connected to the dried first electrode mixture paste through the through-holes. A method for manufacturing electrode sheets for non-aqueous secondary batteries, characterized by the following features.

6. A method for manufacturing electrode sheets for non-aqueous secondary batteries, The electrode composite material constituting the electrode sheet includes an electrode active material and an electrode binder. The electrode substrate constituting the electrode sheet has a plurality of through holes that penetrate from the first surface to the second surface, A first coating step involves applying a first electrode mixture paste, obtained by kneading a first solvent and a first electrode mixture, to the first surface. A first drying step of drying the first electrode composite paste coated on the first surface, A second coating step involves applying a second electrode mixture paste, obtained by kneading a second solvent and a second electrode mixture, to the second surface after the first drying step. The process includes a second drying step of drying the second electrode composite paste applied to the second surface, In the first drying step, vapors generated by the evaporation of the first solvent are discharged from the through-holes. The opening of the through-hole is such that, in the first coating step, the first electrode mixture paste does not reach the second surface through the through-hole, and the second electrode mixture paste is such that it connects to the dried first electrode mixture paste through the through-hole. A method for manufacturing electrode sheets for non-aqueous secondary batteries, characterized by the following features.

7. In the first drying step, the drying atmosphere facing the first electrode composite paste and the drying atmosphere facing the second surface are made different from each other so that the steam flow is formed from the first surface through the through hole to the second surface. A method for manufacturing an electrode sheet for a non-aqueous secondary battery according to any one of claims 1 to 6.

8. A method for manufacturing a non-aqueous secondary battery comprising an electrode sheet and a non-aqueous electrolyte, The process includes manufacturing the electrode sheet using the method for manufacturing an electrode sheet for a non-aqueous secondary battery described in any one of claims 1, 5, or 6. A method for manufacturing a non-aqueous secondary battery, characterized by the following features.

Images