Method for manufacturing power storage device

Abstract

To provide a technique capable of suitably reducing a solvent and a dispersion medium remaining in an electrode body.SOLUTION: One aspect of the method for producing electricity storage devices (for example, batteries) disclosed herein includes an arranging step S1 of arranging an adhesive layer slurry on at least one of the surfaces of the separators 26, a forming step S2 of removing at least one of the solvents and the dispersion media from the adhesive layer slurry to form the adhesive layers 6, and a laminating step S3 of laminating the positive electrodes 22, the separators 26, and the negative electrodes 24. In the laminating step S3, separators 26 having adhesive layers 6 disposed in a plurality of dots on at least one of the surfaces of the separators are used, and the dot-shaped adhesive layers 6 each have a hollow region E at the center in a plan view.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] For example, Japanese Patent No. 5328034 discloses a battery including a wound electrode assembly having a positive electrode, a negative electrode, and a separator, and a heat-resistant porous layer containing an adhesive resin on the surface of the separator. The document states that such a wound electrode assembly is produced by stacking a positive electrode and a negative electrode with a separator interposed between them, winding them, and crushing them into a flat shape. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5328034 Summary of the Invention [Problem to be solved by the invention]

[0004] However, according to the investigations of the present inventors, for example, when an adhesive layer is formed by applying an adhesive to the surface of a separator, if the separator is placed on an electrode while the solvent in the adhesive remains, the solvent may migrate to the electrode, which may result in a decrease in the capacity and input / output of the power storage device (e.g., battery), and is therefore undesirable from the viewpoint of battery performance.

[0005] The present disclosure has been made in view of the above circumstances, and its main purpose is to provide a technique that can suitably reduce the amount of solvent or dispersion medium remaining in an electrode body. [Means for solving the problem]

[0006] To achieve this objective, the present disclosure provides a method for manufacturing an electricity storage device including an electrode assembly including a first electrode, a second electrode, and a separator disposed between the first and second electrodes, the method including: a disposing step of disposing an adhesive layer slurry containing an adhesive and at least one of a solvent and a dispersion medium on at least one surface of the separator; a forming step of removing the solvent and at least one of the dispersion medium from the adhesive layer slurry to form an adhesive layer; and a laminating step of laminating the first electrode, the separator, and the second electrode, wherein the laminating step uses a separator having an adhesive layer disposed in a plurality of dots on at least one surface of the separator, the dot-shaped adhesive layer having a central hollow region in a plan view. As will be described in detail below, this method for manufacturing an electricity storage device can produce an electricity storage device in which the amount of solvent and dispersion medium remaining in the electrode assembly is suitably reduced. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a flowchart illustrating a method for manufacturing a battery according to an embodiment. [Figure 2] FIG. 2 is an explanatory diagram for explaining an electrode body manufacturing apparatus according to one embodiment. [Figure 3] FIG. 2 is a schematic diagram of a separator according to one embodiment after an adhesive layer is formed, as viewed from above. [Figure 4] FIG. 4 is a schematic vertical cross-sectional view taken along line IV-IV in FIG. 3. [Figure 5] FIG. 2 is a schematic diagram illustrating a wound body before a pressing process according to one embodiment. [Figure 6] FIG. 10 is a schematic diagram showing a wound body after a pressing process according to an embodiment. [Figure 7] FIG. 1 is a perspective view schematically illustrating a battery according to an embodiment. [Figure 8] FIG. 8 is a schematic vertical cross-sectional view taken along line VIII-VIII in FIG. 7. [Figure 9] FIG. 8 is a schematic longitudinal sectional view taken along line IX-IX in FIG. 7. [Figure 10] FIG. 8 is a schematic cross-sectional view taken along line XX in FIG. 7. [Figure 11] FIG. 2 is a perspective view schematically showing a wound electrode body attached to a sealing plate. [Figure 12] FIG. 2 is a perspective view schematically showing a wound electrode body to which a positive electrode second current collecting portion and a negative electrode second current collecting portion are attached. [Figure 13] FIG. 2 is a schematic diagram showing the configuration of a wound electrode body of a battery according to one embodiment. [Figure 14] FIG. 2 is an enlarged view schematically illustrating an interface between a positive electrode, a negative electrode, and a separator according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Several embodiments of the technology disclosed herein will be described below with reference to the drawings. Naturally, the following description is not intended to limit the technology disclosed herein to the following embodiments. In the following drawings, components and parts that perform the same function are denoted by the same reference numerals. Furthermore, the dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect actual dimensional relationships. Matters other than those specifically mentioned in this specification that are necessary for implementing the technology disclosed herein (e.g., the general configuration and manufacturing process of a battery that do not characterize the present invention) can be understood as design matters of a person skilled in the art based on prior art in the relevant field. The technology disclosed herein can be implemented based on the content disclosed in this specification and common technical knowledge in the relevant field. In this specification, the expression "A to B" indicating a range means "greater than A and less than B." It also encompasses the meanings of "greater than A" and "less than B."

[0009] In this specification, the term "electricity storage device" refers to a device that can be charged and discharged. Electricity storage devices include batteries such as primary batteries and secondary batteries (for example, non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries, and nickel-metal hydride batteries), and capacitors (physical batteries) such as electric double layer capacitors. The electrolyte may be any of a liquid electrolyte (electrolytic solution), a gel electrolyte, and a solid electrolyte.

[0010] <Battery manufacturing method> Hereinafter, the present technology will be described using as an example a manufacturing method of a lithium-ion secondary battery (hereinafter, also simply referred to as "battery 100"), which is one embodiment of the power storage device disclosed herein. Note that, although the following description will be given of a case where the first electrode is a positive electrode 22 and the second electrode is a negative electrode 24, the technology disclosed herein can also be applied to a case where, for example, the first electrode is a negative electrode 24 and the second electrode is a positive electrode 22. Also, the following description will be given of a case where a wound electrode body is manufactured in which a strip-shaped positive electrode 22 and a strip-shaped negative electrode 24 are wound with a strip-shaped separator 26 interposed therebetween. However, the technology disclosed herein can also be applied to a case where a stacked electrode body is manufactured in which a positive electrode 22 and a negative electrode 24 are stacked with a separator 26 interposed therebetween. The battery manufacturing method disclosed herein may further include other steps at any stage, and if a step is not described as essential, it can be deleted as appropriate. Furthermore, the order of the steps can be reversed as long as the effects of the technology disclosed herein are achieved.

[0011] 1 is a flowchart illustrating a method for manufacturing a battery 100 according to this embodiment. First, the method for manufacturing a battery 100 according to this embodiment is a method for manufacturing a battery provided with an electrode assembly (here, wound electrode assemblies 20a, 20b, 20c) including a first electrode (here, positive electrode 22), a second electrode (here, negative electrode 24), and separators 26 (here, first separator 26S1 and second separator 26S2) disposed between the first electrode and the second electrode. As shown in FIG. 1 , the manufacturing method of the battery 100 according to this embodiment includes a disposing step (step S1) of disposing an adhesive layer slurry containing an adhesive and at least one of a solvent and a dispersion medium on at least one surface of a separator 26; a forming step (step S2) of removing at least one of the solvent and the dispersion medium from the adhesive layer slurry to form an adhesive layer 6; and a laminating step (step S3) of laminating a first electrode (here, a positive electrode 22), a separator 26, and a second electrode (here, a negative electrode 24). The laminating step uses a separator 26 having adhesive layers 6 arranged in a dot pattern on at least one surface of the separator. The dot-patterned adhesive layers 6 are characterized by having a hollow region E in the center in a plan view. The hollow region E can be referred to as a region where no adhesive layer 6 is arranged (formed), i.e., an adhesive layer-free region.

[0012] The manufacturing method of the battery 100 described above includes a forming step of removing at least one of the solvent and the dispersion medium from the adhesive layer slurry disposed in the disposing step to form dot-shaped adhesive layers 6. Furthermore, the dot-shaped adhesive layers 6 have a hollow region E in the center when viewed from above. This facilitates the evaporation of the solvent or dispersion medium remaining in the adhesive layers 6 during electrode assembly fabrication, thereby suitably reducing the amount of the remaining solvent or dispersion medium. This allows for a battery 100 with suitably suppressed performance degradation. In particular, when water is included as the solvent or dispersion medium, water is less likely to volatilize, making it suitable for application of the technology disclosed herein. Below, the manufacturing method of the battery 100 according to this embodiment will be described, along with an electrode assembly manufacturing apparatus 1 that embodies the manufacturing method of the battery 100. The following describes a case in which dot-shaped adhesive layers 6 are disposed on one side of the first separator 26S1 and the second separator 26S2.

[0013] FIG. 2 is a schematic diagram showing the configuration of an electrode assembly manufacturing apparatus 1 according to this embodiment. As shown in FIG. 2, the electrode assembly manufacturing apparatus 1 according to this embodiment includes a plurality of rollers 2 (six in this example), a winding core 3, an adhesive application section 4, and a drying section 5. In this embodiment, the electrode assembly manufacturing apparatus 1 also includes a cutter, a pressing jig, and a control device (not shown). Here, the cutter is a cutter that cuts the first separator 26S1 and the second separator 26S2. The pressing jig is a jig that presses the first separator 26S1 and the second separator 26S2 against the winding core 3. Each component of the electrode assembly manufacturing apparatus 1 has a required actuator, as appropriate. The control device is configured to control each component of the electrode assembly manufacturing apparatus 1 so that required operations are performed at predetermined timings according to a preset program. The control device may be embodied, for example, by a computer such as a microcontroller.

[0014] The positive electrode 22, the negative electrode 24, the first separator 26S1, and the second separator 26S2 are each prepared in a wound state around a reel (not shown) or the like. The positive electrode 22, the negative electrode 24, the first separator 26S1, and the second separator 26S2 are each transported along predetermined transport paths k1 to k4. Transport path k1 is a path along which the negative electrode 24 is fed from a reel (not shown) toward the winding core 3. Transport path k2 is a path along which the second separator 26S2 is fed from a reel (not shown) toward the winding core 3. Transport path k3 is a path along which the positive electrode 22 is fed from a reel (not shown) toward the winding core 3. Transport path k4 is a path along which the first separator 26S1 is fed from a reel (not shown) toward the winding core 3. The conveying paths k1 to k4 may be appropriately provided with dancer roll mechanisms for removing slack from the positive electrode 22, negative electrode 24, first separator 26S1, and second separator 26S2 being fed, tensioners for adjusting tension, and the like.

[0015] The plurality of rollers 2 are arranged on the transport paths k1 to k4 for the positive electrode 22, the negative electrode 24, the first separator 26S1, and the second separator 26S2, respectively. The plurality of rollers 2 are an example of a transport device. The plurality of rollers 2 are arranged at predetermined positions to define the respective transport paths k1 to k4. The positive electrode 22, the negative electrode 24, the first separator 26S1, and the second separator 26S2 are each transported by the plurality of rollers 2. Note that in this embodiment, the number of rollers 2 is six, but in other embodiments, the number of rollers 2 may be other than six.

[0016] The winding core 3 has a function of holding the positive electrode 22, negative electrode 24, first separator 26S1, and second separator 26S2 wound around its circumferential surface. Here, the winding core 3 is a substantially cylindrical member, but a flat winding core may be used when winding into a flat shape. Here, an undivided winding core is used as the winding core 3, but a winding core divided along the radial direction or a winding core with a variable diameter may also be used.

[0017] The winding core 3 may further have suction holes, grooves, and the like. The suction holes are holes for adsorbing, for example, the first separator 26S1 and the second separator 26S2 wound around the side circumferential surface. The suction holes may be circular or rectangular in plan view. Alternatively, the suction holes may be slit-shaped. The suction holes typically include a suction flow path formed inside the winding core 3 and communicating with the suction holes. The suction path is a flow path for creating negative pressure in the suction holes. The suction path may be configured, for example, to be appropriately connected to an external vacuum line to create negative pressure. The grooves can function as a receiving portion for the cutter blade to be lowered when the first separator 26S1 and the second separator 26S2 are cut. This prevents damage to the winding core or the cutter due to contact between the winding core 3 and the cutter blade.

[0018] The adhesive application unit 4 applies adhesive layer slurry to the surface of at least one of the separators 26 (here, the first separator 26S1 and the second separator 26S2) along the conveyance direction. The adhesive application unit 4 is configured to apply a desired amount of adhesive layer slurry to desired areas of the first separator 26S1 and the second separator 26S2. The adhesive layer slurry contains, for example, an adhesive layer binder (adhesive) as described below, and at least one of a solvent and a dispersion medium. Note that the term "slurry" may include ink, paste, etc.

[0019] The solvent contained in the adhesive layer slurry may be any liquid capable of dissolving the adhesive layer binder (adhesive). The dispersion medium contained in the adhesive layer slurry may be any liquid capable of dispersing the adhesive layer binder (adhesive). Examples of such solvents and dispersion media include water, aqueous solvents, organic solvents, and mixed solvents thereof. For example, from the viewpoint of reducing environmental impact, so-called aqueous solvents are preferably used. In this case, water or a mixed solvent mainly composed of water can be used. As the solvent component other than water constituting such a mixed solvent, one or more organic solvents (lower alcohols, lower ketones, etc.) that are uniformly miscible with water can be appropriately selected and used. For example, it is preferable to use an aqueous solvent in which 80% by mass or more (more preferably 90% by mass or more, and even more preferably 95% by mass or more) of the aqueous solvent is water. A particularly preferred example is an aqueous solvent that is essentially composed of water. The solvent for the adhesive layer slurry is not limited to so-called aqueous solvents, and may also be so-called organic solvents. Examples of organic solvents include alcohol-based solvents, ketone-based solvents, ester-based solvents, halogen-based solvents, hydrocarbon-based solvents, and nitrogen-containing solvents. These may be used alone or in combination. The boiling points of the solvent and dispersion medium are preferably, for example, about 50°C to 200°C or about 100°C to 150°C, from the viewpoint of facilitating removal of the solvent during drying after application of the adhesive layer slurry. If the boiling point is too low, the adhesive layer slurry may dry before application, impairing coating stability. Therefore, it is preferable to select the appropriate boiling point depending on the application method. The solvent / dispersion medium ratio in the adhesive layer slurry is adjusted appropriately depending on the application method. For example, in the case of application methods such as gravure printing and inkjet printing, the weight ratio is preferably about 50% to 99%, and more preferably about 80% to 95%. The adhesive layer binder (adhesive) may be dissolved or dispersed in the adhesive layer slurry. Furthermore, if the adhesive layer slurry is a solution in which the adhesive is dissolved, the adhesive may penetrate excessively into the heat-resistant layer 28 described below, so it is preferable that the adhesive layer slurry is a dispersion of the adhesive.Although not particularly limited, the content of the solvent and the dispersion medium in the adhesive layer slurry can be, for example, approximately 50 to 99% by mass (preferably, approximately 80 to 95% by mass) when the entire adhesive layer slurry is taken as 100% by mass.

[0020] Examples of the adhesive layer binder (adhesive) include acrylic resins, fluorine-based resins, rubber-based resins, urethane-based resins, silicone-based resins, and epoxy-based resins. These may be used alone or in combination of two or more. An example of the rubber-based resin is styrene butadiene rubber (SBR). Fluorine-based resins and acrylic resins are preferred because they have high flexibility and can more suitably exhibit adhesiveness to the electrode (here, the positive electrode 22). Examples of fluorine-based resins include polyvinylidene fluoride (PVdF) and polytetrafluoroethylene (PTFE). The type of the adhesive layer binder may be the same as or different from the heat-resistant layer binder described below. From the viewpoint of ease of handling, the adhesive layer binder preferably exhibits adhesiveness (adhesion) at room temperature (for example, about 25°C). On the other hand, the adhesive layer binder may exhibit adhesiveness (adhesion) by heating, pressure, or the like. Here, tackiness (adhesion) can mean, for example, that the peel strength in a 90° peel test based on JIS Z 0237:2009 is 0.00001 N / 20 mm to 0.1 N / 20 mm (preferably, 0.0001 N / 20 mm to 0.01 N / 20 mm). Although not particularly limited, the content of the adhesive layer binder in the adhesive layer slurry can be, for example, about 1 to 50 mass % (preferably, about 5 to 20 mass %) when the entire adhesive layer slurry is taken as 100 mass %.

[0021] The adhesive layer slurry may contain one or more additives, such as known thickeners, surfactants, and inorganic fillers (e.g., alumina, titania, boehmite), as long as they do not impair the effects of the technology disclosed herein. When the adhesive layer slurry contains such an inorganic filler, the inorganic filler is preferably contained in an amount of, for example, about 5 to 20% by mass (preferably about 10 to 15% by mass) when the total mass of the adhesive layer slurry is taken as 100% by mass. The viscosity of the adhesive layer slurry is not particularly limited as long as the effects of the technology disclosed herein are exhibited, but can be approximately 10 to 100 mPa·s (e.g., about 20 to 50 mPa·s). This viscosity can be measured, for example, using a commercially available viscometer.

[0022] As the adhesive application unit 4, various adhesive application units can be used, for example, inkjet printing, various intaglio printing machines such as gravure roll coaters and spray coaters, die coaters such as slit coaters, comma coaters and cap coaters (Capillary Coaters (CAP coaters), lip coaters, calendar machines, etc.

[0023] In a preferred embodiment, the adhesive layer 6 is adhered to the first electrode (here, the positive electrode 22), and the first electrode (here, the positive electrode 22) contains a lithium transition metal composite oxide. An example of such a lithium transition metal composite oxide is a lithium nickel cobalt manganese composite oxide. In the lithium transition metal composite oxide, the ratio of the amount of Ni (moles) to the amount of transition metal (moles) {Ni amount (mol) / transition metal amount (mol)} is 0.7 or more (more preferably, 0.8 or more, 0.9 or more). The adhesive layer slurry also contains water. For example, a lithium transition metal composite oxide having the above-described composition is preferably used from the viewpoint of increasing the capacity of the battery 100, but is known to have particularly low resistance to moisture. Therefore, such a configuration can be said to be suitable for application of the technology disclosed herein.

[0024] The drying section 5 removes at least one of the solvent and the dispersion medium from the adhesive layer slurry. The drying section 5 can volatilize at least one of the solvent and the dispersion medium from the separator 26. The drying method used by the drying section 5 is not particularly limited, and methods such as ventilation drying, heat drying, and vacuum drying can be used. For example, in the case of heat drying, the heating temperature may be about 40°C to 300°C (e.g., about 50°C to 200°C).

[0025] Next, a method for manufacturing the battery 100 according to this embodiment will be described. As described above, the method for manufacturing the battery 100 according to this embodiment includes an arrangement step (step S1), a formation step (step S2), and a stacking step (step S3). Each step will be described below.

[0026] (Step S1: Placement process) As described above, in this process, an adhesive layer slurry containing an adhesive and at least one of a solvent and a dispersion medium is disposed (applied) on at least one surface of the separator 26. As shown in FIG. 2, in this embodiment, the adhesive layer slurry is disposed on one surface of the first separator 26S1 and the second separator 26S2. Here, FIG. 3 is a schematic diagram of the separator 26 as viewed from above after the adhesive layer 6 according to this embodiment has been formed. As shown in FIG. 3, in this embodiment, a dot-shaped adhesive layer 6 having a hollow region E in the center in a plan view is finally formed on the surface of the separator 26. For example, the dot-shaped adhesive layer 6 on the surface of the separator 26 can be formed using an adhesive applicator 4 having an inkjet printing function and a dual-diameter nozzle. Alternatively, the dot-shaped adhesive layer 6 on the surface of the separator 26 can be formed by printing multiple dots using the adhesive applicator 4 having an inkjet printing function. However, these are merely examples, and the adhesive layer slurry may be disposed on the surface of the separator 26 by other methods.

[0027] (Step S2: Forming process) As described above, in this step, at least one of the solvent and the dispersion medium is removed from the adhesive layer slurry to form the adhesive layer 6. That is, a separator 26 having a plurality of dot-shaped adhesive layers 6 arranged thereon can be obtained, as shown in FIG. 3. As shown in FIG. 2, in this embodiment, the adhesive layer 6 arranged on the surface of the separator 26 in the arrangement step is dried by a drying unit 5. By removing the solvent and the dispersion medium, the amount of the solvent and the dispersion medium remaining in the adhesive layer 6 during the electrode assembly production can be suitably reduced. Furthermore, since the adhesive layer 6 has a hollow region E, the solvent and the dispersion medium are suitably evaporated. Note that "removing at least one of the solvent and the dispersion medium from the adhesive layer slurry" can mean removing, for example, 70% by mass or more, 80% by mass or more, preferably 90% by mass or more, 95% by mass or more, or 99% by mass or more (particularly preferably 100% by mass) of the solvent and the dispersion medium in the adhesive layer slurry, where the total amount of the solvent and the dispersion medium in the adhesive layer slurry is 100% by mass. In the technique disclosed herein, it is not necessary to completely remove the solvent or dispersion medium in this step, and some of them may remain.

[0028] As shown in FIG. 3 , in this embodiment, the dot-shaped adhesive layers 6 have a circular shape in a planar view (outer shape), but are not limited thereto. In other embodiments, the dot-shaped adhesive layers 6 may have an elliptical, rectangular, polygonal, or a combination thereof in a planar view. In this embodiment, two adhesive layers 6 are arranged in each of the short sides of the strip-shaped separator 26 (Y direction in FIG. 3 ), but are not limited thereto. In other embodiments, one adhesive layer 6 may be arranged in each of the short sides of the separator 26 (Y direction in FIG. 3 ), or three or more adhesive layers 6 may be arranged in each of the short sides. In this embodiment, the hollow regions E have a circular shape in a planar view of the separator 26, but are not limited thereto. In other embodiments, the hollow regions E may have an elliptical, rectangular, or various other shapes.

[0029] The adhesive layer 6 is preferably composed mainly of the adhesive layer binder as described above. Here, "composed mainly of the adhesive layer binder" can mean that, when the entire adhesive layer 6 is taken as 100% by volume, the adhesive layer binder is contained in an amount of, for example, 50% by volume or more, 60% by volume or more, preferably 70% by volume or more, 80% by volume or more, more preferably 90% by volume or more, or 95% by volume or more (which may be 100% by volume). This allows the predetermined adhesiveness to the electrode (here, the positive electrode 22) to be accurately exhibited.

[0030] As described above, the adhesive layer 6 may contain other materials (for example, inorganic fillers such as alumina, titania, boehmite, etc.) in addition to the adhesive layer binder. When the adhesive layer 6 contains an inorganic filler, the inorganic filler is preferably contained in an amount of, for example, about 10 to 90 mass % (preferably about 20 to 80 mass %) when the entire adhesive layer 6 is taken as 100 mass %.

[0031] Here, when the area of ​​one side of separator 26 in a plan view is S1 and the total area of ​​the portion of one side of separator 26 where adhesive layer 6 is disposed is S2, the ratio of S2 to S1 (S2 / S1) is not particularly limited as long as the effects of the technology disclosed herein are exhibited. The upper limit of the ratio (S2 / S1) is, for example, 0.5 or less or 0.3 or less, and from the viewpoint of more suitably reducing the amount of solvent or dispersion medium remaining in adhesive layer 6 during preparation of the electrode assembly, it is preferably 0.1 or less, and may be 0.07 or less or 0.05 or less. The lower limit of the ratio (S2 / S1) is, for example, 0.01 or more, and from the viewpoint of suitably ensuring adhesive strength between separator 26 and the electrode, it is preferably 0.02 or more, more preferably 0.03 or more. That is, when the area of ​​one side of separator 26 is S1 and the total area of ​​the portion on one side of separator 26 where adhesive layer 6 is arranged is S2, it is preferable that S2 / S1≦0.1 in order to reduce the amount of solvent or dispersion medium remaining in adhesive layer 6 during electrode assembly production. Note that "the total area S2 of the portion on one side of separator 26 where adhesive layer 6 is arranged" can refer to the total area of ​​adhesive layer 6 (peripheral region) arranged in a dot pattern and hollow region E in a plan view of one side of separator 26.

[0032] Furthermore, in a plan view, the ratio of the area of ​​the hollow regions E to the area of ​​the dot-shaped adhesive layer 6 and the area of ​​the dot-shaped adhesive layer 6 is not particularly limited as long as the effects of the technology disclosed herein are exhibited. The lower limit of this ratio is, for example, 0.05% or more, and is preferably 1% or more, more preferably 2% or more, and particularly preferably 5% or more, from the viewpoint of more suitably reducing the amount of solvent or dispersion medium remaining in the adhesive layer 6 during electrode assembly production and from the viewpoint of suitably suppressing a deterioration in the input / output characteristics of the battery 100 due to the placement of the adhesive layer 6. The upper limit of this ratio is, for example, 95% or less, and is preferably 90% or less, more preferably 80% or less, and particularly preferably 50% or less, from the viewpoint of suitably ensuring the adhesive strength between the separator 26 and the electrode. That is, in a plan view, the ratio of the area of ​​the hollow regions E to the area of ​​the dot-shaped adhesive layer 6 is preferably, for example, 1% to 90% from the viewpoint of suitably obtaining the effects described above. In addition, the "area of ​​the dot-shaped adhesive layer 6" can mean the area of ​​the region surrounded by the outer edges of the dots when viewed in a plane of the separator 26, that is, the total area of ​​the dot-shaped adhesive layer 6 and its hollow region E.

[0033] The diameter (diameter, corresponding to d in FIG. 3 ) of the dot-shaped adhesive layer 6 is not particularly limited as long as the effects of the technology disclosed herein are exhibited. The lower limit of d is, for example, 10 μm or more, and is preferably 50 μm or more, more preferably 75 μm or more, and particularly preferably 100 μm or more, from the viewpoint of suitably ensuring the adhesive strength between the separator 26 and the electrode and suitably suppressing variations in adhesive strength. The upper limit of d is, for example, 600 μm or less, and is preferably 500 μm or less, more preferably 300 μm or less, or 200 μm or less, from the viewpoint of more suitably reducing the amount of solvent remaining in the adhesive layer 6 during electrode assembly production and suitably suppressing deterioration in the input / output characteristics of the battery 100 and Li precipitation due to the placement of the adhesive layer 6. That is, in the lamination step, the diameter (diameter) of one dot-shaped adhesive layer 6 is preferably, for example, 50 μm to 500 μm.

[0034] 4 is a schematic longitudinal cross-sectional view taken along line IV-IV in FIG. 3. In the lamination step described below (in other words, in the separator 26 used in the lamination step described below, or after the formation step), the thickness of one of the dot-shaped adhesive layers 6 (length in the MD direction in FIG. 4; corresponding to t in FIG. 4) is not particularly limited as long as the effects of the technology disclosed herein are exhibited. The lower limit of t is preferably 0.1 μm or more, more preferably 0.2 μm or more, and even more preferably 0.5 μm or more. The upper limit of t is preferably 10 μm or less, preferably 5 μm or less, and more preferably 3 μm or less. That is, t is preferably within the range of 0.1 μm to 10 μm, for example.

[0035] Although not particularly limited, the basis weight of the adhesive layer 6 on one side of the separator 26 is, for example, 0.005 g / m 2 or more, preferably 0.01 g / m 2 More preferably, it is 0.02 g / m or more. 2 The upper limit of the basis weight of the adhesive layer 6 is, for example, 2.0 g / m 2 and preferably 1.0 g / m 2 or less, more preferably 0.05 g / m 2 The "weight per unit area" refers to the value obtained by dividing the mass of the adhesive layer by the area of ​​the region where the adhesive layer is formed (mass of adhesive layer / area of ​​the region where the adhesive layer is formed).

[0036] (Step S3: Lamination process) As described above, in this step, the positive electrode 22, the separator 26 (here, the first separator 26S1 and the second separator 26S2), and the negative electrode 24 are stacked. In this embodiment, since a wound electrode body is manufactured as the electrode body, the stacking step can be said to include a winding step in which a strip-shaped first electrode (here, the positive electrode 22), a strip-shaped second electrode (here, the negative electrode 24), and a strip-shaped separator 26 (here, the first separator 26S1 and the second separator 26S2) are wound together to produce the wound body 20A. As shown in FIG. 2 , in this embodiment, the negative electrode 24, the second separator 26S2, the positive electrode 22, and the first separator 26S1 are transported to the winding core 3 via transport paths k1 to k4, respectively, and wound around the winding core 3 to produce the wound body 20A. Although a cylindrical core 3 is used here, this is not limiting and a flat core may also be used. The cross-sectional shape of the wound body 20A may be flat as in this embodiment, or may be other shapes such as a perfect circle, an ellipse, or a track. The sheets are wound so that only the positive electrode tab 22t of the positive electrode 22 protrudes from one side edge in the width direction Y (the left side in FIG. 13 ) and only the negative electrode tab 24t of the negative electrode 24 protrudes from the other side edge (the right side in FIG. 13 ). The number of windings is preferably adjusted appropriately, taking into consideration the performance and manufacturing efficiency of the target battery 100. In some embodiments, the number of windings may be 20 or more or 30 or more. The temperature in the winding process is preferably 50°C or less, more preferably 40°C or less, and even more preferably 35°C or less. The winding process is preferably performed at 10°C or higher. The adhesive layer 6 may be one that has, for example, tackiness (adhesion) under the temperature conditions in the winding step.

[0037] In a preferred embodiment, the lamination step includes a pressing step of pressing the laminated first electrode (here, the positive electrode 22), separator 26 (here, the first separator 26S1 and the second separator 26S2), and second electrode (here, the negative electrode 24). This configuration allows the separator 26 and the electrode to be more suitably bonded. In this embodiment, the wound body 20A obtained in the winding step is press-molded to form a flat wound electrode body 20a. FIG. 5 is a schematic diagram showing the wound body 20A according to this embodiment before the pressing step. FIG. 6 is a schematic diagram showing the wound body 20A according to this embodiment after the pressing step. First, as shown in FIG. 5, the wound body 20A is placed in a press machine 200 having a pair of opposing pressing surfaces, and then pressed in the direction of the outline arrow to obtain a flat wound electrode body 20a. Here, the pressing pressure can be, for example, within a range of 0.1 MPa to 20 MPa (preferably, 5 MPa to 10 MPa). The pressing can be unheated pressing, heated pressing, or both. In the case of heated pressing, the heating temperature can be, for example, within a range of 50°C to 100°C (preferably, 70°C to 90°C). As shown in FIG. 9 , the electrode body 20a in a flat shape after press molding has a pair of curved portions 20r whose outer surfaces are curved and a flat portion 20f whose outer surface is flat and connects the pair of curved portions 20r. Furthermore, a positive electrode tab group 23 in which positive electrode tabs 22t are stacked is formed at one end in the width direction Y of the wound electrode body 20a in a flat shape after press molding, and a negative electrode tab group 25 in which negative electrode tabs 24t are stacked is formed at the other end. A core portion in which the positive electrode active material layer 22a and the negative electrode active material layer 24a face each other is formed at the center of the width direction Y of the wound electrode body.

[0038] In a preferred embodiment, the disposing step and the forming step are performed immediately before the laminating step. As shown in FIG. 2 , in this embodiment, the adhesive layer 6 is disposed and formed immediately before the winding step in which the positive electrode 22, the negative electrode 24, and the separator 26 (here, the first separator 26S1 and the second separator 26S2) are wound together to produce the wound body 20A. This configuration is preferable because it reduces the occurrence of side reactions in the adhesive layer 6 and reduces the adhesion of dust and other particles to the adhesive layer 6. The time from the forming step to the laminating step is preferably within 30 minutes, more preferably within 10 minutes, and particularly preferably within 5 minutes. Furthermore, the shortest distance from the position where the forming step is performed (e.g., the position of the adhesive application unit 4 in FIG. 2 ) to the position where the laminating step is performed (e.g., the position of the winding core 3 in FIG. 2 ) is preferably 30 m or less, more preferably within 10 m, and particularly preferably within 5 m. However, the present invention is not limited thereto.

[0039] Although not shown, in this embodiment, a separator 26 is disposed on the outermost surface of the wound electrode assembly 20a after the pressing process, and a stop tape is attached to the end of the winding of the separator 26 to maintain the shape of the wound electrode assembly 20a. Any conventional stop tape used for wound electrodes can be used without particular limitation. Although not shown, in this embodiment, the end of the winding of the positive electrode 22 is disposed at the curved portion 20r of the electrode assembly 20a. In this manner, the electrode assemblies 20a, 20b, and 20c according to this embodiment can be fabricated.

[0040] Next, an electrode assembly 20 integrated with the sealing plate 14 is produced. Specifically, first, as shown in Fig. 11, three wound electrode bodies 20a, each having a positive electrode second current collecting portion 52 and a negative electrode second current collecting portion 62 attached thereto, are prepared and arranged side by side in the short side direction X as wound electrode bodies 20a, 20b, and 20c. At this time, the wound electrode bodies 20a, 20b, and 20c may all be arranged in parallel such that the positive electrode second current collecting portion 52 is arranged on one side in the long side direction Y (the left side in Fig. 11) and the negative electrode second current collecting portion 62 is arranged on the other side in the long side direction Y (the right side in Fig. 11).

[0041] Next, as shown in FIG. 10 , with the multiple positive electrode tabs 22t bent, the positive electrode first current collecting portion 51 fixed to the sealing plate 14 is joined to the positive electrode second current collecting portion 52 of the wound electrode bodies 20a, 20b, and 20c. Also, with the multiple negative electrode tabs 24t bent, the negative electrode first current collecting portion 61 fixed to the sealing plate 14 is joined to the negative electrode second current collecting portion 62 of the wound electrode bodies 20a, 20b, and 20c. Examples of joining methods that can be used include ultrasonic welding, resistance welding, and laser welding. Welding using high-energy beams such as lasers is particularly preferred. By this welding process, joints are formed in the recesses of the positive electrode second current collecting portion 52 and the negative electrode second current collecting portion 62.

[0042] Next, the combined product prepared as described above is housed in the internal space of the exterior body 12. Specifically, first, an insulating resin sheet made of a resin material such as polyethylene (PE) is folded into a bag or box shape to prepare an electrode assembly holder 29. Next, the electrode assembly group 20 is housed in the electrode assembly holder 29. Then, the electrode assembly group 20 covered by the electrode assembly holder 29 is inserted into the exterior body 12. If the weight of the electrode assembly group 20 is heavy, approximately 1 kg or more, for example 1.5 kg or more, or even 2 to 3 kg, it is advisable to insert the electrode assembly group 20 into the exterior body 12 with the long side wall 12b of the exterior body 12 positioned so as to intersect with the direction of gravity (with the exterior body 12 facing sideways).

[0043] Finally, the sealing plate 14 is joined to the edge of the opening 12h of the exterior body 12 to seal the opening 12h. The exterior body 12 and the sealing plate 14 are then welded together. The exterior body 12 and the sealing plate 14 can be welded together by, for example, laser welding. Thereafter, the electrolyte is injected through the liquid inlet 15, and the liquid inlet 15 is closed with a sealing member 15a to hermetically seal the battery 100. In this manner, the battery 100 can be manufactured.

[0044] <Battery configuration> Next, an example of a battery obtained by the battery manufacturing method disclosed herein will be described.

[0045] FIG. 7 is a perspective view of the battery 100. FIG. 8 is a schematic longitudinal cross-sectional view taken along line VIII-VIII in FIG. 7. FIG. 9 is a schematic longitudinal cross-sectional view taken along line IX-IX in FIG. 7. FIG. 10 is a schematic transverse cross-sectional view taken along line XX in FIG. 7. In the following description, the symbols L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, top, and bottom, and the symbols X, Y, and Z in the drawings represent the short side direction of the battery 100, the long side direction perpendicular to the short side direction, and the up-down direction, respectively. However, these directions are merely used for convenience of description and do not limit the installation form of the battery 100 in any way.

[0046] As shown in Fig. 8, the battery 100 includes a battery case (case) 10 and an electrode assembly 20. In addition to the battery case 10 and the electrode assembly 20, the battery 100 according to this embodiment also includes a positive electrode terminal 30, a positive electrode external conductive member 32, a negative electrode terminal 40, a negative electrode external conductive member 42, an external insulating member 92, a positive electrode current collecting portion 50, a negative electrode current collecting portion 60, a positive electrode internal insulating member 70, and a negative electrode internal insulating member 80. Although not shown, the battery 100 according to this embodiment further includes an electrolyte. The battery 100 here is a lithium-ion secondary battery.

[0047] The battery case 10 is a housing that houses the electrode assembly 20. Here, the battery case 10 has a flat, bottomed, rectangular parallelepiped (rectangular) outer shape. The material of the battery case 10 may be the same as that conventionally used, and is not particularly limited. The battery case 10 is preferably made of a metal having a predetermined strength. Examples of metal materials that constitute the battery case 10 include aluminum, aluminum alloys, iron, and iron alloys.

[0048] The battery case 10 includes an exterior body 12, a sealing plate 14, and a gas release valve 17. The exterior body 12 is a flat, rectangular container with an opening 12h on one side. Specifically, as shown in FIG. 7 , the exterior body 12 includes a substantially rectangular bottom wall 12a, a pair of second side walls 12c extending upward in a U-shape from a short side of the bottom wall 12a and facing each other, and a pair of first side walls 12b extending upward in a U-shape from a long side of the bottom wall 12a and facing each other. The area of ​​the second side walls 12c is smaller than the area of ​​the first side walls 12b. The opening 12h is formed on the upper surface of the exterior body 12, which is surrounded by the pair of first side walls 12b and the pair of second side walls 12c. The sealing plate 14 is attached to the exterior body 12 so as to close the opening 12h of the exterior body 12. The sealing plate 14 is a substantially rectangular plate material in a plan view. The sealing plate 14 faces the bottom wall 12a of the exterior body 12. The battery case 10 is formed by joining (e.g., welding) the sealing plate 14 to the periphery of the opening 12h of the exterior body 12. The sealing plate 14 can be joined by welding, for example, laser welding. Specifically, each of the pair of second side walls 12c is joined to a short side of the sealing plate 14, and each of the pair of first side walls 12b is joined to a long side of the sealing plate 14.

[0049] As shown in FIGS. 7 and 8 , the gas release valve 17 is formed on the sealing plate 14. The gas release valve 17 is configured to open when the pressure inside the battery case 10 reaches or exceeds a predetermined value, thereby releasing gas inside the battery case 10. In this embodiment, the gas release valve 17 is a substantially circular recess in plan view that is recessed from the outer surface of the sealing plate 14 toward the electrode assembly 20. A thin-walled portion that is thinner than the thickness of the sealing plate 14 is formed on the bottom surface of the gas release valve 17. The thin-walled portion of the gas release valve 17 ruptures when the internal case pressure reaches or exceeds a predetermined value. This allows gas inside the battery case 10 to be released to the outside, thereby reducing the increased internal case pressure.

[0050] In addition to the gas release valve 17, the sealing plate 14 is also provided with a liquid inlet 15 and two terminal insertion holes 18 and 19. The liquid inlet 15 is connected to the internal space of the exterior body 12 and is an opening provided for injecting electrolyte during the manufacturing process of the battery 100. The liquid inlet 15 is sealed with a sealing member 15a. A blind rivet, for example, is suitable as the sealing member 15a. This allows the sealing member 15a to be firmly fixed inside the battery case 10. The terminal insertion holes 18 and 19 are formed at both ends of the sealing plate 14 in the long side direction Y. The terminal insertion holes 18 and 19 penetrate the sealing plate 14 in the up-down direction Z. As shown in FIG. 8 , a positive terminal 30 is inserted into the terminal insertion hole 18 on one side (left side) in the long side direction Y. A negative terminal 40 is inserted into the terminal insertion hole 19 on the other side (right side) in the long side direction Y.

[0051] FIG. 11 is a perspective view schematically illustrating a wound electrode body attached to a sealing plate 14. In this embodiment, a plurality of (here, three) wound electrode bodies 20a, 20b, and 20c are housed inside the battery case 10. The number of wound electrode bodies housed inside one battery case 10 is not particularly limited and may be one or two or more (plural). As shown in FIG. 8, a positive electrode current collector 50 is disposed on one side of the long side direction Y of each wound electrode body (the left side in FIG. 8), and a negative electrode current collector 60 is disposed on the other side of the long side direction Y (the right side in FIG. 8). The wound electrode bodies 20a, 20b, and 20c are connected in parallel. However, the wound electrode bodies 20a, 20b, and 20c may also be connected in series. Each wound electrode body is housed inside the exterior body 12 of the battery case 10 while being covered with an electrode body holder 29 (see FIG. 9), which is made of a resin sheet.

[0052] Fig. 12 is a perspective view that schematically shows the wound electrode body 20a. Fig. 13 is a schematic diagram that shows the configuration of the wound electrode body 20a. Here, in Fig. 13, for ease of viewing, the adhesive layer 6 formed on the surface of the separator 26 is omitted. Note that, although the wound electrode body 20a will be described in detail below as an example, the wound electrode bodies 20b and 20c can also have a similar configuration.

[0053] 13, the wound electrode body 20a has a positive electrode 22, a negative electrode 24, and a separator 26. In this example, the wound electrode body 20a is a wound electrode body in which a strip-shaped positive electrode 22 and a strip-shaped negative electrode 24 are stacked with two strip-shaped separators 26 interposed therebetween, and wound around a winding axis WL.

[0054] The wound electrode body 20a has a flat shape. The wound electrode body 20a is disposed inside the exterior body 12 with the winding axis WL oriented substantially parallel to the long side direction Y. Specifically, as shown in Fig. 9, the wound electrode body 20a has a pair of curved portions (R portions) 20r that face the bottom wall 12a and the sealing plate 14 of the exterior body 12, and a flat portion 20f that connects the pair of curved portions 20r and faces the second side wall 12c of the exterior body 12. The flat portion 20f extends along the second side wall 12c.

[0055] As shown in FIG. 13, the positive electrode 22 includes a positive electrode current collector 22c, a positive electrode active material layer 22a, and a positive electrode protective layer 22p adhered to at least one surface of the positive electrode current collector 22c. However, the positive electrode protective layer 22p is not essential and may be omitted in other embodiments. The positive electrode current collector 22c is strip-shaped. The positive electrode current collector 22c is made of a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. In this example, the positive electrode current collector 22c is a metal foil, specifically, an aluminum foil.

[0056] A plurality of positive electrode tabs 22t are provided at one end of positive electrode current collector 22c in long side direction Y (the left end in FIG. 13). The plurality of positive electrode tabs 22t are provided at intervals (intermittently) along the longitudinal direction of band-shaped positive electrode 22. The plurality of positive electrode tabs 22t protrude outward beyond separator 26 toward one axial side of winding axis WL (the left side in FIG. 13). Note that the positive electrode tabs 22t may be provided on the other axial side of winding axis WL (the right side in FIG. 13) or on both axial sides of winding axis WL. The positive electrode tabs 22t are part of positive electrode current collector 22c and are made of metal foil (aluminum foil). However, the positive electrode tabs 22t may be separate members from positive electrode current collector 22c. In at least a part of the positive electrode tab 22t, the positive electrode active material layer 22a and the positive electrode protective layer 22p are not formed, and a region where the positive electrode current collector 22c is exposed is formed.

[0057] As shown in FIG. 10 , the positive electrode tabs 22t are stacked at one axial end of the winding axis WL (the left end in FIG. 10 ) to form a positive electrode tab group 23. The positive electrode tabs 22t are each bent so that their outer ends are aligned. This improves the fitment into the battery case 10 and enables the battery 100 to be miniaturized. As shown in FIG. 8 , the positive electrode tab group 23 is electrically connected to the positive electrode terminal 30 via a positive electrode current collector 50. Specifically, the positive electrode tab group 23 and the positive electrode second current collector 52 are connected at a connection J (see FIG. 10 ). The positive electrode second current collector 52 is electrically connected to the positive electrode terminal 30 via a positive electrode first current collector 51. The size of the positive electrode tabs 22t (the length along the long side direction Y and the width perpendicular to the long side direction Y; see FIG. 13 ) can be appropriately adjusted, for example, by their formation positions, taking into account the state of connection to the positive electrode current collector 50. Here, the sizes of the plurality of positive electrode tabs 22t are different from one another so that the outer ends are aligned when bent.

[0058] As shown in FIG. 13, the positive electrode active material layer 22a is provided in a strip-like shape along the longitudinal direction of the strip-shaped positive electrode current collector 22c. The positive electrode active material layer 22a contains a positive electrode active material (e.g., a lithium transition metal composite oxide such as a lithium nickel cobalt manganese composite oxide) capable of reversibly absorbing and releasing charge carriers. When the total solid content of the positive electrode active material layer 22a is taken as 100 mass%, the positive electrode active material may account for approximately 80 mass% or more, typically 90 mass% or more, for example, 95 mass% or more. The positive electrode active material layer 22a may contain optional components other than the positive electrode active material, such as a conductive material, a binder, various additives, etc. Examples of the conductive material include a carbon material such as acetylene black (AB). Examples of the binder include polyvinylidene fluoride (PVdF).

[0059] As shown in FIG. 13 , the positive electrode protective layer 22p is provided at the boundary between the positive electrode current collector 22c and the positive electrode active material layer 22a in the long side direction Y. Here, the positive electrode protective layer 22p is provided at one end (the left end in FIG. 13 ) of the positive electrode current collector 22c in the axial direction of the winding axis WL. However, the positive electrode protective layer 22p may also be provided at both axial ends. The positive electrode protective layer 22p is provided in a strip shape along the positive electrode active material layer 22a. The positive electrode protective layer 22p contains an inorganic filler (e.g., alumina). When the entire solid content of the positive electrode protective layer 22p is taken as 100 mass%, the inorganic filler may account for approximately 50 mass% or more, typically 70 mass% or more, for example, 80 mass% or more. The positive electrode protective layer 22p may contain optional components other than the inorganic filler, such as a conductive material, a binder, and various additive components. The conductive material and binder may be the same as those exemplified as those that may be contained in the positive electrode active material layer 22a.

[0060] As shown in Fig. 13, the negative electrode 24 includes a negative electrode current collector 24c and a negative electrode active material layer 24a fixed to at least one surface of the negative electrode current collector 24c. The negative electrode current collector 24c is strip-shaped. The negative electrode current collector 24c is made of a conductive metal such as copper, a copper alloy, nickel, or stainless steel. In this example, the negative electrode current collector 24c is a metal foil, specifically a copper foil.

[0061] A plurality of negative electrode tabs 24t are provided at one axial end (the right end in FIG. 13 ) of the winding axis WL of the negative electrode current collector 24c. The plurality of negative electrode tabs 24t are provided at intervals (intermittently) along the longitudinal direction of the strip-shaped negative electrode 24. Each of the plurality of negative electrode tabs 24t protrudes outward from the separator 26 toward one axial end (the right end in FIG. 13 ). However, the negative electrode tab 24t may be provided at the other axial end (the left end in FIG. 13 ) or at each of both axial end portions. The negative electrode tab 24t is part of the negative electrode current collector 24c and is made of metal foil (copper foil). However, the negative electrode tab 24t may be a separate member from the negative electrode current collector 24c. At least a portion of the negative electrode tab 24t has an area where the negative electrode active material layer 24a is not formed and the negative electrode current collector 24c is exposed.

[0062] As shown in FIG. 10 , the negative electrode tabs 24t are stacked at one axial end (the right end in FIG. 10 ) to form a negative electrode tab group 25. The negative electrode tab group 25 is preferably provided symmetrically to the positive electrode tab group 23 in the axial direction. The negative electrode tabs 24t are bent so that their outer ends are aligned. This improves the fitment into the battery case 10 and enables the battery 100 to be miniaturized. As shown in FIG. 8 , the negative electrode tab group 25 is electrically connected to the negative electrode terminal 40 via a negative electrode current collecting portion 60. Specifically, the negative electrode tab group 25 and a negative electrode second current collecting portion 62 are connected at a connection portion J (see FIG. 10 ). The negative electrode second current collecting portion 62 is electrically connected to the negative electrode terminal 40 via a negative electrode first current collecting portion 61. As with the positive electrode tabs 22t, the negative electrode tabs 24t are different in size so that their outer ends are aligned when bent.

[0063] As shown in FIG. 13, the negative electrode active material layer 24a is provided in a strip shape along the longitudinal direction of a strip-shaped negative electrode current collector 24c. The negative electrode active material layer 24a contains a negative electrode active material (e.g., a carbon material such as graphite) that can reversibly store and release charge carriers. When the total solid content of the negative electrode active material layer 24a is taken as 100 mass%, the negative electrode active material may account for approximately 80 mass% or more, typically 90 mass% or more, for example, 95 mass% or more. The negative electrode active material layer 24a may contain optional components other than the negative electrode active material, such as a binder, a dispersant, and various additives. Examples of the binder that can be used include rubbers such as styrene butadiene rubber (SBR). Examples of the dispersant that can be used include celluloses such as carboxymethyl cellulose (CMC).

[0064] As shown in FIGS. 13 and 3, the separator 26 is a strip-shaped member. The separator 26 is an insulating sheet having a plurality of fine through-holes formed therein through which charge carriers can pass. The width of the separator 26 is greater than the width of the negative electrode active material layer 24a. By interposing the separator 26 between the positive electrode 22 and the negative electrode 24, contact between the positive electrode 22 and the negative electrode 24 is prevented and charge carriers (e.g., lithium ions) can be transferred between the positive electrode 22 and the negative electrode 24. Although not particularly limited, the thickness of the separator 26 (the length in the stacking direction MD in FIG. 14; the same applies hereinafter) is preferably 3 μm or more, more preferably 5 μm or more. The thickness of the separator 26 is preferably 25 μm or less, more preferably 18 μm or less, and even more preferably 14 μm or less.

[0065] Here, two separators 26 are used for one wound electrode body 20a. Preferably, two separators 26, i.e., a first separator and a second separator, are used for one wound electrode body 20a as in this embodiment. Here, the two separators each have the same configuration, but they may be different. In other embodiments, a single separator may be used, and for example, when manufacturing a laminated electrode body as the electrode body, a strip-shaped separator folded zigzag may be used.

[0066] 14 is an enlarged view schematically illustrating the interface between the positive electrode 22, the negative electrode 24, and the separator 26 according to this embodiment. As shown in FIG. 14, the separator 26 according to this embodiment has a base layer 27 and a heat resistance layer (HRL) 28 provided on one surface of the base layer 27. An adhesive layer 6 is also present on the surface of the heat resistance layer 28.

[0067] As the substrate layer 27, any microporous film used in a separator of a conventionally known battery can be used without particular limitation. The substrate layer 27 is preferably a porous sheet-like member. The substrate layer 27 may have a single-layer structure or a two- or more-layer structure, for example, a three-layer structure. The substrate layer 27 is preferably made of a polyolefin resin. It is more preferable that the entire substrate layer 27 is made of a polyolefin resin. The substrate layer 27 may be, for example, a microporous film made of polyolefin, preferably a microporous film made of polyethylene. This ensures sufficient flexibility of the separator 26, and facilitates the production (winding and press molding) of the wound electrode body 20a. The polyolefin resin is preferably polyethylene (PE), polypropylene (PP), or a mixture thereof, and more preferably made of PE.

[0068] Although not particularly limited, the thickness of the base layer 27 (length in the stacking direction MD; the same applies below) is preferably 3 μm or more, and more preferably 5 μm or more. The thickness of the base layer 27 is preferably 25 μm or less, more preferably 18 μm or less, and even more preferably 14 μm or less. The air permeability of the base layer 27 is preferably 30 sec / 100cc to 500 sec / 100cc, more preferably 30 sec / 100cc to 300 sec / 100cc, and even more preferably 50 sec / 100cc to 200 sec / 100cc.

[0069] The heat-resistant layer 28 is provided on the substrate layer 27. The heat-resistant layer 28 is preferably formed on the substrate layer 27. The heat-resistant layer 28 may be provided directly on the surface of the substrate layer 27, or may be provided on the substrate layer 27 via another layer. The heat-resistant layer 28 is preferably formed on one or both sides of the substrate layer 27. However, the heat-resistant layer 28 is not essential and may be omitted in other embodiments. Here, the heat-resistant layer 28 is provided on the entire surface of the substrate layer 27 facing the positive electrode 22. This more effectively suppresses thermal shrinkage of the separator 26, contributing to improved safety of the battery 100. The basis weight of the heat-resistant layer 28 is uniform in the longitudinal direction LD and the winding axis direction WD of the separator 26. Although not particularly limited, the thickness of the heat-resistant layer 28 (length in the stacking direction MD; the same applies hereinafter) is preferably 0.3 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more. The thickness of the heat-resistant layer 28 is preferably 6 μm or less, and more preferably 4 μm or less. The heat-resistant layer 28 preferably contains an inorganic filler and a heat-resistant layer binder.

[0070] As the inorganic filler, any inorganic filler conventionally used for this type of application can be used without particular limitation. Preferably, the inorganic filler contains insulating ceramic particles. Among these, inorganic oxides such as alumina, zirconia, silica, and titania, metal hydroxides such as aluminum hydroxide, and clay minerals such as boehmite are preferred in consideration of heat resistance and availability, with alumina and boehmite being more preferred. Furthermore, from the viewpoint of suppressing thermal shrinkage of the separator 26, compounds containing aluminum are particularly preferred. The proportion of the inorganic filler relative to the total mass of the heat-resistant layer 28 is preferably 85% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0071] As the heat-resistant layer binder, any binder known in the art for this type of application can be used without any particular limitation. Specific examples include acrylic resins, fluorine-based resins (e.g., PVdF), epoxy resins, urethane resins, and ethylene vinyl acetate resins. Among these, acrylic resins are preferred.

[0072] Here, the adhesive layer 6 is provided on the surface facing the positive electrode 22 and abuts against the positive electrode 22. As shown in FIG. 14 , the adhesive layer 6 is preferably formed at least on the surface of the separator 26 facing the positive electrode 22. Here, the adhesive layer 6 is provided on the heat-resistant layer 28. The adhesive layer 6 is preferably formed on the heat-resistant layer 28. The adhesive layer 6 may be provided directly on the surface of the heat-resistant layer 28, or may be provided on the heat-resistant layer 28 via another layer. The adhesive layer 6 may be provided directly on the surface of the base layer 27, or may be provided on the base layer 27 via a layer other than the heat-resistant layer 28. The adhesive layer 6 has a relatively higher affinity with the electrolyte solution than, for example, the heat-resistant layer 28, and may be a layer that absorbs the electrolyte solution and swells. Although not particularly limited, the thickness of the adhesive layer 6 in the wound electrode body 20a (the length in the stacking direction MD in FIG. 14, which corresponds to T in FIG. 14; this can also be referred to as the thickness of the adhesive layer 6 after the pressing step) is preferably 0.1 μm or more, more preferably 0.2 μm or more, and even more preferably 0.5 μm or more. The thickness of the adhesive layer 6 is preferably 10 μm or less, preferably 5 μm or less, and more preferably 3 μm or less. That is, the thickness of the adhesive layer 6 in the wound electrode body 20a is preferably within the range of 0.1 μm to 10 μm, for example. By keeping the thickness within this range, it is possible to suitably achieve the adhesiveness of the adhesive layer 6, uniformity in the charge / discharge reaction of the battery 100, and suppression of Li deposition.

[0073] The diameter of the adhesive layer 6 in the wound electrode body 20a (corresponding to D in FIG. 14; this can also be referred to as the diameter of the adhesive layer 6 after the pressing step) is, for example, 10 μm or more, preferably 50 μm or more, more preferably 75 μm or more, and even more preferably 100 μm or more. The thickness of the adhesive layer 6 is, for example, 600 μm or less, preferably 500 μm or less, preferably 300 μm or less, and more preferably 200 μm or less. That is, the thickness of the adhesive layer 6 in the wound electrode body 20a is preferably, for example, within the range of 50 μm to 500 μm. By keeping the thickness within this range, it is possible to suitably achieve the adhesiveness of the adhesive layer 6, uniformity of the charge / discharge reaction of the battery 100, and suppression of Li deposition.

[0074] For details about the resin that constitutes the adhesive layer 6, please refer to the corresponding section in <Battery Manufacturing Method>.

[0075] The electrolyte may be the same as conventional ones and is not particularly limited. The electrolyte is, for example, a non-aqueous electrolyte containing a non-aqueous solvent and a supporting salt. The non-aqueous solvent contains, for example, carbonates such as ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. The supporting salt is, for example, a fluorine-containing lithium salt such as LiPF6. However, the electrolyte may be in a solid state (solid electrolyte) and integrated with the electrode assembly 20.

[0076] As shown in FIG. 8 , the positive electrode terminal 30 is inserted into a terminal insertion hole 18 formed at one end of the sealing plate 14 in the long side direction Y (the left end in FIG. 8 ). The positive electrode terminal 30 is preferably made of metal, more preferably aluminum or an aluminum alloy, for example. Meanwhile, the negative electrode terminal 40 is inserted into a terminal insertion hole 19 formed at the other end of the sealing plate 14 in the long side direction Y (the right end in FIG. 8 ). The negative electrode terminal 40 is preferably made of metal, more preferably copper or a copper alloy, for example. Here, these electrode terminals (positive electrode terminal 30, negative electrode terminal 40) each protrude from the same surface of the battery case 10 (specifically, the sealing plate 14). However, the positive electrode terminal 30 and the negative electrode terminal 40 may each protrude from different surfaces of the battery case 10. The electrode terminals (positive electrode terminal 30, negative electrode terminal 40) inserted into the terminal insertion holes 18, 19 are preferably fixed to the sealing plate 14 by crimping or the like.

[0077] As described above, as shown in FIG. 8 , the positive electrode terminal 30 is electrically connected to the positive electrodes 22 (see FIG. 11 ) of each of the wound electrode bodies 20a, 20b, and 20c inside the exterior housing 12 via the positive electrode current collecting portion 50 (positive electrode first current collecting portion 51, positive electrode second current collecting portion 52). The positive electrode terminal 30 is insulated from the sealing plate 14 by a positive electrode internal insulating member 70 and a gasket 90. The positive electrode internal insulating member 70 includes a base portion 70a interposed between the positive electrode first current collecting portion 51 and the sealing plate 14, and a protrusion portion 70b protruding from the base portion 70a toward the wound electrode body 20a. The positive electrode terminal 30 exposed to the outside of the battery case 10 through the terminal insertion hole 18 is connected to the positive electrode external conductive member 32 outside the sealing plate 14. On the other hand, as shown in FIG. 8, the negative electrode terminal 40 is electrically connected to the negative electrode 24 (see FIG. 11) of each wound electrode body 20a via a negative electrode current collecting portion 60 (negative electrode first current collecting portion 61, negative electrode second current collecting portion 62) inside the exterior body 12. The negative electrode terminal 40 is insulated from the sealing plate 14 by a negative electrode internal insulating member 80 and a gasket 90. Like the positive electrode internal insulating member 70, the negative electrode internal insulating member 80 also has a base portion 80a interposed between the negative electrode first current collecting portion 61 and the sealing plate 14 and a protrusion portion 80b protruding from the base portion 80a toward the wound electrode body 20a. The negative electrode terminal 40 exposed to the outside of the battery case 10 through the terminal insertion hole 19 is connected to a negative electrode external conductive member 42 outside the sealing plate 14. An external insulating member 92 is interposed between the external conductive members (positive electrode external conductive member 32, negative electrode external conductive member 42) and the outer surface 14d of the sealing plate 14. The external insulating member 92 can insulate the external conductive members 32, 42 from the sealing plate 14.

[0078] Furthermore, the protrusions 70b, 80b of the internal insulating members (positive electrode internal insulating member 70, negative electrode internal insulating member 80) described above are disposed between the sealing plate 14 and the wound electrode body 20a. The protrusions 70b, 80b of the internal insulating members restrict upward movement of the wound electrode body 20a, preventing contact between the sealing plate 14 and the wound electrode body 20a.

[0079] <Battery uses> Battery 100 can be used for a variety of purposes, but is preferably used, for example, as a power source (driving power source) for motors mounted on vehicles such as passenger cars and trucks. The type of vehicle is not particularly limited, but examples include plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs), and battery electric vehicles (BEVs). Battery 100 has reduced variation in battery reaction, and is therefore preferably used to construct a battery pack.

[0080] Although one embodiment of the present disclosure has been described above, the above embodiment is merely an example. The present disclosure can be implemented in various other forms. The present disclosure can be implemented based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. The technology described in the claims includes various modifications and alterations of the above-exemplified embodiment. For example, it is possible to replace part of the above-described embodiment with other modified embodiments, and it is also possible to add other modified embodiments to the above-described embodiment. Furthermore, if a technical feature is not described as essential, it can be deleted as appropriate.

[0081] For example, in the above embodiment, the adhesive layer 6 is formed on the surface of the separator 26 facing the positive electrode 22, but this is not limiting. In other embodiments, the adhesive layer 6 may be formed on the surface of the separator 26 facing the negative electrode 24. Alternatively, the adhesive layer 6 may be formed on the surface of the separator 26 facing the positive electrode 22 and on the surface of the separator 26 facing the negative electrode 24. Furthermore, when the electrode body has two separators, an adhesive layer may be disposed on the surface of only one of the separators.

[0082] As described above, specific aspects of the technology disclosed herein include those described in the following items. Item 1: A method for manufacturing an electricity storage device having an electrode assembly including a first electrode, a second electrode, and a separator arranged between the first electrode and the second electrode, the method comprising: a disposing step of disposing an adhesive layer slurry containing an adhesive and at least one of a solvent and a dispersion medium on at least one of the surfaces of the separator; a forming step of removing at least one of the solvent and the dispersion medium from the adhesive layer slurry to form an adhesive layer; and a laminating step of laminating the first electrode, the separator, and the second electrode, wherein in the laminating step, a separator having an adhesive layer arranged in a plurality of dots on at least one of the surfaces of the separator is used, and the dot-shaped adhesive layer has a hollow region in the center when viewed in a plane. Item 2: The method for producing an electricity storage device according to Item 1, wherein when the area of ​​one side of the separator is S1 and the total area of ​​the portion of the one side of the separator where the adhesive layer is arranged is S2, S2 / S1≦0.1. Item 3: The method for manufacturing an electricity storage device according to Item 1 or 2, wherein the laminating step includes a winding step of winding the strip-shaped first electrode and the strip-shaped second electrode with the strip-shaped separator interposed therebetween to produce a wound body. Item 4: The method for producing an electricity storage device according to any one of items 1 to 3, wherein the laminating step includes a pressing step of pressing the laminated first electrode, the separator, and the second electrode. Item 5: The method for producing an electricity storage device according to any one of Items 1 to 4, wherein the adhesive layer is adhered to the first electrode, the first electrode contains a lithium transition metal composite oxide, in which the ratio of the amount (moles) of Ni to the amount (moles) of transition metal in the lithium transition metal composite oxide is 0.7 or more, and the adhesive layer slurry contains water. Item 6: The method for producing an electricity storage device according to any one of items 1 to 5, wherein, in a plan view, the ratio of the area of ​​the hollow regions to the area of ​​the dot-shaped adhesive layer is 1% to 90%. Item 7: The method for producing an electricity storage device according to any one of items 1 to 6, wherein the dot-shaped adhesive layer has a diameter of 50 μm to 500 μm. [Explanation of symbols]

[0083] 1 Electrode body manufacturing equipment 2. Laura 3 Winding core 4 Adhesive application section 5 Drying section 6 Adhesive layer 10 Battery case 12 Exterior body 14 Sealing plate 15 Liquid injection hole 15a Sealing member 17 Gas exhaust valve 18,19 Terminal insertion holes 20 Electrode group 20a~20c electrode body 22 Positive electrode 23 Positive electrode tab group 24 Negative electrode 25 Negative electrode tab group 26 Separator 27 Base material layer 28 Heat-resistant layer 30 Positive terminal 32 Positive electrode external conductive member 40 Negative terminal 42 negative electrode external conductive member 50 Positive electrode current collector 60 Negative electrode current collector 70 Positive electrode internal insulating material 80 Negative electrode internal insulating member 90 Gasket 92 External insulating member 100 batteries 200 press machines E hollow area

Claims

1. A method for manufacturing an electricity storage device including an electrode assembly including a first electrode, a second electrode, and a separator disposed between the first electrode and the second electrode, a disposing step of disposing an adhesive layer slurry containing an adhesive and at least one of a solvent and a dispersion medium on at least one of the surfaces of the separator; a forming step of removing at least one of the solvent and the dispersion medium from the adhesive layer slurry to form an adhesive layer; a lamination step of laminating the first electrode, the separator, and the second electrode; It encompasses In the lamination step, a separator having an adhesive layer arranged in a plurality of dots on at least one surface of the separator is used, The dot-shaped adhesive layer has a hollow region at the center in a plan view, The time from the forming step to the laminating step is within 10 minutes, In plan view, a ratio of an area of ​​the hollow region to an area of ​​the dot-shaped adhesive layer is 1% to 90%; The diameter of the dot-shaped adhesive layer is 50 μm to 500 μm. A method for manufacturing an electricity storage device.

2. 2. The method for manufacturing an electricity storage device according to claim 1, wherein when an area of ​​one surface of the separator is S1 and a total area of ​​a portion of the one surface of the separator where the adhesive layer is arranged is S2, S2 / S1≦0.

1.

3. 3. The method for manufacturing an electricity storage device according to claim 1, wherein the laminating step includes a winding step of winding the strip-shaped first electrode and the strip-shaped second electrode with the strip-shaped separator interposed therebetween to produce a wound body.

4. The method for manufacturing an electricity storage device according to claim 1 , wherein the laminating step includes a pressing step of pressing the laminated first electrode, the separator, and the second electrode.

5. the adhesive layer is adhered to the first electrode; the first electrode includes a lithium transition metal composite oxide; In the lithium transition metal composite oxide, the ratio of the amount (moles) of Ni to the amount (moles) of transition metal is 0.7 or more; The method for manufacturing an electricity storage device according to claim 1 , wherein the adhesive layer slurry contains water.

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