Method for manufacturing a storage device

Abstract

To provide a technique of being able to obtain a power storage device including a wound electrode body with high productivity.SOLUTION: An aspect of a manufacturing method for a power storage device (for example, battery) disclosed herein includes a winding step S3 of manufacturing a wound body 20A by winding a positive electrode 22 and a negative electrode 24 through a separator 26, and a pressing step S4, after the winding step S3, of press-molding the wound body 20A to obtain flat-shaped wound electrode bodies 20a, 20b, and 20c. In the winding step S3, the separator 26 including an adhesive layer 6 disposed in a plurality of dots on at least one surface thereof is used. Each dot of the adhesive layer 6 includes a hollow region E at a center in a plan view. By the pressing step S4, the area of the hollow region E in the plan view is reduced to 1 / 2 or less. Here, before the winding step S3, an arranging step S1 and a removing step S2 are further included.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a power storage device.

Background Art

[0002] For example, Japanese Patent No. 5328034 discloses a battery including a wound electrode body having a positive electrode, a negative electrode, and a separator, the battery having a heat-resistant porous layer containing an adhesive resin on the surface of the separator. It is described that such a wound electrode body is produced by arranging and stacking a positive electrode and a negative electrode with a separator interposed therebetween, winding them, and pressing them into a flat shape.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, according to the studies of the present inventors, when winding each member, if the separator having the adhesive resin as described above strongly adheres to the electrode, when the wound body is pressed and deformed, the positional relationship between the separator and the electrode may not change appropriately, and as a result, it has been found that the separator may be distorted or wrinkled. On the other hand, when the separator does not have such an adhesive resin, there is a risk of winding displacement in the wound body. These are not preferable from the viewpoint of productivity and the like. That is, in the manufacture of a power storage device (for example, a battery) including a wound electrode body having an adhesive layer as described above, it has been found that there is still room for improvement from the viewpoint of improving productivity.

[0005] The present disclosure has been made in view of such circumstances, and its main object is to provide a technique capable of highly productively obtaining a power storage device including a wound electrode body.

Means for Solving the Problem

[0006] To achieve such an object, the present disclosure provides a method for manufacturing a power storage device including a flat wound electrode body in which a strip-shaped first electrode and a strip-shaped second electrode are wound via a strip-shaped separator, the method including: a winding step of winding the first electrode and the second electrode via the separator to manufacture a wound body; and a pressing step of pressing the wound body after the winding step to form a flat wound electrode body. In the winding step, a separator having an adhesive layer disposed in a plurality of dot shapes on at least one surface is used as the separator, each of the dot-shaped adhesive layers has a hollow region at the center in a plan view, and the area of the hollow region in the plan view is reduced to 1 / 2 or less by the pressing step. Although details will be described later, according to the method for manufacturing a power storage device having such a configuration, a power storage device including a wound electrode body can be obtained with high productivity.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

MODE FOR CARRYING OUT THE INVENTION

[0008] Hereinafter, some embodiments of the technology disclosed herein will be described with reference to the drawings. The following description is not, of course, intended to limit the technology disclosed herein to the following embodiments. In the following drawings, members and parts having the same function are denoted by the same reference numerals for description. Also, the dimensional relationships (length, width, thickness, etc.) in each figure do not reflect the actual dimensional relationships. Note that matters other than those specifically mentioned in this specification and matters necessary for the implementation of the technology disclosed herein (for example, the general configuration and manufacturing process of a battery that does not characterize the present invention) can be grasped as design matters of those skilled in the art based on the prior art in the relevant field. The technology disclosed herein can be implemented based on the content disclosed in this specification and common general knowledge in the relevant field. Note that the notation "A to B" indicating a range in this specification means "A or more and B or less". Also, it is intended to include the meanings of "exceeding A" and "less than B".

[0009] Note that in this specification, the "power storage device" refers to a device that can perform charging and discharging. The power storage device includes batteries such as primary batteries and secondary batteries (for example, non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries, nickel metal hydride batteries), and capacitors (physical batteries) such as electric double layer capacitors. Further, the electrolyte may be any of a liquid electrolyte (electrolyte solution), a gel electrolyte, and a solid electrolyte.

[0010] <Method for manufacturing a battery> Hereinafter, the present technology will be described by taking as an example the manufacturing method of a lithium ion secondary battery (hereinafter, also simply referred to as "battery 100"), which is an embodiment of the power storage device disclosed herein. In the following, the case where the first electrode is the positive electrode 22 and the second electrode is the negative electrode 24 will be described, but the technology disclosed herein can also be applied to the case where, for example, the first electrode is the negative electrode 24 and the second electrode is the positive electrode 22. The manufacturing method of the battery disclosed herein may further include other processes at any stage, and can be appropriately deleted if the process is not described as essential. Also, as long as the effects of the technology disclosed herein are exhibited, the order of the processes can be changed.

[0011] FIG. 1 is a flowchart for explaining a method of manufacturing a battery 100 according to the present embodiment. First, the method of manufacturing a battery 100 according to the present embodiment is a method of manufacturing a battery 100 including a flat wound electrode body (here, wound electrode bodies 20a, 20b, 20c) in which a strip-shaped first electrode (here, positive electrode 22) and a strip-shaped second electrode (here, negative electrode 24) are wound via strip-shaped separators 26 (here, first separator 26S1 and second separator 26S2). As shown in FIG. 1, the method of manufacturing a battery 100 according to the present embodiment includes a winding step (step S3) of winding a first electrode (here, positive electrode 22) and a second electrode (here, negative electrode 24) via a separator 26 to manufacture a wound body 20A, and a pressing step (step S4) of pressing the wound body 20A after the winding step to form a flat wound electrode body (here, 20a, 20b, 20c). Further, in the winding step, a separator having an adhesive layer 6 disposed in a plurality of dot shapes on at least one surface is used as the separator 26. Each of the dot-shaped adhesive layers 6 has a hollow region E in the center in plan view, and the area of the hollow region E in plan view is reduced to 1 / 2 or less by the pressing step. Such a hollow region E can be referred to as a region where the adhesive layer 6 is not disposed (formed), that is, an adhesive layer non-formation region.

[0012] As described above, for example, when the positional relationship between the electrode and the separator changes during the pressing process, if the electrode and the separator are strongly adhered to each other, the positional relationship between the electrode and the separator may not change appropriately. As a result, it has been found that the separator may be distorted or wrinkled. On the other hand, according to the method for manufacturing the battery 100 as described above, in the winding process, the electrode (the positive electrode 22 or the negative electrode 24) and the separator 26 are not strongly adhered, and for the first time in the pressing process, they can be strongly adhered to each other. More specifically, in the winding process, the outer peripheral region of the adhesive layer 6 provided in the separator 26 and the electrode come into contact (see FIG. 7), and in the pressing process, a wider surface generated by the crushing of the adhesive layer 6 comes into contact with the electrode (see FIG. 8). According to such a configuration, in the winding process, the electrode and the separator 26 are not strongly adhered, and for the first time in the pressing process, they can be strongly adhered to each other. Therefore, in the pressing process, when the positional relationship between the electrode and the separator 26 changes, the positional relationship can be appropriately changed. As a result, it is possible to preferably suppress the occurrence of distortion, wrinkles, etc. in the separator 26. Further, since the separator 26 has the adhesive layer 6, it is possible to preferably suppress the displacement of the wound body 20A (for example, the displacement of the separator 26 and the electrode in the wound body 20A. In particular, it is likely to occur when the wound body 20A is removed from the winding core 3). That is, according to the method for manufacturing the battery 100 as described above, the battery 100 including the wound electrode bodies 20a, 20b, 20c can be obtained with high productivity.

[0013] Hereinafter, a method for manufacturing the battery 100 according to the present embodiment will be described with reference to the electrode body manufacturing apparatus 1 that embodies the method for manufacturing the battery 100. Further, hereinafter, a case where the dot-shaped adhesive layer 6 is disposed on one side of the first separator 26S1 and the second separator 26S2 will be described. In the technology disclosed herein, the separator 26 with the adhesive layer 6 disposed thereon in advance can also be used. However, hereinafter, a case where the adhesive layer 6 is formed on the surface of the separator 26 by the adhesive application unit 4 will be described. Along with this, as shown in FIG. 1, the method for manufacturing the battery 100 according to the present embodiment further includes a placement step (step S1) and a removal step (step S2) in addition to the above-described winding step (step S3) and pressing step (step S4). However, in other embodiments, these steps may not be included.

[0014] FIG. 2 is a schematic diagram showing the configuration of the electrode body manufacturing apparatus 1 according to the present embodiment. As shown in FIG. 2, the electrode body manufacturing apparatus 1 according to the present embodiment includes a plurality (here, six) of rollers 2, a winding core 3, an adhesive application unit 4, and a drying unit 5. Further, in the present embodiment, the electrode body manufacturing apparatus 1 includes a cutter (not shown), a pressing jig, and a control device. 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 body manufacturing apparatus 1 appropriately has a required actuator. The control device is configured to control each component of the electrode body manufacturing apparatus 1 so that required operations are executed at a predetermined timing in accordance with a preset program. The control device can be embodied by a computer such as a microcontroller, for example.

[0015] The positive electrode 22, the negative electrode 24, the first separator 26S1, and the second separator 26S2 are each prepared in a state of being wound around a reel (not shown). The positive electrode 22, the negative electrode 24, the first separator 26S1, and the second separator 26S2 are each conveyed along predetermined conveyance paths k1 to k4. The conveyance path k1 is a path along which the negative electrode 24 is sent out from a reel (not shown) toward the winding core 3. The conveyance path k2 is a path along which the second separator 26S2 is sent out from a reel (not shown) toward the winding core 3. The conveyance path k3 is a path along which the positive electrode 22 is sent out from a reel (not shown) toward the winding core 3. The conveyance path k4 is a path along which the first separator 26S1 is sent out from a reel (not shown) toward the winding core 3. In the conveyance paths k1 to k4, a dancer roll mechanism for removing the slack of the positive electrode 22, the negative electrode 24, the first separator 26S1, and the second separator 26S2 being sent out, a tensioner for adjusting the tension, and the like may be appropriately arranged respectively.

[0016] The plurality of rollers 2 are respectively arranged in the conveyance paths k1 to k4 of the positive electrode 22, the negative electrode 24, the first separator 26S1, and the second separator 26S2. The plurality of rollers 2 are an example of a conveying device. The plurality of rollers 2 are arranged at predetermined positions to define the respective conveyance paths k1 to k4. The positive electrode 22, the negative electrode 24, the first separator 26S1, and the second separator 26S2 are each conveyed by the plurality of rollers 2. In the present embodiment, the number of rollers 2 is six, but in other embodiments, the number of rollers 2 may be other than six.

[0017] The winding core 3 has a function of holding the positive electrode 22, the negative electrode 24, the first separator 26S1, and the second separator 26S2 wound around the side circumferential surface. Here, the winding core 3 is a substantially cylindrical member, but when winding in a flat shape, a flat winding core may be used. As the winding core 3, a non-divided winding core is used here, but a winding core divided along the radial direction or a winding core with a variable diameter may also be used.

[0018] Further, the winding core 3 may further have suction holes, grooves, etc. The suction holes are, for example, holes for adsorbing the first separator 26S1 and the second separator 26S2 wound around the side peripheral surface. The shape of the suction holes in plan view may be circular or rectangular. Alternatively, the suction holes may be slit-shaped. Typically, the suction holes are provided with a suction flow path which is a flow path formed inside the winding core 3 and communicating with the suction holes. The suction path is a flow path for forming a negative pressure in the suction holes. The suction path may be configured to be appropriately connected to a vacuum line installed outside so as to form a negative pressure. And the groove can function as a receiving portion where the blade of the cutter is lowered when the first separator 26S1 and the second separator 26S2 are cut. Thereby, it is possible to suppress damage to the winding core or the cutter due to contact between the winding core 3 and the blade of the cutter.

[0019] The adhesive application portion 4 applies an adhesive layer slurry along the conveyance direction to at least one surface of the separator 26 (here, the first separator 26S1 and the second separator 26S2). The adhesive application portion 4 is configured to be able to apply the adhesive layer slurry in a desired amount to a desired region of the first separator 26S1 and the second separator 26S2. The adhesive layer slurry includes, for example, an adhesive layer binder (adhesive) as described later and at least one of a solvent and a dispersion medium. Note that "slurry" may include ink, paste, etc.

[0020] The solvent contained in the above-mentioned adhesive layer slurry may be any liquid capable of dissolving the above-mentioned adhesive layer binder (adhesive). Also, the dispersion medium contained in the above-mentioned adhesive layer slurry may be any liquid capable of dispersing the above-mentioned 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 perspective 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 (such as lower alcohols and lower ketones) that can be uniformly mixed 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, still more preferably 95% by mass or more) of the aqueous solvent is water. A particularly preferred example is an aqueous solvent consisting essentially of water. Also, the solvent of the above-mentioned adhesive layer slurry is not limited to a so-called aqueous solvent, and it may be a so-called organic solvent. Examples of organic solvents include alcohol-based solvents, ketone-based solvents, ester-based solvents, halogen-based solvents, hydrocarbon-based solvents, nitrogen-containing solvents, and the like. These may be used alone or in combination of two or more. Also, from the perspective of facilitating removal of the solvent during drying after coating the above-mentioned adhesive layer slurry, the boiling points of the above-mentioned solvent and the above-mentioned dispersion medium are preferably, for example, about 50°C to 200°C or about 100°C to 150°C. If the boiling point is too low, the stability of coating may be impaired, such as the above-mentioned adhesive layer slurry drying before coating, so it is preferably appropriately selected according to the coating method. Note that the ratio of the solvent / dispersion medium in the above-mentioned adhesive layer slurry is appropriately adjusted according to the coating method. For example, in the case of coating methods such as gravure printing and inkjet printing, the weight ratio is preferably about 50 to 99%, and more preferably about 80 to 95%. Also, the above-mentioned adhesive layer binder (adhesive) may be dissolved or dispersed in the above-mentioned adhesive layer slurry. And when the above-mentioned adhesive layer slurry is a solution in which the above-mentioned adhesive is dissolved, the above-mentioned adhesive may excessively penetrate into the heat-resistant layer 28 described later, so the above-mentioned adhesive layer slurry is preferably a dispersion of the above-mentioned adhesive.Although not particularly limited, when the total amount of the adhesive layer slurry is 100% by mass, the content of the solvent and the dispersion medium in the adhesive layer slurry can be, for example, about 50 to 99% by mass (preferably about 80 to 95% by mass).

[0021] Examples of the adhesive layer binder (adhesive) include acrylic resins, fluorine-based resins, rubber-based resins, urethane-based resins, silicone-based resins, epoxy-based resins, and the like. These may be used alone or in combination of two or more. An example of the rubber-based resin is styrene-butadiene rubber (SBR). Further, fluorine-based resins and acrylic resins are preferable because they have high flexibility and can more suitably exhibit adhesiveness to the electrode (here, the positive electrode 22). Examples of the fluorine-based resin 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 later. Further, 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, it may be one that exhibits adhesiveness (adhesion) by heating or pressurization or the like. Here, the adhesiveness (adhesion) may mean that the peel strength by 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, when the total amount of the adhesive layer slurry is 100% by mass, the content of the adhesive layer binder in the adhesive layer slurry can be, for example, about 1 to 50% by mass (preferably about 5 to 20% by mass).

[0022] Further, for example, as the above adhesive layer binder (adhesive), a resin may be used such that the electrode (here, the positive electrode 22) and the separator 26 adhere at room temperature (for example, about 25°C) and / or low pressure (for example, 0.1 MPa or less, preferably 0.05 MPa or more). As such a resin, for example, those having a glass transition temperature of room temperature or lower are preferable, those having a glass transition temperature of 0°C or lower are more preferable, and those having a glass transition temperature of -10°C or lower are even more preferable. Further, the glass transition temperature of such a resin may be, for example, -20°C or higher. Examples of such a resin include PVdF, SBR, acrylic resins, etc. having a low glass transition temperature as described above. Alternatively, as the above adhesive layer binder (adhesive), a resin may be used such that the electrode (here, the positive electrode 22) and the separator 26 adhere by heating (for example, heating at 50°C or higher, 70°C or higher, preferably 150°C or lower, 100°C or lower) and / or pressurization (for example, pressure of 0.1 MPa or more, 1 MPa or more, preferably 20 MPa or lower, 10 MPa or lower) at room temperature. As such a resin, for example, those having a glass transition temperature of room temperature or higher are preferable, those having a glass transition temperature of 30°C or higher are more preferable, and those having a glass transition temperature of 40°C or higher, 50°C or higher are even more preferable. Further, the glass transition temperature of such a resin may be, for example, 60°C or lower. Examples of such a resin include PVdF, acrylic resins having a high glass transition temperature as described above, epoxy resins, etc. Note that the glass transition temperature can be measured, for example, based on the method specified in JIS K 7121. Also, a resin may be used such that the electrode (here, the positive electrode 22) and the separator 26 adhere by irradiation with energy such as light.

[0023] Also, although not particularly limited, the 90° peel strength between the electrode (here, the positive electrode 22) and the separator 26 having the adhesive layer 6 is, for example, 0.00001 N / 20 mm to 0.1 N / 20 mm (preferably, 0.0001 N / 20 mm to 0.01 N / 20 mm). Such a 90° peel test can be measured, for example, by the following method. First, the separator 26 having the adhesive layer 6 and the electrode (here, the positive electrode 22) are each cut out to a size of 2.0 cm in length and 7.0 cm in width, and the cut-out separator 26 and electrode are overlapped. Next, the separator 26 and the electrode are bent so that their angles become 90°. Then, using a tensile tester or the like, one side of the separator 26 opened at 90° and one side of the electrode are gripped, and pulled at a tensile speed of 50 mm / min, and the strength when the two are peeled is measured. In this way, the peel strength can be measured.

[0024] In addition, as long as the above adhesive layer slurry does not interfere with the effects of the technology disclosed herein, it can contain one or more additives such as known thickeners, surfactants, and inorganic fillers (for example, alumina, titania, boehmite). When the above adhesive layer slurry contains such an inorganic filler, when the total mass of the above adhesive layer slurry is 100% by mass, for example, the inorganic filler is preferably contained in an amount of about 5 to 20% by mass (preferably, about 10 to 15% by mass). The viscosity of the above adhesive layer slurry is not particularly limited as long as the effects of the technology disclosed herein are exhibited, but can be generally about 10 to 100 mPa·s (for example, about 20 to 50 mPa·s). Such a viscosity can be measured, for example, by a commercially available viscometer.

[0025] As the adhesive application part 4, for example, various intaglio printing machines such as inkjet printing, gravure roll coater, and spray coater, die coaters such as slit coater, comma coater, and capillary coater (CAP coater), lip coater, calendar machine, and other various adhesive application parts can be used.

[0026] The drying unit 5 removes at least one of the solvent and the dispersion medium from the above-mentioned adhesive layer slurry. By the drying unit 5, at least one of the solvent and the dispersion medium can be volatilized from the separator 26. The drying method by the drying unit 5 is not particularly limited, and for example, 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 (for example, about 50°C to 200°C).

[0027] Subsequently, the manufacturing method of the battery 100 according to the present embodiment will be described. As described above, the manufacturing method of the battery 100 according to the present embodiment includes an arrangement step (step S1), a removal step (step S2), a winding step (step S3), and a pressing step (step S4). Hereinafter, each step will be described.

[0028] (Step S1: Arrangement step) In this step, an adhesive layer slurry containing an adhesive and at least one of a solvent (solvent) and a dispersion medium is arranged (applied) on at least one surface of the surface of the separator 26. As shown in FIG. 2, in the present embodiment, the above-mentioned adhesive layer slurry is arranged on one side of the first separator 26S1 and the second separator 26S2. Here, FIG. 3 is a schematic view when the separator 26 after the formation of the adhesive layer 6 according to the present embodiment is viewed from above. As shown in FIG. 3, in the present embodiment, finally, a dot-shaped adhesive layer 6 having a hollow region E in the center in plan view is formed on the surface of the separator 26. For example, by using an adhesive application unit 4 having an inkjet printing function and further having a double structure for the diameter of the nozzle, a dot-shaped adhesive layer 6 applied to the surface of the separator 26 can be formed. Alternatively, a dot-shaped adhesive layer 6 applied to the surface of the separator 26 can be formed by hitting a plurality of dots with an adhesive application unit 4 having an inkjet printing function. However, these are merely examples, and the above-mentioned adhesive layer slurry may be arranged on the surface of the separator 26 by other methods.

[0029] (Step S2: Removal step) In this process, 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 with a plurality of dot-shaped adhesive layers 6 arranged as shown in FIG. 3 can be obtained. As shown in FIG. 2, in this embodiment, the adhesive layer 6 arranged on the surface of the separator 26 in the placement step is dried by the drying unit 5. By removing such a solvent or dispersion medium, the amount of the solvent or dispersion medium remaining in the adhesive layer 6 during the production of the electrode body can be suitably reduced. Further, since the adhesive layer 6 has a hollow region E, the solvent and the dispersion medium volatilize suitably. Note that "removing at least one of the solvent and the dispersion medium from the adhesive layer slurry" means that when the total amount of the solvent and the dispersion medium in the adhesive layer slurry is 100% by mass, for example, 70% by mass or more, 80% by mass or more, preferably 90% by mass or more, 95% by mass or more, 99% by mass or more (particularly preferably 100% by mass) of the solvent and the dispersion medium is removed. In the technology disclosed herein, in this process, it is not necessary to completely remove the solvent or the dispersion medium, and a small amount may remain.

[0030] Note that, as shown in FIG. 3, in this embodiment, the planar shape (outer shape) of the dot-shaped adhesive layer 6 is circular, but it is not limited thereto. In other embodiments, the planar shape of the dot-shaped adhesive layer 6 can be an elliptical shape, a rectangular shape, a polygonal shape, a combination thereof, or the like. Further, in this embodiment, two adhesive layers 6 are arranged in the short side direction (Y direction in FIG. 3) of the strip-shaped separator 26, but it is not limited thereto. In other embodiments, the adhesive layers 6 may be arranged one by one or three or more in the short side direction (Y direction in FIG. 3) of the separator 26. Also, in this embodiment, in the plan view of the separator 26, the shape of the hollow region E is circular, but it is not limited thereto. In other embodiments, the shape of the hollow region E may be an elliptical shape, a rectangular shape, or various other shapes. On the other hand, when the hollow region E is circular as in this embodiment, it is preferable because the effects of the technology disclosed herein can be easily obtained.

[0031] The subsequent layer 6 is preferably composed mainly of the adhesive layer binder as described above. Here, "composed mainly of the adhesive layer binder" means that when the whole of the adhesive layer 6 is 100% by volume, the adhesive layer binder contains, 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, 95% by volume or more (it may be 100% by volume). Thereby, a predetermined adhesiveness can be accurately exhibited with respect to the electrode (here, the positive electrode 22).

[0032] Also, as described above, in addition to the above adhesive layer binder, the adhesive layer 6 may contain other materials (for example, inorganic fillers such as alumina, titania, boehmite, etc.). When the adhesive layer 6 contains an inorganic filler, when the whole of the adhesive layer 6 is 100% by mass, the inorganic filler preferably contains, for example, about 10 to 90% by mass (preferably about 20 to 80% by mass).

[0033] Here, in the winding process described later (in other words, in the separator 26 used in the winding process described later, or after the above removal process), the ratio of the area of the region where the adhesive layer 6 is disposed on one side of the separator 26 to the area of one side of the separator 26 (area of the region where the adhesive layer is disposed on one side of the separator / area of one side of the separator) is not particularly limited as long as the effects of the technology disclosed herein are exhibited. The upper limit of the above ratio is, for example, 0.5 or less, 0.3 or less, and from the viewpoint of more preferably reducing the amount of the solvent or dispersion medium remaining in the adhesive layer 6 during the production of the electrode body, it is preferably 0.1 or less, and may be 0.07 or less, 0.05 or less. Further, the lower limit of the above ratio is, for example, 0.01 or more, and from the viewpoint of preferably ensuring the adhesive force between the separator 26 and the electrode, it is preferably 0.02 or more, and more preferably 0.03 or more. That is, (area of the region where the adhesive layer is disposed on one side of the separator / area of one side of the separator) being 0.1 or less is preferable from the viewpoint of reducing the amount of the solvent or dispersion medium remaining in the adhesive layer 6 during the production of the electrode body. Note that the "area of the region where the adhesive layer 6 is disposed on one side of the separator 26" may mean the total area of the adhesive layer 6 (outer peripheral region) and the hollow region E disposed in a dot shape in a plan view of one side of the separator 26.

[0034] Also, in a plan view, the ratio of the area of the hollow region E to 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 the ratio is, for example, 0.1 or more. From the viewpoint of more preferably reducing the amount of the solvent or dispersion medium remaining in the adhesive layer 6 during the production of the electrode body, and from the viewpoint of preferably suppressing the deterioration of the input / output characteristics of the battery 100 due to the arrangement of the adhesive layer 6, it is preferably 0.2 or more, more preferably 0.3 or more, and particularly preferably 0.5 or more. Also, the upper limit of the ratio is, for example, 0.9 or less. From the viewpoint of preferably ensuring the adhesive force between the separator 26 and the electrode, and from the viewpoint of preferably suppressing the deterioration of the input / output characteristics of the battery 100 due to the arrangement of the adhesive layer 6, it is preferably 0.8 or less, and more preferably 0.7 or less. That is, in a plan view, the ratio of the area of the hollow region E to the area of the dot-shaped adhesive layer 6 is preferably, for example, 0.2 to 0.8 from the viewpoint of preferably obtaining the effects as described above. The "area of the dot-shaped adhesive layer 6" may mean the area of the region surrounded by the outer peripheral edge of the dot in the plan view of the separator 26, that is, the total area of the dot-shaped adhesive layer 6 and its hollow region E.

[0035] Also, in the winding process described later (in other words, in the separator 26 used in the winding process described later. Or, after the above removal process.), the diameter (the diameter, corresponding to d in FIG. 3) of one of the dot-shaped adhesive layers 6 is not particularly limited as long as the effects of the technology disclosed herein are exhibited. The lower limit of the above d is, for example, 10 μm or more, and from the viewpoint of preferably ensuring the adhesive force between the separator 26 and the electrode and from the viewpoint of preferably suppressing variations in the adhesive force, it is preferably 50 μm or more, more preferably 75 μm or more, and particularly preferably 100 μm or more. Also, the upper limit of the above d is, for example, 600 μm or less, and from the viewpoint of more preferably reducing the amount of solvent remaining in the adhesive layer 6 during the production of the electrode body and from the viewpoint of preferably suppressing a decrease in the input / output characteristics of the battery 100 due to the arrangement of the adhesive layer 6 and the precipitation of Li, etc., it is preferably 500 μm or less, more preferably 300 μm or less, 200 μm or less. That is, in the above winding process, the diameter (the diameter) of one of the dot-shaped adhesive layers 6 is preferably, for example, 50 μm to 500 μm.

[0036] Here, FIG. 6 is a schematic diagram showing the state of the separator before the winding process according to an embodiment. It can also be said that FIG. 6 is a schematic longitudinal sectional view taken along line VI-VI in FIG. 3. In this embodiment, the adhesive layer 6 is disposed on the side facing the positive electrode 22 of the first separator 26S1 and the second separator 26S2. However, for the sake of easy explanation in FIG. 6, only the first separator 26S1 and the positive electrode 22 are shown. However, the same applies to the second separator 26S2 and the positive electrode 22. In the winding process described later (in other words, in the separator 26 used in the winding process described later. Or, after the above removal process.), the thickness of one of the above dot-shaped adhesive layers 6 (the length in the MD direction of FIG. 6. Corresponding to t in FIG. 6.) is not particularly limited as long as the effects of the technology disclosed herein are exhibited. The lower limit of the above t is preferably 0.1 μm or more, more preferably 0.2 μm or more, and still more preferably 0.5 μm or more. Also, the upper limit of the above t is preferably 10 μm or less, preferably 5 μm or less, and more preferably 3 μm or less. That is, the above t is preferably, for example, in the range of 0.1 μm to 10 μm.

[0037] 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 or more, and more preferably 0.02 g / m 2 or more. Also, the upper limit of the basis weight of the adhesive layer 6 is, for example, 2.0 g / m 2 or less, preferably 1.0 g / m 2 or less, and more preferably 0.05 g / m 2 or less. Note that the "basis weight" refers to the value obtained by dividing the mass of the adhesive layer by the area of the formation region (mass of the adhesive layer / area of the formation region).

[0038] (Step S3: Winding Process) As described above, in this process, in this embodiment, in order to manufacture a wound electrode body as the electrode body, in the above winding process, 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 through to produce a 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 respectively conveyed to the winding core 3 by the conveying paths k1 to k4 and wound around the winding core 3 to produce the wound body 20A. As the winding core 3, a cylindrical one is used here, but it is not limited thereto, and for example, a flat-shaped one may be used. Further, the cross-sectional shape of the wound body 20A may be a flat shape as in this embodiment, or may be other shapes such as a perfect circle shape, an ellipse shape, a track shape, etc. Each sheet is wound so that only the positive electrode tab 22t of the positive electrode 22 protrudes from the side edge on one side (the left side in FIG. 15) in the width direction Y, and only the negative electrode tab 24t of the negative electrode 24 protrudes from the side edge on the other side (the right side in FIG. 15). Note that the number of windings is preferably adjusted as appropriate in consideration of the performance and manufacturing efficiency of the target battery 100. In some aspects, such number of windings can be 20 or more or 30 or more. The temperature in the above winding process is preferably 50°C or lower, more preferably 40°C or lower, and even more preferably 35°C or lower. Further, the above winding process is preferably carried out at 10°C or higher. As the adhesive layer 6, for example, one having adhesiveness (adhesive property) can be used under the temperature conditions in the above winding process.

[0039] In the above winding process, when the outer frame portion of the adhesive layer 6 of the separator 26 comes into contact with the electrode (the positive electrode 22 or the negative electrode 24), the winding displacement of the wound body 20A (specifically, the positional displacement of the separator 26 and the electrode in the wound body 20A. In particular, it is likely to occur when the wound body 20A is removed from the winding core 3.) can be preferably suppressed.

[0040] (Step S4: Pressing Process) In a preferred embodiment, the winding process includes a pressing process of pressing the stacked first electrode (here, the positive electrode 22), the separator 26 (here, the first separator 26S1 and the second separator 26S2), and the second electrode (here, the negative electrode 24). According to such a configuration, the separator 26 and the electrode can be more preferably adhered. In the present embodiment, the wound body 20A obtained in the winding process is press-molded into a flat wound electrode body 20a. Here, FIG. 4 is a schematic diagram showing the wound body 20A before the pressing process according to the present embodiment. Further, FIG. 5 is a schematic diagram showing the wound body 20A after the pressing process according to the present embodiment. First, as shown in FIG. 4, after the wound body 20A is disposed on a press 200 having a pair of opposing pressing surfaces, it is pressed in the direction of the white arrow to obtain a flat wound electrode body 20a. Here, the pressing pressure can be, for example, in the range of 0.1 MPa to 20 MPa (preferably, 5 MPa to 10 MPa). Further, such pressing may be pressing without heating, may be hot pressing, or both may be performed. In the case of hot pressing, the heating temperature can be, for example, in the range of 50°C to 100°C (preferably, 70°C to 90°C). As shown in FIG. 11, the flat electrode body 20a after press molding has a pair of curved portions 20r with a curved outer surface and a flat portion 20f with a flat outer surface connecting the pair of curved portions 20r. Further, at one end in the width direction Y of the flat wound electrode body 20a after press molding, a positive electrode tab group 23 in which positive electrode tabs 22t are stacked is formed, and at the other end, a negative electrode tab group 25 in which negative electrode tabs 24t are stacked is formed. And at the central portion in the width direction Y of the wound electrode body, 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.

[0041] As described above, each of the dot-shaped adhesive layers 6 has a hollow region E in the center in plan view. And, by the pressing step, the area of the hollow region E in plan view is reduced to 1 / 2 or less. In other words, in the pressing step, a wider surface generated by the crushing of the adhesive layer 6 comes into contact with the electrodes (the positive electrode 22 and the negative electrode 24). According to such a configuration, in the winding step, the electrodes (the positive electrode 22 and the negative electrode 24) and the separator 26 are not strongly adhered, and for the first time in the pressing step, they can be strongly adhered to each other. Therefore, in the pressing step, when the positional relationship between the electrode and the separator 26 changes, the positional relationship changes appropriately. Also, according to such a configuration, since an increase in the thickness of the wound electrode body after the pressing step can be preferably suppressed, the insertability of the wound electrode body into the case 10 can be preferably improved. Note that, by the pressing step, the area of the hollow region E in plan view may be reduced to 1 / 3 or less, or may be reduced to 1 / 4 or less, or may be 0 (that is, the hollow region E disappears).

[0042] In a preferred embodiment, the arranging step and the removing step are performed immediately before the winding step. As shown in FIG. 2, in the present embodiment, immediately before the winding step of winding the positive electrode 22, the negative electrode 24, and the separator 26 (here, the first separator 26S1 and the second separator 26S2) to produce the wound body 20A, the arranging and forming of the adhesive layer 6 are performed. According to such a configuration, side reactions are less likely to occur in the adhesive layer 6, and dust and the like are less likely to adhere to the adhesive layer 6, which is preferable. The time from the removing step to the winding step is preferably within 30 minutes, more preferably within 10 minutes, and particularly preferably within 5 minutes. Also, the shortest distance from the position where the removing step is performed (for example, the position of the adhesive application portion 4 in FIG. 2) to the position where the winding step is performed (for example, the position of the winding core 3 in FIG. 2) is preferably 30 m or less, more preferably 10 m or less, and particularly preferably 5 m or less. However, it is not limited to these.

[0043] Although not shown in the drawings, in the present embodiment, a separator 26 is disposed on the outermost peripheral surface of the wound electrode body 20a after the pressing step, and a winding tape is attached to the end of the separator 26 at the end of winding to hold the shape of the wound electrode body 20a. As the winding tape, a conventionally known one used for the wound electrode body can be used without particular limitation. Although not shown in the drawings, in the present embodiment, the end of the positive electrode 22 at the end of winding is disposed at the curved portion 20r of the electrode body 20a. In this way, the electrode bodies 20a, 20b, and 20c according to the present embodiment can be manufactured.

[0044] Next, an electrode body group 20 integrated with the sealing plate 14 is manufactured. Specifically, first, as shown in FIG. 13, three wound electrode bodies 20a provided with the positive electrode second current collecting portion 52 and the negative electrode second current collecting portion 62 are prepared and arranged side by side in the short side direction X as the wound electrode bodies 20a, 20b, and 20c. At this time, the wound electrode bodies 20a, 20b, and 20c may be arranged in parallel such that the positive electrode second current collecting portion 52 is disposed on one side in the long side direction Y (the left side in FIG. 13) and the negative electrode second current collecting portion 62 is disposed on the other side in the long side direction Y (the right side in FIG. 13).

[0045] Next, as shown in FIG. 12, in a state where a plurality of positive electrode tabs 22t are curved, the positive electrode first current collecting portion 51 fixed to the sealing plate 14 and the positive electrode second current collecting portions 52 of the wound electrode bodies 20a, 20b, and 20c are joined to each other. Also, in a state where a plurality of negative electrode tabs 24t are curved, the negative electrode first current collecting portion 61 fixed to the sealing plate 14 and the negative electrode second current collecting portions 62 of the wound electrode bodies 20a, 20b, and 20c are joined to each other. As the joining method, for example, welding such as ultrasonic welding, resistance welding, and laser welding can be used. In particular, it is preferable to use welding by irradiation with a high energy beam such as a laser. By such welding, joining portions are formed in the concave portions of the positive electrode second current collecting portion 52 and the negative electrode second current collecting portion 62, respectively.

[0046] Subsequently, the composite body produced as described above is housed in the internal space of the exterior body 12. Specifically, first, for example, an insulating resin sheet made of a resin material such as polyethylene (PE) is bent into a bag shape or a box shape to prepare an electrode body holder 29. Next, the electrode body group 20 is housed in the electrode body holder 29. Then, the electrode body group 20 covered with the electrode body holder 29 is inserted into the exterior body 12. When the weight of the electrode body group 20 is heavy, generally 1 kg or more, for example, 1.5 kg or more, and further 2 to 3 kg, the long side wall 12b of the exterior body 12 may be arranged so as to intersect the gravitational direction (with the exterior body 12 placed horizontally), and the electrode body group 20 may be inserted into the exterior body 12.

[0047] Finally, a sealing plate 14 is joined to the edge of the opening 12h of the exterior body 12 to seal the opening 12h. Then, the exterior body 12 and the sealing plate 14 are joined by welding. The welding joint between the exterior body 12 and the sealing plate 14 can be performed by, for example, laser welding or the like. Thereafter, an electrolytic solution is injected through the liquid injection hole 15, and the liquid injection hole 15 is closed with a sealing member 15a to seal the battery 100. In this way, the battery 100 can be manufactured.

[0048] <Configuration of the battery> Subsequently, an example of a battery obtained by the battery manufacturing method disclosed herein will be described.

[0049] FIG. 9 is a perspective view of the battery 100. FIG. 10 is a schematic longitudinal sectional view taken along the line X-X of FIG. 9. FIG. 11 is a schematic longitudinal sectional view taken along the line XI-XI of FIG. 9. FIG. 12 is a schematic cross-sectional view taken along the line XII-XII of FIG. 9. In the following description, the reference signs L, R, F, Rr, U, D in the drawings represent left, right, front, rear, top, and bottom, respectively, and the reference signs X, Y, Z in the drawings represent the short side direction, the long side direction orthogonal to the short side direction, and the vertical direction of the battery 100, respectively. However, these are merely directions for convenience of explanation and do not limit the installation form of the battery 100 in any way.

[0050] As shown in FIG. 10, the battery 100 includes a battery case (case) 10 and an electrode body group 20. Further, in addition to the battery case 10 and the electrode body group 20, the battery 100 according to the present embodiment 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 collector 50, a negative electrode current collector 60, a positive electrode internal insulating member 70, and a negative electrode internal insulating member 80. Although not shown, the battery 100 according to the present embodiment further includes an electrolytic solution. Here, the battery 100 is a lithium ion secondary battery.

[0051] The battery case 10 is a housing that houses the electrode body group 20. Here, the battery case 10 has an outer shape of a flat and bottomed rectangular parallelepiped (rectangular shape). The material of the battery case 10 may be the same as that conventionally used, and there is no particular limitation. The battery case 10 is preferably made of a metal having a predetermined strength. Examples of the metal material constituting the battery case 10 include aluminum, aluminum alloy, iron, and iron alloy.

[0052] The battery case 10 includes an exterior body 12, a sealing plate 14, and a gas discharge valve 17. The exterior body 12 is a flat rectangular container with one surface being an opening 12h. Specifically, as shown in FIG. 9, the exterior body 12 includes a substantially rectangular bottom wall 12a, a pair of second side walls 12c that extend upward U-shaped from the short sides of the bottom wall 12a and face each other, and a pair of first side walls 12b that extend upward U-shaped from the long sides of the bottom wall 12a and face each other. The area of the second side wall 12c is smaller than the area of the first side wall 12b. The opening 12h is formed on the upper surface of the exterior body 12 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 plate material that is substantially rectangular in plan view. The sealing plate 14 faces the bottom wall 12a of the exterior body 12. The battery case 10 is formed by joining (for example, welding) the sealing plate 14 to the periphery of the opening 12h of the exterior body 12. The joining of the sealing plate 14 can be performed by welding such as laser welding. Specifically, each of the pair of second side walls 12c is joined to the short side of the sealing plate 14, and each of the pair of first side walls 12b is joined to the long side of the sealing plate 14.

[0053] As shown in FIGS. 9 and 10, the gas discharge valve 17 is formed in the sealing plate 14. The gas discharge valve 17 is configured to open when the pressure inside the battery case 10 reaches a predetermined value or more and discharge the gas inside the battery case 10. The gas discharge valve 17 in the present embodiment is a substantially circular recess on the outer surface of the sealing plate 14 that is recessed toward the electrode body group 20 side. A thin portion thinner than the thickness of the sealing plate 14 is formed on the bottom surface of the gas discharge valve 17. When the pressure inside the case reaches a predetermined value or more, the thin portion of the gas discharge valve 17 breaks. Thereby, the gas inside the battery case 10 can be discharged to the outside, and the increased pressure inside the case can be reduced.

[0054] In addition to the gas discharge valve 17, the sealing plate 14 is provided with a liquid injection hole 15, and two terminal insertion holes 18 and 19. The liquid injection hole 15 communicates with the internal space of the outer casing 12 and is an opening provided for injecting electrolyte in the manufacturing process of the battery 100. The liquid injection hole 15 is sealed by a sealing member 15a. As such a sealing member 15a, for example, a blind rivet is suitable. Thereby, the sealing member 15a can be firmly fixed inside the battery case 10. Further, the terminal insertion holes 18 and 19 are respectively formed at both ends in the long side direction Y of the sealing plate 14. The terminal insertion holes 18 and 19 penetrate the sealing plate 14 in the vertical direction Z. As shown in FIG. 9, the positive electrode terminal 30 is inserted into the terminal insertion hole 18 on one side (left side) in the long side direction Y. Also, the negative electrode terminal 40 is inserted into the terminal insertion hole 19 on the other side (right side) in the long side direction Y.

[0055] FIG. 13 is a perspective view schematically showing the wound electrode body attached to the sealing plate 14. In the present embodiment, a plurality (here, three) of wound electrode bodies 20a, 20b, and 20c are accommodated inside the battery case 10. The number of wound electrode bodies accommodated inside one battery case 10 is not particularly limited, and may be one, or may be two or more (plural). As shown in FIG. 10, a positive electrode current collector 50 is arranged on one side (left side in FIG. 10) in the long side direction Y of each wound electrode body, and a negative electrode current collector 60 is arranged on the other side (right side in FIG. 10) in the long side direction Y. And each of the wound electrode bodies 20a, 20b, and 20c is connected in parallel. However, the wound electrode bodies 20a, 20b, and 20c may be connected in series. Each wound electrode body is accommodated inside the outer casing 12 of the battery case 10 in a state covered with an electrode body holder 29 (see FIG. 11) made of a resin sheet here.

[0056] FIG. 14 is a perspective view schematically showing the wound electrode body 20a. FIG. 15 is a schematic diagram showing the configuration of the wound electrode body 20a. Here, in FIG. 15, for the sake of easy viewing, the description of the adhesive layer 6 formed on the surface of the separator 26 is omitted. Hereinafter, the wound electrode body 20a will be described in detail as an example, but the wound electrode bodies 20b and 20c can have the same configuration.

[0057] As shown in FIG. 15, the wound electrode body 20a has a positive electrode 22, a negative electrode 24, and a separator 26. Here, 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 laminated via two strip-shaped separators 26 and wound around a winding axis WL.

[0058] The wound electrode body 20a has a flat shape. The wound electrode body 20a is disposed inside the exterior body 12 in such a direction that the winding axis WL is substantially parallel to the long side direction Y. Specifically, as shown in FIG. 11, the wound electrode body 20a has a pair of curved portions (R portions) 20r facing the bottom wall 12a and the sealing plate 14 of the exterior body 12, and a flat portion 20f connecting the pair of curved portions 20r and facing the second side wall 12c of the exterior body 12. The flat portion 20f extends along the second side wall 12c.

[0059] As shown in FIG. 15, the positive electrode 22 has a positive electrode current collector 22c, and a positive electrode active material layer 22a and a positive electrode protective layer 22p fixed on at least one surface of the positive electrode current collector 22c. However, the positive electrode protective layer 22p is not essential and can 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. Here, the positive electrode current collector 22c is a metal foil, specifically, an aluminum foil.

[0060] At one end (the left end in FIG. 15) in the long side direction Y of the positive electrode current collector 22c, a plurality of positive electrode tabs 22t are provided. The plurality of positive electrode tabs 22t are provided at intervals (intermittently) along the longitudinal direction of the strip-shaped positive electrode 22. The plurality of positive electrode tabs 22t protrude outward from the separator 26 toward one side in the axial direction of the winding axis WL (the left side in FIG. 15). Note that the positive electrode tabs 22t may be provided on the other side in the axial direction of the winding axis WL (the right side as shown in FIG. 15), or may be provided on each of both sides in the axial direction of the winding axis WL. The positive electrode tab 22t is a part of the positive electrode current collector 22c and is made of a metal foil (aluminum foil). However, the positive electrode tab 22t may be a member different from the positive electrode current collector 22c. In at least a part of the positive electrode tab 22t, a region where the positive electrode current collector 22c is exposed is formed without forming the positive electrode active material layer 22a and the positive electrode protective layer 22p.

[0061] As shown in FIG. 12, the plurality of positive electrode tabs 22t are laminated at one end in the axial direction of the winding axis WL (the left end in FIG. 12) to form a positive electrode tab group 23. Each of the plurality of positive electrode tabs 22t is bent so that the outer ends are aligned. Thereby, the battery 100 can be downsized by improving the compatibility with the battery case 10. As shown in FIG. 10, the positive electrode tab group 23 is electrically connected to the positive electrode terminal 30 via the positive electrode current collecting portion 50. Specifically, the positive electrode tab group 23 and the second positive electrode current collecting portion 52 are connected at the connection portion J (see FIG. 12). Then, the second positive electrode current collecting portion 52 is electrically connected to the positive electrode terminal 30 via the first positive electrode current collecting portion 51. Note that the sizes of the plurality of positive electrode tabs 22t (the length along the long side direction Y and the width orthogonal to the long side direction Y, see FIG. 15) can be appropriately adjusted according to, for example, the formation position and the like in consideration of the state of being connected to the positive electrode current collecting portion 50. Here, the sizes of the plurality of positive electrode tabs 22t are different from each other so that the outer ends are aligned when bent.

[0062] As shown in FIG. 15, the positive electrode active material layer 22a is provided in a strip 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 (for example, a lithium transition metal composite oxide such as lithium nickel cobalt manganese composite oxide) that can reversibly occlude and release charge carriers. When the total solid content of the positive electrode active material layer 22a is 100% by mass, the positive electrode active material may generally occupy 80% by mass or more, typically 90% by mass or more, for example 95% by 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, and various additive components. As the conductive material, for example, a carbon material such as acetylene black (AB) can be used. As the binder, for example, polyvinylidene fluoride (PVdF) or the like can be used.

[0063] As shown in FIG. 15, the positive electrode protective layer 22p is provided at the boundary portion 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. 15) in the axial direction of the winding axis WL of the positive electrode current collector 22c. However, the positive electrode protective layer 22p may be provided at both ends in the axial direction. 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 (for example, alumina). When the total solid content of the positive electrode protective layer 22p is 100% by mass, the inorganic filler may generally occupy 50% by mass or more, typically 70% by mass or more, for example 80% by 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 the binder may be the same as those exemplified as being included in the positive electrode active material layer 22a.

[0064] As shown in FIG. 15, the negative electrode 24 has a negative electrode current collector 24c and a negative electrode active material layer 24a fixed on 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. Here, the negative electrode current collector 24c is a metal foil, specifically a copper foil.

[0065] On one end in the axial direction of the winding axis WL of the negative electrode current collector 24c (the right end in FIG. 15), a plurality of negative electrode tabs 24t are provided. 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 side in the axial direction (the right side in FIG. 15). However, the negative electrode tab 24t may be provided at the other end in the axial direction (the left end in FIG. 15), or may be provided at each of both ends in the axial direction. The negative electrode tab 24t is a part of the negative electrode current collector 24c and is made of a metal foil (copper foil). However, the negative electrode tab 24t may be a member different from the negative electrode current collector 24c. In at least a part of the negative electrode tab 24t, a region where the negative electrode current collector 24c is exposed is provided without forming the negative electrode active material layer 24a.

[0066] As shown in FIG. 12, the plurality of negative electrode tabs 24t are laminated at one end in the axial direction (the right end in FIG. 12) to form a negative electrode tab group 25. The negative electrode tab group 25 is preferably provided at a position symmetric to the positive electrode tab group 23 in the axial direction. And each of the plurality of negative electrode tabs 24t is bent so that the outer ends are aligned. Thereby, the compatibility with the battery case 10 can be improved and the battery 100 can be miniaturized. As shown in FIG. 10, the negative electrode tab group 25 is electrically connected to the negative electrode terminal 40 via the negative electrode current collecting portion 60. Specifically, the negative electrode tab group 25 and the second negative electrode current collecting portion 62 are connected at the connection portion J (see FIG. 12). And the second negative electrode current collecting portion 62 is electrically connected to the negative electrode terminal 40 via the first negative electrode current collecting portion 61. Similar to the plurality of positive electrode tabs 22t, here, the sizes of the plurality of negative electrode tabs 24t are different from each other so that the outer ends are aligned when bent.

[0067] As shown in FIG. 15, the negative electrode active material layer 24a is provided in a strip shape along the longitudinal direction of the strip-shaped negative electrode current collector 24c. The negative electrode active material layer 24a contains a negative electrode active material (for example, a carbon material such as graphite) that can reversibly occlude and release charge carriers. When the total solid content of the negative electrode active material layer 24a is 100% by mass, the negative electrode active material may occupy approximately 80% by mass or more, typically 90% by mass or more, for example 95% by 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, various additive components, etc. As the binder, for example, rubbers such as styrene-butadiene rubber (SBR) can be used. As the dispersant, for example, celluloses such as carboxymethyl cellulose (CMC) can be used.

[0068] As shown in FIGS. 15 and 3, the separator 26 is a strip-shaped member. The separator 26 is an insulating sheet in which a plurality of fine through-holes through which charge carriers can pass are formed. The width of the separator 26 is larger 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 (for example, lithium ions) can be moved 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. 16; the same applies hereinafter) is preferably 3 μm or more, more preferably 5 μm or more. Also, 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.

[0069] Here, two separators 26 are used for one wound electrode body 20a. The separator 26 preferably includes two sheets, that is, a first separator and a second separator, for one wound electrode body 20a as in the present embodiment. Also, here, the two separators have the same configuration, but they may be different from each other. And in other embodiments, the separator may be one sheet. For example, when manufacturing a stacked electrode body as the electrode body, a strip-shaped separator folded ninety-nine times may be used.

[0070] Here, FIG. 16 is an enlarged view schematically showing the interface between the positive electrode 22, the negative electrode 24, and the separator 26 according to the present embodiment. As shown in FIG. 16, the separator 26 according to the present embodiment has a base material layer 27 and a heat resistance layer 28 (Heat Resistance Layer: HRL) provided on one surface of the base material layer 27. Further, an adhesive layer 6 exists on the surface of the heat resistance layer 28.

[0071] As the base material layer 27, a microporous membrane used for a conventionally known battery separator can be used without particular limitation. The base material layer 27 is preferably a porous sheet-like member. The base material layer 27 may have a single-layer structure or a structure of two or more layers, for example, a three-layer structure. The base material layer 27 is preferably made of a polyolefin resin. More preferably, the entire base material layer 27 is made of a polyolefin resin. The base material layer 27 may be, for example, a microporous membrane made of polyolefin, preferably a microporous membrane made of polyethylene. Thereby, sufficient flexibility of the separator 26 can be ensured, and the production (winding and press molding) of the wound electrode body 20a can be easily carried out. As the polyolefin resin, polyethylene (PE), polypropylene (PP), or a mixture thereof is preferable, and it is more preferable to be made of PE.

[0072] Although not particularly limited, the thickness of the base material layer 27 (the length in the stacking direction MD; the same applies hereinafter) is preferably 3 μm or more, more preferably 5 μm or more. Also, the thickness of the base material 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 material layer 27 is preferably 30 sec / 100 cc to 500 sec / 100 cc, more preferably 30 sec / 100 cc to 300 sec / 100 cc, and even more preferably 50 sec / 100 cc to 200 sec / 100 cc.

[0073] The heat-resistant layer 28 is provided on the base material layer 27. It is preferable that the heat-resistant layer 28 is formed on the base material layer 27. The heat-resistant layer 28 may be provided directly on the surface of the base material layer 27, or may be provided on the base material layer 27 via another layer. Also, it is preferable that the heat-resistant layer 28 is formed on one or both sides of the base material layer 27. However, the heat-resistant layer 28 is not essential and can be omitted in other embodiments. Here, the heat-resistant layer 28 is provided on the entire surface facing the positive electrode 22 of the base material layer 27. Thereby, the heat shrinkage of the separator 26 can be more accurately suppressed, contributing to the improvement of the 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 here. Although not particularly limited, the thickness of the heat-resistant layer 28 (the length in the lamination 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. Also, the thickness of the heat-resistant layer 28 is preferably 6 μm or less, more preferably 4 μm or less. The heat-resistant layer 28 preferably contains an inorganic filler and a heat-resistant layer binder.

[0074] As the inorganic filler, those conventionally known and used in this kind of application can be used without particular limitation. The inorganic filler preferably contains insulating ceramic particles. Among them, considering heat resistance, availability, etc., inorganic oxides such as alumina, zirconia, silica, and titania, metal hydroxides such as aluminum hydroxide, and clay minerals such as boehmite are preferable, and alumina and boehmite are more preferable. Also, from the viewpoint of suppressing the heat shrinkage of the separator 26, compounds containing aluminum in particular are preferable. The ratio of the inorganic filler 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.

[0075] As the heat-resistant layer binder, those conventionally known and used in this kind of application can be used without particular limitation. Specific examples include acrylic resins, fluorine-based resins (e.g., PVdF), epoxy resins, urethane resins, ethylene vinyl acetate resins, and the like. Among them, acrylic resins are preferable.

[0076] Next, the adhesive layer 6 is provided here on the surface facing the positive electrode 22 and is in contact with the positive electrode 22. As shown in FIG. 16, the adhesive layer 6 is preferably formed at least on the surface of the separator 26 on the positive electrode 22 side. 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. Further, the adhesive layer 6 may be provided directly on the surface of the base material layer 27, or may be provided on the base material layer 27 via a layer other than the heat-resistant layer 28. The adhesive layer 6 can be a layer having a relatively high affinity with the electrolytic solution compared to, for example, the heat-resistant layer 28 and absorbing and swelling with the electrolytic solution. 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. 16. Corresponding to T in FIG. 16. It can also be said as the thickness of the adhesive layer 6 after the above pressing process.) is preferably 0.1 μm or more, more preferably 0.2 μm or more, and even more preferably 0.5 μm or more. Also, 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, for example, within the range of 0.1 μm to 10 μm. By setting it within such a range, the adhesiveness of the adhesive layer 6, the uniformity of the charge and discharge reaction of the battery 100, and the suppression of Li precipitation can be preferably realized.

[0077] Further, the diameter of the adhesive layer 6 in the wound electrode body 20a (corresponding to D in FIG. 16. It can also be said as the diameter of the adhesive layer 6 after the above pressing process.) 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. Also, 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 setting it within such a range, the adhesiveness of the adhesive layer 6, the uniformity of the charge and discharge reaction of the battery 100, and the suppression of Li precipitation can be preferably realized.

[0078] Regarding the resin or the like constituting the next layer 6, refer to the corresponding part in <Method for manufacturing battery>.

[0079] The electrolytic solution may be the same as the conventional one and is not particularly limited. The electrolytic solution is, for example, a non-aqueous electrolytic solution containing a non-aqueous solvent and a supporting salt. The non-aqueous solvent includes, 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 electrolytic solution may be in a solid state (solid electrolyte) and integrated with the electrode body group 20.

[0080] As shown in FIG. 10, the positive electrode terminal 30 is inserted into a terminal insertion hole 18 formed at one end (the left end in FIG. 10) in the long side direction Y of the sealing plate 14. The positive electrode terminal 30 is preferably made of metal, and more preferably made of, for example, aluminum or an aluminum alloy. On the other hand, the negative electrode terminal 40 is inserted into a terminal insertion hole 19 formed at the other end (the right end in FIG. 10) in the long side direction Y of the sealing plate 14. The negative electrode terminal 40 is preferably made of metal, and more preferably made of, for example, copper or a copper alloy. These electrode terminals (positive electrode terminal 30, negative electrode terminal 40) protrude from the same surface (specifically, the sealing plate 14) of the battery case 10 here. However, the positive electrode terminal 30 and the negative electrode terminal 40 may protrude from different surfaces of the battery case 10, respectively. Also, the electrode terminals (positive electrode terminal 30, negative electrode terminal 40) inserted into the terminal insertion holes 18 and 19 are preferably fixed to the sealing plate 14 by caulking or the like.

[0081] As described above, as shown in FIG. 10, the positive electrode terminal 30 is electrically connected to the positive electrodes 22 (see FIG. 13) of the respective wound electrode bodies 20a, 20b, 20c through the positive electrode current collecting portions 50 (the first positive electrode current collecting portion 51 and the second positive electrode current collecting portion 52) inside the exterior body 12. The positive electrode terminal 30 is insulated from the sealing plate 14 by the positive electrode internal insulating member 70 and the gasket 90. The positive electrode internal insulating member 70 includes a base portion 70a interposed between the first positive electrode current collecting portion 51 and the sealing plate 14, and a protruding portion 70b protruding from the base portion 70a toward the wound electrode body 20a side. The positive electrode terminal 30 exposed outside 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. 10, the negative electrode terminal 40 is electrically connected to the negative electrodes 24 (see FIG. 13) of the respective wound electrode bodies 20a through the negative electrode current collecting portions 60 (the first negative electrode current collecting portion 61 and the second negative electrode current collecting portion 62) inside the exterior body 12. The negative electrode terminal 40 is insulated from the sealing plate 14 by the negative electrode internal insulating member 80 and the gasket 90. Similar to the positive electrode internal insulating member 70, the negative electrode internal insulating member 80 also includes a base portion 80a interposed between the first negative electrode current collecting portion 61 and the sealing plate 14, and a protruding portion 80b protruding from the base portion 80a toward the wound electrode body 20a side. The negative electrode terminal 40 exposed outside the battery case 10 through the terminal insertion hole 19 is connected to the negative electrode external conductive member 42 outside the sealing plate 14. An external insulating member 92 is interposed between the above-described external conductive members (the positive electrode external conductive member 32 and the 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 and 42 from the sealing plate 14.

[0082] Further, the protruding portions 70b and 80b of the above-described internal insulating members (the positive electrode internal insulating member 70 and the negative electrode internal insulating member 80) are disposed between the sealing plate 14 and the wound electrode body 20a. The protruding portions 70b and 80b of such internal insulating members restrict the upward movement of the wound electrode body 20a and can prevent contact between the sealing plate 14 and the wound electrode body 20a.

[0083] <Battery Application> The battery 100 can be used for various applications. For example, it can be suitably used as a power source (driving power source) for a motor mounted on vehicles such as passenger cars and trucks. The type of vehicle is not particularly limited, and examples include plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs), battery electric vehicles (BEVs), and the like. Since the variation in battery reactions of the battery 100 is reduced, it can be suitably used for constructing a battery pack.

[0084] As described above, one embodiment of the present disclosure has been explained. However, the above embodiment (the first embodiment) is merely an example. The present disclosure can be implemented in various other forms. The present disclosure can be implemented based on the content disclosed in this specification and common general knowledge in the art. The technology described in the claims includes various modifications and changes of the above-exemplified embodiments. For example, it is possible to replace a part of the above-described embodiment with another modified form, or it is possible to add another modified form to the above-described embodiment. Also, if the technical feature is not described as essential, it can be appropriately deleted.

[0085] For example, in the above embodiment, the adhesive layer 6 is formed on the surface of the separator 26 on the side facing the positive electrode 22, but it is not limited thereto. In other embodiments, the adhesive layer 6 may be formed on the surface of the separator 26 on the side facing the negative electrode 24. Alternatively, the adhesive layer 6 may be formed on the surface of the separator 26 on the side facing the positive electrode 22 and the surface of the separator 26 on the side facing the negative electrode 24. Also, when the electrode body has two separators, the adhesive layer may be disposed only on the surface of one of the separators.

[0086] For example, FIG. 17 is a diagram corresponding to FIG. 3 according to the second embodiment. As shown in FIG. 17, in the second embodiment, in a plan view of the separator 126, the outer shape of the adhesive layer 106 is rectangular, and the hollow region E is also rectangular. The second embodiment may be the same as the above-described first embodiment except for changing the pattern. Note that the shape of the hollow region E in a plan view may be an elliptical shape, a circular shape, or various other shapes.

[0087] For example, FIG. 18 is a diagram corresponding to FIG. 3 according to the third embodiment. As shown in FIG. 18, in the third embodiment, in a plan view of the separator 226, the outer shape of the adhesive layer 206 is elliptical, and the hollow region E is rectangular. The third embodiment may be the same as the above-described first embodiment except for changing the pattern. Note that the shape of the hollow region E in a plan view may be an elliptical shape, a circular shape, or various other shapes.

[0088] As described above, specific aspects of the technology disclosed herein include those described in the following items. Item 1: A method for manufacturing a power storage device including a flat wound electrode body in which a strip-shaped first electrode and a strip-shaped second electrode are wound via a strip-shaped separator, the method including: a winding step of winding the first electrode and the second electrode via the separator to manufacture a wound body; and a pressing step of pressing the wound body after the winding step to form a flat wound electrode body. In the winding step, a separator having an adhesive layer disposed in a plurality of dot shapes on at least one surface is used as the separator. Each of the dot-shaped adhesive layers has a hollow region at the center in a plan view. In the pressing step, the area of the hollow region in a plan view is reduced to 1 / 2 or less. A method for manufacturing a power storage device. Item 2: The method for manufacturing a power storage device according to Item 1, further including: a disposing step of disposing an adhesive layer slurry including an adhesive and at least one of a solvent and a dispersion medium before the winding step; and a removing step of removing at least one of the solvent and the dispersion medium from the adhesive layer slurry. Item 3: The method for manufacturing a power storage device according to Item 1 or Item 2, wherein in the winding step, the ratio of the area of the region where the adhesive layer is disposed on one side of the separator to the area of one side of the separator is 0.1 or less. Item 4: The method for manufacturing a power storage device according to any one of Items 1 to 3, wherein in a plan view, the ratio of the area of the hollow region to the area of the dot-shaped adhesive layer is 0.2 to 0.8.

Explanation of Signs

[0089] 1 Electrode body manufacturing apparatus 2 Roller 3 Winding core 4 Adhesive application part 5 Drying part 6 Adhesive layer 10 Battery case 12 Exterior body 14 Sealing plate 15 Liquid injection hole 15a Sealing member 17 Gas discharge valve 18, 19 Terminal insertion holes 20 Electrode body group 20a - 20c Electrode bodies 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 electrode terminal 32 Positive electrode external conductive member 40 Negative electrode terminal 42 Negative electrode external conductive member 50 Positive electrode current collector 60 Negative electrode current collector 70 Positive electrode internal insulating member 80 Negative electrode internal insulating member 90 Gasket 92 External insulating member 100 Battery 200 Press E Hollow region

Claims

1. A method for manufacturing a power storage device including a flat wound electrode body in which a strip-shaped first electrode and a strip-shaped second electrode are wound via a strip-shaped separator, a winding step of winding the first electrode and the second electrode via the separator to manufacture a wound body, a pressing step of pressing the wound body after the winding step to form a flat wound electrode body, and including: in the winding step, using, as the separator, a separator having an adhesive layer disposed in a plurality of dot shapes on at least one surface, each of the dot-shaped adhesive layers has a hollow region in the center in a plan view, by the pressing step, a method for manufacturing a power storage device in which the area of the hollow region in a plan view is reduced to 1 / 2 or less.

2. before the winding step, a disposing step of disposing an adhesive layer slurry including an adhesive and at least one of a solvent and a dispersion medium, a removing step of removing at least one of the solvent and the dispersion medium from the adhesive layer slurry, The method for manufacturing a power storage device according to claim 1, having.

3. in the winding step, The ratio of the area of the region where the adhesive layer is disposed on one side of the separator to the area of one side of the separator is 0.1 or less. The method for manufacturing a power storage device according to claim 1 or 2.

4. in a plan view, The ratio of the area of the hollow region to the area of the dot-shaped adhesive layer is 0.2 to 0.

8. The method for manufacturing a power storage device according to claim 1 or 2.

Images