Power storage cell

Abstract

To provide a power storage cell excellent in productivity by suppressing or reducing damage to a current collector when a frame member and the current collector are welded.SOLUTION: A power storage cell 10 includes at least a pair of current collectors 11a and 12a disposed to face each other and having a laminated structure, and a frame member 14 provided so as to be positioned between outer peripheral edge portions of the pair of current collectors 11a and 12a. Innermost layers 11c and 12c in the pair of current collectors 11a and 12a and the frame member 14 are welded. A resin material constituting the innermost layers 11c and 12c is the same as that of the frame member 14. A melting point of each of the innermost layers 11c and 12c is lower than that of the other layers 11d and 12d.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an energy storage cell. [Background technology]

[0002] Known conventional energy storage cells include, for example, those described in Patent Document 1. Patent Document 1 discloses an energy storage cell including a pair of current collectors, a positive electrode active material layer provided on one of the pair of current collectors, a negative electrode active material layer provided on the other current collector, a separator interposed between the positive electrode active material layer and the negative electrode active material layer, and spacers (frame members) disposed between the respective outer peripheral edges of the pair of current collectors and surrounding the positive electrode active material layer and the negative electrode active material layer.

[0003] In conventional energy storage cells, the frame member is made of, for example, ethylene vinyl acetate copolymer, and the pair of current collectors is made of a metal material such as aluminum or a conductive resin layer made of a resin material such as polypropylene resin and a conductive filler laminated thereon. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-47702 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in conventional energy storage cells, the adhesion between the frame member and the current collector is low, so when joining the two by welding, sufficient adhesive strength is not obtained despite the long welding time required, and there is also the problem that the long welding process causes damage to the current collector.

[0006] The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide an energy storage cell that suppresses or reduces damage to the current collector when welding the frame member and the current collector, improves the adhesive strength between the frame member and the current collector, and has excellent productivity. [Means for solving the problem]

[0007] To achieve the above object, the present invention provides a storage cell comprising at least a pair of current collectors arranged opposite each other and having a laminated structure, and a frame member positioned between the outer peripheral edges of the pair of current collectors, wherein the innermost layers of the pair of current collectors are welded to the frame member, the resin material of the innermost layers is the same as the resin material of the frame member, and the melting points of the innermost layers are lower than the melting points of the other layers. In this specification, the phrase "the resin material of the innermost layer is the same as the resin material of the frame member" refers not only to cases where the resin material of the innermost layer is the same as the resin material of the frame member, but also to cases where, for example, the monomer as the minimum unit in the resin constituting the innermost layer and the resin constituting the frame member is the same, even if the densities, etc., are different. Furthermore, for example, when a given resin material includes a homopolymer, a random copolymer, and a block copolymer, these are considered to be the same resin material.

[0008] In order to solve the above-mentioned problems, another energy storage cell of the present invention includes at least a pair of current collectors arranged opposite each other and having a laminated structure, and a frame member provided between the outer peripheral edges of the pair of current collectors, wherein the frame member has a first frame member welded to the innermost layer of one of the pair of current collectors, a second frame member welded to the innermost layer of the other of the pair of current collectors, and a bonding layer arranged between the first frame member and the second frame member and having a melting point lower than those of the first frame member and the second frame member, and wherein the melting point of each of the innermost layers of the pair of current collectors is lower than the melting points of the remaining layers.

[0009] In the above-mentioned configuration, a highly conductive layer may be provided on the outermost layer of one of the pair of current collectors on the side opposite to the side facing the other current collector.

[0010] In the above configuration, an intermediate layer containing the resin material constituting the outer layer and the resin material constituting the innermost layer may be provided between the outer layer and the innermost layer of one of the pair of current collectors. [Effects of the Invention]

[0011] According to the present invention, by using the same resin material for the frame member and the resin material for the innermost layer of the current collector that contacts the frame member, welding between the two is improved. Furthermore, in a current collector having a laminated structure, by making the melting points of layers other than the innermost layer higher than that of the innermost layer, damage to the current collector during welding can be suppressed or reduced. As a result, according to the present invention, it is possible to provide an energy storage cell with excellent productivity and high yield. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic cross-sectional view illustrating a main part of a storage cell according to a first embodiment of the present invention. [Figure 2] FIG. 4 is a schematic cross-sectional view showing a main part of another energy storage cell according to the first embodiment of the present invention. [Figure 3] FIG. 4 is a schematic cross-sectional view showing a main part of another energy storage cell according to the first embodiment of the present invention. [Figure 4] Figure 4(a) is a cross-sectional view showing the formation of a first frame member on the outer peripheral edge of the innermost layer of a positive electrode current collector, Figure 4(b) is a cross-sectional view showing the formation of a second frame member on the outer peripheral edge of the innermost layer of a negative electrode current collector, and Figure 4(c) is a cross-sectional view showing the bonding and welding of a positive electrode on which a first frame member has been formed and a negative electrode on which a second frame member has been formed. [Figure 5] FIG. 4 is a schematic cross-sectional view showing a main part of a storage cell according to a second embodiment of the present invention. [Figure 6]Figure 6(a) is a cross-sectional schematic diagram showing how a first frame member is formed on the outer peripheral edge of the innermost layer of a positive electrode current collector, Figure 6(b) is a plan view schematic diagram showing how a bonding layer is formed on the first frame member, Figure 6(c) is a cross-sectional schematic diagram showing how a second frame member is formed on the outer peripheral edge of the innermost layer of a negative electrode current collector, and Figure 6(d) is a cross-sectional schematic diagram showing how a positive electrode on which a bonding layer has been formed and a negative electrode on which a second frame member has been formed are bonded and welded together. DETAILED DESCRIPTION OF THE INVENTION

[0013] (First embodiment) <Energy storage cell> A storage cell according to a first embodiment of the present invention will be described below with reference to Fig. 1. However, parts that are not necessary for the description are omitted, and some parts are illustrated enlarged or reduced to facilitate the description. Fig. 1 is a schematic cross-sectional view showing a main part of a storage cell 10 according to the first embodiment.

[0014] 1, the energy storage cell 10 of this embodiment includes at least a positive electrode 11, a negative electrode 12, a separator (electrolyte layer) 13, and a frame member 14. The energy storage cell 10 of this embodiment can be used, for example, in a stacked type (stacked structure) lithium ion secondary battery or the like including a cell stack formed by stacking a plurality of the energy storage cells 10.

[0015] The positive electrode 11 is, for example, a rectangular electrode in a plan view, and includes a rectangular positive electrode current collector (one of the current collectors) 11a and a positive electrode active material layer 11b.

[0016] The positive electrode current collector 11a has a laminated structure in which an innermost layer 11c and an outer layer (other layers) 11d are laminated in this order. The innermost layer 11c and the outer layer 11d are preferably made of a conductive resin layer.

[0017] The innermost layer 11c is made of a resin material and a conductive filler. By providing the innermost layer 11c on the positive electrode current collector 11a, welding of the positive electrode current collector 11a and the frame member 14 becomes easier.

[0018] The resin material for the innermost layer 11c is not particularly limited as long as it is the same as the resin material constituting the frame member 14 (details will be described later) and can make the melting point of the innermost layer 11c lower than that of the outer layer 11d. Specific examples include polyolefins such as polyethylene and polypropylene, and polyvinylidene fluoride. The content of the resin material is not particularly limited and can be set appropriately as needed. The conductive filler is not particularly limited as long as it can impart conductivity to the innermost layer 11c.

[0019] More specifically, examples of the conductive filler include metal fillers such as nickel, aluminum, stainless steel (SUS), silver, copper, titanium, platinum, gold, and mixtures thereof; non-conductive materials such as particulate ceramic materials and resin materials coated with a metallic conductive material by plating or the like; and conductive carbon fillers such as graphite, carbon black, carbon nanotubes, and mixtures thereof. From the standpoints of cost, availability, and wide variety, conductive carbon fillers are preferred as a constituent material of the innermost layer 11c. Furthermore, the shape, content, and average particle diameter of the conductive filler are not particularly limited and can be set appropriately as needed.

[0020] The melting point of the innermost layer 11c is lower than that of the outer layer 11d. The difference in melting point between the innermost layer 11c and the outer layer 11d depends on the type of material selected, but is preferably 15°C or higher, and more preferably 30°C or higher. By making the melting point difference 15°C or higher, the innermost layer 11c can be easily welded to the frame member 14 in a short time while suppressing or reducing damage to the outer layer 11d. Note that the melting point of the innermost layer 11c must be equal to or higher than the temperature environment in which the battery is used, so it is preferably 50°C or higher, and more preferably 80°C or higher.

[0021] The thickness of the innermost layer 11c is preferably in the range of 1 μm or more and 30 μm or less, and particularly preferably in the range of 5 μm or more and 15 μm or less. By making the thickness of the innermost layer 11c 15 μm or less, it is possible to easily weld the innermost layer 11c to the frame member 14 in a short time while suppressing or reducing damage to the outer layer 11d. On the other hand, by making the thickness of the innermost layer 11c 5 μm or more, it is possible to easily form the innermost layer.

[0022] The outer layer 11d is formed by laminating two conductive resin layers each composed of another resin material and a conductive filler. The other resin material is not particularly limited as long as it can make the melting point of the outer layer 11d higher than that of the innermost layer 11c. Specific examples include, like the innermost layer 11c, polyolefins such as polyethylene and polypropylene, and polyvinylidene fluoride. For example, if the resin material of the innermost layer 11c contains a homopolymer, a random copolymer, or a block copolymer, the other resin material of the outer layer 11d may be appropriately selected and combined from these polymers so that the melting point of the outer layer 11d is higher than that of the innermost layer 11c. The content of the other resin material is not particularly limited and can be set as needed. The conductive filler is not particularly limited and can be the same as that used in the innermost layer 11c. The content of the conductive filler is also not particularly limited and can be set as needed. The outer layer 11d may be formed by laminating three or more conductive resin layers.

[0023] The thickness of the outer layer 11d is preferably in the range of 10 μm or more and 100 μm or less, and particularly preferably in the range of 20 μm or more and 50 μm or less. By making the thickness of the outer layer 11d 100 μm or less, it is possible to prevent poor heat transfer when welding the innermost layer 11c and the frame member 14, and to maintain good welding in a short time. On the other hand, by making the thickness of the outer layer 11d 10 μm or more, it is possible to ensure ease of handling. Note that in this embodiment, an example in which the outer layer 11d is a laminate of three layers has been described. However, the present invention is not limited to this embodiment. For example, the outer layer 11d may be a single layer, or may be composed of multiple layers other than two layers.

[0024] For example, when the power storage cell 10 is applied to a lithium ion battery, the positive electrode active material layer 11b contains a positive electrode active material that absorbs and releases charge carriers such as lithium ions. The positive electrode active material is not particularly limited, and a known material such as a lithium ion composite metal oxide can be used.

[0025] The thickness of the positive electrode active material layer 11b is not particularly limited, but from the viewpoint of battery performance, it is preferably in the range of 100 μm or more and 750 μm or less, and more preferably in the range of 150 μm or more and 550 μm or less.

[0026] The negative electrode 12 is, for example, a rectangular electrode in a plan view, and includes a rectangular negative electrode current collector (the other current collector) 12a and a negative electrode active material layer 12b.

[0027] The negative electrode current collector 12a has a laminated structure in which an innermost layer 12c and an outer layer (other layers) 12d are sequentially laminated. Furthermore, the innermost layer 12c and the outer layer 12d are preferably made of conductive resin layers. A highly conductive layer 12e may be provided on the outermost surface of the innermost layer 12c facing the active material layer to improve the conductivity within the surface of the current collector. The highly conductive layer 12e can also reduce the contact resistance between the active material layer and the current collector. Examples of materials for the highly conductive layer include nickel, stainless steel (SUS), silver, copper, titanium, platinum, and gold, and can be formed by, for example, sputtering, vapor deposition, or plating.

[0028] The innermost layer 12c is composed of a resin material and a conductive filler. The resin material may be the same as the resin material of the innermost layer 11c of the positive electrode current collector 11a. The content of the resin material may be appropriately set, as in the case of the innermost layer 11c. The conductive filler is not particularly limited, and the conductive filler used in the innermost layer 11c may be used without any particular restrictions. The content and average particle diameter of the conductive filler are not particularly limited, and may be appropriately set as needed.

[0029] The outer layer 12d can have the same structure as the outer layer 11d of the positive electrode current collector 11a, and therefore a detailed description thereof will be omitted.

[0030] For example, when the energy storage cell 10 is applied to a lithium-ion battery, the negative electrode active material layer 12b is not particularly limited as long as it contains a negative electrode active material that is an element, alloy, or compound capable of absorbing and releasing charge carriers such as lithium ions. The negative electrode active material is not particularly limited, and known materials that can be used include carbon-based materials such as graphite, non-graphitizable carbon, amorphous carbon, and cokes; silicon-based materials such as silicon oxide (SiOx) and silicon alloys; conductive polymers such as polyacetylene; metals such as tin, aluminum, zirconium, and titanium; metal oxides such as titanium oxide and lithium-titanium oxide; metal alloys such as lithium-aluminum alloys; and mixtures of these with carbon-based materials.

[0031] The thickness of the negative electrode active material layer 12b is preferably in the range of 150 μm or more and 1000 μm or less, and more preferably in the range of 200 μm or more and 700 μm or less.

[0032] The separator 13 functions to prevent short circuits due to contact between the positive electrode 11 and the negative electrode 12 by isolating them, while allowing charge carriers such as lithium ions to pass through. The separator 13 is not particularly limited, and examples thereof include a porous sheet and a nonwoven fabric. The separator 13 may have either a single-layer structure or a multi-layer structure.

[0033] The frame member 14 is provided on the outer peripheral edges of the positive electrode current collector 11a and the negative electrode current collector 12a. More specifically, the frame member 14 is welded to the innermost layer 11c of the positive electrode current collector 11a and the innermost layer 12c of the negative electrode current collector 12a at their contact surfaces. The frame member 14 may also fix the peripheral edge of the separator 13.

[0034] The resin material constituting the frame member 14 is the same as the resin material constituting the innermost layer 11c of the positive electrode current collector 11a and the innermost layer 12c of the negative electrode current collector 12a. Therefore, when heated, the frame member 14 can be welded to the innermost layer 11c and the innermost layer 12c in a short time. Note that the phrase "the resin material constituting the frame member 14 is the same as the resin material constituting the innermost layer 11c of the positive electrode current collector 11a and the innermost layer 12c of the negative electrode current collector 12a" means not only that the resin materials are the same, but also that the resin materials have the same monomer as the minimum unit, such as low-density polyethylene and high-density polyethylene.

[0035] In addition to the case where frame member 14 consists of a single member, as described below, it also includes the case where a first frame member and a second frame member are stacked and arranged, and the first frame member and the second frame member are integrated by welding at their contact surfaces.

[0036] The thickness (height) of the frame member 14 is not particularly limited and can be set appropriately as needed.

[0037] There are no particular limitations on the thickness of each of the positive electrode current collector 11a and the negative electrode current collector 12a, but it is usually in the range of 5 μm or more and 150 μm or less.

[0038] In this embodiment, for example, as in the energy storage cell 20 shown in FIG. 2(a), the highly conductive layer 11e may be provided as the outermost layer of the positive electrode current collector 11a' of the positive electrode 11'. FIG. 2(a) is a schematic cross-sectional view showing a main part of the energy storage cell 20. In this case, the highly conductive layer 11e can improve the in-plane conductivity of the positive electrode current collector 11a'. When the highly conductive layer 11e is formed as the outermost layer in this manner, it is not necessary to process it except for the contact portion with the frame, and therefore processing is easier than when the highly conductive layer 11e is formed on the outermost surface facing the active material layer.

[0039] In this embodiment, as in the energy storage cell 30 shown in FIG. 2(b), the highly conductive layer 12e may be provided on the outermost layer of the negative electrode current collector 12a" of the negative electrode 12". FIG. 2(b) is a schematic cross-sectional view showing a main part of the energy storage cell 30. In this case, the highly conductive layer 12e can improve the in-plane conductivity of the negative electrode current collector 12a".

[0040] When the highly conductive layers 11e and / or 12e are carbon coating layers, the carbon coating layers may be formed by applying a material containing carbon and a binder resin. The carbon is not particularly limited, and examples thereof include carbon black, graphite, carbon nanotubes, and mixtures thereof. The binder resin is also not particularly limited, and examples thereof include polyvinylidene fluoride. When the highly conductive layers 11e and / or 12e are metal layers, the metal layers may be formed by using metals that are stable at the potentials of the positive and negative electrodes from among the metals mentioned as conductive fillers.

[0041] The present invention may also be embodied in an embodiment such as a storage cell 40 shown in Fig. 3, in which an intermediate layer 11f is provided between the innermost layer 11c and the outer layer 11d in a positive electrode current collector 11a''' of a positive electrode 11''', and an intermediate layer 12f is provided between the innermost layer 12c and the outer layer 12d in a negative electrode current collector 12a''' of a negative electrode 12'''. Fig. 3 is a schematic cross-sectional view showing a main part of the storage cell 40.

[0042] The intermediate layer 11f of the positive electrode current collector 11a''' is configured to include the resin material of the innermost layer 11c and another resin material of the outer layer 11d. The intermediate layer 12f of the negative electrode current collector 12a''' is configured to include the resin material of the innermost layer 12c and another resin material of the outer layer 12d. By adopting such a configuration, the positive electrode current collector 11a''' can have the innermost layer 11c and the outer layer 11d well bonded to each other via the intermediate layer 11f. The negative electrode current collector 12a''' can also have the innermost layer 12c and the outer layer 12d well bonded to each other via the intermediate layer 12f. As a result, the innermost layer 11c and the outer layer 11d, and the innermost layer 12c and the outer layer 12d can be more firmly fixed to each other than when they are welded together through direct contact.

[0043] The intermediate layer 11f and the intermediate layer 12f each contain a conductive filler. The conductive filler may be the same as that used in the innermost layers 11c and 12c and the outer layers 11d and 12d. The intermediate layer may be provided on only one of the positive and negative electrodes.

[0044] <Method of manufacturing energy storage cells> Next, a method for manufacturing the energy storage cell 10 according to this embodiment will be described below. The manufacturing method of the energy storage cell 10 of this embodiment includes a first frame member forming step of forming a first frame member on the positive electrode current collector 11a, a second frame member forming step of forming a second frame member on the negative electrode current collector 12a, and a heating step of bonding the positive electrode 11 and the negative electrode 12 together so that the first frame member and the second frame member face each other, and then heating them.

[0045] As shown in FIG. 4(a), the first frame member formation step is a step of forming a first frame member 14a on the outer peripheral edge of the innermost layer 11c of the positive electrode current collector 11a. FIG. 4(a) is a cross-sectional schematic diagram illustrating the formation of the first frame member 14a on the outer peripheral edge of the innermost layer 11c of the positive electrode current collector 11a. The method for forming the first frame member 14a is not particularly limited. For example, the first frame member 14a may be formed in advance by injection molding or the like, and then the first frame member 14a may be placed on the outer peripheral edge of the innermost layer 11c of the positive electrode current collector 11a and welded to the outer peripheral edge. Alternatively, a molten resin material that will form the first frame member 14a may be applied to the outer peripheral edge of the innermost layer 11c of the positive electrode current collector 11a using a dispenser or the like. In either case, the melting point of the outer layer 11d of the positive electrode current collector is higher than that of the innermost layer 11c, which directly contributes to welding to the frame. Therefore, by adjusting the processing temperature to match the innermost layer 11c, the first frame member 14a can be formed on the positive electrode current collector 11a without damaging the entire positive electrode current collector 11a. In the latter case, which uses a coating method, unlike the former, the first frame member 14a is formed on the outer peripheral edge of the innermost layer 11c simply by coating without a welding process. Furthermore, in the latter case, as shown in Figure 4(a), it is preferable to perform the process while adsorbing the outer layer 11d side of the positive electrode current collector 11a. This prevents shrinkage wrinkles on the positive electrode current collector 11a due to volume changes during the solidification process of the molten resin frame. Adsorption methods include vacuum chucking and electrostatic chucking.

[0046] When forming the first frame member 14a, the positive electrode active material layer 11b may be provided in advance on the innermost layer 11c of the positive electrode current collector 11a in a region other than the outer peripheral edge portion of the innermost layer 11c.

[0047] As shown in FIG. 4(b), the second frame member forming step is a step of forming a second frame member 14b on the outer peripheral edge of the innermost layer 12c of the negative electrode current collector 12a. This step can be performed using the same method as described in the first frame member forming step. Therefore, a detailed description thereof will be omitted. FIG. 4(b) is a cross-sectional schematic diagram illustrating the formation of the second frame member 14b on the outer peripheral edge of the innermost layer 12c of the negative electrode current collector 12a.

[0048] When forming the second frame member 14b, the negative electrode active material layer 12b may be previously formed on the innermost layer 12c of the negative electrode current collector 12a in a region other than the outer peripheral edge of the innermost layer 12c. Furthermore, before providing the negative electrode active material layer 12b, the high conductive layer 12e may be previously formed in the region of the negative electrode current collector 12a where the active material layer will be formed. Needless to say, the same applies to the positive electrode. Here, in this embodiment, a separator 13 is previously laminated on the surface of the negative electrode active material layer 12b facing the positive electrode active material layer 11b. However, the present invention is not limited to this embodiment. For example, the separator 13 may be previously formed on the surface of the positive electrode active material layer 11b facing the negative electrode active material layer 12b.

[0049] As shown in FIG. 4(c), the heating step is performed by bonding the positive electrode 11 and the negative electrode 12 together so that the first frame member 14a and the second frame member 14b face each other. FIG. 4(c) is a cross-sectional view showing the bonding and welding process of the positive electrode current collector 11a, on which the first frame member 14a is formed, and the negative electrode current collector 12a, on which the second frame member 14b is formed. After bonding, the outer peripheral edge of the outer layer 11d of the positive electrode current collector 11a and / or the outer peripheral edge of the outer layer 12d of the negative electrode current collector 12a are heated to weld and integrate the contact surfaces of the first frame member 14a and the second frame member 14b, thereby forming the frame member 14. At this time, the integration process may be promoted by applying a predetermined load, for example.

[0050] The heating temperature should be at least high enough to weld the first frame member 14a and the second frame member 14b together, and the upper limit of the temperature is preferably within a range in which the positive electrode current collector 11a and the negative electrode current collector 12a are not damaged by heat, such as thermal deformation. The region to be heated is preferably the outer peripheral edge of the positive electrode current collector 11a and / or the negative electrode current collector 12a. For example, heating regions other than these outer peripheral edges is undesirable because it may damage the positive electrode active material layer 11b, the negative electrode active material layer 12b, etc. In this manner, the energy storage cell 10 according to this embodiment can be manufactured.

[0051] (Second embodiment) The energy storage cell according to the second embodiment of the present invention and the method for manufacturing the same will be described below.

[0052] <Energy storage cell> The energy storage cell according to this embodiment has basically the same configuration as the energy storage cell 10 according to the first embodiment, except that the energy storage cell according to this embodiment uses a frame member made up of a first frame member, a second frame member, and a bonding layer disposed between the first frame member and the second frame member. In the following, components having the same functions as those of the energy storage cell 10 according to the first embodiment will be assigned the same reference numerals and their description will be omitted.

[0053] As shown in FIG. 5, the frame member 21 is provided on the outer peripheral edges of the positive electrode current collector 11a and the negative electrode current collector 12a. FIG. 5 is a schematic cross-sectional view illustrating a main portion of a storage cell 50 according to the second embodiment. The frame member 21 includes a first frame member 21a, a second frame member 21b, and a bonding layer 21c disposed between the first frame member 21a and the second frame member 21b. The first frame member 21a is welded to the innermost layer 11c of the positive electrode current collector 11a at its contact surface. The first frame member 21a is also welded to the bonding layer 21c on the surface opposite to the surface welded to the innermost layer 11c. The second frame member 21b is also welded to the innermost layer 12c of the negative electrode current collector 12a at its contact surface. The second frame member 21b is also welded to the bonding layer 21c on the surface opposite to the surface welded to the innermost layer 12c. As a result, the positive electrode current collector 11a and the negative electrode current collector 12a close the openings of the frame member 21 in the thickness direction. The frame member 21 may also fix the periphery of the separator 13.

[0054] The resin material forming the first frame member 21a and the second frame member 21b is the same as the resin material forming the innermost layer 11c of the positive electrode current collector 11a and the innermost layer 12c of the negative electrode current collector 12a, so that when heated, welding can be achieved in a short time between the first frame member 21a and the innermost layer 11c, and between the second frame member 21b and the innermost layer 12c.

[0055] The bonding layer 21c may be made of the same resin material as that used to form the first frame member 21a and the second frame member 21b.

[0056] The melting point of the bonding layer 21c is lower than the melting points of the first frame member 21a and the second frame member 21b. The difference in melting point between the bonding layer 21c and the first frame member 21a and the second frame member 21b depends on the material selected, but is preferably 15°C or higher, and more preferably 30°C or higher. By making the melting point difference 15°C or higher, the first frame member 21a and the second frame member 21b do not thermally deform, and welding of the bonding layer 21c to the first frame member 21a and the second frame member 21b can be easily performed in a short time. Note that the melting point of the bonding layer 21c must be higher than the temperature environment in which the battery is used, so it is preferably 50°C or higher, and more preferably 80°C or higher.

[0057] The thickness of the bonding layer 21c is not particularly limited as long as it is thick enough to be able to be sufficiently welded to the first frame member 21a and the second frame member 21b.

[0058] The thickness (height) of the frame member 21 is not particularly limited and can be set appropriately as needed.

[0059] <Method of manufacturing energy storage cells> Next, a method for manufacturing the energy storage cell 50 according to this embodiment will be described below. The manufacturing method of the energy storage cell 50 of this embodiment includes a first frame member forming process of forming a first frame member 21a on the positive electrode current collector 11a, a second frame member forming process of forming a second frame member 21b on the negative electrode current collector 12a, a bonding layer forming process of forming a bonding layer 21c on the first frame member 21a, and a heating process of bonding the positive electrode 11 and the negative electrode 12 together via the bonding layer 21c so that the first frame member 21a and the second frame member 21b face each other, and then heating.

[0060] As shown in FIG. 6(a), the first frame member formation step is a step of forming a first frame member 21a on the outer peripheral edge of the innermost layer 11c of the positive electrode current collector 11a. FIG. 6(a) is a cross-sectional schematic diagram illustrating the formation of the first frame member 21a on the outer peripheral edge of the innermost layer 11c of the positive electrode current collector 11a. The method for forming the first frame member 21a is not particularly limited. For example, the first frame member 21a may be formed in advance by injection molding or the like, and then the first frame member 21a may be placed on the outer peripheral edge of the innermost layer 11c of the positive electrode current collector 11a and welded to the outer peripheral edge. Alternatively, a molten resin material that will form the first frame member 21a may be applied to the outer peripheral edge of the innermost layer 11c of the positive electrode current collector 11a using a dispenser or the like. In either case, the melting point of the outer layer 11d of the positive electrode current collector is higher than that of the innermost layer 11c, which directly contributes to welding to the frame. Therefore, by adjusting the processing temperature to match the innermost layer 11c, the first frame member 21a can be formed on the positive electrode current collector 11a without damaging the entire positive electrode current collector 11a. In the latter case, which uses a coating method, unlike the former, the first frame member 21a is formed on the outer peripheral edge of the innermost layer 11c simply by coating without a welding process. Furthermore, in the latter case, as shown in FIG. 6(a), it is preferable to perform the process while adhering the outer layer 11d side of the positive electrode current collector 11a. This prevents shrinkage wrinkles on the positive electrode current collector 11a due to volume changes during the solidification process of the molten resin frame. Adhering methods include vacuum chucking and electrostatic chucking.

[0061] When forming the first frame member 21a, the positive electrode active material layer 11b may be provided in advance on the innermost layer 11c of the positive electrode current collector 11a in a region other than the outer peripheral edge portion of the innermost layer 11c.

[0062] The bonding layer formation process is a process of forming a bonding layer 21c on the first frame member 21a, as shown in FIG. 6(b). FIG. 6(b) is a schematic plan view illustrating the formation of the bonding layer 21c on the first frame member 21a. Specifically, the bonding layer 21c can be formed by applying a molten resin material, which is the constituent material of the bonding layer 21c, to the first frame member 21a using a dispenser or the like. This results in the bonding layer 21c being formed in a state of being welded to the first frame member 21a. Furthermore, the bonding layer 21c is preferably formed while adsorbing the outer layer 11d side of the positive electrode current collector 11a. This prevents thermal deformation of the positive electrode current collector 11a due to volume changes during the solidification process of the molten bonding layer 21c. Adsorption methods include vacuum chucking and electrostatic chucking.

[0063] As shown in Fig. 6(c), the second frame member forming step is a step of forming a second frame member 21b on the outer peripheral edge of the innermost layer 12c of the negative electrode current collector 12a. This step can be performed using the same method as described in the first frame member forming step. Therefore, a detailed description thereof will be omitted. Fig. 6(c) is a cross-sectional schematic diagram illustrating the formation of the second frame member 21b on the outer peripheral edge of the innermost layer 12c of the negative electrode current collector 12a.

[0064] When forming the second frame member 21b, the negative electrode active material layer 12b may be previously formed on the innermost layer 12c of the negative electrode current collector 12a in a region other than the outer peripheral edge of the innermost layer 12c. Furthermore, before providing the negative electrode active material layer 12b, the high conductive layer 12e may be previously formed in the region of the negative electrode current collector 12a where the active material layer will be formed. Needless to say, the same applies to the positive electrode. Here, in this embodiment, a separator 13 is previously laminated on the surface of the negative electrode active material layer 12b facing the positive electrode active material layer 11b. However, the present invention is not limited to this embodiment. For example, the separator 13 may be previously formed on the surface of the positive electrode active material layer 11b facing the negative electrode active material layer 12b.

[0065] As shown in FIG. 6(d), the heating step is performed by bonding the positive electrode 11 and the negative electrode 12 together so that the bonding layer 21c faces the second frame member 21b. FIG. 6(d) is a cross-sectional schematic diagram illustrating the bonding and welding of the positive electrode current collector 11a on which the bonding layer 21c is formed and the negative electrode current collector 12a on which the second frame member 21b is formed. After bonding, the outer peripheral edge of the outer layer 11d of the positive electrode current collector 11a and / or the outer peripheral edge of the outer layer 12d of the negative electrode current collector 12a is heated to weld and integrate the contact surfaces between the bonding layer 21c and the second frame member 21b, thereby forming the frame member 21. At this time, the integration may be promoted by applying a predetermined load, for example. Although FIG. 4 illustrates an example in which the positive electrode 11 is at the top, the present invention is not limited to this embodiment and the negative electrode 12 may also be at the top.

[0066] The heating temperature should be at least high enough to weld the bonding layer 21c and the second frame member 21b to each other, and the upper limit of the temperature is preferably within a range that does not cause damage such as thermal deformation to the positive electrode current collector 11a and the negative electrode current collector 12a. The region to be heated is preferably the outer peripheral edge of the positive electrode current collector 11a and / or the negative electrode current collector 12a. For example, heating regions other than these outer peripheral edges is undesirable because it may damage the positive electrode active material layer 11b and the negative electrode active material layer 12b. While FIG. 6 illustrates an example in which the bonding layer 21c is formed on the first frame member 21a, which is the frame member on the positive electrode side, the bonding layer 21c may also be formed on the second frame member 21b, which is the frame member on the negative electrode side. In this manner, the energy storage cell 50 according to this embodiment can be manufactured. [Explanation of symbols]

[0067] 10, 20, 30, 40, 50... Energy storage cells 11a, 11a', 11a'', 11a'''...Positive electrode current collector 11b...Cathode active material layer 11c, 12c...innermost layer 11e…High conductivity layer 11f…middle class 11d, 12d...outer layer 12a...Negative electrode current collector 12b...Negative electrode active material layer 12e…High conductivity layer 12f…middle class 13...Separator 14, 21...Frame members 14a, 21a...First frame member 14b, 21b...Second frame member 21c...Joining layer

Claims

1. a pair of current collectors arranged opposite to each other and having a laminated structure; a frame member provided so as to be positioned between outer peripheral edges of the pair of current collectors; At least the innermost layers of the pair of current collectors are welded to the frame member, the resin material constituting the innermost layer is the same as the resin material of the frame member, A storage cell, wherein the melting point of each of the innermost layers is lower than the melting points of the other layers.

2. a pair of current collectors arranged opposite to each other and having a laminated structure; a frame member provided between the outer peripheral edges of the pair of current collectors; At least The frame member is a first frame member welded to an innermost layer of one of the pair of current collectors; a second frame member welded to the innermost layer of the other current collector of the pair of current collectors; a bonding layer disposed between the first frame member and the second frame member and having a melting point lower than that of the first frame member and the second frame member; and The melting point of each innermost layer of the pair of current collectors is lower than the melting points of the remaining layers.

3. 3. The energy storage cell according to claim 1, wherein a highly conductive layer is provided on an outermost layer of one of the pair of current collectors on a surface opposite to a surface facing the other current collector.

4. 3. The energy storage cell according to claim 1, wherein an intermediate layer containing the resin material constituting the outer layer and the resin material constituting the innermost layer is provided between the outer layer and the innermost layer of one of the pair of current collectors.

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