Battery

Abstract

To provide a battery that suppresses generation of wrinkles in an uncoated portion of a current collecting foil.SOLUTION: A battery includes an electrode body in which a current collecting foil, a positive electrode active material layer, and a negative electrode active material layer are laminated, the current collecting foil having an uncoated portion in the lamination direction where the positive electrode active material layer and the negative electrode active material layer are not coated, a first sealing body in the shape of a quadrilateral frame arranged so as to cover an end region of the current collecting foil in the uncoated portion, and a second sealing body in the shape of a quadrilateral frame arranged so as to cover the outer surface of the first sealing body, and at least the corner regions of the second sealing body are made of a material having a linear expansion coefficient of 40×10-6 / °C or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to batteries. [Background technology]

[0002] Conventionally, a battery has been used that includes an electrode body in which a current collector foil, a positive electrode active material layer, and a negative electrode active material layer are laminated, a first sealing body arranged to cover an end region of the current collector foil in the uncoated portion, and a second sealing body arranged to cover the outer surface of the first sealing body.

[0003] For example, Patent Document 1 discloses an energy storage module including an electrode stack having a plurality of stacked metal plates and a sealing body for sealing an internal space formed between two adjacent metal plates of the plurality of metal plates, wherein the sealing body has a rectangular annular first sealing portion joined to the peripheral edge of the metal plate and a second sealing portion provided around the stacked first sealing portion, wherein the second sealing portion has a first resin portion provided around the first sealing portion and a second resin portion provided around the first resin portion, and wherein the difference between the linear expansion coefficient of the first sealing portion and the linear expansion coefficient of the first resin portion is smaller than the difference between the linear expansion coefficient of the first sealing portion and the linear expansion coefficient of the second resin portion.

[0004] Patent Document 2 also discloses a method for manufacturing a bipolar battery, including: a first step of preparing a battery structure having an electrode stacking portion and a primary seal portion; a second step of injecting an electrolyte solution into the battery structure through an injection hole in the primary seal portion while restraining the electrode stacking portion with a pair of restraint plates so that the distance between the pair of restraint plates sandwiching the electrode stacking portion in the stacking direction is a specified length; a third step of discharging the electrolyte solution through the injection hole by restraining the electrode stacking portion with the pair of restraint plates so that the distance between the pair of restraint plates is shorter than the specified length; and a fourth step of, after performing the third step, restraining the electrode stacking portion with the pair of restraint plates so that the distance between the pair of restraint plates is the specified length. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-174632 [Patent Document 2] Japanese Patent Application Publication No. 2019-091606 Summary of the Invention [Problem to be solved by the invention]

[0006] In conventional batteries, resin is generally used for the second seal, which is disposed to cover the outer surface of the first seal. Resin-made second seals tend to expand and contract with temperature changes, and in low-temperature environments, the second seal shrinks, sometimes exerting a shrinking force on the corners of the second seal. When this shrinking force occurs at the corners of the second seal, stress is applied to the corners of the uncoated portion of the current collector foil, and this stress can cause wrinkles in the uncoated portion of the current collector foil.

[0007] The present disclosure has been made in view of the above circumstances, and has an object to provide a battery in which the occurrence of wrinkles in the uncoated portions of the current collector foil is suppressed. [Means for solving the problem]

[0008] Means for solving the above problems include the following aspects. <1> an electrode body in which a current collecting foil, a positive electrode active material layer, and a negative electrode active material layer are laminated, and the current collecting foil has an uncoated portion in the lamination direction where the positive electrode active material layer and the negative electrode active material layer are not coated; a first sealing body in the shape of a quadrilateral frame that is arranged to cover an end side region of the current collecting foil in the uncoated portion; a quadrilateral frame-shaped second sealing body arranged to cover the outer surface of the first sealing body; and The second sealing body has a linear expansion coefficient of 40×10 at least in the corner area. -6 A battery made of materials below / ℃. <2> The second sealing body has a linear expansion coefficient of 40×10 -6 / ℃ or less, <1> The battery described in <3> The first sealing body has a linear expansion coefficient of 40×10 at least in the corner area. -6 / ℃ or less, <1> or <2> The battery described in <4> The first sealing body has a linear expansion coefficient of 40×10 -6 / ℃ or less, <3> The battery described in <5> The linear expansion coefficient is 40×10 -6 / °C or less, is at least one selected from the group consisting of glass epoxy resin, Rossnaboard, Miolex, Besthermo, polybutylene terephthalate, polyether ether ketone, polyamide imide, alumina, zirconia, forsterite, steatite, mullite, aluminum nitride, zircon, zircon cordierite, cordierite, low expansion cordierite, aluminum titanate, β-spondumene, and ordinary porcelain, <1> ~ <4> The battery according to any one of claims 1 to 4. [Effects of the Invention]

[0009] According to the present disclosure, a battery is provided in which the occurrence of wrinkles in the uncoated portions of the current collector foil is suppressed. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view illustrating the structure of a bipolar secondary battery according to an embodiment of the present disclosure. [Figure 2] FIG. 10 is a schematic plan view showing the vicinity of a corner of a current collecting foil, a first sealing body, and a second sealing body in a conventional battery. DETAILED DESCRIPTION OF THE INVENTION

[0011] <Battery> A battery according to an embodiment of the present disclosure includes an electrode body in which a current collector foil, a positive electrode active material layer, and a negative electrode active material layer are laminated, a first sealing body, and a second sealing body. The current collector foil in the electrode assembly has an uncoated portion in the stacking direction where the positive electrode active material layer and the negative electrode active material layer are not coated. The first sealing body is disposed so as to cover the uncoated portion of the current collector foil at the end thereof, and has a quadrilateral frame shape. The second sealing body is disposed so as to cover the outer surface of the first sealing body, and has a quadrilateral frame shape. The second sealing body has a corner region (hereinafter simply referred to as "corner region") with a linear expansion coefficient of 40×10 -6 / ℃ or less.

[0012] In the present disclosure, the "corner region" of the second sealing body refers to a region extending from a corner of the quadrilateral second sealing body to one-tenth of the length of one side. Similarly, the "corner region" of the first sealing body refers to a region extending from a corner of the quadrilateral first sealing body to one-tenth of the length of one side. Both the quadrilateral first sealing body and second sealing body have four corners, and each has four corner regions extending from these corners.

[0013] The battery includes, for example, a negative electrode, a positive electrode, a separator, and an electrolyte. The battery according to the embodiment of the present disclosure is preferably used, for example, in a liquid battery having a liquid electrolyte. In particular, a liquid battery having a non-aqueous electrolyte is preferable. Furthermore, the battery may be a bipolar battery having a positive electrode active material layer and a negative electrode active material layer on both sides of a current collector that functions as a positive electrode current collector and a negative electrode current collector.

[0014] Hereinafter, a battery according to an embodiment of the present disclosure will be described in detail with reference to the drawings. Here, the configuration of a battery according to an embodiment of the present disclosure will be described using a bipolar secondary battery as an example.

[0015] In Fig. 1, "top" refers to the upper side of the figure, and "bottom" refers to the lower side of the figure. Fig. 1 is a schematic cross-sectional view illustrating the structure of a bipolar secondary battery, showing one energy storage module 11 of the secondary battery. The secondary battery is provided with a laminate in which multiple such energy storage modules 11 and conductive plates (not shown) are alternately arranged.

[0016] The energy storage module 11 is a quadrilateral, flat-plate-shaped cell overall, and the energy storage module 11 of this embodiment is a bipolar lithium-ion secondary battery. The energy storage module 11 includes an electrode stack formed by stacking multiple bipolar electrodes 12, multiple first sealing bodies 20 provided in each bipolar electrode 12, and second sealing bodies 25 provided to cover the outer surfaces of the multiple first sealing bodies 20 (i.e., the surfaces of the first sealing bodies 20 opposite the electrode stack). The multiple bipolar electrodes 12 are stacked along the thickness direction (thickness direction in the flat plate shape), and a first sealing body 20 is disposed on each bipolar electrode 12. A second sealing body 25 is disposed on the first sealing body 20 to cover the outer surfaces of the multiple first sealing bodies 20.

[0017] The bipolar electrode 12 includes a current collector foil 13, a positive electrode active material layer 14 provided on the lower surface of the current collector foil 13, a negative electrode active material layer 15 provided on the upper surface of the current collector foil 13, and a separator 16. The current collector foil 13 is a foil-shaped conductive member having a quadrilateral shape in a plan view, and is a laminated foil in which multiple dissimilar metal foils are laminated. For example, a laminated foil of aluminum foil and copper foil is used as the current collector foil 13. The current collector foil 13 has uncoated portions 13a in the stacking direction where the positive electrode active material layer 14 and the negative electrode active material layer 15 are not coated.

[0018] The positive electrode active material layer 14 constitutes the positive electrode of the bipolar electrode 12, and is disposed via an adhesive layer on the lower surface of the current collector foil 13. The positive electrode active material layer 14 contains a positive electrode active material, and may further contain a conductive additive, a binder, and the like. Examples of positive electrode active materials include composite oxides, metallic lithium, and sulfur. The composite oxides contain at least one of iron, manganese, titanium, nickel, cobalt, and aluminum, and lithium. Examples of composite oxides include olivine-type lithium iron phosphate (LiFePO4), LiCoO2, and LiNiMnCoO2. Examples of binders include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber; thermoplastic resins such as polypropylene and polyethylene; imide resins such as polyimide and polyamideimide; alkoxysilyl group-containing resins; acrylic resins containing monomer units such as acrylic acid and methacrylic acid; styrene-butadiene rubber (SBR); carboxymethyl cellulose; alginates such as sodium alginate and ammonium alginate; water-soluble cellulose ester crosslinks; and starch-acrylic acid graft polymers. These binders can be used alone or in combination. Examples of conductive additives include acetylene black, carbon black, and graphite.

[0019] The negative electrode active material layer 15 constitutes the negative electrode of the bipolar electrode 12 and is disposed on the upper surface of the current collector foil 13 . The negative electrode active material layer 15 may contain a negative electrode active material, a conductive additive, and a binder. Examples of the conductive additive and binder include those used in the positive electrode active material layer 14. Examples of the negative electrode active material include carbon such as graphite, artificial graphite, highly oriented graphite, mesocarbon microbeads, hard carbon, and soft carbon, metal compounds, elements capable of forming an alloy with lithium or compounds of such elements, and boron-doped carbon. Examples of elements capable of forming an alloy with lithium include silicon and tin.

[0020] The separator 16 is, for example, a porous sheet or nonwoven fabric containing a polymer that absorbs and retains the electrolyte, and is placed on the upper surface of the negative electrode active material layer 15 .

[0021] To form the positive electrode active material layer 14 and the negative electrode active material layer 15 on the current collector foil 13, a conventionally known method such as roll coating, die coating, dip coating, doctor blade coating, spray coating, or caulking coating is used. Specifically, an active material, a solvent, and, if necessary, a binder and a conductive additive are mixed to prepare a slurry, which is then applied to the upper and lower surfaces of the current collector foil 13 and then dried. When forming the positive electrode active material layer 14 and the negative electrode active material layer 15 on the current collector foil 13, the slurries for the positive electrode active material layer and the negative electrode active material layer are applied so as to form uncoated portions 13a.

[0022] In the electrode laminate, adjacent bipolar electrodes 12 in the stacking direction are stacked so that one positive electrode active material layer 14 overlaps the other separator 16. The electrode laminate also has a positive electrode terminal electrode 17 at the top end and a negative electrode terminal electrode 18 at the bottom end of the stack of bipolar electrodes 12. The positive electrode terminal electrode 17 has a current collector foil 13 and a positive electrode active material layer 14 provided on the underside of the current collector foil 13. The positive electrode active material layer 14 is stacked on the adjacent bipolar electrode 12, and the current collector foil 13 is stacked on its upper surface. The negative electrode terminal electrode 18 has a current collector foil 13 and a negative electrode active material layer 15 provided on the upper surface of the current collector foil 13, and a separator 16 stacked on its upper surface. The separator 16 is stacked on the adjacent bipolar electrode 12, and the negative electrode active material layer 15 is stacked on its lower surface, and the current collector foil 13 is stacked on its lower surface. The positive terminal electrode 17 and the negative terminal electrode 18 are each formed by stacking a current collecting foil 13 on the adjacent conductive plate.

[0023] The first sealing body 20 is a quadrilateral, frame-shaped member disposed on the outer peripheral edge of the bipolar electrode 12. The first sealing body 20 seals the bipolar electrode 12. This also seals the gap between adjacent bipolar electrodes 12 in the stacking direction. The first sealing body 20 includes a first sealing member 21, a second sealing member 22, and a spacer 23.

[0024] The first sealing member 21 is a quadrilateral, frame-shaped member that is disposed along the outer peripheral end (outer edge) of the bipolar electrode 12. Specifically, the first sealing member 21 is disposed and joined between the upper surface of the current collector foil 13 and the lower surface of the separator 16 at the outer peripheral end of the bipolar electrode 12, thereby disposing the negative electrode active material layer 15 within the frame. A predetermined gap is provided between the inner edge of the first sealing member 21 and the negative electrode active material layer 15, forming a space. Meanwhile, the outer edge of the first sealing member 21 is configured so that the first sealing member 21 protrudes outward from the current collector foil 13.

[0025] The second seal member 22 is a quadrilateral, frame-shaped member that is disposed along the outer peripheral edge (outer edge) of the bipolar electrode 12. Specifically, the second seal member 22 is disposed and joined between the lower surface of the current collector foil 13 and the upper surface of the spacer 23 at the outer peripheral edge of the bipolar electrode 12, and together with the spacer 23, the positive electrode active material layer 14 is disposed within the frame. A predetermined gap is provided between the inner edge of the second seal member 22 and the positive electrode active material layer 14, forming a space. Meanwhile, the outer edge of the second seal member 22 is configured so that the second seal member 22 protrudes outward from the current collector foil 13, and the upper surface of the second seal member 22 is joined to the lower surface of the first seal member 21. In this way, the first seal member 21 and the second seal member 22 cover the end region of the current collector foil 13 in the uncoated portion 13a.

[0026] The spacer 23 is a quadrilateral, frame-shaped member that is disposed along the outer peripheral edge of the bipolar electrode 12. Specifically, by combining the spacer 23 with the second seal member 22, the spacer 23 is disposed and bonded between the lower surface of the second seal member 22 and the upper surface of the separator 16 of the adjacent bipolar electrode 12 at the outer peripheral edge of the bipolar electrode 12, and the positive electrode active material layer 14 is disposed within this frame. The inner edge of the spacer 23 is disposed spaced apart from the positive electrode active material layer 14. Meanwhile, the outer edge of the spacer 23 protrudes outward from the separator 16, and its lower surface is bonded to the upper surface of the first seal member 21 of the adjacent first sealing body 20.

[0027] The second sealing body 25 is a quadrilateral, frame-shaped member that is arranged along the outer periphery of the multiple first sealing bodies 20. The second sealing body 25 arranges the first sealing body 20 and the bipolar electrode 12 within its frame. The inner edge of the second sealing body 25 is arranged to cover the outer surface of the first sealing body 20.

[0028] The second sealing body 25 has a linear expansion coefficient of 40×10 -6 / °C or less (hereinafter also simply referred to as "low expansion material"). The first sealing member 21, the second sealing member 22, and the spacer 23 that constitute the first sealing body 20 also have a linear expansion coefficient of 40×10 -6 / ℃ or less (low expansion material).

[0029] Here, a conventional battery will be described. Fig. 2 is a schematic plan view showing the vicinity of the corners of the current collecting foil, first sealing body, and second sealing body in a conventional battery. In a conventional battery, a quadrilateral, frame-shaped first sealing body 200 is disposed to cover the end region of the uncoated portion 130a of the current collector foil 130, and a quadrilateral, frame-shaped second sealing body 250 is disposed to cover the outer surface of the sealing body 200. The second sealing body 250 is typically made of resin. As shown in FIG. 2 , the second sealing body 250 tends to expand and contract with temperature changes. In low-temperature environments, the second sealing body 250 may shrink, generating forces in the directions of arrows Y1 and Y2 at the corners of the second sealing body 250. When forces in the directions of arrows Y1 and Y2 are generated at the corners of the second sealing body 250, stress is applied to a location Z1 at the corner of the uncoated portion 130a of the current collector foil 130. As a result, wrinkles may occur at the location Z1 at the corner of the uncoated portion 130a of the current collector foil 130. If the wrinkles become more pronounced, the current collector foil 130 may break.

[0030] Note that a battery may be configured such that the uncoated portion 130a of the current collector foil 130 in the stacking direction is free of any components other than the current collector foil 130 and a separator (not shown). In a battery with this configuration, the second moment of area is small, and buckling (a phenomenon in which the current collector foil 130 undergoes a large bending deformation) may occur at location X1 of the uncoated portion 130a due to the weight of the current collector foil 130. If buckling occurs in the uncoated portion 130a of the current collector foil 130 and the aforementioned wrinkles also occur at location Z1, the combination of buckling and wrinkles may make the current collector foil 130 even more susceptible to fracture.

[0031] In contrast, in the battery according to the embodiment of the present disclosure, at least the corner region of the second sealing body has a linear expansion coefficient of 40×10 -6 / °C or less (low-expansion material). Therefore, expansion and contraction due to temperature changes are suppressed in the corner regions of the second sealing body. This suppresses the generation of forces in the directions of arrows Y1 and Y2 shown in FIG. 2 in the corner regions of the second sealing body even in a low-temperature environment. As a result, the generation of wrinkles in the corners of the uncoated part of the current collecting foil (specifically, point Z1 shown in FIG. 2) is suppressed, and furthermore, the occurrence of breakage due to significant wrinkles is suppressed.

[0032] Although the second sealing body 25 shown in FIG. 1 is entirely made of a low-expansion material, the battery according to the embodiment of the present disclosure is not limited to this configuration. It is sufficient that at least the corner region (i.e., the region extending from the corner of the second sealing body to one-tenth of the length of one side) is made of a low-expansion material. By making the corner region of the second sealing body out of a low-expansion material, the generation of forces in the directions of arrows Y1 and Y2 shown in FIG. 2 is suppressed in the corner region of the second sealing body, even in a low-temperature environment. As a result, the generation of wrinkles at the corners of the uncoated portion of the current collecting foil is suppressed, and furthermore, the occurrence of breakage is also suppressed. However, it is preferable that the entire second sealing body 25 is made of a low-expansion material, as shown in Fig. 1. By making the entire second sealing body out of a low-expansion material, the generation of force in the corner regions of the second sealing body (force in the directions of arrows Y1 and Y2 shown in Fig. 2) is suppressed even in a low-temperature environment, and the generation of wrinkles at the corners of the uncoated part of the current collecting foil is more likely to be suppressed.

[0033] Furthermore, it is preferable that at least the corner regions (i.e., the region extending from the corner of the first sealing body to one-tenth of the length of one side of the first sealing body) of the first sealing body (in FIG. 1, the first sealing member 21, the second sealing member 22, and the spacer 23 that constitute the first sealing body 20) be made of a low-expansion material. In conventional batteries, resin is also generally used for the first sealing body, and the first sealing body shrinks in low-temperature environments, which can apply stress to the corners of the uncoated portion of the current collecting foil (specifically, point Z1 shown in FIG. 2). Therefore, by making the corner regions of the first sealing body out of a low-expansion material, stress is suppressed in the corner regions of the first sealing body even in low-temperature environments, and the occurrence of wrinkles in the corners of the uncoated portion of the current collecting foil is more likely to be suppressed.

[0034] Furthermore, it is more preferable that the entire first sealing body 20 is made of a low-expansion material, as shown in Fig. 1. When the entire first sealing body is made of a low-expansion material, the generation of force in the corner regions of the first sealing body (force in the directions of arrows Y1 and Y2 shown in Fig. 2) is suppressed even in a low-temperature environment, and the generation of wrinkles at the corners of the uncoated part of the current collecting foil is more likely to be suppressed.

[0035] Linear expansion coefficient 40 x 10 -6 / °C or less (low expansion material), for example, at least one material selected from the group consisting of glass epoxy resin, Rossnaboard, Miolex, Besthermo, polybutylene terephthalate, polyether ether ketone, polyamide imide, alumina, zirconia, forsterite, steatite, mullite, aluminum nitride, zircon, zircon cordierite, cordierite, low expansion cordierite, aluminum titanate, β-spondulumen, and ordinary porcelain. These materials have, for example, the following linear expansion coefficients: Glass epoxy resin: 21 x 10 -6 / ℃ or less Rossnaboard: 26 x 10 -6 / ℃ or less Miorex: 23 x 10 -6 / ℃ or less Best Thermo: 40 x 10 -6 / ℃ or less Polybutylene terephthalate: 15 x 10 -6 / ℃ or less Polyether ether ketone: 25 x 10 -6 / ℃ or less Polyamideimide: 30.6 x 10 -6 / ℃ or less Alumina: 8 x 10 -6 / ℃ or less Zirconia: 10 x 10 -6 / ℃ or less Forsterite: 10 x 10 -6 / ℃ or less Steatite: 8×10 -6 / ℃ or less Mullite: 5 x 10 -6 / ℃ or less Aluminum nitride: 5 x 10 -6 / ℃ or less Zircon: 4 x 10 -6 / ℃ or less Zircon cordierite: 4 x 10 -6 / ℃ or less Cordierite: 3 x 10 -6 / ℃ or less Low expansion cordierite: 1 x 10 -6 / ℃ or less Aluminum titanate: 1 x 10 -6 / ℃ or less β Sponge Men: 1 x 10 -6 / ℃ or less Regular porcelain: 7 x 10 -6 / ℃ or less

[0036] The linear expansion coefficients of the materials constituting the first and second sealing bodies are measured by thermomechanical analysis (TMA). For example, the linear expansion coefficient of plastics can be measured according to JIS K7197 (2012, Test method for linear expansion coefficient of plastics by thermomechanical analysis), and the linear expansion coefficient of fine ceramics can be measured according to JIS R1618 (2002, Measurement method for thermal expansion of fine ceramics by thermomechanical analysis).

[0037] Examples of applications of the battery according to the embodiment of the present disclosure include power sources for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and electric vehicles (BEVs). [Explanation of symbols]

[0038] 11 Energy storage module, 12 Bipolar electrode, 13, 130 Current collecting foil, 13a, 130a Uncoated portion, 14 Positive electrode active material layer, 15 Negative electrode active material layer, 16 Separator, 17 Positive electrode terminal electrode, 18 Negative electrode terminal electrode, 20, 200 First sealing body, 21 First sealing member, 22 Second sealing member, 23 Spacer, 25, 250 Second sealing body

Claims

1. an electrode body in which a current collecting foil, a positive electrode active material layer, and a negative electrode active material layer are laminated, and the current collecting foil has an uncoated portion in the lamination direction where the positive electrode active material layer and the negative electrode active material layer are not coated; a first sealing body having a quadrilateral frame shape and arranged to cover an end side region of the current collecting foil in the uncoated portion; a second sealing body in the shape of a quadrilateral frame, which is arranged so as to cover the outer surface of the first sealing body; and The second sealing body has a linear expansion coefficient of 40×10 at least in the corner area. －６ A battery made of materials below / ℃.

2. The second sealing body has a linear expansion coefficient of 40×10 －６ 10. The battery of claim 1, wherein the battery is constructed of materials having a temperature of 0.15 to 1.25°C or less.

3. The first sealing body has a linear expansion coefficient of 40×10 at least in the corner area. －６ 10. The battery of claim 1, wherein the battery is constructed of materials having a temperature of 0.15 to 1.25°C or less.

4. The first sealing body has a linear expansion coefficient of 40×10 －６ 4. The battery of claim 3, which is made of materials having a temperature of 1000 K / °C or less.

5. The linear expansion coefficient is 40×10 －６ 2. The battery according to claim 1, wherein the material having a temperature of 1000 to 1500°C or less is at least one selected from the group consisting of glass epoxy resin, Rossnaboard, Miolex, Besthermo, polybutylene terephthalate, polyether ether ketone, polyamide imide, alumina, zirconia, forsterite, steatite, mullite, aluminum nitride, zircon, zircon cordierite, cordierite, low expansion cordierite, aluminum titanate, β-spongymen, and ordinary porcelain.

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