Bipolar type battery

Abstract

To provide a bipolar type battery capable of suppressing wrinkles and distortions in a positive electrode mixture unformed area of a positive electrode current collector and a negative electrode mixture unformed area of negative electrode current collector.SOLUTION: The bipolar type battery includes: a positive electrode current collector, a positive electrode mixture layer, a separator, a negative electrode mixture layer, and a negative electrode current collector, which are stacked. The bipolar type battery has a resin seal layer that includes: a low-rigidity material layer bonded to the positive electrode current collector or negative electrode current collector, with a tensile modulus of elasticity of less than 35.0 kgf / mm2; and a high-rigidity material layer having a tensile modulus of elasticity of 35.0 kgf / mm2 or more, which is formed over the surface opposite to the surface of the low-rigidity material layer bonded to the positive electrode current collector or negative electrode current collector.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Conventionally, bipolar batteries have been used in which a plurality of bipolar electrodes, each having a negative electrode active material layer on one side of a current collector and a positive electrode active material layer on the other side of the current collector, are stacked with a separator interposed therebetween.

[0003] For example, Patent Document 1 discloses an energy storage cell that includes a reinforcing member that reinforces uncoated portions of a current collector where no positive electrode active material layer or negative electrode active material layer is located, and when viewed from the direction in which the active material layers of the positive and negative electrodes face each other, the current collector has uncoated portions between the spacer and the active material layer, and the reinforcing member is arranged along the uncoated portions so as to straddle the boundaries between the positive electrode active material layer and the negative electrode active material layer and the uncoated portions and the boundary between the spacer and the uncoated portions when viewed from the direction in which the active material layers face each other.

[0004] For example, Patent Document 2 discloses a battery comprising a laminate including a current collector layer, an active material layer, and an electrolyte layer, a resin layer covering at least the side surface of the laminate, and an exterior body that houses the laminate covered with the resin layer, wherein the resin layer comprises at least a first resin layer and a second resin layer from the side surface of the laminate toward the exterior body, the second resin layer is in contact with the exterior body, and the Young's modulus of the second resin layer is smaller than the Young's modulus of the first resin layer.

[0005] For example, Patent Document 3 discloses an all-solid-state battery including a laminate having an anode current collector, an anode active material layer, a solid electrolyte layer, a cathode active material layer, and a cathode current collector in this order, wherein when the anode active material layer, the solid electrolyte layer, and the cathode active material layer are used as power generating elements, the laminate has a protective layer disposed on a side surface of the power generating element, the protective layer contains a resin having tackiness, and the laminate has a film between the anode current collector and the protective layer and / or between the cathode current collector and the protective layer in a cross-sectional view of the all-solid-state battery in the stacking direction. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-069042 [Patent Document 2] Patent Publication No. 2021-197204 [Patent Document 3] Japanese Patent Publication No. 2023-068843 Summary of the Invention [Problem to be solved by the invention]

[0007] Here, a bipolar battery in which a negative electrode current collector, a negative electrode composite layer, a separator, a positive electrode composite layer, and a positive electrode current collector are stacked will be described. When a resin seal layer is stacked on the region of the positive electrode current collector where the positive electrode composite layer is not formed (positive electrode composite non-formed region) and the region of the negative electrode current collector where the negative electrode composite layer is not formed (negative electrode composite non-formed region), respectively, heat sealing (thermal fusion) is performed. During this process, wrinkles or distortions may occur in the positive electrode composite non-formed region of the positive electrode current collector and the negative electrode composite non-formed region of the negative electrode current collector.

[0008] The present disclosure has been made in consideration of the above circumstances, and aims to provide a bipolar battery in which the occurrence of wrinkles and distortions is suppressed in a positive electrode composite unformed region of a positive electrode current collector and in a negative electrode composite unformed region of a negative electrode current collector. [Means for solving the problem]

[0009] Means for solving the above problems include the following aspects. <1> A separator; a positive electrode mixture layer on one surface of the separator; a positive electrode current collector on a surface of the positive electrode mixture layer opposite to the separator; a negative electrode mixture layer on the other surface of the separator; a negative electrode current collector is laminated on a surface of the negative electrode mixture layer opposite to the separator, When viewed from the stacking direction, the positive electrode current collector has a positive electrode composite unformed region where the positive electrode composite layer is not formed, and the negative electrode current collector has a negative electrode composite unformed region where the negative electrode composite layer is not formed, The tensile modulus of the bonded positive electrode current collector or the negative electrode current collector is 35.0 kgf / mm 2 a low-rigidity material layer having a tensile modulus of elasticity of less than 35.0 kgf / mm on the surface of the low-rigidity material layer opposite to the surface bonded to the positive electrode current collector or the negative electrode current collector; 2 A bipolar battery having the above-described high-rigidity material layer and a resin seal layer. <2> the resin seal layer is laminated on a surface of the positive electrode current collector opposite to the positive electrode composite layer in the positive electrode composite unformed region, and on a surface of the negative electrode current collector opposite to the negative electrode composite layer in the negative electrode composite unformed region, <2> The bipolar battery according to claim 1. <3> The low-rigidity material layer has a tensile modulus of 1.4 kgf / mm 2 More than 26.7kgf / mm 2 The high-rigidity material layer has a tensile modulus of elasticity of 42.2 kgf / mm or less. 2 Over 127.0kgf / mm 2 Below is the <1> or <2> The bipolar battery according to claim 1. <4> the low-rigidity material layer contains at least one selected from low-density polyethylene and ethylene-vinyl acetate copolymer resin, and the high-rigidity material layer contains at least one selected from ionomer, unstretched polypropylene, and high-density polyethylene; <1> ~ <3> The bipolar battery according to any one of claims 1 to 4. <5> The resin seal layer is composed of two layers, the low-rigidity material layer and the high-rigidity material layer. <1> ~ <4> 10. The bipolar battery according to claim 9, wherein the first electrode is a conductor. [Effects of the Invention]

[0010] According to the present disclosure, a bipolar battery is provided in which the occurrence of wrinkles and distortions is suppressed in the positive electrode composite material-free region of the positive electrode current collector and the negative electrode composite material-free region of the negative electrode current collector. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating an example of a bipolar battery according to an embodiment of the present disclosure. [Figure 2] 2 is a schematic cross-sectional view showing an enlarged portion of the bipolar battery shown in FIG. 1. FIG. [Figure 3] FIG. 2 is a schematic cross-sectional view showing an enlarged portion of another example of a bipolar battery according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present disclosure will be described. These descriptions and examples are intended to illustrate the embodiment and are not intended to limit the scope of the invention. In the present specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range. In addition, in the present specification, the upper or lower limit of a numerical range may be replaced with a value shown in the examples.

[0013] Each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, the amount refers to the total amount of those multiple substances present in the composition, unless otherwise specified.

[0014] <Bipolar battery> A bipolar battery according to an embodiment of the present disclosure is formed by stacking a separator, a positive electrode composite layer on one side of the separator, a current collector (positive electrode current collector) on the side of the positive electrode composite layer opposite the separator, a negative electrode composite layer on the other side of the separator, and a current collector (negative electrode current collector) on the side of the negative electrode composite layer opposite the separator. The bipolar battery is formed by stacking a plurality of bipolar electrodes, each having a negative electrode composite layer on one side of the current collector and a positive electrode composite layer on the other side of the current collector, with separators interposed between them. When viewed from the stacking direction, the bipolar battery has a positive electrode composite unformed region on the surface of the positive electrode current collector where no positive electrode composite layer is formed, and a negative electrode composite unformed region on the surface of the negative electrode current collector where no negative electrode composite layer is formed. The bipolar battery has a tensile modulus of 35.0 kgf / mm 2 and a low-rigidity material layer having a tensile modulus of 35.0 kgf / mm on the surface opposite to the surface of the low-rigidity material layer joined to the positive electrode current collector or the negative electrode current collector. 2 The resin seal layer has a high-rigidity material layer as described above, and a resin seal layer having the low-rigidity material layer welded to a current collector (positive electrode current collector or negative electrode current collector), and a high-rigidity material layer welded to the surface of the low-rigidity material layer opposite to the surface welded to the current collector.

[0015] Here, the configuration of a bipolar battery according to an embodiment of the present disclosure will be described by way of example with reference to the drawings. Note that the same or corresponding parts in each drawing are designated by the same reference numerals, and redundant description will be omitted.

[0016] Fig. 1 is a schematic cross-sectional view showing the overall configuration of an example of a bipolar battery according to an embodiment of the present disclosure. The bipolar battery 1 shown in Fig. 1 is a bipolar battery used, for example, in batteries for forklifts, hybrid vehicles, electric vehicles, etc. The bipolar battery 1 is, for example, a lithium-ion secondary battery.

[0017] 1, the bipolar battery 1 includes a laminate 3 and a sealing body 5. The laminate 3 includes a plurality of bipolar electrodes 31 stacked in a stacking direction X, a positive terminal electrode 33, and a negative terminal electrode 35. The bipolar electrode 31 includes a current collector 40, a positive electrode composite layer 32, and a negative electrode composite layer 34.

[0018] The current collector 40 has, for example, a rectangular shape when viewed from the stacking direction X. The current collector 40 includes a surface 40a and a surface 40b opposite to the surface 40a. The current collector 40 has a first layer 42 and a second layer 44 stacked in the stacking direction X. The first layer 42 and the second layer 44 are electrically connected. The surface 40a of the current collector 40 is the surface of the first layer 42. The surface 40b of the current collector 40 is the surface of the second layer 44.

[0019] The positive electrode composite layer 32 is provided on a surface 40a of the current collector 40. When viewed from the stacking direction X, the positive electrode composite layer 32 has, for example, a rectangular shape. The surface 40a includes a positive electrode composite unformed region A where the positive electrode composite layer 32 is not provided. When viewed from the stacking direction X, the positive electrode composite unformed region A surrounds the positive electrode composite layer 32. The negative electrode composite layer 34 is provided on a surface 40b of the current collector 40. When viewed from the stacking direction X, the negative electrode composite layer 34 has, for example, a rectangular shape. The surface 40b includes a negative electrode composite unformed region B where the negative electrode composite layer 34 is not provided. The negative electrode composite unformed region B surrounds the negative electrode composite layer 34 when viewed from the stacking direction X. The multiple bipolar electrodes 31 are stacked such that the positive electrode composite layer 32 of one bipolar electrode 31 faces the negative electrode composite layer 34 of another bipolar electrode 31. That is, the multiple bipolar electrodes 31 are stacked such that, of adjacent bipolar electrodes 31, the surface 40a of the current collector 40 of one bipolar electrode 31 faces the surface 40b of the current collector 40 of the other bipolar electrode 31.

[0020] The positive terminal electrode 33 is disposed on one side of the plurality of bipolar electrodes 31 in the stacking direction X. The positive terminal electrode 33 includes a current collector 40 and a positive electrode composite layer 32. The positive terminal electrode 33 differs from the bipolar electrodes 31 in that it does not include a negative electrode composite layer 34. The other configuration of the positive terminal electrode 33 is the same as that of the bipolar electrode 31. The positive terminal electrode 33 is disposed such that the positive electrode composite layer 32 of the positive terminal electrode 33 faces the negative electrode composite layer 34 of the bipolar electrode 31. That is, the positive terminal electrode 33 is stacked such that the surface 40a of the current collector 40 of the positive terminal electrode 33 faces the surface 40b of the current collector 40 of the bipolar electrode 31 adjacent to the positive terminal electrode 33.

[0021] The negative terminal electrode 35 is disposed on the other side of the plurality of bipolar electrodes 31 in the stacking direction X. The negative terminal electrode 35 has a current collector 40 and a negative electrode composite layer 34. The negative terminal electrode 35 differs from the bipolar electrodes 31 in that it does not have a positive electrode composite layer 32. The other configuration of the negative terminal electrode 35 is the same as that of the bipolar electrode 31. The negative terminal electrode 35 is disposed such that the negative electrode composite layer 34 of the negative terminal electrode 35 faces the positive electrode composite layer 32 of the bipolar electrode 31. In other words, the negative terminal electrode 35 is stacked such that the surface 40b of the current collector 40 of the negative terminal electrode 35 faces the surface 40a of the current collector 40 of the bipolar electrode 31 adjacent to the negative terminal electrode 35.

[0022] Between each bipolar electrode 31, between the bipolar electrode 31 and the positive terminal electrode 33, and between the bipolar electrode 31 and the negative terminal electrode 35, an internal space S containing an electrolyte is formed.

[0023] The laminate 3 includes a plurality of separators 22. The separators 22 are disposed between the bipolar electrodes 31, between the bipolar electrodes 31 and the positive terminal electrode 33, and between the bipolar electrodes 31 and the negative terminal electrode 35. The separators 22 are positioned between the opposing positive electrode composite layer 32 and negative electrode composite layer 34. The separators 22 are, for example, sheet-shaped. When viewed from the stacking direction X, the separators 22 are, for example, rectangular. When viewed from the stacking direction X, the outer edges of the separators 22 are positioned outside the outer edges of the positive electrode composite layer 32 and the negative electrode composite layer 34. The separators 22 are a member that allows charge carriers such as lithium ions to pass through. The separators 22 isolate the adjacent electrodes 31, 33, and 35. This prevents electrical short circuits due to contact between the electrodes 31, 33, and 35.

[0024] Current collector 40 is a chemically inert electrical conductor that continues to pass current through positive electrode mixture layer 32 and negative electrode mixture layer 34 during discharge or charge of the lithium-ion secondary battery. In this embodiment, first layer 42 of current collector 40 contains aluminum and is, for example, aluminum foil. In this embodiment, second layer 44 of current collector 40 contains copper and is, for example, copper foil.

[0025] The sealing body 5 is a member that seals the internal space S. The sealing body 5 is provided on the side surface of the laminate 3. The sealing body 5 seals the side surface of the laminate 3. The sealing body 5 has, for example, a rectangular cylindrical shape. The sealing body 5 has electrical insulation properties. The sealing body 5 has a main body portion 81 and a welding portion 70. The main body portion 81 is provided on the outer edge portion of the laminate 3. The main body portion 81 is composed of a plurality of independent members. The main body portion 81 has wrinkle-resistant sealing layers 80 as a plurality of resin sealing layers.

[0026] The peripheral edge portion 22a of the separator 22 is located between a pair of wrinkle-resistant sealing layers 80. The peripheral edge portion 22a of the separator 22 is sandwiched between the pair of wrinkle-resistant sealing layers 80. The separator 22 divides the internal space S into a first region S1 and a second region S2. The first region S1 is a region of the internal space S that is surrounded by the separator 22, the positive electrode composite layer 32, the current collector 40, and the wrinkle-resistant sealing layer 80. The second region S2 is a region of the internal space S that is surrounded by the separator 22, the negative electrode composite layer 34, the current collector 40, and the wrinkle-resistant sealing layer 80.

[0027] The volume of the first region S1 is larger than the volume of the second region S2. Specifically, when viewed from the stacking direction X, the area of ​​the positive electrode composite layer 32 is smaller than the area of ​​the negative electrode composite layer 34. When viewed from the stacking direction X, the outer edge of the positive electrode composite layer 32 is located more inward than the outer edge of the negative electrode composite layer 34. In addition, the peripheral edge portion 22a of the separator 22 is located between the pair of wrinkle-preventing seal layers 80. With this configuration, the volume of the first region S1 is larger than the volume of the second region S2.

[0028] The welded portion 70 is provided on the outside of the main body portion 81. The welded portion 70 has, for example, a rectangular cylindrical shape. The welded portion 70 reaches both ends of the stack 3 in the stacking direction X. The welded portion 70 is integrally formed. The welded portion 70 is formed by melting the outer edge of each wrinkle-preventing sealing layer 80 and then re-solidifying and welding. The welded portion 70 is formed by welding a part of an area of ​​each wrinkle-preventing sealing layer 80 that is located outside the outer edge of the current collector 40 when viewed from the stacking direction X. The welded portion 70 does not reach the outer edge of each current collector 40.

[0029] Next, a description will be given focusing on a pair of adjacent bipolar electrodes 31 with reference to Fig. 2, which shows an enlarged view of a region C of the bipolar battery 1 shown in Fig. 1. Fig. 2 is a schematic cross-sectional view showing an enlarged view of a portion of the bipolar battery shown in Fig. 1. 2 includes a separator 22, a positive electrode composite layer 32 stacked in contact with one surface of the separator 22, a current collector stacked in contact with the surface of the positive electrode composite layer 32 opposite the separator 22 (hereinafter, in FIG. 2, the current collector in contact with the positive electrode composite layer 32 will be referred to as a "positive electrode current collector 40A"), a negative electrode composite layer 34 stacked in contact with the other surface of the separator 22, and a current collector stacked in contact with the surface of the negative electrode composite layer 34 opposite the separator 22 (hereinafter, in FIG. 2, the current collector in contact with the negative electrode composite layer 34 will be referred to as a "negative electrode current collector 40B"). Both the positive electrode current collector 40A and the negative electrode current collector 40B have a first layer 42 and a second layer 44. 1, in this bipolar battery 1, a plurality of bipolar electrodes 31 each having a negative electrode composite layer 34 on one surface of a current collector (positive electrode current collector 40A and negative electrode current collector 40B) and a positive electrode composite layer 32 on the other surface of the current collector are stacked via separators 22. When the bipolar battery 1 is viewed from the stacking direction X, a positive electrode composite unformed region A where the positive electrode composite layer 32 is not formed exists on the surface of the positive electrode current collector 40A, and a negative electrode composite unformed region B where the negative electrode composite layer 34 is not formed exists on the surface of the negative electrode current collector 40B.

[0030] In the positive electrode composite non-formed region A, a wrinkle-reducing sealing layer (hereinafter, in FIG. 2, the wrinkle-reducing sealing layer in contact with the positive electrode current collector 40A is referred to as the "positive electrode-side wrinkle-reducing sealing layer 80A") is disposed as a positive electrode-side resin sealing layer laminated in contact with both the surface of the positive electrode current collector 40A opposite to the positive electrode composite layer 32 (i.e., surface 40Ab) and the surface in contact with the positive electrode composite layer 32 (i.e., surface 40Aa). The positive electrode-side wrinkle-reducing sealing layer 80A is formed by disposing two pairs of a low-rigidity material layer and a high-rigidity material layer on the surface of the positive electrode current collector 40A opposite to the positive electrode composite layer 32 (i.e., surface 40Ab) and the surface in contact with the positive electrode composite layer 32 (i.e., surface 40Aa), respectively, and then heat-sealing (thermal fusing). Specifically, first, a low-rigidity material layer and a high-rigidity material layer are arranged on the surface of the positive electrode collector 40A opposite to the positive electrode composite material layer 32 so as to extend beyond the outer edge of the positive electrode collector 40A (so as to extend into a region to the right of the end of the positive electrode collector 40A in FIG. 2). Also, a low-rigidity material layer and a high-rigidity material layer are arranged on the surface of the positive electrode collector 40A that contacts the positive electrode composite material layer 32 (surface 40Aa) so as to extend beyond the outer edge of the positive electrode collector 40A (so as to extend into a region to the right of the end of the positive electrode collector 40A in FIG. 2). Then, the two pairs of low-rigidity material layers and high-rigidity material layers arranged on the surface of the positive electrode collector 40A opposite to the positive electrode composite material layer 32 (surface 40Ab) and the surface of the positive electrode collector 40A that contacts the positive electrode composite material layer 32 (surface 40Aa) are heat-sealed (thermally fused) to form the positive electrode-side wrinkle-preventing seal layer 80A. The two sets of low-rigidity material layers are integrated by heat sealing in a region outside the outer edge of positive current collector 40A (to the right of the end of positive current collector 40A in FIG. 2 ) to form low-rigidity material layer 82A. That is, low-rigidity material layer 82A is integrally formed in a folded shape at the outer edge of positive current collector 40A, and low-rigidity material layer 82A is arranged to cover both the surface of positive current collector 40A opposite to positive electrode composite material layer 32 (surface 40Ab) and the surface of positive current collector 40A that comes into contact with positive electrode composite material layer 32 (surface 40Aa). High-rigidity material layers 84A are then arranged to cover both sides of low-rigidity material layer 82A covering both sides of positive current collector 40A (i.e., to cover the upper and lower sides of low-rigidity material layer 82A in FIG. 2 ). The low-rigidity material layer 82A in the positive-electrode-side wrinkle-preventing seal layer 80A covers the surface 40Aa of the positive electrode current collector 40A, the surface 40Ab of the positive electrode current collector 40A, and the side surface (surface on the outer edge side) of the positive electrode current collector 40A. The low-rigidity material layer 82A is bonded to the surface 40Aa, the surface 40Ab, and the side surface of the positive electrode current collector 40A.

[0031] In the negative electrode composite material non-formed region B, a wrinkle-reducing sealing layer (hereinafter, in FIG. 2, the wrinkle-reducing sealing layer in contact with the negative electrode current collector 40B is referred to as the "negative electrode-side wrinkle-reducing sealing layer 80B") is disposed as a negative electrode-side resin sealing layer, laminated in contact with both the surface of the negative electrode current collector 40B opposite to the negative electrode composite material layer 34 (i.e., surface 40Ba) and the surface in contact with the negative electrode composite material layer 34 (i.e., surface 40Bb). The negative electrode-side wrinkle-reducing sealing layer 80B is formed by disposing two pairs of a low-rigidity material layer and a high-rigidity material layer on the surface of the negative electrode current collector 40B opposite to the negative electrode composite material layer 34 (i.e., surface 40Ba) and the surface in contact with the negative electrode composite material layer 34 (i.e., surface 40Bb), respectively, and then heat-sealing (thermal fusing). Specifically, first, a low-rigidity material layer and a high-rigidity material layer are arranged on the surface (surface 40Ba) of negative electrode current collector 40B opposite to negative electrode composite material layer 34 so as to protrude from the outer edge of negative electrode current collector 40B (so as to protrude into a region to the right of the end of negative electrode current collector 40B in FIG. 2). Also, on the surface (surface 40Bb) of negative electrode current collector 40B that comes into contact with negative electrode composite material layer 34, a low-rigidity material layer and a high-rigidity material layer are arranged so as to protrude from the outer edge of negative electrode current collector 40B (so as to protrude into a region to the right of the end of negative electrode current collector 40B in FIG. 2). Thereafter, two pairs of low-rigidity material layers and high-rigidity material layers are heat-sealed (thermally fused) together to form a negative-electrode-side wrinkle-preventing seal layer 80B. The two pairs of low-rigidity material layers are disposed on the surface of the negative electrode current collector 40B opposite to the negative electrode composite material layer 34 (surface 40Ba) and on the surface of the negative electrode current collector 40B that comes into contact with the negative electrode composite material layer 34. The two pairs of low-rigidity material layers are integrated by heat sealing to form a low-rigidity material layer 82B in a region outside the outer edge of the negative electrode current collector 40B (to the right of the edge of the negative electrode current collector 40B in FIG. 2). That is, the low-rigidity material layer 82B is integrally formed so as to have a folded-back shape at the outer edge of the negative electrode current collector 40B, and the low-rigidity material layer 82B is disposed so as to cover both the surface of the negative electrode current collector 40B opposite to the negative electrode composite material layer 34 (surface 40Ba) and the surface of the negative electrode current collector 40B that comes into contact with the negative electrode composite material layer 34 (surface 40Bb). High-rigidity material layers 84B are disposed on both sides of the low-rigidity material layers 82B that cover both sides of the negative electrode current collector 40B (i.e., covering the upper and lower sides of the low-rigidity material layers 82B in FIG. 2). The low-rigidity material layer 82B in the negative-electrode-side wrinkle-preventing seal layer 80B covers the surface 40Ba of the negative electrode current collector 40B, the surface 40Bb of the negative electrode current collector 40B, and the side surface (surface on the outer edge side) of the negative electrode current collector 40B. The low-rigidity material layer 82B is bonded to the surface 40Ba, the surface 40Bb, and the side surface of the negative electrode current collector 40B.

[0032] The low-rigidity material layer 82A in the positive electrode side wrinkle-preventing seal layer 80A has a tensile modulus of elasticity of 35.0 kgf / mm 2 The high-rigidity material layer 84A has a tensile modulus of elasticity of 35.0 kgf / mm 2 That's all. The low-rigidity material layer 82B in the negative electrode-side wrinkle-preventing seal layer 80B has a tensile modulus of elasticity of 35.0 kgf / mm 2 The high-rigidity material layer 84B has a tensile modulus of elasticity of 35.0 kgf / mm 2 That's all.

[0033] Here, when the resin seal layer (positive electrode-side wrinkle-preventing seal layer 80A and negative electrode-side wrinkle-preventing seal layer 80B in FIG. 2) is composed of only one resin layer, wrinkles or distortion may occur in the positive electrode current collector and the negative electrode current collector. This is thought to be because heating and cooling during heat sealing (thermal fusion) performed when laminating the resin seal layer to the positive electrode composite material-free region of the positive electrode current collector and the negative electrode composite material-free region of the negative electrode current collector cause thermal expansion and contraction in the positive electrode composite material-free region of the positive electrode current collector and the negative electrode composite material-free region of the negative electrode current collector.

[0034] In contrast, the resin seal layer in the bipolar battery according to the embodiment of the present disclosure (positive electrode-side wrinkle-resistant seal layer 80A and negative electrode-side wrinkle-resistant seal layer 80B in FIG. 2 ) has a low-rigidity material layer on the side that contacts the current collector and a high-rigidity material layer on the side that does not contact the current collector (i.e., on the side opposite the current collector from the low-rigidity material layer). Therefore, when the resin seal layer is welded to the current collector, the high-rigidity material layer suppresses thermal expansion and contraction of the resin seal layer caused by heating and cooling during heat sealing. As a result, stress concentration on the positive electrode current collector and the negative electrode current collector, which could cause wrinkles or distortion, is suppressed. Furthermore, by providing a high-rigidity material layer on the side of the resin seal layer that does not contact the current collector, the effects of the thermal expansion and contraction on the surrounding area are also suppressed. For example, slight waviness may occur in the positive electrode composite-free region and the negative electrode composite-free region of the current collector, which may lead to accumulation of electrode waviness when batteries are stacked and modularized in a subsequent process. However, by providing a high-rigidity material layer, the accumulation of electrode waviness can be suppressed. Furthermore, by providing a high-rigidity material layer, variation in module thickness when batteries are stacked and modularized can be reduced.

[0035] 1 and 2, the positive electrode-side wrinkle-resistant sealing layer 80A and the negative electrode-side wrinkle-resistant sealing layer 80B are interposed between the positive electrode current collector 40A and the separator 22, and between the negative electrode current collector 40B and the separator 22. Therefore, it is possible to omit the placement of a spacer between the positive electrode current collector 40A and the negative electrode current collector 40B. Meanwhile, in the bipolar battery according to the embodiment of the present disclosure, spacers may be provided in the gaps between the positive electrode current collector and the negative electrode current collector in the regions where the positive electrode composite material is not formed and the negative electrode composite material is not formed. The spacers may contain, for example, an insulating material, and may insulate the positive electrode current collector from the negative electrode current collector to prevent short circuits between the current collectors. Examples of materials that can be used to form the spacers include various resin materials, such as polyethylene (PE), polystyrene, ABS resin, modified polypropylene (modified PP), and acrylonitrile styrene (AS) resin.

[0036] 2 shows a configuration in which a resin seal layer is laminated on both the surface (surface 40Ab) of positive electrode current collector 40A opposite to positive electrode composite material layer 32 and the surface (surface 40Aa) in contact with positive electrode composite material layer 32, and on both the surface (surface 40Ba) of negative electrode current collector 40B opposite to negative electrode composite material layer 34 and the surface (surface 40Bb) in contact with negative electrode composite material layer 34, but the present disclosure is not limited to this embodiment. That is, a resin seal layer may be provided on only one surface of each of the positive electrode current collector and the negative electrode current collector. Here, an example of a bipolar battery according to an embodiment of the present disclosure in which a resin seal layer is provided on only one surface of each of the positive electrode current collector and the negative electrode current collector will be described.

[0037] Other aspects FIG. 3 is a schematic cross-sectional view showing another example of a bipolar battery according to an embodiment of the present disclosure. In the bipolar battery 10 shown in FIG. 3, the configurations of the positive electrode composite layer 32, the positive electrode current collector 40A, the negative electrode composite layer 34, and the negative electrode current collector 40B are the same as those shown in FIG. 2, and therefore detailed description thereof will be omitted here.

[0038] In the bipolar battery 10 shown in FIG. 3 , the separator 24 is located between the opposing positive electrode composite layer 32 and negative electrode composite layer 34. The separator 24 has, for example, a sheet shape. When viewed from the stacking direction X, the separator 24 has, for example, a rectangular shape. When viewed from the stacking direction X, the outer edge of the separator 24 is located outside the outer edge of the positive electrode composite layer 32 and the outer edge of the negative electrode composite layer 34. A peripheral portion 24a of the separator 24 bends toward the negative electrode current collector 40B, and a portion of the peripheral portion 24a, including the outer edge, contacts the negative electrode current collector 40B.

[0039] When the bipolar battery 10 is viewed from the stacking direction X, a positive electrode composite unformed region A where the positive electrode composite layer 32 is not formed exists on the surface of the positive electrode current collector 40A, and a negative electrode composite unformed region B where the negative electrode composite layer 34 is not formed exists on the surface of the negative electrode current collector 40B.

[0040] The bipolar battery 10 shown in FIG. 3 has a spacer 92 between the positive electrode composite layer 32 in the positive electrode composite non-formed region A and the negative electrode composite layer 34 in the negative electrode composite non-formed region B. The spacer 92 is sandwiched between the positive electrode composite layer 32 in the positive electrode composite non-formed region A and the negative electrode composite layer 34 in the positive electrode composite non-formed region A. The spacer 92 has, for example, a rectangular frame shape. The spacer 92 forms an internal space for accommodating an electrolyte. The spacer 92 is in contact with both the positive electrode composite layer 32 and the negative electrode composite layer 34. The spacer 92 is in contact with a portion of the peripheral edge portion 24a of the separator 24 that contacts the negative electrode current collector 40B. The spacer 92 is not bonded to the positive electrode composite layer 32, the negative electrode composite layer 34, or the separator 24. When viewed from the stacking direction, the inner edge of the spacer 92 is positioned outwardly away from the positive electrode composite material layer 32 and the negative electrode composite material layer 34. When viewed from the stacking direction, the outer edge of the spacer 92 approximately coincides with the outer edge of the positive electrode-side wrinkle-preventing seal layer 60A and the outer edge of the negative electrode-side wrinkle-preventing seal layer 60B. The spacer 92 includes, for example, an insulating material, and prevents short circuits between the positive electrode current collector and the negative electrode current collector by insulating them from each other. Materials that can be used to form the spacer 92 include various resin materials such as polyethylene (PE), polystyrene, ABS resin, modified polypropylene (modified PP), and acrylonitrile styrene (AS) resin.

[0041] The welded portion 72 is formed by melting the outer edge portions of the positive electrode wrinkle-preventing seal layer 60A, the negative electrode wrinkle-preventing seal layer 60B, and the spacer 92, and then solidifying and welding them together again.

[0042] In the positive electrode composite material unformed region A, a wrinkle-preventing seal layer (hereinafter, in FIG. 3, the wrinkle-preventing seal layer in contact with the positive electrode current collector 40A is referred to as the "positive electrode-side wrinkle-preventing seal layer 60A") is disposed in contact with the surface (i.e., surface 40Ab) of the positive electrode current collector 40A opposite to the positive electrode composite material layer 32. The positive electrode-side wrinkle-preventing seal layer 60A is disposed on the surface (surface 40Ab) of the positive electrode current collector 40A opposite to the positive electrode composite material layer 32 to entirely cover the positive electrode composite material unformed region A and also cover the region that is not the positive electrode composite material unformed region A. The low-rigidity material layer 62A of the positive electrode-side wrinkle-preventing seal layer 60A is bonded to the surface 40Ab of the positive electrode current collector 40A. In the negative electrode composite material unformed region B, a wrinkle-preventing sealing layer (hereinafter, in FIG. 3, the wrinkle-preventing sealing layer in contact with the negative electrode current collector 40B) is disposed as a negative electrode-side resin sealing layer, laminated in contact with the surface (i.e., surface 40Ba) of the negative electrode current collector 40B opposite to the negative electrode composite material layer 34. The negative electrode-side wrinkle-preventing sealing layer 60B is disposed on the surface (surface 40Ba) of the negative electrode current collector 40B opposite to the negative electrode composite material layer 34 to entirely cover the negative electrode composite material unformed region B and also cover the region that is not the negative electrode composite material unformed region B. The low-rigidity material layer 62B of the negative electrode-side wrinkle-preventing sealing layer 60B is bonded to the surface 40Ba of the negative electrode current collector 40B.

[0043] The positive electrode side wrinkle-preventing seal layer 60A has a tensile modulus of 35.0 kgf / mm 2 and a low-rigidity material layer 62A having a tensile modulus of elasticity of less than 35.0 kgf / mm 2 The negative electrode-side wrinkle-preventing seal layer 60B has a tensile modulus of elasticity of 35.0 kgf / mm 2 and a low-rigidity material layer 62B having a tensile modulus of elasticity of less than 35.0 kgf / mm 2 and a high-rigidity material layer 64B having the above structure.

[0044] In the bipolar battery according to the embodiment of the present disclosure, even in an embodiment in which a resin seal layer is provided on only one side of each of the positive electrode current collector and the negative electrode current collector, the occurrence of wrinkles and distortion in the positive electrode composite material-free region A of the positive electrode current collector and the negative electrode composite material-free region B of the negative electrode current collector is suppressed. This is because the resin seal layer has a low-rigidity material layer on the side that contacts the current collector and a high-rigidity material layer on the side that does not contact the current collector. As a result, when the resin seal layer is welded to the current collector, the high-rigidity material layer suppresses thermal expansion and contraction of the resin seal layer caused by heating and cooling during heat sealing. This is thought to be due to the suppression of stress concentration on the positive electrode current collector and the negative electrode current collector. Furthermore, by providing a high-rigidity material layer on the side of the resin seal layer that does not contact the current collector, the effects of the thermal expansion and contraction on the surrounding area are also suppressed. For example, slight waviness may occur in the positive electrode composite-free region and the negative electrode composite-free region of the current collector, which may lead to accumulation of electrode waviness when batteries are stacked and modularized in a subsequent process. However, by providing a high-rigidity material layer, the accumulation of electrode waviness can be suppressed. Furthermore, by providing a high-rigidity material layer, variation in module thickness when batteries are stacked and modularized can be reduced.

[0045] (Resin seal layer) The resin seal layers (positive electrode-side wrinkle-resistant seal layer 80A and negative electrode-side wrinkle-resistant seal layer 80B in FIG. 2, and positive electrode-side wrinkle-resistant seal layer 60A and negative electrode-side wrinkle-resistant seal layer 60B in FIG. 3) have a tensile modulus of elasticity of 35.0 kgf / mm 2 A low-rigidity material layer with a tensile modulus of less than 35.0 kgf / mm 2 and a high-rigidity material layer having a tensile modulus of elasticity of at least 1000 kJ / cm. When the tensile modulus of elasticity of the low-rigidity material layer and the high-rigidity material layer are within the above ranges, the occurrence of wrinkles and distortion in the positive electrode current collector and the negative electrode current collector is suppressed. Furthermore, when the tensile modulus of elasticity of the high-rigidity material layer is within the above ranges, the influence of thermal expansion and contraction caused by heat sealing when laminating the resin seal layer on the surrounding area is suppressed.

[0046] The tensile modulus of the low-rigidity material layer is further increased to 1.4 kgf / mm from the viewpoint of suppressing the occurrence of wrinkles and distortion in the positive electrode current collector and the negative electrode current collector and ensuring the strength of the low-rigidity material layer.2 More than 26.7kgf / mm 2 It is preferable that: The tensile modulus of the high-rigidity material layer is further set to 42.2 kgf / mm from the viewpoints of suppressing the occurrence of wrinkles and distortions in the positive electrode current collector and the negative electrode current collector, suppressing the influence of thermal expansion and contraction on the surroundings, and facilitating the formation of a resin seal layer by heat sealing (thermal fusion). 2 Over 127.0kgf / mm 2 It is preferable that:

[0047] Examples of materials constituting the low-rigidity material layer include materials containing at least one selected from low-density polyethylene (LDPE) and ethylene-vinyl acetate copolymer resin (EVA), and may be materials consisting of one or both of LDPE and EVA. Low-density polyethylene (LDPE) means polyethylene with a density of 0.910 or more and 0.930 or less, and its tensile modulus is, for example, 9.8 kgf / mm 2 More than 26.7kgf / mm 2 The following: Low-density polyethylene (LDPE) also includes linear low-density polyethylene (LLDPE). The tensile modulus of ethylene-vinyl acetate copolymer resin (EVA) is, for example, 1.4 kgf / mm 2 Over 8.4kgf / mm 2 The following is the result.

[0048] Examples of materials constituting the high-rigidity material layer include materials containing at least one selected from ionomer, unstretched polypropylene (CPP), and high-density polyethylene (HDPE), and the material may be composed of one, two, or three of ionomer, CPP, and HDPE. An ionomer is a synthetic resin in which a polymer compound is aggregated by utilizing the cohesive force of metal ions, and an example thereof is a resin in which a polymer having a polyethylene unit and an acrylic acid unit is ionically crosslinked with a metal. Non-oriented polypropylene (CPP) means polypropylene resin that has not been stretched, and its tensile modulus is, for example, 63.2 kgf / mm 2More than 64.3kgf / mm 2 The following is the result. High density polyethylene (HDPE) means polyethylene with a density of 0.942 to 0.970, and its tensile modulus is, for example, 42.2 kgf / mm 2 Over 127.0kgf / mm 2 The following is the result.

[0049] As a combination of materials for the low-rigidity material layer and the high-rigidity material layer, for example, the following combinations (1) to (3) are preferable. (1) A combination of a low-rigidity material layer: a material containing LDPE (more preferably a material made of LDPE) and a high-rigidity material layer: a material containing ionomer (more preferably a material made of ionomer). (2) A combination of a low-rigidity material layer: a material containing L-LDPE (more preferably a material consisting of L-LDPE) and a high-rigidity material layer: a material containing CPP (more preferably a material consisting of CPP). (3) A combination of a low-rigidity material layer: a material containing LDPE (more preferably a material consisting of LDPE) and a high-rigidity material layer: a material containing HDPE (more preferably a material consisting of HDPE).

[0050] In the present disclosure, the tensile modulus is measured in accordance with JIS K 7127 (1999).

[0051] The average thickness of the low-rigidity material layer in the resin seal layer is preferably 10 μm to 100 μm, more preferably 20 μm to 70 μm, from the viewpoints of suppressing wrinkles and distortion in the positive electrode current collector and the negative electrode current collector and ensuring the strength of the low-rigidity material layer. The average thickness of the high-rigidity material layer is preferably 10 μm to 100 μm, more preferably 20 μm to 70 μm, from the viewpoints of suppressing wrinkles and distortion in the positive electrode current collector and the negative electrode current collector, suppressing the influence of thermal expansion and contraction on the surroundings, and facilitating the formation of the resin seal layer by heat sealing (thermal fusion). The average thickness of the entire resin seal layer is preferably 20 μm or more and 300 μm or less, and more preferably 40 μm or more and 200 μm or less. Note that the average thickness means the arithmetic mean value of the thicknesses at 10 arbitrarily selected locations.

[0052] The resin seal layer has at least a low-rigidity material layer and a high-rigidity material layer. That is, it may have a structure composed of two layers, namely, a low-rigidity material layer and a high-rigidity material layer, or it may have a structure composed of three or more layers having at least one of the low-rigidity material layer and the high-rigidity material layer in multiple layers. However, from the perspective of ease of forming the resin seal layer, it is preferable to have a structure composed of two layers, namely, a low-rigidity material layer and a high-rigidity material layer.

[0053] Next, other elements constituting the bipolar battery according to the embodiment of the present disclosure will be described.

[0054] (Positive electrode composite material layer) The positive electrode composite material layer contains a positive electrode active material, and may further contain, for example, a binder. Examples of the positive electrode active material include lithium nickel cobalt manganese composite oxide (hereinafter, may be simply referred to as "LNCM"). The simplest LNCM has the following general formula: LiNi x Co y Mn z O2 (where x, y, z in the formula satisfy 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1). LNCM may contain other additive elements in addition to Li, Ni, Co, and Mn, such as transition metal elements other than Ni, Co, and Mn, and typical metal elements other than Li. LNCM has a layered crystal structure. LNCM preferably exceeds 50% by mass of the entire positive electrode active material, for example, occupies 80 to 100% by mass. The positive electrode active material may be composed of only LNCM. Also, as the positive electrode active material layer, lithium iron phosphate (LiFePO4, LFP), lithium manganese iron phosphate (LMFP), etc. may be used. Examples of other positive electrode active materials include lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel manganese composite oxide, etc.

[0055] Examples of the binder contained in the positive electrode mixture layer include vinyl halide resins such as polyvinylidene fluoride (PVdF). The positive electrode mixture layer may further contain other components, such as a conductive material, etc. Examples of the conductive material include non-graphitizable carbon, easily graphitizable carbon such as carbon black, and graphite.

[0056] (Negative electrode composite layer) The negative electrode mixture layer contains a negative electrode active material and may further contain, for example, a binder. Examples of the negative electrode active material include graphite-based carbon such as natural graphite, artificial graphite, amorphous coated graphite, etc. In graphite-based carbon, the proportion of graphite is generally 50% by mass or more, preferably 80% by mass or more. Examples of the binder contained in the negative electrode active material include rubbers such as styrene butadiene copolymer (SBR) and vinyl halide resins such as polyvinylidene fluoride (PVdF). The negative electrode mixture layer may further contain other components, such as a thickener, etc. Examples of the thickener include celluloses such as carboxymethyl cellulose (CMC).

[0057] (Current collectors: positive electrode current collector and negative electrode current collector) A bipolar battery according to an embodiment of the present disclosure is formed by stacking a plurality of bipolar electrodes, each having a negative electrode composite layer on one side of a current collector (positive electrode current collector 40A and negative electrode current collector 40B in FIGS. 2 and 3) and a positive electrode composite layer on the other side of the current collector, with a separator interposed between them. The current collector is preferably a conductive member made of a metal with good conductivity (e.g., aluminum, stainless steel (SUS), Ni, Cr, Au, Pt, Fe, Ti, Zn, etc.).

[0058] (separator) The separator is an electrically insulating porous film. The separator electrically isolates the positive electrode and the negative electrode. The separator may have a thickness of, for example, 5 to 30 μm. The separator may be made of, for example, a porous polyethylene (PE) film, a porous polypropylene (PP) film, or the like. The separator may have a multilayer structure. For example, the separator may be made by laminating a porous PP film, a porous PE film, and a porous PP film in this order. The separator may have a heat-resistant layer on its surface. The heat-resistant layer contains a heat-resistant material. Examples of the heat-resistant material include metal oxide particles such as alumina, and high-melting-point resins such as polyimide.

[0059] (electrolyte) The bipolar battery according to the embodiment of the present disclosure further includes an electrolyte. Examples of the electrolyte include an electrolytic solution, and non-aqueous electrolytic solutions are particularly preferred. The non-aqueous electrolytic solution will be described below.

[0060] ·solvent The non-aqueous electrolytic solution contains a solvent (non-aqueous solvent) and an electrolyte. Examples of the solvent (non-aqueous solvent) include N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(fluorosulfonyl)imide (DEME), 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMI), and 1-ethyl-2,3-dimethylimidazolium bis(fluorosulfonyl)imide (DEMI-FSI).

[0061] ·Electrolyte The electrolyte in the electrolytic solution may be, for example, a Li salt, such as lithium bis(fluorosulfonyl)imide (LiFSI), LiPF6 (lithium hexafluorophosphate), lithium tetrafluoroborate (LiBF4), or Li[N(CF3SO2)2]. The amount of electrolyte may be, for example, 1.0 to 2.0 mol / L, and is preferably 1.0 to 1.5 mol / L.

[0062] In addition to the solvent and electrolyte, the electrolytic solution may contain various additives such as a thickener, a film-forming agent, a gas generating agent, etc. The electrolyte is typically a non-aqueous electrolytic solution that is liquid at room temperature (e.g., 25±10°C). The electrolytic solution typically remains liquid in the environment in which the battery is used (e.g., a temperature environment of -20 to +60°C).

[0063] (Application) Examples of applications of the bipolar 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]

[0064] REFERENCE SIGNS LIST 1, 10 bipolar battery, 3 laminate, 5 sealing body, 22, 24 separator, 31 bipolar electrode, 32 positive electrode composite layer, 33 positive electrode terminal electrode, 34 negative electrode composite layer, 35 negative electrode terminal electrode, 40 current collector, 40A positive electrode current collector, 40B negative electrode current collector, 42 first layer, 44 second layer, 60A, 80A positive electrode side wrinkle-preventing seal layer, 60B, 80B negative electrode side wrinkle-preventing seal layer, 62A, 62B, 82A, 82B low-rigidity material layer, 64A, 64B, 84A, 84B high-rigidity material layer, 70, 72 welded portion, 80 wrinkle-preventing seal layer, 81 main body, 92 spacer, A positive electrode composite not formed region, B negative electrode composite not formed region, S internal space

Claims

1. A separator; a positive electrode mixture layer on one surface of the separator; a positive electrode current collector on a surface of the positive electrode mixture layer opposite to the separator; a negative electrode mixture layer on the other surface of the separator; a negative electrode current collector is laminated on a surface of the negative electrode mixture layer opposite to the separator, When viewed from the stacking direction, the positive electrode current collector has a positive electrode composite unformed region where the positive electrode composite layer is not formed, and the negative electrode current collector has a negative electrode composite unformed region where the negative electrode composite layer is not formed, The tensile modulus of the bonded positive electrode current collector or the negative electrode current collector is 35.0 kgf / mm ２ a low-rigidity material layer having a tensile modulus of less than 35.0 kgf / mm on a surface of the low-rigidity material layer opposite to a surface bonded to the positive electrode current collector or the negative electrode current collector; ２ A bipolar battery having the above-described high-rigidity material layer and a resin seal layer.

2. 2. The bipolar battery according to claim 1, wherein the resin seal layer is laminated on a surface of the positive electrode current collector opposite to the positive electrode composite layer in the positive electrode composite unformed region, and on a surface of the negative electrode current collector opposite to the negative electrode composite layer in the negative electrode composite unformed region.

3. The low-rigidity material layer has a tensile modulus of 1.4 kgf / mm ２ More than 26.7kgf / mm ２ the tensile modulus of the high-rigidity material layer is 42.2 kgf / mm or less, ２ Over 127.0 kgf / mm ２ 2. The bipolar battery of claim 1, wherein:

4. 2. The bipolar battery according to claim 1, wherein the low-rigidity material layer contains at least one selected from low-density polyethylene and ethylene-vinyl acetate copolymer resin, and the high-rigidity material layer contains at least one selected from ionomer, unstretched polypropylene, and high-density polyethylene.

5. 2. The bipolar battery according to claim 1, wherein the resin sealing layer is made up of two layers: the low-rigidity material layer and the high-rigidity material layer.

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