Battery pack

Abstract

To provide a battery pack in which an abnormality of a cell is hardly linked.SOLUTION: A battery pack contains a module. The module contains a first cell and a second cell. The first cell contains: an exterior casing body; an electrode body; and an electrode terminal. The exterior casing body contains a laminate film. The electrode terminal contains a first main surface and a second main surface. The first main surface is directed to a direction of the second cell. The second main surface is directed to a surface opposite to the first main surface. A sealing part is formed to a peripheral edge of the exterior casing body. The sealing part contains an easy cleavage part. The easy cleavage part is constructed so as to be easier opened than a first region and a third region when at least one of a temperature and an inner pressure of the first cell is increased.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present technology relates to battery packs. [Background technology]

[0002] Japanese Patent Application Laid-Open No. 2003-346768 (Patent Document 1) discloses a laminate cell. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-346768 A Summary of the Invention [Problem to be solved by the invention]

[0004] A laminate film is used as an exterior body of a single battery (cell). The laminate film includes a resin layer and a metal layer. The resin layer covers the metal layer. The laminate film is processed into, for example, a pouch. The resin layer is welded to the periphery of the pouch to form a sealing portion. The formation of the sealing portion seals the exterior body. A cell including an exterior body made of a laminate film is also called a "laminated cell."

[0005] Two or more cells are electrically connected to form a module, in which the two or more cells may form a series or parallel circuit, and one or more modules form a battery pack.

[0006] It is assumed that an abnormality will occur in one cell in a module. For example, it is assumed that an internal short circuit will occur in one cell. The internal short circuit may cause the temperature of the cell to rise. Furthermore, gas may be generated inside the cell. At least one of the temperature rise and the internal pressure rise may cause the seal of the exterior body to rupture. The rupture of the seal may cause gas to eject from the exterior body.

[0007] In conventional laminated cells, the location of the seal rupture may be random. For example, gas may escape between adjacent cells in a location where gas is likely to become trapped. The gas may be hot. The hot gas may become trapped, causing adjacent cells to heat up. The heating of adjacent cells may cause a chain reaction of abnormalities.

[0008] An object of the present technology is to provide a battery pack in which cell abnormalities are less likely to cause a chain reaction. [Means for solving the problem]

[0009] The configuration and effects of the present technology will be described below. However, the mechanism of action in this specification includes assumptions. The mechanism of action does not limit the scope of the present technology.

[0010] [1] The battery pack includes a module. The module includes one or more cell pairs. The cell pair includes a first cell and a second cell. The second cell is adjacent to the first cell. The second cell is electrically connected to the first cell. The first cell includes an exterior body, an electrode body, and an electrode terminal. The exterior body includes a laminate film. The laminate film includes a resin layer and a metal layer. The resin layer coats the metal layer. The resin layer includes a first thermoplastic resin. The exterior body houses the electrode body. A sealing portion is formed on the periphery of the exterior body. The electrode terminal is connected to the electrode body. The electrode terminal penetrates the sealing portion and is led from the inside of the exterior body to the outside. The electrode terminal has a flat plate shape. The electrode terminal includes a first main surface and a second main surface. The first main surface faces the second cell. The second main surface is the opposite surface to the first main surface. The sealing portion includes a first region, a second region, and a third region. The first region is formed between the first main surface and the resin layer. The second region is formed between the second main surface and the resin layer. The third region is formed between the resin layers. The second region includes an easy-to-crack portion that is configured to be more easily cleaved than the first region and the third region when at least one of the temperature and the internal pressure of the first cell increases.

[0011] The module of the present technology includes two or more laminated cells. The two laminated cells constitute a cell pair. The cell pair includes a first cell (also simply referred to as a "cell") and a second cell (also referred to as an "adjacent cell"). The cell pair forms a series circuit or a parallel circuit.

[0012] The sealing portion of the cell can be divided into a first region, a second region, and a third region depending on its relationship with the electrode terminal. The second region includes an easy-to-crack portion. The easy-to-crack portion functions as an explosion-proof valve. In other words, the easy-to-crack portion is more likely to cleave in the event of an abnormality than the first region and the third region. When the easy-to-crack portion cleaves, gas is ejected from the easy-to-crack portion. Since the gas ejection position is within the second region, it is expected that cell abnormalities will not easily lead to a chain reaction.

[0013] FIG. 1 is a schematic diagram showing the flow of gas when the gas is ejected from a first region. The electrode terminal 30a of the first cell 100a and the electrode terminal 30b of the second cell 100b (adjacent cell) are electrically connected. The electrode terminal 30a may be directly connected to the electrode terminal 30b. A bus bar 150 may connect the electrode terminal 30a and the electrode terminal 30b. By connecting the electrode terminal 30a and the electrode terminal 30b, a locally closed space may be formed. The first region 13a faces the adjacent cell. When gas is ejected from the first region 13a in the event of an abnormality, it is considered that the gas tends to flow in the direction of the adjacent cell. Furthermore, it is considered that the gas tends to be trapped in the closed space. When the adjacent cell is heated, an abnormality may be chained to the adjacent cell.

[0014] FIG. 2 is a schematic diagram showing the flow of gas when the gas is ejected from the third region. The gas ejected from the third region 13c is likely to diffuse in multiple directions. The gas may diffuse in multiple directions, which may cause multiple cells to heat up. Furthermore, the gas ejected from the third region 13c is likely to flow toward the storage section of the electrode body. As a result, abnormalities may occur in multiple cells.

[0015] FIG. 3 is a schematic diagram showing the flow of gas when the gas is ejected from the second region. The second region 13b is located on the opposite side to the first region 13a. A locally closed space is formed on the first region 13a side by the connection between the electrode terminal 30a and the electrode terminal 30b. On the other hand, the space is not closed on the second region 13b side. It is considered that the gas ejected from the second region 13b flows easily in one direction. This is considered to be because the first region 13a side is closed. Furthermore, it is considered that the gas is less likely to be trapped on the second region 13b side because the space is not closed. In addition, it is considered that the gas ejected from the second region 13b flows easily in a direction away from the storage section of the electrode body 20. Therefore, it is expected that the gas ejected from the second region 13b will not easily cause a chain reaction of cell abnormalities.

[0016] [2] In the battery pack described in [1] above, for example, the first main surface may include a rough surface portion.

[0017] An anchor effect may occur in the rough surface portion. The anchor effect may increase the adhesive strength. When the first region includes a rough surface portion, the first region may have a higher adhesive strength than the second region. In other words, the second region has a relatively low adhesive strength. When the second region has a relatively low adhesive strength, an easily cleavable portion may be formed in the second region. The easily cleavable portion is expected to cleave, for example, when the internal pressure increases.

[0018] [3] In the battery pack described in [1] or [2] above, the easy-to-crack portion may include a second thermoplastic resin. The second thermoplastic resin has a lower melting point than the first thermoplastic resin.

[0019] When the temperature rises, the second thermoplastic resin may soften prior to the first thermoplastic resin. The easy-to-cleave portion including the second thermoplastic resin is expected to cleave, for example, when the temperature rises.

[0020] [4] The battery pack according to any one of [1] to [3] above may further include, for example, a container. The container houses the module. An exhaust duct is formed inside the container. An easy-to-crack portion is disposed inside the exhaust duct.

[0021] In this technology, it is expected that gas will be ejected from the easy-to-crack part in the event of an abnormality. By disposing the easy-to-crack part inside the exhaust duct, the gas ejected from the easy-to-crack part can be smoothly discharged to the outside of the container.

[0022] [5] The module may include, for example, two or more cell pairs. In each of the two or more cell pairs, the easy-to-crack portion may be disposed inside the exhaust duct.

[0023] When the battery pack includes a plurality of easy-to-crack parts, the exhaust duct may be positioned such that each easy-to-crack part is located inside the exhaust duct. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic diagram showing the flow of gas when the gas is ejected from a first region. [Diagram 2] FIG. 2 is a schematic diagram showing the flow of gas when the gas is ejected from the third region. [Diagram 3] FIG. 3 is a schematic diagram showing the flow of gas when the gas is ejected from the second region. [Figure 4] FIG. 4 is a schematic diagram of the battery pack in this embodiment. [Diagram 5] FIG. 5 is a schematic cross-sectional view of the battery pack in this embodiment. [Figure 6] FIG. 6 is an enlarged view of region VI in FIG. [Figure 7] FIG. 7 is a first plan view of the cell in this embodiment. [Figure 8] FIG. 8 is a second plan view of the cell in this embodiment. [Figure 9]FIG. 9 is a schematic cross-sectional view showing a first example of an easy-to-crack portion. [Figure 10] FIG. 10 is a schematic cross-sectional view showing a second example of the easy-to-crack portion. [Figure 11] FIG. 11 is a schematic cross-sectional view showing a third example of the easy-to-crack portion. [Figure 12] FIG. 12 is a conceptual diagram showing a first example of the sequence of the easily cleavable portion. [Figure 13] FIG. 13 is a conceptual diagram showing a second example of the sequence of the easily cleavable portion. [Figure 14] FIG. 14 is a conceptual diagram showing a third example of the sequence of the easily cleavable portion. [Figure 15] FIG. 15 is a schematic cross-sectional view showing a test sample. [Figure 16] FIG. 16 shows the structure of the test specimen and the results of the nail penetration test. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, an embodiment of the present technology (also referred to as "the present embodiment" in this specification) will be described. However, the following description does not limit the scope of the present technology. For example, a reference to an action or effect in this specification does not limit the scope of the present technology to a range in which all of the action or effect is achieved.

[0026] In this specification, the terms "comprise, include," "have," and variations thereof (e.g., "be composed of," "encompass, involve," "contain," "carry, support," "hold," etc.) are open-ended. The open-ended terms may or may not include additional elements in addition to the essential elements. The term "consist of" is closed-ended. The term "consist essentially of" is semi-closed. The semi-closed terms may include additional elements in addition to the essential elements, as long as the purpose of the present technology is not hindered. For example, elements normally expected in the field to which the present technology belongs (e.g., inevitable impurities, etc.) may be included as additional elements.

[0027] In this specification, the expressions "may" and "can" are used in the permissive sense, "having the possibility of doing something," rather than in the obligatory sense, "must do something." In this specification, the singular forms (a, an, the) include the plural forms, unless otherwise specified.

[0028] Geometric terms (e.g., "parallel") in this specification should not be interpreted in a strict sense. For example, "parallel" may deviate slightly from the strict meaning of "parallel". Geometric terms in this specification may include, for example, tolerances, errors, etc. in design, work, manufacturing, etc. The dimensional relationships in each figure may not match the actual dimensional relationships. In order to facilitate understanding of the present technology, the dimensional relationships (length, width, thickness, etc.) in each figure may be changed. Furthermore, some configurations may be omitted.

[0029] In each figure, the "stacking direction" corresponds to the Z-axis direction. The relationship between the stacking direction and the vertical direction is arbitrary. For example, the stacking direction may be parallel to the vertical direction. For example, the stacking direction may be perpendicular to the vertical direction.

[0030] In this specification, for example, numerical ranges such as "95°C to 140°C" and "95-140°C" include the upper and lower limits unless otherwise specified. That is, "95°C to 140°C" and "95-140°C" indicate a numerical range of "95°C or more and 140°C or less". In addition, numerical values ​​arbitrarily selected from within the numerical range may be set as new upper and lower limits. For example, a new numerical range may be set by arbitrarily combining a numerical value within the numerical range with a numerical value described in another part of this specification.

[0031] In this specification, "abnormal" refers to at least one of a temperature rise and an internal pressure rise. "Temperature rise" refers to the surface temperature of the cell reaching 90°C or higher. The surface temperature of the cell can be measured, for example, by a thermocouple. An internal pressure rise refers to the difference between the internal pressure and the external pressure of the cell reaching 0.1 MPa or higher. The internal pressure can be measured by an internal pressure measuring device.

[0032] In this specification, the "first cell" and the "second cell" may be collectively referred to as "cell."

[0033] <Battery pack> FIG. 4 is a schematic diagram of the battery pack in this embodiment. The battery pack 1000 may be used for any purpose. The battery pack 1000 may be used as a main power source or a power source for power assist in, for example, an electric vehicle. The battery pack 1000 includes a module 500. The battery pack 1000 may include only one module 500. The battery pack 1000 may include two or more modules 500. The battery pack 1000 may further include any configuration as long as it includes the module 500. The battery pack 1000 may further include, for example, a protection circuit, a protection device, a monitoring circuit, a cooling device, and the like.

[0034] "container" The battery pack 1000 may further include, for example, a container 600. The container 600 may also be referred to as a "housing" or the like. The container 600 stores the module 500. The container 600 may store one module 500. The container 600 may store two or more modules 500.

[0035] The container 600 may have any outer shape. The container 600 may be, for example, rectangular. The container 600 may be, for example, made of metal or resin. An exhaust duct 610 may be formed inside the container 600. The exhaust duct 610 leads to the outside of the container 600. The exhaust duct 610 may include, for example, a straight pipe. The exhaust duct 610 may include, for example, an elbow. The exhaust duct 610 guides the gas ejected from the module 500 to the outside of the container 600. The container 600 may further include a fan, a suction blower, or the like to promote exhaust of the gas.

[0036] Module FIG. 5 is a schematic cross-sectional view of the battery pack in this embodiment. Fig. 5 shows a cross section parallel to the YZ plane of Fig. 4. The cross section of Fig. 5 is parallel to the stacking direction (Z-axis direction).

[0037] The battery pack 1000 includes a module 500. The module 500 is formed by stacking two or more cells 100 (single cells) in the Z-axis direction. The number of cells 100 is arbitrary as long as there are two or more cells 100. The module 500 may include, for example, 2 to 100 cells 100. The module 500 may include, for example, 4 to 50 cells 100. The module 500 may include, for example, 6 to 10 cells 100.

[0038] Cell Pair FIG. 6 is an enlarged view of region VI in FIG. The module 500 includes one or more cell pairs 200. The cell pair 200 includes a first cell 100a and a second cell 100b. The second cell 100b is adjacent to the first cell 100a. The second cell 100b may be directly connected to the first cell 100a. The cell pair 200 may include, for example, a bus bar 150. The bus bar 150 is conductive. The bus bar 150 may connect the first cell 100a and the second cell 100b.

[0039] The electrode terminal 30b may have the same polarity as the electrode terminal 30a. That is, the second cell 100b may be connected in parallel with the first cell 100a. The electrode terminal 30b may have a polarity opposite to that of the electrode terminal 30a. That is, the second cell 100b may be connected in series with the first cell 100a. When the cell pairs 200 form a series circuit, there is a tendency for abnormalities to occur more easily than when the cell pairs 200 form a parallel circuit. In this embodiment, it is expected that abnormalities will not occur easily even when the cell pairs 200 form a series circuit.

[0040] There may be any number of cell pairs 200, so long as there is at least one cell pair 200. The module 500 may include, for example, 1 to 50 cell pairs 200. The module 500 may include, for example, 2 to 25 cell pairs 200. The module 500 may include, for example, 3 to 5 cell pairs 200.

[0041] "cell" The first cell 100a and the second cell 100b may be any battery system, independently of each other. The first cell 100a may be, for example, a liquid lithium ion cell, a lithium ion polymer cell, or an all-solid-state lithium ion cell. The first cell 100a may have any outer shape. The first cell 100a may be, for example, flat. The first cell 100a includes an exterior body 10, an electrode body 20, and an electrode terminal 30a. The second cell 100b may have, for example, substantially the same structure as the first cell 100a.

[0042] (Exterior body) The exterior body 10 stores the electrode body 20. The exterior body 10 may be in a pouch shape. The exterior body 10 is sealed. The exterior body 10 includes a laminate film. The exterior body 10 may be, for example, substantially made of a laminate film. The laminate film includes a resin layer 11 and a metal layer 12. The resin layer 11 covers the metal layer 12. For example, the resin layer 11 may be welded to the metal layer 12. The resin layer 11 may cover only one side of the metal layer 12. The resin layer 11 may cover both sides of the metal layer 12. That is, the laminate film may have a two-layer structure (resin layer 11 / metal layer 12) or a three-layer structure (resin layer 11 / metal layer 12 / resin layer 11).

[0043] The resin layer 11 may have a thickness of, for example, 1 μm to 100 μm. The resin layer 11 includes a first thermoplastic resin. The resin layer 11 may be substantially made of the first thermoplastic resin. The first thermoplastic resin may include any component as long as it exhibits thermoplasticity. The first thermoplastic resin may include, for example, at least one selected from the group consisting of polyamide (nylon), polyethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, phenolic resin, polyvinyl alcohol, ethylene vinyl acetate copolymer, polyethylene, polypropylene, polyvinyl chloride, and ionomer. When the laminate film has a three-layer structure, the two resin layers 11 may include the same thermoplastic resin or different thermoplastic resins.

[0044] The metal layer 12 may have a thickness of, for example, 10 μm to 500 μm. The metal layer 12 includes a metal. The metal layer 12 may, for example, consist essentially of a metal. The metal layer 12 may, for example, consist essentially of a metal foil. The metal layer 12 may, for example, be a metal vapor deposition layer. The metal vapor deposition layer may be formed, for example, by vapor-depositing a metal on the surface of the resin layer 11. The metal layer 12 may, for example, contain aluminum (Al), an Al alloy, etc.

[0045] (electrode body) The electrode body 20 includes a positive electrode and a negative electrode. The positive electrode includes a positive electrode active material. The negative electrode includes a negative electrode active material. Each of the positive electrode and the negative electrode may be, for example, in a sheet form. The electrode body 20 may be, for example, a laminate type. That is, the electrode body 20 may be formed by alternately laminating positive electrodes and negative electrodes. The electrode body 20 may be, for example, a wound type. That is, the electrode body 20 may be formed by spirally winding a laminate including a positive electrode and a negative electrode.

[0046] The electrode body 20 may further include a separator. The separator is electrically insulating. The separator separates the positive electrode and the negative electrode. The separator may include, for example, a porous membrane. The electrode body 20 may further include an electrolyte. The electrolyte may be a liquid, a gel, or a solid. For example, the electrode body 20 may be impregnated with a liquid electrolyte (electrolytic solution).

[0047] (electrode terminal) The first cell 100a includes two electrode terminals 30a. One is a positive electrode terminal. The other is a negative electrode terminal. The electrode terminal 30a is connected to the electrode body 20. The electrode terminal 30a may be welded to the electrode body 20. The electrode terminal 30a is flat. The electrode terminal 30a may include, for example, a metal plate. The electrode terminal 30a may have a thickness of, for example, 0.1 mm to 5 mm. The positive electrode terminal may include, for example, an Al plate, etc. The negative electrode terminal may include, for example, a copper (Cu) plate, etc.

[0048] (Sealing part) FIG. 7 is a first plan view of the cell in this embodiment. The exterior body 10 may have any planar shape. The exterior body 10 may be rectangular, for example. A sealing portion 13 is formed on the periphery of the exterior body 10. The sealing portion 13 is formed by thermal welding. The sealing portion 13 may surround a storage portion 15. The storage portion 15 stores the electrode body 20.

[0049] The sealing portion 13 includes a first region 13a, a second region 13b, and a third region 13c. The third region 13c is formed between the resin layers 11 (see FIG. 6). In the third region 13c, the resin layers 11 are welded to each other.

[0050] The electrode terminal 30 penetrates the sealing portion 13 and is led out from the inside to the outside of the exterior body 10. A first region 13a and a second region 13b are formed at the position where the electrode terminal 30 penetrates the sealing portion 13. In Fig. 7, the first region 13a and the second region 13b are in a front-back positional relationship.

[0051] The contour of the exterior body 10 may be formed by, for example, four sides. Electrode terminals 30 (positive electrode terminals or negative electrode terminals) may be disposed on two of the four sides that face each other.

[0052] FIG. 8 is a second plan view of the cell in this embodiment. The contour of the exterior body 10 may be defined by, for example, four sides. Two electrode terminals 30 (a positive electrode terminal and a negative electrode terminal) may be disposed on one of the four sides.

[0053] 《Easy to cleave part》 The electrode terminal 30a includes a first main surface 31 and a second main surface 32 (see FIG. 6). The second main surface 32 is the surface opposite to the first main surface 31. The first main surface 31 faces the direction of the adjacent cell (the second cell 100b).

[0054] The first region 13a is formed between the first main surface 31 and the resin layer 11. In the first region 13a, the resin layer 11 is welded to the first main surface 31. The second region 13b is formed between the second main surface 32 and the resin layer 11. In the second region 13b, the resin layer 11 is welded to the second main surface 32.

[0055] The second region 13b includes an easy-to-crack portion. The easy-to-crack portion is configured to be more easily cleaved than the first region 13a and the third region 13c in the event of an abnormality. In the cell pair 200, the easy-to-crack portion may be formed in either the first cell 100a or the second cell 100b, or may be formed in both the first cell 100a and the second cell 100b. That is, in the cell pair 200, at least one of the first cell 100a and the second cell 100b may include the easy-to-crack portion.

[0056] The easy-to-crack portion may be disposed over the entire area of ​​the second region 13b. The easy-to-crack portion may be disposed in a part of the second region 13b. That is, the easy-to-crack portion may be formed in at least a part of the second region 13b.

[0057] The easy-to-crack portion may extend so as to connect the inside and outside of the exterior body 10. Since the easy-to-crack portion connects the inside and outside of the exterior body 10, it is expected that a gas flow path will be smoothly formed.

[0058] (Rough surface part) FIG. 9 is a schematic cross-sectional view showing a first example of an easy-to-crack portion. The easy-to-crack portion may have any configuration. For example, the first main surface 31 may include the rough surface portion rp. For example, the first main surface 31 may be substantially composed of the rough surface portion rp. When the first main surface 31 includes the rough surface portion rp, the adhesive strength of the first region 13a may be increased. That is, the second region 13b has a relatively low adhesive strength. As a result, the easy-to-crack portion may be formed in the second region 13b. The easy-to-crack portion may be cleaved, for example, when pressure increases.

[0059] The rough surface portion rp includes irregularities on the surface. The rough surface portion rp can be formed, for example, by blasting. The rough surface portion rp may have, for example, an Ra of 0.1 μm or more. The rough surface portion rp may have, for example, an Ra of 0.5 μm or more. The rough surface portion rp may have, for example, an Ra of 10 μm or less. In this specification, "Ra" refers to the "arithmetic mean roughness" defined in "JIS B 0601." Ra can be measured by a laser microscope.

[0060] For example, the second major surface 32 may include a smooth surface. For example, the second major surface 32 may consist of a substantially smooth surface. The smooth surface may have, for example, an Ra of less than 0.1 μm. The smooth surface may have, for example, an Ra of 0.01 μm to 0.05 μm.

[0061] For example, both the first main surface 31 and the second main surface 32 may include a rough surface portion rp. When both the first main surface 31 and the second main surface 32 include a rough surface portion rp, for example, a relationship of "Ra of the first main surface > Ra of the second main surface" may be satisfied. For example, the first main surface 31 may have an Ra that is 2 to 100 times that of the second main surface 32. For example, the first main surface 31 may have an Ra that is 5 to 50 times that of the second main surface 32.

[0062] (Adhesive strength) The second region 13b may have a lower adhesive strength than, for example, the first region 13a and the third region 13c. When the second region 13b has a relatively low adhesive strength, an easily cleavable portion may be formed in the second region 13b. The easily cleavable portion having a low adhesive strength may cleave, for example, when pressure increases.

[0063] For example, the first region 13a and the third region 13c may each independently have an adhesive strength of 5 to 10 kgf / 15 mm. For example, the second region 13b may have an adhesive strength of less than 5 kgf / 15 mm. For example, the second region 13b may have an adhesive strength of 1 kgf / 15 mm or more. In this specification, "adhesive strength" refers to "peel adhesion strength". "Peel adhesion strength" is measured by "peel adhesion strength test (180° peel)" in accordance with "JIS K 6854-2". The peel adhesion strength test may be performed, for example, by "Autograph (registered trademark)" manufactured by Shimadzu Corporation. A tensile tester having the same function as the device may be used. A test piece is prepared. The test piece is cut out from each region. For example, the test piece cut out from the first region 13a includes a part of the electrode terminal 30a and a part of the exterior body 10 (laminate film). A portion of the exterior body 10 is welded to a portion of the electrode terminal 30a. An end of the electrode terminal 30a and an end of the exterior body 10 are fixed to the grips of a tensile tester. The exterior body 10 is peeled off from the electrode terminal 30a at an angle of 180°. The grip movement speed is 100 mm / min. The average peel force (kgf) is obtained from the force-grip movement distance curve. "kgf / 15 mm" indicates the average peel force when the width of the test piece is 15 mm.

[0064] (Low melting point resin) For example, the easy-to-cleave portion may contain a second thermoplastic resin. For example, in the second region 13b, the resin layer 11 may contain a second thermoplastic resin. The second thermoplastic resin has a lower melting point than the first thermoplastic resin. The easy-to-cleave portion containing the second thermoplastic resin is expected to cleave, for example, when the temperature rises. By releasing the internal pressure at an early stage in the event of an abnormality, for example, the exothermic reaction may become slower, and the amount of gas generated may be reduced. Furthermore, the heat generation of the electrode body 20 may become slower.

[0065] In the second region 13b, the resin layer 11 may contain, for example, a mixture of a first thermoplastic resin and a second thermoplastic resin. The mixture may form, for example, a homogeneous phase. The mixture may have, for example, a sea-island structure. For example, the first thermoplastic resin may form a sea phase, and the second thermoplastic resin may form an island phase. For example, the second thermoplastic resin may form a sea phase, and the first thermoplastic resin may form an island phase.

[0066] FIG. 10 is a schematic cross-sectional view showing a second example of the easy-to-crack portion. For example, in the second region 13b, the resin layer 11 may have a multilayer structure. That is, the resin layer 11 may include a first layer 11a and a second layer 11b. The second layer 11b is interposed between the second main surface 32 and the first layer 11a. The second layer 11b may extend so as to connect the inside and the outside of the exterior body 10. For example, the first layer 11a may include a first thermoplastic resin. The first layer 11a may be substantially made of the first thermoplastic resin. For example, the second layer 11b may include a second thermoplastic resin. The second layer 11b may be substantially made of the second thermoplastic resin.

[0067] The second thermoplastic resin may contain any component as long as it has a lower melting point than the first thermoplastic resin. The second thermoplastic resin may contain, for example, at least one selected from the group consisting of polyethylene (melting point: 95 to 140°C), polypropylene (melting point: 160 to 170°C), and polyvinyl chloride (melting point: 180°C). In this specification, the "melting point" of a thermoplastic resin refers to the peak top temperature of a melting peak (endothermic peak) in a DSC (Differential Scanning Calorimetry) curve. The DSC curve may be measured in accordance with "JIS K 7121".

[0068] FIG. 11 is a schematic cross-sectional view showing a third example of the easy-to-crack portion. For example, the easy-to-cleave portion may be formed by either the rough surface portion rp or the low-melting point resin (second thermoplastic resin). For example, the easy-to-cleave portion may be formed by combining the rough surface portion rp with a low-melting point resin. For example, the first main surface 31 may include the rough surface portion rp. Furthermore, the resin layer 11 disposed on the second main surface 32 side may include a first layer 11a and a second layer 11b. The second layer 11b may include the second thermoplastic resin.

[0069] 《Arrangement of easily cleavable parts》 FIG. 12 is a conceptual diagram showing a first example of the sequence of the easily cleavable portion. In each cell 100, the two electrode terminals 30 may be led out alternately in a direction (Y-axis direction) intersecting the stacking direction (Z-axis direction). For example, all the easy cleavage parts 40 may be gathered on one side in the Y-axis direction. By gathering all the easy cleavage parts 40 on one side, all the easy cleavage parts 40 can be easily disposed inside the exhaust duct 610. In other words, the exhaust duct 610 can have a simple structure.

[0070] FIG. 13 is a conceptual diagram showing a second example of the sequence of the easily cleavable portion. The easy-to-crack portions 40 may be disposed on both sides in the Y-axis direction. The exhaust duct 610 may be provided on only one side in the Y-axis direction, or on both sides in the Y-axis direction. All of the easy-to-crack portions 40 may be disposed inside the exhaust duct 610. Some of the easy-to-crack portions 40 may be disposed outside the exhaust duct 610.

[0071] FIG. 14 is a conceptual diagram showing a third example of the sequence of the easily cleavable portion. For example, the easy-to-tear portions 40 may be disposed between all of the electrode terminals 30 and the laminate film.

[0072] The electrode terminal 30x located at the end in the stacking direction does not have a counterpart (cell) to connect to. At the end in the stacking direction, the easy-to-crack portion 40 may be arranged, for example, on a side where there are no adjacent cells. At the end in the stacking direction, the easy-to-crack portion 40 may be arranged, for example, on a side where there are adjacent cells. At the end in the stacking direction, the easy-to-crack portion 40 does not have to be arranged. EXAMPLES

[0073] Hereinafter, an embodiment of the present technology (also referred to as "the present embodiment" in this specification) will be described. However, the following description does not limit the scope of the present technology.

[0074] <Preparation of test specimen> FIG. 15 is a schematic cross-sectional view showing a test sample. The test battery pack 1000 includes a container 600. The container 600 is made of Al. An exhaust duct 610 is provided inside the container 600. An insertion hole 620 is formed in the container 600. The insertion hole 620 has a diameter of 1.2 mm.

[0075] A module is disposed within the container 600. The module is composed of one cell pair 200. The cell pair 200 includes a first cell 100a, a second cell 100b, and a bus bar 150. The cell pair 200 forms a series circuit. The bus bar 150 connects the first cell 100a and the second cell 100b in series. The first cell 100a and the second cell 100b are both liquid-based lithium-ion cells. The exterior body is made of an Al laminate film. The exterior body is sealed by thermal welding. The exterior body houses an electrode body. The electrode body is of a laminated type. The positive electrode terminal is an Al plate. The negative electrode terminal is a Cu plate. A rough surface portion is formed on at least one of the positive electrode terminal and the negative electrode terminal by blasting.

[0076] <Test Method> The nail 300 is prepared. The nail 300 is a round nail (body diameter: 1.0 mm). The nail 300 is inserted through the insertion hole 620. The nail 300 is then inserted into the first cell 100a. The insertion of the nail 300 causes an internal short circuit in the first cell 100a. After gas is ejected from the first cell 100a, the surface temperature of the second cell 100b is measured for 30 minutes.

[0077] No.1 FIG. 16 shows the structure of the test specimen and the results of the nail penetration test. In the battery pack 1000 of No. 1, the rough surface portion rp of the electrode terminal 30a and the rough surface portion rp of the electrode terminal 30b are disposed to face each other.

[0078] No.2 In the No. 2 battery pack 1000, the rough surface portion rp is not formed on either the electrode terminal 30a or the electrode terminal 30b. That is, the No. 2 battery pack 1000 does not include the easy-to-crack portion 40. This is because there is no substantial difference in adhesive strength on all surfaces.

[0079] No.3 In the No. 3 battery pack 1000, the rough surface portion rp of the electrode terminal 30a and the rough surface portion rp of the electrode terminal 30b are arranged to face in opposite directions.

[0080] No.4 In the No. 4 battery pack 1000, the rough surface portion rp is formed on all surfaces of the electrode terminal 30a and the electrode terminal 30b. Therefore, the No. 4 battery pack 1000 does not include the easy-to-crack portion 40. This is because there is no substantial difference in adhesive strength on all surfaces.

[0081] <Result> 16, in the "heat chain reaction" section, "Yes" indicates that the surface temperature of the second cell 100b rose to 90°C or higher after gas was ejected from the first cell 100a. "No" indicates that the surface temperature of the second cell 100b remained below 90°C for 30 minutes after gas was ejected from the first cell 100a.

[0082] In FIG. 16, since the second region 13b includes the easy-to-cleave portion 40, there is a tendency that abnormalities are less likely to occur in the second cell 100b.

[0083] The present embodiment and the present embodiment are illustrative in all respects. The present embodiment and the present embodiment are not restrictive. The scope of the present technology includes all modifications within the meaning and scope equivalent to the description of the claims. For example, it is also planned from the beginning that any configurations can be extracted from the present embodiment and the present embodiment, and that they can be arbitrarily combined. [Explanation of symbols]

[0084] 10 outer casing, 11 resin layer, 11a first layer, 11b second layer, 12 metal layer, 13 sealing portion, 13a first region, 13b second region, 13c third region, 15 storage portion, 20 electrode body, 30, 30a, 30b, 30x electrode terminal, 31 first main surface, 32 second main surface, 40 easily cleavable portion, 100 cell, 100a first cell, 100b second cell, 150 bus bar, 200 cell pair, 300 nail, 500 module, 600 container, 610 exhaust duct, 620 insertion hole, 1000 battery pack, rp rough surface portion.

Claims

1. Includes modules, the module includes a first cell and a second cell; the second cell is adjacent to the first cell, The first cell includes an outer casing, an electrode assembly, and an electrode terminal, The exterior body includes a laminate film, The laminate film includes a resin layer and a metal layer, The exterior housing houses the electrode assembly, A sealing portion is formed on the exterior body, the electrode terminal is connected to the electrode body, the electrode terminal is led from the inside of the exterior body to the outside by penetrating the sealing portion, the electrode terminal has a flat portion that penetrates the sealing portion, the electrode terminal includes a first main surface and a second main surface; The first main surface faces the second cell, The second main surface is an opposite surface to the first main surface, A region of the sealing portion that contacts the second main surface includes an easy-to-crack portion, the easy-to-crack portion is configured to be more easily cleaved than a region of the sealing portion other than the easy-to-crack portion when at least one of a temperature and an internal pressure of the first cell is increased, the electrode terminal of the first cell is connected to the electrode terminal of the second cell; When the module further includes a third cell, and the third cell is disposed adjacent to the first cell and on the opposite side of the second cell, the electrode terminal of the first cell that is connected to the electrode terminal of the second cell is not connected to the electrode terminal of the third cell. Battery pack.

2. The first main surface includes a rough surface portion. The battery pack according to claim 1 .

3. the resin layer includes a first thermoplastic resin, The easy-to-cleave portion includes a second thermoplastic resin, The second thermoplastic resin has a lower melting point than the first thermoplastic resin.

3. The battery pack according to claim 1 or 2.

4. Further comprising a container, the container houses the module; An exhaust duct is formed inside the container, The easy-to-crack portion is disposed inside the exhaust duct. The battery pack according to any one of claims 1 to 3.

5. the module includes two or more cell groups including the first cell and the second cell; In each of the two or more cell groups, the easy-to-crack portion is disposed inside the exhaust duct.

5. The battery pack according to claim 4.

6. further comprising a bus bar; The bus bar connects the electrode terminal of the first cell and the electrode terminal of the second cell. The battery pack according to any one of claims 1 to 5.

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