Power storage module

Abstract

A power storage module (10) includes: a plurality of power storage devices (20); and an upper holder (60) that accommodates the plurality of power storage devices (20) in an accommodation section (61). The power storage devices (20) are immersed in a cooling liquid that is filled into the accommodation section (61) of the upper holder (60). At least one recess (65) is formed in a ceiling surface that is provided in a gap between adjacent power storage devices (20) in the accommodation section (61) and that faces the cooling liquid.

Description

Power storage module

[0001] The present disclosure relates to a power storage module.

[0002] A power storage module may have a plurality of power storage devices and may cool the power storage devices by immersing the plurality of power storage devices in a coolant (for example, Patent Document 1). Thereby, effects such as prevention of performance degradation due to temperature rise of the power storage device, extension of the life of the power storage device, ensuring the safety of the power storage device, improvement of the charge / discharge efficiency of the power storage device, and prevention of overheating during high output of the power storage device can be obtained.

[0003] Japanese Unexamined Patent Application Publication No. 2014-060088

[0004] A certain reliability can be obtained by the power storage module of Patent Document 1 described above. However, it is necessary to further improve the reliability of the power storage module due to more severe environments and usage conditions in the future.

[0005] Therefore, an object of the present disclosure is to provide a power storage module capable of improving reliability.

[0006] The power storage module according to the present disclosure has a plurality of power storage devices and a holder that houses the plurality of power storage devices in a housing portion. The power storage device is immersed in a coolant filled in the housing portion of the holder, and at least one recess is formed on the ceiling surface that faces the coolant and is provided in the gap between adjacent power storage devices in the housing portion.

[0007] According to the power storage module of the present disclosure, reliability can be improved.

[0008] It is a schematic cross-sectional view showing a power storage module which is an example of an embodiment. It is a schematic cross-sectional view showing a power storage device which is an example of an embodiment. It is a plan view of an upper holder which is an example of an embodiment as viewed from below. It is a schematic cross-sectional view showing a power storage module which is another example of an embodiment. It is a plan view of an upper holder which is another example of an embodiment as viewed from below. It is a schematic cross-sectional view showing a power storage module which is another example of an embodiment.

[0009] An example of an embodiment of this disclosure will be described in detail below. In the following description, specific shapes, materials, directions, numerical values, etc., are examples provided to facilitate understanding of this disclosure and can be modified as appropriate to suit the application, purpose, specifications, etc.

[0010] [Energy Storage Module] An example of an embodiment, the energy storage module 10, will be described using Figures 1 to 4.

[0011] The energy storage module 10 is mounted on an electric vehicle as a power source for the motor that drives the electric vehicle. However, the energy storage module of this disclosure is not limited to being mounted on an electric vehicle, and may be used as a power source for electric equipment driven by motors, such as power tools, electric assist bicycles, electric motorcycles, electric wheelchairs, electric tricycles, and electric carts. Furthermore, the applications of the energy storage module of this disclosure are not limited, and may be used as a power source for various electrical equipment used indoors and outdoors, such as cleaners, wireless devices, lighting devices, digital cameras, and video cameras.

[0012] In the following, the axial direction of the energy storage device 20 housed in the energy storage module 10 may be described as the vertical direction. In the vertical direction, each component may be described using either the upper or lower side.

[0013] Each energy storage module 10 comprises a plurality of energy storage devices 20, which will be described in detail later, a holder 40 that houses the plurality of energy storage devices 20, and a coolant that is filled in the holder 40 to cool the plurality of energy storage devices 20.

[0014] As will be described in detail later, the reliability of the energy storage module 10 can be improved by providing a recess 65 on the ceiling surface of the housing section 61 of the upper holder 60.

[0015] [Energy Storage Device] An example of an embodiment, an energy storage device 20, will be described using Figure 2.

[0016] Multiple energy storage devices 20 may be packed as tightly as possible within the energy storage module 10, with safety in mind, and adjacent energy storage devices 20 may be arranged in close proximity to each other. For example, in a plan view, six energy storage devices 20 may surround one energy storage device 20 (or be arranged in a staggered pattern). Alternatively, multiple energy storage devices may be arranged such that the closest energy storage devices are placed on each of the four sides.

[0017] As illustrated in Figure 4, in this embodiment, the energy storage device 20 uses a cylindrical lithium-ion secondary battery, but it may also be a nickel-metal hydride battery, a capacitor, etc. The energy storage device 20 includes, for example, an electrode group 24 in which a strip-shaped positive electrode 21 and a strip-shaped negative electrode 22 are wound with a strip-shaped separator 23 in between, a cylindrical outer container 25 that houses the electrode group 24 together with an electrolyte, a sealing body 26 that seals the opening at one end of the outer container 25 in an insulated state, a foil-shaped positive electrode lead 27 that electrically connects the positive electrode 21 and the sealing body 26, and a negative electrode lead 28 that electrically connects the negative electrode 22 and the outer container 25. An insulating gasket 29 may be placed between the outer circumference of the sealing body 26 and the inner surface of the opening of the outer container 25.

[0018] An annular groove 25A is formed on the outer circumferential surface of the outer can 25 on the opening side. This groove 25A is formed as an annular projection on the inner circumferential surface of the outer can 25. The gasket 29 and the sealing body 26 are placed on this annular projection inside the outer can 25. Furthermore, the opening end of the outer can 25 is crimped so that it bends inward with the gasket 29 positioned on the inner circumferential side. The opening of the outer can 25 is sealed by the sealing body 26 being sandwiched axially between the crimped opening end and the projection via the gasket 29.

[0019] The sealing body 26 may be provided with a current interruption mechanism (CID) or an exhaust valve that ruptures when the pressure inside the outer casing 25 exceeds a predetermined level. An insulating plate 30 may also be provided between the electrode group 24 and the bottom of the outer casing 25, or between the electrode group 24 and the protrusion (groove 25A) to insulate the electrode group 24 from the outer casing 25. If an insulating plate 30 is provided, the positive electrode lead 27 may extend through a through hole formed in the insulating plate 30. The negative electrode lead 28 may extend either through a through hole formed in the insulating plate 30 or by bypassing the insulating plate 30. In the energy storage device 20, as described above, the positive electrode terminal is configured on the top surface of the sealing body 26, and the negative electrode terminal is configured on the crimped shoulder portion 25B of the outer casing 25.

[0020] [Holder] Using Figures 1, 3, and 4, an example of an embodiment, including a holder 40 and coolant, will be described.

[0021] The holder 40 houses multiple energy storage devices 20 in its storage section (a space partitioned by the storage section 51 of the lower holder 50 and the storage section 61 of the upper holder 60, which will be described later). The storage section of the holder 40 is filled with coolant. As a result, the energy storage devices 20 are immersed in the coolant within the holder 40, and the energy storage devices 20 are cooled by the coolant.

[0022] The holder 40 is made of a material that has electrical insulating properties, such as a thermoplastic resin. Thermoplastic resins are broadly classified into general-purpose plastics and engineering plastics, and polycarbonate, polybutylene terephthalate, etc., are used.

[0023] The holder 40 is divided vertically (Z direction) and has a lower holder 50 that accommodates the lower part of the energy storage device 20 and an upper holder 60 that accommodates the upper part of the energy storage device 20. The lower holder 50 and the upper holder 60 may be fixed to each other via a fixing member or using locking parts provided on each holder. The gap between the lower holder 50 and the upper holder 60 may be sealed with an adhesive or the like.

[0024] The lower holder 50 houses multiple energy storage devices 20 and is filled with coolant. The lower holder 50 has a housing section 51 for housing multiple energy storage devices 20 (details of which will be described later), a side wall 52 surrounding the housing section 51, a holding section 53 for holding the lower ends of the energy storage devices 20, a coolant inlet 58 connected to the housing section 51, and a coolant outlet 59 connected to the housing section 51. In the energy storage module of this disclosure, if the coolant is not circulated, the coolant inlet 58 and the coolant outlet 59 may be omitted.

[0025] Multiple energy storage devices 20 are housed in the housing section 51. The vertical length of the housing section 51 is approximately the same as the axial length of the energy storage devices 20. The housing section 51 is also filled with coolant. As a result, in the lower holder 50, the energy storage devices 20 are immersed in the coolant and cooled by the coolant.

[0026] The retaining portion 53 is formed at the bottom of the housing portion 51. The retaining portion 53 is formed as a cylindrical recess so that the lower end of the energy storage device 20 fits into it. As a result, the lower end of the energy storage device 20 is held in place by the housing portion 51.

[0027] The coolant inlet 58 is formed, for example, on the right side wall 52 of the lower holder 50, which is opposite to the lower holder 50 in the longitudinal direction, and is connected to an inlet pipe (not shown). The coolant outlet 59 is formed, for example, on the left side wall 52 of the lower holder 50, which is opposite to the lower holder 50 in the longitudinal direction, and is connected to an outlet pipe (not shown). This creates a flow path in the housing 51, allowing the coolant to flow through the housing 51. The inlet and outlet pipes constitute a cooling circuit through which the coolant circulates.

[0028] The upper holder 60 houses the upper part of the energy storage device 20. The upper holder 60 has a housing section 61 for housing multiple energy storage devices 20, which will be described in detail later, a side wall 62 surrounding the housing section 61, a holding section 63 for holding the upper end of the energy storage device 20, an overhanging section 64 that extends into the gap between adjacent energy storage devices 20, a recess 65 formed on the bottom surface of the overhanging section 64, and an opening 66 formed in the holding section 63.

[0029] Multiple energy storage devices 20 are housed in the housing section 61. The housing section 51 is filled with coolant. As a result, in the upper holder 60, the energy storage devices 20 are immersed in the coolant, and the energy storage devices 20 are cooled by the coolant.

[0030] The holding portion 63 is formed on the bottom surface of the upper holder 60. The holding portion 63 is formed as a cylindrical recess so that the upper end of the energy storage device 20 fits into it. As a result, the upper end of the energy storage device 20 is held by the upper holder 60.

[0031] The protruding portion 64 is provided in the gap between three adjacent energy storage devices 20. The protruding portion 64 supports the side surface of the energy storage device 20. However, the protruding portion of the present invention is not limited to this and may be provided in the gap between two or four adjacent energy storage devices. The protruding portion 64 is formed in a substantially triangular prism shape. However, the recess of the present invention is not limited to this and may be formed in a cylindrical or other polygonal prism shape. For example, the lower end of the protruding portion 64 is formed to the vicinity of the groove 25A of the outer casing 25 of the energy storage device 20.

[0032] The recess 65 is a portion that collects vaporized high-temperature coolant when the energy storage device 20 becomes overheated in an unsafe state and the coolant vaporizes. The coolant that collects in the recess in this disclosure does not necessarily have to be vaporized; it may simply be heated liquid. Hereinafter, vaporized liquid and heated liquid will be collectively referred to as heated liquid. Furthermore, heated liquid may collect in the recess even when the energy storage device is not unsafe (under normal conditions). Moreover, the recess in this disclosure does not necessarily have to be filled with coolant. As will be described in detail later, the reliability of the energy storage module 10 can be improved by the recess 65. The recess 65 is formed on the bottom surface of the protruding portion 64. In other words, the recess 65 is formed on the ceiling surface of the gap between the energy storage devices 20 in the housing portion 51 of the upper holder 60. Also, the recess 65 is provided in the gap between the energy storage device 20 and the side wall 62 in the housing portion 61 of the upper holder 60 and is formed on the ceiling surface facing the coolant.

[0033] The recess 65 is formed, for example, as a triangular prism. However, the recess of the present invention is not limited to this, and may be formed as a cylindrical or other polygonal prism. Furthermore, the recess of the present invention may be formed as a cone or other polygonal pyramidal.

[0034] The volume of the recess 65 should preferably be as large as possible to hold the heated liquid. However, even when the recess 65 is formed, it is preferable that the strength of the upper holder 60 be greater than or equal to a predetermined strength.

[0035] As illustrated in Figure 4, the cross-section of the recess 65 (the cross-section when the energy storage device 10 is cut in the vertical direction) may have a tapered shape, where the internal dimensions of the recess decrease from the opening (lower end of the recess) to the bottom (upper end of the recess). This shape makes it easier to ensure sufficient wall thickness in the space above the recess where hotter heating liquid tends to accumulate.

[0036] The recess 65 allows a heating liquid to be stored within it. This prevents heat transfer between the heating liquid stored in the recess 65 and the energy storage device 20. As a result, it is possible to suppress the melting of heat-sensitive components (e.g., the gasket 29) in the energy storage device 20 due to high temperatures, which could cause a short circuit in the energy storage device 20. This improves the reliability of the energy storage module 10.

[0037] The opening 66 is formed in a circular shape on the ceiling surface of the holding portion 63 at a position corresponding to the top surface of the sealing body 26. This allows the top surface of the sealing body 26 (positive terminal) and the shoulder portion 25B of the outer can 25 (negative terminal) to be exposed from the upper holder 60. A positive current collector plate (not shown) is connected to the top surface of the sealing body 26 exposed through the opening 66, and a negative current collector plate (not shown) is connected to the shoulder portion 25B of the outer can 25 exposed through the opening 66. The gap between the opening 66 and the energy storage device 20 may be sealed with adhesive or the like. The opening that exposes the shoulder portion 25B is not shown.

[0038] [Coolant] The coolant is preferably one that has high thermal conductivity and insulating properties. Suitable coolants include, for example, water coolant, oil coolant, fluorocarbons (liquid coolants), liquid cooling gas (refrigerant), and non-aqueous coolants (special coolants). Water coolants may contain ethylene glycol or propylene glycol. Insulating mineral oil or synthetic oil may be used as the oil coolant.

[0039] [Upper Holder (Other Embodiments)] Using Figures 5 and 6, upper holders 160 and 260, which are other examples of embodiments, will be described.

[0040] The following describes a configuration that differs from the upper holder 60 described above. Furthermore, the description of a configuration similar to the upper holder 60 described above may be omitted.

[0041] As illustrated in Figure 4, the upper holder 160 houses the upper part of the energy storage device 20. The upper holder 160 has a housing section 161 for housing multiple energy storage devices 20, which will be described in detail later, a side wall 162 surrounding the housing section 161, a holding section 163 for holding the upper end of the energy storage device 20, an overhanging section 164 that extends into the gap between adjacent energy storage devices 20, a recess 165 formed on the bottom surface of the overhanging section 164, and an opening 166 formed in the holding section 163.

[0042] The protruding portion 164 is formed in the shape of a punched plate with holes that, when viewed from below, have a diameter slightly larger than the outer diameter of the energy storage device 20. In other words, the protruding portion 164 is formed by the portion of the housing portion 161 of the upper holder 160 that protrudes downward, excluding the holding portion 163. The protruding portion 164 supports the side surface of the energy storage device 20.

[0043] The recess 165 is a portion for storing the heating liquid generated within the holder. According to the recess 165, although details will be described later, the reliability of the power storage module 10 can be improved. The recess 65 is formed on the bottom surface of the protruding portion 164. In other words, the recess 165 is formed on the ceiling surface of the gap between the power storage devices 20 in the accommodating portion 161 of the upper holder 160. Further, the recess 165 is formed on the ceiling surface of the gap between the power storage device 20 and the side wall 162 in the accommodating portion 161 of the upper holder 160.

[0044] The recess 165 is formed so as to at least surround the power storage device 20 on the bottom surface of the protruding portion 164. Further, the recess 165 is formed in a groove shape communicating with each other on the bottom surface of the protruding portion 164.

[0045] According to the recess 165, the heating liquid can be stored. Thereby, the transfer of heat from the heating liquid to the power storage device 20 is hindered. As a result, it is possible to avoid a member (for example, the gasket 29) that is vulnerable to the heat of the power storage device 20 from becoming high temperature and melting, and the power storage device 20 from short-circuiting. Thereby, the reliability of the power storage module 10 can be improved. Further, by the recesses 165 communicating with each other, the volume for storing the heating liquid can be increased. Further, when the recess 165 is filled with the coolant, the heating liquid can be cooled more quickly. Furthermore, the opening area of the recess 165 increases, and the opportunity to accommodate the heating liquid in the recess 165 increases.

[0046] As illustrated in FIG. 5, the upper holder 260 houses the upper portion of the power storage device 20. The upper holder 260 has an accommodating portion 261 for accommodating a plurality of power storage devices 20, a side wall 262 surrounding the accommodating portion 261, a holding portion 263 for holding the upper end portion of the power storage device 20, a protruding portion 264 that protrudes into the gap between adjacent power storage devices 20, a recess 265 formed on the bottom surface of the protruding portion 264, and an opening 266 formed in the holding portion 263, the details of which will be described later.

[0047] The protruding portion 264 is provided in the gap between three adjacent power storage devices 20. However, the protruding portion of the present invention is not limited to this, and it may be provided in the gap between two or four adjacent power storage devices. The protruding portion 264 is formed in a substantially triangular prism shape. However, the recess of the present invention is not limited to this, and it may be recessed and formed in a cylindrical shape or other polygonal prism shape. The protruding portion 264 is formed such that, for example, the lower end of the protruding portion 264 extends below the groove portion 25A of the outer can 25 of the power storage device 20.

[0048] The recess 265 is a portion for storing the heating liquid. The recess 265 is formed on the bottom surface of the protruding portion 264. In other words, the recess 265 is formed on the ceiling surface of the gap between the power storage devices 20 in the accommodating portion 261 of the upper holder 260. Also, the recess 265 is formed on the ceiling surface of the gap between the power storage device 20 and the side wall 262 in the accommodating portion 261 of the upper holder 260.

[0049] The recess 265 is formed to be recessed, for example, in a triangular prism shape. However, the recess of the present invention is not limited to this, and it may be recessed and formed in a cylindrical shape or other polygonal prism shape. Also, the recess of the present invention may be recessed and formed in a conical shape or other polygonal pyramid shape.

[0050] The recess 265 is formed below the groove portion 25A of the outer can 25 of the power storage device 20. In other words, the ceiling surface of the recess 265 is located below the groove portion 25A of the outer can 25 of the power storage device 20. The volume of the recess 265 is preferably as large as possible for storing the heating liquid. However, even when the recess 265 is formed, it is preferable that the strength of the upper holder 260 is not less than a predetermined strength.

[0051] According to the recess 265, the heating liquid can be stored in the recess 265. Also, since the recess 265 is formed below the groove portion 25A of the outer can 25 of the power storage device 20, the transfer of heat from the heating liquid to the gasket 29 of the power storage device 20 is surely prevented. As a result, it is possible to avoid the gasket 29 of the power storage device 20 becoming high temperature and melting, and the power storage device 20 short - circuiting. Thereby, the reliability of the power storage module 10 can be improved.

[0052] [Summary] The present disclosure will be further described by the following embodiments. Configuration 1: A power storage module comprising a plurality of energy storage devices and a holder that houses the plurality of energy storage devices in a housing section, wherein the energy storage devices are immersed in a coolant filled in the housing section of the holder, and at least one recess is formed in the ceiling surface facing the coolant, which is provided in the gaps between adjacent energy storage devices in the housing section. Configuration 2: The power storage module according to Configuration 1, wherein the housing section is surrounded by side walls, and at least one of the recesses is formed in the ceiling surface in the gap between the energy storage device and the side wall. Configuration 3: The power storage module according to Configuration 1, wherein the plurality of energy storage devices include three or more energy storage devices, at least one of the recesses includes a plurality of recesses formed between these three or more energy storage devices, at least one of the recesses is formed in regions corresponding to a plurality of gaps, and the plurality of gaps are in communication with each other. Configuration 4: The energy storage module according to Configuration 1, wherein at least one of the recesses is formed below the groove of the outer casing of the energy storage device. Configuration 5: The energy storage module according to Configuration 1, wherein the cross-section of at least one of the recesses is formed as a tapered shape in the height direction, with the inner dimensions decreasing as it approaches the bottom from the opening. Configuration 6: The energy storage module according to any one of Configurations 1 to 5, wherein the holder is divided into a lower holder that accommodates the axial lower part of the energy storage device and an upper holder that accommodates the axial upper part of the energy storage device, and at least one of the recesses is provided in the upper holder.

[0053] It should be noted that this disclosure is not limited to the embodiments and their modifications described above, and various changes and improvements are possible within the scope of the claims of this application.

[0054] 10 Energy storage module, 20 Energy storage device, 21 Positive electrode, 22 Negative electrode, 23 Separator, 24 Electrode group, 25 Outer casing, 25A Groove, 25B Shoulder, 26 Sealing body, 27 Positive electrode lead, 28 Negative electrode lead, 29 Gasket, 30 Insulating plate, 40 Holder, 50 Lower holder, 51 Housing section, 52 Side wall, 53 Retaining section, 55 Recess, 58 Coolant inlet, 59 Coolant outlet, 60, 160, 260 Upper holder, 61, 161, 261 Housing section, 62, 162, 262 Side wall, 63, 163, 263 Retaining section, 64, 164, 264 Protruding section, 65, 165, 265 Recess, 66, 166, 266 Opening

Claims

1. An energy storage module comprising a plurality of energy storage devices and a holder that houses the plurality of energy storage devices in a housing section, wherein the energy storage devices are immersed in a coolant filled in the housing section of the holder, and at least one recess is formed in the ceiling surface facing the coolant, which is provided in the gaps between adjacent energy storage devices in the housing section.

2. The storage module according to claim 1, wherein the housing is surrounded by side walls, and at least one of the recesses is formed in the ceiling surface in the gap between the energy storage device and the side wall.

3. The energy storage module according to claim 1, wherein the plurality of energy storage devices comprises three or more energy storage devices, at least one recess comprises a plurality of recesses formed between the three or more energy storage devices, at least one recess is formed in a region corresponding to a plurality of gaps, and the plurality of gaps are in communication with each other.

4. The energy storage module according to claim 1, wherein at least one of the recesses is formed below the groove of the outer casing of the energy storage device.

5. The energy storage module according to claim 1, wherein the cross-section of at least one of the recesses is formed as a tapered shape in the height direction, with the inner dimensions decreasing as it approaches the bottom from the opening.

6. The holder is divided into a lower holder for housing the lower part of the energy storage device in the axial direction and an upper holder for housing the upper part of the energy storage device in the axial direction, and at least one of the recesses is provided in the upper holder, the energy storage module according to any one of claims 1 to 5.

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