Electric power storage module

Abstract

A battery pack (1) comprises: a case (10); a plurality of batteries (30) that are accommodated in the case (10); a cooling liquid (50) that fills the case (10); a first holder (61) that is disposed in the case (10) and accommodates the upper parts of the plurality of batteries (30); and a filling member (80) that is disposed between the plurality of batteries (30) and the first holder (61) and prevents the cooling liquid (50) from circulating. The plurality of batteries (30) are immersed in the cooling liquid (50) in the case (10).

Description

Energy storage module

[0001] The present disclosure relates to an energy storage module that houses a plurality of energy storage devices.

[0002] Conventionally, a power storage module accommodates multiple power storage devices, which are connected in parallel and in series to obtain a predetermined capacity and voltage. Power storage devices include secondary batteries such as lithium-ion batteries and capacitors.

[0003] In conventional energy storage modules, the energy storage device generates heat in response to charging and discharging, etc., and this heat needs to be cooled. For example, in a battery pack, which is an energy storage module that uses batteries as the energy storage device and houses multiple batteries, a liquid immersion cooling method that uses an insulating coolant is known as a cooling method.

[0004] Patent document 1 discloses that a cooling method using a coolant is adopted, and when gas is generated due to a battery abnormality, the gas is not discharged directly to the outside, but is discharged to the outside through a separate space within the battery pack, thereby preventing the coolant from leaking to the outside.

[0005] Japanese Patent Application Laid-Open No. 2008-276997

[0006] An energy storage module according to one embodiment of the present disclosure comprises a case, a plurality of energy storage devices housed within the case, a coolant filled within the case, a holder disposed within the case and housing the upper portions of the plurality of energy storage devices, and a filling member disposed between the plurality of energy storage devices and the holder and preventing the flow of the coolant, and the plurality of energy storage devices are immersed in the coolant within the case.

[0007] According to the present disclosure, the reliability of the energy storage module is improved.

[0008] Fig. 2 is a perspective view of a battery pack, which is an example of a power storage module according to an embodiment; Fig. 3 is a cross-sectional view taken along the line AA in Fig. 1; Fig. 4 is a plan view of a first holder, viewed from below, with a battery removed; Fig. 5 is a cross-sectional view of a filling member, viewed from below, with a battery removed; Fig. 6 is a cross-sectional view showing the configuration of an example of a battery;

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the following embodiments do not limit the present disclosure, and configurations formed by selectively combining multiple examples are also included in the present disclosure.

[0010] The power storage device of the present disclosure may be a secondary battery using an aqueous electrolyte or a secondary battery using a nonaqueous electrolyte. The power storage device of the present disclosure may be a cylindrical battery equipped with a cylindrical (e.g., bottomed cylindrical) outer can, or a prismatic battery equipped with a prismatic outer can. In these batteries, the cylindrical outer can or prismatic outer can constitutes an outer body. Alternatively, the power storage device of the present disclosure may be a capacitor that is repeatedly charged and discharged.

[0011] In addition, in the present disclosure, a battery pack in which a plurality of batteries are housed in a case is employed as the power storage module.

[0012] "Configuration of Battery Pack" FIG. 1 is a perspective view of a battery pack 1, which is an example of an energy storage module according to an embodiment. The battery pack 1 accommodates a plurality of batteries in a case 10. An insulating coolant is stored inside the case 10, and at least a portion of the batteries are immersed in the coolant. In other words, the coolant fills at least a portion of the gaps in the case (gaps between the energy storage devices and between the holder and the case). The battery 30 may be referred to as an "energy storage device." The battery pack 1 may be referred to as an "energy storage module."

[0013] The case 10 is made of a metal such as aluminum and has a substantially rectangular parallelepiped shape. The case 10 is not limited to being made of metal, but may also be made of resin. The shape of the case 10 is also not limited to being a substantially rectangular parallelepiped.

[0014] The battery pack 1 is used as a power source for motor-driven electric devices such as electric vehicles, power tools, power-assisted bicycles, electric motorcycles, electric wheelchairs, electric tricycles, and electric carts. However, the use of the battery pack 1 is not limited to a specific purpose, and the battery pack 1 may also be used as a power source for various electric devices used indoors and outdoors, such as vacuum cleaners, radios, lighting devices, digital cameras, and video cameras, other than electric devices.

[0015] FIG. 2 is a cross-sectional view taken along line AA in FIG. 1 (a diagram schematically showing a cross section when cut along the XZ plane passing through the center of the battery pack 1 in the width direction).

[0016] The battery pack 1 includes a battery block 20 that houses multiple batteries 30 inside a case 10. In this example, cylindrical lithium-ion batteries are used as the batteries 30. A cap 45 is placed on top of the batteries 30.

[0017] Coolant 50 is stored inside the case 10, and at least a portion of the battery 30 is immersed in the coolant 50. In this example, the entire battery 30 is immersed in the coolant 50.

[0018] The coolant 50 has insulating properties, which can prevent leakage of electricity from the plurality of batteries 30 through the coolant 50. Examples of the coolant 50 include insulating oil, transformer oil, silicone oil, and fluorine-based inert liquids such as hydrofluoroether.

[0019] The battery block 20 includes a plurality of batteries 30 and a holder 60 that holds the batteries 30. The holder 60 includes a first holder 61 that holds the upper ends of the batteries 30 and a second holder 62 that holds the lower ends, and both ends in the Z direction of the plurality of batteries 30 are inserted into and held in the first holder 61 and the second holder 62, respectively.

[0020] An exhaust chamber 12 is formed in the upper part of the case 10, into which gas exhausted from the safety valve of the battery 30 flows. The exhaust chamber 12 is formed between the top plate of the case 10 and the first holder 61. The exhaust chamber 12 is formed on the surface of the coolant inside the case 10, and an exhaust port 14 is provided in part of the side wall of the case 10, which exhausts gas inside the exhaust chamber 12 to the outside of the case 10. Therefore, if the pressure inside the battery 30 increases due to abnormal heat generation of the battery 30, the gas generated inside the battery 30 is exhausted to the outside of the case 10 via the safety valve, exhaust chamber 12, and exhaust port 14.

[0021] "Holder Configuration" As described above, the holder 60 of the battery block 20 includes a plurality of batteries 30, a first holder 61 that holds the upper ends of the batteries 30, and a second holder 62 that holds the lower ends of the batteries 30.

[0022] 3 is a view of the first holder 61 as seen from above. As such, the first holder 61 includes a cylindrical recess 63 that accommodates the upper shoulder of the battery 30, and an opening 64 that exposes the top surface of the cap 45 of the battery 30. The recess 63 is formed on the lower surface of the first holder 61, is circular when viewed from below in the Z direction, and has concave cross sections in the X and Y directions.

[0023] The opening 64 is formed as a circular hole having a diameter smaller than the diameter of the circular recess 63 when viewed from below in the Z direction. Furthermore, the recess 63 and the opening 64 are formed so that their centers coincide with each other when viewed from below in the Z direction.

[0024] A positive electrode wiring may be provided on the surface of the first holder 61, and a positive electrode lead may be extended from this into the opening 64 and connected to the positive electrode external terminal of the battery 30. The cap 45 may also serve as the positive electrode external terminal. Depending on the battery 30, the negative electrode external terminal may also be accessible from the top end. In this case, a negative electrode wiring may also be provided on the first holder 61 and connected to the negative electrode external terminal of the battery 30 via the negative electrode lead.

[0025] The second holder 62 holds the lower shoulder (bottom) of the battery 30, and can have the same structure as the first holder 61 simply by turning it upside down.

[0026] The holder 60 (61, 62) may be made of, for example, a highly thermally conductive PPS (polyphenylene sulfide) resin, a resin containing a heat-dissipating filler, an injection-moldable thermosetting resin, etc. More specifically, the holder 60 may be made of a phenolic resin, an unsaturated polyester, an unsaturated polyester mixed with a heat-absorbing agent, etc. The holder 60 may also be made of an inorganic mineral such as mica, or a resin material mixed with an inorganic mineral such as mica.

[0027] Furthermore, when the battery 30 generates abnormal heat, gas discharged from the safety valve of the battery 30 can flow into the exhaust chamber 12 through the opening 64 .

[0028] "Configuration of Filler Member" In this embodiment, the filler member 80 is arranged so as to cover the lower side (lower side and bottom surface) of the first holder 61. The filler member is also arranged so as to fill the gap between the first holder 61 and the power storage device.

[0029] FIG. 4 shows the filler member 80 viewed from below with the batteries 30 removed. The filler member 80 has a bottom 81 located between the side walls of the batteries 30 and a wall 82 extending from the bottom 81 upward along the side of the batteries 30 and toward the top of the batteries 30. The wall 82 terminates at a position equivalent to the opening 64 of the first holder 61, forming an opening 83. The wall 82 may terminate just before the opening 64 of the first holder 61, or may extend into the opening 64 and terminate there. As long as it can fill the gap, it may be formed only below the top of the batteries in the axial direction. The filler member may also extend outward from the holder opening. It is preferable that the filler member 80 cover the surface of the upper part of the exterior can, such as the shoulder of the battery 30, that faces the resin member, such as a gasket.

[0030] The filling member 80 may be formed in the first holder 61 in advance, and the battery 30 may be inserted later, or the filling member 80 may be inserted after the battery 30 is accommodated in the recess 63 of the first holder 61. The first holder 61 and the upper surface of the filling member 80 may also be bonded together with an adhesive or the like.

[0031] The filling member 80 is preferably made of a resin material that does not melt when exposed to high-temperature coolant. Furthermore, the filling member 80 can be elastically deformable to prevent coolant from flowing between the filling member 80 and the battery 30. In other words, by compressing and deforming the filling member 80, the gaps around the battery 30 can be reliably filled. Materials such as rubber and foamed resin can be used for the filling member 80. Furthermore, UV-curable resin can be used for the filling member 80. In the case of UV-curable resin, the gaps around the battery 30 can be filled by applying a liquid material before hardening and then hardening it. This effectively prevents high-temperature coolant from flowing through the gaps. Furthermore, if the filling member 80 is made of a material with better thermal insulation properties than the holder, thermal damage to the upper part of the battery can be reduced.

[0032] In this manner, in this embodiment, the filler member 80 is placed on the side so as to cover the underside of the first holder 61 that holds the upper ends of the batteries 30. Therefore, if one battery 30 experiences thermal runaway due to an abnormality and the coolant around it becomes hot (or vaporizes), the high-temperature coolant below the filler member 80 can be prevented from reaching the top of the battery 30 from the periphery. This prevents the heat from the high-temperature coolant from heating the top of the battery 30 and melting or softening the resin parts.

[0033] This prevents the battery pack 1 from being put into a dangerous state due to a short circuit of surrounding normal batteries 30 when one battery 30 experiences thermal runaway.

[0034] "Battery Configuration" FIG. 3 is a cross-sectional view showing an example of the configuration of a battery 30, which is an example of an electricity storage device. The battery 30 is a cylindrical battery and a lithium ion battery. However, the battery 30 is not limited to a cylindrical battery, and may be a prismatic battery, a laminated battery, or the like. The battery 30 may also be an aqueous battery or a non-aqueous battery. A lithium ion battery is preferably used as an example of a non-aqueous battery.

[0035] The battery 30 has an electrode assembly 34, an electrolyte (not shown), and an exterior body 35 that houses the electrode assembly 34 and the electrolyte. The electrode assembly 34 has a positive electrode 31, a negative electrode 32, and a separator 33, and has a wound structure in which the positive electrode 31 and the negative electrode 32 are wound in a spiral shape with the separator 33 interposed therebetween.

[0036] The exterior body 35 has a cylindrical shape with a bottom and an open top, and the opening of the exterior body 35 is closed by a sealing body 36 .

[0037] The battery 30 includes insulating plates 37, 38 disposed above and below the electrode body 34. In the example shown in Fig. 3, a positive electrode lead 39 attached to the positive electrode 31 passes through a through-hole in the insulating plate 37 and extends toward the sealing body 36, and a negative electrode lead 40 attached to the negative electrode 32 passes outside the insulating plate 38 and extends toward the bottom side of the exterior body 35. The positive electrode lead 39 is connected by welding or the like to the underside of an internal terminal plate 41, which is the bottom plate of the sealing body 36, and a cap 45, which is the top plate of the sealing body 36 and is electrically connected to the internal terminal plate 41, serves as a positive electrode external terminal. The negative electrode lead 40 is connected by welding or the like to the inner surface of the bottom of the exterior body 35, and the bottom of the exterior body 35 serves as a negative electrode external terminal.

[0038] The sealing body 36 has a structure in which, in order from the electrode body 34 side, an internal terminal plate 41, a lower valve body 42, an insulating member 43, an upper valve body 44, and a cap 45 are stacked. The components constituting the sealing body 36 are, for example, disk-shaped or ring-shaped, and all components except for the insulating member 43 are electrically connected to one another. The lower valve body 42 and the upper valve body 44 are connected to one another at their respective centers, with the insulating member 43 interposed between their respective peripheral edges.

[0039] The peripheral portion of sealing body 36, which is formed by laminating internal terminal plate 41, lower valve body 42, insulating member 43, upper valve body 44, and cap 45, is covered by resin gasket 46 and exterior body 35 located on the outside thereof. In other words, exterior body 35 is crimped so as to enclose the peripheral portion of sealing body 36, thereby sealing the peripheral portion of sealing body 36 with gasket 46.

[0040] The lower valve body 42, upper valve body 44, and cap 45 constitute a safety valve for the sealing body 36. When the internal pressure rises due to abnormal heat generation in the battery 30, the lower valve body 42 deforms and ruptures, pushing the upper valve body 44 toward the cap 45, thereby interrupting the current path between the lower valve body 42 and the upper valve body 44. When the internal pressure rises further, the upper valve body 44 ruptures, and gas is exhausted from an exhaust hole 45A formed on the side of the convex portion of the cap 45.

[0041] DESCRIPTION OF SYMBOLS 1 Battery pack (energy storage module) 10 Case 12 Exhaust chamber 20 Battery block 30 Battery (energy storage device) 31 Positive electrode 32 Negative electrode 33 Separator 34 Electrode body 35 Exterior body 36 Sealing body 37 Insulating plate 38 Insulating plate 39 Positive electrode lead 40 Negative electrode lead 41 Internal terminal plate 42 Lower valve body 43 Insulating member 44 Upper valve body 45 Cap 45A Exhaust hole 46 Gasket 50 Coolant 60 Holder 61 First holder 62 Second holder 63 Recess 64 Opening 80 Filling member 81 Bottom 82 Wall 83 Opening

Claims

1. An energy storage module comprising: a case; a plurality of energy storage devices housed within the case; a cooling liquid filled within the case; a holder disposed within the case and housing upper portions of the plurality of energy storage devices; and a filling member disposed between the plurality of energy storage devices and the holder and blocking the flow of the cooling liquid, wherein the plurality of energy storage devices are immersed in the cooling liquid within the case.

2. The energy storage module according to claim 1, wherein the filling member is in contact with sides of the plurality of energy storage devices so as to prevent the cooling liquid located below the filling member from reaching the tops of the plurality of energy storage devices.

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