Battery pack

Abstract

The battery pack accommodates a plurality of batteries in a case. The plurality of batteries are provided with safety valves, and are immersed in the cooling liquid in the housing, and the safety valves are opened due to an increase in internal pressure and discharge internal gas. The housing is provided with: a liquid sealing part in which a cooling liquid is sealed; and a wall part which is provided below the liquid sealing part and which separates the liquid sealing part from the cooling liquid non-sealing space. End portions of the plurality of batteries close to the safety valve are in contact with or closely opposed to a surface of the wall portion close to the liquid sealing portion.

Description

Technical Field

[0001] The present invention relates to a battery pack that houses a plurality of batteries. Background Art

[0002] Regarding secondary batteries such as lithium ion batteries, they are used in the form of a battery pack in which a plurality of batteries are electrically connected and housed in a case. A battery pack is disclosed in Patent Document 1: a battery is housed in a space filled with a coolant to cool the battery.

[0003] Prior art documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2014 - 60088 Summary of the Invention

[0006] When a battery in the battery pack is abnormal, heat is generated inside the battery, and the surface of the outer package of the battery becomes high temperature. Moreover, if the abnormality further progresses, high-temperature gas will soon be generated from inside the battery. In the battery pack disclosed in Patent Document 1, a structure is considered in which the battery has a safety valve that opens due to an increase in internal pressure. In this structure, when the battery is abnormal, gas is discharged from the safety valve to prevent damage to the battery case caused by the increase in the internal pressure of the battery.

[0007] In addition, when a part of the batteries in the battery pack undergoes thermal runaway due to an abnormality, it is considered that the thermal runaway will spread chain-reaction to the surrounding batteries. To suppress the spread of this thermal runaway, consideration is given to increasing the distance between adjacent batteries in the battery pack, that is, the neighboring batteries. However, in this case, there is a problem that the volume of the battery pack increases.

[0008] In addition, to suppress the spread of the above-mentioned thermal runaway, consideration is given to providing a member with a low thermal conductivity or a member with a high heat capacity between adjacent batteries. However, in this case, since the number of components of the battery pack increases, the cost of the battery pack increases or the energy density decreases.

[0009] A battery pack according to one aspect of the present invention includes: a case; and a plurality of batteries housed in the case, wherein the plurality of batteries have safety valves and are immersed in a coolant in the case, the safety valve opens due to an increase in internal pressure and discharges the internal gas, the case has: a liquid enclosure portion that encloses the coolant; and a wall portion provided below the liquid enclosure portion that separates the liquid enclosure portion from a space not filled with the coolant, and an end portion of the plurality of batteries near the safety valve contacts or faces relatively close to a surface of the wall portion near the liquid enclosure portion.

[0010] According to the battery pack of one aspect of the present invention, it is possible to suppress an increase in the volume of the battery pack and an increase in the number of components, and to suppress the expansion of thermal runaway among a plurality of batteries when an abnormality occurs in a battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a perspective view of a battery pack as an example of an embodiment.

[0012] Figure 2 yes Figure 1 A-A section view.

[0013] Figure 3 It is a cross-sectional view of a battery constituting the battery pack according to the embodiment.

[0014] Figure 4 In the embodiment, when an abnormality occurs in a part of the batteries, the batteries are cooled preferentially. Figure 2 The corresponding figure.

[0015] Figure 5 In another example of the embodiment, a battery pack is provided with Figure 2 The enlarged view of part B corresponds to the figure.

[0016] Figure 6 It means in Figure 5 Middle Edge Figure 5 A schematic diagram showing the state of the battery and the wall portion when viewed in the direction of arrow C.

[0017] Figure 7 is another example of an embodiment in which a state in which a part of the batteries is cooled preferentially when an abnormality occurs in the batteries. Figure 5 The corresponding figure.

[0018] Figure 8 In another example of the embodiment, a battery pack is provided with Figure 2 The corresponding figure. DETAILED DESCRIPTION

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, schematic diagrams are included in a plurality of drawings, and the dimensional ratios of the length, width, height, etc. of each component may not be consistent between different drawings. In addition, among the constituent elements described below, constituent elements not described in the independent claims representing the highest concept are arbitrary constituent elements and are not essential constituent elements.

[0020] In addition, in the following embodiments, the case where the battery pack 1 has a substantially rectangular parallelepiped outer shape will be described as an example. In the drawings and the description of the embodiments, the X direction represents the length direction of the battery pack 1 (the housing 10), the Y direction represents the width direction of the battery pack 1 (the housing 10), and the Z direction represents the up-down direction (height direction) of the battery pack 1 (the housing 10). The X direction, the Y direction, and the Z direction are orthogonal to each other. In addition, in the Z direction, Figure 3 the side of the battery 30 shown in which the lid 45 is provided is set as the "lower side", and the opposite side thereof is set as the "upper side".

[0021] Refer to Figure 1 and Figure 2 to describe the schematic structure of the battery pack 1. Figure 1 is a perspective view of the battery pack 1 as an example of the embodiment. Figure 2 is Figure 1 a sectional view taken along line A-A (a sectional view when cutting by the XZ plane passing through the center in the width direction of the battery pack 1).

[0022] The battery pack 1 includes a battery block 20 having a plurality of batteries 30 and a housing 10 that houses the battery block 20. The battery 30 uses a non-aqueous electrolyte secondary battery such as a lithium ion battery, and there are no particular limitations on its shape, size, etc., but a cylindrical battery is preferably used. Hereinafter, the case where the battery 30 is a cylindrical battery will be mainly described.

[0023] The housing 10 is in the shape of a box having a substantially rectangular parallelepiped outer shape. A liquid filling portion 11 filled with an insulating coolant 50 is provided inside the housing 10, and a part of each battery 30 is immersed in the coolant 50 in the liquid filling portion 11. Thus, since the coolant 50 is in direct contact with each battery 30, the cooling performance of each battery 30 can be improved.

[0024] Each of the plurality of batteries 30 has a safety valve 37, and the safety valve 37 opens due to an increase in internal pressure and discharges the internal gas. The housing 10 includes a first holding member 61 described later, and the first holding member 61 is provided on the lower side of the liquid filling portion 11 and separates the liquid filling portion 11 from a liquid discharge chamber 12 on the lower side of the liquid filling portion 11. The liquid discharge chamber 12 corresponds to a space where the coolant is not filled. The first holding member 61 corresponds to a wall portion. The lower end portions of the plurality of batteries 30 on the side of the safety valve 37 are in contact with or relatively close to the surface of the first holding member 61 on the side of the liquid filling portion 11. Thus, as described later, an increase in the volume of the battery pack 1 and an increase in the number of components can be suppressed, and the spread of thermal runaway between the plurality of batteries 30 when an abnormality occurs in the battery 30 can be suppressed.

[0025] The battery pack 1 is mainly used as a power source for driving. The battery pack 1 is used, for example, as a power source for electric devices driven by a motor such as an electric vehicle, an electric tool, an electric assist bicycle, an electric motorcycle, an electric wheelchair, an electric tricycle, an electric handcart, etc. In addition, the use of the battery pack 1 is not specific, and it can also be used as a power source for electrical devices other than electric devices, such as various electrical devices used indoors and outdoors, such as a cleaner, a wireless device, a lighting device, a digital camera, a video camera, etc.

[0026] The battery block 20 has a plurality of batteries 30 and a battery holder 60 into which both end portions in the vertical direction Z of the battery 30 are inserted and held. The battery block 20 is disposed in a portion of the housing 10 from the upper end portion inside to the middle portion in the vertical direction Z. Thereby, a liquid discharge chamber 12 described later is formed at the lower end portion inside the housing 10.

[0027] The battery 30 has a safety valve 37, and the safety valve 37 opens due to an increase in internal pressure and discharges the internal gas. In the present embodiment, the safety valve 37 is provided at the lower end portion of the battery 30, and details will be described later. Specifically, taking the first direction as the vertical direction, a plurality of batteries 30 are arranged in the housing 10 in the vertical direction such that the safety valve 37 is located at the lower end portion which is one end portion in the first direction. When the internal pressure of the battery 30 rises due to an abnormality in the battery 30, the gas is discharged from an exhaust hole 45a formed in the lid 45 constituting the safety valve 37 (refer to Figure 3 ).

[0028] The battery holder 60 includes a first holder 61 that holds the lower side of the battery 30 and a second holder 62 that holds the upper side of the battery 30. The first holder 61 has a recess 63 into which the lid 45, which is the front end of the lower end portion of the battery 30, enters. At the opening end portion of the recess 63, a stepped portion 64 having a circular cross section is formed over the entire circumference. The lower end portion of the battery 30 is held at the stepped portion 64. The lid 45 constitutes the safety valve 37 of the battery 30.

[0029] Refer to Figure 1 and Figure 2 The housing 10 will be described in detail.

[0030] The housing 10 is made of a metal such as aluminum or a resin and has a substantially rectangular parallelepiped outer shape. Specifically, the housing 10 has two first side walls 10a, 10b disposed at both ends in the length direction X and two second side walls 10c disposed at both ends in the width direction Y. The housing 10 has a function of protecting the batteries 30 stored inside from dust and water.

[0031] As Figure 2 shown, a liquid enclosure portion 11 for enclosing a coolant 50 is provided inside the housing 10. The liquid enclosure portion 11 also functions as a battery storage chamber for storing a plurality of batteries 30.

[0032] Specifically, the liquid enclosure portion 11 is a portion defined by the housing 10, the first holding member 61, and the second holding member 62, and is a portion where the batteries 30 are disposed except for both ends in the vertical direction Z. A coolant 50 is enclosed in the liquid enclosure portion 11, and parts of the respective batteries 30 are partially immersed in the coolant 50. From the viewpoint of efficiently cooling the batteries 30, it is preferable that the coolant 50 occupies more than half of the volume of the liquid enclosure portion 11. In the Figure 2 example, the coolant 50 fills the entire liquid enclosure portion 11. Alternatively, the coolant 50 may be enclosed only in a part of the liquid enclosure portion 11, and a space is formed in the remaining part. In this way, the batteries 30 are in contact with the coolant 50 and are directly cooled, so that the batteries 30 can be efficiently cooled. Thereby, the charging performance, durability, and safety of the batteries 30 can be improved.

[0033] In addition, the coolant 50 has insulating properties. Thereby, it is possible to prevent the batteries 30 from leaking electricity to other batteries 30 via the coolant 50. Examples of the coolant 50 include insulating oils, transformer oils, silicone oils, and fluorine-based inactive liquids such as hydrofluoroethers.

[0034] As Figure 2 shown, a liquid discharge chamber 12 is provided below the lower end portion inside the housing 10 and below the liquid enclosure portion 11 with the first holding member 61 interposed therebetween. The liquid discharge chamber 12 is a coolant-unenclosed space provided below the first holding member 61. The first holding member 61 is provided below the liquid enclosure portion 11 and separates the liquid enclosure portion 11 and the liquid discharge chamber 12 so that liquid does not flow between them. For this purpose, the outer peripheral surface of the first holding member 61 is hermetically fixed to the inner peripheral surface of the housing 10, and there is no hole penetrating the first holding member 61 in the thickness direction. In addition, as described above, the lower end portions of the plurality of batteries 30, which are the end portions on the side of the safety valve 37, contact or face closely to the surface of the first holding member 61 on the liquid enclosure portion 11 side. When the pressure inside the battery 30 rises in the event of an abnormality in the battery 30, the gas generated inside the battery 30 is discharged from the exhaust hole 45a of the lid 45 (refer to Figure 3 ), and the details will be described later. At this time, the portion of the first holding member 61 that contacts or faces closely to the lower end portion of the battery 30 in which the abnormality has occurred is melted and damaged under the influence of contact with the high-temperature gas. In this way, when the first holding member 61 is damaged, the liquid discharge chamber 12 receives the coolant 50 discharged from the liquid enclosure portion 11.

[0035] The housing 10 is provided at one end in the length direction X as the second direction ( Figure 2At the lower end of the first side wall 10a (on the right end) facing the liquid discharge chamber 12, there is an exhaust portion 13 which is a through hole. As described above, when the first holding member 61 is damaged under the influence of contact with the high-temperature gas from the battery 30 and the coolant 50 is discharged from the liquid filling portion 11 to the liquid discharge chamber 12, the high-temperature and high-pressure gas from the abnormal battery 30 is also discharged to the liquid discharge chamber 12. At this time, the above-mentioned exhaust portion 13 discharges the gas from the liquid discharge chamber 12 to the outside of the housing 10.

[0036] The size of the exhaust portion 13 is not particularly limited as long as it can discharge the gas inside the housing 10 and suppress the rupture of the housing 10. The exhaust portion 13 may always be open, but may also be a structure having a function of breaking and opening in response to the increase in the pressure inside the housing 10 when an abnormality occurs. Thereby, it is possible to prevent dust and water from entering the inside of the housing 10 while suppressing the rupture of the housing 10.

[0037] The housing 10 may also have a covering member covering the exhaust portion 13. Thereby, it is possible to further suppress dust and water from entering the inside of the housing 10. The covering member is fixed to the outer surface or the inner surface of the housing 10 by fixing means such as an adhesive so as to block the exhaust portion 13. The covering member may also be made of a breathable and waterproof material such as GORE-TEX (registered trademark) that allows the exhaust from the inside of the housing 10 to pass through and blocks liquids such as water from the outside.

[0038] Refer to Figure 2 The battery block 20 will be described. As described above, the battery block 20 has a battery holding member 60 into which the axial end portions of a plurality of batteries 30 are inserted and held.

[0039] The battery block 20 includes a positive terminal plate 70 that abuts against the lower surface of the first holding member 61 and a negative terminal plate 80 that abuts against the upper surface of the second holding member 62. The positive terminal plate 70 and the lid 45 which is the positive external terminal of the battery 30 are electrically connected by a positive lead portion (not shown). In addition, the negative terminal plate 80 and the bottom of the outer package 35 (refer to Figure 3 ) which is the negative external terminal of the battery 30 are electrically connected by a negative lead portion (not shown). The positive terminal plate 70 and the negative terminal plate 80 connect a plurality of batteries 30 in parallel.

[0040] The battery holder 60 may also be made of, for example, PC (polycarbonate) resin, high thermal conductivity PPS (polyphenylene sulfide) resin, resin containing a heat dissipation filler, an injectable thermosetting resin, etc. More specifically, the battery holder 60 may also be made of phenolic resin, unsaturated polyester, or unsaturated polyester mixed with an endothermic agent. The first holder 61 of the battery holder 60 preferably uses the following resin material, which is liable to melt and be destroyed under the action of contact with the high-temperature gas discharged from the battery 30 when an abnormality occurs in the battery 30.

[0041] The recess 63 of the first holder 61 is a circular and bottomed hole formed in the upper surface of the first holder 61. A stepped portion 64 having a circular cross-section is provided at the opening end of the recess 63. The shoulder 46 (see Figure 3 ) of the outer peripheral surface of the lower end portion of the battery 30, which has an outer diameter larger than the outer diameter of the lid 45, is fitted and contacts the cylindrical portion of the stepped portion 64. Thus, the first holder 61 holds the lower side of the battery 30.

[0042] In addition, a space is formed between the recess 63 and the outer surface of the lid 45. Therefore, a gap is formed between the exhaust hole 45a (described later) opened in the outer peripheral surface of the lid 45 and the inner peripheral surface of the recess 63. In addition, the lower end surface of the lid 45, which is the front end surface, and the bottom surface of the recess 63 are opposed to each other with a small gap therebetween. The exhaust hole 45a of the lid 45 communicates with the space inside the recess 63. The plate thickness of the portion of the first holder 61 where the bottom of the recess 63 is formed is made to be a size that is liable to melt under the action of contact with the high-temperature gas.

[0043] A part of the above-mentioned positive electrode lead portion connected to the positive electrode terminal plate 70 is partially buried near the recess 63 of the first holder 61. The portion of the positive electrode lead that is led out from the inner surface of the recess 63 of the first holder 61 is electrically connected to the lid 45. The positive electrode lead portion may also be a portion integrally formed with the positive electrode terminal plate 70.

[0044] The second holder 62 includes a holding portion 65 that holds the upper end portion of the battery 30 and an opening portion 66 that exposes the bottom surface of the battery 30 toward the top plate side of the housing 10. The holding portion 65 of the second holder 62 is a circular hole formed in the lower surface of the second holder 62. By fitting the upper end portion of the battery 30 into the holding portion 65, the upper side of the battery 30 is held.

[0045] The opening portion 66 is formed to penetrate the second holder 62 in the vertical direction. The above-mentioned negative electrode lead portion is connected to the bottom of the battery 30 through the opening portion 66. The negative electrode lead portion may also be a portion integrally formed with the negative electrode terminal plate 80.

[0046] Refer to Figure 3 Describe the battery 30. In Figure 3is shown in a state where the orientation of the battery 30 in the vertical direction is opposite to that in the case where the battery 30 is assembled into the battery pack 1 and used as shown in Figure 2 . That is, Figure 2 the bottom of the battery 30 shown in Figure 3 is the upper side of the battery 30 in the actual use state. Figure 3 The battery 30 is a cylindrical battery and is a lithium-ion battery. In addition, the battery 30 is not limited to a cylindrical battery, and may also be a square battery, a laminated battery, etc. Further, the battery 30 may be an aqueous battery or a non-aqueous battery. As an example of the non-aqueous battery, a lithium-ion battery is preferably used.

[0047] The battery 30 has an electrode body 34, an electrolyte (not shown), and an outer package 35 that houses the electrode body 34 and the electrolyte. The electrode body 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 therebetween. The outer package 35 has a bottomed cylindrical shape with an opening on the lower side (

[0048] the upper side of Figure 3 ), and the opening of the outer package 35 is blocked by a sealing body 36. Figure 3 The battery 30 includes insulating plates 38a and 38b respectively disposed on the lower side and the upper side (

[0049] the upper side and the lower side of Figure 3 ) of the electrode body 34. In the example shown in Figure 3 , the positive electrode lead 39 attached to the positive electrode 31 extends toward the sealing body 36 side through the through hole of the insulating plate 38a, and the negative electrode lead 40 attached to the negative electrode 32 extends toward the bottom side of the outer package 35 through the through hole of the insulating plate 38b. The positive electrode lead 39 is connected to the surface of the internal terminal plate 41 on the electrode body 34 side, which is the bottom plate of the sealing body 36, by welding or the like. The internal terminal plate 41 is electrically connected to the top plate of the sealing body 36 and is a cover 45 that serves as an external positive electrode terminal. The negative electrode lead 40 is connected to the inner surface of the bottom of the outer package 35 by welding or the like, and the bottom of the outer package 35 serves as an external negative electrode terminal. Figure 3 The sealing body 36 has a structure in which an internal terminal plate 41, a first valve element 42, an insulating member 43, a second valve element 44, and a cover 45 are laminated in order from the electrode body 34 side. Each member constituting the sealing body 36 is, for example, in a disk shape or a ring shape, and the members other than the insulating member 43 are electrically connected to each other. The first valve element 42 and the second valve element 44 are connected to each other at their respective central portions, and the insulating member 43 is sandwiched between their respective peripheral portions. Figure 3 The positive electrode lead 39 extends toward the sealing body 36 side through the through hole of the insulating plate 38a, and the negative electrode lead 40 extends toward the bottom side of the outer package 35 through the through hole of the insulating plate 38b. The positive electrode lead 39 is connected to the surface of the internal terminal plate 41 on the electrode body 34 side, which is the bottom plate of the sealing body 36, by welding or the like. The internal terminal plate 41 is electrically connected to the top plate of the sealing body 36 and is a cover 45 that serves as an external positive electrode terminal. The negative electrode lead 40 is connected to the inner surface of the bottom of the outer package 35 by welding or the like, and the bottom of the outer package 35 serves as an external negative electrode terminal.

[0050] The sealing body 36 has a structure in which an internal terminal plate 41, a first valve element 42, an insulating member 43, a second valve element 44, and a cover 45 are laminated in order from the electrode body 34 side. Each member constituting the sealing body 36 is, for example, in a disk shape or a ring shape, and the members other than the insulating member 43 are electrically connected to each other. The first valve element 42 and the second valve element 44 are connected to each other at their respective central portions, and the insulating member 43 is sandwiched between their respective peripheral portions.

[0051] In the present embodiment, a safety valve 37 of the sealing body 36 is constituted by a first valve element 42, a second valve element 44, and a lid 45. When the internal pressure rises in the event of an abnormality in the battery 30, the first valve element 42 deforms and breaks in a manner that pushes the second valve element 44 toward the lid 45 side, cutting off the current path between the first valve element 42 and the second valve element 44. If the internal pressure further rises, the second valve element 44 breaks, and gas is discharged from an exhaust hole 45a formed on the side surface of the convex portion of the lid 45.

[0052] In addition, the arrangement position of the safety valve is not limited to the present embodiment, and it may also be configured such that a safety valve is provided at the bottom of the outer package 35 of the battery 30 and internal gas is discharged from the bottom when the internal pressure of the battery rises. In this case, the safety valve at the bottom of the battery 30 is opposed to the bottom surface of a recess 63 provided on the surface of the battery 30 side of the first holding member 61, and the shoulder portion on the bottom side of the outer package 35 of the battery 30 is fitted into the cylindrical portion of a stepped portion provided at the opening end of the recess 63. At this time, the vertical orientation during use of the battery 30 is the same as Figure 3 the vertical orientation of

[0053] As described above, in the housing 10, a first holding member 61 that separates the liquid filling portion 11 and the liquid discharge chamber 12 is provided below the liquid filling portion 11. In addition, the shoulder portions 46 at the lower ends of the plurality of batteries 30, which are the ends on the safety valve side, are in contact with the surface of the first holding member 61 on the liquid filling portion 11 side, and the lid 45 is opposed to the recess 63 on the surface of the first holding member 61 on the liquid filling portion 11 side in a close manner. Thus, if the internal pressure of the battery 30 rises in the event of an abnormality in the battery 30, the gas generated inside the battery 30 is discharged into the recess 63 from the exhaust hole 45a of the lid 45 (refer to Figure 3 ). At this time, the portion of the first holding member 61 that is in contact with or opposed to the lower end of the battery 30 in which the abnormality has occurred melts and is damaged by contact with the high-temperature gas. Thus, as Figure 4 shown, a gap is generated between the lower end of a part of the battery 30 in which the abnormality has occurred and the first holding member 61, and the coolant 50 is discharged from the liquid filling portion 11 toward the liquid discharge chamber 12 in the arrow α direction from this gap. And, as Figure 4 the arrow β in Figure 4 shows, the coolant 50 diffuses in the liquid discharge chamber 12. At this time, as Figure 4 the arrow γ in

[0054] shows, the gas discharged from the battery 30 in which the abnormality has occurred is discharged to the outside of the housing 10 through an exhaust portion 13 provided on the first side wall 10a.When the coolant 50 is discharged into the liquid discharge chamber 12 through the gap between the lower end of a part of the battery 30 and the first holding member 61 like this, the coolant 50 contacts the lower end of the battery 30 while flowing. In addition, the entire coolant 50 in the liquid enclosure part 11 flows into the gap between the lower end of the battery 30 and the first holding member 61. Therefore, this battery 30 is cooled preferentially compared to other batteries 30, and thus the spread of thermal runaway between multiple batteries 30 when an abnormality occurs in the battery 30 can be suppressed.

[0055] Moreover, in order to suppress the spread of the above-mentioned thermal runaway, in the embodiment, it is not necessary to increase the distance between adjacent batteries, or to provide a member with a low thermal conductivity or a large heat capacity between adjacent batteries. Thereby, an increase in the volume of the battery pack 1 and an increase in the number of components can be suppressed.

[0056] In addition, in the housing 10, a liquid discharge chamber 12 is provided below the first holding member 61. The liquid discharge chamber 12 receives the coolant 50 discharged from the liquid enclosure part 11 when the first holding member 61 is damaged. Thereby, leakage of the coolant 50 from the liquid discharge chamber 12 to the outside of the housing 10 can be suppressed. Moreover, even when the coolant 50 is discharged to the outside of the housing 10 through the exhaust part 13, the moving speed of the coolant 50 near the battery 30 can be adjusted by adjusting the size of the exhaust part 13. Thereby, it is easy to balance the suppression of the discharge speed of the coolant 50 discharged to the outside of the housing 10 and the improvement of the cooling performance of the battery 30.

[0057] In addition, even when the coolant 50 is discharged to the outside of the housing 10 through the exhaust part 13, the position of the exhaust part 13 can be adjusted to prevent the coolant 50 from leaking to an inappropriate position outside the housing 10 through the exhaust part 13.

[0058] Figure 5 is a diagram corresponding to the enlarged view of part B in the battery pack 1a which is another example of the embodiment Figure 2 of. Figure 6 is a diagram showing Figure 5 in Figure 5 a schematic view of the state observed by viewing the battery 30 and the first holding member 61 in the direction of arrow C. Figure 7 is a diagram corresponding to Figure 5 showing the state where the battery 30 is preferentially cooled when an abnormality occurs in a part of the battery 30 in another example of the embodiment.

[0059] In the structure of this example, as Figure 5 , Figure 6As shown, a small recess 81 having a circular cross-section is locally formed in the circumferential direction so as to cover both the stepped portion 64 of the plurality of recesses 63 provided on the liquid injection portion 11 side surface of the first holding member 61 and a portion adjacent to the radially outer side of the stepped portion 64. Thus, in the first holding member 61, the distance between the recess 63 and the small recess 81 is small. Therefore, when high-temperature gas is discharged from the exhaust hole 45a of the lid 45 (refer to Figure 3 ) into the recess 63 when an abnormality occurs in the battery 30, the portion between the small recess 81 and the recess 63 of the first holding member 61 is liable to melt and be damaged under the action of the temperature of the gas. Thus, as Figure 7 shown, it is easy to generate a gap d between the outer peripheral surface of the shoulder portion at the lower end of the battery and the circumferential portion of the first holding member 61, and it is easy to discharge the coolant 50 in the liquid injection portion 11 to the liquid discharge chamber 12 through the gap d. Also in this case, similar to the structure of Figures 1 to 3 , it is possible to suppress the spread of thermal runaway between the plurality of batteries 30 when an abnormality occurs in the battery 30. Thus, in the embodiment, it is also possible to cool the battery 30 by using the coolant 50 discharged from the liquid injection portion 11 only by forming a gap between the circumferential portion of the outer peripheral surface of the battery 30 and the first holding member 61. In this example, other structures and functions are the same as those of the structure of Figures 1 to 3 .

[0060] Figure 8 FIG. is a view corresponding to Figure 2 in the battery pack 1b of another example of the embodiment. In the structure of this example, the housing 90 is the same as the structure in which the bottom plate is removed from the housing 10 and the exhaust portion 13 is omitted in the structure of Figures 1 to 3 (refer to Figure 2 ).

[0061] Thus, in the structure of this example, the liquid discharge chamber 12 (refer to Figure 2 ) is not formed at a position lower than the first holding member 61. The first holding member 61 separates the liquid injection portion 11 and the space outside the housing 90 which is a space where the coolant is not filled. In addition, the lower surface 61a on the side of the space where the coolant is not filled in the first holding member 61 forms the outer surface of the housing 90.

[0062] According to the structure of this example as well, when an abnormality occurs in the battery 30, the gas generated inside the battery 30 is discharged from the battery 30, and the portion of the first holding member 61 that contacts or faces relatively close to the lower end portion of the battery 30 melts and is damaged. As a result, a gap is generated between the lower end portion of the battery 30 and the first holding member 61, and the coolant 50 is discharged from this gap to a space outside the housing 90. Therefore, the battery 30 in which an abnormality has occurred is cooled preferentially compared to other batteries 30, and thus the spread of thermal runaway among the multiple batteries 30 when an abnormality occurs in the battery 30 can be suppressed. In this example, other structures and operations are the same as those of Figures 1 to 3 the structure.

[0063] In addition, in each of the above-described embodiments, the case where a gap is provided between the concave portion 63 of the first holding member 61 and the lid 45 of the battery 30 has been described, but the inner surface of the concave portion 63 may also be in contact with the outer surface of the lid 45 in a close-fitting manner or the like.

[0064] Furthermore, in each of the above-described embodiments, the liquid encapsulation portion 11 and the coolant non-encapsulation space are partitioned by the first holding member 61, but it is not limited thereto. For example, a wall portion formed of resin or metal may be provided inside the housing 10, and the liquid encapsulation portion 11 and the coolant non-encapsulation space may be separated by this wall portion so that the liquid does not flow between them. In this case, the safety valve side end portions of the multiple batteries 30 are brought into contact with or face relatively close to the liquid encapsulation portion 11 side surface of the wall portion. Also in this way, similar to the above-described embodiments, an increase in the volume of the battery pack and an increase in the number of components can be suppressed, and the spread of thermal runaway among the multiple batteries when an abnormality occurs in the battery can be suppressed.

[0065] In addition, in each of the above-described embodiments, the positive terminal plate 70 for electrically connecting the positive electrode external terminals of the multiple batteries 30 and the negative terminal plate 80 for electrically connecting the bottom of the outer package 35 (refer to Figure 3 ) which is the negative electrode external terminal of the multiple batteries 30 are provided at positions outside the upper and lower ends of the battery 30 in the vertical direction and are arranged to face each other in the vertical direction has been described. However, it may also be the case that both the positive terminal plate 70 for electrically connecting the positive electrode external terminals of the multiple batteries 30 and the negative terminal plate 80 for electrically connecting the outer package 35 (refer to Figure 3 ) which is the negative electrode external terminal of the multiple batteries 30 are arranged on one side in the vertical direction of the battery 30. In addition, in this case, a short circuit between the positive terminal plate 70 and the negative terminal plate 80 can be reliably prevented by sandwiching a plate made of an insulating material between the positive terminal plate 70 for electrically connecting the positive electrode external terminals of the multiple batteries 30 and the negative terminal plate 80 for electrically connecting the bottom of the outer package 35 (refer to Figure 3 ) which is the negative electrode external terminal of the multiple batteries 30. For example, inFigure 2 In the structure shown, it is also possible to have a structure in which the vertical directions of a plurality of batteries 30 are reversed and a positive terminal plate 70 and a negative terminal plate 80 are provided on the upper side of the plurality of batteries 30, and an exhaust portion (safety valve) composed of a thin wall portion or the like is formed at the bottom of the outer package 35 that becomes the lower side of each of the plurality of batteries 30, and the end portions on the exhaust portion side of each battery are in contact with or close to the wall portion of a battery holder or the like and face each other.

[0066] In addition, in each of the above-described embodiments, an example in which the battery holder melts to form a flow path is given, but it is not limited thereto, and other structures such as the following structure may be used: a thin wall portion is provided on the wall portion of the battery holder or the like and breaks under the pressure of the gas discharged from the safety valve of the battery, thereby forming a flow path in the wall portion.

[0067] Furthermore, the present invention is not limited to the above-described embodiments, and various improvements and changes can be made within the scope of the matters described in the claims of this application and their equivalents.

[0068] Explanation of reference numerals

[0069] 1, 1a, 1b, battery pack; 10, housing; 10a, 10b, first side wall; 10c, second side wall; 11, liquid filling portion; 12, liquid discharge chamber; 13, exhaust portion; 16, exhaust path; 18, storage portion; 20, battery block; 30, battery; 31, positive electrode; 32, negative electrode; 33, separator; 34, electrode body; 35, outer package; 36, sealing body; 37, safety valve; 38a, 38b, insulating plate; 39, positive electrode lead; 40, negative electrode lead; 41, internal terminal plate; 42, first valve element; 43, insulating member; 44, second valve element; 45, cover (positive external terminal); 45a, exhaust hole; 46, shoulder; 50, coolant; 60, battery holder; 61, first holder; 61a, surface; 62, second holder; 63, concave portion; 64, step portion; 65, holding portion; 66, opening; 70, positive terminal plate; 80, negative terminal plate; 81, small concave portion; 90, housing.

Claims

1. A battery pack, comprising: a housing; and a plurality of batteries housed in the housing, wherein the plurality of batteries have safety valves and are immersed in a coolant within the housing, and the safety valves open due to an increase in internal pressure to discharge internal gas, the housing has: a liquid encapsulation portion that encapsulates the coolant; and a wall portion provided below the liquid encapsulation portion to separate the liquid encapsulation portion from a space not encapsulated with the coolant, an end portion of the plurality of batteries near the safety valve contacts or is disposed in close proximity to a surface of the wall portion near the liquid encapsulation portion.

2. The battery pack according to claim 1, wherein the wall portion has a recess on the surface near the liquid encapsulation portion for the front end of the end portion of the plurality of batteries near the safety valve to enter, a shoulder on the outer peripheral surface of the plurality of batteries having an outer diameter larger than that of the front end of the end portion near the safety valve contacts the opening end of the recess, an exhaust hole formed on the outer peripheral surface of the front end for discharging gas within the battery communicates with a space within the recess.

3. The battery pack according to claim 1 or 2, wherein the housing has a liquid discharge chamber that receives the coolant discharged from the liquid encapsulation portion when the wall portion is damaged, the liquid discharge chamber is a space not encapsulated with the coolant provided below the wall portion.

4. The battery pack according to claim 1 or 2, wherein the space not encapsulated with the coolant is a space outside the housing, a surface of the wall portion near the space not encapsulated with the coolant forms an outer surface of the housing.

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