Battery pack

Abstract

This battery pack comprises: a plurality of secondary battery cells each having a gas charge valve that opens in response to a rise in internal pressure and that is provided at one of cell end surfaces; a battery holder that holds the plurality of secondary battery cells and that has a principal surface; an external case that houses the battery holder holding the plurality of secondary battery cells; and a heat-resistant spacer member that is provided on the principal surface of the battery holder so as to be interposed between the principal surface and the external case. Between an inner surface of the external case and the principal surface of the battery holder, the spacer member forms a gas discharge space for discharging gas released from the gas discharge valves.

Description

Battery pack

[0001] The present disclosure relates to a battery pack.

[0002] Battery packs that house rechargeable secondary battery cells, such as lithium-ion secondary batteries, inside an exterior case to power electrical devices are used for a variety of purposes (see, for example, Patent Documents 1 and 2). In such battery packs, if any abnormality occurs in one of the secondary battery cells housed inside the exterior case and high-pressure gas is generated inside the exterior case, a gas exhaust valve provided in the exterior case is configured to open. A structure is required to exhaust the high-pressure gas released inside the exterior case from the exterior case to the outside.

[0003] However, in recent years, there has been a demand for smaller and lighter battery packs, and it has not been easy to provide the space required for gas discharge.

[0004] JP 2016-072039 A JP 2017-212065 A

[0005] One object of the present disclosure is to provide a battery pack that makes it easy to provide a space for discharging gas. Another object is to provide a battery pack with improved reliability. Note that the description of these objects and objects of the present disclosure does not preclude the existence of other objects and objects. Furthermore, it is not necessary for one embodiment of the present disclosure to solve all of these objects. Furthermore, other objects can be extracted from the description of the specification, drawings, and claims of the present disclosure.

[0006] A battery pack according to one embodiment of the present disclosure comprises a plurality of secondary battery cells, each having a gas exhaust valve on one of its cell end faces that opens in response to an increase in internal pressure, a battery holder having a main surface that holds the plurality of secondary battery cells, an outer case that houses the battery holder holding the plurality of secondary battery cells, and a heat-resistant spacer member interposed between the main surface of the battery holder and the outer case, wherein the spacer member forms a gas exhaust space between the inner surface of the outer case and the main surface of the battery holder to exhaust gas released from the gas exhaust valve.

[0007] According to the battery pack according to one aspect of the present disclosure, a gas discharge space can be easily formed between the inner surface of the exterior case and the main surface of the battery holder by using a spacer member.

[0008] 1. A perspective view showing a battery pack according to Embodiment 1. A perspective view of the battery pack of FIG. 1, as seen from the rear side. A cross-sectional view taken along line III-III of FIG. 1. A cross-sectional view taken along line IV-IV of FIG. 1. An exploded perspective view of the outer case of the battery pack of FIG. 1. A perspective view of the inner bag of FIG. 5, as seen from the rear side. A plan view of the inner bag of FIG. 6. A developed view of the protective sheet of FIG. 6. An exploded perspective view of the inner bag of FIG. 5. An exploded perspective view of the inner bag with the battery module removed from the inner bag of FIG. 9. A plan view of the battery module of FIG. 10. A rear view of the battery module of FIG. 10. An exploded perspective view showing the battery module of FIG. 10 with the spacer member removed. An exploded perspective view showing the battery holder of FIG. 13 with the lead plate further removed. A further exploded perspective view of the battery holder of FIG. 14. A perspective view showing the spacer member.

[0009] The embodiments of the present disclosure may be specified by the following configurations and features.

[0010] In a battery pack according to another aspect of the present disclosure, in the above aspect, the spacer member is made of a flexible material, and with this configuration, even if an external force is applied to the battery pack, the flexible spacer member can mitigate the external force and protect the battery holder.

[0011] In addition, in a battery pack according to another aspect of the present disclosure, in any of the above aspects, the spacer members are provided on at least some of the cell end faces of the secondary battery cells that do not have the gas release valves. With this configuration, if gas is to be released through the gas release valve, the spacer members do not hinder the release of gas, and smooth gas release can be maintained even when the spacer members are attached to the battery holder.

[0012] In a battery pack according to another aspect of the present disclosure, in any of the above aspects, the battery pack further includes a protective sheet covering a pair of main surfaces of the battery holder, the protective sheet being configured to continuously cover the main surfaces and at least a portion of the side surfaces connected to the main surfaces, and the protective sheet being configured to cover the cell end surfaces on which the gas release valves are provided. With this configuration, by using the protective sheet that covers the battery holder to improve impact resistance, etc. to cover the cell end surfaces on which the gas release valves are provided, the protective sheet can prevent flames from escaping even if high-temperature, high-pressure gas is released from the gas release valve of one of the secondary battery cells.

[0013] In a battery pack according to still another aspect of the present disclosure, in any of the above aspects, the protective sheet has a plurality of first openings that expose, from the protective sheet, at least some of the cell end faces of the plurality of secondary battery cells that do not have the gas release valves, the cell end faces that do not have the spacer members. With this configuration, in the unlikely event that high-temperature, high-pressure gas is released from the gas release valve of any of the secondary battery cells, the gas is not released directly from the cell end face that has the gas release valve, but is instead moved to the position of another cell end face and then released. This lengthens the gas movement path, weakens the gas's force and temperature, and is expected to allow the gas to be released more safely to the outside.

[0014] In particular, the cell end face where the gas exhaust valve is installed can be covered with a protective sheet to prevent fire leakage, while simultaneously regulating and exhausting the gas.

[0015] In addition, in a battery pack according to another aspect of the present disclosure, in any of the above aspects, the battery pack further includes lead plates connecting the cell end faces of the plurality of secondary battery cells, the battery holder includes guide walls on its main surface for positioning the lead plates, and the spacer members are fixed to the main surface of the battery holder along the guide walls. With this configuration, the guide walls that position the lead plates can also be used to position the spacer members.

[0016] Furthermore, in the battery pack according to any one of the above aspects, the spacer member is formed in a wave shape in a plan view.

[0017] In addition, in the battery pack according to any one of the above aspects, a plurality of the spacer members are fixed to the main surface of the battery holder while being spaced apart from each other.

[0018] In a battery pack according to another aspect of the present disclosure, in any of the above aspects, the spacer member extends along the main surface of the battery holder so as to cover the continuous cell end faces, forming a space between the spacer member and the end of the main surface of the battery holder. With this configuration, the main surface of the battery holder is not completely partitioned by the spacer member, forming a space. This prevents the spacer member from blocking the gas being released along the main surface of the battery holder when gas is released from the gas release valve, and maintains smooth gas release even when the spacer member is attached to the battery holder.

[0019] In addition, in a battery pack according to another aspect of the present disclosure, in any of the above aspects, the outer case further includes a waterproof inner bag that covers the outer periphery of the battery holder, and the spacer member is disposed inside the inner bag. With this configuration, the battery holder is housed in the inner bag to achieve waterproofing, while a gas exhaust space is formed inside the inner bag to maintain gas exhaust.

[0020] In a battery pack according to another aspect of the present disclosure, in any of the above aspects, the spacer member is formed shorter than the width of the battery holder in the short direction, forming a step between the edge of the main surface of the battery holder and the end of the spacer member. With this configuration, the end faces of the cells located at the terminal ends are not covered by the spacer member, thereby preventing excessive load on the inner bag and causing it to break.

[0021] In addition, in the battery pack according to any one of the above aspects, the spacer member is fixed to the main surface of the battery holder by an adhesive layer.

[0022] Furthermore, in the battery pack according to any one of the above aspects, the spacer member is a heat-resistant rubber sheet.

[0023] In addition, in the battery pack according to any one of the above aspects, the spacer member is a chloroprene-based rubber sheet.

[0024] In a battery pack according to another aspect of the present disclosure, in any of the above aspects, the spacer members have a common shape on each main surface of the battery holder. With this configuration, the spacer members have a common shape on both sides of the battery holder, thereby reducing the number of parts required during assembly.

[0025] Embodiments of the present disclosure will be described below with reference to the drawings. However, the embodiments described below are merely examples for embodying the technical concepts of the present disclosure, and the present disclosure is not limited to the following. Furthermore, this specification does not in any way specify the components set forth in the claims to be those of the embodiments. The dimensions, materials, shapes, relative positions, etc. of components described in the embodiments are not intended to limit the scope of the present disclosure, and are merely illustrative examples, unless otherwise specified. The size and positional relationships of components shown in the drawings may be exaggerated for clarity. Furthermore, in the following description, the same names and symbols indicate components that are identical or of the same quality, and detailed descriptions will be omitted as appropriate. Furthermore, the elements constituting the present disclosure may be configured with the same components, such that multiple elements are shared by one component, or conversely, the functions of one component may be shared by multiple components.

[0026] The battery pack of the present disclosure can be used as a driving power source for mobile objects such as electric carts, electric scooters, and assisted bicycles, as a power source for portable electrical devices such as radios, electric cleaners, and power tools, as a backup power source for servers in stationary power storage applications, as a power supply device for home, office, or factory use, and as a driving power source for vehicles such as hybrid cars and electric automobiles. Hereinafter, a battery pack used as a driving power source for an electric motorcycle will be described as one embodiment of the present invention.

[0027] [Embodiment 1] A battery pack 100 according to embodiment 1 of the present disclosure is shown in Figures 1 to 16. In these figures, Figure 1 is a perspective view showing the battery pack 100 according to embodiment 1, Figure 2 is a perspective view of the battery pack 100 of Figure 1 as seen from the rear side, Figure 3 is a cross-sectional view taken along line III-III of Figure 1, Figure 4 is a cross-sectional view taken along line IV-IV of Figure 1, Figure 5 is an exploded perspective view of the outer case 10 of the battery pack 100 of Figure 1, Figure 6 is a perspective view of the inner bag 20 of Figure 5 as seen from the rear, Figure 7 is a plan view of the inner bag 20 of Figure 6, Figure 8 is a development view of the protective sheet 30 of Figure 6, and Figure 9 is an exploded perspective view of the inner bag 20 of Figure 5. Fig. 10 is an exploded perspective view of the battery module 2 removed from the inner bag 20 of Fig. 9, Fig. 11 is a plan view of the battery module 2 of Fig. 10, Fig. 12 is a rear view of the battery module 2 of Fig. 10, Fig. 13 is an exploded perspective view showing the battery module 2 of Fig. 10 with the spacer member 40 removed, Fig. 14 is an exploded perspective view showing the battery holder 5 of Fig. 13 with the lead plates 4 further removed, Fig. 15 is a further exploded perspective view of the battery holder 5 of Fig. 14, and Fig. 16 is a perspective view showing the spacer member 40. The battery pack 100 shown in these figures includes an outer case 10 and an inner bag 20.

[0028] (External Case 10) The external case 10 houses the inner bag 20. The external shape of the external case 10 can be any shape that has an internal storage space. In the example shown in Figures 1 to 4, the external case 10 has a box-like shape extending in one direction. The box-shaped external case 10 is divided into an upper case 11 and a lower case 12, which are divided vertically or horizontally. This external case 10 is preferably made of a material with excellent insulating properties, such as a resin such as polycarbonate or PC-ABS alloy. It may also be made of a metal material such as aluminum or its alloy. Furthermore, the external case 10 has an internal space for housing the inner bag 20, as shown in Figure 5.

[0029] (Inner bag 20) The inner bag 20 covers the outer periphery of the battery holder 5 inside the outer case 10. The inner bag 20 is waterproof, and protects the secondary battery cells 1 housed in the outer case 10 from water. For this reason, the inner bag 20 is made of a waterproof material.

[0030] The inner bag 20 is made of a flexible material. While the inner bag 20 is shown in a box shape in the examples shown in Figures 5 to 7, 9 and 10, the shape is not limited to these and may be an irregular shape such as a bag. For such an inner bag 20, a resin having excellent heat resistance, flame retardancy, flexibility, and abrasion resistance may be used, such as a polyolefin resin or a polyethylene resin, such as a PET resin. Alternatively, a heat-shrinkable tube that shrinks when heated may be used.

[0031] Furthermore, the inner bag 20 is provided with a check valve 22 that exhausts internal gas while preventing moisture from passing through from the outside.

[0032] (Protective sheet 30) The surface of the inner bag 20 is covered with a protective sheet 30. In the example shown in Figures 6 to 9, a protective sheet 30 is attached to each of a pair of main surfaces of the inner bag 20. This protective sheet 30 is configured to continuously cover the main surface of the inner bag 20 and at least a portion of the side surface continuous with this main surface. In this way, the surface of the inner bag 20 is protected by the protective sheet 30.

[0033] The protective sheet 30 is made of an elastic material. By interposing the elastic inner bag 20 between the outer surface of the flexible inner bag 20 and the inner surface of the hard outer case 10, the inner bag 20 and the battery modules 2 housed in the inner bag 20 can be protected. Specifically, the inner bag 20 and the battery modules 2 can be protected from external forces such as impact and vibration. Furthermore, the flexible inner bag 20 can be prevented from being torn by friction caused by impact, vibration, or the like. The protective sheet 30 is made of an insulating material, such as a heat-resistant or flame-retardant rubber sheet. Preferably, a CR (chloroprene rubber) rubber sheet can be used.

[0034] (Battery Module 2) As shown in Figures 3, 4, and 10, a battery module 2 is housed inside the inner bag 20. The battery module 2 is also called a core pack, and is composed of a battery block that houses multiple secondary battery cells 1 and a circuit board 3. As shown in Figures 10 to 13, a spacer member 40 is attached to the surface of the battery module 2.

[0035] The battery block is composed of a battery holder 5. The battery holder 5 is divided into multiple sub-holders 5a that sandwich the rechargeable battery cells 1. In the examples shown in Figures 3, 4, 14, and 15, the battery holder 5 holds a large number of cylindrical rechargeable battery cells 1 in a vertical orientation. The multiple rechargeable battery cells 1 are connected in series or parallel via lead plates 4 or the like. The number of series connections or parallel connections can be set as desired according to the required specifications. In the examples shown in Figures 14 and 15, 112 rechargeable battery cells 1 are used in the battery module 2, forming a 14 series x 8 parallel configuration, but this configuration is not limited to this. The battery module 2 may also be composed of multiple battery blocks, each containing multiple rechargeable battery cells 1.

[0036] The battery holder 5 has multiple storage cylinders 6 that individually store the rechargeable battery cells 1. In the example shown in Figure 15, the battery holder 5 is divided into two, an upper part and an lower part, and the two storage cylinders 6 hold the rechargeable battery cells 1 from above and below. The number of battery holder sections is not limited to two, and may be three or more. The battery holder 5 can be made of a resin such as polycarbonate, which has excellent insulating properties.

[0037] (Secondary battery cells 1) Each secondary battery cell 1 may be a secondary battery cell with a cylindrical or rectangular outer shape. In the examples shown in Figures 3, 4, 15, etc., cylindrical secondary battery cells 1 are used in a staggered arrangement in a vertical orientation. Note that the number and arrangement of the secondary battery cells 1 are not limited to this example, and any number and arrangement can be used as appropriate. For example, cylindrical secondary battery cells may be arranged in a matrix.

[0038] Each secondary battery cell 1 has a positive and negative electrode, which are preferably provided on one end surface of the secondary battery cell 1. The secondary battery cell 1 may be any known secondary battery, such as a lithium-ion secondary battery, a nickel-metal hydride battery, or a nickel-cadmium battery.

[0039] (Gas Release Valve) Each exterior can of the secondary battery cell 1 is provided with a gas release valve. The gas release valve opens in response to an increase in the internal pressure of the exterior can, releasing gas inside the exterior can to the outside. The gas release valve is provided on one of the cell end faces of the secondary battery cell 1. In the example shown in FIG. 15 etc., the gas release valve is provided on the positive electrode side of the secondary battery cell 1.

[0040] (Gas exhaust port 13) Meanwhile, the exterior case 10 has a gas exhaust port 13 formed in a portion thereof for releasing high-pressure gas to the outside when the gas exhaust valve of the secondary battery cell 1 is opened and the gas is released. In the example of Fig. 2, the gas exhaust port 13 is provided on the rear side of the lower case 12 of the exterior case 10. In these examples, the gas exhaust port 13 is rectangular, but the shape of the gas exhaust port 13 is not limited to rectangular and may be polygonal, such as octagonal, hexagonal, or square, or may be circular, track-shaped, elliptical, or the like.

[0041] The lead plates 4 are disposed on the main surfaces of the battery holder 5. The battery holder 5 also has guide walls 7 on its main surfaces for positioning the lead plates 4 to be fixed.

[0042] (Lead Plates 4) The lead plates 4 connect the electrodes on the end faces of the rechargeable battery cells 1 to each other, connecting multiple rechargeable battery cells 1 in series or parallel. In the example of Figures 13 and 14, the end faces of 112 rechargeable battery cells 1 are connected to each other with lead plates 4, and the rechargeable battery cells 1 are connected in a 14 series x 8 parallel configuration. Note that the number and arrangement of rechargeable battery cells, the number of series or parallel connections, etc. are not limited to this example, and any number and arrangement can be used as appropriate. These lead plates 4 are made of metal plates with excellent conductivity, such as aluminum plates or nickel plates.

[0043] An insulating plate may also be placed on the end surface of the lead plate 4. The insulating plate is formed to a size that covers the entire surface of the lead plate 4. An electrode window is also partially opened to expose the electrode portion of the lead plate 4. Such an insulating plate is made of a material with excellent insulating properties and fire resistance, such as mica.

[0044] (Circuit Board 3) As shown in Figures 13 and 14, the battery module 2 is connected to the circuit board 3 via lead plates 4. The circuit board 3 is equipped with a charge / discharge circuit that charges and discharges the rechargeable battery cells 1, and a protection circuit that monitors the voltage and temperature of the rechargeable battery cells 1 and cuts off the current in the event of an abnormality. The circuit board 3 is made of a glass epoxy board or the like. A board holder for holding such a circuit board 3 may also be provided.

[0045] (Spacer Member 40) A spacer member 40 is provided on the main surface of the battery holder 5. The spacer member 40 is interposed between the exterior case 10 and the battery module 2. As shown in FIG. 4 , the spacer member 40 forms a space between the inner surface of the exterior case 10 and the main surface of the battery holder 5. This space functions as a gas discharge space GS for discharging gas released from the gas discharge valve. The spacer member 40 is made of a heat-resistant material. This prevents the spacer member 40 from immediately melting due to high heat, ensuring the gas discharge space GS, even in the unlikely event that high-temperature, high-pressure gas is discharged from the gas discharge valve. CR (chloroprene rubber)-based rubber can be used for such spacer member 40.

[0046] Furthermore, the spacer member 40 is made of a flexible material. With this configuration, even if an external force is applied to the battery pack 100, the spacer member 40 can absorb the external force and protect the battery holder 5.

[0047] The spacer members 40 are preferably provided on the cell end faces 1b of the multiple secondary battery cells 1 that do not have gas release valves. If the spacer members 40 were provided on the cell end faces 1a that have gas release valves, in the event that high-temperature, high-pressure gas were to be released through the gas release valves, the spacer members 40 would hinder the gas release, preventing it from being smoothly released to the outside, and the pressure inside the outer can could build up and cause it to burst. Therefore, by positioning the spacer members 40 away from the cell end faces 1a that have gas release valves, even if high-temperature, high-pressure gas were to be released through the gas release valves, the spacer members 40 would not hinder the release of the gas, and smooth gas release can be maintained even when the spacer members 40 are attached to the battery holder 5.

[0048] The spacer member 40 is fixed to the main surface of the battery holder 5 by an adhesive layer. The adhesive layer can be double-sided tape. Alternatively, the spacer member 40 may be fixed by adhesive or the like.

[0049] It is also preferable to fix the spacer members 40 to the main surfaces of the battery holders 5 along the guide walls 7. This allows the guide walls 7, which position the lead plates 4, to also be used to position the spacer members 40.

[0050] The spacer members 40 are arranged so that the cell end faces are flush with each other, and continuously cover the cell end faces of the multiple connected secondary battery cells 1. Therefore, the spacer members 40 are formed according to the stacking pattern of the multiple secondary battery cells 1. For example, as shown in Fig. 16 , the spacer members 40 are formed in a wavy shape in a plan view.

[0051] 11 and 12, multiple spacer members 40 are fixed at a distance from each other on the main surfaces of the battery holder 5. It is preferable that the spacer members 40 have the same shape on each main surface of the battery holder 5. Additionally, it is preferable that the spacer members 40 on each main surface be mirror-symmetric. This allows the same spacer member 40 to be used on both the left and right sides by flipping the spacer member 40, thereby reducing the number of parts required when assembling the battery pack 100.

[0052] Furthermore, the spacer member 40 extends along the main surface of the battery holder 5 so as to cover the continuous cell end faces. Additionally, a space is formed between the spacer member 40 and the edge of the main surface of the battery holder 5. This configuration ensures that the main surface of the battery holder 5 is not completely partitioned by the spacer member 40. By creating a space, if gas is to be released from the gas release valve, the spacer member 40 will not block the gas being released along the main surface of the battery holder 5. This allows smooth gas release to be maintained even when the spacer member 40 is attached to the battery holder 5.

[0053] The spacer members 40 also protect the inner bag 20. The spacer members 40 are formed in a continuous line on the main surface of the battery holders 5 so as to cover the continuous cell end faces. However, it is preferable not to cover the cell end faces located at the ends with the spacer members 40. This allows the battery holders 5 to be housed in the inner bag 20 for waterproofing, while not covering the cell end faces located at the ends, thereby preventing the inner bag 20 from being subjected to excessive load and breaking.

[0054] The protective sheet 30 is configured to cover the cell end surface 1a where the gas release valve is located. By using the protective sheet 30, which covers the battery holder 5 to improve impact resistance, to cover the cell end surface 1a where the gas release valve is located, even if high-temperature, high-pressure gas is released from the gas release valve of one of the secondary battery cells 1, the gas will not be immediately released from the battery pack, preventing a situation in which the flame caused by the gas ignition would leak directly outside the battery pack.

[0055] Generally, in a battery pack, if any abnormality occurs in any of the secondary battery cells housed in the outer case and high-pressure gas is generated inside the outer case, a gas release valve provided in the outer case is configured to open. In this case, a structure is required to safely release the high-pressure gas released inside the outer case to the outside.

[0056] However, it has not been easy to realize such a structure. In particular, in recent years, there has been a demand for battery packs to be smaller and lighter, while at the same time there has been a demand for cost reduction, and it has not been easy to secure the space and cost required to add a structure for safely venting exhaust gas. In contrast, this embodiment has the advantage that the protective sheet 30, which is intended to improve impact resistance, can also be used as a member for suppressing the occurrence of fire leakage while ensuring the gas vent space GS.

[0057] (First openings 31) Furthermore, the protective sheet 30 has multiple first openings 31. As shown in Fig. 7 , each of the first openings 31 exposes a portion of each of the multiple cell end faces 1b that do not have a gas release valve. As a result, in the unlikely event that high-temperature, high-pressure gas is released from the gas release valve of one of the secondary battery cells 1, the gas is not released directly from the cell end face 1a where the gas release valve is provided, but is instead moved to the position of another cell end face 1b, i.e., to the position of the first opening 31, and then released. This lengthens the gas movement path, weakens the gas's force and temperature, and is expected to allow it to be released more safely to the outside.

[0058] Furthermore, the first opening 31 exposes, from the protective sheet 30, the cell end faces 1b that are not provided with the spacer members 40, among the cell end faces 1b that are not provided with the gas release valves. In Fig. 7, the spacer members 40 provided on the inside of the inner bag 20 are indicated by dashed lines. With this configuration, the cell end faces 1a that are provided with the gas release valves are closed with the protective sheet 30, which makes it possible to both regulate and release the gas while suppressing the occurrence of fire leaks.

[0059] The spacer member 40 forms the gas discharge space GS, and is therefore made thicker than the protective sheet 30. On the other hand, the protective sheet 30 is made thin so that it can be easily attached to the surface of the inner bag 20 and also prevents the battery module 2 from becoming thick.

[0060] (Second openings 32) Furthermore, the protective sheet 30 has a plurality of second openings 32 formed along the boundary between the main surface and the side surface connected to the main surface, as shown in Fig. 8. This makes it possible to make the protective sheet 30, which is made of an elastic material and is difficult to fold, easier to fold by forming a plurality of second openings 32 at intervals along the boundary line between the main surface and the side surface, as shown in Fig. 9.

[0061] It is preferable that each of the second openings 32 is smaller than each of the first openings 31. This increases the area of ​​the first openings 31, which are mainly responsible for discharging gas, and enables smooth gas discharge.

[0062] 8 , the protective sheet 30 preferably has a plurality of third openings 33 formed at positions corresponding to the check valves 22 of the inner bag 20. This allows gas generated inside the inner bag 20 to be discharged to the outside through the check valves 22 and the third openings 33.

[0063] It is preferable that each of the third openings 33 be smaller than each of the second openings 32. This allows the area of ​​the first openings 31, which are used to urgently discharge gas that is suddenly generated, to be larger than the area of ​​the third openings 33, which are used to discharge a relatively small amount of gas, making it possible to discharge gas smoothly.

[0064] In the above example, the battery pack is used as a power source for an electric scooter. However, the present disclosure is not limited to this. The battery pack can also be used for other purposes, such as attaching it to an electric device to be driven and supplying power to the electric device. Examples of electric devices include mobile objects such as electric vehicles and electric carts, as well as portable electric devices. In such electric devices, when the remaining capacity of the battery pack becomes low or the battery pack deteriorates over time, the battery pack can be replaced to continue using the electric device. However, the present disclosure is not limited to replaceable battery packs that mainly house secondary battery cells, but can also be applied to battery packs in which secondary battery cells are housed within the housing of the electric device. In the present disclosure, a battery pack is defined as a battery pack that houses secondary battery cells in a case, and also includes battery packs in which secondary battery cells for driving the electric device are built into the housing of the electric device itself. In other words, the present disclosure is not limited to replaceable battery packs, but can also be applied to electric devices that house secondary battery cells.

[0065] The battery pack according to the present invention can be suitably used as a driving power source for mobile objects such as electric scooters, electric carts and assisted bicycles, as a power source for radios, and as a power source for portable electrical equipment such as electric cleaners and power tools, as a backup power source for servers and the like, and as a stationary power storage device for home, office and factory use, etc.

[0066] DESCRIPTION OF SYMBOLS 100...Battery pack 1...Secondary battery cell 1a...Cell end face provided with gas release valve 1b...Cell end face without gas release valve 2...Battery module 3...Circuit board 4...Lead plate 5...Battery holder 5a...Sub-holder 6...Storage cylinder 7...Guide wall 10...External case 11...Upper case 12...Lower case 13...Gas release port 20...Inner bag 22...Check valve 30...Protective sheet 31...First opening 32...Second opening 33...Third opening 40...Spacer member GS...Gas release space

Claims

1. A battery pack comprising: a plurality of secondary battery cells having cell end faces at both ends; a battery holder having a main surface that holds the plurality of secondary battery cells; an exterior case that houses the battery holder; and a heat-resistant spacer member interposed between the exterior case and the main surface of the battery holder, wherein the plurality of cell end faces are a plurality of first cell end faces that are provided with gas release valves that open in response to an increase in internal pressure, or a plurality of second cell end faces that are not provided with the gas release valves, and the spacer member occupies a portion of the space between the inner surface of the exterior case and the main surface of the battery holder, with the remaining space being a gas release space for releasing gas released from the gas release valves.

2. A battery pack according to claim 1, wherein the spacer member is made of a flexible material.

3. A battery pack according to claim 1, wherein the spacer member is provided on at least one of the second cell end faces.

4. A battery pack as claimed in claim 3, further comprising a protective sheet covering the main surface of the battery holder and the spacer member, the protective sheet being configured to continuously cover the main surface and at least a portion of the side surface connected to the main surface, and the protective sheet being configured to cover the end faces of the plurality of first cells.

5. A battery pack according to claim 4, wherein the protective sheet has at least one first opening that exposes at least one of the second cell end faces that is not provided with the spacer member from the protective sheet.

6. A battery pack as claimed in claim 1, further comprising lead plates connecting the cell end faces of the secondary battery cells together, the battery holder comprising guide walls for positioning the lead plates on the main surface of the battery holder, and the spacer members fixed to the main surface of the battery holder along the guide walls.

7. A battery pack according to claim 1, wherein the spacer member is wavy in plan view.

8. A battery pack according to claim 1, wherein the spacer member is one of a plurality of spacer members, and the plurality of spacer members are fixed to the main surface of the battery holder while being spaced apart from each other.

9. A battery pack as claimed in claim 8, wherein the spacer member extends on the main surface of the battery holder so as to cover the continuous end faces of the plurality of second cells, forming a space between the spacer member and the end of the main surface of the battery holder.

10. A battery pack as claimed in claim 9, further comprising a waterproof inner bag inside the outer case that covers the outer periphery of the battery holder, and the spacer member is disposed inside the inner bag.

11. A battery pack as claimed in claim 1, wherein the spacer member is shorter than the width of the battery holder in the short direction, and a space is formed between the edge of the main surface of the battery holder and the end of the spacer member.

12. A battery pack according to any one of claims 1 to 11, wherein the spacer member is fixed to the main surface of the battery holder by an adhesive layer.

13. A battery pack according to any one of claims 1 to 11, wherein the spacer member is a heat-resistant rubber sheet.

14. A battery pack according to any one of claims 1 to 11, wherein the spacer member is a chloroprene rubber sheet.

15. A battery pack according to any one of claims 1 to 11, wherein the spacer members have a common shape on the main surfaces of the plurality of battery holders.

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