Battery pack
Patent Information
- Application Number
- PCT/JP2026/012025
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-03-28
- Filing Date
- 2026-03-25
- Publication Date
- 2026-10-01
Smart Images
Figure JP2026012025_01102026_PF_FP_ABST
Abstract
Description
Battery pack
[0001] The present disclosure relates to a battery pack.
[0002] Battery packs using rechargeable secondary battery cells such as lithium-ion secondary battery cells are used in a wide range of applications, including battery packs for supplying power to drive electric bicycles and electric motorcycles. Such a battery pack is configured by inserting a battery block called a core pack or the like, in which a plurality of secondary battery cells are connected in series or parallel, into an outer case. In recent years, in order to meet the demand for higher capacity and higher output of battery packs, secondary battery cells with high energy density have been used in such battery packs. As a result, a high safety structure is required in preparation for the event that any one of the plurality of secondary battery cells experiences thermal runaway. When a secondary battery cell undergoes thermal runaway, gas is released from the outer can of the secondary battery cell. This gas is at a high temperature, and it can burn and cause ignition. Against this background, in order to prevent ignition outside the battery pack, configurations using a metal case for the outer case and designing a long gas exhaust flow path have been considered.
[0003] However, the use of a metal case increases the weight of the battery pack. In addition, lengthening the gas exhaust flow path increases the size of the battery pack. As described above, there are restrictions on the allowable weight and size of the battery pack, and as a result of the increase in size of the battery pack, there has been a problem that the energy density of the battery pack itself decreases.
[0004] Japanese Unexamined Patent Publication No. 2019-029086
[0005] One object of an embodiment of the present disclosure is to provide a battery pack that can safely discharge gas to the outside in the event that gas is released. Another object of another embodiment is to provide a battery pack with improved safety while avoiding structural complication. The description of these objects and problems in the present disclosure does not preclude the existence of other objects and problems. In addition, it is not necessary for one aspect of the present disclosure to solve all of these problems. Furthermore, other problems 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 battery block composed of a plurality of secondary battery cells, each having a gas discharge port on its end face for discharging gas when the internal pressure rises, and an outer case that houses the battery block in an internal storage space, wherein the outer case comprises a cylindrical case body with at least one end open and a case lid that closes the open end of the case body, and the case lid comprises a first lid surface facing the block end face of the battery block and a first lid second surface opposite to the first lid surface, and has an opening for a first gas discharge port. The device comprises a first lid, a second lid which is superimposed on the first lid and has a first surface of the second lid facing the second surface of the first lid, and a second surface of the second lid opposite to the first surface of the second lid, and has an opening for a second gas outlet which communicates with the first gas outlet, the second lid defines a second gas discharge path between the first surface of the second lid and the second surface of the first lid which guides the gas discharged from the first gas outlet to the second gas outlet, and the second gas discharge path is provided with a gas flow obstruction structure which changes the direction of gas travel from the first gas outlet to the second gas outlet.
[0007] According to one embodiment of the battery pack of this disclosure, the case lid of the outer case is doubled into a first lid and a second lid, and a second gas exhaust path is defined between the first lid and the second lid. By lowering the temperature of the gas traveling through this second gas exhaust path and preventing powders such as metal powder from escaping to the outside of the battery pack, safety can be enhanced.
[0008] This is a perspective view showing a battery pack according to an embodiment. This is a cross-sectional view of the battery pack in Figure 1 along line II-II. This is a cross-sectional view of the battery pack in Figure 1 along line III-III. This is an exploded perspective view of the battery pack in Figure 1. This is an exploded perspective view of the battery pack in Figure 4 viewed from the rear. This is a cross-sectional view of the case lid along line VI-VI in Figure 1. This is a plan view showing the second surface of the first lid of the first lid. This is a plan view showing the first surface of the second lid of the second lid. This is a cross-sectional perspective view of the case lid along line IX-IX in Figure 1. This is a cross-sectional perspective view of the case lid taken from diagonally above along line X-X in Figure 1. This is a cross-sectional perspective view of the case lid taken from diagonally below along line X-X in Figure 1. This is an exploded perspective view of the first and second lids in Figure 11. This is an exploded perspective view of the first and second lids taken from the rear in Figure 12. This is a cross-sectional view of the first lid along line XIV-XIV in Figure 4. This is a plan view showing a cross section along line XV-XV in Figure 14. This is a plan view showing a cross section along line XVI-XVI in Figure 14.
[0009] The form of this disclosure may be specified by the following configurations and features.
[0010] In other embodiments of the present disclosure, the battery pack is configured such that the gas flow inhibiting structure is defined by a first lid wall portion protruding from the second surface of the first lid of the first lid and a second lid wall portion protruding from the first surface of the second lid of the second lid.
[0011] In addition, in any of the above embodiments of the battery pack, the first lid wall and the second lid wall are arranged to surround the first gas outlet.
[0012] Furthermore, in other embodiments of the present disclosure, the battery pack in any of the above embodiments has the first gas outlet opening in the central region of the first lid and the second gas outlet opening in the peripheral region of the second lid. With this configuration, the temperature of the gas is reduced as it diffuses from the center outwards through the gas flow inhibiting structure, allowing it to be safely discharged from the battery pack.
[0013] Furthermore, in other embodiments of the present disclosure, the battery pack is formed such that the outer shape of the second lid is smaller than that of the first lid. With this configuration, a gas advance obstruction structure can be constructed by attaching the second lid to the first lid while the first lid closes the open end of the case body.
[0014] Furthermore, in any of the above embodiments of the battery pack, the first lid has a plurality of case wall portions formed spaced apart on the first surface of the first lid so as to surround the first gas outlet.
[0015] Furthermore, in other embodiments of the present disclosure, the battery pack in any of the above embodiments has an uneven surface formed on each of the multiple case walls. With this configuration, when the gas released from the secondary battery cell flows over the surface of the case wall, powders and other particles contained in the gas are trapped in the uneven surface, and when the gas is discharged from the outer case, the amount of powder is reduced, thereby suppressing the generation of flames and enhancing safety.
[0016] Furthermore, in any of the above embodiments, the battery pack is made of resin.
[0017] Furthermore, in other embodiments of the present disclosure, the battery pack is made of metal in any of the above embodiments. This configuration makes it possible to maintain safety when gas is released while increasing rigidity by making the case body that constitutes the side portion of the outer case out of metal, and reducing weight by making the case lid out of resin.
[0018] The embodiments of this disclosure will be described below with reference to the drawings. However, the embodiments shown below are examples for concretizing the technical concept of this disclosure, and this disclosure is not limited to the following. Furthermore, this specification does not limit the members shown in the claims to the members of the embodiments. In particular, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments are not intended to limit the scope of this disclosure to those, unless specifically stated otherwise, but are merely illustrative examples. Note that the size and positional relationships of the members shown in each drawing may be exaggerated for clarity of explanation. Furthermore, in the following description, the same name and reference numerals indicate the same or similar members, and detailed explanations are omitted as appropriate. Furthermore, each element constituting this disclosure may be configured such that multiple elements are made of the same member, with one member serving multiple elements, or conversely, the function of one member may be shared among multiple members.
[0019] The battery pack disclosed herein can be used as a power source for portable electrical equipment such as power tools and electric cleaners, as a power source for mobile devices such as electric carts, electric scooters, and electric assist bicycles, as a backup power source for servers or as a battery pack for home, business, and factory use in stationary energy storage applications, and as a power source for vehicles such as hybrid cars and electric vehicles. Hereinafter, an embodiment of the present invention will be described as a battery pack used as a power source for power tools. [Embodiment 1]
[0020] Figures 1 to 13 show a battery pack 100 according to Embodiment 1 of the present disclosure. In these figures, Figure 1 is a perspective view showing the battery pack 100 according to the embodiment, Figure 2 is a cross-sectional view of the battery pack 100 in Figure 1 along line II-II, Figure 3 is a cross-sectional view of the battery pack 100 in Figure 1 along line III-III, Figure 4 is an exploded perspective view of the battery pack 100 in Figure 1, Figure 5 is an exploded perspective view of the battery pack 100 in Figure 4 viewed from the rear side, Figure 6 is a cross-sectional view of the case lid 12 along line VI-VI in Figure 1, Figure 7 is a plan view showing the second surface 12A2 of the first lid 12A, and Figure 8 is Figure 9 is a plan view showing the first surface 12B1 of the second lid 12B, Figure 10 is a cross-sectional perspective view of the case lid 12 along the line IX-IX in Figure 1, Figure 11 is a cross-sectional perspective view of the case lid viewed from diagonally above along the line X-X in Figure 1, Figure 12 is an exploded perspective view of the first lid 12A and the second lid 12B in Figure 11, and Figure 13 is an exploded perspective view of the first lid 12A and the second lid 12B in Figure 12 viewed from the rear side. The battery pack 100 shown in these figures comprises an outer case 10, a battery module 2, and a circuit board 3. (Outer case 10)
[0021] The outer casing 10 is a component for housing the battery module 2. The outer casing 10 can have any shape that provides internal storage space. The outer casing 10 may also house other components, such as a circuit board 3, within its storage space. In the examples shown in Figures 1 to 4, the outer casing 10 is formed in a box shape with its exterior extended in one direction. The box-shaped outer casing 10 comprises a cylindrical case body 11 and case lids 12 that close the cylindrical end faces of the case body 11. However, this disclosure is not limited to this configuration. For example, the outer casing may be a bottomed cylinder, divided into two sections with only one open end closed by a case lid, or divided into four or more sections. The case body may also be divided vertically or horizontally. The divided outer casings are waterproofed by a waterproof structure. (Case body 11)
[0022] The case body 11 is formed in a cylindrical shape with at least one end open. Preferably, this case body 11 is made of a metal such as aluminum or an alloy thereof. This allows for increased rigidity by using a metal case body 11 that constitutes the side portion of the outer case 10, while maintaining safety when gas is released, and reducing weight by using a resin case lid 12. However, the outer case 10 may also be made of a material with excellent insulating properties, such as polycarbonate or a resin such as PC-ABS alloy. Furthermore, the inside of the outer case 10 is provided with an internal space for housing the battery module 2 and the circuit board 3, as shown in Figures 2 and 3. (Case lid 12)
[0023] The case lid 12 closes the open end of the case body 11. Preferably, the case lid 12 is made of a resin such as polycarbonate or PC-ABS alloy. As shown in Figures 4 to 6, the case lid 12 is composed of a first lid 12A and a second lid 12B. By doubling the case lid 12 of the outer case 10 into a first lid 12A and a second lid 12B in this way, the rigidity of the case lid 12 can be improved, and the situation in which flames leak out of the outer case 10 when gas is discharged can be suppressed. In particular, while making the case lid 12 out of metal reduces weight and provides insulation, the problem of relatively reduced strength and reduced resistance to high temperature and high pressure gases is resolved by doubling the resin first lid 12A and second lid 12B.
[0024] In the examples shown in Figures 4 and 5, the left-side case lid 12' is formed integrally, while the left-side case lid 12 is composed of a first lid 12A and a second lid 12B. However, this disclosure is not limited to this configuration, and the case lid 12 may be composed of only the first lid 12A. (First lid 12A)
[0025] The first lid portion 12A and the second lid portion 12B are superimposed to form the case lid portion 12. As shown in Figures 4 and 5, the first lid portion 12A has a first lid surface 12A1 that closes the open end of the case body 11 and faces the block end surface 21 of the battery block 20, and a first lid second surface 12A2 that is opposite to the first lid surface 12A1. At the interface between the first lid portion 12A and the case body 11, members such as connectors and gaskets may be interposed as needed. In the example shown in Figures 12 and 13, a sealing member 40 is interposed on the first lid surface 12A1 of the first lid portion 12A to liquid-tightly close the open end of the case body 11. (First gas outlet 13A)
[0026] Furthermore, the first lid portion 12A has an opening for the first gas outlet 13A. Preferably, the first gas outlet 13A is opened in the central region of the first lid portion 12A. In the example shown in Figure 7, the first gas outlet 13A is opened in the shape of multiple concentric slits. By dividing the opening into multiple holes in this way, the opening area of the first gas outlet 13A can be increased while making each hole small, preventing foreign matter from entering the outer casing 10 from the outside, and also hindering the discharge of combustible materials during gas discharge, thereby enhancing safety. (Second lid portion 12B)
[0027] The second lid portion 12B is superimposed on the first lid portion 12A and comprises a first surface 12B1 of the second lid facing the second surface 12A2 of the first lid portion 12A, and a second surface 12B2 of the second lid opposite to the first surface 12B1. The second lid portion 12B also has a second gas outlet 13B that communicates with the first gas outlet 13A. Preferably, the second gas outlet 13B is opened in the peripheral region of the second lid portion 12B. In the example in Figure 6, the second gas outlet 13B is located between the joining interface of the first lid portion 12A and the second lid portion 12B.
[0028] Furthermore, a gasket to prevent gas leakage, or busbars or lead plates for electrical connections may be interposed between the first lid 12A and the second lid 12B as needed. In the example shown in Figures 12 and 13, a filter 42 and a leaf spring 44 are interposed around the first gas outlet 13A on the second surface 12A2 of the first lid 12A. The filter 42 is a component that allows air to pass through and prevents the ingress of liquid. The leaf spring 44 is a component that prevents rattling when the first lid 12A and the second lid 12B are joined together. (Battery module 2)
[0029] The battery module 2, also called a core pack, houses multiple secondary battery cells 1. Alternatively, the battery module 2 may be composed of one or more battery blocks 20, with each battery block 20 housing multiple secondary battery cells 1. In the examples in Figures 2 and 4, the battery module 2 is constructed by connecting four battery blocks 20, each housing seven secondary battery cells 1 in a stacked configuration, in a horizontal direction. A circuit board 3 is placed on the bottom surface of the battery module 2.
[0030] Furthermore, within the storage space of the outer case 10, the battery module 2 has its end face facing the inner surface of the case lid 12. Specifically, among the multiple battery blocks 20 that make up the battery module 2, the end face 21 of the battery block 20 located at the end faces the inner surface of the case lid 12. (Battery holder 22)
[0031] Each battery block 20 comprises a battery holder 22, a secondary battery cell 1, and a lead plate 5. As shown in Figures 4 and 5, the battery holder 22 has multiple cylindrical holder sections 23, into which the secondary battery cell 1 is inserted and held. The battery holder 22 can house all the secondary battery cells 1 as a single unit, or it may be divided into multiple sub-holders, with some of the secondary battery cells housed in the sub-holders. Alternatively, the battery holder may be divided along the length of the secondary battery cell. In the example shown in Figures 4 and 5, the secondary battery cell 1 is housed in the holder section 23 by a sub-holder divided into two along the length of the secondary battery cell 1, sandwiching it from each cell end face 1a. Such a battery holder 22 is made of a material with excellent insulating properties. Preferably, it is made of a resin such as polycarbonate or PC-ABS alloy. (Lead plate 5)
[0032] The battery block 20 also includes lead plates 5 for electrically connecting the secondary battery cells 1 to each other. The lead plates 5 are preferably positioned on the outer side of the battery holder 22. The lead plates 5 are electrically connected to the terminals of the secondary battery cells 1 exposed through electrode windows opened in the battery holder 22. Each lead plate 5 connects the electrodes on the cell end faces 1a of the secondary battery cells 1, thereby connecting multiple secondary battery cells 1 together. The lead plates 5 are made of highly conductive metal plates such as aluminum, nickel, or copper. Multiple secondary battery cells 1 are connected in series or parallel via the lead plates 5. The number of series and parallel connections can be arbitrarily set according to the required specifications. In the example shown in Figure 4, each lead plate 5 primarily connects the end faces of 28 secondary battery cells 1, and the four battery blocks 20 as a whole connect 4 series and 7 parallel secondary battery cells 1. However, the number of secondary battery cells and connection configurations, i.e., the number of series and parallel connections, are not limited to this configuration. (Circuit board 3)
[0033] The battery block 20 is connected to the circuit board 3 via lead plates 5. The circuit board 3 implements a charge / discharge circuit for charging and discharging the secondary battery cell 1, and a protection circuit that monitors the voltage and temperature of the secondary battery cell 1 and cuts off the current in case of abnormalities. The circuit board 3 is made of a glass epoxy substrate or the like. A substrate holder may also be provided as a component to hold the circuit board 3.
[0034] In addition to lead plates, busbars can also be used. In the example shown in Figure 5, a busbar 6 is provided to connect the total output of the battery module 2 to the case lid 12.
[0035] In the examples shown in Figures 2 and 3, the circuit board 3 is placed on the bottom surface of the battery module 2. However, the disclosure is not limited to this configuration, and a single circuit board may be placed on the top or side surface of the battery module. Furthermore, multiple circuit boards may be provided, or the circuit board may be divided for each battery block. (Secondary battery cell 1)
[0036] Each battery block 20 houses a secondary battery cell 1 within a battery holder 22, as shown in Figures 2 to 4. The secondary battery cell 1 can be a cylindrical or rectangular cell. In the examples shown in Figures 2 to 3, a secondary battery cell 1 with a cylindrical outer casing is used, arranged horizontally in a staggered pattern. The number and arrangement of the secondary battery cells 1 are not limited to this example; any number and arrangement can be used as appropriate. For example, cylindrical secondary battery cells may be arranged in a matrix. The secondary battery cell 1 can be any known secondary battery, such as a lithium-ion battery, nickel-metal hydride battery, or nickel-cadmium battery.
[0037] Each secondary battery cell 1 has a positive electrode and a negative electrode. The terminals of the positive or negative electrode are preferably provided on one cell end face 1a of the secondary battery cell 1. In the example shown in Figure 2, the positive electrode terminal is provided on one cell end face 1a of the secondary battery cell 1, and the other side of the outer casing is used as the negative electrode.
[0038] Furthermore, each secondary battery cell 1 is provided with a gas discharge section 1c on its outer casing. The gas discharge section 1c releases gas from inside the outer casing to the outside when the internal pressure of the outer casing rises. The gas discharge section 1c is provided on one of the cell end faces 1a of the secondary battery cell 1. In the example shown in Figure 2, the gas discharge section 1c is provided on the first cell end face, which is the positive electrode side of the secondary battery cell 1. Such a gas discharge section 1c can be configured as a gas discharge valve that opens in response to an increase in the internal pressure of the outer casing.
[0039] The battery holder 22 stacks multiple secondary battery cells 1 in multiple layers in the vertical direction, with each cell end face 1a in a state where they are on the same plane. Furthermore, the cell end faces 1a of adjacent secondary battery cells 1 in the vertical direction of the multiple layers are offset, with the centers of the circles shifted. As a result, the assembly of multiple secondary battery cells 1 housed in the battery block 20 is flat on the vertical surface, but on the side surface, the centers of each cell end face 1a are offset, creating an uneven surface. Therefore, as shown in Figure 3, the side surface of the battery holder 22 is curved to follow the outer shape of the casing of the secondary battery cell 1. (Gas flow inhibiting structure 19)
[0040] In the event that gas is discharged from the gas discharge port 1c of any of the secondary battery cells 1, the outer casing 10 allows the gas to be discharged through the first gas discharge port 13A of the first lid 12A and then through the second gas discharge port 13B of the second lid 12B, as shown in the cross-sectional view of Figure 6. The second lid 12B also defines a second gas discharge path 18 between the first surface 12B1 of the second lid and the second surface 12A2 of the first lid, which guides the gas discharged from the first gas discharge port 13A to the second gas discharge port 13B. The second gas discharge path 18 is provided with a gas flow obstruction structure 19 that changes the direction of gas flow from the first gas discharge port 13A to the second gas discharge port 13B. This allows for the creation of a second gas discharge path 18 between the first lid 12A and the second lid 12B by utilizing the space created when the case lid 12 of the outer case 10 is doubled up, and by inhibiting the force of the gas moving through this second gas discharge path 18 with the gas progress inhibiting structure 19, the gas can be discharged to the outside of the battery pack 100 in a reduced pressure state, thereby enhancing safety.
[0041] Furthermore, the gas flow obstructing structure 19 can be defined by a first lid wall portion 12A2a protruding from the second surface 12A2 of the first lid portion 12A, and a second lid wall portion 12B1a protruding from the first surface 12B1 of the second lid portion 12B. It is preferable to arrange the first lid wall portion 12A2a and the second lid wall portion 12B1a so as to surround the first gas outlet 13A. (First lid wall portion 12A2a)
[0042] The first lid wall portion 12A2a is formed in multiple sections spaced apart from each other. In the example shown in Figure 7, which illustrates the first lid second surface 12A2 of the first lid portion 12A, the first wall portion is generally formed in a concentric circular shape surrounding the first gas outlet 13A formed in the central region of the first lid portion 12A. In this example, it is composed of an annular first wall portion formed in an arc shape with a portion open, surrounding the first gas outlet 13A; a first wall portion formed in a concentric circular shape with a larger diameter surrounding that; and a pair of first wall portions formed in a concentric circular shape with the same radius, spaced apart from each other, and bent into parallel lines. By forming multiple first lid wall portions 12A2a in a concentric circular shape surrounding the first gas outlet 13A in this way, and partially cutting out a part of the annular shape, it is possible to allow gas to enter through the cut-out portion, but to restrict the entry point and cause it to travel around, thereby reducing the gas pressure. The number and shape of the first lid wall portions 12A2a are not limited to this example. For example, in the example shown in Figure 7, they are formed in a concentric circular shape, but they may be concentric triangular, rectangular, polygonal, or flat first lid wall portions arranged in parallel. (Second lid wall portion 12B1a)
[0043] Furthermore, between the first surface 12B1 of the second lid and the second surface 12A2 of the first lid, a gas flow obstruction structure 19 is provided that obstructs the progress of gas guided into this second gas discharge path 18, while the first lid wall portion 12A2a is combined with the second lid wall portion 12B1a to define the second gas discharge path 18. Specifically, the second lid wall portion 12B1a protruding from the first surface 12B1 of the second lid 12B is also arranged to surround the first gas outlet 13A. Multiple second lid wall portions 12B1a are also formed spaced apart from each other. In the example shown in Figure 8, which illustrates the first surface 12B1 of the second lid 12B, the second lid wall portion 12B1a is also generally formed in a concentric circle shape surrounding the first gas outlet 13A when the second lid 12B is combined with the first lid 12A. In this example, the lid wall portion 12B1a is composed of a closed annular second lid wall portion 12B1a surrounding the first gas outlet 13A, through which a cross-shaped partition plate passes through the center of the annular portion; a larger diameter concentric second lid wall portion 12B1a surrounding it; and a parallel linear second lid wall portion 12B1a provided at a distance from it.
[0044] By joining the second lid first surface 12B1 of the second lid portion 12B having such a second lid wall portion 12B1a to the first lid second surface 12A2 of the first lid portion 12A, as shown in FIGS. 9 to 13, the first lid wall portion 12A2a and the second lid wall portion 12B1a form a second gas discharge path 18 provided with a gas progress inhibition structure 19. Here, as shown in the cross-sectional views of FIGS. 6 and 11, the heights of the first lid wall portion 12A2a and the second lid wall portion 12B1a are basically such that when the second lid portion 12B and the first lid portion 12A are in a joined state, they do not come into contact with opposing surfaces, that is, a gap is formed between the respective edge of the first lid wall portion 12A2a and the second lid wall portion 12B1a and the opposing surface, and are designed to be lower than the height of the second gas discharge path 18. As a result, as shown in the cross-sectional view of FIG. 6, when the gas guided from the central first gas discharge port 13A to the second gas discharge path 18 travels toward the surrounding second gas discharge port 13B, with the first lid wall portion 12A2a protruding from the opposing first lid second surface 12A2 and the second lid wall portion 12B1a protruding from the opposing second lid first surface 12B1, the gas is caused to travel in a zigzag manner through gaps alternately formed on the wall surface of the second gas discharge path 18. By forcibly changing the traveling direction of the gas in this way and lengthening the path, pressure loss is caused, and the gas is allowed to travel while reducing the pressure of the gas and simultaneously removing the temperature of the gas. When the gas finally reaches the second gas discharge port 13B, it is discharged to the outside from the outer case 10 in a state where the pressure and temperature of the gas are reduced to a level that does not lead to ignition, whereby safety can be ensured.
[0045] Furthermore, it is preferable to form the outer shape of the second lid portion 12B to be smaller than that of the first lid portion 12A. This allows the gas advance obstruction structure 19 to be constructed by attaching the second lid portion 12B to the first lid portion 12A while the first lid portion 12A closes the open end of the case body 11. As shown in Figures 7, 9 to 12, the second surface 12A2 of the first lid portion 12A forms a frame-shaped peripheral wall 46 along its periphery. The second lid portion 12B is formed to have an outer shape that follows this peripheral wall 46, and the second lid portion 12B is fixed to the second surface 12A2 of the first lid portion 12A with its periphery inserted into the inner surface of the peripheral wall 46. With this configuration, as shown in the cross-sectional view of Figure 6, the second gas outlet 13B is formed in the peripheral region of the second lid 12B, and the gas can be bent 90° from the gap at the joint interface between the first lid 12A and the second lid 12B to communicate with the second gas outlet 13B. By bending the direction of gas travel, the force of the gas can be suppressed and discharged to the outside. Screwing, welding, or fitting can be used to fix the second lid 12B and the first lid 12A. (First gas discharge path 18A)
[0046] In the above example, a second gas discharge path 18 is formed between the second surface 12A2 of the first lid 12A and the first surface 12B1 of the second lid 12B, with a gas flow inhibiting structure 19 provided, thereby reducing the pressure and temperature of the gas discharged from the secondary battery cell 1 and discharging it from the outer casing 10. In addition to this, the present disclosure also describes a first gas discharge path 18A provided prior to the second gas discharge path 18, that is, between the first surface 12A1 of the first lid 12A and the block end face of the battery block, and also provides a gas flow inhibiting structure 19 in this first gas discharge path 18A to lengthen the gas flow path and reduce the gas pressure. (Fire-resistant material 30)
[0047] Furthermore, the battery pack 100 may further include a refractory material 30. By disposing the refractory material 30 upstream of the first gas discharge path 18A, the first lid portion 12A is protected from high-temperature and high-pressure gas, and the traveling direction of the gas is once directed to the outer peripheral side to lengthen the path length, which can contribute to reducing the pressure of the gas. As shown in FIG. 5, the refractory material 30 is disposed between the inner surface of the case lid portion 12 and the block end surface 21 of the battery block 20 in the accommodation space of the outer case 10. This refractory material 30 is made of a heat-resistant material. The refractory material 30 is also formed in a plate shape. An inorganic material can be used for such a refractory material 30. Preferably, a sheet material made of mica can be used. A metal plate, ceramic, enamel or the like can also be used as the refractory material 30. The thickness of the refractory material 30 is 0.5 mm to 2.0 mm, preferably 0.8 mm to 1.0 mm.
[0048] In a state where the refractory material 30 is disposed on the block end surface 21 of the battery block 20, the refractory material 30 is disposed in a posture that covers the gas discharge portion 1c provided on the cell end surface 1a of the secondary battery cell 1 located on the block end surface 21 of the battery block 20. With such a configuration, even if gas is discharged from any of the secondary battery cells 1 located on the block end surface 21 of the battery block 20, the refractory material 30 disposed so as to cover the gas discharge portion 1c provided on the cell end surface 1a can avoid a situation where the gas directly irradiates the cell end surface 1a, and by guiding the gas to the cell end surface 1a in a state where the momentum of the gas is weakened by the heat-resistant refractory material 30, damage to the cell end surface 1a can be avoided and safety can be improved.
[0049] As also shown in FIG. 5, a plurality of positioning holes 32 for positioning are provided in the refractory material 30. Guide pins 16 to be inserted into the positioning holes 32 are provided on the first lid portion 12A. Furthermore, in the example of FIG. 5, a bus bar connection portion 17 for connecting the bus bar 6 for leading out the output of the battery module 2 to the outside is provided on the first first lid surface 12A1 of the first lid portion 12A of the case lid portion 12. In order to connect this bus bar connection portion 17 to the bus bar 6, the refractory material 30 is provided with an opening of a connection hole 33. This connection hole 33 can also be used for positioning the refractory material 30. (Gap space 35)
[0050] Furthermore, by forming the outer shape of the fire-resistant material 30 to be slightly smaller than the inner surface of the case lid 12, a gap space 35 can be created between the inner surface of the first lid 12A that constitutes the case lid 12 and the periphery of the fire-resistant material 30, as shown in Figures 14 and 15. With this configuration, as shown in Figure 14, if gas is discharged from a part of the secondary battery cell 1, the fire-resistant material 30 placed in the storage space prevents the gas from being directly released to the outside at high temperature and pressure through the gas outlet 13 of the case lid 12. In addition, by first dispersing the gas around the fire-resistant material 30, allowing it to flow around to the back side of the fire-resistant material 30 through the gap space 35, and then discharging it from the gas outlet 13, the distance over which the gas discharged from the secondary battery cell 1 is discharged from the outer case 10 can be increased. As a result, by diverting the gas through the gap space 35 and then discharging it from the gas outlet 13, the pressure and temperature of the gas can be reduced as it progresses, and the risk of ignition is reduced when the gas is discharged from the gas outlet 13, thereby improving safety. In particular, when the case lid is made of resin, if the high temperature and pressure of the gas are blown directly onto the case lid, the possibility of damage increases. Therefore, by protecting the case lid 12 with fire-resistant material 30 and further increasing the path length to the gas discharge, the temperature and pressure of the gas can be reduced to a level that prevents damage even to resin cases.
[0051] In this disclosure, the aim is to suppress the situation in which flames erupt from the outer casing 10 when gas is discharged from the gas discharge section 1c of some of the multiple secondary battery cells 1 contained in the battery pack 100. It is desirable to design the device in such a way that flames do not leak from the outer casing 10 even when gas is discharged from a secondary battery cell 1 located on the block end face 21 side, facing the inner surface of the case lid 12, where the gas pressure and temperature are expected to be highest. With such a specification, it is assumed that the gas pressure and temperature will be relatively lower even when gas is released from a secondary battery cell 1 that does not face the block end face 21. (Case wall 14)
[0052] Gas that has passed through the gap space 35 formed by the fire-resistant material 30 is guided to the first gas discharge path 18A. The first gas discharge path 18A has a case wall portion 14 formed therein. Specifically, the first lid portion 12A, which constitutes the case lid portion 12, has multiple case wall portions 14 formed at intervals, intersecting the direction from the periphery of the fire-resistant material 30 toward the gas discharge port 13. With this configuration, when gas is discharged from a part of the secondary battery cell 1, the fire-resistant material 30 placed in the storage space prevents the gas from directly irradiating the first lid portion 12A. In addition, by having multiple case wall portions 14 intersect with the gas moving from the periphery of the fire-resistant material 30 toward the gas discharge port 13, the path through which the gas flows is lengthened, the force of the gas is weakened and the temperature is lowered, resulting in a safer state.
[0053] Furthermore, it is preferable to arrange the multiple case walls 14 so as to surround the gas outlet 13, as shown in Figures 5 and 16. This way, the gas released from the secondary battery cell 1 is interfered with by the multiple case walls 14 before being discharged from the gas outlet 13, weakening its force and pressure each time, thereby improving safety in the event of runaway overheating.
[0054] It is preferable that multiple case wall portions 14 are arranged in a ring around the gas outlet 13. More preferably, multiple case wall portions 14 are arranged concentrically around the gas outlet 13. As shown in Figures 5 to 16, the multiple case wall portions 14 are formed in a partial arc shape that constitutes concentric circles of different radii. By making them partial arc shapes, the case wall portions 14 of different radii are arranged so that they overlap the area where the ring is cut out. This causes the gas to be obstructed by the case wall portions 14, and the gas that passes over these case wall portions 14 through the cut-out area is further obstructed by other case wall portions 14, resulting in the gas traveling around multiple case wall portions 14. This causes a pressure loss in the gas, simultaneously lowers the temperature, lengthens the path the gas travels to the outlet, and reduces the gas's force and temperature to a safe level.
[0055] In addition, it is preferable to form uneven surfaces 15 on each of the multiple case wall portions 14. This allows flammable materials such as powder contained in the gas to be trapped in the uneven surfaces 15 as the gas released from the secondary battery cell 1 flows over the surface of the case wall portion 14, thereby reducing the amount of powder contained in the gas when it is discharged from the outer case 10. This suppresses the generation of flames due to the combustion of such powder and enhances safety.
[0056] In the above example, for illustrative purposes, the fire-resistant material 30 and case wall 14 near the gas outlet 13 on the left case lid 12 in Figure 1 have been described. However, it goes without saying that a gas outlet may also be provided on the right case lid 12, and fire-resistant material and case wall may be provided in its vicinity as well. In particular, it is preferable to provide such fire-resistant material 30 and case wall 14 on the case lid 12 that faces the cell end face 1a of the secondary battery cell 1 that has the gas outlet 1c. In other words, for example, in the case lid 12 on the right side of Figure 1, if only the cell end face of a secondary battery cell without a gas outlet faces the block end face that faces the inner surface of this case lid 12, then it is not necessary to provide such fire-resistant material or case wall.
[0057] In the above example, the battery pack is attached to the electrical device to be powered, and power is supplied to the electrical device. When the remaining capacity of the battery pack becomes low or the battery pack deteriorates over time, the battery pack can be replaced, allowing the electrical device to continue to be used. However, the present invention is not limited to replaceable battery packs that mainly house secondary battery cells, but can also be applied to configurations in which secondary battery cells are housed within the casing of the electrical device. In this disclosure, a battery pack is defined as a device in which secondary battery cells are housed within a case, and also includes devices in which the secondary battery cells for driving are built into the casing of the electrical device itself. In other words, the present invention is not limited to replaceable battery packs, but can also be applied to electrical devices that have built-in secondary battery cells.
[0058] The battery pack disclosed herein can be suitably used as a power source for electric assist bicycles, as well as for self-propelled delivery robots, electric carts for delivery and golf courses, electric scooters, construction machinery, hybrid vehicles, and electric vehicles. It can also be used as a power source for portable electrical equipment such as wireless devices, electric cleaners, and power tools. Furthermore, it can be applied not only to power sources but also to cooling mechanisms for electrical equipment containing heat-generating elements. Alternatively, it can be used for stationary energy storage devices, such as battery packs for homes, businesses, and factories, or as backup power sources for servers.
[0059] 100...Battery pack 1...Secondary battery cell; 1a...Cell end face; 1c...Gas outlet 2...Battery module 3...Circuit board 5...Lead board 6...Bus bar 10...Outer case 11...Case body 12, 12'...Case lid; 12A...First lid; 12A1...First surface of first lid; 12A2...Second surface of first lid 12A2a...First lid wall 12B...Second lid; 12B1...First surface of second lid; 12B2...Second surface of second lid 12B1a...Second lid wall 13...Gas outlet; 13A...First gas outlet; 13B...Second gas outlet 14...Case wall 15...Rubber section 16...Guide pin 17...Bus bar connection section 18A...First gas outlet path 18...Second gas outlet path 19...Gas flow obstruction structure 20...Battery block 21...Block end face 22...Battery holder 23...Holder cylinder 30...Fireproof material 32...Positioning hole 33...Connection hole 35...Gap space 40...Sealing material 42...Filter 44...Fitting hardware 46...Surrounding wall
Claims
1. A battery pack comprising: a battery block composed of a plurality of secondary battery cells, each having a gas discharge port on its end face for discharging gas when the internal pressure rises; and an outer case that houses the battery block in an internal storage space, wherein the outer case comprises: a cylindrical case body with at least one end open; and a case lid that closes the open end of the case body; the case lid comprises: a first lid portion having a first lid surface facing the block end face of the battery block and a first lid second surface opposite to the first lid surface, and having a first gas discharge port opening; and a second lid portion superimposed on the first lid portion, having a second lid surface facing the first lid second surface of the first lid portion and a second lid second surface opposite to the second lid surface, and having a second gas discharge port opening that communicates with the first gas discharge port; The battery pack comprises a second lid portion which defines a second gas discharge path between the first surface of the second lid and the second surface of the first lid for guiding the gas discharged from the first gas discharge port to the second gas discharge port, and the second gas discharge path which is provided with a gas flow obstruction structure that changes the direction of gas flow from the first gas discharge port to the second gas discharge port.
2. A battery pack according to claim 1, wherein the gas advance inhibiting structure is defined by a first lid wall portion protruding from the second surface of the first lid of the first lid, and a second lid wall portion protruding from the first surface of the second lid of the second lid.
3. A battery pack according to claim 2, wherein the first lid wall and the second lid wall are arranged to surround the periphery of the first gas outlet.
4. A battery pack according to claim 1, wherein the first gas outlet is opened in the central region of the first lid, and the second gas outlet is opened in the peripheral region of the second lid.
5. A battery pack according to claim 1, wherein the outer shape of the second lid is formed to be smaller than that of the first lid.
6. A battery pack according to any one of claims 1 to 5, wherein the first lid portion is formed on the first surface of the first lid portion with a plurality of case wall portions spaced apart from each other so as to surround the first gas outlet.
7. A battery pack according to claim 6, wherein each of the plurality of case walls has an uneven surface.
8. A battery pack according to any one of claims 1 to 5, wherein the case lid is made of resin.
9. A battery pack according to claim 8, wherein the case body is made of metal.