Battery pack

Abstract

A battery pack includes a plurality of battery cells each having a discharge valve that opens when an internal pressure exceeds a set pressure, a housing that houses the plurality of battery cells, and an exhaust duct disposed inside the housing to discharge exhaust gas from the discharge valve outside the housing. The plurality of battery cells are arranged in parallel in the same plane to form a battery block. The housing has a diffusion space inside that diffuses the exhaust gas ejected from the discharge valve. The exhaust duct has an exhaust side that opens to the outside of the housing and an inflow side that opens to the diffusion space. The exhaust duct is configured so that the exhaust gas ejected from the discharge valve passes through the diffusion space and is then discharged outside the housing via the exhaust duct. The exhaust duct is filled with heat-resistant fibers.

Description

[0001] This application is a divisional application of the invention application filed on December 9, 2019, with the international filing date of 2019 and the national application number of 201980087986.1, entitled "Battery Pack". Technical Field

[0002] This invention relates to a battery pack that houses a rechargeable battery in an outer casing. Background Technology

[0003] Battery packs used as power sources for portable electrical devices have seen increasing demands for higher output in recent years, leading to the adoption of non-aqueous electrolyte secondary batteries such as lithium-ion batteries with high efficiency per unit volume. While lithium-ion batteries offer high output, their internal pressure can sometimes rise for various reasons. To ensure safety in the face of rising internal pressure, a discharge valve is installed to prevent rupture by setting a pressure to open. When the discharge valve opens, the battery is in an abnormally heated state, violently ejecting high-temperature gas from the valve. To allow the discharged gas from the discharge valve to escape to the outside, battery packs with holes in the outer casing have been developed. (See Patent Document 1)

[0004] Furthermore, a design was developed that incorporates multiple through-holes in the outer casing to improve internal ventilation, dissipate heat from the battery, and prevent heat buildup within the casing. (Refer to Patent Document 2)

[0005] Prior art literature

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2001-196039

[0008] Patent Document 2: Japanese Patent Application Publication No. 10-162795 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] In conventional battery packs, holes are provided in the outer casing to allow exhaust gases ejected from the vent valve to escape to the outside. This makes it difficult to safely exhaust the high-temperature exhaust gases violently ejected from the individual battery cells. In particular, since the exhaust gases ejected from the vent valve of lithium-ion batteries (non-aqueous electrolyte secondary batteries) are abnormally hot (above 400°C) and violently ejected, the exhaust gases can thermally melt the outer casing, leading to smoke and fire due to the high-temperature exhaust gases ejected outside the casing, compromising safety. Furthermore, flames generated inside the outer casing are released to the outside through the holes in the outer casing, further compromising safety.

[0011] This invention was developed to prevent the above-mentioned drawbacks. The main objective of this invention is to provide a battery pack that suppresses the drawbacks caused by high-temperature exhaust gas ejected from the open exhaust valve and the release of flames outside the casing, thereby ensuring safety.

[0012] Methods for solving problems

[0013] The battery pack of the present invention comprises: a battery cell 1 having a discharge valve that opens when the internal pressure exceeds a set pressure; and a housing 2 that houses the battery cell 1. An exhaust pipe 5 is disposed within the housing to discharge exhaust gas from the discharge valve to the outside of the housing. The exhaust pipe 5 opens outward on the discharge side and inward on the inflow side. The housing 2 is configured such that a diffusion space 25 for the discharged gas is provided internally, the discharge valve injects the discharged gas into the diffusion space 25, and the discharged gas from the diffusion space 25 is discharged to the outside of the housing via the exhaust pipe 5.

[0014] Invention Effects

[0015] The battery pack of the present invention can suppress the drawbacks caused by the high-temperature exhaust gas ejected from the exhaust valve of the battery cell, thereby improving safety. This is because the battery pack has an exhaust pipe inside the casing, with the inflow side of the exhaust pipe opening inwards and the exhaust side opening outwards. Furthermore, it is constructed with a diffusion space for the exhaust gas inside the casing. The exhaust valve ejects exhaust gas into the diffusion space, where it expands and is then concentrated in the exhaust pipe, thus being discharged outside the casing. The battery pack further attenuates the energy of the exhaust gas ejected from the battery cell by expanding and diffusing it in the diffusion space, causing energy decay through collisions. This concentrates the energy of the diffused exhaust gas into the exhaust pipe and discharges it outside the casing, further attenuating the energy and discharging it outside the casing. In other words, the battery pack attenuates and discharges the energy of the exhaust gas ejected from the exhaust valve in the following two steps: after attenuation using the diffusion space, the energy is concentrated and flows into the exhaust pipe from the diffusion space; and through the exhaust pipe, the high-temperature exhaust gas violently ejected from the exhaust valve is discharged outside the casing due to the attenuation of both thermal and kinetic energy. Therefore, the battery pack described above is characterized by exhausting the high-temperature exhaust gas violently ejected from the exhaust valve to the outside of the casing in a low-energy state to suppress the reduction in safety caused by the high-temperature exhaust gas; and by weakening the flame through the exhaust pipe to suppress the release of the flame generated inside the casing to the outside of the casing. Attached Figure Description

[0016] Figure 1 This is a schematic horizontal cross-sectional view showing the internal structure of the battery pack according to Embodiment 1 of the present invention.

[0017] Figure 2This is a vertical longitudinal sectional view of the battery pack according to Embodiment 1 of the present invention.

[0018] Figure 3 This is a vertical cross-sectional view of the battery pack involved in Embodiment 1 of the present invention.

[0019] Figure 4 This is a schematic perspective view showing the internal structure of the battery pack according to Embodiment 1 of the present invention.

[0020] Figure 5 This is a vertical cross-sectional view showing the internal structure of the battery pack according to Embodiment 2 of the present invention. Detailed Implementation

[0021] The first invention is a battery pack comprising: a battery cell having a discharge valve that opens when the internal pressure exceeds a set pressure; and a housing housing the battery cell, wherein an exhaust pipe is disposed within the housing to discharge exhaust gas from the discharge valve to the outside of the housing, the exhaust pipe opening to the outside of the housing on the discharge side and opening to the inside of the housing on the inflow side, the housing being configured such that a diffusion space for the exhaust gas is provided inside, the discharge valve injects exhaust gas into the diffusion space, and the exhaust gas from the diffusion space is discharged to the outside of the housing via the exhaust pipe.

[0022] In the second invention, the exhaust pipe is a thin cylindrical pipe with a thickness smaller than its width, and the thickness direction of the thin cylindrical pipe is used as the thickness direction of the housing to arrange the exhaust pipe within the housing. This configuration allows the exhaust pipe to be arranged in a narrower area within the housing. Furthermore, by reducing the thickness of the exhaust pipe and increasing the flow resistance, the energy of the exhaust gas can be more effectively attenuated, and the intensity of the flame can be reduced.

[0023] In the third embodiment of the present invention, multiple battery cells are arranged in a parallel orientation on the same plane to form a battery block, and a thin cylindrical pipe is disposed between the battery block and the inner surface of the casing. This battery pack structure, by making the battery block composed of multiple battery cells thinner while simultaneously distributing the thin cylindrical pipe between the battery block and the inner surface of the casing, enables the overall battery pack to be thinner and allows for space-saving placement of the exhaust pipe.

[0024] The fourth invention relates to an exhaust pipe disposed along an edge opposite to the interior of the housing. This configuration allows for the placement of multiple exhaust pipes within the housing, ensuring smooth exhaust of gases to the outside of the housing.

[0025] In the fifth embodiment of the present invention, the exhaust pipe is configured to extend along the width direction of the housing, such that the total length of the exhaust pipe is 60% longer than the width direction of the housing. This extension of the exhaust pipe relative to the width direction of the housing by the battery pack effectively attenuates the energy of the exhaust gas during exhaust.

[0026] In the sixth embodiment of the present invention, the exhaust pipe is configured to extend along the longitudinal direction of the housing, such that the total length of the exhaust pipe is 60% longer than the longitudinal direction of the housing. This battery pack can extend the exhaust pipe, thereby increasing the resistance to the exhaust gas.

[0027] In the seventh invention, the exhaust pipe is disposed within the housing in a configuration that extends in a direction intersecting the longitudinal direction of the battery cell. Because this battery pack is configured such that the injection direction of the exhaust gas and the exhaust direction of the exhaust pipe intersect each other, the energy of the exhaust gas can be effectively attenuated by changing the direction of the exhaust gas injected from the battery cell within the housing and discharging it to the outside.

[0028] In the eighth invention, a tag that is peeled off by the exhaust gas discharged from the exhaust valve is attached to the exhaust side of the exhaust pipe. Since the battery pack can seal the exhaust side of the exhaust pipe with the tag, it can effectively prevent foreign objects from entering the exhaust pipe from the outside.

[0029] The ninth invention of the present invention uses a battery cell as a non-aqueous electrolyte secondary battery. Furthermore, the tenth invention of the present invention uses a battery cell as a lithium-ion battery.

[0030] The present invention will now be described in detail with reference to the accompanying drawings. Furthermore, in the following description, terms indicating specific directions or positions (e.g., "upper," "lower," and other terms including these terms) are used as needed, but their use is merely to facilitate understanding of the invention with reference to the drawings and does not limit the technical scope of the invention based on the meaning of these terms. Additionally, the same reference numerals appearing in multiple drawings denote the same or equivalent parts or components.

[0031] Furthermore, the embodiments shown below represent specific examples of the technical concept of the present invention and are not intended to limit the invention to these embodiments. Additionally, the dimensions, materials, shapes, and relative arrangements of the constituent components described below are illustrative unless otherwise specified, and are not intended to limit the scope of the invention. Furthermore, the content described in one embodiment or example can be applied to other embodiments or examples. Moreover, the size and positional relationships of the components shown in the accompanying drawings are exaggerated for clarity.

[0032] (Implementation Method 1)

[0033] Figures 1-4 The battery pack 100 shown includes: a rechargeable battery cell 1; a housing 2 for housing the battery cell 1; an exhaust pipe 5 housed in the housing 2; and a circuit board 3 for mounting electronic components such as a protection circuit for the battery.

[0034] (Battery cell 1)

[0035] Battery cell 1 is a cylindrical battery. The cylindrical battery houses the electrodes and electrolyte within a cylindrical metal casing. The metal casing is a sealed structure in which a sealing plate is airtightly fixed to the opening of an outer can with a closed bottom. The outer can is manufactured by stamping a metal sheet. The sealing plate is airtightly fixed to the periphery of the opening of the outer can by riveting insulating gaskets.

[0036] Although not illustrated, a discharge valve is provided on the sealing plate of the battery cell 1 to prevent damage caused by abnormally high internal pressure in the metal casing. The discharge valve is an opening in the sealing plate that discharges internal gases, etc. However, the battery cell can also have a discharge valve and its opening at the bottom of the outer casing. The discharge valve opens when the internal pressure exceeds a set pressure, for example, 1.5 MPa, to prevent damage to the metal casing due to increased internal pressure. The discharge valve opens under abnormal conditions. Therefore, when the discharge valve is open, the temperature of the battery cell 1 becomes extremely high. Consequently, the gas and electrolyte (ejected material) discharged from the open discharge valve reach abnormally high temperatures. In particular, in battery packs where the battery cell 1 is a non-aqueous electrolyte secondary battery such as a lithium-ion battery, the discharged gas reaches abnormally high temperatures of over 400°C. Furthermore, since lithium-ion batteries are filled with non-aqueous electrolytes, if this electrolyte is discharged outside the casing at high temperatures, it may ignite upon contact with air, resulting in further abnormally high temperatures. This is not limited to lithium-ion batteries. In other rechargeable batteries, the exhaust gas ejected from the open exhaust valve becomes hot, thus causing the energy of the exhaust gas to decay and be exhausted outside the casing, which is important from a safety perspective.

[0037] (Shell 2)

[0038] The housing 2 is made of thermoplastic resin such as polycarbonate and is integrally molded into a quadrilateral box shape. Inside, it houses the battery cell 1, circuit board 3, and exhaust pipe 5. The housing 2 in the figure consists of an upper housing 2A and a lower housing 2B. Both the lower housing 2B and the upper housing 2A are quadrilateral, and in the figure, a peripheral wall 22 is provided around the rectangular surface plate 21. The lower housing 2B and the upper housing 2A are connected by the opening end face of the peripheral wall 22 as a mating surface. The peripheral wall 22 of the lower housing 2B and the upper housing 2A is composed of side walls 23 extending along the longitudinal direction of the rectangular surface plate 21 on both sides, and an end wall 24 orthogonal to the side walls 23. A heat-resistant cover 6 is disposed on the inner side of the end wall 24 opposite to the opening of the exhaust valve. The heat-resistant cover 6 is a heat-resistant plate or sheet material with heat resistance to the temperature of the exhaust gas. The heat-resistant cover 6 prevents the exhaust gas ejected from the exhaust valve from being directly ejected onto the end wall 24, causing the exhaust gas to disperse in all directions. The shell, with its end walls formed from heat-resistant materials, allows exhaust gases to disperse into the surrounding environment without the need for a heat-resistant cover.

[0039] Figures 1-3 The battery pack 100 has battery blocks 10 disposed within the housing. The battery block 10 is composed of two sets of battery assembly units 11. Each battery assembly unit 11 inserts individual battery cells 1 into a battery holder 4, thus fixing the individual battery cells 1 in a fixed position. The battery holder 4 is arranged in four rows of battery cells 1 parallel to the side wall 23 of the housing 2. The two sets of battery assembly units 11 are arranged in two levels along the longitudinal direction of the housing 2, forming a battery block 10 that connects eight individual battery cells 1 in series and parallel. Each battery assembly unit 11 has the openings of the discharge valves of two individual battery cells 1 facing each other against the end wall 24 within the housing. The battery pack 100 in the figure consists of four individual battery cells 1 forming a battery assembly 11, and two sets of battery assembly units 11 forming a battery block 10, which is disposed within the housing. However, the number of individual battery cells housed within the housing and their connection status are not specified in the present invention.

[0040] (Circuit board 3)

[0041] The circuit board 3 is connected to the battery cell 1 and houses electronic components (not shown) that implement the protection circuit for the battery cell 1. The protection circuit is a circuit that prevents overcharging or over-discharging of the battery cell 1, or a circuit that prevents overcurrent, or a circuit that cuts off the current when the temperature rises abnormally.

[0042] (Exhaust pipe 9)

[0043] The battery pack 100 has an exhaust pipe 5 inside the housing 2 for discharging exhaust gas ejected from the opening of the exhaust valve to the outside of the housing 2. The exhaust pipe 5 is open to the inside of the housing on the inflow side and open to the outside of the housing on the discharge side, so that exhaust gas can flow into the housing and be discharged to the outside of the housing. Figure 1 The battery pack 100 has a tag 7 attached to the exhaust side of the exhaust pipe 5, which is either peeled off or melted by the exhaust gas. The battery pack 100 uses the tag 7 to block the exhaust side of the exhaust pipe 5, preventing foreign matter from entering. The battery pack 100 ejects the exhaust gas from the exhaust valve into a diffusion space 25 located within the housing, flows from the diffusion space 25 into the exhaust pipe 5, and is then discharged outside the housing via the exhaust pipe 5. The housing 2 has a diffusion space 25 located inside. Figures 1-4The battery pack 100 uses the space formed inside the housing 2 as a diffusion space 25 for exhaust gas. The diffusion space 25 is a gap that guides the exhaust gas injected into the housing to the exhaust pipe 5. In the figure, the battery pack 100 has battery blocks 10 and circuit boards 3 as built-in structures inside the housing, so the diffusion space 25 is formed by the gap between the housing 2 and the built-in structures. Furthermore, the battery blocks 10 use battery holders 4 to fix the battery cells 1 in a fixed position, but the gap formed between the battery holders 4 and the battery cells 1 and the housing 2 also becomes the diffusion space 25. The diffusion space 25 diffuses the exhaust gas that is instantaneously discharged from the exhaust valve, causing the energy of the exhaust gas to decrease and flow into the exhaust pipe 5.

[0044] The battery pack 100 diffuses the exhaust gas ejected from the exhaust valve of the individual battery cell 1 into the diffusion space 25. After energy decay in the diffusion space 25, the energy is further decayed and discharged outside the casing via the exhaust pipe 5. The exhaust pipe 5 uses the internal resistance of the exhaust gas to decay the energy of the exhaust gas and discharge it outside the casing. Furthermore, even if a flame is generated inside the casing, the flame can be extinguished by the exhaust pipe 5, preventing the flame from being released outside the casing. Figures 1-4 The exhaust pipe 5 is a thin cylindrical pipe 5A with a thickness less than its width. The thin cylindrical pipe 5A has the following characteristics: it is thin enough to increase the resistance to the passage of exhaust gas, thereby effectively attenuating energy, and it can be configured in narrow spaces.

[0045] Figure 2 and Figure 3 The battery pack 100 has a thin cylindrical pipe 5A disposed on the inner side of the surface plate 21 of the housing 2 in the gap formed between it and the battery block 10. Figure 3 The battery pack 100 has two rows of thin cylindrical tubes 5A arranged on both sides of the circuit board 3. The thin cylindrical tubes 5A are arranged on the inner side of the surface plate 21 of the housing 2 with the thickness direction set to the thickness direction of the housing 2. Figure 3 and Figure 4 The battery pack 100 has a pair of exhaust pipes 5 arranged along opposite sides inside the housing. The housing 2 is a cuboid, and two rows of exhaust pipes 5 are arranged at both ends of the inner side of the rectangular surface plate 21, extending along the width direction of the housing 2. The resistance to the exhaust gas passing through the exhaust pipes 5 increases proportionally to their length. Figure 1 and Figure 2 In the battery pack 100, the length of the exhaust pipe 5 is approximately equal to the lateral width of the housing 2 to increase the resistance to gas passage. Preferably, the exhaust pipe 5 is longer than 60% of the lateral width of the housing 2, thereby efficiently attenuating the energy of the exhaust gas and venting it.

[0046] Figure 4The schematic perspective view of the battery pack 100 shows a battery cell 1 and an exhaust pipe 5 arranged in a configuration where they extend in intersecting directions within the housing. The battery cell 1 is arranged to extend along the longitudinal direction of the rectangular surface plate 21, and the exhaust pipe 5 is arranged to extend along its width, thus aligning the battery cell 1 and the exhaust pipe 5 in orthogonal directions. The battery cell 1 ejects exhaust gas from its open exhaust valve into the longitudinal direction of the housing 2, and the exhaust pipe 5 allows the incoming exhaust gas to flow and exhaust in the width direction of the housing 2. That is, the ejection direction of the exhaust gas and the exhaust direction of the exhaust pipe 5 are intersecting, orthogonal in the figure, and the exhaust gas changes direction within the housing to exhaust to the outside.

[0047] In addition, Figures 1-4 In this configuration, the battery cell 1 is arranged to extend along the longitudinal direction of the rectangular surface plate 21, but it can also be arranged to extend along the width direction of the rectangular surface plate. In this case, the exhaust pipe is arranged to extend along the longitudinal direction of the rectangular surface plate. With this configuration, the direction of the exhaust gas ejected from the exhaust valve of the battery cell intersects with the exhaust direction of the exhaust pipe. Furthermore, if the battery cell is arranged to extend along the height direction within the casing, the exhaust pipe can also be arranged to extend either along the longitudinal direction or along the width direction of the rectangular surface plate. In either configuration, the direction of the exhaust gas ejected from the battery cell intersects with the exhaust direction of the exhaust pipe.

[0048] The exhaust gas injected into the housing from the exhaust valve... Figure 4 The exhaust gas flows in the direction indicated by the arrow and is exhausted out of the casing. The exhaust valve of the battery cell 1 has its opening facing the end wall 24 of the casing 2. The exhaust gas ejected from the exhaust valve is sprayed toward the end wall 24. Since a heat-resistant cover 6 is disposed on the inner side of the end wall 24, the exhaust gas collides with the heat-resistant cover 6 and disperses to the surroundings. The exhaust gas that collides with the heat-resistant cover 6 flows into the diffusion space 25 and diffuses. The exhaust gas flowing into the diffusion space 25, as shown by the arrow, collides with the inner surface of the casing 2 and disperses, changing direction and flowing into the exhaust pipe 5. Figure 4 As indicated by the arrow, the energy is attenuated by colliding with, dispersing, and reversing its direction with the inner surface of the casing 2, and then flows into the exhaust pipe 5. The resistance of the exhaust pipe 5 further attenuates the energy, causing it to be exhausted outside the casing. This energy-attenuating exhaust structure can suppress drawbacks such as fires outside the casing, thus improving safety.

[0049] (Implementation Method 2)

[0050] Figure 5The battery pack 200 shown in the cross-sectional view has heat-resistant fibers 8 inside the exhaust pipe 5. The heat-resistant fibers 8 can be inorganic fibers such as asbestos or metal fibers. The exhaust pipe 5 filled with heat-resistant fibers 8 has the following characteristics: it is short, which increases the resistance to exhaust gas; in addition, the filling density of the heat-resistant fibers 8 can be adjusted to control the passage resistance of the exhaust gas.

[0051] Industrial availability

[0052] This invention can be effectively used in battery packs that safely vent gases.

[0053] -Explanation of Figure Markers-

[0054] 100, 200… battery packs

[0055] 1…cell battery

[0056] 2…shell

[0057] 2A… Upper casing

[0058] 2B…lower housing

[0059] 3…Circuit board

[0060] 4…Battery holder

[0061] 5…exhaust pipe

[0062] 5A…thin cylindrical pipe

[0063] 6…Heat-resistant cover

[0064] 7… Tags

[0065] 8…Heat-resistant fiber

[0066] 10… battery blocks

[0067] 11… Battery Assembly

[0068] 21… Surface Panel

[0069] 22… Zhou Bi

[0070] 23…Side wall

[0071] 24…end wall

[0072] 25…Diffusion space.

Claims

1. A battery pack, comprising: Multiple battery cells, each having a discharge valve that opens if the internal pressure exceeds a set pressure; A housing that houses the plurality of battery cells; and An exhaust pipe, disposed within the housing, discharges exhaust gas from the exhaust valve to the outside of the housing. The multiple battery cells are arranged in a parallel orientation on the same plane to form a battery block. The housing has an internal diffusion space that allows the exhaust gas ejected from the exhaust valve to diffuse. The exhaust pipe will discharge through the opening laterally to the outside of the housing and flow into the opening laterally to the diffusion space. The configuration is such that the exhaust gas injected from the exhaust valve passes through the diffusion space and is then discharged to the outside of the housing via the exhaust pipe. The interior of the exhaust pipe is filled with heat-resistant fiber.

2. The battery pack according to claim 1, wherein, The heat-resistant fiber is an inorganic fiber or a metal fiber.

3. The battery pack according to claim 2, wherein, The inorganic fiber is asbestos.

4. The battery pack according to any one of claims 1 to 3, wherein, The filling density of the heat-resistant fiber is set to adjust the resistance of the exhaust gas in the exhaust pipe.

5. The battery pack according to any one of claims 1 to 3, wherein, The exhaust pipe is a thin-walled cylindrical pipe with a thickness that is shorter in the thickness direction than in the width direction. The thin-tube pipe is disposed within the housing with its thickness direction set in the thickness direction of the housing.

6. The battery pack according to claim 5, wherein, The thin-tube pipe is disposed between the inner surface of the battery block and the housing.

7. The battery pack according to any one of claims 1 to 3, wherein, The exhaust pipe is disposed within the housing in an orientation that extends in a direction intersecting the longitudinal direction of the battery cell.

8. The battery pack according to any one of claims 1 to 3, wherein, The opening of the discharge valve is disposed opposite to the end wall of the housing. A heat-resistant shield is disposed on the inner side of the end wall. The structure is designed such that the exhaust gas ejected from the exhaust valve collides with the heat-resistant cover and then flows into the diffusion space.

9. The battery pack according to any one of claims 1 to 3, wherein, A pair of exhaust pipes are arranged along opposite sides within the housing.

10. The battery pack according to any one of claims 1 to 3, wherein, A label is attached to the discharge side of the exhaust pipe that is peeled off or melted by the exhaust gas discharged from the discharge valve.

11. The battery pack according to any one of claims 1 to 3, wherein, The battery cell is a non-aqueous electrolyte secondary battery.

12. The battery pack according to claim 11, wherein, The battery cell is a lithium-ion battery.

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