Battery

Abstract

Provided is a battery equipped with a gas discharge mechanism capable of increasing a gas discharge capacity without increasing the proportions of the gas discharge mechanism.　The battery comprises a gas discharge mechanism for discharging gas inside a battery container when the gas pressure inside the battery container reaches a predetermined value. The gas discharge mechanism comprises: a first gas discharge passage 51 that is connected to the inside of the battery container; a second gas discharge passage 52 that is connected to the first gas discharge passage, and that is connected to the outside of the battery container; and a gas discharge valve that is provided in a part of a gas discharge passage comprising the first gas discharge passage and the second gas discharge passage, and that performs an opening operation so as to connect the inside and the outside of the battery container with the gas discharge passage when the gas pressure of the inside of the battery container reaches a predetermined value. Further, the cross-sectional shape of the second gas discharge passage 52 viewed in a gas outflow direction of when the gas discharge valve 54 is opened is formed in a shape that does not hinder the flow of a streamline of the gas flowing out from the first gas discharge passage 51.

Description

Technical Field

[0001] The present invention relates to a battery.

Background Art

[0002] In recent years, the development of lithium-ion secondary batteries with high energy density has been promoted as a power source for electric vehicles, hybrid vehicles, and the like. This lithium-ion secondary battery includes, for example, a wound electrode body and a battery can that houses the wound electrode body. The battery can includes an exterior body that is a box-shaped container with one surface being an opening, and a battery lid that closes the opening of the exterior body. Further, in this type of lithium-ion secondary battery, a gas discharge mechanism is provided in the battery lid for improving safety.

[0003] This gas discharge mechanism is a battery component provided with a discharge valve designed to be opened at a predetermined pressure and discharge the gas inside the battery can when gas is generated inside the battery can. For example, the lithium-ion secondary battery described in Japanese Unexamined Patent Application Publication No. 2012-252809 (Patent Document 1) has a lid member (battery lid) in which a base portion forming an upper surface, a peripheral wall portion forming a recess recessed from the base portion, and a cleavage-type gas discharge valve (safety valve) connected and supported on the inner peripheral surface of the peripheral wall portion are integrally formed.

[0004] In this Patent Document 1, an aluminum flat plate is press-worked to form a recess, and a thin-film gas discharge valve is integrally formed at the bottom of this recess. Then, when the gas pressure reaches a predetermined value, the thin film forming the gas discharge valve is cleaved, and the gas pressure is released to the outside to ensure safety.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] As mentioned above, in batteries used in lithium-ion secondary batteries, a gas release mechanism is provided to enhance safety by releasing the gas pressure even when the internal electrolyte and active material decompose, generating gas and increasing the internal pressure.

[0007] Incidentally, this type of lithium-ion secondary battery is used in mobile or stationary battery-powered devices. For example, batteries for electric vehicles (BEVs / Battery Electric Vehicles) have a large battery capacity per cell, which in turn increases the cell size and the number of components per cell (electrode group, electrolyte, active material, etc.). Therefore, it is necessary to increase the gas emission capacity of the gas emission mechanism to cope with the increase in the amount of gas generated due to the increase in components.

[0008] One way to increase the gas emission capacity of a gas emission mechanism is to increase its size. On the other hand, there is a need to develop lithium-ion secondary batteries equipped with a gas emission mechanism that can increase gas emission capacity without increasing the size of the gas emission mechanism itself.

[0009] Furthermore, the embodiment described below can be applied to batteries other than lithium-ion secondary batteries. In addition, the embodiment described below can be applied to stationary battery-using devices other than those for automobiles (for example, household or commercial energy storage devices).

[0010] The object of the present invention is to provide a battery equipped with a gas discharge mechanism that can enhance gas discharge capacity. [Means for solving the problem]

[0011] The present invention is characterized by a battery comprising an energy storage element, a battery container housing the energy storage element, and a gas discharge mechanism that fluidly connects the inside and outside of the battery container and discharges the gas inside the battery container when the gas pressure inside the battery container reaches a predetermined value, wherein the gas discharge mechanism comprises a first gas discharge passage connected to the inside of the battery container, a second gas discharge passage connected to the first gas discharge passage and connected to the outside of the battery container, and the second gas discharge passage on the side of the second gas discharge passage or the battery container of the second gas discharge passage that is closer to the inside end of the first gas discharge passage on the battery container side. The device includes a gas discharge valve provided in a portion of the gas discharge passage on the side of the first gas discharge passage that is closer to the outer end of the battery container. When the gas pressure inside the battery container reaches a predetermined value, the valve opens to connect the inside and outside of the battery container through the gas discharge passage. When the valve opens, it opens in a shape that conforms to the cross-sectional shape of the gas discharge passage. Furthermore, the cross-sectional shape of the second gas discharge passage, as viewed in the direction of gas outflow when the gas discharge valve is opened, is formed in a shape that does not obstruct the flow of gas streamlines flowing out from the first gas discharge passage. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a battery equipped with a gas discharge mechanism that can enhance gas discharge capacity. [Brief explanation of the drawing]

[0013] [Figure 1] This is an external perspective view showing the appearance of a lithium-ion secondary battery. [Figure 2] This is a disassembled perspective view showing the components of a lithium-ion secondary battery. [Figure 3] This is a cross-sectional view showing a cross-section of a gas discharge mechanism to explain the concept of the present invention. [Figure 4A] This is a cross-sectional view showing the configuration of a gas discharge mechanism according to the first embodiment of the present invention. [Figure 4B] This is a cross-sectional view showing the configuration of a gas discharge mechanism which is a first modified example of the first embodiment. [Figure 4C] This is a cross-sectional view showing the configuration of a gas discharge mechanism which is a second modified example of the first embodiment. [Figure 5] It is a cross-sectional view showing the types of parameters for simulating the gas discharge mechanism of FIG. 4. [Figure 6A] It is an explanatory view showing the values of parameters when executing the simulation of the gas discharge mechanism according to the first embodiment. [Figure 6B] It is an explanatory view showing the simulation result when executing the simulation of the gas discharge mechanism according to the first embodiment. [Figure 7A] It is an explanatory view showing the values of parameters when executing the simulation by changing the plate thickness of the battery lid of the gas discharge mechanism according to the first embodiment. [Figure 7B] It is an explanatory view showing the simulation result when executing the simulation by changing the plate thickness of the battery lid of the gas discharge mechanism according to the first embodiment. [Figure 8] It is a cross-sectional view showing the configuration of the gas discharge mechanism according to the second embodiment of the present invention. [Figure 9] It is a cross-sectional view showing the types of parameters for simulating the gas discharge mechanism of FIG. 8. [Figure 10A] It is an explanatory view showing the values of parameters when executing the simulation of the gas discharge mechanism according to the second embodiment. [Figure 10B] It is an explanatory view showing the simulation result when executing the simulation of the gas discharge mechanism according to the second embodiment. [Figure 11] It is a cross-sectional view showing the configuration of the gas discharge mechanism according to the third embodiment of the present invention. [Figure 12] It is a cross-sectional view showing the configuration of the gas discharge mechanism according to the fourth embodiment of the present invention. [Figure 13] It is a cross-sectional view showing the types of parameters for simulating the gas discharge mechanism of FIG. 12. [Figure 14A] It is an explanatory view showing the values of parameters when executing the simulation of the gas discharge mechanism according to the fourth embodiment. [Figure 14B]This is an explanatory diagram showing the simulation results when a simulation of the gas emission mechanism, which is the fourth embodiment, was performed. [Figure 15] This is a cross-sectional view showing the configuration of a gas discharge mechanism according to a fifth embodiment of the present invention. [Figure 16] This is a cross-sectional view showing the configuration of a gas discharge mechanism according to the sixth embodiment of the present invention. [Figure 17] This is a perspective view of a disassembled battery having a configuration suitable for the present invention, viewed from an oblique angle above. [Modes for carrying out the invention]

[0014] The embodiments of the present invention will be described in detail below with reference to the drawings, but the present invention is not limited to the embodiments described below, and various modifications and applications are also included within the scope of the technical concept of the present invention. [Examples]

[0015] Embodiments of the present invention will be described with reference to the drawings, and in the following embodiments, a lithium-ion secondary battery used in hybrid vehicles and electric vehicles will be described as an example of a battery. Figure 1 shows the appearance of a typical lithium-ion secondary battery to which this embodiment is applied, viewed from diagonally above.

[0016] As shown in Figure 1, the lithium-ion secondary battery C1 comprises a battery case 1 and a lid member (hereinafter referred to as the battery lid) 6. These are collectively defined as the "battery container." Inside the battery case 1, which has an opening, is a wound electrode body 3 (see Figure 2) which serves as an "energy storage element" that outputs stored electricity, and the opening 1a (see Figure 2) of the battery case 1 is sealed by the battery lid 6. For example, the battery case 1 contains an electrolyte, and the wound electrode body 3 is immersed in the electrolyte. Alternatively, an electrolyte other than a liquid electrolyte, such as a solid electrolyte, may be used.

[0017] The battery cover 6 is joined to the battery can 1 by laser welding, forming a sealed battery container with the battery can 1 and the battery cover 6. The battery cover 6 is provided with a positive electrode external terminal 8A and a negative electrode external terminal 8B. The lithium-ion secondary battery C1 charges the wound electrode body 3 via the positive electrode external terminal 8A and the negative electrode external terminal 8B, and also supplies power to an external load.

[0018] The battery cover 6 is integrally equipped with a gas discharge mechanism 10. If the gas pressure inside the battery container rises to a predetermined pressure for any reason, the gas discharge valve of the gas discharge mechanism 10 opens, and gas is discharged from the inside. This reduces the gas pressure inside the battery container, ensuring the safety of the lithium-ion secondary battery C1. The battery cover 6 is also provided with an electrolyte filling port 9 (see Figure 2), which is closed by an electrolyte plug 11 after the electrolyte has been injected.

[0019] The gas discharge mechanism 10 fluidly connects the inside and outside of the battery container. Fluidly connected means that the fluid (gas or liquid) in the space between the inside and outside of the battery container, separated by the gas discharge valve 54 (see Figure 4), can flow when the gas discharge valve 54 is opened. Although the gas discharge mechanism 10 is described as being integrally mounted on the battery cover 6, the structure of the gas discharge mechanism 10 may be manufactured separately and placed on the battery cover 6.

[0020] Figure 2 shows the external appearance of the disassembled lithium-ion secondary battery shown in Figure 1, viewed from an oblique angle above.

[0021] The battery casing 1 of the lithium-ion secondary battery C1 is a so-called rectangular shape, and has a rectangular bottom 22, rectangular cylindrical side walls (sometimes referred to as side circumferential surfaces) 21 rising from the four sides of the bottom 22 in the cell height direction (+Y direction), and an opening 1a that is open in the cell height direction at the upper end of the side walls 21. The side walls 21 of the battery casing 1 have a pair of wide side walls 21a that are spaced apart and facing each other in the cell thickness direction (+Z direction), and a pair of narrow side walls 21b that are spaced apart and facing each other in the cell width direction (+X direction).

[0022] The wound electrode body 3 is housed inside the battery case 1, wrapped and covered with an insulating protective film 2. The wound electrode body 3 has a roughly rectangular parallelepiped shape, with a pair of flattened surfaces and a pair of curved surfaces with a circular arc cross-section facing each other, separated by these flattened surfaces. The wound electrode body 3 is inserted into the battery case 1 from one of the curved surfaces and housed inside the battery case 1 in a lateral position with the winding axis direction aligned with the cell width direction (+X direction). Note that instead of a wound electrode body 3, a stacked electrode body can also be used. The electrode body has a positive electrode with a positive electrode material and a negative electrode with a negative electrode material.

[0023] The positive electrode foil connection portion 31d and the negative electrode foil connection portion 32d of the wound electrode body 3, which are the exposed electrode foil portions, are at least partially bundled in the direction of flattened thickness to form a flat plate, and are joined to the positive electrode side connection end 42A of the positive electrode current collector plate (current collector terminal) 4A and the negative electrode side connection end 42B of the negative electrode current collector plate (current collector terminal) 4B, respectively, by ultrasonic welding.

[0024] The base ends of the positive electrode current collector plate 4A and the negative electrode current collector plate 4B are connected to the positive electrode external terminal 8A and the negative electrode external terminal 8B, respectively. The battery cover 6 is provided with a gasket 5 and an insulating plate 7, which electrically insulate the positive electrode current collector plate 4A and the negative electrode current collector plate 4B, and the positive electrode external terminal 8A and the negative electrode external terminal 8B from the battery cover 6.

[0025] The battery casing 1 and battery cover 6 are made of aluminum or an aluminum alloy, which are metal materials. The positive electrode current collector plate 4A and positive electrode external terminal 8A are made of aluminum or an aluminum alloy. The negative electrode current collector plate 4B and negative electrode external terminal 8B are made of copper or a copper alloy.

[0026] The positive external terminal 8A and the negative external terminal 8B have welded joints that are welded to a busbar or the like (not shown). The welded joint has a rectangular block shape that protrudes upward from the battery cover 6, with its lower surface facing the surface of the battery cover 6 and its upper surface parallel to the battery cover 6 at a predetermined height.

[0027] The positive electrode connection portion 12A and the negative electrode connection portion 12B each protrude from the lower surface of the positive electrode external terminal 8A and the negative electrode external terminal 8B, respectively, and have a cylindrical shape at their tips that can be inserted into the positive electrode side through hole 6A and the negative electrode side through hole 6B of the battery cover 6. The positive electrode connection portion 12A and the negative electrode connection portion 12B pass through the battery cover 6 and protrude inward from the positive electrode current collector plate base 41A and the negative electrode current collector plate base 41B of the positive electrode current collector plate 4A and the negative electrode current collector plate 4B, and their tips are crimped to integrally fix the positive electrode external terminal 8A and the negative electrode external terminal 8B and the positive electrode current collector plate 4A and the negative electrode current collector plate 4B to the battery cover 6.

[0028] A gasket 5 is interposed between the positive external terminal 8A and the negative external terminal 8B and the battery cover 6, and an insulating plate 7 is interposed between the positive current collector plate 4A and the negative current collector plate 4B and the battery cover 6.

[0029] The positive electrode current collector plate 4A and the negative electrode current collector plate 4B each have a rectangular plate-shaped positive electrode current collector plate base 41A and a negative electrode current collector plate base 41B positioned opposite the lower surface of the battery cover 6, and positive electrode side connection ends 42A and negative electrode side connection ends 42B that are bent at the side ends of the positive electrode current collector plate base 41A and the negative electrode current collector plate base 41B, extending along the wide side surface of the battery can 1 toward the can bottom 22, and connected in a state where they are overlapped opposite the positive electrode foil connection portion 31d and the negative electrode foil connection portion 32d of the wound electrode body 3.

[0030] The positive electrode current collector plate base 41A and the negative electrode current collector plate base 41B are formed with a positive electrode side opening hole 43A and a negative electrode side opening hole 43B, respectively, through which the positive electrode connection portion 12A and the negative electrode connection portion 12B are inserted.

[0031] The positive terminal component is formed by the positive external terminal 8A and the positive current collector plate 4A described above, and the negative terminal component is formed by the negative external terminal 8B and the negative current collector plate 4B. These positive and negative terminal components are then integrally assembled to the battery cover 6 via the gasket 5 and the insulating plate 7 to form the battery cover assembly. The energy storage element assembly is then assembled by attaching the wound electrode body 3 to the battery cover assembly.

[0032] The wound electrode body 3 is supported between the positive electrode current collector plate 4A and the negative electrode current collector plate 4B of the battery cover assembly, with its winding axis direction extending parallel to the battery cover 6, and its flattened surface extending in a direction perpendicular to the lower surface of the battery cover 6, with a pair of curved surfaces of the wound electrode body 3 positioned on the side of the battery cover 6 and on the side of the bottom 22 of the battery can 1.

[0033] The insulating protective film 2 covers the wound electrode body 3, which is assembled to the battery cover assembly, from the outside, along with the positive electrode current collector plate 4A and the negative electrode current collector plate 4B, and is interposed between the side wall portion 21 and the bottom of the battery can 1, respectively.

[0034] The insulating protective film 2 is made of an insulating synthetic resin material and insulates the battery can 1 from the wound electrode body 3, the positive electrode current collector plate 4A, and the negative electrode current collector plate 4B. It also protects the wound electrode body 3, the positive electrode current collector plate 4A, and the negative electrode current collector plate 4B from direct contact with the battery can 1 when the lithium-ion secondary battery C1 is subjected to external shocks or vibrations.

[0035] The battery can 1 has dimensions and a shape such that when the wound electrode body 3 is inserted into the battery can 1 through the opening 1a with the wound electrode body 3 covered with an insulating protective film 2, the pair of flat surfaces of the wound electrode body 3 and the wide side wall portion 21a of the side wall portion 21 of the battery can 1 come into contact with the insulating protective film 2 sandwiched between them, and the wound electrode body 3 can be inserted by pressing with a slight pressing force. In addition, a slight gap is formed between the end faces on both sides of the winding axis direction of the wound electrode body 3 and the narrow side wall portion 21b of the side wall portion 21 of the battery can 1.

[0036] As described above, the opening 1a of the battery case 1 is closed by the battery cover 6, and the battery cover 6 is sealed by laser welding to the battery case 1. After that, the battery case 1 is filled with electrolyte. The electrolyte is injected into the battery case 1 through the injection port 9 of the battery cover 6. After the electrolyte is injected, the injection port 9 is closed by the injection plug 11, and the injection plug 11 is sealed by laser welding to the battery cover 6.

[0037] In lithium-ion secondary batteries with the above configuration, for example, batteries for BEVs have a large battery capacity per cell, which in turn increases the cell size, and consequently the number of components per cell, such as electrode groups, electrolytes, and active materials. Therefore, the amount of gas generated during thermal runaway of the cell also increases due to the increase in components, making it necessary to improve the gas exhaust capacity of the gas exhaust mechanism.

[0038] To increase the gas discharge capacity of a gas discharge mechanism, it is possible to increase its size. However, this would significantly increase the area occupied by the gas discharge mechanism in the battery container.

[0039] Therefore, there is a need for the development of a lithium-ion secondary battery equipped with a gas exhaust mechanism that can increase gas exhaust capacity without increasing the size of the gas exhaust mechanism itself. Accordingly, this embodiment proposes the configuration shown below.

[0040] In this embodiment, the gas discharge mechanism provided in the battery cover comprises a first gas discharge passage connected to the inside of the battery container, a second gas discharge passage connected to the first gas discharge passage and also connected to the outside of the battery container, and a gas discharge valve provided in the first gas discharge passage which opens to connect the first and second gas discharge passages when the gas pressure inside the battery container reaches a predetermined value, and when opening, opens to a shape that conforms to the cross-sectional shape of the gas discharge passage. Furthermore, the cross-sectional shape of the second gas discharge passage, as viewed in the direction of gas outflow when the gas discharge valve is opened, is formed to be an inclined shape that does not obstruct the flow of gas streamlines flowing out from the first gas discharge passage.

[0041] According to this embodiment, since the streamlines of the outflowing gas are not obstructed by the second gas discharge passage, the gas can flow smoothly, and the gas discharge capacity can be increased. In the following description, the opening shape (passage cross-sectional shape) of the gas discharge passage will be described as being circular.

[0042] Figure 3 is a diagram illustrating the basic concept of this embodiment, schematically showing the configuration of the gas discharge mechanism and the flow of gas. Note that in this figure and subsequent drawings, the plate thickness (t) of the battery cover 6 in the portion where the gas discharge path is formed and the opening diameter (d) of the gas discharge passage are not in an exact dimensional relationship; the plate thickness (t) is depicted larger than it actually is.

[0043] In Figure 3, the battery cover 6 has a plate thickness (t), and a gas discharge passage 50 is formed in the direction of the plate thickness (the direction perpendicular to the front and back surfaces of the battery cover). Note that the gas discharge valve is omitted. The gas discharge passage 50 consists of a first gas discharge passage 51 which is fluidly connected to the inside side (SPin) of the battery container, and a second gas discharge passage 52 which is fluidly connected to the first gas discharge passage 51 and also fluidly connected to the outside side (SPout) of the battery container.

[0044] Here, "fluidically connected" means that the fluid (gas or liquid) in the space between the inside and outside of the battery container, separated by the gas discharge valve, can flow through the first gas discharge passage 51 and the second gas discharge passage 52 when the gas discharge valve is opened.

[0045] The cross-sectional shape of the passages, including the openings of the first gas discharge passage 51 and the second gas discharge passage 52 (in the direction perpendicular to the plate thickness direction), is circular, and the first gas discharge passage 51 and the second gas discharge passage 52 are formed on the same axis. For this reason, the outlet opening of the first gas discharge passage 51 and the inlet opening of the second gas discharge passage 52 are the same diameter and are aligned and connected.

[0046] The first gas discharge passage 51 is formed in a cylindrical shape (actually an empty space, and can also be described as a cylindrical shape) in the plate thickness direction, and the second gas discharge passage 52 is formed in a frustoconical shape (actually an empty space, and can also be described as a frustoconical cylinder shape) in the plate thickness direction. The connection between the first gas discharge passage 51 and the second gas discharge passage 52 has the same opening diameter (d). As shown in the figure, as you approach the outside side (SPout) of the battery container, the opening diameter (d) of the second gas discharge passage is formed to gradually increase, and the cross-sectional shape viewed in the direction of gas outflow is formed as a linearly inclined inclined portion 53 that widens in the direction away from the axis of the second gas discharge passage 52.

[0047] Next, we will explain the behavior of the gas flowing through the first gas discharge passage 51 and the second gas discharge passage 52. As shown in the gas streamlines (FLW) of the battery container, when the gas generated inside the battery container flows into the first gas discharge passage 51, it forms an accretionary flow section (ACF) midway through the first gas discharge passage 51, and then, as it flows out of the first gas discharge passage 51, it expands outwards. The streamlines on the outer circumference, in particular, tend to expand outwards. Note that the gas streamlines shown here are hypothetical representations of gas flow based on the streamlines in fluid dynamics.

[0048] Furthermore, the gas discharge passage of the gas discharge mechanism used as a comparative example to this embodiment has a shape that is an extension of the first gas discharge passage 51, as shown by the dashed line (DL). In this section, the flow of gas streamlines that have been expanded is obstructed, and the amount of gas discharged tends to be suppressed. This is due to the disturbance of streamlines in the region of the dashed line (DL). Obstruction of streamline flow refers to the phenomenon in which gas flowing on the outside of the gas flow is hindered by other physical obstacles (in this case, the passage walls of the gas discharge passage), forming vortices and preventing it from flowing smoothly, thus disturbing the streamlines.

[0049] Therefore, in this embodiment, in order to avoid disturbing the direction of the gas streamlines flowing out from the first gas discharge passage 51, the opening diameter (d) of the second gas discharge passage 52 is continuously and gradually increased as it approaches the outside side (SPout) of the battery container. In other words, the cross-sectional shape viewed in the direction of gas discharge is formed as an inclined portion 53 that slopes to expand in the direction away from the axis of the second gas discharge passage 52. This inclined portion 53 is shaped so as not to obstruct the flow of gas streamlines flowing out from the first gas discharge passage 51 to the second gas discharge passage 52.

[0050] Here, a shape that does not obstruct the flow of streamlines refers to a shape that does not hinder the flow of gas on the outside of the gas flow, allowing the gas to flow smoothly. In other words, the shape is formed so that the streamlines of the gas on the outside of the gas flow do not come into contact with or collide with other obstacles (in this case, the passage walls of the gas discharge passage).

[0051] As a result, the streamlines of the gas flowing out from the first gas discharge passage 51 can flow out smoothly without being disturbed as in the conventional configuration, thus avoiding the suppression of gas discharge. This makes it possible to reduce the weight of the battery cover 6 while ensuring sufficient gas discharge.

[0052] Next, the specific configuration of the first embodiment will be described. Figure 4 shows a configuration in which a gas discharge valve is placed in the gas discharge mechanism shown in Figure 3. Here, as mentioned above, the plate thickness (t) of the battery cover 6 in the part where the gas discharge path is formed and the opening diameter (d) of the gas discharge passage are not in an exact dimensional relationship, and the plate thickness (t) is depicted larger than it actually is. The same reference numerals in Figure 4 as in Figure 3 indicate the same configuration, so a further explanation will be omitted here.

[0053] In Figure 4, a gas discharge valve 54 is press-fitted into the first gas discharge passage 51 at the connection point between the first gas discharge passage 51 and the second gas discharge passage 52. The gas discharge valve 54 has a pressure-receiving surface 55 that receives gas pressure and a press-fitting surface 56 integrally formed with the pressure-receiving surface 55. The press-fitting surface 56 is press-fitted into the inner circumferential wall surface of the first gas discharge passage 51. The opening timing of the gas discharge valve 54 can be adjusted based on the relationship between this press-fitting force, the area of ​​the pressure-receiving surface, and the gas pressure.

[0054] In addition to the press-fitted gas discharge valve 54, a gas discharge valve 54 can also be integrally formed with the battery cover 6 on the side of the first gas discharge passage 51 at the connection point between the first gas discharge passage 51 and the second gas discharge passage 52. In other words, the gas discharge valve 54 is a thin membrane that crosses to close the first gas discharge passage 51, and this thin membrane is integrally formed with the battery cover 6. The opening timing of the gas discharge valve 54 can be adjusted by the thickness of this membrane.

[0055] Furthermore, the gas discharge passage 51 is shown as having a flow path that has substantially the same area (or opening diameter) as the gas discharge flow path 51 side of the gas discharge valve 54, at least in the portion leading to the gas discharge valve 54. For example, the first gas flow path 51 has an opening area (or opening diameter) of the inlet opening 51in that is substantially the same as that of the gas discharge valve 54. Alternatively, the inlet opening 51in has a flow path portion with a larger area (or opening diameter) than the gas discharge valve 54, and the main portion of the first gas flow path 51 on the gas discharge valve 54 side has substantially the same area (or opening diameter) as the first discharge flow path side of the gas discharge valve 54.

[0056] Here, it is important that the gas discharge valve 54 does not disturb the gas streamline as much as possible when it is opened. In conventional split-type valves, the streamline is often disturbed when they are opened. For this reason, in this embodiment, the gas discharge valve 54 is a valve that detaches from the gas discharge passage 51 when opened. The state in which the gas discharge valve 54 has detached is as shown in Figure 3. In other words, when the gas discharge valve 54 is opened, it opens in a shape that follows the cross-sectional shape of the gas discharge passage.

[0057] Then, if the gas pressure inside the battery container reaches a predetermined value for any reason, the gas release valve 54 will pop out against the input pressure due to the gas pressure and detach from the battery cover 6. Here, the predetermined gas pressure at which the gas release valve 54 detaches is the gas pressure at which the gas release valve 54 opens as a safety valve before the internal gas of the battery container reaches a pressure that would damage the battery container. This predetermined value is appropriately selected depending on the strength of the battery container, etc.

[0058] Furthermore, instead of the press-fit type gas discharge valve 54 shown in Figure 4, it is also possible to integrally form a gas discharge valve consisting of a thin membrane portion on the battery cover 6 by machining, as described above. In other words, a membrane portion thinner than the plate thickness of the battery cover 6 is integrally formed in a part of the first gas discharge passage 51 to serve as the gas discharge valve 54.

[0059] As shown in the drawing, if the gas discharge valve 54 is formed on the side of the first gas discharge passage 51, including the boundary portion where the first gas discharge passage 51 and the second gas discharge passage 52 are connected, the gas discharge valve 54 can be formed by machining. This allows the gas discharge valve 54 to be a thin-walled membrane portion formed integrally with the battery cover 6.

[0060] Furthermore, the pressure-receiving surface of the membrane portion of the gas discharge valve 54 is not of uniform thickness, but rather forms an annular thin-walled portion where the side adjacent to the wall of the first gas discharge passage 51 is thinner than the central part. For example, an annular groove is formed along the peripheral edge of the pressure-receiving surface. As a result, when gas pressure is applied, the membrane portion of the gas discharge valve 54 ruptures in a circular shape from this annular groove, and the pressure-receiving surface peels off cleanly.

[0061] Alternatively, a single-opening gas exhaust valve can be used, although this may slightly disrupt the streamlines. For example, this configuration involves leaving a portion of the circumferential end where the annular groove is formed ungrooved. When cleavage occurs, the ungrooved portion of the annular groove remains intact, resulting in a single-opening pressure-receiving surface for the membrane.

[0062] Thus, when the gas discharge valve 54 is opened, it opens in a shape that conforms to the cross-sectional shape of the gas discharge passage.

[0063] Furthermore, the gas discharge valve 54 can be formed by machining, as described above. For example, the gas discharge valve 54 can be formed at the boundary by creating a cylindrical space, the first gas discharge passage 51, by cutting, and similarly creating a second gas discharge passage 52 consisting of an inclined portion 53 by cutting. Alternatively, the gas discharge valve 54 can be formed by press working (drawing with a punch and die).

[0064] Figure 4B shows a first modified example of the first embodiment, in which the gas discharge valve 54 is formed by press working. In this case, the second gas discharge passage 52 is formed by punching and the first gas discharge passage 51 is formed by die, so that a membrane-like gas discharge valve 54 is integrally formed in the battery section 6 at the boundary. Here, the first gas discharge passage 51 has a straight tubular cross-section in the axial direction, and the second gas discharge passage 52 has a trapezoidal cross-section in the axial direction, so by using a die and punch with shapes that match these, gas discharge passages 51 and 52 of the required shape can be formed.

[0065] Figure 4C shows a second modified example, in which the gas discharge valve 54 is also formed by press working. In this case, the second gas discharge passage 52 is formed by punching and the first gas discharge passage 51 is formed by die, so that a membrane-like gas discharge valve 54 is integrally formed in the battery section 6 at the boundary.

[0066] Here, the first gas discharge passage 51 has a trapezoidal cross-section in the axial direction, and the second gas discharge passage 52 also has a trapezoidal cross-section in the axial direction. Therefore, the connection point between the first gas discharge passage 51 and the second gas discharge passage 52 is the narrowest passage, and a membrane-shaped gas discharge valve 54 is formed in this section. Thus, by using a die and punch with a similar shape, gas discharge passages 51 and 52 of the required shape can be formed.

[0067] Furthermore, it is preferable from the viewpoint of uniformity of the gas discharge flow that the axis C of the first gas discharge passage 51 and the second gas discharge passage 52 be the same.

[0068] When the gas discharge valve 54 is detached, the configuration becomes as shown in Figure 3, and the gas flowing out of the first gas discharge passage 51 can flow out smoothly without being disturbed as in the conventional configuration, thus avoiding a reduction in gas discharge volume. This makes it possible to lighten the battery cover 6 and ensure sufficient gas discharge volume. In this case as well, when the gas discharge valve 54 is opened, it opens in a shape that conforms to the cross-sectional shape of the gas discharge passage.

[0069] Next, we will explain the effect of the inclined portion 53 formed in the second gas discharge passage 52. Simulations have confirmed that the inclined portion 53 affects the streamlines on the outer circumference of the gas flow, and an example of this will be briefly explained below. Note that the configuration of the gas discharge passages 51 and 52 and the gas discharge valve 54 of the battery cover 6 used in the following simulations is the configuration shown as the first modified example in Figure 4B.

[0070] The parameters used in the simulation gas flow model were the plate thickness (t) of the battery cover 6 in the portion where the gas discharge path is formed as shown in Figure 5, the arrangement length (l) of the gas discharge valve 54, the opening diameter (din) of the inlet opening 51in of the first gas discharge passage 51, and the inclination angle (θ) of the inclined section 53. The plate thickness (t) of the battery cover 6, the arrangement length (l) of the gas discharge valve 54, and the inlet opening diameter (din) of the first gas discharge passage 51 were kept as constant values, and the simulation was performed with the inclination angle (θ) of the inclined section 53 as the variable.

[0071] The results are shown in Figure 6. As shown in Figure 6, the inlet opening diameter (din) of the first gas discharge passage 51 is 5 mm, the plate thickness (t) of the battery cover 6 in the part where the gas discharge path is formed is 2 mm, the arrangement length (l) of the gas discharge valve 54 is 1 mm, and the inclination angle (θ) of the inclined portion 53 is used as a variable.

[0072] Furthermore, the "angle of inclination (θ) = 0°" on the vertical axis of the graph in Figure 6 corresponds to the outlet opening when the first gas discharge passage 51 is extended, as shown by the dashed line (DL) in Figure 3. Also, the gas flow rate is the flow rate at the outlet opening 52out of the second gas discharge passage 52, and the effect of the change in the angle of inclination (θ) is expressed as a ratio to the flow rate when the angle of inclination (θ) = 0.

[0073] As can be seen in the graph in Figure 6, the flow rate ratio increases as the inclination angle (θ) of the inclined section 53 increases. This indicates that the gas flow rate increases as the flow rate ratio increases. In particular, it can be seen that the gas flow rate increases when the inclination angle (θ) reaches 55°. Therefore, in actual design, setting the inclination angle (θ) to 55° or higher will effectively increase the gas flow rate.

[0074] Furthermore, at an inclination angle of around 60°, the flow rate ratio is 110%, resulting in a substantial effect. Ideally, the inclination angle should be 60° or greater. Also, at an inclination angle of around 75°, the flow rate ratio is 120%, yielding a significant effect. For more effective gas discharge, an inclination angle of 60° or greater is preferable.

[0075] Furthermore, increasing the inclination angle (θ) reduces the plate thickness (t) in this section, thereby decreasing mechanical strength. Therefore, it is necessary to select an inclination angle (θ) that ensures sufficient plate thickness (t) from a mechanical strength perspective. This should be determined as part of the battery's design specifications.

[0076] Next, Figure 7 shows the simulation results when the plate thickness (t) of the battery cover 6 in the area where the gas discharge path is formed is changed. The parameters are the same as in Figure 6, but the results are for when the plate thickness (t) of the battery cover 6 is changed to 0.2 mm, 2 mm, and 10 mm.

[0077] As can be seen from Figure 7, even with the same inclination angle (θ), the gas flow rate increases as the plate thickness (t) increases. In actual design, setting a larger plate thickness (t) will effectively increase the gas flow rate.

[0078] Compared to the inlet opening diameter (din) of the first gas discharge passage 51, the plate thickness (t) of the battery cover 6 in the portion where the gas discharge path is formed is preferably 40% or more of the length of the inlet opening diameter (din). More preferably, the plate thickness (t) of the battery cover 6 in the portion where the gas discharge path is formed is preferably twice or more the length of the inlet opening diameter (din).

[0079] However, increasing the plate thickness (t) will lead to an increase in the weight of the battery cover 6, so it is necessary to select a battery cover 6 with the required plate thickness (t) from a weight perspective. This should be determined as part of the battery's design specifications.

[0080] If the thickness of the battery cover 6 does not need to be increased, for example, the thickness (t) of the battery cover 6 in the portion where the gas discharge mechanism 10 (gas discharge path) is formed can be made thicker than the surrounding area of ​​the gas discharge mechanism 10. When the gas discharge mechanism 10 is attached to the battery cover 6 (when the gas discharge mechanism 10 is not an integral part of the battery cover 6 but a separate structure), setting the thickness becomes easier and is preferable. Also, for example, the first gas discharge passage 51 and the second gas discharge passage 52 have circular openings in cross-section. The axes of the first gas discharge passage 51 and the second gas discharge passage 52 are common (coaxial). Other embodiments can have a similar structure, except for embodiments that modify this structure.

[0081] Thus, in this embodiment, the gas discharge mechanism provided in the battery cover 6 comprises a first gas discharge passage 51 connected to the inside (SPin) of the battery container, a second gas discharge passage 52 connected to the first gas discharge passage 51 and also connected to the outside (SPout) of the battery container, and a gas discharge valve 54 provided in the first gas discharge passage 51 which opens to connect the first gas discharge passage 51 and the second gas discharge passage 52 when the gas pressure inside the battery container reaches a predetermined value. Furthermore, the cross-sectional shape of the second gas discharge passage 52, as viewed in the direction of gas outflow when the gas discharge valve 54 is opened, is formed in an inclined shape that does not obstruct the flow of gas streamlines flowing out from the first gas discharge passage 51.

[0082] According to this embodiment, since the streamlines of the outflowing gas are not obstructed by the second gas discharge passage 52, the gas can flow smoothly, and the gas discharge capacity can be increased.

[0083] Furthermore, the location of the gas discharge mechanism 10 is not limited to the battery cover 6; the gas discharge mechanism 10 can also be provided in any part of the battery container housing the energy storage elements. Therefore, it can also be applied when the battery container does not have a battery cover 6. In this embodiment, the gas discharge mechanism 10 is provided on the battery cover 6 on which the positive electrode external terminal 8A and the negative electrode external terminal 8B are formed. As in this embodiment, since the gas discharge mechanism 10 is provided on the battery cover 6 which has a predetermined thickness and predetermined rigidity, a highly reliable valve opening operation can be obtained. Forming the gas discharge valve 54 integrally with the battery container is also easier.

[0084] In this embodiment, the gas discharge valve 54 is formed at a position that enters the second gas passage 52 side from the end of the inlet opening 51in side of the first gas passage 51. This is preferable because a stable gas flow passes through the gas discharge valve. [Examples]

[0085] Next, a second embodiment of the present invention will be described. In the first embodiment, the passage cross-sectional shape of the second gas discharge passage 52 was a straight inclined portion 53, but the second embodiment differs in that the passage cross-sectional shape of the second gas discharge passage 52 is a convex arc-shaped portion 57. As shown in Figure 8, the arc-shaped portion 57 has a rounded shape at the corner of the outlet opening 52out (the part indicated by the dashed line (DL) in Figure 3), and in this embodiment, what is called "R" in mechanical drawing is adopted.

[0086] In other words, the cross-sectional shape of the second gas discharge passage 52 is formed such that the opening diameter of the second gas discharge passage 52 continuously and gradually increases as it approaches the outside side (SPout) of the battery container, and the cross-sectional shape viewed in the direction of gas outflow is formed as an arc shape (arc-shaped portion 57) that expands at a predetermined radius in the direction away from the axis of the second gas discharge passage 52. (Here, in this embodiment, a circular arc is given as an example of an arc shape, but other shapes are also acceptable. Note that in this embodiment, the arc-shaped portion 57 is given as an example of a circular arc, so it will be referred to as the arc-shaped portion 57 below). Furthermore, the arc-shaped portion 57 consists of a convex circular arc that protrudes toward the axis (C). This arc-shaped portion 57 is shaped so as not to obstruct the flow of gas streamlines flowing from the first gas discharge passage 51 to the second gas discharge passage 52.

[0087] In Figure 8, a gas discharge valve 54 is press-fitted into the connection point between the first gas discharge passage 51 and the second gas discharge passage 52, on the side of the first gas discharge passage 51. The position of the gas discharge valve 54 depends on the radius of the arc (r). That is, if the radius of the arc (r) is long, the press-fitted position of the gas discharge valve 54 is closer to the inlet opening 51in, and if the radius of the arc (r) is short, the press-fitted position of the gas discharge valve 54 is further away from the inlet opening 51in.

[0088] The gas discharge valve 54 includes a pressure-receiving surface 55 that receives gas pressure and a press-fitting surface 56 integrally formed with the pressure-receiving surface 55. The press-fitting surface 56 is press-fitted into the inner circumferential wall surface of the first gas discharge passage 51. The opening timing of the gas discharge valve 54 can be adjusted based on the relationship between this press-fitting force, the area of ​​the pressure-receiving surface, and the gas pressure.

[0089] Here, it is important that the gas discharge valve 54 does not disturb the gas streamline as much as possible when it is opened. In conventional split-type valves, the streamline is often disturbed when they are opened. For this reason, in this embodiment, the gas discharge valve 54 is a valve that pops out and detaches from the gas discharge passage 51 when it is opened.

[0090] Then, if the gas pressure inside the battery container reaches a predetermined value for any reason, the gas discharge valve 54 is ejected by the gas pressure against the input force and detaches from the battery cover 6. Once the gas discharge valve 54 detaches, the streamline of the gas flowing out from the first gas discharge passage 51 flows along the arc portion 57. In this way, the gas streamline is not disturbed as in the conventional configuration, allowing it to flow out smoothly and avoiding the suppression of gas discharge. This makes it possible to lighten the battery cover 6 and ensure sufficient gas discharge.

[0091] Next, we will explain the effect of the arc portion 57 formed in the second gas discharge passage 52. Simulations have confirmed that the arc portion 57 affects the streamlines on the outer circumference of the gas flow, and an example of this will be briefly explained below.

[0092] The parameters used in the simulation gas flow model were the plate thickness (t) of the battery cover 6 in the portion where the gas discharge path is formed as shown in Figure 9, the arrangement length (l) of the gas discharge valve 54, the inlet opening diameter (din) of the inlet opening 51in of the first gas discharge passage 51, and the arc radius (r) of the arc portion 57. The plate thickness (t) of the battery cover 6 and the inlet opening diameter (din) of the first gas discharge passage 51 were kept constant values, and the simulation was performed with the arc radius (r) of the arc portion 57 as the variable. The arrangement length (l) of the gas discharge valve 54 depends on the arc radius (r), so it was calculated each time.

[0093] The results are shown in Figure 10. As shown in Figure 10, the inlet opening diameter (din) of the first gas discharge passage 51 is 5 mm, the plate thickness (t) of the battery cover 6 in the part where the gas discharge path is formed is 2 mm, and the arc radius (r) of the arc portion 57 is used as a variable.

[0094] Furthermore, the "arc radius (r) = 0.001 mm" on the vertical axis of the graph in Figure 10 represents the arc radius of the corner of the outlet opening when the first gas discharge passage 51, shown by the dashed line (DL) in Figure 4, is extended. The gas flow rate is the flow rate at the outlet opening 52out of the second gas discharge passage 52, and the effect of the change in arc radius (r) is expressed as a ratio to the flow rate when arc radius (r) = 0.001 mm.

[0095] As can be seen in the graph in Figure 10, the flow rate ratio increases as the radius (r) of the arc section 57 increases. This indicates that the gas flow rate increases as the flow rate ratio increases. In particular, it can be seen that the gas flow rate increases when the radius (r) of the arc section (r) is 1 mm. Therefore, in actual design, setting the radius (r) of the arc section (r) based on the graph in Figure 10 will allow for an effective increase in the gas flow rate.

[0096] The convex arc-shaped flow path does not have to be a precise circumferential shape. For example, the flow path of the second gas discharge passage 52 may have a shape in which the change in the opening diameter d (in the direction perpendicular to t) Δd2 at a location (t2+Δt) on the outlet opening 52out side by Δt from a first location (t1) to a location (t1+Δt) on the outlet opening 52out side by Δt is greater than the change in the opening diameter d (in the direction perpendicular to t) Δd1 at a location (t2+Δt) on the outlet opening 52out side by Δt from a first location (t1).

[0097] Furthermore, for example, in the plate thickness (t) direction of the battery cover 6 in the portion where the gas discharge path is formed, it is preferable that the arc portion 57 is formed to be larger than half. Specifically, the length of the second gas discharge passage 52 is greater than the length of the first gas discharge passage 51.

[0098] Thus, in this embodiment, the gas discharge mechanism provided in the battery cover 6 comprises a first gas discharge passage 51 connected to the inside (SPin) of the battery container, a second gas discharge passage 52 connected to the first gas discharge passage 51 and also connected to the outside (SPout) of the battery container, and a gas discharge valve 54 provided in the first gas discharge passage 51 which opens to connect the first gas discharge passage 51 and the second gas discharge passage 52 when the gas pressure inside the battery container reaches a predetermined value. Furthermore, the cross-sectional shape of the second gas discharge passage 52, as viewed in the direction of gas outflow when the gas discharge valve 54 is open, is formed as a convex arc shape that does not obstruct the flow of gas streamlines flowing out from the first gas discharge passage 51.

[0099] According to this embodiment, since the streamlines of the outflowing gas are not obstructed by the second gas discharge passage 52, the gas can flow smoothly, and the gas discharge capacity can be increased. [Examples]

[0100] Next, a third embodiment of the present invention will be described. In the second embodiment, the passage cross-sectional shape of the second gas discharge passage 52 was a convex arc-shaped portion 57, but in the third embodiment, the passage cross-sectional shape of the second gas discharge passage 52 is a concave arc-shaped portion 58. As shown in Figure 11, the arc-shaped portion 58 is formed by cutting off the material of the corner of the outlet opening 52out (the part indicated by the dashed line (DL) in Figure 3) in an arc shape with a predetermined radius (r).

[0101] In other words, the cross-sectional shape of the second gas discharge passage 52 is formed such that the opening diameter of the second gas discharge passage 52 gradually increases as it approaches the outside side (SPout) of the battery container, and the cross-sectional shape viewed in the direction of gas outflow is formed as an arc (arc-shaped portion 58) that expands at a predetermined radius in the direction away from the axis of the second gas discharge passage 52 (here, in this embodiment, a circular arc is given as an example of an arc shape, but other shapes are also acceptable. Note that in this embodiment, the arc-shaped portion 58 is given as an example of a circular arc, so it will be referred to as the arc-shaped portion 58 below). Furthermore, the arc portion 58 is a concave arc that moves away from the axis (C). This arc portion 58 is shaped so as not to obstruct the flow of gas streamlines as they flow out from the first gas discharge passage 51 to the second gas discharge passage 52.

[0102] In Figure 11, a gas discharge valve 54 is press-fitted into the connection point between the first gas discharge passage 51 and the second gas discharge passage 52, on the side of the first gas discharge passage 51. The position of the gas discharge valve 54 depends on the arc radius (r). That is, if the arc radius (r) is long, the press-fitted position of the gas discharge valve 54 is closer to the inlet opening 51in, and if the arc radius (r) is short, the press-fitted position of the gas discharge valve 54 is further away from the inlet opening 51in.

[0103] The gas discharge valve 54 includes a pressure-receiving surface 55 that receives gas pressure and a press-fitting surface 56 integrally formed with the pressure-receiving surface 55. The press-fitting surface 56 is press-fitted into the inner circumferential wall surface of the first gas discharge passage 51. The opening timing of the gas discharge valve 54 can be adjusted based on the relationship between this press-fitting force, the area of ​​the pressure-receiving surface, and the gas pressure.

[0104] Here, it is important that the gas discharge valve 54 does not disturb the gas streamline as much as possible when it is opened. In conventional split-type valves, the streamline is often disturbed when they are opened. For this reason, in this embodiment, the gas discharge valve 54 is a valve that pops out and detaches from the first gas discharge passage 51 when it is opened.

[0105] Then, if the gas pressure inside the battery container reaches a predetermined value for any reason, the gas discharge valve 54 is ejected by the gas pressure against the input force and detaches from the battery cover 6. Once the gas discharge valve 54 detaches, the gas streamline that flows out from the first gas discharge passage 51 flows along the arc portion 58. In this way, the gas streamline is not disturbed as in the conventional configuration, and it becomes possible to have the gas discharge amount suppressed. This makes it possible to lighten the battery cover 6 and ensure sufficient gas discharge.

[0106] The concave arc-shaped flow path does not have to be a precise circumferential shape. For example, in the plate thickness (t) direction of the second gas discharge passage 52, the flow path may have a shape in which the change in the opening diameter d (in the direction perpendicular to t) Δd2 at a location Δt further out of the outlet opening 52 (t2+Δt) from a second location (t2) further out of the outlet opening 52 (t2+Δt) is smaller than the change in the opening diameter d (in the direction perpendicular to t) Δd1 from a first location (t1) to a location Δt further out of the outlet opening 52 (t1+Δt).

[0107] Thus, in this embodiment, the gas discharge mechanism provided in the battery cover 6 comprises a first gas discharge passage 51 connected to the inside (SPin) of the battery container, a second gas discharge passage 52 connected to the first gas discharge passage 51 and also connected to the outside (SPout) of the battery container, and a gas discharge valve 54 provided in the first gas discharge passage 51 which opens to connect the first gas discharge passage 51 and the second gas discharge passage when the gas pressure inside the battery container reaches a predetermined value. Furthermore, the cross-sectional shape of the second gas discharge passage 52, as viewed in the direction of gas outflow when the gas discharge valve 54 is open, is formed as a concave arc shape that does not obstruct the flow of gas streamlines flowing out from the first gas discharge passage 51.

[0108] According to this embodiment, since the streamlines of the outflowing gas are not obstructed by the second gas discharge passage 52, the gas can flow smoothly, and the gas discharge capacity can be increased. [Examples]

[0109] Next, a fourth embodiment of the present invention will be described. In the first to third embodiments, the cross-sectional shape of the second gas discharge passage 52 consisted of an inclined portion 53, a convex arc portion 57, and a concave arc portion 58. However, the fourth embodiment differs in that the cross-sectional shape of the second gas discharge passage 52 is a stepped diameter enlargement portion 59 relative to the first gas discharge passage 51.

[0110] As an example of forming a stepped section, the large-diameter section 59 is cylindrical (actually a space, and can also be described as cylindrical) as shown in Figure 12, and is formed with an outlet opening diameter (dout) that is larger than the inlet opening diameter (din) of the first gas discharge passage 51 (see Figure 14). This large-diameter section 59 is shaped so as not to obstruct the flow of gas streamlines flowing out from the first gas discharge passage 51 to the second gas discharge passage 52.

[0111] In Figure 12, the first gas discharge passage 51 is formed in a cylindrical shape (actually an empty space, which can also be described as a cylindrical shape) in the plate thickness direction, and the second gas discharge passage 52 is also formed in a cylindrical shape (actually an empty space, which can also be described as a cylindrical shape) in the plate thickness direction. A gas discharge valve 54 is press-fitted into the first gas discharge passage 51 side of the connection between the first gas discharge passage 51 and the second gas discharge passage 52.

[0112] The gas discharge valve 54 includes a pressure-receiving surface 55 that receives gas pressure and a press-fitting surface 56 integrally formed with the pressure-receiving surface 55. The press-fitting surface 56 is press-fitted into the inner circumferential wall surface of the first gas discharge passage 51. The opening timing of the gas discharge valve 54 can be adjusted based on the relationship between this press-fitting force, the area of ​​the pressure-receiving surface, and the gas pressure.

[0113] Then, if the gas pressure inside the battery container reaches a predetermined value for any reason, the gas discharge valve 54 is ejected by the gas pressure against the input force and detaches from the battery cover 6. When the gas discharge valve 54 detaches, the gas streamline that has flowed out from the first gas discharge passage 51 flows into the second gas discharge passage 52, which has a larger outlet opening diameter (dout). This allows the gas to flow out smoothly without being disturbed as in the conventional configuration, thus avoiding the suppression of gas discharge. This makes it possible to lighten the battery cover 6 and ensure sufficient gas discharge.

[0114] Next, we will explain the effect of the enlarged diameter section 59 formed in the second gas discharge passage 52. Simulations have confirmed that the enlarged diameter section 59 affects the streamlines on the outer circumference of the gas flow, and an example of this is briefly explained below.

[0115] The parameters used in the simulation gas flow model were the plate thickness (t) of the battery cover 6 in the portion where the gas discharge path is formed as shown in Figure 13, the arrangement length (l) of the gas discharge valve 54, the opening diameter (din) of the inlet opening 51in of the first gas discharge passage 51, and the opening diameter (dout) of the outlet opening 52out. The plate thickness (t) of the battery cover 6, the arrangement length (l) of the gas discharge valve 54, and the inlet opening diameter (din) of the first gas discharge passage 51 were kept constant values, and the simulation was performed with the outlet opening diameter (dout) of the outlet opening 52out as the variable.

[0116] The results are shown in Figure 14. As shown in Figure 14, the inlet opening diameter (din) of the first gas discharge passage 51 is 5 mm, the plate thickness (t) of the battery cover 6 in the part where the gas discharge path is formed is 2 mm, the arrangement length (l) of the gas discharge valve 54 is 1 mm, and the outlet opening diameter (dout) of the second gas discharge passage 52 is used as a variable.

[0117] Furthermore, the "outlet opening diameter 5 mm" on the vertical axis of the graph in Figure 14 corresponds to the outlet opening when the first gas discharge passage 51 is extended, as shown by the dashed line (DL) in Figure 4. The gas flow rate is the flow rate at the outlet opening 52out of the second gas discharge passage 52, and the effect of the change in outlet opening diameter (dout) is expressed as a ratio to the flow rate when the outlet opening diameter is 5 mm.

[0118] As can be seen in the graph in Figure 14, the flow rate ratio increases as the outlet diameter (dout) increases. This indicates that the gas flow rate increases as the flow rate ratio increases. In particular, it can be seen that the gas flow rate increases when the outlet diameter (dout) reaches 7 mm. Therefore, in actual design, setting the outlet diameter (dout) based on the graph in Figure 14 will allow for an effective increase in gas flow rate.

[0119] The outlet opening diameter of 5 mm can be considered as the opening diameter of the second gas discharge passage 52 at the end of the first gas discharge passage 51. Therefore, it is preferable that the outlet opening diameter (dout) is greater than 1.5 times the opening diameter of the second gas discharge passage 52 at the end of the first gas discharge passage 51. Furthermore, with an outlet opening diameter (dout) of 10 mm, the flow rate ratio is 110%, and a substantial effect is obtained. Preferably, it is 2 times or more. Also, with an outlet opening diameter (dout) of 15 mm, the flow rate ratio is approximately 120%, and a remarkable effect is obtained. To discharge gas more effectively, it is preferable to make it 3 times or more.

[0120] The stepped diameter section can, for example, have multiple stepped sections. Between the end of the second gas discharge passage 52 on the side of the first gas discharge passage 51 and the outlet, a structure (intermediate step) may be provided, having an opening diameter that is larger than the opening diameter of the end of the second gas discharge passage 52 on the side of the first gas discharge passage 51 and smaller than the outlet opening diameter (dout). This is preferable because it is easier to manufacture than the inclined shape, and the difference in adjacent opening diameters is smaller than in the structure shown in the figure.

[0121] Thus, in this embodiment, the gas discharge mechanism provided in the battery cover 6 comprises a first gas discharge passage 51 connected to the inside (SPin) of the battery container, a second gas discharge passage 52 connected to the first gas discharge passage 51 and also connected to the outside (SPout) of the battery container, and a gas discharge valve 54 provided in the first gas discharge passage 51 which opens to connect the first gas discharge passage 51 and the second gas discharge passage when the gas pressure inside the battery container reaches a predetermined value. Furthermore, the cross-sectional shape of the second gas discharge passage 52, as viewed in the direction of gas outflow when the gas discharge valve 54 is open, is formed in a stepped diameter section that does not obstruct the flow of gas streamlines flowing out from the first gas discharge passage 51.

[0122] According to this embodiment, since the streamlines of the outflowing gas are not obstructed by the second gas discharge passage 52, the gas can flow smoothly, and the gas discharge capacity can be increased. [Examples]

[0123] Next, a fifth embodiment of the present invention will be described. In the fourth embodiment, the axes of the first gas discharge passage 51 and the second gas discharge passage 52 were common (coaxial), but in the fifth embodiment, the axes of the first gas discharge passage 51 and the second gas discharge passage 52 are different.

[0124] As shown in Figure 15, the first gas discharge passage 51 and the second gas discharge passage 52 are cylindrical in shape (actually empty space, and can also be described as cylindrical), and the outlet opening diameter (dout) of the first gas discharge passage 51 is larger than the inlet opening diameter (din). Furthermore, the axis (C2) of the second gas discharge passage 52 is formed eccentrically by a predetermined distance (Δd) with respect to the axis (C1) of the first gas discharge passage 51.

[0125] Even in this configuration, if the gas pressure inside the battery container reaches a predetermined value for any reason, the gas discharge valve 54 will pop out against the input pressure due to the gas pressure and detach from the battery cover 6. When the gas discharge valve 54 detaches, the gas streamline that has flowed out from the first gas discharge passage 51 flows into the second gas discharge passage 52, which has a larger outlet opening diameter. This allows the gas to flow out smoothly without being disturbed as in the conventional configuration, thus avoiding the suppression of gas discharge. This makes it possible to reduce the weight of the battery cover 6 and ensure sufficient gas discharge.

[0126] Thus, in this embodiment, the gas discharge mechanism provided in the battery cover 6 comprises a first gas discharge passage 51 connected to the inside side (SPin) of the battery container, a second gas discharge passage 52 connected to the first gas discharge passage 51 with an axis eccentric to the axis of the first gas discharge passage 51 and also connected to the outside side (SPout) of the battery container, and a gas discharge valve 54 provided in the first gas discharge passage 51 which opens to connect the first gas discharge passage 51 and the second gas discharge passage when the gas pressure inside the battery container reaches a predetermined value. Furthermore, the cross-sectional shape of the second gas discharge passage 52, as viewed in the direction of gas outflow when the gas discharge valve 54 is opened, is formed in a stepped diameter section that does not obstruct the flow of gas streamlines flowing out from the first gas discharge passage 51.

[0127] According to this embodiment, since the streamlines of the outflowing gas are not obstructed by the second gas discharge passage 52, the gas can flow smoothly, and the gas discharge capacity can be increased.

[0128] In the first to fifth embodiments, examples were shown in which the gas discharge valve 54 is provided in the first gas passage 51. Of these, an example is shown in which the gas discharge valve 54 is provided at the end of the second gas passage side 52 of the first gas passage 51. In addition, the gas discharge valve 54 may be provided on the second gas passage side 52 of the first gas passage 51, and on the inlet opening 51in side of the second gas passage 52.

[0129] Furthermore, in the first to fifth embodiments, examples are shown in which the area (or opening diameter) of at least the main part of the first gas passage 51, or the area (or opening diameter) of the inlet opening 51in, is substantially the same as that of the gas discharge valve 54. In addition, the first gas passage 51 may be configured such that the area (or opening diameter) of the gas discharge valve 54 is smaller than that of the inlet opening 51in of the first gas passage 51. This may make it easier to operate in terms of inserting and removing the equipment being processed. In this case, it is preferable from the standpoint of gas discharge that the value obtained by dividing the area (or opening diameter) of the outlet opening 51out by the area (or opening diameter) of the gas discharge valve 52 (52out / 54) is larger than the value obtained by dividing the area (or opening diameter) of the inlet opening 51in by the area (or opening diameter) of the gas discharge valve 52 (51in / 54).

[0130] As an example, as shown in the cross-section of Figure 4C mentioned earlier, the first gas flow path 51 and the second gas flow path are not straight, but can have a shape with a straight slope that widens outward. In other forms, the cross-sections of the first gas flow path 51 and the second gas flow path 52 may be curved slopes. [Examples]

[0131] Next, a sixth embodiment of the present invention will be described. In the first to fifth embodiments, the gas discharge valve 54 is provided in the first gas discharge passage 51, but in this embodiment, the gas discharge valve 54 is provided in the second gas discharge passage 52, which is a difference.

[0132] As shown in Figure 16, based on the configuration of the first embodiment, a gas discharge valve 60 is provided on the side of the second gas discharge passage 52 when viewed from the connection point between the first gas discharge passage 51 and the second gas discharge passage 52. As described in the first embodiment, the gas discharge valve 60 operates to detach from the second gas discharge passage 52 when the gas pressure inside the battery container exceeds a predetermined value.

[0133] Here, the gas discharge valve 60 is fixed to the wall surface of the second gas discharge passage 52, in this case to the inclined section 53, by welding or other methods. By using welding or other methods in this way, the gas discharge valve 60 can be fixed to any location on the inclined section 53.

[0134] Furthermore, as shown in the drawing, if the gas discharge valve 60 is formed on the side of the second gas discharge passage 52, including the boundary portion where the first gas discharge passage 51 and the second gas discharge passage 52 are connected, the gas discharge valve 60 can be formed by machining. Here, the gas discharge valve 60 can be a membrane portion formed integrally with the battery cover 6, as described in the first embodiment.

[0135] For example, a membrane-like gas discharge valve 60 can be formed by creating a first gas discharge passage 51, which is a cylindrical space toward the boundary, through cutting, and similarly creating a second gas discharge passage 52, which consists of an inclined portion 53 toward the boundary, through cutting.

[0136] Alternatively, the gas discharge valve 60 can be formed by press working (drawing with a punch and die). In this case, the second gas discharge passage 52 is formed by the punch and the first gas discharge passage 51 is formed by the die, thereby forming a membrane-like gas discharge valve 60. Of course, by forming an annular thin-walled portion where the pressure-receiving surface of the membrane of the gas discharge valve 60 is not of uniform thickness, but rather thinner on the side connected to the wall of the second gas discharge passage 52 than near the center, when gas pressure is applied, the membrane of the gas discharge valve 60 will rupture in a circular shape from this annular groove, and the pressure-receiving surface will peel off cleanly.

[0137] Here, since the gas discharge valve 60 is formed at the boundary, the inclined portion 53 functions as a punch taper, enabling drawing. As mentioned earlier, if an annular groove formed by drawing is provided at the connection point between the gas discharge valve 60 and the inclined portion 53, the gas discharge valve 60 can be detached.

[0138] Furthermore, in this embodiment, the gas discharge valve 60 can be formed such that the area (or opening diameter) on the second gas discharge passage 52 side is larger than the area (or opening diameter) on the first gas discharge passage 51 side.

[0139] In this embodiment as well, since the streamlines of the outflowing gas are not obstructed by the second gas discharge passage, the gas can flow smoothly, and the gas discharge capacity can be increased. Although Figure 16 is based on the configuration of the first embodiment, a similar gas discharge valve can be provided in the configurations of the second to fifth embodiments as well.

[0140] Furthermore, in the first to sixth embodiments described above, the cross-sectional shape perpendicular to the axis of the gas discharge passage was circular, but it is not limited to this; rectangular, oval, or elliptical shapes are also acceptable as long as they allow for smooth streamline formation.

[0141] As described in the embodiments above, the battery of the present invention includes a gas discharge mechanism comprising: a first gas discharge passage connected to the inside of the battery container; a second gas discharge passage connected to the first gas discharge passage and connected to the outside of the battery container; and a gas discharge valve provided in a part of the gas discharge passage consisting of the first and second gas discharge passages, which opens when the gas pressure inside the battery container reaches a predetermined value, thereby connecting the inside and outside of the battery container with the gas discharge passage. Furthermore, the cross-sectional shape of the second gas discharge passage, as viewed in the direction of gas outflow when the gas discharge valve is opened, is formed in such a way that it does not obstruct the flow of gas streamlines flowing out from the first gas discharge passage.

[0142] According to this, since the streamlines of the outflowing gas are not obstructed by the second gas discharge passage, the gas can flow smoothly, and the gas discharge capacity can be increased.

[0143] In the above embodiments, the length of the first gas discharge channel 51 in the thickness (t) direction can be formed to be 5% to 80% of the thickness (t) of the battery cover from the viewpoint of manufacturability. From the viewpoint of gas flow, it is preferable that it be 10% to 50%.

[0144] Furthermore, in this embodiment, the gas discharge valve 54 is provided in a part of the gas flow path having a first gas flow path 51 and a second gas flow path 52, and the second gas discharge passage has a larger opening diameter than the opening diameter of the first gas discharge passage 51, and it is preferable that the battery has any of the following characteristics A to C.

[0145] A: The second gas passage 52 is formed such that the opening diameter of the second gas discharge passage 52 gradually increases as it approaches the outside of the battery container, and the cross-sectional shape viewed in the direction of gas outflow has a linearly inclined portion 53 that widens in the direction away from the axis of the second gas discharge passage 52. B: The second gas passage 52 is formed such that as it approaches the outside of the battery container, the opening diameter of the second gas discharge passage 52 continuously and gradually increases, and the cross-sectional shape viewed in the direction of gas outflow is an arc-shaped portion that expands in the direction away from the axis of the second gas discharge passage 52 (for example, the arc-shaped portion is a convex circular arc portion that protrudes toward the axis side of the second gas discharge passage 52, or the arc-shaped portion is a concave circular arc portion that moves away from the axis side of the second gas discharge passage 52). C: The second gas discharge passage 52 is formed in a stepped shape, with a larger opening diameter on the outside of the battery container.

[0146] Next, a battery configuration that can efficiently guide the gas generated inside the battery container to the first gas discharge passage 51 will be briefly described. In this case, the gas discharge mechanism 10 of the battery container is located above the battery can 1 in the direction of gravity.

[0147] In Figure 17, the battery casing 1 houses the electrode body 3 surrounded by the separator 61. The battery casing 1 is made of a rectangular metal can and has an opening 1a that opens along its longitudinal direction and a housing section 1b that is connected to the opening 1a. This battery casing 1 is made of, for example, aluminum or an aluminum alloy.

[0148] The upper end portion 3a of the electrode body 3 is formed on the opposite side of the bottom portion 22 of the battery can 1. Terminal tabs 62A and 62B are arranged on this upper end portion 3a. Terminal tab 62A is electrically connected to the positive electrode external terminal 8A, and terminal tab 62B is electrically connected to the negative electrode external terminal 8B. The electrode bodies 3 are stacked along the vertical direction (direction of gravity), and minute gaps are formed between adjacent surfaces, with these gaps connecting to the upper end portion 3a.

[0149] The battery cover 6 seals the opening 1a of the battery case 1. The battery cover 6 is formed from a long, plate-shaped metal sheet, and a positive electrode insertion hole, which is a circular through-hole, is formed at one end in the longitudinal direction. The insertion portion of the positive electrode external terminal 8A is inserted into the positive electrode insertion hole. Similarly, the battery cover 6 has a negative electrode insertion hole, which is a circular through-hole, formed at the other end in the longitudinal direction. The insertion portion of the negative electrode external terminal 8B is inserted into the negative electrode insertion hole.

[0150] Furthermore, the battery cover 6 has a liquid injection hole formed by a circular through-hole between the positive external terminal 8A and the negative external terminal 8B. A sealing plug 11 is inserted into the liquid injection hole.

[0151] Furthermore, a gas discharge mechanism 10 is formed in the center of the longitudinal direction of the battery cover 6, and the battery cover 6 is welded to the battery can 1. The battery cover 6 is made of, for example, aluminum or an aluminum alloy. The gas discharge mechanism 10 has the configuration of some of the embodiments described above.

[0152] The insulating cover 63 covers the electrode body 3, exposing the upper end portion 3a of the electrode body 3 to the outside, while covering the portion of the electrode body 3 other than the upper end portion 3a. The insulating cover 63 is formed, for example, in a pentahedral shape and is constructed by folding into a box shape. The insulating cover 63 is made of, for example, polypropylene.

[0153] In this battery structure, the electrode bodies 3 are stacked along the vertical direction (direction of gravity), forming tiny gaps between adjacent surfaces. These gaps are connected to the upper end 3a, allowing the gas generated from the electrode bodies 3 to be smoothly guided upwards in the direction of gravity into the space between the electrode bodies 3 and the battery cover 6. This enables a compact design with improved gas discharge capabilities.

[0154] Furthermore, the present invention is not limited to the embodiments described above, and various modifications are included. The embodiments described above are explained in detail for the purpose of clearly illustrating the present invention, and are not necessarily limited to those having all the configurations described. In addition, it is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace other configurations for the configuration of each embodiment. [Explanation of symbols]

[0155] C1...Lithium-ion secondary battery, 1...Battery can, 1a...Opening, 2...Insulating protective film, 3...Wound electrode body, 3a...Front flat surface, 3a...Back flat surface, 4A...Positive electrode current collector plate, 4B...Negative electrode current collector plate, 5...Gasket, 6...Battery cover, 6A...Positive electrode through hole, 6B...Negative electrode through hole, 7...Insulating plate, 8A...Positive electrode external terminal, 8B...Negative electrode external terminal, 9...Filling port, 10...Gas discharge mechanism, 11...Filling plug, 12A...Positive electrode connection part, 12B...Negative electrode connection part, 50...Gas discharge passage, 51...First gas discharge passage, 52...Second gas discharge passage, 53...Inclined part, 54...Gas discharge valve, 55...Pressure receiving surface, 56...Pressure-fitting surface structure, 57...Convex arc part, 58...Concave arc part, 59...Large diameter part.

Claims

1. A battery comprising an energy storage element, a battery container housing the energy storage element, and a gas discharge mechanism that fluidly connects the inside and outside of the battery container and discharges the gas inside the battery container when the gas pressure inside the battery container reaches a predetermined value, The battery container comprises a battery can having an opening in which the energy storage element is housed, and a battery lid that seals the battery can. The battery cover has a positive external terminal, a negative external terminal, and a gas discharge mechanism for supplying power from the energy storage element to the outside. The aforementioned gas discharge mechanism is A first gas discharge passage connected to the inside of the battery container, A second gas discharge passage is connected to the first gas discharge passage and to the outside of the battery container, The battery container is equipped with a gas discharge valve that, when the gas pressure inside the battery container reaches a predetermined value, opens to connect the inside and outside of the battery container through the first gas discharge passage and the second gas discharge passage. The gas discharge valve is provided on the side of the first gas discharge passage, including the boundary of the connection portion between the first gas discharge passage and the second gas discharge passage. The gas discharge valve is a membrane portion formed integrally with the battery cover, and a thin annular groove is formed in the portion of the membrane portion that is connected to the wall surface of the first gas discharge passage. The first gas discharge passage is formed with a straight pipe-like cross-sectional shape when viewed in the direction of gas outflow. The second gas discharge passage is formed such that its opening diameter gradually increases as it approaches the outside of the battery cover, and its cross-sectional shape, when viewed in the direction of gas outflow, has an inclined portion that is linearly inclined and expands away from the axis of the second gas discharge passage so as not to obstruct the flow of gas streamlines flowing out from the first gas discharge passage. A battery characterized by the following features.

2. In the battery according to Claim 1, The inclination angle of the inclined portion is set to 55° or more, with reference to the extension line of the wall surface of the first gas discharge passage. A battery characterized by the following features.

3. In the battery according to Claim 1, The thickness of the battery cover in the portion where the first gas discharge passage and the second gas discharge passage are formed is 40% or more of the length of the inlet opening diameter of the first gas discharge passage. A battery characterized by the following features.

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