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

battery

[0001] The present invention relates to a battery.

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

[0003] The gas release mechanism is a battery component equipped with a release valve designed to open at a predetermined pressure when gas is generated inside the battery can and release the gas inside the battery can. For example, the lithium ion secondary battery described in JP 2012-252809 A (Patent Document 1) has a lid member (battery lid) integrally formed with a base forming an upper surface, a peripheral wall portion forming a recessed portion recessed from the base, and a split-type gas release valve (safety valve) connected to and supported by the inner peripheral surface of the peripheral wall portion.

[0004] In this patent document, a recess is formed by pressing an aluminum plate, and a thin-film gas release valve is integrally formed at the bottom of the recess. When the gas pressure reaches a predetermined value, the thin film forming the gas release valve is ruptured, allowing the gas pressure to escape to the outside, ensuring safety.

[0005] JP 2012-252809 A

[0006] As described above, in batteries used in lithium-ion secondary batteries, a gas exhaust mechanism is provided for the purpose of releasing gas pressure and increasing safety even if the internal electrolyte or active material is decomposed, generating gas and causing an increase in internal pressure.

[0007] However, 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 leads to a larger cell size and an increase in the number of components per cell (electrode group, electrolyte, active material, etc.). Therefore, it is necessary to improve the gas discharge capacity of the gas discharge mechanism so as to be able to cope with the increase in the amount of gas generated due to the increase in the number of components.

[0008] In order to increase the gas discharge capacity of the gas discharge mechanism, it is possible to increase the size of the gas discharge mechanism. On the other hand, there is a demand for the development of a lithium-ion secondary battery equipped with a gas discharge mechanism that can increase the gas discharge capacity without increasing the size of the gas discharge mechanism.

[0009] The present embodiment described below can be applied to batteries other than lithium-ion secondary batteries, and can also be applied to stationary battery-powered devices other than those for automobiles (for example, electrical storage devices for home or commercial use).

[0010] An object of the present invention is to provide a battery equipped with a gas discharge mechanism that can improve gas discharge capacity.

[0011] The present invention is characterized by a battery including an electric storage element, a battery container accommodating the electric storage element, and a gas discharge mechanism that fluidly connects the inside of the battery container with the outside of the battery container and discharges gas from inside the battery container when the gas pressure inside the battery container reaches a predetermined value, the gas discharge mechanism including 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 passage that is closer to the second gas discharge flow path than the inner end of the battery container of the first gas discharge passage or the battery container of the second gas discharge passage. and a gas exhaust valve which, when the gas pressure inside the battery container reaches a predetermined value, performs an opening operation to connect the inside and outside of the battery container with the gas exhaust passage, and when performing the opening operation, opens to a shape that follows the cross-sectional shape of the gas exhaust passage, and further, the cross-sectional shape of the second gas exhaust passage when viewed in the gas outflow direction when the gas exhaust valve is opened is formed to a shape that does not obstruct the streamlined flow of gas flowing out from the first gas exhaust passage.

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

[0013] 1 is an external perspective view showing the appearance of a lithium ion secondary battery. FIG. 2 is an exploded perspective view showing the component parts of a disassembled lithium ion secondary battery. FIG. 3 is a cross-sectional view showing a cross section of a gas discharge mechanism for explaining the concept of the present invention. FIG. 4 is a cross-sectional view showing the configuration of a gas discharge mechanism according to a first embodiment of the present invention. FIG. 5 is a cross-sectional view showing the configuration of a gas discharge mechanism according to a first modified example of the first embodiment. FIG. 6 is a cross-sectional view showing the configuration of a gas discharge mechanism according to a second modified example of the first embodiment. FIG. 7 is a cross-sectional view showing types of parameters used to simulate the gas discharge mechanism of FIG. 4. FIG. 8 is an explanatory diagram showing parameter values ​​when a simulation of the gas discharge mechanism according to the first embodiment is performed. FIG. 9 is an explanatory diagram showing simulation results when a simulation of the gas discharge mechanism according to the first embodiment is performed. FIG. 10 is an explanatory diagram showing parameter values ​​when a simulation is performed with different plate thicknesses of the battery lid of the gas discharge mechanism according to the first embodiment. FIG. 11 is an explanatory diagram showing simulation results when a simulation is performed with different plate thicknesses of the battery lid of the gas discharge mechanism according to the first embodiment. FIG. 12 is a cross-sectional view showing the configuration of a gas discharge mechanism according to a second embodiment of the present invention. FIG. 13 is a cross-sectional view showing types of parameters used to simulate the gas discharge mechanism of FIG. 8. FIG. 14 is an explanatory diagram showing parameter values ​​when a simulation of the gas discharge mechanism according to the second embodiment is performed. FIG. 13 is a cross-sectional view showing the configuration of a gas discharge mechanism according to a third embodiment of the present invention. FIG. 14 is a cross-sectional view showing the configuration of a gas discharge mechanism according to a fourth embodiment of the present invention. FIG. 15 is a cross-sectional view showing types of parameters for simulating the gas discharge mechanism of FIG. 12. FIG. 16 is an explanatory diagram showing parameter values ​​when a simulation of the gas discharge mechanism according to the fourth embodiment is performed. FIG. 17 is an explanatory diagram showing simulation results when a simulation of the gas discharge mechanism according to the fourth embodiment is performed. FIG. 18 is a cross-sectional view showing the configuration of a gas discharge mechanism according to a fifth embodiment of the present invention. FIG. 19 is a cross-sectional view showing the configuration of a gas discharge mechanism according to a sixth embodiment of the present invention. FIG. 20 is an external perspective view of a battery having a configuration suitable for the present invention, disassembled and viewed obliquely from above.

[0014] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiment, and various modifications and application examples within the technical concept of the present invention are also included within its scope.

[0015] The present invention will be described with reference to the accompanying drawings, in which a lithium-ion secondary battery used in a hybrid vehicle or an electric vehicle is used as an example of the battery. Fig. 1 shows the external appearance of a typical lithium-ion secondary battery to which the present invention is applied, viewed obliquely from above.

[0016] As shown in FIG. 1 , the lithium-ion secondary battery C1 includes a battery can 1 and a lid member (hereinafter referred to as the battery lid) 6. These are collectively defined as the "battery container." The battery can 1 has an opening, and a wound electrode assembly 3 (see FIG. 2 ) serving as an "electricity storage element" that outputs stored electricity is housed inside the battery can 1, and the opening 1 a (see FIG. 2 ) of the battery can 1 is sealed by the battery lid 6. For example, an electrolyte solution is housed in the battery can 1, and the wound electrode assembly 3 is immersed in the electrolyte solution. Alternatively, an electrolyte other than a liquid electrolyte solution, such as a solid electrolyte, may be used.

[0017] The battery lid 6 is joined to the battery can 1 by laser welding, and the battery can 1 and the battery lid 6 form a sealed battery container. A positive electrode external terminal 8A and a negative electrode external terminal 8B are provided on the battery lid 6. 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] A gas exhaust mechanism 10 is integrally provided with the battery lid 6, and if the gas pressure inside the battery container rises to a predetermined pressure for some reason, the gas exhaust valve of the gas exhaust mechanism 10 opens to exhaust gas from the inside. This reduces the gas pressure inside the battery container and ensures the safety of the lithium-ion secondary battery C1. The battery lid 6 also has a liquid filling port 9 (see FIG. 2) for filling the battery with electrolyte, which is closed by a liquid filling tap 11 after the electrolyte is injected.

[0019] The gas discharge mechanism 10 fluidly connects the inside of the battery container to the outside of the battery container. Fluid connection means that fluid (gas or liquid) in the space inside and outside the battery container separated by a gas discharge valve 54 (see FIG. 4 ) can flow when the gas discharge valve 54 is opened. Although an example in which the gas discharge mechanism 10 is provided integrally with the battery lid 6 has been described, the structure of the gas discharge mechanism 10 may also be manufactured separately and placed on the battery lid 6.

[0020] FIG. 2 shows the appearance of the disassembled parts of the lithium ion secondary battery shown in FIG. 1 as viewed obliquely from above.

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

[0022] The wound electrode body 3 is housed in the battery can 1 in a state where it is wrapped and covered with an insulating protective film 2. The wound electrode body 3 has a flat, approximately rectangular parallelepiped shape, with a pair of flat surfaces and a pair of curved surfaces with an arc-shaped cross section that face each other with the pair of flat surfaces in between. The wound electrode body 3 is inserted into the battery can 1 from one of the curved surfaces and housed in the battery can 1 in a horizontal position with the winding axis direction along the cell width direction (+X direction). Note that a stacked electrode body can also be used as the wound electrode body 3 instead of a wound electrode body. The electrode body has a positive electrode containing a positive electrode material and a negative electrode containing a negative electrode material.

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

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

[0025] The battery can 1 and the battery lid 6 are made of a metallic material such as aluminum or an aluminum alloy. The positive electrode current collector 4A and the positive electrode external terminal 8A are made of aluminum or an aluminum alloy. The negative electrode current collector 4B and the negative electrode external terminal 8B are made of copper or a copper alloy.

[0026] The positive electrode external terminal 8A and the negative electrode external terminal 8B have welded joints that are welded to a bus bar or the like (not shown). The welded joints have a rectangular parallelepiped block shape that protrudes upward from the battery lid 6, and are arranged so that their lower surfaces face the surface of the battery lid 6 and their upper surfaces are parallel to the battery lid 6 at a predetermined height.

[0027] The positive electrode connecting portion 12A and the negative electrode connecting portion 12B have a cylindrical shape that protrudes from the lower surfaces of the positive electrode external terminal 8A and the negative electrode external terminal 8B, respectively, and has a tip that can be inserted into the positive electrode side through-hole 6A and the negative electrode side through-hole 6B of the battery lid 6. The positive electrode connecting portion 12A and the negative electrode connecting portion 12B penetrate the battery lid 6 and protrude further into the battery can 1 than the positive electrode current collector base portion 41A and the negative electrode current collector base portion 41B of the positive electrode current collector 4A and the negative electrode current collector 4B, and their tips are crimped to fix the positive electrode external terminal 8A and the negative electrode external terminal 8B and the positive electrode current collector 4A and the negative electrode current collector 4B integrally to the battery lid 6.

[0028] Gaskets 5 are interposed between the positive external terminal 8A and the battery lid 6, and between the negative external terminal 8B and the battery lid 6, and insulating plates 7 are interposed between the positive current collector plate 4A and the battery lid 6, and between the negative current collector plate 4B and the battery lid 6.

[0029] The positive current collector plate 4A and the negative current collector plate 4B have a rectangular plate-shaped positive current collector base 41A and a negative current collector base 41B that are arranged opposite the underside of the battery lid 6, and a positive electrode side connection end 42A and a negative electrode side connection end 42B that are bent at the side edges of the positive current collector base 41A and the negative current collector base 41B and extend toward the can bottom 22 along the wide side surface of the battery can 1, and are connected in a superimposed state opposite the positive electrode foil connection portion 31 d and the negative electrode foil connection portion 32 d of the wound electrode body 3.

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

[0031] The positive electrode external terminal 8A and the positive electrode current collector plate 4A described above constitute a positive electrode side terminal component, and the negative electrode external terminal 8B and the negative electrode current collector plate 4B constitute a negative electrode side terminal component. These positive electrode side terminal component and negative electrode side terminal component are integrally assembled to the battery lid 6 via the gasket 5 and the insulating plate 7, thereby forming a battery lid assembly. The wound electrode body 3 is then assembled to the battery lid assembly, thereby forming an electricity storage element assembly.

[0032] The wound electrode body 3 is supported between the positive electrode current collector 4A and the negative electrode current collector 4B of the battery lid assembly, with the winding axis direction extending parallel to the battery lid 6 and the flat surface extending along a direction perpendicular to the underside of the battery lid 6, and a pair of curved surfaces of the wound electrode body 3 being arranged separately on the side of the battery lid 6 and the side of the can bottom 22 of the battery can 1.

[0033] The insulating protective film 2 covers the wound electrode body 3 assembled to the battery lid assembly from the outside, together 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 can bottom 22 inside the battery can 1, respectively.

[0034] The insulating protective film 2 is made of an insulating synthetic resin material, and provides insulation between the battery can 1 and the wound electrode body 3, positive electrode current collector 4A, and negative electrode current collector 4B, and also protects the wound electrode body 3, positive electrode current collector 4A, and negative electrode current collector 4B so that they do not come into direct contact with the battery can 1 when an external impact or vibration is applied to the lithium ion secondary battery C1.

[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 around the periphery with the insulating protective film 2, a pair of flat surfaces of the wound electrode body 3 and the wide side wall portions 21a of the side wall portions 21 of the battery can 1 abut against each other with the insulating protective film 2 sandwiched therebetween, and the wound electrode body 3 can be inserted by pressing with a slight pressure. 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 portions 21b of the side wall portions 21 of the battery can 1.

[0036] As described above, the opening 1a of the battery can 1 is closed by the battery lid 6, and the battery lid 6 is sealed by laser welding to the battery can 1. Then, the battery can 1 is filled with an electrolyte. The electrolyte is injected into the battery can 1 through the liquid filling port 9 of the battery lid 6. After the electrolyte is injected, the liquid filling port 9 is closed by the liquid filling plug 11, and the liquid filling plug 11 is sealed by laser welding to the battery lid 6.

[0037] In lithium-ion secondary batteries configured as described above, for example, batteries for BEVs have a large battery capacity per cell, which leads to a larger cell size and an increase in the number of components per cell, such as an electrode group, electrolyte, active material, etc. Therefore, the increase in components increases the amount of gas generated during thermal runaway of the cell, and therefore it is necessary to improve the gas discharge capacity of the gas discharge mechanism.

[0038] The gas discharge capacity of the gas discharge mechanism can be increased by increasing the size of the gas discharge mechanism, but this would result in a significant increase in the area of ​​the battery container occupied by the gas discharge mechanism.

[0039] Therefore, there is a demand for the development of a lithium ion secondary battery equipped with a gas discharge mechanism that can increase the gas discharge capacity without increasing the size of the gas discharge mechanism. Therefore, the present embodiment proposes the following configuration.

[0040] In this embodiment, the gas exhaust mechanism provided in the battery lid comprises a first gas exhaust passage connected to the inside of the battery container, a second gas exhaust passage connected to the first gas exhaust passage and connected to the outside of the battery container, and a gas exhaust valve provided in the first gas exhaust passage that performs an opening operation to connect the first gas exhaust passage and the second gas exhaust passage when the gas pressure inside the battery container reaches a predetermined value, and that opens in a shape that follows the cross-sectional shape of the gas exhaust passage when performing the opening operation, and further characterized in that the cross-sectional shape of the second gas exhaust passage when viewed in the gas outflow direction when the gas exhaust valve is opened is formed into an inclined shape that does not obstruct the streamlined flow of gas flowing out from the first gas exhaust passage.

[0041] According to this embodiment, the flow line of the outflowing gas is not obstructed by the second gas exhaust passage, so the gas can flow smoothly and the gas exhaust capacity can be improved. Note that in the following description, the opening shape (cross-sectional shape of the passage) of the gas exhaust passage will be described as being circular.

[0042] 3 is a diagram for explaining the basic concept of this embodiment, and is a schematic diagram showing the configuration of the gas discharge mechanism and the gas flow. Note that in this figure and the following figures, the plate thickness (t) of the battery lid 6 at the portion where the gas discharge path is formed and the opening diameter (d) of the gas discharge passage are not accurately dimensionally related, and the plate thickness (t) is exaggerated.

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

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

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

[0046] The first gas discharge passage 51 is formed in a cylindrical shape (actually a space, which can also be considered a cylindrical shape) in the plate thickness direction, and the second gas discharge passage 52 is formed in a truncated cone shape (actually a space, which can also be considered a truncated cone cylinder shape) in the plate thickness direction. The connection portion of the first gas discharge passage 51 and the second gas discharge passage 52 has the same opening diameter (d). Here, as shown in the figure, the opening diameter (d) of the second gas discharge passage is formed to continuously and gradually increase as it approaches the exterior side (SPout) of the battery container, and the cross-sectional shape as viewed in the gas outflow direction 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, the behavior of the gas flowing through the first gas discharge passage 51 and the second gas discharge passage 52 will be described. As shown by the gas flow lines (FLW), when gas generated inside the battery container flows into the first gas discharge passage 51, it forms a contracted flow section (ACF) midway through the first gas discharge passage 51, and then when it flows out of the first gas discharge passage 51, it spreads outward. In particular, the flow lines on the outer periphery have a strong tendency to spread outward. Note that the gas flow lines shown here are hypothetical representations of gas flow based on the flow lines in fluid mechanics.

[0048] The gas exhaust passage of the gas exhaust mechanism as a comparative example to this embodiment has a shape that is an extension of the first gas exhaust passage 51, as shown by the dashed line (DL), and the expanded gas streamline flow in this portion is obstructed, tending to suppress the amount of gas exhaust. This is due to the streamline being disturbed in the area indicated by the dashed line (DL). Note that obstruction of the streamline flow particularly refers to the phenomenon in which gas flowing outside the gas flow is obstructed by other physical obstacles (here, the passage wall of the gas exhaust passage), forming vortices and preventing smooth flow, resulting in disturbance of the streamline.

[0049] Therefore, in this embodiment, the opening diameter (d) of the second gas discharge passage 52 is formed to gradually increase continuously as it approaches the exterior side (SPout) of the battery container so as not to disturb the flow direction of the gas flowing out from the first gas discharge passage 51. In other words, the cross-sectional shape as viewed in the gas outflow direction is formed as an inclined portion 53 that is inclined so as to widen in a direction away from the axis of the second gas discharge passage 52. This inclined portion 53 has a shape that does not obstruct the flow of the streamline of the gas flowing out from the first gas discharge passage 51 to the second gas discharge passage 52.

[0050] Here, the term "shape that does not obstruct the flow of streamlines" refers to a shape that does not obstruct the flow of gas flowing outside the gas flow and allows the gas to flow smoothly. In other words, the shape is such that the gas streamlines outside the gas flow do not come into contact with or collide with other obstacles (here, the passage wall of the gas discharge passage).

[0051] This allows the flow line of the gas flowing out of the first gas discharge passage 51 to flow out smoothly without being disturbed as in the conventional configuration, and prevents the suppression of gas discharge, thereby making it possible to reduce the weight of the battery lid 6 and ensure sufficient gas discharge.

[0052] Next, a specific configuration of the first embodiment will be described. Fig. 4 shows a configuration in which a gas exhaust valve is arranged in the gas exhaust mechanism shown in Fig. 3. As mentioned above, the plate thickness (t) of the battery lid 6 at the portion where the gas exhaust path is formed and the opening diameter (d) of the gas exhaust passage are not accurately dimensionally related, and the plate thickness (t) is exaggerated. The same reference numerals in Fig. 4 as in Fig. 3 indicate the same configuration, so a repeated description will be omitted here.

[0053] 4, 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. The gas discharge valve 54 has a pressure-receiving surface 55 that receives gas pressure and a press-fit surface 56 that is formed integrally with the pressure-receiving surface 55. The press-fit surface 56 is press-fitted into the inner peripheral 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-fit force, the area of ​​the pressure-receiving surface, and the gas pressure.

[0054] Furthermore, separate from this press-fitted gas release valve 54, a gas release valve 54 can be formed integrally with the battery lid 6 on the first gas release passage 51 side of the connection between the first gas release passage 51 and the second gas release passage 52. That is, the gas release valve 54 is a thin membrane portion that crosses the first gas release passage 51 so as to close it, and this thin membrane portion is formed integrally with the battery lid 6. The opening timing of the gas release valve 54 can be adjusted by the thickness of this membrane portion.

[0055] In this example, at least the portion of the gas discharge passage 51 leading to the gas discharge valve 54 has a flow path having an area (or opening diameter) substantially the same as the area (or opening diameter) of the gas discharge valve 54 on the gas discharge flow path 51 side. For example, the opening area (or opening diameter) of the inlet opening 51 in of the first gas flow path 51 is substantially the same as the area of ​​the gas discharge valve 54. Alternatively, the inlet opening 51 in has a flow path portion having 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 an area (or opening diameter) substantially the same as the area (or opening diameter) of the gas discharge valve 54 on the first discharge flow path side.

[0056] Here, it is important that the gas release valve 54 does not disturb the gas flow lines as much as possible when it is opened. With a conventional split type valve, the flow lines are often disturbed when it is opened. For this reason, in this embodiment, the gas release valve 54 is a valve that pops out and disengages from the gas release passage 51 when opened. The disengaged state of the gas release valve 54 is as shown in FIG. 3. In other words, when the gas release valve 54 opens, it opens in a shape that follows the cross-sectional shape of the gas release passage.

[0057] If the gas pressure inside the battery container reaches a predetermined value for some reason, the gas pressure will cause the gas release valve 54 to pop out against the pressure force and separate from the battery lid 6. The predetermined gas pressure at which the gas release valve 54 separates is the gas pressure at which the gas release valve 54 opens as a safety valve before the internal gas pressure 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] 4, a gas release valve made of a thin membrane portion can be formed integrally with the battery lid 6 by machining, as described above. That is, the gas release valve 54 is formed by integrally forming a membrane portion thinner than the plate thickness of the battery lid 6 in part of the first gas release passage 51.

[0059] As shown in the drawings, if the gas exhaust valve 54 is formed on the side of the first gas exhaust passage 51 including the boundary portion where the first gas exhaust passage 51 and the second gas exhaust passage 52 are connected, the gas exhaust valve 54 can be formed by machining. In this way, the gas exhaust valve 54 can be a thin membrane portion formed integrally with the battery lid 6.

[0060] The pressure-receiving surface of the membrane of the gas release valve 54 is not uniform in thickness, but is configured to have an annular thin portion that is thinner on the side that connects to the wall surface of the first gas release passage 51 than near the center. 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 of the gas release valve 54 tears open in a circular shape from the annular groove, allowing the pressure-receiving surface to peel off cleanly.

[0061] Alternatively, a one-way opening type gas release valve can be used, although this will slightly disrupt the flow lines. For example, a configuration in which a groove is not formed in a portion of the peripheral edge where the annular groove is formed as described above is used. When the valve is ruptured, the non-grooved portion of the annular groove remains without peeling off, so the pressure-receiving surface of the membrane opens in one direction.

[0062] In this way, 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] The gas exhaust valve 54 can be formed by machining, as described above. For example, the first gas exhaust passage 51, which is a cylindrical space, can be formed by cutting, and the second gas exhaust passage 52, which is made of the inclined portion 53, can be formed at the boundary portion by similarly cutting. Alternatively, the gas exhaust valve 54 can be formed by pressing (drawing using a punch and die).

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

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

[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, so the connection between the first gas discharge passage 51 and the second gas discharge passage 52 becomes the narrowest passage, and this section forms the membrane-like gas discharge valve 54. Therefore, by using a die and punch shaped in accordance with this, the gas discharge passages 51, 52 can be formed in the required shape.

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

[0068] 3, the flow path of the gas flowing out of the first gas discharge passage 51 can flow out smoothly without being disturbed as in the conventional configuration, and suppression of the amount of gas discharged can be avoided. This makes it possible to reduce the weight of the battery lid 6 and ensure sufficient gas discharge. In this case, too, when the gas discharge valve 54 is opened, it opens in a shape that follows the cross-sectional shape of the gas discharge passage.

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

[0070] 5, the plate thickness (t) of the battery lid 6 at the portion where the gas discharge path is formed, 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 tilt angle (θ) of the inclined portion 53. The simulation was performed with the plate thickness (t) of the battery lid 6, the arrangement length (l) of the gas discharge valve 54, and the inlet opening diameter (din) of the first gas discharge passage 51 set as constant fixed values, and the tilt angle (θ) of the inclined portion 53 as a variable.

[0071] The results are shown in Fig. 6. As shown in Fig. 6, the inlet opening diameter (din) of the first gas discharge passage 51 is 5 mm, the plate thickness (t) of the battery lid 6 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 a variable.

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

[0073] As can be seen from the graph in Figure 6, the flow rate ratio increases as the inclination angle (θ) of the inclined portion 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, if the inclination angle (θ) is set to 55° or more, the gas flow rate can be effectively increased.

[0074] Furthermore, at an inclination angle of approximately 60°, the flow rate ratio is 110%, which provides a substantial effect. An inclination angle of 60° or more is preferable. At an inclination angle of approximately 75°, the flow rate ratio is 120%, which provides a significant effect. For more effective gas discharge, an inclination angle of 60° or more is preferable.

[0075] In addition, if the inclination angle (θ) is increased, the plate thickness (t) of this portion becomes thin and the mechanical strength decreases, so it is necessary to select an inclination angle (θ) that can ensure a sufficient plate thickness (t) from the viewpoint of mechanical strength. This can be determined as a battery design specification.

[0076] Next, Fig. 7 shows the results of a simulation when the plate thickness (t) of the battery lid 6 at the portion where the gas discharge path is formed is changed. The parameters are the same as those in Fig. 6, but the plate thickness (t) of the battery lid 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 the plate thickness (t) to a larger value will effectively increase the gas flow rate.

[0078] Compared with the inlet opening diameter (din) of the first gas exhaust passage 51, the plate thickness (t) of the battery lid 6 at the portion where the gas exhaust 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 lid 6 at the portion where the gas exhaust path is formed is preferably twice or more the length of the inlet opening diameter (din).

[0079] However, increasing the plate thickness (t) leads to an increase in the weight of the battery lid 6, so it is necessary to select a battery lid 6 with the necessary plate thickness (t) from the perspective of weight. This can be determined as a design specification of the battery.

[0080] If it is not desired to increase the thickness of the battery lid 6, for example, the thickness (t) of the battery lid 6 at the portion where the gas discharge mechanism 10 (gas discharge path) is formed is made thicker than the periphery of the gas discharge mechanism 10. When the gas discharge mechanism 10 is attached to the battery lid 6 (when the gas discharge mechanism 10 is not integral with the battery lid 6 but is a separate structure), this is preferable as it makes it easier to set the thickness. Furthermore, for example, the first gas discharge passage 51 and the second gas discharge passage 52 have openings with circular cross sections. The first gas discharge passage 51 and the second gas discharge passage 52 share a common axis (the same axis). Other embodiments may also have a similar structure, except for those in which this structure is modified.

[0081] As described above, in this embodiment, the gas exhaust mechanism provided in the battery lid 6 comprises a first gas exhaust passage 51 connected to the inside side (SPin) of the battery container, a second gas exhaust passage 52 connected to the first gas exhaust passage 51 and connected to the outside side (SPout) of the battery container, and a gas exhaust valve 54 provided in the first gas exhaust passage 51, which opens to connect the first gas exhaust passage 51 and the second gas exhaust passage 52 when the gas pressure inside the battery container reaches a predetermined value, and further characterized in that the cross-sectional shape of the second gas exhaust passage 52 when viewed in the gas outflow direction when the gas exhaust valve 54 is opened is formed into an inclined shape that does not obstruct the streamlined flow of gas flowing out from the first gas exhaust passage 51.

[0082] According to this embodiment, the flow line of the outflowing gas is not obstructed by the second gas discharge passage 52, so the gas can flow smoothly, and the gas discharge capacity can be improved.

[0083] The location where the gas release mechanism 10 is formed is not limited to the battery lid 6, and the gas release mechanism 10 can also be provided in any of the battery containers that house the electricity storage element. Therefore, this is applicable even when the battery container does not have a battery lid 6. In this embodiment, the gas release mechanism 10 is provided in the battery lid 6 on which the positive electrode external terminal 8A and the negative electrode external terminal 8B are formed. As in this embodiment, the gas release mechanism 10 is provided in the battery lid 6 that has a predetermined thickness and predetermined rigidity, so that a highly reliable valve opening operation can be obtained. Forming the gas release valve 54 integrally with the battery container is also easy.

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

[0085] Next, a second embodiment of the present invention will be described. In the first embodiment, the cross-sectional shape of the second gas discharge passage 52 is a straight inclined portion 53. However, in the second embodiment, the cross-sectional shape of the second gas discharge passage 52 is a convex arc-shaped portion 57. As shown in Fig. 8, the arc-shaped portion 57 is formed by rounding the corner of the outlet opening 52out (the portion indicated by the dashed line (DL) in Fig. 3), and in this embodiment, what is called an "R" in mechanical drawings is adopted.

[0086] That is, 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 exterior side (SPout) of the battery container, and the cross-sectional shape as viewed in the gas outflow direction is formed into an arc shape (arc-shaped portion 57) that expands at a predetermined radius in a direction away from the axis of the second gas discharge passage 52. (Here, in this embodiment, a circular arc is exemplified as an example of the arc shape, but shapes other than a circular arc are also acceptable. Note that, since the arc-shaped portion 57 is exemplified as a circular arc in this embodiment, it will be referred to as the arc portion 57 below.) Furthermore, the arc portion 57 is formed into a convex arc that protrudes toward the axis (C). This arc portion 57 is shaped so as not to obstruct the streamlined flow of gas flowing from the first gas discharge passage 51 to the second gas discharge passage 52.

[0087] 8, a gas discharge valve 54 is press-fitted on the first gas discharge passage 51 side of the connection between the first gas discharge passage 51 and the second gas discharge passage 52. 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-fit position of the gas discharge valve 54 is closer to the inlet opening 51 in, and if the arc radius (r) is short, the press-fit position of the gas discharge valve 54 is farther from the inlet opening 51 in.

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

[0089] It is important that the gas exhaust valve 54 does not disturb the gas flow lines as much as possible when it is opened. With a conventional split-type valve, the flow lines are often disturbed when it is opened. For this reason, the gas exhaust valve 54 used in this embodiment is a valve that pops out and separates from the gas exhaust passage 51 when opened.

[0090] If the gas pressure inside the battery container reaches a predetermined value for some reason, the gas release valve 54 will pop out due to the gas pressure against the press-fitting force and detach from the battery lid 6. When the gas release valve 54 detaches, the flow line of the gas flowing out of the first gas release passage 51 will flow along the arc portion 57. In this way, the gas flow line is not disturbed as in the conventional configuration, allowing the gas to flow out smoothly, preventing the suppression of gas release. This makes it possible to reduce the weight of the battery lid 6 and ensure sufficient gas release.

[0091] Next, we will explain the influence of the arc portion 57 formed in the second gas discharge passage 52. It has been confirmed by simulation that the arc portion 57 affects the streamline of the gas flow on the outer periphery, and an example of this will be briefly explained below.

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

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

[0094] The "arc radius (r) = 0.001 mm" on the vertical axis of the graph in Fig. 10 is the arc radius of the corner of the outlet opening when first gas discharge passage 51 is extended as indicated by the dashed line (DL) in Fig. 4. The gas flow rate is the flow rate at outlet opening 52out of second gas discharge passage 52, and the effect of changes 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 from the graph in Figure 10, the flow rate ratio increases as the arc radius (r) of the arc portion 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 arc radius (r) reaches 1 mm. Therefore, in actual design, if the arc radius (r) is set based on the graph in Figure 10, the gas flow rate can be effectively increased.

[0096] For example, the second gas discharge passage 52 may have a shape in which a change Δd2 in the opening diameter d (in the direction perpendicular to t) from a first location (referred to as t1) that is closer to the outlet opening 52out than the first location to a location (t2 + Δt) that is closer to the outlet opening 52out than the first location is larger than a change Δd1 in the opening diameter d (in the direction perpendicular to t) from a first location (referred to as t1) to a location (t1 + Δt) that is closer to the outlet opening 52out than the first location.

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

[0098] As described above, in this embodiment, the gas exhaust mechanism provided in the battery lid 6 comprises a first gas exhaust passage 51 connected to the inside side (SPin) of the battery container, a second gas exhaust passage 52 connected to the first gas exhaust passage 51 and connected to the outside side (SPout) of the battery container, and a gas exhaust valve 54 provided in the first gas exhaust passage 51, which opens to connect the first gas exhaust passage 51 and the second gas exhaust passage 52 when the gas pressure inside the battery container reaches a predetermined value, and further characterized in that the cross-sectional shape of the second gas exhaust passage 52 viewed in the gas outflow direction when the gas exhaust valve 54 is opened is formed into a convex arc shape that does not obstruct the streamlined flow of gas flowing out from the first gas exhaust passage 51.

[0099] According to this embodiment, the flow line of the outflowing gas is not obstructed by the second gas discharge passage 52, so the gas can flow smoothly, and the gas discharge capacity can be improved.

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

[0101] That is, 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 exterior side (SPout) of the battery container, and the cross-sectional shape as viewed in the gas outflow direction is formed into an arc shape (arc-shaped portion 58) that expands at a predetermined radius in a direction away from the axis of the second gas discharge passage 52 (here, in this embodiment, a circular arc is exemplified as an example of the arc shape, but shapes other than a circular arc are also acceptable. Note that, since the arc-shaped portion 58 is exemplified as a circular arc in this embodiment, it will be referred to as the arc portion 58 below). Furthermore, the arc portion 58 is formed into a concave arc that extends away from the axis (C). This arc portion 58 is shaped so as not to obstruct the streamlined flow of gas flowing from the first gas discharge passage 51 to the second gas discharge passage 52.

[0102] 11 , a gas discharge valve 54 is press-fitted on the first gas discharge passage 51 side of the connection between the first gas discharge passage 51 and the second gas discharge passage 52. 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-fit position of the gas discharge valve 54 is closer to the inlet opening 51 in, and if the arc radius (r) is short, the press-fit position of the gas discharge valve 54 is farther from the inlet opening 51 in.

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

[0104] It is important that the gas discharge valve 54 does not disturb the gas flow lines as much as possible when it is opened. With a conventional split-type valve, the gas flow lines are often disturbed when it is opened. For this reason, the gas discharge valve 54 used in this embodiment is a valve that jumps out and separates from the first gas discharge passage 51 when opened.

[0105] If the gas pressure inside the battery container reaches a predetermined value for some reason, the gas release valve 54 pops out due to the gas pressure against the press-fitting force and separates from the battery lid 6. When the gas release valve 54 is separated, the flow line of the gas flowing out of the first gas release passage 51 flows along the arc portion 58. In this way, the gas flow line is not disturbed as in the conventional configuration, allowing the gas to flow out smoothly, preventing the suppression of gas release. This makes it possible to reduce the weight of the battery lid 6 and ensure sufficient gas release.

[0106] For example, the second gas discharge passage 52 may have a shape in which a change Δd2 in the opening diameter d (in the direction perpendicular to t) from a first location (referred to as t1) that is closer to the outlet opening 52out than the first location to a location (t2 + Δt) that is closer to the outlet opening 52out than the first location is smaller than a change Δd1 in the opening diameter d (in the direction perpendicular to t) from a first location (referred to as t1) to a location (t1 + Δt) that is closer to the outlet opening 52out than the first location.

[0107] As described above, in this embodiment, the gas exhaust mechanism provided in the battery lid 6 comprises a first gas exhaust passage 51 connected to the inside side (SPin) of the battery container, a second gas exhaust passage 52 connected to the first gas exhaust passage 51 and connected to the outside side (SPout) of the battery container, and a gas exhaust valve 54 provided in the first gas exhaust passage 51, which opens to connect the first gas exhaust passage 51 and the second gas exhaust passage when the gas pressure inside the battery container reaches a predetermined value, and further characterized in that the cross-sectional shape of the second gas exhaust passage 52 viewed in the gas outflow direction when the gas exhaust valve 54 is opened is formed into a concave arc shape that does not obstruct the streamlined flow of gas flowing out from the first gas exhaust passage 51.

[0108] According to this embodiment, the flow line of the outflowing gas is not obstructed by the second gas discharge passage 52, so the gas can flow smoothly, and the gas discharge capacity can be improved.

[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 is formed by the inclined portion 53, the convex arc portion 57, and the concave arc portion 58. However, in the fourth embodiment, the cross-sectional shape of the second gas discharge passage 52 is formed by a stepped enlarged diameter portion 59 relative to the first gas discharge passage 51.

[0110] 12, the large-diameter portion 59, which is an example of the stepped portion, has a columnar shape (actually, it is an empty space and can also be considered cylindrical), 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 FIG. 14). The large-diameter portion 59 is shaped so as not to obstruct the streamlined flow of gas flowing from the first gas discharge passage 51 to the second gas discharge passage 52.

[0111] 12 , the first gas discharge passage 51 is formed in a columnar shape (actually a space, which can also be considered a cylindrical shape) in the plate thickness direction, and the second gas discharge passage 52 is also formed in a columnar shape (actually a space, which can also be considered 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 release valve 54 has a pressure-receiving surface 55 that receives gas pressure and a press-fit surface 56 that is formed integrally with this pressure-receiving surface 55. The press-fit surface 56 is press-fitted into the inner peripheral wall surface of the first gas release passage 51. The opening timing of the gas release valve 54 can be adjusted based on the relationship between this press-fit force, the area of ​​the pressure-receiving surface, and the gas pressure.

[0113] If the gas pressure inside the battery container reaches a predetermined value for some reason, the gas pressure will cause the gas exhaust valve 54 to pop out against the press-fit force and detach from the battery lid 6. When the gas exhaust valve 54 detaches, the flow line of the gas flowing out from the first gas exhaust passage 51 flows into the second gas exhaust passage 52, which has a larger outlet opening diameter (dout), allowing the gas to flow out smoothly without being disturbed as in the conventional configuration, thereby avoiding the suppression of gas exhaust. This makes it possible to reduce the weight of the battery lid 6 and ensure sufficient gas exhaust.

[0114] Next, we will explain the influence of the large diameter portion 59 formed in the second gas discharge passage 52. It has been confirmed by simulation that the large diameter portion 59 affects the streamlines of the gas flow on the outer periphery, and an example of this will be briefly explained below.

[0115] The parameters used in the gas flow model of the simulation were the plate thickness (t) of the battery lid 6 at the portion where the gas discharge path is formed, 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, as shown in Fig. 13. The plate thickness (t) of the battery lid 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 set as constant fixed values, and the outlet opening diameter (dout) of the outlet opening 52out was used as a variable in the simulation.

[0116] The results are shown in Fig. 14. As shown in Fig. 14, the inlet opening diameter (din) of the first gas discharge passage 51 is 5 mm, the plate thickness (t) of the battery lid 6 at the portion 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 a variable.

[0117] The "outlet opening diameter 5 mm" on the vertical axis of the graph in Fig. 14 corresponds to the outlet opening when the first gas discharge passage 51 is extended, as indicated by the dashed line (DL) in Fig. 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 changes in the 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 from the graph in Figure 14, the larger the outlet opening diameter (dout), the larger the flow rate ratio. This indicates that the larger the flow rate ratio, the greater the gas flow rate. In particular, it can be seen that the gas flow rate increases when the outlet opening diameter (dout) reaches 7 mm. Therefore, in actual design, if the outlet opening diameter (dout) is set based on the graph in Figure 14, the gas flow rate can be effectively increased.

[0119] The outlet opening diameter of 5 mm can be considered to be the opening diameter of the end of the second gas discharge passage 52 on the first gas discharge passage 51 side. Therefore, the outlet opening diameter (dout) is preferably 1.5 times larger than the opening diameter of the end of the second gas discharge passage 52 on the first gas discharge passage 51 side. Furthermore, when the outlet opening diameter (dout) is 10 mm, the flow rate ratio is 110%, and a substantial effect is obtained. Preferably, it is 2 times or more. Furthermore, when the outlet opening diameter (dout) is 15 mm, the flow rate ratio is approximately 120%, and a significant effect is obtained. For more effective gas discharge, it is preferably 3 times or more.

[0120] The stepped enlarged diameter portion may be, for example, a plurality of stepped portions. A structure (intermediate step) having an opening diameter larger than the opening diameter of the first gas discharge passage 51 side end of the second gas discharge passage 52 and smaller than the outlet opening diameter (dout) may be provided between the first gas discharge passage 51 side end of the second gas discharge passage 52 and the outlet. This is easier to manufacture than an inclined shape, and the difference in diameter between adjacent openings is smaller than in the structure shown in the figure, making it preferable.

[0121] As described above, in this embodiment, the gas exhaust mechanism provided in the battery lid 6 comprises a first gas exhaust passage 51 connected to the inside side (SPin) of the battery container, a second gas exhaust passage 52 connected to the first gas exhaust passage 51 and connected to the outside side (SPout) of the battery container, and a gas exhaust valve 54 provided in the first gas exhaust passage 51 that opens to connect the first gas exhaust passage 51 and the second gas exhaust passage when the gas pressure inside the battery container reaches a predetermined value, and further characterized in that the cross-sectional shape of the second gas exhaust passage 52 viewed in the gas outflow direction when the gas exhaust valve 54 is opened is formed into a stepped enlarged diameter section that does not obstruct the streamlined flow of gas flowing out from the first gas exhaust passage 51.

[0122] According to this embodiment, the flow line of the outflowing gas is not obstructed by the second gas discharge passage 52, so the gas can flow smoothly, and the gas discharge capacity can be improved.

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

[0124] 15 , the first gas discharge passage 51 and the second gas discharge passage 52 are cylindrical (actually, they are spaces, and can also be said to be cylindrical), and are formed with an outlet opening diameter (dout) that is larger than the inlet opening diameter (din) of the first gas discharge passage 51. 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 with this configuration, if the gas pressure inside the battery container reaches a predetermined value for some reason, the gas pressure will cause the gas release valve 54 to pop out against the press-fit force and detach from the battery lid 6. When the gas release valve 54 detaches, the flow path of the gas flowing out of the first gas release passage 51 flows into the second gas release passage 52, which has a larger outlet opening diameter, allowing the gas to flow out smoothly without being disturbed as in the conventional configuration, thereby avoiding the suppression of gas release. This makes it possible to reduce the weight of the battery lid 6 and ensure sufficient gas release.

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

[0127] According to this embodiment, the flow line of the outflowing gas is not obstructed by the second gas discharge passage 52, so the gas can flow smoothly, and the gas discharge capacity can be improved.

[0128] In the first to fifth embodiments, an example has been shown in which the gas exhaust valve 54 is provided in the first gas flow path 51. Among these, an example has been shown in which the gas exhaust valve 54 is provided at the end of the first gas flow path 51 on the second gas flow path side 52. Alternatively, the gas exhaust valve 54 may be provided on the second gas flow path side 52 of the first gas flow path 51, closer to the inlet opening 51in than the second gas flow path 52.

[0129] In the first to fifth embodiments, an example is illustrated in which the area (or opening diameter) of at least a main portion of the first gas flow path 51 or the area (or opening diameter) of the opening of the inlet opening 51in has substantially the same area (opening diameter) as the gas exhaust valve 54. Alternatively, the first gas flow path 51 may have an area (or opening diameter) at the gas exhaust valve 54 smaller than the inlet opening 51in of the first gas flow path 51. This may facilitate operation in terms of inserting and ejecting processing equipment. In this case, it is preferable from the standpoint of gas exhaustion that the value (52out / 54) obtained by dividing the area (or opening diameter) of the outlet opening 51out by the area (or opening diameter) of the gas exhaust valve 52 is larger than the value (51in / 54) obtained by dividing the area (or opening diameter) of the inlet opening 51in by the area (or opening diameter) of the gas exhaust valve 52.

[0130] 4C , the first gas flow path 51 and the second gas flow path 52 may have a shape that is not linear but has a linear slope that widens outward. Alternatively, the cross sections of the first gas flow path 51 and the second gas flow path 52 may have an arc-shaped slope.

[0131] Next, a sixth embodiment of the present invention will be described. While the first to fifth embodiments each have the gas exhaust valve 54 provided in the first gas exhaust passage 51, this embodiment differs in that the gas exhaust valve 54 is provided in the second gas exhaust passage 52.

[0132] 16 , based on the configuration in the first embodiment, a gas discharge valve 60 is provided on the second gas discharge passage 52 side as viewed from the connection portion 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 separate from the second gas discharge passage 52 when the gas pressure inside the battery container exceeds a predetermined value.

[0133] Here, the gas release valve 60 is fixed to the wall surface of the second gas release passage 52, in this case, to the inclined portion 53, by a method such as welding. By using a method such as welding in this manner, the gas release valve 60 can be fixed to any position on the inclined portion 53.

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

[0135] For example, a first gas exhaust passage 51, which is a cylindrical space, is formed toward the boundary portion by cutting, and a second gas exhaust passage 52, which is made of an inclined portion 53, is similarly formed toward the boundary portion by cutting, thereby forming a membrane-shaped gas exhaust valve 60.

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

[0137] Here, since the gas release valve 60 is formed at the boundary portion, the inclined portion 53 functions as a punch taper, making drawing possible. As mentioned above, if an annular groove formed by drawing is provided at the portion of the gas release valve 60 connecting to the inclined portion 53, the gas release valve 60 can be removed.

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

[0139] In this embodiment, the flow line of the outflowing gas is not obstructed by the second gas exhaust passage, so the gas can flow smoothly and the gas exhaust capacity can be improved. Note that, although Figure 16 is based on the configuration of the first embodiment, a similar gas exhaust valve can also be provided in the configurations of the other embodiments, namely the second to fifth embodiments.

[0140] Furthermore, in the first to sixth embodiments described above, the cross-sectional shape of the gas discharge passage perpendicular to the axis is circular, but this is not limited thereto, and any shape that allows smooth flow lines to be formed may be used, such as rectangular, oval, or elliptical.

[0141] As described in the above embodiments, in the battery of the present invention, 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 a gas discharge valve provided in a part of the gas discharge passage consisting of the first gas discharge passage and the second gas discharge passage, which opens to connect the inside and outside of the battery container via the gas discharge passage when the gas pressure inside the battery container reaches a predetermined value, and further, the cross-sectional shape of the second gas discharge passage as viewed in the gas outflow direction when the gas discharge valve is opened is formed in a shape that does not obstruct the streamlined flow of gas flowing out from the first gas discharge passage.

[0142] According to this, the flow line of the outflowing gas is not obstructed by the second gas discharge passage, so that the gas can flow smoothly, and the gas discharge capacity can be improved.

[0143] In the above embodiment, the length of the first gas discharge flow path 51 in the plate thickness (t) direction can be set to 5% to 80% of the plate thickness (t) of the battery lid from the viewpoint of manufacturability, and is preferably set to 10% to 50% from the viewpoint of gas flow.

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

[0145] A: The second gas flow path 52 is formed so that the opening diameter of the second gas discharge passage 52 becomes gradually larger as it approaches the exterior of the battery container, and the cross-sectional shape viewed in the gas outflow direction has a linearly inclined inclined portion 53 that widens in a direction away from the axis of the second gas discharge passage 52; B: The second gas flow path 52 is formed so that the opening diameter of the second gas discharge passage 52 becomes gradually larger as it approaches the exterior of the battery container, and the cross-sectional shape viewed in the gas outflow direction is an arc-shaped portion that widens in a direction away from the axis of the second gas discharge passage 52 (for example, the arc-shaped portion is a convex arc portion that protrudes toward the axis of the second gas discharge passage 52, or the arc-shaped portion is a concave arc portion that widens in a direction away from the axis 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, we will briefly explain the configuration of a battery that can efficiently guide gas generated inside the battery container to the first gas discharge passage 51. 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] 17 , a battery can 1 contains an electrode assembly 3 surrounded by a separator 61 and other components. The battery can 1 is a rectangular metal can with an opening 1a extending along the longitudinal direction and a housing portion 1b connected to the opening 1a. The battery can 1 is made of, for example, aluminum or an aluminum alloy.

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

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

[0150] The battery lid 6 has a liquid injection insertion hole formed as a circular through-hole between the positive electrode external terminal 8A and the negative electrode external terminal 8B. A sealing plug 11 is inserted into the liquid injection insertion hole.

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

[0152] The insulating cover 63 covers the electrode body 3, exposing the upper end 3a of the electrode body 3 to the outside, and covering the electrode body 3 except for the upper end 3a. The insulating cover 63 is formed, for example, in a pentahedral shape and configured by being folded into a box shape. The insulating cover 63 is formed, for example, from polypropylene.

[0153] In a battery of this structure, the electrode bodies 3 are stacked in the vertical direction (the direction of gravity), and tiny gaps are formed between adjacent surfaces.This gap is connected to the upper end portion 3a, so that gas generated from the electrode body 3 is smoothly guided upward in the direction of gravity to the space between the electrode body 3 and the battery lid 6, making it possible to increase the gas exhaust capacity while keeping the battery small.

[0154] It should be noted that the present invention is not limited to the above-described embodiments and includes various modifications. The above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part 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 with respect to the configuration of each embodiment.

[0155] C1...lithium ion secondary battery, 1...battery can, 1a...opening, 2...insulating protective film, 3...wound electrode body, 3a...front flat surface, 3a...rear flat surface, 4A...positive electrode current collector plate, 4B...negative electrode current collector plate, 5...gasket, 6...battery lid, 6A...positive electrode side through-hole, 6B...negative electrode side through-hole, 7...insulating plate, 8A...positive electrode external terminal, 8B...negative electrode external terminal, 9...filling port, 10...gas discharge mechanism, 11...liquid filling plug, 12A...positive electrode connecting portion, 12B...negative electrode connecting portion, 50...gas discharge passage, 51...first gas discharge passage, 52...second gas discharge passage, 53...inclined portion, 54...gas discharge valve, 55...pressure receiving surface, 56...pressure-fitting surface structure, 57...convex arc portion, 58...concave arc portion, 59...large diameter portion.

Claims

1. A battery comprising: an electricity storage element; a battery container accommodating the electricity storage element; and a gas exhaust mechanism fluidly connecting an interior side of the battery container to an exterior side of the battery container, and exhausting gas from within the battery container when gas pressure within the battery container reaches a predetermined value, the gas exhaust mechanism comprising: a first gas exhaust passage connected to the interior side of the battery container; a second gas exhaust passage connected to the first gas exhaust passage and connected to the exterior side of the battery container; and a gas exhaust valve provided in a part of the gas exhaust passage on the second gas exhaust flow path side of an inner end of the battery container of the first gas exhaust passage or on the first gas exhaust flow path side of an outer end of the battery container of the second gas exhaust passage, the gas exhaust valve performing an opening operation to connect the interior side and exterior side of the battery container via the gas exhaust passage when the gas pressure within the battery container reaches a predetermined value, and opening to a shape that follows the passage cross-sectional shape of the gas exhaust passage when performing the opening operation; The battery further comprises a second gas exhaust passage having a cross-sectional shape as viewed in the gas outflow direction when the gas exhaust valve is opened, the cross-sectional shape being formed in a shape that does not obstruct the flow of the streamline of the gas flowing out of the first gas exhaust passage.

2. The battery according to claim 1, wherein the gas exhaust valve is provided on the side of the first gas exhaust passage.

3. A battery according to claim 2, characterized in that the gas exhaust valve is provided on the side of the first gas exhaust passage including the boundary of the connecting portion between the first gas exhaust passage and the second gas exhaust passage.

4. The battery according to claim 1, wherein the gas exhaust valve is provided on the side of the second gas exhaust passage.

5. A battery according to claim 4, characterized in that the gas exhaust valve is provided on the side of the second gas exhaust passage including the boundary of the connecting portion between the first gas exhaust passage and the second gas exhaust passage.

6. A battery as claimed in claim 3 or claim 5, wherein the battery container comprises a battery can having an opening in which the power storage element is housed, and a battery lid for sealing the battery can, the battery lid having a positive external terminal, a negative external terminal and the gas exhaust passage for supplying power from the power storage element to the outside, the gas exhaust valve being a membrane portion formed integrally with the battery lid, and further comprising a thin-walled annular groove formed in a portion of the membrane portion connected to the wall surface of the gas exhaust passage.

7. A battery as described in claim 2 or claim 4, characterized in that the cross-sectional shape of the second gas discharge passage is formed so that the opening diameter of the second gas discharge passage continuously and gradually increases as it approaches the exterior side of the battery container, and the cross-sectional shape viewed in the gas outflow direction has an inclined portion that is linearly inclined and expands in a direction away from the axis of the second gas discharge passage.

8. A battery as described in claim 2 or claim 4, characterized in that the cross-sectional shape of the second gas discharge passage is such that the opening diameter of the second gas discharge passage is continuously and gradually larger as it approaches the exterior side of the battery container, and the cross-sectional shape viewed in the gas outflow direction is an arc-shaped portion formed in an arc that expands in the direction away from the axis of the second gas discharge passage.

9. A battery as set forth in claim 8, characterized in that the arc-shaped portion is a convex arc-shaped portion projecting in a direction toward the axial side of the second gas discharge passage.

10. A battery as claimed in claim 8, characterized in that the arc-shaped portion is a concave arc portion extending in a direction away from the axis of the second gas discharge passage.

11. A battery as claimed in claim 2 or claim 4, characterized in that the first gas exhaust passage and the second gas exhaust passage are cylindrical spaces, the second gas exhaust passage has an opening diameter larger than the opening diameter of the first gas exhaust passage, and the second gas exhaust passage is formed in a step shape by the larger opening diameter.

12. The battery according to claim 11, wherein the first gas exhaust passage and the second gas exhaust passage have the same axial center.

13. The battery according to claim 11, wherein the axial centers of the first gas exhaust passage and the second gas exhaust passage are eccentric.

14. A battery as described in claim 11, characterized in that the gas exhaust mechanism is provided in a part of a gas exhaust passage consisting of the first gas exhaust passage and the second gas exhaust passage, and when the gas pressure inside the battery container reaches a predetermined value, performs an opening operation to connect the inside and outside of the battery container with the gas exhaust passage, and when performing the opening operation, is provided with a gas exhaust valve that opens in a shape that follows the passage cross-sectional shape of the gas exhaust passage.

15. A battery as claimed in claim 2 or 4, characterized in that the gas exhaust valve is a valve that is detached from the first gas exhaust passage when opened.