JP2011175937A - Sealed battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealed battery with a safety mechanism in which no leakage of an electrolyte solution is caused by a shock of falling or the like. <P>SOLUTION: In the sealed battery provided with a safety mechanism in which a valve is crushed to discharge the gas inside the battery out of the battery, when a battery inner pressure rises, the valve is arranged on a sealing port plate for sealing an outer can bottom or an opening of the outer can, and the thickness of the valve is thinner than the thickness of the outer can bottom or the sealing port plate and moreover the valve has a crushing groove to open the valve, and a chamfering part of which the corners are chamfered are formed on at least part of a battery outside face of the body in an interface between the valve and the can bottom of the outer can where the valve is arranged or the body of the sealing port plate. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sealed battery provided with a safety mechanism that discharges gas in the battery when the battery internal pressure increases.

  In recent years, mobile information terminals such as mobile phones and notebook personal computers have been rapidly reduced in size and weight, and batteries as drive power sources are required to have higher capacity and higher energy density. Non-aqueous electrolyte secondary batteries represented by lithium ion secondary batteries have high energy density and high capacity, and are therefore widely used as drive power sources for mobile information terminals.

  By the way, the non-aqueous electrolyte secondary battery, when exposed to high temperature or improper charging / discharging, reacts with the electrode and the electrolytic solution to decompose the electrolytic solution, and the gas generated by the decomposition Battery internal pressure increases. When the battery internal pressure increases, there is a risk that the battery may burst, so it is necessary to quickly release the gas in the battery to the outside of the battery.

  Therefore, as a technique for quickly releasing the gas in the battery to the outside of the battery, various techniques for providing a groove on the sealing plate for sealing the battery to form a gas discharge hole by crushing and cleaving when the battery internal pressure increases are proposed. (For example, refer to Patent Documents 1 and 2.)

JP 2003-187774 A JP 2007-141518 A

  In Patent Document 1, a thin-walled valve body is provided with an annular crushing groove for opening the valve body, and the remaining thickness is larger than the crushing groove provided in an inner region of the crushing groove, and one end is connected to the crushing groove. This is a technique for forming a crushing auxiliary groove.

  In Patent Document 2, a second processed recess having a second remaining thickness is provided at a predetermined position of a first processed recess having a first remaining thickness t1 provided in a plate material of a sealing plate, and the second processed recess is thinner. It has a third remaining thickness t3 and is provided with a groove portion with a corrugated bent portion on the outer periphery. A curved portion is formed near the inner periphery of this groove portion. This technology relates to an explosion-proof structure that is configured to operate a safety valve by letting go.

  However, the techniques according to Patent Documents 1 and 2 have a problem that although the gas in the battery can be discharged quickly, it is not possible to sufficiently prevent the electrolyte from leaking due to malfunction due to an impact such as dropping. .

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sealed battery including a gas discharge mechanism that can prevent an electrolyte from leaking due to malfunction due to an impact or the like.

  In order to achieve the above object, the present invention provides a sealed battery having a safety mechanism in which a valve body is crushed when a battery internal pressure rises and discharges gas in the battery to the outside of the battery. Provided on a sealing plate that seals the bottom of the outer can or the opening of the outer can, the thickness of the valve body is smaller than the thickness of the bottom surface of the outer can or the sealing plate, and has a crushing groove that opens the valve body. In addition, at least a part of the battery outer surface of the main body portion at the boundary between the valve body and the bottom surface of the outer can or the main body portion of the sealing plate provided with the valve body is a chamfered portion with chamfered corners. Is formed.

  Impact such as dropping acts on the sealing plate part and the outer can part that are in direct contact with the floor surface, etc., which propagates to the valve body, and the propagated impact accumulates, causing the valve body to break up and cause leakage. . Here, the impact transmitted to the valve body increases as the portion that receives the direct impact is closer to the valve body and as the area that receives the direct impact is larger. In the above configuration, since at least part of the corner of the battery outer surface of the main body at the boundary between the valve body and the main body of the outer can or the sealing plate provided with the valve body is chamfered, the vicinity of the valve body It is difficult for an impact to act directly on the main body of the outer can or the sealing plate, and the area of the main body of the outer can or the sealing plate near the valve body is reduced. For this reason, since the impact transmitted to the valve body is also reduced, it is possible to prevent malfunction of the valve body due to impact such as dropping.

  In addition, the valve body may further include a dome portion protruding toward the inside or outside of the battery, and the crushing groove may be formed so as to surround the dome portion.

  In this configuration, the entire crushing groove is reliably crushed by the effect of residual stress when forming the dome portion, so that the gas inside the battery can be discharged more quickly.

  Further, when the dome portion protruding inside the battery is provided, the dome portion acts so as to alleviate a change in the internal pressure of the battery due to the movement of the electrolytic solution or the electrode body due to an impact such as dropping. For this reason, it is possible to prevent a valve body malfunction caused by a change in the battery internal pressure due to an impact such as dropping.

  Further, the valve body is configured between the bottom surface of the outer can or the outer surface of the sealing plate on which the valve body is formed and the virtual surface that is flush with the inner surface of the sealing plate and the virtual surface that is flush with the sealing plate. It can be.

  According to this structure, the malfunction of the valve body by contact with a processing tool, a connection terminal, etc. can be prevented.

  Here, the cross-sectional shape parallel to the height direction of the battery in the chamfered portion may be a polygonal shape, an arc shape, an elliptical arc shape, or any other indefinite shape. In order to reduce the impact transmitted to the valve body, the cross-sectional shape of the chamfered portion 20 parallel to the height direction of the battery is such that the sealing plate 13 provided with the valve body has a cross-sectional shape as shown in FIG. When the distance between the outer surface of the battery and the root portion of the valve body 6 is t, it is preferable to have an R shape (arc shape) with a radius of curvature of 0.5 t to t. When the present invention is applied to a battery in which the valve body 6 is provided on the sealing plate and the fitting portion between the sealing plate and the outer can is sealed by laser welding, the end of the chamfered portion 20 does not cover the laser welding portion 2a. It is preferable to make it.

  Further, the chamfered portion may be formed in the vicinity of a portion of the valve body where stress is most concentrated.

  Since the portion of the valve body where stress is most concentrated is most easily cleaved by impact or the like, it is preferable to provide a chamfered portion in the vicinity of this portion. Most preferably, chamfers are formed at all the boundaries so as to completely surround the valve body. Here, the part where the stress is most concentrated on the valve body can be determined in the following order (a) to (c).

(A) The portion where the remaining thickness is the thinnest (b) Intersection where the crushing grooves intersect (c) The edge of the sealing plate surface or can bottom surface where the disc is formed (the sealing plate surface or bottom surface of the can and The closest point to the boundary

  When there are a plurality of portions where stress is most concentrated determined by the above method, a chamfered portion is provided in the vicinity of all the portions.

  As described above, according to the present invention, it is possible to realize a sealed battery equipped with a gas discharge mechanism that can prevent an electrolyte from leaking due to malfunction due to an impact or the like.

FIG. 1 is a perspective view of a battery according to the present invention. 2 is a partial cross-sectional view taken along line AA in FIG. FIG. 3 is a view showing a valve body of a sealed battery according to the present invention, in which FIG. 3 (a) is a plan view, FIG. 3 (b) is a cross-sectional view taken along the line AA ′ of FIG. FIG. 3C is a cross-sectional view taken along the line BB ′ of FIG. FIG. 4 is a plan view showing a modification of the valve body used in the present invention. FIG. 5 is a plan view showing a modified example of the location where the chamfered portion is formed. 6A and 6B are diagrams showing a valve body of a sealed battery according to Comparative Example 1, in which FIG. 6A is a plan view, and FIG. 6B is a cross-sectional view taken along line AA ′ in FIG. FIG. 6C is a cross-sectional view taken along line BB ′ of FIG.

(Embodiment)
EMBODIMENT OF THE INVENTION The form for implementing this invention is demonstrated below based on drawing. 1 is a perspective view of a sealed battery according to the present invention, FIG. 2 is a cross-sectional view taken along line AA of FIG. 1, and FIG. 3 is a diagram illustrating a safety mechanism according to the present invention. 3A is a plan view, FIG. 3B is a cross-sectional view taken along line AA ′ in FIG. 3A, and FIG. 3C is a cross-sectional view taken along line BB ′ in FIG.

  As shown in FIGS. 1 and 2, the sealed battery according to the present invention is hermetically sealed by sealing the sealing body 1 in the opening of the outer can 2 and laser welding the fitting. . As shown in FIGS. 1 and 2, the sealed battery sealing body 1 according to the present invention includes a valve body 6 that discharges gas inside the battery to the outside of the battery when the internal pressure of the battery rises abnormally, and electrolysis. It has a sealing plug 8 having a pressing plate and a projecting portion for sealing a liquid injection hole for injecting liquid into the outer can 2, and an electrode external terminal (terminal plate) 11. The liquid injection hole and the sealing plug 8 are not essential components of the present invention.

  As shown in FIG. 2, the sealed battery sealing body according to the present invention includes a sealing plate 13, a terminal plate 11, an insulating gasket 12, a terminal rivet 15, and an insulating plate 14. The sealing body 1 is formed by inserting a terminal rivet 15 into a through hole provided in each of the terminal plate 11, the insulating gasket 12, the sealing plate 13, and the insulating plate 14, and crushing and crimping the tip of the terminal rivet 15. It is the structure where each said member is fixed. The electrode external terminal includes a terminal rivet 15 and a terminal plate 11 which are involved in current extraction, and an insulating plate 14 and an insulating gasket 12 for fixing them. Note that the sealing body is not limited to this configuration.

  As shown in FIG. 2, an electrode body 3 having a positive electrode and a negative electrode is accommodated in the outer can 2, and an insulating member 4 that insulates the electrode body 3 and the sealing plate 13 is provided between the electrode body 3 and the sealing plate 13. Has been placed. In addition, the electrode body 3 and the terminal plate 11 are connected via the current collecting tab 31 and the terminal rivet 15, whereby a current is taken out to the outside.

  Here, an opening hole 17 is formed in the insulating plate 4, and a valve body 6 (integrally formed with the sealing plate 13 is formed on the opening hole 17 as shown in FIGS. 1 and 2. As with the sealing plate 13, an aluminum alloy is disposed. As shown in FIGS. 3B and 3C, the valve body 6 is thinner than the thickness of the main body portion of the sealing plate 13. Further, the valve body 6 is formed with a dome portion 6b having a dome shape projecting inward of the battery, and a crushing groove 6a for facilitating the crushing of the valve body is formed at the periphery of the dome portion 6b. Has been. Further, the entire valve body 6 is formed between a virtual surface 18a flush with the outer surface of the sealing plate 13, and a virtual surface 18b flush with the inner side surface of the sealing plate 1 (FIG. 3 (c). )reference).

  Hereinafter, the manufacturing method of the sealed battery according to the present invention will be described.

<Preparation of positive electrode>
9 parts by mass of lithium cobalt oxide (LiCoO ₂ ) powder as a positive electrode active material and 1 part by mass of artificial graphite powder as a conductive agent are mixed to prepare a positive electrode mixture. The positive electrode mixture and a binder solution obtained by dissolving 5% by mass of polyvinylidene fluoride in N-methyl-2-pyrrolidone (NMP) have a solid content mass ratio after drying of the positive electrode mixture: polyvinylidene fluoride = 95. : Knead | mixing so that it may become 5, and prepare a positive electrode active material slurry.

  This slurry is applied to both surfaces of an aluminum foil (foil thickness: 15 μm) as a positive electrode current collector. Then, it dries and compresses after that and produces a positive electrode plate. Thereafter, the positive electrode plate is cut to fit the battery height to form a positive electrode.

<Preparation of negative electrode>
Scattered natural graphite (d002 value: 3.356 mm, Lc value: 1000 mm, average particle size: 20 μm) and styrene-butadiene rubber (SBR) dispersion (solid content: 48%) are dispersed in water to increase A negative electrode active material slurry is prepared by adding carboxymethylcellulose (CMC) as a sticking agent. The solid content mass composition ratio is prepared so as to be, for example, graphite: SBR: CMC = 100: 3: 2.

  After apply | coating this slurry to both surfaces of the copper foil (foil thickness: 10 micrometers) as a negative electrode collector, it is made to dry and is compressed after that, and a negative electrode plate is produced. Thereafter, the negative electrode plate is cut to fit the battery height, and then a current collecting tab is attached to form a negative electrode.

<Production of electrode body>
The above-described positive electrode and negative electrode are wound through a separator made of a polyethylene microporous film, and then pressed, and a current collecting tab is attached to the outermost periphery of the positive electrode, thereby producing a flat spiral electrode body 3.

<Preparation of electrolyte>
As a non-aqueous electrolyte, LiPF ₆ is dissolved in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 50:50 (25 ° C.) so as to be 1 mol / liter to obtain an electrolytic solution. .

<Preparation of sealing plate>
Thin portion (1.8 × 5.0 mm size oval shape) with a thickness of 40 μm so that the depth t is 0.4 mm from the top surface (battery outer surface) of the sealing plate 13 (plate thickness 1.0 mm). (Semi-circular shape with a radius of 0.9 mm at both ends and a line segment length of 3.2 mm) is formed by forging. At this time, by setting the tip of the punch used for forging to a predetermined R shape, the top side corner of the sealing plate main body at the boundary between the sealing plate main body and the thin-walled portion is chamfered (R-shaped. ) To form the chamfered portion 20. Thereafter, the thin portion is coined, and the dome portion 6b and the crushing groove 6a are integrally molded to produce the sealing plate 13 including the valve body 6.

  In addition, about the formation method of the chamfer part 20, it is not limited to the said method, For example, after forming the valve body 6 like the past, the method of cutting and chemical corrosion can be employ | adopted. .

<Assembly of sealing body>
Thereafter, terminal rivets 15 are inserted into through holes provided in the insulating plate 14, the sealing plate 13, the insulating gasket 12, and the terminal plate 11. Thereafter, by crushing the tip of the terminal rivet 15, the terminal plate 11, the insulating gasket 12, the insulating plate 14, and the terminal rivet 15 are fixed to the sealing plate 13 to obtain the sealing body 1.

<Assembly of battery>
The negative electrode current collecting tab 31 attached to the electrode body 3 is connected to the terminal rivet 15. After this electrode body 3 is inserted into a bottomed rectangular outer can 2 made of aluminum alloy, a positive electrode current collecting tab attached to the electrode body 3 is sandwiched between the outer can 2 and the sealing body 1. Thereafter, the opening of the outer can 2 and the sealing body 1 are laser welded, and the electrolytic solution is injected from the liquid injection hole of the sealing body 1. Thereafter, the liquid injection hole is sealed with a sealing plug 8 having a pressing plate and a protruding portion, and the sealing plate 13 and the outer peripheral edge of the pressing plate of the sealing plug 8 are laser welded to 4.0 ( A non-aqueous electrolyte secondary battery according to the present embodiment of (thickness) × 42 (width) × 61 mm (height) is manufactured.

Example 1
A battery according to Example 1 was fabricated in the same manner as in the above embodiment.

(Example 2)
The battery size was 3.6 (thickness) × 44 (width) × 61 mm (height), and a battery was fabricated in the same manner as in the above embodiment. In the produced battery, lead plates (not shown) were attached to the terminal plate 11 and the sealing plate 13 of the battery, respectively. A protection circuit board (not shown) having external terminals was connected to the lead plate. The protection circuit board connected to the battery was fixed on the sealing plate 13 so that the external terminals were exposed to the outside and covered with a resin cap (not shown). Further, a resin cover (not shown) was attached to the bottom of the battery. Then, a battery pack (not shown) according to Example 2 was manufactured by attaching a label (not shown) coated with an adhesive on one side so as to cover the entire circumference of the side surface of the outer can 2.

(Comparative Example 1)
As shown in FIGS. 6A to 6C, a battery according to Comparative Example 1 was fabricated in the same manner as in Example 1 except that the chamfered portion was not formed.

(Comparative Example 2)
As shown in FIGS. 6A to 6C, a battery pack according to Comparative Example 2 was fabricated in the same manner as in Example 2 except that the chamfered portion was not formed.

(Drop test 1)
Ten batteries of Example 1 and Comparative Example 1 were prepared. These batteries were dropped 50 times from a height of 1.65 m onto a concrete floor from a predetermined height with the upper surface facing downward. Then, the number of drops until the occurrence of leakage from the valve body was visually measured. The test results are shown in Table 1 below. The number of samples is 10 batteries.

(Drop test 2)
Ten battery packs of Example 2 and Comparative Example 2 were prepared. These battery packs were dropped from a height of 1.65 m onto a concrete floor with the front, back, right side, left side, top, and bottom facing down. This fall was performed 40 cycles, with 6 faces being taken as one cycle. And the number of fall cycles until it came to the liquid leak generation | occurrence | production from a valve body was measured visually. The test results are shown in Table 2 below.

  From Table 1, it can be seen that in Comparative Example 1, leakage occurred in all the batteries in 40 times or less, whereas in Example 1, leakage due to 50 times of dropping did not occur.

  Moreover, from Table 2, it was found that leaks occurred in all batteries in 35 cycles or less in Comparative Example 2, whereas no leaks occurred in 8 out of 10 in Example 2. .

  Moreover, it turns out that generation | occurrence | production of the liquid leakage by the fall is suppressed not only in the state of a battery (Example 1) but in the state of the pack battery (Example 2) which processed the battery.

  These are considered as follows. When an impact such as a drop is applied to the battery, the impact is propagated to the valve body, the impact applied to the valve body is accumulated, the valve body is destroyed, and the liquid leaks. Here, the impact transmitted to the valve body increases as the portion that receives the direct impact is closer to the valve body and as the area that receives the direct impact is larger. In Examples 1 and 2, the chamfered portion 20 is formed by chamfering the corners of the battery outer surface of the main body portion at the boundary between the valve body 6 and the main body portion of the sealing plate 13 provided with the valve body 6. Therefore, it is difficult for an impact to act directly on the main body of the sealing plate 13 near the valve body 6, and the area of the main body of the sealing plate 13 near the valve body 6 is reduced (see FIG. 3). For this reason, the impact propagating to the valve body is smaller than those of Comparative Examples 1 and 2 (see FIG. 6) having no chamfered portion, and the malfunction of the valve body due to the drop impact occurs more markedly than Comparative Examples 1 and 2. It becomes difficult.

〔extra content〕
In the above embodiment, the planar shape of the valve body is a track shape, but it can be a perfect circle shape as shown in FIG. 4A or an elliptical shape as shown in FIG. Other oval shapes may be used.

  In the said embodiment, although the chamfering part was provided so that the whole valve body might be enclosed, the structure provided only in a part may be sufficient. In this case, it is preferable to provide a chamfered portion at least near the portion of the valve body where the stress is most concentrated. Here, the part where the stress is most concentrated on the valve body can be determined in the following order (a) to (c).

(A) The portion where the remaining thickness is the thinnest (b) Intersection where the crushing grooves intersect (c) The edge of the sealing plate surface or can bottom surface where the disc is formed (the sealing plate surface or bottom surface of the can and The closest point to the boundary

  When there are a plurality of portions where stress is most concentrated, which is determined by the above method, at least all of the portions are chamfered in the vicinity of the portion where stress is most concentrated.

  For example, when there are two intersecting points where the crushing grooves intersect at the same distance from the edge of the sealing plate surface or the bottom surface of the can on which the valve body is formed, and one of the remaining thicknesses is thinner, FIG. As shown, the chamfered portion 20 is provided in the vicinity of the intersection (the upper side in the figure) of the thinner remaining thickness.

  If there are two intersections where the crushing grooves intersect at the same distance from the edge of the sealing plate surface or the bottom of the can where the valve body is formed, and the remaining thickness is equal, the chamfered portion 20 is located near the two intersections. Provide.

  In the case of the track shape, a chamfered portion is preferably provided in all the portions close to the long side portion including the portion where the stress is most concentrated. Further, in the case of a perfect circle shape as shown in FIG. 4A, preferably, an axis (long axis) parallel to the long side of the sealing plate 13 in the valve body 6 and an axis parallel to the short side of the sealing plate 13 are used. Centering on the intersection with (short axis), it is provided in the range of 45 ° on both the left and right sides including the short axis. Also, as shown in FIG. 4B, in the case of an elliptical shape, the intersection point between the major axis and the minor axis is set as the center point, and the left and right ranges including the minor axis are provided in a range of 60 °.

  Moreover, the thickness of a valve body can be made into the range of 0.1-20% of sealing plate thickness, and 40 micrometers-100 micrometers.

  In addition to the sealing plate, the valve body can be provided on the bottom surface of the outer can. Further, the present invention can be applied to a battery using a cylindrical outer can in addition to a battery using a rectangular outer can.

  Further, the material of the sealing plate and the valve body is not limited to the aluminum alloy, and iron, stainless steel, pure aluminum or the like may be used. Among them, it is preferable to use light pure aluminum or aluminum alloy because the weight energy density is improved. The present invention is not limited to non-aqueous electrolyte secondary batteries, and can be used for non-aqueous electrolyte primary batteries.

  In addition, when the present invention is applied to the non-aqueous electrolyte secondary battery, as the positive electrode material, in addition to the lithium cobaltate, for example, lithium nickelate, lithium manganate, lithium nickel manganate, nickel manganese cobaltate Lithium, lithium ferrate, lithium iron phosphate having an olivine structure or a mixture thereof, a compound containing other elements in the crystal lattice of these compounds, and the like are preferably used. As the negative electrode material, a carbon material, a lithium metal, a lithium alloy, silicon, a silicon compound, a metal oxide (such as tin oxide) capable of occluding and desorbing lithium ions, and a mixture thereof are preferably used. Used.

Furthermore, the solvent of the electrolytic solution is not limited to the above, but cyclic carbonates typified by propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, lactones typified by γ-butyrolactone, γ-valerolactone, diethyl carbonate, A chain carbonate represented by dimethyl carbonate and methyl ethyl carbonate, an ether represented by tetrahydrofuran, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, 1,3-dioxolane, 2-methoxytetrahydrofuran, and diethyl ether alone, or Two or more kinds can be mixed and used. In addition to LiPF ₆ , LiAsF ₆ , LiClO ₄ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ or the like can be used as the electrolyte of the electrolytic solution.

  As described above, according to the present invention, it is possible to realize a sealed battery equipped with a gas discharge mechanism that can prevent malfunction due to impact or the like and leakage of the electrolyte. Therefore, industrial applicability is great.

1: Sealing body 2: Exterior can 2a: Laser welding part 3: Electrode body 4: Insulating plate 6: Valve body 6a: Crushing groove 6b: Dome part 8: Seal plug 11: Terminal board 12: Insulating gasket 13: Sealing board 14: Insulating plate 15: Terminal rivet 17: Open hole 18a: Virtual surface 18b: Virtual surface 20: Chamfered portion 31: Current collecting tab

Claims (6)

In a sealed battery equipped with a safety mechanism that breaks the valve body when the battery internal pressure rises and releases the gas in the battery to the outside of the battery,
The valve body is provided on a sealing plate that seals the bottom surface of the outer can or the opening of the outer can, and the thickness of the valve body is smaller than the thickness of the bottom surface of the outer can or the sealing plate, and the valve body is opened. Crushing groove to
At least a part of the battery outer surface of the main body at the boundary between the valve body and the bottom of the outer can or the main body of the sealing plate provided with the valve body is formed as a chamfered portion with chamfered corners. Being
A sealed battery characterized by that. The sealed battery according to claim 1,
The valve body is formed on a sealing plate,
A sealed battery characterized by that. The sealed battery according to claim 1 or 2,
The valve body further includes a dome portion protruding to the inside or outside of the battery,
The crushing groove is formed so as to surround the dome portion.
A sealed battery characterized by that. The sealed battery according to claim 1, 2, or 3,
The valve body is between the bottom surface of the outer can of the outer can in which the valve body is formed or the outer surface of the sealing plate and the virtual surface that is flush with the inner surface of the sealing plate and the virtual surface that is flush with the sealing plate.
A sealed battery characterized by that. The sealed battery according to any one of claims 1 to 4,
The cross-sectional shape parallel to the height direction of the sealed battery of the chamfered portion is the distance between the bottom surface of the outer can where the valve body is provided or the battery outer surface of the sealing plate and the root portion of the valve body. where t is an R shape with a radius of curvature of 0.5 to t.
A sealed battery characterized by that. The sealed battery according to any one of claims 1 to 5,
The chamfered portion is formed in the vicinity of the portion of the valve body where stress is most concentrated,
A sealed battery characterized by that.

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