JP5365856B2 - Sealed battery, method for manufacturing the same, and vehicle including the battery - Google Patents

Description

  The present invention relates to a structure of a sealed battery, and more specifically, a sealing structure in which a sealing lid member that closes an opening formed in a part of a battery case is welded to a peripheral portion of the opening, and the sealing structure The present invention relates to a battery having

In recent years, lithium ion batteries, nickel metal hydride batteries, and other types of sealed secondary batteries have become increasingly important as power sources for vehicles or power sources for personal computers and portable terminals. In particular, a sealed battery constituting a lithium ion battery that is lightweight and has a high energy density is expected to be preferably used as a high-output power source for mounting on a vehicle.
As an example of such a sealed battery, a rolled electrode body obtained by winding a positive electrode and a negative electrode with a separator interposed between them is flattened (or a sheet-like positive electrode, negative electrode and separator are laminated). A flat laminated electrode body may be housed in a corresponding flat rectangular metal battery case, and then the case opening surface is covered and sealed (sealed). For example, a sealed battery of a mold shape is used.
Usually, this type of sealed battery is formed with at least one opening different from an opening for accommodating the electrode body. A typical example of such an opening is an electrolyte injection port. That is, in this type of sealed battery, after the electrode body is accommodated and the case opening surface is sealed, a predetermined electrolytic solution is injected into the case from the liquid injection port. After the injection of the electrolytic solution is completed, a lid member is attached to the opening (liquid injection port), and the opening (liquid injection port) is typically welded to the periphery of the opening by laser beam welding. It is sealed. Patent Documents 1 and 2 each describe an example of the prior art relating to sealing a liquid injection port by welding a lid member (sealing member) having a predetermined shape around the liquid injection port periphery of the battery case.

JP 2006-324108 A JP 2000-21437 A

After the opening such as the liquid injection port is sealed in the course of the battery manufacturing process, in other words, after the sealed battery (product) is constructed, the sealing is permanently maintained. There is a need. For this reason, when welding a lid-like member for closing the opening (hereinafter referred to as “sealing lid member”) to the periphery of the opening, it is important to appropriately control the welding amount. That is, if the amount of welding is too small, a gap is generated at the boundary between the sealing lid member and the periphery of the opening, which is a disadvantage in welding failure. On the other hand, if the amount of welding is too large, it is not preferable because energy costs are wasted and the heat during welding may adversely affect the case body and battery components (electrode bodies, etc.) in the case. In addition, regarding the appropriate control of the welding amount, it is important to take into account the form change of the case that may occur when the battery is used.
For example, in the case of a sealed battery constituting a lithium ion battery, the battery case may bulge outward when a gas is generated for some reason in the sealed battery case. The sealing lid member and the peripheral edge of the opening are welded so that the sealed state can be maintained, and the welding amount is not so large as to be a wasteful and excessive welding amount that increases the influence of heat during the welding. It is important to control. However, such consideration is not made in the prior art described in the above-mentioned patent documents.

  Therefore, the present invention is an invention created to solve the above-described conventional problems, and the object of the present invention is at the periphery of the opening provided in the case of the square-shaped sealed battery as described above. It is an object of the present invention to provide a sealed battery having a structure in which a sealing lid member is welded without excess or deficiency and the opening is sealed. In order to provide such a sealed battery, a method for sealing the opening by welding a sealing lid member to the periphery of the opening provided in the battery case without excess or deficiency is performed. It is another object of the present invention to provide a method for manufacturing a desired sealed battery.

A battery according to one aspect provided by the present invention is a sealed battery including a flat electrode body that constitutes a positive electrode and a negative electrode, and a sealed square case that houses the electrode body. The rectangular case is formed in a flat shape corresponding to the flat electrode body. Further, any rectangular case surface adjacent to the wide surface of the case facing the wide surface of the flat electrode body in the case (that is, a rectangular case constituted by a pair of long sides and a pair of short sides) At least one opening is formed in the surface . A sealing lid member is attached to the opening so as to close the opening, and the opening is sealed by welding the sealing lid member to the periphery of the opening.
In the sealed battery disclosed herein, the welding between the sealing lid member and the peripheral edge portion of the opening has a welding depth at a portion facing the long side of the rectangular case surface. It is characterized by being carried out so that it may become deeper than the welding depth in the site | part which faces the short side of a surface.
The portion facing the long side of the rectangular case surface is the sum of 45 ° on both sides of the virtual perpendicular when the virtual perpendicular to the long side is drawn from the center of the opening, or an angle of more than that. It is defined as a portion (D region) belonging to a range of 90 ° or more. In addition, the portion facing the short side of the rectangular case surface is a total of 45 ° on both sides of the virtual perpendicular when the virtual perpendicular to the short side is drawn from the center of the opening, or an angle of less than that. It is defined as a part (S region) belonging to a range of 90 ° or less.

  The sealed battery having such a configuration includes a rectangular case having the above shape and a rectangular case surface other than the wide surface (for example, a rectangular plate-shaped case lid that closes the opening surface of the case body after housing the electrode body) In a portion facing the long side of the rectangular case surface in a form in which a sealing structure in which the opening is sealed by a sealing lid member is provided by welding. The welding depth (that is, the depth from the surface at the welding site (typically the surface of the bead) to the bottom of the portion where the structure is changed by welding) is the surface on the short side of the rectangular case surface. The welding amount (particularly the degree of welding in the depth direction: the penetration depth) is different for each part so as to be deeper than the welding depth at the part to be welded.

The inventor forms an opening (typically, a liquid injection port) in the surface of the rectangular case surface , and welds a sealing lid member to the periphery of the opening. The state of stress generated when the internal pressure of the case rises for some reason during discharge and the case bulges outward was investigated. As a result, when the case internal pressure rises for some reason and the case bulges outward, the stress is less likely to concentrate in the direction along the long side of the rectangular case surface (long axis direction). It was clarified that stress tends to concentrate in the direction along the short side of the shape case surface (short axis direction) (see FIGS. 8 to 9 described later).
Thus, in the sealed battery disclosed here, the surface is formed on the long side of the rectangular case surface that exists in the portion where the stress concentration occurs (that is, the direction along the short side of the rectangular case surface (short axis direction)). A sufficient depth of welding, while the stress does not easily concentrate on the short side of the rectangular case surface in the direction along the long side (long axis direction) of the rectangular case surface. In the part facing the side), the welding depth is relatively reduced to avoid meaningless excessive welding.
As described above, according to the present invention, it is possible to weld the sealing lid member to the peripheral edge of the opening provided in the case of the above-described square-shaped sealed battery without excess or deficiency. For this reason, waste of energy costs is eliminated, and adverse effects of excessive heat generation during excessive welding on battery components (case body, electrode body, electrolyte, etc.) are prevented, and a highly reliable sealed battery is provided. Can do. Further, the control of the welding depth is realized that suitably corresponds to the generation of stress due to the outward swelling of the case when the case internal pressure increases.

In a preferred aspect of the sealed battery disclosed herein, the opening is composed of a recess recessed from the surface of the rectangular case surface and a through-hole formed in the center of the recess that communicates with the inside and outside of the case. Yes. Further, at least a part of the sealing lid member is fitted in the recess of the opening. And the periphery in the part inserted in the said recessed part of the said sealing lid member and the outer peripheral part of the said recessed part of the said rectangular case surface which contact | connects this periphery are welded mutually.
According to the sealed battery of this aspect, the sealing lid member can be welded more stably.

In another preferred embodiment of the sealed battery disclosed herein, the relationship between the average welding depth D in the D region and the average welding depth S in the S region: S / D is 0.5. It is characterized by being 0.9 or less.
According to the sealed battery of this aspect, it is possible to prevent damage to the case due to the welding depth becoming too deep.

In another preferred embodiment of the sealed battery disclosed herein, welding of the sealing lid member and the peripheral edge portion of the opening is performed by irradiating a beam over the entire circumference of the sealing lid member. It is done by continuous beam welding. Then, in a continuous weld bead (that is, a welding mark) formed on the entire circumference of the sealing lid member based on the welding by the beam irradiation, a tip region of the bead formed at the welding start time by the beam irradiation; The overlapping portion of the end region of the beat formed at the end of welding (that is, the overlapping portion of the beam irradiation) is formed at a portion facing the short side of the rectangular case surface. And
As described above, the rectangular case is a portion where the stress concentration is unlikely to occur in a portion where the beams overlap in beam welding (typically laser beam welding) (that is, a portion where the degree of welding may be relatively unstable). By placing the portion facing the short side of the surface, it is possible to stably perform sufficient welding of the portion facing the long side of the rectangular case surface, which is a portion where stress concentrates when the case internal pressure increases. .

Preferably, the opening is a liquid inlet for injecting an electrolyte into the battery case. According to the present invention, it is possible to perform the welding of the liquid injection port periphery and the sealing lid member, which ensures that the liquid injection port is not opened carelessly when the internal pressure of the case rises, without excess or deficiency.
Also preferably, the present invention provides a battery constituting a lithium secondary battery (typically a lithium ion battery) as the sealed battery disclosed herein. A lithium secondary battery is suitable as an object to which the present invention is applied because gas is easily generated inside the battery case and the internal pressure of the case tends to increase.

  The sealed battery disclosed herein has an opening (for example, a liquid injection port) sealing structure that realizes the sealing of the opening by welding without excess or deficiency while reducing the energy cost for welding. In particular, it can be suitably used as a power source for a motor (electric motor) mounted on a vehicle such as an automobile. Therefore, the present invention provides a vehicle (typically an automobile) that includes, as a power source, any of the sealed batteries disclosed herein (typically, an assembled battery in which a plurality of the sealed batteries are electrically connected to each other). , In particular, vehicles equipped with electric motors such as hybrid vehicles, electric vehicles, and fuel cell vehicles.

Moreover, this invention provides the method of manufacturing the battery disclosed here as another aspect. That is, the manufacturing method disclosed herein, the electrode body flattened shape constituting the positive and negative electrodes, and a rectangular case that houses the該扁flat-shaped electrode body electrode body is formed in a flat shape corresponding to the And at least one opening is formed in the surface of any rectangular case surface adjacent to the wide surface of the case facing the wide surface of the flat electrode body in the case, and the opening is formed in the opening. A method for manufacturing a sealed battery having a configuration in which a sealing lid member is attached so as to be closed, including sealing the opening by welding the sealing lid member to the periphery of the opening. Here, the welding depth at the portion facing the long side of the rectangular case surface faces the short side of the rectangular case surface. Do so that it is deeper than the welding depth at the part. A method characterized by and.
However, the portion facing the long side of the rectangular case surface is the sum of 45 ° on both sides of the virtual perpendicular when the virtual perpendicular to the long side is drawn from the center of the opening, or an angle of more than that. It is defined as a portion (D region) belonging to a range of 90 ° or more. In addition, the portion facing the short side of the rectangular case surface is a total of 45 ° on both sides of the virtual perpendicular when the virtual perpendicular to the short side is drawn from the center of the opening, or an angle of less than that. It is defined as a part (S region) belonging to a range of 90 ° or less.

In the manufacturing method according to a preferred aspect disclosed herein, the opening includes a recess recessed from the surface of the rectangular case surface and a through-hole formed in the center of the recess that communicates with the inside and outside of the case. Here, at least a part of the sealing lid member is fitted in the concave portion of the opening, and the peripheral edge of the portion of the sealing lid member fitted in the concave portion is in contact with the peripheral edge. The outer peripheral portion of the concave portion of the rectangular case surface is welded to each other.
Furthermore, in a more preferable manufacturing method, the relationship between the average welding depth D in the D region and the average welding depth S in the S region: S / D is 0.5 or more and 0.9 or less. It is characterized by that.

Further, in another preferable aspect of the manufacturing method disclosed herein, the sealing lid member and the peripheral portion of the opening are welded with a beam over the entire circumference of the sealing lid member. Perform by beam welding. And in the continuous weld bead formed on the entire circumference of the sealing lid member based on the welding by the beam irradiation, the tip end region of the bead formed at the welding start time by the beam irradiation and the end time of the welding The beam welding is performed so that the overlapping portion of the end region of the beat formed on the short side of the rectangular case surface is formed.
By the manufacturing method as described above, a sealed battery provided with the sealing structure disclosed herein can be provided.

1 is a perspective view schematically showing a sealed battery according to an embodiment. It is a typical side view showing the electrode body and electrode terminal concerning one embodiment. It is a top view which shows typically the sealing structure of the opening part (injection port) provided in the rectangular-shaped case surface (case cover body) of the sealed battery which concerns on one Embodiment. It is sectional drawing which shows typically the sealing structure of the opening part (liquid injection port) provided in the rectangular-shaped case surface (case cover body) of the sealed battery which concerns on one Embodiment. It is the VV sectional view taken on the line in FIG. It is the VI-VI sectional view taken on the line in FIG. It is a top view explaining the site | part from which the welding depth differs in welding with the periphery of the opening part (injection port) which concerns on one Embodiment, and a sealing lid member. It is a figure which illustrates typically the state where the case surface expands outward (curves) in the direction along the short side of the rectangular case surface (short axis direction) when the case internal pressure increases. It is a figure which illustrates typically the state where the case surface expands outward (curves) in a direction along the long side (long axis direction) of the rectangular case surface when the case internal pressure increases. It is a figure which illustrates typically suitable embodiment in the case of carrying out beam welding of the periphery of an opening part (liquid injection port), and a sealing lid member. 1 is a side view schematically showing a vehicle equipped with a sealed battery according to an embodiment of the present invention.

Preferred embodiments of the present invention will be described below with reference to the drawings. In addition, matters other than matters specifically mentioned in the present specification and matters necessary for the implementation of the present invention (for example, a method for constructing an electrode body, a material used for constructing the electrode body, and beam welding are performed. The case conditions and the like) can be grasped as design matters of those skilled in the art based on the prior art in the field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.
Although not intended to be particularly limited, in the following, a wound type electrode body (hereinafter referred to as a “wound electrode body”) and a non-aqueous electrolyte are accommodated in a rectangular (box-shaped) case. A sealed lithium secondary battery (lithium ion battery) will be described as an example. Note that the dimensional relationship (length, width, thickness, etc.) in each drawing does not reflect the actual dimensional relationship. Further, members / parts having the same action are denoted by the same reference numerals, and redundant description is omitted or simplified.

In the lithium ion battery 10 according to the present embodiment, a flat wound electrode body 30 as shown in FIG. 2 corresponds to the shape of the wound electrode body 30 together with a liquid electrolyte (electrolytic solution) not shown in FIG. It has the structure accommodated in the battery case (namely, exterior container) 20 of a flat square shape as shown.
The case 20 has a box-shaped (that is, a bottomed rectangular tube-like) case main body 21 having an opening surface at one end (corresponding to an upper end portion in a normal use state of the battery 10 according to the present embodiment), attached to an opening surface composed of the lid (case component) 22 for formed of a rectangular plate member for closing the opening surface. The lid body 22 is welded to the peripheral edge of the opening surface of the case body 21, so that a pair of case wide surfaces 23 facing the wide surface of the flat wound electrode body 30, and 4 adjacent to the case wide surface 23. A hexahedral case 20 with two rectangular case surfaces 22 and 24 (that is, one of the rectangular case surfaces is constituted by a lid 22) is formed. Although it does not restrict | limit in particular, As a suitable size of the hexahedral shape case of this kind of square battery, the length of the long side of the case main body 21 and the cover body 22: about 80-150 mm (here about 110 mm), The length of the short side of the case body 21 and the lid body 22 (that is, the thickness of the case): about 10 to 25 mm (here about 14 mm), and the height of the case body 21: about 70 to 120 mm (here about 90 mm) It can be illustrated.

The material of the case 20 may be the same as that used in the conventional sealed battery, and is not particularly limited. A case 20 mainly composed of a metal material that is lightweight and has good thermal conductivity is preferable. Examples of such a metal material include aluminum, stainless steel, and nickel-plated steel. The case 20 (specifically, the main body 21 and the lid body 22) according to the present embodiment is made of aluminum or an alloy mainly composed of aluminum.
Further, the thickness of the case 20 (the main body 21 and the lid body 22) is not particularly limited, but in the case of constituting a vehicle-mounted sealed battery, about 0.3 mm to 2 mm is appropriate, and about 0.5 mm to 1 mm ( Here, about 0.8 mm to 0.9 mm) is preferable.

As shown in FIGS. 1 and 3, a positive terminal 14 and a negative terminal 16 for external connection are fixed to a lid (rectangular case surface) 22. One end (outer end) of the electrode terminals 14 and 16 protrudes outward from the case (lid body 22), and the other end (inner end) is electrically connected to the positive electrode 32 and the negative electrode 34 of the electrode body 30, respectively. Has been.
At the center in the width direction of the portion located between the electrode terminals 14 and 16 of the lid (rectangular case surface) 22, the internal pressure of the case 20 is at a predetermined level (for example, a set valve opening pressure of 0.3 to 1.0 MPa). A thin safety valve 40 configured to release the internal pressure when the pressure rises above, and a liquid injection port 50 as an opening according to the present embodiment are formed. The liquid filling port 50 is covered with a sealing lid member 60, and the sealing lid member 60 is welded to the periphery of the liquid filling port 50. As a result, the liquid injection port 50 is sealed (sealed). Details of the sealing structure will be described later.

  As shown in FIG. 2, the wound electrode body 30 includes a long sheet-like positive electrode (positive electrode sheet) 32 and a negative electrode (negative electrode sheet) 34 in total, like the wound electrode body of a normal lithium ion battery. It is produced by laminating together with a sheet-like separator (separator sheet) 36 and winding it in the longitudinal direction, and then crushing the obtained winding body from the side direction and causing it to be ablated. Specifically, the positive electrode sheet 32 and the negative electrode sheet 34 are stacked so that the positions in the width direction are slightly shifted and one end in the width direction of the sheets 32 and 34 protrudes from one end and the other end in the width direction of the separator sheet. It is wound in the state. As a result, one end in the width direction of the positive electrode sheet 32 is disposed at one end and the other end in the winding axis direction of the wound electrode body 30 (that is, the positive electrode sheet 32, the negative electrode sheet 34, and the separator sheet). And a portion where one end in the width direction of the negative electrode sheet 34 protrudes outward from the wound core portion 31 is formed. The electrode terminals 14 and 16 are coupled to the protruding portion.

The material and the member constituting the wound electrode body 30 may be the same as the electrode body provided in the conventional lithium ion battery, and are not particularly limited. For example, the positive electrode sheet 32 may have a configuration in which a positive electrode active material layer is formed on a long positive electrode current collector (for example, an aluminum foil). As the positive electrode active material used for forming this positive electrode active material layer, one or two or more materials conventionally used in lithium ion batteries can be used without particular limitation. Preferable examples include lithium transition metal oxides such as LiMn ₂ O ₄ , LiCoO ₂ , and LiNiO ₂ . The negative electrode sheet 34 may have a configuration in which a negative electrode active material layer is formed on a long negative electrode current collector (for example, a copper foil). As the negative electrode active material used for forming this negative electrode active material layer, one or two or more materials conventionally used in lithium ion batteries can be used without particular limitation. Preferable examples include carbon-based materials such as graphite carbon and amorphous carbon, lithium transition metal oxides, lithium transition metal nitrides, and the like. Preferable examples of the separator sheet include those made of a porous polyolefin resin.

As the liquid electrolyte (electrolytic solution), the same non-aqueous electrolytic solution conventionally used in lithium ion batteries can be used without particular limitation. Such a nonaqueous electrolytic solution typically has a composition in which a supporting salt is contained in a suitable nonaqueous solvent. Examples of the non-aqueous solvent include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,3-dioxolane, and the like. One kind or two or more kinds selected from the group can be used. Examples of the supporting salt include LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) _{3 and the} like. Lithium salts can be used. In this embodiment, an electrolytic solution in which LiPF ₆ is contained in a mixed solvent of ethylene carbonate and diethyl carbonate (for example, a mass ratio of 1: 1) at a concentration of about 1 mol / liter is used. A solid or gel electrolyte may be used instead of the electrolytic solution.

A preferred embodiment for manufacturing the lithium ion battery 10 including the members having the above-described configuration will be briefly described.
First, the outer ends of the positive and negative electrode terminals 14 and 16 are projected outward from the lid body 22, and the terminals 14 and 16 are fixed to the lid body 22. By connecting (for example, welding) the inner ends of the terminals 14 and 16 to the positive electrode 32 and the negative electrode 34 of the wound electrode body 30, the lid body 22 and the electrode body 30 are coupled. Then, put the lid 22 on the open surface so as to fit inside the electrode body 30 coupled to the lid body 22 from the opening surface of the case body 21, for example, electrons seam the lid 22 and the case body 21 Sealing is performed by beam welding (typically laser beam welding) that irradiates a beam or a laser beam.
Next, an electrolytic solution is injected into the case 20 from the liquid injection port (opening) 50. Thereafter, the liquid injection port 50 is sealed by covering the liquid injection port 50 with a sealing lid member (cap) 60 and welding.
In this way, the sealed lithium ion battery 10 can be manufactured (constructed). In addition, since the battery construction process itself does not characterize the present invention, further detailed description is omitted. Hereinafter, the sealing structure of the liquid injection port 50 according to the present embodiment will be described in detail with reference to the drawings.

4 is a cross-sectional view showing the structure of the liquid injection port 50 shown in FIG. 3 and the peripheral portion thereof. As shown in this figure, the liquid injection port 50 which is an opening according to the present embodiment is a lid formed near the center of the lid 22 corresponding to the upper surface of the rectangular case in the battery case 20 according to the present embodiment. A concave portion 52 that is circularly recessed from the outer surface of the body 22 and a through hole 51 that is formed in the central portion of the concave portion 52 and communicates with the inside and outside of the case. Of the inner bottom surface of the recess 52, a peripheral edge portion 52 </ b> A that is in contact with the through hole 51 is formed to be thick over the entire circumference, and a sealing lid member described later between the thick portion 52 </ b> A and the side wall of the recess 52. A mounting groove 52B in which a part of 60 is disposed is formed in an annular shape. An annular groove 58 is formed concentrically with the recess 52 in the outer peripheral portion of the recess 52 on the surface of the lid 22.
The depth of the recess 52 from the surface of the case (here, the lid body 22) is not particularly limited, but is preferably about 1/3 to 1/2 of the thickness of the case (lid body) (here, for example, 0.4 mm). Moreover, although it does not specifically limit, the diameter of the recessed part 52 which concerns on this embodiment is 7-8 mm in general.

On the other hand, as shown in FIGS. 1 and 4, the sealing lid member 60 according to the present embodiment includes a main body portion 64 formed in a circular bowl (deep dish) shape, and outward from the periphery of the main body portion 64. It is the member formed in the hat shape comprised from the attachment flange part 62 extended | stretched to (3). Although not particularly limited, the diameter of the sealing lid member 60 according to the present embodiment is approximately 7 to 8 mm corresponding to the diameter of the recess 52, and the diameter of the main body 64 is approximately 5 to 6 mm.
Thus, as shown in FIG. 4, the sealing lid member 60 is disposed on the liquid injection port 50 so that the mounting flange portion 62 is fitted into the recess 52 (specifically, the mounting groove 52 </ b> B). As shown in FIG. 4, in the present embodiment, the upper surface of the mounting flange portion 62 of the sealing lid member 60 and the periphery of the concave portion 52 of the lid (rectangular case surface) 22 when mounted in the concave portion 52. It is designed to be flush with the upper surface (the same height). As a result, accurate and reliable welding can be performed.
And the periphery in the attachment flange part 62 of the sealing lid member 60 and the outer peripheral part of the recessed part 52 of the cover body 22 which contact | connects this periphery are mutually welded over a perimeter. Thus, the liquid injection port 50 (that is, the through hole 51) can be completely sealed (sealed) by the sealing lid member 60.
The thickness of the sealing lid member 60 is not particularly limited, but is preferably about 1/3 to 1/2 (for example, 0.3 mm to 0.5 mm) of the thickness of the case (lid 22). In particular, since the mounting flange portion 62 is preferably flush with the recess 52 when fitted into the recess 52, a thickness equivalent to the depth of the recess 52 is preferable (here, 0.4 mm, for example).

Next, the welding mode according to this embodiment will be described with reference to the drawings. As shown in FIG. 5 which is a sectional view taken along line VV in FIG. 3 and FIG. 6 which is a sectional view taken along line VI-VI, in this embodiment, the welding depth (penetration depth) is set for each part as described above. This makes it possible to achieve welding that is sufficient, but that is free of excess and deficiency and has excellent energy costs.
Specifically, as is clear from a comparison between FIG. 5 and FIG. 6, the portion (region) shown by the VV line cross section of FIG. 3, in other words, the short side of the lid surface (rectangular case surface) 22. The welded portion 72 at the portion facing the surface is formed so that the welding depth (penetration depth) becomes relatively shallow. On the other hand, the welding part 74 in the site | part (area | region) shown in the VI-VI line cross section of FIG. 3, in other words, the site | part which faces the long side of the cover surface (rectangular case surface) 22, is the welding depth (penetration depth). Is) relatively deep.

Preferably, as shown in FIG. 7, the portion (region) for relatively increasing the welding depth (penetration depth) is the lid (rectangular case surface) 22 from the center of the liquid injection port (opening) 50. In the figure, the reference sign D belongs to a total angle range of 90 ° or more (90 ° in this case) of 45 ° or more on both sides of the virtual perpendicular L1 when the virtual perpendicular L1 is drawn on both long sides. It can prescribe | regulate as a welding area | region (part) shown by. Further, a region (region) where the welding depth (penetration depth) is relatively shallow is a virtual perpendicular from the center of the liquid injection port (opening) 50 to both short sides of the lid (rectangular case surface) 22. As a welding region (part) indicated by symbol S in the drawing belonging to an angle range of 90 ° or less (90 ° in this case) of 45 ° or less on both sides of the virtual perpendicular line L2 when L2 is drawn Can be prescribed. Note that the S region and the D region roughly indicate a preferable region of the welding depth, and do not strictly limit the boundary. For example, the vicinity of the boundary between the S region and the D region may be an intermediate welding depth between the welded part (shallow) 72 shown in FIG. 5 and the welded part (deep) 74 shown in FIG. Further, the ratio between the angle range of the D region (each 90 ° or more) and the angle range of the S region (each 90 ° or less) may be different depending on the shape of the case. Typically, the angle range of the D region can be set to 90 ° or more and 120 ° or less in both directions facing the long side, and the angle range of the S region is 60 ° or more and 90 ° or less in both directions facing the short side. Can be set to
Hereinafter, the reason why the welding depth is changed as described above in each part shown in FIGS. 5 and 6 will be described with reference to the drawings.

FIG. 8 is a schematic cross-sectional view in the direction along the short side (short axis direction) of the lid (rectangular case surface) 22, and FIG. 9 is the direction along the long side of the lid (rectangular case surface) 22 ( It is a typical sectional view of (long axis direction). In addition, these are explanatory drawings, and since it is not necessary to accurately show the scale and shape of each member in the drawing, they do not coincide with those described in each drawing.
When the battery according to the present embodiment generates gas in the case 20 due to some cause during charge / discharge, for example, and the internal pressure of the case increases, the lid 22 is in the direction along the short side as shown in the lower part of FIG. It tends to be greatly curved and bulge outward from the case. When such bending occurs, the welded portion in the direction (short axis direction) along the short side of the lid (rectangular case surface) 22, that is, the portion facing the long side of the lid 22 (that is, in FIG. 7). A relatively large stress concentration occurs in the (D region). Therefore, it is desired to perform welding with a sufficient welding amount, specifically, a welding depth (penetration depth) in this part (region).

On the other hand, as described in the lower part of FIG. 9, when gas is generated in the case 20 for some reason and the internal pressure of the case is increased, the degree of bending in the direction along the long side of the lid 22 is the short side described above. Is not as large as the curvature in the direction along. As a result, stress concentration in that direction is unlikely to occur. For this reason, a welding depth sufficient to be performed at a portion facing the long side of the lid body 22 (region D in FIG. 7) is necessary at a portion facing the short side of the lid body 22 (region S in FIG. 7). A shallower welding depth is sufficient.
The amount of welding (welding depth) when the sealing lid member is welded to the periphery of the opening provided on the rectangular case surface in this way is the degree of deformation (curvature) of the case surface when the case internal pressure increases. Depending on the side facing the long side (typically the above-mentioned D region) and the side facing the short side (typically the above-mentioned S region). While realizing a corresponding strong sealing (welding) structure, it is possible to reduce energy costs by carrying out welding without excess or deficiency. Further, it is possible to prevent the battery components from being damaged by excessive heat during welding.

It should be noted that the actual welding depth of the battery can vary depending on the type and shape of the target battery (especially the thickness of the case and the ratio of the long side to the short side of the case). In the form, about 0.15 to 0.2 mm in the S region and about 0.25 to 0.4 mm in the D region are appropriate.
Relationship between the average welding depth in the D region and the average welding depth in the S region: S / D is suitably 0.5 or more and 0.9 or less (more preferably 0.6 or more and 0.8 or less). .
Preferably, the welding depth is set to be shallower than the thickness of the sealing lid member 60 (here, the mounting flange portion 62). Thereby, damage to the case due to the welding depth becoming too deep can be prevented.

While the welding depth as described above is varied, the peripheral edge of the sealing lid member 60 (here, the mounting flange portion 62) and the outer peripheral portion of the concave portion 52 of the lid body 22 in contact with the peripheral edge are welded to each other over the entire circumference. Various welding means can be used as the means for performing the welding, but beam welding such as laser beam welding or electron beam welding is preferably performed. Laser beam welding is preferred from the viewpoint that it can be performed at low cost under atmospheric pressure conditions.
Specifically, as shown in FIG. 10, an appropriate beam (for example, a laser beam such as a YAG laser or a CO ₂ laser) is applied to the boundary between the sealing lid member 60 and the peripheral portion of the liquid injection port 50 (recess 52). Irradiation is performed, and beam irradiation is performed over the entire circumference of the periphery of the sealing lid member 60 while moving the irradiation site. A symbol B in the drawing indicates a continuous welded portion (weld mark or weld bead) B formed on the entire circumference of the sealing lid member 60 by the beam welding.
At this time, the welding depth (welding amount) can be changed by appropriately controlling the power of the irradiated beam, the irradiation time per point, and the like for each irradiation site. Since the welding strength control method itself is merely a conventional method and does not characterize the present invention, a detailed description (such as a method of handling a laser irradiation apparatus or other welding tool) is omitted.

In the case where the beam irradiation as described above is performed over the entire periphery of the sealing lid member 60, as shown in FIG. 10, the bead tip region formed at the welding start time by the beam irradiation and the end time of the welding are formed. The portion where the end region of the bead formed on (i.e., the overlap portion indicated by the symbol OV in the drawing) faces the short side of the lid (rectangular case surface) 22 (i.e., the above S). It is preferable to perform beam welding so as to be formed in the region.
By performing the beam irradiation in such a form, the beam irradiation overlap portion OV that may be relatively unstable in the degree of welding is a portion that faces the short side of the lid 22 that is a portion where the stress concentration hardly occurs. By placing in (that is, the S region), it is possible to stably perform sufficient welding of the portion facing the long side of the lid 22 (that is, the D region), where stress is concentrated when the case internal pressure increases. it can.

As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible. For example, the type of battery is not limited to the above-described lithium ion battery, but batteries having various contents with different electrode body constituent materials and electrolytes, for example, lithium secondary batteries having a negative electrode made of lithium metal or lithium alloy, nickel hydrogen batteries, nickel cadmium It may be a battery.
Moreover, since the sealed battery disclosed here has a highly reliable sealing structure for the liquid injection port and other openings, it is particularly suitable for use as a power source for a motor (electric motor) mounted on a vehicle such as an automobile. Can be done. Therefore, as schematically shown in FIG. 11, a vehicle (typically an automobile) including a sealed battery 10 (typically, a battery pack formed by electrically connecting a plurality of the batteries 10) as a power source. In particular, an automobile 100 including an electric motor such as a hybrid car or an electric car is provided.

10 Sealed battery (lithium ion battery)
20 Case 21 Case body 22 Lid (rectangular case surface)
30 Winding electrode body 32 Positive electrode 34 Negative electrode 40 Safety valve 50 Injection port (opening)
51 Through-hole 52 Recessed portion 60 Sealing lid member 64 Main body portion 62 Mounting flange portion 72 Welded portion (shallow)
74 Welded part (depth)
100 Vehicle L1, L2 Virtual perpendicular S Welding area (shallow)
D Welding area (depth)
Overlap part of B bead OV bead

Claims (11)

A sealed battery comprising a flat electrode body that constitutes a positive electrode and a negative electrode, and a sealed square case that houses the electrode body,
The rectangular case is formed in a flat shape corresponding to the flat electrode body, and the rectangular case surface is adjacent to the wide case surface facing the wide surface of the flat electrode body in the case . At least one opening is formed in the plane ,
A sealing lid member is attached to the opening so as to close the opening, and the sealing of the opening is realized by welding the sealing lid member to the periphery of the opening.
Here, the welding between the sealing lid member and the peripheral edge portion of the opening is performed at a portion where the welding depth at the portion facing the long side of the rectangular case surface faces the short side of the rectangular case surface. It is done to be deeper than the welding depth ,
The portion facing the long side of the rectangular case surface is a total of 90 ° at 45 ° on both sides of the virtual normal when the virtual normal to the long side is drawn from the center of the opening or more than that. Or defined as a part (D region) belonging to a range beyond that, and
The portion facing the short side of the rectangular case surface is a total of 90 ° at 45 ° on both sides of the virtual perpendicular when the virtual perpendicular to the short side is drawn from the center of the opening or less. A sealed battery characterized by being defined as a portion (S region) belonging to a range below that. The opening is composed of a recess recessed from the surface of the rectangular case surface and a through-hole communicating with the inside and outside of the case formed in the central portion of the recess,
The sealing lid member is disposed such that at least a part thereof is fitted in the recess of the opening,
2. The peripheral edge of the portion of the sealing lid member fitted into the concave portion and the outer peripheral portion of the concave portion of the rectangular case surface in contact with the peripheral edge are welded to each other. The sealed battery according to 1. The relationship between the average welding depth D of the D region and the average welding depth S of the S region: S / D is 0.5 or more and 0.9 or less, and the sealed mold according to claim 1 or 2. battery. The welding of the sealing lid member and the peripheral edge portion of the opening is performed by beam welding in which a beam is irradiated over the entire circumference of the sealing lid member.
Here, in a continuous weld bead formed on the entire circumference of the sealing lid member based on the welding by the beam irradiation, the tip end region of the bead formed at the welding start time by the beam irradiation and the end time of the welding The overlapped portion of the end region of the beat formed in is formed in a portion facing the short side of the rectangular case surface, according to any one of claims 1 to 3. Sealed battery.   The sealed battery according to claim 1, wherein the opening is a liquid injection port for injecting an electrolytic solution into the battery case.   The sealed battery according to claim 1, which constitutes a lithium secondary battery.   A vehicle comprising the sealed battery according to claim 1. A flat electrode body constituting a positive electrode and a negative electrode, and a rectangular case formed in a flat shape corresponding to the flat electrode body and containing the electrode body, the width of the flat electrode body in the case A structure in which at least one opening is formed in the surface of any rectangular case surface adjacent to the case wide surface facing the surface, and a sealing lid member is attached to the opening so as to close the opening. A method of manufacturing a sealed battery of
Including sealing the opening by welding the sealing lid member to the periphery of the opening;
Here, welding between the sealing lid member and the peripheral edge portion of the opening is performed at a portion where the welding depth at the portion facing the long side of the rectangular case surface faces the short side of the rectangular case surface. It is characterized by being performed to be deeper than the welding depth.
However, the portion facing the long side of the rectangular case surface is the sum of 45 ° on both sides of the virtual perpendicular when the virtual perpendicular to the long side is drawn from the center of the opening, or an angle of more than that. Defined as a region (D region) belonging to a range of 90 ° or more, and
A portion facing the short side of the rectangular case surface is a total of 90 ° at 45 ° on both sides of the virtual normal when the virtual normal to the short side is drawn from the center of the opening or less. Or a sealed battery manufacturing method , which is defined as a portion (S region) belonging to a range below that . The opening is composed of a recess recessed from the surface of the rectangular case surface and a through-hole communicating with the inside and outside of the case formed in the central portion of the recess,
Here, at least a part of the sealing lid member is fitted in the concave portion of the opening, and is arranged.
The hermetic seal according to claim 8, wherein a peripheral edge of a portion of the sealing lid member fitted into the concave portion and a peripheral portion of the concave portion of the rectangular case surface in contact with the peripheral edge are welded to each other. Type battery manufacturing method. The relationship between the average welding depth D of the D region and the average welding depth S of the S region: The sealed mold according to claim 8 or 9 , wherein S / D is 0.5 or more and 0.9 or less. Battery manufacturing method. The welding of the sealing lid member and the peripheral edge portion of the opening is performed by beam welding in which a beam is irradiated over the entire circumference of the sealing lid member,
Here, in a continuous weld bead formed on the entire circumference of the sealing lid member based on the welding by the beam irradiation, the tip end region of the bead formed at the welding start time by the beam irradiation and the end time of the welding The beam welding is performed so that the overlapping portion of the end region of the beat formed on the short side of the rectangular case surface is formed. The sealed battery manufacturing method according to any one of the above.

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