JP2008159313A - Safety valve structure for secondary battery, and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a safety valve structure for a secondary battery which bursts open all at once, in a state that is close to thin-film cladding at the time of operation of internal pressure established on the secondary battery, before significantly deforming by receiving the effect of swelling of outer package can, and which realizes opening operation as a safety valve, and to provide its manufacturing method. <P>SOLUTION: This is a safety valve structure for the secondary battery which has a safety valve 5, installed by a press forming at a sealing plate 1a, provided at the outer package can 1 end of a secondary battery. The safety valve 5 consists of an outer peripheral fringe 5a of a first processed part, which is press formed into recessed shape by a base coining from the material thickness of the sealing plate, an outer peripheral fringe 5b of a second processed part which is press formed by a preliminary coining, and a valve portion 6, which is press formed as a third processed part by a final coining at the inside and has a groove portion 6a and a plurality of projection parts 6b on one face of a thin-film material of dome-shape projected to the outside. When the battery internal pressure of a prescribed pressure or higher is actuated, the safety valve 5 instantaneously bursts open from a burst point of an unspecified position into an unspecified shape, before significantly receiving the effect of the swelling of the outer package can. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention includes an organic electrolyte battery (non-aqueous electrolyte battery) such as a lithium ion battery, and is formed on a sealing plate provided at an outer can end of a sealed secondary battery in which the organic electrolyte is isolated from the outside air. The present invention relates to a safety valve structure for a secondary battery and a method for manufacturing the same.

  Secondary batteries that are widely used in small electronic devices such as mobile phones, laptop computers, and other portable terminals (PADs) are now organic electrolyte batteries (non-aqueous electrolytes) such as lithium ion secondary batteries. Battery) is the mainstream. A lithium ion polymer battery using a gel polymer as an electrolyte is already on the market. Lithium ion secondary batteries use non-aqueous electrolytes, so high voltages exceeding the electrolysis voltage of water are obtained, and they are often used in portable information devices such as laptop computers for reasons such as high energy density. ing.

  A sealed secondary battery with an organic electrolyte isolated from the outside air, such as a lithium ion secondary battery, causes a large current to flow in an overcharged state due to an overcurrent supply or a short circuit due to misuse, and the negative electrode and positive electrode are dangerous. As a result, the gas generated by the rapid decomposition of the electrolyte is filled in the battery, generating a large internal pressure, and an explosion may occur. In addition, if external force is applied to the can or bent, it may cause a short circuit inside the battery and cause thermal runaway. Generally, the top cover is used in preparation for temperature rise and internal pressure rise due to internal short circuit due to battery deformation. There is a safety valve that shuts off the current when the gas pressure rises and discharges the gas to the outside.

  The following patent documents are known as the safety valve. Patent Document 1 “Explosion-proof structure of secondary battery” consists of a safety valve provided on a sealing plate or a bottom plate fixed to the end of an outer can, and this safety valve forms a first processed portion of a flat plate-like recess on the outer peripheral surface, A second processed portion of the notch groove is provided in the concave portion, and the second remaining thickness has a plate thickness that is torn by a pressure of explosion-proof pressure + α. A third processed portion having a bent cross section is formed in the second processed portion. The third remaining thickness is set to a thickness that operates with explosion-proof pressure.

  This explosion-proof safety valve for a secondary battery is generally called a press vent type, and presses the aluminum plate of the sealing plate provided at the end of the outer can to form a thin part (groove) in a predetermined shape (circle or oval). ). As the metal substrate, a steel plate, a stainless steel plate, a copper plate, or an aluminum plate is used.

  On the other hand, a safety valve called a clad vent type is known, and as an example thereof, a “cleavable safety valve for a sealed battery container” in Patent Document 2 is known. This safety valve says, "The metal airtight battery container vent is closed with a metal foil joined by cold rolling, and the metal foil is shaped like a dome so that the center is convex toward the inside of the sealed battery container. When the thin-walled part is formed by deformation and the pressure in the sealed battery container rises to a specified value within the safe range, the thin-walled part formed on the metal foil is ruptured by receiving the pressure to prevent explosion of the sealed battery container. This is a cleavable safety valve for a sealed battery container.

This safety valve is press-contacted with a metal foil of less than 0.03 mm so as to close the vent hole, and the thickness of the foil is 1/2 or less by pressing (pressing) the press-contacting mold between the press-contact portion and its side. A thin-walled portion reduced in thickness is formed, and by adjusting the thickness of the thin-walled portion, the safety valve is operated with an appropriate cleavage pressure. In this type of safety valve, the material of the membrane part of the valve is not specified, but it is assumed to be aluminum, the valve membrane part is convex on the inside of the battery, and the central part is formed in a dome shape.
JP 2001-23596 A JP 09-139196 A

  By the way, the above-mentioned clad vent type safety valve is flexible, has excellent drop / deformation strength, and the vent operation (cleavage) pressure is determined by the foil thickness (film thickness) of the metal foil. It is stable and operates at low operating pressure. However, since the metal foil is laminated on the metal substrate by thermocompression bonding or cold pressure welding, it takes time for processing, and the metal foil generally has pinholes due to foreign matters mixed in the processing process. The inspection of all pinholes is required, and it takes time to install the metal foil laminated board to the outer can so that the metal foil is not damaged, which increases the cost. is there.

  On the other hand, the conventional press vent type safety valve is generally low in cost because it presses a concave groove on the sealing plate, but there is a problem with the deformation strength in particular, and the vent operation (cleavage) pressure is mainly due to the swelling of the can The deformation of the lid is involved, and the venting action starts with a crack caused by the deformation. That is, the internal pressure is generated and the can is swollen. When the can is deformed, a crack is generated in the concave groove of the safety valve and the safety valve is activated. For this reason, vent openability is inferior, gas is not immediately released at the time of vent operation, and a problem remains in gas release properties.

  This invention is a safety valve of the press vent type of the sealing plate by press working attached to the end of the outer can in consideration of the above problems, but when the gas is generated as in the conventional case, it is deformed by the swelling of the outer can. It is not a safety valve that operates with an initial leak, but before it is greatly deformed due to the swelling of the outer can, it is cleaved at a stroke close to the thin film clad when the internal pressure set for the secondary battery is operated, and reliably It is an object of the present invention to provide a safety valve structure for a secondary battery that realizes open operation as a safety valve and a method for manufacturing the same.

  As a means for solving the above problems, the present invention includes a safety valve provided by press molding on a sealing plate provided at an end of an outer can of a secondary battery, and this safety valve is shown in a sectional view from a material thickness T of the sealing plate. Consists of an outer peripheral edge of the concave part formed into a concave shape, and a thin film-like valve part having a groove part and a plurality of convex parts formed on at least one side of the inner region of the outer peripheral edge. The secondary battery safety valve structure was formed so as to have the following predetermined area ratio, and when the internal pressure of the battery was activated, the secondary battery safety valve structure was ruptured from the cleavage point at an unspecified position. In addition, the convex part of a valve part is formed in the single side | surface or both surfaces of a sealing board.

  The safety valve structure for a secondary battery of the present invention configured as described above is formed on a sealing plate formed in advance as a shape that fits the end of a sealed secondary battery containing an organic electrolyte such as a lithium ion secondary battery. Used as a safety valve provided by press molding. According to this safety valve, when the internal pressure of the secondary battery becomes equal to or higher than a set value, the valve portion of the safety valve is cleaved and broken from the boundary between the groove portion and the convex portion at an unspecified position. At this time, the valve part is left so that one side of the fractured piece of unspecified shape remains uncut along the outer peripheral edge, and the battery setting is such that most of the broken piece is bent at a substantially right angle and rises from that side. Large deformation instantly due to operating pressure.

  Therefore, the valve portion of the safety valve operates simultaneously with the operation of the internal pressure, and operates before the outer can is greatly deformed by the internal pressure. For this reason, the internal pressure of the secondary battery outer can does not become high, the risk of the outer can exploding due to the increase of the internal pressure is low, and it operates safely. Further, in the secondary battery, in a normal state where the valve portion of the safety valve does not operate, the valve portion is a thin film, but since the convex portion is included in a part thereof, the flexibility and impact resistance of the thin film are reduced. Therefore, even if the secondary battery is accidentally dropped, it has sufficient impact resistance. In addition, the thin film-like part has the effect of preventing the occurrence of scratches due to the impact of foreign matters (mainly collision of products in the press working process or unexpected work mistakes in the working process) due to the action of the convex part. ing.

  In this safety valve structure, the film thickness of the valve portion of the safety valve is compression-molded into a thin film of 20 to 50 μm in the thinnest groove portion by press molding, but when an aluminum alloy is used as a material, for example, The thin film material is close to the general thickness of aluminum foil. However, since the material is compression-molded by press working, scratches and gaps between the material particles generated during rolling molding of the sealing plate or press molding of the safety valve are crushed and no pinholes are generated. And even if it is a press vent type, the thin film material of a valve part can obtain the thing close | similar to the operating characteristic of the aluminum foil of a clad vent. In addition, the valve part of this safety valve is set so that the convex part is less than or equal to the area of the groove part, and the groove part occupies approximately 70 to 90% of the total area of the valve part.

As a method of manufacturing the safety valve structure for the secondary battery, at least one side of the sealing plate provided on the outer can end of the secondary battery incorporating the power generation element is press-molded with basic coining to form the outer peripheral edge from the material thickness T to a predetermined shape. The first processed part having a flat plate surface with a remaining thickness t ₁ is press-molded at the concave part, and then pressed by a preliminary coining having a predetermined area smaller than that of the first processed part at the concave part having a predetermined cross-sectional shape on the outer peripheral edge. Then, the second processed part having a flat plate surface with a remaining thickness t _{2 that} is thinner than the remaining thickness t ₁ is press-formed, and the remaining thickness is determined by coining with respect to the flat plate surface with the remaining thickness t ₂ of the second processed part. A method of manufacturing a safety valve structure for a secondary battery in which a third processed portion including a valve portion having a groove portion at t ₃ and a plurality of convex portions is press-molded to form a safety valve can be employed.

In this manufacturing method, the first processed portion is formed into a thin film having a thickness of about one-tenth of the material thickness T on at least one surface of the sealing plate by a first press punch of basic coining, and the first processed portion is a flat plate surface having a remaining thickness t ₁ . It forms as a recessed part which has. Remaining the second processing unit further compression molded into a thin film in the first processing unit of the pre-coining to a thickness of about approximately half of the remaining thickness t ₁ in a little further second press punch small size surface of the flat sheet It shaped as a recess having a flat plate surface of the thickness t _2. Thereafter, further comprising a third in the press punch residual thickness t ₃ of the groove of the third machining unit relative to the flat surface of the residual thickness t ₂ is the thinnest of the order substantially half residual thickness t ₂ thickness of small size.

  In addition, when forming the said press molding on both surfaces of a sealing board, the said press process is performed symmetrically on both surfaces of a sealing board, and it forms so that several convex part may become object on both surfaces. With this press work, the groove of the safety valve can be compression-molded into a thin film, and a thin film equivalent to metal foil can be formed on the safety valve. Therefore, high-quality and reliable safety valves can be continuously produced at low cost. Can be manufactured automatically.

  The safety valve structure for a secondary battery according to the present invention is a thin film having an outer peripheral edge of a concave portion formed from a material thickness T of a sealing plate, and a groove portion and a plurality of convex portions formed on at least one side of an inner region of the outer peripheral edge. Since the convex part is shaped so that the convex part has a predetermined area ratio equal to or less than the area of the groove part, when the internal pressure of the battery is activated, the thin part of the thin part of the valve part breaks from the cleavage point. Although it is a press vent type safety valve, its operation is almost the same as that of a clad vent type, and it operates as a safety valve instantly and reliably at a low operating pressure like an aluminum foil safety valve, and its thin-film part is convex. By the action of the part, there is also an effect that it is possible to prevent the occurrence of scratches caused by foreign object hits (mainly collision between products in the press working process or unexpected work mistakes in the working process).

The manufacturing method of the safety valve structure for a secondary battery includes a first machining portion having a flat surface of a remaining thickness t ₁ with a concave portion having a predetermined outer periphery from a material thickness T by basic coining by press molding, and then the flat plate. A concave portion whose outer peripheral edge has a predetermined cross-sectional shape on the surface is pressed by a preliminary coining that is smaller than the first processing portion by a predetermined coining area, and a second processing portion having a flat plate surface having a thin film-like remaining thickness t ₂ than the remaining thickness t ₁ is pressed. molded, further press molding a third processing unit comprising a valve portion having grooves and a plurality of protrusions of the remaining thickness t ₃ on at least one surface with coining determined for the flat plate surface of the residual thickness t ₂ of the second processing unit As a safety valve is formed, the safety valve structure can be formed at a low cost on a sealing plate having a safety valve that operates instantaneously and reliably at a low operating pressure, similar to an aluminum foil safety valve. can get.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an external perspective view of a lithium ion secondary battery according to an embodiment. The illustrated lithium ion secondary battery is a prismatic battery, but the following configuration is similarly applied to secondary batteries having a circular cross section, an oval cross section, and other various cross sectional shapes. However, since the present invention mainly includes the structure of a press vent type safety valve, the details of the power generation element built in the secondary battery, its connection fitting, the control circuit, etc. are omitted. In the following, the schematic structure of the secondary battery will be briefly described.

  As shown in the figure, the outer can 1 is closed by the lower bottom plate 1b, the power generation element 2 is accommodated therein, the upper end is closed by the sealing plate 1a, and the sealing plate 1a formed in a sealed shape is not shown. Circular holes 3 and 4 for providing electrode portions are provided, and a safety valve 5 is formed near one end thereof. The safety valve 5 constitutes an explosion-proof structure. In addition, 5F is an outer end surface of the sealing plate 1a. The sealing plate 1a is made of an aluminum alloy in this example, but may be a steel plate, a stainless steel plate, or a copper plate, and the outer can 1 is made of an iron-based material including the lower bottom plate 1b.

In secondary batteries with the above configuration, the safety valve structure A ₁ is provided with a safety valve 5 provided in the press molding to the sealing plate 1a provided at the end of the outer can 1 of the rechargeable battery, the safety valve 5, the sealing plate A thin-film valve portion 6 having outer peripheral edges 5a and 5b of concave portions press-formed in a concave shape in cross-sectional view from 1a, and a groove portion 6a formed on one surface of an inner region of the outer peripheral edges 5a and 5b and a plurality of convex portions 6b. The valve portion 6 is formed such that the convex portion 6b has a predetermined area ratio equal to or less than the area of the groove portion 6a.

For details of the safety valve structure A ₁ configured as described above will be explained. An enlarged cross-sectional shape of the safety valve 5 is shown in FIG. 2A is a partial cross-sectional view taken along arrow IIa-IIa in FIG. 1, FIG. 2B is a partial cross-sectional view taken along arrow IIb-IIb, and FIG. 2C is a partially enlarged view of the safety valve 5. . The safety valve 5 is obtained by performing a plurality of stages of press processing from the thickness T of the plate material of the sealing plate 1a, and is formed in an oval shape as shown in FIG. Below, the structure of the said safety valve 5 is demonstrated corresponding to the process mentioned later. As shown, the first processing section P ₁ is formed as a safety valve recess for forming a safety valve 5 close to one end position of the sheet of the sealing plate 1a.

The first processing section outer peripheral edge 5a of the P _1, as will be described later, is formed by molding an oval recess having a first pressing the flat plate surface of the first residual thickness t ₁ in a part of the plate material It is the outer periphery of the processed part. Then, the outer peripheral edge 5b of the second processing section P _2, as the small recess a little area than the first outer peripheral edge 5a of the cutting portion P ₁ by a second pressing of the first residual thickness t ₁ thinner residual thickness t ₂ than When formed on the flat plate surface, the outer peripheral edge 5b is formed on the outer peripheral edge. In this case, the outer peripheral edge 5b has various deformation states depending on the size (area) of the press punch. Shows a case where is transformed into a small mountain shape. Details thereof will be described later.

The valve unit 6 of the third processing unit P ₃ includes a plurality of mesh-like groove 6a by the third press working with respect to the second processing unit flat thin film material of the remaining thickness t ₂ of P ₂ is a thin film material area It is molded so as to occupy a predetermined ratio or more (most), and at the time of molding, the material meat part compressed by the press pressing force moves in the lateral direction, and is pulled up by the lifting force of the press punch, entire third processing portion P ₃ of the valve unit 6 shape is deformed to the shape of an outwardly convex dome. If the formation of the groove 6a, the remaining thickness t ₃ when left in the compression becomes a thickness of several picking [mu] m, the thickness of the plurality of convex portions 6b between the groove 6a and the groove 6a remains of residual thickness t _2, or slightly becomes thicker, the remaining thickness t ₃ of the groove 6a is about half the residual thickness t ₂ of the convex portion.

In the illustrated example, the press vent type safety valve 5 formed by the above pressing is processed so as to have the following remaining thickness from the plate material T of the sealing plate 1a.
T = 0.7-1.0 mm (Material: Aluminum alloy)
Remaining thickness _t 1 = _0.06~0.1 mm
Remaining thickness _t 2 = _0.04~0.07mm
Remaining thickness t ₃ = 0.02 to 0.05 mm

Incidentally, the groove 6a of the plural rows mesh of the illustrated example of leaving the residual thickness t ₃ are cross shape formed by the cross 45 degrees each groove strip with one another (see FIG. 3), Therefore Although the convex portion 6b is a square, the angle at which each groove crosses is not limited to 45 degrees, and the convex portion 6b may intersect at an angle that forms a rhombus, or otherwise. In addition, various shapes such as a circle, an ellipse, and a triangle can be arranged. In the above example, a regular arrangement of the convex portions 6b is shown, but an irregular arrangement may be used. However, it is the same that the groove portion 6a occupies most of the safety valve 5 as a proportion of the total area of the valve portion 6 and the convex portion 6b is partly formed. In the illustrated example, the groove portion 6a has an area. The ratio accounts for 70 to 90%.

As described above, the recesses of the first processed part P ₁ and the second processed part P ₂ having the remaining thicknesses t ₁ and t ₂ are formed in the sealing plate 1a, and the third processed part P ₃ is formed in the second processed part P ₂ . the safety valve 5 is set to residual thickness t ₃ in the groove 6a of the multiple strip in mesh-like by the valve unit 6 of, for using the groove 6a of the mesh number Article as the primary member to form a safety valve 5, the press vent as a whole However, the groove 6a in the state close to the clad vent film makes the cleavage point an unspecified position and has flexibility against the external force transmitted from the outer can 1 through the sealing plate 1a. By making the entire valve portion 6 flexible, it is possible to obtain a characteristic close to that of a thin film clad with a characteristic more than that of a conventional press vent shape.

  The material of the outer can is made of aluminum or steel, and the sealing plate 1a is made of aluminum or steel. The power generation element 2 is not a feature of the present invention, and a detailed configuration thereof is omitted. For example, the positive electrode contains lithium transition metal oxide such as lithium cobaltate, the negative electrode contains carbon, and the electrolyte solution contains ethylene carbonate. A lithium ion secondary battery using an organic solvent is used. Further, the periphery of the hole 3 is formed in a recessed shape so that an electrode portion (not shown) does not protrude near the center portion of the sealing plate 1a.

  The secondary battery safety valve structure for a lithium ion secondary battery of this embodiment formed in this way is at once when excessive charging, discharging, etc. are performed and an internal pressure higher than the setting that should be activated in the outer can is generated. Therefore, the safety valve 5 operates reliably within a safe range and within a slight error range from the set explosion-proof pressure, and the safety valve 5 is destroyed even if there is an impact such as when the battery is accidentally dropped. It will never be done. It should be noted that the process of forming the safety valve 5 on the sealing plate and welding it to the battery outer can, or various processes until the battery element is assembled, and dents received during the assembly process (the damage caused by collision between products) The possibility of processing scratches, etc. is less dangerous than the clad type because the processing process of the press vent type manufacturing method is far less than the case of the clad type, as explained in the following manufacturing method. Of course, the possibility is lower than the conventional press vent type. This is a big difference in the stability of the product of the secondary battery as the final product.

A method of manufacturing the safety valve 5 having the above configuration will be briefly described with reference to FIG. Figure 4 is the process of forming the outer peripheral edge 5a, the second processing section P ₂ of the outer peripheral edge 5b, the valve unit 6 of the third processing unit P ₃ containing grooves meshed number Article of the first processing section P ₁ Indicates. (A) In view of FIG. 4 press working of the first processing unit P ₁ including the outer peripheral edge 5a to the position where the safety valve 5 with respect to the material of the sealing plate 1a is performed. 10 is a press stand, and 11a is a press punch. The thickness of the plate material of the sealing plate 1a is T, this press molding the first recess of the machining portion P ₁ in the press punch 11a.

In this case, the remaining thickness t ₁ of the flat plate surface of the first processed portion P ₁ after pressing is compressed to about 1/10 of the material thickness T. The press punch uses a first press punch 11a of size Da (oval width), and the press stand uses a press stand 10 of the same size as Da. In this example, the processing shape of the first processing unit P _1, as shown in FIG. 1, FIG. 3, and is formed in an oval shape. Note that the press surface of the first press punch 11a is planar.

In FIG. 4B, the second press punch 11b or the second press punch 11b ′ having a smaller size (size Db or Db ′, oval width, size Db> Db ′) than the first press punch 11a. performing a second processing of the processing portion P ₂ using a press table 10 with. In this case, as shown in case (b), if the size of the second press punch 11b is Db, the inside of the residual thickness t ₂ inclined side is formed cross-sectional shape of the second processing section P ₂ on the outer peripheral edge Since the second press punch 11b ′ of size Db ′ (<Db) is used in the case (b), a bent outer peripheral edge 5b ′ is formed on the outer peripheral edge thereof, and the same remaining inside is formed. flat surface with a thickness t ₂ is formed.

Accordingly, the case and the case (i) and (ii), the shape of the second outer peripheral edge 5b of the processing unit P ₂ is slightly different (5b ') state. In fact, the shape of the second press punch 11b outer peripheral edge 5b size by how much and whether the second processing section P ₂ of the case comprising a case (A) and the intermediate shape of the case (b) There are different depending on the size of the press punches 11a and 11b with respect to the shape and size of the safety valve 5, respectively. The valve unit 6 of the third machining portion P ₃ of the following is formed on the second flat surface of the working portion P ₂ formed as described above.

As shown in FIG. 4 (c) and the case in FIG. (B) Case (b), the valve unit 6 of the third processing unit _{P 3,} the second pressing punches 11b, still smaller size than 11b 'of (Dc) It is formed by press working using the third press punch 11c and the press table 10. Pulling punch after being processed by the third press punch 11c, the surface of the third valve portion 6 around the side of the processing unit P _3, as shown in (c) FIG. 4, the shape of an outwardly convex dome It is formed. This is because the material of the groove on the pressed surface moves and flows to the convex portion 6b, and this movement of the material pushes up the convex portion 6b and is pulled up by the lifting force of the press punch. This is because it is deformed into a convex dome shape.

Although the example which deform | transforms into the dome shape convex outside on the one side (outside) of the valve part 6 was shown in the said embodiment, before pulling up the 3rd press punch 11c, it goes orthogonally to the sealing plate 1a with the axial direction of a press punch. in addition a shot direction, so slight gap occurs in the press-fitting state of the valve unit 6 of the press punch, then if to pull the pressing punch, the valve unit 6 of the third processing unit P ₃ most outer It does not have a convex dome shape and can hold a flat plate surface in an ideal state.

In a safety valve structure A ₁ above secondary battery, the groove 6a and a plurality of protrusions 6b the valve unit 6 on one side of a thin film-like valve member in a predetermined arrangement, has been to form a convex to the outer dome The predetermined array may be a regular array or an irregular array. Moreover, in the said example, although it formed so that it might become an outward convex dome shape with the pulling-up force by a press punch, you may form as an inward convex dome shape. In this case, the third processing unit or attract the valve unit 6 on the press table side P _3, or after the completion of the third stage processing of, the extrusion so as to project inwardly.

However, in the case of the convex on the inside, in order to avoid interference with the battery element that is built in, the outer side of the convex part has a dome shape that does not protrude below the lower surface of the sealing plate. Furthermore, heat treatment such as annealing may be performed on the sealing plate 1a in order to suppress variation in strength of the thin-film valve portion 6 after the processing. After being heated to the treatment temperature, it is cooled for a predetermined time. Since the film thickness of the groove portion 6a of the valve portion 6 is formed as extremely thin as 20 to 50 μm, the variation in the set pressure is averaged by heat treatment. This process is applied as required in the case of the secondary battery safety valve structure A ₂ of the second embodiment.

FIG. 6 shows a secondary battery safety valve structure A2 of the _second embodiment. In this safety valve structure, the first processed part P ₁ formed by the two-stage press, the outer peripheral edges 5a and 5b of the concave part of the second processed part P ₂ , and the groove part 6a of the valve part 6 of the third processed part P ₃ and a plurality of parts. The convex portions 6b are formed in a predetermined arrangement symmetrically on both surfaces of the sealing plate. Also in this case, the predetermined arrangement may be either regular or irregular arrangement. In addition, it is desirable that the symmetric arrangement is perfectly symmetric, but it may be within a range that can be regarded as being almost symmetric.

  The manufacture of the secondary battery safety valve structure of this embodiment is based on the case where the safety valve 5 of the first embodiment is formed on one side of the sealing plate 1a and presses the press punch symmetrically on both sides of the safety valve 5. The detailed processing steps are not shown. The number of press stages is the same as in the first embodiment. When the groove portion 6a and the plurality of convex portions 6b are formed on both surfaces of the valve member, if the upper and lower press punches are formed so that the respective processed uneven surfaces are completely symmetric, the formed valve portion is processed. The surface is flat and flat. However, when there is a slight difference in the shape of the upper and lower press punches, the press punch may be formed in a wave shape in either the outer or inner direction.

According to the secondary battery safety valve structure of the second embodiment having the above-described configuration, as described in the first embodiment, excessive charging, discharging, etc. are performed and more than the setting to be operated in the outer can. When internal pressure is generated, it is released at a stroke, so that the safety valve 5 operates safely and reliably, the safety valve 5 will not be destroyed even if it is accidentally dropped, and there is low risk of dents, processing scratches, etc. etc. it is the same as the first embodiment but, in particular grooves 6a and a plurality of protrusions 6b of the valve portion 6 of the working portion P ₃ in the second embodiment, in a predetermined array symmetrically on both sides of the sealing plate Therefore, the processed surface of the formed valve portion 6 is a flat flat surface. Therefore, the groove portion 6a, which is a thin-film portion of the secondary battery safety valve structure of the first embodiment, is formed on the convex portion 6b. Due to the action, foreign matter (mainly the product in the press working process) It is even more effective than both sides to prevent the occurrence of scratches due to the collision of workers or unexpected work mistakes in the machining process.

  The safety valve of the safety valve structure for a secondary battery according to the present invention comprises an outer peripheral edge of a recess of a sealing plate and a thin film-like valve part formed in an inner region of the outer peripheral edge. And can be widely used not only for lithium ion secondary batteries, but also for various types of secondary batteries using an electrolytic solution such as lithium ion polymer secondary batteries and lithium secondary batteries.

External perspective view of secondary battery of embodiment (A) Sectional view of the secondary battery of the above embodiment as viewed from the arrow IIa-IIa in FIG. 1, (b) Sectional view as viewed from the arrow IIb-IIb in FIG. 1, (c) Partial enlarged view of the safety valve. Partial enlarged perspective view of the configuration near the safety valve (A) Explanatory drawing of molding of the first machining section, (b) Explanatory drawing of molding of the second machining section, (c) Explanatory drawing of molding of the third machining section of the press working method for machining the safety valve. Schematic diagram explaining the cleavage state Main sectional view of the secondary battery of the second embodiment

Explanation of symbols

1 exterior can 1a sealing plate 2 generating element 3, 4 circular hole 5 a safety valve 5a, 5b outer peripheral edge 6 valve portion 6a groove 6b protrusion 10 third press punch press table 11a first press punch 11b second press punch 11c _{P 1} 1st processing part P ₂ 2nd processing part P ₃ 3rd processing part

Claims (4)

  The sealing plate 1a provided at the end of the outer can 1 of the secondary battery is provided with a safety valve 5 provided by press molding. The safety valve 5 is a concave portion press-formed in a concave shape in a sectional view from the material thickness T of the sealing plate 1a. The outer peripheral edges 5a and 5b, and a groove portion 6a formed on at least one side of the inner region of the outer peripheral edge and a thin-film valve portion 6 having a plurality of convex portions 6b. The valve portion 6 has the convex portions 6b and the groove portions 6a. A safety valve structure for a secondary battery, which is molded so as to have a predetermined area ratio equal to or less than the above-mentioned area, and is to be broken from a cleavage point at an unspecified position when the battery internal pressure is activated.   2. The thin film-like valve portion 6 is formed as a convex dome shape with a groove 6a and a plurality of convex portions 6b on a single side of the valve portion 6 in a predetermined arrangement. Safety valve structure for secondary batteries.   2. The safety valve structure for a secondary battery according to claim 1, wherein the thin-film valve portion 6 is formed with groove portions 6 a and a plurality of convex portions 6 b in a predetermined arrangement on both surfaces of the valve portion 6. At least one surface recess in the flat plate surface of the remaining thickness t ₁ of the outer peripheral edge 5a of a material thickness T the basis coining by press molding a predetermined shape of the sealing plate 1a provided on the outer can end of a secondary battery having a built-in power generating element a first processing section P ₁ having press molded, then residual thickness t ₁ this flat surface is concave outer peripheral edge 5b has a predetermined cross-sectional shape, and pressed with a predetermined area smaller pre coining than the first processing unit P ₁ a second processing section P ₂ having a more thin-film flat plate surface of the residual thickness t ₂ by press molding, and further the groove of residual thickness t ₃ at coining determined with respect to the flat surface of the residual thickness t ₂ of the second processing unit the third processing unit manufacturing method of the secondary battery safety valve structure to the P ₃ by press-forming to form a safety valve 5 consisting of a valve unit 6 having a 6a and a plurality of protrusions 6b.

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