JP4854208B2 - Sealed battery and manufacturing method thereof - Google Patents

Description

  The present invention relates to a sealed battery having a sealing body at the opening of a metal outer can, and in particular, includes a sealing body having a safety mechanism capable of interrupting an overcharge current during overcharge or a short circuit current during short circuit. The present invention relates to a sealed battery and a method for manufacturing the same.

  Generally, in non-aqueous electrolyte secondary batteries such as lithium-ion batteries, when a device including a charger fails or is overcharged or misused, the power generation elements such as the electrolyte and active material inside the battery undergo chemical changes. Wake up. For example, the electrolyte solution or the active material is decomposed by an abnormal reaction due to overcharge or short circuit, and abnormally gas is generated inside the battery, so that the battery internal pressure becomes excessive. In such a case, there is a risk of the battery exploding or damaging the equipment used, so a safety mechanism has been conventionally added to this type of battery. As a battery to which such a safety mechanism is added, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2000-36293) is known.

  As shown in FIG. 3A, the nonaqueous electrolyte battery proposed in Patent Document 1 includes a stainless steel first valve cap 31 formed in a cap shape and a stainless steel plate formed in a dish shape. The sealing body 30 comprised from the 2nd valve cap 32 is provided. The 1st valve cap 31 consists of the convex part 31a which bulges toward the battery exterior, and the flat flange part 31b which comprises the base part of this convex part 31a, and there are several in the corner | angular part of the convex part 31a. A gas vent hole 31c is provided. On the other hand, the 2nd valve cap 32 consists of the recessed part 32a which bulges toward the inside of a battery, and the flat flange part 32b which comprises the bottom part of this recessed part 32a. Degassing holes 32c are provided at the corners of the recesses 32a.

  Inside these first valve cap 31 and second valve cap 32, there is housed a conductive elastic deformation plate 33 that deforms when the gas pressure inside the battery rises and exceeds a predetermined pressure. The conductive elastic deformation plate 33 serves as a valve member, and includes a concave portion 33a and a flange portion 33b. The lowest portion of the recess 33a is fixedly disposed on the upper surface of the recess 32a of the second valve cap 32 by ultrasonic welding or laser welding, and the flange portion 33b is connected to the flange portion 31b of the first valve cap 31 and the second portion. The two valve caps 32 are sandwiched between the flange portions 32b.

  A ring-shaped PTC (Positive Temperature Coefficient) thermistor element 34 is disposed at a part of the upper portion of the flange portion 32b. When an overcurrent flows in the battery and an abnormal heat generation phenomenon occurs, the PTC thermistor element 34 The resistance value increases to reduce the overcurrent. When the gas pressure inside the battery rises and exceeds a predetermined pressure, the concave portion 33a of the conductive elastic deformation plate 33 is deformed, so that the contact between the conductive elastic deformation plate 33 and the concave portion 32a of the second valve cap 32 is prevented. As a result, the overcurrent or short circuit current is cut off. Further, when the gas pressure inside the battery further rises after the overcurrent or short circuit current is cut off, the notch portion 33c formed in the conductive elastic deformation plate 33 is cleaved and the gas is released from the gas vent hole 31c. It has become so.

  In this case, a sealing member gasket 35 made of polypropylene (PP) is placed on the flange portion 32 b of the second valve cap 32, and the flange portion of the conductive elastic deformation plate 33 is placed on the sealing member gasket 35. 33b and the PTC thermistor element 34 are mounted. Thereafter, the end portion of the flange portion 32b of the second valve cap 32 is caulked inward, whereby the first valve cap 31 is sealed by the sealing member gasket 35 and held by the second valve cap 32 in an airtight state. A body 30 is formed. Then, the sealing body 30 is placed in the opening of the outer can 20 together with the gasket 36 for the outer can made of polypropylene (PP), and the upper end portion (caulking portion) 21 of the outer can 20 in which the power generation element (not shown) is accommodated is placed inside. The battery is manufactured by sealing by caulking.

  By the way, in the battery provided with the sealing body 30 described above, when the internal pressure of the battery rises above a predetermined pressure, the conductive elastic deformation plate 33 is deformed, and the conductive elastic deformation plate 33 and the second valve cap 32 Contact with the recess 32a is blocked, preventing overcurrent and short-circuit current from flowing through the battery. For this reason, in order to transmit the internal pressure of the battery to the conductive elastic deformation plate 33, gas vent holes 32 c are provided at the corners of the recesses 32 a of the second valve cap 32.

However, when the battery provided with the sealing body 30 is subjected to an impact such as dropping, the sealing property of the sealing body 30 is broken, and mainly through the gas vent hole 32c , indicated by the arrow 3 in FIG. There was a problem that the electrolyte leaked to the outside of the battery through the route 6. On the other hand, since the gasket 36 for exterior cans made of polypropylene (PP) having a large thickness is interposed between the caulked portion 21 of the exterior can 20 and the sealing body 30, an arrow (FIG. 3B) The electrolyte solution hardly leaks outside the battery through the paths 1 and 2 shown in FIG.

  However, since the sealing member gasket 35 disposed between the flange portion 31b of the first valve cap 31 and the flange portion 32b of the second valve cap 32 is formed thin, it does not cause an impact such as dropping. When the sealing body 30 is deformed in response, the path between the flange portion 32b of the second valve cap 32 and the sealing body gasket 35 (indicated by an arrow 3 in FIG. 3B), and the sealing body gasket 35 and the conductive elasticity. The electrolyte leaks to the outside of the battery through a path (4 indicated by an arrow in FIG. 3B) between the flange portions 33b of the deformation plate 33.

  Further, metal parts are in direct contact between the flange portion 31b of the first valve cap 31 and the PTC thermistor element 34 and between the PTC thermistor element 34 and the flange portion 33b of the conductive elastic deformation plate 33. When the sealing body 30 is deformed due to an impact such as a drop due to insufficient sealing performance, the path between the flange portion 31b of the first valve cap 31 and the PTC thermistor element 34 (see FIG. 3B). The electrolyte leaks to the outside of the battery through 5) indicated by an arrow and a path (6 indicated by an arrow in FIG. 3B) between the PTC thermistor element 34 and the flange portion 33b of the conductive elastic deformation plate 33.

  For this reason, in order to improve the sealing performance, various studies were made on the sealing material, gasket material, gasket shape, caulking shape, etc., but when the battery was deformed, the sealing performance at the gasket portion for the sealing body and the contact between the metal parts It was difficult to ensure the sealability at the part.

  In view of this, the inventors of the present invention have proposed a sealed battery having improved sealing performance while maintaining a safety mechanism in Japanese Patent Application Laid-Open No. 2004-139809. In the sealed battery proposed in Patent Document 2, as shown in FIG. 2, the first valve cap 11 serving as an external terminal and the first valve cap are held in an insulated state, and one electrode in the battery is connected. A sealing body 10 composed of a conductively connected second valve cap 12 is disposed in an opening of a metal outer can 20 containing a power generation element. Then, when the battery internal pressure rises to the first set pressure, the conductive elastic deformation plate 14 that is elastically deformed and interrupts the electrical connection state with the second valve cap is provided between the first valve cap 11 and the second valve cap 12. These are provided in conductive connection with these. The thin portion 13 formed integrally with a part of the second valve cap 12 is provided with a notch portion 13a that breaks when the battery internal pressure reaches a second set pressure lower than the first set pressure. Yes.

As a result, since the inside of the battery is kept sealed by the second valve cap 12 until the battery internal pressure reaches the second set pressure, even if the sealing body is deformed due to an impact such as dropping, the sealing body 10 The sealing property can be maintained, and the electrolyte can be prevented from leaking outside the battery. When the battery internal pressure reaches the second set pressure, the notch portion 13a formed integrally with a part of the second valve cap 12 is broken, so that the conductive elastic deformation until the first set pressure is reached. by a plate 14 in the battery is kept in a sealed state. Thereafter, when the battery internal pressure reaches the first set pressure, the conductive elastic deformation plate 14 is deformed, and the electrically connected state between the conductive elastic deformation plate 14 and the second valve cap 12 is cut off. .
JP 2000-36293 A JP 2004-139809 A

However, even in the sealed battery proposed in Patent Document 2 described above, the leakage paths of the path 1 and the path 2 indicated by the arrows in FIG. 2 remain. Therefore, when the battery sealing portion is deformed by an impact such as dropping or the battery temperature rises due to an overcharged state or the like, and the gasket (mainly, the outer can gasket 18) is softened, the arrow in FIG. There was a problem that leakage occurred through the route 1 or the route 2 shown.
Therefore, the present invention has been made to solve the above-described problems, and the gasket is deformed in the sealing portion of the battery due to an impact such as dropping, or the battery temperature rises due to an overcharged state, etc. It is an object of the present invention to provide a sealed battery that is less likely to leak even when softened and has excellent sealing properties.

The sealed battery of the present invention includes a first valve cap serving as an external terminal, the first valve cap being held via a gasket for sealing body and a conductive elastic deformation plate, and electrically connected to one electrode in the battery. A sealing body including the second valve cap is disposed in the opening of the metal outer can containing the power generation element via the outer can gasket, and the opening is sealed. In order to achieve the above object, the first valve cap is held by the flange portion of the second valve cap by caulking the end of the flange portion of the second valve cap inward, A portion protruding from the end of the caulking portion of the second valve cap of the gasket for sealing body and a portion protruding from the end of the caulking portion of the outer can of the gasket for outer can are welded.

Thus, when the portion protruding from the end of the caulking portion of the second valve cap of the gasket for sealing body and the portion protruding from the end of the caulking portion of the outer can of the outer can gasket are welded, Even if the sealing portion of the battery is deformed due to an impact such as dropping, or the battery temperature rises due to an overcharged state or the like and the gasket for the sealing body or the gasket for the outer can is softened, the path 2 indicated by the arrow in FIG. Will be blocked. For this reason, the problem that the electrolyte solution leaks through the path 2 can be prevented.

  In this case, the conductive elastic deformation plate is disposed in conductive connection with the second valve cap, and is elastically deformed when the battery internal pressure rises to the first set pressure, and is electrically connected to the second valve cap. Is cut off, and a part of the second valve cap is provided with a notch portion that breaks when the battery internal pressure reaches a second set pressure lower than the first set pressure. desirable.

In order to manufacture such a sealed battery, the end of the flange portion of the second valve cap is caulked inward, and the first valve cap is held by the flange portion of the second valve cap. A sealing body forming step for forming a sealing body , a sealing body arranging step for arranging the sealing body described above at an opening of a metal outer can containing a power generation element via a gasket for an outer can, and a sealing body are arranged. A first caulking step for caulking the tip of the opening of the outer can to the sealing body side, a portion protruding from the end of the second valve cap of the gasket for the sealing body, and an caulking portion for the outer can of the gasket for the outer can What is necessary is just to provide the welding process which welds the part which protruded from the edge part of this, and the 2nd crimping process which crimps the front-end | tip part of the opening part of an exterior can again to the said sealing body side.

  Hereinafter, a preferred embodiment when the sealed battery of the present invention is applied to a lithium ion battery will be described with reference to the drawings. However, the present invention is not limited to this embodiment, and the present invention is not limited to this embodiment. It is possible to carry out by appropriately changing without changing the purpose. FIG. 1 is a cross-sectional view showing the main part in a state where the sealing body of the embodiment of the present invention is attached to the opening of the outer can of the lithium ion battery. FIG. 2 is a cross-sectional view showing the main part of the comparative example (conventional example) 1 of the present invention attached to the opening of the outer can of the lithium ion battery. FIG. 3 is a cross-sectional view showing the main part in a state where the sealing body of Comparative Example 2 (conventional example) of the present invention is attached to the opening of the outer can of the lithium ion battery.

1. Sealing Body The sealing body 10 of the present invention includes a first valve cap 11 serving as a positive electrode cap formed in a cap shape, and a second valve cap 12 serving as a bottom lid formed in a dish shape. The first valve cap 11 is made of stainless steel, and includes a convex portion 11a that bulges toward the outside of the battery, and a flat flange portion 11b that forms the bottom of the convex portion 11a. A plurality of vent holes 11c are provided at the corners. On the other hand, the second valve cap 12 is made of stainless steel, and includes a recess 12a that bulges toward the inside of the battery, and a flat flange portion 12b that constitutes the bottom of the recess 12a. A thin portion 13 is provided in a part of the recess 12b, and the thin portion 13 is broken when the internal pressure of the battery reaches a second set pressure (for example, 0.78 to 1.08 MPa). Thus, a later-described notch portion 13a that communicates the inside and outside of the second valve cap 12 is formed.

  Inside these first valve cap 11 and second valve cap 12, there is housed a conductive elastic deformation plate 14 which deforms when the gas pressure inside the battery rises and reaches a first set pressure (for example, 14 MPa). Has been. The conductive elastic deformation plate 14 serves as a valve member, and includes a concave portion 14a and a flange portion 14b. For example, the conductive elastic deformation plate 14 is formed of an aluminum foil having a thickness of 0.2 mm and a surface irregularity of 0.005 mm. . The lowest part of the recessed part 14a is fixedly disposed on the upper surface of the recessed part 12a of the second valve cap 12 by ultrasonic welding or laser welding, and the flange part 14b is connected to the flange part 11b of the first valve cap 11 and the second part. The two-valve cap 12 is sandwiched between the flange portion 12b.

  A ring-shaped PTC (Positive Temperature Coefficient) thermistor element 15 is disposed at a part of the upper portion of the flange portion 14b. When an overcurrent flows in the battery and an abnormal heat generation phenomenon occurs, the PTC thermistor element 15 The resistance value increases to reduce the overcurrent. And if the gas pressure inside a battery rises and becomes more than 1st setting pressure (for example, 14 Mpa), the recessed part 14a of the electroconductive elastic deformation board 14 will deform | transform. For this reason, the part fixed by ultrasonic welding or laser welding is peeled off, the contact between the conductive elastic deformation plate 14 and the recess 12a of the second valve cap 12 is cut off, and the overcurrent or short circuit current is cut off. It becomes like this. Further, when the gas pressure inside the battery further increases after the overcurrent or the short-circuit current is cut off, the notch portion 14c formed in the conductive elastic deformation plate 14 is cleaved, and the gas is released from the gas vent hole 11c. It has become so.

  Then, on the flange portion 12a of the second valve cap 12, a ring-shaped sealing body gasket 16 made of polypropylene (PP) having an L-shaped cross section and a thickness of 0.25 mm is placed. The flange portion 14 b of the conductive elastic deformation plate 14 and the PTC thermistor element 15 were placed on the gasket 16 for use. Next, the contact portion between the lower surface of the sealing insulating gasket 16 and the upper surface of the flange portion 12b of the second valve cap 12 was closely integrated by heat welding or bonding with an adhesive. Thereafter, the first valve cap 11 is held by the flange portion 12b of the second valve cap 12 via the sealing member gasket 16 by crimping the end portion of the flange portion 12b of the second valve cap 12 inward. Thus, the sealing body 10 is formed.

2. Next, the lithium ion battery A of the example using the sealing body 10 configured as described above, the lithium ion battery X of the comparative example 1 using the sealing body 10, and the thin portion as shown in FIG. A method for manufacturing the lithium ion battery Y of Comparative Example 2 using the sealing body 30 provided with the vent holes 32c at the corners of the recesses 32a will be described below.

  First, a negative electrode active material made of natural graphite and a binder made of polyvinylidene fluoride (PVDF) dissolved in an organic solvent made of N-methylpyrrolidone were mixed to obtain a slurry or paste. Apply these slurries or pastes uniformly in the case of a slurry using a die coater, a doctor blade, etc., and in the case of a paste, the entire surface of both sides of a metal core (for example, copper foil) by a roller coating method, A negative electrode plate coated with an active material layer was formed. Thereafter, the negative electrode plate coated with the active material layer was passed through a drier to remove the organic solvent necessary for slurry or paste preparation and dried. The dried negative electrode plate was rolled with a roll press and then cut into a predetermined shape to obtain a negative electrode plate.

On the other hand, a positive electrode active material made of LiCoO ₂ , a carbon conductive agent such as acetylene black or graphite, and a binder made of polyvinylidene fluoride (PVDF) are dissolved in an organic solvent made of N-methylpyrrolidone. These were mixed to form a slurry or paste. Apply these slurries or pastes uniformly on both sides of a metal core (for example, aluminum foil) by using a die coater, doctor blade, etc. in the case of a slurry, or a roller coating method in the case of a paste. A positive electrode plate coated with the layer was formed. Thereafter, the positive electrode plate coated with the active material layer is passed through a dryer to remove the organic solvent necessary for slurry or paste preparation and dried, and then the dried positive plate is rolled by a roll press. Then, it was cut into a predetermined shape to obtain a positive electrode plate.

  The negative electrode plate and the positive electrode plate produced as described above are sandwiched between a microporous membrane made of a polyolefin resin, preferably a polyethylene microporous membrane, which has low reactivity with an organic solvent and is inexpensive. And then wound with a winder. Thereafter, the outermost periphery was taped to form a spiral electrode body. Next, after the insulating plates are arranged above and below the spiral electrode body produced as described above from the opening 21 of the bottomed cylindrical outer can 20 that also serves as a stainless steel negative electrode terminal, this spiral shape is arranged. The electrode body was inserted into the outer can 20. At this time, the negative electrode conductive tab extending from the negative electrode plate of the spiral electrode body was welded to the outer can.

Thereafter, the upper portion of each outer can 20 was grooved to form an annular groove 20a, and then the outer can gasket 18 (36) was mounted on the annular groove 20a. Then, the positive electrode conductive tab extended from the positive electrode plate of a spiral electrode body was welded to the lower surface of the recessed part 12a (32a) of the 2nd valve cap 12 (32) of the sealing body 10 (30). Next, a non-aqueous electrolyte (ethylene carbonate (EC) and diethyl carbonate (DEC) mixed in an equal volume ratio to the opening of the outer can 20 is mixed with 1 mol / liter of lithium hexafluorophosphate (LiPF ₆ ). Each dissolved solution was injected. Thereafter, the sealing body 10 (30) is placed in the opening of the outer can 20 via the outer can gasket 18 (36), and the upper end (caulking portion) 21 of the opening of the outer can 20 is sealed. It was caulked to the (30) side and sealed in a liquid-tight manner. Thus, a lithium ion battery X of Comparative Example 1 as shown in FIG. 2 was produced, and a lithium ion battery Y of Comparative Example 2 as shown in FIG. 3 was produced. Here, the lithium ion battery X of Comparative Example 1 was prepared using the sealing body 10, and the lithium ion battery Y of Comparative Example 2 was manufactured using the sealing body 30.

Next, using the lithium ion battery X of Comparative Example 1, the sealing member gasket 16 protrudes from the end of the caulking portion of the second valve cap 12 and the caulking portion of the outer can 20 of the outer can gasket 18. The portion 18a protruding from 21 was welded. In this case, as shown in FIG. 1B, the heat welding ring 19 heated to about 210 ° C. is pressed for 10 seconds to the portion 18a of the outer can gasket 18 protruding from the caulking portion 21 of the outer can 20. The portion 18a is thermally welded to the portion 16a where the sealing member gasket 16 protrudes from the end portion of the caulking portion of the second valve cap 12. Thereafter, the caulking portion 21 of the outer can 20 was caulked again and sealed in a liquid-tight manner. Thereby, the lithium ion battery A of an Example as shown to Fig.1 (a) was produced.

3. Liquid Leakage Test (1) Dropping Experiment Next, 10 lithium ion batteries A, X, and Y prepared as described above were prepared, and 10 of each of these lithium ion batteries A, X, and Y were put into concrete. When the number of batteries in which liquid leakage (leakage) occurred when dropped from a height of 1.5 m was measured, the results shown in Table 1 below were obtained. In this liquid leakage test, the battery was dropped once with the sealing body 10 (30) facing down, then dropped once with the sealing body 10 (30) facing upward, and then the side of the battery faced downward. Then, it was dropped once to make one set, and 10 sets were performed.

(2) Overcharge test Next, 10 lithium ion batteries A, X, and Y produced as described above were used to charge the battery voltage to 4.1 V with a charging current of 1 It, and then The battery was charged at a constant voltage of 4.1 V for 3 hours to be fully charged. In this way, a charging current of 2 It flows between the positive and negative terminals of each of the fully charged lithium ion batteries A, X, and Y to perform overcharging from the start of overcharging until the temperature of each battery reaches 130 ° C. When the number of batteries in which leakage (leakage) occurred after overcharging was measured, the results shown in Table 1 below were obtained. Note that, when the battery is overcharged from the start of overcharge until the temperature reaches 130 ° C., the gas pressure in the battery rises and the notch portion 13a formed in the second valve cap 12 breaks.

  As is apparent from the results of Table 1 above, in the battery A, the number of leaked liquids was 0, even though the battery A was dropped from a height of 1.5 m on the concrete, whereas in the battery X, 10 It can be seen that liquid leakage occurred in one (10%) of the batteries, and in battery Y, three of the 10 batteries (30%). In the battery Y, since the gas vent holes 32c are provided at the corners of the concave portions 32a of the second valve cap 32, the sealing performance of the sealing body 30 is broken due to the impact of the drop, and mainly the gas vent. It is considered that the electrolyte leaked from the hole 32c to the outside of the battery through the paths indicated by arrows 3 to 6 in FIG.

Further, in the battery A and the battery X, the second valve cap 12 is not provided with a gas vent hole (the notch portion 13a is provided in the thin wall portion 13), and thus the sealing property of the sealing body 10 due to the impact of dropping. Will not break. However, in the battery X, it is considered that the sealing performance between the second valve cap 12 and the outer can gasket 18 was broken by the impact of the drop, and the electrolyte leaked to the outside of the battery through the path indicated by the arrow 2 in FIG. It is done. On the other hand, in the battery A, a portion 16 a where the sealing body gasket 16 protrudes from the end portion of the caulking portion of the second valve cap 12, and a portion 18 a which protrudes from the caulking portion 21 of the outer can 20 of the outer can gasket 18. This is because no leakage occurs between the second valve cap 12 and the outer can gasket 18.

  Further, as is apparent from the results in Table 1, the battery A is overcharged from the start of overcharge until the inside of the battery reaches 130 ° C., the gas pressure in the battery rises, and the second valve cap 12 The number of leaked liquids is 2 out of 10 (20%), while the battery X has 4 (40%) despite the fact that the notch portion 13a formed in FIG. In the battery Y, it can be seen that liquid leakage occurred in 4 out of 10 batteries (40%).

In the battery Y, as the temperature in the battery rises, the outer can gasket 36 is softened, so that leakage occurs from the path indicated by arrows 1 and 2 in FIG. It is considered that the electrolyte solution leaked from the gas vent hole 32c to the outside of the battery through the path of arrows 3 to 6 in FIG. Further, in the battery X, as the temperature inside the battery rises, the outer can gasket 18 is softened, so that leakage occurs from the path indicated by arrows 1 and 2 in FIG. 2 and the sealing member gasket 16 is softened. Thus, it is considered that the electrolyte leaked from the broken notch portion 13a to the outside of the battery through the path indicated by arrows 3 to 6 in FIG. On the other hand, in battery A, the sealing member gasket 16 protruded from the end 16a of the second valve cap 12 from the end portion of the caulking portion and from the caulking portion 21 of the outer can 20 of the outer can gasket 18. Since the portion 18a is welded, leakage does not occur from the path indicated by arrows 2 and 3 in FIG. 3B, but the path indicated by arrow 1 in FIG. This is probably because leakage occurred through the route indicated by arrows 4-6 in FIG.

  In the above-described embodiment, an example in which natural graphite is used as the negative electrode active material has been described. However, in addition to natural graphite, a carbon-based material that can occlude / desorb lithium ions, such as graphite, carbon black, coke, and glass. Like carbon, carbon fiber, or a fired body thereof is preferable. Further, an oxide capable of inserting and extracting lithium ions such as tin oxide and titanium oxide may be used.

In the above-described embodiment, an example in which LiCoO ₂ is used as the positive electrode active material has been described. However, in addition to LiCoO ₂ , lithium-containing transition metal compounds that can accept lithium ions as guests, such as LiNiO ₂ , LiCo _X Ni _{( 1-X)} O ₂ , LiCrO ₂ , LiVO ₂ , LiMnO ₂ , αLiFeO ₂ , LiTiO ₂ , LiScO ₂ , LiYO ₂ , LiMn ₂ O _4, etc. are preferred, and in particular, LiNiO ₂ , LiCo _X Ni _(1-X) It is preferable to use O ₂ alone or a mixture of two or more of these. Further, a conductive polymer such as polyacetylene or polyaniline may be used.

Furthermore, the electrolyte is an ionic conductor in which a lithium salt is dissolved as a solute in an organic solvent, has high ionic conductivity, is chemically and electrochemically stable for both positive and negative electrodes, and is used. If the possible temperature range is wide, the safety is high, and the cost is low, it can be used. For example, as the organic solvent, in addition to the mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC), propylene carbonate (PC), sulfolane (SL), tetrahydrofuran (THF), γ-butyrolactone (GBL), dimethyl Carbonate (DMC), ethyl methyl carbonate (EMC), 1,2 dimethoxyethane (DME) and the like, or a mixed solvent thereof is preferable. Further, a lithium salt having a strong electron-withdrawing property is used as a solute. In addition to LiPF ₆ , for example, LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO _{3 and the} like are preferable.

  In the above-described embodiment, an example in which the present invention is applied to a lithium ion battery has been described. However, in addition to the lithium ion battery, the present invention is also applied to various sealed batteries such as a nickel-cadmium storage battery and a nickel-hydrogen storage battery. It is possible to apply.

It is sectional drawing which shows the principal part of the state which attached the sealing body of the Example of this invention to the exterior can of the lithium ion battery. It is sectional drawing which shows the principal part of the state which attached the sealing body of the comparative example 1 of this invention to the opening part of the exterior can of a lithium ion battery. It is sectional drawing which shows the principal part of the state which attached the sealing body of the comparative example 2 of this invention to the opening part of the exterior can of a lithium ion battery.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Sealing body, 11 ... 1st valve cap, 11a ... Convex part, 11b ... Flange part, 11c ... Gas vent hole, 12 ... 2nd valve cap, 12a ... Recessed part, 12b ... Flange part, 13 ... Thin part, 13a DESCRIPTION OF SYMBOLS ... Notch part, 14 ... Conductive elastic deformation board, 14a ... Recessed part, 14b ... Flange part, 14c ... Notch part, 15 ... Ring-shaped PTC thermistor element, 16 ... Gasket for sealing body, 18 ... Gasket for outer can, 19 ... Thermal welding ring, 20 ... outer can, 20a ... annular groove, 21 ... upper end of the outer can (caulking)

Claims (3)

A first valve cap serving as an external terminal; and a second valve cap that holds the first valve cap via a sealing body gasket and a conductive elastic deformation plate and is conductively connected to one electrode in the battery. A sealed battery in which a sealing body is disposed at an opening of a metal outer can containing a power generation element via a gasket for an outer can, and the opening is sealed;
The first valve cap is held by the flange portion of the second valve cap by caulking the end of the flange portion of the second valve cap inward,
The portion protruding from the end portion of the caulking portion of the second valve cap of the gasket for sealing body and the portion protruding from the end portion of the caulking portion of the outer can of the gasket for outer can are welded. A sealed battery. The conductive elastic deformation plate is disposed in a conductive connection state with the second valve cap. When the battery internal pressure rises to the first set pressure, the conductive elastic deformation plate is elastically deformed and an electrical connection state with the second valve cap is established. Are designed to be blocked,
The notch part which fractures | ruptures when the battery internal pressure reaches the 2nd setting pressure lower than the said 1st setting pressure is arrange | positioned in a part of said 2nd valve cap. Sealed battery. A first valve cap serving as an external terminal; and a second valve cap that holds the first valve cap via a sealing body gasket and a conductive elastic deformation plate and is conductively connected to one electrode in the battery. A method for producing a sealed battery in which a sealing body is disposed in an opening of a metal outer can containing a power generation element via a gasket for an outer can, and the opening is sealed,
A sealing body forming step in which an end portion of the flange portion of the second valve cap is caulked inward to hold the first valve cap by the flange portion of the second valve cap, thereby forming a sealing body;
A sealing body arranging step of arranging the sealing body in an opening of a metal outer can containing a power generation element via the gasket for the outer can;
A first caulking step of caulking the tip of the opening of the outer can where the sealing body is disposed to the sealing body side;
A welding step of welding a portion protruding from the end of the caulking portion of the second valve cap of the gasket for sealing body and a portion protruding from an end of the caulking portion of the outer can of the gasket for outer can;
A method for producing a sealed battery, comprising a second caulking step of caulking the tip of the opening of the outer can again to the sealing body side.

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