JP4708052B2 - Sealed battery - Google Patents

Description

  The present invention relates to a sealed battery, and more particularly, to a sealed battery in which a battery lid provided with a gas release valve for releasing internal pressure and an electrical connection terminal is caulked on a battery container having parallel plane portions.

  Generally, in a sealed battery, a battery can made of metal or the like is used for a battery container, and a battery lid is caulked to the open end of the battery can via a sealing insulating member or the like to ensure sealing. The battery cover is usually provided with a gas release valve for releasing the internal pressure when the internal pressure is increased, and a terminal for electrical connection with an external load and the like. In a sealed battery such as a substantially flat shape having a flat part in which the battery can is parallel, the sealing part (caulking part) in which the battery lid is caulked has a substantially straight part or a straight part, so that a cylindrical shape having only a curved part, etc. Compared with the sealed battery, it is difficult to make the caulking part such as a substantially straight part strong against a stress accompanying an increase in internal pressure (to ensure a sealing force). This is because when the battery lid is caulked to the open end of a battery can having only a curved portion, the volume of the material changes due to bending of the open end of the battery can, resulting in residual stress. This is because the battery can having a substantially straight portion or the like is not accompanied by such a volume change of the material, while acting as a shape holding force of the battery can (open end portion thereof).

  On the other hand, in an assembled battery or the like using a plurality of sealed batteries, a sealed battery having a rectangular shape or a shape close thereto is desired from the viewpoint of volume energy density. The above-described sealing of the battery can that is sealed by sealing the battery lid is a technique that is meaningful for a sealed battery having a square shape or the like because the processing step is low-cost and the number of parts is easily reduced. There is a problem of the sealing force described above. That is, when the sealing force of the caulking part is insufficient, the opening of the caulking part is not intended before the internal pressure is released by the operation of the gas release valve, etc. The contents may be scattered.

  In order to prevent the caulking portion from opening to this problem, for example, a sealed thin battery in which a metal beam member is fixed inside a battery can near the caulking portion is disclosed (see Patent Document 1). Further, a sealed flat battery in which a metal plate having a U-shaped cross section is fitted and welded so as to straddle the caulked portion between the battery lid and the battery can is also disclosed (see Patent Document 2).

JP-A-6-310119 JP 2002-279842 A

  However, in the technique of Patent Document 1, since the beam member is fixed inside the battery can, the volume energy density of the sealed battery is lowered. Further, since the beam member is made of metal, it is necessary to dispose the insulating member inside the battery can or to provide an insulating coating on the beam member in order to ensure insulation from other members. For this reason, the volume energy density is further reduced, the manufacturing process becomes complicated, and the battery becomes expensive. On the other hand, in the technique of Patent Document 2, since the metal plate is fitted and welded so as to straddle the caulking portion, the problem of volume energy density does not occur, but the position of the terminal and the gas release valve arranged on the battery lid is avoided. Since the metal plate is fitted and welded, the length of the metal plate relative to the length of the substantially straight portion or the straight portion of the battery can is reduced. For this reason, it cannot be said that it is sufficient to prevent the caulking portion from opening when the internal pressure rises or when the external force is deformed. When the length of the metal plate is increased, the metal plate covers the terminal and the gas release valve, and thus the electrical connection and the operation of the gas release valve are hindered.

  An object of the present invention is to provide a sealed battery that can prevent the caulking portion between the battery lid and the battery container from being opened and can ensure the electrical connection and the operation of the gas release valve. .

  In order to solve the above-mentioned problems, the present invention provides a sealed battery in which a battery lid provided with a gas release valve for releasing internal pressure and an electrical connection terminal is caulked in a battery container having parallel plane portions. A central portion located above the battery lid and legs bent from the central portion along both sides of the flat portion of the battery container to seal the opening of the caulking portion between the battery lid and the battery container; A sealing member is disposed across the battery lid so that the leg portion is in contact with the flat surface portion, and the end portion of the leg portion is the flat surface over 70% or more of the length in the longitudinal direction of the flat surface portion. A through hole or a notch is formed at a position above the gas release valve and the terminal in the central portion.

  In the present invention, the central portion located above the battery lid and the legs bent along the both sides of the flat portion of the battery container from the central portion, the opening of the caulking portion between the battery lid and the battery container is sealed. The sealing member is disposed across the battery lid so that the leg is in contact with the flat part, and the end of the leg is fixed to the flat part over 70% of the length in the longitudinal direction of the flat part. Therefore, it is possible to reliably prevent the caulking portion between the battery lid and the battery container from opening against deformation due to an increase in internal pressure or external force when the battery is abnormal, and gas discharge disposed on the battery lid at the center portion Since the through hole or notch is formed at a position above the valve and the terminal, it is possible to ensure the connection between the terminal and the external load and the operation of the gas release valve.

  In this case, the leg portion is formed with a non-contact portion that is not in contact with the flat portion, and the length of the non-contact portion is preferably less than 15% with respect to the total length in the longitudinal direction of the flat portion. . Also, if the surface of the center and legs facing the battery lid is covered with an insulating member, the sealing member connected to the opposite polarity electrode and the battery lid can be electrically insulated. it can. At this time, if the periphery of the through hole or notch formed at a position above the terminal in the center is covered with an insulating member, when connecting the terminal and an external load or the like through the through hole or notch, Insulation between the terminal having the opposite polarity and the sealing member can be ensured. Furthermore, when a connecting member for electrically connecting to an external load is connected to the terminal, an insulating member that insulates the connecting member from the sealing member is preferably interposed between the sealing member and the connecting member. At this time, the connecting member may have a protruding portion protruding toward the terminal, and the protruding portion may be electrically and mechanically connected to the terminal.

  According to the present invention, the central portion located above the battery lid and the legs bent along the both sides of the flat portion of the battery case from the central portion, the opening of the caulking portion between the battery lid and the battery case is sealed. The sealing member to be stopped is disposed across the battery lid so that the leg part contacts the flat part, and the end part of the leg part is fixed to the flat part over 70% of the length of the flat part in the longitudinal direction. Therefore, it is possible to reliably prevent the caulked portion between the battery lid and the battery container from opening against deformation due to an internal pressure increase or external force when the battery is abnormal, and the battery lid is disposed at the center portion. Since a through hole or a notch is formed at a position above the gas release valve and the terminal, it is possible to obtain an effect that the connection between the terminal and an external load and the operation of the gas release valve can be ensured.

  Hereinafter, an embodiment in which the present invention is applied to a flat wound lithium ion secondary battery will be described with reference to the drawings.

(Constitution)
As shown in FIG. 1, a flat wound lithium ion secondary battery 20 includes a battery can 7 as a bottomed flat battery container and a battery lid 8 that can be fitted to an opening of the battery can 7. Yes. The side surface of the battery can 7 has parallel plane parts 4, and the upper ends of both plane parts 4 form a straight part parallel to the longitudinal direction. The battery can 7 is made of rolled steel and is formed so as to be capable of deep drawing, and is electroplated with nickel including the inner surface. In the battery can 7, a flat wound group (not shown) in which the positive electrode plate and the negative electrode plate are wound in a flat shape is accommodated.

  In the flat wound group (not shown), a positive electrode plate and a negative electrode plate are wound around a flat shaft core made of an electrically insulating material via a separator. In this example, a microporous polyethylene film having a thickness of 30 μm is used as the separator. The uncoated portions for collecting current formed on the positive electrode plate and the negative electrode plate are led out to the opposite sides from both end faces of the flat wound group. The plain portion of the positive electrode plate derived from the flat wound group is electrically connected to the battery lid 8 through the block-shaped positive electrode current collecting member in the battery can 7. On the other hand, the plain portion of the negative electrode plate is electrically connected to the battery can 7 through the block-shaped negative electrode current collecting member in the battery can 7.

  In the positive electrode plate constituting the flat wound group, the positive electrode mixture is applied substantially uniformly on both surfaces of the aluminum foil of the positive electrode current collector. The positive electrode mixture contains a lithium transition metal composite oxide as a positive electrode active material, carbon powder as a conductive material, and a binder. A solid portion where a positive electrode mixture is not applied for current collection is formed on part of the positive electrode plate. On the other hand, in the negative electrode plate, the negative electrode mixture is applied substantially uniformly on both surfaces of the copper foil of the negative electrode current collector. The negative electrode mixture contains a graphite powder and a binder capable of reversibly occluding and releasing lithium ions as a negative electrode active material. A solid portion where no negative electrode mixture is applied for current collection is also formed on a part of the negative electrode plate.

  The battery cover 8 is made of an aluminum alloy plate, and a positive external terminal 12 protruding upward is formed at a position deviated from the center to one side in the longitudinal direction. A positive electrode current collecting member is connected to the external terminal 12 in the battery can 7. A gas release valve 13 that releases the internal pressure when the internal pressure rises is disposed at a position that deviates from the center of the battery lid 8 to the other side in the longitudinal direction. The battery lid 8 is caulked to the opening of the battery can 7 via an electrically insulating gasket to form a sealing portion 5. Note that a predetermined amount of an electrolyte that infiltrates the flat wound group is injected into the battery can 7. As the electrolytic solution, a solution obtained by dissolving lithium hexafluorophosphate in a carbonate-based mixed solvent such as ethylene carbonate (EC) or dimethyl carbonate (DMC) so as to be 1 mol / L is used.

  On the upper side of the battery lid 8, an opening stopper 1 as a metal sealing member is disposed so as to straddle the battery lid 8 in both longitudinal directions of the sealing portion 5. The opening stopper 1 has a central portion 1a located above the battery lid 8, and leg portions 1b bent downward along the both sides of the flat portion 4 from the central portion 1a. A substantially semicircular cutout is formed in the lower portion of the leg 1b. The leg part 1b is in contact with both sides of the flat part 4, and the lower end part of the leg part 1b is joined (fixed) to the flat part 4 by resistance welding. For this reason, the stopper 1 is electrically connected to the negative electrode plate. The length in the longitudinal direction of the leg portion 1 b fixed to the plane portion 4 is set to 70% or more of the length in the longitudinal direction of the plane portion 4. The leg portion 1b has a non-contact portion that is not in contact with the plane portion 4, that is, a portion from both ends in the longitudinal direction of the leg portion 1b to both ends in the longitudinal direction of the plane portion 4 and a substantially semicircular shape of the leg portion 1b. A notched portion is formed. The length of the non-contact portion is set to be less than 15% with respect to the entire length of the flat portion 4 in the longitudinal direction. In the central portion 1a, through holes 2 are formed at positions above the external terminal 12 and above the gas release valve 13, respectively. The center portion 1a, the surface of the leg portion 1b facing the battery lid 8, and the periphery of the through hole 2 formed at a position above the external terminal 12 are electrically insulated resin exterior 18a (insulating member) and Each is covered with a resin exterior 18b (insulating member). Note that a through hole having the same size as the through hole 2 is formed at the position of the through hole 2 in the resin exterior 18a.

(Action etc.)
Next, the operation and the like of the lithium ion secondary battery 20 of the present embodiment will be described.

  In the lithium ion secondary battery 20 of the present embodiment, the opening stopper 1 is disposed so as to straddle the battery lid 8 in both longitudinal directions of the sealing portion 5, and the lower end portion of the leg portion 1 b is a flat portion of the battery can 7. 4 is joined to both sides by resistance welding. For this reason, even if the internal pressure of the lithium ion secondary battery 20 rises when the battery is abnormal (when the battery is used), the sealing portions 5 in both longitudinal directions are prevented from being easily opened by the holding force of the opening stopper 1. (The opening of the sealing portion 5 can be sealed).

  Further, the length in the longitudinal direction of the leg portion 1 b fixed to the plane portion 4 is less than 70% of the length in the longitudinal direction of the plane portion 4, or the non-contact portion where the leg portion 1 b is not in contact with the plane portion 4. If the length is 15% or more with respect to the total length in the longitudinal direction of the flat surface portion 4, it is substantially difficult to prevent unintended opening of the sealing portions 5 in both longitudinal directions when the internal pressure is increased. In the lithium ion secondary battery 20 of the present embodiment, the lower end portion of the leg portion 1b is fixed to the plane portion 4 over 70% of the length in the longitudinal direction of the plane portion 4, and the leg portion 1b is not covered. The length of the contact portion is set to less than 15%. For this reason, the opening of the sealing part 5 can be reliably sealed.

  Furthermore, in the lithium ion secondary battery 20 of the present embodiment, the through holes 2 are formed at positions above the external terminal 12 and the gas release valve 13 in the central portion 1a. For this reason, when connecting an external load to the external terminal 12 or connecting a plurality of batteries to form an assembled battery, it is possible to ensure an electrical connection without the obstruction 1 becoming an obstacle. Further, when the battery internal pressure rises due to gas generation at the time of battery abnormality or the like and the gas release valve operates, the battery internal pressure can be released without hindering gas release.

  Furthermore, in the lithium ion secondary battery 20 of the present embodiment, the leg portion 1b is welded to the flat portion 4 of the battery can 7 connected to the negative electrode plate, so that it is connected to the stopper 1 and the positive electrode plate. The battery lid 8 has the opposite polarity. Since the surfaces facing the battery cover 8 of the central part 1a and the leg part 1b are covered with a resin exterior 18a having electrical insulation, insulation between the stopper 1 and the battery cover 8 is secured, and the positive and negative electrodes are short-circuited. Can be prevented. Further, the periphery of the through hole 2 formed at a position above the external terminal 12 of the stopper 1 is covered with a resin exterior 18b having electrical insulation. For this reason, even if an external load or the like is connected to the external terminal 12, insulation between the external terminal 12 having the opposite polarity and the opening stopper 1 is ensured, and a short circuit between the positive and negative electrodes can be prevented.

  Furthermore, in the lithium ion secondary battery 20 of the present embodiment, the leg portion 1b is brought into contact with both sides of the flat portion 4 so as to straddle both longitudinal directions of the sealing portion 5, and the lower end portion of the leg portion 1b is a flat portion. The opening stopper 1 can be attached simply by resistance welding to 4. For this reason, it is possible to prevent the volume efficiency (volume energy density) from being lowered without fixing the reinforcing member or the insulating plate in the battery as in the conventional example, and to reduce the number of processing steps and the number of parts when manufacturing the battery. be able to.

  In the present embodiment, resistance welding that is less likely to come off even when the temperature rises is exemplified as a method of fixing the leg portion 1b to the flat portion 4, but the present invention is not limited to this, for example, It may be fixed by fastening a wire or the like. For example, as shown in FIG. 2, when a groove (groove) is formed on the lower side of the sealing portion 5 where the battery lid 8 is crimped to the battery can 7, the shape along the groove is formed. This can be realized by fastening the opening stopper 1 having the leg portion 1 b with the wire 3. The surfaces of the central part 1a and the leg part 1b facing the battery cover 8 electrically insulate the battery cover 8 from the central part 1a and the leg part 1b having the opposite polarities, so that an electrically insulating resin exterior 18a is provided. Covered with. It is important to select a fastening member such as the wire 3 having sufficient strength, and to secure a sufficient fastening strength by, for example, welding after twisting metal wires together. Considering preparation and fastening of the wire 3 and the like, it is preferable to join by resistance welding.

  Further, when connecting the lithium ion secondary battery 20 to an external load or another lithium ion secondary battery, a connection member such as a metal plate is connected to the external terminal 12 disposed on the battery lid 8 to form an energization path. To do. This can be done, for example, by fixing the connecting member 15 to the external terminal 12 and electrically connecting it as shown in FIG. The connection member 15 is formed with a protrusion 16 protruding toward the lithium ion secondary battery 20 side. By connecting the projection 16 to the external terminal 12 and pressurizing and welding from the upper side of the connection member 15, the connection member 15 and the external terminal 12 can be electrically and mechanically connected. The surface of the central portion 1a facing the connecting member 15 is covered with an electrically insulating resin sheath 18c in order to electrically insulate the opening stopper 1 having the opposite polarity from the connecting member 15. In this case, instead of forming the protrusion 16 on the connecting member 15, the external terminal 12 may be protruded by an amount corresponding to the thickness of the stopper 1. Considering pressurization from the upper side of the connection member 15 and welding, it is easier to form the protrusion 16 on the connection member 15 from the viewpoint of securing the strength. In addition, if the connection member 15 is formed by cutting and raising a part of the leg portion 1b, the number of parts is reduced and the cost is reduced in manufacturing an assembled battery or the like for connecting a plurality of lithium ion secondary batteries 20. be able to. By cutting and raising a part of the leg portion 1b, the length of the leg portion 1b fixed to the flat surface portion 4 may be less than 70% with respect to the total length of the flat surface portion 4. It has been confirmed that the opening of the sealing part 5 can be prevented if it is 70% or more on one side of the flat part 4.

  Furthermore, in this embodiment, although the example which forms the through-hole 2 in the center part 1a was shown, this invention is not limited to this. For example, instead of the through hole 2 depending on the position of the external terminal 12 and the gas release valve 13 and the length of the opening stopper 1, notches may be formed at both ends in the longitudinal direction of the central portion 1a. One through hole may be formed above 12 and the gas release valve 13. In addition, the size of the through hole 2 (or notch) is such that the unintentional opening of the sealing portion 5 is prevented and the mechanical strength of the locking stopper 1 is ensured, the connection between the external terminal 12 and an external load, etc. It is desirable to make it as small as possible as long as the operation of the discharge valve 13 is not hindered.

  Furthermore, in the present embodiment, an example in which one part is fixed so that the opening stopper 1 straddles the battery lid 8 in both longitudinal directions of the lithium ion secondary battery 20 is shown, but the present invention is limited to this. Instead, it may be two or more parts. In consideration of the reduction in the number of parts and the number of battery assembly steps, it is desirable to dispose the one-part stopper 1 at substantially the center in both longitudinal directions. Further, for example, if the opening stopper 1 has a cross-sectional shape along the battery can 7 (see also FIG. 2), the opening stopper 1 is required when a plurality of batteries are connected or when the battery is assembled to an electric device or the like. Space can be reduced.

  Furthermore, in the present embodiment, the surfaces facing the battery lid 8 of the central portion 1a and the leg portion 1b are covered with the resin outer casing 18a, and the periphery of the through hole 2 formed at a position above the external terminal 12 is made of the resin outer casing. Although the example which covers with 18b and covers the surface which faces the connection member 15 of the center part 1a with the resin exterior 18c was shown, this invention is not restrict | limited to this. The resin exteriors 18a, 18b, and 18c may be made of the same material instead of different members. For example, the central part 1a and the leg part 1b other than the part where the leg part 1b is welded to the flat part 4 are made of a heat-shrinkable insulating film or the like. It may be coated.

  Further, in the present embodiment, the flat wound lithium ion secondary battery 20 is illustrated, but the present invention is not limited to this, and a sealed battery using a battery can having parallel flat portions, in other words, Then, it can be applied to a sealed battery such as a square, for example, which includes a substantially straight part or a straight part in the sealing part between the battery lid and the battery can. In addition to the lithium ion secondary battery, examples of the battery to which the present invention can be applied include a nickel hydrogen battery and a nickel cadmium battery. Furthermore, there is no restriction | limiting in materials, such as a positive / negative electrode active material, a electrically conductive material, and electrolyte solution, It cannot be overemphasized that the material used normally may be used.

  Hereinafter, examples of the lithium ion secondary battery 20 manufactured according to the present embodiment will be described. In addition, it describes together about the lithium ion secondary battery of the comparative example produced for the comparison.

Example 1
In Example 1, the length of the locking stopper 1 is set to 70% of the longitudinal direction of the flat surface portion 4, and the locking stopper 1 is fixed substantially at the center in both longitudinal directions so as to straddle the battery lid 8. 20 was produced.

(Comparative Example 1)
In Comparative Example 1, a flat sealed lithium ion secondary battery in which the length of the opening stopper was about 50% of the longitudinal direction of the plane portion and the opening stopper was fixed at substantially the center in both longitudinal directions so as to straddle the battery lid was produced. .

(Comparative Example 2)
In Comparative Example 2, a conventional flat sealed lithium ion secondary battery that does not use an opening stopper was produced.

(Evaluation)
For each of the 20 batteries of each of the examples and comparative examples that were produced, after being charged to a fully charged state (battery open circuit voltage OCV of about 4.15 V), it was placed horizontally and approximately in the center of the flat wound group A nail penetration test was conducted in which a nail was pierced and the internal short circuit was intentionally made. The results of observing the behavior of the battery are: 1. There is no opening of the unintended part (sealing part 5). 2. There is an opening of an unintended part, but there is no scattering of contents. Evaluation is divided into three stages: unintentional opening occurs and contents are scattered, and the safety score for each stage is 2 points for stage 1, 1 point for stage 2, and 0 point for stage 3 The safety scores for 20 batteries tested were totaled. The results of the nail penetration test are shown in Table 1 below.

  As shown in Table 1, in the battery of Comparative Example 1 in which the length of the stopper is 50% of the length in the longitudinal direction of the flat surface portion, 13 of the 20 batteries tested were unintended opening portions. The contents were scattered in 9 of them. The safety score was 9 points for 0 points and 4 points for 13 points (13 to 9 points), for a total of 18 points. In the battery of Comparative Example 2 that did not use an opening stopper, scattering of the contents was observed in all the batteries, and the total safety score was 0. On the other hand, in the lithium ion secondary battery 20 of Example 1 in which the length of the stopper 1 is 70% of the longitudinal direction of the plane portion 4, no unintended opening is recognized in all the batteries tested. The score was 40, and the highest safety score was obtained.

  Therefore, by setting the length of the opening stopper 1 to 70% of the longitudinal direction of the flat surface portion 4, even if the internal pressure of the battery increases during battery abuse, the sealing portion 5 of the lithium ion secondary battery 20 is not intended. It was found that the safety can be improved because the opening is prevented and the scattering of the contents is avoided.

  The present invention provides a sealed battery that can prevent the caulking portion between the battery lid and the battery container from being opened and that can ensure electrical connection and operation of the gas release valve. Therefore, it has industrial applicability.

It is a perspective view which shows the flat winding type lithium ion secondary battery of embodiment to which this invention is applied. It is a fragmentary sectional view which shows the part which fastened the opening stop with the wire according to the hollow of the grooving of the flat battery which can apply this invention.

Explanation of symbols

1 Opening stopper (sealing member)
1a Center part 1b Leg part 2 Through hole 4 Plane part 5 Sealing part (caulking part)
7 Battery can (battery container)
8 Battery cover 12 External terminal (terminal)
13 Gas release valve 20 Flat wound type lithium ion secondary battery (sealed battery)

Claims (6)

  In a sealed battery in which a battery lid provided with a gas release valve for releasing internal pressure and a terminal for electrical connection is caulked in a battery container having parallel plane portions, a central portion located above the battery lid and the center A sealing member that has a leg portion bent along both sides of the flat portion of the battery container from a portion and seals an opening of a caulking portion between the battery lid and the battery container, and the leg portion is connected to the flat portion. The end of the leg is fixed to the flat part over 70% or more of the length in the longitudinal direction of the flat part, and the center part has A sealed battery, wherein a through hole or a notch is formed at a position above the gas release valve and the terminal.   The leg portion is formed with a non-contact portion that is not in contact with the flat portion, and the length of the non-contact portion is less than 15% with respect to the total length in the longitudinal direction of the flat portion. The sealed battery according to claim 1.   3. The sealed battery according to claim 1, wherein the center portion and the leg portion are covered with an insulating member on a surface facing the battery lid. 4.   The sealed battery according to claim 3, wherein the central portion is covered with an insulating member around a through hole or notch formed at a position above the terminal.   The terminal is connected to a connecting member for electrically connecting to an external load, and an insulating member for insulating the connecting member from the sealing member is interposed between the sealing member and the connecting member. The sealed battery according to any one of claims 1 to 4, wherein the battery is a sealed battery.   The sealed type according to claim 5, wherein the connecting member has a protruding portion protruding toward the terminal, and the protruding portion is electrically and mechanically connected to the terminal. battery.

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