JP2014107054A - Sealed battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealed battery including a sealing body with a gas discharge valve having excellent conductivity, with high productivity.SOLUTION: In a sealed battery where the opening of a bottomed cylindrical outer can is sealed with a sealing body having a terminal cap and a gas discharge valve, the terminal cap includes an outer terminal projecting convexly outward of the battery, a flange located on the periphery of the outer terminal, a degassing hole provided at the projection corner of the outer terminal, and a slit provided in the projection side sidewall of the outer terminal in the circumferential direction of the sidewall.

Description

  The present invention relates to a sealed battery, and more particularly to a sealed battery including a sealing body with a gas discharge valve.

  Nonaqueous electrolyte secondary batteries have high energy density and high capacity, and are therefore widely used as drive power sources for portable devices and electric tools.

  Since nonflammable secondary batteries use flammable organic solvents, it is required to ensure the safety of the batteries. For this reason, a gas discharge mechanism that discharges gas inside the battery to the outside of the battery when the internal pressure of the battery rises is incorporated in a sealing body that seals the battery (see, for example, Patent Document 1).

JP2009-272085

  The technique according to Patent Document 1 will be described with reference to FIG. 6A and 6B are diagrams showing a terminal cap of a sealing body used in a sealed battery according to Patent Document 1, wherein FIG. 6A is a plan view, FIG. 6B is an end view, and FIG. It is an end elevation at the time of battery internal pressure rise.

  The sealing body of the sealed battery according to Patent Document 1 includes a terminal cap 18 and a gas discharge valve (not shown). In addition, a gas vent hole 18c for discharging the gas generated inside the battery is provided at a corner of the terminal cap 18, and a thin wall portion 18f having a small thickness is formed on a top surface portion continuous with the gas vent hole 18c. Is provided. According to this technique, the gas discharge valve operates when the battery internal pressure rises, and the gas in the battery can be discharged to the outside of the battery via the gas discharge valve and the gas vent hole 18c. In addition, the thin wall portion 18f is deformed toward the outside of the battery due to the gas pressure, or the thin wall portion 18f is melted or melted by the heat of the discharged gas, thereby expanding the area where the gas can be discharged, It is said that it can be discharged quickly.

  By the way, with the recent increase in capacity of batteries, gas is rapidly generated, and a problem arises that a battery element is pushed up by gas pressure and a vent hole is blocked. Yes. However, the technique of Patent Document 1 does not consider such a problem. Moreover, in the technique of patent document 1, since the intensity | strength of a terminal cap falls by a thin part, there also existed a problem that there exists a possibility of deform | transforming at the time of welding or receiving an impact.

  This invention solves the said subject, and it aims at providing the sealed battery provided with the sealing body with a gas exhaust valve which has high safety | security without causing the remarkable fall of intensity | strength.

  The present invention for solving the above-mentioned problems is a sealed battery in which an opening of a bottomed cylindrical outer can is sealed by a sealing body having a terminal cap and a gas discharge valve. An external terminal portion protruding in a convex shape toward the direction, a flange portion located at the periphery of the external terminal portion, a gas vent hole provided in a protruding corner portion of the external terminal portion, and a protrusion of the external terminal portion And a slit provided in the side wall portion along the circumferential direction of the side wall.

  The effect of the above configuration will be described with reference to FIG. 2A and 2B are diagrams showing a terminal cap of a sealing body used for a sealed battery according to the present invention, in which FIG. 2A is a plan view, and FIG. 2B is a BB line in FIG. FIG. 2C is an end view taken along the line AA of FIG. 2A, and FIG. 2D is an end view taken along the line AA when the battery internal pressure is increased.

  As shown in FIGS. 2 (a) to 2 (c), the terminal cap 18 of the sealed battery sealing body according to the present invention includes a gas vent 18c provided in the protruding corner portion of the external terminal portion 18a, and an external terminal. And a slit 18d provided in the protruding side wall portion 181a of the portion 18a and parallel to the circumferential direction of the side wall. For this reason, when the internal pressure of the battery rises and a gas discharge valve (not shown) is operated, the gas is quickly discharged from the gas vent hole 18c. When the gas discharge becomes abrupt, the terminal cap 18 is deformed so as to swell outward by the gas pressure, but the strength of the terminal cap 18 against such deformation is weakened by the slit 18d. . For this reason, the top surface of the external terminal portion 18a is opened upward by the deformation force, and a large gas venting path is formed (see FIG. 2D). As a result, even when gas is rapidly generated or when the gas vent hole 18c is blocked by another battery element, it is possible to quickly release the gas, and the safety of the battery is dramatically increased.

  Further, even if the slit 18d is provided in the terminal cap 18, the strength is not reduced so as to cause deformation during welding. Therefore, according to the said structure, the sealed battery provided with the sealing body with the gas exhaust valve which improved safety can be provided, without causing a remarkable fall of intensity | strength.

  The said structure WHEREIN: It can be set as the structure by which the resin component or the metal component is pinched | interposed into the said slit. Moreover, the said resin component or the said metal component can be set as the structure currently fixed to the said slit with the adhesive.

  If the terminal cap 18 is provided with the slit 18d, the strength of the terminal cap 18 is reduced until the slit 18d is closed when pressed from above the battery. Here, when a resin part or a metal part is sandwiched in the slit 18d, or a resin part or a metal part sandwiched by an adhesive is fixed to the slit 18d, the compression strength from above can be increased. Note that even if a resin part or a metal part is sandwiched in the slit 18d or is fixed with an adhesive, the deformability of the top surface of the external terminal portion with respect to the pressure from the inside of the battery is not reduced.

  Polycarbonate, phenol resin, or the like can be used as the material for the resin component, and nickel, stainless steel, or the like can be used as the material for the metal component. Moreover, as an adhesive, an acrylic adhesive material, a rubber-type adhesive material, etc. can be used.

  Here, as shown in FIG. 2B, when the end of the gas vent hole 18c is provided so as to be in contact with the flange portion 18b, the protruding side wall portion 181a of the external terminal portion 18a of the terminal cap 18 It becomes a structure which exists only in the area | region between the punch holes 18c. Further, when the end portion of the gas vent hole 18c is provided so as not to contact the flange portion 18b, the protruding side wall portion of the external terminal portion 18a of the terminal cap 18 has a region between the gas vent holes and the gas vent hole 18c. And the region between the flange portion 18b. In the latter case, it is preferable to provide a slit in the protruding side wall portion 181a existing in the region between the vent holes. When the slit 18d is provided in the region between the gas vent holes, the length of the slit 18d (the length in the circumferential direction) is the length of the region between the gas vent holes in which the slit 18d is provided (the protruding side wall portion 181a). (Circumferential length) or less. Further, the slit 18d and the gas vent hole 18c may or may not be connected, but it is preferable that at least one end of the slit 18d is connected to the gas vent hole.

  The width of the slit 18d is preferably 0 to 0.2 mm. Here, the width of the slit 18d being 0 mm means that the slit 18d is deformed so as to fill the gap of the slit 18d after being provided.

  Further, the gas vent hole 18c and the slit 18d may be plural in number. The number of slits 18d is preferably 30 to 50% of the number of protruding side wall portions (30 to 50% of the number of gas vent holes 18c). Further, when a plurality of slits 18d are provided, it is preferably provided asymmetrically with respect to the battery axis. For example, when the number of protruding side wall parts 181a is four and two slits 18d are provided, it is preferable to provide the slits 18d on adjacent protruding side wall parts 181a. By arranging the slits 18d so as to be biased in this way, the strength against the gas pressure generated in the battery becomes unbalanced, so that the top surface of the external terminal portion 18a can be quickly opened upward.

  Moreover, it is preferable that the total length at the protruding corner portion of the gas vent hole 18c is about 50% of the peripheral length at the protruding corner portion.

  According to the present invention, a sealing body with a gas discharge valve capable of quickly discharging gas can be realized without causing a significant decrease in strength, and the safety of a sealed battery using the same can be improved.

FIG. 1 is an exploded perspective view of a cross section of a sealed battery according to the present invention. 2A and 2B are diagrams showing a terminal cap of a sealing body used in the sealed battery according to Example 1, in which FIG. 2A is a plan view and FIG. 2B is a cross-sectional view taken along line BB in FIG. FIG. 2C is an end view taken along the line AA of FIG. 2A, and FIG. 2D is an end view taken along the line AA when the battery internal pressure is increased. 3A and 3B are diagrams showing a terminal cap of a sealing body used for a sealed battery according to Example 2, in which FIG. 3A is a plan view, and FIG. 3B is an AA of FIG. FIG. 3C is an end view when the internal pressure of the battery is increased. 4A and 4B are diagrams showing a terminal cap of a sealing body used in a sealed battery according to Comparative Example 1, in which FIG. 4A is a plan view, and FIG. 4B is an AA of FIG. FIG. 4C is an end view when the battery internal pressure is increased. 5A and 5B are diagrams showing a terminal cap of a sealing body used for a sealed battery according to Comparative Example 3, in which FIG. 5A is a plan view, and FIG. 5B is an AA of FIG. 5A. FIG. 5C is an end view when the internal pressure of the battery is increased. 6A and 6B are diagrams showing a terminal cap of a sealing body used for a sealed battery according to the prior art, in which FIG. 6A is a plan view and FIG. 6B is an AA line in FIG. 6A. FIG. 6C is an end view when the internal pressure of the battery is increased.

(Embodiment 1)
The form for implementing this invention is demonstrated in detail using drawing, using the example applied to the lithium ion secondary battery. FIG. 1 is an exploded perspective view of a cross-section part of a sealed battery according to the present embodiment, and FIG. 2 is a diagram showing a terminal cap of a sealing body used in the sealed battery according to the present invention. 2A is a plan view, FIG. 2B is an end view, and FIG. 2C is an end view when the battery internal pressure increases.

  As shown in FIG. 1, the nonaqueous electrolyte secondary battery 10 according to the present embodiment includes a spiral electrode body 14 in which a positive electrode plate 11 and a negative electrode plate 12 are spirally wound via a separator 13. Yes. The spiral electrode body 14 has insulating plates 15 and 15 arranged on the upper and lower sides, respectively, and is housed inside a bottomed cylindrical metal outer can 16. The current collecting tab 12 a of the negative electrode plate 12 is welded to the inner bottom portion of the outer can 16, and the current collecting tab 11 a of the positive electrode plate 11 is welded to the lower surface of the sealing body 20. Thereby, the armored can 16 functions as a negative electrode external terminal, and the sealing body 20 functions as a positive electrode external terminal. A non-aqueous electrolyte (not shown) is injected into the exterior can 16, and the opening of the exterior can 16 is sealed with a sealing body 20 via a gasket 19. Further, the sealing body 20 is provided with a gas discharge valve 17 that operates when the battery internal pressure rises.

  2A to 2C, the terminal cap 18 includes an external terminal portion 18a protruding outward from the battery, a flange portion 18b positioned at the periphery of the external terminal portion 18a, and an external terminal portion. A gas vent hole 18c provided in the protruding corner portion of 18a and a slit 18d provided in the protruding side wall portion of the external terminal portion 18a and parallel to the circumferential direction of the side wall are provided. In the present embodiment, there are six gas vent holes, and the end portions of the gas vent holes 18c are provided so as to contact the flange portion 18b (see FIGS. 2A and 2B). Therefore, the protruding side wall portion 181a of the external terminal portion 18a of the terminal cap 18 is configured to exist only in the region between the gas vent holes (there are six protruding side wall portions 181a). The number of slits is two, and two continuous sidewall portions 181a are provided so that both ends thereof are in contact with the gas vent holes 18c.

  In this configuration, when the internal pressure of the battery rises and a gas discharge valve (not shown in FIG. 2) operates, the gas is quickly discharged from the gas vent hole 18c. When the gas discharge becomes abrupt, the terminal cap 18 is deformed so as to swell outward by the gas pressure, but the strength of the terminal cap 18 against such deformation is weakened by the slit 18d. . For this reason, the top surface of the external terminal portion 18a is opened upward by the deformation force, and a large gas venting path is formed (see FIG. 2D). As a result, even when gas is rapidly generated or when the gas vent hole 18c is blocked by another battery element, it is possible to quickly release the gas, and the safety of the battery is dramatically increased.

  Moreover, even if the slit is provided, there is no reduction in strength that causes deformation during welding. Therefore, according to the present embodiment, it is possible to provide a sealed battery including a sealing body with a gas discharge valve with improved safety without causing a significant decrease in strength.

  Here, in order to increase the pressure resistance from above the terminal cap 18, as shown in FIG. 3A, a resin part (or metal part) 18e may be sandwiched between the slits 18d. You may fix to a slit with an adhesive. Note that even if a resin part or a metal part is sandwiched in the slit or is fixed with an adhesive, the deformability of the external terminal top surface against the pressure from the inside of the battery does not deteriorate.

  The number of the gas vent holes 18c and the slits 18d may be one or plural, but the number of the slits 18d may be the protruding side wall portion 181a (when the gas vent hole is not in contact with the flange portion). 30 to 50% of the number of regions between the gas vent holes) (2 to 3 when the number of gas vent holes is six). Moreover, when providing the slit 18d with two or more, it is preferable to provide asymmetrically with respect to the axis | shaft of a cylindrical battery. For example, when the number of protruding side wall parts 181a is six and two slits 18d are provided, it is preferable to provide the slits 18d continuously to the adjacent protruding side wall parts 181a. By arranging the slits 18d so as to be biased in this way, the strength against the gas pressure generated in the battery becomes unbalanced, so that the top surface of the external terminal portion 18a can be quickly opened upward.

  The width of the slit 18d is preferably 0 to 0.2 mm. Here, the width of the slit 18d being 0 mm means that the slit 18d is deformed so as to fill the gap of the slit 18d after being provided. Moreover, it is preferable that the length (circumferential length) of the slit 18d is equal to or less than the length (circumferential length) of the protruding sidewall portion 181a provided with the slit 18d. The total length of the gas vent holes 18c (the length at the protruding corner) is preferably about 50% of the peripheral length of the protruding corner. Further, the slit 18d and the gas vent hole 18c may or may not be connected, but it is preferable that at least one end of the slit 18d and the gas vent hole 18c are connected.

  Next, the present invention will be further described using examples.

Example 1
<Preparation of positive electrode>
A positive electrode active material made of lithium cobaltate (LiCoO ₂ ), a carbon-based conductive agent such as artificial graphite, and a binder made of polyvinylidene fluoride (PVDF) are in a mass ratio of 85.5: 9.5: 5. These were weighed and mixed with an organic solvent composed of N-methyl-2-pyrrolidone to prepare a positive electrode active material slurry.

  Next, this positive electrode active material slurry was applied with a uniform thickness on both surfaces of a positive electrode core made of aluminum foil (thickness: 20 μm) using a doctor blade.

  This electrode plate is passed through a dryer to remove the organic solvent, and a dry electrode plate is produced. The dried electrode plate was rolled using a roll press and cut. Then, the positive electrode current collection tab 11a which consists of aluminum foil was attached by ultrasonic welding, and the positive electrode plate 11 was produced.

<Production of negative electrode>
A negative electrode active material made of graphite particles, a binder made of styrene butadiene rubber, and a thickener made of carboxymethyl cellulose are mixed at a mass ratio of 100: 3: 2, and these are mixed with an appropriate amount of water. A negative electrode active material slurry was prepared.

  Next, using a doctor blade, the negative electrode active material slurry was applied to both surfaces of a negative electrode core made of copper foil (thickness: 15 μm) with a uniform thickness.

  The electrode plate is passed through a dryer to remove moisture, and a dried electrode plate is produced. Then, this dry electrode plate was rolled with a roll press and cut. Then, the negative electrode current collection tab 12a which consists of copper foils was attached by ultrasonic welding, and the negative electrode plate 12 was produced.

<Production of electrode body>
The positive electrode, the negative electrode, and the separator 13 made of a polyethylene microporous film were wound by a winder, and an insulating anti-winding tape was provided to complete the wound electrode body 14.

<Preparation of sealing body>
External terminal portion 18a protruding outward from the battery, flange portion 18b positioned at the periphery of external terminal portion 18a, and gas vent hole 18c provided at the protruding corner of external terminal portion 18a so as to be in contact with flange portion 18b And a terminal cap 18 having a slit 18d provided in the protruding side wall portion of the external terminal portion 18a is manufactured by a known method such as plastic working. The terminal cap is made of iron and has a thickness of 0.3 mm. Here, the slit 18d may be provided before the formation of the external terminal portion 18a, or may be provided after the formation of the external terminal portion 18a.

  Using this terminal cap 18, a sealing body 20 was produced by a known method. The gas discharge valve 17 of the sealing body 20 is provided with a circumferential notch (diameter 4 mm) that facilitates breakage due to battery internal pressure. Moreover, the slit was provided in three continuous protrusion side wall parts 181a among the six protrusion side wall parts 181a. The width of the slit 18d is 0.2 mm, and the length is the same as the length of the protruding side wall 181a. That is, the adjacent vent holes 18c are connected by the slit 18c.

<Preparation of non-aqueous electrolyte>
LiPF ₆ as an electrolyte salt is 1.0 M in a non-aqueous solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed at a volume ratio of 1: 1 (when converted to 1 atm and 25 ° C.). What was melt | dissolved in the ratio of (mol / liter) was made into the nonaqueous electrolyte.

<Battery assembly>
The insulating plates 15 and 15 were placed above and below the electrode body, and the negative electrode current collecting tab 12a and the bottom of the cylindrical outer can were welded. Thereafter, the non-aqueous electrolyte was injected into the cylindrical outer can 16 to electrically connect the terminal plate of the sealing body 20 and the positive electrode current collecting tab 11a. Thereafter, the opening of the outer can 16 was sealed by caulking using the sealing body 20 and the gasket 19 to produce a sealed battery according to Example 1 having a height of 65 mm and a diameter of 18 mm.

(Example 2)
As shown in FIG. 3, a sealed battery according to Example 2 was manufactured in the same manner as in the above embodiment except that a polycarbonate resin part 18e was fitted in the slit 18d.

(Comparative Example 1)
As shown in FIGS. 4A and 4B, a sealed battery according to Comparative Example 1 was manufactured in the same manner as in the above embodiment, except that a terminal cap having no slit was used.

(Comparative Example 2)
A sealed battery according to Comparative Example 2 is the same as Comparative Example 1 except that a stainless steel center pin having an inner diameter of 2.7 mm, an outer diameter of 3 mm, and a length of 60 mm is fitted after the winding core of the electrode body is removed. Was made.

(Comparative Example 3)
As shown in FIGS. 5A and 5B, except that the area of the vent hole of the terminal cap is 1.5 times (the size of the vent hole is increased 1.5 times in the circumferential direction). Produced a sealed battery according to Comparative Example 3 in the same manner as in Comparative Example 1 above.

(Comparative Example 4)
As shown in FIGS. 6 (a) and 6 (b), similarly to Patent Document 1, there are three gas vent holes 18c and a thin portion 18f (residual thickness 0.1 mm) in the region connected to the three gas vent holes 18c. A sealed battery according to Comparative Example 4 was produced in the same manner as Comparative Example 1 except that was formed.

[Safety test]
Thirty sealed batteries according to Examples 1 and 2 and Comparative Examples 1 to 4 were prepared, and these batteries had a voltage of 4.4 V at a constant current of 1 It (2850 mA) in a room temperature (25 ° C.) atmosphere. The battery was then charged at a constant voltage of 4.4 V until the current reached 0.02 It (57 mA) (overcharged). Thereafter, the number of ruptured batteries was confirmed when the battery was burned by heating with a burner. The results are shown in Table 1 below.

[Lead tab welding reliability test]
30 sealing bodies of sealed batteries according to Examples 1 and 2 and Comparative Examples 1 to 4 were prepared, and nickel lead tabs (thickness 0.2 μm) were resistance-welded at a pressure of 3 kg and a current of 5 kA. . The welding range was 8 mm in diameter. The terminal cap shape before and after the test was measured with a micrometer at four points, and a deformation of 0.2 mm or more that was even one point was determined as being deformed. The results are shown in Table 1 below.

  From Table 1 above, Examples 1 and 2 in which the slit 18d was provided in the terminal cap 18 were not confirmed to burst in the combustion test, whereas Comparative Examples 1 to 4 in which no slit was provided in the terminal cap were: In the combustion test, 2-9 bursts in 30 cells have been confirmed, and it can be seen that Examples 1 and 2 have higher safety.

  This is considered as follows. When the gas discharge becomes abrupt, the terminal cap 18 is deformed so as to swell outward from the battery due to the gas pressure, but the strength of the terminal cap 18 against such deformation is weakened by the slit 18d. For this reason, the top surface of the external terminal portion 18a is opened upward by the deformation force, and a large gas venting path is formed, so that quick gas discharge is possible (see FIGS. 2D and 3C). On the other hand, when there is no slit 18d, such a large gas venting path is not formed, so that the gas in the battery cannot be released quickly, the deformation of the terminal cap 18 is increased, and some batteries are It will rupture (refer FIG.4 (c), FIG.5 (c), FIG.6 (c)).

  Further, in Examples 1 and 2 and Comparative Examples 1 and 2 in which the size of the gas vent hole is the same, deformation in tab welding was not confirmed, whereas Comparative Example 3 in which the diameter of the gas vent hole was increased. Then, deformation of the tab was confirmed in 15 of 30 cases, and deformation of the tab was confirmed in 30 of 30 cases in Comparative Example 4 provided with a thin portion, and Examples 1, 2 and the like were superior. I understand that That is, it can be seen that there is no adverse effect on welding even if a slit is provided. On the other hand, it can be seen that providing a thin part or enlarging the vent hole has an adverse effect on welding.

  Further, when Examples 1 and 2 are compared, it can be seen that there is no influence on safety even if the resin component 18e is fitted into the slit 18d. This is considered to be because, even when resin parts are used, the deformability of the top surface of the terminal cap when the terminal cap is pushed up from the inside of the battery is not affected. In addition, when a resin part is used, there exists an effect that the compression strength from the upper direction of a battery increases.

  Further, when Comparative Examples 1 and 2 were compared, it was confirmed that Comparative Example 2 using a center pin had a smaller number of bursts. This is considered to be because the gas generated on the bottom side of the can can be quickly sent to the sealing body side by using the center pin, thereby partially preventing the gas vent hole from being blocked due to the pushing up of the electrode body. . In addition, the terminal cap at the time of battery internal pressure rise was larger in Comparative Example 2 than in Comparative Example 1, and the amount of deformation was larger. From this result, it can be seen that a center pin may be used in the battery of the present invention.

  From the above test results, it was found that according to the present invention, a sealed battery equipped with a sealing body with a gas discharge valve with improved safety can be realized without causing deformation due to welding.

  As described above, according to the present invention, it is possible to provide a sealed battery including a sealing body with a gas discharge valve with improved safety without causing a significant decrease in strength. Therefore, the industrial significance is great.

DESCRIPTION OF SYMBOLS 10 Nonaqueous electrolyte secondary battery 11 Positive electrode plate 11a Positive electrode current collection tab 12 Negative electrode plate 12a Negative electrode current collection tab 13 Separator 14 Winding electrode body 15 Insulation plate 16 Outer can 17 Gas exhaust valve 18 Terminal cap 18a External terminal part 181a Projection side wall Portion 18b Flange 18c Gas vent 18d Slit 18e Resin component 18f Thin portion 19 Gasket 20 Sealing body

Claims (3)

In the sealed battery in which the opening of the bottomed cylindrical outer can is sealed by a sealing body having a terminal cap and a gas discharge valve,
The terminal cap includes an external terminal portion protruding in a convex shape toward the outside of the battery, a flange portion positioned at the periphery of the external terminal portion, and a gas vent hole provided at a protruding corner portion of the external terminal portion. , Provided in the protruding side wall portion of the external terminal portion, and a slit along the circumferential direction of the side wall,
A sealed battery characterized by that. In the sealed battery according to claim 1,
Resin parts or metal parts are sandwiched between the slits,
A sealed battery characterized by that. The sealed battery according to claim 2,
The resin part or the metal part is fixed to the slit by an adhesive,
A sealed battery characterized by that.