JPH07105218B2 - Method for manufacturing battery container used for explosion-proof sealed battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a battery container used for an explosion-proof sealed battery.

[Conventional technology]

Thionyl chloride-A non-aqueous liquid active material that uses an oxyhalide-based liquid such as thionyl chloride, sulfuryl chloride, or phosphoryl chloride as a positive electrode active material typified by a lithium battery, and an alkali metal such as lithium, sodium, or potassium in the negative electrode. The material battery has a very tight seal because it has a hermetically sealed structure, but on the other hand, due to its high tightness, it is exposed to high temperature heating and is charged at high voltage. When an abnormal situation such as the above is encountered, the internal pressure of the battery rises abnormally and the battery explodes, which may cause a loud popping noise and the battery contents may scatter around and contaminate the battery-using device. .

Therefore, regarding alkaline batteries that also have a sealed structure,
As proposed in JP-B-58-17332 and JP-B-58-26460, a groove is formed in a part of the battery container to provide a thin portion in the battery container, and the battery is provided at the thin portion. A so-called groove formation that partially lowers the withstand pressure of the container and reduces the internal pressure of the battery by breaking the thin part when the internal pressure of the battery starts to rise abnormally, preventing the battery from bursting at high pressure. It is considered necessary to provide the non-aqueous liquid active material battery having the hermetically sealed structure with the explosion-proof function of (1).

By the way, when forming the explosion-proof groove as described above,
Although the method by press molding is adopted, in non-aqueous liquid active material batteries, corrosion resistance is required for the battery constituent members to withstand the strong corrosion resistance of the positive electrode active material, and since stainless steel is generally used for the battery container, The hardness of the battery container is high, and when a groove is formed in the battery container by press molding, the load applied to the groove forming punch becomes extremely high.

Therefore, regarding the cross-sectional shape of the groove to be formed, see
It is considered that the groove can be formed most easily when the tip of the groove, that is, the bottom of the groove is V-shaped, as shown in Japanese Patent No. 17332, but the bottom of the groove is sharpened. In this case, since the tip of the punch for forming the groove is immediately damaged, it is not industrially applicable from the viewpoint of durability of the punch. Therefore, as shown in Japanese Utility Model Publication No. 58-26460, it is also considered that the durability of the groove forming punch is improved by rounding the groove bottom with 0.1 to 0.2 mmR even if the cross section is V-shaped. However, according to the study by the present inventors,
When the tip of the groove is rounded, the effect of simply reducing the thickness is exhibited, and almost no additional effects such as the notch effect are added, so a high-strength material such as stainless steel was used. In the battery container, unless the thickness of the thin part is made very thin, the breaking pressure of the thin part does not become low,
In addition, the non-aqueous liquid active material battery that has a hermetically sealed structure such as thionyl chloride-lithium battery does not exhibit a stable explosion-proof function when rapidly heated at high temperature because the opening part is narrow due to the destruction of the thin wall part. It was

Therefore, the present inventors have made the explosion-proof function stable by flattening the bottom of the groove. However, in order to form such a groove, the tip of the groove forming punch is flattened. Therefore, the load applied to the punch with a flat tip is increased, and as a result, the durability of the punch is reduced.

Therefore, the present inventors do not apply a restraining force in the thickness direction of the portion other than the groove forming portion of the battery container bottom, that is, in the thickness direction of the constituent material of the portion that is not grooved, and of the groove forming protrusion of the punch. By setting the groove forming angle to 50 to 80 °, the groove forming protrusion of the punch is pushed into the bottom of the battery container while applying tensile stress to the material forming the bottom of the groove to be formed. A flat groove can be formed on a stainless steel battery container with a low punch load, and a patent application has already been filed (Japanese Patent Application No. 61).
-228761 [JP-A-63-86244]).

However, as described above, when the groove is formed without restraint, that is, without giving a restraining force in the thickness direction of the constituent material of the portion where the groove is not processed, the portion other than the groove is projected by the reaction when the groove is formed. .

The degree of protrusion varies depending on the part, but in any case, the height of the battery container becomes higher than the planned height, which causes the total height of the battery to become large and causes the total height failure. Due to its high height, during the battery assembly process,
The battery container gets caught in the parts feeder machine, and there is a problem that the battery container cannot be supplied to the assembly line.

[Problems to be solved by the invention]

According to the present invention, when a groove for imparting an explosion-proof function to a battery is formed in the bottom of a battery container without restraint, a portion other than the groove on the bottom of the battery container partially protrudes to reduce the total height of the battery. Solved the problems that caused the problem and that the battery container could not be supplied to the assembly line during battery assembly, and while maintaining the superiority of the groove formation without restraint, the total battery height was poor. The purpose is to make it possible to manufacture battery containers that do not cause problems during battery assembly.

[Means for solving problems]

The present invention, after forming a groove for imparting an explosion-proof function to the battery in the bottom portion of the battery container without restraint, by flattening by press molding the portion protruding by the groove formation of the bottom portion of the battery container, The above object is achieved.

To flatten the part that protrudes due to the groove formation,
The battery container is placed so that the upper surface of the battery container is covered with a cylindrical lower mold having a shape conforming to the shape of the inner surface of the bottom of the battery container before the groove is formed, and the lower surface of the battery container is formed on the bottom of the battery container before the groove is formed. Press molding is used in which a molding die having a shape that conforms to the outer surface shape of the bottom is lowered and the bottom of the battery container is pressed between the lower mold and the molding die to form a desired shape.

That is, in the case where a protrusion is provided on the bottom of the battery container to facilitate the terminal connection and a groove is formed in the protrusion,
The upper surface of the lower mold has a shape in which a protrusion having a shape conforming to the inner surface shape of the protrusion of the battery container bottom is provided in the center thereof, and the lower surface of the molding die has the protrusion of the battery container bottom in the center thereof. With a shape having a recessed portion conforming to the outer surface shape, and placing the battery container on the lower mold,
Then, the molding die is lowered and pressed to flatten the projected portion due to the formation of the groove. When the bottom of the battery container is not provided with such a protrusion, the upper surface of the lower mold is flat and the lower surface of the molding die is flat, and press molding may be performed as described above. .

In the present invention, in order to carry out unconstrained formation of the groove on the bottom of the battery container, in order to prevent the base portion of the groove forming punch from coming into contact with the battery container, the height of the groove forming protrusion of the punch is set. Must be larger than the depth of the groove to be formed. In particular, in order to stably form the groove without restraint, the height H of the groove forming protrusion of the groove forming punch is determined by the groove structure of the battery container, as will be described later with reference to FIG. With respect to the thickness of the material, that is, the thickness T of the battery container and the thickness t of the thin portion provided by forming the groove, H ≧ 1.5 (T−
t) is preferred. Further, the groove forming angle θ (see FIG. 1) of the groove forming protrusion of the punch is set to 50 to 80 ° because the tensile stress applied to the material forming the bottom of the groove is insufficient when the groove forming angle is less than 50 °. Therefore, since the load applied to the groove forming protrusion of the punch becomes large, it becomes difficult to form the groove.
If the groove formation angle exceeds 80 °, it is possible to form the groove itself, but the resistance to the pressure applied from the inside of the battery due to the pressure rise inside the battery increases, so it is difficult to obtain a battery with excellent explosion-proof function. Because it will be.

〔Example〕

 Next, an embodiment of the present invention will be described with reference to the drawings.

1 to 4 are cross-sectional views showing a state in which a groove is formed in the bottom of a battery container by the method of the present invention, and a portion protruding by the groove is flattened. FIG. FIG. 2 is an enlarged cross-sectional view of an essential part of a state in which the punch is lowered and the groove forming protrusion of the punch is pushed into the bottom of the battery container, and FIG. 2 is an overall cross-sectional view before the punch is lowered. FIG. 3 is a cross-sectional view of the battery container when the groove is formed by the method shown in FIGS. FIG. 4 is a cross-sectional view showing a state in which the protruding portion due to the formation of the groove is flattened, and shows a state before the molding die for flattening is lowered. FIG. 5 is a cross-sectional view of the battery container after flattening the protruding portion by forming the groove.

First, in forming the groove, the whole will be described based on FIG. 2. In the figure, 1 is a battery container, and the battery container 1 has a diameter of 14 mm.
mm and height is 47 mm. Reference numeral 21 is a groove forming punch, 21a is a groove forming protrusion, and 21b is a punch base. The battery container 1 has a bottomed cylindrical shape,
In the drawing, it is placed so as to cover the lower mold 22 in an inverted state. And 23 is the base. The groove is formed in the battery case 1 by lowering the punch 21 from the state shown in FIG. 2 and pushing the groove forming protrusion 21a of the punch 21 into the bottom part 2 of the battery case 1 as shown in FIG. The groove 3 is formed. Tip 2 of groove forming protrusion 21a of punch 21
1a ₁ is formed as a flat surface, and the bottom of the groove 3 formed thereby becomes a flat surface. Groove forming protrusion of punch 21
The groove forming angle θ of the groove 21a is formed to be 50 to 80 °. Therefore, the constituent material of the groove bottom portion pressed by the tip 21a ₁ of the groove forming protrusion 21a of the punch 21 is shown in FIG. As described above, since the tensile stress f is applied and the portion not grooved is not restrained and is not restrained, the portion to be molded of the bottom portion 2 of the battery container 1 is easily deformed, and the deformation resistance of the portion is increased. Also, the frictional force between the groove forming protrusion 21a of the punch and the molded portion of the battery container 1 becomes small, and the groove 3 can be formed with a relatively low punch load.

However, in the unconstrained groove formation as described above, due to the formation of the groove, the bottom of the battery container is projected as shown in FIG. 3, and the total height is 47.5 mm. In addition, this may cause the total height of the battery to be defective, or make it impossible to supply the battery container to the assembly line during battery assembly.

Therefore, in the present invention, the portion that is projected by the groove formation is flattened as shown in FIG.

In FIG. 4, 31 is a molding die, 31a is a lower surface of the molding die, that is, a pressing surface, 31a ₁ is a concave portion formed in the lower surface 31a of the molding die, and this concave portion 31a ₁ is before the formation of the groove. It is formed in a shape that matches the outer surface shape of the protruding portion 2a of the bottom portion 2 of the battery container 1. 32 is a lower mold and 33 is a base.
The lower die 32 has a columnar shape, the upper surface of which has a shape conforming to the inner surface shape of the bottom portion 2 of the battery container 1 before groove formation, and the central portion of which has a protrusion 32a. The battery case 1 is placed so as to cover the cylindrical lower mold 32.

Then, the molding die 31 is attached to the bottom portion 2 of the battery container 1 on the lower die 32.
By lowering the pressure to 20 kg / cm ² and press-molding at 20 kg / cm ² , the protruding portion at the time of forming the groove was flattened to obtain a battery container 1 as shown in FIG. The height of the battery container 1 is 47 mm, which is the same height as before the groove formation.

In addition, in this embodiment, as shown in FIG.
The groove forming protrusion 21a of the groove forming punch 21 has a cross shape because it is formed to have a cross shape in a plan view. However, in FIG. However, it is not shown in the figure, but is shown in a mode in which one groove is linearly formed.

In this embodiment, the battery case 1 is formed of a stainless steel plate having a thickness of 0.3 mm, the groove forming protrusion 21a of the punch has an angle θ of 60 °, and the groove forming protrusion 21a has a tip 21a. ₁ is flat, its width is 0.15 mm, the depth of the groove 3 is 0.23 mm, the thinned portion by the formation of the groove, that is, the thin wall provided on the bottom 2 of the battery container 1 by the formation of the groove 3. The thickness of the portion 4 is 0.07 mm, and the width of the thin portion 4 is 0.15 mm. However, even if pressing is performed using general lubricating oil (such as machine oil), it is for forming the groove of the punch. The load applied to the tip of the protruding portion 21a can be set to 240 kg / mm ² or less, and the groove can be formed with high productivity. The height of the groove forming protrusion 21a of the punch is 0.7 mm, and the ungrooved portion of the battery container bottom is protruded by the pressing when forming the groove, but the upper surface of the protrusion and the punch 21 are still formed. Since there is a space of 0.07 mm between the base portion 21b and the base portion 21b, press molding without constraint is possible. The cross-sectional shape of the formed groove 3 is an inverted trapezoidal shape ( In terms of shape, the expression "inverted trapezoidal shape" represents the shape when the groove bottom portion 3a is arranged on the lower side).

In order to stably form the groove without restraint, as shown in FIG. 1, the height of the groove forming protrusion 21a of the groove forming punch 21 is H, the wall thickness of the battery container 1 is T, When the thickness of the thin portion 4 is t, the height H of the groove forming protrusion 21a of the punch 21 is H ≧ 1.5 with respect to the thickness T of the battery container and the thickness t of the thin portion.
It is preferably (T-t). This is because the vicinity of the groove forming portion is deformed and protrudes at the time of forming the groove, and thus the punch base forming portion of the punch is not applied to the portions other than the groove forming portion by the restraining force of the punch base. This is because, in order to stably reduce the load applied to the groove 21a, it is preferable to make the height H of the groove forming protrusion 21a of the punch larger than the depth of the groove to be formed.

Further, in order to exert a stable explosion-proof function, it is preferable that the width W of the thin portion 4 formed under the groove bottom portion 3a of the groove 3 is 1.4 to 15 times the thickness t of the thin portion 4. That is, when the width W of the thin portion 4 is 1.4 times or more the thickness t of the thin portion 4, when the internal pressure of the battery rises, the tensile force due to the internal pressure and the tensile force due to the bending are combined at the end of the groove bottom 3a. As a result, tear breakage occurs at the end of the groove bottom 3a in response to the pressure increase inside the battery, and a stable explosion-proof function is exhibited. This is because if W is 15 times or less the thickness t of the thin portion, the force from the outside of the battery is not applied to the thin portion and the thin portion is not broken.

The flattening of the part protruding by the groove formation is only to return the other parts to the state before the groove formation except the groove, and the press molding is no different from the normal press molding. The pressure may be as high as 10 to 50 kg / cm ² as it is molded.

In this embodiment, the protrusion 2a is provided at the center of the bottom 2 of the battery case 1 so that the lead terminals can be easily attached at a stable position. Therefore, the groove 3 is formed in the protrusion 2a. Department
2a is not always necessary, and the bottom portion 2 of the battery container 1 may be flat. In that case, the groove 3 may be provided in the central portion of the flat bottom portion 2 of the battery container 1, but even in that case, the explosion-proof function is reduced as compared with the case where the groove 3 is provided in the protrusion 2a. In addition, the workability and the like of the groove formation by press molding do not deteriorate.

FIG. 7 is a thionyl chloride-lithium battery assembled using a battery container in which an explosion-proof groove is formed by the groove forming method described with reference to FIGS. 1 to 4 and the protruding portion of the groove is flattened. In the figure, 1 is a battery container in which the battery is provided with an explosion-proof function by forming the groove 3 as described above. Reference numeral 11 denotes a negative electrode made of an alkali metal, which is formed by pressing a lithium plate onto the inner peripheral surface of the battery container 1 in this embodiment. Therefore, in this battery, the battery container 1 functions as a negative electrode terminal. Have Reference numeral 12 denotes a separator, which is made of glass fiber non-woven fabric and has a cylindrical shape, and separates the cylindrical negative electrode 11 and the cylindrical positive electrode 13 from each other. The positive electrode 13 is made of a carbon porous molded body formed of carbonaceous material containing acetylene black as a main component, and 14 is a positive electrode current collector made of a stainless steel rod. Reference numeral 15 denotes a battery lid, which is made of stainless steel and whose rising outer peripheral portion is joined to the opening end portion of the battery container 1 by welding, and the inner peripheral side of the battery lid 15 is connected to the positive electrode terminal 17 by a glass. The layer 16 is interposed. The glass layer 16 insulates between the battery lid 15 and the positive electrode terminal 17, and
The constituent glass is fused to the inner peripheral surface of the battery lid 15 on the outer peripheral surface thereof, and the constituent glass is fused to the outer peripheral surface of the positive electrode terminal 17 on the inner peripheral surface of the battery lid 15 and the positive electrode terminal 17. Seal the space between
The opening of the battery container 1 is closed by a so-called hermetic seal. The positive electrode terminal 17 is made of stainless steel and has a pipe shape at the time of battery assembly, and is used as an electrolyte injection port. It is welded and sealed. 18 is an electrolytic solution, and this electrolytic solution 18 contains 1.2 mol / L of lithium aluminum tetrachloride as a supporting electrolyte in thionyl chloride.
Thionyl chloride is a solvent of the electrolytic solution as described above, and is a positive electrode active material in this battery.
On the surface of the positive electrode 13, this thionyl chloride reacts with the lithium ions ionized from the negative electrode 11. The upper portion of the electrolytic solution 18 is a space, and 19 and 20 are a bottom separator and an upper separator made of glass fiber nonwoven fabric, respectively.

As described above, the thionyl chloride-lithium battery using the battery container with the explosion-proof groove formed in the bottom was put into a fire, and it was investigated whether or not the battery exploded with a loud popping sound. Shown in the table. For comparison, a groove with a rounded bottom as proposed in alkaline batteries (with a groove forming angle of 90 °,
A burst test was also conducted on a battery using a battery container with rounded groove bottom 0.2 mm R and thin portion thickness 0.07 mm).
The results are shown in Table 1. The denominator in the "Number of burst batteries in fire" column in Table 1 indicates the number of batteries used in the test, and the numerator is a burst in fire (batteries with large explosion noise at high pressure without the explosion-proof function working). The number of batteries that caused a burst) is shown.

As shown in Table 1, the battery produced by using the battery container in which the groove was formed according to the present invention showed no explosion in fire and exhibited an excellent explosion-proof function.

Note that FIG. 8 shows the relationship between the thickness of the explosion-proof thin-walled portion and the cleavage pressure of the explosion-proof thin-walled portion, and the solid line a in FIG.
Shows the case of a battery container in which a groove is formed on the bottom of the battery container, and the protruding portion due to the groove formation is flattened. The dotted line b in FIG. Shows the case of a battery container in which is not flat. As is clear from FIG. 8, the flattened portion formed by the groove formation has the same thickness (thickness of the thin explosion-proof portion as compared to the case where the portion formed by the groove formation is not flattened). The cleavage pressure of the thin part is low when compared with).
From this, it can be seen that by flattening the protruding portion by forming the groove, it is possible to operate the explosion-proof function at a lower pressure even with the same thickness, and to exhibit the explosion-proof function more stably.

In addition, in the above-mentioned embodiment, the groove is formed so that the planar shape is a cross shape. However, the planar shape of the groove is not limited to such a cross shape, and as shown in FIG. 9, for example, Grooves such as a Y shape (see FIG. 9 (a)), an asterisk (star) shape (see FIG. 9 (b)), an H shape (see FIG. 9 (c)), and an X shape. It is possible that a plurality of grooves are provided and the grooves intersect at at least one position. In particular, when the internal pressure is applied to the battery, the largest deformation at the bottom of the battery container is at the center, so the planar shape having the intersection at the center of the bottom is cross-shaped, X-shaped, Y-shaped, or asterisk-shaped. Grooves are preferred.

〔The invention's effect〕

As described above, in the present invention, the groove forming angle is 50 to 80 ° without restraint, and the groove forming is performed on the bottom of the battery container by press molding, so that the tensile stress is applied to the material forming the bottom of the groove. By reducing the deformation resistance of the material to be molded and the frictional force between the groove forming punch and the material to be molded, a groove with a flat bottom is formed with a punch life that enables mass production.
By flattening the protruding portion due to the groove formation, it is possible to eliminate the occurrence of the total height defect of the battery caused by the protruding portion due to the groove formation and the trouble of supplying the battery container to the assembly line during the battery assembly. did it.

[Brief description of drawings]

1 to 4 show a state in which an explosion-proof groove is formed on the bottom of a battery container by the method of the present invention, and the protruding portion is flattened by the groove formation. FIG. 1 shows the groove formation. FIG. 2 is an enlarged cross-sectional view of an essential part showing a state in which the groove punch is lowered and the groove forming protrusion of the punch is pushed into the bottom of the battery container. FIG. 2 is an overall cross section of the groove forming punch before being lowered. It is a figure. FIG. 3 is a cross-sectional view of the battery container when the groove is formed by the method shown in FIGS. FIG. 4 is a cross-sectional view showing a state in which the protruding portion due to the formation of the groove is flattened, and shows a state before the molding die for flattening is lowered. FIG. 5 shows an example of a battery container in which an explosion-proof groove is formed by the method of the present invention, and the protruding portion is flattened by forming the groove.
Is a plan view thereof, and FIG. 5 (b) is a sectional view taken along line XX of FIG. 5 (a). FIG. 6 is an enlarged sectional view of part A in FIG. 5 (b). FIG. 7 is a cross-sectional view showing an example of a thionyl chloride-lithium battery using a battery container in which an explosion-proof groove is formed by the method of the present invention, and a convex portion formed by the groove formation is flat. FIG. 8 is a diagram showing the relationship between the thickness of the explosion-proof thin-walled portion and the cleavage pressure of the thin-walled portion. FIG. 9 is for showing the planar shape of another example of the groove formed by the method of the present invention, the upper stage shows a schematic front view of each battery container, and the lower stage shows a schematic bottom view thereof. 1 ... Battery container, 2 ... bottom, 3 ... groove, 3a ... groove bottom, 4 ... thin-walled portion, 21 ... groove forming punch, 21a ... groove forming protrusion, 21a ₁ ... … Tip, 31 …… Molding die, 32… Lower mold

Front Page Continuation (72) Inventor Shigeru Ikenari 1-88, Torora, Ibaraki-shi, Osaka, Hitachi Maxel Co., Ltd. (72) Inventor Kenichi Yokoyama 1-88, Torora, Ibaraki, Osaka Within the corporation

Claims (1)

[Claims] 1. A groove forming punch having a flat tip and a groove forming angle of 50 to 80 ° is formed as a groove forming punch for forming a groove for providing an explosion proof function to a battery. Using a punch having a protrusion, without applying a restraining force in the thickness direction of the portion other than the groove forming portion of the bottom of the battery container, the groove forming protrusion of the punch is pushed into the bottom of the battery container, A method for producing a battery container for use in an explosion-proof closed battery, characterized in that a flat groove is formed on the bottom of the battery container, and then the portion of the bottom of the battery container that is projected by the groove is flattened by press molding. .