JPS6386244A - Manufacture of battery container for explosionproof type sealed battery - Google Patents

Abstract

PURPOSE:To reduce the friction between a groove forming punch and a part where a groove is formed of the bottom and to lengthen the life of the groove forming by specifying the groove forming angle of the punch, and forming a groove in the bottom of a battery container in a free state by press work. CONSTITUTION:A groove forming punch 21 is lowered and a groove forming projection 21a of the punch 21 is pressed to the bottom 2 of a battery container 1 to form a groove 3. The tip 21a1 of the projection 21a is formed in a flat state and the bottom of the groove 3 is also formed in a falt state. The groove forming angle theta of the projection 21a is 50-80 deg.. The tensile stress f is applied to the groove forming part of the bottom 2 pressed with the tip 21a1 of the projection 21a and the part where no groove is formed is free from the pressure. The groove forming part of the bottom 2 is easy to be deformed, and the resistance to deformation in this part and the friction between the projection 21a and the part where the groove is formed are reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a battery container used in an explosion-proof sealed battery.

[Conventional technology]

A liquid active material battery that uses an oxyhalide liquid such as thionyl chloride, sulfuryl chloride, or phosphoryl chloride as the positive electrode active material, and uses an alkali metal such as lithium, sodium, or potassium as the negative electrode, as typified by a thionyl chloride-lithium battery. Since it has a completely hermetic structure with a hermetic seal, it has excellent airtightness, but on the other hand, because of its high airtightness, it cannot be exposed to high temperature heating or charged with high voltage. When an abnormal situation occurs, the internal pressure of the battery increases abnormally, causing the battery to explode, making a loud bursting sound, and causing the contents of the battery to fly out into the surrounding area, potentially contaminating equipment that uses the battery. .

Therefore, regarding alkaline batteries that have a similarly sealed structure,
Utility Model Publication No. 58-17332 and Utility Model Publication No. 58-2646
Publication No. 0 discloses that a groove is formed in a part of the battery container to provide a thin part in the battery container, and the withstand pressure of the battery container is partially lowered at the thin part, causing an abnormal increase in the pressure inside the battery. When the battery is tightened, the thin wall portion ruptures and the gas inside the battery, which causes battery rupture, is released to the outside of the battery,
Since it has been proposed to prevent batteries from exploding at high pressures, it is necessary for liquid active material batteries with this hermetic-n-rule structure to also have an explosion-proof function by forming such grooves. Conceivable.

By the way, when forming the above-mentioned explosion-proof grooves,
A method using press molding is adopted, but in order to withstand the strong corrosion resistance of the positive electrode active material in liquid active material batteries, the battery components must have excellent corrosion resistance, and battery containers are generally made of stainless steel 8'V! Since the battery container is used, the hardness of the battery container is high, and if a groove is to be formed in the battery container by press molding, the load applied to the groove-forming punch will be extremely high.

Therefore, as shown in the above-mentioned Japanese Utility Model Publication No. 58-17332, the best way to expand and soften the cross section of the groove to be formed is to form it in a 7-shape shape and make the tip, that is, the bottom of the groove, sharp. Although it is thought that groove formation is easy, if the bottom of the groove is made sharp, the tip of the groove-forming punch will be easily damaged, so it is difficult to use it industrially due to the durability of the punch. Therefore, as shown in the above-mentioned Japanese Utility Model Publication No. 58-26460, even if the cross section is a figure 7 shape, the bottom of the groove has a 0.
It is possible to improve the durability of the groove forming punch by rounding the tip of the groove by 1 to 0.2 nu+R, but according to the research of the present inventors, if the tip of the groove is rounded, The effect of reducing the thickness is only achieved, and additional effects such as the notch effect are hardly added. Therefore, in battery containers made of high-strength materials such as stainless steel, the thickness of the thin part should be made much thinner. It has also been found that the burst pressure of the thin-walled part will not decrease unless the battery is heated, and that hermetically sealed liquid active material batteries such as lithium thionyl chloride batteries do not exhibit stable explosion protection when rapidly heated to high temperatures. ing.

Therefore, the inventors made the bottom of the groove a flat surface so that the explosion-proof function could be stably exhibited.
To form such a groove, the tip of the groove-forming punch must be made flat, and if the tip is made flat, the load on the punch will increase, resulting in a reduction in the durability of the punch. Occurred.

[Problem that the invention seeks to solve]

The present invention solves the problem that the conventional groove forming method described above cannot produce a battery container with a highly reliable explosion-proof function, or the groove forming punch has low durability and is not suitable for mass production. It is an object of the present invention to solve this problem and to make it possible to form a groove with a punch life that can be mass-produced even when the groove shape has a flat portion at the bottom of the groove.

[Means for solving problems]

The present invention does not apply a restraining force in the thickness direction of the parts other than the groove forming part at the bottom of the battery container, that is, in the thickness direction of the constituent material of the part where the grooves are not processed, and the groove forming angle of the groove forming protrusion of the punch is controlled. By applying tensile stress to the material constituting the bottom of the groove to be formed by pushing the groove-forming convex part of the punch into the bottom of the battery container to form a flat part at an angle of 50 to 80 degrees, the bottom part has a flat part. This makes it possible to form grooves even in stainless steel battery containers with a low punch load.

That is, forging and coining (coining) by press forming are generally performed by material movement due to plastic flow of the material to be formed, and the internal structure of the material to be formed exhibits fiber flow (fibrous soft tissue caused by plastic flow). At this time, the force necessary for forming is the force that counteracts the deformation resistance of the material to be formed and the frictional force generated between it and the forming tool. Both frictional forces are applied together to the forming tool. Therefore, when the material to be formed is a hard corrosion-resistant gold mud like stainless steel, when coining is done narrowly and deeply, the load per unit area is large even if the groove is processed.

Therefore, in the present invention, in order to minimize both the deformation resistance of the battery container, which is the material to be molded, and the frictional force generated between it and the punch for forming the groove, a restraining force is applied in the thickness direction of the constituent material in the part where the groove is not formed. By setting the groove forming angle to 50 to 80 degrees without applying any constraint, the tensile stress of 1! ) By pushing the groove-forming convex part of the groove-forming punch into the bottom of the battery container to form the groove, it is possible to form a groove with a flat part on the bottom with a low punch load. For example, in the past, when trying to form a groove with a flat bottom, the load applied to the punch reached over 300 kir/mm, but with the present invention, the durability of the punch has been improved. For example, it is possible to form grooves with a punch load of 240 kg/- or less using general lubricating oil.

To perform press forming without restraint as described above, in order to prevent the base of the groove-forming punch from coming into contact with the battery container, the height of the groove-forming protrusion of the punch should be adjusted to the height of the groove to be formed. It is necessary to make it larger than the depth. In particular, in order to stably form grooves without restraint, the height H of the groove-forming protrusion of the groove-forming punch must be It is preferable that H≧1.5 (Tt) 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. Also, the groove forming angle θ (
The reason for setting the groove forming angle (see Figure 1) to 50 to 80 degrees is that if the groove forming angle is less than 50 degrees, the tensile stress applied to the bottom constituent material of the groove will be insufficient, and the load applied to the groove forming protrusion of the punch will be large. If the groove formation angle exceeds 80°, it is possible to form the groove itself, but the resistance to the pressurizing force from inside the battery increases due to the pressure increase inside the battery. This is because it is difficult to obtain batteries with excellent explosion-proof functionality.

〔Example〕

Next, the first to second embodiments of the present invention will be explained based on the drawings.
The figure is a cross-sectional view showing the state in which grooves are formed in a battery container by the method of the present invention, and FIG. FIG. 2 is an enlarged cross-sectional view of the main part in the state when the punch is pushed in, and FIG. 2 is a cross-sectional view of the whole in the state before the punch is lowered.

First, the whole will be explained based on FIG. 2. In the figure, 1 is a battery container, 21 is a punch for forming grooves, 21a is a protruding part of the punch for forming grooves, and 21b is a base part of the punch. . The battery container 1 has a cylindrical shape with a bottom, and is placed on the lower mold 22 in an inverted state in the drawing. And 23 is its base.

To form a groove in the battery container L, the punch 21 is lowered from the state shown in FIG. 2, and the groove forming protrusion 21a of the punch 21 is pushed into the bottom 2 of the battery container B1 as shown in FIG. A groove 3 is formed by this. The tip 21a1 of the groove forming convex portion 21a of the punch 21 is formed into a flat surface,
The bottom of the groove 3 thus formed becomes a flat surface. The groove forming angle θ of the groove forming convex portion 21a of the punch 21 is 50.
~80°, so this punch 21
As shown in FIG. 1, tensile stress (f
), and since no restraining force is applied to the part that is not grooved and the part is left unrestrained, the part to be formed on the bottom 2 of the battery container 1 is easily deformed, and the deformation resistance of this part and the groove of the punch are reduced. The frictional force between the forming convex portion 21a and the molded portion of the battery container 1 becomes smaller.

In addition, in this embodiment, as shown in FIG. 3(a), the groove 3
is formed so that its planar shape is cross-shaped, so the groove-forming convex portion 21a of the groove-forming punch 21 is cross-shaped, but for the sake of simplicity in FIGS. It is not shown in the figure, but is shown in such a manner that one groove is formed in a straight line.

In this embodiment, the battery container 1 is made of a stainless steel plate with a thickness of 0.3 mm, and the protrusion 21 for forming grooves of the punch
The angle θ of a is 70°, the tip 21a1 of the groove forming protrusion 21a is flat, and its width is 0.15 mm, and the groove 3
The depth of is 0.23 mm, and the thinned part 4 formed by forming the groove, that is, the thinned part 4 provided by forming a3.
The thickness of the groove is 0.07 mm, and the width of the groove bottom 3a is 0.15 m.
Although a flat portion 3a1 (see FIG. 4) of m is formed,
General /I2i? Even if pressing is performed using 'h oil (for example, machine oil), the groove forming protrusion 21a of the punch
The load applied to the tip could be reduced to 240 kg/- or less, making it possible to form grooves with high productivity. Note that the height of the groove forming protrusion 21a of the punch is 0.7+u+,
Although the part of the bottom of the battery container where the groove is not processed is slightly raised due to pressing during groove formation, there is still a space of 0.07 mm between the top surface of this part and the base part 21b of the punch 21, so that pressing without restraint is possible. It made molding possible. Also,
The cross-sectional shape of the formed groove 3 is an inverted trapezoid shape (υ shape) as shown in FIG.

When groove forming was performed by press forming under unrestricted conditions as described above, the life of the punch was over 200,000 times. When grooves were formed at the same depth as the grooves to be formed, the life of the punch did not reach 50,000 cycles.

In order to stably form grooves without restraint, as shown in FIG. Thickness of thin part 4 is t
When, the height H of the groove-forming convex portion 21a of the punch 21 is H≧1.5 (T-t) with respect to the wall thickness T of the battery container and the thickness t of the thin wall portion. This is preferable because when forming grooves, the vicinity of the groove forming part tends to deform and swell slightly, so the base of the punch does not apply a restraining force to the parts other than the groove forming part, and the groove forming part of the punch is prevented. This is because, in order to stably reduce the load applied to the groove-forming protrusion 21a, it is preferable that the height H of the groove-forming protrusion 21a of the punch is greater than the depth of the groove to be formed.

In addition, in order to exhibit a stable explosion-proof function, the width W of the flat part 3a1 (see Fig. 4) of the groove bottom 3a of the groove 3 should be 1.4 to 15 times the thickness t of the thin part 4. Preferably, when the width W of the flat portion 3a1 of the groove bottom 3J is 1.4 times or more the thickness t of the thin wall portion 4, when the internal pressure of the battery increases, the end 3a2 of the groove bottom 3a is pulled by the internal pressure. The force and the tensile force due to bending are applied in combination, and the end 3 of the groove bottom 3a responds sharply to the increase in pressure inside the battery.
Tear failure occurs at a2, and a stable explosion-proof function is achieved, and the flat part 3a1 of the groove bottom 3a
When the width W is less than 15 times the thickness t of the thin part, 1! This is because there is almost no possibility that a force from outside the pond will be applied to the thin-walled portion and the thin-walled portion will be destroyed before it operates as an explosion-proof valve.

In this embodiment, a protrusion 2a is provided at the center of the bottom 2 of the battery container l so that the mounting position of the lead terminal can be easily stabilized.
Since the groove 3 is provided in the protruding part 2a, the protruding part 2a is not necessarily necessary.
may be flat.

In that case, the groove 3 is located on the flat bottom 2 of the battery container 1.
However, even if this is done, the explosion-proof function will not deteriorate compared to the case where the groove 3 is provided in the protruding part 2a, and the groove formation by press molding will not deteriorate. However, it does not cause any deterioration in terms of workability.

FIG. 5 shows a thionyl chloride-lithium battery assembled using a battery container in which explosion-proof grooves were formed by the groove forming method explained based on FIGS. This is a battery container in which the battery is provided with an explosion-proof function by forming grooves 3 as shown in FIG. Reference numeral 11 denotes a negative electrode made of an alkaline fully bent material, which in this embodiment is formed by pressing a lithium plate onto the inner circumferential surface of the battery container 1. Therefore, in this battery, the battery container 1 does not function as a negative electrode terminal. have. Reference numeral 12 denotes a separator, which is made of glass fiber nonwoven fabric and has a cylindrical shape, separating the cylindrical negative electrode 11 and the cylindrical positive electrode 13. The positive electrode 13 is made of a carbon porous molded body made of carbon whose main component is acetylene black.
is the positive electrode current collector, which is made of a stainless steel rod. Reference numeral 15 denotes a battery lid, which is made of stainless steel, and its raised outer periphery is joined to the open end of the battery container 1 by welding. A layer 16 is interposed. The glass layer 16 insulates between the battery lid 15 and the positive electrode terminal 17, and the glass layer 16 is fused to the inner peripheral surface of the battery lid 15 on its outer peripheral surface, and the glass layer 16 is connected to the positive terminal on its inner peripheral surface. 17 to seal between the battery lid 15 and the positive electrode terminal 17, and the opening of the battery container l is sealed with a so-called hermetic seal. The positive electrode terminal 17 is made of stainless steel and has a pipe shape when the battery is assembled, and is used as an electrolyte inlet, and its upper end is connected to the upper part of the positive electrode current collector 14 inserted into the hollow part after the electrolyte is injected. It is welded and sealed. 1
8 is an electrolytic solution, and this electrolytic solution 18 contains 1.2 m of lithium aluminum tetrachloride as a supporting electrolyte in thionyl chloride.
ol/! The dissolved thionyl chloride is not only an electrolyte solvent as described above, but also a positive electrode active material in this battery, and on the surface of the positive electrode 13, this thionyl chloride and ionized lithium ions from the negative electrode 11 cause a reaction. , and 19 and 20 are a bottom separator and an upper separator, respectively, made of glass fiber nonwoven fabric.

A lithium thionyl chloride battery with an explosion-proof groove formed at the bottom of the battery container as described above was thrown into a fire, and the results were shown in Table 1 to see if the battery exploded with a loud popping sound. For comparison, a battery with a rounded groove on the bottom as proposed for alkaline batteries (groove formation angle 90", groove bottom roundness 0.2IR1 thin part thickness 0.07mm) is shown. Batteries using containers were also subjected to burst tests in fire, and the results are shown in Table 1.
The denominator in the column ``Number of batteries that exploded in fire'' indicates the number of batteries that were subjected to the test, and the numerator is the number of batteries that exploded in fire (batteries that exploded under high pressure and with a loud bursting sound because the explosion protection function did not activate). In addition, since the grooves were all formed by press molding, after the grooves were formed, they were annealed at 1010° C. for 10 minutes to remove work hardening caused by the groove formation.

Table 1 As shown in Table 1, the batteries manufactured using the battery containers in which the grooves were formed according to the present invention did not burst during fire at all, and exhibited excellent explosion-proof function.

In the above embodiment, the grooves were formed to have a cross-shaped planar shape, but the planar shape of the grooves is not limited to such a cross-shaped one. For example, as shown in FIG. Y-shape (see Figure 5(a)), asterisk
(see Figure 5(b)), H-shape (see Figure 5(C))
It is possible to have a plurality of grooves, such as, where the grooves intersect at least one place. In particular, when internal pressure is applied to the battery, the part of the bottom of the battery container that deforms the most is the center, so the planar shape with the intersection at the center of the bottom is cross-shaped (X
It is preferable to use a Y-shaped groove, a Y-shaped groove, or an asterisk-shaped groove.

〔Effect of the invention〕

As explained above, in the present invention, tensile stress is applied to the material forming the bottom of the groove by forming the groove at the bottom of the battery container by press molding with the groove forming angle set at 50 to 80 degrees without restraint. By reducing the deformation resistance of the material to be formed and the frictional force between the groove-forming punch and the material to be formed, it was possible to form grooves with a flat bottom portion within the life of the punch that allows for mass production.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams showing the state in which an explosion-proof groove is formed at the bottom of a battery container by the method of the present invention. FIG. 2 is an enlarged cross-sectional view of the main part showing the state when the groove-forming punch is pushed into the bottom of the battery container, and FIG. 2 is a cross-sectional view of the entire groove-forming punch in the state before being lowered. FIG. 3 shows an example of a battery container in which explosion-proof grooves are formed by the method of the present invention. FIG. 3(a) is a plan view thereof, and FIG. 3(b) is a plan view thereof.
It is a cross-sectional surface taken along the XX line. Figure 4 is similar to Figure 3 (t
1) is an enlarged sectional view of part A of FIG. FIG. 5 is a sectional view showing an example of a thionyl chloride-lithium battery using a battery container in which explosion-proof grooves are formed by the method of the present invention. FIG. 6 is for showing the planar shape of another example of the groove formed by the method of the present invention, the upper row shows a schematic front view of each battery container, and the lower row shows a schematic bottom view thereof. 1...Battery container, 2...Bottom, 3...Groove, 3
a...bottom of groove, 3a1...flat part, 21...
・Groove forming punch, 21a...Groove forming protrusion, 2
1a1...Tip Fig. 6 (a) (b) (C) 3...Groove 1 Fig. 22 1...Battery container 2...Bottom 3...Groove 21...Groove forming punch 21a ...Groove forming protrusion 21a +...Tip Fig. 2 Fig. 3 1...Battery container (a) Fig. 4 Fig. 5 (b)

Claims (2)

[Claims] (1) When forming a groove on the bottom of a battery container to provide an explosion-proof function to the battery, a groove forming protrusion with a flat tip and a groove forming angle of 50 to 80 degrees is used as a groove forming punch. Using a punch having a groove-forming part, push the groove-forming protrusion of the punch into the bottom of the battery container without applying a restraining force in the thickness direction of the part other than the groove-forming part at the bottom of the battery container,
1. A method of manufacturing a battery container for use in an explosion-proof sealed battery, comprising forming a groove having a flat portion at the bottom of the battery container. (2) When the height of the groove-forming convex part of the groove-forming punch is H, the wall thickness of the battery container is T, and the thickness of the thin-walled part provided by forming the groove is t, then the above-mentioned groove-forming punch Claims characterized in that the height H of the groove-forming convex portion satisfies H≧1.5 (T-t) with respect to the wall thickness T of the battery container and the thickness t of the thin wall portion. A method for manufacturing a battery container for use in the explosion-proof sealed battery according to item 1.