JPH0789482B2 - 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]

A liquid active material battery using an oxyhalide-based liquid such as thionyl chloride, sulfuryl chloride, or phosphoryl chloride as a positive electrode active material typified by a thionyl chloride-lithium battery and an alkali metal such as lithium, sodium, or potassium as a negative electrode. In this case, since it has a completely hermetically sealed structure, it has excellent sealing performance, but on the other hand, due to its high sealing performance, it is exposed to high temperature heating and is charged at high voltage. When an abnormal situation is encountered, the internal pressure of the battery rises abnormally, causing the battery to burst, producing a loud burst noise, and the battery contents may scatter around and contaminate the battery-using device.

Therefore, regarding alkaline batteries that also have a sealed structure,
In Japanese Utility Model Publication No. 58-17332 and Japanese Utility Model Publication No. 58-26460, a groove is formed in a part of the battery container to provide a thin portion in the battery container, and the pressure resistant portion of the battery container is partially formed at the thin portion. When the pressure inside the battery starts to rise abnormally, the thin wall part is broken and the gas inside the battery, which becomes a factor of battery explosion, is released to the outside of the battery to prevent battery explosion at high pressure. Therefore, it is considered that it is necessary to provide the liquid active material battery having the hermetically sealed structure with the explosion-proof function by such groove formation.

By the way, when forming the explosion-proof groove as described above,
Although the method by press molding is adopted, in the liquid active material battery, the corrosion resistance of the battery component is required to withstand the strong corrosion resistance of the positive electrode active material, and stainless steel is generally adopted for the battery container. Has a high hardness, and if a groove is formed on the groove by press molding, the load applied to the groove forming punch becomes very high.

For this reason, the cross-sectional shape of the groove to be formed is
As shown in Japanese Patent Laid-Open No. 58-17332, it is considered that the groove is most easily formed when the tip of the groove, that is, the bottom of the groove is formed in a V shape, so that the groove can be easily formed. When sharpened, the tip of the punch for forming the groove is immediately damaged, and therefore it is not industrially applicable from the viewpoint of durability of the punch. Therefore, as shown in Japanese Utility Model Publication No. 58-26460, 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. According to the research conducted by the present inventors, however, when the tip of the groove is rounded, only the effect of reducing the thickness is exhibited, and an additional effect such as a notch effect is added. Therefore, in a battery container made of high-strength material such as stainless steel, unless the thickness of the thin-walled part is made very thin, the breaking pressure of the thin-walled part does not become low. It has also been found that liquid active material batteries do not exhibit a stable explosion-proof function when heated rapidly at high temperatures.

Therefore, the present inventors have made the explosion-proof function stable by making the bottom of the groove a flat surface.
In order to form such a groove, the tip of the groove forming punch must be flattened, and the load applied to the punch with the flattened tip is increased, resulting in a problem that the durability of the punch is reduced. Occurred.

[Problems to be solved by the invention]

The present invention has a problem that a battery container having a highly reliable explosion-proof function cannot be obtained by the above-described conventional groove forming method, or the groove forming punch has low durability and is poor in mass productivity. It is an object of the present invention to solve the above problem and to enable the formation of a groove with a punch life that can achieve mass production even when the groove shape has a flat portion at the groove bottom.

[Means for solving problems]

The present invention does not apply a restraining force in the thickness direction of the portion other than the groove forming portion of the bottom of the battery container, that is, in the thickness direction of the constituent material of the portion that is not grooved, and the groove forming angle of the groove forming protrusion of the punch By setting the groove 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 form a flat portion at the bottom. The groove can be formed with a low punch load even in a battery container made of stainless steel.

That is, forging and coining (coining) by press molding are generally performed by moving the material by plastic flow of the molding material, and the internal structure of the molding material shows a fiber flow (fibrous structure generated by the plastic flow). At this time, the force required for molding is a force that overcomes the deformation resistance of the material to be molded and the frictional force generated between it and the molding tool. Is applied to the forming tool together. Therefore, when the material to be molded is a corrosion-resistant metal that is hard, such as stainless steel, the load per unit area is large even when groove machining is performed when narrowing and deep coining.

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 the material and the punch for forming the groove, the binding force in the thickness direction of the constituent material of the portion not grooved is set. Is given, that is, without restraint, and by setting the groove forming angle to 50 to 80 °, the groove forming protrusion of the groove forming punch is applied while applying tensile stress to the material forming the bottom of the groove. By pushing into the bottom of the battery container to form a groove, a groove having a flat portion at the bottom can be formed with a low punch load, and the durability of the groove forming punch is improved. For example, when forming a groove having a flat portion at the bottom up to now, the load applied to the punch reached 300 kg / mm ² or more, but according to the present invention, a punch of 240 kg / mm ² or less in general lubricating oil is used. It is possible to form a groove with a load.

As described above, in order to perform the press molding without restraint, the height of the groove forming protrusion of the punch is set so that the base of the groove forming punch does not come into contact with the battery container. It needs to be larger than the depth. In particular, in order to perform groove formation stably without restraint, as will be described later with reference to FIG. 1, the height H of the groove forming protrusion of the groove forming punch is determined by the structure of the battery container. It is preferable that H ≧ 1.5 (T−t) 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. In addition, the groove forming angle θ (see FIG. 1) of the groove forming protrusion of the punch is set to 50 to 80 ° when the groove forming angle is less than 50 °, the tensile stress applied to the material forming the bottom of the groove is insufficient. Since the load applied to the groove forming protrusion of the punch becomes large, it becomes difficult to form the groove, and when the groove forming angle exceeds 80 °, it is possible to form the groove itself. This is because the resistance to the pressure applied from the inside of the battery due to the increase becomes large, and it becomes difficult to obtain a battery having an excellent explosion-proof function.

〔Example〕

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

1 and 2 are sectional views showing a state in which a groove is formed in a battery container by the method of the present invention, and FIG. 1 is a drawing in which the groove forming punch is lowered and the groove forming protrusion is formed in the battery. FIG. 2 is an enlarged cross-sectional view of an essential part in a state in which the punch is pushed into the bottom portion, and FIG. 2 is an overall cross-sectional view in a state before the punch is lowered.

First of all, referring to FIG. 2, in the drawing, 1 is a battery container, 21 is a groove forming punch, 21a is a groove forming protrusion, and 21b is a punch base. . The battery case 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 the base. To form the groove in the battery case 1, 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 case 1 as shown in FIG. Thereby forming the groove 3. The tip 21a ₁ of the groove forming protrusion 21a of the punch 21 is formed into a flat surface,
The bottom of the groove 3 formed thereby has a flat surface. The groove forming angle 21a of the groove forming protrusion 21a of the punch 21 is formed to be 50 to 80 °, and therefore the groove bottom portion pressed by the tip 21a ₁ of the groove forming protrusion 21a of the punch 21 is formed. As shown in FIG. 1, a tensile stress (f) is applied to the constituent materials, and the portion not grooved is not restrained and is not restrained. Therefore, the portion to be molded of the bottom portion 2 of the battery container 1 is formed. Is easily deformed, and the deformation resistance of the portion and the frictional force between the groove forming protrusion 21a of the punch and the molded portion of the battery container 1 are reduced.

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 70 °, 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, and the thickness of the thin portion 4 formed by forming the groove 3, that is, the thin portion 4 formed by forming the groove 3 is 0.07 mm. And the groove bottom 3a
Although a flat part 3a ₁ (see Fig. 4) with a width of 0.15 mm is formed on the inner surface of the punch, even if a general lubricating oil (such as machine oil) is used for pressing, the protrusions for forming the groove of the punch are formed. The load applied to the tip of the portion 21a can be set to 240 kg / mm ² or less, which enables highly productive groove formation. The height of the groove-forming protrusions 21a of the punch is 0.7 mm, and a portion of the bottom of the battery container that is not grooved is slightly raised due to the indentation at the time of groove formation. There is a 0.07 mm space between it and 21b, which enables press molding without constraint. The cross-sectional shape of the formed groove 3 is an inverted trapezoidal shape as shown in FIG. Is.

The punch life was 200,000 times or more when the groove was formed by press molding without constraint as described above, but the height of the groove forming protrusion of the groove forming punch was restricted. When the groove was formed with the same depth as the groove to be formed, the punch life did not reach 50,000 times.

In order to perform the groove shape stably 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 when the groove is formed, the vicinity of the groove forming portion tends to be deformed and slightly swelled, so that the punch base for forming the groove is not applied to the portion other than the groove forming portion by the constraint of the punch base. This is because, in order to stably reduce the load applied to the projecting portion 21a, it is preferable to make the height H of the groove-forming projecting portion 21a of the punch larger than the depth of the groove to be formed.

Further, in order to exert a stable explosion-proof function, the groove 3 has the width W of the flat portion 3a ₁ (see FIG. 4) of the groove bottom 3a and the thin portion 4a.
The thickness t is preferably 1.4 to 15 times. That is, when the width W of the flat portion 3a ₁ of the groove bottom 3a is 1.4 times or more the thickness t of the thin portion 4, when the internal pressure of the battery rises, the end portion 3a ₂ of the groove bottom 3a is stretched and bent by the internal pressure. It will be applied in combination with the tensile force due to, the tear breakage will occur at the end 3a ₂ of the groove bottom 3a in response to the pressure rise inside the battery, and a stable explosion-proof function will be exerted. Also,
If the width W of the flat portion 3a ₁ of the groove bottom portion 3a is 15 times or less than the thickness t of the thin wall portion, force from the outside of the battery is applied to the thin wall portion so that the thin wall portion is destroyed before it operates as an explosion-proof valve. This is because almost nothing happens.

In addition, in this embodiment, since the protruding portion 2a is provided in the central portion of the bottom portion 2 of the battery container 1 so that the mounting position of the lead terminal is easily stabilized, the groove 3 is formed in the protruding portion 2a. , Protruding part
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 better than that in the case where the groove 3 is provided in the protruding portion 2a. It does not decrease, and the groove formation by press molding does not cause a decrease in workability.

FIG. 5 shows a thionyl chloride-lithium battery assembled using a battery container having a groove for explosion protection formed by the groove forming method described with reference to FIGS. The battery container has an explosion-proof function by forming the groove 3 as described above. Reference numeral 11 is a negative electrode made of an alkali metal. In this embodiment, a lithium plate is used for the battery container 1 described above.
It is formed by pressure-bonding to the inner peripheral surface of the battery. Therefore, in this battery, the battery container 1 has a function as a negative electrode terminal. 12 is a separator, and this separator
Reference numeral 12 is made of a 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 the positive electrode terminal on the inner peripheral surface.
The outer peripheral surface of 17 is fused and sealed between the battery lid 15 and the positive electrode terminal 17, and the opening of the battery container 1 is sealed 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, which is thionyl chloride containing lithium aluminum tetrachloride as a supporting electrolyte 1.
2 mol / mol, thionyl chloride is an electrolyte solution solvent as described above, and is a positive electrode active material in this battery.Thionyl chloride reacts with ionized lithium ions from the negative electrode 11 on the surface of the positive electrode 13. Cause And 19
Reference numerals 20 and 20 are a bottom separator and a top separator made of glass fiber non-woven fabric, respectively.

A thionyl chloride-lithium battery having an explosion-proof groove formed in the bottom of the battery container as described above was put into a fire, and the results of examining whether or not the battery explodes with a loud popping sound are shown in Table 1. Show. For comparison, use a battery container with a rounded groove (a groove forming angle of 90 °, roundness of the groove bottom 0.2 mm R, thickness of thin portion 0.07 mm) as proposed for alkaline batteries. The rupture test in fire was also performed on the batteries that were present, and 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 (the explosion-proof function does not operate, and the battery is accompanied by a loud popping noise at high pressure). The number of batteries that caused a burst) is shown.
Further, since the grooves are formed by press molding in all cases, after forming the grooves, annealing was performed at 1010 ° C. for 10 minutes in order to remove the work hardening caused by the groove formation.

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.

In addition, in the above 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. 6, for example, There are a plurality of grooves such as a Y shape (see FIG. 5 (a)), an asterisk (star mark) shape (see FIG. 5 (b)), and an H shape (see FIG. 5 (c)). It is possible that the grooves intersect at least one place. Especially, when the internal pressure is applied to the battery, the most deformation occurs at the bottom of the battery case at the center. Therefore, the planar shape with the intersection at the center of the bottom is a cross shape (X shape) or Y shape. An asterisk groove is preferable.

〔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. Thus, the deformation resistance of the material to be molded and the frictional force between the groove forming punch and the material to be molded can be reduced to form a groove having a flat portion at the bottom with a punch life that enables mass production.

[Brief description of drawings]

FIGS. 1 and 2 are views showing a state in which an explosion-proof groove is formed on the bottom of a battery container by the method of the present invention. FIG. 1 shows a groove-forming punch that is lowered and a groove-forming protrusion of the punch. FIG. 2 is an enlarged cross-sectional view of an essential part showing a state where the part is pushed into the bottom part of the battery container, and FIG. 2 is an overall cross-sectional view of the groove forming punch before being lowered. FIG. 3 shows an example of a battery container having an explosion-proof groove formed by the method of the present invention. FIG. 3 (a) is its plan view and FIG. 3 (b) is FIG. 3 (a).
3 is a cross-sectional view taken along line XX of FIG. FIG. 4 is an enlarged sectional view of part A in FIG. 3 (b). FIG. 5 is a cross-sectional view showing an example of a thionyl chloride-lithium battery using a battery container having a groove for explosion protection formed by the method of the present invention. Sixth
The figure 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, 3a ₁ ... flat part, 21 ... groove forming punch, 21a ... groove forming protrusion, 21a ₁ ……tip

Claims (2)

[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, push the groove forming protrusion of the punch into the bottom of the battery container, to the bottom. A method of manufacturing a battery container used for an explosion-proof sealed battery, comprising forming a groove having a flat portion on the bottom of the battery container. 2. When the height of the groove forming protrusion of the groove forming punch is H, the wall thickness of the battery container is T, and the thin portion formed by forming the groove is t, the groove forming is performed. The height H of the groove forming protrusion of the punch is H ≧ 1.5 (T−t) with respect to the wall thickness T of the battery container and the thickness t of the thin portion. A method of manufacturing a battery container used for the explosion-proof sealed battery according to item 1.