JP2005276579A - Flat square battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat square battery with an enough volume in the battery, and to surely prevent wrinkles from occurring in caulking a corner. <P>SOLUTION: A raw material for a positive electrode can 5 is a ferrite stainless steel or a cladding material which uses it as a base material. The radius of a corner 19 of the bottom wall of the positive electrode can 5 satisfies a relation R/t=8 to 20, where t is the thickness of the opening top of the peripheral side wall to be processed by caulking toward the inside. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the present invention, a battery can containing a power generation element is a flat plate-shaped positive electrode can in which the peripheral side wall is bent upward from the outer periphery of the rectangular bottom wall, and the peripheral side wall is downward from the outer periphery of the rectangular top wall. The present invention relates to a flat rectangular battery including a bent flat plate-shaped negative electrode can, the upper end portion of the opening of the peripheral side wall of the positive electrode can being crimped through a sealing gasket inward.

  As in the present invention, in the field of flat rectangular batteries in which the corner portion of the bottom wall of the positive electrode can is rounded, the radius dimension (R) of the corner portion (see FIG. 1) It is known in Japanese Patent Application Laid-Open No. H11-228707 that the thickness is defined in relation to the plate thickness dimension (t) (see FIG. 3). There, the radius dimension (R) of the corner portion is set so as to satisfy the relational expression of R / t = 2 to 20 (Claim 5). It can be formed into a square with a small corner radius ”(paragraph number 0015). In Patent Document 1, a stainless steel plate is used for the positive electrode can (paragraph number 0022).

JP 2002-124219 A (Claim 5, FIG. 3, paragraph number 0015, paragraph number 0022)

  Even if the radius dimension (R) of the corner portion is in the above range, the problem with the above patent document is that the applied pressure between the linear portion and the corner portion is not uniform during caulking, and as a result, as shown in FIG. This is because wrinkles 30 are easily formed in the corner portion 19 of the positive electrode can 5. When the wrinkles 30 are formed in the corner portion 19 in this manner, the appearance of the entire battery is significantly impaired, and the sealing performance is lowered to cause liquid leakage. If the radius dimension (R) of the corner portion is large, the generation of wrinkles 30 can be prevented satisfactorily, but in that case, the dead space becomes large and the battery internal volume is reduced.

  The object of the present invention is that, with respect to a flat rectangular battery, wrinkles are generated in the corner portion due to non-uniform pressure applied between the linear portion and the corner portion during caulking while ensuring a good battery internal volume. Therefore, it is possible to prevent the deterioration of the leakage resistance due to the deterioration of the sealing performance and to prevent the appearance appearance from being damaged.

  As shown in FIG. 2, the present invention is a flat square dish in which a battery can 1 containing power generation elements such as a positive electrode material 10 and a negative electrode material 11 is bent with a peripheral side wall 3 upward from an outer periphery of a rectangular bottom wall 2. 3 and a flat plate-shaped negative electrode can 9 in which the peripheral side wall 7 is bent downward from the outer periphery of the rectangular upper wall 6, and as shown in FIG. This is a flat rectangular battery in which the opening upper end portion 3a of the side wall 3 is caulked through a sealing gasket 17 inward.

  In addition, the positive electrode can 5 is made of a ferritic stainless steel or a clad material using this as a base material. And as shown in FIG. 1, the corner part 19 of the said bottom face wall 2 of the said positive electrode can 5 is made into the round shape, and the said radial side wall 3 by which the radial dimension (R) is crimped toward inward. The thickness dimension (t) of the upper end portion 3a of the opening and the relationship of R / t = 8-20 are set.

  The stainless steel preferably has a Vickers hardness of 130 to 300. Specific examples of the ferritic stainless steel satisfying the Vickers hardness include SUS430 and SUS444.

  The inner volume of the flat rectangular battery is maximized when the corner portion 19 of the bottom wall 2 of the positive electrode can 5 is set to a right angle (R = 0). Therefore, the corner portion 19 is rounded to facilitate the caulking process. Even in the case of the shape, it is preferable to make the radial dimension (R) as small as possible in order to secure a large internal volume. However, if the radial dimension (R) is too small, wrinkles 30 as shown in FIG. 4 may occur when compressive stress is applied to the corner portion 19 by caulking. The lower limit value of the radius dimension (R) that the wrinkle 30 can be formed in this way is not only the plate thickness dimension (t) of the opening upper end portion 3a of the peripheral side wall 3 that is caulked inward, but also the material of the positive electrode can 5 ( It depends greatly on the type of stainless steel.

  Therefore, the present inventors made the positive electrode can 5 using various stainless steels, and changed the radius dimension (R) of the corner portion 19 as appropriate. As a result, A clad material as a base material is selected as a material of the positive electrode can 5, and the minimum value of the radial dimension (R) in which the wrinkle 30 does not occur during caulking is the plate thickness of the upper end portion 3 a of the opening of the peripheral side wall 3. It was found that R / t = 8 was satisfied with respect to the dimension (t). That is, if the radius dimension (R) of the corner portion 19 is R / t = 8 or more, the corner portion 19 is not wrinkled 30 during the caulking process, and a flat rectangular battery having excellent leakage resistance is obtained. be able to. Moreover, since wrinkles 30 do not occur, there is no problem that the appearance on the appearance is lowered. In addition, if R / t = 20 or less, a generally good battery internal volume can be secured.

  For example, when the battery can 1 is formed by using SUS430 stainless steel having a plate thickness dimension (t) of 0.25 mm and setting the radius dimension (R) of the corner portion 19 to 2 mm or more ( R / t = 8), no wrinkles 30 were seen at the corner 19. In addition, in the case of a square-shaped flat rectangular battery having a vertical and horizontal dimension of 24 mm × 24 mm and a thickness dimension of 3 mm, if the radius dimension (R) is 5 mm or less (R / t = 20), a battery of 97% or more An internal volume ratio can be obtained. Here, the battery internal volume ratio means a ratio to the battery internal volume when the corner portion 19 of the bottom wall 2 of the positive electrode can 5 is a right angle (R = 0).

  The mechanical properties of the material include tensile strength, elongation and hardness, and the relationship between them is that if the material hardness is low, the tensile strength is small and the elongation is large. Conversely, the higher the hardness, the higher the tensile strength, but the lower the elongation. Therefore, the present inventors set the hardness suitable as a material for the positive electrode can 5 of the flat rectangular battery in the range of 130 to 300 in Vickers hardness. This is because caulking becomes insufficient when the value is less than 130, resulting in poor liquid leakage resistance, and when it exceeds 300, wrinkles are likely to occur, resulting in deterioration of liquid resistance and poor appearance.

  1 to 3 show a flat rectangular battery according to an embodiment of the present invention. The battery can 1 that accommodates the power generation element includes a metal positive electrode can 5 bent vertically from the outer periphery of the square bottom wall 2 and the peripheral side wall 7 from the outer periphery of the square top wall 6. And a metal negative electrode can 9 facing downward. The positive electrode can 5 is made of a ferritic stainless steel represented by SUS430 or an aluminum clad material using the ferritic stainless steel as a base material. The Vickers hardness of SUS430 is about 170.

As a power generation element, the positive electrode can 5 contains a positive electrode material 10 obtained by press-molding manganese dioxide, which is an active material, and the negative electrode can 9 contains a negative electrode material 11 made of metallic lithium. A separator 12 made of a polypropylene nonwoven fabric is interposed between the positive electrode material 10 and the negative electrode material 11. The electrolytic solution was prepared by dissolving 0.5M lithium perchlorate (LiCl ₄ ) as a solute in propylene carbonate (PC) /1.2-ditomexitan (DME) = 1/1 (volume ratio) as a solvent. Using.

  The positive electrode can 5 in a blank state before battery assembly has a square dish shape with an upper surface opened as shown in FIG. On the other hand, the negative electrode can 9 in the blank state has a square dish shape whose bottom surface is open as shown in FIG.

  As shown in FIG. 3, the peripheral side wall 7 of the negative electrode can 9 has a step portion 13 projecting outward in the middle between the upper and lower sides, and a lower end portion 15 below the step portion 13 is formed in a vertical shape. A spring piece 16 is formed on the outside of the portion 15 so as to be folded upward from the entire periphery of the lower end of the lower end portion 15.

  When assembling the battery, as shown in FIG. 2, a sealing gasket 17 is attached to the peripheral side wall 7 of the negative electrode can 9, the negative electrode can 9 is fitted to the positive electrode can 5, and the upper end of the peripheral wall 3 of the positive electrode can 5 is opened. Caulking is performed with the portion 3a facing inward. The sealing gasket 17 is processed into a compressed state between the peripheral side wall 3 of the positive electrode can 5 and the step portion 13, the lower end portion 15 and the spring piece 16 of the peripheral side wall 7 of the negative electrode can 9. The sealing gasket 17 is formed by injection molding using an insulating material such as polypropylene resin or polyphenylin sulfide resin as a raw material.

  Thus, the obtained battery can 1 was a square whose one side of the bottom wall 2 was 24 mm, and the battery thickness was 3 mm. In addition, the radius dimension (R) of the arc related to the corner portions 19 at the four corners is R / t = 8 to 20 with respect to the plate thickness dimension (t) of the peripheral side wall 3. Specifically, when the thickness (t) including the peripheral side wall 3 is 0.25 mm, the preferable range of the R value is 2 to 5 mm. In this way, the radial dimension R is defined as long as it is within the numerical range, the reduction of the battery internal volume can be minimized, and above all, the ferritic stainless steel represented by SUS430 as the material of the positive electrode can 5 Combined with the selection of steel or an aluminum clad material based on the ferritic stainless steel, the formation of wrinkles 30 (see FIG. 4) at the corner portion 19 is prevented, and the occurrence of liquid leakage and appearance This is because it is possible to surely prevent deterioration in appearance.

  Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

(Example 1)
Using a stainless steel plate of SUS430 (Vickers hardness 170), which is a ferritic stainless steel, a positive electrode can 5 as shown in FIGS. 1 to 3 was produced. The plate thickness dimension of the stainless steel plate including the plate thickness dimension (t) of the opening upper end portion 3a of the peripheral side wall 3 was 0.25 mm. The battery can 1 was a flat square shape of 24 mm × 24 mm, and the radius dimension (R) of the corner portions 19 at the four corners was 3 mm. The thickness dimension of the battery can 1 was 3 mm. The R / t value at this time is 12.

(Example 2)
A flat rectangular battery according to Example 2 was produced in the same manner as in Example 1 except that the radius dimension (R) of the corner portion 19 was set to 2 mm. The R / t value at this time is 8.

(Example 3)
A flat rectangular battery according to Example 3 was produced in the same manner as in Example 1 except that the radius dimension (R) of the corner portion 19 was 4 mm. The R / t value at this time is 16.

Example 4
A flat rectangular battery according to Example 4 was manufactured in the same manner as in Example 1 except that the positive electrode can 5 was manufactured using a clad material having SUS430 as a base material. This clad material had a thickness dimension of SUS430 of 285 μm, an aluminum thickness dimension of 15 μm, and a plate thickness dimension of 0.3 mm as a whole. The R / t value at this time is 10.

(Comparative Example 1)
A flat rectangular battery according to Comparative Example 1 was produced in the same manner as in Example 1 except that the radius dimension (R) of the corner portion 19 was set to 1.5 mm. The R / t value at this time is 6.

(Comparative Example 2)
A flat rectangular battery according to Example 3 was produced in the same manner as in Example 1 except that the radius dimension (R) of the corner portion 19 was 6 mm. The R / t value at this time is 24.

  The battery content ratio was determined for the flat rectangular batteries according to Examples 1 to 4 and Comparative Examples 1 and 2 as described above. Here, the battery content ratio means a ratio with respect to the battery internal volume when the corner portion 19 is a right angle (R = 0). In addition, the occurrence of wrinkles in the corner 19 after the caulking process and a leak resistance test were performed. The liquid leakage resistance test shows the result after 80 days of storage at 60 ° C. and 90% RH. The results are shown in Table 1.

  The inner volume of the flat rectangular battery is maximum when the corner portion 19 is a right angle, that is, when it is a perfect square, but in order to seal the positive electrode can 5 by caulking, the corner portion 19 has an arc shape (R shape). It is necessary to The present inventors consider that the internal volume ratio is 0.97 or more and is acceptable as a product. From this point of view, as in Comparative Example 2, the radius dimension (R value) of the corner portion 19 is considered. Is 6 mm (R / t = 24), the internal volume is too small, and there is a practical problem. On the other hand, in the forms of Examples 1 to 4, the internal volume ratio is 0.97 or more, which is preferable as a flat rectangular battery.

  On the other hand, from Comparative Example 1, when the R / t value is 6, although the radial volume is small, the internal volume ratio shows a good value, but the corner portion 19 may be wrinkled or liquid leakage may occur. Understand. On the other hand, as in Examples 1 to 4, the material of the positive electrode can 5 is ferritic stainless steel or a clad material using this as a base material, and the R / t value is about 8 to 20. It can be seen that the corner portion 19 is not wrinkled, so that the appearance of the battery can be kept good, there is no liquid leakage, and there are no operational problems. As mentioned above, while making the material of the positive electrode can 5 into a ferritic stainless steel or a clad material using this as a base material, and having an R / t value of 8 to 20, it is possible to ensure a good battery internal volume, It was confirmed that a flat rectangular battery excellent in appearance and liquid leakage resistance was obtained.

  In the above embodiment, SUS430 is used as the ferritic stainless steel, but SUS444 may be used, for example.

1 is a plan view of a flat rectangular battery according to the present invention. It is a longitudinal cross-sectional view in an exploded state. It is a longitudinal cross-sectional view of the principal part. It is a figure which shows the problem of the conventional flat rectangular battery.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery can 2 Bottom wall 3 of positive electrode can Peripheral side wall 3a of positive electrode can Opening upper end part 5 of peripheral side wall Positive electrode can 6 Upper surface wall of negative electrode can 7 Peripheral side wall 9 of negative electrode can Negative electrode can 17 Sealing gasket 19 Corner part R Corner part R Radial dimension t Thickness dimension of the upper end of the opening on the peripheral side wall

Claims (2)

The battery can that houses the power generation element is a flat rectangular plate-shaped positive electrode can with the peripheral side wall bent upward from the outer periphery of the rectangular bottom wall, and the flat angle with the peripheral side wall bent downward from the outer periphery of the rectangular top wall A flat rectangular battery including a dish-shaped negative electrode can, wherein the upper end of the opening of the peripheral side wall of the positive electrode can is caulked through a sealing gasket toward the inside,
The positive electrode can is made of a ferritic stainless steel, or a clad material made of this as a base material,
The corner portion of the bottom wall of the positive electrode can is rounded, and the radial dimension (R) is the plate thickness dimension (t) of the upper end portion of the opening of the peripheral side wall that is caulked inward. , R / t = 8-20. The flat rectangular battery is characterized by being set.   The flat rectangular battery according to claim 1, wherein the stainless steel has a Vickers hardness of 130 to 300.

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