JP2005259569A - Flat shaped electrochemical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat shaped electrochemical element in which liquid leakage resistance is not damaged, dimension specification failures caused by swelling after assembling or the like can be reduced, and deterioration of electric properties can be suppressed by setting shapes and dimensions of the case and the gasket appropriately. <P>SOLUTION: The shapes of the case 1 and the gasket 3 are regulated so that the inner circumferential diameter D1 of the case 1 and the outer circumferential diameter D2 of the gasket 3 are in the relationship of (D1-D2)/2≤0.1 mm, and so that the inner curvature radius R1 of the side wall rising part 1b and the outer curvature radius R2 of the side wall rising part 3b of the gasket 3 are in the relationship of R1≤R2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an improvement in productivity and electrical characteristics of a flat electrochemical element by optimizing the shape of a case and a gasket used in the flat electrochemical element.

  In general, a flat electrochemical element is greatly advantageous in that it is small and lightweight, and is used for various applications. For example, there are a lithium primary battery, a secondary battery, and an electric double layer capacitor that are used for memory backup in electronic devices such as PCs and mobile phones. In these, the electrode and the electrolytic solution are caulked and sealed in the housing part through the separator in the center, thereby constituting a flat electrochemical element.

  As an example, the structure of a flat lithium primary battery is shown in FIG. A gasket 1 made of polypropylene that insulates the sealing plate 2 and a case 1 that also serves as a positive electrode terminal made of stainless steel is fitted to the outer periphery of the sealing plate 2 that also serves as a negative electrode terminal made of stainless steel. The case 1 accommodates a positive electrode 4 that contacts the case 1, a negative electrode 5 that contacts the sealing plate 2, and a polypropylene separator 6 that is interposed between the two electrodes and holds the electrolytic solution. The part is sealed by caulking through a gasket 3 made of polypropylene.

This flat electrochemical element has a small number of parts and high productivity. In general, the volume of the case, sealing plate, and gasket that can be filled with the active material or electrolyte as a power generation element increases as the component fitting dimension, which is the gap between the diameter direction sealing plate and the case, is reduced. Moreover, since the airtightness is improved, it is possible to suppress the phenomenon that the electrolytic solution leaks from the inside of the battery (so-called leakage). For example, Patent Document 1 and Patent Document 2 show the optimal relationship between the inner diameter of the case and the outer diameter of the gasket in a flat alkaline battery, and suppress the phenomenon of electrolyte leakage from the battery (so-called leakage), that is, leakage resistance. A manufacturing method for improving liquid properties is disclosed. Thus, reducing the fitting dimension as much as possible and increasing the internal volume at the same time have a merit such that a large amount of power generating elements inside the battery can be filled and the leakage resistance is improved.
Japanese Patent Laid-Open No. 62-8442 JP-A-9-92299

  However, since the flat electrochemical element has a simple configuration, the dimensional shape of the housing parts to be configured has a great influence not only on leakage resistance but also on its electrical characteristics and productivity. In particular, from the viewpoint of leakage resistance, a technique is generally used in which the gasket is sandwiched to reduce the component fitting dimension, which is the gap between the sealing plate and the case in the diametrical direction, so that the components are brought into close contact with each other to eliminate the path for electrolyte leakage. . However, when the fitting dimension is small, depending on the combination of housing part shapes, even if the housing part itself is a dimensional design within the part standard, excess air inside the caulking seal when assembling to a product such as a battery or a capacitor is used. As a result, the assembled product may have a swollen shape, resulting in a production defect that deviates from the dimensional standard of the product. Unlike a cylindrical battery that mechanically connects the electrical connection from the active material to the outside with lead parts, the flat electrochemical element presses the internal electrode body against the case or sealing plate to When the product is swelled due to such a cause, the contact pressure between the internal electrode body and the case or the sealing plate is reduced, the contact resistance is increased, and the electrical characteristics are deteriorated.

It is an object of the present invention to improve the productivity and electrical characteristics of a flat electrochemical device by optimizing the shape of parts of a case and a gasket.

  In order to solve the above problems, the flat electrochemical device of the present invention has a bottomed cylindrical shape including a flat bottom portion, a side rising portion, and a side surface portion, and a bottomed cylindrical shape. The sealing plate is caulked with an insulating gasket formed in an annular shape with an outer wall portion, an outer wall rising portion and a bottom surface portion, and a power generation element is sealed in these internal spaces, and the inner periphery of the case The diameter D1 and the outer peripheral diameter D2 of the gasket are in a relationship of (D1-D2) /2≦0.1 mm, and the inner radius of curvature R1 of the side surface rising portion of the case and the outer radius of curvature of the outer wall rising portion of the gasket R2 is in a relationship of R1 ≦ R2.

  Here, the inner peripheral diameter D1 of the case represents the diameter of the circumference formed by the intersection of straight lines extending from the bottom flat portion and the side surface inside the cross section, and the outer peripheral diameter D2 of the gasket is It represents the diameter of the circumference formed by the intersection of straight lines extending from the outer wall portion and the bottom surface portion.

  The inner peripheral diameter D1 of the case and the outer peripheral diameter D2 of the gasket are set to (D1-D2) /2≦0.1 mm, the inner curvature radius R1 of the side surface rising portion of the case, and the outer wall of the gasket facing the same By setting the outer radius of curvature R2 of the rising portion to R1 ≦ R2, when the gasket and the case are combined, the outer wall rising portion from the bottom surface portion of the gasket is not caught by the side rising portion from the bottom surface flat portion of the case. In addition, when the gasket and the case are combined, excess air sandwiched between the gasket bottom and the case bottom flat part escapes between the side rising part and the outer wall rising part. Adhere closely to each other. As a result, the space surrounded by the sealing plate, gasket and case is minimized, and there is no swelling of the product after the case and sealing plate are sandwiched between the gaskets to seal the power generation element inside. Since a good contact pressure between the power generation element and the case or the sealing plate can be maintained, a decrease in electrical characteristics can be suppressed. In particular, the effect is great when the electrochemical element has a wide diameter and is thin, or when the case plate is thin.

  By optimizing the shape of the parts of the case and the gasket, it is possible to reduce dimensional standard defects due to product swelling in product assembly of flat electrochemical elements and improve electrical characteristics.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of a flat battery according to an embodiment of the present invention. A bottomed cylindrical case 1 and a bottomed cylindrical sealing plate 2 are caulked with an annular gasket 3 interposed therebetween. The positive electrode 4, the negative electrode 5, and the separator 6 holding the electrolytic solution are sealed in these internal spaces, and the positive electrode 4 and the case 1, and the negative electrode 5 and the sealing plate 2 are in pressure contact with each other at an appropriate contact pressure. The electrical connection is made.

FIG. 2 shows a sectional view of the case 1, and FIG. 3 shows a sectional view of the gasket 3. The case 1 is formed by drawing to form a side surface 1c with the bottom flat portion 1a having an inner curvature radius R1 and a side rising portion 1b. 2, each of the inner surface of the bottom flat portion 1a and the inner surface of the side surface portion 1c is extended, and the diameter of the circumference formed by the intersection 1d of the extension lines is defined as the inner peripheral diameter D1 of the case 1. On the other hand, the gasket 3 made of an insulating resin material has an outer wall rising portion 3b with a bottom surface portion 3a having an outer radius of curvature R2 to form an outer wall portion 3c, and an inner wall portion 3d is also formed on the inner side. In FIG. 3, the bottom surface portion 3 a and the outer wall portion 3 c extend the surfaces in contact with the case, and the circumference diameter formed by the intersection 3 e of the extension lines is defined as the outer peripheral diameter D <b> 2 of the gasket 3. Here, D1 and D2 are set to satisfy (D1-D2) /2≦0.1 mm, and R1 and R2 are set to satisfy R1 ≦ R2.

  FIG. 4 is a cross-sectional view of the flat battery according to one embodiment of the present invention before caulking and sealing of the case 1, the gasket 3, and the sealing plate 2. D1 and D2 are set to satisfy (D1-D2) /2≦0.1 mm, and R1 and R2 are set to satisfy R1 ≦ R2, so when the sealing plate 2 is pressed from above, Air sandwiched between the bottom surface portion 3a of the gasket 3 or the positive electrode 4 and the bottom flat portion 1a of the case 1 escapes between the side surface rising portion 1b of the case 1 and the outer wall rising portion 3b of the gasket 3, and the bottom surface portion 3a of the gasket 3 or The positive electrode 4 and the bottom flat portion 1a of the case 1 are in close contact with each other.

  When the case 1 is crimped in this state, the flat battery shown in FIG. 1 is completed. In this battery, there is no excess air between the bottom surface portion 3a of the gasket 3 or the portion sandwiched between the positive electrode 4 and the bottom flat portion 1a of the case 1, so that the positive electrode 4 and the case 1, the negative electrode 5 and the sealing plate 2 are in proper contact. While maintaining pressure, it does not swell after assembly. Therefore, the electrical characteristics are not deteriorated, and the product dimensions are not out of specification after assembly. By caulking the case 1, the case 1 and the gasket 3 are deformed, and the inner radius of curvature of the side surface rising portion 1b of the case 1 and the outer radius of curvature of the outer wall rising portion 3b of the gasket 3 are changed. A slight gap is formed between the side rising portion 1 b and the outer wall rising portion 3 b of the gasket 3.

  FIG. 5 is a cross-sectional view of the flat battery as a comparative example before caulking and sealing of the case 1, the gasket 3, and the sealing plate 2. D1 and D2 are set to satisfy (D1-D2) /2≦0.1 mm, but case 1 and gasket 3 are set so that R1 and R2 satisfy R1> R2. In this case, since the outer wall rising portion 3 b of the gasket 3 corresponds to the side surface rising portion 1 b of the case 1, the bottom surface portion 3 a of the gasket 3 or the positive electrode 4 is not in close contact with the bottom surface flat portion 1 a of the case 1.

  In this state, when the case 1 is crimped, the gasket 3 is sealed with excess air remaining in the bottom surface portion 3 a of the gasket 3 or a portion sandwiched between the positive electrode 4 and the bottom surface flat portion 1 a of the case 1. Therefore, even if it is caulked as specified, the internal pressure increases due to excess air remaining in the air and the product expands, resulting in a flat battery as shown in FIG. turn into. In addition, an appropriate contact pressure between the positive electrode 4 and the case 1 and the negative electrode 5 and the sealing plate 2 cannot be obtained, resulting in a decrease in electrical characteristics.

  In order to secure a good adhesion between the case and the gasket and obtain a liquid leakage resistance, it is preferable to set R1 and R2 so that R1 ≦ R2 <R1 × 3.

  R1 and R2 are set to satisfy R1 ≦ R2. However, when D1 and D2 are set to satisfy (D1−D2) / 2> 0.1 mm, Since the fitting dimension, which is the gap between the cases, becomes larger, it is preferable for the problem of sealing with excess air trapped in the bottom surface of the gasket or the portion sandwiched between the positive electrode and the bottom flat portion of the case, On the other hand, there is a risk that the adhesion between the case and the gasket will be lowered and the leakage resistance will be lowered.

Next, as a more specific example, an example of a flat manganese dioxide lithium battery using manganese dioxide as a positive electrode and lithium as a negative electrode is shown. In flat manganese lithium battery CR2012 (diameter 20.0 mm, thickness 1.2 mm, electric capacity 55 mAh), D1 and D2 are (D1−D2) /2=0.10 mm, and various combinations of R1 and R2 100 batteries A1, B1, C1, D1, E1, F1, G1, H1, and I1 were each assembled using a case made of stainless steel with a thickness of 0.20 mm and a gasket made of polypropylene. At this time, the product size standard defect occurrence rate exceeding 1.20 mm, the upper limit of battery thickness standard in CR2012, the average internal resistance value of the battery in AC method 1 kHz, and the temperature environment of −10 ° C. and 60 ° C. for 1 hour Table 1 shows the liquid leakage occurrence rate after 10 days of the thermal shock test in which the films are alternately exposed.

  As is clear from this, compared with the batteries A1, B1, C1, H1, and I1 according to the examples of the present invention, the batteries D1, E1, F1, and G1 according to the comparative examples have a product dimension defect rate, an internal resistance value, Both leak rates have deteriorated. This is because when the combination of the case and gasket is R1> R2, the internal air does not escape well when assembling the battery. It is thought that the thickness exceeding the thickness increased. Moreover, since it became a bulging shape, it is considered that the contact pressure between the positive electrode and the case, and the negative electrode and the sealing plate in the battery decreased, the contact resistance value increased, and the internal resistance value of the battery itself increased. At the same time, the contact pressure between the case and the gasket decreases or disperses due to the bulging shape or the gasket itself being sealed without being in contact with the bottom surface of the case. It seems that it became easy to do.

Next, as another embodiment, an example of a flat manganese dioxide battery using manganese dioxide as the positive electrode and lithium as the negative electrode will be described. In a flat manganese lithium battery CR2012 (diameter 20.0 mm, thickness 1.2 mm, electric capacity 55 mAh), R1 = 0.10 and R2 = 0.20 so that R1 ≦ R2, and (D1-D2) /2=0.05, 0.08, 0.10, 0.12 mm in various combinations, using a 0.20 mm thick stainless steel case and polypropylene gasket, batteries A2, B2, 100 C2 and D2 were assembled. At this time, the product size standard defect occurrence rate exceeding 1.20 mm, the upper limit of battery thickness standard in CR2012, the average internal resistance value of the battery in AC method 1 kHz, and the temperature environment of −10 ° C. and 60 ° C. for 1 hour Thermal shock test 1 to expose alternately
Table 2 shows the incidence of leakage after 0 days.

  As is clear from this, compared with the batteries A2, B2, and C2 according to the examples of the present invention, the battery D2 according to the comparative example has a good dimensional standard defect occurrence rate and an internal resistance value, but has a reduced leakage resistance. doing. It is considered that this is because the fitting between the case and the gasket is loosened, the adhesion between the side surface portion of the case and the outer wall portion of the gasket is lowered, and the liquid is easily leaked.

  As described above, by appropriately setting the shapes of the case and the gasket, it is possible to reduce product dimension defects due to battery swelling and improve electrical characteristics.

  In addition, although the Example of invention demonstrated manganese dioxide lithium battery, even if it uses fluorinated graphite, vanadium oxide, niobium oxide, lithium manganate, lithium titanate, carbon etc. for a positive electrode, it is applicable. Moreover, Li / Al alloy, lithium titanate, etc. can also be used for a negative electrode. Further, an aqueous electrolytic solution or a polymer electrolytic solution can be used instead of the non-aqueous electrolytic solution. Further, it can be applied to an electric double layer capacitor instead of the battery.

  In the flat electrochemical element, appropriately setting the shape of the case and gasket as in the present invention is useful for reducing dimensional standard defects due to swelling of the electrochemical element and improving the electrical characteristics.

Sectional drawing of the flat battery concerning one Example of this invention. Case cross section Cross section of gasket 1 is a cross-sectional view of a flat battery before sealing in an embodiment of the present invention. Cross-sectional view of flat battery before sealing in comparative example Cross-sectional view of flat battery in comparative example Cross-sectional view of a conventional flat battery

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Case 1a Bottom flat part 1b Side surface rising part 1c Side surface part 2 Sealing plate 3 Gasket 3a Bottom surface part 3b Outer wall rising part 3c Outer wall part 4 Positive electrode 5 Negative electrode 6 Separator

Claims (1)

A case having a bottomed flat part, a side rising part, and a side part and formed into a bottomed cylindrical shape, and a sealing plate formed into a bottomed cylindrical shape, includes an outer wall part, an outer wall rising part, and a bottom part. A flat electrochemical element formed by sandwiching an insulating gasket formed in an annular shape and sealing a power generation element in these internal spaces,
The inner peripheral diameter D1 of the case and the outer peripheral diameter D2 of the gasket are in a relationship of (D1-D2) /2≦0.1 mm, and the inner curvature radius R1 of the side surface rising portion of the case and the outer wall rising of the gasket The flat electrochemical element, wherein the outer radius of curvature R2 of the portion is in a relationship of R1 ≦ R2.