JP2006092761A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coin-shaped nonaqueous electrolyte secondary battery maintaining high reliability without being influenced by an increase of internal pressure of the battery due to gas produced in the battery in using and storing over a long period of time. <P>SOLUTION: In the nonaqueous electrolyte secondary battery having power generation elements sealed up by a positive electrode case, a negative electrode case for sealing an opening of the positive electrode case and a gasket disposed between the positive electrode case and the negative electrode case, the secondary battery has a projection portion at an arbitrary part on the side of an end portion against a flat surface of the opening end of the negative electrode case on the inside of the battery at the opening of the positive electrode case. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to improvement of long-term reliability of a nonaqueous electrolyte battery in which a power generation element is liquid-tightly sealed with a positive electrode case, a negative electrode case, and a gasket.

  Nonaqueous electrolyte batteries are widely used as main power sources and memory backup power sources for various electronic devices. In particular, in recent years, with the increase in small portable devices such as mobile phones, the demand for non-aqueous electrolyte batteries has been increasing year by year. In such a background, it is required to ensure high reliability over a long period of time for nonaqueous electrolyte batteries that are important components of these electronic devices.

  A conventional structure of a coin-type non-aqueous electrolyte battery is shown in FIG.

  In assembling the battery, the negative electrode 5, the separator 6, the positive electrode 4 and the electrolyte solution 7 are filled in the positive electrode case 1, and the opening of the positive electrode case 1 facing the opening of the negative electrode case 2 is connected to the positive electrode case 1 and the negative electrode case 2. It seals by crimping inside through the gasket 3 which is an insulator between both.

In order to secure higher reliability, as a method of improving the sealing structure particularly for the purpose of improving the leakage resistance, as shown in Patent Document 1, for example, the inner surface of a concave can (case that also serves as a positive electrode terminal) There is a method of providing a protrusion at the contact portion with the gasket. In the battery, the projecting portion is preferably located at the contact portion with the bottom surface of the gasket, and this method aims to improve the liquid leakage resistance particularly during reflow soldering.
JP 2001-357823 A

  However, non-aqueous electrolyte batteries are used for a long time in the equipment used, and have high long-term reliability, including not only leakage resistance, but also charge / discharge cycle characteristics in secondary batteries. Maintaining it is also a very important issue.

  A non-aqueous electrolyte battery generates gas inside the battery during long-term use and storage. In particular, in a coin-type non-aqueous electrolyte battery, as the internal pressure of the battery increases due to gas generation, the portion corresponding to the battery bottom surface of the positive electrode case swells, thereby relaxing the compression of the gasket bottom. As a result, in the structure described in Patent Document 1, the electrolyte solution may leak or foreign matter such as water vapor may enter from the outside of the battery. Furthermore, leakage of electrolyte causes problems that corrode peripheral devices and cause various harmful effects. If water vapor enters, the battery reaction does not proceed smoothly due to the decomposition reaction of the electrolyte, resulting in deterioration of battery performance. .

  The present invention has been made in view of the above-described problems, and has an object of further ensuring sealing in a nonaqueous electrolyte battery and ensuring higher reliability over a long period of time.

  In order to achieve the above object, the battery according to the present invention includes a positive electrode case, a negative electrode case that seals the opening of the positive electrode case, and a gasket that is interposed between the positive electrode case and the negative electrode case. A non-aqueous electrolyte secondary battery having a protrusion at an arbitrary portion on the end side of a plane formed by the opening end of the negative electrode case inside the battery in the opening portion of the positive electrode case. .

  According to such a configuration, by providing a protrusion on the positive electrode case, the opening of the positive electrode case disposed on the end side from the plane formed by the opening of the negative electrode case, and the opening of the negative electrode case disposed via the gasket are provided. The degree of compression of the gasket in the portion co-pressed with the portion above the plane formed can be increased.

  Furthermore, with respect to the swelling of the positive electrode case caused by gas generation in the long-term use of the battery, in the battery of the present invention, the opening of the positive electrode case arranged on the end side from the plane formed by the opening of the negative electrode case and the gasket are used. The compressibility of the gasket in the part co-pressed with the upper part of the plane formed by the opening of the negative electrode case is increased, and in this part, the compression in the lateral direction is performed, and the influence of relaxation of the compressibility in the longitudinal direction is completely eliminated. Even when the battery is used over a long period of time, it is not affected by the expansion of the positive electrode case accompanying the increase in the internal pressure of the battery due to gas generation.

  According to the present invention, the positive electrode is provided on the end side with respect to the plane formed by the opening of the negative electrode case by providing the protrusion on the end side from the plane formed by the opening of the negative electrode case on the battery inner side of the positive electrode case opening. Highly stable and reliable even in long-term use because the compression of the gasket in the part that is co-pressed by the opening of the case and the part above the plane formed by the opening of the negative electrode case arranged via the gasket It is possible to provide a battery having

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

  The battery in the present invention is a coin-type non-aqueous electrolyte secondary battery, and as shown in FIG. 1, a positive electrode case 1 having a protrusion 1a inside, a negative electrode case 2 also serving as a negative electrode terminal, a positive electrode case 1 and a negative electrode A gasket 3, a positive electrode 4, a negative electrode 5, a separator 6, and an electrolyte solution 7, which are present as insulators between the case 2, and a battery assembly, a negative electrode 5, a separator 6, a positive electrode 4, and a nonaqueous electrolyte solution 7 By filling the inside of the battery case and sealing the opening of the positive electrode case 1 of the present invention having the protruding portion 1a by crimping the opening inside the positive electrode case 1 and the negative electrode case 2 via the gasket 3 which is an insulator. went.

  It is preferable that the protruding portion 1 a is provided on the end side of the plane formed by the opening of the negative electrode case 2 and on the battery inner side of the positive electrode case 1.

  The battery according to the present invention is co-pressured by the opening of the positive electrode case disposed on the end side from the plane formed by the opening of the negative electrode case and the portion above the plane formed by the opening of the negative electrode case disposed via the gasket. The compression of the gasket in the part is increased, and the electrolyte solution leaks from the inside of the battery and from the outside of the battery without being affected by the swelling of the part that corresponds to the battery bottom of the positive electrode case due to long-term use and storage. Has the effect of preventing the intrusion of water vapor. This effect makes it possible to provide a battery having long-term high reliability.

  The protrusion 1a of the positive electrode case 1 is provided inside the opening of the positive electrode case 1 disposed on the end side from the plane formed by the opening of the negative electrode case 2, and is located at a portion where the positive electrode case 1 and the negative electrode case 2 are closest to each other. If provided, it is more preferable. The portion where the positive electrode case and the negative electrode case are closest to each other is the portion having the highest compressibility of the gasket. By increasing the compressibility of this portion, further effects are exerted in suppressing leakage and water vapor intrusion.

  At this time, the portion where the gasket is co-pressed by the opening of the positive electrode case arranged on the end side from the plane formed by the opening of the negative electrode case and the portion above the plane formed by the opening of the negative electrode case arranged via the gasket In the above, it is preferable that the portion of the gasket corresponding to the protruding portion 1a provided on the positive electrode case has a compression rate of 25 to 60% after caulking and sealing.

  Further, as shown in FIG. 2, it is more preferable to provide a notch 1b outside the opening of the positive electrode case disposed on the end side from the plane formed by the opening of the negative electrode case. This notch portion 1b absorbs stress at the time of sealing well, reduces the spring back of the positive electrode case, passes through the opening of the positive electrode case disposed on the end side from the plane formed by the opening of the negative electrode case, and the gasket. The effect of reducing the relaxation of the compression of the gasket at the portion co-pressed with the portion above the plane formed by the opening of the negative electrode case arranged in a row can be expected. This effect provides a more reliable sealing and brings about a synergistic effect on long-term reliability as well as leakage resistance.

  Further, when the cutout portion 1b is provided outside the positive electrode case corresponding to the protrusion inside the positive electrode case, it is easy to manufacture a component.

  In addition, the protrusion part and notch part of the positive electrode case of this invention may be provided continuously, or may be provided intermittently.

  Subsequently, a more specific embodiment of the present invention will be described.

Example 1
As a specific example of the present invention, a battery having a size of 2020 (diameter 20 mm, thickness 2.0 mm) was manufactured. As shown in FIG. 1, this battery is composed of a positive electrode case 1 having a protrusion 1 a inside, a negative electrode case 2 also serving as a negative electrode terminal, and polypropylene present as an insulator between the positive electrode case 1 and the negative electrode case 2. A gasket 3, a positive electrode 4, a negative electrode 5 using a lithium-aluminum alloy as an active material, a separator 6 made of a polypropylene non-woven fabric existing as an insulator between the positive electrode and the negative electrode, and an electrolytic solution 7. The positive electrode 4 is 4% carbon powder as a conductive agent and 7% tetrafluoroethylene-hexafluoropropylene copolymer (solid component) as a fluororesin as a binder, based on the weight of lithium manganate as an active material. And water were kneaded and pressure-molded to form a pellet. The electrolyte solution 7 was prepared by dissolving lithium perchlorate (LiClO ₄ ) as an electrolyte in a mixed solvent composed of propylene carbonate (PC) and dimethoxyethane (DME).

  The battery is assembled by filling the inside of the battery case with the negative electrode 5, the separator 6, the positive electrode 4 and the electrolyte 7, and the opening of the positive electrode case 1 of the present invention is an insulator between both the positive electrode case 1 and the negative electrode case 2. A battery with a compression rate of 25% corresponding to the protrusion of the positive electrode case provided at the portion where the positive electrode case and the negative electrode case are closest to each other is sealed with a battery A. did.

  On the other hand, as shown in FIG. 3, a battery manufactured using a positive electrode case having no protrusions was designated as a battery P. In addition, a battery was manufactured using a positive electrode case in which a protrusion was provided on the contact portion with the gasket bottom surface, and a battery in which the ratio of the height of the protrusion to the gasket thickness was 20% was designated as battery Q.

  Here, each battery is a portion that is co-pressed by the opening of the positive electrode case disposed above the lower end of the opening of the negative electrode case and the upper portion of the opening of the negative electrode case disposed via the gasket. Therefore, the compression ratio of the gasket at the portion where the positive electrode case and the negative electrode case are closest to each other was set to 25%.

  Table 1 shows the leak rate after 50 cycles of the leak test of the thermal shock cycle in which the battery A, the battery P, and the battery Q are held at 60 ° C. for 1 hour and at −10 ° C. for 1 hour.

  From Table 1, it is clear that the leakage characteristics of the battery A and the battery Q are lower than that of the battery P, so that the leakage characteristics can be remarkably improved by having the protrusions inside the positive electrode case.

  Subsequently, the battery A, the battery P, and the battery Q were each completely discharged, and then a cycle test was repeated in which the battery was charged with 3.1 V-160Ω for 35 hours and then discharged with 1.5 kΩ to 2.0 V. Table 1 shows the number of cycles when the discharge capacity of the battery becomes half of the initial value after the cycle. The cycle life of the battery A is longer than that of the battery P and the battery Q, and it can be seen from this that the battery cycle characteristics are remarkably improved by having the configuration of the battery A.

  Furthermore, the battery A, the battery P, and the battery Q were each completely discharged, and then an overcharge resistance test in which the battery A, the battery P, and the battery Q were always charged at 3.1 V-160Ω in a constant temperature bath at 60 ° C. was performed. The battery taken out after a certain period of time was discharged to 2.0 V at 1.5 kΩ, and the remaining capacity was confirmed. FIG. 4 shows the results of the 60 ° C. overcharge resistance test, in which the horizontal axis represents the storage days and the vertical axis represents the remaining capacity (initial capacity ratio).

  From FIG. 4, it can be seen that the battery A is less deteriorated in the 60 ° C. overcharge resistance test of the battery A than the batteries P and Q, and the overcharge resistance of the battery A is improved.

  From the above, by providing a protrusion on the inside of the positive electrode case and installing it on the inside of the battery of the positive electrode case above the lower end of the opening of the negative electrode case, not only leakage resistance but also long-term reliability is achieved. It turns out that it improves.

(Example 2)
As shown in FIG. 2, a battery manufactured with the same structure as the battery A except that the protrusions on the battery inner side of the positive electrode case are aligned with each other and have a notch on the battery outer side. did.

  After the battery B was completely discharged, a cycle test was repeated in which the battery B was charged at 3.1 V-160Ω for 35 hours and then discharged at 1.5 kΩ to 2.0 V. Table 2 shows the number of cycles when the discharge capacity of the battery becomes half of the initial value after the cycle. From Table 2, it can be seen that the battery B further improves the cycle characteristics as compared with the battery A.

  Therefore, it is more preferable to have a notch part on the battery outer side which is made to face the back and back with the protrusion part which exists in the positive electrode case battery inner side of the edge part side from the plane which the opening part of a negative electrode case makes.

(Example 3)
Next, batteries C to G having the same configuration as that of the battery A, in which the compressibility of the gasket corresponding to the protrusion of the positive electrode case provided at the portion where the positive electrode case and the negative electrode case are closest to each other, were manufactured.

  Each battery was held at 60 ° C. for 1 hour and at −10 ° C. for 1 hour, and the leakage rate after 50 cycles of leakage test of the thermal shock cycle and after each battery was completely discharged, 3.1 V Table 3 shows the results of a cycle test in which the battery was charged at −160Ω for 35 hours and then discharged at 1.5 kΩ to 2.0 V.

  From the results of Table 3, the positive electrode case according to the present invention is used, and the opening of the positive electrode case arranged on the end side from the plane formed by the opening of the negative electrode case, and the opening of the negative electrode case arranged via the gasket By setting the compression rate of the gasket corresponding to the protrusion provided at the portion where the positive electrode case and the negative electrode case are closest to each other to be co-pressed with the portion above the plane formed, the leakage rate is set to 25 to 60%. It turns out that the outstanding effect which prevents a liquid is acquired.

  Furthermore, it can be seen from the cycle test results in Table 3 that the cycle characteristics are further improved when the compression rate of the gasket corresponding to the protrusions of the positive electrode case is 25 to 60%, as in the case of the liquid leakage resistance.

  From the above, when the positive electrode case of the present invention is used, it is preferable that the compression ratio of the gasket corresponding to the protrusion provided at the portion where the positive electrode case and the negative electrode case are closest to each other is 25 to 60%.

  The nonaqueous electrolyte battery of the present invention is useful in ensuring high reliability over a long period of time.

Cross-sectional schematic diagram of a non-aqueous electrolyte battery in this example Cross-sectional schematic diagram of a non-aqueous electrolyte battery in this example Cross-sectional schematic diagram of a conventional non-aqueous electrolyte battery Overcharge characteristics in this example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode case 1a Protrusion part 1b Notch 2 Negative electrode case 3 Gasket 4 Positive electrode 5 Negative electrode 6 Separator 7 Electrolyte

Claims (5)

A non-aqueous electrolyte secondary battery in which a power generation element is hermetically sealed by a positive electrode case, a negative electrode case that seals the opening of the positive electrode case, and a gasket that is interposed between the positive electrode case and the negative electrode case, A non-aqueous electrolyte secondary battery having a protrusion on an end portion side of a plane formed by an opening end of the negative electrode case on the battery inner side of the opening portion of the positive electrode case. The nonaqueous electrolyte secondary battery according to claim 1, wherein the protrusion is provided at a portion where the positive electrode case and the negative electrode case are closest to each other. 2. The nonaqueous electrolyte secondary battery according to claim 1, further comprising a notch on the battery outer side of the opening of the positive electrode case. 4. The nonaqueous electrolyte secondary battery according to claim 3, wherein the cutout portion is provided on the outside of the positive electrode case battery so as to coincide with a protrusion on the battery inner side of the positive electrode case. 5. . 2. The nonaqueous electrolyte secondary battery according to claim 1, wherein the compression ratio of the gasket in contact with the protruding portion is in a range of 25 to 60%.

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