JP2009140738A - Flat type battery with terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat type battery with terminals for preventing an internal short circuit while lithium to constitute the negative electrode is liquified and contacts a positive electrode through a separator due to heat concentration to a negative electrode containing lithium when welding a negative electrode terminal. <P>SOLUTION: In the flat battery, the negative electrode 15 containing lithium, the positive electrode 16, an organic electrolytic solution, and the separator 18 are air-tightly sealed by a sealing plate 11, a gasket 19, and a positive electrode case 12. A negative electrode terminal 20 is welded to the sealing plate 11, and by installing a heat diffusion material 13 such as a graphite sheet having conductivity between the negative electrode 15 and an inside plane part of the sealing plate 11, suppression of heat concentration to the negative electrode 15 when welding the negative electrode is achieved, and the internal short circuit caused by liquefaction of lithium is prevented. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a small and thin flat battery, and in particular, a highly reliable terminal characterized in that a conductive heat diffusion material is provided between the negative electrode and the inner flat portion of the sealing plate. The present invention relates to an attached flat battery.

  In recent years, a flat nonaqueous electrolyte battery (hereinafter simply referred to as a “flat battery”) in which a power generation element in which a nonaqueous electrolyte is combined with an alkali metal or an alloy thereof is housed in a flat battery case is excellent. Since it has reliability and high energy density, it is suitably used as a driving power source for various small electronic devices and a memory backup power source.

  Up to now, this type of battery has been mainly a primary battery that cannot be recharged. However, in recent years, various rechargeable secondary batteries have been developed, and the demand is increasing as a backup power source for memory and clock functions. Recently, the demand for electronic devices such as mobile phones and digital still cameras has been increasing rapidly. However, along with the downsizing and thinning of these electronic devices, the flat batteries placed inside the devices are also small and thin. Is required.

  The flat battery can be attached to these electronic devices using a battery holder, or the flat battery can be attached to a terminal and soldered to the electronic device. However, from the viewpoint of miniaturization and thinning, the battery holder Compared to the above, advantageous flat batteries with terminals are becoming mainstream.

  As shown in FIG. 3, a general flat battery with a terminal seals a negative electrode containing lithium, a separator, a positive electrode, and an organic electrolyte solution with a sealing plate made of stainless steel and a positive electrode case via a gasket. It is obtained by resistance welding or laser welding of a terminal made of stainless steel to the positive electrode case.

Further, in a primary battery using a lithium metal simple substance for the negative electrode and a pellet-shaped or sheet-shaped molded body for the positive electrode, a carbon coating layer is provided on the inner plane portion of the positive electrode case by the method shown in Patent Document 1, and the positive electrode and the positive electrode Enhancing the electrical contact of the case. On the other hand, in a secondary battery that uses a molded body in which a negative electrode is made of an oxide or nitride containing lithium in the form of a pellet or sheet, a carbon coating layer is provided on the positive electrode case to increase the electrical contact between the positive electrode and the positive electrode case. At the same time, a carbon coating layer is provided on the inner plane portion of the sealing plate to enhance electrical contact between the negative electrode and the sealing plate.
JP-A-11-135083

  However, in the battery having the structure shown in FIG. 3, particularly in a thin battery, it is essential to make the sealing plate, the positive electrode case, and the terminal material thin. To obtain a flat battery with a terminal, a thin stainless steel material is used. It is necessary to weld them together. In order to weld stainless steels, it is necessary to apply heat of 1300 ° C or higher to the welding point, but stainless steel is known as a material with low thermal conductivity among metals. During terminal welding, heat of 200 ° C. or higher is locally concentrated on the negative electrode and the positive electrode. In particular, welding of the negative electrode terminal to the sealing plate has a negative electrode containing lithium having a melting point of about 180 ° C. at a position in contact with the inner plane portion of the sealing plate, and when heat of 200 ° C. or higher is locally applied to the negative electrode, Liquefies and penetrates the separator. This caused a problem of causing an internal short circuit.

  An object of the present invention is to solve such a problem, and an object of the present invention is to provide a highly reliable flat battery with a terminal which does not cause an internal short circuit during terminal welding even if it is thin.

  In order to solve the above problems, a flat battery with a terminal of the present invention is a flat battery in which a negative electrode containing lithium, a positive electrode, an organic electrolyte, and a separator are sealed with a sealing plate, a gasket, and a positive electrode case, A negative electrode terminal is welded to the sealing plate, and a conductive heat diffusing material is provided between the negative electrode and the inner flat portion of the sealing plate.

  By using the battery structure of the present invention, the thermal diffusion material relaxes the heat concentration on the negative electrode containing lithium when the negative electrode terminal is welded to the sealing plate of the flat battery. The occurrence of a short circuit can be prevented.

  According to the present invention, it is possible to provide a highly reliable flat battery with a terminal that does not cause an internal short circuit during terminal welding even if it is a small and thin flat battery.

  The invention according to claim 1 of the present invention is a flat battery in which a negative electrode containing lithium, a positive electrode, an organic electrolyte, and a separator are hermetically sealed with a sealing plate, a gasket, and a positive electrode case, and the negative electrode terminal is provided on the sealing plate. Is welded, and a heat diffusion material having conductivity is provided between the negative electrode and the inner flat surface of the sealing plate, and when the negative electrode terminal is welded to the sealing plate of the flat battery, the heat diffusion material It reduces the heat concentration on the negative electrode.

  Preferred embodiments of the present invention will be described below with reference to the drawings, taking a flat primary battery with terminals as an example. The present invention is not limited to primary batteries.

  The flat primary battery with a terminal of the present invention shown in FIG. 1 includes a positive electrode 16 molded into a pellet or sheet, a carbon coating layer 14 that improves the electrical contact between the positive electrode case 12 and the positive electrode 16 made of stainless steel, lithium It consists of a negative electrode 15 made of metal, a heat diffusion material 13 having conductivity, a carbon coating layer 17 that enhances electrical contact between the sealing plate 11 made of stainless steel and the heat diffusion material 13, and a resin that separates the positive electrode 16 and the negative electrode 15. The separator 18 and the organic electrolyte solution are used as power generation elements, and the sealing plate 11 and the positive electrode case 12 of the flat primary battery are hermetically sealed with the sealing plate 11 and the positive electrode case 12 via the gasket 19 made of resin. The terminal 20 and the positive electrode terminal 21 are welded.

  In the present embodiment, the greatest feature is that the thermal diffusion material 13 is provided between the inner surface plane portion of the sealing plate 11 and the negative electrode 15. Since stainless steel is inexpensive and excellent in corrosion resistance, it is generally used as a battery material. However, thermal conductivity is about 15 to 30 W / m · K, which is low among metals. On the other hand, since the melting point of stainless steel is as high as 1300 ° C. or higher, it is necessary to apply heat above this temperature to the welding point when the stainless steels are welded together. If a thick stainless steel material is used for the sealing plate 11, the physical distance between the welding point and the negative electrode 15 can be increased, so that heat conduction to the negative electrode 15 can be suppressed, but the discharge capacity is reduced due to the decrease in the internal volume. This is disadvantageous. When a stainless steel material having a small thickness is used for the sealing plate 11, the physical distance between the welding point and the negative electrode 15 becomes small, and heat concentration on the negative electrode 15 occurs. In the present invention, the heat diffusing material 13 is disposed between the inner surface flat portion of the sealing plate 11 and the negative electrode 15, whereby the negative electrode 15 is locally generated when the negative electrode terminal 20 is welded to the sealing plate 11 of the flat primary battery. Since the heat diffusing material 13 suppresses heat concentration, the lithium does not liquefy and has an effect of preventing an internal short circuit due to lithium penetrating the separator 17.

  The present invention according to claim 2 is characterized in that a copper foil is used for the thermal diffusion material 13. Since the copper foil is excellent in workability and has electrical conductivity, it does not cause an increase in the internal resistance of the battery due to a decrease in electrical contact between the sealing plate 11 and the negative electrode 15. Moreover, since the thickness can be easily reduced and the thermal conductivity is as large as 390 W / m · K, local heat concentration on the negative electrode 16 that occurs when the negative electrode terminal 20 is welded to the sealing plate 11 of the flat battery is suppressed, It has an effect of preventing an internal short circuit due to lithium penetrating the separator 17.

  According to a third aspect of the present invention, in the second aspect, the thickness of the copper foil is limited to 0.02 mm or more. By this limitation, a higher internal short-circuit prevention effect can be obtained.

  The present invention according to claim 4 is characterized in that a graphite sheet is used for the thermal diffusion material 13. Due to the conductivity of the graphite sheet, the increase in the internal resistance of the battery due to a decrease in the electrical contact between the sealing plate 11 and the negative electrode 15 is not caused. Further, because of its structure, the thermal conductivity in the planar direction can be made significantly higher than the thermal conductivity in the thickness direction, the negative electrode produced when the negative electrode terminal 20 is welded to the sealing plate 11 of the flat battery even if it is thin. 16 has an effect of suppressing local heat concentration to 16 and preventing an internal short circuit due to lithium penetrating the separator 17.

  Hereinafter, preferred embodiments of the present invention will be described.

(Example 1)
FIG. 1 is a sectional view of a flat battery with a terminal according to the present invention.

  As Example 1, a flat battery having a diameter of 6.8 mm and a thickness of 1.0 mm was produced under the following conditions, and a negative electrode terminal and a positive electrode terminal were attached thereto by welding to obtain a flat battery with a terminal shown in FIG. It was. A stainless steel material (SUS304, thickness 0.10 mm) having excellent corrosion resistance is used for the sealing plate 11, and a carbon coating layer 17 is formed by applying a carbon coating on the inner plane portion of the sealing plate. A copper foil having a thickness of 0.05 mm and a thermal conductivity of 390 W / m · K is punched into a circular shape having a diameter of 4.2 mm as the heat diffusion material, and this is formed into a sealing plate 11 having a negative electrode 15 made of lithium metal and a carbon coating layer 17. It arrange | positioned between the inner side plane parts.

  The positive electrode case 12 is made of a stainless material (SUS444, thickness 0.10 mm) having excellent corrosion resistance, and a carbon coating is applied to the inner surface of the positive electrode case 12 to form a carbon coating layer 14. For the separator 18 disposed between the positive electrode 16 and the negative electrode 15, a nonwoven fabric made of polypropylene was used. The gasket 19 insulates the sealing plate 11 and the positive electrode case 12 and physically seals the power generation element in the battery container, and uses polypropylene. The peripheral portion of the separator 18 is accommodated in a separator accommodating portion formed by the rising portion of the gasket 19 and the sealing plate 11 so that the shape thereof is cup-shaped. A solution obtained by diluting butyl rubber with toluene was applied between the gasket 19 and the sealing plate 11 and between the positive electrode case 12 and the gasket 19, and the toluene was evaporated to obtain a sealant made of a butyl rubber film.

  The positive electrode 16 is formed by adding water to a mixed powder of fluorinated graphite, a conductive agent carbon black, and a fluororesin binder, kneading, granulating, drying, and press-molding to a certain size, in a pellet form Is molded. As the organic electrolyte, a solution obtained by dissolving lithium borofluoride at a ratio of 1 mol / liter in an equal volume mixed solvent of gamma butyrolactone and 1,2-dimethoxyethane was used.

The negative electrode terminal 20 is made of stainless steel (SUS304, thickness 0.08 mm), and the sealing plate 1
The negative electrode terminal 20 was attached to 1 by resistance welding. Similarly to the negative electrode terminal 20, the positive electrode terminal 21 was made of stainless steel (SUS304, thickness 0.08 mm) and attached to the positive electrode case 12 by resistance welding.

(Example 2)
As Example 2, a flat battery with a terminal shown in FIG. No carbon coating is applied to the inner flat surface of the sealing plate 11, and the heat diffusing material 13 is obtained by punching a copper foil having a thickness of 0.05 mm and a thermal conductivity of 390 W / m · K into a circular shape having a diameter of 4.2 mm. The negative electrode 15 made of lithium metal and the inner flat portion of the sealing plate 11 are disposed. Other configurations are the same as those of the first embodiment.

(Comparative Example 1)
As Comparative Example 1, a flat battery with a terminal shown in FIG. The inner flat portion of the sealing plate 11 is not coated with carbon, and since there is no heat diffusion material, the negative electrode 15 made of lithium metal is directly bonded to the inner surface of the sealing plate 11. Other configurations are the same as those of the first embodiment.

  100 batteries each of Example 1, Example 2, and Comparative Example 1 were prepared, and the ratio of the batteries that caused an internal short circuit was confirmed by measuring the battery voltage immediately after terminal welding. The results are shown in Table 1.

  In the batteries of Example 1 and Example 2, the thermal diffusion material 13 is provided between the negative electrode 15 and the sealing plate 11, and when the negative electrode terminal 20 is welded to the sealing plate 11, the thermal diffusion material 13 leads to the negative electrode 15. Lithium is not liquefied in order to alleviate heat concentration. For this reason, the internal short circuit by the lithium penetration of the separator 17 does not occur. On the other hand, in the battery of Comparative Example 1, the heat diffusing material 13 is not provided between the negative electrode 15 and the sealing plate 11, and heat concentration on the negative electrode 15 occurs when the negative electrode terminal 20 is welded to the sealing plate 11. Liquefies. This lithium is thought to have penetrated the separator 17 and contacted the positive electrode 16 to cause an internal short circuit.

Next, the internal resistance of the battery was measured with an alternating current method of 1 kHz. Table 2 shows the average value of the internal resistance of 100 batteries.

  Regarding the internal resistance, there is no significant difference between Example 1 and Comparative Example 1. In the case of Example 1, since there is the carbon coating layer 17 on the inner plane part of the sealing plate 11, the electrical contact between the heat diffusion material 13 made of copper foil and the sealing plate 11 is well maintained and made of copper foil. The thermal diffusion material 13 and the negative electrode 15 made of lithium are also kept in good electrical contact by pressure bonding. In the case of Comparative Example 1, the carbon layer is not formed on the inner flat surface portion of the sealing plate 11, but the negative electrode 15 made of lithium is pressure-bonded to the inner flat surface portion of the sealing plate 11, so that the electrical contact is kept good. It is considered that there is no significant difference.

  On the other hand, in Example 2, the thermal diffusion material 13 made of copper foil and the negative electrode 15 made of lithium are kept in good electrical contact by pressure bonding, but a carbon coating layer is formed on the inner plane portion of the sealing plate 11. Therefore, it is considered that the electrical contact became unstable and increased compared to Example 1 and Comparative Example 1. From the viewpoint of preventing an internal short circuit, there is no difference due to the presence or absence of the carbon coating layer formed on the inner plane portion of the sealing plate 11, but it is better to form the carbon coating layer on the inner plane portion of the sealing plate 11. Since resistance can be stabilized, it is more preferable.

  In this embodiment, SUS304 is used as the sealing plate, SUS444 is used as the positive electrode case, and SUS304 is used as the negative electrode terminal and the positive electrode terminal. However, the same effect can be obtained by using a stainless material such as SUS316 or SUS430.

  The present invention is not limited to a primary battery using lithium metal for the negative electrode, but can also be applied to a secondary battery using an oxide or nitride containing lithium for the negative electrode. Furthermore, it is not limited to the kind of positive electrode active material or electrolyte solution.

  Next, detailed examination was performed using heat diffusion materials with different materials and thicknesses.

(Example 3)
A battery of Example 3 similar to the battery of Example 1 was prepared, except that a copper foil having a thickness of 0.02 mm was used as the thermal diffusion material 13.

Example 4
A battery of Example 4 similar to the battery of Example 1 was produced, except that a copper foil having a thickness of 0.015 mm was used as the thermal diffusion material 13.

(Example 5)
The thermal diffusion material 13 has a planar thermal conductivity of 1500 to 1700 W / m · K, a thickness direction thermal conductivity of 15 W / m · K, and a 0.025 mm thick graphite sheet with a diameter of 4.2 mm. A battery of Example 5 was manufactured in the same manner as the battery of Example 1 except that two of the punched sheets were stacked to a thickness of 0.05 mm.

(Example 6)
The thermal diffusion material 13 has a planar thermal conductivity of 1500 to 1700 W / m · K, a thickness direction thermal conductivity of 15 W / m · K, and a 0.025 mm thick graphite sheet with a diameter of 4.2 mm. A battery of Example 6 was produced in the same manner as the battery of Example 1 except that one punched out was used.

  100 batteries of each of Examples 3 to 6 were prepared, and the ratio of the batteries that caused an internal short circuit was confirmed by measuring the battery voltage immediately after terminal welding. The results are shown in Table 3.

  In the batteries of Example 3 and Examples 5 to 6, when the negative electrode terminal 20 was welded to the sealing plate 11, the thermal diffusion material 13 provided between the negative electrode 15 and the inner flat portion of the sealing plate 11 was the negative electrode 15. Lithium is not liquefied in order to alleviate heat concentration on the surface. For this reason, an internal short circuit due to the penetration of lithium through the separator 17 does not occur. On the other hand, in the case of Example 4, since the copper foil is as thin as 0.015 mm, the heat is quickly transmitted to the surface of the negative electrode 15 before sufficient thermal diffusion is performed, which causes liquefaction of lithium and internal short circuit. It is thought that it was made.

  Further, when a graphite sheet is used as the heat diffusing material, the thermal conductivity in the plane direction is very large and the thermal conductivity in the thickness direction is extremely small due to the structure of the graphite.

  In this embodiment, SUS304 is used as the sealing plate, SUS444 is used as the positive electrode case, and SUS304 is used as the negative electrode terminal and the positive electrode terminal. However, the same effect can be obtained by using a stainless material such as SUS316 or SUS430.

  The present invention is not limited to a primary battery using lithium metal for the negative electrode, but can also be applied to a secondary battery using an oxide or nitride containing lithium for the negative electrode. Furthermore, it is not limited to the kind of positive electrode active material or electrolyte solution.

  Moreover, this invention is not limited to the kind of positive electrode active material or electrolyte solution.

  In the present invention, by providing a heat diffusion material between the negative electrode containing lithium and the inner flat portion of the sealing plate, the heat concentration on the negative electrode when the negative electrode terminal is welded to the sealing plate is alleviated, and lithium is liquefied. Prevents internal short circuit due to lithium penetration of separator. Thereby, the flat battery with a terminal which has high reliability can be provided.

Sectional drawing of the flat battery with a terminal in Example 1 and Examples 3-5 of this invention Sectional drawing of the flat battery with a terminal in Example 2 of this invention Sectional drawing of the flat battery with a terminal in the conventional comparative example 1

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Sealing plate 12 Positive electrode case 13 Thermal diffusion material 14 Carbon coating layer 15 Negative electrode 16 Positive electrode 17 Carbon coating layer 18 Separator 19 Gasket 20 Negative electrode terminal 21 Positive electrode terminal

Claims (4)

  A flat battery in which a negative electrode containing lithium, a positive electrode, an organic electrolyte, and a separator are hermetically sealed with a sealing plate, a gasket, and a positive electrode case, and a negative electrode terminal is welded to the sealing plate, and the inner surface of the negative electrode and the sealing plate A flat battery with a terminal, wherein a heat diffusion material having conductivity is provided between the two.   The flat battery with a terminal according to claim 1, wherein the heat diffusion material is a copper foil.   The flat battery with a terminal according to claim 2, wherein the copper foil has a thickness of 0.02 mm or more.   The flat battery with a terminal according to claim 1, wherein the thermal diffusion material is a graphite sheet.

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