JPS6127070A - Thermal battery - Google Patents

Abstract

PURPOSE:To make temperature distribution inside a battery uniform to increase battery performance by making larger the diameter of a metal plate of the center unit cell of a stack than the inner diameter of a case, bending excess part of the metal plate, and bringing it into contact with the inner surface of the case. CONSTITUTION:A metal plate 8 of the center unit cell of a stack is formed to bend its excess part in the circumference and to bring the bent part into contact with the inside of a battery case 1. Thereby, heat near the center of the stack is transmitted to the case 1 having large heat capacity by heat conduction and excess heat increase near the center is prevented. The metal plate 8 for heat radiation is formed in a shallow plate shape by drawing or formed by installing a large number of slits in the circumference and mutually bending the slits to the upper side and the lower side.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to an improvement in a thermal battery that operates in a high temperature area and can supply a large amount of power in a short period of time to a flying object, an emergency power source, etc. More specifically, it measures the internal temperature of the battery to make it possible to improve performance.

Conventional configurations and problems The most typical thermal battery is a pellet-type configuration, which uses calcium chromate as the positive electrode, a eutectic salt of potassium chloride and lithium chloride as the electrolyte, and metallic calcium as the negative electrode. is used in some cases. When using it, the exothermic agent built into the battery is ignited, and the generated heat melts the stain solute, activating the battery.
Electric power can be extracted. The most common conventional configuration will be explained below with reference to FIG.

In FIG. 1, 1 is a battery case, and 2 is a heat generating agent that heats the unit cell. 3 is called DEB pellet,
C a Cr O4 powder as the positive electrode active material, eutectic salt powder of KCA and LiCl1 as the electrolyte, and binder powder (fine S X 02
The three components (powder) were mixed uniformly, heat treated, crushed, and then molded into pellets.

This is combined with a negative electrode made of metal calcium 4 crimped onto a plate 6 of iron or the like, and a heat generating agent 2 is combined as shown in the figure to constitute a unit cell. For actual batteries, depending on the required voltage,
A required number of unit cells are stacked, the stain pressure terminals are taken out from the upper and lower ends, and the cells are housed in a battery case 1 having a heat insulating material 6. Furthermore, a igniter 7 for igniting the exothermic agent is provided.

In use, when an electric signal is sent to the igniter 7 and the exothermic agent 2 between the individual cells is ignited, the electrolyte is melted by the heat, making it possible to extract electric power from the battery terminals. However, thermal batteries typically operate at temperatures of several hundred degrees, and their performance is highly temperature dependent. Therefore, it is desirable that each unit cell operate at the same temperature to the extent possible.

However, as shown in FIG. 2, the temperature of the unit cell at the center of the stack is generally the highest, and the temperature decreases as you move up and down. This is natural when considering heat radiation. Conventionally, as a method to solve this tendency, it has been considered to reduce the amount of exothermic agent toward the center of the cell stack.

This method is, of course, extremely effective, but when actually making batteries, it is necessary to prepare many types of heating elements with different amounts of heating agent, and it is definitely necessary to assemble batteries with skill and precise work procedures. The purpose of the present invention is not to use the complicated method described above.
The object of the present invention is to provide a configuration that can uniformize the temperature of a unit cell stack using an extremely simple method.

Structure of the Invention The main point of the present invention is to make the diameter of the metal plate (which serves as the calcium lining) of the central unit cell in the stacked unit cell group larger than the inner diameter of the battery case, and to make use of the excess. It is bent and the bent portion is inscribed in the battery case to release heat from the center of the stack to the case, thereby making the temperature of the unit cell stack uniform. The specific configuration will be explained with reference to FIG. 1 is a battery case, and 2 is a heat generating agent, which is usually formed by mixing fine iron powder with a small amount (10 to 20 wt%) of potassium perchlorate powder. Since it remains conductive even after combustion, it also serves as a connector between unit cells. 3 is D
EB pellet 4 is a metal calcium plate, which is lined by a metal plate 5.

6o is insulated to prevent excessive cooling of the battery.

7 is an igniter for igniting the exothermic agent 2;

Reference numeral 8 denotes a metal plate of the unit cell at the center of the stack, which is the key point of the present invention, and the excess portion around the metal plate is bent and brought into contact with the inside of the battery case 1. In Fig. 3, there are a total of 9 cells in the unit battery, so the 6th cell in the center is used. In this way, heat near the center cell is transferred to the battery case 1 having a large heat capacity through thermal conduction of the metal plate 8, and an excessive rise in temperature near the center can be prevented. As shown in FIG. 4, this heat dissipating metal plate 8 may be used in the form of a petri dish by squeezing a disc-shaped plate, or as shown in FIG. The separated portions 11 may be bent upwardly and downwardly.

Description of Examples Hereinafter, as an example of the present invention, a stacked battery consisting of 9 cell units as shown in FIG. 3 was assembled. The heat dissipation metal plate 8 was installed in the fifth unit cell counted from the top, and its shape was as shown in FIG. To measure the cell temperature, thermocouples were inserted into the DEB pellets of the first, fifth, and ninth cells, and their leads were pulled out to measure the temperature. For comparison, we assembled a battery that was identical except for the heat dissipation metal plate. Thermocouples for the three thermometers were installed in similar locations.

The battery is discharged at a constant current of 5A, and the discharge end voltage is 1
It was set to 8v. FIG. 6 is a plot of the temperature of each cell at 20 seconds after the start of discharge. Further, FIG. 7 shows the discharge characteristic curves of both the batteries of Example A and Comparative Example B.

As is clear from FIG. 6, in Comparative Example B, the temperature at the center cell is significantly higher than at both ends. This is thought to be due to the fact that the amount of heat generating agent is the same for all unit cells, so no heat is radiated from the center, and the self-depletion of the unit cells becomes severe. As evidence of this, as shown in Figure 7, the discharge duration is also short. On the other hand, in Example A of the present invention, heat can be dissipated near the center cell of the laminate, so the temperature difference with the unit cells at both ends is extremely small, temperature uniformity is maintained, and the discharge duration is It has also been improved by about 70%.

Effects of the Invention As is clear from the above results, the present invention can uniformize the temperature inside a thermal battery using an extremely simple method.
Thereby, the discharge life can be significantly improved.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the structure of a conventional stacked thermal battery, Fig. 2 is a diagram showing the relationship between the position of the cell stack and the cell temperature, and Fig. 3 is the structure of a stacked thermal battery in an example of the present invention. Schematic diagram, 4th
The figure is a perspective view of the heat dissipation metal plate in the same thermal battery, and FIG. 5 is another view of the heat dissipation metal plate. FIG. 6 is a diagram showing the relationship between each cell in the laminate and temperature, and FIG. 7 is a diagram showing the relationship between discharge time and voltage. 1... Battery case, 2... Exothermic agent, 3
... DBE pellet, 4 ... Negative electrode active material, 5 ... Metal plate, 8 ... Metal plate for heat dissipation. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Cell stack Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] It is a thermal battery in which a stacked unit cell consisting of a combination of a homogeneous molded mixture of a positive electrode active material, an electrolyte, and a binder, a negative electrode active material lined with a metal plate, and a powder molded exothermic agent is housed in a cylindrical case. The thermal battery has a diameter of the metal plate of the cell at the substantially center of the laminate that is larger than the inner diameter of the case, and the excess portion thereof is bent and inscribed in the case.