JPS6123626B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal battery containing a unit cell and a heat generating agent.The purpose of the present invention is to remove the heat generated by the reaction between negative electrode calcium produced during battery operation and lithium salt in the electrolyte layer. It is an object of the present invention to provide a highly reliable battery that avoids short circuiting of the battery due to outflow of low melting point metal and has excellent output characteristics.

Thermal batteries use CaCrO ₄ , PbCrO ₄ , etc. for the positive electrode and
This is a battery that uses eutectic salts such as Ca, Mg, etc., Ni, Fe, etc. for the positive and negative electrode current collector plates, and KCl-LiCl, KBr-LiBr, etc. for the electrolyte, because the electrolyte is a solid salt that is non-conductive at room temperature. As a battery, it is in an inactive state, but when heated to a high temperature, the electrolyte becomes highly ionic conductive, making it possible to supply power to the outside. This type of battery is known to have the following features. (1) Self-discharge during storage is negligible, and even after long storage, the same discharge characteristics as immediately after manufacture can be obtained. (2) A heat-generating agent for heating the unit cell is incorporated during manufacturing, and when the battery is used, the heat-generating agent is activated to activate the battery in a short time, making it convenient for emergency use. (3) Since the electrolyte is anhydrous, it is possible to use ultra-low potential negative electrode materials, which increases the voltage per unit cell, resulting in small size, light weight, and high output. (4)−50℃～＋70℃
Can be used in a wide temperature range. It is being put into practical use as a rocket and emergency power source.

The most common type of thermal battery of this kind and the battery system that is said to have good discharge characteristics is Ni-Ca|KCl-LiCl|CaCrO ₄ |Ni. However, the problem with this battery system is that the negative electrode calcium exchanges ions with lithium ions in the electrolyte, producing metallic lithium, which further reacts with calcium to form a low melting point alloy.
It can generate CaLi ₂ (melting point 230℃). This leaks out of the battery system, causing positive,
An electric bridge is formed between the negative electrodes, and if this is slight, it will appear as voltage fluctuation, and in extreme cases, a complete short circuit will occur, making it impossible to supply power to the outside. .

Several measures have been taken to prevent such phenomena. An example is shown in FIGS. 1 and 2. In both figures, 1 is a negative electrode current collector plate made of nickel, 2 is a calcium negative electrode, and 3 is a negative electrode current collector plate made of nickel.
is an electrolyte layer formed by molding powder made of NiCl-KCl adsorbed on kaolin, and is a two-layer integrated pellet with a positive electrode active material mainly composed of calcium chromate formed on the back side. 4 is a positive electrode current collector plate made of nickel. As can be seen from this figure, no special improvements were made to the electrolyte layer. In such a configuration, measures have been taken to reduce the amount of exothermic agent used to heat each unit cell and generate electricity. According to this, since the rise in cell temperature is limited to a relatively low temperature, the formation of the low melting point alloy mentioned above is suppressed, and the frequency of short circuits is considerably improved. In particular, as shown in FIG. 2, the degree of improvement was more remarkable when the outer diameter of the calcium negative electrode was made smaller and the inner diameter larger than the outer diameter and inner diameter of the electrolyte layer. However, in all of these cases, the temperature drops quickly below a predetermined temperature, resulting in a short discharge life, and the rise time to a predetermined voltage is slow. In addition to preventing voltage fluctuations and short circuits, a configuration shown in FIG. 3 has been proposed as a method. In FIG. 3, 1 is a negative electrode current collector plate, 2 is a calcium negative electrode, and 3 is a two-layer integrated pellet consisting of an electrolyte layer and a positive electrode active material layer.

The cell shown in Fig. 3 is significantly different from those shown in Figs. 5 to form a unit cell. In this case, most of the low melting point alloy produced is in the groove 5 provided in the electrolyte layer.
Although it is no longer necessary to limit the amount of exothermic agent as much as in the previous example, because there are no grooves formed in the electrolyte layer where the outer and inner peripheries of the negative electrode come into contact, It was not possible to completely prevent the low melting point alloy from flowing out and causing voltage fluctuations.
Another problem is that because many grooves are formed on the surface of the electrolyte layer facing the calcium negative electrode, the calcium negative electrode does not come into contact with these grooves, resulting in a decrease in the reaction area, and the rate of decrease is usually ranges from 20 to 30%, and the allowable load current relative to the apparent area of the unit cell becomes 20 to 30% smaller.
This caused a loss in output characteristics.

Due to the nature of its use, thermal batteries are required to have high output and high reliability, and the present invention addresses these demands by improving the above-mentioned conventional drawbacks.

Hereinafter, the present invention will be explained with reference to examples thereof. FIG. 4 is a longitudinal sectional view showing the overall structure of the thermal battery.
In the figure, 6 is a unit cell having an electrolyte layer according to the present invention, which will be described in detail later, and is a main part of power generation that is heated to a high temperature to generate electricity, and an arbitrary number of unit cells are connected in series to form a whole. It is constructed to generate the necessary voltage. 7 is an exothermic agent, which is made by adding a small amount of binder to zirconium powder and lead chromate powder and molding it into a sheet shape, and is used to heat the unit cell 6 to generate electricity through an exothermic reaction. 8 is an igniter, which is connected to a pair of starting terminals 9 for a short time.
It is provided to activate the unit cell 6 by generating a flame when an electric current is passed therethrough and igniting the exothermic agent 7 through the vent hole 10. Reference numeral 11 denotes an output terminal which is electrically connected to a predetermined position of the unit cell assembly. Reference numeral 12 denotes a heat insulating layer made of heat-resistant heat insulating material such as asbestos paper, mica sheet, glass cloth, etc., to keep the unit cell 6 warm and to prevent the high temperature of the unit cell 6 from causing thermal damage to surrounding materials. It is prepared for. 13 is an exterior body consisting of a metal case and a metal lid, and has a sealed structure in which the fitting portions of the two are welded.

Figures 5 to 8 show examples of unit cell configurations having an electrolyte layer according to the present invention. In each figure, 1 is a negative electrode current collector plate made of nickel, which is integrated with a calcium negative electrode 2 by welding or crimping. . 3 is a pellet formed by integrally molding two layers: an electrolyte layer and a positive electrode active material layer.The electrolyte layer consists of a layer in which LiCl-KCl is adsorbed on kaolin, and the positive electrode active material layer is formed mainly of calcium chromate. There is. Reference numeral 5 denotes a groove provided on the electrolyte layer side of the two-layer integrated pellet 3, which differs from the conventional structure shown in FIG. The feature is that a groove is formed outside the outer diameter of the electrode 2 and inside the inner diameter (the part where the negative electrode 5 is not present). 4 is a positive electrode current collector plate made of nickel, and 14 is a flat or inverted L-shaped protection ring made of asbestos paper, fiber flux paper, etc., which is provided to surround the periphery of the negative electrode 2 to protect it. There is. (See Figures 7 and 8). Further, reference numeral 15 denotes an upwardly protruding embankment formed inside and outside the groove 5.

Conventionally, in order to prevent the outflow of the low melting point alloy CaLi ₂ generated during discharge, it was common knowledge to form a large number of grooves on the surface of the electrolyte layer facing the negative electrode. It has been found that the outflow of the alloy can be prevented by forming grooves in only two areas of the electrolyte layer, one outside the negative electrode outer diameter and one inside the negative electrode inner diameter. This is because the low melting point alloy that accumulates little by little in the grooves is oxidized and consumed by the positive electrode active material eluted from the positive electrode active material layer and becomes no longer fluid, or the products that have been oxidized and have lost their conductivity are deposited in the grooves. It is presumed that this is due to the accumulation of water.

Examples of the present invention will be further described. In the structure shown in Figure 5, the outer and inner surfaces of the negative electrode are open, so if the grooves formed in the electrolyte layer are not able to absorb all the low melting point alloy, the remaining low melting point alloy will flow out. , there remains a slight risk of contact with the positive electrode current collector plate. Therefore, as shown in FIG. 6, it is preferable to provide the electrolyte layer with a bank portion 15 formed integrally therewith. Providing the protective ring 14 as shown in FIGS. 7 and 8 makes it possible to prevent the low melting point alloy from being absorbed by the grooves formed in the electrolyte layer.
This is an even more reliable configuration that can prevent leakage. Although Figures 5 to 8 show the calcium negative electrode not covering the grooves formed in the electrolyte layer at all, due to tolerances of each component, the calcium negative electrode does not cover the grooves formed in the electrolyte layer. Of course, it is possible for the groove to slightly cover the groove width.
If it is about 1/5 or less, it does not impede the gist and effects of the present invention. In addition, in the examples, the electrolyte layer is a two-layer integral pellet with the positive electrode active material layer, but
The same effect can be obtained even if the layers are formed into separate layers and used in a stacked manner. In the example, the case where the grooves formed in the electrolyte layer are formed in two places, one outside and one inside the part where the negative electrode faces, was described in detail. If it is determined that the objective can be achieved by forming a groove in both places, the present invention also includes forming a groove in only one of the two places, regardless of whether the grooves are provided in both places.

In this way, by forming grooves for absorbing low melting point alloys in a part of the electrolyte layer, that is, on the outside and inside of the surface where the negative electrode faces, and preventing the low melting point alloy from flowing out, the amount of heat generating agent can be reduced as compared to conventional methods. There is no loss of reaction area due to the formation of numerous grooves on the negative electrode side of the electrolyte layer, so there is no loss of rise time, discharge life, or output characteristics, and there is no need to worry about voltage fluctuations or short circuits. It is possible to provide a highly reliable thermal battery without

[Brief explanation of the drawing]

FIGS. 1 to 3 are cross-sectional views showing the structure of a conventional unit cell, FIG. 4 is a longitudinal cross-sectional view showing the overall structure of a thermal battery in an embodiment of the present invention, and FIGS. 5 to 8 are views of the present invention. FIG. 2 is a cross-sectional view showing a unit cell configuration in an example. DESCRIPTION OF SYMBOLS 1... Negative current collector plate, 2... Negative electrode, 3... Integrally molded pellet of electrolyte layer and positive electrode active material layer, 4... Positive electrode current collector plate, 5... Formed on the surface of the electrolyte layer facing the negative electrode. groove, 6...Battery, 7...Heating agent.

Claims (1)

[Scope of Claims] 1. A thermal battery in which calcium is used for the negative electrode, lithium salt is contained in the electrolyte layer, and the electrolyte layer and the positive electrode active material layer are integrally molded, wherein A thermal battery characterized in that a unit cell is constructed by forming grooves on the outer and inner parts. 2. The thermal battery according to claim 1, wherein the electrolyte layer has bank portions integrally formed therewith inside and outside the groove. 3. The thermal battery according to claim 1, wherein a flat ring or an inverted L-shaped ring surrounding the periphery of the negative electrode is inserted between the negative electrode current collector plate and the electrolyte layer.