JPS6123625B2 - - 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 prevent the negative electrode from being excessively heated and melted due to the rapid temperature rise at the beginning of combustion of the heating agent, and to prevent the negative electrode from colliding with the positive electrode. It is an object of the present invention to provide a thermal battery in which there is no risk of impairing reliability by forming an electric bridge between the two and causing a short circuit.

Thermal batteries use CaCrO ₄ and PbCrO ₄ for the positive electrode and negative electrode.
Mg, Ca, Ni, Fe for positive and negative current collector plates, KC1 for electrolyte
- LiC1, KBr - A battery that uses LiBr eutectic salt, etc. At room temperature, the electrolyte is a non-conductive solid salt, so it is inactive as a battery, but when heated to high temperatures, the electrolyte melts. This battery has good ionic conductivity and can supply power to an external device. This type of battery is known to have the following features. (1) There is practically no self-depletion during storage, and even after long-term storage, it exhibits the same discharge characteristics as immediately after manufacture. (2) A heat-generating agent for heating the unit cell is incorporated during manufacturing, and the heat-generating agent is used when the battery is used, allowing the battery to be utilized in a short time, making it convenient for emergency use. (3) Since the electrolyte is anhydrous, it is possible to use an ultra-low potential negative electrode material and the voltage per unit cell can be increased, which is advantageous in reducing size and weight. (4)−50℃〜＋70
Can be used in a wide temperature range up to ℃. It is being put into practical use as a rocket and emergency power source.

However, a problem that remains with thermal batteries is that the instantaneous high heat of around 1000°C generated when the exothermic agent burns is applied to the negative electrode via the negative electrode current collector plate, which has good heat conduction, resulting in excessive heating of the negative electrode. For example, in the case of a low melting point (mp. 650℃) negative electrode such as magnesium, a part or most of it melts and flows out of the battery system, forming an electric bridge between the positive and negative electrodes, and if this is slight. This appears as fluctuations in the voltage, and in extreme cases, a complete short circuit is often observed, making it impossible to supply power to the outside world. Furthermore, when calcium is used in the negative electrode, excessive heating causes ion replacement between lithium ions in the electrolyte and calcium, producing lithium, which reacts with calcium to form CaLi ₂ , a low melting point alloy (mp. 230°C). This can generate an excessive amount of ions, which can flow out of the battery system and form a bridge between the positive and negative electrodes, causing instantaneous fluctuations in voltage. In extreme cases, the same phenomenon as with magnesium negative electrodes can occur. sometimes recognized. Conventionally, measures to eliminate this phenomenon have been taken to reduce the amount of heat generating agent, but this has the disadvantages of speeding up the cooling characteristic of thermal batteries, shortening the discharge time, and delaying start-up. It was hot. Another way to avoid these drawbacks is to (a) insert a heat-resistant insulating material, such as asbestos paper, glass cloth, or mica, between the exothermic agent contacting surface of the negative electrode current collector plate and the exothermic agent; (b) A means of forming a heat generating agent on a heat-resistant heat insulating substrate such as asbestos paper to integrate the heat insulating material and the heat generating agent, and placing the heat insulating material side facing the negative electrode current collector plate. was taken.

Although these methods have eliminated the problems encountered when reducing the amount of heat generating agent used, new problems have arisen in the case of method (a), such as forgetting to insert a heat insulating plate or placing the heat insulating plate between the positive electrode current collector plate. It was unavoidable that mistakes would occur from time to time when inserting the paper into the machine. Again (b)
Even in the case of the above method, it was not possible to completely eliminate the error of placing the heat insulating layer surface on the positive electrode side when inserting the layer integrated with the heat insulating layer. Thermal batteries produced with such operational errors result in inconveniences such as voltage fluctuations or voltage drops, and since they are intended for emergency use, a more reliable countermeasure has been desired.

The present invention is an attempt to meet these demands, and solves the above-mentioned problems by making improvements to prevent the negative electrode from being excessively heated due to operator carelessness during battery assembly, thereby impairing reliability. .

The present invention will be explained below with reference to Examples. 1st
The figure is a longitudinal sectional view showing the overall configuration of the thermal battery. In the figure, 1 is a unit cell in which a heat insulating layer is interposed between the negative electrode and the negative electrode current collector plate, which is a feature of the present invention, and is the main power generation part that generates electricity by being heated to a high temperature, which will be described in detail later. An arbitrary number of unit cells are connected in series to generate the necessary voltage as a whole. 2 is an exothermic agent, which is made by adding a small amount of binder to zirconium powder and lead chromate powder and forming it into a sheet shape, and is used to heat the unit cell to generate electricity through an exothermic reaction. Reference numeral 3 denotes an igniter, which generates a flame when an instantaneous current is passed through a pair of starting terminals 4, and activates the unit cell 1 by igniting the exothermic agent 2 through the vent hole 5. . Reference numeral 6 denotes an output terminal which is electrically connected to a predetermined position of the unit cell assembly. Reference numeral 7 denotes a heat insulating layer that surrounds the outside of the unit cell 1 and is made of insulating materials such as asbestos paper, mica sheet, glass cloth, etc., and is designed to keep the unit cell 1 warm and prevent the high temperature of the unit cell 1 from causing thermal damage to surrounding materials. Provisions are made to prevent this from occurring. 8 is an exterior body consisting of a metal case and a metal lid, both of which are welded at the fitting part to form a hermetically sealed structure.

As mentioned above, FIGS. 2 to 7 show examples of the structure of a unit cell in which the negative electrode heat prevention measures of the present invention are taken,
In each figure, 9 is a positive electrode current collector plate made of nickel, 10 is an electrolyte layer made of eutectic salt of potassium chloride and lithium chloride mixed with kaolin, and a positive electrode mixture layer mainly made of calcium chromate. It is an integrally molded pellet. Note that the electrolyte layer and the positive electrode mixture layer may be formed separately. Reference numeral 11 denotes a negative electrode made of magnesium or calcium, which is pressed into a protrusion provided on a negative electrode current collector plate 13 made of nickel through a heat-insulating insulating sheet 12 made of asbestos paper, fiber flux paper, etc. The current collector 13 is integrated with the current collector 13 while maintaining electrical continuity therebetween. In this case, a heat-insulating insulating sheet 12 interposed between the negative electrode 11 and the negative electrode current collector plate 13
In this case, the negative electrode 11 and the negative electrode current collector plate 13 are connected to each other because the protrusion provided on the negative electrode current collector plate 13 bites through the protrusion, or the protrusion is removed in advance. in direct contact. Fifth
14 and 15 in FIG. 6 are concentric circles for protecting the protective ring negative electrode 11 made of asbestos paper, fiber flux paper, or the like.

The unit cell in this embodiment of the present invention will be further explained. The unit cell shown in FIG. 2 is the simplest example in which a hard sheet such as a mica sheet is used as the heat insulating sheet 12, and the inner and outer peripheral edges of the negative electrode 11 are exposed. On the other hand, in FIGS. 5 and 6, protective rings 14 and 15 made of asbestos paper, ceramic paper such as fiber flux, etc. are arranged to protect the inner and outer peripheral edges of the negative electrode 11 from flames during combustion of the exothermic agent. This further enhances safety against overheating. 3 and 4, in order to protect the inner and outer edges of the negative electrode 11 from the flame of the exothermic agent, in the example in FIG. 3, convex portions are provided on the inner and outer edges of the electrolyte layer, By using an elastic material such as fiber flux felt, fiber flux blanket, or low-density asbestos paper for the heat insulating sheet 12, the original thickness is maintained except for the portion compressed by the negative electrode 11 and the negative electrode current collector plate 13. Since the taste is maintained, the state shown in the figure is achieved, and the inner and outer peripheral edges of the negative electrode 11 are protected. Therefore, the implementation rows shown in Figures 3 and 4 are comparable to the embodiments shown in Figures 5 and 6 in terms of protection from overheating, and there is no need to prepare a protective ring. Therefore, it is a convenient configuration that can also save the number of man-hours for assembling the unit cell. FIG. 7 shows a so-called cup-shaped cell, in which a negative electrode 11 made of calcium is integrated with the current collector plate 13 in an electrically conductive state through a heat insulating sheet 12 on both sides of the negative electrode current collector plate 13, and the moment when the exothermic agent burns, the negative electrode 11 is electrically conductive. The effect of high temperature is only from the direction of the positive electrode current collector plate, so the aspect is different from the embodiments shown in FIGS. 2 to 6. By using the heat insulating sheet 12 made of a material such as fiber flux felt, the peripheral edge of the negative electrode is protected as in the case of the example shown in FIG. The excess electrolyte present on the inner and outer edges of the negative electrode is absorbed by the heat insulating sheet 12, and CaLi ₂ , a low melting point alloy, which is produced in an appropriate amount when there is a large amount of excess electrolyte or when the cell temperature is too high, is minimized. , or even if some amount is generated, it does not lead to leakage,
Therefore, there is no need to worry about voltage fluctuations or short circuits. In FIGS. 2 to 6, the inner diameter and outer diameter of the heat insulating sheet 12 are approximately the same as those of the negative electrode current collector plate 13, but the dimensions may be changed to be larger or smaller as long as it does not interfere with the assembly process. You may. However, it should be avoided to make the diameter smaller than the outer diameter of the negative electrode 11 and larger than the inner diameter, as this is not preferable for the purpose of thermal insulation of the negative electrode 11. Furthermore, although the thickness of the heat insulating sheet 12 was not mentioned in each of the embodiments, what material should be used for the heat insulating sheet 12 when a fast rise that can supply a predetermined output within 1 second is required. The thickness of the portion compressed by the negative electrode 11 and the negative electrode current collector plate 13 is preferably about 50 to 200 μm, although it varies depending on the selection. If it is too thin, the heat insulating effect will be insufficient, and if it is too thick, the rise will be slow. However, if it is functionally acceptable even if the rise is a little slow, a thicker one can be used. As the material for the heat insulating sheet 12, other than those mentioned in the above embodiments, glass cloth or carbon fiber cloth can also be used. In some cases, a coating may be formed using a heat insulating paint.
Also, two or more types of heat insulating materials may be used in combination.

In this way, in the present invention, a layered heat insulating material is interposed between the negative electrode and the negative electrode current collector plate, and the negative electrode and the negative electrode current collector plate are integrated in a state where sufficient electrical conduction is maintained to take out the current. , and constructed a unit cell.
The negative electrode can be prevented from being excessively heated without inserting a heat insulating plate between the exothermic agent and the negative electrode current collector plate as in the conventional case. Moreover, unlike this heat insulating board, there is no need to worry about insertion errors. Furthermore, when using an integrated layer consisting of a heat insulating layer and a heat generating layer, there were cases where the front and back sides were inserted incorrectly, and the heat generating layer side was placed on the negative electrode current collector side, but these concerns created opportunities for mistakes. This completely eliminates the problem of voltage fluctuations and short circuits, making it possible to provide a thermal battery that is even more reliable than conventional batteries.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing the overall structure of a thermal battery according to an embodiment of the present invention, and FIGS. 2 to 7 are cross-sectional views showing examples of the structure of a unit cell according to the present invention. 1...Battery, 1...Exothermic agent, 3...Igniter,
9... Positive electrode current collector plate, 10... Positive electrode mixture/electrolyte layer, 11... Negative electrode, 12... Heat insulation sheet (layer),
13...Negative electrode current collector plate.

Claims (1)

[Claims] 1 A structure in which a unit cell and a heat generating agent are alternately laminated, a heat insulating layer is interposed between the negative electrode of the unit cell and a negative electrode current collector plate, and the negative electrode and the negative electrode current collector plate are mutually electrically conductive. A thermal battery characterized by being integrated while maintaining continuity.