JPS6074267A - Thermal battery - Google Patents

Abstract

PURPOSE:To prevent decomposition of iron sulfide and melting of lithium alloy by the heat generated from heat pat by forming heat insulating layers both sides of heat pat in a thermal battery where an iron sulfide is used for positive electrode while a lithium alloy for negative electrode. CONSTITUTION:A power generating cell 2 integrating a positive electrode consisting of iron sulfide, a negative electrode consisting of lithium-aluminum alloy and an electrolyte layer and a heat pat 1 integrating heat insulating layers 21, 22 such as kaoline at both sides of a power generating layer 23 which is a mixure of zirconium and barium chlomate are laminated and these are housed within a case 11 in order to form a thermal battery. Accordingly, when the heat pad 1 is fired with a firing ball 8 through a fusing plate 10, a high temperature does not reach directly the power generating cell 2. Therefore, the electrolyte layer can be melted and operating condition can be obtained without decomposition of iron sulfide of the positive electrode and melting of lithium alloy of the negative electrode and thereby, life span of battery can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a thermal battery using iron sulfide as a positive electrode and a lithium alloy as a negative electrode.

Conventional thermal batteries use calcium chromate as the positive electrode and calcium as the negative electrode, but since calcium chromate dissolves in the electrolyte, a eutectic mixture of lithium chloride and potassium chloride, the dissolved calcium chromate is used as the negative electrode. It has the disadvantage of short discharge life because it reacts with calcium and self-discharges.

In order to overcome this drawback of conventional calcium chromate-calcium thermal batteries, a new iron sulfide-lithium alloy thermal battery was introduced that uses iron sulfide, which does not dissolve in the electrolyte, as the positive electrode. In alloy thermal batteries, the melting point of lithium alloy is about 150℃ lower than that of calcium.
When a heat bat, which is a conventional exothermic agent, was used, the lithium alloy often melted, resulting in a short circuit between the positive and negative electrodes, a serious problem.

The present invention is an iron sulfide-lithium alloy system having a long discharge life, and enables a high performance and highly reliable thermal battery without short circuits. In other words, a heat insulating layer is formed on both sides of a heat bat made of a heat generating agent made of zirconium and barium chromate, which instantly prevents heat from being transferred to the negative electrode lithium alloy and the positive electrode iron sulfide, thereby causing the lithium alloy to melt. By preventing iron sulfide from decomposing, it enables high-performance thermal batteries without short circuits.

Lithium alloys used include lithium-aluminum alloys and lithium-silicon alloys, and their melting points are lithium-aluminum alloys and lithium-silicon alloys.
680℃ for aluminum alloy, 70℃ for lithium-silicon
It is 0°C. Note that the melting point of calcium is 838°C.

The decomposition temperature of iron sulfide (FeS2) is about 600°C,
A desirable battery operating temperature is 550°C.

When the mixture of zirconium and barium chromate, which are exothermic agents, is ignited, it instantly generates heat, and its surface reaches a temperature of 1200°C.
reach even. Therefore, if the exothermic agent is in direct contact with the lithium alloy or iron sulfide, the lithium alloy will melt or the iron sulfide will decompose, making it impossible for the battery to exhibit satisfactory performance.

That is, when the lithium alloy melts, the molten lithium alloy comes into contact with the positive electrode, causing a short circuit, and the discharge voltage rapidly decreases.

Also, when iron sulfide (FeS2) decomposes, it produces sulfur (S) and 1
Iron sulfide (FeF2) is generated and the discharge voltage is lowered.

In order to solve the above-mentioned problems, the present invention forms a heat insulating layer on both sides of a hit bat made of a plate-shaped heat generating agent mainly composed of a mixture of zirconium and barium chromate, so that the heat generated from the exothermic agent can be prevented. This prevents instantaneous transmission to the electrode plate layer and negative electrode layer, thereby eliminating the decomposition of iron sulfide and the melting of the lithium alloy. The method of forming a heat insulating layer on both sides of a heat pad is to use a so-called heat pad with a heat insulating layer, in which the heat generating layer and the heat insulating layer of the heat pad are integrated, or to form a heat insulating layer between the heat pad and the positive electrode layer and the negative electrode layer. There is a method of interposing a thin heat insulating plate. The heat insulating layer or board is preferably a paper-like or felt-like material with a thickness of 0.05 mm to 0.2 mm made of inorganic powder such as kaolin, magnesia, or alumina and inorganic fiber such as glass fiber or ceramic fiber. This heat insulating layer made of inorganic powder and inorganic fiber has a very low thermal conductivity, for example, a layer made of carrion and ceramic fiber has a thermal conductivity of 0.1 Kcal/mh.
rC, and the heating layer of the heat pad itself instantly becomes 12
Although the temperature rises to 00°C, when a 0.1 mm thick heat insulating layer is interposed, the temperature rise remains at 580°C, and neither decomposition of iron sulfide nor melting of the lithium alloy occurs.

Next, embodiments of the present invention will be described with reference to the drawings. 1st
The figure is a sectional view of a battery showing one embodiment of the present invention, and FIGS. 2 and 3 are perspective views of a heat pad and pellets used in the battery of the present invention. In the figure, (1) is a heat pad with heat insulating layers (21) and (22) on both sides of a heat generating layer (23), and the heat generating agent in the heat generating layer is a mixture of zirconium and barium chromate. of ceramic fibers and molded into a plate with a thickness of 1 mm. The heat insulating layer is made of 0.00 mm made of kaolin and ceramic fiber.
It is a plate shape with a thickness of 1 mm. Although it is easier and more convenient to handle the heat generating layer and the heat insulating layer in lamination when they are manufactured integrally, the heat generating layer and the heat insulating layer may be separate.

(2) is a pellet consisting of three layers: a positive electrode layer (24), an electrolyte layer (25), and a negative electrode layer (26).
4) is made of iron sulfide, and the electrolyte layer (25) is a 60% eutectic mixture of lithium chloride and potassium chloride with magnesia 4.
The negative electrode layer (26) is made of a lithium-aluminum alloy. These three layers are integrally molded. This pellet is a power generation cell, and the voltage of one cell is 1.7V. (3) is a connection plate that electrically connects cells.

(4) is a positive electrode plate, which is a positive electrode layer (2) of pellet (1).
4) and is connected to the positive electrode terminal (6) via a lead wire. (5) is a negative electrode current collector plate that is in contact with the negative electrode layer (26) of the pellet (1) and connected to the negative electrode terminal (7) via a lead wire. (8) is an ignition ball, and (9) is an ignition terminal. (10) is a fuse plate consisting of a heat generating layer. In this example, there are 5 heat pads and 5 heat pads.
The pellets are stacked on top of each other to form a laminate stack.

(11) is a battery case made of stainless steel,
(12) is a battery cover made of stainless steel, and the terminals (6, 7, 9) and the battery cover are electrically insulated by glass (13). A heat insulating material (14) such as asbestos or ceramic fiber is filled between the battery case (11) and the laminated stack. Thus, when electricity is applied to the ignition terminal (9), the ignition ball (8) ignites, the fuse plate ignites, and then the heat generating layer of the heat pad (1) ignites, and the heat generating layer itself reaches 1200°C. reach The heat emitted from the heat generating layer gradually travels through both heat insulating layers (21, 23) and reaches the positive and negative electrode layers of the pellet, so the temperature of both layers does not rise above 600°C, and the iron sulfide in the positive electrode layer There is no decomposition of the lithium alloy and no melting of the lithium alloy in the negative electrode layer, and the eutectic mixture of lithium chloride and potassium chloride (melting point 352) in the electrolyte layer does not occur.
°C) melts and becomes conductive, and the power generating cell reaches its operating state.

When 10 batteries were assembled and tested using a heat pad that did not have a heat insulating layer formed on both sides, 7 batteries were short-circuited. When 10 batteries were assembled and tested, none were short-circuited and all discharged normally.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a battery showing an embodiment of the present invention. FIG. 2 is a perspective view of a heat pad and pellets used in the battery of the present invention.

Claims (1)

[Claims] The positive electrode uses iron sulfide and the negative electrode uses lithium alloy.
A thermal battery in which a pellet consisting of three layers of an electrolyte and a negative electrode and a heat pad as a heat generating material are laminated, characterized in that a heat insulating layer is formed on both sides of the heat pad as a heat generating material.