JPH0782859B2 - Thermal battery - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal battery in which a heating agent is incorporated inside a battery and the heating agent is ignited when the battery is used to heat the inside of the battery to a high temperature for activation. Thus, a thermal battery having a high capacity and capable of discharging for a long time and having a high energy density is provided.

2. Description of the Related Art A thermal battery is a battery that uses a molten salt containing a heating agent as an electrolyte. Since the electrolyte is a non-conducting solid salt during storage, it is in an inactive state as a battery, but by burning a heating agent to heat the inside of the battery to a high temperature, the electrolyte melts and exhibits conductivity. And the battery is activated.

A thermal battery is a type of storage battery that has little self-discharge during storage, can be stored for a long period of time, and can be instantly activated when necessary. Also, −55 to 100 ° C
It is a high energy density battery that can be used under a wide range of environmental temperatures. Due to such many features, thermal batteries have become indispensable as power sources for missiles, rockets, and other flying objects, and various emergency power sources.

Conventionally, a system using calcium for the negative electrode and calcium chromate for the positive electrode has been used as the active material of this type of thermal battery, but for higher capacity and high output, lithium or lithium alloy is used for the negative electrode. Thermal batteries using sulfides have been developed.

As the lithium alloy, an alloy of lithium and boron, aluminum, silicon, gallium, germanium, or the like can be used.

Iron sulfide, which has high heat resistance, is mainly used as the sulfide of the positive electrode active material, but nickel, chromium, cobalt,
Sulfides of copper, tungsten, molybdenum, etc., and sulfides of the Svrel phase containing these metals can also be used.

As the electrolyte, a eutectic salt of LiCl-59 mol% and KCl-41 mol% is generally used. This eutectic salt is relatively inexpensive, has a low melting point of 352 ° C., and has high insulation resistance at room temperature. As the electrolyte, a material obtained by mixing lithium in the negative electrode with an insulating powder such as magnesium oxide, boron oxide, or zirconium oxide having corrosion resistance so as to have no fluidity is used. The electrolyte layer is a conductor of ions during the operation of the thermal battery, and at the same time, acts as a separator for the positive electrode and the negative electrode.

As the exothermic agent, a molded product of a mixture of iron powder and potassium perchlorate is used by being alternately laminated with cells. When the heating agent is ignited when the battery is activated, it causes an oxidation-reduction reaction to generate heat and heats the inside of the battery to the operating temperature.
This exothermic agent contains iron in excess of the amount required for the exothermic reaction, has high conductivity even after the exothermic reaction, and acts as a connecting body between adjacent unit cells.

An ignition ball is generally used as a means for activating a thermal battery. When a thermal battery is used, it can be ignited by energizing an ignition ball built into the thermal battery from an external power source to ignite a heat generating agent. It can also be activated by a percussion primer that is ignited by the impact of a hammer. This system does not require an external power source and can activate the thermal battery by mechanical action.

Problems to be Solved by the Invention Thermal batteries are storage-type batteries that can instantly obtain electric power when needed, and because of their high reliability, their applications and usages are on an increasing trend. , Higher capacity,
What can be discharged for a long time is required. However, it is difficult to manufacture a large-area cell due to structural restrictions, and a plurality of power generation block laminates that are electrically connected in parallel are used for high capacity and high output applications.

The discharge capacity of a thermal battery is limited by the discharge capacity of the active material as well as the operating temperature within the battery. Therefore, in designing a thermal battery, it is necessary to optimize not only the amount of active material used but also the method of heat insulation. The inside of the thermal battery is heated uniformly at the time of activation, but with the passage of time, a temperature distribution occurs in which the central portion is high and the surrounding area is low. The long-term thermal battery has a limited discharge life due to the temperature drop of the cells at both ends. In order to design a thermal battery with a long discharge time, it is necessary to prevent the temperature drop of the cells at both ends, but if many heat insulators are used for that purpose, the volume efficiency is lowered.

Means for Solving the Problems The present invention provides a thermal battery that can be discharged for a long period of time without increasing a heat insulating body for keeping heat, and includes three or more sets of power generating blocks electrically connected in parallel. In a thermal battery in which the power generation blocks are stacked in the same container, the active material discharge capacity of the inner power generation blocks is made larger than the active material discharge capacities of the power generation blocks at both ends.

Action The present invention focuses on the temperature distribution inside the thermal battery after a long time has passed after activation. Even after the temperature at both ends of the power generation block laminate has dropped below the operating temperature, the central portion is still hot and discharge is possible. Therefore, by making the discharge capacity of the inner power generation block larger than the discharge capacity of the power generation blocks at both ends, it became possible to discharge for a long time without increasing the number of heat insulators. That is, reducing the amount of active material in the cells of the power generation blocks at both ends where the temperature drop is large,
By increasing the amount of active material in the cells of the inner power generation block where the temperature drop is small, the inner power generation blocks continue to discharge even after the discharge of the power generation blocks at both ends is completed, enabling long-term discharge. .

Conventionally, the cells of the power generation block are the same at both ends and center. For this reason, the power generation blocks at both ends cannot be discharged even though the active material remains due to the temperature decrease, and the inner power generation blocks are in a temperature state where discharge is possible, but the discharge ends due to lack of active material. did.

Examples Hereinafter, the present invention will be described using preferred examples.

FIG. 1 is a sectional view of a thermal battery having a configuration in which a plurality of power generation blocks are electrically connected in parallel. 1, 2, 3, and 4 are power generation blocks in which a plurality of cells and heat generating agents are alternately laminated,
1, 4 are power generation blocks at both ends, and 2 and 3 are power generation blocks inside. One or more inner power generation blocks are used according to the required capacity, and the respective power generation blocks are electrically connected to each other in parallel. Reference numeral 5 is a connection lead wire on the positive electrode side, and 6 is a connection lead wire on the negative electrode side. In order to simplify the wiring, the power generation blocks are arranged so that the same poles face each other. Reference numeral 7 denotes an explosive charge provided on the central axis of the power generation block for transmitting the ignition energy of the ignition ball 8 to the heat generating agent in the power generation block. Reference numeral 9 denotes an ignition terminal, which can ignite the ignition ball 8 by passing an ignition current from an external power supply. Reference numerals 10 and 11 denote a positive electrode terminal and a negative electrode terminal for taking out an electric current. Reference numeral 12 is a container of the thermal battery, and the inside thereof is filled with a heat insulator 13 for keeping the thermal battery warm.

FIG. 2 is a diagram showing a combination of a cell used in a power generation block and a heat generating agent. Reference numeral 14 denotes a cell, which is composed of three layers of a positive electrode active material layer 15, an electrolyte layer 16, and a negative electrode active material layer 17. 18 is a heat generating agent, and 19 is a metal plate for separating the cell and the heat generating agent.

As an example of the present invention, a thermal battery in which four sets of power generation blocks composed of five sets of disc-shaped cells and a heating agent connected in series are stacked in the same container will be described.

A cell having a diameter of 50 mm was constructed by using iron disulfide as a positive electrode, a lithium-aluminum alloy as a negative electrode, and a mixture of LiCl-KCl eutectic salt and MgO as an electrolyte layer. Two types of cells and an exothermic agent are used in the thermal battery of the present invention. The active material discharge capacity of the cells for the power generation blocks at both ends is 130 A · second, and the active material discharge capacity of the cells for the power generation blocks on the inner side is 170 A · second. The amount of exothermic agent is adjusted according to the heat capacity of the cell used. Four power generation blocks were produced by stacking 5 sets of such cells and heating agents in series. The power generation blocks are stacked in the same container, but are electrically connected in parallel. The thermal battery of Example has a nominal voltage of 8 V and a capacity of 600 A · sec.

As a comparative example, a thermal battery having a conventional structure was manufactured in which cells having an active material discharge capacity of 150 A · sec were used for all power generation blocks.
The example battery and the comparative example battery differ only in the distribution of the amount of active material in the power generation block, and the amount of active material used, the amount of heat insulator used, the nominal voltage, the design capacity, the battery shape, the battery weight, etc. are the same. is there.

When discharged at a current of 40 A at an ambient temperature of −45 ° C., the discharge time of the battery of the present invention was 150 seconds and the discharge time of the comparative battery was 140 seconds. The battery according to the present invention could discharge 100% of the active material discharge capacity, whereas the conventional battery could discharge only 93%.

EFFECTS OF THE INVENTION As described above, the battery of the present invention can increase the capacity and the life of a thermal battery having a parallel configuration without increasing the amount of a heat insulator, and discharge due to a decrease in operating temperature. A more excellent effect is exhibited in a limited long-term discharge type thermal battery.

[Brief description of drawings]

FIG. 1 is a sectional view of a thermal battery having a configuration in which a plurality of power generation blocks are electrically connected in parallel. FIG. 2 is a diagram showing a combination of a cell used in a power generation block and a heat generating agent. 1, 4 ...... Power generation block at both ends 2, 3 ...... Inside power generation block 10 …… Positive electrode terminal 11 …… Negative electrode terminal 14 …… Cell 18 …… Heating agent 19 …… Metal plate

Claims (1)

[Claims] 1. In a thermal battery comprising three or more sets of power generation blocks electrically connected in parallel, wherein these power generation blocks are stacked in the same container, the active material discharge capacity of the inner power generation block is A thermal battery characterized by having a discharge capacity higher than that of the power generation block.