JPH01115065A - Thermal battery - Google Patents

Abstract

PURPOSE:To lengthen the temperature holding time of a stack and to remarkably improve the discharge life of a battery by using a battery case obtained by sealing a double battery case under reduced pressure below a specified value. CONSTITUTION:A double battery case having a space between an inner battery case 1 and an outer battery case 2 is used. Both battery cases 1, 2 are joined by welding or silver soldering, and the space 9 is sealed under a reduced pressure of 1X10<3>Torr or less to form a heat insulating layer. Even if the thickness of the heat insulating layer is thin, the stack temperature inside a battery is held at operating temperature for a long time. If the reduced pressure value is 1X10<2>Torr or more, the outflow of heat is sharply increased, however, if it is 1X10<3>Torr or less, the outflow of heat is remarkably decreased provided the thickness of the heat insulating layer is 1mm or more. The outflow of heat value generated in a battery for operation is retarded, and a thermal battery which is operable for a long time is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to improvements in heat retention technology for thermal batteries that require long-term operation.

BACKGROUND TECHNOLOGY A thermal battery is inactive at room temperature, but becomes active when heated to a high temperature and can supply power to the outside, and is a type of storage battery. Therefore, even after storage for 5 to 10 years or more, the battery characteristics remain the same as immediately after manufacture, so they are used as an emergency power source. In addition, since it is operated at high temperatures, the electrode reaction progresses easily, so there is little polarization, so it has excellent large current discharge properties, and when you wish to use it, you can instantly extract electricity by inputting a start signal.
On the other hand, it has the disadvantage that it can only be used for a short period of time, within a few minutes.

Research that has been carried out to overcome this problem has focused on (1) improving battery systems, (2) improving insulation technology, and (3) improving heat insulation technology.
) This is an improvement in heat storage technology. Regarding (1), from O&/OILCrO4 battery using calcium as the negative electrode to Li/Fe battery using lithium or lithium alloy as the negative electrode.
The battery was replaced with an S2 type battery, and the operating temperature range was expanded.

(In terms of effectiveness, we have changed from conventional natural insulation materials mainly made of asbestos and mica to Fiber-Flax (Fiber 7 Lux (manufactured by Carborundum)) and MIN-K.
There has been a shift to synthetic insulation materials with low thermal conductivity (for example, 0.03 Kam//th,'c) such as (manufactured by Zume Zuman Building Co., Ltd.). Furthermore, regarding (3), the heat insulating layers at both ends of the stack consisting of unit cells and heat generating agent pellets do not use metal plates or simply use a large amount of heat generating agent, but rather efficiently generate latent heat of solidification at the optimum temperature for battery operation. A Li25O4-Hace heat storage layer is used, and the above (1)
By combining the techniques of (3) to (3), it is becoming possible to create batteries that can operate for a long time.

The present invention aims to realize a battery that can operate for a longer period of time by further improving insulation technology. In addition to the above-mentioned improvements in materials, efforts related to heat insulation have included the following:

(1) A mixture of inorganic fibers and a binder, silicone rubber, or the like is formed as a heat insulating layer on the outside of the battery.

(2) A heating element is placed between heat insulating layers formed inside the battery so as to surround the stack.

(3) Heat the battery from the outside using a heating wire heater to raise the temperature.

The problem to be solved by the invention (1) above is solved by U.S. Pat.
However, the method disclosed in No. 015 has drawbacks such as insufficient strength of the heat insulating layer, high thermal conductivity as a heat insulating material, and deterioration of heat insulation due to dew condensation in high temperature and high humidity tests. (2) is an example disclosed in Japanese Patent Publication No. 4B-33457, in which the heat insulating layer is forcibly heated, so the temperature difference with the battery case becomes large, making it difficult for heat to flow, and the temperature of the battery exterior increases. There are growing drawbacks. Further, (3) is not practical because it requires an external power source.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a thermal battery that can operate for a long time by suppressing the outflow of heat generated inside the battery for battery operation. shall be.

Means for Solving the Problems To solve this problem, the present invention uses a double battery case that forms a space layer between the inner battery case and the outer battery case, and welds the inner and outer battery cases. , silver soldering, etc., and the space layer is 1X10tOr.
It is sealed under reduced pressure below r to form a heat insulating layer.

Effect: According to this configuration, even if the thickness of the heat insulating layer is thin, the stack temperature inside the battery can be maintained at an operable temperature for a long period of time. At reduced pressure values of 1 x 102 torr or more, heat flow increases rapidly, but below 1 x 105 torr,
Hopefully, the thickness of the spatial layer is 1f below lX10tOrr.
At f or more, it becomes irrelevant, and the heat outflow becomes significantly small, showing a large effect. Therefore, MIN is expensive and has poor workability.
-It is cheaper and easier to process than using other materials, and a thin layer can provide the same or better insulation effect.
A long-lasting battery can be designed to be small and lightweight. Also (1)
The disadvantages of method (2) and the temperature rise on the battery exterior surface of method (2) are also suppressed, and the ultimate heat insulating layer for thermal batteries can be obtained.

EXAMPLES Examples of the present invention will be described below with reference to FIGS. 1 to 5.

FIG. 1 shows a cross-sectional view of the double battery case. In the figure,
1 is a cylindrical internal battery case made of stainless steel with a thickness of 0.5 ff and has a diameter of 85 ff, 2 is the lid welded part with the battery lid, 3
is a V-groove for assisting welding with the external battery case. 4 is a cylindrical external battery case with a diameter of 90 fl made of the same stainless steel with the same thickness of 0.5 ff, 5 is a V groove for assisting welding with the internal battery case, and the joint 6 of the internal and external battery cases is TIG welded. It was integrated to prevent pinholes from forming. 7 is a degassing knob for deaerating the air in the space layer 9, and 8 is its outlet. The thickness of the double battery case constructed in this way is 2.5 mm including the space layer of 15 ff and the case thickness. Incidentally, both inner surfaces of the space layer are plated with silver in each case.

Fig. 2 shows an example in which the joint 6' between the internal battery case 1' and the external battery case 4' is provided inside the battery case, and Fig. 3 shows an example in which the joint 6' between 1' and 4' is provided at the abutting part. This is an example.

FIG. 4 is a cross-sectional structural diagram of a stacked non-battery using the present invention.
1o is lithium or lithium alloy (LiA/.

11 is LiC3-KCe (47
: 53% by weight, melting point 352°C) and magnesium oxide (
The electrolyte layer of the mixed molded body of MgO), 12 is iron disulfide (F
eS2) and a positive electrode layer made of the electrolyte material described above, the unit cell 13 has a diameter of 76 mm and includes these three layers as one body. Reference numeral 14 denotes exothermic agent pellets, which are formed into pellets by pressure molding a mixture of iron powder and potassium perchlorate (88:12% by weight), and are laminated alternately with unit cells 13 in arbitrary numbers to form a stack.

Reference numeral 16 denotes a heat storage layer, which is a layer in which, for example, a molten salt of lithium sulfate and sodium chloride is melted and injected into a metal container and then sealed, and is placed above and below the stack. Reference numeral 16 denotes an electric igniter whose lead wires are connected to a pair of starting terminals 17, and when a pulse current is applied from these terminals, a flame is emitted, burning the heat pad 18, and further spreading the combustion to the fuse cord 19. .

20 and 21 are a pair of power output terminals to which lead wires drawn out from the top and bottom of the stack are respectively connected. 22 is a heat insulating layer whose thermal conductivity at 500'C is 0. o6Koa//
Fiber flux paper with a thickness of 6M, which is inexpensive and has good workability, and has dimensions m, h, and 'c is used for the top, bottom, and sides. 23 is a starting terminal 17 consisting of a glass hermetic seal' terminal. Battery cover with output terminals 20 and 21 attached,
24 is the TI of the lid welding part 2 and battery lid 23 of the double battery case.
This is the welded part of the lid case that is completely sealed using G welding. 25 is 2
This is a sealing part where the outlet 8 is closed after the space layer 9 of the heavy battery case is depressurized.

Next, a method for manufacturing the double battery case of this example will be described. After the cleaned outer surface of the internal battery case 1 and the inner surface of the external battery case 4 are first silver-plated,
Dry under reduced pressure at 20°C for 24 hours or more, and apply gas absorbent gela p-8T-707 (manufactured by Seeds Inc.) to the bottom of the external battery case.
500111g and fit the internal battery case. In this case, in order to make the formed space layer 9 uniform, spacers with good heat insulation properties may be used at arbitrary locations. While rotating the joint part 6 on a turntable, it was joined by TIG welding so that there were no through holes such as pinholes, and then it was degassed with a vacuum pump from the degassing knob T, and then placed in a 400'C furnace.
Trace amount of N2. The remaining gas such as N2 is absorbed by the getter,
The outlet 8 is strictly sealed. This space-time layer is I
Torr vacuum value preferably 1X 10 torr
It is important to do the following.

In addition to the above-mentioned method, the sealing method can also be performed without using a degassing knob. In other words, a cap with 7 lunges is placed over the hole to be sealed, silver solder is applied to the flange and the main body, the silver solder is melted under heating and reduced pressure, and then the cap is allowed to cool.

In this case, the appearance is excellent because there are no protrusions, but a heating and depressurizing device is required.

FIG. 6 is a diagram showing the relationship between the spatial layer pressure and the value of heat escape (heat flow value). In the figure, internal battery case temperature 1
00°C and external battery case temperature 2°0C, lX1
At 0tOrr, it is 0.8. 9 for lX1O-3torr.
1 X10 torr is not displayed but 250
The heat flow value was Kcad/m2h. In addition, the heat flow value is 1
rr? It is a unit that indicates the amount of heat transferred per hour from the area of KCILl, and it is better to indicate a smaller value. In thermal battery design, the temperature difference between double battery cases is 100~
Since the temperature is expanded to about 300° C., it is best if the temperature is 1XIQ torr or less, and it is best if it is IX10-torr or less. In this case, if the mean free path of gas molecules such as N2 or N2 is 1ff or more in the spatial layer, it is sufficiently long, so if it is longer than this, there is no problem.

Next, the effects of this embodiment will be described in comparison with the conventional example.

The table below shows the discharge life (seconds) and energy density (wh) until 75% of the maximum voltage is maintained when the discharge current density is SOWmu/i for a unit cell diameter of 76fl, battery diameter of 9Qjfl, and battery height of 9011. /e) and battery weight (kq
).

Effects of the Invention As is clear from the above explanation, when a battery case is used in which the space of the double battery case is sealed under a reduced pressure of 1×10 tOrr or less, the stack temperature retention time is extended and the discharge life is greatly improved. The energy density is improved and the weight of the battery is also reduced.

[Brief explanation of the drawing]

FIG. 1 is an unsealed sectional view of a double battery case according to an embodiment of the present invention, and FIGS. 2 and 3 are partial sectional views showing other joint structures of the internal and external battery cases of the same double battery case. , FIG. 4 is a longitudinal cross-sectional view of a stacked battery using the double battery case of the present invention, and FIG. 5 is a correlation diagram between space layer pressure and heat flow value. 1... Internal battery case, 2... External battery case, 6... Joint, 7... Deaeration knob, 9... Space layer, 13... Unit cell, 14... Exothermic agent pellet, 22...
Heat insulation layer, 26... Sealing part. Name of agent: Patent attorney Toshio Nakao and 1 other person1-
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Claims (1)

[Claims] A double battery case is provided in which a space layer is formed between an inner battery case and an outer battery case, and the inner and outer battery cases are joined together, and the space layer is sealed at a reduced pressure of 1×10^-^3 torr or less. , a thermal battery whose internal battery case is loaded with a unit cell, exothermic pellets, and heat insulating material.