JP2808627B2 - Thermal battery - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an improved thermal storage layer provided above and below a laminate composed of a unit cell of a thermal battery and a heating agent, and has an excellent heat retaining effect and is operated for a long time. The present invention relates to a thermal battery for use.

2. Description of the Related Art Thermal batteries are inactive at room temperature, but become active when heated to a high temperature, and can supply power to the outside, and are a type of storage battery. Therefore, it has very good storability and can be used without any change in battery characteristics even after storage for 5 to 10 years. In addition, it operates at a high temperature, and the electrode reaction is easy to proceed and the polarization is small, so it can withstand large output discharge well.In use, it has a feature such as instantaneous voltage generation when a start signal is input, but only for a short time within several minutes. It has the disadvantage that it cannot be used.

However, in recent years, a battery operated for 15 minutes has been announced, and in the future, there is a tendency that applications for a large current, a high output, and a large capacity for a relatively long time of several tens of minutes to one hour are increasing. For that purpose, it is necessary to keep the electrolyte in a molten state for a long time during the operation of the battery, and as a result, the discharge life can be extended. Therefore, thermal insulation technology for thermal batteries will become an increasingly important issue in the future.

Heat insulation technology is centered on insulation technology and heat storage technology. For the former, studies have been made on storage batteries using a special heat insulating material having a low thermal conductivity coefficient called MIN-K and Microtherm, and using the heat storage agent utilizing the latent heat of solidification of molten salt for the latter. This molten salt heat storage agent is formed into pellets and used together with a heating agent for heating and melting at both ends of the laminate of the unit cell and the heating agent.

 Hereinafter, a conventional heat storage layer for a thermal battery will be described.

FIG. 2 is a sectional view of a conventional molten salt heat storage layer. In a, 3 is lithium sulfate and sodium chloride (Li ₂ SO ₄ —Na
Cl) 10 to 15% by weight of a binder of silicon dioxide (SiO ₂ ) is added to the molten salt heat storage agent, and this is a fixed heat storage layer that is uniformly impregnated and held by heat treatment. This is a heating agent composed of iron powder and potassium perchlorate. 5 is integrally formed from above as a reinforcing body. In FIG. 2B, reference numeral 13 denotes a sealed metal container into which a molten salt heat storage agent 14 comprising lithium sulfate and sodium chloride is injected in a molten state, and then sealed.

When these heat storage layers are used in a battery, the heat storage layers processed in layers are alternately stacked with a heating agent. The effect is that the heat storage agent of lithium sulfate and sodium chloride generates a latent heat of solidification of 90 cal / g at 498 ° C, supplies heat to the unit cell-heating agent stack, and the temperature becomes constant at around 500 ° C. By forming a gentle state, the molten state of the electrolyte layer of the unit cell can be maintained for a long time.

Problems to be Solved by the Invention However, each of the above-mentioned conventional heat storage layers has a problem. That is, in the configuration of a, the immobilized heat storage layer 3 has sufficient mechanical strength because it is formed on the heating agent 5, but if the heat storage agent does not contain a sufficient inorganic binder when heated and melted, the layer And the configuration is not stable.
In addition, since the heating agent and the fixed heat storage layer are in direct contact, potassium chloride (KCl) generated when the heating agent consisting of iron and potassium perchlorate causes an exothermic reaction
Diffuses into the immobilized heat storage layer 3 to form Li ₂ SO ₄ —NaCl—KCl
Eutectic point of Li ₂ SO ₄ —NaCl
It works around 450 ° C, which is lower than 8 ° C, and generates latent heat of low calories. Therefore, and if the 200 mA / cm ² or more high-rate discharge, not obtained and held for a long time the operating temperature of 480 ° C. or higher to necessary if the 2000 mA / cm ² or more of the pulse current is applied.

In addition, in the configuration of b, since the inorganic adsorbent is not used, the molten salt heat storage agent is used in a large amount, so that the volume ratio is improved,
The number of steps of the pouring step, the sealing step, and the cooling and solidifying step increases, and the operation becomes complicated, resulting in high cost.

The present invention is to solve the above problems, the configuration of the heat storage layer is stabilized before and after use, easy manufacture, the heating agent and the heat storage agent is not suitable intermingled, the Li ₂ SO ₄ -NaCl It is an object of the present invention to improve the heat retention technology of a long-time thermal battery having inherent physical properties.

Means for Solving the Problems In order to solve the above problems, the present invention provides the above Li ₂ SO ₄
-Place the heat storage agent fixed by heat-treating the powder mainly composed of the homogeneous mixture of the NaCl molten salt heat storage agent and the inorganic adsorbent at the melting point of the molten salt heat storage agent or higher into a metal cup. By installing the heat storage layer for the heat battery obtained by covering with the lid at the top and bottom of the stacked body composed of the unit cells and the heating agent alternately stacked, the immobilized heat storage agent and the heating agent do not directly contact I do.

Using this thermal storage layer, the immobilized thermal storage agent is bound in the metal cup, which increases the mechanical strength.Therefore, it is possible to reduce the amount of the inorganic adsorbent and increase the amount of the thermal storage agent, and to reduce the powder. Since it is a simple process of simply pressing the cover after placing it in a metal cup, it can be easily manufactured. Further, since there is no direct contact with the heating agent, there is no danger of lowering the melting point or calorie due to potassium chloride (KCl) generated when iron and potassium perchlorate cause an exothermic reaction. As a result, an optimal heat storage layer for the thermal battery is obtained.

Examples The following describes typical examples of the present invention.

FIG. 1 is a diagram in which a fixed heat storage layer 3 is surrounded by a metal cup 1 and a metal lid 2. The fixed thermal storage layer is a molten salt thermal storage agent
After uniformly mixing in a ball mill of Li ₂ SO ₄ -88% by weight of NaCl and 12% by weight of inorganic adsorbent SiO ₂ , heat treatment is performed at 600 ° C. for 16 hours to convert L to SiO ₂ .
i ₂ SO ₄ immobilizing -NaCl. After that, it is ground and granulated to obtain a fixed heat storage agent, and a metal cup, a fixed heat storage agent,
The metal lid is inserted and caulked while being molded to form a heat storage layer for a thermal battery as shown. In more detail, the metal cup is also used for the negative electrode of the unit cell and has a thickness of 0.1 m
m is pressed into a cup with a height of 1.5 mm. Put the powder of the immobilized heat storage agent in this metal cup and after evenly dispersing, the whole is 0.1 ~ 0.2 to
Pre-press molding at n / cm ² , and the same thickness as cup
Insert a 0.1mm disc-shaped metal lid and cover the molding surface. It is obtained by caulking the periphery of the cup with a plate and then subjecting it to full-pressure molding at 2.6 ton / cm ² per unit area. The heat storage layer for a heat battery thus obtained is a flat plate having a thickness of about 1 mm, and the powder compact of the fixed heat storage layer has a slightly lower strength than the conventional SiO _{2 of} 15% by weight. Since the battery is enclosed in a metal cup, it does not easily collapse or fall down on the floor when the battery is assembled, and it is very easy to handle and improved. In addition, since the immobilized heat storage layer is separated from the heating agent by the metal cup and the lid and does not come into direct contact with the heating agent, it is not affected by KCl generated as a product by the exothermic reaction of the heating agent, so the latent heat of solidification from the heat storage layer is always 500. Appears around ℃.

FIG. 3 is a sectional view showing a thermal battery using the present invention.
Reference numeral 4 denotes a unit cell in the case of the present invention in which ten cells are stacked in series, and heating agents 5 are inserted between the unit cells 4 alternately.
Reference numerals 6 and 6 'denote heat storage layers for the thermal battery of the present invention provided on the upper and lower parts, and two sets of upper and lower thermal storage layers for heating the same with the same heating agent inserted between the cells. did. Reference numeral 7 denotes an electric igniter, and reference numeral 8 ignites the heating agent 5 in each layer when burning in a fuse zone. Reference numeral 9 denotes an external terminal of the igniter, which is used for a trigger input for supplying a small current. Reference numerals 10 and 10 'denote a positive terminal and a negative terminal of the thermal battery, which are used by attaching a hermetic seal to the battery outer cover 11. Reference numeral 12 denotes an outer case, and 13 denotes a heat insulating material provided between the outer case and the inner laminate.

In the battery of the present invention, when a micro-ignition trigger is applied to the external terminal 9 of the igniter, the igniter 7 emits a flame, ignites the heating agent disposed thereunder, and further propagates by combustion to the squib 8. Then, the cell heating agent 5 of each layer burns and the heat dissolves the molten salt electrolyte of the unit cell 3 to activate the cell. At this time, the heat storage agent of the heat storage layer for the heat battery is also heated and melted to about 600 ° C., and when it is cooled to around 500 ° C. by the subsequent heat radiation, latent heat is generated and this temperature is maintained for a certain time.

FIG. 4 is an internal temperature measurement curve of the thermal battery of FIG. The vertical axis represents the internal temperature of the unit cell, and the horizontal axis represents the discharge time.
The internal temperature was measured by inserting a thermocouple into the unit cell located at the bottom of the laminate. 1 is a case where the heat storage layer for a thermal battery according to the embodiment of the present invention is used, 2 is a case where a fixed heat storage layer formed on the conventional heating agent of FIG. 2a is used, and 3 is FIG. 2b. This is the internal temperature when using the conventional heat storage layer in which only the conventional molten salt heat storage agent is sealed.

From this figure, Examples 1 and 3 in which the heat storage agent is separated from the heating agent, such as enclosing the heat storage agent in a metal case, are excellent in the heat retaining effect and exhibit a constant temperature at about 500 ° C. where latent heat of solidification is generated. The time required to reach 400 ° C., at which it becomes difficult to extract a large current from the battery, is 24 minutes in Example 1 and 25 minutes in Example 3, and the difference in heat generation efficiency due to the inclusion of the binder is only 1 minute.
However, when the heat storage layer and the heating agent were in direct contact as in Example 2, the ternary composition of Li ₂ SO ₄ —NaCl—KCl was determined by the reaction product KCl of the heating agent. 450 ° C with no visible flat area due to latent heat generation
Since only a small amount of heat storage effect was observed in the vicinity, the time required to reach 400 ° C was 21 minutes, which was a result of a shorter temperature maintenance time than the above.

Effects of the Invention As described above, according to the present invention, the immobilized heat storage agent can be sealed in a metal cup in an easy step, so that the amount of the inorganic salt adsorbent can be reduced and the molten salt heat storage agent can be increased, and It is practically extremely useful because it can generate a large latent heat of solidification at around 500 ° C. without being affected by a heating agent and can maintain a constant temperature for a long time.

[Brief description of the drawings]

FIG. 1 is a sectional view of a heat storage layer for a thermal battery according to an embodiment of the present invention.
FIGS. A and b are cross-sectional views of a heat storage layer in a conventional example, FIG. 3 is a cross-sectional view of a stacked thermal battery using the heat storage layer, and FIG. 4 is a diagram showing a carp for measuring an internal temperature. DESCRIPTION OF SYMBOLS 1 ... Metal cup, 2 ... Metal lid, 3 ... Fixed thermal storage layer, 4 ... Unit cell, 5 ... Heating agent, 6 ... Thermal storage layer for upper thermal battery, 6 '... Lower thermal battery Thermal storage layer.

Continued on the front page (72) Hiroshi Yamazaki, Inventor 1006 Odakadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) H01M 6/36

Claims (1)

(57) [Claims] 1. A powder mainly composed of a homogeneous mixture of a molten salt heat storage agent composed of a mixed salt of lithium sulfate and sodium chloride and an inorganic adsorbent is heat-treated at a temperature equal to or higher than the melting point of the molten salt heat storage agent to form a powder. A solidified heat storage agent is prepared, the fixed heat storage agent is surrounded by a metal cup and a metal lid to form a heat storage layer for a heat battery, and the upper and lower parts of the stacked body obtained by alternately stacking the unit cells and the heating agent are formed. A thermal battery, wherein the fixed thermal storage agent and the heating agent are not in direct contact with each other by providing the thermal storage layer for the thermal battery.