KR20100088492A - Cathodal pellet for thermal battery, method for fablicatign the same, and thermal battery having the same - Google Patents

Abstract

PURPOSE: A positive electrode pellet for a thermal battery, a manufacturing method thereof, and the thermal battery are provided to increase the contact area between FeS_2 particles by coating the particle surface of lithium eutectic salt. CONSTITUTION: A manufacturing method of a positive electrode pellet for a thermal battery comprises the following steps: forming mixed powder by mixing FeS_2 powder, electrolyte binder powder, and Li_2O powder; melting the mixed powder, and cooling the melted product to form a mixed powder particle in which the electrolyte is coated on the FeS_2; and crushing the particle to form positive electrode powder, and mold-pressing the positive electrode powder.

Description

Anode Pallet for Thermoelectric Battery, Method for Manufacturing the Same, and Thermoelectric Battery Having the Same {CATHODAL PELLET FOR THERMAL BATTERY, METHOD FOR FABLICATIGN THE SAME, AND THERMAL BATTERY HAVING THE SAME}

The present invention relates to a positive electrode pallet for a thermocell that can be manufactured to have high strength even at low pressure, a method for manufacturing the same, and a thermocell having the same.

The thermal battery refers to a battery that generates an electromotive force when the thermal battery is stored in an inactive state of the battery at room temperature, and then activated when subjected to heat of 300 to 500 ° C.

In a thermo battery, an electrolyte that enables ion migration between a positive electrode and a negative electrode exists in a solid state at room temperature. When the electrolyte receives heat at a high temperature of 300 to 500 ° C, the electrolyte melts to have ion conductivity, and thus electromotive force is generated to generate high output electricity.

As such, the thermal battery is not self-discharged because the electrolyte exists in the solid phase which is an insulator at room temperature. Therefore, the thermocell can be stored for a long time for more than 20 years and expresses high output during operation, and is used for military use, emergency use in large buildings, power plants, and the like.

In general, thermoelectric cells have a form in which positive and negative pellets and an electrolyte separator in the form of pellets or discs are stacked. The positive and negative pellets of thermoelectric cells have generally been manufactured utilizing powder uniaxial press molding methods.

FeS _{2, which} is most commonly used as a positive electrode for thermoelectric batteries, has high hardness and is difficult to form into pellets having high strength due to the small contact area between particles during compression. Therefore, in order to increase the bonding force between FeS ₂ particles, a number of methods for compression molding by mixing with eutectic salt powder having excellent ductility have been performed.

However, even if this method was applied, cracking or breaking of the pellets could be observed during pellet production, and a press having a high pressure capability was required for the anode molding having excellent strength, which caused the cost of manufacturing the thermocell. do.

The present invention is to increase the ductility and inter-particle contact area of the FeS ₂ particles during compression molding to be able to produce high-strength anode pellets even at low pressure.

Method for producing a cathode pellet for a thermo battery according to the present invention for achieving the above object comprises the steps of forming a mixed powder by mixing FeS ₂ powder, electrolyte binder powder and Li ₂ O powder; Melting and cooling the mixed powder to form the mixed powder mass coated with the electrolyte on FeS ₂ ; And forming the positive electrode powder by pulverizing the mixed powder agglomerate, and molding and compressing the positive electrode powder.

The electrolyte binder powder may be formed by lithium eutectic salt powder and MgO powder, and the lithium eutectic salt powder may include LiCl-KCl eutectic salt powder.

The preparing of the electrolyte binder powder may include mixing and melting the LiCl powder and the KCl powder and then cooling to form a eutectic salt lump; Grinding the eutectic salt mass to form a eutectic salt powder; Mixing the eutectic salt powder with MgO powder to melt and then cool to form a mixture of eutectic salt and MgO mixed mass; And grinding the eutectic salt and MgO mixed mass to form the electrolyte binder powder.

The FeS ₂ and Li ₂ O powder has a weight ratio of 75%, the electrolyte binder powder has a weight ratio of 25%, the Li ₂ O powder has a weight ratio of 0.5% to 1.5% Method for producing pellets.

The mixed powder may be melted for 2 hours to 8 hours at a temperature of 300 to 500 ℃ in an inert gas atmosphere.

On the other hand, the present invention is a positive electrode pellet for a thermal cell formed of FeS ₂ and an electrolyte, comprising the steps of mixing the FeS ₂ powder, electrolyte binder powder and Li ₂ O powder to form a mixed powder; Melting and cooling the mixed powder to form the mixed powder mass coated with the electrolyte on FeS ₂ ; And forming a positive electrode powder by pulverizing the mixed powder agglomerate, and molding the compressed positive electrode powder.

In addition, the present invention positive electrode pellets and negative electrode pellets; And an electrolyte separator disposed between the anode pellet and the cathode pellet, the electrolyte separator including a solid electrolyte which is melted by an increase in temperature to have ion conductivity, wherein the cathode pellet comprises: FeS ₂ powder and electrolyte binder powder; Mixing the Li ₂ O powder to form a mixed powder; Melting and cooling the mixed powder to form the mixed powder mass coated with the electrolyte on FeS ₂ ; And forming a positive electrode powder by pulverizing the mixed powder agglomerate, and then molding and compressing the positive electrode powder.

In the present invention as described above, the lithium eutectic salt is added to the surface of the FeS ₂ particles by adding Li ₂ O in the preparation of the positive electrode powder, thereby increasing the ductility and inter-particle contact area of the FeS ₂ particles, and thus having high strength even at low pressure. Anode pellets can be prepared.

In addition, through the present invention, it is possible to manufacture high-strength anode pellets at low molding pressure and to use a press of a smaller capacity, thereby reducing investment cost and cost.

In addition, the present invention has the effect of increasing the thermal stability of the positive electrode pellets by minimizing the heat generated from the FeS ₂ powder during operation of the thermal cell.

Hereinafter, a cathode pellet for a thermocell according to the present invention, a manufacturing method thereof, and a thermocell having the same will be described in more detail with reference to the accompanying drawings.

1 is a cross-sectional view schematically showing a thermo battery according to an embodiment of the present invention.

Referring to FIG. 1, a thermo battery includes a positive electrode pellet 10, a negative electrode pellet 20, and an electrolyte separator 30 disposed between the positive electrode pellet 10 and the negative electrode pellet 20.

The cathode pellets 10 may be made of a material such as FeS _2, and the anode pellets 20 may be made of lithium or a lithium alloy (eg, Li—Al alloy, Li—Si alloy, etc.).

The anode pellets 10 and the cathode pellets 20 are not in electrical contact at room temperature by the electrolyte separator 30. In addition, current collectors 11 and 21 are provided in the anode pellet 10 and the cathode pellet 20 to collect electrical energy from the thermoelectric cell.

The positive electrode pellets 10, the negative electrode pellets 20, and the electrolyte separator 30 may have a form of a disk stacked in layers.

The electrolyte separator 30 is provided with an electrolyte salt in a solid state, and the electrolyte salt may be a lithium eutectic salt containing lithium, for example, a LiCl-KCl based lithium eutectic salt or a LiCl-LiF-LiBr based lithium eutectic salt. have.

When the ignition unit mounted on the thermocell generates a flame by an electrical signal, the temperature inside the thermocell increases to 300 to 500 ° C. Accordingly, the lithium eutectic salt in the solid state is melted, and thus the lithium eutectic salt has ion conductivity. In addition, electromotive force is generated in the thermoelectric battery by ion movement between the cathode pellets 10 and the anode pellets 20. Here, the anode pellets 10 and the cathode pellets 20 may also be provided with an electrolyte salt which is melted with an increase in temperature and has ion conductivity.

Hereinafter, a method of manufacturing the anode pellet 10 having the structure as described above will be described in detail.

Method for producing a positive electrode pellet 10 according to an embodiment of the present invention comprises the steps of mixing FeS ₂ powder and electrolyte binder powder (lithium eutectic salt and MgO mixed powder) and Li ₂ O powder to form a mixed powder and Melting and cooling the mixed powder to form a mixed powder mass in which the electrolyte is coated on FeS ₂ , and pulverizing the mixed powder mass to form a positive powder and then compacting and compacting the positive powder.

First, the process of manufacturing the electrolyte binder powder is as follows.

In order to prepare the electrolyte binder powder, first, a lithium eutectic salt powder should be prepared. Here, the lithium eutectic salt powder may be used LiCl-KCl eutectic salt powder.

First, LiCl powder having a weight ratio of 45% and KCl powder having a weight ratio of 55% are mixed. Here, the mixing of LiCl and KCl powder may be performed using a ball-mill mixer or a high speed mixer.

Next, the mixed LiCl and KCl powder is heat treated in an inert gas atmosphere. The LiCl and KCl powders are subjected to a temperature above the melting point (462 ° C.) of the LiCl-KCl eutectic salts, and when the molten LiCl-KCl eutectic salts are quenched, a lump of eutectic salts is formed.

The eutectic salt mass formed as described above is pulverized using a ball-mill grinder, an autogenerator or a shatter box to form lithium eutectic salt powder. In addition, the lithium eutectic salt powder formed by grinding may be sieved to have a powder size suitable for the purpose.

The lithium eutectic salt powder thus prepared is mixed with MgO powder. The lithium eutectic salt powder is mixed with the MgO powder through a ball-mill mixer or a high speed mixer as described above. Here, the lithium eutectic salt powder has a weight ratio of 65%, and the MgO powder is mixed to have a weight ratio of 35%.

Lithium common salt, which is a component of the electrolyte binder, is melted by an increase in temperature to have ion conductivity. MgO serves to support lithium eutectic salts so that lithium eutectic salts do not leak.

When the mixed lithium eutectic salt and MgO powder are melted by applying a temperature above the melting point of the eutectic salt in an inert gas atmosphere and then quenched, a mixture of eutectic salt and MgO is formed.

In addition, when the eutectic salt and the MgO mixed agglomerates are pulverized using a ball-mill grinder, an autogenerator or a shatter box, the preparation of the electrolyte binder powder is completed. Here, the electrolyte binder powder may be sieved to have a powder size suitable for the purpose.

After weighing the electrolytic binder powder prepared in this way, FeS ₂ powder and Li ₂ O powder in a weight ratio within a desired range, and uniformly mixing each weighed powder using a ball-mill mixer or a high speed mixer, The preparation of the powder is completed.

Here, the FeS ₂ and Li ₂ O powder to have a weight ratio of 75%, the electrolyte binder powder to have a weight ratio of 25% and mix them. It was confirmed through experiments that the electrolyte binder powder had the most efficient ion conductivity in the range of such weight ratio.

In addition, the weight ratio of Li ₂ O is preferably between 0.5% and 1.5%. Li ₂ O, although the electrolyte binder is FeS to one serves to ensure good adhesion to the _second surface by default oxide because not only is the electrode resistance upon being excessive addition of more than 1.5% by weight increasing reaction with FeS ₂ FeS ₂ electrochemical capacity Care should be taken as this will cause a decrease.

By the combination of the weight ratio of FeS _{2, the} electrolyte binder, and Li ₂ O as described above, the weight ratio of FeS ₂ : electrolyte binder: Li ₂ O will be 74.5: 25: 0.5 to 73.5: 25: 1.5.

In addition, the mixed powders mixed as described above may be filtered to have a particle size of 500 μm or less.

Next, the process of forming the mixed powder mass by heat-treating the mixed powder prepared as described above will be described.

The mixed powder is placed in a ceramic bowl to minimize reaction with the vessel. Then, heat treatment is performed for 2 hours to 24 hours at a temperature of 300 ° C to 500 ° C in an inert gas (argon or nitrogen gas) atmosphere. Here, more preferable heat treatment time is between 2 hours and 8 hours.

The mixed powder is heat treated in this manner to form a mixed powder mass. In this process, the lithium eutectic salt of the electrolyte binder is melted and coated on the FeS ₂ powder surface by Li ₂ O.

Next, the mixed powder mass is pulverized using a ball-mill grinder, an autogenerator or a shatter box to form an anode powder. The positive electrode powder may be sieved to have a size of 10 μm to 200 μm, more preferably 50 μm to 150 μm, using a particle size classifier.

Next, when a certain amount of the positive electrode powder is put into a mold of a predetermined shape (for example, a circular shape) and molded and compressed, the production of a disk-shaped positive electrode pellet is completed.

According to the manufacturing method as described above, the lithium eutectic salt may be coated on the surface of the FeS ₂ particles as Li ₂ O is added during the production of the cathode powder. In this way, and lithium molten salt can be increased, the flexible and the contact area between particles of the FeS ₂ particles at the time of compression shaping of the cathode powder as the coating on the surface of FeS ₂ particles, whereby a positive electrode pellet having also a high strength to a low pressure in accordance with It can manufacture.

Hereinafter, the production of the anode pellets related to the present invention will be described in more detail with reference to the following examples.

2a to 2d are photographs showing the mixed powder related to the present invention.

FeS ₂ powder having a weight ratio of 73.5%, electrolyte binder powder having a weight ratio of 25% (mixed powder of 65% LiCl-KCl and 35% MgO), and Li ₂ O powder having a weight ratio of 1.5% with a high speed mixer Mixed.

Then, the mixed powder thus prepared was divided into four equal parts, and one mixed powder was not heat treated, and the remaining three mixed powders were heat treated at 350 ° C., 400 ° C., and 450 ° C. for 4 hours in an argon gas atmosphere.

Then, using a shatter box pulverized and sieved (100-325 mesh) to produce a total of four kinds of positive electrode powder.

2A to 2D are scanning electron microscope (Scanning Electron Microscope, SEM) photographs of anode powders not heat-treated, anode powders heat-treated at 350 ° C., anode powders heat-treated at 400 ° C., and anode powders heat-treated at 450 ° C., respectively.

As can be seen in Figures 2a to 2d, it can be seen that a certain material is coated on the surface of the FeS ₂ particles by heat treatment.

3 is a graph showing the chemical composition of the surface component of the heat treated positive electrode powder. Figure 3 is the result of measuring the surface component of the anode powder by the SEM (Electron Dispersive X-ray spectroscopy, Electron Dispersive X-ray spectroscopy) mounted on the SEM.

According to the graph of FIG. 3, in addition to iron (Fe) and sulfur (S), potassium (K) and chlorine (Cl), and trace oxygen (O) peaks were observed. From this result, it can be seen that the material coated on FeS ₂ particles is LiCl-KCl eutectic salt.

Figure 4 is a transmission electron microscope (Transmission Electron Microscope, TEM) photograph of the anode powder heat-treated at 450 ℃ of Figure 2d. As a result of more detailed analysis of the surface components of the positive electrode powder through Figure 4, it can be seen that the phase consisting of Fe-SK and the phase consisting of Fe-SKO on the surface of the FeS ₂ particles. This is also evidence that the LiS—KCl eutectic salt is coated on the FeS ₂ surface.

The four powders were uniaxially compressed into disk type anode pellets having a diameter of 56 mm by applying a pressure of about 1.7 ton / cm 2, and then the formed anode pellets were used with a push-pull gauge. Mechanical strength was measured.

5 is a graph showing the results of measuring the strength of the positive electrode pellets for thermo batteries.

As can be seen in Figure 5, it can be seen that the positive electrode pellets related to the present invention has a molding strength increased more than two times compared to the positive electrode pellets made of a simple mixed powder.

[Comparative Example]

In this comparative example it was investigated whether the eutectic salt is coated on the FeS ₂ particles or the role of Li ₂ O. This can be done by comparing Li ₂ O with and without Li ₂ O during the heat treatment of the mixed powder of FeS ₂ and the electrolyte binder.

FeS ₂ powder having a weight ratio of 75% and electrolyte binder powder having a weight ratio of 25% were mixed with a high speed mixer. Then, the mixed powders thus mixed were divided into four equal parts, and one mixed powder was not heat treated, and the remaining three mixed powders were heat treated at 350 ° C., 400 ° C., and 450 ° C. for 4 hours in an argon gas atmosphere. Then, using a shatter box, it was pulverized and sieved (100-325 mesh) to prepare a total of four kinds of positive electrode powder.

6A to 6D are scanning electron microscope (Scanning Electron Microscope, SEM) photographs of anode powders not heat-treated, anode powders heat-treated at 350 ° C., anode powders heat-treated at 400 ° C., and anode powders heat-treated at 450 ° C., respectively.

As can be seen from the photo, the surface of FeS ₂ particles is clean with or without heat treatment.

7 is a graph showing the chemical composition of the surface component of the cathode powder heat-treated as described above.

According to the graph of FIG. 7, only peaks of iron (Fe) and sulfur (S) could be observed as surface components of the positive electrode powder. From this result, it can be seen that the FeS ₂ particles were not coated with any substance.

These four powders were uniaxially compression molded into a disk having a diameter of 56 mm by applying a pressure of about 1.7 ton / cm 2. Thereafter, the molded anode pellets were measured for mechanical strength by using a push-pull gauge.

8 is a graph showing the results of measuring the strength of the anode pellets prepared above.

As can be seen in the graph of FIG. 8, the mixed powder of FeS ₂ and the electrolyte binder to which Li ₂ O was not added showed almost similar low forming strength regardless of heat treatment. This demonstrates that the eutectic salt is coated on the FeS ₂ particle surface only by heat treatment by addition of Li ₂ O as well as heat treatment as described in the present invention, and as a result, the strength of the compression molded anode pellets is remarkably improved. will be.

9A and 9B are graphs showing thermal characteristics of the cathode powders prepared in Examples and Comparative Examples. This is a result of measuring the thermal characteristics of the cathode powder by a differential scanning calorimeter (DSC).

As can be seen in Figure 9a, the positive electrode powder is not added Li ₂ O has the property of generating heat at a high temperature of 400 ℃ or more. This means that more heat is generated when operating as a positive electrode in the thermocell, and at temperatures above 550 ° C, FeS ₂ begins to decompose and cause thermal runaway, so the anode pellets without Li ₂ O are thermally unstable. .

On the other hand, as can be seen in Figure 9b the anode powder added Li ₂ O hardly generates heat at a high temperature of more than 400 ℃ and shows an endothermic reaction that absorbs heat near 500 ℃. This can be said to have the effect of improving the stability of the thermal battery due to the suppression of the heat generation of the positive electrode pellets through the addition of Li ₂ O and thus the decomposition of FeS ₂ does not occur.

In the above described with reference to the accompanying drawings, a thermoelectric cathode pellet and a method for manufacturing the same, and a thermocell having the same according to the present invention, the present invention is not limited by the embodiments and drawings disclosed herein, Various modifications can be made by those skilled in the art within the scope of the technical idea of the invention.

1 is a cross-sectional view schematically showing a thermo battery according to an embodiment of the present invention.

Figures 2a to 2d are photographs showing the mixed powder associated with one embodiment of the present invention.

3 is a graph showing the chemical composition of the surface component of the positive electrode powder according to an embodiment of the present invention.

4 is a transmission electron microscope photograph of the anode powder heat-treated at 450 ℃.

5 is a graph showing the results of measuring the strength of the positive electrode pellets for thermoelectric cells according to the embodiment of the present invention.

6a to 6d are photographs showing the mixed powder associated with the comparative example of the present invention.

7 is a graph showing the chemical composition of the surface component of the positive electrode powder according to a comparative example of the present invention.

8 is a graph showing the results of measuring the strength of the positive electrode pellets according to the comparative example of the present invention.

9A and 9B are graphs showing thermal characteristics of the cathode powders prepared in Examples and Comparative Examples.

Claims (15)

Mixing FeS ₂ powder, electrolyte binder powder, and Li ₂ O powder to form a mixed powder; Melting and cooling the mixed powder to form the mixed powder mass coated with the electrolyte on FeS ₂ ; And And pulverizing the mixed powder agglomerate to form a cathode powder and then compacting and compacting the cathode powder. The method of claim 1, The electrolyte binder powder is a lithium eutectic salt powder and MgO powder, characterized in that the manufacturing method of the positive electrode pellets for thermal cells. The method of claim 2, The lithium eutectic salt powder is LiCl-KCl eutectic salt powder manufacturing method of the anode pellets, characterized in that the powder. The method of claim 3, wherein preparing the electrolyte binder powder, Mixing and melting the LiCl powder and the KCl powder to form a eutectic salt mass; Grinding the eutectic salt mass to form a eutectic salt powder; Mixing the eutectic salt powder with MgO powder to melt and then cool to form a mixture of eutectic salt and MgO mixed mass; And And pulverizing the eutectic salt and MgO mixed agglomerates to form the electrolyte binder powder. The method of claim 1, The FeS ₂ and Li ₂ O powder has a weight ratio of 75%, the electrolyte binder powder has a weight ratio of 25%, The Li ₂ O powder has a weight ratio of 0.5% to 1.5% of the manufacturing method of the positive electrode pellets for thermal cells. The method of claim 1, The mixed powder is melted for 2 hours to 8 hours at a temperature of 300 to 500 ℃ in an inert gas atmosphere, the method of manufacturing a cathode pellets for thermo batteries. In the positive electrode pallet for thermal cells formed of FeS ₂ and an electrolyte, Mixing FeS ₂ powder, electrolyte binder powder, and Li ₂ O powder to form a mixed powder; Melting and cooling the mixed powder to form the mixed powder mass coated with the electrolyte on FeS ₂ ; And And pulverizing the mixed powder agglomerate to form a cathode powder, followed by molding and compacting the cathode powder. The method of claim 7, wherein The electrolyte binder powder is a positive electrode pellets for thermal cells, characterized in that formed by lithium eutectic salt powder and MgO powder. The method of claim 8, The lithium eutectic salt powder is a cathode pellet for thermoelectric battery, characterized in that the LiCl-KCl eutectic salt powder. The method of claim 7, wherein The FeS ₂ and Li ₂ O powder has a weight ratio of 75%, the electrolyte binder powder has a weight ratio of 25%, The Li ₂ O powder has a weight ratio of 0.5% to 1.5%. Anode pellets and cathode pellets; And An electrolyte separator disposed between the anode pellet and the cathode pellet, the electrolyte separator comprising a solid electrolyte that is melted by an increase in temperature to have ion conductivity; The anode pellets, Mixing FeS ₂ powder, electrolyte binder powder, and Li ₂ O powder to form a mixed powder; Melting and cooling the mixed powder to form the mixed powder mass coated with the electrolyte on FeS ₂ ; And And forming a positive electrode powder by pulverizing the mixed powder agglomerate and then molding and compressing the positive electrode powder. The method of claim 11, The electrolyte binder powder is a thermal cell, characterized in that formed by lithium eutectic salt powder and MgO powder. The method of claim 12, The lithium eutectic salt powder is a thermal cell, characterized in that LiCl-KCl eutectic salt powder. The method of claim 11, The FeS ₂ and Li ₂ O powder has a weight ratio of 75%, the electrolyte binder powder has a weight ratio of 25%, The Li ₂ O powder has a weight ratio of 0.5% to 1.5%. The method of claim 11, The positive and negative pellets and the electrolyte separator is a thermo-cell, characterized in that formed in the form of a disk.

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