JP2012221849A - Manufacturing method of electrode of molten salt battery, manufacturing method of molten salt battery, and electrode of molten salt battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of the electrode of a molten salt battery in which the electrode can be impregnated easily with a molten salt, and to provide a manufacturing method of a molten salt battery, and the electrode of a molten salt battery.SOLUTION: When the positive electrode (electrode) of a molten salt battery is manufactured, solid powder of the molten salt to be contained in the electrolyte of the molten salt battery is mixed with a powdery positive electrode material (electrode) containing a positive electrode active material, i.e. NaCrO. Furthermore, the molten salt battery is manufactured while omitting a step for impregnating the positive electrode with the molten salt. Since the molten salt is contained previously in the positive electrode, a molten salt battery in which the interior of the positive electrode is impregnated uniformly with the molten salt can be obtained easily and reliably by adjusting the temperature in the molten salt battery above the melting point of the molten salt.

Description

  The present invention relates to a method for manufacturing an electrode for a molten salt battery using a molten salt as an electrolyte, a method for manufacturing a molten salt battery, and an electrode for a molten salt battery.

  In recent years, utilization of natural energy such as sunlight or wind power has been promoted. When power is generated using natural energy, the amount of power generation is likely to fluctuate. Therefore, in order to supply the generated power, it is necessary to level the supplied power by charging and discharging using a storage battery. . For this reason, in order to promote utilization of natural energy, a storage battery with high energy density and high efficiency is indispensable. As such a storage battery, there is a sodium-sulfur battery disclosed in Patent Document 1. Another high energy density and high efficiency storage battery is a molten salt battery.

JP 2007-273297 A

The molten salt battery is a battery using a molten salt as an electrolyte, and operates in a state where the molten salt is melted. During operation of the molten salt battery, the temperature in the molten salt battery is maintained at or above the melting point of the molten salt. The electrode of the molten salt battery is mainly composed of an active material that exchanges electric charge with the molten salt, and is impregnated with the molten salt. Conventionally, this electrode is made by mixing an electrode material containing an active material such as NaCrO ₂ and a liquid dispersion medium such as an organic solvent, supporting the mixture on a metal current collector, drying the mixture, and then drying the mixture. It is manufactured by pressing. After the manufactured electrode, the other polarity electrode, and the separator disposed between the electrodes are disposed in the battery container, in the final stage, both the electrode and the separator are impregnated with the molten salt, and the molten salt battery is assembled. . Usually, since the molten salt is solid at room temperature, the molten salt in the solid state is first incorporated in the battery container in which the electrode and the separator are arranged.

  The molten salt that is the electrolyte of the molten salt battery needs to be uniformly impregnated to the inside of the electrode. When the impregnation of the molten salt into the electrode is insufficient, the reaction in the electrode necessary for the operation of the battery becomes insufficient, and the capacity of the molten salt battery becomes low. On the other hand, an electrolyte using a molten salt has an advantage of high ion conductivity. In a molten salt battery, the thickness of the electrode can be increased to increase the capacity density. That is, since the ion conductivity is high, ions related to charge / discharge are easily distributed to the active material inside the electrode, and even if the electrode is thicker than other batteries, it is not necessary to reduce the charge / discharge current. Therefore, the molten salt battery has a technical problem that it is necessary to impregnate a solid state electrolyte into the thicker electrode than other batteries.

  In the conventional molten salt battery, in order to sufficiently impregnate the electrode with the molten salt, the temperature of the entire battery container is raised and the molten salt is melted, and the impregnation is performed for several days in a vacuum. There is a problem that it takes time and effort, such as performing an aging process in which the salt battery is charged for a certain period of time.

  The present invention has been made in view of such circumstances, and its object is to provide a molten salt that can be easily impregnated in the electrode by mixing the molten salt at the time of manufacturing the electrode. It is providing the manufacturing method of the electrode of a salt battery, the manufacturing method of a molten salt battery, and the electrode of a molten salt battery.

  A method for producing an electrode for a molten salt battery according to the present invention is a method for producing an electrode for a molten salt battery having an electrolyte composed of one or more types of molten salts, and a part of the molten salt contained in the electrolyte. Alternatively, a mixture is prepared by adding the same type of molten salt and a liquid dispersion medium to the electrode material containing the active material, and the prepared mixture is applied to a current collector, and the liquid dispersion medium is removed from the mixture. It is characterized by.

  A method for producing a molten salt battery according to the present invention is characterized in that a molten salt battery is assembled using at least one of the electrodes produced by the method for producing an electrode of a molten salt battery according to claim 1.

  The method for manufacturing a molten salt battery according to the present invention is characterized in that the step of impregnating an electrode with molten salt as an electrolyte is not performed.

  An electrode of a molten salt battery according to the present invention is an electrode of a molten salt battery having an electrolyte composed of one or a plurality of types of molten salt, and the molten salt battery contains an electrolyte in a state before being incorporated in the molten salt battery. It is characterized by containing a solid substance of a molten salt of the same kind as part or all.

  In the present invention, when manufacturing an electrode of a molten salt battery using a molten salt as an electrolyte, the molten salt is uniformly contained in the electrode by manufacturing the electrode after mixing the electrolyte with the electrode material.

  Further, in the present invention, when manufacturing the molten salt battery, the step of impregnating the electrode with the molten salt is omitted. By adjusting the temperature in the molten salt battery to be equal to or higher than the melting point of the molten salt, the electrode is impregnated with the molten salt without requiring a step of impregnating the electrode with the molten salt.

  In the present invention, since the molten salt is mixed in the electrode at the time of manufacturing the electrode, a molten salt battery in which the molten salt serving as an electrolyte is uniformly impregnated inside the electrode is easier and more reliable than before. It is possible to obtain an excellent effect.

It is typical sectional drawing which shows the structural example of a molten salt battery. It is explanatory drawing explaining the manufacturing method of a positive electrode and a molten salt battery.

Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.
FIG. 1 is a schematic cross-sectional view showing a configuration example of a molten salt battery. FIG. 1 shows a schematic cross-sectional view of a molten salt battery cut longitudinally. The molten salt battery is configured such that a positive electrode 1, a separator 3, and a negative electrode 2 are arranged side by side in a rectangular parallelepiped box-shaped battery container 51 whose upper surface is open, and a lid 52 is attached to the battery container 51. The battery container 51 and the lid 52 are made of aluminum. The positive electrode 1 and the negative electrode 2 are formed in a rectangular flat plate shape, and the separator 3 is formed in a sheet shape. The separator 3 is interposed between the positive electrode 1 and the negative electrode 2. The positive electrode 1, the separator 3, and the negative electrode 2 are stacked and arranged vertically with respect to the bottom surface of the battery container 51.

  A spring 41 made of corrugated metal is disposed between the negative electrode 2 and the inner wall of the battery case 51. The spring 41 is made of an aluminum alloy and biases a flat plate-like presser plate 42 having inflexibility to press the negative electrode 2 toward the separator 3 and the positive electrode 1 side. The positive electrode 1 is pressed by the reaction of the spring 41 from the inner wall opposite to the spring 41 to the separator 3 and the negative electrode 2 side. The spring 41 is not limited to a metal spring or the like, and may be an elastic body such as rubber, for example. When the positive electrode 1 or the negative electrode 2 expands or contracts due to charge / discharge, the volume change of the positive electrode 1 or the negative electrode 2 is absorbed by the expansion and contraction of the spring 41.

The positive electrode 1 is formed by integrally forming a positive electrode material 12 containing NaCrO ₂ as a positive electrode active material with a rectangular plate-shaped positive electrode current collector 11 made of an aluminum porous body. The positive electrode 1 is an electrode of the present invention. A detailed manufacturing method of the positive electrode 1 will be described later. In the negative electrode 2, a negative electrode material 22 containing a negative electrode active material made of tin is formed on a rectangular negative electrode current collector 21 made of aluminum by plating. When the negative electrode material 22 is plated on the negative electrode current collector 21, tin plating is performed after zinc is plated on the base as a zincate treatment. The negative electrode active material is not limited to tin by plating. For example, tin may be replaced with metal such as sodium metal, silicon, indium, graphite or non-graphitizable carbon, or lithium titanate (Li ₄ Ti ₅ O ₁₂ ). . The negative electrode material 22 may be formed by, for example, including a binder in a negative electrode active material powder and applying the powder onto the negative electrode current collector 21 made of copper. The separator 3 is an insulating material such as silicate glass or resin, and is formed in a shape capable of holding an electrolyte therein and allowing sodium ions to pass therethrough. The separator 3 is a resin formed in, for example, a glass cloth or a porous shape.

  In the battery container 51, the positive electrode material 12 and the negative electrode material 22 face each other, and the separator 3 is interposed between the positive electrode 1 and the negative electrode 2. The positive electrode 1, the negative electrode 2, and the separator 3 are impregnated with an electrolyte made of a molten salt. In order to prevent a short circuit between the positive electrode 1 and the negative electrode 2, the inner surface of the battery container 51 has an insulating structure by a method such as coating with an insulating resin. A positive terminal 53 and a negative terminal 54 for connecting to the outside are provided on the outside of the lid 52. The positive electrode terminal 53 and the negative electrode terminal 54 are insulated from each other, and the portion of the lid 52 facing the inside of the battery container 51 is also insulated by an insulating film or the like. One end of the positive electrode current collector 11 is connected to the positive electrode terminal 53 with a lead wire, and one end portion of the negative electrode current collector 21 is connected to the negative electrode terminal 54 with a lead wire. The lead wire is insulated from the lid portion 52. The lid 52 is attached to the battery container 51 by welding.

The electrolyte is a molten salt that becomes a conductive liquid in a molten state. At a temperature equal to or higher than the melting point of the molten salt, the molten salt melts into an electrolytic solution, and the molten salt battery operates as a secondary battery. In order to lower the melting point, it is desirable that the electrolyte is a mixture of a plurality of types of molten salts. For example, the electrolyte is a mixed salt of NaFSA with sodium ion as a cation and FSA (bisfluorosulfonylamide; (FSO ₂ ) ₂ N ⁻ ) as an anion, and KFSA with potassium ion as a cation and FSA as an anion. Note that the molten salt that is an electrolyte is TFSA (bistrifluoromethylsulfonylamide; (CF ₃ SO ₂ ) ₂ N ⁻ ) or FTA (fluorotrifluoromethylsulfonylamide; (FSO ₂ ) (CF ₃ SO ₂ ) N ⁻ ). Other anions may be included, and other cations such as organic ions may be included. In this form, sodium ions serve as charge carriers in the electrolyte. Moreover, the structure of the molten salt battery shown in FIG. 1 is a schematic structure, and the molten salt battery may include other components (not shown) such as a heater for heating the inside or a temperature sensor. Good. Moreover, although the form provided with one pair of the positive electrode 1 and the negative electrode 2 was shown in FIG. 1, the molten salt battery of this invention is a form with which the some positive electrode 1 and the negative electrode 2 were piled up alternately via the separator 3. There may be.

FIG. 2 is an explanatory view for explaining a method of manufacturing the positive electrode 1 and the molten salt battery. Cr ₂ O ₃ (III) and Na ₂ CO ₃ which are raw materials for the positive electrode active material are mixed, and the mixture is fired at a temperature of 950 ° C. for 5 hours in an argon atmosphere. Cr ₂ O ₃ (III) reacts with Na ₂ CO _3, and the generated CO ₂ is released to produce NaCrO ₂ . By pulverizing NaCrO ₂ produced by firing, a powder of NaCrO ₂ that is a positive electrode active material is obtained. Carbon powder such as acetylene black and binder powder such as PVDF are mixed with NaCrO ₂ powder. This mixture is the positive electrode material 12 and is an electrode material in the present invention. Further, a solid powder of molten salt is mixed into the positive electrode material 12. The molten salt mixed with the positive electrode material 12 is a molten salt used as an electrolyte of a molten salt battery. By making the temperature of the molten salt lower than the melting point, the molten salt becomes a solid. The powdered solid molten salt is mixed with the positive electrode material 12. The step of mixing the molten salt is performed at a temperature lower than the melting point of the molten salt. Further, a liquid dispersion medium such as an organic solvent is mixed with the positive electrode material 12. The positive electrode material 12 mixed with the liquid dispersion medium is fluid.

  Next, the fluid positive electrode material 12 is applied to the rectangular plate-shaped positive electrode current collector 11 made of an aluminum porous body. The fluid positive electrode material 12 is filled in the cavity of the porous body of the positive electrode current collector 11. Next, the positive electrode material 12 filled in the positive electrode current collector 11 is dried. By drying, the liquid dispersion medium is evaporated and removed, and the positive electrode material 12 is solidified. Next, the solidified positive electrode material 12 is pressed into a rectangular plate shape. The positive electrode 1 which is an electrode of this invention is manufactured by the above operation | work. A positive electrode 1 that is an electrode of the present invention has a configuration in which a positive electrode material 12 is formed integrally with a positive electrode current collector 11. The positive electrode current collector 11 is embedded in a positive electrode material 12 formed into a rectangular plate shape. The positive electrode material 12 is mixed with a solid powder of a molten salt to be an electrolyte of a molten salt battery.

  Next, the molten salt battery is manufactured by assembling the molten salt battery as shown in FIG. 1 using the manufactured positive electrode 1, the negative electrode 2, and other components necessary for the molten salt battery such as the separator 3. . After assembling the molten salt battery, the molten salt is melted by adjusting the internal temperature to be equal to or higher than the melting point of the molten salt mixed in the positive electrode material 12. The molten salt melted acts as an electrolyte for the molten salt battery, and the molten salt battery becomes operable. That is, in the molten salt battery manufacturing method according to the present embodiment, the step of impregnating the positive electrode 1 with the molten salt is omitted.

As described above, in the present embodiment, the positive electrode 1 is manufactured after mixing the solid powder of the molten salt with the powdered positive electrode material 12 containing NaCrO ₂ which is the positive electrode active material, and the molten salt is added to the positive electrode 1. A molten salt battery is manufactured by omitting the impregnation step. The molten salt mixed with the positive electrode material 12 is melted at a temperature equal to or higher than the melting point to become an electrolytic solution of a molten salt battery. Since the molten salt solid powder is mixed with the powdered cathode material 12 when the cathode 1 is manufactured, the cathode 1 contains the molten salt uniformly from the beginning. For this reason, by adjusting the temperature in the molten salt battery to a temperature equal to or higher than the melting point of the molten salt, the positive electrode 1 uniformly impregnated with the liquid molten salt is obtained. That is, impregnation and aging that takes several days, such as conventional impregnation work that takes time and labor, are unnecessary, and a molten salt battery in which the molten salt is uniformly impregnated into the positive electrode 1 can be easily obtained. And it becomes possible to obtain reliably. Further, by omitting the step of impregnating the positive electrode 1 with the molten salt, the method for manufacturing the positive electrode 1 and the method for manufacturing the molten salt battery are simplified. Moreover, since the positive electrode 1 is uniformly impregnated with the molten salt to the inside, the reaction between the positive electrode active material and the electrolyte is performed in the whole of the positive electrode 1 during charging and discharging, and the capacity of the molten salt battery is increased. improves.

  In the present invention, in addition to the molten salt contained in the positive electrode 1, it is also possible to perform a step of adding the molten salt into the molten salt battery. In the molten salt addition step, the solid body of the molten salt is further introduced into the battery container 51 in a state where the positive electrode 1, the separator 3, and the negative electrode 2 are stacked in the battery container 51 as shown in FIG. 1. . The molten salt to be added is a molten salt used as a part of the electrolyte of the molten salt battery. The molten salt to be added may be the same molten salt as the molten salt mixed in the positive electrode material 12 or may be a molten salt used as an electrolyte excluding the molten salt mixed in the positive electrode material 12. It may be a mixture of a plurality of types of molten salts including mixed molten salts. After assembling the molten salt battery, the molten salt contained in the positive electrode 1 and the added molten salt are melted and mixed by adjusting the internal temperature to be equal to or higher than the melting point of the molten salt. work. Even in the form of performing the molten salt step, since the molten salt is already mixed in the positive electrode material 12, the molten salt is uniformly and uniformly impregnated in the positive electrode 1 more easily and reliably than in the past. That is, it is possible to easily and surely obtain a molten salt battery in which the molten salt is uniformly impregnated in the positive electrode 1 without requiring time-consuming and troublesome impregnation work. Become.

The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims. For example, in the above embodiment, the positive electrode current collector 11 is an aluminum porous body. However, the present invention is not limited to this, and in the present invention, the positive electrode current collector 11 is an aluminum foil. The form which becomes may be sufficient. In the above embodiment, the positive electrode current collector 11 and the negative electrode current collector 21 are made of aluminum, but may be made of other conductors. In the above embodiment, the positive electrode active material is NaCrO _2. However, the present invention is not limited to this, and the molten salt battery produced in the present invention has a form in which other materials are used as the positive electrode active material. Also good. Further, the shape of the molten salt battery is not limited to a rectangular parallelepiped shape, and may be other shapes. For example, the shape of the molten salt battery may be cylindrical. Moreover, in the above embodiment, although the form which uses the electrode of this invention as the positive electrode 1 was shown, this invention is a form which manufactures the molten salt battery which used the manufactured electrode of this invention as the negative electrode 2. FIG. May be. Further, by replacing the positive electrode active material powder in the method for manufacturing positive electrode 1 with the negative electrode active material powder, negative electrode 2 is manufactured by the same manufacturing method as the positive electrode 1 manufacturing method in the present embodiment. Can be produced. Thus, also in the form which manufactures the negative electrode 2 and a molten salt battery, the effect similar to the case where the positive electrode 1 is manufactured by this invention can be acquired.

1 Positive electrode (electrode)
11 Positive current collector 12 Positive electrode material (electrode material)
2 Negative electrode 21 Negative electrode current collector 22 Negative electrode material 3 Separator

Claims (4)

A method for producing an electrode of a molten salt battery having an electrolyte composed of one or more types of molten salt,
A molten salt of the same type as part or all of the molten salt contained in the electrolyte and a liquid dispersion medium are added to an electrode material containing an active material to prepare a mixture, and the prepared mixture is applied to a current collector. A method for producing an electrode of a molten salt battery, wherein the liquid dispersion medium is removed from the mixture.   A method for producing a molten salt battery, comprising assembling a molten salt battery using at least one of the electrodes produced by the method for producing an electrode for a molten salt battery according to claim 1.   The method for manufacturing a molten salt battery according to claim 2, wherein the step of impregnating the electrode with molten salt as an electrolyte is not performed. An electrode of a molten salt battery having an electrolyte composed of one or more types of molten salt,
An electrode of a molten salt battery, comprising a solid material of the same type of molten salt as a part or all of the molten salt contained in the electrolyte before being incorporated in the molten salt battery.

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