JPS6362165A - Manufacture of sodium-sulfur battery - Google Patents

Abstract

PURPOSE:To intend to reduce mechanical stress in a solid electrolyte and decrease internal resistance thereof by binding an electron conductive material, of which the central part is cleared away, on an inside wall of positive electrode vessel, then impregnating the electron conductive material with a positive electrode active substance and by inserting a solid electrolyte vessel, which is filled with a negative electrode active substance, into the central vacant part. CONSTITUTION:A molten sodium 2, a negative electrode active substance, is contained in an integrated vessel, comprising a solid electrolyte vessel 5, which is selectively conductive for sodium ions, and a negative vessel 1 with an insulating material 3. On the other hand, an electron conductive material 8, which is impregnated with a molten sulfur 7, an positive electrode active substance, constitutes a positive electrode structure 9, and it is contained in a positive electrode vessel 6. After the electron conductive material 8 is made to adhere to the inside wall of the positive electrode vessel 6, the electron conductive material 8 is calcined to be fixed on the inside wall of the positive electrode vessel 6 and impregnated with molten sulfur 7. In this state, the solid electrolyte vessel is inserted into the positive electrode structure, and then a positive electrode supplementary vessel 4, which is preliminarily joined to an insulation ring, is joined to the positive electrode vessel 6 at an end face 10 and sealed. With the arrangement, heat distortion of the positive electrode structure doesn't exert asymmetrical pressure on the solid electrolyte vessel and damage of the solid electrolyte during high temperature is reduced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for manufacturing a sodium-sulfur battery, and in particular, a method suitable for reducing mechanical stress generated in a solid electrolyte, reducing internal resistance, and simplifying the manufacturing process. This invention relates to a method for manufacturing a sodium-sulfur battery.

[Conventional technology]

Conventional methods for making sodium-sulfur batteries are described in U.S. Pat.
No. 188463, Patent Publication No. 109134/1983.

As described in JP-A No. 55-108183, a cathode structure in which an electron conductive material is impregnated with sulfur, which is a cathode active material, and solidified is combined with a separately manufactured cathode container, a solid electrolyte container, an insulating material, and a negative electrode. The container was inserted into an annular gap between the positive electrode container and the solid electrolyte container in a member integrated with the container.

[Problem that the invention seeks to solve]

However, in sodium-sulfur batteries made using this manufacturing method, expansion of the positive electrode active material and electron conductive material applies uneven pressure to the solid electrolyte container due to eccentricity between the solid electrolyte container and the positive electrode container. , damage to the solid electrolyte container occurs.

Furthermore, according to the conventional manufacturing method, a positive electrode structure divided into several parts is inserted, making the manufacturing of the battery complicated and time-consuming. Furthermore, in the manufacturing method of inserting a prefabricated positive electrode structure, the contact resistance at the contact surface between the positive electrode container and the electron conductive material is considerably high, and the loss at this portion is large.

An object of the present invention is to provide a sodium-sulfur battery that reduces non-axial symmetry such as eccentricity between a solid electrolyte container, a positive electrode structure, and a positive electrode container, and also reduces contact resistance between an electronic conductive material and a positive electrode container. The purpose is to provide a manufacturing method.

[Means for solving problems]

The gist of the present invention to achieve the above object is that after bonding an electron conductive material to the inner wall of a positive electrode container except for the central part, the electron conductive material is impregnated with a positive electrode active material, and the interior of the central cavity is This is a method for manufacturing a sodium-sulfur battery in which a solid electrolyte container filled with a negative electrode active material is inserted into the battery.

[Effect]

According to the present invention, the solid electrolyte container, the positive electrode structure, and the positive electrode container can be joined without asymmetry such as eccentricity, so that it is possible to reduce the application of asymmetric pressure on the solid electrolyte container due to thermal deformation of the positive electrode structure. The solid electrolyte container during heating can be reduced. Further, since the contact between the positive electrode container and the electron conductive material can be made uniform and good, variations in internal resistance and a reduction in resistance value can be achieved. Furthermore, since the positive electrode portion is manufactured in one piece, the battery manufacturing process is simplified.

〔Example〕

The present invention will be explained in further detail by way of examples.

Example 1 FIG. 1 is a diagram for explaining the present invention in detail, and shows one step in assembling a sodium-sulfur battery.

Molten sodium 2, which is a negative electrode active material, is contained in a solid electrolyte container 5 that selectively conducts sodium ions, a negative electrode container 1, and an insulating material 3, which are joined and integrated. On the other hand, molten sulfur 7, which is a positive electrode active material, is impregnated into an electron conductive material 8 to form a positive electrode structure 9, which is housed in a positive electrode container 6. The method for manufacturing a positive electrode container having a positive electrode structure is as follows: First, the electron conductive material 8 is closely attached to the inner wall of the positive electrode container 6, and then fired to bind the electron conductive material 8 to the inner wall of the positive electrode container 6, and then subjected to appropriate treatment. Impregnate with molten sulfur 7 using a tool.

In this state, as shown in FIG. 1, after the solid electrolyte container is inserted into the positive electrode structure, the positive electrode auxiliary container 4 and the positive electrode container 6, which have been joined to the insulating ring in advance, are joined at the end surface 10 and sealed. and a sodium-sulfur battery is formed.

Now, the battery reaction of a sodium-sulfur battery is expressed by: During discharge, molten sodium that has become ions in front of the electrons enters the positive electrode through the solid electrolyte, reacts with molten sulfur, becomes sodium polysulfide, and becomes neutral by receiving electrons. During this process, if it is connected to an external circuit, electrons are driven from the negative electrode to the positive electrode with an electromotive force of about 2V, and it functions as a battery. Furthermore, since molten sulfur does not have electron conductivity, the positive electrode is filled with an electron conductive material so that electrons flowing from the outside through the positive electrode container can enter the inside of the positive electrode.

During charging, a potential difference greater than the electromotive force of one battery is applied between the two electrodes. At this time, the molten sodium that forms sodium polysulfide in the positive electrode becomes ions, returns to the negative electrode through the solid electrolyte, receives electrons, and becomes neutralized.

The operating temperature of the battery is selected to be 300 to 350"C based on the relationship with the melting point of sodium polysulfide. Therefore, temperature rises and falls during operation and stoppage are unavoidable. Also, sodium and sulfur, which are active materials for both electrodes, are not stable at room temperature. It is in a solid phase, and melting and solidification occur during the above temperature raising and lowering process.

At this time, the solid electrolyte may be damaged and the two electrodes may be short-circuited, causing the battery to lose its function. Damage to the solid electrolyte may cause a direct reaction between sodium and sulfur, which can melt the battery container due to the large amount of heat generated.

This damage during temperature rise and fall is basically due to pure mechanical stress, and the causes are as follows.

Carbon fiber mats are usually used as the electron conductive material filled in the positive electrode, but this is done in order to reduce the contact resistance with the positive electrode container, which is also an external terminal.

It is filled in a radially compressed state.

On the other hand, a material called β'-alumina is usually used for the solid electrolyte, and α-alumina is used for the insulating ring. The β'-alumina is bonded to the α-alumina ring at its open end using glass solder or the like. The α-alumina ring and the positive electrode container are bonded together by thermopressure bonding using an A11 washer or the like. When these are joined, defects such as eccentricity and perpendicularity may remain. Since the positive electrode portion is elongated in the axial direction, problems with eccentricity or perpendicularity at the joint are amplified at the tip. When the solid electrolyte container and the cathode container are integrated in advance and the cathode structure is inserted later as in the conventional assembly method, there is no way to correct the eccentricity and perpendicularity problems described above.

In this way, if eccentricity, etc. remains between the solid electrolyte container and the positive electrode container, when the aforementioned carbon fiber mat is released from its restraints when sulfur melts and tries to return to its original thickness and shape, the solid electrolyte This will result in an asymmetrical force being applied to the container.

The solid electrolyte container is fixed in a cantilever shape within the battery, and the load at the tip acts as a large moment at the base. This moment turns into stress and damages the solid electrolyte. “According to this embodiment, the cathode container and the cathode structure are manufactured integrally, and the concentricity with the solid electrolyte tube can be adjusted and joined at the end, so the above-mentioned damage can be reduced.

In addition, the contact between the electron conductive material in the positive electrode and the positive electrode container must be good as described above.According to the conventional method, the electron conductive material first contacts the positive electrode container when the sulfur melts during the initial temperature rise. Since contact is realized, defects and variations in contact properties occur.If the components are integrated in advance, as in this embodiment, such defects can be reduced, and the internal resistance of the battery can also be reduced.

Example 2 The production of the positive electrode portion will be explained using FIGS. 2 and 3. In FIG. 2, the electron conductive material 8 is a carbon fiber mat cut into rectangular shapes and packed in the positive electrode container 6. In FIG. 3, a plurality of ring-shaped carbon fiber mats are punched out and packed into a positive electrode container. When these are vacuum-fired, the zero-order core bar 11 that binds the positive electrode container and the carbon fibers is inserted concentrically with the positive electrode container and heated, and then the carbon fibers are impregnated with molten sulfur, and the temperature is lowered and solidified. Here, if the outer diameter of the core bar 11 is made larger than the outer diameter of the solid electrolyte container, assembly of the battery becomes easier.

As described above, the process can be simplified by manufacturing the positive electrode part as one piece.

Further, as shown in FIG. 4, if the upper surface of the positive electrode container 6 and the lower surface of the positive electrode auxiliary container 4 are made spherical, it becomes easy to correct the eccentricity described above.

〔Effect of the invention〕

According to the present invention, non-axisymmetric properties such as eccentricity between the solid electrolyte, the cathode structure, and the cathode container can be corrected during battery assembly, so non-axisymmetric pressure on the solid electrolyte can be reduced, and the resulting solid electrolyte container Can reduce damage.

Furthermore, since the contact resistance between the electron conductive material and the positive electrode container can be reduced, the internal resistance of the battery is reduced.

Furthermore, since the positive electrode portion is manufactured in one piece, the process can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the present invention, and FIG. 2 is a sectional view of an embodiment of the present invention. FIG. 3 is a partial sectional view of the positive electrode portion, and FIG. 4 is a sectional view of another embodiment of the joint portion between the positive electrode container and the positive electrode auxiliary container. 4... Positive electrode auxiliary container, 5... Solid electrolyte, 6...
Positive electrode container, 7... Positive electrode active material, 8... Electronic conductive material,
9...Positive electrode rate 1 ward Kei 7 figure high 4 figure high 3 figure

Claims (1)

[Claims] 1. After bonding an electron conductive material to the inner wall of the positive electrode container except for the center part, the electron conductive material is impregnated with a positive electrode active material, and the central cavity is filled with a negative electrode active material. 1. A method for manufacturing a sodium-sulfur battery, which comprises inserting a solid electrolyte container. 2. The method for manufacturing a sodium-sulfur battery according to claim 1, wherein the positive electrode container has a cylindrical shape with one end sealed. 3. The negative electrode active material is sealed by a solid electrolyte container, a negative electrode container, and an insulator bonded to the solid electrolyte and the negative electrode container, respectively. A method for making a sodium-sulfur battery. 4. Separate the cathode container into a cathode container and a cathode auxiliary container, join the cathode auxiliary container to an insulator, insert the fixed electrolyte into the central cavity of the electron conductive material, and then separate the cathode container and the cathode auxiliary container. 4. A method for manufacturing a sodium-sulfur battery according to claim 3, characterized in that the two are joined together. 5. The method for manufacturing a sodium-sulfur battery according to claim 1, wherein the electron conductive material is bonded to the inner wall of the positive electrode container by firing.