SODIUM-ION-PERMEABLE PLATE-LIKE PARTITIONING WALL AND METHOD FOR MANUFACTURING SAME

Abstract

An object is to provide a plate-like partitioning wall allowing permeation of sodium ions therethrough and having high safety and durability.

A plate-like partitioning wall 2 of the present invention is formed from a solid electrolyte allowing permeation of sodium ions therethrough. The plate-like partitioning wall 2 has a plate-like shape having, in a center part in the thickness direction thereof, a negative electrode chamber 20 to which molten sodium is supplied. This negative electrode chamber 20 is formed as a foil-like space extending in two-dimensional directions or as a pore-like space extending in two-dimensional directions in a net-like shape.

The negative electrode chamber 20 of this plate-like partitioning wall 2 is formed as a thin foil-like space or as a fine pore-like space, and thus, the amount of molten sodium stored therein is very small. Therefore, even when this plate-like partitioning wall 2 is broken and reaction with molten sulfur occurs, the amount of heat generation is small, ignition is not caused, and thus, safety is high.

The burn-out pattern and the organic matter powder forming the negative electrode chamber may also be those that are thin or fine. Thus, a small crack or the like is less likely to occur in the compacted body, and durability of the plate-like partitioning wall is high and manufacture thereof is facilitated.

Claims

1. A plate-like partitioning wall formed from a solid electrolyte allowing permeation of sodium ions therethrough, the plate-like partitioning wall having a plate-like shape and having, in a center part in a thickness direction thereof, a negative electrode chamber to which molten sodium is supplied, the negative electrode chamber being formed as a foil-like space extending in two-dimensional directions or as a pore-like space extending in two-dimensional directions in a net-like shape.

2. The plate-like partitioning wall according to claim 1, wherein the foil-like space has a thickness of not greater than 0.5 mm.

3. The plate-like partitioning wall according to claim 1, wherein the foil-like space has a thickness of not greater than 0.1 mm.

4. The plate-like partitioning wall according to claim 1, wherein the foil-like space has a support part penetrating the foil-like space in a thickness direction of the space.

5. The plate-like partitioning wall according to claim 1, wherein the pore-like space has a pore system of not greater than 0.5 mm.

6. The plate-like partitioning wall according to claim 5, wherein the pore-like space has a pore system of not greater than 0.1 mm.

7. A method for manufacturing a plate-like partitioning wall, the method comprising: a step of forming a compacted body by pressing a burn-out pattern composed of a foil-like organic matter having a small thickness, the burn-out pattern being for forming a negative electrode chamber which extends in two-dimensional directions and to which molten sodium is supplied, and a granulated powder of a solid electrolyte allowing permeation of sodium ions therethrough, the granulated powder covering an outer peripheral face of the burn-out pattern and having an outer peripheral shape being a plate-like shape; and a firing step of heating the compacted body to decompose and remove the burn-out pattern, and degreasing and sintering the granulated powder, thereby producing the solid electrolyte having a plate-like shape and having the negative electrode chamber therein.

8. The method for manufacturing the plate-like partitioning wall according to claim 7, wherein the burn-out pattern has a penetration hole or a penetration wall penetrating a front face and a back face of the burn-out pattern.

9. The method for manufacturing the plate-like partitioning wall according to claim 7, wherein the foil-like organic matter is a fiber formed article.

10. The method for manufacturing the plate-like partitioning wall according to claim 9, wherein the fiber formed article is a cellulose product or a polyvinyl alcohol product.

11. A method for manufacturing a plate-like partitioning wall, the method comprising: a step of forming a compacted body by pressing a continuous pore formation member having a sheet-like shape and composed of a mixed powder of an organic matter powder and a ceramic powder for forming a net-like negative electrode chamber which extends at least in two-dimensional directions and to which molten sodium is supplied, and a granulated powder of a solid electrolyte allowing permeation of sodium ions therethrough, the granulated powder covering an outer peripheral face of the continuous pore formation member and having an outer peripheral shape being a plate-like shape; and a firing step of heating the compacted body to decompose and remove the organic matter powder of the continuous pore formation member, and degreasing and sintering the granulated powder, thereby producing the solid electrolyte having a plate-like shape and having the negative electrode chamber therein.

12. The method for manufacturing the plate-like partitioning wall according to claim 11, wherein the organic matter powder forming the mixed powder is a cellulose powder, a carbohydrate powder, or a polyvinyl alcohol powder.

13. A method for manufacturing a plate-like partitioning wall, the method comprising: a step of obtaining a front-side member and a back-side member each having a flat plate shape formed from a solid electrolyte allowing permeation of sodium ions therethrough; a step of providing a frame member precursor which is composed of a glass joining material having a loop shape, and in which both ends having predetermined widths are opposed to each other at a predetermined interval along an outer peripheral end side of one plane of at least one member of the front-side member and the back-side member; and a joining step of performing heating in a state where another member of the front-side member and the back-side member is in contact with the frame member precursor side of the one member, to melt the frame member precursor to join the front-side member and the back-side member, and causing the frame member precursor to be a frame member having a foil-like negative electrode chamber between the front-side member and the back-side member.

14. The method for manufacturing the plate-like partitioning wall according to claim 13, wherein the step of providing the frame member precursor includes forming, together with the frame member precursor having the loop shape, a support part precursor positioned in the loop and joining the front-side member and the back-side member to each other.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0045] FIG. 1 is a perspective view of the entirety of a ?-alumina plate-like partitioning wall according to Embodiment 1;

[0046] FIG. 2 is a perspective view of the entirety of a ?-alumina plate-like partitioning wall according to Embodiment 2;

[0047] FIG. 3 shows a photograph of a ?-alumina plate-like partitioning wall joined with an alumina-made nipple and an alumina tube, according to Embodiment 2; and

[0048] FIG. 4 is a cross sectional view at the center in the thickness direction of a ?-alumina plate-like partitioning wall according to Embodiment 3.

DESCRIPTION OF EMBODIMENTS

(1) ?-Alumina Plate-Like Partitioning Wall of Embodiment 1

[0049] FIG. 1 shows a perspective view of the entirety of a ?-alumina plate-like partitioning wall 1 of Embodiment 1. This plate-like partitioning wall 1 has a plate-like shape having a lateral width of about 20 mm, a height of about 63 mm, and a thickness of about 10 mm, and the entirety of the plate-like partitioning wall 1 is formed from ?-alumina. This plate-like partitioning wall 1 has, in a center part in the thickness direction thereof, a negative electrode chamber 10.

[0050] This negative electrode chamber 10 is exposed in the form of an opening 13 in an upper face 11 of the plate-like partitioning wall 1. The negative electrode chamber 10 is, with the shape thereof indicated by a dotted line in FIG. 1, formed as a space having a rectangular shape: extending from the upper face 11 to about 5 mm above a lower face 12 of the plate-like partitioning wall 1; and extending by about 9 mm in the lateral width direction, at the center in the lateral width direction. A cross section in the lateral direction of the negative electrode chamber 10 is considered to be similar to that of the opening 13. This opening 13 has a void-like shape extending in a zigzag manner in the width direction.

[0051] In the void-like space forming the negative electrode chamber 10, innumerable fine columnar connection parts integrally coupling both sides of this void-like space are considered to be present. The front-face-side portion and the back-face-side portion of the plate-like partitioning wall 1 on both sides of this void-like space are considered to be integrally connected by these innumerable columnar connection parts, to serve as an integrated object and contribute to improvement of mechanical strength.

[0052] Next, a method for manufacturing this plate-like partitioning wall 1 will be described. As the mold, a female mold having a cylindrical shape having a cylinder-like mold space whose cross-sectional space has a rectangular shape measuring, in a cross section, about 25 mm vertically and about 80 mm laterally; and two piston-like male molds each having a rectangular cross section and configured to enter the cylinder-like space of this female mold, were prepared.

[0053] A male mold was inserted a little into the female mold from below, and a shallow rectangular recess space defined by an upper portion of the inner peripheral face of the female mold and the upper face of the inserted male mold was formed. About 25 g of a ?-alumina granulated powder was put into this recess space, and the thickness of the granulated powder was uniformly smoothed. On this granulated powder, a band-like to-be-lost pattern composed of four medical gauzes superposed on each other and measuring about 74 mm vertically, about 12 mm laterally, and about 0.4 mm in thickness was disposed so as to be positioned at the center in the recess space and in a state where one end of the band-like to-be-lost pattern is in contact with a mold face of the female mold and the other end thereof is separated from the opposing mold face of the female mold.

[0054] Then, over this to-be-lost pattern, about 25 g of the ?-alumina granulated powder was placed and the thickness was uniformly smoothed. Then, the other male mold was pressed into the female mold from above, and the ?-alumina granulated powder having the to-be-lost pattern at the center was compacted between both male molds. The obtained compacted body was further subjected to CIP forming, to produce a denser compacted body. This compacted body was heated and fired up to 1600? C., to manufacture the plate-like partitioning wall 1 of the present embodiment.

[0055] A trial to confirm whether or not molten sodium entered a negative electrode chamber 2 of the obtained plate-like partitioning wall 1 was performed. In this trial, one end opening of a glass tube was pressed against the opening 13 of this plate-like partitioning wall 1, this state was fixed by a heat-resistant epoxy resin adhesive, whereby the glass tube and the plate-like partitioning wall were integrally coupled to each other, and the negative electrode chamber 2 of the plate-like partitioning wall 1 and the glass tube were joined to each other in an airtight manner. The other end of this glass tube was immersed in molten sodium heated to 130? C., the surface of the molten sodium was subjected to pressure reduction and pressure increase with argon gas, and this was repeated several times, whereby a trial of causing the molten sodium to enter the negative electrode chamber 10 was performed.

[0056] In this state, cooling to room temperature was performed, an electric lamp was lit against the back-side surface of the plate-like partitioning wall 1, and light transmitted to the front-side surface of the plate-like partitioning wall 1 was observed. The front-side surface of the plate-like partitioning wall 1 glowed white in a rectangular shape due to the transmitted light of the electric lamp, and in a portion, in a center portion of the rectangular shape, that corresponds to the negative electrode chamber 10, a dim shadow in which light was blocked by sodium held in the negative electrode chamber 10, was observed. Accordingly, a fact that molten sodium enters the negative electrode chamber 10 of the plate-like partitioning wall 1 was confirmed.

[0057] That is, a fact that this negative electrode chamber 10 is connected to the outside through the opening 13 and is held inside the plate-like partitioning wall 1 was confirmed. No defect such as a crack was observed in the entire outer peripheral face of this plate-like partitioning wall 1. Accordingly, it was made clear that this plate-like partitioning wall 1 functions as a ?-alumina partitioning wall for a sodium-sulfur battery.

[0058] The plate-like partitioning wall 1 of the present embodiment is obtained such that: four medical gauzes superposed on each other, used as a to-be-lost pattern, are disposed in a ?-alumina granulated powder, are subjected to pressure forming in a mold, and are further subjected to CIP forming, to obtain a green compact; and then, the green compact is fired in an ordinary manner. That is, no special operation is performed except that four medical gauzes superposed on each other are used as a to-be-lost pattern. Nonetheless, the negative electrode chamber 10 considered to be perfect without any crack is formed in a slit-shape, in a center part in the thickness direction of a plate-like p-alumina sintered body.

(2) ?-Alumina Plate-Like Partitioning Wall of Embodiment 2

[0059] FIG. 2 shows a perspective view of the entirety of a ?-alumina plate-like partitioning wall 2 of Embodiment 2. This plate-like partitioning wall 2 has a plate-like shape measuring about 10 cm vertically and laterally, and about 0.7 cm in thickness, and the entirety of the plate-like partitioning wall 2 is formed from ?-alumina. This plate-like partitioning wall 2 has, in a center part in the thickness direction thereof, a negative electrode chamber 20.

[0060] This negative electrode chamber 20 is, with the shape thereof indicated by a dotted line in FIG. 2, composed of a void-like space: extending in two-dimensional directions in a center part in the thickness direction of the plate-like partitioning wall 2; having a square shape measuring about 7.5 cm vertically and laterally; and having a thickness of about 0.01 mm. This negative electrode chamber 20 has an opening part 202 exposed in the form of an opening 201 at the upper end of the negative electrode chamber 20. This opening part 202 is also formed as a part of a burn-out pattern composed of four gauzes, simultaneously with the negative electrode chamber 20, and is composed of a void-like space having a thickness of about 0.01 mm.

[0061] This negative electrode chamber 20 is also composed of a void-like thin space, similar to the negative electrode chamber 10 of the plate-like partitioning wall 1 of Embodiment 1, and innumerable fine columnar connection parts integrally coupling both sides of this void-like space are considered to be present. The front-face-side portion and the back-face-side portion of the plate-like partitioning wall 1 on both sides of this void-like space are considered to be integrally connected by these innumerable columnar connection parts, to serve as an integrated object and contribute to improvement of mechanical strength.

[0062] For this plate-like partitioning wall 2, the same ?-alumina granulated powder and the same four medical gauzes superposed on each other to serve as a burn-out pattern as those of the plate-like partitioning wall 1 of Embodiment 1, were used. For a compression forming device, a commercially-available 500 ton press for manufacturing tiles and a mold for producing tiles of about 10 cm vertically and laterally were used. Half of the granulated powder was placed in the mold, four gauzes were superposed thereon, further, the remainder of the granulated powder was placed thereon, and pressure was applied, to produce a plate-like compacted body. Then, the plate-like compacted body was subjected to CIP forming, and then heated to about 1600? C. to be sintered. In this manner, the plate-like partitioning wall 2 shown in FIG. 2 was manufactured.

[0063] An alumina-made nipple having an axial pore was disposed so as to cover the opening 201 of this plate-like partitioning wall 2, further, an alumina tube was fitted to the axial pore of this nipple, and an integrally joined part was produced by using a glass joining material. FIG. 3 shows a photograph of this part. The negative electrode chamber 20 of the plate-like partitioning wall 2 forming this part is in communication with the void of the opening part 202, the axial pore of the nipple, and the axial pore of the alumina tube, so as to allow molten sodium to flow.

[0064] A sodium-sulfur single battery was produced by using this part. The plate-like partitioning wall 2 of this part was stored in a stainless steel sulfur container in a state where a glass fiber cloth as an electric insulator and a carbon fiber felt as a collector were stacked on each of the front face and the back face of the plate-like partitioning wall 2, such that an upper portion of the alumina tube protrudes from the upper end of the sulfur container. 347 g of sulfur was put in this sulfur container, and the sulfur container was sealed under reduced pressure in an airtight manner. An upper end portion of the alumina tube protruding from the sulfur container was inserted in an airtight manner from a lower end of a stainless steel sodium container, 56 g of sodium was put in the sodium container, and the sodium container was sealed under reduced pressure in an airtight manner. Accordingly, a sodium-sulfur single battery using the plate-like partitioning wall 2 of the present Embodiment 2 was produced.

[0065] This sodium-sulfur single battery was placed in a thermostat bath kept at about 300? C., an external circuit of about 0.7 ? was formed between the sulfur container and the sodium container, and a discharge test was performed, whereby discharging current of about 3.5 A to 6.7 A was obtained. Charging current obtained when charging was performed by applying charging voltage of 2.57 V between the sulfur container and the sodium container was about 1 A to 2 A. Further, a cycle test of discharging and charging was performed by using this sodium-sulfur single battery. A discharge time period of one time was set to 20 hours, a charge time period of one time was set to 100 hours, and cycle tests of discharging and charging were continuously performed for about one month. In this period, during discharging and charging, no problem such as abnormal decrease in current occurred. Thus, it was made clear that the plate-like partitioning wall 2 of the present Embodiment 2 is usable as a partitioning wall of a sodium-sulfur battery.

(3) ?-Alumina Plate-Like Partitioning Wall of Embodiment 3

[0066] FIG. 4 shows a cross section at the center in the thickness direction of a ?-alumina plate-like partitioning wall 3 of Embodiment 3. This plate-like partitioning wall 3 has a plate-like shape measuring about 40 mm vertically and laterally, and about 4.5 mm in thickness. The plate-like partitioning wall 3 is composed of: a front-side wall part 31 made of ?-alumina and measuring about 40 mm vertically and laterally and about 2.0 mm in thickness; a back-side wall part (not shown) having the same shape as that of the front-side wall part 31; and a frame part 35 having a width of about 7 mm and a thickness of about 0.5 mm in a square shape devoid of a part thereof, and a support part 36 having a diameter of about 7 mm and a thickness about 7 mm, the frame part 35 and the support part 36 being indicated by oblique lines and being formed by melting a glass joining material. The frame part 35 and the support part 36 are present between peripheral edge portions of both opposing faces of the front-side wall part 31 and the back-side wall part and in a center portion of said both opposing faces, respectively, and integrally join both.

[0067] This plate-like partitioning wall 3 has a negative electrode chamber 30 having a square shape whose one side is about 26 mm and whose thickness is about 0.5 mm, the negative electrode chamber 30 being defined by the opposing faces of the front-side wall part 31 and the back-side wall part and the inner peripheral face of the frame part 35. The support part 36 is positioned in a center portion of this negative electrode chamber 30. This plate-like partitioning wall 3 has an opening part 302 defined by both end opposing faces of the frame part 35 and the opposing faces of the front-side wall part 31 and the back-side wall part and connected to the negative electrode chamber 30. This opening part 302 is open as an opening 302 in a center part of the upper end face of the plate-like partitioning wall 3. Manufacture of the plate-like partitioning wall 3 of the present Embodiment 3 will be described. For the ?-alumina sintered bodies, on thin plates, to serve as the front-side wall part 31 and the back-side part of this plate-like partitioning wall 3, the same ?-alumina granulated powder as that used in manufacture of the plate-like partitioning wall 1 of Embodiment 1 was used and pressed by a forming mold, to form a compacted body. Without being subjected to CIP forming, the compacted body was heated to 1600? C. in a firing furnace, to produce a sintered body. A glass joining material was applied into a frame shape and a circular shape shown in FIG. 4, to one face of each of the obtained two ?-alumina sintered bodies. Then, the applied glass joining material was brought into contact with these two ?-alumina sintered bodies such that the ?-alumina sintered bodies are superposed on each other, and the resultant matter was disposed in a firing furnace. Then, the firing furnace was heated to melt the glass joining material, to integrally attach the two ?-alumina sintered bodies to each other, whereby the plate-like partitioning wall 3 of the present Embodiment 3 was manufactured.

[0068] Molten sodium was put, under pressure, into the negative electrode chamber 30 of this plate-like partitioning wall 3, in the same manner as that in Embodiment 1. The presence of the molten sodium in the negative electrode chamber 30 was confirmed in a manner similar to that in Embodiment 1.

[0069] Accordingly, the plate-like partitioning wall 3 of the present Embodiment 3 was also clarified to be usable as a partitioning wall of a sodium-sulfur battery.

Description of Reference Characters

[0070] 1, 2, 3 plate-like partitioning wall

[0071] 10, 20, 30 negative electrode chamber

[0072] 13, 201, 301 opening

[0073] 202, 302 opening part