JPH06501339A - Sodium electrode energy conversion device and method for closing the case of the sodium electrode energy conversion device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Sodium electrode energy conversion device and sodium electrode energy conversion device case How to close the space The present invention relates to sodium electrode energy conversion devices, and more particularly to such devices. Concerning how to close the case of the device. Example of sodium electrode energy conversion device Sodium sulfur cells, sodium metal chloride cells and sodium-nat An example is Lium Cell.

In conventional lead-acid batteries, a liquid electrolyte, dilute sulfuric acid, separates two solid electrodes.

In contrast, a sodium/sulfur cell uses two liquid electrodes: liquid sulfur and liquid sulfur. sodium electrode, which uses a solid electrolyte, typically beta alumina, to separate the There is.

Such a sodium/sulfur cell is shown in FIG. Figure 1 shows the structure of , is a perspective view of the cell with a portion of the case removed.

As can be seen from the figure, the cell has a case, for example aluminum or aluminum for corrosion protection. The case is made of steel coated on the inside with an aluminum alloy. It has a right cylindrical shape. The case contains a beta-alumina solid electrolyte cup 2; The top 2 includes a sodium electrode 3. A sulfur electrode 4 is placed in the space between the case 1 and the cup 2. is included. For use, maintain the cell at a temperature between 300°C and 400°C. , so that the sodium and sulfur electrodes 3, 4 are liquid.

The open end of cup 4 is closed with an insulating disc of alpha alumina. Case 1 itself is made of anti-corrosion material. A ring made of steel with an aluminum or aluminum alloy coating on the inside for It is closed by a sealing disc 6 of the shape.

Case 1 acts as a terminal for sulfur electrode 4. The sodium electrode 3 passes through the disk 5. It includes an elongated metal current collector 8 extending in the axial direction of the case 1 . On disk 5, the gold The main current collector is connected to a central terminal disc 7 placed on the disc 5. need The connections are made by welding.

Since sulfur is essentially a non-conductor, there is no electrical connection between case 1 and cup 2. We must provide the means to do so. This is generally carbon soaked with sulfur. This is achieved by forming the sulfur electrode 4 as a fiber mat.

With such a cell, the sodium and sulfur electrodes 3.4 are in opposite positions. It will be understood that it is possible.

When using such a cell, the α-alumina disk 5 is inserted into the opening of the β-alumina cup 2. This is necessary to seal the exposed edges. This is achieved by glazing technology . A disk 6 and a terminal disk 7 are also required to ensure that the alpha alumina disk 5 is tightly sealed. Ru.

It is also necessary to securely fasten the disk 6 to the case 1, which is generally done by using an electron beam, This can be accomplished by laser or TIG fusion welding techniques.

However, when using the above technique, the necessary heat causes This may damage the anti-corrosion coating placed on the disc or A difficulty arises in that thermally sensitive zones may be formed in the contact area.

Either way, corrosion attack by the cell electrode material can cause This results in faster local deterioration than the local deterioration of the Providing a well-tight joint between the sulfur/sulfur cell case and the closure member is It has been discovered that it is difficult.

It is an object of the present invention to provide an improved sodium electrode energy conversion device and the manufacture of such cells. The purpose is to provide a method for manufacturing.

According to a first aspect of the invention, the sodium electrode energy conversion device comprises a closure member the case and the closure member are tightly held together at their contact surfaces. and the case and at least one of the closure members includes a metal substrate and at least one of the closure members. Also formed from a composite material with a layer of metal more ductile than the substrate on the contact surface of the substrate The case and the closure member are joined by a roll seam.

If made, it can be formed by a roll seam between the case and the closure member. I found out what I can do. Roll seams allow sodium/sulfur cells in operation, etc. Experiments were carried out using a sodium electrode energy conversion device from atmospheric temperature to 350°C (cell contact of the deformable metal with the substrate through a temperature range up to the nominal operating temperature of It was found that sufficient sealing was obtained except for the mismatch in thermal expansion between the two surfaces. It was.

According to a second aspect of the invention, the closure member provides for a sodium electrode energy conversion device. A method of closing a housing case, wherein the housing and closure member are sealed together at their contact surfaces. and at least one of the case and the closure member has a metal substrate and at least a connection of the substrate. one made of a composite material with a layer of metal more ductile than the substrate on the contact surface; the method includes the step of rolling the closure member and adjacent portions of the case together; This forms a roll seam.

As outlined above, the inventors have surprisingly used roll seams to In some cases, the case of sodium electrode energy conversion devices such as sodium/sulfur electrodes may It has been found that a sufficient seal can be provided between the base and the closing member. . According to the method of the present invention, there is no need for localized temperature rise in conventional methods, and sealing Anti-corrosion coating in the (seal) area or thermal damage in heat-sensitive zones disappears. Therefore, corrosion attack of the casing or closure parts by the cell electrode material The problem with the prior art is that the degradation occurs more quickly than normal local degradation in cells due to resolved.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIG.

Figure 1 shows the prior art sodium/sulfur cell previously described; Figure 2 shows the present invention. FIGS. 3 and 4 are flowcharts outlining a preferred embodiment of the method of 1A and 1B are first and second embodiments of closure members for use in the present invention.

FIG. 5 is a case of a sodium/sulfur cell for use with the present invention.

Figure 6 schematically shows the stages of a rolling operation to form a roll seam; 7 is a diagram showing a part of the sodium/sulfur cell according to the present invention, showing the roll seam shows: Figure 8 is a cross-sectional photograph of a roll seam in a sodium/sulfur cell according to the present invention. This is a drawing.

A schematic diagram of a preferred embodiment of the invention is shown in FIG. As shown, the first step has at least one surface made of aluminum or an aluminum alloy. Closing member made of composite material consisting of a steel substrate mechanically fixed to a solid metal layer and a step of forming a case. The ductile metal is more ductile than the substrate.

In one practical example, the composite material is made of 60 micron thick aluminum on the negative side. 25 micron thick aluminum coating on the other side Consists of a 250 micron thick low carbon steel substrate of deep drawing quality with other actual In this example, the composite material was coated with a 300 micron thick aluminum coat on the negative side. with a 60 micron thick aluminum coating on the other side. Consists of a 250 micron thick low carbon steel substrate. Aluminum coating thickness The thicker surface is the inner surface of the case and closure that requires corrosion protection.

FIG. 3 is a cross-sectional view of one embodiment of a closure member 10 for use with the present invention. . As previously explained, the inner surface 12 requiring corrosion protection is made of 60 micron thick aluminum. aluminum coating, and the outer surface 14 is a 25 micron thick aluminum coating. has a ting. Closure member 10 includes an outwardly extending annular flange 16, which The details are shown enlarged in FIG. 3A. As shown in Figure 3A, the annular ring A tip 18 is located at the end of flange 16. Typically about 54mm outer For a closure member with a diameter "D", the flange 16 has a radius dimension "B" of approximately 5 mm. have

FIG. 4 shows a second embodiment 20 of a closure member for use with the present invention. Figure 3 As shown in the example, the interior surface 22 of the closure requiring corrosion protection is 60 microns thick. The outer surface 24 has a 25 micron thick aluminum coating. Has a nilam coating. The closure member 20 includes an outwardly extending annular flange 26. , the details of which are shown enlarged in FIG. 4A. But at the end of the flange No lip is provided. Typically an outer diameter "D" closure of approximately 58 mm. flange 26 has a radius dimension "B" of approximately 7 mm.

FIG. 5 is a schematic diagram of a case 30 for a sodium/sulfur cell according to an embodiment of the invention. It is. As previously explained, the case 30 has a thickness of 60 microns on its inner surface 32. with a 20 micron thick aluminum coating on its outer surface 34. It is formed from a 0.25 mm thick steel substrate with a minium coating. composite The thickness of the material is indicated by "t". The case 30 has an annular flange 3 extending outward. It has 6. Typically, for a case with an outer diameter "d" of approximately 50 mm, the flap The radius 36 has a radius dimension "A" of approximately 4 mm. As shown in Figure 6, the case 30 may also have a king 38 at its open end. Closing member 10° 20 and case 30 are formed from composite materials by methods known to those skilled in the art. Figure 2 The case and closure member are then heated to an elevated temperature and maintained for a period of time, as shown in FIG. It is heat treated by maintaining that temperature for a while and then slowly cooling to ambient temperature. It is convenient to A typical thermal profile for that mode is as follows: Raise the temperature to 375°C at a gradient of 7°C per minute; Hold at 375℃ for 1 hour: Cooling to ambient temperature at 7°C or more per hour; This heat treatment prevents springback in the steel after the roll seam is formed. aluminum during stress relief or roll seam formation. It is believed that the aluminum is annealed to aid in its deformation.

The inventors heat-treat at least one of the closure member and the cell case before rolling. It was found that when applied, it had a dramatic effect on the airtightness of the formed roll seam. .

This heat treatment step is an auxiliary step in the method of making sodium/sulfur cells. or other fabrications such as diffusion bonding of the closure to an alpha alumina disc. It should be noted that this can be done by a manufacturing process.

As shown in Figure 2, after heat treatment of the cell and closure member, the sodium/sulfur cell is assembled. Stand up and place on roll forming equipment. The structure of the case and closing member at this stage is shown below. Shown in 6A.

Roll-forming devices are known to those skilled in the art and will therefore not be described in detail. After placement, Pull the cell assembly onto the center mandrel. The cell assembly is connected to the mandrel. Upon contact with the rollers, the clutch is actuated and the first set of rollers is engaged for the first rolling operation. controller is connected onto the cell assembly. During rolling operations, the cell assembly is stationary, and the first set of rollers is at flange 16. 26. Or connect to 36 When it's close, it's rotating. Structure of the cell assembly after the first rolling operation A schematic diagram is shown in Figure 6b.

Once the first rolling operation is completed, the first set of rollers is "oven" Returning to position, the second set of rollers is activated for a second rolling operation. . The structure of the cell assembly after the second rolling operation is shown in FIG. 6C.

FIG. 7 shows a cross section of a portion of a sodium/sulfur cell 40 according to one embodiment of the present invention. It is shown. The sodium electrode 42 and the sulfur electrode 44 contain β containing liquid sodium. They are separated by an alumina solid electrolyte cup 46. The electrolyte cup 46 is An insulating disc 48 of alpha alumina is coated on the cup 46 by a lath seal 50 is blocked by. A sulfur electrode 44 is contained within the cell case 52.

As previously outlined, closure member 54 is rolled to close case 52. A seam 56 seals the case 52 . To apply roll seam 56 , twist the case 52 inward at 58 until the entire diameter of the sodium/sulfur cell is The diameter should not be larger than the maximum diameter of the base 52. Possible contact with sulfur-44 That portion of the roll seam 56 is shown in more detail in Figure 7a. 60 micron thick Aluminum coating is the letter “a” and is a 25 micron thick aluminum coating. The marking is indicated by the letter “b”. From Figure 7, at the roll seam, the inside of the cell The potential for damage to the protective aluminum coatings 52a, 54a is that sulfur That portion of the coatings 52A, 54A that can be contacted by 44 forms the seam. It can be seen that there is almost no effect because it is not affected that much by the formation.

The amount of material caught in the roll seam 56 can affect the tightness of the joint. It has been discovered.

If B-t>2A-1-πt/2 (1), the joint will be airtight. Dew.

In the case of B-t=2A-t-πt/2 (2), the joint will vary. cormorant.

If B-t<2.4-t-πt/2 (3), the joint will leak. cormorant.

Those skilled in the art will understand that the airtightness required for a joint or seal in a structure is It will be appreciated that this depends on the position of the joint or seal.

In formulas (1), (2), and (3), the values of B, t, and A are shown in Figure 3 of the attached drawings. 4, and 5. That is: B = flap of closure member t is the thickness of the composite material, i.e. of the case or closure member. It's the thickness.

A is the radius of the flange on the case; if there is a defect in the material at C; If so, the roll seam will leak.

As previously explained, there is a roller between the closure member and the case made in accordance with the present invention. Sodium/sulfur cells with seams are designed for 50 heat cycles up to 350°C as follows: Attached to the cycle: Heats up to 350℃ at 3℃ per minute.

Maintained at 350°C for 3 hours: Cools down to 20℃ at 3℃ per minute.

The roll seams were airtight during manufacture and remained airtight after the thermal cycling described above.

Aluminum components on the case and closure members to maximize the tightness of the roll seams. A certain amount of relative movement and configuration should be introduced between mappings. Therefore, the closure material whose closure member flange folds onto itself during the rolling operation. It is formed as follows. FIG. 8 shows such a structure between the case 62 and the closing member 64. A roll seam 60 formed in the same manner as shown in FIG. For clarity, case The ends of the composite steel substrate from which the base and closure members are manufactured are 62S and 64, respectively. Indicated as S. Aluminum in the roll seam is designated by the number 66. Figure 8? Under pressure, a certain amount of phase builds up between the aluminum coating of the case and the closure. Displacement and strain occur during rolling operations resulting in the formation of cold welds. I understand. Therefore, the relative movement between the case and the aluminum coating of the closure member The flange of the closure member (front) to provide sufficient composite material to cause ) is formed with a sufficiently large radius, or as explained with reference to Figure 3. It can include a lip as disclosed. Therefore, the inside of the case and closing member Preferably, the front and outer surfaces are provided with a deformable aluminum coating. Ino would be obvious. However, roll seams with sufficient airtightness cannot be The base and the closing member each have a deformable metal layer on only one side. It is thought that it can be achieved.

Table 1 shows information on the airtightness of joints created by rolling. The results of a study on the effect of combining different materials on seams are presented. three Each of the different material combinations is controlled by the configuration of the case/closure. I investigated. The tightness of the rolled joint is affected by the rolling order of the components. one set from each group of material combinations to ensure that In turn, they involved each other. After rolling, individual assemblies were leak tested.

After leak testing, all assemblies were ramped to 400°C at a 15°C/min ramp. A thermal cycle with a 1 hour hold was applied. Leak again into assembly after thermal cycle The test was conducted.

(Torr 1/sec) (Torr 1/sec) 1 5X10-' 5X10- ’ 2 2.8X10-' 6X10-' 3 4X10-' lXl0-' 4 1.5X10-' 2X10-' 5 3X 10-3 3X 10” 6 NDL NDL 7 111DL NDL 8 1XIO-' lXl0-' 9 NDL NDL lo 5X10-' 8X10→ 11　7xlO°'4X10-' 12 6xlO~’2X10-’ 13 4xlO" 2xlO-' I4 5xlO~'lXl0-' 15 2xlO-’ 6xlO-” (NDL indicates no leak detected) case for each individual sample. The combinations of materials used for the and closure members are shown in Table 2 below.

Table 2 1 to 5 Composite material steel 25 micron aluminum on a 250 micron mild steel substrate minium coati 60mm with the textured side facing inside. Ron's aluminum coating Al/Fe with the treated side facing outside /At composite material embossed cell case.

Heat at 400℃ for 1 hour before rolling. Neilled cell case.

Aluminum coated on both sides Stamped steel top cap with no Up.

Table 2 (continued) 6 to 10 Composite material Composite material 25 micron on a 250 micron mild steel substrate Aluminum coating 60mm with the textured side facing inside. Ron's aluminum coating Al/Fe with the treated side facing outside /At composite material embossed cell case.

Heat at 400℃ for 1 hour before rolling. Neilled cell case.

Before rolling both components, Annealed at 400℃ for 1 hour.

11 to 15 Steel composite material 300 micron thick mild steel spuncell case (stainless steel 250 miku before pinning Ron) 2 on a 250 micron mild steel substrate. 5 micron aluminum coating 60mm with the textured side facing inside. Ron's aluminum coating Span AI with applied side facing outside /Fe/AI composite material top cap P.

Heat at 400℃ for 1 hour before rolling. Nealed top cap.

From Table 1, we can see that both the cell case and top case are made of composite materials. The Buri group is an assembly in which only one of its components is made of composite material. It can be seen that the roll seam had a higher airtightness compared to the original. Therefore, the For roll seams where roll sealing is important, both components are composite materials. Seals made of are preferred.

A sample in which only one of the cell case and top gap is made of composite material ( Samples 1 to 5 and 11 to 15) have both components made from composite materials. They had a more variable airtightness compared to the non-containing group. However, in reality It has been found that the hermeticity of the seal can be improved by thermal cycling. Configuration essentials Roll seams made of only one element of composite material, especially after thermal cycling, It can be sufficiently airtight for certain applications.

In roll seams where both components are made from composite materials, aluminum The coating provides some degree of corrosion protection for both components. roll Corrosion protection at seams can be improved by increasing the thickness of the aluminum coating. Can be done. In roll seams where only one of the components is made of composite material, the other The material of the components must be chosen according to the envisaged roll seam environment. do not have. For example, structures with steel and aluminum interfaces are susceptible to sodium attack. Easy to remove. Therefore, the roll seam in contact with the sodium is one made of composite material. and another component made of a material other than mild steel, such as Inconel. can be done. For cells where the roll seam is on the outer edge of one end, the cell Lithium-sodium cell, central sulfur cell or central metal chloride cell , the outer electrode is adjacent to the roll seam, and the outer electrode is called the sodium electrode. It's going to happen.

An important advantage of the present invention is that roll seam but can be manufactured using standard machinery and pressure to provide a practical example. That is to say. All of the metal coatings are more ductile than steel (no two mild steels) Attempts were made to create assemblies with sealed seams between components. but However, any seal created between two mild steel components is poor; Reducing the pressure within the assembly to a level that allows the assembly to be leak tested. I couldn't do it. This ensures that the airtightness of any seal created is as shown in Tables 1 and 2. This suggests that the airtightness of the assembly was at least two orders of magnitude worse. be done.

A roll seam that has at least some degree of airtightness reduces the with a layer of aluminum or other ductile material of at least 5 microns. It is thought that it can be created between two components if manufactured with a composite material that Ru. This thickness of coating provides enough aluminum to fill in all surface irregularities. should include the Aluminum of such thickness also This should mean that relative movement of the contact surfaces can occur during the formation of the roll seam. be. This relative movement at the aluminum surface causes aluminum oxide to move away from that surface. can be split, and a diffusion bond can be formed between them, essentially at atmospheric temperature. Creates a clean aluminum surface that can be cold welded. Both components are In roll seams formed from composite materials, the relative movement of the aluminum on the two components between the contact surfaces of the coating. Only one component is composite material In rolled seams made with , the relative movement of the aluminum between the contact surfaces is This will occur once a component made of material is rolled onto itself. . bulk aluminum to allow relative movement at the surface of the aluminum. The aluminum coating has a small thickness (both 10 microns thick). preferably at least 25 microns. aluminum Providing a thicker coating of aluminum for roll seams Both can be used to improve the corrosion protection of components.

It will be obvious to those skilled in the art that modifications to the described embodiments may be made within the scope of the invention. cormorant. In particular, the sodium/sulfur cell according to the invention has separate layers of aluminum and steel. It can be manufactured from a composite type of material formed by.

/λ negative! Wa 1.16--1l--I A#111=-11-wc PCT/Ga 9110 1652 International Search Report “:a”,=;mZ-241Sr:h;,-:2=nee2’em’lR11n? #rese62°knee), @, :::, j:;;73 F7■G1==””e l+m　Is　IM　　1-3+i7. ;7H-Nm-1-1-e--L? 11 1KuIgHmPSI@mellfi1ml++55mpH#m@let+h message+cw+ar+m+c++srsms+f+-kaiF@l+w+16 11M-11-r-1-11ag-eMlslc-r--1-11ag, front page Continuation of Ji (72) Inventor: Matsu Cracklan, Stuart UK, Cdbrew 9 ・6 Kewsey, Cheshire, Northwinch, Comberbatch, Foxley -No. 1 (72) Inventor Gee, Paul United Kingdom, Cedar 9.8 GA, Cheshire, Northwich , No. 3 Firthfields Close, Dubenham.

Claims (40)

[Claims] 1. including a case closed by a closure member, the case and the closure member having contact surfaces thereof; and at least one of the case and closure member includes a metal substrate; a metal layer that is more ductile than the substrate formed on at least one contact surface of the substrate; formed from a composite material consisting of The case and closure member are joined together by a roll seam. Lugie conversion device. 2. 2. The device of claim 1, wherein said composite material has ductile metal on individual surfaces. 3. Claim 1, wherein said ductile metal layer is mechanically secured to said metal substrate. or the device described in 2. 4. Claim: wherein the closure member is formed to include an outwardly extending annular flange. The apparatus described in any one of 1 to 3. 5. Claims 1 to 4, wherein the annular flange is provided with an annular lip. Any device described in any of the above. 6. Claim 1: The green color of the case determines an opening to be closed by a closing member. 5. The device according to any one of 5. 7. 7. The device of claim 6, wherein the case edge is at one end of the case. 8. 8. The edge of the case includes an outwardly extending annular flange. equipment. 9. B-t≧2A-t+πt/2 (4), where A=extends outside the case. is the radius of the extended annular flange; B = the radius of the extended annular flange; where t=thickness of the composite material, 9. A device according to claim 8 as dependent on claim 4 or 5. 10. In the case, the overall diameter of the cell is larger than the basic diameter of the case. A claim in which the roll seam is twisted inwardly under the position of the roll seam to prevent 10. The device according to any one of 1 to 9. 11. A claim in which the ductile metal is aluminum or an aluminum alloy. 11. The device according to any one of 1 to 10. 12. Claim 1: The layer of ductile metal has a thickness of at least 5 microns. 13. The device according to any one of Items 12 to 12. 13. 12. The layer of ductile metal has a thickness of at least 10 microns. The device described. 14. 13. The layer of ductile metal has a thickness of at least 25 microns. The device described. 15. Claims 1 to 14, wherein the metal substrate is made of steel. equipment. 16. Only one of the case and closure member is made of composite material; Claim 12, wherein the base and the other one of the closure members are made of a material other than soft steel. 16. The device according to any one of item 15. 17. 18. The material other than soft rope is resistant to sodium attack. equipment. 18. Materials other than soft steel mentioned above are selected from the group including Inconel and Feclaroy. 18. The device of claim 17, wherein the device is selected. 19. 19. The method of claims 16 to 18, wherein the sodium electrode is adjacent to the roll seam. The device described in any of the above. 20. Claim 1, wherein both the case and the closure member are made of composite material. 16. The device according to any one of item 15. 21. 21. The device according to claim 1, wherein the device is a sodium sulfur cell. equipment. 22. A method for closing the case of a sodium electrode energy conversion device using a closing member The law is The case and closure member are sealed together at their contact surfaces, and the case and closure member are sealed together at their contact surfaces; is provided on the metal substrate and at least one contact surface of the metal substrate. a composite material comprising a metal layer that is more ductile than the substrate; The method includes rolling the closure member and adjacent portions of the case together. method to form a roll seam. 23. 22. The composite material has a ductile metal layer on each surface. Method described. 24. 3. The ductile metal layer is mechanically secured to the metal substrate. 2 or 23. 25. further comprising forming an outwardly extending annular flange on the closure member. 25. A method according to any one of claims 22 to 24, comprising: the closure member and the case. The step of rolling together the outwardly extending annular flange of the closure member and the adjacent A method including the step of rolling together the contacting case parts. 26. further comprising forming an annular lip on the annular flange of the closure member. 26. The method according to claim 25. 27. Further, the adjacent part of the case is formed as an annular flange extending outward. 27. A method according to any of claims 22 to 26, comprising the steps of: 28. forming an adjacent portion of said casing as an outwardly extending annular flange; 27. The method according to claim 25 or 26, wherein the closure member and the case are adjacent to each other. The step of rolling the closure member and the outwardly extending annular flange of the case and rolling together. 29. B-t≧2A-t+πt/2 (4), where A=outside the case is the radius of the extended annular flange; B = the radius of the extended annular flange; is the size of the radius of the flange, and t = thickness of the composite material, 29. The method of claim 28. 30. Claims 22 to 2 further comprising the step of closing one end of the case with the closing member. 9. The method according to any one of 9. 31. Further, the overall diameter of the cell is larger than the basic diameter of the case. Twist the above case inward below the above roll seam location to avoid 31. A method according to any of claims 22 to 30, comprising the step of forming. 32. Furthermore, after the rolling process, heat treatment is applied to the closing member and the case. 32. A method according to any one of claims 22 to 31, comprising the step of: 33. Furthermore, the method includes a step of applying heat treatment to the composite material before the rolling step. 33. A method according to any of claims 22 to 32. 34. Heat is applied to at least one of the closure member and the case before the rolling process. 34. The method of claim 33, including the step of applying a treatment. 35. The method includes the step of forming only one of the closure member and the case from a composite material. 35. The method according to any one of claims 22 to 34. 36. A process in which the adjacent bale portions of both the closing member and the case are formed from a composite material. 35. A method according to any of claims 22 to 34, comprising the steps of: 37. Before the rolling process, both the closure member and the case are heat treated. 38. The method according to any one of claims 22 to 37, comprising the step of: 38. A claim for closing the case of a sodium sulfur cell with a closing member. 38. The method according to any one of claims 22 to 37. 39. A sodium electrode energy conversion device substantially as described above. 40. In effect, the case of the sodium electrode energy conversion device described above the closing method.