Manufacturing method for joined body constituting part of battery using na for electrode

Abstract

The present invention is for stably manufacturing a joined body that constitutes a part of a battery using Na for a positive electrode and / or a negative electrode and that has excellent durability and corrosion resistance. Provided is a manufacturing method for a joined body, the method including solid-phase bonding of a ceramic component for insulating between the positive electrode and the negative electrode of the battery and a metal component on the positive-electrode side or the negative-electrode side via an Al-Si alloy-based brazing material. The solid-phase bonding includes: a step for heating, without pressurizing, a laminated part that includes the ceramic component, the Al-Si alloy-based brazing material, and a joined part of the metal component in this order, under a predetermined high vacuum atmosphere, such that the temperature of the Al-Si alloy-based brazing material rises to a prescribed holding temperature range; a step for applying a high pressure to the laminated part for a prescribed time in the lamination direction while keeping the temperature of the Al-Si alloy-based brazing material in the holding temperature range; and a step for cooling the laminated part such that the temperature of the Al-Si alloy-based brazing material falls within a prescribed time from the holding temperature range to the room temperature after the pressurization to the laminated part is stopped.

Description

Method for manufacturing a joint that forms part of a battery using sodium as an electrode

[0001] The present invention relates to a method for manufacturing an assembly that constitutes a part of a battery that uses sodium as an electrode. In particular, the present invention relates to a method for manufacturing an assembly that constitutes a part of a sodium-sulfur battery that can be used as a secondary battery for power storage, etc.

[0002] A sodium-sulfur battery (hereinafter also referred to as a "NAS battery") has a configuration in which, for example, a bottomed cylindrical part made of a solid electrolyte such as β-alumina is placed inside a metal container on the positive electrode side, which serves as a storage case, and sodium is housed inside the bottomed cylindrical part as a negative electrode active material, and sulfur is housed outside the bottomed cylindrical part as a positive electrode active material. During discharge, sodium-sulfur batteries generate electricity as ionized sodium permeates the solid electrolyte and reacts with sulfur to produce sodium polysulfide, while charging is achieved by the reverse reaction, which produces sodium and sulfur.

[0003] Such sodium-sulfur batteries have anode and cathode metal fittings for extracting generated electricity or for supplying electricity during charging. Because the two need to be installed in an electrically insulated state, a hollow cylindrical insulating ring made of an insulating material such as alpha alumina is interposed between the two. For example, the cathode metal fitting is thermocompression bonded to the upper end surface of the insulating ring, and the cathode metal fitting is thermocompression bonded to the lower end surface of the insulating ring (Patent Document 1).

[0004] Thermocompression bonding is known to be performed at a temperature below the solidus temperature under high vacuum using an aluminum-based brazing filler metal such as an Al-Si alloy-based brazing filler metal as the bonding material (Patent Documents 1, 2, and 3).

[0005] JP 2000-149882 JP 4-089367 JP 4-160071

[0006] In batteries that use sodium in the electrodes, the joints are susceptible to corrosion by sodium. For example, sodium-sulfur batteries are used in a heated state of 300 to 350°C, so corrosion resistance at high temperatures is required. Therefore, it is desirable for the brazing filler metal to have excellent sodium resistance. On the other hand, since the brazing filler metal is also required to be workable, it is desirable for the brazing filler metal to contain Si, which improves workability. However, when thermocompression bonding is performed at a high temperature where a liquid phase is formed, coarse Si particles tend to remain. Such coarse Si particles are prone to corrosion by sodium, which is a problem. For this reason, the conventional technique of thermocompression bonding at or below the solidus temperature is useful for increasing the joint strength and corrosion resistance of the bonded body.

[0007] However, conventional thermocompression bonding methods have room for improvement in terms of stably obtaining a bonded body having excellent durability and corrosion resistance. In view of the above circumstances, an object of the present invention is to provide, in one embodiment, a method for manufacturing a bonded body constituting a part of a battery using Na for the positive electrode and / or the negative electrode, which method enables stable production of a bonded body having excellent durability and corrosion resistance.

[0008] The present inventors have conducted extensive research to solve the above problems and have created the present invention, which is exemplified below.

[0009] [Aspect 1] A method for manufacturing a joined body constituting a part of a battery using Na as a positive electrode and / or a negative electrode, comprising solid-state joining a ceramic part for insulating between the positive electrode and the negative electrode of the battery and a metal part on the positive electrode side or the negative electrode side via an Al-Si alloy-based brazing material, wherein the solid-state joining is performed by -2heating, without applying pressure, a laminated portion comprising the ceramic part, the Al-Si alloy-based brazing filler metal, and the joining portion of the metal part in this order in a high vacuum atmosphere of 100 Pa or less (absolute pressure) so that the temperature of the Al-Si alloy-based brazing filler metal rises from room temperature to a holding temperature range of not less than solidus temperature -15°C and not more than solidus temperature, wherein the average temperature rise rate from 400°C to the holding temperature range of the Al-Si alloy-based brazing filler metal is 3.5°C / min or less; then, while maintaining the temperature of the Al-Si alloy-based brazing filler metal within the holding temperature range, applying a high pressure of 60 MPa or more (gauge pressure) to the laminated portion for 2 minutes or more; and then, after stopping the pressure on the laminated portion, cooling the laminated portion so that the temperature of the Al-Si alloy-based brazing filler metal falls from the holding temperature range to room temperature over 10 minutes or more. [Aspect 2] A method for producing a joined body according to Aspect 1, wherein, after the heating step and before the high-pressure step, a low-pressure step is performed on the laminated portion in the stacking direction at a pressure of 11 to 14 MPa (gauge pressure) for 5 to 20 seconds while maintaining the temperature of the Al—Si alloy-based brazing filler metal within the holding temperature range. [Aspect 3] A method for producing a joined body according to Aspect 2, wherein the pressure increase time from the end of the low-pressure step to the start of the high-pressure step is 20 seconds or less. [Aspect 4] A method for producing a joined body according to any of Aspects 1 to 3, wherein the Al—Si alloy-based brazing filler metal is an Al—Si—Mg alloy-based brazing filler metal with alloy number 4004 specified in JIS Z3263:2002. [Aspect 6] A method for producing a joined body according to any of Aspects 1 to 5, wherein the ceramic part contains aluminum oxide and the metal part contains pure aluminum or an aluminum alloy. [Aspect 7] The method for producing a joined body according to any one of Aspects 1 to 6, wherein the reduction in thickness in the lamination direction of the pressure-receiving portion of the metal component before and after the solid-state joining is 2.0 to 3.0 mm.Aspect 8: The method for manufacturing a joined body according to any one of Aspects 1 to 7, comprising monitoring the temperature of the Al-Si alloy-based brazing filler metal by measuring it using a thermocouple placed in the vicinity of the Al-Si alloy-based brazing filler metal, the thermocouple being connected to a memory-type thermometer including a measuring instrument that measures the temperature based on a voltage generated by the thermocouple and a data logger that can store the temperature measured by the measuring instrument in association with time, the memory-type thermometer being housed in the smallest lower container of a metal insulating box that is composed of a plurality of lower containers and a plurality of upper containers stacked in a nested manner, and the plurality of lower containers and the plurality of upper containers being stacked with an insulating space provided between adjacent containers. [Aspect 9] A method for manufacturing a joined body constituting a part of a battery using Na as a negative electrode, comprising the steps of: preparing a first ceramic component having a first surface and a second surface opposite to the first surface, for insulating between a positive electrode and a negative electrode of the battery; assembling a laminated section comprising, on the first surface of the first ceramic component, a first Al-Si alloy-based brazing filler metal, a joining portion of a metal component on the negative electrode side, a second Al-Si alloy-based brazing filler metal, and a second ceramic component for preventing adhesion, in this order; and assembling a laminated section comprising, on the second surface of the first ceramic component, a third Al-Si alloy-based brazing filler metal, a joining portion of a metal component on the positive electrode side, and a metal fitting for preventing adhesion, in this order; and (a) solid-state joining the first ceramic component and the joining portion of the metal component on the negative electrode side via the first Al-Si alloy-based brazing filler metal, while applying heat and pressure to the laminated section sandwiched between pressure jigs in the stacking direction. (b) solid-state joining the joining portion of the negative electrode side metal component and the second ceramic component for preventing sticking via the second Al-Si alloy-based brazing filler metal, and (c) solid-state joining the first ceramic component and the joining portion of the positive electrode side metal component via the third Al-Si alloy-based brazing filler metal, and the step of simultaneously performing (a), (b), and (c) is 10. -2heating the laminated portion without applying pressure in a high vacuum atmosphere of 400 Pa or less (absolute pressure) so that the temperatures of the first, second, and third Al-Si alloy-based brazing filler metals rise from room temperature to a holding temperature range of at least the solidus temperature minus 15°C and the solidus temperature, wherein the average heating rate from 400°C to the holding temperature range of the Al-Si alloy-based brazing filler metals is 3.5°C / min or less; then applying high pressure to the laminated portion in the stacking direction at a pressure of 60 MPa or more (gauge pressure) for 2 minutes or more while maintaining the temperatures of the first, second, and third Al-Si alloy-based brazing filler metals in the holding temperature range; and then, after stopping the application of pressure to the laminated portion, cooling the laminated portion so that the temperatures of the first, second, and third Al-Si alloy-based brazing filler metals fall from the holding temperature range to room temperature over 10 minutes or more. [Aspect 10] A method for producing a joined body according to Aspect 9, wherein, after the heating step and before the high-pressure step, a low-pressure step is performed on the laminated portion in the stacking direction at a pressure of 11 to 14 MPa (gauge pressure) for 5 to 20 seconds while maintaining the temperature of the Al—Si alloy-based brazing filler metal within the holding temperature range. [Aspect 11] A method for producing a joined body according to Aspect 10, wherein, after the low-pressure step, the pressure on the laminated portion is increased and the high-pressure step is started within 20 seconds. [Aspect 12] A method for producing a joined body according to any of Aspects 9 to 11, wherein the first, second, and third Al—Si alloy-based brazing filler metals are composed primarily of Al and contain Si and Mg as additive elements. [Aspect 13] A method for producing a joined body according to any of Aspects 9 to 11, wherein the first, second, and third Al—Si alloy-based brazing filler metals are Al—Si—Mg alloy-based brazing filler metals with alloy number 4004 specified in JIS Z3263:2002. [Aspect 14] The method for manufacturing a joined body according to any one of Aspects 9 to 13, wherein one or both of the first ceramic component and the second ceramic component contain aluminum oxide, and one or both of the negative electrode side metal component and the positive electrode side metal component contain pure aluminum or an aluminum alloy. [Aspect 15] The method for manufacturing a joined body according to any one of Aspects 9 to 14, wherein the anti-sticking fitting contains stainless steel.[Aspect 16] The method for producing a joined body according to any one of Aspects 9 to 15, wherein a decrease in thickness in the lamination direction at the joint portion of the negative electrode metal component and the joint portion of the positive electrode metal component before and after the steps (a), (b), and (c) are 2.0 to 3.0 mm. [Aspect 17] The method for producing a joined body according to any one of Aspects 9 to 16, comprising monitoring the temperatures of the first, second, and third Al-Si alloy-based brazing filler metals by measuring them using thermocouples installed in the vicinity of the first, second, and third Al-Si alloy-based brazing filler metals, the thermocouples being connected to a memory thermometer including a measuring instrument that measures temperature based on a voltage generated by the thermocouple and a data logger that can store the temperature measured by the measuring instrument in association with time, the memory thermometer being housed in a smallest lower container of a metal insulating box composed of a plurality of lower containers and a plurality of upper containers stacked in a nested manner, and the plurality of lower containers and the plurality of upper containers being stacked with an insulating space provided between adjacent containers. [Aspect 18] The method for manufacturing a joined body according to Aspect 9, including a step of performing a penetrant inspection on the second ceramic component before performing the step of assembling the laminated portion, and then heating the second ceramic component to 900° C. or higher. [Aspect 19] The method for manufacturing a joined body according to Aspect 18, wherein the heating step heats the second ceramic component to 900° C. or higher for 30 minutes or longer.

[0010] According to the manufacturing method of a joined body according to one embodiment of the present invention, it is possible to stably manufacture a joined body having excellent durability and corrosion resistance, and therefore, the manufacturing method can contribute to stabilizing the quality of, for example, sodium-sulfur batteries.

[0011] Fig. 1 is a schematic longitudinal sectional view of a NAS battery according to one embodiment of the present invention; Fig. 2 is a schematic partial longitudinal sectional view for explaining the stacking structure of a stacked portion according to one embodiment of the present invention; Fig. 3 is a schematic partial longitudinal sectional view for explaining the stacking structure of a joined body according to one embodiment of the present invention; Fig. 4 is a schematic longitudinal sectional view of an insulating box that houses a memory-type thermometer;

[0012] Next, an embodiment of the present invention will be described in detail with reference to the drawings, taking as an example a sodium-sulfur battery, which is a battery that uses Na in the negative electrode. However, it should be understood that the present invention is not limited to the following embodiment, and that appropriate design changes and improvements may be made based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention.

[0013] (1. Overall Structure of NAS Battery) FIG. 1 is a schematic longitudinal cross-sectional view illustrating an example of the overall structure of a sodium-sulfur battery (NAS battery) 10. In one embodiment, the sodium-sulfur battery 10 includes a positive electrode side body portion 21, a positive electrode side bottom cover 24 joined to the lower end of the positive electrode side body portion 21, a positive electrode ring fitting 22 joined to the upper end of the positive electrode side body portion 21, a positive electrode terminal 23 joined to the upper end of the positive electrode ring fitting 22, a negative electrode ring fitting 31 disposed more inwardly than the positive electrode ring fitting 22 while being electrically insulated from the positive electrode ring fitting 22 by an insulating ring 40, and a negative electrode side upper cover 32 joined to the upper end of the negative electrode ring fitting 31. A negative electrode terminal 39 is provided on the upper surface of the negative electrode side upper cover 32. The negative electrode side upper cover 32 and the negative electrode terminal 39 can be provided, for example, as an integrally molded product.

[0014] The NAS battery (single cell) is housed in a sleeve tube 80. A heat-insulating and / or insulating covering 82 is wrapped and fixed around the outer periphery of the sleeve tube 80. Examples of the covering 82 include mica sheets and fire-resistant carbon sheets. Mica sheets have heat-insulating and insulating properties and can be used for a variety of purposes. For example, flexible mica of MT66 as specified in JIS C2255:1992 can be suitably used. For example, the covering 82 can be formed by wrapping a heat-insulating mica sheet, a fire-resistant carbon sheet, and an insulating mica sheet around the sleeve tube 80 in this order from the inner periphery to the outer periphery. In addition, a heat-insulating and / or insulating plate material 84 is adhesively fixed to the bottom surface of the sleeve tube 80. Examples of the plate material 84 include an insulating mica plate.

[0015] Metals such as aluminum or aluminum alloys can be used as materials for the positive electrode side body portion 21, the positive electrode side bottom cover 24, the positive electrode ring fitting 22, the positive electrode terminal 23, the negative electrode ring fitting 31, and the negative electrode side top cover 32. For example, an aluminum alloy A3003 as defined in JIS H4000:2014 can be suitably used. Furthermore, welding, particularly electron beam welding, can be suitably employed for joining metal parts, such as the joining between the positive electrode side body portion 21 and the positive electrode side bottom cover 24, the joining between the positive electrode side body portion 21 and the positive electrode ring fitting 22, the joining between the positive electrode ring fitting 22 and the positive electrode terminal 23, and the joining between the negative electrode ring fitting 31 and the negative electrode side top cover 32.

[0016] The insulating ring 40 is preferably made of aluminum oxide such as α-alumina. The insulating ring 40 is joined to the outer periphery of the upper end of a bottomed tubular (typically cylindrical) solid electrolyte 50. The solid electrolyte 50 is preferably made of one or both of β-alumina and β"-alumina. The insulating ring 40 and the solid electrolyte 50 can be joined by glass.

[0017] A bottomed cylindrical anode container 36 (typically cylindrical) is provided inside the bottomed cylindrical solid electrolyte 50, containing sodium 3 as the anode active material. A small hole 36a is provided at the bottom of the anode container 36. Materials that can be used for the anode container 36 include high-chromium steel, stainless steel (e.g., SUS304), aluminum alloys, and SPCC (cold-rolled steel plate). A bottomed cylindrical safety tube 70 is provided outside the anode container 36 and inside the solid electrolyte 50. Aluminum or an aluminum alloy can be used as the material for the safety tube 70. For example, an aluminum alloy A3003 as specified in JIS H4000:2014 can be suitably used. The gap between the solid electrolyte 50 and the safety tube 70 (the gap in the radial direction (horizontal direction in the figure)) is preferably 30 to 100 μm, more preferably 50 to 80 μm. A thickness of 30 μm or more is preferable because sodium can be moved without increasing pressure loss, and a thickness of 100 μm or less is preferable from the standpoint of safety.

[0018] Additionally, sulfur 2 as a positive electrode active material is contained within a space (positive electrode space) 28 surrounded by the positive electrode side body 21 and the positive electrode side bottom lid 24 outside the bottomed tubular solid electrolyte 50. Because sulfur 2 is an insulator, a positive electrode current collector 27 is generally provided to ensure electrical continuity between the positive electrode and the negative electrode and reduce the internal resistance of the battery. The positive electrode current collector 27 may be a member made of a felt material made of conductive carbon fiber and / or graphite fiber. By impregnating the positive electrode active material sulfur 2 and arranging the positive electrode current collector 27 so as to abut both the inner circumferential surface of the positive electrode side body 21 and the outer circumferential surface of the bottomed tubular solid electrolyte 50, electrical continuity between the positive electrode and the negative electrode is ensured and the internal resistance of the battery is also reduced.

[0019] An inert gas such as argon, helium, or neon is sealed in the space 37 inside the negative electrode container 36 as a pressure (negative electrode side pressure) generating source, and nitrogen gas is sealed in the positive electrode space 28 as a pressure (positive electrode side pressure) generating source.

[0020] During discharge, sodium 3 molten in the anode container 36 is supplied into the safety tube 70 through the small hole 36a due to the pressure of the inert gas, filling the safety tube 70. Furthermore, overflowing sodium 3 is supplied to the space (anode space) 38 between the solid electrolyte 50 and the safety tube 70. Some of the sodium 3 supplied between the solid electrolyte 50 and the safety tube 70 has released electrons to the external circuit through the anode terminal 39 in the anode space 38, becoming sodium ions. These sodium ions then pass through the solid electrolyte 50 and enter the cathode space 28, where they react with sulfur 2 and electrons supplied from the external circuit through the cathode terminal 23 to produce sodium polysulfide. This allows a voltage of, for example, about 1.8 to 2.3 V to be generated.

[0021] During charging, when a voltage is applied from an external circuit via the positive electrode terminal 23 and the negative electrode terminal 39, the sodium polysulfide releases electrons to the external circuit via the positive electrode terminal 23 to generate sulfur and sodium ions, and the generated sodium ions permeate (pass) through the solid electrolyte 50 and move to the negative electrode space 38. The sodium ions that have moved to the negative electrode space 38 move inward, over the upper end of the safety tube 70, and then move through the small hole 36a into the negative electrode container 36. They then react with electrons supplied from the external circuit via the negative electrode terminal 39 to become electrically neutral (become sodium 3), thereby converting electrical energy into chemical energy.

[0022] The following method can be used to seal the inert gas in the anode can 36. First, the anode can 36 is inverted so that the small hole 36a is at the top, and heated and melted sodium 3 is poured into the anode can 36 through the small hole 36a. The sodium 3 is cooled and solidified. Next, the anode can 36 is turned upside down and placed in the solid electrolyte 50. Next, the opening of the solid electrolyte 50 is sealed under an inert gas atmosphere, and the sodium 3 is melted by heating. At this time, the molten sodium moves to the bottom of the anode can 36, and the inert gas moves to the top instead. In this way, the inert gas is sealed in the upper part of the anode can 36. Using an inert gas as the gas to be sealed in the anode can 36 prevents the material constituting the anode can 36 from reacting with the sealed gas and consuming it, thereby preventing a decrease in the pressure of the inert gas.

[0023] A preferred method for sealing nitrogen gas in the positive electrode space 28 is to place solid sodium azide, such as in pellet form, in the positive electrode space 28 during battery assembly, and then generate nitrogen gas by thermal decomposition after the positive electrode space 28 is sealed. This is because electron beam welding, which has high joining reliability, can be performed in a vacuum during battery assembly.

[0024] The positive electrode side body portion 21 may have a constriction 21 a. The constriction 21 a provides the positive electrode side body portion 21 with a spring effect, which can mitigate expansion and contraction of the positive electrode side body portion 21 due to thermal changes. After the positive electrode solidifies, the portion where the positive electrode current collector 27 is present is fixed with sulfur or sodium polysulfide and becomes immobile, so the constriction 21 a is preferably located above the position where the positive electrode current collector 27 is housed.

[0025] (2. Manufacturing Method of Joint) In the manufacturing process of a battery using Na as the positive and / or negative electrode, such as an NAS battery, a step of manufacturing a joint by thermocompression bonding a ceramic part for insulating the positive and negative electrodes of the battery to a metal part on the positive or negative electrode side via a brazing material may be performed. As a method of thermocompression bonding, a laminated part including a ceramic part, an Al-Si alloy-based brazing material, and a metal part in this order is prepared, and the laminated part is solid-state bonded, which is preferable in terms of improving the joint strength, durability, and corrosion resistance of the jointed body. Furthermore, it is preferable to use aluminum oxide for the ceramic part and pure aluminum or an aluminum alloy for the metal part, taking into account ease of assembly with the positive electrode side body part 21 and compatibility with the brazing material.

[0026] 2 is a schematic partial longitudinal cross-sectional view illustrating the structure of a laminated portion 100 of a NAS battery according to one embodiment of the present invention. The laminated portion 100 has a first surface 111 and a second surface 112 located opposite the first surface 111. It can be fabricated by a process that includes preparing a first ceramic component 110 for insulating between the positive and negative electrodes of the battery, stacking a first Al-Si alloy-based brazing filler metal 121, a joint portion 132 of a negative electrode-side metal component 130, a second Al-Si alloy-based brazing filler metal 122, and a second ceramic component 150 for preventing adhesion, in this order, on the first surface 111 of the first ceramic component 110, and stacking a third Al-Si alloy-based brazing filler metal 123, a joint portion 162 of a positive electrode-side metal component 160, and a metal fitting 170 for preventing adhesion, in this order, on the second surface 112 of the first ceramic component 110. For ease of understanding, the negative electrode side upper cover 32 and the positive electrode side body portion 21 are shown by dotted lines in FIG. 2, but they do not exist at the stage of solid-state joining.

[0027] In a typical embodiment, the laminated unit 100 is fabricated by the following steps: preparing an insulating ring (first ceramic component for insulating between the positive and negative electrodes of a battery) 110 having an upper surface (first surface) 111 and a lower surface (second surface) 112 located opposite the upper surface (first surface) 111; and attaching a ring-shaped first Al-Si alloy-based brazing filler metal 121 and an annular protrusion (joining portion) 122 formed on the outer peripheral surface of a negative electrode ring metal fitting (metal component on the negative electrode side) 130 to the upper surface (first surface) 111 of the insulating ring (first ceramic component) 110. 32, a ring-shaped second Al-Si alloy-based brazing filler metal 122, and a backup ring (second ceramic part for preventing adhesion) 150 are laminated in this order, and a ring-shaped third Al-Si alloy-based brazing filler metal 123, an annular protrusion (joint portion) 162 formed on the inner peripheral surface of the lower end of a positive electrode ring metal part (metal part on the positive electrode side) 160, and a ring cap (metal part for preventing adhesion) 170 are assembled in this order on the lower surface (second surface) 112 of an insulating ring (first ceramic part).

[0028] The backup ring 150 (second ceramic part) is, for example, an annular ceramic part that prevents adhesion between the pressing jig and the annular protrusion 132 during solid-state bonding and also prevents expansion / contraction, warping, etc. of the negative electrode ring metal fitting 130 during high-temperature operation after the battery is completed. It is preferable to perform a penetrant inspection on the backup ring 150 (second ceramic part) before fabricating the laminated unit 100. By using a backup ring 150 (second ceramic part for preventing sticking) that has passed the penetrant inspection, the quality stability of the backup ring 150 (second ceramic part) can be ensured.

[0029] Generally, penetrant testing involves the following steps in order: pretreatment (removal of grease and dirt using a cleaning fluid, followed by drying), penetrant treatment (penetration of the test piece with the penetrant), removal / cleaning treatment (removal of the penetrant using a rag and cleaning fluid), development treatment (application of a developer to the test piece), and observation (observation of the test piece surface). Penetrants containing hydrocarbon oils, solvents, surfactants, and organic substances such as red dyes are used. Remaining organic substances on the backup ring 150 (second ceramic component) may adversely affect solid-state bonding. Furthermore, carbon cannot be removed in the vacuum heat treatment furnace used to perform solid-state bonding. Therefore, it is preferable to thoroughly remove any remaining penetrant components, especially organic substances, from the backup ring 150 (second ceramic component) after penetrant testing.

[0030] One method for removing components of the penetrant remaining in the backup ring 150 (second ceramic part) is to heat treat the backup ring 150 (second ceramic part). During the heat treatment, the backup ring 150 (second ceramic part) is preferably heated to 900°C or higher, more preferably 950°C or higher, for example, 900 to 1000°C. The time for heating the backup ring 150 (second ceramic part) to 900°C or higher is preferably 30 minutes or longer, more preferably 45 minutes or longer, for example, 30 to 60 minutes. There are no particular limitations on the atmospheric gas used during the heat treatment, and the heat treatment can be carried out in air, for example.

[0031] When performing a penetrant testing on the insulating ring (first ceramic component) 110, it is preferable to perform the same heat treatment as on the backup ring 150 (second ceramic component). However, if a penetrant testing is performed during the manufacturing process and then a manufacturing process that satisfies the above-mentioned heat treatment conditions is performed, there is no need to perform a separate heat treatment to sufficiently remove organic matter.

[0032] The ring cap 170 is, for example, a metal part having an annular bottom surface and an outer peripheral wall erected on the outer periphery of the bottom surface, and is intended to prevent adhesion between the pressure jig and the positive electrode ring metal fitting 160 during solid-state welding. Stainless steel is a material that has a high melting point relative to the welding temperature and is also easily available, so the ring cap 170 is preferably made of stainless steel.

[0033] From the viewpoint of suppressing stress generation due to a difference in thermal expansion, it is preferable that both the insulating ring (first ceramic component) 110 and the backup ring (second ceramic component for preventing sticking) contain aluminum oxide, more preferably contain 99.5 mass % or more of aluminum oxide (α-alumina), and even more preferably be made of aluminum oxide (α-alumina). The higher the purity of the aluminum oxide (α-alumina), the better, and although no particular upper limit is set, aluminum oxide (α-alumina) with a purity of 99.9 mass % or less is typically used in consideration of the balance with manufacturing costs.

[0034] Furthermore, pure aluminum or an aluminum alloy can be used for the negative electrode ring fitting (negative electrode side metal part) 130 and the positive electrode ring fitting (positive electrode side metal part) 160. Examples of pure aluminum include 1000 series aluminum (purity of 99.00 mass% or more) such as alloy numbers 1085, 1080, and 1070 specified in JIS H4000:2014. Examples of aluminum alloys include aluminum alloys such as alloy numbers 3003, 3004, 5024, and 6101 specified in JIS H4000:2014. From the viewpoint of ensuring high-temperature strength, aluminum alloys are preferable to pure aluminum.

[0035] It is preferable that the insulating ring 110 is previously joined to the open upper end 181 of the bottomed cylindrical solid electrolyte 180. As a method for joining the insulating ring 110 to the open upper end 181 of the solid electrolyte 180, there is a method in which an expanded diameter portion 114 is formed on the lower inner periphery of the insulating ring 110, and the open upper end 181 of the bottomed cylindrical solid electrolyte 180 is inserted into the expanded diameter portion 114 of the insulating ring 110 with glass sandwiched therebetween, thereby performing glass joining.

[0036] When assembling the stacked unit 100, the negative electrode ring fitting 130 can be fitted onto the upper inner circumferential side of the insulating ring 110, and the insulating ring 110 can be fitted onto the lower inner circumferential side of the positive electrode ring fitting 160. In addition, the backup ring 150 can be fitted between the outer circumferential surface of the negative electrode ring fitting 130 and the inner circumferential surface of the positive electrode ring fitting 160. The ring cap 170 can be fitted so as to cover the lower surface 163 of the annular protrusion 162 of the positive electrode ring fitting 160 and the lower end outer circumferential surface 164 of the positive electrode ring fitting 160.

[0037] For joining the laminated portion 100, a brazing filler metal formed by rolling or the like into a predetermined shape according to the joining location, typically a brazing filler metal formed by rolling or the like into a ring shape, is preferably used. For this reason, an Al-Si alloy-based brazing filler metal can be preferably used due to its ease of processing, and among Al-Si alloy-based brazing filler metals, an Al-Si-Mg alloy-based brazing filler metal is particularly preferred because it is likely to achieve high joining strength. In one embodiment, the Al-Si alloy-based brazing filler metal contains Al as a main component, typically at 70 mass% or more, and also contains Si and Mg as additional elements. In a preferred embodiment, the Al-Si alloy-based brazing filler metal contains 86 to 90 mass% Al and 9.0 to 10.5 mass% Si. In a more preferred embodiment, the Al—Si alloy-based brazing filler metal is an Al—Si—Mg alloy-based brazing filler metal of Alloy No. 4004 specified in JIS Z3263:2002 (containing 9.0 to 10.5 mass % of Si and 1.0 to 2.0 mass % of Mg).

[0038] Although the present invention is not intended to be limited by theory, the mechanism by which the addition of Mg to the brazing filler metal improves joint strength is believed to be as follows. Mg atoms in the brazing filler metal become unstable at high temperatures and diffuse and migrate. Because the Al2O3 in the material constituting the insulating ring is stable, Mg atoms migrate to the joint with Al2O3 (joint interface) and react with Al2O3 to form MgO, stabilizing the Mg atoms. However, Al2O3 loses its oxygen to Mg, causing it to lose its balance and become unstable. Therefore, to maintain a stable state, it bonds with MgO to form an Al2O3-MgO composite oxide. This composite oxide further reacts at the joint interface under high vacuum, high temperature, and high pressure to form MgAl2O4 (spinel) with a cubic crystal system, which is believed to contribute to joint strength.

[0039] The solid-state joining of the laminated portion is preferably performed under high pressure and in a high vacuum atmosphere by maintaining the brazing filler metal at a high temperature close to the solidus temperature but below the solidus temperature where a liquid phase does not occur. Furthermore, in order to stably manufacture a joined body having excellent joining strength, durability, and corrosion resistance, it is preferable to reduce the heating and cooling rates of the brazing filler metal and reduce the temperature difference between the inner and outer peripheries of the laminated portion 100. Furthermore, it is preferable to apply pressure in two stages: low pressure and high pressure.

[0040] Specifically, solid-state bonding is -2 Pa or less (absolute pressure), preferably 10 -3 To ensure excellent joining strength, it is necessary to perform the process in a high vacuum atmosphere of 100 Pa or less (absolute pressure). By performing solid-state joining in a high vacuum atmosphere, oxidation of the metal parts and the brazing filler metal can be prevented. It can also prevent gas entrapment at the joining interface.

[0041] The solid-state bonding preferably includes the following steps in such a high vacuum atmosphere: a step of heating the laminated portion without applying pressure so that the temperature of the Al-Si alloy-based brazing filler metal rises from room temperature to a holding temperature range of not less than the solidus temperature -15°C and not more than the solidus temperature, wherein the average temperature rise rate from 400°C to the holding temperature range of the Al-Si alloy-based brazing filler metal is 2.5 to 3.5°C / min; a step of applying high pressure to the laminated portion in the lamination direction at a pressure of not less than 60 MPa (gauge pressure) for not less than 2.5 minutes while maintaining the temperature of the Al-Si alloy-based brazing filler metal within the holding temperature range; and a step of cooling the laminated portion so that the temperature of the Al-Si alloy-based brazing filler metal falls from the holding temperature range to room temperature over not less than 10 minutes, after stopping the application of pressure to the laminated portion.

[0042] In the heating process, when the temperature of the Al-Si alloy-based brazing filler metal is raised from room temperature (e.g., 28°C) to a holding temperature range of at least 15°C below the solidus temperature (solidus temperature), it is important to reduce the average heating rate from 400°C to the holding temperature range in order to reduce thermal stress caused by the temperature difference between the inner and outer peripheries of the laminate and prevent cracks from occurring in the brazing filler metal. Even minute cracks in the brazing filler metal adversely affect durability and corrosion resistance, so it is desirable to eliminate them as much as possible. Suppressing the average heating rate is also important in preventing the brazing filler metal temperature from overshooting above the solidus temperature. If the average heating rate near the solidus temperature is high, the temperature control may be unable to keep up, resulting in the formation of a liquid phase even if the brazing filler metal temperature exceeds the solidus temperature for a short period of time.

[0043] Specifically, the average heating rate of the Al-Si alloy-based brazing filler metal from 400°C to the holding temperature range is preferably 3.5°C / min or less, more preferably 3.4°C / min or less. There is no particular lower limit to the average heating rate of the Al-Si alloy-based brazing filler metal, but the effect of suppressing cracks will saturate if the heating rate is excessively slow. Furthermore, from the viewpoint of production efficiency, it is not necessary to excessively extend the heating time. Therefore, the average heating rate of the Al-Si alloy-based brazing filler metal from 400°C to the holding temperature range is preferably 2.5 to 3.5°C / min, more preferably 3.0 to 3.4°C / min.

[0044] In the heating step, the average rate of temperature rise from room temperature to 400°C has almost no effect on the occurrence of cracks, so there is no need to particularly control it, and it may be set appropriately from the viewpoint of production efficiency. For example, the average rate of temperature rise from room temperature (e.g., 28°C) to 400°C may be 20 to 50°C / min, or 30 to 40°C / min.

[0045] The reason why the lower limit of the holding temperature range is set to the solidus temperature −15°C or higher is that the bonding reaction rate decreases when the holding temperature range is lower than the solidus temperature −15°C. The lower limit of the holding temperature range is preferably the solidus temperature −13°C or higher, and more preferably the solidus temperature −10°C or higher. The reason why the upper limit of the holding temperature range is set to the solidus temperature or lower is that when the holding temperature range exceeds the solidus temperature, a liquid phase is generated, and coarse Si particles with low corrosion resistance to Na tend to remain. From the perspective of risk management, the upper limit of the holding temperature range is preferably the solidus temperature −3°C or lower, and more preferably the solidus temperature −5°C or lower. Therefore, the holding temperature range is preferably, for example, the solidus temperature −13°C or higher and the solidus temperature −3°C or lower, and more preferably the solidus temperature −10°C or higher and the solidus temperature −5°C or lower.

[0046] For example, when an Al-Si-Mg alloy brazing filler metal (e.g., alloy number 4004 specified in JIS Z3263:2002) having a solidus temperature of 560°C is used as the Al-Si alloy brazing filler metal, the holding temperature range is preferably 545 to 560°C, more preferably 547 to 557°C, and even more preferably 550 to 555°C.

[0047] It is not necessary to apply pressure to the laminate when the temperature is rising. On the other hand, applying pressure when the temperature is rising will cause thermal expansion in the pressurized and fixed state, generating stress on the bonding surface, which is not desirable in terms of obtaining a bond that is highly safe and has excellent durability. Note that pressurization means applying pressure to the laminate from the outside, and does not take into account the pressure applied by the weight of the laminate itself.

[0048] After reaching the predetermined holding temperature range, the high-pressure step involves applying a high pressure of 60 MPa or more (gauge pressure) to the laminated portion in the lamination direction for 2.5 minutes or more while maintaining the temperature of the Al-Si alloy-based brazing filler metal within the holding temperature range. Because a reaction via the brazing filler metal contributes to the bonding, a pressure time of 2 minutes or more is required, preferably 2.5 minutes or more. One method of applying pressure involves clamping the laminated portion between a pair of pressure jigs and applying pressure. By setting the pressure and time under appropriate conditions, excellent bonding strength, durability, and corrosion resistance can be achieved. However, excessively high pressure or excessively long pressing time within the holding temperature range will cause plastic deformation of the metal parts, reducing dimensional accuracy, while saturating bonding strength, durability, and corrosion resistance. Therefore, in a preferred embodiment, the high-pressure step involves applying a high pressure of 70 to 80 MPa (gauge pressure) to the laminated portion in the lamination direction for 2.5 to 3.5 minutes while maintaining the temperature of the Al-Si alloy-based brazing filler metal within the holding temperature range.

[0049] It is preferable to perform a preliminary low-pressure step before the high-pressure step. This allows the metal oxide film on the surface of the metal part to be removed in advance, exposing a fresh metal surface, thereby increasing the joining strength. Specifically, before the high-pressure step, it is preferable to apply a low pressure of 11 to 14 MPa (gauge pressure) to the laminated part in the lamination direction for 5 to 20 seconds while maintaining the temperature of the Al-Si alloy-based brazing filler metal within the above-mentioned holding temperature range, and it is more preferable to apply a low pressure of 12 to 13 MPa (gauge pressure) to the laminated part in the lamination direction for 8 to 15 seconds.

[0050] Furthermore, it is preferable that the pressure increase process from low pressure to high pressure be carried out in a short time. Specifically, after the end of the low pressure application process, the pressure on the laminated portion is increased and the pressure increase time until the high pressure application process is started is preferably within 20 seconds, more preferably within 15 seconds, and can be, for example, 5 to 15 seconds. By increasing the pressure from low pressure to high pressure in one go, the bonding time can be shortened. Furthermore, the desired bonding strength is easily obtained stably. The end of low pressure application means the time when the pressure on the laminated portion first exceeds 15 MPa (gauge pressure). The start of high pressure application means the time when the pressure on the laminated portion first exceeds 50 MPa (gauge pressure).

[0051] In the cooling step, after the pressure on the laminated portion is stopped, in order to reduce the thermal stress caused by the temperature difference between the inner and outer peripheries of the laminated portion and suppress the occurrence of cracks in the bonded body, it is preferable to cool the laminated portion so that the temperature of the Al-Si alloy-based brazing filler metal decreases from the holding temperature range to room temperature (e.g., 28°C) over 10 minutes or more, and more preferably over 30 minutes. There is no particular upper limit to the cooling time of the Al-Si alloy-based brazing filler metal, but from the perspective of production efficiency, it is not necessary to make it excessively slow. Therefore, in the heating step, it is preferable to cool the Al-Si alloy-based brazing filler metal so that the temperature decreases from the holding temperature range to room temperature over 10 to 60 minutes, and more preferably over 30 to 50 minutes.

[0052] The cooling step is preferably carried out after the pressure on the laminated portion is stopped, thereby obtaining a stable bond.

[0053] When the laminated portion has the laminated structure shown in Fig. 2 , the laminated portion is sandwiched between a pair of pressure jigs in the stacking direction (the vertical direction in Fig. 2 ) and heated and pressurized while simultaneously performing the following steps (a), (b), and (c): (a) solid-state joining of an insulating ring (first ceramic component) 110 and an annular protrusion (joining portion) 132 formed on the outer peripheral surface of a negative electrode ring fitting (negative electrode side metal component) 130 via a first Al-Si alloy-based brazing filler metal 121; and (b) solid-state joining of an annular protrusion (joining portion) 132 formed on the outer peripheral surface of the negative electrode ring fitting (negative electrode side metal component) 130 and a backup ring (second ceramic component for preventing sticking) 150 via a second Al-Si alloy-based brazing filler metal 122. (c) Solid-state joining of the insulating ring (first ceramic part) 110 and the annular protrusion (joining portion) 162 formed on the inner peripheral surface of the lower end of the positive electrode ring fitting (positive electrode side metal part) 160 via a third Al-Si alloy-based brazing material.

[0054] The suitable conditions for the solid-state bonding in the above (a), (b), and (c) are the same as those described above for the solid-state bonding of the laminated portion. -2 Pa or less (absolute pressure), preferably 10 -3 the laminated portion is heated without applying pressure in a high vacuum atmosphere of 400 Pa or less (absolute pressure) so that the temperatures of the first, second, and third Al-Si alloy-based brazing filler metals rise from room temperature to a holding temperature range of not less than the solidus temperature -15°C and not more than the solidus temperature, wherein the average temperature rise rate from 400°C to the holding temperature range of the Al-Si alloy-based brazing filler metals is 3.5°C / min or less; next, while maintaining the temperatures of the first, second, and third Al-Si alloy-based brazing filler metals within the holding temperature range, the laminated portion is pressurized in the lamination direction at a pressure of 60 MPa or more (gauge pressure) for 2 minutes or more; and next, after stopping the pressure on the laminated portion, cooling the laminated portion so that the temperatures of the first, second, and third Al-Si alloy-based brazing filler metals fall from the holding temperature range to room temperature over 10 minutes or more.

[0055] One method of applying pressure to the laminated portion is to sandwich the laminated portion between a pair of pressure jigs (not shown) in the stacking direction (the vertical direction in FIG. 2 ) and apply pressure. Specifically, one method involves pressing the backup ring (second ceramic part for preventing adhesion) 150 from above and the ring cap (metal part for preventing adhesion) 170 from below with the pressure jigs.

[0056] The thickness reduction in the lamination direction of the pressure-receiving portion of the metal component (for example, in the case of the laminated component 100 having the laminated structure shown in FIG. 2 , the joining portion 132 of the negative electrode metal component and the joining portion 162 of the positive electrode metal component before and after the steps (a), (b), and (c) are simultaneously performed) is preferably 2.0 to 3.0 mm, and more preferably 2.4 to 2.6 mm. The thickness reduction of the metal component can be one indicator for determining whether the temperature, pressure, and time during joining were appropriate. For example, when the laminated component has the laminated structure shown in FIG. 2 , the pressure-receiving portion of the metal component is the annular protrusion (joining portion) 132 and the annular protrusion (joining portion) 162.

[0057] FIG. 3 is a schematic partial vertical cross-sectional view illustrating the stack structure of the joined body 200 after solid-state welding of the stacked portion 100 shown in FIG. 2 is completed. By measuring the height (height C) to the top end of the positive ring metal fitting 160 and the height (height B) to the top end of the backup ring 150 using the lower surface 163 of the annular protrusion 162 as a reference, it is possible to determine whether the thickness reduction in the stacking direction of the annular protrusion (joining portion) 132 and the annular protrusion (joining portion) 162 is appropriate. Specifically, since the thicknesses of the annular protrusion (joining portion) 132 and the annular protrusion (joining portion) 162 before solid-state welding are known, the total thickness reduction in the annular protrusion (joining portion) 132 and the annular protrusion (joining portion) 162 can be determined from height B. The thickness reduction in the annular protrusion (joining portion) 162 can be determined from height C. The amount of thickness reduction of the annular protrusion (joining portion) 132 can be determined based on the total amount of thickness reduction of the annular protrusion (joining portion) 132 and the annular protrusion (joining portion) 162, and the amount of thickness reduction of the annular protrusion (joining portion) 162. Height B and Height C can be measured using a laser rangefinder, and are given as the average values ​​when measurements are taken at 12 locations every 30° in the circumferential direction.

[0058] (3. Temperature Monitoring of Brazing Filler Metal) As described above, in order to obtain a bonded body having excellent bond strength, durability, and corrosion resistance by solid-state bonding, it is necessary to maintain the brazing filler metal at a high temperature near the solidus temperature but below the solidus temperature at which a liquid phase does not form. Therefore, it is preferable to be able to monitor the temperature of the brazing filler metal during solid-state bonding to determine whether the solid-state bonding has been performed correctly. While it is relatively easy to measure the ambient temperature inside a vacuum heat treatment furnace, the temperature of the brazing filler metal is not strictly the same as the ambient temperature inside the vacuum heat treatment furnace. For this reason, it is desirable to install a thermocouple near the brazing filler metal to measure the temperature of the brazing filler metal as accurately as possible. In particular, when mass-producing bonded bodies, the laminate may be transported inside a continuous furnace, so it is desirable to place the laminate on a cart together with a memory thermometer connected to a thermocouple. As the memory thermometer, a device equipped with a measuring device that measures the temperature based on the voltage generated by the thermocouple and a data logger that can store the temperature measured by the measuring device in association with time, such as the Furnace Tracker System (trade name) manufactured by Datapack (UK), is preferably used.

[0059] Here, "near the brazing filler metal" means that the distance between the brazing filler metal and the temperature measurement junction of the thermocouple connected to the memory thermometer is within 5 cm. This distance is preferably within 5 cm, and more preferably within 3 cm. In the case of the laminated part 100 having the laminated structure shown in FIG. 2, the temperature measurement junction of the thermocouple may be disposed near each of the first Al-Si alloy-based brazing filler metal 121, the second Al-Si alloy-based brazing filler metal 122, and the third Al-Si alloy-based brazing filler metal 123. However, since the three are close to each other, one temperature measurement junction of the thermocouple may be disposed midway between them.

[0060] However, in this case, it is preferable to house the memory-type thermometer in an insulated box to prevent it from being exposed to high temperatures. FIG. 4 shows a schematic longitudinal cross-sectional view of an insulated box 400 suitable for protecting a memory-type thermometer 500. The insulated box 400 is composed of multiple lower containers 410 and multiple upper containers 420 stacked in a nested manner. Each lower container 410 has a bottom wall 411 and a side wall 412 extending upward from the outer periphery of the bottom wall 411. Each lower container 410 preferably has an upper lid 413. Each upper container 420 has a ceiling wall 421 and a side wall 422 extending downward from the outer periphery of the ceiling wall 421. For reasons of heat resistance and durability, the insulated box 400 is preferably made of a metal such as stainless steel. The number of stacked lower containers 410 and multiple upper containers 420 may be appropriately set so as not to exceed the heat resistance temperature (e.g., 100° C.) of the memory-type thermometer 500 .

[0061] The memory thermometer 500 is housed in the smallest lower container 410. The multiple lower containers 410 and the multiple upper containers 420 are stacked with an insulating space between adjacent containers. Because solid-state welding is performed in a vacuum, the presence of the insulating space can provide a significant insulating effect. It is preferable to provide spacers 440 between the multiple lower containers 410 stacked one above the other to ensure a predetermined gap.

[0062] Each of the containers 410, 420 constituting the heat insulating box 400 has a hole 450 for passing the thermocouple 430. For example, in the heat insulating box 400 shown in Fig. 4, the hole 450 is provided in the top lid 413 and the ceiling wall 421 of the lower container 410. The memory thermometer 500 is connected to the thermocouple 430, which has a temperature measuring junction 431 outside the heat insulating box 400, via this hole 450.

[0063] Example 1 A stacked portion (before solid-state welding) of a NAS battery having the structure shown in Fig. 2 was assembled. The materials of each part were as follows. Insulating ring 110 (first ceramic part): aluminum oxide (inner diameter: 59 mm, outer diameter: 74 mm) Ring-shaped first Al-Si alloy-based brazing filler metal 121: Al-Si-Mg alloy-based brazing filler metal of alloy number 4004 (solidus temperature: 560°C) Ring-shaped second Al-Si alloy-based brazing filler metal 122: Al-Si-Mg alloy-based brazing filler metal of alloy number 4004 (solidus temperature: 560°C) Ring-shaped third Al-Si alloy-based brazing filler metal 123: Al-Si-Mg alloy-based brazing filler metal of alloy number 4004 (solidus temperature: 560°C) Negative electrode ring metal (metal part on the negative electrode side) 130: aluminum alloy of alloy number 3003 Backup ring (second ceramic part for preventing sticking) 150: aluminum oxide Positive electrode ring metal (metal part on the positive electrode side) 160: aluminum alloy of alloy number 3003 Ring cap (metal part for preventing sticking) 170: stainless steel

[0064] Next, while the laminated portion was sandwiched between pressure jigs in the lamination direction and heated and pressurized, the following (a), (b), and (c) were simultaneously performed: (a) solid-state joining of the insulating ring (first ceramic component) 110 and the joint portion of the negative electrode ring metal component (negative electrode side metal component) 130 via a first Al-Si alloy-based brazing filler metal, (b) solid-state joining of the joint portion of the negative electrode ring metal component (negative electrode side metal component) 130 and the backup ring (second ceramic component for preventing sticking) 150 via a second Al-Si alloy-based brazing filler metal, and (c) solid-state joining of the joint portion of the insulating ring (first ceramic component) 110 and the positive electrode ring metal component (positive electrode side metal component) 160 via a third Al-Si alloy-based brazing filler metal.

[0065] The steps (a), (b), and (c) were carried out simultaneously in the following order: The laminated part was placed in a continuous furnace and heated for 10 minutes. -3The laminate was heated without applying pressure under a high vacuum atmosphere of 0.1 Pa or less (absolute pressure) so that the temperature of the first, second, and third Al-Si alloy-based brazing filler metals rose from room temperature (28°C) to a holding temperature of approximately 552°C. The heater output was adjusted so that the average temperature rise rate when the temperature of the Al-Si alloy-based brazing filler metal rose from room temperature (28°C) to 400°C was approximately 37°C / min, and the average temperature rise rate from 400°C to the holding temperature was 3.3°C / min. Next, while maintaining the temperatures of the first, second, and third Al-Si alloy-based brazing filler metals at the holding temperature, the laminate was subjected to low pressure in the lamination direction at a pressure of 12 MPa (gauge pressure) for 15 seconds. After the low pressure application step was completed, the pressure increase time until the high pressure application step was started was set to 13 seconds, and the pressure on the laminate was increased. Next, the laminate was subjected to high pressure in the lamination direction at a pressure of 60 MPa (gauge pressure) for 2 minutes. After the pressure on the laminated portion was stopped, the laminated portion was cooled so that the temperatures of the first, second and third Al-Si alloy-based brazing materials were decreased from the holding temperature to room temperature (28°C) over 30 minutes.

[0066] When carrying out the solid-state joining, in order to measure the temperatures of the first, second, and third Al-Si alloy-based brazing filler metals, a Furnace Tracker System (trade name) manufactured by Datapac (UK) was housed in an insulated box (number of lower containers 410=5, number of upper containers 420=4) as shown in Fig. 4. The hot junctions of the thermocouples connected to the system were positioned so as to be within 2 cm of each of the first Al-Si alloy-based brazing filler metal 121, the second Al-Si alloy-based brazing filler metal 122, and the third Al-Si alloy-based brazing filler metal 123.

[0067] The reduction in thickness in the stacking direction at the joining portion of the negative electrode ring fitting (metal part on the negative electrode side) 130 and the joining portion of the positive electrode ring fitting (metal part on the positive electrode side) 160 before and after the steps (a), (b), and (c) were simultaneously performed was within a range of 2.0 to 3.0 mm in all cases of Example 1.

[0068] Five joined bodies according to Example 1 manufactured under the above manufacturing conditions were prepared, and the laminated portions of each joined body were immersed in a 430°C Na solution for 4,800 hours. After 4,800 hours had elapsed, the joined bodies were disassembled to expose the first Al-Si alloy-based brazing filler metal 121 on the insulating ring (first ceramic part) 110. Then, using the inner peripheral edge of the insulating ring (first ceramic part) 110 as a reference, the Na erosion distance in the radial direction of the first Al-Si alloy-based brazing filler metal 121 was measured by observing from above using a microscope. For each joined body, the Na erosion distance was measured at the most eroded point on the entire circumference. The average Na erosion distance for the five joined bodies was 0.8 mm, with a standard deviation of 0.063 mm. As a result, the joined bodies of Example 1 exhibited a short Na erosion distance after long-term immersion in Na and little variation between bodies, demonstrating stable durability and corrosion resistance.

[0069] On the other hand, when bonded bodies were manufactured under various conditions, based on the conditions of Example 1, in which the average heating rate from 400°C to the holding temperature exceeded 3.5°C / min, and similar Na immersion tests were conducted, the variation in the Na erosion distance between individual bodies increased. It was also confirmed that as the average heating rate increased, an overshoot occurred above the solidus temperature, making it easier for a liquid phase to occur.

[0070] 2: Sulfur 3: Sodium 10: Sodium-sulfur battery (NAS battery) 21: Positive electrode side body portion 21a: Narrowed portion 22: Positive electrode ring metal fitting 23: Positive electrode terminal 24: Positive electrode side bottom lid 27: Positive electrode current collector 28: Positive electrode space 31: Negative electrode ring metal fitting 32: Negative electrode side upper lid 36: Negative electrode container 36a: Small hole 37: Space 38: Negative electrode space 39: Negative electrode terminal 40: Insulating ring 50: Solid electrolyte 70: Safety tube 80: Sleeve tube 82: Cover 84: Plate material 100: Laminated portion 110: Insulating ring (first ceramic part) 111: Upper surface (first surface) 112: Lower surface (second surface) 114: Expanded diameter portion 121 : First Al-Si alloy-based brazing filler metal 122 : Second Al-Si alloy-based brazing filler metal 123 : Third Al-Si alloy-based brazing filler metal 130 : Negative electrode ring metal fitting (metal part on the negative electrode side) 132 : Annular protrusion (joining portion) 132 : Joining portion 150 : Second ceramic part (backup ring) 160 : Positive electrode ring metal fitting (metal part on the positive electrode side) 162 : Annular protrusion (joining portion) 163 : Lower surface 164 : Lower end outer peripheral surface 170 : Ring cap (metal part for preventing adhesion) 180 : Solid electrolyte 181 : Open upper end 200 : Joint 400 : Heat-insulating box 410 : Lower container 411 : Bottom wall 412 : Side wall 413 : Upper lid 420 : Upper container 421 : Ceiling wall 422 : Side wall 430: Thermocouple 431: Temperature measuring junction 450: Hole 500: Memory type thermometer

Claims

1. A method for manufacturing a joined body that constitutes a part of a battery that uses Na for the positive and / or negative electrodes, which includes solid-state joining of a ceramic part for insulating between the positive and negative electrodes of the battery and a metal part on the positive or negative electrode side via an Al-Si alloy brazing material, and the solid-state joining is performed by -2 heating, without applying pressure, a laminated portion comprising the ceramic part, the Al-Si alloy-based brazing filler metal, and the joining portion of the metal part in this order in a high vacuum atmosphere of 100 Pa or less (absolute pressure) so that the temperature of the Al-Si alloy-based brazing filler metal rises from room temperature to a holding temperature range of not less than solidus temperature -15°C and not more than solidus temperature, wherein the average temperature rise rate from 400°C to the holding temperature range of the Al-Si alloy-based brazing filler metal is 3.5°C / min or less; then, while maintaining the temperature of the Al-Si alloy-based brazing filler metal within the holding temperature range, applying a high pressure of 60 MPa or more (gauge pressure) to the laminated portion for 2 minutes or more; and then, after stopping the pressure on the laminated portion, cooling the laminated portion so that the temperature of the Al-Si alloy-based brazing filler metal falls from the holding temperature range to room temperature over 10 minutes or more.

2. The method for manufacturing a joined body according to claim 1, wherein after the heating step and before the high pressure step, a low pressure of 11 to 14 MPa (gauge pressure) is applied to the laminated portion in the lamination direction for 5 to 20 seconds while maintaining the temperature of the Al-Si alloy-based brazing filler metal within the holding temperature range.

3. The method for manufacturing a bonded body according to claim 2, wherein the pressure increase time from the end of the low pressure application step to the start of the high pressure application step is within 20 seconds.

4. The method for manufacturing a joined body according to claim 1, wherein the Al-Si alloy brazing filler metal contains Al as a main component and Si and Mg as additive elements.

5. The method for manufacturing a joined body according to claim 1, wherein the Al-Si alloy brazing filler metal is an Al-Si-Mg alloy brazing filler metal of alloy number 4004 specified in JIS Z3263:2002.

6. The method for manufacturing a joined body according to claim 1, wherein the ceramic part contains aluminum oxide and the metal part contains pure aluminum or an aluminum alloy.

7. The method for manufacturing a joined body according to claim 1, wherein the reduction in thickness in the lamination direction at the pressure-receiving portion of the metal part before and after the solid-state joining is 2.0 to 3.0 mm.

8. A method for manufacturing a joined body according to claim 1, comprising monitoring the temperature of the Al-Si alloy-based brazing filler metal by measuring it using a thermocouple placed in the vicinity of the Al-Si alloy-based brazing filler metal, the thermocouple being connected to a memory-type thermometer comprising a measuring instrument that measures the temperature based on the voltage generated by the thermocouple and a data logger that can store the temperature measured by the measuring instrument in association with time, the memory-type thermometer being housed in the smallest lower container of a metal insulating box consisting of a plurality of lower containers and a plurality of upper containers stacked in a nested manner, the plurality of lower containers and the plurality of upper containers being stacked with an insulating space provided between adjacent containers.

9. A method for manufacturing a joined body constituting a part of a battery using sodium as the negative electrode, comprising the steps of: preparing a first ceramic component having a first surface and a second surface opposite to the first surface, for insulating between the positive and negative electrodes of the battery; assembling a laminated section comprising, on the first surface of the first ceramic component, a first Al-Si alloy-based brazing filler metal, a joining portion for a metal component on the negative electrode side, a second Al-Si alloy-based brazing filler metal, and a second ceramic component for preventing adhesion, in this order; and assembling, on the second surface of the first ceramic component, a third Al-Si alloy-based brazing filler metal, a joining portion for a metal component on the positive electrode side, and a metal fitting for preventing adhesion, in this order; and (a) solid-state joining the first ceramic component and the joining portion for the metal component on the negative electrode side via the first Al-Si alloy-based brazing filler metal while clamping the laminated section with a pressure jig in the stacking direction and applying heat and pressure thereto. (b) solid-state joining the joining portion of the negative electrode-side metal component and the second ceramic component for preventing sticking via the second Al-Si alloy-based brazing filler metal, and (c) solid-state joining the first ceramic component and the joining portion of the positive electrode-side metal component via the third Al-Si alloy-based brazing filler metal, and the steps of simultaneously performing (a), (b), and (c) are carried out in a manner similar to that of the method of the present invention. -2 heating the laminated portion without applying pressure in a high vacuum atmosphere of 400 Pa or less (absolute pressure) so that the temperatures of the first, second, and third Al-Si alloy-based brazing filler metals rise from room temperature to a holding temperature range of at least the solidus temperature minus 15°C and the solidus temperature, wherein the average heating rate from 400°C to the holding temperature range of the Al-Si alloy-based brazing filler metals is 3.5°C / min or less; then applying high pressure to the laminated portion in the stacking direction at a pressure of 60 MPa or more (gauge pressure) for 2 minutes or more while maintaining the temperatures of the first, second, and third Al-Si alloy-based brazing filler metals in the holding temperature range; and then, after stopping the application of pressure to the laminated portion, cooling the laminated portion so that the temperatures of the first, second, and third Al-Si alloy-based brazing filler metals fall from the holding temperature range to room temperature over 10 minutes or more.

10. A method for producing a joined body according to claim 9, wherein after the heating step and before the high pressure step, a low pressure is applied to the laminated portion in the lamination direction at a pressure of 11 to 14 MPa (gauge pressure) for 5 to 20 seconds while maintaining the temperature of the Al-Si alloy-based brazing filler metal within the holding temperature range.

11. The method for manufacturing a bonded body according to claim 10, wherein the pressure increase time from the end of the low pressure application step until the start of the high pressure application step by increasing the pressure on the laminated portion is within 20 seconds.

12. The method for producing a joined body according to claim 9, wherein the first, second and third Al-Si alloy brazing filler metals contain Al as a main component, with Si and Mg as additive elements.

13. The method for producing a joined body according to claim 9, wherein the first, second, and third Al-Si alloy-based brazing filler metals are Al-Si-Mg alloy-based brazing filler metals of alloy number 4004 specified in JIS Z3263:2002.

14. The method for manufacturing a joined body according to claim 9, wherein one or both of the first ceramic part and the second ceramic part contain aluminum oxide, and one or both of the negative electrode side metal part and the positive electrode side metal part contain pure aluminum or an aluminum alloy.

15. The method for manufacturing a joint body according to claim 9, wherein the anti-sticking metal fittings contain stainless steel.

16. The method for producing a joined body according to claim 9, wherein the reduction in thickness in the lamination direction at the joint portion of the negative electrode metal component and the joint portion of the positive electrode metal component before and after the steps (a), (b), and (c) are performed simultaneously is 2.0 to 3.0 mm.

17. A method for producing a joined body according to claim 9, comprising monitoring the temperatures of the first, second and third Al-Si alloy-based brazing filler metals by measuring them using thermocouples placed in the vicinity of the first, second and third Al-Si alloy-based brazing filler metals, the thermocouples being connected to a memory-type thermometer comprising a measuring instrument that measures temperature based on a voltage generated by the thermocouples and a data logger that can store the temperature measured by the measuring instrument in association with time, the memory-type thermometer being housed in the smallest lower container of a metal insulating box consisting of a plurality of lower containers and a plurality of upper containers stacked in a nested manner, and the plurality of lower containers and the plurality of upper containers being stacked with an insulating space provided between adjacent containers.

18. A method for manufacturing a joined body according to claim 9, further comprising the steps of: conducting a penetrant inspection on the second ceramic part before assembling the laminated part; and thereafter heating the second ceramic part to 900°C or higher.

19. The method for manufacturing a joined body according to claim 18, wherein the second ceramic part is heated to 900°C or higher for 30 minutes or longer in the heating step.

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