A SOC stack current collecting electrode, a brazing tool and a brazing method thereof

Abstract

The application discloses a SOC stack current collecting electrode, a brazing tool and a brazing method thereof, and relates to the technical field of high-temperature solid oxide batteries. The SOC stack current collecting electrode is provided with vertical grooves and multiple horizontal grooves on the welding area of the current collecting electrode. The vertical grooves are located on the central axis of the current collecting electrode, and the multiple horizontal grooves are uniformly and separately arranged on the central axis of the current collecting electrode and the two sides of the current collecting electrode. The application is designed to release the thermal stress better during high-temperature welding, avoid the warping of the current collecting electrode in the vertical direction, and establish a close full-surface connection between the connecting body end plate and the current collecting electrode through the design of the brazing tool and the corresponding brazing tool, so that the contact resistance is minimized, the ohmic loss of the connecting point is minimized, and the welding quality of vacuum brazing is ensured.

Description

Technical Field

[0001] This application relates to the field of high-temperature solid oxide battery technology, and in particular to a SOC stack current collector electrode, brazing fixture and brazing method thereof. Background Technology

[0002] High-temperature solid oxide batteries (SOCs) are a general term for high-temperature solid oxide fuel cells (SOFCs) and high-temperature solid oxide electrolyzers (SOECs). An SOC stack consists of multiple identical single-cell units stacked together. Current collectors are typically assembled with the upper and lower end plates of the SOC stack and connected to external circuits or electrical equipment. The current generated by the SOC stack is output through the current collectors, which are usually assembled to the upper and lower end plates using welding. However, traditional welding methods easily lead to deformation of the joint area of ​​the current collectors and connectors under high-temperature welding, and the contact resistance at the weld is relatively high. This results in a reduction in the output power of the SOC stack, thus affecting its performance. Based on this, this application proposes an SOC stack current collector, brazing fixture, and brazing method. Summary of the Invention

[0003] The main objective of this application is to provide a current collector electrode for a SOC stack, a brazing fixture, and a brazing method thereof, which aims to solve the technical problems of easy deformation and high contact resistance at the weld joint of the current collector electrode in the prior art.

[0004] To achieve the above objectives, this application proposes a SOC stack current collector electrode, wherein a vertical groove and a plurality of horizontal grooves are provided on the welding area of ​​the current collector electrode, the vertical groove is located on the central axis of the current collector electrode, and the plurality of horizontal grooves are evenly spaced on the central axis of the current collector electrode and on both sides of the current collector electrode.

[0005] Optionally, the current collector electrode is made of either 1.4760 stainless steel or 445 stainless steel.

[0006] This application also proposes a brazing fixture for a current collector electrode of a SOC stack, comprising a lower substrate, a connector, an upper substrate, and a pressure block. The connector is located between the upper substrate and the lower substrate, and a welding groove is formed on the connector. The current collector electrode is accommodated in the welding groove, and the bottom end of the pressure block is pressed against the upper substrate.

[0007] Optionally, the pressing block is provided in multiple forms.

[0008] Optionally, the gap between the current collector electrode and the welding groove is 0.5mm-1mm.

[0009] Optionally, the gap between the current collector electrode and the welding groove is filled with welding foil, the thickness of which is 20μm-100μm, and the material of which is a nickel-based alloy.

[0010] This application also proposes a brazing method for the current collector electrode of a SOC fuel cell stack, using the aforementioned brazing fixture for the current collector electrode of the SOC fuel cell stack, including the following steps:

[0011] The connector and the upper substrate are placed sequentially on the lower substrate, and the current collector electrode is accommodated in the welding groove on the connector. The welding foil is filled in the gap between the current collector electrode and the welding groove.

[0012] The pressure block is placed on the upper substrate and the upper substrate is pressed to complete the assembly of the current collector electrode and the brazing fixture.

[0013] The assembled current collector electrode and the brazing device are placed in a vacuum brazing furnace, and vacuum brazing is performed by heating in stages. After natural cooling to room temperature, the brazing of the current collector electrode is completed.

[0014] Optionally, in the step of vacuum brazing by staged heating, the first stage is heated to 950℃-1000℃ and held for 15min-25min, and the second stage is heated to 1100℃-1150℃ and held for 25min-35min.

[0015] Optionally, the heating rate in the first stage is 5K / min-10K / min, and the heating rate in the second stage is 3K / min-5K / min.

[0016] Optionally, the vacuum level in the vacuum brazing furnace is controlled to be below 5 × 10⁻⁶. -3 Pa.

[0017] The beneficial effects of this application include:

[0018] This application designs the structure of the current collector electrode welding surface by creating vertical and multiple horizontal grooves in the welding area, making the current collector electrode structure at the welding point "S"-shaped. At high temperatures, the vertical and multiple horizontal grooves provide space for deformation, thereby releasing internal thermal stress in the material. This greatly avoids warping of the current collector electrode in the vertical direction, reducing thermal deformation during high-temperature welding. By designing appropriate welding fixtures and vacuum brazing temperatures, a good weld between the current collector electrode and the connector is achieved. The weld has good thermal and electrical conductivity, with less heat input at the welding point, resulting in less deformation. Furthermore, the weld joint is protected from oxidation in a vacuum environment, facilitating the establishment of a tight full-surface connection between the connector end plate and the current collector electrode. This increases the effective contact area between the connector and the current collector electrode, minimizing contact resistance and ohmic losses at the connection point. It also prevents deformation of the connector and the current collector electrode in the joint area, better ensuring the welding quality of the vacuum brazing and thus guaranteeing the performance of the SOC stack. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the current collector electrode structure described in an embodiment of this application;

[0021] Figure 2 This is a schematic diagram of the brazing fixture described in the embodiments of this application;

[0022] Figure 3 This is a schematic diagram of the assembly of the current collector electrode and the connector as described in the embodiments of this application;

[0023] Figure 4 This is a metallographic structure diagram of the welded area after the current collector electrode and the connector are brazed, as described in Embodiment 3 of this application.

[0024] Figure 5 This is a metallographic structure diagram of the welded area cross-section after the current collector electrode is welded using the traditional welding method in Comparative Example 1.

[0025] Figure label:

[0026] 1-Current collector electrode; 11-Vertical groove; 12-Horizontal groove; 2-Connector; 21-Welding groove; 3-Lower substrate; 4-Upper substrate; 5-Pressure block; 6-Welding foil.

[0027] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0028] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0029] Example 1

[0030] A type of SOC stack collector electrode, such as Figure 1 As shown, the welding area of ​​the current collector electrode 1 is provided with a vertical groove 11 and a plurality of horizontal grooves 12. The vertical groove 11 is located on the central axis of the current collector electrode 1, and the plurality of horizontal grooves 12 are evenly spaced on the central axis of the current collector electrode 1 and on both sides of the current collector electrode 1.

[0031] Because the current collector electrode 1 is very thin, typically between 0.5mm and 1mm, it is extremely prone to warping during welding at high temperatures. Since the SOC stack must be firmly integrated into the clamping device during use, the current collector electrode 1 and the end plate of the connector 2 must be parallel after welding. Once the current collector electrode 1 warps severely, it is impossible to guarantee that the current collector electrode 1 and the connector 2 remain parallel. Therefore, this application provides a vertical groove 11 and multiple horizontal grooves 12 on the welding area of ​​the current collector electrode 1. Through these grooves, the structure of the current collector electrode 1 at the welding point can be "S" shaped. At high temperatures, the vertical groove 11 and multiple horizontal grooves 12 can provide space for deformation, thereby releasing the internal thermal stress of the material and reducing the occurrence of thermal deformation. This can greatly avoid the warping of the current collector electrode 1 in the vertical direction.

[0032] In specific implementation, the material of the current collector 1 is either 1.4760 stainless steel or 445 stainless steel.

[0033] Specifically, the selection of current collector electrode materials needs to consider the following aspects: sufficient high-temperature strength and corrosion stability at the operating temperature and welding temperature of the SOC stack; excellent conductivity; good compatibility with solder and connector materials; and a similar coefficient of thermal expansion with the connector 2 of the SOC stack. Based on this, this application uses 1.4760 stainless steel or 445 stainless steel as the current collector electrode material.

[0034] Example 2

[0035] A brazing fixture for the current collector electrode of a SOC stack, such as Figure 2 and Figure 3 As shown, it includes a lower substrate 3, a connector 2, an upper substrate 4, and a pressing block 5. The connector 2 is located between the upper substrate 4 and the lower substrate 3. A welding groove 21 is provided on the connector 2. The current collector 1 is accommodated in the welding groove 21. The bottom end of the pressing block 5 is pressed against the upper substrate 4.

[0036] Specifically, the lower substrate 3, upper substrate 4, and pressure block 5 are all made of alumina ceramic. Alumina ceramic has high thermal conductivity, which can effectively help heat dissipate from the brazing area, avoid the impact of heat accumulation on the welding area, help maintain temperature uniformity, and ensure the stability and quality of the welding process. In addition, the brazing process needs to be carried out at high temperatures, and alumina ceramic has excellent high temperature resistance, which can ensure the stability of the tooling during the welding process. At the same time, alumina ceramic also has high mechanical strength and hardness, which can maintain shape stability under high temperature and high pressure, preventing deformation or damage caused by pressure or thermal expansion during the welding process. In the brazing tooling, the pressure block 5 is used to apply uniform pressure to make the brazing filler metal flow evenly and ensure a perfect joint area. The hardness of alumina ceramic enables the pressure block 5 to distribute pressure evenly in a high temperature environment, thereby improving the welding quality.

[0037] In the specific implementation process, multiple pressure blocks 5 are provided. Under the gravity of multiple pressure blocks 5, the current collector 1 and the connector 2 can be tightly attached. After the welding foil 6 melts, it seals and wets the part to be welded under capillary action, so that the weld between the current collector 1 and the connector 2 is sealed, thereby ensuring the welding reliability and strength of the current collector 1.

[0038] In the specific implementation process, the gap between the current collecting electrode 1 and the welding groove 21 is 0.5mm-1mm.

[0039] Specifically, in order to ensure that the current collector electrode 1 has a certain space for thermal expansion during welding at high temperature, this application controls the gap between the current collector electrode 1 and the welding groove 21 to be 0.5mm-1mm, which also provides a certain space for the flow of the welding foil 6 after melting.

[0040] In the specific implementation process, the gap between the current collector 1 and the welding groove 21 is filled with welding foil 6, and the thickness of the welding foil 6 is 20μm-100μm.

[0041] Preferably, the solder foil 6 is in the form of a thin sheet with a thickness controlled between 20μm and 100μm. This is more conducive to the solder foil 6 fully wetting the surfaces of the connector 2 and the current collector 1 after melting at the brazing temperature, thereby forming a good bonding surface.

[0042] Specifically, the welding foil 6 is made of a nickel-based alloy. The nickel-based alloy has a similar coefficient of thermal expansion to the metal connector 2 of the SOC stack, giving it good chemical compatibility. Furthermore, the nickel-based alloy has sufficient high-temperature strength and corrosion stability at both the operating temperature and welding temperature of the SOC stack, which can improve the welding quality of vacuum brazing and ensure the normal operation of the SOC stack.

[0043] Example 3

[0044] A brazing method for the current collector electrode of a SOC (Surface Mount Technology) battery pack, using the aforementioned brazing fixture for the current collector electrode of the SOC battery pack, includes the following steps:

[0045] The connector 2 and the upper substrate 4 are placed sequentially on the lower substrate 3, and the current collector 1 is accommodated in the welding groove 21 on the connector 2. The welding foil 6 is filled in the gap between the current collector 1 and the welding groove 21.

[0046] The pressure block 5 is placed on the upper substrate 4 and the upper substrate 4 is pressed to complete the assembly of the current collector 1 and the brazing fixture.

[0047] The assembled current collector electrode 1 is placed in a vacuum brazing furnace with a brazing device, and vacuum brazing is performed by heating in stages. After natural cooling to room temperature, the brazing of the current collector electrode 1 is completed.

[0048] This application employs vacuum brazing to weld the current collector 1 to the connector 2. Compared with traditional welding, vacuum brazing has good thermal and electrical conductivity at the weld joint, and less heat is input at the weld joint, resulting in less deformation at the weld joint. Furthermore, the weld joint does not need to be accessible, and the vacuum environment ensures that the weld joint is not oxidized. This facilitates the establishment of a tight full-surface connection between the connector 2 end plate and the current collector 1, thereby minimizing contact resistance, ohmic loss at the connection point, and preventing deformation of the connector 2 and the current collector 1 in the joint area.

[0049] In the specific implementation process, in the step of vacuum brazing by staged heating, the first stage heats up to 980°C and holds for 20 minutes, and the second stage heats up to 1120°C and holds for 30 minutes.

[0050] In the specific implementation process, the heating rate in the first stage is 7K / min, and the heating rate in the second stage is 4K / min.

[0051] In the specific implementation process, the vacuum level in the vacuum brazing furnace is controlled to be lower than 5×10⁻⁶. -3 Pa.

[0052] This application first raises the furnace temperature to 980℃ at a heating rate of 7K / min and holds it for 20min. At this temperature, the solder foil 6 begins to melt but does not completely melt. At this time, the solder foil 6 begins to wet the surface of the connector 2 and the current collector 1. Holding the temperature for 20min ensures that the temperature of the contact area between the connector 2 and the current collector 1 is uniform, thereby forming a good bonding surface. Then, the temperature is raised to 1120℃ at a heating rate of 4K / min and held for 30min. At this temperature, the solder foil 6 completely melts and has optimal fluidity. Under the pressure of the pressure block 5, it can better fill the weld gap. Holding the temperature for 30min ensures sufficient diffusion and alloy reaction between the solder and the connector 2 and the current collector 1, improving the performance and quality of the weld. This establishes a tight full-surface connection between the end plate of the connector 2 and the current collector 1, minimizing contact resistance.

[0053] Example 4

[0054] A brazing method for the current collector electrode of a SOC (Surface Mount Technology) battery pack, using the aforementioned brazing fixture for the current collector electrode of the SOC battery pack, includes the following steps:

[0055] The connector 2 and the upper substrate 4 are placed sequentially on the lower substrate 3, and the current collector 1 is accommodated in the welding groove 21 on the connector 2. The welding foil 6 is filled in the gap between the current collector 1 and the welding groove 21.

[0056] The pressure block 5 is placed on the upper substrate 4 and the upper substrate 4 is pressed to complete the assembly of the current collector 1 and the brazing fixture.

[0057] The assembled current collector 1 and the brazing device are placed in a vacuum brazing furnace, and the vacuum level in the vacuum brazing furnace is controlled to be lower than 5 × 10⁻⁶. -3 Pa, in the first stage, the temperature is increased to 950℃ at a heating rate of 5K / min and held for 25min. In the second stage, the temperature is increased to 1100℃ at a heating rate of 3K / min and held for 35min. After natural cooling to room temperature, the brazing of the current collector electrode 1 is completed.

[0058] Example 5

[0059] A brazing method for the current collector electrode of a SOC (Surface Mount Technology) battery pack, using the aforementioned brazing fixture for the current collector electrode of the SOC battery pack, includes the following steps:

[0060] The connector 2 and the upper substrate 4 are placed sequentially on the lower substrate 3, and the current collector 1 is accommodated in the welding groove 21 on the connector 2. The welding foil 6 is filled in the gap between the current collector 1 and the welding groove 21.

[0061] The pressure block 5 is placed on the upper substrate 4 and the upper substrate 4 is pressed to complete the assembly of the current collector 1 and the brazing fixture.

[0062] The assembled current collector 1 and the brazing device are placed in a vacuum brazing furnace, and the vacuum level in the vacuum brazing furnace is controlled to be lower than 5 × 10⁻⁶. -3 Pa, in the first stage, the temperature is increased to 1000℃ at a heating rate of 5K / min and held for 15min. In the second stage, the temperature is increased to 1150℃ at a heating rate of 3K / min and held for 25min. After natural cooling to room temperature, the brazing of the current collector 1 is completed.

[0063] Example 6

[0064] A brazing method for the current collector electrode of a SOC (Surface Mount Technology) battery pack, using the aforementioned brazing fixture for the current collector electrode of the SOC battery pack, includes the following steps:

[0065] The connector 2 and the upper substrate 4 are placed sequentially on the lower substrate 3, and the current collector 1 is accommodated in the welding groove 21 on the connector 2. The welding foil 6 is filled in the gap between the current collector 1 and the welding groove 21.

[0066] The pressure block 5 is placed on the upper substrate 4 and the upper substrate 4 is pressed to complete the assembly of the current collector 1 and the brazing fixture.

[0067] The assembled current collector 1 and the brazing device are placed in a vacuum brazing furnace, and the vacuum level in the vacuum brazing furnace is controlled to be lower than 5 × 10⁻⁶. -3 Pa, in the first stage, the temperature is increased to 970℃ at a heating rate of 7K / min and held for 20min. In the second stage, the temperature is increased to 1130℃ at a heating rate of 4K / min and held for 32min. After natural cooling to room temperature, the brazing of the current collector 1 is completed.

[0068] Comparative Example 1

[0069] The current collector 1 and the connector 2 are welded at high temperature using a traditional welding method.

[0070] Experimental Example

[0071] Observe the metallographic structure diagram of the welded area cross-section after the current collector electrode is brazed in Embodiment 3 of this application (e.g.) Figure 4 (as shown), and the metallographic structure diagram of the welded area cross-section after welding the current collector electrode using the conventional welding method in Comparative Example 1 (as shown). Figure 5 (As shown), for comparison.

[0072] exist Figure 4 and Figure 5 In the image, the black shading represents stomata, which can be seen... Figure 5 There are numerous pores between the current collector electrode and the metal connector, and the two are not well connected. Figure 4 The significant reduction in pores indicates a substantial improvement in the connection between the current collector electrode and the metal connector. Poor contact and pores between the current collector electrode and the metal connector reduce the effective contact area, thus decreasing the actual area through which current flows and significantly increasing contact resistance. However, the brazing method described in this application establishes a tight, full-surface connection between the metal connector end plate and the current collector electrode, thereby minimizing contact resistance and reducing ohmic losses at the connection point.

[0073] In summary, the embodiments of this application provide a SOC stack current collector electrode, a brazing fixture, and a brazing method thereof, which have the following beneficial effects:

[0074] This application designs the structure of the welding surface of the current collector 1 by creating a vertical groove 11 and multiple horizontal grooves 12 in the welding area, making the structure of the current collector 1 at the welding point "S"-shaped. At high temperatures, the vertical groove 11 and multiple horizontal grooves 12 provide space for deformation, thereby releasing the internal thermal stress of the material. This greatly avoids warping of the current collector 1 in the vertical direction, reducing thermal deformation during high-temperature welding. Furthermore, by designing appropriate welding fixtures and vacuum brazing temperatures, a good weld between the current collector 1 and the connector 2 is achieved. The joint has good thermal and electrical conductivity, resulting in less heat input at the welding point and thus less deformation. It also ensures that the weld joint is not oxidized in a vacuum environment, which is conducive to establishing a tight full-surface connection between the connector 2 end plate and the collector electrode 1. This increases the effective contact area between the connector 2 and the collector electrode 1, thereby minimizing contact resistance and ohmic loss at the connection point. It also avoids deformation of the connector 2 and the collector electrode 1 in the joint area, better ensuring the welding quality of vacuum brazing and thus ensuring the performance of the SOC stack.

[0075] The above description is merely an optional embodiment of this application and does not limit the patent scope of this application. Any equivalent structural transformations made based on the inventive concept of this application and the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A brazing fixture for the current collector electrode of a SOC (System-on-a-Chip) stack, characterized in that, The brazing fixture includes a lower substrate, a connector, an upper substrate, and a pressure block. The welding area of ​​the current collector electrode is provided with a vertical groove and multiple horizontal grooves. The vertical groove is located on the central axis of the current collector electrode, and the multiple horizontal grooves are evenly spaced on the central axis of the current collector electrode and on both sides of the current collector electrode. The current collector electrode is housed in a welding groove on the connector of the brazing fixture. The gap between the current collector electrode and the welding groove is filled with welding foil. The thickness of the welding foil is 20μm-100μm, and the material of the welding foil is a nickel-based alloy.

2. The brazing fixture for the current collector electrode of the SOC stack according to claim 1, characterized in that, The current collector electrode is made of either 1.4760 stainless steel or 445 stainless steel.

3. The brazing fixture for the SOC stack current collector electrode according to claim 1, characterized in that, The connector is located between the upper substrate and the lower substrate, and the bottom end of the pressure block is pressed against the upper substrate.

4. The brazing fixture for the SOC stack current collector electrode according to claim 1, characterized in that, The pressure block is provided in multiple forms.

5. The brazing fixture for the SOC stack current collector electrode according to claim 1, characterized in that, The gap between the current collector electrode and the welding groove is 0.5mm-1mm.

6. A brazing method for the current collector electrode of a SOC (System-on-a-Chip) stack, characterized in that, The brazing fixture for the SOC stack current collector electrode as described in any one of claims 1-5 includes the following steps: The connector and the upper substrate are placed sequentially on the lower substrate, and the current collector electrode is accommodated in the welding groove on the connector. The welding foil is filled in the gap between the current collector electrode and the welding groove. The pressure block is placed on the upper substrate and the upper substrate is pressed to complete the assembly of the current collector electrode and the brazing fixture. The assembled current collector electrode and the brazing device are placed in a vacuum brazing furnace, and vacuum brazing is performed by heating in stages. After natural cooling to room temperature, the brazing of the current collector electrode is completed.

7. The brazing method for the current collector electrode of the SOC stack according to claim 6, characterized in that, In the step of vacuum brazing by staged heating, the first stage heats up to 950℃-1000℃ and holds for 15min-25min, and the second stage heats up to 1100℃-1150℃ and holds for 25min-35min.

8. The brazing method for the current collector electrode of the SOC stack according to claim 7, characterized in that, The heating rate in the first stage is 5K / min-10K / min, and the heating rate in the second stage is 3K / min-5K / min.

9. The brazing method for the current collector electrode of the SOC stack according to claim 6, characterized in that, The vacuum level in the vacuum brazing furnace is controlled to be below 5 × 10⁻⁶. -3 Pa.

Images