Repairing method for local leakage of redox flow battery stack

Abstract

The invention discloses a method for repairing local leakage of a galvanic pile of a flow battery, which comprises the following steps of: 1, carrying out airtight test on the galvanic pile to determine a local leakage point; 2, area measurement and marking are carried out on the local leakage points; 3, a repairing material made of the same material as the liquid flow frame is prepared, the area of the repairing material is 1-3 times that of the leakage points, and the thickness of the repairing material is 1-3 mm; 4, the leakage area is cleaned and dried; 5, a hot air heating device is adopted to conduct local preheating on the leakage part; step 6, synchronously heating the leakage part and the repairing material to the softening temperature of the thermoplastic material by adopting a hot air heating device, and laminating, pressurizing and welding the leakage part and the repairing material; and step 7, after cooling, carrying out airtight test again, and verifying the repairing effect. The method has the advantages that the operation is convenient, the process is simple, the leakage part can be effectively sealed, and the material utilization rate is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of flow batteries in electrochemical energy storage; specifically, it relates to a method for repairing local leakage of a flow battery stack, especially applicable to the problem of local leakage of a flow battery stack caused by laser welding virtual soldering or material deformation. It realizes efficient repair through a hot melt pressure welding process, improving the sealing performance of the stack and the material utilization rate. Background Art

[0002] As one of the energy storage technologies, flow batteries have broad development prospects in the energy storage field due to their high reliability, long cycle life, etc. A flow battery forms a stack by stacking a certain number of single cells. Therefore, the stacking structure of single cells in the stack poses high requirements for its sealing performance. However, the sealing problem of the flow battery stack has always been a bottleneck restricting the development of flow battery technology.

[0003] Most traditional flow batteries use rubber sealing rings and bolts for sealed connection. However, after long-term use, these sealing methods have problems such as aging of the sealing material and decline in elasticity, resulting in a risk of liquid leakage in the stack.

[0004] With the development of flow battery energy storage technology, laser welding technology has gradually been applied to the sealing of flow batteries. "A flow battery electrode frame structure and a flow battery stack that can be laser welded" (Publication No. CN214226959U, Publication Date: September 17, 2021). This technology designs a laser-weldable flow battery electrode frame structure with non-oily coating dark treatment. The sealing method of bonding each component by laser heating and melting the components reduces the production difficulty and improves the sealing strength of the flow battery.

[0005] However, when stacking multiple electrode frames, due to problems such as the flatness of the welding material and local stress, the laser welding structure still has problems such as local insecure welding and virtual soldering, resulting in local leakage, electrolyte leakage problems, and affecting the effective sealing of the stack. When the traditional laser welding components have airtight leakage problems, only scrapping treatment is possible. This will inevitably lead to waste of materials. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for repairing local leakage of a flow battery stack in view of the deficiencies of the prior art. This method is easy to operate and has a simple process, can effectively seal the leakage part, and effectively improves the material utilization rate.

[0007] The technical purpose of the present invention is achieved through the following technical solutions: A method for repairing local leakage of a flow battery stack includes the following steps: Step 1: Conduct an airtight test on the stack to determine the local leakage point; Step 2: Measure and mark the area of the local leakage point; Step 3: Prepare a repair material made of the same material as the liquid flow frame. The area of the repair material is 1 - 3 times the area of the leakage point, and the thickness is 1 - 3 mm; Step 4: Clean and dry the leakage area; Step 5: Use a hot air heating device to locally preheat the leakage part; Step 6: Use a hot air heating device to synchronously heat the leakage part and the repair material to the softening temperature of the thermoplastic material, bond them together, and apply pressure welding; Step 7: Conduct an airtight test again after cooling to verify the repair effect.

[0008] Preferably, in Step 1, the pressure of the airtight test is 0.05 - 0.15 MPa, and the test medium is an inert gas or air.

[0009] Preferably, in Step 3, the repair material and the liquid flow frame are made of one of PP, PVDF, or PE.

[0010] Preferably, in Step 3, the area of the repair material is 2 times the area of the leakage point, and the thickness is 2 mm.

[0011] Preferably, in Step 4, the cleaning treatment is carried out by wiping with anhydrous ethanol or isopropanol, and the drying treatment is carried out by blowing with compressed air.

[0012] Preferably, in Step 5, the temperature of the local preheating is 200 - 250 °C, and the preheating time is 10 - 30 seconds.

[0013] Preferably, in Step 6, the heating temperature during synchronous heating is 300 - 350 °C, and the temperature control accuracy of the hot air heating device is ±5 °C.

[0014] Preferably, in Step 6, the pressure of the pressure welding is 0.2 - 0.5 MPa, and the pressure tool is a roller or a pressing plate.

[0015] Compared with the prior art, the beneficial effects of the present invention are: The present invention repairs by hot melting, works using the plastic melting characteristics, hot melts and fills the virtual welding gaps, forms a molten layer to strengthen the bonding, and locks the local leakage points. The hot air heating device is used to conduct molten repair on the leakage part to complete the sealing of the leakage part of the stack welding of the flow battery. The present invention has the advantages of convenient operation, simple process, effective sealing of the leakage part, and effectively improving the material utilization rate. Description of the Drawings

[0016] Figure 1 is the flow chart of the present invention; Detailed Embodiments

[0017] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0018] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0019] It should be noted that: similar reference numerals and letters denote similar items in the following accompanying drawings. Therefore, once an item is defined in one accompanying drawing, it does not need to be further defined and explained in subsequent accompanying drawings. In addition, terms such as "first", "second", etc. are only used for descriptive distinction and cannot be understood as indicating or implying relative importance.

[0020] As Figure 1 shown, a method for repairing local leakage of a flow battery stack includes the following steps: Step 1: Perform an airtight test on the stack to determine the local leakage point; Step 2: Measure and mark the area of the local leakage point; Step 3: Prepare a repair material made of the same material as the flow frame, where the area of the repair material is 1 - 3 times the area of the leakage point and the thickness is 1 - 3 mm; Step 4: Clean and dry the leakage area; Step 5: Use a hot air heating device to locally preheat the leakage part; Step 6: Synchronously heat the leakage part and the repair material to the softening temperature of the thermoplastic material, bond the two together and apply pressure welding; Step 7: After cooling, perform an airtight test again to verify the repair effect.

[0021] Precisely locate the leakage point through the airtight test (Step 1) to avoid blind repair; combined with hot melt welding (Step 6), local repair is achieved without overall disassembly of the stack, saving more than 90% of the repair time; it has the advantages of precise positioning and efficient repair. Use a repair material made of the same material as the flow frame (Step 3) to ensure molecular-level bonding at the molten interface, and the sealing strength is consistent with the original welding area; ensure material compatibility. Synchronously heat the leakage part and the repair material to eliminate stress concentration caused by temperature gradient and avoid secondary cracking.

[0022] The hot melt method is used for repair, and the melting characteristics of plastic are used to work. The hot melt fills the virtual welding gap, forms a molten layer to strengthen the bond, and locks the local leakage point. The hot air heating device is used to melt the leakage part to complete the sealing of the superimposed welding leakage part of the flow battery. This method is easy to operate and simple in process. It can effectively seal the leakage part and effectively improve the material utilization rate.

[0023] In this embodiment, the battery stack includes a plurality of groups of liquid flow batteries stacked and welded components, and the liquid flow frame of the battery stack is made of thermoplastic material. In a specific implementation, the liquid flow frame is made of one of PP, PVDF or PE.

[0024] In this embodiment, there are ten groups of superimposed welded components of the flow battery, assuming that there are two leakage points.

[0025] Step 1: Perform an airtight test on the fuel cell stack to identify two local leakage points.

[0026] In specific implementation, the pressure of the airtight test is 0.05-0.15 MPa, and the test medium is an inert gas or air. In this embodiment, the pressure of the airtight test is 0.1 MPa.

[0027] 0.05-0.15MPa pressure can detect micron-level leakage, while avoiding excessive pressure to damage the stack structure. Inert gas (such as nitrogen) prevents oxidation, while the cost of air testing is reduced by 80% (no gas replacement equipment is required). Single test time is ≤10 minutes, supporting online detection without disassembly of the stack, saving more than 80% of testing time.

[0028] Step 2: Measure and mark the area of the local leakage point; When measuring in large quantities, laser scanning or optical measuring instruments (accuracy ±0.1mm) can be used to accurately measure the leakage area to avoid insufficient (incomplete coverage) or excessive (waste of material) patching materials. Use a high-temperature marking pen or laser scoring to mark the leakage boundary to ensure that the mark does not disappear during subsequent heating (traditional ink markings fail above 200°C).

[0029] Step 3: Prepare a patch material of the same material as the liquid flow frame. The area of the patch material should be 1-3 times the area of the leakage point and the thickness should be 1-3 mm.

[0030] In this embodiment, the flow frame is made of pp material. The material of the repair material is the same as that of the flow frame, and the material of the repair material is also PP. In specific implementation, the area of the repair material is twice the area of the leakage point, and the thickness is 2 mm. The area of the repair material is set to be twice the area of the leakage point to ensure complete coverage of the crack propagation area (the area within 1-2 mm around the crack is the stress concentration area), while avoiding material waste. The 2-mm-thick repair patch can provide enough molten volume to fill the gap and will not cause uneven heat conduction due to excessive thickness (experiments show that when the thickness > 3 mm, hot air is difficult to penetrate the material).

[0031] Step 4: Clean and dry the leakage area; In this embodiment, the cleaning treatment is carried out by wiping with anhydrous ethanol or isopropanol, and the drying treatment is carried out by purging with compressed air. Anhydrous ethanol / isopropanol can dissolve grease and particulate contaminants, increasing the surface energy to more than 50 mN / m (less than 30 mN / m before cleaning), promoting the spreading of the molten material. Ethanol / isopropanol has no corrosion to materials such as PP and PVDF, and the tensile strength retention rate of the material after cleaning is ≥99%. Purging with compressed air can make the surface residual solvent content < 0.1% within 10 seconds (when not dried, the residual solvent vaporizes during heating to form bubbles, resulting in a 50% decrease in the bonding strength).

[0032] Step 5: Locally preheat the leakage part with a hot air heating device; In this embodiment, the hot air heating device is a hot air gun. The local preheating temperature is 200-250 °C, and the preheating time is 10-30 seconds. Preheating at 200-250 °C eliminates processing residual stress (such as microcracks caused by laser welding), reducing the deformation amount during subsequent hot melt welding. The 10-30 second preheating time softens the material surface layer, shortening the energy input in the main heating stage.

[0033] Step 6: Synchronously heat the leakage part and the repair material to the softening temperature of the thermoplastic material with a hot air heating device, and bond and press-weld the two together.

[0034] In this embodiment, a hot air gun is used to heat the leakage part and the repair material simultaneously; after the material surface is softened, the two are bonded and press-welded together. Among them, the heating temperature during synchronous heating is 300-350 °C, and the temperature control accuracy of the hot air heating device is ±5 °C. Through hot melt repair, the voided welding gaps can be filled to form a molecular-level bond, completing the sealing of the leakage part of the flow battery stack welding, and then solving the problems of local welding failure and voided welding in the laser welding structure in the prior art, which cause local leakage.

[0035] The softening temperature range covering PP (melting point 160 - 170°C), PVDF (melting point 170 - 180°C), and PE (melting point 120 - 140°C) is 300 - 350°C, ensuring that the materials are fully melted and flowing without decomposition (PP starts to degrade at >350°C). The accuracy of ±5°C avoids local overheating (causing material carbonization) or underheating (poor soldering), improving welding consistency.

[0036] The pressure for pressure welding is 0.2 - 0.5 MPa, and the pressing tools are rollers or platens. The pressure of 0.2 - 0.5 MPa enables the molten material to fully fill the gaps (porosity <0.5%), while preventing excessive extrusion that may cause material extrusion (extrusion volume >20% when the pressure >0.5 MPa). Synchronous heating forms a uniform molten layer (thickness 0.1 - 0.3 mm) between the repair material and the substrate, with the interfacial bonding strength reaching over 95% of the raw material. Rollers are suitable for curved surface repair, and platens are suitable for flat areas, ensuring uniform pressure distribution.

[0037] Step 7: After cooling, conduct an airtight test again to verify the repair effect.

[0038] In this embodiment, after the material cools down, an airtight test is conducted on the stack. The airtight test is qualified, and the local repair of the leakage point is completed.

[0039] The pressure during the secondary airtight test is 0.05 - 0.15 MPa. By conducting the airtight test again, it is ensured that there is no secondary leakage in the repaired area, avoiding the scrapping of the stack caused by repair failure. In this embodiment, the pressure of the airtight test is 0.1 MPa.

[0040] The technical solutions provided by the embodiments of the present invention have been introduced in detail above. Specific examples are used in this article to elaborate on the principles and implementation manners of the embodiments of the present invention. The descriptions of the above embodiments are only applicable to help understand the principles of the embodiments of the present invention; at the same time, for those of ordinary skill in the art, based on the embodiments of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A repair method for local leakage of a flow battery stack, characterized in that, It includes the following steps: Step 1: Conduct an airtight test on the stack to determine local leakage points; Step 2: Measure and mark the area of the local leakage points; Step 3: Prepare a repair material made of the same material as the flow field plate. The area of the repair material is 1 - 3 times the area of the leakage point, and the thickness is 1 - 3 mm; Step 4: Clean and dry the leakage area; Step 5: Use a hot air heating device to locally preheat the leakage part; Step 6: Use a hot air heating device to synchronously heat the leakage part and the repair material to the softening temperature of the thermoplastic material, bond them together and perform pressure welding; Step 7: Conduct an airtight test again after cooling to verify the repair effect.

2. The method for repairing local leakage of a flow battery stack according to claim 1, characterized in that: In Step 1, the pressure of the airtight test is 0.05 - 0.15 MPa, and the test medium is an inert gas or air.

3. The method for repairing local leakage of a flow battery stack according to claim 1, wherein: In Step 3, the material of the repair material and the flow field plate is one of PP, PVDF or PE.

4. The method for repairing local leakage of a flow battery stack according to claim 1, wherein: In Step 3, the area of the repair material is 2 times the area of the leakage point, and the thickness is 2 mm.

5. The method for repairing local leakage of a flow battery stack according to claim 1, characterized in that: In Step 4, the cleaning treatment is carried out by wiping with anhydrous ethanol or isopropanol, and the drying treatment is carried out by purging with compressed air.

6. The method for repairing local leakage of a flow battery stack according to claim 1, characterized in that: In Step 5, the temperature of the local preheating is 200 - 250 °C, and the preheating time is 10 - 30 seconds.

7. The method for repairing local leakage of a flow battery stack according to claim 1, characterized in that: In Step 6, the heating temperature during synchronous heating is 300 - 350 °C, and the temperature control accuracy of the hot air heating device is ±5 °C.

8. The method for repairing local leakage of a flow battery stack according to claim 1, characterized in that: In Step 6, the pressure of the pressure welding is 0.2 - 0.5 MPa, and the pressure tool is a roller or a pressing plate.

Images