Integrally-formed graphite-based multifunctional bipolar plate

Abstract

The invention discloses an integrally formed graphite-based multifunctional bipolar plate which is characterized by comprising a substrate formed by compounding graphite and resin, a sealing layer and an enclosure frame prepared by fusing the graphite and the resin, which are sequentially arranged from outside to inside and then compounded on working surfaces on two sides of the substrate, the sealing layer is arranged on the surrounding frame, so that the contact surfaces of the substrate, the surrounding frame and the sealing layer form an integrated structure which is fused together without layer gaps, the sealing layer and the surrounding frame can form gapless combination after combination and curing, and leakage is completely eradicated; a film frame component in the prior art is omitted, and all troubles related to the film frame, namely warping troubles of a large film frame, are avoided; the membrane frame material restricts the service life of the battery; the cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid flow batteries, and in particular to an integrally formed graphite-based multifunctional bipolar plate. Background Art

[0002] Liquid flow battery is a kind of energy storage device with high capacity, wide application field and long cycle life. Liquid flow battery consists of battery stack unit, electrolyte, electrolyte storage and supply unit and management control unit, etc. It uses the positive and negative electrolytes to exchange at the diaphragm to realize the mutual conversion between chemical energy and electrical energy, thereby completing the charging and discharging process.

[0003] Bipolar plates are important components of the battery stack in the flow battery system, used to achieve the current conduction in series and the separation of electrolytes in multiple batteries, the conduction of current generated in the battery, and provide support for the reaction electrodes in the flow battery. Therefore, ideal bipolar plate materials usually need to have good conductivity, liquid resistance, electrochemical stability, corrosion resistance, mechanical strength, and long life.

[0004] When assembling bipolar plates in existing flow battery technology, it is necessary to stack multiple components such as bipolar plates, membrane frames, and sealing components in multiple layers, and then fix them together by gluing, and stack multiple cells. In order to prevent electrolyte leakage, the edges of the contact surfaces of all the above components must be well sealed.

[0005] In the prior art, for example, the patent publication number is CN114005994B, and the name of the patent is an integrated bipolar plate structure bonded by height compensation, which discloses an integrated bipolar plate structure bonded by height compensation. In the integrated bipolar plate, the membrane electrode frame and the bipolar plate assembly are integrated with each other to form a single battery. This structure is mainly composed of a bipolar plate and a membrane electrode structure bonded to each other and integrated into one, and a sealing structure injection-molded on the cathode side. The bipolar plate is connected to the membrane electrode frame at the compensation position through appropriate height compensation to ensure that the gas diffusion layer of the membrane electrode has a suitable compression rate suitable for the efficient reaction of the battery; the sealing structure injection-molded on the cathode side also provides effective protection and precise positioning for the overall sealing through appropriate height and width. It can comprehensively improve the production efficiency and assembly efficiency of metal bipolar plates and ensure sufficient sealing effect.

[0006] In the prior art, this method of integrating the components by gluing them together still retains obvious stratification, so that each component remains independent. During use, multiple leakage points are prone to occur between the multi-layer structure, posing a risk of sealing failure. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention provides an integrally formed graphite-based multifunctional bipolar plate with a simple structure and a stable sealing effect.

[0008] In order to solve the above technical problems, the present invention is solved by the following technical solutions: an integrally formed graphite-based multifunctional bipolar plate, characterized in that it includes a substrate formed by a composite of graphite and resin, a sealing layer and a surrounding frame made by a fusion of graphite and resin, which are arranged in sequence from the outside to the inside and then composited on the working surfaces on both sides of the substrate, so that an integrated structure fused together without a layer gap is formed between the contact surfaces of the substrate, the surrounding frame and the sealing layer. The bipolar plates of the present invention are combined with each other to produce a space for the battery cell of the liquid flow battery. The two contacting sealing layers form a complete battery electrochemical reaction space due to the installation pressure, or bonding, or laser welding, and the membrane frame between the two bipolar plates in the traditional structural design is no longer required.

[0009] In the above technical solution, the substrate and the surrounding frame are both formed by fusion molding of natural flake expanded graphite and resin.

[0010] In the above technical solution, interconnected flow channels are integrally provided on the substrate.

[0011] In the above technical solution, the flow channel includes an inlet and an outlet, and a plurality of inter-connected meandering flow channels are arranged between the inlet and the outlet.

[0012] In the above technical solution, the surrounding frame is a hollow structure in the middle, and is combined with the substrate to form a structure with a reaction space in the middle and a sealing surface in the circumferential direction.

[0013] In the above technical solution, a sealing structure including ridges or tooth-like protrusions may be provided on the sealing surface.

[0014] In the above technical solution, the sealing layer is a hot-melt material layer with a thickness of less than 0.6 mm.

[0015] In the above technical solution, the hot-melt material can be resin PP, PE, HDPE, PTFE and all fluorine-based resins.

[0016] In the above technical solution, the substrate, the sealing layer and the surrounding frame are all provided with flow channel holes which are connected with the inlet and the outlet of the flow channel and allow liquid to pass through.

[0017] The manufacturing process of the integrally formed graphite-based multifunctional bipolar plate comprises the following steps: Step 1: expansion, the natural flake graphite is oxidized and intercalated and then expanded at high temperature to obtain expanded graphite worms, and the expansion temperature is controlled to be 900°C to 1200°C; Step 2: Fabrication: The expanded graphite worms prepared in step 1 are settled to the wind-controlled fabrication channel, and the temperature of the fluffy worms is controlled at 20-40°C by stirring with hot air; Step 3: Mixing: Use dry compressed air to evenly spray the resin on the graphite worms and mix them evenly; Step 4: pressing, the graphite worms mixed evenly in step 3 are pressed by a pressing roller to obtain a composite material of expanded graphite and resin, which is the initial substrate material; Step 5: channel forming, the composite substrate raw material is pressed into a channel by a forming machine and a mold, that is, a substrate, and a surrounding frame integrally connected to the substrate is formed by molding; Step seven: Compounding: stacking the sealing layers on the upper working surface of the substrate and the lower working surface of the substrate in sequence for hot pressing compounding to obtain a multifunctional bipolar plate, with the temperature controlled at 170°C~250°C.

[0018] Compared with the prior art, the present invention has the following beneficial effects: by adopting a composite material to realize the integration of the bipolar plate substrate and the surrounding frame, the leakage channel between the two structures of the bipolar plate and the membrane frame in the prior art disappears, and the sealing layer material on the surface of the surrounding frame and the resin material in the initial material of the bipolar plate have the same molecular structure and have the property of being compatible; after the combination is cured, the sealing layer and the surrounding frame can be seamlessly combined to prevent leakage; such a design naturally forms a battery electrochemical reaction space, that is, generates a carbon felt installation position, cancels the membrane frame component in the prior art, and avoids all the troubles related to the membrane frame: in the battery assembly, there is no need for the alignment requirements of the bipolar plate and the membrane frame in the prior art, which greatly facilitates the installation of the carbon felt; the warping trouble of the large membrane frame; the restriction of the membrane frame material on the battery life, etc., and reduces the cost; such a design, as long as the sealing material of the proton membrane of another component in the battery stack is also designed to be the same material, laser welding can be used during installation, and the integrally formed graphite-based multifunctional bipolar plate and proton membrane assembly are welded into one, so that a leakage-free battery stack can be made, solving the troubles in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a schematic diagram of the structure of the present invention.

[0021] Figure 2 The schematic diagram of the flow channel structure is provided in the reaction area of ​​the present invention.

[0022] Figure 3It is a schematic diagram of the splitting of the structure of the present invention in an uncombined state. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below with reference to the accompanying drawings.

[0024] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art can think of other obvious variations. The basic principles of the present invention defined in the following description can be used for other embodiments, variations, improvements, equivalents, and other technical solutions that do not deviate from the spirit and scope of the present invention.

[0025] Those skilled in the art should understand that, in the disclosure of the present invention, the directions or positions indicated by the terms "longitudinal", "lateral", "up", "down", "left", "right", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the directions or positional relationships shown in the accompanying drawings, which are only simplified descriptions for the convenience of describing the present invention, and do not indicate or imply that the device or component referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the above terms should not be understood as limitations on the present invention.

[0026] It is to be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the element may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0027] See also Figures 1 to 3 An integrally formed graphite-based multifunctional bipolar plate includes a substrate 1, a frame 2 and a sealing layer 3, wherein the frame 2 and the sealing layer 3 are symmetrically composited on two working surfaces of the substrate 1 in sequence with the substrate 1 as the center, that is, the frame 2 and the sealing layer 3 each have two groups.

[0028] The base plate 1 is formed by the fusion of graphite and resin. The surrounding frame 2 is formed on the graphite fusion layer by further molding the graphite and resin fusion material on its surface. Preferably, natural flake expanded graphite and resin fusion are used.

[0029] The other side is also formed by molding a material that is a fusion of graphite and resin on its surface, so that the frame 2 and the substrate 1 are made of the same material, which reduces stratification. At the same time, one material is used to realize two structures, which reduces material costs and simplifies the process. After molding, the contact surfaces are fused with each other after the resin is hot-melted to form an integrated structure without layer gaps. This is not only conducive to simplifying the processing technology, but also reduces leakage points and improves sealing performance. The frame 2 is a hollow structure in the middle, forming a structure with a reaction space in the middle, and a sealing surface is formed at the non-hollow part of the frame 2 to cooperate with the sealing layer 3.

[0030] Since the sealing layer 3 is a hot-melt material layer, the hot-melt material with a thickness of less than 0.6 mm can be resin PP, PE, HDPE, PTFE and all fluorine resins; the resin material mixed with the hot-melt material and graphite has an equivalent molecular structure and has a miscible property. Therefore, after hot-pressing and compounding, the contact surfaces of the sealing layer 3 and the surrounding frame 2 can be fused with each other to form a combination without a layer gap, effectively preventing sealing failure caused by stratification.

[0031] Of course, in order to improve the fusion effect, a sealing structure including ridges or tooth-like protrusions is provided on the sealing surface to promote sealing.

[0032] At the same time, in order to make the reaction more uniform, the graphite fusion layer in the reaction space in the middle of the frame 2 is integrally provided with a flow channel interconnected by flow channel holes 4, the flow channel includes an inlet and an outlet, and a plurality of interconnected meandering flow channels 11 are arranged between the inlet and the outlet, and the substrate 1, the sealing layer 3 and the frame 2 are all provided with flow channel holes 4 connected to the flow channel inlet and the flow channel outlet and for liquid to pass through.

[0033] Since both natural flake expanded graphite and resin are plastic, the flow channel set in the reaction area is not limited to a meandering flow channel, but can also be a planar structure or a concave-convex structure flow channel, and the flow channel structure size can be diversified to meet a variety of design and performance requirements.

[0034] The specific manufacturing process of the above structure includes the following steps: Step 1: expansion, the natural flake graphite is oxidized and intercalated and then expanded at high temperature to obtain expanded graphite worms, and the expansion temperature is controlled to be 900°C to 1200°C; Step 2: Fabrication: The expanded graphite worms prepared in step 1 are settled to the wind-controlled fabrication channel, and the temperature of the fluffy worms is controlled at 20-40°C by stirring with hot air; Step 3: Mixing: Use dry compressed air to evenly spray the resin on the graphite worms and mix them evenly; Step 4: pressing, the graphite worms mixed evenly in step 3 are pressed by a pressing roller to obtain a composite material of expanded graphite and resin, which is the initial substrate material; Step 5: channel molding, the molding machine and the mold press the composite substrate raw material into a channel, that is, the substrate; at the same time, the molding press forms a surrounding frame connected to the substrate in one piece. When the high thickness of the surrounding frame is not required or the requirement is relatively low, the molding machine and the mold can be used to mold the combination of the substrate raw material and the surrounding frame in one step; Step 7: Combined curing, use hot-melt material with a thickness of less than 0.6mm, which can be all fluorine resins such as resin PP, PE, HDPE, PTFE, etc. Select the material, thickness and shape according to the design requirements, punch out the sealing layer, and stack the sealing layer, frame, substrate, frame, and sealing layer in sequence to form a complete structure, and then perform hot pressing and curing in the mold to obtain an one-piece graphite-based multifunctional bipolar plate. The temperature is controlled at 170℃~250℃, and the time is 5-30 minutes.

[0035] Through the above process, the product performance obtained is as follows: Those skilled in the art should understand that the embodiments of the present invention described above and shown in the accompanying drawings are only examples and do not limit the present invention. The purpose of the present invention has been fully and effectively achieved. The functions and structural principles of the present invention have been demonstrated and explained in the embodiments, and the embodiments of the present invention may be deformed or modified in any way without departing from the principles.

Claims

1. An integrally formed graphite-based multifunctional bipolar plate, characterized in that: The invention comprises a substrate (1) formed by fusing graphite and resin, a sealing layer (3) and a surrounding frame (2) formed by fusing graphite and resin, which are arranged in sequence from the outside to the inside and then composited on the working surfaces on both sides of the substrate (1), so that a one-piece structure is formed between the contact surfaces of the substrate (1), the surrounding frame (2) and the sealing layer (3) which are fused together without a gap.

2. The integrally formed graphite-based multifunctional bipolar plate according to claim 1, characterized in that: The substrate (1) and the surrounding frame are both formed by fusion molding of natural flake expanded graphite and resin.

3. The integrally formed graphite-based multifunctional bipolar plate according to claim 2, characterized in that: A flow channel is integrally arranged on the substrate (1).

4. The integrally formed graphite-based multifunctional bipolar plate according to claim 3, characterized in that: The flow channel comprises an inlet and an outlet, and a plurality of inter-connected meandering flow channels (11) are arranged between the inlet and the outlet.

5. The integrally formed graphite-based multifunctional bipolar plate according to claim 2, characterized in that: The surrounding frame (2) is a hollow structure in the middle, and is combined with the substrate (1) to form a structure with a reaction space in the middle and a sealing surface in the circumferential direction.

6. The integrally formed graphite-based multifunctional bipolar plate according to claim 5, characterized in that: The sealing surface may be provided with a sealing structure including ridges or tooth-shaped protrusions.

7. The integrally formed graphite-based multifunctional bipolar plate according to claim 5, characterized in that: The sealing layer (3) is a hot-melt material layer with a thickness of less than 0.6 mm.

8. The integrally formed graphite-based multifunctional bipolar plate according to claim 7, characterized in that: The hot melt material includes resin PP, PE, HDPE, PTFE and fluorine resin.

9. The integrally formed graphite-based multifunctional bipolar plate according to claim 4, characterized in that: The substrate (1), the sealing layer (3) and the surrounding frame (2) are all provided with flow channel holes (4) which are connected to the inlet and outlet of the flow channel and allow liquid to pass through.

10. The manufacturing process of the integrally formed graphite-based multifunctional bipolar plate according to claim 1, characterized in that: The steps include: Step 1: expansion, the natural flake graphite is oxidized and intercalated and then expanded at high temperature to obtain expanded graphite worms, and the expansion temperature is controlled to be 900°C to 1200°C; Step 2: Fabrication: The expanded graphite worms prepared in step 1 are settled to the wind-controlled fabrication channel, and the temperature of the fluffy worms is controlled at 20-40°C by stirring with hot air; Step 3: Mixing: Use dry and pure compressed air to evenly spray the resin on the graphite worms and mix them evenly; Step 4: Pressing, the graphite worms mixed evenly in step 3 are pressed by a pressing roller to obtain a substrate raw material; Step 5: channel forming, the composite substrate raw material is pressed into a channel by a forming machine and a mold, that is, a substrate, and a surrounding frame integrally connected to the substrate is formed by molding; Step six: Combine and solidify. The sealing layers are stacked in sequence on the upper working surface of the bipolar plate and the lower working surface of the bipolar plate, and placed on the outside of the frame. The combination sequence is a complete structure stacked with sealing layer, frame, substrate, frame, and sealing layer. Then, hot pressing and solidifying are performed in a mold to obtain a graphite-based multifunctional bipolar plate with a multifunctional bipolar plate integrally formed. The temperature is controlled at 170°C to 250°C for 5 to 30 minutes.

Images