Method of manufacturing bipolar plates, fuel cell

Abstract

This application relates to the field of fuel cell technology, and discloses a method for preparing bipolar plates and a fuel cell. A sacrificial mold is placed in the cavity of a bipolar plate mold, and bipolar plate raw material is placed around the periphery of the sacrificial mold for molding treatment to obtain a pre-formed bipolar plate. The sacrificial mold includes at least one of inorganic mixture, organic mixture, and metal mixture, and the bipolar plate raw material includes graphite and resin powder. A solvent is used to perform a solvent treatment on the pre-formed bipolar plate to remove the sacrificial mold, thereby obtaining the bipolar plate. The method proposed in this application utilizes a sacrificial mold-assisted one-step molding technology to prepare bipolar plates, eliminating the sealing risks at the interface between the two single plates and reducing fuel cell failure problems caused by cracking at the bipolar plate connection.

Description

Technical Field

[0001] This application relates to the field of fuel cell technology, and more specifically, to a method for preparing bipolar plates and a fuel cell. Background Technology

[0002] The bipolar plate (BP) of a fuel cell, also known as a flow field plate, is the "skeleton" of the fuel cell stack. It is stacked with the membrane electrode assembly to form the fuel cell stack. In the fuel cell, it plays a role in supporting, collecting current, providing channels for coolant, and separating oxidant and reductant.

[0003] Fuel cell bipolar plates typically employ a two-plate, three-field structure, consisting of an air field, a hydrogen field, and a water field formed by the combination of a cathode plate and an anode plate. The cathode plate integrates the air channel and water cavity, while the anode plate integrates the hydrogen channel and water cavity. Traditional manufacturing processes require separate processing of the cathode and anode plates, followed by bonding to join the water cavities of the two plates to form a complete bipolar plate. However, this method is not only cumbersome but also presents sealing risks at the bonding interface, making it difficult to meet the long-term operating requirements of high-performance fuel cells.

[0004] It should be noted that the above statements are only used to provide background information related to this application and do not necessarily constitute prior art. Summary of the Invention

[0005] In a first aspect of this application, a method for preparing a bipolar plate is proposed, comprising: placing a sacrificial mold in a cavity of a bipolar plate mold, and placing bipolar plate raw material on the periphery of the sacrificial mold for molding treatment to obtain a pre-formed bipolar plate, wherein the sacrificial mold comprises at least one of an inorganic mixture, an organic mixture, and a metal mixture, and the bipolar plate raw material comprises graphite and resin powder; and performing a solvent treatment on the pre-formed bipolar plate to remove the sacrificial mold to obtain the bipolar plate.

[0006] The method proposed in this application utilizes a sacrificial mold-assisted one-step molding technology to fabricate bipolar plates. Since the cathode and anode plates are integrally molded during the fabrication process, the potential sealing risks caused by sealing the connection between the two plates via an adhesive interface are reduced, significantly minimizing fuel cell failures due to cracking at the plate connection points.

[0007] In some embodiments, at least one of the following conditions is met: the inorganic mixture comprises 90 to 98 parts by weight of a soluble inorganic salt and 1 to 5 parts by weight of a water-soluble binder; the organic mixture comprises 60 to 85 parts by weight of a soluble organic material and 5 to 20 parts by weight of a water-soluble binder; and the metal mixture comprises at least one of nickel, aluminum, zinc, magnesium, copper, and manganese metals.

[0008] In some embodiments, at least one of the following conditions is met: the soluble inorganic salt includes at least one of sodium chloride, sodium sulfate, and sodium carbonate; the soluble organic material includes at least one of high amylose corn starch, polyimide, sucrose, polyethylene glycol, polyvinyl alcohol, chitosan, and paraffin wax; and the water-soluble binder includes at least one of hydroxypropyl methylcellulose, high amylose (amylose content ≥70%), low-polymerization polyvinyl alcohol, sodium carboxymethyl cellulose, guar gum, polyethylene glycol, and gum arabic. This facilitates the complete dissolution and removal of the sacrificial mold.

[0009] In some embodiments, at least one of the following conditions is met: the inorganic mixture further includes 0.1 to 2 parts by weight of filler, the filler including at least one of nano-silica, alumina, silica sand, nano-calcium carbonate, and mica powder; the inorganic mixture further includes 0.5 to 3 parts by weight of surface modifier, the surface modifier including at least one of fluorosilane, aminosilane coupling agent (KH550, KH792), epoxysilane coupling agent (KH560, KH570), and titanate coupling agent (TMC-201, TC-114). This is beneficial for improving the structural accuracy of the sacrificial mold and enhancing the structural stability of the prepared bipolar plate.

[0010] In some embodiments, at least one of the following conditions is met: the organic mixture further comprises 1 to 10 parts by weight of a plasticizer, the plasticizer comprising at least one of glycerol, ethylene glycol, propylene glycol, triethyl citrate, sorbitol, and polyethylene glycol 400; the organic mixture further comprises 1 to 5 parts by weight of an auxiliary agent, the auxiliary agent comprising at least one of sodium stearoyl lactylate, monoglyceride, sucrose fatty acid ester (SE-11), microcrystalline cellulose, sodium alginate, and sorbitan monostearate (Span-60); the organic mixture further comprises 1 to 5 parts by weight of a reinforcing phase, the reinforcing phase comprising at least one of nanocellulose, microfibrillated cellulose, chitosan nanocrystals, lignin nanoparticles, and calcium alginate nanofibers. This is beneficial for improving the structural stability of sacrificial molds.

[0011] In some embodiments, the metal mixture further includes a dopant metal, which includes at least one of copper and manganese, wherein the amount of zinc added is 1 wt% to 3 wt%, the amount of aluminum added is 0.5 wt% to 1 wt%, the amount of copper added is 0.1 wt% to 0.5 wt%, and the amount of manganese added is 0.05 wt% to 0.3 wt%. This is beneficial for improving the dimensional accuracy of the sacrificial mold and increasing the structural accuracy of the prepared bipolar plate.

[0012] In some embodiments, at least one of the following conditions is met: the compressive strength of the sacrificial mold is 2 MPa to 35 MPa; the surface roughness of the sacrificial mold is 0.1 μm to 1.6 μm; and the porosity of the sacrificial mold is 5% to 20%. Therefore, the sacrificial mold exhibits high structural stability during the fabrication of bipolar plates.

[0013] In some embodiments, the molding process includes at least one of injection molding, compression molding, casting, and extrusion molding. This facilitates the fabrication of bipolar plates with internal accommodating spaces of various shapes using sacrificial molds of different shapes.

[0014] In some embodiments, at least one of the following conditions is met: the sacrificial mold comprises an inorganic mixture, and the solvent comprises one of potassium hydroxide, sodium hydroxide, ammonia, and deionized water; the sacrificial mold comprises an organic mixture, and the solvent comprises one of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, amylase, cellulase, ethanol, potassium hydroxide, sodium hydroxide, and deionized water; the sacrificial mold comprises a metal mixture, and the solvent comprises one of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, potassium hydroxide, and sodium hydroxide. This facilitates the safe and efficient removal of the sacrificial mold from the preformed bipolar plate cavity.

[0015] In a second aspect, this application proposes a fuel cell comprising a bipolar plate prepared by the method proposed in this application. Consequently, this fuel cell exhibits high structural stability, high safety, and a long service life. Attached Figure Description

[0016] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0017] Figure 1 This is a schematic diagram of the sacrificial mold in one embodiment of this application; Figure 2 This is a schematic diagram of the process of fabricating a bipolar plate in one embodiment of this application; Figure 3 This is a schematic diagram of the process of preparing a bipolar plate in one embodiment of this application.

[0018] Explanation of reference numerals in the attached figures: Sacrificial mold 1; cathode plate 2; anode plate 3; air flow channel 4; hydrogen flow channel 5; water cavity 6. Detailed Implementation

[0019] The embodiments of this application are described in detail below, with examples of these embodiments shown in the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0020] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit this application; unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0021] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are open-ended expressions, meaning they include what is specified in this application but do not exclude other aspects.

[0022] In the description of this application, all figures disclosed herein, whether or not the words "approximately" or "about" are used, are approximate values. Each figure may vary by less than 10% or by a difference that is considered reasonable by one of the art, such as 1%, 2%, 3%, 4%, or 5%.

[0023] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for a specific parameter, it is also expected that ranges of 60~110 and 80~120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this application, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0024] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0025] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0026] In related technologies, the processing of graphite bipolar plates for fuel cells typically involves a two-step process: First, the cathode and anode plates of the graphite bipolar plate are machined separately through processes such as mechanical cutting, grinding, and milling. Second, the cathode and anode plates are bonded together using methods such as adhesives to obtain a complete bipolar plate. This step-by-step production and assembly process for bipolar plates is complex, and the sealing connection between the cathode and anode plates carries the risk of seal failure, which can lead to numerous problems such as fuel cell performance degradation, shortened lifespan, and safety risks.

[0027] This application proposes a method for fabricating bipolar plates using a sacrificial mold-assisted one-time molding technology. Since the cathode and anode plates are integrally molded during the fabrication process, the potential sealing risks caused by sealing the connection between the two plates via an adhesive interface are reduced. This significantly reduces fuel cell failure problems caused by structural changes in the bipolar plates, such as cracking at the connection point.

[0028] In a first aspect of this application, a method for fabricating a bipolar plate is proposed, comprising: S1: A sacrificial mold is placed in the cavity of a bipolar plate mold, and bipolar plate raw material is placed around the periphery of the sacrificial mold for molding to obtain a pre-formed bipolar plate. The sacrificial mold used in this method has different properties from the graphite-containing material of the bipolar plate. It can be dissolved and removed using a corresponding solvent without damaging the graphite-containing material of the bipolar plate. Therefore, by utilizing the three-dimensional structure of the sacrificial mold, bipolar plates with the flow channels, water cavities, and other structures required for fuel cells can be prepared through one-time molding processes such as assisted injection molding and compression molding.

[0029] In some embodiments, the bipolar plate raw materials include graphite and resin powder.

[0030] In some embodiments, reference Figures 1-3 A sacrificial mold 1 can be used to fabricate bipolar plates with cavity structures, and its processing method is shown in the figure. The sacrificial mold 1 is placed between the cavities of the bipolar plate mold used to fabricate the cathode plate 2 and anode plate 3. The sacrificial mold 1 fills the space within the bipolar plate mold, occupying the space of the internal cavity structures such as the air channel 4, hydrogen channel 5, and water cavity 6. Bipolar plate raw materials are then filled into the mold, and the bipolar plate is integrally formed through injection molding or compression molding. After the above process, a bipolar plate with a complete cavity structure is obtained without additional sealing steps. The cavity structure of the bipolar plate forms an integrated structure with the bipolar plate body, and there are no processing gaps between the cathode plate 2 and anode plate 3, avoiding the defects of separately fabricating the cathode plate 2 and anode plate 3 and then performing subsequent processing or bonding processes. Therefore, by utilizing the dissolvable and removable characteristics of this sacrificial mold, an integrated structure of bipolar plates containing internal structures such as water cavities and air channels can be fabricated, eliminating the sealing risks at the bonding interface from the root, simplifying the process flow, and facilitating the fabrication of bipolar plates with high structural stability. Therefore, the sealing performance of the prepared bipolar plate can be significantly improved, meeting the long-term operation requirements of fuel cells.

[0031] In some embodiments, the sacrificial mold includes at least one of inorganic mixture, organic mixture, and metal mixture.

[0032] In some embodiments, at least one of the following conditions is met: the inorganic mixture comprises 90 to 98 parts by weight of a soluble inorganic salt and 1 to 5 parts by weight of a water-soluble binder; the organic mixture comprises 60 to 85 parts by weight of a soluble organic material and 5 to 20 parts by weight of a water-soluble binder; and the metal mixture comprises at least one of nickel, aluminum, zinc, magnesium, copper, and manganese metals.

[0033] As an example, the mass fraction of soluble inorganic salt in the inorganic mixture may be 90 parts by mass, 91 parts by mass, 92 parts by mass, 93 parts by mass, 94 parts by mass, or 95 parts by mass.

[0034] As an example, the mass fraction of the water-soluble binder in the inorganic mixture may be 1 part, 2 parts, 3 parts, 4 parts, or 5 parts.

[0035] As an example, the mass fraction of soluble organic material in the organic mixture may be 60 parts by mass, 65 parts by mass, 70 parts by mass, 75 parts by mass, or 80 parts by mass.

[0036] As an example, the mass fraction of the water-soluble binder in the organic mixture may be 5 parts by mass, 15 parts by mass, or 20 parts by mass.

[0037] In some embodiments, the soluble inorganic salt includes at least one selected from sodium chloride, sodium sulfate, and sodium carbonate. The aforementioned soluble inorganic salts have superior water solubility and a certain degree of crystal hardness, and can be removed by aqueous solvents. The graphite-containing material itself is insoluble in water, thereby facilitating the complete dissolution and removal of the sacrificial mold.

[0038] As an example, the soluble inorganic salt is high-purity NaCl (purity ≥ 99.5%). High-purity sodium chloride has fewer grain boundary defects, which is beneficial for improving the dimensional stability of the sacrificial mold. It can form a flexible network after curing with a water-soluble binder at low temperature (60℃~80℃), which is beneficial for improving the compressive strength of the sacrificial mold.

[0039] In some embodiments, the soluble organic material includes at least one selected from high-amylose corn starch (amylose content ≥70%), polyimide, sucrose, polyethylene glycol, polyvinyl alcohol, chitosan, and paraffin wax. The aforementioned soluble organic materials have high crystallinity, low dimensional shrinkage after molding, and high stability at the molding temperature containing graphite materials, which is beneficial for improving the basic rigidity of the sacrificial mold. This, in turn, helps to improve the processing accuracy of the sacrificial mold and the bipolar plates it assists in preparing.

[0040] In some embodiments, the water-soluble binder includes at least one of hydroxypropyl methylcellulose (HPMC), high-amylose starch, low-polymerization-degree polyvinyl alcohol (PVA1788), sodium carboxymethyl cellulose, guar gum, polyethylene glycol, and gum arabic. The aforementioned water-soluble binder can form a network structure in inorganic or organic mixtures, improving the compressive strength of the sacrificial mold. This helps reduce creep deformation of the sacrificial mold during bipolar plate forming, improving the precision of the prepared bipolar plate.

[0041] In some embodiments, the inorganic mixture further includes 0.1 to 2 parts by weight of filler, wherein the filler comprises at least one selected from nano-silica, alumina, silica sand, nano-calcium carbonate, and mica powder. The aforementioned filler can be uniformly dispersed in the gaps of the inorganic mixture, reducing the porosity of the inorganic material. This helps to reduce the surface roughness of the sacrificial mold and decrease the profile deviation of the prepared bipolar plate.

[0042] In some embodiments, the inorganic mixture further includes 0.5 to 3 parts by weight of a surface modifier, wherein the surface modifier includes at least one selected from fluorosilanes, aminosilane coupling agents (KH550, KH792), epoxysilane coupling agents (KH560, KH570), and titanate coupling agents (TMC-201, TC-114). The aforementioned surface modifier can effectively block substances such as moisture in the environment that affect the chemical stability of soluble inorganic salt crystals, which helps reduce structural distortion of the sacrificial mold caused by deliquescence and other reasons. Therefore, it is beneficial to improve the structural stability of the sacrificial mold.

[0043] In some embodiments, the organic mixture further includes 1 to 10 parts by weight of a plasticizer, wherein the plasticizer includes at least one selected from glycerol, ethylene glycol, propylene glycol, triethyl citrate, sorbitol, and polyethylene glycol 400. The aforementioned plasticizer helps improve the toughness of the sacrificial mold, reduces cracking during its preparation and demolding processes, and improves the stability of the sacrificial mold during bipolar plate processing.

[0044] In some embodiments, the organic mixture further includes 1 to 5 parts by weight of an additive, wherein the additive includes at least one selected from sodium stearoyl lactylate (SSL), monoglyceride, sucrose fatty acid ester (SE-11), microcrystalline cellulose, sodium alginate, and sorbitan monostearate (Span-60). Sodium stearoyl lactylate, as an additive, forms a hydrophobic film on the surface of the sacrificial mold, which can reduce dimensional deviations in the sacrificial mold caused by the moisture absorption and expansion of soluble organic materials, and also assists in the demolding process during the preparation of the sacrificial mold.

[0045] In some embodiments, the organic mixture further includes 1 to 5 parts by weight of a reinforcing phase, wherein the reinforcing phase includes at least one selected from nanocellulose, microfibrillated cellulose, chitosan nanocrystals, lignin nanoparticles, and calcium alginate nanofibers. Nanocellulose, as a reinforcing phase, can fill the micropores between granular soluble organic material particles. This reduces the surface roughness of the sacrificial mold and improves the precision of the prepared bipolar plate internal cavity structure.

[0046] In some embodiments, the metal mixture further includes a dopant metal, which includes at least one of copper and manganese. The amount of zinc added is 1 wt% to 3 wt%, the amount of aluminum added is 0.5 wt% to 1 wt%, the amount of copper added is 0.1 wt% to 0.5 wt%, and the amount of manganese added is 0.05 wt% to 0.3 wt%. Copper, as a dopant metal, can reduce the cutting resistance of the metal mixture, reduce burrs and errors formed during the machining of the sacrificial die, and improve the dimensional control accuracy during the finishing of the sacrificial die. Manganese-copper, as a dopant metal, can suppress the formation of grains in the metal mixture at high temperatures, which is beneficial for reducing the surface roughness of the sacrificial die and improving the accuracy of the prepared bipolar plate internal cavity structure.

[0047] In some embodiments, the compressive strength of the sacrificial mold is 2 MPa to 35 MPa. This reduces the deformation of the sacrificial mold under pressure during the preparation of the bipolar plate, thereby improving the quality of the prepared bipolar plate.

[0048] In some embodiments, the surface roughness of the sacrificial mold is 0.1 μm to 1.6 μm. This improves the smoothness of the inner surface of the prepared bipolar plate.

[0049] In some embodiments, the porosity of the sacrificial mold is 5% to 20%.

[0050] In some embodiments, the sacrificial mold is prepared by at least one of injection molding, compression molding, casting molding, and extrusion molding.

[0051] As an example, sacrificial molds can be prepared using organic mixtures containing polyethylene glycol or polyimide as the main components. Specifically, organic mixtures can be prepared by mixing ingredients according to the corresponding mixture formula, and the plasticized or dry-mixed organic mixtures can be injected into the mold for injection molding. After cooling and demolding, the sacrificial molds can be obtained by drying or trimming.

[0052] As an example, inorganic mixtures can be dry-mixed and then molded and cured at low temperature, or organic mixtures can be plasticized and then molded and cooled under pressure, or metal powder mixtures can be mixed and then molded. Subsequently, they can be demolded, trimmed, dried, sintered and finished to obtain sacrificial molds.

[0053] As an example, organic mixtures (such as starch and chitosan) and some inorganic mixtures can be mixed and processed to prepare a liquid or gel state. After being poured into a mold for casting, the mixture can be cured at room temperature or low temperature. After demolding, it can be dried or trimmed to obtain a sacrificial mold.

[0054] As an example, different mixtures can be uniformly mixed according to the formula ratio, extruded and molded using an extruder, and then, depending on the type of mixture, processed by low-temperature curing (for inorganic mixtures), cooling and drying (for organic mixtures), and sintering finishing (for metal mixtures) to obtain a sacrificial mold.

[0055] In some embodiments, the molding process includes at least one of injection molding, compression molding, casting molding, and extrusion molding.

[0056] As an example, the molding process for preparing bipolar plates includes: preparing a mixture of graphite powder and resin (e.g., 80% graphite powder and 20% phenolic resin), drying and pulverizing it, and then preheating it together with a sacrificial mold. The mixture is fed into the hopper of an injection molding machine. The mixture is heated and melted inside the injection molding machine barrel, and after being pressurized by the screw, it is injected through a nozzle into a closed mold cavity containing a pre-formed bipolar plate mold. After holding the pressure and cooling, it is demolded to obtain a graphite bipolar plate with a water-filled mold. Thus, under the polymer melting temperature and pressure, the mixture flows and fills the mold cavity of the bipolar plate mold, and after holding the pressure and solidifying, it is demolded to form a pre-formed bipolar plate with the sacrificial mold located in the cavity.

[0057] S2: The preformed bipolar plate is treated with a solvent to remove the sacrificial mold, thereby obtaining the bipolar plate. refer to Figure 3 The fluidity of the solvent can efficiently remove the sacrificial mold 1 from the cavity of the preformed bipolar plate. By selecting a suitable solvent, the impact on the bipolar plate structure can be controlled while removing the sacrificial mold 1, thereby obtaining a bipolar plate with a cavity structure including a pre-formed internal air channel 4, hydrogen channel 5, and water cavity 6.

[0058] In some embodiments, the sacrificial mold comprises an inorganic mixture, and the solvent comprises one of potassium hydroxide, sodium hydroxide, ammonia, and deionized water. This facilitates the safe and efficient removal of the sacrificial mold from the preformed bipolar plate cavity.

[0059] In some embodiments, the sacrificial mold comprises an organic mixture, and the solvent comprises one of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, amylase, cellulase, ethanol, potassium hydroxide, sodium hydroxide, or deionized water. This facilitates the safe and efficient removal of the sacrificial mold from the preformed bipolar plate cavity.

[0060] In some embodiments, the sacrificial mold comprises a metal mixture, and the solvent comprises one of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, potassium hydroxide, and sodium hydroxide. This facilitates the safe and efficient removal of the sacrificial mold from the preformed bipolar plate cavity.

[0061] As an example, the removal of the sacrificial mold from the NaCl-soluble inorganic salt inorganic mixture includes: placing the pre-formed bipolar plate obtained in S1 in water (room temperature - 60°C) for 0.1 h to 1 h to remove the sacrificial mold from the pre-formed bipolar plate. Thus, the sodium chloride main structure of the sacrificial mold dissolves in water, and the water-soluble binder contains a large number of hydroxyl groups, which are easily dissolved in water, allowing the filler to be discharged with the solution. Therefore, the sacrificial mold can be gently removed without damaging the bipolar plate structure.

[0062] As an example, sacrificial molds containing nickel (Ni) metal mixtures can be dissolved by immersing them in a solvent containing nitric acid (20%~50% nitric acid (HNO3), 2%~10% hydrogen peroxide (H2O2) and deionized water) at room temperature for 2h~12h.

[0063] As an example, a sacrificial mold containing an aluminum metal mixture can be removed by a solvent (sodium hydroxide solution).

[0064] As an example, sacrificial molds containing polyimide organic blends can be removed by a solvent (65%~70% concentrated nitric acid or 10%~20% potassium hydroxide solution).

[0065] As an example, sacrificial molds containing sucrose organic blends can be removed using a solvent (water).

[0066] As an example, sacrificial molds containing high amylose organic mixtures can be removed by soaking in a solvent (0.5% α-amylase solution) at 50°C for 1 to 30 minutes.

[0067] In a second aspect, this application proposes a fuel cell comprising a bipolar plate prepared by the method proposed in this application. Consequently, this fuel cell exhibits high structural stability, high safety, and a long service life.

[0068] The following specific embodiments illustrate the solution of this application. It should be noted that these embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0069] Example 1 The sacrificial mold employs an inorganic mixture comprising 96 parts by mass of high-purity NaCl, 1.5 parts by mass of water-soluble binder hydroxypropyl methylcellulose (HPMC), 1.2 parts by mass of filler nano-silica, and 1.3 parts by mass of surface modifier fluorosilane.

[0070] The sacrificial mold is placed in the cavity of the bipolar plate mold and extruded to obtain a preformed bipolar plate.

[0071] The preformed bipolar plate was treated with a solvent water solution. The preformed bipolar plate was placed in water (60°C) for 30 minutes, and the sacrificial mold was removed to obtain the bipolar plate.

[0072] Example 2 The sacrificial mold employs an inorganic mixture comprising 92 parts by mass of high-purity NaCO3, 4 parts by mass of water-soluble binder hydroxypropyl methylcellulose (HPMC), 2 parts by mass of filler nano-silica, and 2 parts by mass of surfactant aminosilane KH550.

[0073] The sacrificial mold is placed in the cavity of the bipolar plate mold and extruded to obtain a preformed bipolar plate.

[0074] The preformed bipolar plate was treated with a solvent water solution. The preformed bipolar plate was placed in water (60°C) for 30 minutes, and the sacrificial mold was removed to obtain the bipolar plate.

[0075] Example 3 The sacrificial mold employs an organic compound comprising 80 parts by weight of high amylose corn starch (amylose content ≥70%), 10 parts by weight of water-soluble binder low-polymer polyvinyl alcohol (PVA1788), 2 parts by weight of water-soluble binder hydroxypropyl methylcellulose, 5 parts by weight of plasticizer glycerin, 1.5 parts by weight of auxiliary agent (anti-hygroscopic agent) sodium stearoyl lactylate (SSL), and 1.5 parts by weight of reinforcing phase nanocellulose.

[0076] The sacrificial mold is placed in the cavity of the bipolar plate mold and extruded to obtain a preformed bipolar plate.

[0077] The preformed bipolar plate was treated with a solvent to remove the mold, and the preformed bipolar plate was placed in an α-amylase solution (concentration 0.5%, 50℃, pH 5.5~6.5) for 15 min. The sacrificial mold was then removed to obtain the bipolar plate.

[0078] Example 4 The sacrificial mold employs an organic compound comprising 65 parts by weight of chitosan, 3 parts by weight of a water-soluble binder low-polymerization polyvinyl alcohol (PVA1788), 10 parts by weight of a plasticizer glycerin, 3 parts by weight of an auxiliary agent (anti-hygroscopic agent) sodium stearoyl lactylate (SSL), 2 parts by weight of a reinforcing phase nanocellulose, and 17 parts by weight of citric acid.

[0079] The sacrificial mold is placed in the cavity of the bipolar plate mold and extruded to obtain a preformed bipolar plate.

[0080] The preformed bipolar plate is treated with a solvent to remove the mold. The preformed bipolar plate is then placed in a 1%-2% dilute acetic acid solution (65°C) for 30 minutes to remove the sacrificial mold and obtain the bipolar plate.

[0081] Example 5 The sacrificial mold employs an organic compound comprising 75 parts by weight of sucrose, 10 parts by weight of the water-soluble binder hydroxypropyl methylcellulose, 6 parts by weight of the plasticizer ethylene glycol, 3 parts by weight of the auxiliary agent sodium alginate, 2 parts by weight of the auxiliary agent sorbitan monostearate, and 4 parts by weight of the reinforcing phase chitosan nanocrystals.

[0082] The sacrificial mold is placed in the cavity of the bipolar plate mold and extruded to obtain a preformed bipolar plate.

[0083] The preformed bipolar plate was treated with a solvent to remove the mold, and the preformed bipolar plate was immersed in hot water at 70°C for 30 minutes. The sacrificial mold was then removed to obtain the bipolar plate.

[0084] Example 6 The sacrificial mold employs an organic compound comprising 67 parts by weight of polyethylene glycol (PEG6000), 18 parts by weight of a water-soluble binder low-polymerization-degree polyvinyl alcohol (PVA1788), 7 parts by weight of a plasticizer glycerin, 3 parts by weight of an auxiliary agent (anti-hygroscopic agent) sodium stearoyl lactylate (SSL), and 3 parts by weight of a reinforcing phase nanocellulose.

[0085] The sacrificial mold is placed in the cavity of the bipolar plate mold and extruded to obtain a pre-formed bipolar plate. The pre-formed bipolar plate is then treated with a solvent, and the processed pre-formed bipolar plate is immersed in hot water at 80°C for 30 minutes. The sacrificial mold is then removed to obtain the bipolar plate.

[0086] Example 7 The sacrificial mold employs a metal mixture comprising 96 wt% nickel, 2.5 wt% zinc, 1 wt% aluminum, 0.3 wt% copper, and 0.2 wt% manganese.

[0087] The sacrificial mold is placed in the cavity of the bipolar plate mold and extruded to obtain a preformed bipolar plate.

[0088] The preformed bipolar plate is treated with a solvent by soaking it in a mixed solution of 30% nitric acid, 5% hydrogen peroxide and deionized water for 6 hours at room temperature. The sacrificial mold is then removed to obtain the bipolar plate.

[0089] Comparative Example 1 The sacrificial mold employs an inorganic mixture comprising 87 parts by mass of high-purity NaCl, 8 parts by mass of water-soluble binder hydroxypropyl methylcellulose (HPMC), 3.5 parts by mass of filler nano-silica, and 1.5 parts by mass of surface modifier fluorosilane.

[0090] The sacrificial mold is placed in the cavity of the bipolar plate mold and extruded to obtain a preformed bipolar plate.

[0091] The preformed bipolar plate was treated with a solvent water solution. The preformed bipolar plate was then placed in water at 60°C for 30 minutes. The sacrificial mold was then removed to obtain the bipolar plate.

[0092] Comparative Example 2 The sacrificial mold employs an organic compound comprising 90 parts by weight of high amylose corn starch (amylose content ≥70%), 3 parts by weight of water-soluble binder low-polymer polyvinyl alcohol (PVA1788), 0.8 parts by weight of plasticizer glycerin, 2.2 parts by weight of auxiliary agent (anti-hygroscopic agent) sodium stearoyl lactylate (SSL), 3 parts by weight of reinforcing phase nanocellulose, and 1 part by weight of auxiliary agent sodium alginate.

[0093] The sacrificial mold is placed in the cavity of the bipolar plate mold and extruded to obtain a preformed bipolar plate.

[0094] The preformed bipolar plate was treated with a solvent to remove the mold, and the preformed bipolar plate was placed in an α-amylase solution (concentration 0.5%, 50℃) for 15 min. The sacrificial mold was then removed to obtain the bipolar plate.

[0095] Comparative Example 3 A sacrificial mold containing an inorganic mixture is used, the inorganic mixture comprising 80 parts by weight of high-purity NaCO3, 14 parts by weight of water-soluble binder hydroxypropyl methylcellulose (HPMC), 2 parts by weight of filler nano-silica, and 4 parts by weight of surfactant aminosilane KH550.

[0096] The sacrificial mold is placed in the cavity of the bipolar plate mold and extruded to obtain a preformed bipolar plate.

[0097] The preformed bipolar plate was treated with a solvent water solution. The preformed bipolar plate was placed in water (60°C) for 30 minutes, and the sacrificial mold was removed to obtain the bipolar plate.

[0098] Test method: 1. The conductivity test adopts the four-probe method. At room temperature (25℃±2℃), the bipolar plate sample is cut into 10mm×10mm×2mm size. The four-probe tester is used to measure the sample at different positions 5 times, and the average value is taken as the conductivity of the bipolar plate.

[0099] 2. Bending strength test The bipolar plate was processed into a 60mm x 25mm x 2mm sample. A universal testing machine was used to apply a uniform load to the sample at a loading rate of 1mm / min until the sample fractured. The fracture load value was then recorded. The test standard was GB / T 20042.6-2024.

[0100] 3. Sealing performance test The bipolar plates were assembled into a simulated fuel cell single cell, and nitrogen gas at 0.1 MPa was introduced. The soap bubble method was used to detect whether bubbles were generated at the bipolar plate seal. If no bubbles appeared within 5 minutes, the sealing performance was qualified. At the same time, the nitrogen leakage rate was recorded, and the leakage rate was ≤1x10. -6 Pa m 3 / s.

[0101] Test results: See Table 1.

[0102] Table 1

[0103] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.

[0104] In this application, the order in which the steps are written does not imply a strict execution order and does not limit the implementation process. The specific execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps in this application can be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0105] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing a bipolar plate, characterized in that, include: A sacrificial mold is placed in the cavity of a bipolar plate mold, and bipolar plate raw material is placed on the periphery of the sacrificial mold for molding treatment to obtain a pre-formed bipolar plate. The sacrificial mold includes at least one of inorganic mixture, organic mixture, and metal mixture, and the bipolar plate raw material includes graphite and resin powder. The preformed bipolar plate is subjected to a solvent treatment to remove the sacrificial mold, thereby obtaining the bipolar plate.

2. The method according to claim 1, characterized in that, At least one of the following conditions must be met: The inorganic mixture includes 90 to 98 parts by weight of soluble inorganic salt and 1 to 5 parts by weight of water-soluble binder. The organic mixture comprises 60 to 85 parts by weight of soluble organic material and 5 to 20 parts by weight of water-soluble binder. The metal mixture includes at least one of nickel, aluminum, zinc, magnesium, copper, and manganese.

3. The method according to claim 2, characterized in that, At least one of the following conditions must be met: The soluble inorganic salt includes at least one of sodium chloride, sodium sulfate, and sodium carbonate. The soluble organic materials include high-amylose corn starch, polyimide, sucrose, polyethylene glycol, polyvinyl alcohol, chitosan, and paraffin wax; The water-soluble binder includes at least one of hydroxypropyl methylcellulose, high amylose, low degree of polymerization polyvinyl alcohol, sodium carboxymethyl cellulose, guar gum, polyethylene glycol, and gum arabic.

4. The method according to any one of claims 1 to 3, characterized in that, At least one of the following conditions must be met: The inorganic mixture also includes 0.1 to 2 parts by weight of filler, wherein the filler includes at least one of nano-silica, alumina, silica sand, nano-calcium carbonate, and mica powder; The inorganic mixture further includes 0.5 to 3 parts by weight of a surface modifier, wherein the surface modifier includes at least one of fluorosilane, aminosilane coupling agent, epoxysilane coupling agent, and titanate coupling agent.

5. The method according to any one of claims 1 to 3, characterized in that, At least one of the following conditions must be met: The organic mixture also includes 1 to 10 parts by weight of a plasticizer, wherein the plasticizer includes at least one of glycerol, ethylene glycol, propylene glycol, triethyl citrate, sorbitol, and polyethylene glycol; The organic mixture also includes 1 to 5 parts by weight of additives, which include at least one of sodium stearoyl lactylate, monoglyceride, sucrose fatty acid ester, microcrystalline cellulose, sodium alginate, sorbitan monostearate, and ammonium polyphosphate. The organic mixture further includes 1 to 5 parts by weight of a reinforcing phase, wherein the reinforcing phase includes at least one of nanocellulose, microfibrillated cellulose, chitosan nanocrystals, lignin nanoparticles, and calcium alginate nanofibers.

6. The method according to any one of claims 1 to 3, characterized in that, The metal mixture further includes a dopant metal, which includes at least one of copper and manganese, wherein the amount of copper added is 0.1wt% to 0.5wt% and the amount of manganese added is 0.05wt% to 0.3wt%.

7. The method according to any one of claims 1 to 3, characterized in that, At least one of the following conditions must be met: The compressive strength of the sacrificial mold is 2MPa~35MPa; The surface roughness of the sacrificial mold is 0.1 μm to 1.6 μm; The porosity of the sacrificial mold is 5% to 20%.

8. The method according to any one of claims 1 to 3, characterized in that, The molding process includes at least one of injection molding, compression molding, casting molding, and extrusion molding.

9. The method according to any one of claims 1 to 3, characterized in that, At least one of the following conditions must be met: The sacrificial mold comprises an inorganic mixture, and the solvent comprises one of potassium hydroxide, sodium hydroxide, ammonia, and deionized water. The sacrificial mold comprises an organic mixture, and the solvent comprises one of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, amylase, cellulase, ethanol, potassium hydroxide, sodium hydroxide, and deionized water. The sacrificial mold comprises a metal mixture, and the solvent comprises one of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, potassium hydroxide, and sodium hydroxide.

10. A fuel cell, characterized in that, Includes bipolar plates prepared by the method described in any one of claims 1 to 9.

Images