A fuel cell composite bipolar plate based on liquid metal anchoring and electrochemical deposition and a method for manufacturing the same

Abstract

The application relates to the technical field of fuel cells, in particular to a fuel cell composite bipolar plate based on liquid metal anchoring and electrochemical deposition, which presents an integrated layered structure from outside to inside, and the structural arrangement is as follows: a flaky graphite / resin layer, a polyaniline / carbon nanotube composite film layer, a liquid metal modified foam nickel skeleton layer, a polyaniline / carbon nanotube composite film layer and a flaky graphite / resin layer; the liquid metal modified foam nickel skeleton layer adopts foam nickel containing nanoscale pores and rough etching sites as a three-dimensional bottom skeleton, and the surface and pores are fixedly anchored with liquid gold. Nano-scale etching sites are constructed on the surface of the foam nickel by an acid etching-weak oxidation etching two-step method, and liquid metal is introduced, so that the liquid metal can be fixedly anchored and uniformly dispersed, and the high fluidity and excellent conductivity of the liquid metal can be used to fully fill the porous defects, and a continuous end-to-end three-dimensional conductive path is constructed.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, specifically to a composite bipolar plate for fuel cells based on liquid metal anchoring and electrochemical deposition, and its preparation method. Background Technology

[0002] As a core component of proton exchange membrane fuel cells (PEMFCs), bipolar plates perform multiple functions, including distributing reactant gases, collecting current, transferring heat, and providing mechanical support. To meet the stringent requirements of commercial applications, bipolar plate materials must simultaneously possess excellent electrical and thermal conductivity, good corrosion resistance, and reliable airtightness.

[0003] Existing technologies attempt to introduce a three-dimensional conductive framework into composite bipolar plate material systems to construct a continuous and efficient conductive network. Patent CN119526670A proposes impregnating soft-cut carbon fiber foam in liquid resin and hot-pressing it together with pre-cooled expanded graphite to form a sandwich structure. Another patent, CN121215797A, proposes using metal foam as a framework and ultrasonically blending polyaniline and carbon nanotubes onto the pore walls to form a conductive intermediate layer, attempting to improve interfacial compatibility.

[0004] Existing conventional technologies still have significant limitations and technical defects. The interfacial bonding between the soft-cut carbon fiber skeleton and expanded graphite mainly relies on physical interlocking, which is prone to delamination during long-term service, leading to a decline in electrical and mechanical properties. The interfacial bonding strength of conventional physically coated conductive fillers in metal foam is limited, the filler is prone to detachment, and physical coating alone cannot completely block the penetration of acidic media in PEMFCs, leaving the metal components at a high risk of corrosion. Although liquid metals possess outstanding electrical and thermal conductivity and wetting properties, their interfacial compatibility with graphite-resin systems is extremely poor, and direct introduction may even exacerbate the corrosion risk in acidic environments. These inherent contradictions have consistently hindered substantial breakthroughs in the overall performance of composite bipolar plates. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a composite bipolar plate for fuel cells based on liquid metal anchoring and electrochemical deposition, and its preparation method. Through multi-level structural design and in-situ interface modification, the synergistic optimization of conductivity, mechanical properties and corrosion resistance is achieved.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: a composite bipolar plate for fuel cells based on liquid metal anchoring and electrochemical deposition, wherein the composite bipolar plate presents an integrated layered structure from the outside to the inside, and the structure is arranged in the following order: flake graphite / resin layer, polyaniline / carbon nanotube composite film layer, liquid metal modified nickel foam skeleton layer, polyaniline / carbon nanotube composite film layer and flake graphite / resin layer; The liquid metal modified nickel foam skeleton layer uses nickel foam containing nanoscale pores and rough etching sites as a three-dimensional bottom skeleton, with liquid metal anchored at fixed points on the surface and in the pores. A conductive composite film of polyaniline and carbon nanotubes, constructed by electrochemical deposition, is grown in situ on the surface of the liquid metal modified nickel foam skeleton layer.

[0007] Preferably, the thickness of the three-dimensional nickel foam substrate is 1 mm and the porosity is 90 ppi; In the overall mass proportion of the composite bipolar plate, the nickel foam skeleton accounts for 12% to 14%, the liquid metal accounts for 2% to 3%, and the polyaniline / carbon nanotube composite film accounts for 0.8% to 1.5%.

[0008] Preferably, the composite bipolar plate has a planar conductivity ≥ 384.6 S / cm and an area resistivity ≤ 7.47 mΩ·cm. 2 Mechanical bending strength ≥ 57.04 MPa; surface water contact angle ≥ 106.4°; corrosion current density in corrosive media ≤ 1 μA / cm² 2 .

[0009] This invention also provides a method for preparing a composite bipolar plate for a fuel cell based on liquid metal anchoring and electrochemical deposition, characterized by comprising the following steps: S1. Multi-stage surface modification treatment of nickel foam The nickel foam was completely immersed in a 10 vol.% HCl solution and ultrasonically vibrated for 10 min. It was then rinsed repeatedly with deionized water until neutral and dried in a vacuum drying oven at 60°C. The dried nickel foam was then immersed in a mixed solution containing 10 wt.% Na2SO4 and 5 wt.% NaH2PO2 and allowed to react at room temperature for 15 min to remove the oxide layer and induce nanoscale pores and rough interface structures on the nickel metal framework surface. After the reaction, it was rinsed and vacuum dried to obtain surface-etched nickel foam material. S2. Introduction of liquid metal vacuum impregnation The foamed nickel material obtained in step S1 was completely immersed in a liquid metal dispersion and continuously immersed in a vacuum pressure device at 60°C for 2 hours to allow the liquid metal nanoparticles to penetrate and anchor into the pores, thereby obtaining a liquid metal modified foamed nickel skeleton layer. S3. In-situ deposition and coating of polyaniline / carbon nanotube composite layer Using the liquid metal-modified nickel foam framework layer obtained in step S2 as the working electrode, in-situ deposition was performed in a composite electrolyte using a three-electrode system via cyclic voltammetry. The reference electrode was a saturated calomel electrode, and the counter electrode was a platinum sheet electrode. At room temperature, the voltage range was set to -0.2 to 1.0 V, the scan rate was 80 mV / s, and 50 cycles were performed continuously. After scanning, the residue was peeled off and vacuum dried to obtain a functional core framework with a polyaniline / carbon nanotube composite film coating on the surface. S4. Preparation of graphite-resin layer powder substrate Solid thermosetting resin was dissolved in acetone solvent at a solid-liquid mass-volume ratio of 1g:25mL. After the resin was dissolved, flake graphite powder was mixed in and ultrasonically dispersed for 60min, while maintaining the operation with a magnetic stirrer for 60min. The mixture was then dried at 60℃ for 12h to volatilize free acetone and a homogeneous graphite-resin mixed powder was collected. S5. High-temperature molding and lamination curing The graphite-resin mixed powder obtained in step S4 is evenly spread on the upper and lower surfaces of the bipolar plate. It is then bonded and stacked with the functional core skeleton obtained in step S3 and placed in a hot press mold. A surface pressure of 15 MPa is applied and the temperature is raised to 150°C. Under this condition, the pressure is maintained and cured for 1 hour. After natural cooling, the plate is demolded to obtain the composite bipolar plate.

[0010] Preferably, in step S2, the liquid metal dispersion uses gallium-indium alloy as the liquid metal source, sodium dodecyl sulfate as the dispersant, and ethanol as the carrier solvent.

[0011] Preferably, in step S3, the preparation process of the composite electrolyte is as follows: Preparation of aqueous dispersion of carbon nanotubes: Carbon nanotube powder and sodium dodecylbenzenesulfonate were injected into deionized water and ultrasonically dispersed for 2 hours; Preparation of acidic aniline solution: Concentrated hydrochloric acid is added dropwise to deionized water to form a diluted hydrochloric acid solution with a concentration of 0.5 mol / L. Liquid aniline monomer is then added dropwise and mechanically stirred until miscible. Liquid phase blending: The aqueous dispersion of carbon nanotubes and the acidic aniline solution were mixed in proportion and magnetically stirred at room temperature for 1 h; the resulting composite electrolyte contained 0.037–0.183 mol / L of aniline monomer and 0.2–0.8 mg / mL of carbon nanotubes.

[0012] Preferably, in the composite electrolyte, the concentration of aniline monomer is 0.146 mol / L and the concentration of carbon nanotubes is 0.4 mg / mL.

[0013] Preferably, in step S4, the solid thermosetting resin is selected from one or more of epoxy vinyl resin, epoxy resin, and phenolic resin; the dry weight ratio of the flake graphite powder to the solid thermosetting resin is 4:1.

[0014] This invention provides a composite bipolar plate for fuel cells based on liquid metal anchoring and electrochemical deposition, and its preparation method. It has the following beneficial effects: 1. This invention constructs nanoscale corrosion sites on the surface of nickel foam using a two-step method of acid etching and weak oxidation etching, and introduces liquid metal to anchor and uniformly disperse the liquid metal. Relying on its high fluidity and excellent conductivity, the liquid metal fully fills the porous defects, constructing a continuous end-to-end three-dimensional conductive path, which greatly improves the overall charge transport capability of the composite bipolar plate, resulting in a leap in the planar conductivity of the product to 384.6 S / cm.

[0015] 2. This invention constructs a polyaniline / carbon nanotube composite film in situ on the surface of a liquid metal modified nickel foam skeleton using an electrochemical deposition method. This operation completely changes the drawback of poor adhesion of conventional physical coating, induces carbon nanotubes to be uniformly coated and fixed during the polymerization process, forming a highly dense interface reinforcement layer. This significantly improves the structural compatibility between the liquid metal substrate and the external graphite-resin matrix, suppresses the generation of interface cracks during the stress process, and promotes the mechanical bending strength of the composite plate to reach above 57.04 MPa.

[0016] 3. This invention utilizes the dense physical barrier and chemical corrosion protection provided by the in-situ grown polyaniline / carbon nanotube composite film. This film structure effectively isolates the inner liquid metal and the bottom foamed nickel from direct exposure in the acidic fuel cell operating environment, fundamentally blocking the microscopic pathways through which corrosive media penetrate the metal skeleton. This ensures that the metal skeleton is not prone to electrochemical dissolution reactions, thus firmly limiting the corrosion current density of the composite bipolar plate to 1 μA / cm under harsh operating conditions. 2 Within the safe range.

[0017] 4. The integrated sandwich layered structure constructed in this invention deeply integrates the flake graphite surface layer with the liquid metal functional framework. This multi-dimensional thermally conductive network design breaks through the physical limitation of excessive interlayer thermal resistance in traditional composite materials, enabling the waste heat generated during operation to dissipate rapidly along the continuous metal-carbon-based network. This achieves synergistic enhancement of the composite bipolar plate's in-plane and out-of-plane omnidirectional thermal conductivity, giving the bipolar plate a thermal conductivity as high as 12.74 W·m. -1 ·K -1 Out-of-plane thermal conductivity. Attached Figure Description

[0018] Figure 1 The surface morphology of nickel foam after treatment with a mixed solution of Na2SO4 and NaH2PO2; Figure 2 The surface morphology of nickel foam after vacuum impregnation with liquid metal; Figure 3 The surface morphology of nickel foam after vacuum impregnation with liquid metal at high magnification; Figure 4 The surface morphology of nickel foam after electrochemical deposition of polyaniline / carbon nanotubes; Figure 5 The surface morphology of the composite bipolar plate prepared for the example; Figure 6 The image shows a physical sample of the composite bipolar plate prepared for this example. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1: like Figure 1-6 As shown, this embodiment of the invention provides a method for preparing a composite bipolar plate for a fuel cell based on liquid metal anchoring and electrochemical deposition, comprising the following steps: S1. Surface modification treatment of nickel foam Commercially available nickel foam with a nominal thickness of 1 mm and an initial porosity of 90 ppi was used as the three-dimensional substrate. The cut nickel metal skeleton components were thoroughly immersed in a pre-prepared 10 vol.% HCl aqueous solution. Ultrasonic cleaning was used with assisted vibration for 10 minutes to forcefully peel off the native oxide film and processing residues adhering to the nickel phase surface. After initial acid washing, the components were transferred to a pure water rinsing station, where continuous reciprocating rinsing with large volumes of deionized water was applied until the collected waste liquid tested and showed absolute neutrality. The cleaned nickel foam was then rapidly transferred to a drying oven under vacuum and at a constant temperature of 60°C for thorough drying. To further etch the ideal anchoring interface structure at the microscopic level, the dried substrate components were directly immersed in a specific weakly oxidizing mixed solution containing 10 wt.% Na2SO4 and 5 wt.% NaH2PO2. The reaction vessel was kept at room temperature for 15 minutes. Through the weak oxidation etching effect at the interface, numerous irregularly distributed nanoscale micropores were induced on the originally smooth nickel metal framework, accompanied by a rough microstructure. The etched and modified material was then subjected to final deionized water rinsing and secondary vacuum drying to obtain a customized nickel foam material with highly active anchoring sites. Its characteristic surface morphology is as follows: Figure 1 As shown.

[0021] S2. Liquid metal anchoring A specific ratio of gallium-indium alloy was used as the main source material for liquid metal, along with sodium dodecyl sulfate (SDS) as a stabilizing dispersant. Both were suspended in an ethanol carrier solvent to construct a liquid metal dispersion. Modified nickel foam monomers were then immersed in a sealed tank containing this dispersion. The temperature of the processing environment was controlled to 60°C, and a vacuum pump was activated to maintain a vacuum pressure for continuous immersion for 2 hours. This allowed the liquid metal nanoparticles to fully penetrate and anchor to the etched pore sites of the nickel foam framework, resulting in a liquid metal-modified nickel foam composite substrate (denoted as LM@NI), with 0.29 g of liquid metal and approximately 1.25 g of nickel foam. After this process, a liquid metal-modified nickel foam framework layer was produced, with the characteristic morphology as shown below. Figure 2 and under high magnification Figure 3 As shown.

[0022] S3. Electrochemically deposited PANI / CNTs composite layer Using the liquid metal-modified nickel foam composite substrate obtained in step (2) as the working electrode, a CNTs and PANI composite layer was deposited in situ on its surface by cyclic voltammetry (CV). First, the composite electrolyte was prepared: 0.4 mg / mL of CNTs and a certain amount of sodium dodecylbenzenesulfonate (SDBS) were added to deionized water and ultrasonically dispersed for 2 h to obtain an aqueous dispersion of CNTs; 15 mL of concentrated hydrochloric acid was slowly added dropwise to 135 mL of deionized water and magnetically stirred until homogeneous to prepare a 0.5 mol / L dilute hydrochloric acid solution, and then 0.146 mol / L aniline monomer was added dropwise and stirred continuously until completely dissolved to obtain an acidic aniline solution; the above CNTs dispersion and acidic aniline solution were mixed in proportion and magnetically stirred at room temperature for 1 h to ensure that CNTs and aniline molecules were fully and uniformly dispersed to obtain the composite electrolyte. Subsequently, a three-electrode system was used, with LM@NI as the working electrode, a saturated calomel electrode (SCE) as the reference electrode, and a platinum sheet as the counter electrode. CV scanning was performed at room temperature, with deposition parameters set as follows: voltage range -0.2~1.0 V (vs SCE), scan rate 80 mV / s, and 50 scan cycles. After deposition, the sample was repeatedly rinsed with deionized water to remove residual electrolyte and unreacted monomers, and then dried in a vacuum oven at 60°C to obtain the LM@NI / CNTs composite foam, denoted as LM@NI / CNTs-0.4. The material obtained in this stage exhibits a uniform, continuous polyaniline / carbon nanotube synergistic composite film coating on its surface, and its actual film coating morphology is shown below. Figure 4 As shown.

[0023] S4. Preparation of graphite-resin mixed powder 2g of epoxy vinyl resin was completely dissolved in 25mL of acetone solvent. After the resin was fully dissolved, 8g of flake graphite powder was added. The mixture was placed in an ultrasonic cleaner and ultrasonically dispersed for 60min. Then it was transferred to a magnetic stirrer and stirred continuously at 400r / min for 60min to allow the resin molecules to fully impregnate and coat the surface of the flake graphite. The resulting suspension was transferred to an oven and dried at 60℃ for 12h to completely remove the acetone solvent, resulting in a uniform graphite-resin mixed powder.

[0024] S5. Compression molding The graphite-resin mixed powder was divided into upper and lower surface layers, and the LM@NI / CNTs-0.4 composite foam was used as the middle functional layer. The laminated structure was placed in a hot press and molded at 15 MPa and 150°C for 1 hour. After demolding, a fuel cell composite bipolar plate was obtained, denoted as LM@NI / CNTs-0.4 composite bipolar plate. For the specific surface morphology of the bipolar plate, please refer to [link to relevant documentation]. Figure 5 Its engineering samples are macroscopically displayed as follows: Figure 6 As shown.

[0025] After systematic testing, the composite bipolar plate prepared in Example 1 achieved extremely high performance: the absolute conductivity in the vertical cross-section direction reached 384.6 S / cm; and the area resistivity (ASR) under a simulated assembly pressure of 1.55 MPa was 7.47 mΩ·cm. 2 The mechanical bending fracture strength, measured using a universal testing machine, reached 57.04 MPa, fully meeting the high-voltage locking requirements of the fuel cell stack. The in-plane and out-of-plane thermal conductivity were measured to be 25.63 W·m. -1 ·K -1 and 12.74 W·m -1 ·K -1 The static water contact angle in the surface region reaches 106.4°, indicating strong hydrophobic properties; the corrosion current density measured in the simulated strong acid corrosion medium of a fuel cell is as low as an extremely small 0.98 μA / cm. 2 Meanwhile, tests have shown that its physical structure has zero air leakage and is airtight.

[0026] Example 2: This invention provides a method for preparing a fuel cell composite bipolar plate based on liquid metal anchoring and electrochemical deposition. The preparation method in this embodiment is consistent with the preparation steps of Example 1, except that the amount of liquid metal used in step S2 is 0.22g, and the mass of nickel foam is 1.25g. The composite plate produced under these conditions is denoted as LM@NI / CNTs-0.4 (LM content 1.5%).

[0027] Its electrical conductivity was measured to be 388.4 S / cm, its flexural strength increased to 62.73 MPa, and its thermal conductivity was 24.33 W·m. -1 ·K -1 The area resistivity at 1.55 MPa is 7.96 mΩ·cm. 2 The water contact angle is 101°, and the corrosion resistance current is 0.96 μA / cm. 2 .

[0028] Example 3: This invention provides a method for preparing a fuel cell composite bipolar plate based on liquid metal anchoring and electrochemical deposition. The preparation method in this embodiment is consistent with the preparation steps of Example 1, except that the amount of liquid metal used in step S2 is 0.36g, and the mass of nickel foam is 1.25g. The composite plate produced under these conditions is denoted as LM@NI / CNTs-0.4 (LM content 2.9%).

[0029] Its planar conductivity was measured to be 322.8 S / cm, and its area resistivity was 8.99 mΩ·cm. 2 The flexural strength is 40.57 MPa, and the in-plane thermal conductivity is 25.01 W·m. -1 ·K-1 The out-of-plane thermal conductivity is 11.26 W·m. -1 ·K -1 The water contact angle is 90.4°, and the corrosion current density is 1.46 μA / cm. 2 There was no gas leakage due to poor gas permeability.

[0030] Example 4: This invention provides a method for preparing a composite bipolar plate for a fuel cell based on liquid metal anchoring and electrochemical deposition. The preparation method in this embodiment is the same as the preparation steps in Example 1, except that the aniline concentration in step S3 is 0.037 mol / L, denoted as LM@NI / CNTs-0.4 (AN-0.037).

[0031] Its planar conductivity was measured to be 263.2 S / cm, and its area resistivity was 12.63 mΩ·cm. 2 The flexural strength is 46.21 MPa, and the in-plane thermal conductivity is 24.57 W·m. -1 ·K -1 The out-of-plane thermal conductivity is 10.98 W·m. -1 ·K -1 The water contact angle was 98.3°, and the corrosion current density was 1.27 μA / cm. 2 There was no gas leakage due to poor gas permeability.

[0032] Example 5: This invention provides a method for preparing a composite bipolar plate for a fuel cell based on liquid metal anchoring and electrochemical deposition. The preparation method in this embodiment is the same as the preparation steps in Example 1, except that the aniline concentration in step S3 is 0.073 mol / L, denoted as LM@NI / CNTs-0.4 (AN-0.073).

[0033] Its planar conductivity was measured to be 270.3 S / cm, and its area resistivity was 12.14 mΩ·cm. 2 The flexural strength is 48.73 MPa, and the in-plane thermal conductivity is 24.82 W·m. -1 ·K -1 The out-of-plane thermal conductivity is 10.45 W·m. -1 ·K -1 The water contact angle is 101.2°, and the corrosion current density is 1.18 μA / cm. 2 There was no gas leakage due to poor gas permeability.

[0034] Example 6: This invention provides a method for preparing a composite bipolar plate for a fuel cell based on liquid metal anchoring and electrochemical deposition. The preparation method in this embodiment is the same as the preparation steps in Example 1, except that the aniline concentration in step S3 is 0.183 mol / L and LM@NI / CNTs-0.4 (AN-0.183).

[0035] Its planar conductivity was measured to be 255.8 S / cm, and its area resistivity was 13.12 mΩ·cm. 2 The flexural strength is 53.90 MPa, and the in-plane thermal conductivity is 23.96 W·m. -1 ·K -1 The out-of-plane thermal conductivity is 9.52 W·m. -1 ·K -1 The water contact angle is 106.8°, and the corrosion current density is 1.09 μA / cm². 2 There was no gas leakage due to poor gas permeability.

[0036] Example 7: This invention provides a method for preparing a composite bipolar plate for a fuel cell based on liquid metal anchoring and electrochemical deposition. The preparation method in this embodiment is the same as the preparation steps in Example 1, except that the aniline concentration in step S3 is 0.146 mol / L and the CNTs concentration is 0.2 mg / mL, denoted as LM@NI / CNTs-0.2.

[0037] Its planar conductivity was measured to be 303.0 S / cm, and its area resistivity was 8.26 mΩ·cm. 2 The flexural strength is 55.70 MPa, and the in-plane thermal conductivity is 24.33 W·m. -1 ·K -1 The out-of-plane thermal conductivity is 11.89 W·m. -1 ·K -1 The water contact angle is 103.7°, and the corrosion current density is 1.47 μA / cm². 2 There was no gas leakage due to poor gas permeability.

[0038] Example 8: This invention provides a method for preparing a composite bipolar plate for a fuel cell based on liquid metal anchoring and electrochemical deposition. The preparation method in this embodiment is the same as the preparation steps in Example 1, except that the aniline concentration in step S3 is 0.146 mol / L and the CNTs concentration is 0.6 mg / mL, denoted as LM@NI / CNTs-0.6.

[0039] Its planar conductivity was measured to be 370.4 S / cm, and its area resistivity was 7.86 mΩ·cm. 2 The flexural strength is 51.89 MPa, and the in-plane thermal conductivity is 25.15 W·m.-1 ·K -1 The out-of-plane thermal conductivity is 12.58 W·m. -1 ·K -1 The water contact angle is 105.2°, and the corrosion current density is 0.95 μA / cm. 2 There was no gas leakage due to poor gas permeability.

[0040] Example 9: This invention provides a method for preparing a composite bipolar plate for a fuel cell based on liquid metal anchoring and electrochemical deposition. The preparation method in this embodiment is the same as the preparation steps in Example 1, except that the aniline concentration in step S3 is 0.146 mol / L and the CNTs concentration is 0.8 mg / mL, denoted as LM@NI / CNTs-0.8.

[0041] Its planar conductivity was measured to be 357.2 S / cm, and its area resistivity was 8.03 mΩ·cm. 2 The flexural strength is 48.34 MPa, and the in-plane thermal conductivity is 24.88 W·m. -1 ·K -1 The out-of-plane thermal conductivity is 12.41 W·m. -1 ·K -1 The water contact angle is 104.5°, and the corrosion current density is 0.92 μA / cm. 2 There was no gas leakage due to poor gas permeability.

[0042] Comparative Example 1: This comparative example provides a method for preparing a composite bipolar plate, including the following steps: (1) Preparation of graphite-resin mixed powder: 2g of epoxy vinyl resin was completely dissolved in 25mL of acetone solvent. After the resin was fully dissolved, 8g of flake graphite powder was added, ultrasonically dispersed for 60min, magnetically stirred for 60min, and dried at 60℃ for 12h to obtain graphite-resin mixed powder.

[0043] (2) Molding: The above graphite-resin mixed powder is loaded into the mold and molded for 1 hour at 15 MPa and 150°C. After demolding, GR composite board is obtained.

[0044] Its planar conductivity was measured to be 149.2 S / cm, and its area resistivity was 15.34 mΩ·cm. 2 The flexural strength is 58.84 MPa, and the in-plane thermal conductivity is 19.58 W·m. -1 ·K -1 The out-of-plane thermal conductivity is 1.87 W·m. -1 ·K -1 The water contact angle is 89°, and the corrosion current density is 0.24 μA / cm. 2There was no gas leakage due to poor gas permeability.

[0045] Comparative Example 2: This comparative example provides a method for preparing a composite bipolar plate. The preparation method is the same as the preparation steps in Example 1, except that the weak oxidation etching treatment in step (1) is not performed (i.e., the nickel foam is only acid-washed with 10 vol.% HCl and not soaked in a mixed solution of Na2SO4 and NaH2PO2), which is denoted as LM@NI (no etching) / CNTs-0.4.

[0046] Its planar conductivity was measured to be 312.5 S / cm, and its area resistivity was 8.89 mΩ·cm. 2 The flexural strength is 50.23 MPa, and the in-plane thermal conductivity is 23.47 W·m. -1 ·K -1 The out-of-plane thermal conductivity is 11.23 W·m. -1 ·K -1 The water contact angle is 98.6°, and the corrosion current density is 1.67 μA / cm². 2 There was no gas leakage due to poor gas permeability.

[0047] Comparative Example 3: This comparative example provides a method for preparing a composite bipolar plate. The preparation method is the same as the preparation steps in Example 1, except that the liquid metal anchoring treatment in step (2) is not performed (i.e., the nickel foam is not loaded with LM), denoted as NI / CNTs-0.4.

[0048] Its planar conductivity was measured to be 262.7 S / cm, and its area resistivity was 8.54 mΩ·cm. 2 The flexural strength is 61.24 MPa, and the in-plane thermal conductivity is 23.41 W·m. -1 ·K -1 The out-of-plane thermal conductivity is 9.03 W·m. -1 ·K -1 The water contact angle is 90°, and the corrosion current density is 2.48 μA / cm. 2 There was no gas leakage due to poor gas permeability.

[0049] Comparative Example 4: This comparative example provides a method for preparing a composite bipolar plate. The preparation method is the same as the preparation steps in Example 1, except that the electrochemical deposition treatment in step (3) is not performed (i.e., no PANI / CNTs composite film layer is deposited on the LM@NI surface), and it is referred to as the LM@NI composite plate.

[0050] Its planar conductivity was measured to be 344.8 S / cm, and its area resistivity was 8.71 mΩ·cm. 2 The flexural strength is 40.57 MPa, and the in-plane thermal conductivity is 25.01 W·m.-1 ·K -1 The out-of-plane thermal conductivity is 9.04 W·m. -1 ·K -1 The water contact angle is 90.4°, and the corrosion current density is 3.78 μA / cm. 2 There was no gas leakage due to poor gas permeability.

[0051] Comparative Example 5: This comparative example provides a method for preparing a composite bipolar plate, which is the same as the preparation steps of Comparative Example 4, except that the mass ratio of liquid metal is 3.5%, denoted as LM@NI-3.5%.

[0052] Its planar conductivity was measured to be 322.8 S / cm, and its area resistivity was 8.99 mΩ·cm. 2 The flexural strength is 38.24 MPa, and the in-plane thermal conductivity is 24.32 W·m. -1 ·K -1 The out-of-plane thermal conductivity is 8.76 W·m. -1 ·K -1 The water contact angle was 87.3°, and the corrosion current density was 4.12 μA / cm. 2 There was no gas leakage due to poor gas permeability.

[0053] Comparative Example 6: This comparative example provides a method for preparing a composite bipolar plate. The preparation method is the same as the preparation steps in Example 1, except that CNTs are not added in step (3) (i.e., only PANI is deposited), denoted as LM@NI / AN-0.146.

[0054] Its planar conductivity was measured to be 263.2 S / cm, and its area resistivity was 12.97 mΩ·cm. 2 The flexural strength is 53.90 MPa, and the in-plane thermal conductivity is 24.88 W·m. -1 ·K -1 The out-of-plane thermal conductivity is 8.96 W·m. -1 ·K -1 The water contact angle is 106.8°, and the corrosion current density is 1.34 μA / cm. 2 There was no gas leakage due to poor gas permeability.

[0055] Comparative Example 7: This comparative example provides a method for preparing a composite bipolar plate. The preparation method is the same as the preparation steps in Example 1, except that the concentration of CNTs in the composite electrolyte in step (3) is 1.0 mg / mL and the concentration of aniline is 0.146 mol / L.

[0056] Its planar conductivity was measured to be 340.1 S / cm, and its area resistivity was 8.56 mΩ·cm.2 The flexural strength is 42.15 MPa, and the in-plane thermal conductivity is 24.56 W·m. -1 ·K -1 The out-of-plane thermal conductivity is 12.18 W·m. -1 ·K -1 The water contact angle is 102.3°, and the corrosion current density is 0.91 μA / cm. 2 There was no gas leakage due to poor gas permeability. Excessive CNT content led to agglomeration, resulting in a significant decrease in flexural strength.

[0057] The performance tests of the composite bipolar plates obtained in Examples 1-9 and Comparative Examples 1-7 are shown in Table 1: (1) Bending strength test of bipolar plates: The bending strength of bipolar plates was tested using a three-point bending method on an electronic universal testing machine (Shimadzu, 33012). The span of the test sample was 32 times the thickness. The sample had a uniform length of 60 mm, a width of 10 mm, and a thickness of 1.2-1.5 mm. The test speed was 2 mm / s, and the lower span was 45 mm.

[0058] (2) Conductivity test: The planar conductivity of the composite bipolar plate was tested using a four-probe body resistivity tester (Keithley, 2400).

[0059] (3) Area resistivity test: The test is conducted according to GB / T20042.6 standard. The support layer is carbon paper used for the diffusion layer of fuel cells, and the electrode is gold-plated electrode.

[0060] (4) Thermal conductivity test: The thermal conductivity of the composite bipolar plate was tested using a laser thermal conductivity meter (Netzsch, Germany, LFA467).

[0061] (5) Water contact angle test: The surface hydrophobicity of the composite bipolar plate was tested using a water contact angle measuring instrument (JC2000DS2B, Shanghai Zhongchen Digital Technology Equipment Co., Ltd.).

[0062] (6) Corrosion resistance test: The electrochemical performance of the composite bipolar plate was tested using an electrochemical workstation (Shanghai Chenhua, CHI660E). A three-electrode system was used for the test, with a 1cm electrode spacing. 2 The sample was used as the working electrode, the calomel electrode as the reference electrode, and the platinum sheet as the counter electrode. The experiment used 0.5 M H₂SO₄ + 2 ppm HF as the electrolyte, and Tafel curves were performed at 80 °C and a scan rate of 2 mV / s to measure the corrosion current of the composite bipolar plate.

[0063] (7) Gas permeability test: The gas tightness of the composite bipolar plate was tested using a gas leak meter (AIRTEEK, N50).

[0064] Table 1 Performance test table of composite bipolar plates in Examples 1-9 and Comparative Examples 1-7 ; As shown in Table 1, the composite bipolar plates prepared in Examples 1 to 9 all exhibit high electrical conductivity, thermal conductivity, flexural strength, and water contact angle. All performance indicators meet or exceed the target standards set by the U.S. Department of Energy (DOE), namely: electrical conductivity greater than 100 S / cm, flexural strength greater than 40 MPa, and thermal conductivity greater than 20 W·m. -1 ·K -1 The area resistivity is less than 10 mΩ·cm 2 Gas permeability less than 2.0 × 10⁻⁶ -6 cm 3 ·cm -2 ·s -1 Corrosion current less than 1 μA / cm 2 .

[0065] Comparative Example 1 is a simple graphite-resin composite bipolar plate (GR plate) without the addition of liquid metal and without electrochemical deposition of PANI / CNTs. Although this composite plate meets the requirements in terms of flexural strength and corrosion resistance, its electrical conductivity is only 149.2 S / cm, and its out-of-plane thermal conductivity is as low as 1.87 W·m. -1 ·K -1 The area resistivity is as high as 15.34 mΩ·cm. 2 None of the above three key indicators meet the DOE standard, making it difficult to meet the requirements of high power density fuel cells for the electrical and thermal conductivity of bipolar plates.

[0066] Comparative Examples 2 and 3 are composite bipolar plates without weak oxidation etching treatment or without the addition of liquid metal, respectively. Experimental results show that without weak oxidation etching treatment, the anchoring effect of the liquid metal on the nickel foam surface is significantly reduced, leading to a decrease in the conductivity of the composite plate and an increase in corrosion current to 1.67 μA / cm. 2 Without the addition of liquid metal, the composite plate maintains high flexural strength (61.24 MPa), but its electrical conductivity (262.7 S / cm) and out-of-plane thermal conductivity (9.03 W·m) are significantly lower. -1 ·K -1 ) and corrosion resistance (corrosion current 2.48μA / cm) 2 All of them are significantly inferior to Example 1, in which the corrosion current has exceeded the DOE standard limit.

[0067] Comparative Examples 4 and 5 are LM@NI composite plates without electrochemical deposition of PANI / CNTs. The results show that the corrosion resistance of the composite plates without PANI / CNTs coating is severely inadequate: the corrosion current density of LM@NI-2.5% (Comparative Example 4) is as high as 3.78 μA / cm². 2 The flexural strength of LM@NI-3.5% (Comparative Example 5) decreased to 38.24 MPa, which is lower than the DOE standard requirement (≥40 MPa). These results indicate that direct exposure to liquid metal and excessive addition both have significant adverse effects on the mechanical properties and corrosion resistance of the composite plate.

[0068] Comparative Example 6 is a composite bipolar plate (LM@NI / AN-0.146) with only PANI deposition and no CNTs added. Test results show that although the introduction of PANI improves interfacial compatibility and surface hydrophobicity (water contact angle reaches 106.8°), due to the poor intrinsic conductivity of PANI, the composite plate's electrical conductivity (263.2 S / cm) and out-of-plane thermal conductivity (8.96 W·m) are significantly lower. -1 ·K -1 All values ​​were significantly lower than in Example 1, and the areal resistivity was as high as 12.97 mΩ·cm. 2 This exceeds the DOE standard limit and cannot meet the requirements of practical applications.

[0069] Comparative Example 7 shows a composite bipolar plate with an excessively high CNT content (1.0 mg / mL). Experimental results indicate that excessive CNTs agglomerate during electrochemical deposition, leading to a significant decrease in the flexural strength of the composite plate to 42.15 MPa, a 26.1% reduction compared to Example 1. Simultaneously, the conductivity also decreased. This demonstrates that the amount of CNTs added needs to be controlled within a suitable range; both excessively high and low amounts are detrimental to optimizing the overall performance of the composite plate.

[0070] In summary, this invention constructs nanoscale corrosion sites on the surface of nickel foam using a two-step acid etching-weak oxidation etching method, achieving targeted anchoring and uniform dispersion of liquid metal. Furthermore, it employs electrochemical deposition to in-situ construct a PANI / CNTs composite film on the LM@NI framework surface, effectively solving the key technical challenges of poor interfacial compatibility between liquid metal and the graphite-resin system, as well as insufficient corrosion resistance of the metal framework. Under optimized conditions (aniline concentration 0.146 mol / L, CNTs concentration 0.4 mg / mL), the LM@NI / CNTs-0.4 composite bipolar plate prepared in Example 1 achieves synergistic optimization of conductivity, thermal conductivity, mechanical properties, and corrosion resistance, with significantly better overall performance than the comparative examples, demonstrating optimal potential for practical fuel cell applications.

[0071] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A composite bipolar plate for fuel cells based on liquid metal anchoring and electrochemical deposition, characterized in that, The composite bipolar plate exhibits an integrated layered structure from the outside to the inside, and the structure is arranged in the following order: flake graphite / resin layer, polyaniline / carbon nanotube composite film layer, liquid metal modified nickel foam skeleton layer, polyaniline / carbon nanotube composite film layer and flake graphite / resin layer. The liquid metal modified nickel foam skeleton layer uses nickel foam containing nanoscale pores and rough etching sites as a three-dimensional bottom skeleton, with liquid metal anchored at fixed points on the surface and in the pores. A conductive composite film of polyaniline and carbon nanotubes, constructed by electrochemical deposition, is grown in situ on the surface of the liquid metal modified nickel foam skeleton layer.

2. The fuel cell composite bipolar plate based on liquid metal anchoring and electrochemical deposition according to claim 1, characterized in that, The thickness of the three-dimensional nickel foam substrate is 1 mm, and the porosity is 90 ppi. In the overall mass proportion of the composite bipolar plate, the nickel foam skeleton accounts for 12% to 14%, the liquid metal accounts for 2% to 3%, and the polyaniline / carbon nanotube composite film accounts for 0.8% to 1.5%.

3. A composite bipolar plate for fuel cells based on liquid metal anchoring and electrochemical deposition according to claim 1 or 2, characterized in that, The composite bipolar plate has a planar conductivity ≥384.6 S / cm and an area resistivity ≤7.47 mΩ·cm. 2 Mechanical bending strength ≥ 57.04 MPa; surface water contact angle ≥ 106.4°; corrosion current density in corrosive media ≤ 1 μA / cm² 2 .

4. A method for preparing a fuel cell composite bipolar plate based on liquid metal anchoring and electrochemical deposition according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Multi-stage surface modification treatment of nickel foam The nickel foam was completely immersed in a 10 vol.% HCl solution and ultrasonically vibrated for 10 min. It was then rinsed repeatedly with deionized water until neutral and dried in a vacuum drying oven at 60°C. The dried nickel foam was then immersed in a mixed solution containing 10 wt.% Na2SO4 and 5 wt.% NaH2PO2 and allowed to react at room temperature for 15 min to remove the oxide layer and induce nanoscale pores and rough interface structures on the nickel metal framework surface. After the reaction, it was rinsed and vacuum dried to obtain surface-etched nickel foam material. S2. Introduction of liquid metal vacuum impregnation The foamed nickel material obtained in step S1 was completely immersed in a liquid metal dispersion and continuously immersed in a vacuum pressure device at 60°C for 2 hours to allow the liquid metal nanoparticles to penetrate and anchor into the pores, thereby obtaining a liquid metal modified foamed nickel skeleton layer. S3. In-situ deposition and coating of polyaniline / carbon nanotube composite layer Using the liquid metal-modified nickel foam framework layer obtained in step S2 as the working electrode, in-situ deposition was performed in a composite electrolyte using a three-electrode system via cyclic voltammetry. The reference electrode was a saturated calomel electrode, and the counter electrode was a platinum sheet electrode. At room temperature, the voltage range was set to -0.2 to 1.0 V, the scan rate was 80 mV / s, and 50 cycles were performed continuously. After scanning, the residue was peeled off and vacuum dried to obtain a functional core framework with a polyaniline / carbon nanotube composite film coating on the surface. S4. Preparation of graphite-resin layer powder substrate Solid thermosetting resin was dissolved in acetone solvent at a solid-liquid mass-volume ratio of 1g:25mL. After the resin was dissolved, flake graphite powder was mixed in and ultrasonically dispersed for 60min, while maintaining the operation with a magnetic stirrer for 60min. The mixture was then dried at 60℃ for 12h to volatilize free acetone and a homogeneous graphite-resin mixed powder was collected. S5. High-temperature molding and lamination curing The graphite-resin mixed powder obtained in step S4 is evenly spread on the upper and lower surfaces of the bipolar plate. It is then bonded and stacked with the functional core skeleton obtained in step S3 and placed in a hot press mold. A surface pressure of 15 MPa is applied and the temperature is raised to 150°C. Under this condition, the pressure is maintained and cured for 1 hour. After natural cooling, the plate is demolded to obtain the composite bipolar plate.

5. The method for preparing a fuel cell composite bipolar plate based on liquid metal anchoring and electrochemical deposition according to claim 4, characterized in that, In step S2, the liquid metal dispersion uses gallium-indium alloy as the liquid metal source, sodium dodecyl sulfate as the dispersant, and ethanol as the carrier solvent.

6. The method for preparing a composite bipolar plate for a fuel cell based on liquid metal anchoring and electrochemical deposition according to claim 4, characterized in that, In step S3, the preparation process of the composite electrolyte is as follows: Preparation of aqueous dispersion of carbon nanotubes: Carbon nanotube powder and sodium dodecylbenzenesulfonate were injected into deionized water and ultrasonically dispersed for 2 hours; Preparation of acidic aniline solution: Concentrated hydrochloric acid is added dropwise to deionized water to form a diluted hydrochloric acid solution with a concentration of 0.5 mol / L. Liquid aniline monomer is then added dropwise and mechanically stirred until miscible. Liquid phase blending: The aqueous dispersion of carbon nanotubes and the acidic aniline solution were mixed in proportion and magnetically stirred at room temperature for 1 h; the resulting composite electrolyte contained 0.037–0.183 mol / L of aniline monomer and 0.2–0.8 mg / mL of carbon nanotubes.

7. The method for preparing a fuel cell composite bipolar plate based on liquid metal anchoring and electrochemical deposition according to claim 6, characterized in that, In the composite electrolyte, the concentration of aniline monomer is 0.146 mol / L and the concentration of carbon nanotubes is 0.4 mg / mL.

8. The method for preparing a composite bipolar plate for a fuel cell based on liquid metal anchoring and electrochemical deposition according to claim 4, characterized in that, In step S4, the solid thermosetting resin is selected from one or more of epoxy vinyl resin, epoxy resin, and phenolic resin; the dry weight ratio of the flake graphite powder to the solid thermosetting resin is 4:1.

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