A multi-chamber deposition system for carbon coating of fuel cell bipolar plates and its application

Abstract

The present invention provides a multi-chamber deposition system for carbon coatings on bipolar plates of fuel cells, comprising: a film feed chamber, an ion cleaning chamber, a PVD process chamber group, a transition chamber, a PECVD process chamber group, a cooling chamber and a film discharge chamber, wherein each chamber is connected in series in sequence through a gate valve; a conveying device is provided at the bottom of each chamber, which is connected in series throughout the entire deposition system; a sample is mounted on the conveying device; a guide device is provided at the top of each chamber; a bias roller is provided at the upper end of the conveying device and is connected to an external bias power supply; except for the film feed chamber, each of the other chambers has a vacuum system and an air path system, and an exhaust port is provided at the bottom. The present invention combines the PECVD method with the PVD method to realize the continuous preparation of the carbon coating, adopts a metal mesh structure to form a hollow cathode discharge, enhances the plasma density and uniformity, improves the compactness of the carbon coating and its deposition efficiency, and improves the commercial application prospects of the amorphous carbon coatings on bipolar plates of fuel cells.

Description

Technical Field

[0001] The invention belongs to the technical field of fuel cells and relates to a multi-chamber deposition system for a carbon coating on a bipolar plate of a fuel cell and an application thereof. Background Art

[0002] A fuel cell is a power generation device that converts the chemical energy of a fuel and an oxidant directly into electrical energy through an electrochemical reaction. Among the many types of fuel cells, the proton exchange membrane fuel cell (PEMFC) with hydrogen as the main fuel has been widely used and has attracted the attention of many researchers. As one of the core components of a proton exchange membrane fuel cell, the bipolar plate is responsible for the distribution of current and heat in the fuel cell and has a certain supporting role for the membrane electrode. During the operation of the fuel cell, the bipolar plate is located in an acidic environment with a pH of 3, and the fuel cell potential can reach 0.6 to 1.6 V, and the operating temperature is 65 to 85 ° C. For traditional metal bipolar plates, severe electrochemical corrosion will cause serious attenuation of the battery life. Therefore, modifying the traditional metal bipolar plate to improve the corrosion resistance of the metal plate and reduce the contact resistance between the plate and the gas diffusion layer is a current research hotspot.

[0003] Carbon coating is widely used in bipolar plate coating due to its excellent conductivity and corrosion resistance. It can be prepared by physical vapor deposition (PVD), chemical vapor deposition (CVD), ion plating (IP) and other methods. Among them, plasma enhanced chemical vapor deposition (PECVD) combines the advantages of traditional chemical vapor deposition and physical vapor deposition, with low sputtering temperature, fast deposition rate, and controllable film composition and thickness. It has gradually become one of the main methods for preparing carbon coatings. Although plasma enhanced chemical vapor deposition has these advantages, it still has shortcomings such as insufficient density of the structure. Therefore, it is necessary to further increase the plasma density and energy to improve the density of the prepared coating.

[0004] If the carbon coating grows directly on the metal substrate, the coating will be loose and porous, and the bonding performance with the substrate will be poor. Therefore, a transition layer must be added between the carbon coating and the metal substrate. The transition layer composition includes metal or metal carbide, which is mainly prepared by physical vapor deposition. For traditional single-chamber equipment, because different deposition methods have huge differences in deposition pressure, deposition temperature, etc., it is impossible to achieve continuous deposition of both physical vapor deposition and plasma enhanced chemical vapor deposition on the device at the same time. Multi-chamber deposition equipment can overcome these shortcomings and integrate different deposition methods to complete the preparation of the coating. Patent Publication No. CN206502860U discloses a PECVD and PVD mixed continuous coating device, which is mainly used for roll-to-roll flexible film coating and is not suitable for the preparation of carbon coatings for fuel cell bipolar plates. Summary of the invention

[0005] The purpose of the present invention is to provide a multi-chamber deposition system for carbon coatings on bipolar plates of fuel cells and its application, so as to overcome the defects of the prior art.

[0006] A multi-chamber deposition system for carbon coating of bipolar plates of fuel cells, characterized in that it mainly comprises: a film feeding chamber, an ion cleaning chamber, a PVD process chamber group, a transition chamber, a PECVD process chamber group, a cooling chamber and a film discharging chamber, and each chamber is connected in series in sequence through a gate valve; a conveying device is provided at the bottom of each chamber, which is connected in series throughout the entire deposition system; a sample rack is arranged on the conveying device; a guide device is provided at the top of each chamber, which controls the sample rack to be sequentially conveyed to each chamber along the track of the conveying device, so that the sample is cleaned, heated, coated and cooled; a bias roller is provided at the upper end of the conveying device and is connected to an external bias power supply, and the bias is connected to the sample rack; the ion cleaning chamber, PVD process chamber group, transition chamber, PECVD process chamber group and cooling chamber are also respectively equipped with independent vacuum systems and gas circuit systems, and each has an exhaust port at the bottom;

[0007] The ion cleaning chamber wall is provided with cleaning devices on both sides, and the cleaning methods include bipolar pulse cleaning, radio frequency self-bias cleaning, pulse bias cleaning, and ion source cleaning symmetrically arranged on both sides of the chamber;

[0008] The PVD process chamber group is composed of 2 to 10 PVD process chambers connected in series, which are isolated from each other by gate valves; the heating device and the magnetron target are symmetrically and evenly arranged on the two side walls of the PVD process chamber; the heating device and the magnetron target on each side wall are arranged at intervals; the working temperature of the heating device is 0 to 1000°C; the number of target positions of the magnetron target is 1 to 10 pairs, and the magnetic lines of force of adjacent and opposite target positions are closed to form an unbalanced closed magnetic field structure, and the magnetic field strength of the target surface is between 200 and 1500Gs;

[0009] The PECVD process chamber group is composed of 2 to 10 PECVD process chambers connected in series, which are isolated from each other by gate valves; a plurality of metal discharge electrodes of inverted U-shaped structure are installed in the PECVD process chamber, which are fixed to the left and right walls of the PECVD process chamber by high-temperature resistant insulating columns; a heating device is also provided between every two adjacent metal discharge electrodes on the wall of the PECVD process chamber, and its working temperature is 0 to 1000°C; the two ends of the gas circuit board are respectively connected to the insulating columns up and down, and are arranged between the wall of the PECVD process chamber and the metal discharge electrodes; the gas circuit board evenly distributes the gas sent from the air inlet to the entire chamber;

[0010] A cooling plate is hung on the side wall of the cooling chamber for cooling the sample.

[0011] The multi-chamber deposition system of a carbon coating for a fuel cell bipolar plate of the present invention is applied to the preparation of a carbon coating for a fuel cell bipolar plate, and is characterized in that a plasma enhanced chemical vapor deposition method is adopted to apply voltages of different magnitudes to a sample and a metal discharge electrode respectively, so that the negative glow is merged together, thereby ionizing a carbon source gas for rapid and uniform deposition of the carbon coating; the metal discharge electrode is an electrode to which radio frequency, direct current, pulsed direct current, or high-power pulsed direct current can be applied, and a direct current or pulse bias of -50 to -1000 V is applied to the surface of the substrate.

[0012] Furthermore, if the metal discharge electrode is a metal mesh electrode structure, an air distribution plate is arranged behind the metal mesh; if it is a foldable plate electrode structure, air distribution holes are arranged on the foldable plate, and the size of the air holes gradually increases from the center of the plate to the surrounding areas, so that the gas around the discharge electrode is evenly distributed.

[0013] Compared with the prior art, the present invention has the following characteristics:

[0014] (1) Using multi-chamber equipment to combine plasma-enhanced chemical vapor deposition and physical vapor deposition methods to achieve rapid and continuous deposition of fuel cell bipolar plates, overcoming the limitations of single-chamber equipment in preparing coating types.

[0015] (2) The PECVD method is used to deposit the carbon coating, which can effectively improve the deposition efficiency of the carbon coating and reduce the damage to the equipment caused by heat accumulation during deposition.

[0016] (2) A discharge electrode with a stainless steel metal mesh structure or plate structure is added into the PECVD process chamber to form a hollow cathode discharge, which improves the plasma density and uniformity during the plasma enhanced chemical vapor deposition process, further improves the compactness of the carbon coating, and improves its corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The overall structural schematic diagram of the multi-chamber deposition system of the present invention;

[0018] Figure 2 It is a schematic diagram of the top view of the structure of the PVD process chamber 3;

[0019] Figure 3 Schematic diagram of cathode magnetic field arrangement in a multi-chamber system PVD process chamber;

[0020] Figure 4 It is a side view structural schematic diagram of the PECVD process chamber 5;

[0021] Figure 5 This is the gas path layout diagram of the gas path plate.

[0022] Explanation of marks in the figure: 1-film feeding chamber, 2-ion cleaning chamber, 3-PVD process chamber group, 4-transition chamber, 5-PECVD process chamber group, 6-cooling chamber, 7-film discharging chamber, 8-sample rack, 9-transport device, 10-exhaust port, 11-heater, 12-magnetron target, 13-metal discharge electrode, 14-cooling plate, 15-baffle, 16-air pipe, 17-air inlet, 18-air path plate, 19-insulating column, 20-guide device, 21-bias roller. DETAILED DESCRIPTION

[0023] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0024] Reference Figure 1 , Figure 2 and Figure 4 A multi-chamber deposition system for carbon coating of bipolar plates of fuel cells mainly comprises: a film inlet chamber 1, an ion cleaning chamber 2, a PVD process chamber group 3, a transition chamber 4, a PECVD process chamber group 5, a cooling chamber 6 and a film outlet chamber 7, wherein each chamber is connected in series in sequence through a gate valve; a conveying device 9 is provided at the bottom of each chamber, which is connected in series throughout the entire deposition system; a sample rack 8 is provided on the conveying device 9; a guide device 20 is provided at the top of each chamber, which controls the sample rack 8 to be sequentially conveyed to each chamber along the track of the conveying device 9, so that the sample is cleaned, heated, deposited and cooled; a bias roller 21 is provided at the upper end of the conveying device 9 and connected to an external bias power supply, and the bias is connected to the sample rack 8; the ion cleaning chamber 2, the PVD process chamber group 3, the transition chamber 4, the PECVD process chamber group 5 and the cooling chamber 6 are also respectively equipped with independent vacuum systems and gas circuit systems, and each has an exhaust port 10 at the bottom.

[0025] Furthermore, cleaning devices are installed on both sides of the wall of the ion cleaning chamber 2, and the cleaning methods include bipolar pulse cleaning, radio frequency self-bias cleaning, pulse bias cleaning, and ion source cleaning symmetrically arranged on both sides of the cavity.

[0026] Furthermore, the heating device 11 and the magnetron target 12 are symmetrically and evenly arranged on the two side walls of each PVD process chamber; the heating device 11 and the magnetron target 12 on each side wall are arranged at intervals; the working temperature of the heating device 11 is 0-1000° C.; the number of target positions of the magnetron target 12 is 1-10 pairs, and the magnetic lines of force of adjacent and opposite target positions are closed to form an unbalanced closed magnetic field structure, and the magnetic field strength of the target surface is between 200 and 1500 Gs; Figure 3 Shown is a schematic diagram of the cathode magnetic field arrangement of a multi-chamber system PVD process chamber.

[0027] Furthermore, the PECVD process chamber group 5 is composed of 2 to 10 PECVD process chambers connected in series, which are isolated from each other by gate valves; a plurality of metal discharge electrodes 13 of an inverted U-shaped structure are installed in the PECVD process chamber, which are fixed to the left and right walls of the PECVD process chamber by high-temperature resistant insulating columns 19; a heating device 11 is also provided between every two adjacent metal discharge electrodes 13 on the wall of the PECVD process chamber, and its operating temperature is 0 to 1000°C; both ends of the gas circuit board 18 are respectively connected to the insulating columns 19 up and down, and are arranged between the wall of the PECVD process chamber and the metal discharge electrodes 13; the gas sent from the air inlet 17 enters the process chamber through the gas circuit board 18; Figure 5 : is a gas path layout diagram of the gas path plate 18. The diameter of the air holes of the gas path plate 18 gradually increases from the center to the surroundings, so that the gas sent from the air inlet 17 can be evenly distributed in the entire chamber.

[0028] Furthermore, a cooling plate 14 is hung on the side wall of the cooling chamber 6 for cooling the sample, so that the temperature of the sample is reduced to below 150°C.

[0029] Furthermore, a certain number of heaters 11 are evenly arranged on both sides of the inner wall of the ion cleaning chamber 2 to ensure that the working temperature is 200-500°C.

[0030] Furthermore, the distance between each target position of the magnetron target 12 should be greater than the width of a target material to avoid interference between the sputtering areas of the target materials at the two target positions, and baffles 15 are installed on both sides of the target position to prevent contamination of the heater 11. The gas pipes 16 arranged on both sides of the target position introduce gas from the gas source into the cavity.

[0031] Furthermore, the metal discharge electrode 13 includes a detachable mesh structure or a foldable plate structure. When the sample holder passes through the inside of the metal discharge electrode, it can form an equipotential body with it, thereby forming a closed loop, forming a hollow cathode discharge, and then ionizing the gas for coating deposition; the distance between two adjacent discharge electrodes is 5 to 30 cm, and the length along the forward direction of the sample holder is 0.5 to 2 m; the substrate holder passes through the plasma discharge space in a straight line.

[0032] Furthermore, an electric grating valve structure for independently adjusting the gas is provided on each of the gas extraction ports 10 to ensure that the pumping speed of each chamber is independently adjustable.

[0033] Specific coating preparation process and related parameters: Turn on the power of the equipment, keep the sample conveying device, vacuum pumping device and heating and cooling device in operation; the sample enters the ion cleaning chamber from the film feeding chamber 1, and argon gas of 10 to 100 sccm is introduced from the porous air pipe. A bias voltage of -100 to -1000V is applied to the sample to perform bias cleaning to remove surface oxides and impurities; then the sample enters the PVD process chamber group 3 for deposition of a carbon coating transition layer, and the pure metal target or metal carbide target current of 2 to 20A, the argon gas flow rate of 10 to 100 sccm, and the sample bias voltage of -20 to -500V are turned on to complete the plating of the transition layer in sequence. The total thickness of the transition layer is 0.01 ~1μm; then the sample passes through the transition chamber and enters the PECVD process chamber group 5 for deposition of the surface carbon coating, the bottom of the sample holder 8 contacts the metal discharge electrode 13 to form an equipotential body, a voltage of -50 to -1000V is applied thereon, and a voltage of -50 to -1000V is applied to the sample, an argon gas flow rate of 10 to 100sccm is introduced, and the carbon source gas (methane or acetylene) enters the chamber through the gas path plate with a flow rate of 30 to 300sccm, and the total thickness of the surface carbon coating is 0.01 to 5μm; the sample leaves the PECVD process chamber 5 and enters the cooling chamber 6, and enters the sheet discharge chamber 7 until the temperature is lower than 150°C, completing the preparation of a set of coatings.

Claims

1. A multi-chamber deposition system for carbon coating of bipolar plates of fuel cells, characterized in that: Mainly include: A film inlet chamber (1), an ion cleaning chamber (2), a PVD process chamber group (3), a transition chamber (4), a PECVD process chamber group (5), a cooling chamber (6) and a film outlet chamber (7), wherein each chamber is connected in series in sequence through a gate valve; a conveying device (9) is provided at the bottom of each chamber, which is connected in series throughout the entire deposition system; a sample rack (8) is provided on the conveying device (9); a guide device (20) is provided at the top of each chamber; a bias roller (21) is provided at the upper end of the conveying device (9) and is connected to an external bias power supply, so that the bias is connected to the sample rack (8); an exhaust port (10) is provided at the bottom of the ion cleaning chamber (2), the PVD process chamber group (3), the transition chamber (4), the PECVD process chamber group (5) and the cooling chamber (6), and each is also equipped with an independent vacuum system and a gas path system; The PVD process chamber group (3) is composed of 2 to 10 PVD process chambers connected in series, which are isolated from each other by gate valves; the PECVD process chamber group (5) is composed of 2 to 10 PECVD process chambers connected in series, which are isolated from each other by gate valves; heating devices (11) and magnetron targets (12) are symmetrically and evenly arranged on the two side walls of the PVD process chamber; the heating devices (11) and the magnetron targets (12) on each side wall are arranged at intervals; the magnetic lines of force of adjacent and opposite target positions of the magnetron targets (12) are closed to form an unbalanced closed magnetic field structure; the spacing between each target position of the magnetron targets (12) is greater than the width of a target material, and baffles (1 5), gas pipes (16) arranged on both sides of the target position introduce gas from the gas source into the cavity; a plurality of metal discharge electrodes (13) of an inverted U-shaped structure are installed in the PECVD process chamber and are fixed to the left and right walls of the PECVD process chamber through high-temperature resistant insulating columns (19); a heating device (11) is arranged between every two adjacent metal discharge electrodes (13) on the wall of the PECVD process chamber; both ends of a gas circuit plate (18) are respectively connected to the insulating columns (19) at the top and bottom, and are arranged between the wall of the PECVD process chamber and the metal discharge electrodes (13); the gas circuit plate (18) evenly distributes the gas sent from the gas inlet (17) to the entire chamber; The metal discharge electrode (13) comprises a detachable mesh structure or a foldable plate structure; the distance between two adjacent metal discharge electrodes (13) is 5 to 30 cm, and the length along the forward direction of the sample rack is 0.5 to 2 m; if the metal discharge electrode (13) is a metal mesh electrode structure, an air distribution plate is arranged behind the metal mesh; if it is a foldable plate electrode structure, air distribution holes are arranged on the foldable plate, and the size of the air holes gradually increases from the center of the plate to the surrounding areas.

2. The multi-chamber deposition system according to claim 1, characterized in that: The ion cleaning chamber (2) is provided with cleaning devices on both sides of the wall, and the cleaning methods include bipolar pulse cleaning, radio frequency self-bias cleaning, pulse bias cleaning, and ion source cleaning symmetrically arranged on both sides of the cavity.

3. The multi-chamber deposition system according to claim 2, characterized in that: A certain number of heaters are evenly arranged on both sides of the inner wall of the ion cleaning chamber (2) to ensure that the operating temperature is 200-500°C.

4. The multi-chamber deposition system according to claim 1, characterized in that: The working temperature of the heating device (11) is 0-1000° C.; the number of target positions of the magnetron target (12) is 1-10 pairs, and the magnetic field intensity on the target surface is between 200-1500 Gs.

5. The multi-chamber deposition system according to claim 1, characterized in that: The diameter of the air holes of the air path plate (18) gradually increases from the center to the periphery.

6. The multi-chamber deposition system according to claim 1, characterized in that: A cooling plate (14) is suspended on the side wall of the cooling chamber (6).

7. The multi-chamber deposition system according to claim 1, characterized in that: An electric grating valve structure for independently regulating gas is provided on each of the gas extraction ports (10).

8. An application method of the multi-chamber deposition system according to any one of claims 1 to 7, characterized in that: The power of the equipment is turned on, and the sample conveying device, vacuum pumping device and heating and cooling device are kept in operation; the sample enters the ion cleaning chamber (2) from the film feeding chamber (1), argon gas of 10 to 100 sccm is introduced from the porous gas pipe, a bias voltage of -100 to -1000 V is applied to the sample, and bias cleaning is performed to remove surface oxides and impurities; the sample then enters the PVD process chamber group (3) for deposition of a carbon coating transition layer, a pure metal target or a metal carbide target current of 2 to 20 A, an argon gas flow rate of 10 to 100 sccm, a sample bias voltage of -20 to -500 V, and the plating of the transition layer is completed in sequence, wherein the total thickness of the transition layer is 0.01 to 1 μm; then The sample passes through the transition chamber and enters the PECVD process chamber group (5) for deposition of a surface carbon coating. The bottom of the sample holder (8) contacts the metal discharge electrode (13) to form an equipotential body, a voltage of -50 to -1000 V is applied thereto, and a voltage of -50 to -1000 V is applied to the sample. Argon gas is introduced at a flow rate of 10 to 100 sccm, and a carbon source gas enters the chamber through the gas path plate at a flow rate of 30 to 300 sccm. The total thickness of the surface carbon coating is 0.01 to 5 μm. The sample leaves the PECVD process chamber group (5) and enters the cooling chamber (6), and enters the sheet discharge chamber (7) until the temperature is lower than 150°C, completing the preparation of a set of coatings.

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