Metal bipolar plate composite coating and preparation method thereof, metal bipolar plate and fuel cell

Abstract

The invention provides a metal bipolar plate composite coating, a preparation method thereof, a metal bipolar plate and a fuel cell, and belongs to the technical field of fuel cell metal bipolar plates. The metal bipolar plate composite coating sequentially comprises a metal base layer and a mixed metal transition layer in the direction away from a metal base material, and the mixed metal transition layer comprises a first metal material and a second metal material; in the mixed metal transition layer, the content of the first metal material and the content of the second metal material change in a gradient mode in the thickness direction of the metal base material. According to the invention, the metal base layer and the mixed metal gradient transition layer are introduced on the bipolar plate base material, so that the technical problem that the metal base layer is easy to peel off under ultrahigh potential can be solved in a targeted manner.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal bipolar plates for fuel cells, and in particular relates to a metal bipolar plate composite coating and a preparation method thereof, a metal bipolar plate and a fuel cell. Background Art

[0002] Stainless steel bipolar plates for hydrogen fuel cells are currently the most widely studied substrate material. Compared to graphite and titanium, stainless steel offers excellent toughness and plasticity, making it easier to form and process. It is also low-cost and readily available, making it more suitable for large-scale mass production. However, stainless steel is prone to forming a passivation film in acidic environments, increasing contact resistance and thus affecting the overall performance of hydrogen fuel cells. Therefore, surface coating modification of stainless steel bipolar plates is often required to improve their electrochemical and resistive properties.

[0003] The current mainstream coating technology mainly uses corrosion-resistant materials such as titanium and chromium as a base layer, and then sequentially applies a transition layer, a carbon layer, or other conductive and corrosion-resistant thin film layers. In addition, during the preparation of bipolar plates, a conventional coating process is usually used, that is, a base layer of titanium or chromium is directly deposited on the surface of the stainless steel substrate. Because the stainless steel and the base layer are both made of metal, a good interface bonding effect can be achieved, and general physical characterization methods are difficult to damage the interface between the stainless steel and the metal base layer.

[0004] However, under high potential conditions, intense galvanic corrosion occurs at the interface between the two dissimilar metals, dissolving the previously securely bonded interface and causing the metal base layer to peel directly from the stainless steel substrate, rendering the coating ineffective. This phenomenon frequently occurs during bipolar plate operation, particularly during abnormal battery startup and shutdown, or during load changes. This occurs when hydrogen or air starvation creates a hydrogen-air interface on the cathode side, causing electrons to move in the opposite direction, generating a potential of 1.6V (vs. SHE) or even higher on the stainless steel plate surface. When the potential reaches a certain level, corrosion and dissolution occur at various interfaces between the coating and the metal plate. This can include corrosion and dissolution between layers within the coating, or electrochemical corrosion and spalling between the stainless steel substrate and the metal base layer. Furthermore, the greater the number of metallurgical and machining defects on the stainless steel substrate and the poorer the surface finish, the higher the probability of electrochemical corrosion and spalling between the metal base layer and the stainless steel substrate.

[0005] To address these issues, existing technologies typically employ high-quality bipolar plate substrates, or employ techniques such as improving the cleanliness of coating pre-cleaning and increasing ion etching intensity. While improving substrate quality and cleaning can reduce defects and the probability of corrosion spalling to a certain extent, and increasing ion etching intensity can improve interfacial bonding strength, these methods are unable to effectively enhance the interface's resistance to high-potential corrosion.

[0006] Therefore, how to overcome the shortcoming that the composite coating of the existing stainless steel bipolar plate is easily peeled off under high potential conditions is a technical problem that technicians in this field urgently need to solve. Summary of the Invention

[0007] In response to the technical problems in the prior art such as corrosion and dissolution easily occurring inside the bipolar plate coating and at the interface between the bipolar plate substrate and the metal layer in a high potential environment, the purpose of the present invention is to provide a metal bipolar plate composite coating and its preparation method, a metal bipolar plate and a fuel cell to solve the above problems.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a metal bipolar plate composite coating, which comprises a metal base layer and a mixed metal transition layer in sequence along a direction away from a metal substrate, wherein the mixed metal transition layer comprises a first metal material and a second metal material.

[0010] In the mixed metal transition layer, the content of the first metal material and the content of the second metal material vary in a gradient along the thickness direction of the metal substrate.

[0011] By introducing a metal basecoat and a mixed metal gradient transition layer onto the bipolar plate substrate, this invention specifically addresses the technical issue of the metal basecoat being susceptible to peeling at ultra-high potentials. Even if the surface modification layer fails, the metal bipolar plate composite coating provided by this invention maintains a firm bond between the metal layer and the bipolar plate substrate surface, thereby preventing perforation of the bipolar plate substrate and excessive precipitation of iron ions.

[0012] Specifically, on the one hand, the use of a metal base layer can compensate for microscopic anomalies such as metallurgical defects and processing defects on the surface of the bipolar plate substrate, thereby improving the flatness and corrosion resistance of the bipolar plate substrate; on the other hand, the present invention adjusts the content changes of the two metal materials in the mixed metal transition layer, so that the prepared bipolar plate material has good conductivity and corrosion resistance at high potential, and gives the fuel cell excellent quality and durability.

[0013] Preferably, in the mixed metal transition layer, the content of the first metal material decreases gradually in a direction away from the metal substrate.

[0014] Preferably, in the mixed metal transition layer, the content of the second metal material increases gradually in a direction away from the metal substrate.

[0015] In the present invention, by regulating the content variation trends of the first and second metal materials, galvanic corrosion at the interface between the bipolar plate substrate and the metal layer is avoided. Without the gradient treatment, a distinct interface would form between the two, hindering the corrosion resistance of the bipolar plate material at high potentials.

[0016] Preferably, the first metal material includes stainless steel, and the material of the stainless steel may be, for example, SUS316L, SUS304, or the like.

[0017] Preferably, the second metal material includes any one of titanium, chromium or niobium.

[0018] Preferably, the thickness of a single layer of the mixed metal transition layer is 100 nm to 500 nm, for example, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, or 500 nm, etc., and is not limited to the values listed above; other values not listed within this range are also applicable. The present invention controls the thickness of the mixed metal transition layer to an appropriate range to avoid the undesirable phenomenon of obvious delamination of the two metal materials in the microstructure.

[0019] Preferably, the material of the metal primer layer is the same as that of the metal substrate.

[0020] Preferably, the metal base layer is made of stainless steel, for example, SUS316L, SUS304, etc.

[0021] Preferably, the single layer thickness of the metal base layer is 50nm-500nm, for example, it can be 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm or 500nm, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0022] Preferably, the metal bipolar plate composite coating further comprises a first metal layer and a conductive carbon layer sequentially arranged on the surface of the mixed metal transition layer in a direction away from the metal substrate.

[0023] In the present invention, the single layer thickness of the first metal layer is 50nm-500nm, for example, it can be 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm or 500nm, etc., and is not limited to the listed values. Other unlisted values within this numerical range are also applicable.

[0024] Preferably, a metal / carbon transition layer is further provided between the first metal layer and the conductive carbon layer, and the metal elements in the first metal layer and the metal / carbon transition layer independently include any one of titanium, chromium or niobium.

[0025] In the present invention, the metal / carbon transition layer can be prepared by referring to the preparation method of the metal / carbon transition layer in document 202410526398.6, or by conventional magnetron sputtering technology.

[0026] In the present invention, the conductive carbon layer can be prepared by referring to the preparation method of the sputtered carbon layer in document 202410526398.6, or by conventional magnetron sputtering technology, or by filtered cathode vacuum arc technology.

[0027] Preferably, the metal bipolar plate composite coating further comprises a second metal layer and a metal oxide layer sequentially arranged on the surface of the mixed metal transition layer in a direction away from the metal substrate.

[0028] In the present invention, the material of the metal oxide layer exemplarily includes tetratitanium heptoxide.

[0029] In the present invention, the metal oxide layer can be prepared by arc ion plating technology.

[0030] Preferably, the metal elements in the second metal layer and the metal oxide layer independently include any one of titanium, chromium or niobium.

[0031] In a second aspect, the present invention provides a method for preparing the metal bipolar plate composite coating according to the first aspect, the preparation method comprising the following steps:

[0032] S1. The metal substrate is placed in a multi-target magnetron sputtering chamber, wherein a first metal target and a second metal target are pre-set in the multi-target magnetron sputtering chamber, and a first sputtering deposition is performed on at least one side of the metal substrate to form a metal base layer;

[0033] S2. performing a second sputtering deposition on the side of the metal base layer away from the metal substrate, adjusting the deposition power parameters of the first metal target and the second metal target respectively to form a mixed metal transition layer to obtain the metal bipolar plate composite coating.

[0034] Preferably, in step S1, the metal substrate is sequentially subjected to ultrasonic cleaning and plasma cleaning.

[0035] Specifically, the specific steps of the ultrasonic cleaning are as follows: placing the metal substrate to be cleaned in an ultrasonic cleaning machine, and cleaning it in analytical pure anhydrous alcohol and acetone using 15kHz to 30kHz ultrasonic waves; the specific steps of the plasma cleaning are as follows: placing the metal substrate after ultrasonic cleaning in a vacuum chamber, and evacuating the vacuum chamber to a pressure of 4×10 -3 Pa, introduce argon gas to maintain the vacuum degree at 2Pa-4Pa, and use a medium frequency power supply to bombard the metal substrate with ions.

[0036] Preferably, in step S1, the first sputtering deposition process includes: turning on the first metal target, adjusting the first power applied to the first metal target to a preset power parameter, and adjusting the bias applied to the metal substrate to a first preset bias parameter, and sputtering and depositing a metal base layer on at least one side of the metal substrate.

[0037] Preferably, the material of the first metal target is the same as that of the metal substrate.

[0038] Preferably, the preset power parameter range is 8KW-10KW, for example, it can be 8KW, 8.2KW, 8.5KW, 8.8KW, 9KW, 9.2KW, 9.5KW, 9.8KW or 10KW, etc., and is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0039] Preferably, the first preset bias voltage parameter range is 200V-600V, and may be, for example, 200V, 250V, 300V, 350V, 400V, 450V, 500V, 550V, or 600V, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable. In the present invention, the first preset bias voltage parameter range is determined based on the depth and width of the bipolar plate flow channel groove.

[0040] Preferably, in step S2, the second sputtering deposition process includes: adjusting the bias voltage applied to the metal substrate to a second preset bias parameter, and keeping the first metal target material turned on, adjusting the first power applied to the first metal target material to gradually decrease from the preset power parameter to the initial preset power parameter, and at the same time turning on the second metal target material, and adjusting the second power applied to the second metal target material to gradually increase from the initial preset power parameter to the preset power parameter, and depositing to form a mixed metal transition layer.

[0041] Preferably, the second preset bias parameter range is not higher than 200V, for example, it can be 50V, 80V, 100V, 120V, 150V, 180V or 200V, etc., and is not limited to the listed values. Other unlisted values within the numerical range are also applicable.

[0042] Preferably, the initial preset power parameter is 0.1KW-1KW, for example, it can be 0.1KW, 0.2KW, 0.3KW, 0.4KW, 0.5KW, 0.6KW, 0.7KW, 0.8KW, 0.9KW or 1KW, etc., and is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0043] In the present invention, the furnace rack in the multi-target magnetron sputtering apparatus can realize self-rotation to ensure the effective gradient transition of each element in the mixed metal transition layer. For example, it can be a continuous coating furnace, and it is also necessary to satisfy the requirement that the furnace rack can realize self-rotation during the mixed metal transition layer deposition stage.

[0044] Furthermore, during the deposition of the mixed metal transition layer, the rotation speed of the above-mentioned furnace rack is not less than 1 rpm, for example, it can be 5 rpm, 8 rpm, 10 rpm, 12 rpm or 15 rpm, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0045] In a third aspect, the present invention provides a metal bipolar plate, comprising a metal bipolar plate composite coating prepared by the preparation method described in the first aspect or the second aspect.

[0046] The metal bipolar plate composite coating provided by the present invention effectively reduces the galvanic corrosion effect between the bipolar plate substrate and the metal layer at high potential, thereby significantly improving the ability of the interface to resist high potential corrosion.

[0047] In a fourth aspect, the present invention provides a fuel cell comprising the metal bipolar plate as described in the third aspect.

[0048] The numerical range described in the present invention includes not only the point values listed above, but also any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] The present invention provides a metal bipolar plate composite coating. By introducing a metal base layer and a mixed metal gradient transition layer onto the bipolar plate substrate, this coating specifically addresses the technical issue of the metal base layer being susceptible to peeling at ultra-high potentials. Even in the event of failure of the surface modification layer, the metal bipolar plate composite coating provided by the present invention maintains a firm bond between the metal layer and the bipolar plate substrate surface, thereby preventing perforation of the bipolar plate substrate and excessive precipitation of iron ions. DETAILED DESCRIPTION

[0051] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0052] Example 1

[0053] This embodiment provides a stainless steel bipolar plate composite coating and a stainless steel bipolar plate containing the same. The stainless steel bipolar plate includes a stainless steel substrate and a stainless steel bipolar plate composite coating disposed on both sides of the stainless steel substrate. The stainless steel bipolar plate composite coating comprises, in order from the direction away from the stainless steel substrate (made of SUS316L), a stainless steel base layer, a mixed metal transition layer, a titanium metal layer, and a titanium heptoxide layer.

[0054] Among them, the single layer thickness of the stainless steel base layer is 100nm, and the material of the stainless steel is SUS316L; the mixed metal transition layer includes stainless steel material (made of SUS316L) and titanium material, the content of the stainless steel material gradually decreases in the direction away from the stainless steel substrate, and the content of the titanium material gradually increases in the direction away from the stainless steel substrate, and the single layer thickness is 100nm; the single layer thickness of the titanium metal layer is 50nm; the single layer thickness of the titanium heptoxide layer is 200nm.

[0055] This embodiment also provides a method for preparing the above-mentioned stainless steel bipolar plate composite coating and a stainless steel bipolar plate containing the same, the preparation method comprising the following steps:

[0056] S1. Place the cleaned SUS316L stainless steel substrate into a magnetron sputtering coater equipped with an arc ion plating device. The coater is pre-installed with SUS316L stainless steel and titanium targets. Maintaining the oven speed at 3 rpm, the coater chamber is evacuated to 4 mPa. Ion cleaning is performed on the surface of the SUS316L stainless steel substrate to facilitate subsequent coating.

[0057] S2. Turn on the SUS316L stainless steel target, adjust the power applied to the stainless steel target to 10 kW, and adjust the bias voltage applied to the SUS316L stainless steel substrate to 300 V. Deposit a 100 nm thick stainless steel base layer on both sides of the SUS316L stainless steel substrate.

[0058] S3. Adjust the bias voltage applied to the SUS316L stainless steel substrate to 100V, and keep the SUS316L stainless steel target on. Adjust the power of the stainless steel target to gradually decrease from 10KW to 0.1KW. Simultaneously, turn on the titanium target and adjust the power applied to the titanium target to gradually increase from 0.1KW to 10KW, depositing a single layer of mixed metal transition layer with a thickness of 100nm.

[0059] S4. The stainless steel target is turned off, and a single layer of 50nm thick titanium is deposited on the surface of the mixed metal transition layer. Finally, the titanium target arc cathode is turned on, and oxygen is introduced at a flow rate of 40sccm to deposit a single layer of 200nm thick titanium tetraoxide directly on the titanium layer.

[0060] Example 2

[0061] This embodiment provides a stainless steel bipolar plate composite coating and a stainless steel bipolar plate containing the same. The stainless steel bipolar plate includes a stainless steel substrate and a stainless steel bipolar plate composite coating disposed on both sides of the stainless steel substrate. The stainless steel bipolar plate composite coating comprises, in order from the direction away from the stainless steel substrate (made of SUS316L), a stainless steel base layer, a mixed metal transition layer, a titanium metal layer, a Ti / C transition layer, and a conductive carbon layer.

[0062] Among them, the single layer thickness of the stainless steel base layer is 100nm, and the material of the stainless steel is SUS316L; the mixed metal transition layer includes stainless steel material (made of SUS316L) and titanium material, the content of the stainless steel material decreases gradually in the direction away from the stainless steel substrate, and the content of the titanium material increases gradually in the direction away from the stainless steel substrate, and the single layer thickness is 100nm; the single layer thickness of the titanium metal layer is 20nm; the single layer thickness of the Ti / C transition layer is 50nm; the single layer thickness of the conductive carbon layer is 200nm.

[0063] This embodiment also provides a method for preparing the above-mentioned stainless steel bipolar plate composite coating and a stainless steel bipolar plate containing the same, the preparation method comprising the following steps:

[0064] S1. Place the cleaned SUS316L stainless steel substrate into a magnetron sputtering coater equipped with an electromagnetic plasma assist device. The coater is pre-installed with SUS316L stainless steel targets, titanium targets, and graphite targets. Maintain a furnace speed of 3 rpm and evacuate the coater chamber to 4 mPa. Ion cleaning is performed on the surface of the SUS316L stainless steel substrate to facilitate the subsequent coating process.

[0065] S2. Turn on the SUS316L stainless steel target, adjust the power applied to the stainless steel target to 10 kW, and adjust the bias voltage applied to the SUS316L stainless steel substrate to 300 V. Deposit a 100 nm thick stainless steel base layer on both sides of the SUS316L stainless steel substrate.

[0066] S3. Adjust the bias voltage applied to the SUS316L stainless steel substrate to 100V, and keep the SUS316L stainless steel target on. Adjust the power of the stainless steel target to gradually decrease from 10KW to 0.1KW. Simultaneously, turn on the titanium target and adjust the power applied to the titanium target to gradually increase from 0.1KW to 10KW, depositing a single layer of mixed metal transition layer with a thickness of 100nm.

[0067] S4. Turn off the stainless steel target, and then deposit a single titanium metal layer with a thickness of 20nm on the surface of the mixed metal transition layer. Turn on the graphite target, set the bias voltage applied to the SUS316L stainless steel substrate to 100V, and adjust the power applied to the graphite target from 0.5KW to 10KW in a step-by-step manner with a ramp-up time of 20 minutes. Simultaneously, adjust the power applied to the titanium target from 10KW to 0.5KW in a step-by-step manner. At the same time, start the electromagnetic plasma assist device to generate a magnetic field perpendicular to the motion trajectory of the deposited particles, so that the magnetic field strength on the surface of the SUS316L stainless steel substrate is 6mT, and a magnetic field strength of 0.55A / cm 2 A single metal / carbon transition layer with a thickness of 50 nm was deposited with a bias current of .

[0068] Then, the titanium target was turned off, leaving only the graphite target on. The bias voltage applied to the surface of the SUS316L stainless steel substrate was set to 50 V, the deposition time was 30 min, and the power applied to the graphite target was maintained at 10 kW to deposit a single-layer sputtered carbon layer with a thickness of 200 nm.

[0069] Example 3

[0070] This embodiment provides a stainless steel bipolar plate composite coating and a stainless steel bipolar plate containing the same. The stainless steel bipolar plate includes a stainless steel substrate and a stainless steel bipolar plate composite coating disposed on both sides of the stainless steel substrate. The stainless steel bipolar plate composite coating comprises, in order from the direction away from the stainless steel substrate (made of SUS316L), a stainless steel base layer, a mixed metal transition layer, a titanium metal layer, a Ti / C transition layer, and a conductive carbon layer.

[0071] Among them, the single layer thickness of the stainless steel base layer is 150nm, and the material of the stainless steel is SUS316L; the mixed metal transition layer includes stainless steel material (made of SUS316L) and titanium material, the content of the stainless steel material gradually decreases in the direction away from the stainless steel substrate, and the content of the titanium material gradually increases in the direction away from the stainless steel substrate, and the single layer thickness is 200nm; the single layer thickness of the titanium metal layer is 50nm; the single layer thickness of the Ti / C transition layer is 100nm; the single layer thickness of the conductive carbon layer is 150nm.

[0072] This embodiment also provides a method for preparing the above-mentioned stainless steel bipolar plate composite coating and a stainless steel bipolar plate containing the same, the preparation method comprising the following steps:

[0073] S1. Place the cleaned SUS316L stainless steel substrate into a magnetron sputtering coater equipped with an electromagnetic plasma assist device. The coater is pre-installed with SUS316L stainless steel targets, titanium targets, and graphite targets. Maintain a furnace speed of 2.5 rpm and evacuate the coater chamber to 4 mPa. Ion cleaning is performed on the surface of the SUS316L stainless steel substrate to facilitate the subsequent coating process.

[0074] S2. Turn on the SUS316L stainless steel target, adjust the power applied to the stainless steel target to 8 kW, and adjust the bias voltage applied to the SUS316L stainless steel substrate to 400 V. Deposit a 150 nm thick stainless steel base layer on both sides of the SUS316L stainless steel substrate.

[0075] S3. Adjust the bias voltage applied to the SUS316L stainless steel substrate to 100V, and keep the SUS316L stainless steel target on. Adjust the power of the stainless steel target to gradually decrease from 8 kW to 0.1 kW. Simultaneously, turn on the titanium target and adjust the power applied to the titanium target to gradually increase from 0.1 kW to 8 kW to deposit a single layer of mixed metal transition layer with a thickness of 200 nm.

[0076] S4. Turn off the stainless steel target, and then deposit a single titanium metal layer with a thickness of 50nm on the surface of the mixed metal transition layer. Turn on the graphite target, set the bias voltage applied to the SUS316L stainless steel substrate to 100V, and adjust the power applied to the graphite target from 1KW to 10KW in a step-by-step manner with a ramp-up time of 30 minutes. Simultaneously, adjust the power applied to the titanium target from 10KW to 1KW in a step-by-step manner. At the same time, start the electromagnetic plasma assist device to generate a magnetic field perpendicular to the motion trajectory of the deposited particles, so that the magnetic field strength on the surface of the SUS316L stainless steel substrate is 6mT, and a magnetic field strength of 0.55A / cm 2 A single metal / carbon transition layer with a thickness of 100 nm was deposited with a bias current of .

[0077] Then, the titanium target was turned off, leaving only the graphite target on. The bias voltage applied to the surface of the SUS316L stainless steel substrate was set to 50 V, the deposition time was 20 min, and the power applied to the graphite target was maintained at 10 kW to deposit a single-layer sputtered carbon layer with a thickness of 150 nm.

[0078] Example 4

[0079] This embodiment provides a stainless steel bipolar plate composite coating and a stainless steel bipolar plate containing the same. The stainless steel bipolar plate includes a stainless steel substrate and a stainless steel bipolar plate composite coating disposed on both sides of the stainless steel substrate. The stainless steel bipolar plate composite coating comprises, in order, along a direction away from the stainless steel substrate (made of SUS316L), a stainless steel base layer, a mixed metal transition layer, a titanium metal layer, and a conductive carbon layer.

[0080] Among them, the single layer thickness of the stainless steel base layer is 100nm, and the material of the stainless steel is SUS316L; the mixed metal transition layer includes stainless steel material (made of SUS316L) and titanium material, the content of the stainless steel material gradually decreases in the direction away from the stainless steel substrate, and the content of the titanium material gradually increases in the direction away from the stainless steel substrate, and the single layer thickness is 100nm; the single layer thickness of the titanium metal layer is 30nm; the single layer thickness of the conductive carbon layer is 150nm.

[0081] This embodiment also provides a method for preparing the above-mentioned stainless steel bipolar plate composite coating and a stainless steel bipolar plate containing the same, the preparation method comprising the following steps:

[0082] S1. Place the cleaned SUS316L stainless steel substrate into a magnetron sputtering coater equipped with a filtered cathode vacuum arc device. The coater is pre-installed with SUS316L stainless steel targets, titanium targets, and arc graphite targets. Maintain the furnace speed at 3 rpm, evacuate the coater chamber to 4 mPa, and perform ion cleaning on the surface of the SUS316L stainless steel substrate to facilitate the subsequent coating process.

[0083] S2. Turn on the SUS316L stainless steel target, adjust the power applied to the stainless steel target to 10 kW, and adjust the bias voltage applied to the SUS316L stainless steel substrate to 300 V. Deposit a 100 nm thick stainless steel base layer on both sides of the SUS316L stainless steel substrate.

[0084] S3. Adjust the bias voltage applied to the SUS316L stainless steel substrate to 100V, and keep the SUS316L stainless steel target on. Adjust the power of the stainless steel target to gradually decrease from 10KW to 0.1KW. Simultaneously, turn on the titanium target and adjust the power applied to the titanium target to gradually increase from 0.1KW to 10KW, depositing a single layer of mixed metal transition layer with a thickness of 100nm.

[0085] S4. Turn off the stainless steel target and deposit a 30nm thick titanium layer on the surface of the mixed metal transition layer. Finally, turn on the magnetic filtration system, set the bias voltage to 1200V, and use an arc graphite target to deposit a 150nm thick conductive carbon layer directly on the titanium layer.

[0086] Example 5

[0087] This embodiment provides a stainless steel bipolar plate composite coating and a stainless steel bipolar plate containing the same. The stainless steel bipolar plate includes a stainless steel substrate and a stainless steel bipolar plate composite coating disposed on both sides of the stainless steel substrate. The stainless steel bipolar plate composite coating comprises, in order from the direction away from the stainless steel substrate (made of SUS316L), a stainless steel base layer, a mixed metal transition layer, a titanium metal layer, a Ti / C transition layer, and a conductive carbon layer.

[0088] Among them, the single layer thickness of the stainless steel base layer is 100nm, and the material of the stainless steel is SUS316L; the mixed metal transition layer includes stainless steel material (made of SUS316L) and titanium material, the content of the stainless steel material decreases gradually in the direction away from the stainless steel substrate, and the content of the titanium material increases gradually in the direction away from the stainless steel substrate, and the single layer thickness is 100nm; the single layer thickness of the titanium metal layer is 50nm; the single layer thickness of the Ti / C transition layer is 50nm; the single layer thickness of the conductive carbon layer is 200nm.

[0089] This embodiment also provides a method for preparing the above-mentioned stainless steel bipolar plate composite coating and a stainless steel bipolar plate containing the same, the preparation method comprising the following steps:

[0090] S1. Place the cleaned SUS316L stainless steel substrate into a magnetron sputtering coater. The coater is pre-installed with SUS316L stainless steel, titanium, and graphite targets. Maintain a grate speed of 3 rpm and evacuate the coater chamber to 4 mPa. Ion clean the surface of the SUS316L stainless steel substrate to facilitate subsequent coating.

[0091] S2. Turn on the SUS316L stainless steel target, adjust the power applied to the stainless steel target to 10 kW, and adjust the bias voltage applied to the SUS316L stainless steel substrate to 300 V. Deposit a 100 nm thick stainless steel base layer on both sides of the SUS316L stainless steel substrate.

[0092] S3. Adjust the bias voltage applied to the SUS316L stainless steel substrate to 100V, and keep the SUS316L stainless steel target on. Adjust the power of the stainless steel target to gradually decrease from 10KW to 0.1KW. Simultaneously, turn on the titanium target and adjust the power applied to the titanium target to gradually increase from 0.1KW to 10KW, depositing a single layer of mixed metal transition layer with a thickness of 100nm.

[0093] S4. The stainless steel target is turned off, and a titanium metal layer with a single thickness of 50 nm is deposited on the surface of the mixed metal transition layer. A metal / carbon transition layer with a single thickness of 50 nm is deposited using conventional magnetron sputtering technology.

[0094] Then, the titanium target is turned off, leaving only the graphite target open, and conventional magnetron sputtering technology is used to deposit a sputtered carbon layer with a single layer thickness of 200 nm.

[0095] Comparative Example 1

[0096] The difference between this comparative example and Example 1 is that the stainless steel bipolar plate composite coating includes a titanium metal layer and a titanium tetraoxide layer in the direction away from the stainless steel substrate (made of SUS316L), and the thickness of the titanium metal layer is 200 nm.

[0097] And the preparation method is adjusted to the following steps:

[0098] S1. Place the cleaned SUS316L stainless steel substrate into a magnetron sputtering coater equipped with an arc ion plating device. A titanium target is pre-installed in the coater. Maintaining the oven speed at 3 rpm, the coater chamber is evacuated to 4 mPa. Ion cleaning is performed on the surface of the SUS316L stainless steel substrate to facilitate subsequent coating.

[0099] S2. A titanium target was activated, and a 200 nm thick titanium metal layer was deposited on the surface of a SUS316L stainless steel substrate. Finally, the titanium target arc cathode was activated, and oxygen gas was introduced at a flow rate of 40 sccm to deposit a 200 nm thick titanium tetraoxide layer directly on the titanium metal layer. All other conditions were the same as in Example 1.

[0100] Comparative Example 2

[0101] The difference between this comparative example and Example 2 is that the stainless steel bipolar plate composite coating includes a titanium metal layer, a Ti / C transition layer, and a conductive carbon layer in the direction away from the stainless steel substrate (made of SUS316L), and the thickness of the titanium metal layer is 200 nm.

[0102] And the preparation method is adjusted to the following steps:

[0103] S1. Place the cleaned SUS316L stainless steel substrate into a magnetron sputtering coater equipped with an electromagnetic plasma assist device. Titanium and graphite targets are pre-set in the coater. Maintain a furnace speed of 3 rpm and evacuate the coater chamber to 4 mPa. Ion cleaning is performed on the surface of the SUS316L stainless steel substrate to facilitate subsequent coating.

[0104] S2. Turn on the titanium target and deposit a 200nm thick titanium metal layer on the surface of the SUS316L stainless steel substrate. Turn on the graphite target and set the bias voltage applied to the SUS316L stainless steel substrate to 100V. Adjust the power applied to the graphite target from 0.5kW to 10kW in a stepwise manner with a ramp-up time of 20 minutes. Simultaneously, adjust the power applied to the titanium target from 10kW to 0.5kW in a stepwise manner. Simultaneously, activate the electromagnetic plasma assist device to generate a magnetic field perpendicular to the trajectory of the deposited particles, so that the magnetic field strength on the surface of the SUS316L stainless steel substrate is 6mT, and a magnetic field strength of 0.55A / cm 2 A single metal / carbon transition layer with a thickness of 50 nm was deposited with a bias current of .

[0105] Then, the titanium target was turned off, leaving only the graphite target on. The bias voltage applied to the surface of the SUS316L stainless steel substrate was set to 50 V, the deposition time was 30 min, the power applied to the graphite target was maintained at 10 kW, and a single-layer sputtered carbon layer with a thickness of 200 nm was deposited. The rest was the same as in Example 2.

[0106] Comparative Example 3

[0107] The difference between this comparative example and Example 5 is that the stainless steel bipolar plate composite coating includes a titanium metal layer, a Ti / C transition layer and a conductive carbon layer in the direction away from the stainless steel substrate (made of SUS316L), and the thickness of the single layer of the titanium metal layer is 200 nm;

[0108] And the preparation method is adjusted to the following steps:

[0109] S1. Place the cleaned SUS316L stainless steel substrate into a magnetron sputtering coater with titanium and graphite targets pre-installed. Maintain the oven speed at 3 rpm and evacuate the chamber to 4 mPa. Ion clean the surface of the SUS316L stainless steel substrate to facilitate subsequent coating.

[0110] S2. A titanium target was activated, and a 200-nm thick titanium metal layer was deposited on the surface of a SUS316L stainless steel substrate. A 50-nm thick metal / carbon transition layer was deposited using conventional magnetron sputtering technology.

[0111] Then, the titanium target was turned off, leaving only the graphite target on, and conventional magnetron sputtering technology was used to deposit a sputtered carbon layer with a single layer thickness of 200 nm. Other conditions were the same as those in Example 5.

[0112] Comparative Example 4

[0113] The difference between this comparative example and Example 1 is that the stainless steel bipolar plate composite coating includes a stainless steel base layer, a titanium metal layer and a titanium tetraoxide layer in the direction away from the stainless steel substrate (made of SUS316L), and the thickness of the titanium metal layer is 150 nm.

[0114] In the preparation method, step S3 is not performed, and the titanium metal layer is directly deposited on the surface of the stainless steel base layer. The single-layer deposition thickness of the titanium metal layer in step S4 is adjusted to 150 nm. Others are the same as in Example 1.

[0115] Test conditions

[0116] The stainless steel bipolar plates provided in Examples 1 to 5 and Comparative Examples 1 to 4 were subjected to performance tests. The test conditions were based on the method required in Part 6: Bipolar Plate Characteristics Test Method 7.3.3 Constant Potential Test of GB / T 20042.6-2024 Proton Exchange Membrane Fuel Cell. A silver / silver chloride electrode (Ag / AgCl) reference electrode was used to perform a constant potential test on the composite coating on the surface of the stainless steel bipolar plate for 1 hour. After the test, the coating corrosion and peeling were observed.

[0117] The test results are shown in Table 1:

[0118] Table 1

[0119]

[0120] As shown in Table 1, compared with Comparative Examples 1-3, Examples 1-5 of the present invention, by introducing a specific type of metal primer layer and a mixed metal gradient transition layer onto the stainless steel substrate, specifically address the technical issue of the metal primer layer being susceptible to peeling at ultra-high potentials. Even in the event of failure of the surface modification layer, the metal bipolar plate composite coating provided by the present invention can still maintain a firm bond between the metal layer and the stainless steel substrate surface, thereby preventing perforation of the stainless steel substrate and excessive precipitation of iron ions.

[0121] Comparison of Example 1 and Comparative Example 4 shows that the present invention is beneficial to improving the flatness and corrosion resistance of the bipolar plate material by providing a composite coating of a metal base layer and a mixed metal gradient transition layer on a stainless steel substrate, and both are indispensable.

[0122] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A metal bipolar plate composite coating, characterized in that: The metal bipolar plate composite coating comprises a metal base layer and a mixed metal transition layer in sequence in a direction away from the metal substrate, wherein the mixed metal transition layer comprises a first metal material and a second metal material; In the mixed metal transition layer, the content of the first metal material and the content of the second metal material vary in a gradient along the thickness direction of the metal substrate.

2. The metal bipolar plate composite coating according to claim 1, characterized in that: In the mixed metal transition layer, the content of the first metal material decreases gradually in a direction away from the metal substrate; And / or, in the mixed metal transition layer, the content of the second metal material increases gradually in a direction away from the metal substrate.

3. The metal bipolar plate composite coating according to claim 1 or 2, characterized in that: The first metal material includes stainless steel; And / or, the second metal material includes any one of titanium, chromium or niobium; And / or, the single layer thickness of the mixed metal transition layer is 100 nm-500 nm.

4. The metal bipolar plate composite coating according to claim 1, characterized in that: The material of the metal base layer is the same as that of the metal substrate; And / or, the metal base layer is made of stainless steel; And / or, the thickness of a single layer of the metal primer layer is 50 nm to 500 nm.

5. The metal bipolar plate composite coating according to claim 1, characterized in that: The metal bipolar plate composite coating further comprises a first metal layer and a conductive carbon layer sequentially arranged on the surface of the mixed metal transition layer in a direction away from the metal substrate; A metal / carbon transition layer is further provided between the first metal layer and the conductive carbon layer, wherein the metal elements in the first metal layer and the metal / carbon transition layer independently include any one of titanium, chromium or niobium; And / or, the metal bipolar plate composite coating further comprises a second metal layer and a metal oxide layer sequentially arranged on the surface of the mixed metal transition layer in a direction away from the metal substrate; The metal elements in the second metal layer and the metal oxide layer independently include any one of titanium, chromium or niobium.

6. A method for preparing a metal bipolar plate composite coating according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: S1. The metal substrate is placed in a multi-target magnetron sputtering chamber, wherein a first metal target and a second metal target are pre-set in the multi-target magnetron sputtering chamber, and a first sputtering deposition is performed on at least one side of the metal substrate to form a metal base layer; S2. performing a second sputtering deposition on the side of the metal base layer away from the metal substrate, adjusting the deposition power parameters of the first metal target and the second metal target respectively to form a mixed metal transition layer to obtain the metal bipolar plate composite coating.

7. The method according to claim 6, characterized in that In step S1, the metal substrate is sequentially subjected to ultrasonic cleaning and plasma cleaning; And / or, in step S1, the first sputtering deposition process includes: turning on a first metal target, adjusting a first power applied to the first metal target to a preset power parameter, and adjusting a bias voltage applied to the metal substrate to a first preset bias parameter, and sputtering and depositing a metal base layer on at least one side of the metal substrate; The material of the first metal target is the same as that of the metal substrate; The preset power parameter range is 8KW-10KW; The first preset bias voltage parameter range is 200V-600V.

8. The method according to claim 6, characterized in that In step S2, the second sputtering deposition process includes: adjusting the bias voltage applied to the metal substrate to a second preset bias parameter, keeping the first metal target turned on, adjusting the first power applied to the first metal target to gradually decrease from the preset power parameter to the initial preset power parameter, and simultaneously turning on the second metal target, and adjusting the second power applied to the second metal target to gradually increase from the initial preset power parameter to the preset power parameter, thereby depositing a mixed metal transition layer; The second preset bias voltage parameter range is no higher than 200V; The initial preset power parameter is 0.1KW-1KW.

9. A metal bipolar plate, characterized in that: The metal bipolar plate includes a metal bipolar plate composite coating prepared by the preparation method according to any one of claims 1 to 5 or any one of claims 6 to 8.

10. A fuel cell, characterized in that: The fuel cell includes the metal bipolar plate according to claim 9.

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