Flow field plate, bipolar plate and electrolysis unit
By designing a porous transport layer with a thickness varying in the first direction in the electrolytic stack and cooperating with the contact surface of the electrode plate, the limitations of the existing electrolytic stack in terms of heat transfer and mass transfer and conductivity are solved, and the efficiency of the electrolytic stack is improved.
Patent Information
- Application Number
- CN202422166727.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-04
- Publication Date
- 2025-06-13
- Estimated Expiration
- 2034-09-04
AI Technical Summary
The flow field plates, bipolar plates and electrolytic units of existing electrolytic reactors have limitations in terms of heat transfer and mass transfer and conductivity, resulting in low efficiency.
A porous transport layer having a thickness varying in the first direction is designed, and the contact surface of the combined electrode plate is combined with the shape of the porous transport layer to increase the contact area and improve the fluid mechanical environment of the electrolyte.
By increasing the contact area between the porous transport layer and the plate and improving the fluid mechanical environment, the heat transfer and conductivity are improved, and the efficiency of the electrolytic reactor is improved.
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Figure CN222975308U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the field of electrolytic cells, and in particular to a flow field plate, a bipolar plate and an electrolytic unit. Background Art
[0002] With the development of new energy technologies, hydrogen energy, as a centralized renewable energy carrier, has received increasing attention due to its characteristics of zero pollution, high energy, and wide sources. There are many current hydrogen production methods, and among them, hydrogen production using an electrolyzer stack has become a research hotspot in the current hydrogen production field. An electrolyzer stack usually includes a plurality of electrolytic units stacked together, an end plate for fixing the plurality of electrolytic units together, and pipelines and circuits for supplying electrolyte (water or alkaline solution), coolant, and power to the plurality of electrolytic units. Each electrolytic unit usually includes an anode flow field plate (including an anode plate and an anode porous transport layer), a membrane electrode assembly MEA (including an anode catalyst layer, an exchange membrane (such as a proton exchange membrane PEM or an anion exchange membrane AEM), and a cathode catalyst layer), and a cathode flow field plate (a cathode porous transport layer and a cathode plate). Among them, the anode flow field plate and the cathode flow field plate can be formed into a bipolar plate or a monopolar plate.
[0003] Among the above components, the porous transport layer PTL (including the anode porous transport layer and the cathode porous transport layer, also known as the gas diffusion layer GDL) is an important component. Its main purposes include gas transport, water management, and electrical and thermal conduction. In traditional electrolyzer stacks, porous materials (such as foams, mesh materials, or felts) are usually used as the PTL, and its thickness is fixed, and the porosity is also fixed everywhere in the PTL. In this case, when the electrolyzer stack operates, the gas bubbles formed will gradually accumulate from the fluid inlet to the fluid outlet, which will cause, for example, ohmic and mass transfer losses and uneven distribution of the electrolyte, thus affecting the efficiency of the electrolyzer stack. In addition, the contact area between the PTL with a fixed thickness and the plate is not large enough, and it cannot fully stimulate the potential of the electrolyzer stack.
[0004] In summary, the existing flow field plates, bipolar plates, and electrolytic units have limitations in heat and mass transfer and electrical conduction, so it is necessary to improve them in order to improve the efficiency of the electrolyzer stack. Summary of the Utility Model
[0005] The purpose of this application is to provide a flow field plate, a bipolar plate including the flow field plate, and an electrolytic unit including the flow field plate to solve at least one problem existing in the prior art.
[0006] According to one aspect of the present application, a flow field plate is provided. The flow field plate is used in an electrolysis cell and includes a plate electrode having a contact surface and a porous transport layer that contacts and is electrically connected to the contact surface. An inlet channel and an outlet channel are provided at both ends of the plate electrode along a first direction, and fluid flows from the inlet channel to the outlet channel. The porous transport layer includes a first end and a second end that are opposite to each other. The first end is configured to be disposed close to the inlet channel of the plate electrode, and the second end is configured to be disposed close to the outlet channel of the plate electrode. The porous transport layer further includes a first side configured to face the contact surface of the plate electrode and a second side configured to face the membrane electrode assembly of the electrolysis cell. Wherein, the porous transport layer has a thickness that varies along the first direction, and the contact surface of the plate electrode has a shape that matches the porous transport layer.
[0007] According to an embodiment of the present application, the thickness varies continuously along the first direction.
[0008] According to an embodiment of the present application, the thickness varies uniformly along the first direction.
[0009] According to an embodiment of the present application, the thickness gradually decreases from the first end to the second end, such that the cross-sectional area for fluid flow also gradually decreases from the first end to the second end.
[0010] According to an embodiment of the present application, the thickness is equal at the first end and at the second end.
[0011] According to an embodiment of the present application, the thickness of the porous transport layer is greater than or equal to the thickness at the first end, and the thickness of the porous transport layer reaches a maximum value at the center of the porous transport layer.
[0012] According to an embodiment of the present application, the porous transport layer has additional recesses, and the contact surface has additional protrusions, and the protrusions and the recesses are complementary.
[0013] According to an embodiment of the present application, the porous transport layer has a porosity that varies along the first direction.
[0014] According to another aspect of the present application, a bipolar plate is provided. Wherein, the bipolar plate is formed by a first flow field plate and a second flow field plate, and at least one of the first flow field plate and the second flow field plate is the flow field plate as described above.
[0015] According to still another aspect of the present application, an electrolysis cell is provided. Wherein, the electrolysis cell includes a membrane electrode assembly and a third flow field plate and a fourth flow field plate disposed on both sides of the membrane electrode assembly. Wherein, at least one of the third flow field plate and the fourth flow field plate is the flow field plate as described above.
[0016] By changing the porous transport layer with a uniform thickness to a porous transport layer with a non-uniform thickness, on the one hand, the contact area between the porous transport layer and the electrode plate can be increased, and on the other hand, the hydrodynamic environment of the electrolyte is changed. These two together improve the heat transfer and conduction characteristics between the porous transport layer and the flow field plate, thereby improving the limitations of the flow field plate, bipolar plate and electrolysis unit, and improving the efficiency of the electrolyzer stack. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The exemplary embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be understood that the embodiments described below are only for explaining the present application and not for limiting the scope of the present application. In the drawings:
[0018] Figure 1 Shows a sectional view of a flow field plate along a second direction according to an exemplary embodiment of the present application, where the second direction is a direction perpendicular to the first direction and the stacking direction;
[0019] Figure 2 Shows a sectional view of a flow field plate along the second direction according to another exemplary embodiment of the present application;
[0020] Figure 3 Shows a sectional view of a flow field plate along the second direction according to another exemplary embodiment of the present application;
[0021] Figure 4 Shows a sectional view of a bipolar plate along the second direction according to an embodiment of the present application; and
[0022] Figure 5 Shows a sectional view of an electrolysis unit along the second direction according to an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0023] The preferred embodiments of the present application will be described in detail below with reference to examples. In the embodiments of the present application, the flow field plate, bipolar plate and electrolysis unit for a water electrolyzer stack are taken as examples to describe the present application. However, those skilled in the art should understand that these exemplary embodiments do not mean any limitation to the present application. In addition, the features in the embodiments of the present application can be combined with each other without conflict. In different drawings, the same components are denoted by the same reference numerals, and for the sake of brevity, other components are omitted, but this does not mean that the flow field plate, bipolar plate and electrolysis unit of the present application cannot include other components. It should be understood that the dimensions, proportional relationships and the number of components in the drawings are not limitations to the present application.
[0024] It will be understood that although terms such as "first", "second" may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element, without departing from the scope of the present application.
[0025] Figure 1 FIG. 4 shows an exploded cross-sectional view of the flow field plate 100 according to an exemplary embodiment of the present application in a second direction, which is a direction perpendicular to the first direction x and the stacking direction.
[0026] As Figure 1 shown, according to an exemplary embodiment of the present application, a flow field plate 100 is provided, which can be used in an electrolysis unit. As described above, the flow field plate 100 includes a plate electrode 110 and a porous transport layer 120 connected (in contact) with the plate electrode 110.
[0027] The plate electrode 110 may also be referred to as a "separator", which is substantially impermeable to the electrolyte and electrolysis products. Generally, an inlet channel for introducing the electrolyte and an outlet channel for discharging the electrolyte and / or products (hydrogen and oxygen in a water electrolyzer) are provided on the plate electrode 110. The electrolyte (water) flows into the electrolysis unit from the inlet channel and flows out from the outlet channel. In addition, the plate electrode 110 has a contact surface 113, on which grooves may be formed to form a flow field (flow channels, not shown) conducive to fluid flow. Since the plate electrode 110 needs to maintain functions such as electrical connection, supply of reactants, and heat and mass transfer in the working environment of the electrolysis unit under high pressure, oxidation (anode) or reduction (cathode) conditions, this requires the plate electrode 110 to have high conductivity, corrosion resistance, impermeability, low cost, and sufficient mechanical strength. Therefore, not many materials can be used to manufacture the plate electrode 110. Currently, materials that can be used as the plate electrode 110 include graphite, titanium, stainless steel, etc. The plate electrode is a common component in the electrolytic cell system, so it will not be further described in detail herein.
[0028] The porous transport layer 120 is a component manufactured independently of the electrode plate 110, which can be a metal mesh, metal foam, or other porous conductive material (e.g., aluminum, nickel or its alloy, titanium or its alloy, stainless steel, carbon, or graphite, etc.) typically with a mesh size or pore diameter less than 1 mm, so as to direct the electrolyte to the catalyst layer (in the membrane electrode assembly) to generate hydrogen or oxygen. The porous transport layer 120 includes opposite first end 121 and second end 122. The first end 121 is configured to be disposed near the inlet channel of the electrode plate 110, and the second end 122 is configured to be disposed near the outlet channel of the electrode plate 110. The porous transport layer 120 further includes a first side 123 configured to face the contact surface 113 of the electrode plate 110 and a second side 124 configured to face the membrane electrode assembly of the electrolysis unit, and has a certain porosity between the first side 123 and the second side 124, thereby allowing the electrolyte to pass through the porous transport layer 120 from the first side 123 of the porous transport layer 120 to its second side 124 at an appropriate rate and contact the catalyst layer, while allowing the generated gas to pass through the porous transport layer 120 from the second side 124 of the porous transport layer 120 to its first side 123 and reach the outlet channel of the electrode plate 110. The porous transport layer 120 is configured to be in contact with the electrode plate 110 such that current can be transmitted between the membrane electrode assembly and the electrode plate 110 through the porous transport layer 120. In some embodiments, as shown in the figure, the porous transport layer 120 is embedded in a groove (optionally, a flow channel is provided in the groove) of the electrode plate 110, thereby facilitating the sealing of the electrolysis unit. Alternatively, in other embodiments, the electrode plate 110 may not have a groove and a larger seal (e.g., a sealing gasket) is used to enhance the sealing of the electrolysis unit.
[0029] Preferably, the porous transport layer 120 has a thickness that varies along the first direction x. Here, the first direction x refers to the direction from one end of the electrode plate 110 provided with the inlet channel to the opposite end of the electrode plate 110 provided with the outlet channel, which is perpendicular to the stacking direction of the electrolytic cell (each component of the electrolytic cell is assembled along this direction, and the stacking direction is also the direction in which the thickness of the porous transport layer is measured). At the same time, the contact surface 113 of the electrode plate 110 has a shape that matches the porous transport layer 120, such that the contact surface 113 of the electrode plate 110 can closely adhere to the first side 123 of the porous transport layer 120. The so-called matching shape means that for any shape of the first side 123, there is always a certain structure on the contact surface 113 corresponding to the first side 123. For example, the contact surface 113 of the electrode plate 110 is complementary to the first side 123 of the porous transport layer 120. Therefore, except for the flow channels formed by the electrode plate 110 (as described above, the flow channels may not exist either), there is no gap between the first side 123 and the contact surface 113. In addition, generally, the second side 124 of the porous transport layer 120 should be set perpendicular to the stacking direction, so as to be adapted to the MEA of the existing electrolytic cell. Therefore, the contact surface 113 of the electrode plate 110 in the present application is set not to be perpendicular to the stacking direction, so as to achieve the thickness of the porous transport layer 120 that varies along the first direction x and matches the shape of the contact surface. In this way, the contact area between the contact surface 113 of the electrode plate 110 and the porous transport layer 120 can be significantly increased, thereby increasing the heat transfer capacity and electrical conductivity of the porous transport layer 120 to the electrode plate 110. In addition, the changed thickness will bring about a changed hydrodynamic environment, thereby further improving the mass transfer capacity of the porous transport layer 120. Thus, setting the varying thickness avoids the decrease in the electrolysis reaction rate caused by local overheating and insufficient electrical conductivity and mass transfer capacity, and improves the efficiency of the electrolytic cell.
[0030] According to an exemplary embodiment of the present application, the thickness of the porous transport layer 120 varies continuously along the first direction x, thereby avoiding sudden changes in thickness. In this way, the accumulation of bubbles generated by the reaction product gas at the thickness mutation is avoided (such accumulation will seriously affect the electrical and thermal conductivity efficiency of the porous transport layer 120), thereby improving the efficiency of the electrolytic cell.
[0031] More preferably, the thickness varies uniformly along the first direction x. That is to say, the thickness change rate in the first direction x is equal. Correspondingly, the first side 123 of the porous transport layer 120 and the contact surface 113 of the electrode plate 110 are formed as planes without vertices, thereby further reducing the accumulation of bubbles.
[0032] In addition, the thickness of the porous transport layer 120 can gradually decrease from its first end 121 to its second end 122. Since the flow rate of the electrolyte in the electrolytic cell is fixed, the decreasing thickness (i.e., the decreasing cross-sectional area for flow) necessarily results in an increasing flow velocity. Therefore, the gradually decreasing thickness will lead to a gradually decreasing cross-sectional area for flow, and thus a gradually increasing flow velocity. This makes it more difficult for the generated gas to form bubbles and get stuck in the voids of the porous transport layer 120, which affects heat and mass transfer, and improves the reaction efficiency of the electrolytic cell. At the same time, the porous transport layer 120 can be formed by pressing an existing porous transport layer with a uniform thickness, such that its porosity also gradually decreases from its first end 121 to its second end 122 (i.e., reducing the cross-sectional area for flow). This further increases the flow velocity of the electrolyte and increases the possibility of breaking up the generated bubbles through the flow of the fluid.
[0033] It should be noted that, as shown in the figure, the thickness of the porous transport layer 120 can also gradually increase from its first end 121 to its second end 122, while the porosity therein still gradually decreases. Such a design allows the bipolar plate formed by the two flow field plates 100 to have a sufficient thickness at any position in the first direction (see Figure 4 ), making the bipolar plate more reliable and having a longer lifespan, and also facilitating the setting of the coolant channels.
[0034] Figure 2 FIG. shows a cross-sectional view of the flow field plate 100 along the second direction according to another exemplary embodiment of the present application; Figure 3 FIG. shows a cross-sectional view of the flow field plate 100 along the second direction according to another exemplary embodiment of the present application.
[0035] As Figure 2 and Figure 3 shown, according to an exemplary embodiment of the present application, the thickness at the first end 121 and at the second end 122 can be equal to facilitate the manufacture and reliability of the bipolar plate. At the same time, in such an embodiment, the contact surface 113 and the first side 123 can be arranged to continuously protrude and recess (e.g., in a form similar to a sine wave). Compared with a porous transport layer having a uniformly decreasing thickness or a uniformly increasing thickness, such a porous transport layer 120 can achieve a larger contact area with the contact surface 113, enhancing the heat transfer and electrical conductivity between the porous transport layer 120 and the plate 110, and improving the efficiency of the electrolytic cell.
[0036] Generally, the plates are designed to be symmetric in shape. For example, circular plates or rectangular plates. Therefore, when the electrolyte flows from the inlet channel to the outlet channel, there is a need for diffusion in the circumferential direction of the plate at different positions, and the farther away from the center of the plate, the farther the required diffusion distance is. Providing flow channels on the contact surface is a solution, but it is still not sufficient. Thus, as Figure 2As shown, in the above embodiment, the thickness of the porous transport layer 120 can be set to be greater than or equal to the thickness at the first end 121 and reach the maximum value of the thickness at its central position. Similar to the principle of changing the porosity, the increase in thickness brings an increase in the flow-through cross-section and a decrease in the flow velocity, enabling the electrolyte to stay near the central position for a longer time. This enhances the diffusion of the electrolyte in the circumferential direction, thereby not only increasing the amount of electrolyte that can react simultaneously but also making components such as the porous transport layer and MEA at different positions more evenly utilized, and further extending the lifespan of these components.
[0037] Alternatively, the thickness of the porous transport layer 120 can be less than or equal to the thickness at its first end, thereby increasing the flow velocity of the electrolyte and reducing the presence of bubbles. The principle is the same as that of the embodiment of the porous transport layer 120 with a gradually decreasing thickness, and will not be elaborated here.
[0038] As Figure 3 shown, according to an exemplary embodiment of the present application, the porous transport layer 120 has additional recesses 125 while the electrode plate 110 (contact surface 113) has additional protrusions 115, and the protrusions 115 are complementary to the recesses 125. In this way, the additional protrusions 115 on the contact surface 113 are formed as anchors, and the porous transport layer 120 with recesses 125 is anchored on the electrode plate 110, thereby increasing the fastening force between the electrode plate 110 and the porous transport layer 120. When the electrolyte continuously flows through the inlet channel to the outlet channel and flushes the porous transport layer 120, it will be more difficult for the porous transport layer 120 to separate from the electrode plate 110, resulting in the failure of the electrolysis unit. At the same time, this also increases the contact area between the electrode plate 110 and the porous transport layer 120, improving the efficiency of the electrolysis unit.
[0039] It should be noted that although only the improvement of the function of the flow field plate due to the change in porosity is mentioned in combination with the Figure 1 embodiment, however, such a change in porosity is not limited to this, and it can also be used in other embodiments to achieve the same function with the same principle. Such a change can be formed by pressing the existing porous transport layer in the same way, or by redesigning the porous transport layer, and is not limited thereto.
[0040] The flow field plate according to an exemplary embodiment of the present application increases the contact area between the contact surface of the electrode plate and the first side of the porous transport layer and improves the hydrodynamic environment of the electrolyte by setting the porous transport layer to have a thickness that varies in the first direction while making the contact surface of the electrode plate have a shape that matches the porous transport layer. This is beneficial to improving the heat transfer and conductivity between the electrode plate and the porous transport layer, and further improving the operating efficiency of the electrolysis unit including this flow field plate.
[0041] Figure 4Shows a cross-sectional view of the bipolar plate 200 along the second direction according to an embodiment of the present application.
[0042] According to another embodiment of the present application, a bipolar plate 200 is provided. The bipolar plate 200 is formed by the back side (the side opposite to the contact surface) of the first flow field plate 211 and the back side of the second flow field plate 212. Preferably, a coolant channel 220 is provided between the first flow field plate 211 and the second flow field plate 212. Wherein, at least one of the first flow field plate 211 and the second flow field plate 212 is the flow field plate 100 in any one of the above embodiments.
[0043] Figure 5 Shows a cross-sectional view of the electrolysis cell 300 along the second direction according to an embodiment of the present application.
[0044] According to other embodiments of the present application, an electrolysis cell 300 is provided. The electrolysis cell 300 includes a membrane electrode assembly 310 and a third flow field plate 321 and a fourth flow field plate 322 arranged on both sides of the membrane electrode assembly 310. Wherein, at least one of the third flow field plate 321 and the fourth flow field plate 322 is the flow field plate in any one of the above embodiments. It also includes additional seals 330 to achieve the sealing of the fluid inside the electrolysis cell 300.
[0045] The above embodiments of the present application provide a flow field plate, a bipolar plate and an electrolysis cell. According to the technical solution of the present application, by providing a porous transport layer with a thickness varying along the first direction and matching the shape of the first side of the porous transport layer with the contact surface of the plate, the contact area between the porous transport layer and the plate is increased and the hydrodynamic environment of the electrolyte is improved, thereby improving the heat transfer and conductivity between the plate and the porous transport layer. This not only improves the efficiency of the electrolysis reaction in the electrolysis stack including the flow field plate, bipolar plate or electrolysis cell, but also extends the life of each component.
[0046] The present application has been described in detail above in conjunction with specific embodiments. Obviously, the above description and the embodiments shown in the drawings should be understood as exemplary and do not constitute a limitation to the present application. Those skilled in the art can make various variations or modifications to it without departing from the spirit of the present application, and these variations or modifications do not depart from the scope of the present application.
Claims
1. A flow field plate (100) used in an electrolysis unit, the flow field plate (100) comprising an electrode plate (110) having a contact surface (113) and a porous transport layer (120) in contact with and electrically connected to the contact surface, an inlet channel and an outlet channel being arranged at both ends of the electrode plate along a first direction (x), an electrolyte flowing from the inlet channel to the outlet channel, the porous transport layer comprising a first end (121) and a second end (122) opposite to each other, the first end being configured to be arranged close to the inlet channel of the electrode plate, and the second end being configured to be arranged close to the outlet channel of the electrode plate, the porous transport layer further comprising a first side (123) arranged to face the contact surface of the electrode plate and a second side (124) arranged to face the membrane electrode assembly of the electrolysis unit, It is characterized in that The porous transport layer has a thickness that varies along the first direction, and the contact surface of the electrode plate has a shape that matches the porous transport layer.
2. The flow field plate according to claim 1, characterized in that: The thickness varies continuously along the first direction.
3. The flow field plate according to claim 2, characterized in that: The thickness varies uniformly along the first direction.
4. The flow field plate according to claim 3, characterized in that: The thickness gradually decreases from the first end to the second end, so that the flow cross section gradually decreases from the first end to the second end.
5. The flow field plate according to claim 2, characterized in that: The thickness is equal at the first end and at the second end.
6. The flow field plate according to claim 5, characterized in that: The thickness of the porous transmission layer is greater than or equal to the thickness at the first end, and the thickness of the porous transmission layer reaches a maximum value at the center of the porous transmission layer.
7. The flow field plate according to any one of claims 1 to 6, characterized in that: The porous transport layer has additional recesses (125) and the contact surface has additional protrusions (115) which are complementary to the recesses.
8. The flow field plate according to claim 7, characterized in that: The porous transport layer has a porosity that varies along the first direction.
9. A bipolar plate (200), characterized in that: The bipolar plate is formed by a first flow field plate (211) and a second flow field plate (212), at least one of the first flow field plate and the second flow field plate being the flow field plate (100) according to any one of claims 1 to 8.
10. An electrolysis unit (300), characterized in that: The electrolysis unit comprises: a membrane electrode assembly (310); and A third flow field plate (321) and a fourth flow field plate (322) are arranged on both sides of the membrane electrode assembly, Wherein, at least one of the third flow field plate and the fourth flow field plate is the flow field plate (100) according to any one of claims 1 to 8.