Vanadium redox flow electrolytic cell

Abstract

This utility model relates to a full vanadium redox flow electrolytic stack. The full vanadium redox flow electrolytic stack includes two opposing inlet end plates, with two opposing embedded current collectors between them. Multiple integrated titanium bipolar plates are arranged at intervals along the opposing direction of the current collectors. Each bipolar plate has a titanium cathode plate and a titanium anode plate on its two sides, with the cathode and anode plates of adjacent bipolar plates facing each other. Both the titanium cathode and anode plates have an electrolyte reaction zone, an electrode groove surrounding the reaction zone, and an outer non-electrolyte reaction zone. A composite-coated titanium mesh is disposed in the anode plate reaction zone and embedded in the groove, and a composite-coated titanium mesh is disposed in the cathode plate reaction zone and embedded in the groove. A membrane electrode is disposed between the cathode and anode plates of adjacent bipolar plates. This utility model proposes a full vanadium redox flow electrolytic stack with high integration, good sealing performance, strong corrosion resistance, and high electrolysis efficiency.

Description

Technical Field

[0001] This utility model relates to the field of electrolytic cell stack technology, and in particular to an all-vanadium liquid flow electrolytic cell stack. Background Technology

[0002] As a highly efficient long-term energy storage device, the core performance of vanadium redox flow batteries depends, in part, on the volume and concentration of the electrolyte. Currently, electrolysis is the mainstream preparation method due to its ability to continuously produce high-concentration vanadium electrolytes; however, existing electrolytic stacks suffer from the following technical problems:

[0003] 1. Dispersed bipolar plate structure: Traditional bipolar plates mostly adopt the combination of "main plate + electrode frame", which has low integration and poor sealing, and is prone to electrolyte leakage;

[0004] 2. Insufficient corrosion resistance: Carbon steel electrode frames are easily corroded in high-temperature, high-concentration acidic electrolytes, while metal bipolar plates have high strength but high processing costs;

[0005] 3. Limited electrolysis efficiency: The contact resistance between the bipolar plates and the electrodes is high, and the bypass current phenomenon is obvious, resulting in low current efficiency.

[0006] 4. Complex manufacturing process: Composite bipolar plates require multiple assembly steps, resulting in a long production cycle and relatively poor sealing, making it difficult to meet the needs of industrial mass production.

[0007] Therefore, the development of a highly integrated, corrosion-resistant, and efficient all-vanadium redox flow electrolytic cell stack has become an urgent need in this field. Utility Model Content

[0008] To address the aforementioned problems in the prior art, this utility model proposes an all-vanadium redox flow electrolytic stack, which features high integration, good sealing, strong corrosion resistance, and high electrolysis efficiency.

[0009] Specifically, this utility model proposes an all-vanadium redox flow electrolytic cell stack, comprising,

[0010] Two inlet end plates are set opposite to each other;

[0011] Two embedded manifolds are arranged opposite each other and located between the two liquid inlet end plates;

[0012] Multiple integrated titanium bipolar plates are arranged at intervals between two embedded current collectors along the relative direction of the embedded current collectors. The two opposite surfaces of each integrated titanium bipolar plate are a titanium cathode plate and a titanium anode plate, respectively. The titanium cathode plates and titanium anode plates of two adjacent integrated titanium bipolar plates are arranged opposite to each other. An electrolyte reaction zone, an electrode groove surrounding the electrolyte reaction zone, and a non-electrolyte reaction zone are respectively provided on the titanium cathode plate and the titanium anode plate.

[0013] The titanium mesh has an anode composite coating and a cathode composite coating. The anode composite coating titanium mesh is disposed in the electrolyte reaction zone of the titanium anode plate and embedded in the corresponding electrode groove of the titanium anode plate. The cathode composite coating titanium mesh is disposed in the electrolyte reaction zone of the titanium cathode plate and embedded in the corresponding electrode groove of the titanium cathode plate.

[0014] The membrane electrode is disposed between the titanium cathode plate and the titanium anode plate of the two adjacent integrated titanium bipolar plates.

[0015] According to one embodiment of the present invention, a conductive NC titanium composite coating is provided on the surface of the electrolyte reaction zone.

[0016] According to one embodiment of the present invention, the thickness of the integrated titanium bipolar plate is 5.6 to 7.2 mm, and the depth of the electrode groove is 2 to 2.3 mm.

[0017] According to one embodiment of the present invention, a reaction zone channel is formed on the electrolyte reaction zone, and the channel parameters are as follows: channel ridge width 1-3mm, channel width 1-5mm, ridge center distance length 2-11mm, and channel depth 1-2mm.

[0018] According to one embodiment of the present invention, the anode composite coated titanium mesh is an iridium-tantalum composite coated titanium mesh, the cathode composite coated titanium mesh is a Magnesite phase sub-titanium oxide composite coated titanium mesh, and the thickness of both the anode composite coated titanium mesh and the cathode composite coated titanium mesh is 2-2.3 mm; the thickness of the membrane electrode is 320-370 μm.

[0019] According to one embodiment of the present invention, a non-reaction zone flow channel is formed on the non-electrolyte reaction zone, and the non-reaction zone flow channel is connected to the reaction zone flow channel.

[0020] According to one embodiment of the present invention, the integrated titanium bipolar plate further includes a titanium cover plate, which is fixed in conjunction with the non-electrolyte reaction zone structure to enhance the sealing of the non-reaction zone flow channel.

[0021] The present invention provides a full vanadium redox flow electrolytic cell stack, which adopts an integrated titanium bipolar plate integrating titanium anode plate and titanium cathode plate, an anode composite coated titanium mesh and a cathode composite coated titanium mesh, resulting in a full vanadium redox flow electrolytic cell stack with high integration, good sealing performance, strong corrosion resistance and high electrolysis efficiency.

[0022] It should be understood that the above general description and the following detailed description of the present invention are exemplary and illustrative, and are intended to provide further explanation of the present invention. Attached Figure Description

[0023] The accompanying drawings are included to provide a further explanation of the present invention. They are incorporated in and constitute a part of this application. The drawings illustrate embodiments of the present invention and, together with this specification, serve to explain the principles of the present invention. In the drawings:

[0024] Figure 1 A schematic diagram of the structure of an all-vanadium liquid flow electrolytic stack according to an embodiment of the present invention is shown.

[0025] Figure 2 A schematic diagram of the structure of an integrated titanium bipolar plate according to an embodiment of the present invention is shown.

[0026] Figure 3 A partial schematic diagram of an integrated titanium bipolar plate according to an embodiment of the present invention is shown.

[0027] Figure 4 A flowchart illustrating a method for preparing an integrated titanium bipolar plate according to an embodiment of the present invention is shown.

[0028] Figure 5 A flowchart illustrating a method for preparing an anodized composite coated titanium mesh according to an embodiment of the present invention is shown.

[0029] Figure 6 A flowchart illustrating a method for preparing a cathode composite coated titanium mesh according to an embodiment of the present invention is shown.

[0030] The above figures include the following reference numerals:

[0031] 100 vanadium redox flow electrolytic cell stack

[0032] Inlet end plate 110

[0033] Embedded manifold 120

[0034] Integrated titanium bipolar plate 130

[0035] Electrolyte reaction zone 131

[0036] Electrode slot 132

[0037] Non-electrolyte reaction zone 133

[0038] Reaction zone flow channel 134

[0039] Non-reactive zone flow channel 135

[0040] Public flow channel 1351

[0041] Branch channel 1352

[0042] 140 anodized composite coated titanium mesh

[0043] Cathode Composite Coated Titanium Mesh 150

[0044] Membrane electrode 160

[0045] Titanium cover plate 170 Detailed Implementation

[0046] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0047] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0048] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0049] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0050] In the description of this application, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0051] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, these terms have no special meaning and therefore should not be construed as limiting the scope of protection of this application. In addition, although the terminology used in this application is selected from commonly known and used terms, some terms mentioned in this application's specification may have been chosen by the applicant according to his or her judgment, and their detailed meanings are explained in the relevant sections of this description. Moreover, this application should be understood not only through the actual terms used, but also through the meaning implied by each term.

[0052] Figure 1 Figure 1 shows a schematic diagram of the structure of a vanadium redox flow electrolytic stack according to an embodiment of the present invention. Figure 2 shows a schematic diagram of the structure of an integrated titanium bipolar plate according to an embodiment of the present invention. As shown in the figures, a vanadium redox flow electrolytic stack 100 mainly includes two liquid inlet end plates 110, two embedded current collectors 120, and multiple integrated titanium bipolar plates 130. The various components cooperate with each other to achieve efficient electrolysis of the electrolyte and stable operation.

[0053] Two liquid inlet end plates 110 are arranged opposite each other. As the outermost structure of the fuel cell stack, the liquid inlet end plate 110 is responsible for the introduction and export of electrolyte to ensure that the reaction medium flows along the preset path. At the same time, the liquid inlet end plate 110 also serves to secure the fuel cell stack and provide insulation protection, avoiding unnecessary electrical connections between the fuel cell stack and the external environment, and providing safe isolation for the entire device.

[0054] Two embedded current collectors 120 are arranged opposite each other and located between two liquid inlet plates 110. The embedded current collectors 120 are used to achieve efficient current conduction. One end is connected to the external circuit, and the other end forms a low-resistance electrical connection with the integrated titanium bipolar plate 130 on the inner side, providing a stable electron supply and outlet channel for the electrolysis reaction and reducing energy loss during electron transport.

[0055] Multiple integrated titanium bipolar plates 130 are arranged at intervals between two embedded current collectors along the relative direction of the current collectors, serving as the core component of the all-vanadium redox flow electrolytic stack 100. In this example, two integrated titanium bipolar plates 130 are sequentially placed between two embedded current collectors 120. The entire all-vanadium redox flow electrolytic stack 100 is shown in unfolded form to clearly demonstrate the mating relationship between the integrated titanium bipolar plates 130 and surrounding components. The two opposing surfaces of each integrated titanium bipolar plate 130 are a titanium cathode plate and a titanium anode plate, respectively, with the titanium cathode plate of the preceding integrated titanium bipolar plate 130 facing the titanium anode plate of the following adjacent integrated titanium bipolar plates 130. An electrolyte reaction zone 131, an electrode groove 132 surrounding the electrolyte reaction zone 131, and a non-electrolyte reaction zone 133 surrounding the electrode groove 132 are respectively provided on the titanium cathode plate and the titanium anode plate. The electrolyte reaction zone 131 on the titanium anode plate is the anode electrolyte reaction zone, and the electrolyte reaction zone 131 on the titanium cathode plate is the cathode electrolyte reaction zone.

[0056] An anode composite-coated titanium mesh 140 is disposed outside the anolyte reaction zone, serving as the anode electrode embedded in the corresponding electrode groove 132. Similarly, a cathode composite-coated titanium mesh 150 is disposed outside the cathode electrolyte reaction zone, serving as the negative electrode and also embedded in the corresponding electrode groove 132. The matching of these two electrodes with their corresponding reaction zones together constructs a highly efficient electrochemical reaction system, ensuring a stable and efficient preparation process for the vanadium electrolyte.

[0057] A membrane electrode 160 is provided between the titanium cathode plate and the titanium anode plate of two adjacent integrated titanium bipolar plates 130. The membrane electrode 160 serves two purposes: firstly, it separates the positive and negative electrolytes to prevent cross-contamination; secondly, it allows protons to migrate in a directional manner to maintain charge balance. Together with the electrodes on both sides and the reaction zone, it forms a "electrode-membrane-reaction zone" interface, ensuring the continuous and stable operation of the electrolysis process.

[0058] In some examples, conductive NC titanium composite coatings are applied to the surfaces of both the anolyte and negative electrolyte reaction zones to improve the stack's reaction efficiency and durability. The conductive NC titanium composite coating forms an interface layer with both high conductivity and corrosion resistance through the outward diffusion of titanium elements from the titanium matrix and the composite effect of carbon particles. On one hand, its excellent conductivity reduces the contact resistance between the reaction zone and the electrode, accelerating electron transfer at the reaction interface and reducing energy loss. On the other hand, its dense composite structure effectively blocks the corrosion of the integrated titanium bipolar plate 130 by acidic electrolytes, preventing structural failure caused by substrate corrosion and extending the bipolar plate's service life. Simultaneously, the tight bonding between the conductive NC titanium composite coating and the electrolyte reaction zone 131 ensures a stable and unobstructed charge transfer path when vanadium ions in the electrolyte undergo electrochemical reactions on the electrode surface. Combined with optimized electrolyte transport in the electrolyte surface channels, this further improves the reaction uniformity and overall electrolysis efficiency, enabling the stack to maintain stable performance output during long-term operation.

[0059] In some examples, the thickness of the integrated titanium bipolar plate 130 is 5.6–7.2 mm, and the depth of the electrode groove 132 is 2–2.3 mm. Specifically, the thickness of the individual titanium anode plate and titanium cathode plate constituting the integrated titanium bipolar plate 130 is 3.3–3.6 mm. The difference between the thickness of the individual titanium anode plate and titanium cathode plate and the depth of the electrode groove 132 thereon is 1–1.6 mm. This design ensures that the electrode groove 132 can stably accommodate the anode and negative electrodes, avoiding electrode protrusion or poor contact due to insufficient groove depth, while maintaining the overall rigidity of the bipolar plate by retaining sufficient residual electrode thickness, preventing deformation under assembly pressure or electrolyte impact.

[0060] Figure 3 shows a partial schematic diagram of an integrated titanium bipolar plate 130 according to an embodiment of the present invention. As shown in the figure, in some examples, a reaction zone channel 134 is formed on the electrolyte reaction zone 131 of the integrated titanium bipolar plate 130. The flow parameters of the reaction zone channel 134 are as follows: the channel ridge width D1 is 1-3 mm, the channel width D2 is 1-5 mm, the ridge center distance length D3 is 2-11 mm, and the channel depth D4 is 1-2 mm. The setting of the channel parameters directly affects the electrolyte transfer efficiency and reaction uniformity. The channel ridge width D1 of 1-3 mm provides sufficient contact area between the electrode and the bipolar plate, ensuring the stability of the electron conduction path. The combination of the channel width D2 of 1-5 mm and the channel depth D4 of 1-2 mm can optimize the flow resistance according to the viscosity characteristics of the electrolyte, avoiding local stagnation or excessive flow rate. The 2-11mm center-to-back distance length D3 ensures that the electrolyte can uniformly cover the entire electrolyte reaction zone 131 through a reasonable flow channel distribution density, so that vanadium ions can fully contact the electrode surface and improve the reaction conversion rate.

[0061] In some examples, the anode composite coated titanium mesh 140 is an iridium-tantalum composite coated titanium mesh, and the cathode composite coated titanium mesh 150 is a Magneille phase sub-titanium oxide composite coated titanium mesh. The iridium-tantalum composite coated titanium mesh exhibits excellent catalytic activity and corrosion resistance, efficiently promoting the oxidation reaction on the anode side; the Magneille phase sub-titanium oxide composite coated titanium mesh possesses good conductivity and hydrogen evolution inhibition capability, stably driving the reduction reaction on the negative electrode side. The thickness of the anode composite coated titanium mesh 140 and the cathode composite coated titanium mesh 150 is 2–2.3 mm. This dimension is adapted to the depth of the electrode groove 132, ensuring that the electrode can be fully embedded in the groove for accurate positioning, while sufficient thickness ensures the integrity and mechanical strength of the coating structure, preventing damage during electrolyte scouring or assembly, and providing ample active area for the electrochemical reaction. The membrane electrode 160 has a thickness of 320–370 μm and typically consists of a CCM, a cathode / anode gas diffusion layer, and a frame structure. The thickness design of the membrane electrode 160 ensures efficient proton conduction while effectively preventing the mixing of positive and negative electrolytes and preventing cross-contamination. Its close fit with the electrodes on both sides and the reaction zone further constructs a "electrode-membrane-reaction zone" interface, which allows ions generated by the electrochemical reaction to migrate in a directional manner to maintain charge balance and ensure the continuous and stable operation of the electrolysis process.

[0062] In some examples, the non-electrolyte reaction zone 133 of the integrated titanium bipolar plate 130 is provided with a non-reaction zone flow channel 135, which is connected to the reaction zone flow channel 134 of the electrolyte reaction zone 131 to form a complete electrolyte transport path. The non-reaction zone flow channel 135 includes a common flow channel 1351 and a branch flow channel 1352. The common flow channel 1351 receives the electrolyte diverted from the embedded current collector 120. Through the connection design between the branch flow channel 1352 and the reaction zone flow channel 134, the electrolyte is evenly introduced into the entire electrolyte reaction zone 131, while the electrolyte after the reaction is discharged in a timely manner, ensuring that the vanadium ion concentration is uniform throughout the reaction zone and avoiding local reaction efficiency differences.

[0063] In some examples, the all-vanadium redox flow electrolyzer stack 100 also includes a titanium cover plate 170, which is adapted to the non-reactive flow channel 135 area structure of the integrated titanium bipolar plate 130. It can be fixed by laser welding and forms a sealing fit with the sealing groove and sealing ring on the edge of the bipolar plate. Under the assembly clamping force, the titanium cover plate 170 fits tightly against the frame area of ​​the membrane electrode 160, further blocking the possibility of electrolyte leakage from the flow channel to the outside, enhancing the sealing effect on the non-reactive flow channel 135, and improving the long-term operational reliability in conjunction with the overall stacked sealing structure of the stack.

[0064] Figure 4A flowchart illustrating a method for preparing an integrated titanium bipolar plate according to an embodiment of the present invention is shown. As shown, the method for preparing the integrated titanium bipolar plate in the all-vanadium redox flow electrolytic cell 100 includes the following steps:

[0065] S1, titanium matrix annealing, eliminates internal stress through heat treatment at a specific temperature, while controlling the gas environment to reduce the influence of impurities;

[0066] S2 involves applying carbon coating to the surface of a titanium substrate, essentially creating a carbon particle layer as the base component of the composite coating. The primary function of the carbon particles is to enhance electrical conductivity. Based on the conductivity calculation formula, if the composite coating is an NC coating, its conductivity can be improved by increasing the cross-sectional area or decreasing the resistivity. The cross-sectional area can be increased by using carbon particles with high packing density.

[0067] S3 forms a composite coating on the surface of a titanium substrate, utilizing the diffusion characteristics of titanium to combine with carbon particles, forming a composite structure on the surface of the titanium substrate that combines electrical conductivity and corrosion resistance.

[0068] S4. Titanium cathode plates and titanium anode plates with electrolyte reaction zones, electrode grooves and non-electrolyte reaction zones are generated by stamping. Titanium bipolar plates are generated by back-to-back welding of single titanium anode plates and single titanium cathode plates by laser process. After the welding airtightness test, the surface of the titanium bipolar plates is ultrasonically cleaned.

[0069] S5, an insulating coating is applied to the non-electrolyte reaction zone to form an effective insulating layer through vapor deposition process, blocking unnecessary current paths;

[0070] S6 involves sealing the surface of the titanium bipolar plate to enhance overall sealing and prevent electrolyte leakage. Specifically, the sealing process must be tailored to the sealing requirements of the fuel cell stack's operating environment. First, based on parameters such as the stack's operating pressure and electrolyte characteristics, binary high-fluorine rubber is selected as the sealing material. This material possesses excellent acid and temperature resistance, making it suitable for the acidic operating environment of a full vanadium redox flow electrolysis stack. Building upon this, pressure distribution and deformation range required for the sealing structure are determined through stack pressure calculations and stress simulations, ensuring effective sealing contact during assembly and operation. In practice, the sealing groove area of ​​the titanium bipolar plate is a recessed structure surrounding the edge or non-reactive area of ​​the integrated titanium bipolar plate, used to accommodate the sealing component. Sealing lines or adhesive application can be used. Sealing lines, in conjunction with sealing grooves, undergo elastic deformation under pressure to fill the gaps. Adhesive application, on the other hand, forms a continuous sealing layer through the curing of fluid adhesive. Both methods can achieve complete coverage of the sealing groove area, thereby constructing a reliable sealing barrier to prevent electrolyte leakage from the edges or interfaces of the bipolar plates and ensure the long-term stable operation of the fuel cell stack.

[0071] In some examples, in step S1, the titanium substrate is placed in an annealing furnace, and the air inside the furnace is fully replaced by an argon purging system to reduce the amount of nitrogen absorbed by the titanium substrate at high temperatures, thus avoiding adverse effects of nitrogen on the performance of the titanium substrate. The annealing furnace is then heated to 720–780°C and maintained at this temperature for heat treatment for 60–600 seconds. This operation eliminates internal stress within the titanium substrate and stabilizes its crystal structure.

[0072] In step S3, titanium elements diffuse outward from the titanium substrate in the roll-to-roll heat treatment equipment to form an oxide film. This oxide film then combines with the previously coated carbon particles to form an NC titanium coating with a thickness of 50 nm to 500 nm. Controlling the oxygen partial pressure is one of the core parameters of this process. It is set to a specific value that allows titanium elements to diffuse outward and undergo oxidation, ensuring sufficient oxidation of titanium to form a dense oxide film while preventing excessive oxidation of carbon particles due to high oxygen content, which would degrade conductivity. Simultaneously, optimizing the coating time and temperature is equally crucial. A suitable temperature provides the energy conditions for the diffusion and oxidation reactions of titanium, ensuring the reaction rate and coating structural stability; a reasonable time ensures sufficient coating growth, forming a uniform thickness and stable composition, avoiding performance defects caused by insufficient growth. The NC titanium composite coating formed through the aforementioned process combines the excellent corrosion resistance of titanium oxide films with the high conductivity of carbon particles. It can resist the erosion of the titanium substrate by acidic electrolytes and provide an efficient channel for electron transport in electrochemical reactions.

[0073] In some examples, after step S3 and before step S4, the removal of excess carbon particles on the titanium substrate surface is performed. This prevents the excess carbon particles from falling off during subsequent processing or use, ensuring the cleanliness and smoothness of the coating surface, and laying a good foundation for subsequent stamping.

[0074] In some examples, the insulating coating treatment of the non-electrolyte reaction zone in step S5 is performed using a vapor deposition process to form an effective insulating layer. This layer blocks unnecessary current paths in the non-reaction zone, thereby eliminating bypass current and improving the current efficiency of the electrolytic cell stack. The process specifically includes the following steps:

[0075] S51, powdered p-xylene is sublimated into a gaseous raw material. The gaseous form ensures that the raw material can diffuse uniformly in a vacuum environment. Specifically, the powdered p-xylene raw material is placed in the evaporation furnace of the coating equipment and heated to about 150°C under vacuum conditions, causing it to sublimate into a gaseous state.

[0076] S52 decomposes gaseous raw materials into active monomers at 650-700℃. The high temperature causes the molecular chains of the raw materials to break down and form reactive fragments, which prepares for subsequent deposition polymerization.

[0077] S53 involves depositing active monomers at nanoscale rates in a non-electrolyte reaction zone at room temperature. During this process, the monomers spontaneously polymerize to form a phenelzine coating.

[0078] The pyrene coating formed by this process has a thickness between 0.1 and 100 μm and is characterized by transparency and complete surface conformability. It can adhere tightly to various shaped surfaces of non-reactive channels, including sharp edges, cracks, and internal and external surfaces. Using vapor phase deposition instead of liquid phase, the coating does not accumulate in low-lying areas, does not bridge the substrate, and does not exhibit liquid properties such as meniscus or capillary action. Furthermore, the coating is pinhole-free, completely covering non-reactive areas, effectively blocking bypass current conduction, and further ensuring the current efficiency of the electrolytic cell.

[0079] Figure 5 A flowchart illustrating a method for preparing an anode composite-coated titanium mesh according to an embodiment of the present invention is shown. As shown, the method for preparing an anode composite-coated titanium mesh in a vanadium redox flow electrolytic cell includes the following steps:

[0080] For substrate treatment, industrial pure titanium TA1 is selected for pretreatment. This pretreatment removes surface impurities and creates a rough interface. This process not only cleans the titanium mesh surface but also strengthens the adhesion between the coating and the substrate by increasing the contact area, preventing the coating from peeling off during subsequent use.

[0081] The coating solution is prepared by dissolving chloroiridium acid and tantalum chloride in n-butanol to form a homogeneous and stable system. n-Butanol, as a solvent, ensures the complete dissolution of iridium and tantalum ions and allows for uniform evaporation after coating, improving the uniformity of the coating. The appropriate ratio of iridium to tantalum ensures that the coating possesses high oxidation catalytic activity.

[0082] For industrial pure titanium, the coating is applied to the titanium mesh using dip coating or spray coating methods, consisting of 4 layers, with each layer applied 3 to 5 times, and the error in the amount of each layer applied is ≤±10%. This multi-layer, multi-stage coating method avoids cracking or uneven accumulation of the coating caused by excessive thickness in a single application. By gradually building up the coating thickness, it ensures that the coating is dense and adheres tightly to the substrate.

[0083] Thermal decomposition oxidation, carried out at temperatures ranging from 420 to 880 K, causes the iridium and tantalum precursors coated on the titanium mesh surface to decompose and oxidize, transforming into a stable iridium-tantalum composite oxide coating. This temperature range ensures sufficient decomposition of the precursors while preventing performance degradation of the titanium mesh substrate due to high temperatures. The resulting coating exhibits both good catalytic activity and acid resistance, effectively promoting the oxidation reaction on the anode side and improving the overall performance of the electrolytic cell stack.

[0084] In some examples, the pretreatment of industrially pure titanium includes the following steps:

[0085] Industrial pure titanium TA1 is selected as the matrix material. Its hardness HRB value is less than 80, and it has good plasticity and processing performance, which can meet the process requirements of subsequent cutting, forming and coating preparation. At the same time, the corrosion resistance of titanium itself also provides a guarantee for the long-term use of the electrode in acidic electrolyte.

[0086] Cutting and shaping: The titanium material is processed into the required shape with dimensional accuracy controlled within ±0.75mm to ensure the matching of the electrode with the corresponding mounting structure; after laser cutting, the surface is treated without burning and polished to avoid cutting defects affecting the uniformity of the subsequent coating.

[0087] The roughening process involves two steps: sandblasting and etching, to create a suitable surface roughness. During sandblasting, a pressure of 0.7–0.8 MPa combined with 18–60 mesh mixed abrasive creates a uniform uneven structure on the titanium surface. Replacing the abrasive every 2 hours ensures consistency in the sandblasting effect, achieving a surface roughness of 5–10 μm. Subsequent etching uses a 100–120 g / L oxalic acid solution at 310–330 K for 2–12 hours to further refine the surface microstructure, resulting in a uniform grayish-white surface. This process significantly increases the contact area between the coating and the substrate by increasing the micro-roughness of the substrate surface, thereby enhancing the adhesion between them and providing a foundation for stable adhesion of the subsequent coating.

[0088] Figure 6 A flowchart illustrating a method for preparing a cathode composite-coated titanium mesh according to an embodiment of the present invention is shown. As shown, the method for preparing a cathode composite-coated titanium mesh in a vanadium redox flow electrolytic cell stack includes the following steps:

[0089] For substrate treatment, industrial pure titanium TA1 is selected for pretreatment. The substrate treatment process is consistent with that for titanium mesh with iridium-tantalum composite coating, using industrial pure titanium TA1 as the substrate and undergoing pretreatment. Pretreatment not only removes impurities such as oil and oxide layers from the surface of the titanium mesh, but also creates a suitable rough surface, increasing the contact area between the coating and the substrate, thereby enhancing the adhesion between the two and preventing the coating from peeling off during use.

[0090] The coating solution was prepared by hydrolyzing TiOSO4 to produce a TiO2 precursor, which was then dissolved in polyethylene glycol and stirred to form a homogeneous slurry. The TiO2 precursor is the basic material for forming the titanium suboxide coating. Polyethylene glycol acts as a dispersant and binder, which not only ensures the uniform dispersion of the precursor but also temporarily maintains the coating morphology after application, providing a stable structural basis for subsequent high-temperature calcination.

[0091] For the coating process, industrial pure titanium is coated onto the titanium mesh using either dip-coating or spraying methods. The process involves four layers, with each layer applied 3-5 times, and the coating thickness error for each application is ≤±10%. This coating procedure is consistent with the treatment of titanium mesh with a precious metal iridium-tantalum composite coating. This avoids localized areas of excessively thick or thin coatings, ensuring uniform coating thickness, a dense structure, and close adhesion to the titanium mesh substrate. This creates conditions for the subsequent formation of a continuous and stable sub-titanium oxide coating.

[0092] High-temperature calcination, specifically calcination and reduction at 1223–1273 K for 4 hours, transforms the TiO2 precursor into sub-titanium oxide with a Magneille phase structure, particularly Ti4O7, which exhibits the best conductivity, with a single-crystal conductivity of 1500 S / cm. This temperature range and time setting ensures both sufficient reduction of the precursor to form the target phase structure and a strong bond between the coating and the substrate. The resulting Magneille phase sub-titanium oxide composite coating exhibits high conductivity and good corrosion resistance, while effectively suppressing hydrogen evolution reaction, ensuring efficient and stable reduction on the negative electrode side, and improving the overall performance of the electrolytic cell stack.

[0093] Compared with the prior art, the present invention has the following advantages:

[0094] 1. High integration: The integrated titanium bipolar plate integrates the electrode frame, flow channel and bipolar plate, reducing assembly gap and improving sealing performance;

[0095] 2. Excellent corrosion resistance: NC titanium composite coating, anodic composite coating titanium mesh, and cathode composite coating titanium mesh ensure long-term stable operation in acidic environments;

[0096] 3. High-efficiency electrolysis performance: The Parylene insulating coating eliminates bypass current, and the special flow channel design optimizes electrolyte distribution and improves current efficiency;

[0097] 4. Low-cost mass production: The stamping and forming of thin titanium plates and the application of non-precious metal coatings effectively reduce material costs.

[0098] It will be apparent to those skilled in the art that various modifications and variations can be made to the exemplary embodiments of the present invention without departing from the spirit and scope of the present invention. Therefore, it is intended that the present invention cover modifications and variations falling within the scope of the appended claims and their equivalents.

Claims

1. A vanadium redox flow electrolytic cell stack, characterized in that, include, Two inlet end plates are set opposite to each other; Two embedded manifolds are arranged opposite each other and located between the two liquid inlet end plates; Multiple integrated titanium bipolar plates are arranged at intervals between two embedded current collectors along the relative direction of the embedded current collectors. The two opposite surfaces of each integrated titanium bipolar plate are a titanium cathode plate and a titanium anode plate, respectively. The titanium cathode plates and titanium anode plates of two adjacent integrated titanium bipolar plates are arranged opposite to each other. An electrolyte reaction zone, an electrode groove surrounding the electrolyte reaction zone, and a non-electrolyte reaction zone are respectively provided on the titanium cathode plate and the titanium anode plate. The titanium mesh has an anode composite coating and a cathode composite coating. The anode composite coating titanium mesh is disposed in the electrolyte reaction zone of the titanium anode plate and embedded in the corresponding electrode groove of the titanium anode plate. The cathode composite coating titanium mesh is disposed in the electrolyte reaction zone of the titanium cathode plate and embedded in the corresponding electrode groove of the titanium cathode plate. The membrane electrode is disposed between the titanium cathode plate and the titanium anode plate of the two adjacent integrated titanium bipolar plates.

2. The all-vanadium redox flow electrolytic cell stack as described in claim 1, characterized in that, A conductive NC titanium composite coating is provided on the surface of the electrolyte reaction zone.

3. The all-vanadium redox flow electrolytic cell stack as described in claim 1, characterized in that, The thickness of the integrated titanium bipolar plate is 5.6–7.2 mm, and the depth of the electrode groove is 2–2.3 mm.

4. The all-vanadium redox flow electrolytic cell stack as described in claim 1, characterized in that, A reaction zone flow channel is formed on the electrolyte reaction zone. The flow channel parameters are as follows: the ridge width of the flow channel is 1-3 mm, the flow channel width is 1-5 mm, the ridge center distance length is 2-11 mm, and the flow channel depth is 1-2 mm.

5. The all-vanadium redox flow electrolytic cell stack as described in claim 1, characterized in that, The anode composite coated titanium mesh is an iridium-tantalum composite coated titanium mesh, and the cathode composite coated titanium mesh is a Magnetoli phase suboxide composite coated titanium mesh. The thickness of both the anode and cathode composite coated titanium mesh is 2–2.3 mm; the thickness of the membrane electrode is 320–370 μm.

6. The all-vanadium redox flow electrolytic cell stack as described in claim 1, characterized in that, A non-reaction zone flow channel is formed on the non-electrolyte reaction zone, and the non-reaction zone flow channel is connected to the reaction zone flow channel.

7. The all-vanadium redox flow electrolytic cell stack as described in claim 6, characterized in that, The all-vanadium liquid flow electrolytic stack also includes a titanium cover plate, which is fixed in conjunction with the non-electrolyte reaction zone structure of the integrated titanium bipolar plate.

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