High-current-density liquid flow bipolar plate flow channel structure

Abstract

The invention relates to a high-current-density liquid flow bipolar plate flow channel structure which is composed of a bipolar plate substrate, a cathode flow channel plate and an anode flow channel plate. The bipolar plate substrate is divided into a cathode surface and an anode surface, and is provided with an anode inlet, an anode outlet and a cathode outlet; the cathode / anode runner plate is composed of 2n (n = 1, 2, 3...) sub-runner plates, straight-through runners are arranged on the two sides of the 2n sub-runner plates, and the runners of the sub-runner plates are connected in a staggered mode and are in central symmetry at joints when the 2n sub-runner plates form the cathode / anode runner plate. The cathode runner plate is arranged on the cathode surface of the bipolar plate substrate, the anode runner plate is arranged on the anode surface of the bipolar plate substrate, and runners of the cathode / anode runner plate are respectively parallel to the inlet direction and the outlet direction of the cathode / anode surface of the bipolar plate substrate and are fixed on the surface of the bipolar plate substrate. Under the condition of not changing the pressure difference between the inlet and the outlet, the electrolyte flow is increased, the polarization internal resistance is reduced, the temperature distribution is homogenized, and the electrochemical conversion efficiency is improved.

Description

Technical Field

[0001] The invention relates to the field of liquid flow battery / electrolytic cell and electrochemistry, and in particular to a liquid flow bipolar plate flow channel structure with high current density. Background Art

[0002] As an important component of liquid flow batteries, electrolytic cells and other devices, bipolar plates play the role of conducting electricity, frame support and fluid distribution. When making them, good conductors of electricity are usually selected as the bipolar plate substrate, and then the flow channels are formed on the surface of the active area by carving, etching, collage of other structures, etc., so that the bulk resistance, polarization internal resistance, fluid resistance, and temperature difference distribution of the electrochemical units they constitute are at a relatively low level during operation, thereby improving the energy conversion efficiency and the performance of the battery or electrolytic cell. However, the bulk resistance of the bipolar plate is a material property, which is determined by the selected material. Generally, the contact resistance is reduced by processing the coating on the surface of the plate. The other indicators such as "polarization internal resistance, fluid resistance, temperature difference distribution" are closely related to the flow channel design and fluid control, so the quality of the bipolar plate flow channel design directly affects the final performance of the battery or electrolytic cell.

[0003] There are many forms and types of bipolar plate flow channels at present, which vary slightly according to the shape of the active area of ​​the bipolar plate, mainly including annular, serpentine, Z-shaped, interdigitated, etc., and their main function is to quickly replace the fluid medium in the reaction unit. Similar views are also recognized in the academic community. In the article "Experimental study of the effect of mechanical vibration and water velocity on bubble management in PEM electrolysis cell" published by Science Direct in 2023, the authors clearly pointed out: The main purpose of bubble management in PEMEC is to reduce the accumulation of bubbles. Under high current density, a large amount of oxygen produced will cover the surface of the catalyst layer, block the PTL pores, and affect the electrochemical reaction performance. At the same time, the author concluded through experiments in the article that increasing the fluid flow rate within a certain range can effectively reduce the polarization rate and improve the electrochemical performance. In addition, the article “Effects of the Transport / Catalyst Layer Interface and Catalyst Loading on Mass and Charge Transport Phenomena in Polymer Electrolyte Membrane Water Electrolysis Devices” points out from the side that “in the impedance analysis of a single-section electrolytic cell, the amount of gas in the water flow gradually increases, and the impedance value also increases during the process of transitioning from bubble flow to slug flow.”

[0004] However, in terms of the existing bipolar plate flow channel form, the structural trend of highly compressed battery stacks, and the electrochemical characteristics of polarization, increasing the flow rate is almost the only way to increase the flow rate. However, increasing the flow rate will increase the pressure difference between the inlet and outlet of the battery / electrolyzer, greatly increasing the auxiliary energy consumption. Moreover, the existing technology has also shown that increasing the flow rate can only improve the electrochemical reaction performance within a certain range. Therefore, how to design a bipolar plate flow channel structure that can reasonably set the fluid flow rate while increasing the fluid flow rate without changing or slightly changing the pressure difference between the inlet and outlet of the battery / electrolyzer has become the key to solving the problem.

[0005] Patent CN115911439B discloses a double-helix structure of a flow battery bipolar plate flow channel, which is designed to open positive and negative electrode outlets in the center of the bipolar plate flow channel structure, and open positive and negative electrode inlets at the diagonal of the flow channel structure surface; this design reduces the length of the flow channel through which the electrolyte flows and reduces the fluid pressure drop. However, the electrolyte outlet is set in the center of the flow channel, which limits the applicability of multi-cell battery assembly to a certain extent (the patent only uses a single battery to list embodiments). When applied to multi-cell assembly, an electrolyte lead must be set inside the bipolar plate, which will also increase the thickness of the bipolar plate and increase material costs.

[0006] Patent CN112687906B discloses a multi-layer composite bipolar plate with flow channels, its production method and use, wherein the multi-layer composite bipolar plate with flow channels comprises 2 to 100 stacked plate units, wherein the plate unit comprises carbon paper and a carbon-plastic composite layer coated on one side of the carbon paper, and the outer wall of the multi-layer composite bipolar plate with flow channels is a carbon-plastic composite layer; the plate unit is provided with flow channels. However, the bipolar plate is mainly for vanadium battery stacks, and mainly improves the bipolar plate's ability to withstand high current density by changing the material.

[0007] In summary, it can be seen that increasing the fluid flow rate and flow velocity through flow channel design and flow field control in the battery or electrolytic cell, quickly transporting the reaction products (such as generated gases) to the reaction zone, and reducing the accumulation of reaction products in the battery / electrolytic cell unit are important means to improve the electrochemical performance. Summary of the invention

[0008] In view of the problems and optimization directions of the prior art, the present invention provides a high current density liquid flow bipolar plate channel structure to effectively solve the problems mentioned in the background technology. The bipolar plate channel structure of the present invention can provide a double-layer fluid space on the basis of the traditional channel function, increase the fluid flow rate of the reaction unit without increasing the pressure difference between the inlet and outlet of the fluid, and realize the double-layer control of the fluid flow rate and flow rate. It has the functions of reducing the polarization internal resistance, homogenizing the temperature of the reaction zone, and improving the performance of the battery / electrolytic cell, which is of great significance, especially in the development and design of large-area, high-density batteries / electrolytic cells.

[0009] A high current density liquid flow bipolar plate flow channel structure, characterized in that: the bipolar plate flow channel structure is composed of a bipolar plate substrate, a cathode flow channel plate and an anode flow channel plate; the bipolar plate substrate distinguishes between the cathode side and the anode side, and is provided with channels such as an anode inlet, an anode outlet, and a cathode outlet; the cathode / anode flow channel plates are each composed of 2n (n=1, 2, 3...) diverter channels, both sides of the 2n diverter channels are provided with straight flow channels, and when the 2n diverter channels are respectively formed into cathode / anode flow channel plates, the flow channels of each diverter channel plate are staggered and connected and are centrally symmetrical at the joints; the cathode flow channel plate is arranged on the cathode side of the bipolar plate substrate, and the anode flow channel plate is arranged on the anode side of the bipolar plate substrate, and the flow channel directions of the cathode / anode flow channel plates are respectively consistent with the inlet and outlet directions of the cathode / anode sides of the bipolar plate substrate and are fixed on the surface of the bipolar plate substrate.

[0010] In the above features, the bipolar plate flow channel structure is composed of a bipolar plate substrate, a cathode flow channel plate and an anode flow channel plate; further, the material of the bipolar plate substrate, the cathode flow channel plate and the anode flow channel plate can be one of stainless steel, titanium and its alloys, nickel and its alloys, and can be surface-coated after processing and forming according to the difference in the use environment; the thickness of the bipolar plate substrate is 0.3 to 10 mm, and the thickness of the flow channel plate meets the requirements of both conductivity and mechanical deformation.

[0011] In the above features, the bipolar plate substrate distinguishes between the cathode side and the anode side, and is provided with channels such as an anode inlet, an anode outlet, and a cathode outlet; further, the bipolar plate substrate is a flat plate, and the inlets and outlets are symmetrically distributed at the four edge parts of the plate, and are all through-holes perpendicular to the plate surface, wherein the anode inlet and the anode outlet are distributed on opposite sides, and the two cathode outlets are distributed on opposite sides.

[0012] In the above features, the bipolar plate substrate is divided into a cathode surface and an anode surface; further, the cathode surface of the bipolar plate substrate is in contact with the cathode electrolyte of the electrolytic cell, and the anode surface of the bipolar plate substrate is in contact with the anode electrolyte of the electrolytic cell.

[0013] In the above features, the cathode / anode flow plate is composed of 2n branch flow plates; further, the 2n branch flow plates assembled into the cathode flow plate have exactly the same size and shape, and the 2n branch flow plates assembled into the anode flow plate have exactly the same size and shape, and the size, shape and value of n of the cathode flow plate and the anode flow plate may be different.

[0014] In the above features, straight flow channels are provided on both sides of the 2n manifold plates; further, the straight flow channels provided on the manifold plates are groove-ridge type flow channels, and there are flow channels on both sides, wherein the "ridge" of the flow channel on one side is formed just to form the "groove" of the flow channel on the other side, and the ridge flow channel and the groove flow channel have equal width, equal height, and equal flow channel spacing thickness.

[0015] In the above features, when the 2n manifold plates are used to form the cathode / anode manifold plates respectively, the flow channels of each manifold plate are staggered and connected and are centrally symmetrical at the joints; further, the two edges of the manifold plate parallel to the flow channel direction are symmetrically arranged, and the width is 1 / 2 of the width of the flow channel of the manifold plate, which is used to fit and fix the manifold plate to the surface of the bipolar plate substrate; a "ridge" adjacent to one of the edges of the manifold plate is selected and arranged into a single small groove-ridge flow channel according to the flow channel structure trend, and the width of the internal groove flow channel and the ridge flow channel is set to

[0016] In the above features, when the 2n manifold plates are used to form the cathode / anode manifold plates respectively, the flow channels of each manifold plate are staggered and connected and are centrally symmetrical at the joints; further, during the composition process, each manifold plate is parallelly joined in a staggered manner, so that the ridge of the first manifold plate will face the groove of the second manifold plate, and then the groove of the second manifold plate will face the ridge of the third manifold plate, and they are arranged in sequence; from the two manifold plate edges of each manifold plate in claim 6, only the "ridge" adjacent to one of the manifold plate edges is selected and arranged into a single small groove-ridge flow channel according to the trend of the flow channel structure, so that the central symmetry, manifold plate edge alignment and flow channel staggered can be simultaneously met at the joint.

[0017] In the above features, the cathode flow channel plate is arranged on the cathode surface of the bipolar plate substrate, and the anode flow channel plate is arranged on the anode surface of the bipolar plate substrate; further, there are two ways of setting the 2n branch flow plates when they are respectively composed of the cathode / anode flow channel plates. One is to first laser weld the 2n branch flow plates to form the cathode flow channel plate and the anode flow channel plate respectively, and then adhere them to the surface of the bipolar plate substrate, which can be removed at any time; the other is to first arrange the various branch flow plates on the bipolar plate substrate, and then laser weld each branch flow plate in turn to the surface of the bipolar plate substrate to form an integrated structure.

[0018] Among the above characteristics, the ridge flow channel and the groove flow channel have equal width, equal height, and equal channel spacing thickness; further, the ridge of the flow channel structure is in indirect contact with the bipolar plate substrate, and the current transmitted from the ridge of the flow channel plate to the bipolar plate substrate is transmitted through the groove and the spacing between the ridge flow channels. Because the ridge part of the flow channel structure branch flow channel plate is supported by the flow channel spacing on both sides, it may deform under high assembly pressure, affecting the contact between the bipolar plate and other materials. Therefore, the design of the width and flow spacing of the ridge flow channel and the groove flow channel should take into account both their conductive properties and mechanical deformation deflection requirements.

[0019] The electrical conductivity can be determined according to the following formula (1):

[0020]

[0021] In the above formula (1), a is the width of the groove or ridge flow channel, mm;

[0022] c——channel spacing width, mm;

[0023] I tot ——Design current density of flow battery / electrolyzer, A / mm 2 ;

[0024] T——The width of the flow channel plate perpendicular to the flow channel direction, as shown in Figure (2) T 阳 、T 阴 As shown;

[0025] k2——current ratio, A; where: R c is the resistivity of the flow channel plate material, Ω×m; R Cu is the resistivity of pure copper, i.e. 1.75×10 -8 Ω×m.

[0026] The mechanical deformation deflection can be determined according to the following formula (2):

[0027]

[0028] In the above formula (2), E is the elastic modulus of the material, Pa / mm 2 ;

[0029] I——axial moment of inertia of the cross section, mm 4 ;

[0030] ω——Bending deflection of beam (ω max Indicates the maximum deflection value), mm;

[0031] q——uniformly distributed load, N / mm;

[0032] a——groove or ridge flow channel width, mm.

[0033] In the above features, further, formula (1) is obtained by the following method:

[0034] The current density conducted through the flow channel interval is shown in formula (3), and the meanings of the letters involved in the formula are the same as those in the aforementioned formula (1).

[0035]

[0036] In the above formula (3), I c ——Current density transmitted by the flow channel (I c-max represents the maximum current density achievable), A / mm 2 ;

[0037] k1——channel groove-ridge structural unit period, Where T is the width of the flow channel plate perpendicular to the flow channel direction.

[0038] Standard copper busbar (100×10mm 2 ) is used as the design reference standard for the current carrying capacity of the flow channel plate, that is, the current density through the flow channel interval should not exceed the current carrying density converted to the standard copper busbar according to the material resistivity, that is This ensures that the flow channel plate itself has extremely low resistance.

[0039] So formula (3) is transformed into Further derive formula (1).

[0040] In the above characteristics, further, formula (2) is obtained by the following method:

[0041] The bipolar plate flow channel structure is similar to a simply supported beam, and the restriction conditions are shown in formula (4). The meanings of the letters involved in the formula are the same as those in the aforementioned formula (2).

[0042]

[0043] In the above formula (4), χ is the deflection calculation position, (0≤χ≤a).

[0044] According to the structural symmetry, when When , the deflection ω takes the maximum value, from which formula (2) is derived.

[0045] Formula (2) expresses the relationship between the elastic modulus of the manifold material, the uniformly distributed load q, the groove or ridge channel width a, and the channel spacing c in terms of mechanical mechanics. The calculation of mechanical deformation deflection here is particularly important when the pressure difference between the cathode and anode of the flow battery / electrolyzer is large (such as 1-3.5MPa), and it can be ignored when the cathode and anode are operated in an approximately isobaric environment.

[0046] The beneficial effects of the present invention compared with the prior art are:

[0047] (1) The high current density liquid flow bipolar plate flow channel structure provided by the present invention can double the electrolyte flow rate through the battery cell without changing the inlet and outlet pressure difference, compared with the traditional flow channel type (for example, see the concave liquid groove in the CN112687906B patent, in which adjacent flow channels of the flow channel structure are usually spaced apart, and the liquid cannot flow in the space, which limits the liquid flow rate). The increase in flow rate can dilute the concentration of the reactants, which not only reduces the concentration polarization and improves the electrochemical conversion efficiency, but also can take away the heat generated by the reaction more quickly and equalize the temperature of the reaction zone.

[0048] (2) The bipolar plate flow channel structure provided by the present invention breaks away from the pattern of linear increase in polarization between the inlet and outlet of the electrolytic unit using the traditional flow channel structure, which will result in low voltage at the inlet of the reaction zone and high voltage at the outlet, generating lateral current and causing energy waste. This phenomenon is particularly obvious for large-area, high-density electrolytic units. In the present invention, the product of the current section of the electrolytic unit reaction zone is carried by the electrolyte, then fully mixed in the ridge flow channel of the next section, and then flows to the next section of the reaction zone. Each contact is in the most uniform state of electrolyte concentration, ensuring efficient accommodation of the reaction products, greatly reducing the polarization internal resistance of the electrode surface, and improving the performance of the liquid flow battery / electrolytic cell.

[0049] (3) The bipolar plate flow channel structure provided by the present invention has a wide range of applications, good flexibility, is easy to implement, and can be used in large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to clearly demonstrate the bipolar plate flow channel structure of the present invention, in the design and implementation, the cathode / anode flow channel plates are composed of two (ie, n=1) branch flow channel plates.

[0051] Figure 1 It is a structural schematic diagram of the present invention;

[0052] Figure 2 It is a top view of the flow channel structure on the cathode and anode surfaces of the bipolar plate;

[0053] Figure 3 for Figure 1 Structural cross-section of the middle anode shunt plate;

[0054] Figure 4 for Figure 1 Schematic diagram of the two anode shunt plates before and after joining;

[0055] Figure 5 for Figure 1 The edge alignment of the flow channel plate after the central anode manifold plate is symmetrically joined, and the design diagram of the small groove-ridge flow channel structure;

[0056] Figure 6 The electrolysis voltage-time and anode inlet and outlet temperature difference-time variation curves in Example 1 and Comparative Example 1 are shown;

[0057] Figure 7 The electrolysis voltage-time and anolyte flow-time variation curves in Example 2 and Comparative Example 2;

[0058] Wherein: 1 is a bipolar plate substrate, 101 is an anode inlet, 102 is an anode outlet, 103 is a cathode outlet, 2 is an anode manifold plate, 201 is a ridge of the anode manifold plate 2, 202 is a groove of the anode manifold plate 2, 203 is a ridge flow channel of the anode manifold plate 2, 204 is a groove flow channel of the anode manifold plate 2, 205 is a flow channel interval of the anode manifold plate 2, 206 is a flow channel edge of the anode manifold plate 2, 207 is a small groove-ridge flow channel of the anode manifold plate 2, 3 is an anode manifold plate, 303 is a ridge flow channel of the anode manifold plate 3, 304 is a groove flow channel of the anode manifold plate 3, 4 is a cathode manifold plate, and 5 is a cathode manifold plate. DETAILED DESCRIPTION

[0059] The present invention is described in detail below by specific examples, but the protection scope of the present invention is not limited. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment and materials used can be obtained from commercial channels.

[0060] The present invention believes that the application of bipolar plate flow channel structure in liquid flow batteries and electrolytic cells is undifferentiated, and its purpose is mainly centered around two aspects: temperature transfer and mass transfer, that is, to achieve better temperature uniformity management and to bring out the reaction products on the electrode surface in time, and ultimately reduce the polarization effect. Therefore, the present invention only uses one set of equipment, namely a PEM water electrolysis hydrogen production device, to verify the invention content during the implementation process.

[0061] The configuration of the PEM water electrolysis hydrogen production device used in the embodiment is: power 50kW, temperature control at 60±5°C, control accuracy ±1°C; flow range 2~50L / min, control accuracy ±50mL / min; DC power supply voltage 0~40V, accuracy 10mV; current 0~3500A, accuracy ±10A; operating pressure 0~3.5MPa, control accuracy ±50kPa.

[0062] Example 1

[0063] A high current density liquid flow bipolar plate flow channel structure, the specific embodiment parameters are as follows:

[0064] The bipolar plate substrate 1, cathode / anode flow plate (the cathode flow plate is composed of the cathode shunt plate 4 and the cathode shunt plate 5; the anode flow plate is composed of the anode shunt plate 2 and the anode shunt plate 3) are all made of pure nickel. The overall length of the bipolar plate is 550mm, the width is 350mm, and the thickness is 2.0mm; the bipolar plate substrate 1 is 0.6mm thick, and the middle 399.4×250.6mm rectangle is the flow area. The anode inlet 101 and the anode outlet 102 are symmetrically distributed on the two short sides, and 2 outlets are set on each side; the cathode outlet 103 is symmetrically distributed on the two long sides, and 3 outlets are set on each side. The size and type of the anode shunt plate 2 and the anode shunt plate 3 are exactly the same (the anode shunt plate 3 can be obtained by rotating the anode shunt plate 2 180° in the plane). It is formed by stamping process, and the size is 199.7mm long and T wide. 阳 250.6mm, thickness 0.7mm; groove / ridge channels (groove channels 204 and ridge channels 203) are 0.5mm deep and 1.0mm wide, channel interval 205 is 0.2mm thick, and after joining, the channels are parallel to the long side of the bipolar plate substrate 1. The cathode shunt channel plate 4 and the cathode shunt channel plate 5 are exactly the same in size and type (the cathode shunt channel plate 5 can be obtained by rotating the cathode shunt channel plate 4 180° in the plane), and are formed by stamping process, with a size of 125.3mm long and T wide. 阴 399.4mm, thickness 0.7mm; groove / ridge channel depth 0.5mm, width 1.0mm, channel interval thickness 0.2mm, after joining, the channel is parallel to the short side of the bipolar plate substrate 1. The channel edge of each cathode / anode shunt channel plate (such as Figure 5 The flow channel edge 206 of the anode manifold plate 2 is reserved with 0.5 mm.

[0065] Forming process of bipolar plate flow channel:

[0066] The anode shunt plate 2 and the anode shunt channel plate 3 are aligned and placed in a centrally symmetrical manner in the anode surface flow channel area of ​​the bipolar plate substrate 1, and then fixed to the anode surface of the bipolar plate substrate 1 by laser welding in sequence. At this time, the ridge flow channel 203 of the anode shunt channel plate 2 is just docked with the groove flow channel 304 of the anode shunt channel plate 3, and the groove flow channel 204 of the anode shunt channel plate 2 is just docked with the ridge flow channel 303 of the anode shunt channel plate 3, finally forming an integrated structure of the bipolar plate anode flow channel plate.

[0067] The preparation of the integrated structure of the cathode flow channel plate of the bipolar plate refers to the above-mentioned integrated structure molding process of the anode flow channel plate.

[0068] Design analysis of bipolar plate flow channels:

[0069] It is known that the conductivity of pure nickel is 6.83×10 -8 Ω×m, elastic modulus is 207GPa, and the uniform load on the flow channel plate during assembly is 0.024N / mm2 , design current density 3A / cm 2 .

[0070] The maximum value of a calculated by formula (1) is 3.18 mm. In the embodiment, a=1.0 mm is designed to meet the requirement of reference copper conductivity without increasing resistance.

[0071] The deflection ω at a / 2 calculated by formula (2) is max =0.23×10 -5 mm, ignored here.

[0072] Performance test of bipolar plate flow channel:

[0073] The bipolar plate flow channel structure is assembled into a PEM electrolyzer. The fluid pipeline of the electrolyzer is provided with 1 anode inlet, 1 anode outlet and 2 cathode outlets, which correspond to the anode inlet 101, anode outlet 102 and cathode outlet 103 of the bipolar plate respectively; the cathode and anode diffusion layers are made of carbon paper and titanium felt, respectively, with a thickness of 400um, and the membrane electrode with DuPont N117 membrane as the proton exchange membrane has a total of 6 sections, and the cell core is assembled at a compression ratio of 12%. The flow rate is set to 30L / min, the temperature is set to 65℃, the pressure is 3.0MPa, and the electrolysis is adjusted to 2000A constant current mode. After stabilization, the electrolysis is continued for 24h. Three parallel tests are carried out to record the electrolysis voltage, anode inlet and outlet temperatures and pressure difference under stable operation.

[0074] Comparative Example 1

[0075] The bipolar plate material, thickness, cathode / anode inlet and outlet, and flow channel area are the same as those in Example 1. The flow channel area is processed into a traditional straight groove-ridge flow channel (the structure is similar to the concave liquid tank flow channel in the CN112687906B patent) by etching technology. The difference from the bipolar plate flow channel structure in Example 1 is that: ① Each flow channel is a straight-through type connecting the outlets on both sides (the anode side connects the inlet and outlet), without detours, interruptions, and misalignment; ② The bottom of the flow channel ridge (such as Figure 3 The solid structure of the bipolar plate substrate is still maintained at the position shown in 203 in the figure, so that the fluid cannot pass through. In addition, the flow rate of the electrolyte is one of the main factors affecting the electrochemical polarization, and its level is completely determined by the subjective control strategy. In order to maintain the comparability of the experiment, this comparative example adopts the same anode inlet and outlet pressure difference as Example 1 in terms of electrolyte flow control.

[0076] A PEM electrolyzer was assembled using the same carbon paper, membrane electrode and assembly process as in Example 1 except for the bipolar plate. The electrolyzer performance was tested using the same test device and procedure, and the electrolysis voltage under stable operation and the anode inlet and outlet temperatures were recorded.

[0077] Example 2

[0078] The performance test of the electrolytic cell under high current density was carried out. On the basis of Example 1, the current in the constant current mode was modulated to 3000A. After stabilization, electrolysis was performed for 24 h. Other conditions remained unchanged. The electrolysis voltage, anolyte flow rate, and inlet and outlet pressure difference under stable operation were recorded.

[0079] Comparative Example 2

[0080] The performance test of the electrolytic cell under high current density was carried out. On the basis of Comparative Example 1, the current in the constant current mode was modulated to 3000A, and the pressure difference of the electrolyte at the anode inlet and outlet was set to be consistent with that in Example 2. After stabilization, electrolysis was carried out for 24 hours. Other conditions remained unchanged, and the electrolysis voltage and anode electrolyte flow rate under stable operation were recorded.

[0081] Data analysis

[0082] According to the 2A / cm cut from Example 1 and Comparative Example 1 2 After stable operation, the electrolysis data for 24 hours is used to make the electrolysis voltage-time and anode inlet and outlet temperature difference-time curves, such as Figure 6 Compared with the conventional straight-through groove-ridge flow channel, the electrolytic cell assembled by the bipolar plate flow channel structure provided by the present invention has an 8% increase in electrolysis voltage efficiency at the same current density, and a reduction of nearly 2°C in the temperature difference between the anode inlet and outlet.

[0083] According to the 3A / cm cut from Example 2 and Comparative Example 2 2 After stable operation, the electrolysis data for 24 hours is used to make the electrolysis voltage-time and anode flow-time change curves, such as Figure 7 Compared with the conventional straight-through groove-ridge flow channel, the electrolytic cell assembled with the bipolar plate flow channel structure provided by the present invention has an electrolysis voltage efficiency increased by 10.5% at the same high current density, and an electrolyte flow rate increased by about 1 times at the same anode inlet and outlet pressure difference.

[0084] The above embodiments and comparative examples illustrate that the bipolar plate flow channel structure of the present invention has obvious advantages in electrolytic cell performance over the traditional straight-through groove-ridge flow channel. However, the above embodiment is only a single technical solution of the present invention, which is used to illustrate the technical effect of the present invention and is not a limitation thereof. For those skilled in the art, technical modifications and equivalent substitutions in the direction of liquid flow batteries or other types of electrolytic cells developed on this basis should be considered to be included in the scope of protection of the claims of the present invention.

Claims

1. A high current density liquid flow bipolar plate flow channel structure, characterized in that: The bipolar plate flow channel structure is composed of a bipolar plate substrate, a cathode flow channel plate and an anode flow channel plate; the bipolar plate substrate distinguishes between the cathode side and the anode side, and is provided with channels such as an anode inlet, an anode outlet, and a cathode outlet; the cathode / anode flow channel plates are each composed of 2n (n=1, 2, 3...) diverter channels, and both sides of the 2n diverter channels are provided with straight flow channels. When the 2n diverter channels are respectively formed into cathode / anode flow channel plates, the flow channels of each diverter channel plate are staggered and connected and are centrally symmetrical at the joints; the cathode flow channel plate is arranged on the cathode side of the bipolar plate substrate, and the anode flow channel plate is arranged on the anode side of the bipolar plate substrate. The flow channel directions of the cathode / anode flow channel plates are respectively consistent with the inlet and outlet directions of the cathode / anode sides of the bipolar plate substrate and are fixed on the surface of the bipolar plate substrate.

2. According to claim 1, the bipolar plate flow channel structure is composed of a bipolar plate substrate, a cathode flow channel plate and an anode flow channel plate; further, the material of the bipolar plate substrate, the cathode flow channel plate and the anode flow channel plate can be one of stainless steel, titanium and its alloys, nickel and its alloys, and can be surface-coated after processing and forming according to the difference in the use environment; the thickness of the bipolar plate substrate is 0.3 to 10 mm, and the thickness of the flow channel plate meets the requirements of both conductivity and mechanical deformation.

3. According to claim 1, the bipolar plate substrate distinguishes between the cathode side and the anode side, and is provided with channels such as an anode inlet, an anode outlet, and a cathode outlet; further, the bipolar plate substrate is a flat plate, and the inlet and outlet are symmetrically distributed at the four edge parts of the plate, and are all through-holes perpendicular to the plate surface, wherein the anode inlet and the anode outlet are distributed on opposite sides, and the two cathode outlets are distributed on opposite sides.

4. According to claim 1, the bipolar plate substrate is divided into a cathode surface and an anode surface; further, the cathode surface of the bipolar plate substrate is in contact with the cathode electrolyte of the electrolytic cell, and the anode surface of the bipolar plate substrate is in contact with the anode electrolyte of the electrolytic cell.

5. According to claim 1, the cathode / anode flow channel plates are composed of 2n shunt flow channel plates; further, the 2n shunt flow channel plates assembled into the cathode flow channel plate have exactly the same size and shape, and the 2n shunt flow channel plates assembled into the anode flow channel plate have exactly the same size and shape, and the size, shape and value of n of the cathode flow channel plate and the anode flow channel plate may be different.

6. According to claim 1, both sides of the 2n manifold plates are provided with straight flow channels; further, the straight flow channels arranged on the manifold plates are groove-ridge type flow channels, and there are flow channels on both sides, wherein the "ridge" of the flow channel on one side is formed just to form the "groove" of the flow channel on the other side, and the ridge flow channel and the groove flow channel have equal width, equal height, and equal flow channel spacing thickness.

7. According to claim 1, when the 2n manifold plates are used to form cathode / anode manifold plates respectively, the flow channels of each manifold plate are staggered and connected and are centrally symmetrical at the joints; further, the two edges of the manifold plate parallel to the flow channel direction are symmetrically arranged, and the width is 1 / 2 of the width of the flow channel of the manifold plate, which is used to fit and fix the manifold plate to the surface of the bipolar plate substrate; the "ridge" adjacent to one of the edges of the manifold plate is selected to be arranged into a single small groove-ridge flow channel according to the flow channel structure trend, and the width of the internal groove flow channel and the ridge flow channel is set to 8. According to claim 1, when the 2n manifold plates are used to form cathode / anode manifold plates respectively, the flow channels of each manifold plate are staggered and connected and are centrally symmetrical at the joints; further, during the composition process, each manifold plate is parallelly joined in a staggered manner, so that the ridge of the first manifold plate will face the groove of the second manifold plate, and then the groove of the second manifold plate will face the ridge of the third manifold plate, and they are arranged in sequence; from the two manifold plate edges of each manifold plate in claim 6, only the "ridge" adjacent to one of the manifold plate edges is selected and arranged into a single small groove-ridge flow channel according to the trend of the flow channel structure, so that the central symmetry, manifold plate edge alignment and flow channel staggered can be simultaneously met at the joint.

9. According to claim 1, the cathode flow plate is arranged on the cathode surface of the bipolar plate substrate, and the anode flow plate is arranged on the anode surface of the bipolar plate substrate; further, there are two ways of setting the 2n diverter plates when they are respectively composed of the cathode / anode flow plates. One is to firstly form the cathode flow plate and the anode flow plate by laser welding of the 2n diverter plates respectively, and then affix them to the surface of the bipolar plate substrate, which can be removed at any time; the other is to first arrange the various diverter plates on the bipolar plate substrate, and then fix each diverter plate on the surface of the bipolar plate substrate in turn by laser welding to form an integrated structure.

10. According to claim 6, the ridge flow channel and the groove flow channel have equal width, equal height, and equal channel spacing thickness; further, the ridge of the flow channel structure is in indirect contact with the bipolar plate substrate, and the current transmitted from the ridge of the flow channel plate to the bipolar plate substrate is transmitted through the groove and the spacing between the ridge flow channels. Because the ridge part of the flow channel structure branch flow channel plate is supported by the flow channel spacing on both sides, it may deform under high assembly pressure, affecting the contact between the bipolar plate and other materials. Therefore, the design of the width and flow spacing of the ridge flow channel and the groove flow channel should take into account their conductive properties and mechanical deformation deflection requirements at the same time. The electrical conductivity can be determined according to the following formula (1): In the above formula (1), a is the width of the groove or ridge flow channel, mm; c——channel spacing width, mm; I tot ——Design current density of flow battery / electrolyzer, A / mm 2 ; T——The width of the flow channel plate perpendicular to the flow channel direction, as shown in Figure (2) T 阳 , T 阴 As shown; k2——current ratio, A; where: R c is the resistivity of the flow channel plate material, Ω×m; R Cu is the resistivity of pure copper, i.e. 1.75×10 -8 Ω×m. The mechanical deformation deflection can be determined according to the following formula (2): In the above formula (2), E is the elastic modulus of the material, Pa / mm 2 ; I——axial moment of inertia of the cross section, mm 4 ; ω——Bending deflection of beam (ω max Indicates the maximum deflection value), mm; q——uniformly distributed load, N / mm; a——groove or ridge flow channel width, mm.

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