A flow channel field structure of a flow battery bipolar plate and a flow battery bipolar plate

Abstract

The application belongs to the technical field of liquid flow batteries, and provides a liquid flow battery bipolar plate flow channel field structure and a liquid flow battery bipolar plate. A plurality of interdigital flow channels are uniformly distributed along the width direction of the flow channel area of the positive electrolyte. The flow channels on the left and right sides in the flow channel area are symmetrically designed. Each adjacent two ridges are a serpentine ridge and a rectangular ridge. The transformation period of the serpentine ridge and the rectangular ridge is Z1=4-64 mm. The ridge width of each ridge in the flow channel area on the two sides is J1=0.5-32 mm. The narrowest flow channel width of each flow channel is C1=0.3-8 mm. The widest flow channel width of each flow channel is C2=0.3-16 mm. Z1=C1+C2+2J1. The bending period of the serpentine ridge along the length direction of the flow channel area is Z2=4-100 mm. Each bending period of the serpentine ridge is composed of at least one straight line segment and at least one curve segment. The special-shaped flow channel field structure and the design of the flow channel parameters can significantly improve the consistency of the electrolyte distribution in the interdigital flow channel, maintain low mainstream field flow resistance, and provide a new approach to improve the electrical performance of the liquid flow battery stack.

Description

Technical Field

[0001] This invention belongs to the field of flow battery technology, specifically relating to a flow battery bipolar plate flow channel structure and a flow battery bipolar plate. Background Technology

[0002] With the large-scale development and utilization of renewable energy sources such as wind, solar, and tidal power, the instability of their power generation and the mismatch between peak and trough power consumption and daily peak and trough periods have caused significant disruptions to the overall stable operation of the national power grid. Therefore, more efficient energy storage technologies are needed to improve the grid connection rate of renewable energy and reduce the curtailment rate. Flow batteries, as a novel electrochemical energy storage technology, have significant advantages in large-scale energy storage, particularly in terms of safety, environmental adaptability, long lifespan, and flexibility. Their most prominent advantage is scalability; the power and energy density of flow batteries can be increased by adding electrode materials or electrolyte solutions without requiring major changes to the battery structure. This makes flow batteries an ideal choice for large-scale energy storage applications.

[0003] As a core component of flow batteries, bipolar plates primarily serve the following functions: 1) Structural function: providing good mechanical strength, supporting the overall stack structure, and separating individual cells and the positive and negative electrolytes; 2) Conductivity function: offering good conductivity and low internal resistance; 3) Gas-tight function: ensuring good gas-tightness, preventing leakage and cross-contamination of the positive and negative electrolytes; 4) Fluid transport: responsible for the transport and distribution of the positive and negative electrolytes; 5) Chemical stability: exhibiting high resistance to strong acids and alkalis and strong oxidation-reduction reactions. The flow field structure design of the bipolar plates determines the uniformity of the positive and negative electrolyte distribution and the electrolyte resistance within the flow battery, ultimately affecting the stack performance.

[0004] In existing technologies, the flow field structures of bipolar plates in flow batteries are mainly parallel flow fields, interdigitated flow fields, and serpentine flow fields, as well as some modified structures based on the above three basic flow field structures. Compared with the other two basic flow fields, the interdigitated flow field has advantages in terms of liquid flow resistance and electrolyte distribution consistency. The interdigitated flow channel has the characteristics of forced convection, and the electrochemical reaction on the electrode surface is more complete; at the same time, the electrolyte is diverted from the main channel to each branch channel, and only needs to flow through the width of a single rib in the electrode to flow out from the outlet branch channel, resulting in a shorter path and smaller pressure drop. In traditional interdigitated flow channel structures, the electrolyte flows in from one side of the main channel and sequentially into the branch channels. Due to the large area of ​​the active region and the large number of branch channels, the electrolyte distribution becomes less uniform, leading to a large concentration overpotential. Furthermore, because the electrolyte is not evenly distributed to each branch channel, excessive electrolyte concentrates in a few channels, resulting in convection and a rapid increase in pressure drop and pump consumption. Therefore, to address the problems of existing interdigitated flow channel structures, researchers have conducted new studies.

[0005] Patent CN108987763A discloses a bipolar plate for a flow battery with a graded interdigitated flow field. This technical solution employs a bipolar plate where the electrolyte supply and drainage channels are each configured with several branch channels. The final-stage supply and drainage branch channels are arranged in an interdigitated pattern and are not interconnected. This forces the electrolyte to be supplied from the final-stage supply branch channels to the porous electrode and then collected in the final-stage drainage branch channels for discharge. This enhances mass transfer and improves the battery system efficiency.

[0006] Patent CN114824338A discloses a flow battery channel with a bifurcation finger structure on a bipolar plate. This technical solution utilizes a step-by-step bifurcation method to uniformly distribute the electrolyte from the inlet to the inlet channels of each sub-unit of the channel. Similarly, the electrolyte in the outlet channels is collected step-by-step to the outlet in a bifurcation manner. The inlet and outlet channels are arranged alternately in a bifurcation pattern and are not interconnected, forcing the electrolyte to enter the porous electrode from the inlet channels and then flow into the outlet channels for discharge. This structure ensures uniform distribution of the electrolyte in each channel.

[0007] The two existing technical solutions described above are essentially similar in principle, both improving electrolyte distribution rather than the flow channel structure. While this does significantly improve the overall consistency of electrolyte distribution within the electrode plate, it fails to improve the consistency of electrolyte distribution along the flow channel direction within a single channel. Furthermore, when improving existing technologies using these two solutions, the structure at the electrolyte distribution point and the position of the flow channel structure both require uniform adjustments, and other corresponding components also need to be modified accordingly. Summary of the Invention

[0008] In view of this, the purpose of the present invention is to provide a flow channel structure for a flow battery bipolar plate and a flow battery bipolar plate.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows:

[0010] A flow channel structure for a bipolar plate in a flow battery is disclosed, wherein several interdigitated flow channels are uniformly distributed along the width of the positive electrode electrolyte flow channel region, and the protrusions between adjacent flow channels are ridges. Each pair of adjacent ridges is either a serpentine ridge or a rectangular ridge. The flow channels on the left and right sides of the positive electrode electrolyte flow channel region are symmetrically designed.

[0011] The transformation period Z1 of the serpentine ridges and rectangular ridges on the left and right sides of the flow channel area is 4~64mm. The ridge width J1 of each ridge in each period is 0.5~32mm. The narrowest flow channel width C1 of each flow channel is 0.3~8mm. The widest flow channel width C2 of each flow channel is 0.3~16mm. C1≤C2. Z1=C1+C2+2J1. The ridge width J1 / (C1+C2)=0.3~3.0. The bending period Z2 of the serpentine ridge along the length of the flow channel area is 4~100mm. Each bending period of the serpentine ridge consists of at least one straight segment and at least one curved segment. The ratio of the total length of the straight segment to the total length of the curved segment in each bending period is (1:10)~(10:1).

[0012] The flow channels in the positive electrode electrolyte flow channel area and the flow channels in the negative electrode electrolyte flow channel area are arranged alternately.

[0013] The transformation period Z1 is the transformation period of two adjacent groups of serpentine spines and rectangular spines. Further, the ratio of the transformation period Z1 to the width W on the left and right sides of the electrolyte flow channel area is Z1 / W=1:(10~20).

[0014] Furthermore, the spine width J1 / (C1+C2) = 0.6~1.5.

[0015] Furthermore, each bending cycle of the serpentine spine consists of at least one straight segment and at least one curved segment, and the ratio of the total length of the straight segment to the total length of the curved segment in each bending cycle is 1:(0.3~10); preferably 1:(4~10), for example 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10.

[0016] It should be noted here that the total length of the straight lines in a curve segment is the sum of the lengths of the vertical lines between the starting points of each curve segment.

[0017] Furthermore, the width of the straight section of each flow channel is C5 = 0.3~12mm, and C5 = (C1 + C2) / 2.

[0018] Furthermore, the thickness of the bipolar plate is D1 = 0.8~5mm, the depth of each channel in the positive electrolyte flow channel area and the negative electrolyte flow channel area is D2 = 0.2~4.9mm, and (D1-D2) ≥ 0.1mm.

[0019] Furthermore, the minimum sidewall thickness W1 of each flow channel is 0.3~25mm.

[0020] Furthermore, the draft angle R1 of the bipolar plate flow channel is 5°~45°.

[0021] Furthermore, one bending cycle of the serpentine spine includes two bending segments and two straight segments, which are spaced apart and have chamfers between them. The two bending segments are designated as a first bending segment and a second bending segment, respectively. The bending radius of the first bending segment is R2 = 1-40mm, and the bending radius of the second bending segment is R3 = R2 + J1. The two straight segments are located at both ends of the first bending segment, and a first chamfer is provided between both ends of the first bending segment and the two straight segments. The other ends of the two straight segments are connected to the second bending segment through a second chamfer. The bending radius of the second chamfer is R4 = 0.1~20mm, the bending radius of the first chamfer is R5 = R4 + J1, and the length of each straight segment is Z3 = 0.1~60mm.

[0022] Furthermore, the bending radius of the first curved segment R2 = 1-10 mm, the bending radius of the second chamfer R4 = 0.5~5.0 mm, and the length of the straight segment Z3 = 0.5~20 mm.

[0023] Furthermore, the ratio of the bending period Z2 to the length L (along the liquid inlet and outlet direction) of the front and rear sides of the positive electrode electrolyte flow channel region is Z2 / L=1:(3~10).

[0024] The present invention also provides a flow battery bipolar plate, including a positive electrolyte outlet, a positive electrolyte outlet distribution area, a positive electrolyte flow channel area, a negative electrolyte outlet, a positive electrolyte inlet, a positive electrolyte inlet distribution area, and a negative electrolyte inlet, wherein the positive electrolyte flow channel area and the negative electrolyte flow channel area adopt the above-mentioned bipolar plate flow channel field structure.

[0025] Compared with the prior art, the present invention has the following beneficial effects: The technical solution of the present invention creatively proposes a periodic variable-diameter flow channel structure formed by the periodic combination of rectangular ridges and serpentine ridges. By adopting this irregular flow channel structure and limiting the flow channel parameters, the consistency of electrolyte distribution in the interdigitated flow channel is significantly improved, while maintaining a low mainstream flow resistance. This effectively promotes the flow and transport of electrolyte, reduces the concentration loss of the stack, and provides a new way to improve the electrical performance of flow battery stacks. Attached Figure Description

[0026] Figure 1 This is the bipolar plate flow channel structure of Example 1.

[0027] Figure 2 This is a cross-sectional schematic diagram of the flow channel structure in Example 1.

[0028] Figure 3 for Figure 1 Enlarged schematic diagram of the flow channel structure in the positive electrode electrolyte flow channel region.

[0029] Figure 4 This is the bipolar plate flow channel structure of Example 2.

[0030] Figure 5 This is a schematic diagram of the bipolar plate structure of the flow battery in Comparative Example 1.

[0031] Figure 6 The simulated pressure cloud diagrams are for Example 1 and Comparative Example 1.

[0032] Figure 7 The simulated flow velocity cloud diagrams are for Example 1 and Comparative Example 1.

[0033] Figure 8 The vector diagrams are local simulation flow velocity diagrams for Example 1 and Comparative Example 1.

[0034] Figure 1 and Figure 3 In the middle, 1-1, bipolar plate; 1-2, positive electrolyte outlet; 1-3, positive electrolyte outlet distribution area; 1-4, positive electrolyte flow channel area; 1-5, negative electrolyte outlet; 1-6, positive electrolyte inlet; 1-7, positive electrolyte inlet distribution area; 1-8, negative electrolyte inlet; 3-1, serpentine spine; 3-1-1, first curved section; 3-1-2, straight section; 3-1-3, first chamfer; 3-1-4, second chamfer; 3-1-5, second curved section; 3-2, rectangular spine. Detailed Implementation

[0035] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings. It should be understood that the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of the present invention.

[0036] Example 1

[0037] refer to Figures 1-3 A flow battery bipolar plate 1-1 includes a positive electrolyte outlet 1-2, a positive electrolyte outlet distribution area 1-3, a positive electrolyte flow channel area 1-4, a negative electrolyte outlet 1-5, a positive electrolyte inlet 1-6, a positive electrolyte inlet distribution area 1-7, and a negative electrolyte inlet 1-8. The bipolar plate 1-1 has a thickness D1 of 1.5 mm. The positive and negative electrolyte flow channel areas 1-4 and 1-5 have a plurality of interdigitated flow channels evenly distributed along their width. The protrusions between adjacent flow channels form ridges, with each pair of adjacent ridges being a serpentine ridge 3-1 and a rectangular ridge 3-2, respectively. The flow channels on the left and right sides of the positive electrolyte flow channel area 1-4 are symmetrically designed.

[0038] The transformation period Z1 of the serpentine ridges 3-1 and rectangular ridges 3-2 on both sides of the flow channel region is 6 mm. The ratio of the transformation period Z1 to the width W of the electrolyte flow channel region is Z1 / W = 1:(10~20). The width J1 of each ridge in each cycle is 1.75 mm. In this embodiment, since the number of flow channels in the flow channel region is even, the design of the serpentine ridges between the two symmetrical flow channels in the middle of the flow channel region differs from that of the serpentine ridges 3-1 in other cycles.

[0039] The bending period of the serpentine spine 3-1 along the length of the flow channel region has a straight line length Z2 = 20 mm. The ratio of the bending period Z2 to the length L of the positive electrode electrolyte flow channel region 1-4 is Z2 / L = 1:(3~10). Each bending period of the serpentine spine 3-1 consists of at least one straight segment and at least one curved segment, and the total length of the straight segment in each bending period is 2 mm, and the total straight line length of the curved segment is 18 mm. In this embodiment, one bending period of the serpentine spine 3-1 includes two curved segments and two straight segments, with the curved segments and straight segments spaced apart, and a chamfer is provided between the curved segments and straight segments; specifically as follows... Figure 3As shown, the structure includes a first curved segment 3-1-1 and straight segments 3-1-2 at both ends of the first curved segment 3-1-1. A first chamfer 3-1-3 is provided between both ends of the first curved segment 3-1-1 and between the two straight segments 3-1-2. The other ends of the two straight segments 3-1-2 are connected to the second curved segment 3-1-5 through a second chamfer 3-1-4. The bending radius of the first curved segment 3-1-1 is R2=5mm, the bending radius of the second curved segment 3-1-5 is R3=R2+J1=6.75mm, the length of the straight segment 3-1-2 is Z3=1mm, the bending radius of the second chamfer 3-1-4 is R4=1mm, and the bending radius of the first chamfer 3-1-3 is R5=R4+J1=2.75mm.

[0040] In the positive electrode electrolyte flow channel region, the narrowest flow channel width C1 = 1 mm, the widest flow channel width C2 = 1.5 mm, and the straight section flow channel width C5 = 1.25 mm; that is, the narrowest and widest flow channels are the flow channel widths when the two sides of the flow channel are respectively a curve and a straight line. Similarly, in the negative electrode electrolyte flow channel region, the narrowest flow channel width C3 = 1 mm, and the widest flow channel width C4 = 1.5 mm.

[0041] The depth of the positive electrolyte channel in the bipolar plate is D2=1mm, and the plate thickness at the bottom of the channel is W2=0.5mm; the depth of the negative electrolyte channel in the bipolar plate is D3=1mm, and the plate thickness at the bottom of the channel is W3=0.5mm; the draft angle of the bipolar plate channel is R1=10°, and the minimum wall thickness of the channel sidewall is W1=1.2mm.

[0042] Example 2

[0043] like Figure 4 As shown, in this embodiment, the number of channels in the flow channel region is odd; therefore, the middle of the flow channel region is a rectangular flow channel. The thickness of the bipolar plate 1-1 is D1=4mm, the transition period of the serpentine ridge 3-1 and the rectangular ridge 3-2 within the bipolar plate is Z1=24mm, the narrowest width of the positive electrolyte flow channel is C1=3mm, the widest width is C2=5mm, and the width of the straight section of the flow channel is C5=4mm; the depth of the positive electrolyte flow channel within the bipolar plate is D2=3mm, and the thickness of the bottom plate of the flow channel is W2=1mm; the depth of the negative electrolyte flow channel within the bipolar plate is D3=3mm, and the thickness of the bottom plate of the flow channel is W=31mm; the draft angle of the bipolar plate flow channel is R1=45°, and the minimum wall thickness of the flow channel sidewall is W1=2mm.

[0044] Similar to Example 1, in this example, the serpentine spine 3-1 has one bending cycle consisting of two bending segments and two straight segments, with the bending segments and straight segments spaced apart. A chamfer is provided between the bending segments and the straight segments. The difference lies in the specific parameters. In this example, the bending cycle Z2 of the serpentine spine 3-1 within the bipolar plate is 40mm, the length Z3 of the straight segment 3-1-2 in the serpentine spine is 3mm, the spine width J1 is 8mm, the bending radius R2 of the serpentine spine 3-1 is 15mm, and the chamfer R4 between the bending segment and the straight segment in the serpentine spine 3-1 is 5mm.

[0045] Example 3

[0046] A flow battery bipolar plate, compared with Example 1, differs in that: the switching period Z1 of the serpentine ridge 3-1 and the rectangular ridge 3-2 is 24 mm, the narrowest flow channel width C1 is 2 mm, the widest flow channel width C2 is 4 mm, the bending period Z2 of the serpentine ridge 3-1 is 20 mm, the depth of the positive electrode electrolyte flow channel in the bipolar plate is D2 is 1.5 mm, and the thickness of the bipolar plate is 2.5 mm.

[0047] Comparative Example 1

[0048] A flow battery bipolar plate, reference Figure 5 Compared with Example 1, the difference is that there is no serpentine spine in this comparative example; all spines are rectangular. Everything else is the same as in Example 1. That is, the narrowest flow channel width and the widest flow channel width C1=C2=C3=C4=1.25mm.

[0049] Comparative Example 2

[0050] A flow battery bipolar plate, compared with Example 1, differs in that: the serpentine spine 3-1 consists only of curved segments and has no straight segments, while the rest are the same. The bending period Z2 of the serpentine spine 3-1 is 20mm and the bending radius R2=5mm.

[0051] Comparative Examples 3-10

[0052] A flow battery bipolar plate differs from Embodiment 1 in that the switching period Z1 of the serpentine ridge 3-1 and the rectangular ridge 3-2, the narrowest flow channel width C1, the widest flow channel width C2, the bending period Z2 of the serpentine ridge 3-1, the depth D2 of the positive electrode electrolyte flow channel within the bipolar plate, and the thickness of the bipolar plate are different. Specific parameters are shown in Table 1 below. It should be noted that the thickness values ​​of each bipolar plate are not given in Table 1 because, in the effect verification experiment of this invention, only the flow channel thickness D2 needs to be considered. For the bipolar plate thickness D1, it is only necessary to ensure that D1-D2≥0.1mm, without requiring special design.

[0053] Table 1. Flow channel structure parameters of Comparative Examples 3-10

[0054]

[0055] Effect verification

[0056] Fluid dynamics simulations were performed on the above embodiments and comparative examples. The simulation results of the bipolar plates of the flow batteries in all embodiments and comparative examples are shown in Table 2 below. The simulation results for Embodiment 1 and Comparative Example 1 are shown in the figure below. Figures 6-8 As shown.

[0057] Table 2 Fluid dynamics simulation results

[0058]

[0059] Depend on Figure 6 and Figure 7 It can be seen that, compared to Comparative Example 1, the flow resistance of the bipolar plate in Example 1, which has an irregular structure, is slightly higher, but the consistency of flow velocity distribution within the bipolar plate channel is significantly higher, which is beneficial to improving the overall performance of the stack. Figure 8 It can be seen that the "irregular" structure in Example 1 is more conducive to the lateral flow and distribution of electrolyte in the carbon felt, thereby improving the consistency of electrolyte distribution. According to the data in Table 2, it can be seen that the bipolar plate flow channel field structure of Examples 1-3 using the technical solution of the present invention can achieve a significant improvement in electrolyte distribution consistency, with a consistency result of >90%, while maintaining a mainstream flow resistance of <4.0 kPa.

[0060] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the scope of protection of this patent.

Claims

1. A flow channel structure for a flow battery with bipolar plates, characterized in that, The positive electrode electrolyte flow channel region has several interdigitated flow channels evenly distributed along the width direction of the flow channel region. The protrusion between two adjacent flow channels is a ridge. Each pair of adjacent ridges is a serpentine ridge and a rectangular ridge, respectively. The flow channels on the left and right sides of the positive electrode electrolyte flow channel region are symmetrically designed. The transformation period Z1 of the serpentine ridges and rectangular ridges on the left and right sides of the flow channel area is 4~64mm. The ridge width J1 of each ridge in each period is 0.5~32mm. The narrowest flow channel width C1 of each flow channel is 0.3~8mm. The widest flow channel width C2 of each flow channel is 0.3~16mm. C1≤C2. Z1=C1+C2+2J1. The ridge width J1 / (C1+C2)=0.3~3.

0. The bending period Z2 of the serpentine ridge along the length of the flow channel area is 4~100mm. Each bending period of the serpentine ridge consists of at least one straight segment and at least one curved segment. The ratio of the total length of the straight segment to the total length of the curved segment in each bending period is (1:10)~(10:1). The flow channels in the positive electrode electrolyte flow channel area and the flow channels in the negative electrode electrolyte flow channel area are arranged alternately.

2. The flow channel structure of a flow battery bipolar plate according to claim 1, characterized in that, Each bending cycle of the serpentine spine consists of at least one straight segment and at least one curved segment, and the ratio of the total length of the straight segment to the total length of the straight segment in each bending cycle is 1:(0.3~10).

3. The flow channel structure of a flow battery bipolar plate according to claim 1, characterized in that, The serpentine spine includes two curved segments and two straight segments in one bending cycle. The curved segments and straight segments are spaced apart and have a chamfer between them. The two curved segments are designated as the first curved segment and the second curved segment, respectively. The bending radius of the first curved segment is R2 = 1-40mm, and the bending radius of the second curved segment is R3 = R2 + J1. Two straight segments are respectively located at both ends of the first curved segment. A first chamfer is provided between the two ends of the first curved segment and the two straight segments. The other ends of the two straight segments are respectively connected to the second curved segment through a second chamfer. The bending radius of the second chamfer is R4 = 0.1~20mm, and the bending radius of the first chamfer is R5 = R4 + J1. The length of each straight segment is Z3 = 0.1~60mm.

4. The flow channel structure of a flow battery bipolar plate according to claim 3, characterized in that, The bending radius of the first curved section is R2 = 1-10 mm, the bending radius of the second chamfer is R4 = 0.5~5.0 mm, and the length of the straight section is Z3 = 0.5~20 mm.

5. The flow channel structure of a flow battery bipolar plate according to claim 1, characterized in that, The width of the straight section of each flow channel is C5 = 0.3~12mm, and C5 = (C1 + C2) / 2.

6. The flow channel structure of a flow battery bipolar plate according to claim 1, characterized in that, The thickness of the bipolar plate is D1 = 0.8~5mm, the depth of each channel in the positive electrolyte flow channel area and the negative electrolyte flow channel area is D2 = 0.2~4.9mm, and (D1-D2) ≥ 0.1mm.

7. The flow channel structure of a flow battery bipolar plate according to claim 1, characterized in that, The minimum sidewall thickness of each flow channel is W1 = 0.3~25mm.

8. The flow channel structure of a flow battery bipolar plate according to claim 1, characterized in that, The draft angle R1 of the bipolar plate flow channel is 5°~45°.

9. A bipolar plate for a flow battery, comprising a positive electrolyte outlet, a positive electrolyte outlet distribution region, a positive electrolyte flow channel region, a negative electrolyte outlet, a positive electrolyte inlet, a positive electrolyte inlet distribution region, and a negative electrolyte inlet; characterized in that, The positive electrode electrolyte flow channel region and the negative electrode electrolyte flow channel region adopt the bipolar plate flow channel field structure of the flow battery described in any one of claims 1 to 8.

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