Variable-rib-width snake-shaped flow channel structure of flow battery

Abstract

The invention discloses a snake-shaped flow channel structure of a flow battery, and particularly relates to a variable-rib-width snake-shaped flow channel structure of a flow battery, and the rib width between adjacent flow channels from the connecting end to the opening end of a U-shaped part in the snake-shaped flow channel structure is increased from small; the flow channel on one side of the adjacent flow channels of each U-shaped part is in a step shape, each U-shaped part is equally divided into two parts in the extending direction of the adjacent flow channels, the rib width of the part close to the connecting end is smaller, and the rib width of the part close to the opening end is larger. According to the invention, the technical problem that the permeation distribution uniformity of the electrolyte is improved by the distribution change of the flow resistance between the adjacent flow channels in the flow battery electrode adopting the snake-shaped flow channel structure is solved. According to the invention, by changing the rib width distribution between the adjacent flow channels in each U-shaped part, the matching between the flow resistance distribution and the pressure difference distribution is improved, so that the electrolyte infiltration distribution uniformity in the plane direction of the electrode is obviously improved, namely the reaction ion concentration distribution uniformity in the plane direction of the electrode is improved.

Description

Technical Field

[0001] The invention relates to a serpentine flow channel structure of a liquid flow battery, in particular to a serpentine flow channel structure with variable rib width of a liquid flow battery. Background Art

[0002] The traditional flow channel design of flow batteries usually continues to use parallel flow channels, cross flow channels and serpentine flow channels in fuel cells. A large number of previous experimental and simulation results have shown that compared with no flow channels, cross-type and serpentine flow channels can effectively reduce the pressure drop when the electrolyte flows through the porous electrode, and improve the uniformity of the electrolyte flow rate distribution and the reaction ion concentration distribution in the electrode.

[0003] Figure 1 and Figure 2 This is a schematic diagram of the traditional serpentine flow channel structure. As shown in the figure, a complete serpentine flow channel is composed of multiple identical U-shaped parts connected end to end.

[0004] When studying the electrolyte penetration in existing flow battery electrodes using serpentine flow channel structures, it was found that the flow of electrolyte between adjacent flow channels in each U-shaped part includes the flow in the flow channel (such as Figure 2 The solid arrows in the middle) and the subcostal flow in the electrode (as shown in Figure 2 The distribution of the flow rate between the electrolyte flowing in the flow channel and the flow under the rib depends on the pressure distribution and flow resistance distribution in the current area. The amount of electrolyte infiltration from the connection end to the opening end of each U-shaped part shows a gradual increase. This is due to the gradual increase in the pressure difference between adjacent flow channels (the farther from the connection end, the greater the pressure difference) while the flow resistance under the rib remains basically unchanged.

[0005] Therefore, the existing liquid flow battery electrodes using a serpentine flow channel structure have the problem of "significantly uneven pressure distribution between adjacent flow channels, resulting in uneven distribution of electrolyte in the electrode, resulting in low uniformity of reaction ion concentration in the planar direction, which in turn affects battery performance." Summary of the invention

[0006] The purpose of the present invention is to solve the problem of uneven electrolyte infiltration distribution between adjacent flow channels in a liquid flow battery using a traditional serpentine flow channel structure. By optimizing the study on the influence of the change of flow resistance distribution between adjacent flow channels in the serpentine flow channel structure on improving the uniformity of electrolyte infiltration distribution, a variable rib width serpentine flow channel structure of a liquid flow battery is proposed to adjust the flow resistance distribution under the ribs between adjacent flow channels in the traditional serpentine flow channel, thereby improving the uniformity of electrolyte infiltration distribution.

[0007] In order to achieve the above object, the present invention designs a variable rib width serpentine flow channel structure of a liquid flow battery, in which the rib width between adjacent flow channels from the connecting end to the opening end of the U-shaped part of the serpentine flow channel structure changes from small to large.

[0008] The present invention proposes a novel variable rib width serpentine flow channel structure design, which improves the matching of flow resistance distribution and pressure difference distribution by changing the rib width distribution between adjacent flow channels in each U-shaped part. That is, the variable rib width serpentine flow channel design has a small pressure difference at the connecting end of the U-shaped part, an extremely small rib width, and a small flow resistance, and a large pressure difference at the opening end, but the rib width becomes larger, so the flow resistance is large, thereby significantly improving the uniformity of electrolyte penetration distribution in the electrode plane direction, that is, improving the uniformity of reaction ion concentration distribution in the electrode plane direction.

[0009] Preferably, in the variable rib width serpentine flow channel structure of the above-mentioned liquid flow battery, one side of the flow channels in the adjacent flow channels of each U-shaped part of the structure is stepped.

[0010] In the above preferred technical solution, each U-shaped part is evenly divided into two parts in the extension direction of adjacent flow channels, wherein the rib width close to the connecting end is smaller and the rib width close to the opening end is larger, thus showing a trend that the rib width between adjacent flow channels from the connecting end of the U-shaped part to the opening end increases.

[0011] In addition, when implementing the variable rib width design, the above preferred scheme only changes the design of the flow channel on one side of each U-shaped part, while the flow channel on the other side is exactly the same as the design in the traditional serpentine flow channel. This is to ensure that the total number of horizontal flow channels in the complete serpentine flow channel remains unchanged and is evenly distributed, thereby ensuring the uniformity of the penetration and distribution of the electrolyte in the entire electrode.

[0012] Compared with the prior art, the variable rib width serpentine flow channel structure of a flow battery obtained by the present invention has the following technical effects: At the same electrolyte inlet flow rate, the overpotential loss of the flow battery with a variable rib width serpentine flow channel structure is lower than that of the flow battery with a traditional serpentine flow channel structure. This advantage is more obvious at higher current densities (i.e., the mass transfer loss control area of ​​the flow battery polarization curve). When using a traditional serpentine flow channel structure, the limiting current density of the flow battery is about 230 mA / cm 2 The limiting current density of the flow battery with a new variable rib width serpentine flow channel structure is increased to 350 mA / cm 2 (Step-type flow channel structure design). Compared with the limit current density of flow batteries with traditional serpentine flow channel structure, it is increased by more than 50%. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the traditional serpentine flow channel structure; Figure 2 yes Figure 1 A partial enlarged view of the middle A; Figure 3 It is a schematic diagram of the structure of a stepped variable rib width serpentine flow channel; Figure 4 yes Figure 1 A partial enlarged view of point B in the middle; Figure 5 It is a schematic diagram of the structure of an inclined variable rib width serpentine flow channel; Figure 6 yes Figure 1 A partial enlarged view of point C in the middle; Figure 7 It is a schematic diagram of the structure of a semi-inclined variable rib width serpentine flow channel; Figure 8 yes Figure 1 A partial enlarged view of point D in the middle; Fig. 9 This is the polarization curve of the flow battery with different flow channel structures (the electrolyte flow rate at the flow battery inlet is 30 mL / min); Fig.10 The charge and discharge curves of flow batteries with different flow channel structures (the applied current density and electrolyte inlet flow rate are 100 mA / cm 2 and 30 mL / min); Fig.11 The inlet and outlet pressure drop curves of flow batteries with different flow channel structures (the applied battery inlet electrolyte flow rate range is 20 mL / min–80 mL / min); Fig.12 It is the current efficiency histogram, voltage efficiency histogram, battery energy efficiency histogram and system energy efficiency histogram of liquid flow batteries with different flow channel structures.

[0014] In the figure: U-shaped part 1, horizontal flow channel 2, inclined flow channel 3, bipolar plate 4. DETAILED DESCRIPTION

[0015] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention. Embodiment 1:

[0016] like Figure 3 and Figure 4 As shown, as an embodiment of the present invention, a variable rib width serpentine flow channel structure of a liquid flow battery provided in this embodiment is a stepped structural design, composed of a plurality of completely identical U-shaped parts 1 connected end to end, wherein one side of the flow channel in the adjacent horizontal flow channel 2 of each U-shaped part 1 is stepped, and each U-shaped part 1 is evenly divided into two parts in the horizontal direction, wherein the rib width close to the connection end part is smaller and the rib width close to the opening end part is larger. Embodiment 2:

[0017] like Figure 5 and Figure 6 As shown, as a second embodiment of the present invention, a variable rib width serpentine flow channel structure of a liquid flow battery provided in this embodiment is an inclined structural design.

[0018] Consistent with the first embodiment described above, the variable rib width serpentine flow channel structure described in this embodiment is also composed of multiple identical U-shaped parts 1 connected end to end, but in this embodiment, one side of the adjacent flow channel of each U-shaped part 1 is a horizontal flow channel 2, and the other side is an inclined flow channel 3, wherein the rib width close to the connecting end is smaller and the rib width close to the opening end is larger. Embodiment 3:

[0019] like Figure 7 and Figure 8 As shown, as a third embodiment of the present invention, a variable rib width serpentine flow channel structure of a liquid flow battery provided in this embodiment is a semi-inclined structural design.

[0020] Consistent with the first embodiment described above, the variable rib width serpentine flow channel structure described in this embodiment is also composed of multiple completely identical U-shaped parts 1 connected end to end, but in this embodiment, one side of the adjacent flow channel of each U-shaped part 1 is a horizontal flow channel 2, and the middle section of the flow channel on the other side is an inclined flow channel 3, wherein the rib width close to the connecting end is smaller and the rib width close to the opening end is larger.

[0021] The present invention verifies the application of the above-mentioned flow channel structure in the all-vanadium liquid flow battery through experiments.

[0022] Four flow channel structures (conventional serpentine flow channel structure, stepped variable rib width serpentine flow channel structure, semi-inclined variable rib width serpentine flow channel structure and inclined variable rib width serpentine flow channel structure) are processed on the bipolar plate 4 of a liquid flow battery with an electrode area of ​​5 cm × 5 cm.

[0023] The detailed design parameters of the four flow channel structures are shown in Table 1. The cross-section of the flow channels in all flow channels is 1 mm × 1 mm. The rib width distribution of different flow channel structures is different, and the total number of horizontal flow channels 2 contained in the flow channels is the same.

[0024]

[0025] Fig. 9 The polarization curves of flow batteries with different flow channel structures are shown (the electrolyte flow rate at the flow battery inlet is 30 mL / min); Fig.10The charge and discharge curves of flow batteries with different flow channel structures are shown (the applied current density and electrolyte inlet flow rate are 100 mA / cm 2 and 30 mL / min); Fig.11 The inlet and outlet pressure drop curves of flow batteries with different flow channel structures are shown (the applied battery inlet electrolyte flow rate range is 20 mL / min – 80 mL / min).

[0026] In the verification experiment, the area of ​​the electrode in the flow battery is 5 cm × 5 cm, and the electrode material is five layers of carbon paper (SGL 38AA) with an original thickness of 280 um. In addition, a polytetrafluoroethylene electrode frame is used in the battery to control the actual thickness of the electrode material, and the electrode compression rate is controlled at 30%. Finally, based on the charge and discharge curves and the inlet and outlet pressure drop curves of the flow battery, the current efficiency, voltage efficiency, battery energy efficiency (without considering pump power loss) and system energy efficiency (considering pump power loss) of the flow battery with different flow channel structures can be calculated. Fig.12 As shown in the figure, the current efficiency of flow batteries using different channel structures is basically the same. However, due to the reduction of polarization loss during battery charging and discharging, the voltage efficiency of flow batteries using variable rib width serpentine channel structures is higher than that of flow batteries using traditional serpentine channel structures. Among them, the stepped variable rib width serpentine channel structure brings the highest improvement in voltage efficiency, which is about 4.1%.

[0027] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that are the same or similar to those of the present application fall within the protection scope of the present invention.

Claims

1. A variable rib width serpentine flow channel structure of a flow battery, characterized in that: The rib width between adjacent flow channels from the connection end to the opening end of the U-shaped part in the serpentine flow channel structure increases from small to large.

2. The variable rib width serpentine flow channel structure of a flow battery according to claim 1, characterized in that: One side of the adjacent flow channels of each U-shaped portion is stepped, and each U-shaped portion is evenly divided into two parts in the extension direction of the adjacent flow channels, wherein the rib width near the connecting end portion is smaller and the rib width near the opening end portion is larger.

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