Bipolar plate and electrode composite structure and flow battery stack

Abstract

The utility model provides a bipolar plate and electrode composite structure and a redox flow battery stack, the bipolar plate and electrode composite structure comprises a bipolar plate and an electrode in contact with the bipolar plate, the bipolar plate is provided with a liquid inlet flow channel, and the electrode is provided with a liquid outlet flow channel. The liquid inlet flow channel and the liquid outlet flow channel are respectively arranged on one surface, in contact with the electrode, of the bipolar plate, and form a flow field. According to the utility model, the mass transfer quality of the electrolyte of the flow battery in the direction perpendicular to the plane of the electrode in the electrode can be improved, the concentration polarization of the flow battery is reduced, and the performance of the flow battery is improved.

Description

Technical Field

[0001] The utility model mainly relates to the technical field of liquid flow batteries, and in particular to a bipolar plate and electrode composite structure and a liquid flow battery stack. Background Art

[0002] The problem of global warming caused by carbon dioxide can be mitigated by wind and solar energy, but they are limited by intermittency and volatility. It is generally believed that commercial energy storage devices based on electrochemistry are one of the more mature technologies, mainly flow battery technology. In recent years, many studies have been carried out to enhance the mass transfer quality of flow batteries to improve the performance of flow batteries.

[0003] Liquid flow batteries are mainly composed of battery stack units, electrolytes, electrolyte storage and supply units, and management and control units. They are high-performance batteries that separate positive and negative electrolytes and circulate them separately. They use electroactive elements as catalysts for electrochemical reactions to directly and reversibly convert chemical energy into electrical energy. Liquid flow batteries have the characteristics of high capacity, wide application range, and long cycle life, and are a new type of energy storage product.

[0004] With the continuous advancement of technology and the reduction of costs, the application field of liquid flow batteries will continue to expand and contribute to the sustainable development of energy. Therefore, improving the performance of liquid flow batteries is one of the goals that are pursued unremittingly. In one way, improving the uniform distribution of active substances in the electrodes of liquid flow batteries is conducive to improving the performance of liquid flow batteries, and adding a flow field is an important means to improve the uniform distribution of active substances in the electrodes of liquid flow batteries. The flow field of the prior art is generally set on the bipolar plate. Although this improves the mass transfer quality in the electrode plane (xy plane) to a certain extent, since the inlet and outlet flow channels of the flow field are located in the same plane, the mass transfer in the direction perpendicular to the electrode plane (z direction) is still not ideal. Utility Model Content

[0005] The technical problem to be solved by the utility model is to provide a bipolar plate and electrode composite structure and a liquid flow battery stack, so as to improve the mass transfer quality of the liquid flow battery electrolyte in the electrode in a direction perpendicular to the electrode plane, reduce the concentration polarization of the liquid flow battery, and improve the performance of the liquid flow battery.

[0006] To solve the above technical problems, in the first aspect, the utility model provides a bipolar plate and electrode composite structure, comprising: a bipolar plate, and an electrode in contact with the bipolar plate, wherein a liquid inlet channel is arranged on the bipolar plate, a liquid outlet channel is arranged on the electrode, and the liquid inlet channel and the liquid outlet channel are respectively arranged on a side of the bipolar plate in contact with the electrode, and the liquid inlet channel and the liquid outlet channel form a flow field.

[0007] Optionally, the liquid inlet channel and the liquid outlet channel are arranged in sequence and spaced apart.

[0008] Optionally, the distance from each of the liquid inlet flow channels to the adjacent liquid outlet flow channels is equal, and the distance from each of the liquid outlet flow channels to the adjacent liquid inlet flow channels is equal.

[0009] Optionally, the flow field includes a parallel flow field, an interdigitated flow field or a serpentine flow field.

[0010] Optionally, the depth of the liquid inlet channel is less than the thickness of the bipolar plate.

[0011] Optionally, the depth of the liquid inlet channel on the bipolar plate is between 0.01 mm and 5 mm.

[0012] Optionally, the depth of the liquid outlet channel is less than or equal to the thickness of the electrode.

[0013] Optionally, the width of the liquid inlet channel is between 0.01 mm and 3 mm, and the width of the liquid outlet channel is between 0.01 mm and 3 mm.

[0014] Optionally, the flow channel porosity of the flow field on the bipolar plate and the electrode is between 0.01% and 50%, and the flow channel porosity is the ratio of all flow channel areas to the corresponding active region area.

[0015] In the second aspect, the utility model provides a liquid flow battery stack, including an electrode frame, and also including a bipolar plate and an electrode composite structure as described in the first aspect, wherein the electrode frame is sleeved on the bipolar plate and the electrode composite structure, and the liquid inlet branch flow channel of the electrode frame matches the liquid inlet flow channel on the bipolar plate, and the liquid outlet branch flow channel of the electrode frame matches the liquid outlet flow channel on the electrode.

[0016] Compared with the prior art, the utility model has the following advantages: a liquid inlet flow channel is provided on the bipolar plate, a liquid outlet flow channel is provided on the electrode, and the liquid inlet flow channel and the liquid outlet flow channel are respectively provided on the side of the bipolar plate in contact with the electrode, thereby improving the mass transfer quality of the electrolyte of the liquid flow battery in the electrode in a direction perpendicular to the electrode plane, reducing the concentration polarization of the liquid flow battery, and improving the performance of the liquid flow battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings are included to provide a further understanding of the present application. They are included and constitute a part of the present application. The accompanying drawings illustrate embodiments of the present application and together with the present specification serve to explain the principles of the present application. In the accompanying drawings:

[0018] Figure 1 It is a top view of the traditional bipolar plate and electrode composite structure;

[0019] Figure 2It is a side view of the traditional bipolar plate and electrode composite structure;

[0020] Figure 3 yes Figure 2 The enlarged schematic diagram at A in the middle;

[0021] Figure 4 This is a top view of a bipolar plate and electrode composite structure according to an embodiment of the utility model;

[0022] Figure 5 It is a side view of a bipolar plate and electrode composite structure of an embodiment of the utility model;

[0023] Figure 6 yes Figure 5 The enlarged schematic diagram of point B in the middle;

[0024] Figure 7 It is a schematic diagram of an electrode frame that cooperates with a bipolar plate and an electrode composite structure in one embodiment of the utility model.

[0025] in, Figure 2 and Figure 5 The arrow in the lower middle section indicates the inflow of electrolyte, and the arrow in the upper section indicates the outflow of electrolyte. They do not represent the actual inflow and outflow directions of the electrolyte.

[0026] The symbols in the figure represent:

[0027] 101 - electrode, 102 - bipolar plate, 103 - liquid inlet channel, 104 - liquid outlet channel, 105 - electrode frame, 106 - liquid inlet, 107 - liquid outlet, 108 - liquid inlet branch channel, 109 - liquid outlet branch channel. DETAILED DESCRIPTION

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios based on these drawings without creative work. Unless it is obvious from the language environment or otherwise explained, the same reference numerals in the figures represent the same structure or operation.

[0029] As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an", "an" and / or "the" do not refer to the singular and may also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0030] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0031] refer to Figure 1 to Figure 3 As shown, the conventional flow field is to set both the inlet flow channel 103 and the outlet flow channel 104 on the bipolar plate 102. When the electrolyte flows inside the flow field, it enters the inlet flow channel 103 of the flow field along the direction of the arrow, then flows inside the electrode 101, and finally flows out through the outlet flow channel 104 of the flow field. In this flow field structure, since the inlet flow channel 103 and the outlet flow channel 104 of the flow field are both located in the same plane and on one side of the bipolar plate 102, the mass transfer efficiency on the electrode 101 in the direction perpendicular to the electrode plane (z direction) is limited.

[0032] refer to Figures 4 to 6 As shown, an embodiment of the utility model provides a bipolar plate and electrode composite structure, including a bipolar plate 102 and an electrode 101 in contact with the bipolar plate 102, a liquid inlet channel 103 is provided on the bipolar plate 102, a liquid outlet channel 104 is provided on the electrode 101, and the liquid inlet channel 103 and the liquid outlet channel 104 are respectively provided on a side of the bipolar plate 102 in contact with the electrode 101, and the liquid inlet channel 103 and the liquid outlet channel 104 form a flow field.

[0033] The present embodiment designs a novel flow field structure, in which the liquid inlet flow channel 103 and the liquid outlet flow channel 104 are separately arranged on the bipolar plate 102 and the electrode 101, and the liquid inlet flow channel 103 and the liquid outlet flow channel 104 have a certain degree of independence. Compared with the traditional structure in which the liquid inlet flow channel 103 and the liquid outlet flow channel 104 are at the same height, the liquid inlet flow channel 103 and the liquid outlet flow channel 104 in the present embodiment have a certain height difference, so that the flow field has a drainage effect on the electrolyte in a direction perpendicular to the plane of the electrode 101, thereby improving the mass transfer quality of the electrolyte inside the electrode 101 in a direction perpendicular to the plane of the electrode 101, and further improving the voltage efficiency and energy efficiency of the liquid flow battery.

[0034] In one example, the liquid inlet channel 103 and the liquid outlet channel 104 are arranged in sequence and spaced apart.

[0035] In this embodiment, reference Figure 5 As shown, the first three liquid inlet channels 103 and three liquid outlet channels 104 from the left are used as examples for explanation. At the same time, for a simpler expression, the three liquid inlet channels 103 are sequentially represented as channels 1, channels 2 and channels 3, and the three liquid outlet channels 104 are sequentially represented as channels 1', channels 2' and channels 3'. As can be seen from the figure, channel 1 is followed by channel 1', channel 1' is followed by channel 2, channel 2 is followed by channel 2', channel 2' is followed by channel 3, and channel 3 is followed by channel 3'. The remaining channels are also based on the same rule, that is, although the liquid inlet channels 103 and the liquid outlet channels 104 are not on the bipolar plate 102 at the same time, the liquid inlet channels 103 and the liquid outlet channels 104 are sequentially arranged at intervals, and there is a liquid outlet channel 104 between every two liquid inlet channels 103, and there is a liquid inlet channel 103 between every two liquid outlet channels 104. It can also be said that the flow field of the liquid flow battery is located in the flow channel on the bipolar plate 102 facing the ridge of the flow field of the electrode 101, and the flow channel on the electrode 101 faces the ridge of the flow field of the bipolar plate 102, thereby making the mass transfer effect of the electrolyte in the electrode better.

[0036] In one example, the distance from each liquid inlet channel 103 to the adjacent liquid outlet channel 104 is equal, and the distance from each liquid outlet channel 104 to the adjacent liquid inlet channel 103 is equal.

[0037] Still refer to Figure 5 As shown, flow channel 1, flow channel 2, flow channel 3, flow channel 1′, flow channel 2′ and flow channel 3′ are used as examples for explanation. For flow channel 1′, its distance to flow channel 1 and flow channel 2 is equal, and for flow channel 2′, its distance to flow channel 2 and flow channel 3 is equal; similarly, for flow channel 2, its distance to flow channel 1′ and flow channel 2′ is equal, and for flow channel 3, its distance to flow channel 2′ and flow channel 3′ is equal, and the remaining flow channels also have the same rule, that is, the distance between any two adjacent flow channels (including the inlet flow channel 103 and the outlet flow channel 104) is equal, so that the mass transfer of the electrolyte in the electrode 101 can be guaranteed to be as evenly distributed as possible, avoiding excessive differences in mass transfer quality at different locations of the electrode 101, which affects the performance of the liquid flow battery.

[0038] In one example, the flow field includes a parallel flow field, an interdigitated flow field, or a serpentine flow field.

[0039] In one example, the depth of the liquid inlet channel 103 is less than the thickness of the bipolar plate 102. Further, the depth of the liquid inlet channel 103 on the bipolar plate 102 is between 0.01 mm and 5 mm.

[0040] In one example, the depth of the liquid outlet channel 104 is less than or equal to the thickness d of the electrode 101 , that is, the depth of the flow channel set on the electrode 101 by the flow field of the flow battery satisfies 0<d≤h, where h is the electrode thickness.

[0041] The electrode 101 in the flow battery is the place where the electrochemical reaction occurs. Generally, the depth of the liquid outlet channel 104 is less than the thickness of the electrode. When special design and consideration are required, the depth of the liquid outlet channel 104 can also be equal to the thickness of the electrode, so that the electrolyte forms a uniform coverage on the surface of the electrode 101, ensuring the uniformity and stability of the electrochemical reaction.

[0042] In one example, the width of the liquid inlet channel 103 is between 0.01 mm and 3 mm, and the width of the liquid outlet channel 104 is between 0.01 mm and 3 mm.

[0043] In one example, the flow channel porosity of the flow field on the bipolar plate 102 and the electrode 101 is between 0.01% and 50%, and the flow channel porosity is the ratio of all flow channel areas to the corresponding active area areas.

[0044] The size of the flow channel opening rate will affect the performance and efficiency of the liquid flow battery, so it needs to be reasonably determined according to the design and requirements of the liquid flow battery. The flow channel opening rate of the flow field on the bipolar plate 102 and the electrode 101 is set between 0.01% and 50%, which basically meets the battery performance requirements. Figure 4 For example, the active area is the area of ​​the entire electrode 101 currently displayed, and the area of ​​all flow channels is Figure 4 The total area of ​​all liquid inlet channels 103 (7 channels) and all liquid outlet channels 104 (8 channels).

[0045] To further illustrate the bipolar plate and electrode composite structure and its beneficial effects in this embodiment, this embodiment uses an all-vanadium liquid flow battery for experimental description. The flow field structure in this embodiment is also applicable to other liquid flow batteries. The key materials used in the battery stacks of the following experimental examples and comparative examples are all products from the same batch, and are all tested at the same ambient temperature of 33°C to 37°C.

[0046] Experimental Example 1: An interdigital flow field is used to set the inlet channel 103 and the outlet channel 104 on the bipolar plate 102 and the electrode 101. The width of the inlet channel 103 on the bipolar plate 102 is 3mm, and the channel depth is 1.6mm. 2.5mm graphite carbon felt is used as the electrode 101. The width of the outlet channel 104 on the electrode 101 is 3mm, and the channel depth is consistent with the thickness of the electrode 101. The sum of the channel opening rates of the inlet channel 103 and the outlet channel 104 is 15.7%, and the electrode compression rate is 32%. Assembled into 20-cell stacks, the reaction area area is 1280cm 2 . At 150mA / cm 2The constant current charge and discharge were carried out with a current density of , and the data of the 4th cycle were selected as the initial performance data.

[0047] Comparative Example 1: A conventional interdigital flow field is used, the depth of the inlet flow channel 103 and the outlet flow channel 104 is 1.6 mm, and the flow channel width is 3 mm. The flow field opening rate is 15.7%, and a 2.5 mm graphite felt is used as the electrode 101, and the electrode compression rate is 32%. A 20-cell stack is assembled, and the reaction area is 1280 cm 2 . At 150mA / cm 2 The constant current charge and discharge were carried out with a current density of , and the data of the 4th cycle were selected as the initial performance data.

[0048] Experimental Example 2: A serpentine flow field is used to set the inlet channel 103 and the outlet channel 104 on the bipolar plate 104 and the electrode 101. The width of the inlet channel 103 on the bipolar plate 102 is 3.5 mm, and the channel depth is 1.5 mm. 2.5 mm graphite carbon felt is used as the electrode 101. The width of the outlet channel 104 on the electrode 101 is 3.5 mm, and the channel depth is consistent with the thickness of the electrode 101. The sum of the channel opening rates of the inlet channel 103 and the outlet channel 104 is 20.4%, and the electrode compression rate is 27%. Assembled into 20-cell stacks, the reaction area area is 1280 cm 2 . At 150mA / cm 2 The constant current charge and discharge were carried out with a current density of , and the data of the 4th cycle were selected as the initial performance data.

[0049] Comparative Example 2: A conventional serpentine flow field was used, the depth of the inlet flow channel 103 and the outlet flow channel 104 was 1.5 mm, and the flow channel width was 3.5 mm. The flow field opening rate was 20.4%, 2.5 mm graphite felt was used as the electrode 101, and the electrode compression rate was 27%. A 20-cell stack was assembled, and the reaction area was 1280 cm 2 . At 150mA / cm 2 The constant current charge and discharge were performed with a current density of , and the data of the 4th cycle were selected as the initial performance data. The measured data are shown in Table 1.

[0050] Table 1 Performance data of the 4th cycle of Experimental Example 1, Experimental Example 2 and Comparative Example 1, Comparative Example 2

[0051] Voltage efficiency (%) Energy efficiency (%) Example 1 86.3 83.2 Comparative Example 1 85.2 81.8 Example 2 85.9 82.6 Comparative Example 2 85.0 81.2

[0052] It can be seen from Table 1 that, under the same other conditions, the voltage efficiency and energy efficiency of the experimental example under the same flow field are generally higher than those of the comparative example. It can be seen that the use of the bipolar plate and electrode composite structure of this embodiment improves the voltage efficiency and energy efficiency of the battery stack.

[0053] The bipolar plate and electrode composite structure provided in this embodiment has a liquid inlet channel 103 on the bipolar plate 102, and a liquid outlet channel 104 on the electrode 101, and the liquid inlet channel 103 and the liquid outlet channel 104 are respectively arranged on the side of the bipolar plate 102 in contact with the electrode 101, thereby improving the mass transfer quality of the electrolyte of the liquid flow battery in the direction perpendicular to the plane of the electrode 101, reducing the concentration polarization of the liquid flow battery, and improving the performance of the liquid flow battery.

[0054] Another embodiment of the utility model provides a liquid flow battery stack, which includes an electrode frame 105, and a bipolar plate and electrode composite structure, wherein the bipolar plate and electrode composite structure can adopt the bipolar plate and electrode composite structure mentioned in the above embodiment, the electrode frame 105 is sleeved on the composite structure of the bipolar plate and the electrode, one side of the electrode frame 105 has a liquid inlet 106 and a liquid inlet branch channel 108 communicating with the liquid inlet 106, the other side of the electrode frame 105 has a liquid outlet 107 and a liquid outlet branch channel 109 communicating with the liquid outlet 107, and the liquid inlet branch channel 108 of the electrode frame 105 is also matched with the liquid inlet channel 103 on the bipolar plate 102, and the liquid outlet branch channel 109 of the electrode frame 105 is also matched with the liquid outlet channel 104 on the electrode 101.

[0055] For other details about the bipolar plate and electrode composite structure in this embodiment, reference may be made to the aforementioned embodiments and will not be elaborated here.

[0056] The liquid flow battery stack provided in this embodiment adopts an improved bipolar plate and electrode composite structure. A liquid inlet channel 103 is provided on the bipolar plate 102, and a liquid outlet channel 104 is provided on the electrode 101, and the liquid inlet channel 103 and the liquid outlet channel 104 are respectively provided on the side of the bipolar plate 102 in contact with the electrode 101, thereby improving the mass transfer quality of the liquid flow battery electrolyte in the electrode 101 perpendicular to the plane of the electrode 101, reducing the concentration polarization of the liquid flow battery, and improving the performance of the liquid flow battery.

[0057] The basic concepts have been described above. Obviously, for those skilled in the art, the above utility model disclosure is only used as an example and does not constitute a limitation of the present application. Although not explicitly stated here, those skilled in the art may make various modifications, improvements and corrections to the present application. Such modifications, improvements and corrections are suggested in the present application, so such modifications, improvements and corrections still belong to the spirit and scope of the exemplary embodiments of the present application.

[0058] Similarly, it should be noted that in order to simplify the description of the disclosure of this application and thus help understand one or more utility model embodiments, in the above description of the embodiments of this application, multiple features are sometimes combined into one embodiment, drawing or description thereof. However, this disclosure method does not mean that the features required by the object of this application are more than the features mentioned in the claims. In fact, the features of the embodiments are less than all the features of the single embodiment disclosed above.

[0059] In some embodiments, numbers describing the number of components and attributes are used. It should be understood that such numbers used in the description of the embodiments are modified by the modifiers "about", "approximately" or "substantially" in some examples. Unless otherwise specified, "about", "approximately" or "substantially" indicate that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may change according to the required features of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining digits. Although the numerical domains and parameters used to confirm the breadth of their range in some embodiments of the present application are approximate values, in specific embodiments, the setting of such numerical values ​​is as accurate as possible within the feasible range.

[0060] Although the present application has been described with reference to the current specific embodiments, ordinary technicians in this technical field should recognize that the above embodiments are only used to illustrate the present application, and various equivalent changes or substitutions may be made without departing from the spirit of the present application. Therefore, as long as the changes and modifications to the above embodiments are within the essential spirit of the present application, they will fall within the scope of the claims of the present application.

Claims

1. A bipolar plate and electrode composite structure, characterized in that: include: A bipolar plate, and an electrode in contact with the bipolar plate, wherein: The bipolar plate is provided with a liquid inlet channel, the electrode is provided with a liquid outlet channel, and the liquid inlet channel and the liquid outlet channel are respectively provided on a side of the bipolar plate in contact with the electrode, and the liquid inlet channel and the liquid outlet channel form a flow field.

2. The bipolar plate and electrode composite structure according to claim 1, characterized in that: The liquid inlet channel and the liquid outlet channel are arranged in sequence and spaced apart from each other.

3. The bipolar plate and electrode composite structure according to claim 2, characterized in that: The distance between each of the liquid inlet flow channels and the adjacent liquid outlet flow channels is equal, and the distance between each of the liquid outlet flow channels and the adjacent liquid inlet flow channels is equal.

4. The bipolar plate and electrode composite structure according to claim 1, characterized in that: The flow field includes a parallel flow field, an interdigitated flow field or a serpentine flow field.

5. The bipolar plate and electrode composite structure according to claim 1, characterized in that: The depth of the liquid inlet channel is less than the thickness of the bipolar plate.

6. The bipolar plate and electrode composite structure according to claim 5, characterized in that: The depth of the liquid inlet channel on the bipolar plate is between 0.01 mm and 5 mm.

7. The bipolar plate and electrode composite structure according to claim 1, characterized in that: The depth of the liquid outlet channel is less than or equal to the thickness of the electrode.

8. The bipolar plate and electrode composite structure according to claim 1, characterized in that: The width of the liquid inlet channel is between 0.01 mm and 3 mm, and the width of the liquid outlet channel is between 0.01 mm and 3 mm.

9. The bipolar plate and electrode composite structure according to claim 1, characterized in that: The flow channel opening rate of the flow field on the bipolar plate and the electrode is between 0.01% and 50%, and the flow channel opening rate is the ratio of all flow channel areas to the corresponding active area areas.

10. A liquid flow battery stack, comprising an electrode frame, characterized in that: It also includes the bipolar plate and electrode composite structure according to any one of claims 1 to 9, wherein: The electrode frame is sleeved on the bipolar plate and electrode composite structure, and the liquid inlet branch flow channel of the electrode frame matches the liquid inlet flow channel on the bipolar plate, and the liquid outlet branch flow channel of the electrode frame matches the liquid outlet flow channel on the electrode.

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