Bipolar plate of flow battery and preparation method of bipolar plate

Abstract

The invention relates to a flow battery, and discloses a metal bipolar plate for the flow battery and a preparation method of the metal bipolar plate. Common metal does not have corrosion resistance, and metal with corrosion resistance is precious metal, so that bipolar plates in current flow batteries are all made of non-metal materials. However, due to the excellent conductivity of the metal material, the internal resistance of the flow battery can be greatly reduced, the energy efficiency and the electrolyte utilization rate of the flow battery are improved, and the system cost is reduced. According to the invention, the metal plate is processed, so that the metal plate has corrosion resistance while maintaining excellent conductivity. The bipolar plate comprises a metal base layer, a corrosion-resistant protective layer and a graphite layer for reducing contact resistance.

Description

Technical Field

[0001] The present application relates to liquid flow batteries, and in particular to bipolar plate technology for liquid flow batteries. Background Art

[0002] This section is intended to provide a background or context to the embodiments of the present application as recited in the claims. The description herein is not admitted to be prior art as disclosed by inclusion in this section.

[0003] In liquid flow batteries, the bipolar plates currently used widely are mainly carbon bipolar plates, composite bipolar plates and flexible graphite plates.

[0004] Carbon bipolar plates are usually conductive plastic plates made of polyethylene, polypropylene, polyphenylene sulfide, etc. as the base material, and pressed with conductive carbon black and other materials. Their conductivity and mechanical properties are closely related to the proportion of carbon black. The larger the amount of carbon black, the poorer the mechanical properties of the bipolar plate, and the smaller the amount of carbon black, the poorer the mechanical properties.

[0005] The composite bipolar plate is a bipolar plate made by adding a substrate such as polyethylene or polypropylene filled with conductive carbon black into a porous carbon felt or graphite felt through hot pressing. After heating and pressing, a lightweight and conductive bipolar plate is formed. This bipolar plate has the advantages of good conductivity and light weight, but its performance in blocking the penetration of vanadium ions is relatively poor.

[0006] Flexible graphite is made by bonding multiple layers of ultra-thin graphite paper together with a binder. This flexible graphite sheet has low density, light weight, good conductivity, and low surface resistance. Its conductivity is second only to the brittle pure graphite sheet. It is currently widely used in high-density batteries. The disadvantage is that it has low strength.

[0007] The above three bipolar plates in the prior art have poor conductivity, resulting in low battery voltage efficiency and ultimately low battery energy efficiency. Summary of the invention

[0008] The purpose of the present application is to provide a bipolar plate for a liquid flow battery and a preparation method thereof, which can reduce the internal resistance of the liquid flow battery and improve the energy efficiency of the liquid flow battery.

[0009] The present application discloses a bipolar plate in a flow battery, comprising:

[0010] Metal base;

[0011] A dense, corrosion-resistant conductive material layer deposited on both sides of the metal base layer;

[0012] Two graphite layers are deposited on the outer sides of the two corrosion-resistant conductive material layers respectively.

[0013] In a preferred example, the metal base layer is aluminum, steel, iron, copper, zinc or an alloy.

[0014] In a preferred example, the material of the corrosion-resistant conductive material layer is titanium, iridium, platinum, tantalum, platinum, chromium, or molybdenum.

[0015] In a preferred example, the conductivity of the metal base layer is better than that of the corrosion-resistant conductive material layer and the graphite layer.

[0016] The present application also discloses a method for preparing a bipolar plate in a flow battery, comprising:

[0017] Provide a metal base layer;

[0018] Depositing a dense, corrosion-resistant conductive material layer on both sides of the metal base layer;

[0019] Graphite layers are deposited on the outer sides of the two corrosion-resistant conductive material layers respectively.

[0020] In a preferred embodiment, in the step of depositing a dense corrosion-resistant conductive material layer on both sides of the metal base layer, the deposition is performed using any one of the following methods:

[0021] Physical vapor deposition, chemical vapor deposition, electroplating, spraying.

[0022] In a preferred embodiment, in the step of depositing a graphite layer on the outside of the corrosion-resistant conductive material layer, the deposition is performed using any one of the following methods:

[0023] Physical vapor deposition, chemical vapor deposition.

[0024] The present application also discloses a liquid flow battery, wherein the bipolar plate of the liquid flow battery comprises:

[0025] The metal base layer is located in the middle;

[0026] A dense, corrosion-resistant conductive material layer deposited on both sides of the metal base layer;

[0027] Two graphite layers are respectively deposited on the outside of the two corrosion-resistant conductive material layers, and the graphite layers are in contact with the graphite felt electrodes of the liquid flow battery.

[0028] In a preferred example, the electrolyte of the flow battery is an acidic electrolyte.

[0029] In the embodiments of the present application, the internal resistance of the flow battery is greatly reduced, and the energy efficiency of the flow battery is improved. By improving the electrical performance, the energy density of the electrolyte can be improved. The electrical density of the flow battery can be improved. Under the same volume and material usage, the power of the battery is increased, and the cost of the battery stack is correspondingly reduced.

[0030] Each technical feature disclosed in the above invention content, each technical feature disclosed in each implementation mode and example below, and each technical feature disclosed in the accompanying drawings can be freely combined with each other to form various new technical solutions (these technical solutions should be deemed to have been recorded in this specification), unless such combination of technical features is technically infeasible. For example, in one example, feature A+B+C is disclosed, and in another example, feature A+B+D+E is disclosed, and features C and D are equivalent technical means that play the same role. Technically, only one of them can be used, and it is impossible to use them at the same time. Feature E can be combined with feature C technically. Then, the solution of A+B+C+D should not be deemed to have been recorded because it is technically infeasible, while the solution of A+B+C+E should be deemed to have been recorded. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the bipolar plate structure in the liquid flow battery according to the first embodiment of the present application. DETAILED DESCRIPTION

[0032] In the following description, many technical details are provided to help readers better understand the present application. However, those skilled in the art can understand that the technical solution claimed in the present application can be implemented even without these technical details and various changes and modifications based on the following embodiments.

[0033] The first embodiment of the present application relates to a metal bipolar plate in a flow battery, such as Figure 1 As shown, the bipolar plate comprises:

[0034] The metal base layer 101 is located in the middle as the foundation. Optionally, in one embodiment, the material of the metal base layer can be aluminum, iron, copper, zinc, etc. In other embodiments, other metal materials can also be used as long as they are metals or alloys with good conductivity and reasonable cost.

[0035] A dense corrosion-resistant conductive material layer 102 is deposited on both sides of the metal base layer 101. The corrosion-resistant conductive material layer can effectively prevent the corrosion of the metal base layer by the electrolyte in the flow battery. The material of this layer must meet the following three conditions: 1) excellent conductivity; 2) strong bonding with the metal layer; 3) dense structure, which can prevent corrosion and diffusion. For example, the material of this layer can be titanium, iridium, platinum, tantalum, platinum, chromium, molybdenum, etc. Optionally, in one embodiment, the thickness of the corrosion-resistant conductive material layer is 50A-200A.

[0036] The graphite layer 103 is deposited on the side of the two corrosion-resistant conductive material layers 102 facing away from the metal base layer. Optionally, in one embodiment, the graphite layer is about 100A (eg, 80A-150A).

[0037] In flow batteries, the electrode material is generally graphite felt, and the graphite layer can effectively reduce the contact resistance between the two. The reasons are: 1) The graphite layer of the metal bipolar plate is similar to the graphite felt in properties. 2) The roughness and density of the graphite layer can improve the contact force with the graphite felt.

[0038] Optionally, in one embodiment, the conductivity of the metal base layer is better than that of the corrosion-resistant conductive material layer and the graphite layer. The conductivity of the corrosion-resistant conductive material layer is also preferably better than that of the graphite layer.

[0039] The second embodiment of the present application relates to a method for preparing a bipolar plate in a flow battery, which is used to prepare the bipolar plate in the first embodiment, and comprises the following steps:

[0040] Provides a metal base layer.

[0041] A dense layer of corrosion-resistant conductive material is deposited on both sides of the metal base layer. The deposition of the corrosion-resistant conductive material can be achieved by physical vapor deposition (PVD), chemical vapor deposition (CVD), electroplating, or spraying.

[0042] A graphite layer is deposited on the outer side of the corrosion-resistant conductive material layer (the inner side of the two corrosion-resistant conductive material layers is a metal base layer). The graphite deposition can be achieved by physical vapor deposition (PVD) or chemical vapor deposition (CVD).

[0043] The third embodiment of the present application relates to a liquid flow battery, the battery comprising the bipolar plate as described in the first embodiment. The electrolyte of the liquid flow battery can be an acidic electrolyte or an alkaline electrolyte.

[0044] With the above bipolar plates, flow batteries can:

[0045] 1. Greatly reduce the internal resistance of the battery and improve the battery energy efficiency.

[0046] The energy efficiency of the DC side of the flow battery = voltage efficiency × coulomb efficiency. When the coulomb efficiency remains unchanged, an increase in voltage efficiency will lead to an increase in system efficiency.

[0047] Charging voltage = polarization voltage + resistance voltage drop + open circuit voltage

[0048] Discharge voltage = open circuit voltage - polarization voltage - resistance voltage drop

[0049] For example, at 100 electrical density: the voltage drop of the bipolar plate of the present application is 0.3V less than that of the flexible graphite plate, the average discharge voltage of the flexible graphite plate is about 1.25V, the average charging voltage is about 1.47V, the average discharge voltage of the bipolar plate of the present application is about 1.28V, the average charging voltage is about 1.44V, the voltage efficiency of the flexible graphite plate is ≈1.25 / 1.47=85.03%, the voltage efficiency of the bipolar plate of the present application is ≈1.28 / 1.44=88.89%

[0050] 2. Improve performance by reducing internal resistance, and ultimately increase energy density.

[0051] The internal resistance is reduced. Under the condition of 100 electrical density, the average discharge voltage of the metal bipolar plate is 1.28V, and the average discharge voltage of the flexible graphite plate is about 1.25V. When the coulomb amount remains unchanged, the energy density is increased to 1.28 / 1.25=1.024, that is, the energy density is increased by 2.4%. And when the charge and discharge cut-off voltage remains unchanged, the coulomb amount of charge and discharge will also increase. According to experimental data, the capacity can be increased by about 4%.

[0052] 3. Improve the electrical density of flow batteries. Under the same volume and material usage, the battery power becomes higher and the corresponding battery stack cost is reduced.

[0053] The internal resistance is reduced, and at the same electrical density, the resistance of the metal bipolar plate is small, resulting in a smaller resistance voltage drop. When the electrical density increases, the voltage drop of the metal bipolar plate will become higher, and at the same power, its production cost can be greatly reduced.

[0054] It should be noted that, in the disclosure, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the term "include", "comprise" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements defined by the sentence "include one" do not exclude the existence of other identical elements in the process, method, article or equipment including the elements. In this application, if it is mentioned that a certain action is performed according to a certain element, it means that at least the action is performed according to the element, which includes two situations: performing the action only according to the element and performing the action according to the element and other elements. Multiple, multiple, multiple, etc. expressions include 2, 2 times, 2 kinds and more than 2, more than 2 times, more than 2 kinds.

[0055] This specification includes combinations of the various embodiments described herein. Individual references to an embodiment (e.g., "one embodiment" or "some embodiments" or "preferred embodiments") do not necessarily refer to the same embodiment; however, these embodiments are not mutually exclusive unless indicated as mutually exclusive or it is clear to a person skilled in the art that they are mutually exclusive. It should be noted that the word "or" is used in this specification in a non-exclusive sense unless the context clearly indicates or requires otherwise.

[0056] All documents mentioned in this application are considered to be included in the disclosure of this application as a whole, so that they can be used as the basis for modification when necessary. In addition, it should be understood that after reading the content of this application, those skilled in the art can make various changes or modifications to this application, and these equivalent forms also fall within the scope of protection claimed in this application.

Claims

1. A bipolar plate in a flow battery, characterized in that: include: Metal base; A dense, corrosion-resistant conductive material layer deposited on both sides of the metal base layer; Two graphite layers are deposited on the outer sides of the two corrosion-resistant conductive material layers respectively.

2. The bipolar plate in the flow battery according to claim 1, characterized in that: The metal base layer is aluminum, steel, iron, copper, zinc or an alloy.

3. The bipolar plate in the flow battery according to claim 2, characterized in that: The material of the corrosion-resistant conductive material layer is titanium, iridium, platinum, tantalum, platinum, chromium, or molybdenum.

4. The bipolar plate in the flow battery according to claim 3, characterized in that: The conductivity of the metal base layer is better than that of the corrosion-resistant conductive material layer and the graphite layer.

5. A method for preparing a bipolar plate in a flow battery, characterized in that: include: Provide a metal base layer; Depositing a dense, corrosion-resistant conductive material layer on both sides of the metal base layer; Graphite layers are deposited on the outer sides of the two corrosion-resistant conductive material layers respectively.

6. The method for preparing a bipolar plate in a flow battery according to claim 5, characterized in that: In the step of depositing a dense corrosion-resistant conductive material layer on both sides of the metal base layer, the deposition is performed using any one of the following methods: Physical vapor deposition, chemical vapor deposition, electroplating, spraying.

7. The method for preparing a bipolar plate in a flow battery according to claim 5, characterized in that: In the step of depositing a graphite layer on the outer side of the corrosion-resistant conductive material layer, the deposition is performed using any one of the following methods: Physical vapor deposition, chemical vapor deposition.

8. A liquid flow battery, characterized in that: The bipolar plates of the flow battery include: The metal base layer is located in the middle; A dense, corrosion-resistant conductive material layer deposited on both sides of the metal base layer; Two graphite layers are respectively deposited on the outside of the two corrosion-resistant conductive material layers, and the graphite layers are in contact with the graphite felt electrodes of the liquid flow battery.

9. The liquid flow battery in the liquid flow battery according to claim 8, characterized in that: The electrolyte of the liquid flow battery is an acidic electrolyte.

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