Composite bipolar plate and flow battery

Abstract

A metal plate and a graphite plate are made into the composite bipolar plate through a hot pressing process, so that an air gap between the metal plate and the graphite plate is eliminated, the contact resistance is reduced, and the acting force of a fastener of the battery is applied to the metal plate, so that the metal plate and the graphite plate are not damaged. And enough surface pressure can be ensured so as to ensure the sealing performance of the flow battery. The composite bipolar plate greatly reduces the material cost under the condition of meeting the performance, also reduces the volume and weight of the battery, and is the trend of market development.

Description

Technical Field

[0001] The utility model relates to a flow battery, in particular to a bipolar plate of a flow battery. Background Art

[0002] At present, the country vigorously develops green power sources such as wind energy and solar energy. However, due to their uncertain characteristics, they pose risks to the stability of the power grid, and energy storage technologies are needed to increase the flexibility of the power grid. The flow battery energy storage technology has great development potential due to its advantages such as long life, high safety, and high power. The flow battery also has wide application values in the fields of wind power generation, photovoltaic power generation, power grid peak shaving, electric vehicle power supply, uninterruptible power supply and emergency power supply, power supply system, military energy storage, etc. The flow battery energy storage system mainly consists of a stack, electrolyte, inverter, intelligent control, storage tank, container, pipe pump valve sensor, etc. The most important core components are the stack and the electrolyte. The stack is the place where the electrochemical reaction occurs, integrating material components such as electrodes, diaphragms, and bipolar plates. Its sealing design, assembly process, etc. have crucial impacts on the reliability, power density, and overall cost of the battery. The main structure of the stack includes a proton exchange membrane, carbon felt, bipolar plate, copper current collector plate, flow membrane frame, end plate, and connectors, etc.

[0003] At present, the bipolar plate is generally an expensive metal plate or a graphite bipolar plate. The former is expensive because the metal surface needs a corrosion-resistant coating, and the latter has a graphite plate thickness of up to 0.8 mm or more due to the requirements of conductive efficiency and mechanical strength. After multiple layers are connected in series, the volume of the stack is large, which greatly limits the application scenarios of the flow battery. In order to reduce costs, in addition to diversifying the electrolyte and not being restricted by rare substances, there are already demonstration applications of all-vanadium flow batteries, all-iron flow batteries, iron-chromium flow batteries, zinc-bromine flow batteries, zinc-iron-based flow batteries, etc. New structures must also be developed for the bipolar plate, which is the core component of the stack. Content of the Utility Model

[0004] In view of the above-mentioned defects of the prior art, the utility model first provides a composite bipolar plate, which is a composite bipolar plate formed by hot pressing a graphite plate and a metal plate of a flow battery.

[0005] Further, the graphite layer is made by fusing graphite and resin.

[0006] Further, a flow hole is provided on the composite bipolar plate.

[0007] Further, a fastening hole can be provided on the composite bipolar plate.

[0008] Further, the total thickness of the composite bipolar plate does not exceed 0.4 mm.

[0009] Further, the metal layer is made of copper or stainless steel material.

[0010] Further, in the middle section of the three-layer structure, the thickness of the metal layer is 0.1 mm - 0.2 mm.

[0011] Further, in the end collector plate of the two-layer structure, the thickness of the metal layer is 0.1 mm - 10 mm.

[0012] Further, the composite bipolar plate is made into a wavy bipolar plate, and its wavy structure serves as the flow channel for the electrolyte.

[0013] The present utility model also provides a flow battery, including the composite bipolar plate as described above.

[0014] The composite bipolar plate provided by the present utility model is made by a hot pressing process to form a composite bipolar plate from a metal plate and a graphite plate, thereby eliminating the air gap between the metal plate and the bipolar plate, reducing the contact resistance. At the same time, the force of the fastener of the battery is applied to the metal plate, which can ensure sufficient surface pressure to guarantee the sealing performance of the flow battery.

[0015] The following will further illustrate the concept, specific structure and technical effects of the present utility model in conjunction with the accompanying drawings to fully understand the purpose, features and effects of the present utility model. Description of the Drawings

[0016] Figure 1 is a schematic diagram of the combination of the graphite layer and the metal plate in a preferred embodiment of the present utility model;

[0017] Figure 2 is a schematic diagram of the composite two-layer bipolar plate in a preferred embodiment of the present utility model;

[0018] Figure 3 is a cross-sectional view of the composite three-layer bipolar plate in a preferred embodiment of the present utility model;

[0019] Figure 4 is a front view of the wavy bipolar plate in a preferred embodiment of the present utility model;

[0020] Figure 5 is a cross-sectional view of the wavy bipolar plate in a preferred embodiment of the present utility model;

[0021] Figure 6 is a schematic diagram of the stack assembly of the wavy bipolar plate in a preferred embodiment of the present utility model. Detailed Embodiments

[0022] The following describes multiple preferred embodiments of the present utility model with reference to the accompanying drawings of the specification, making its technical content clearer and easier to understand. The present utility model can be embodied in many different forms of embodiments, and the protection scope of the present utility model is not limited to the embodiments mentioned in the text.

[0023] In the embodiment as shown in Figure 1-2 , the present utility model adopts a composite bipolar plate. First, a graphite plate 2 is made by fully fusing graphite powder and resin, and then a metal plate 1 and the graphite plate 2 are bonded and hot-pressed to form a composite bipolar plate as shown in Figure 2 .

[0024] Liquid flow holes 3 and fastener holes 4 are provided on the composite bipolar plate.

[0025] In the embodiment as shown in Figure 3 , the composite bipolar plate includes three layers of graphite plate - metal plate - graphite plate, that is, two graphite plate layers 20, 21 sandwich a metal plate 22.

[0026] The composite bipolar plate formed by hot pressing can completely eliminate the air gap between the metal plate and the graphite plate, effectively reducing the contact resistance between the graphite plate and the metal plate.

[0027] The hot pressing forming technology of the composite bipolar plate is a technology without a bonding coating, using a graphite resin prepress plate with self-adhesive properties. The performance meets the application evaluation indicators, such as conductivity, resistance to electrolyte, electrocorrosion, impermeability, etc.

[0028] The resistivity comparison test results of the end collector plate structure are shown in the following table:

[0029]

[0030]

[0031] Through hot pressing and compounding, the peel strength between the graphite plate and the metal plate is significantly improved, and the force of the fastener acts on the metal plate rather than directly on the graphite plate, so sufficient surface pressure can be ensured, thus guaranteeing the sealing performance of the battery.

[0032] In a specific embodiment, the combined metal layer uses stainless steel with excellent ductility and plasticity, and the characteristics of the upper and lower prefabricated graphite bipolar plate layers meet mechanical forming processing, and are realized by adjusting the density, resin ratio, graphite grade, etc.

[0033] The graphite can be expanded graphite, graphite powder, and conductive high-quality carbon materials can be added.

[0034] The resin can be bakelite powder, polyphenylene sulfide, polyvinylidene fluoride, polyethylene, etc. with excellent corrosion resistance.

[0035] The total thickness of the composite bipolar plate may not exceed 0.4 mm, usually 0.3 mm - 0.4 mm. It can also be in a specification with a thickness greater than 0.4 mm according to application requirements.

[0036] The metal layer is mainly made of stainless steel, such as conventional specifications like SUS316, SUS304, etc. The thickness is generally 0.1 mm - 0.2 mm. Other metals and specifications with high mechanical strength and corrosion resistance can also be used according to application requirements.

[0037] As Figure 4-6 shown, in a further embodiment, the above composite bipolar plate can also be made into a wavy bipolar plate through seamless mechanical rolling, molding, etc. Its wavy structure serves as the flow channel for the electrolyte, and an electric stack of this wavy structure bipolar plate can be further manufactured from this, which also solves the problem of the large volume of graphite bipolar plate electric stacks currently on the market.

[0038] Thermal pressing and compounding can be carried out before the two groups of materials are formed, or after they are formed (such as pressing grooves separately).

[0039] The wavy structure and dimensions formed by the composite bipolar plate can be diversified and designed according to the performance of the electric stack, such as flow rate, etc.

[0040] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field based on the concept of the present invention through logical analysis, reasoning, or limited experiments on the basis of the existing technology should fall within the protection scope determined by the claims.

Claims

1. A composite bipolar plate, characterized in that: It is a composite bipolar plate formed by hot pressing of metal plates and graphite layers. The total thickness of the bipolar plate does not exceed 0.4 mm. The composite bipolar plate includes three layers of graphite layer-metal plate-graphite layer, that is, a metal plate is sandwiched between two graphite layers.

2. The composite bipolar plate according to claim 1, wherein: The metal layer is made of copper or stainless steel.

3. The composite bipolar plate according to claim 1, wherein: The thickness of the metal layer is 0.1mm-0.2mm.

4. The composite bipolar plate according to claim 1, wherein: The composite bipolar plate is made into a wave-type bipolar plate, and its wave structure is used as a flow channel for the electrolyte.

5. A liquid flow battery, characterized in that: It comprises a composite bipolar plate as described in any one of claims 1 to 4.

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