Three-in-one assembly of electrode, bipolar plate and runner plate for flow battery

Abstract

The invention relates to the technical field of flow batteries, and discloses a three-in-one assembly of an electrode, a bipolar plate and a runner plate for a flow battery. The method comprises the following steps: activating a whole piece of electrode material to obtain an electrode for a battery, placing the electrode for the battery in a specific mold, dipping or coating a layer of conductive polymer filler at the center position of the electrode, performing hot-pressing shaping, coating a layer of thermoplastic resin to form a transition layer with conductive inside and insulated outside, and cooling to obtain an integrated composite electrode. And folding the integrated composite electrode, placing the runner plate in the middle of the folded integrated composite electrode, and welding the integrated composite electrode on the runner plate through flat plate hot welding to form a three-in-one assembly of the electrode, the bipolar plate and the runner plate. The three-in-one assembly replaces the traditional physical superposition of an electrode, a conductive bipolar plate and a conductive current channel plate, and the contact resistance between materials is greatly reduced, so that the ohmic polarization of the battery is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid flow batteries, and in particular to a three-in-one assembly of electrodes, bipolar plates and flow channel plates for liquid flow batteries. Background Art

[0002] Liquid flow batteries have become one of the large-scale energy storage methods for renewable energy such as wind energy and solar energy, and peak shaving and valley filling of electricity due to their high energy conversion efficiency, long service life, environmental friendliness, customizable capacity according to user requirements, and high safety.

[0003] As a multifunctional key component in the liquid flow battery system, the bipolar plate can collect and conduct the current generated during the battery charging and discharging process, provide effective mechanical support for the membrane and electrodes, connect multiple single cells and prevent the mixing of positive and negative electrolytes and direct contact of the electrodes, which has a significant impact on the energy efficiency of the battery stack. Therefore, the ideal bipolar plate material usually needs to have good conductivity, electrochemical stability, corrosion resistance and a certain mechanical strength, etc., but it is often difficult to take all these characteristics into account. At present, liquid flow battery bipolar plates are mainly divided into three types: metal bipolar plates, graphite bipolar plates and carbon-plastic composite bipolar plates. Among them, metal bipolar plates are not corrosion-resistant and are gradually abandoned. Although the coating and coating methods can effectively reduce the corrosion of the metal bipolar plate surface by the electrolyte, the stability of the coating and coating needs further research; graphite bipolar plates have high chemical stability and low resistance. It is the most commonly used material for making bipolar plates in liquid flow batteries. However, graphite bipolar plates still have problems such as low mechanical strength, poor processability, positive electrode surface corrosion, negative electrode blistering, swelling in corrosive electrolytes, and high manufacturing costs; although carbon-plastic composite bipolar plates have good corrosion resistance and toughness, their resistivity is 1 to 2 orders of magnitude higher than that of metal bipolar plates and graphite bipolar plates, and their conductivity is not as good as the latter two. Moreover, when there is a flow channel in the liquid flow battery, the above-mentioned bipolar plate contacts the conductive flow channel plate, further increasing the contact resistance of the battery.

[0004] In summary, the existing bipolar plates of liquid flow batteries cannot effectively solve the problem, and there is an urgent need to develop a bipolar plate or bipolar plate assembly with good conductivity, high chemical and electrochemical stability, and high mechanical strength. Summary of the invention

[0005] In view of the above problems or shortcomings, the present invention provides a three-in-one assembly of electrodes, bipolar plates and flow channel plates for liquid flow batteries. The technical solution adopted by the present invention is as follows: A three-in-one assembly of an electrode, a bipolar plate and a flow channel plate for a liquid flow battery, comprising the following preparation steps: Step S1: activating the entire electrode material to obtain a battery electrode; Step S2: placing the battery electrode in a specific mold, dipping or coating the center of the electrode with a layer of conductive polymer filler, and then coating it with a layer of thermoplastic resin after hot pressing to form a transition layer with internal conductivity and external insulation, and obtaining an integrated composite electrode after cooling; Step S3: Fold the integrated composite electrode in half and place the flow channel plate in the middle of the folded integrated composite electrode, and weld the integrated composite electrode to the flow channel plate by flat plate heat welding to form a three-in-one assembly of electrode, bipolar plate and flow channel plate.

[0006] Preferably, the electrode material in step S1 is carbon cloth, the thickness of the carbon cloth is 0.8-2.2 mm, and the surface density is 200-500 g / m 2 .

[0007] Preferably, in step S2, the center of the electrode is impregnated or coated with a layer of conductive polymer filler with a width of 10-30 mm.

[0008] Preferably, the conductive polymer filler in step S2 includes a conductive agent and a thermoplastic resin, and the content of the conductive agent is 30-70%.

[0009] Preferably, the flow channel plate in step S3 is a common corrosion-resistant and oxidation-resistant engineering plastic plate, including but not limited to polyethylene, polypropylene, polyvinyl chloride, and polystyrene.

[0010] Preferably, the flow field shape of the flow channel plate in step S3 is at least one of an interdigitated shape, a serpentine shape, and a parallel shape.

[0011] Preferably, the thickness of the flow channel plate in step S3 is 1-6 mm.

[0012] Preferably, the operating temperature of the flat plate heat welding in step S3 is consistent with the melting point of the runner plate material, and the operating pressure is 100-500 kg / m 2 .

[0013] The present invention also provides a liquid flow battery stack, which is assembled from a three-in-one component of a liquid flow battery electrode, a bipolar plate and a flow channel plate. Compared with the existing battery stack technology, the voltage efficiency is significantly improved.

[0014] The beneficial effects of the present invention include at least: 1. The three-in-one assembly of electrodes, bipolar plates and flow channel plates for a liquid flow battery prepared by the present invention does not contain a traditional conductive bipolar plate. The current conduction relies on a whole carbon cloth electrode, which has high electrochemical reaction activity, good conductivity and strong corrosion resistance. It is not only a place for electrochemical reaction, but also collects current to act as a conductive electrode plate. The current flows to the other pole through a transition layer in the middle of the integrated composite electrode (the transition layer is conductive inside and insulated outside, and its function is to conduct current and prevent internal electrolyte from leaking through the electrode). This not only saves the high cost of the bipolar plate, but also will not be affected by the resistance of the traditional bipolar plate. Moreover, the three-in-one assembly replaces the physical overlap of the traditional electrode, conductive bipolar plate and conductive flow channel plate, and the contact resistance between the materials is greatly reduced. The final result is that the ohmic polarization of the battery is greatly reduced.

[0015] 2. The three-in-one component prepared by the present invention is simple to prepare, easy to mass produce and apply, and has the advantages of good conductivity, high chemical and electrochemical stability, and high mechanical strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the integrated composite electrode structure in the three-in-one component of the present invention.

[0017] Figure 2 This is a schematic diagram of the structure of a single cell of an existing liquid flow battery.

[0018] Figure 3 This is a schematic diagram of the structure of a three-in-one assembly of an electrode, a bipolar plate and a flow channel plate for a liquid flow battery in Example 1 of the present invention.

[0019] Figure 4 This is a schematic diagram of the structure of a single cell of a flow battery in Example 1 of the present invention.

[0020] Figure numerals: 1. Battery electrode; 2. Transition layer with internal conductivity and external insulation; 3. Flow channel plate; 4. End plate; 5. Current collecting plate; 6. Diaphragm; 7. Traditional bipolar plate. DETAILED DESCRIPTION

[0021] The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Referring to the technical solution of the present invention, the whole carbon cloth electrode material is activated to obtain a battery electrode, the battery electrode is placed in a specific mold, a layer of conductive polymer filler is impregnated or coated in the center of the electrode, and after hot pressing and shaping, a layer of thermoplastic resin is coated to form a transition layer with internal conductivity and external insulation, and after cooling, an integrated composite electrode is obtained, such as Figure 1 As shown, 1 is a battery electrode, 2 is a transition layer with conductive interior and insulating exterior; the integrated composite electrode is folded in half and the flow channel plate is placed in the middle of the folded integrated composite electrode, and the integrated composite electrode is welded to the flow channel plate by flat plate heat welding to form a three-in-one assembly of electrode, bipolar plate and flow channel plate, as shown in FIG. Figure 3 As shown, 3 is a flow channel plate. The present invention also provides a flow battery stack, which is assembled from a three-in-one assembly of a flow battery electrode, a bipolar plate and a flow channel plate. Compared with the existing stack technology, the voltage efficiency is significantly improved.

[0023] Example 1: A three-in-one assembly of an electrode, a bipolar plate and a flow channel plate for a liquid flow battery, comprising the following preparation steps: Step S1: The entire sheet with a thickness of 0.8 mm and a surface density of 200 g / m 2 The carbon cloth is activated to obtain battery electrodes.

[0024] Step S2: placing the battery electrode in a specific mold, dipping or coating a layer of conductive polymer filler in the center of the electrode, with a coating width of 10 mm, and a conductive agent content of 30% in the conductive polymer filler. After hot pressing and shaping, coating a layer of thermoplastic resin to form a transition layer with internal conductivity and external insulation. After cooling, an integrated composite electrode is obtained, such as Figure 1 shown.

[0025] Step S3: Fold the integrated composite electrode in half and place the flow channel plate in the middle of the folded integrated composite electrode, and weld the integrated composite electrode to the finger-shaped flow channel plate made of polyethylene by flat plate heat welding. The heat welding temperature is 140°C and the operating pressure is 200 kg / m 2 , forming a three-in-one assembly of electrodes, bipolar plates and flow channel plates, such as Figure 3 shown.

[0026] A three-in-one assembly of an electrode, a bipolar plate and a flow channel plate for a liquid flow battery prepared according to the technical solution of Example 1 is assembled into a single cell, and the structural schematic diagram is shown in FIG. Figure 4 As shown, the test results show that the voltage efficiency is 86.6%.

[0027] Example 2: A three-in-one assembly of an electrode, a bipolar plate and a flow channel plate for a liquid flow battery, comprising the following preparation steps: Step S1: The entire sheet with a thickness of 1.2 mm and a surface density of 300 g / m 2 The carbon cloth is activated to obtain battery electrodes.

[0028] Step S2: placing the battery electrode in a specific mold, dipping or coating the center of the electrode with a layer of conductive polymer filler, with a coating width of 15 mm, and a conductive agent content of the conductive polymer filler of 45%. After hot pressing and shaping, coating a layer of thermoplastic resin to form a transition layer with internal conductivity and external insulation, and obtaining an integrated composite electrode after cooling.

[0029] Step S3: Fold the integrated composite electrode in half and place the flow channel plate in the middle of the folded integrated composite electrode, and weld the integrated composite electrode to the finger-shaped flow channel plate made of polypropylene by flat plate heat welding. The heat welding temperature is 170°C and the operating pressure is 300 kg / m 2 , forming a three-in-one component of electrode, bipolar plate and flow channel plate.

[0030] A three-in-one assembly of an electrode, a bipolar plate and a flow channel plate for a liquid flow battery prepared according to the technical solution of Example 1 was assembled into a single cell. Test results showed that the voltage efficiency reached 86.6%.

[0031] Example 3: A three-in-one assembly of an electrode, a bipolar plate and a flow channel plate for a liquid flow battery, comprising the following preparation steps: Step S1: The thickness of the whole sheet is 1.6 mm and the surface density is 400 g / m 2 The carbon cloth is activated to obtain battery electrodes.

[0032] Step S2: placing the battery electrode in a specific mold, dipping or coating the center of the electrode with a layer of conductive polymer filler, with a coating width of 20 mm, and a conductive agent content of 60% in the conductive polymer filler. After hot pressing and shaping, coating a layer of thermoplastic resin to form a transition layer with internal conductivity and external insulation, and obtaining an integrated composite electrode after cooling.

[0033] Step S3: Fold the integrated composite electrode in half and place the flow channel plate in the middle of the folded integrated composite electrode, and weld the integrated composite electrode to the serpentine flow channel plate made of polyvinyl chloride by flat plate heat welding. The heat welding temperature is 220°C and the operating pressure is 500 kg / m 2 , forming a three-in-one component of electrode, bipolar plate and flow channel plate.

[0034] A three-in-one assembly of an electrode, a bipolar plate and a flow channel plate for a liquid flow battery prepared according to the technical solution of Example 1 was assembled into a single cell. Test results showed that the voltage efficiency reached 86.7%.

[0035] Example 4: A three-in-one assembly of an electrode, a bipolar plate and a flow channel plate for a liquid flow battery, comprising the following preparation steps: Step S1: The thickness of the whole sheet is 2.2 mm and the surface density is 500 g / m 2The carbon cloth is activated to obtain battery electrodes.

[0036] Step S2: placing the battery electrode in a specific mold, dipping or coating the center of the electrode with a layer of conductive polymer filler, with a coating width of 30 mm, and a conductive agent content of the conductive polymer filler of 70%. After hot pressing and shaping, coating a layer of thermoplastic resin to form a transition layer with internal conductivity and external insulation, and obtaining an integrated composite electrode after cooling.

[0037] Step S3: Fold the integrated composite electrode in half and place the flow channel plate in the middle of the folded integrated composite electrode, and weld the integrated composite electrode to the parallel flow channel plate made of polystyrene by flat plate heat welding. The heat welding temperature is 120°C and the operating pressure is 100 kg / m 2 , forming a three-in-one component of electrode, bipolar plate and flow channel plate.

[0038] A three-in-one assembly of an electrode, a bipolar plate and a flow channel plate for a liquid flow battery prepared according to the technical solution of Example 1 was assembled into a single cell. Test results showed that the voltage efficiency reached 86.8%.

[0039] Comparative Example 1: like Figure 2 As shown, according to the existing liquid flow battery technology, a single cell is assembled using conventional materials and stacking methods, wherein the carbon cloth electrode used has a thickness of 1.2 mm and a surface density of 300 g / m 2 The bipolar plate uses conductive graphite bipolar plate, and the flow channel plate is 2mm thick finger-shaped conductive graphite paper. They are assembled into a single cell. The test results show that the voltage efficiency is only 83.3%.

[0040] The three-in-one assembly of electrodes, bipolar plates and flow channel plates prepared in Examples 1 to 4 and Comparative Example 1 was assembled into a single cell for testing, and the average coulombic efficiency, voltage efficiency and energy efficiency of the first 10 cycles were tested and recorded under the same test conditions. Embodiments 1-4 have better performance than comparative example 1. This is because the three-in-one assembly of electrodes, bipolar plates and flow channel plates for liquid flow batteries prepared by the present invention does not contain traditional conductive bipolar plates. Current conduction relies on a whole piece of carbon cloth electrode, which has high electrochemical reaction activity, good conductivity and strong corrosion resistance. It is not only a place for electrochemical reaction, but also collects current to act as a conductive electrode plate. The current flows to the other pole through the transition layer in the middle of the integrated composite electrode (the transition layer is conductive inside and insulated outside, and its function is to conduct current and prevent internal electrolyte from leaking through the electrode). It not only saves the high cost of the bipolar plate, but also will not be affected by the resistance of the traditional bipolar plate. Moreover, the three-in-one assembly replaces the physical overlap of the traditional electrode, conductive bipolar plate and conductive flow channel plate, and the contact resistance between the materials is greatly reduced. The final result is that the ohmic polarization of the battery is greatly reduced.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A three-in-one assembly of an electrode, a bipolar plate and a flow channel plate for a liquid flow battery, characterized in that: The method comprises the following preparation steps: Step S1: activating the entire electrode material to obtain a battery electrode; Step S2: placing the battery electrode in a specific mold, dipping or coating the center of the electrode with a layer of conductive polymer filler, and then coating it with a layer of thermoplastic resin after hot pressing to form a transition layer with internal conductivity and external insulation, and obtaining an integrated composite electrode after cooling; Step S3: Fold the integrated composite electrode in half and place the flow channel plate in the middle of the folded integrated composite electrode, and weld the integrated composite electrode to the flow channel plate by flat plate heat welding to form a three-in-one assembly of electrode, bipolar plate and flow channel plate.

2. A three-in-one assembly of an electrode, a bipolar plate and a flow channel plate for a liquid flow battery according to claim 1, characterized in that: The electrode material in step S1 is carbon cloth with a thickness of 0.8-2.2 mm and a surface density of 200-500 g / m 2 .

3. The three-in-one assembly of an electrode, a bipolar plate and a flow channel plate for a liquid flow battery according to claim 1, characterized in that: In the step S2, the center of the electrode is impregnated or coated with a layer of conductive polymer filler with a width of 10-30 mm.

4. The three-in-one assembly of an electrode, a bipolar plate and a flow channel plate for a liquid flow battery according to claim 1, characterized in that: The conductive polymer filler in step S2 includes a conductive agent and a thermoplastic resin, and the content of the conductive agent is 30-70%.

5. The three-in-one assembly of an electrode, a bipolar plate and a flow channel plate for a liquid flow battery according to claim 1, characterized in that: In step S3, the flow channel plate is a common corrosion-resistant and oxidation-resistant engineering plastic plate, and the material includes but is not limited to polyethylene, polypropylene, polyvinyl chloride, and polystyrene.

6. The three-in-one assembly of an electrode, a bipolar plate and a flow channel plate for a liquid flow battery according to claim 1, characterized in that: In the step S3, the flow field shape of the flow channel plate is at least one of an interdigitated shape, a serpentine shape, and a parallel shape.

7. The three-in-one assembly of an electrode, a bipolar plate and a flow channel plate for a liquid flow battery according to claim 1, characterized in that: In step S3, the thickness of the flow channel plate is 1-6 mm.

8. The three-in-one assembly of an electrode, a bipolar plate and a flow channel plate for a liquid flow battery according to claim 1, characterized in that: The operating temperature of the flat plate heat welding in step S3 is consistent with the melting point of the runner plate material, and the operating pressure is 100-500 kg / m 2 .

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