Integrated side plate for flow battery as well as preparation method and application of integrated side plate

Abstract

The invention belongs to the technical field of energy storage, and discloses an integrated side plate for a flow battery and a preparation method and application thereof, the integrated side plate comprises a copper plate and a bipolar plate, the thickness of the copper plate is 0.3 mm-5. 0mm, the thickness of the bipolar plate is 0.5 mm-1. 5mm, the mass ratio of the bipolar plate to the copper plate is 1: (0.8-40), and the copper plate and the bipolar plate are integrally formed through hot pressing. According to the flow battery integrated side plate provided by the invention, the mode that a side bipolar plate and a copper plate of an existing flow battery are respectively used as independent parts to be assembled is changed, so that the problem of low charge-discharge efficiency caused by poor contact between the side plate and the copper plate in the charge-discharge process of the battery or an electric pile is solved; the thickness of the copper plate can reach 0.3-5.0 mm, and the copper plate and the bipolar plate are stably, uniformly and integrally formed, so that the sealing problem caused by a non-uniform coating and the problem of resistance increase caused by an over-thin copper layer are further avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage, and in particular relates to an integrated side plate for a liquid flow battery, a preparation method and an application thereof. Background Art

[0002] As one of the main technologies of new energy storage batteries, flow batteries have the advantages of high safety, long life, and independent design of power and capacity. For flow batteries, the battery stack is the power unit of the battery system. The internal resistance of the battery directly affects the performance of the flow battery. The copper plate serves as a bridge for electronic conduction between the bipolar plate and the load end, which directly affects the energy efficiency of charging and discharging.

[0003] At present, the bipolar plate and copper plate in the flow battery stack mainly rely on physical pressure contact. Affected by the deformation and flatness of the copper plate and the bipolar plate, there is a large contact resistance between the interfaces. Poor contact during charging and discharging leads to low energy conversion efficiency of the battery or stack. There is a process to copper-plate one side of the bipolar plate to replace the current collector, but this process is still subject to the thickness of the copper plating and the uniformity of the plating: first, for high-power flow batteries, the plating thickness is less than 1mm, which will increase the resistance of the stack. Second, for the assembly process, the uneven plating affects the overall flatness, which in turn affects the sealing of the flow battery and has the risk of leakage.

[0004] Therefore, the art still lacks an effective and feasible solution to improve the connection structure between the copper plate and the bipolar plate. Summary of the invention

[0005] The technical problem to be solved by the present invention is that the current contact mode between the copper plate and the bipolar plate of the liquid flow battery has a large contact resistance. In order to overcome the deficiencies and defects mentioned in the above background technology, an integrated side plate for a liquid flow battery and a preparation method and application thereof are provided.

[0006] In order to solve the above technical problems, the technical solution proposed by the present invention is: An integrated side plate for a liquid flow battery, the integrated side plate comprising a copper plate and a bipolar plate, the copper plate having a thickness of 0.3-5.0 mm, the bipolar plate having a thickness of 0.5-1.5 mm, the mass ratio of the bipolar plate to the copper plate being 1:0.8-40, and the copper plate and the bipolar plate being hot-pressed into one piece.

[0007] The integrated side plate provided by the present invention changes the existing way of assembling the side bipolar plate and the copper plate as separate components in a flow battery, so as to solve the problem of low charge and discharge efficiency often caused by poor contact between the side plate and the copper plate during the charge and discharge process of the battery or the stack, and can avoid poor sealing caused by uneven plating, further resulting in the infiltration of the electrolyte into the copper plate, causing corrosion of the copper plate surface, and ultimately leading to the scrapping of the stack; the copper plate and the bipolar plate are integrally hot-pressed without gaps, and there will be no phenomenon of uneven copper plate thickness. The copper plating thickness is moderate, greatly reducing the risk of liquid leakage and avoiding copper plate corrosion.

[0008] Preferably, the integrated side plate for a flow battery comprises a copper plate layer and a bipolar plate layer, and is integrally formed by hot-pressing a bipolar plate raw material and a copper plate. The bipolar plate raw material includes graphite powder and conductive plastic, wherein the mass content of the conductive plastic is 5-30% of that of the graphite powder, and the conductive plastic is a composite additive conductive plastic.

[0009] Preferably, the integrated side plate for a flow battery comprises a copper plate layer, a bonding layer and a bipolar plate layer, and is integrally formed by hot-pressing a bipolar plate and a copper plate. The thickness of the bonding layer is 0.05-0.5 mm; the raw materials of the bipolar plate include graphite powder and conductive plastic, wherein the mass content of the graphite powder is 75-95% of the raw materials of the bipolar plate, and the conductive plastic is a composite additive conductive plastic.

[0010] Under the same technical concept, the present application also provides a preparation method for an integrated side plate for a flow battery, including the following two preparation schemes: Scheme 1: (1) Perform surface treatment on the copper plate; (2) Put the surface-treated copper plate into a mold for preheating; (3) Mix the conductive plastic and the graphite powder to obtain a mixed powder material, pour the mixed powder material into the mold, and hot-press it to form an integrated side plate for a flow battery; Scheme 2: (1) Perform surface treatment on the copper plate and prepare a finished bipolar plate; (2) Mix the conductive plastic and the graphite powder to obtain a mixed powder material, and coat the mixed powder material on the surface of the bipolar plate in step (1) with a coating thickness of 0.2-1.0 mm; (3) Put the coated bipolar plate into a mold, then put in the copper plate, and hot-press it to form an integrated side plate for a flow battery.

[0011] The solution of this application can be made by using a finished bipolar plate and a copper plate through conductive plastic, graphite powder, binder and hot pressing molding, or can be integrally formed by directly combining the raw materials of the bipolar plate with the copper plate; when using the raw materials of the bipolar plate, the copper plate needs to be preheated to ensure the effect of integrally hot pressing with the bipolar plate. The conductive plastic has viscosity at high temperature, and the copper plate and the bipolar plate of the obtained integrated side plate are directly integrally formed without gaps or interlayers, and the bonding performance is better; when using a finished bipolar plate, the preparation process is simple, and the copper plate does not need to be preheated. The conductive plastic, graphite powder and binder form a bonding layer between the copper plate and the bipolar plate, but do not affect the fitting and conductivity between the bipolar plate and the copper plate, and the preparation cost is lower.

[0012] Preferably, the surface treatment is specifically as follows: first, one side of the copper plate is subjected to corrosion treatment, and then chemical cleaning is carried out. The corrosion treatment can increase the bonding surface area of the copper plate, and the chemical cleaning can further improve the surface bonding force between the copper plate and the graphite powder, which is helpful for its combination with the bipolar plate.

[0013] Preferably, in step (2) of Solution 1, the preheating temperature is 200 - 260 °C and the time is 1 - 3 min.

[0014] Preferably, when the conductive plastic and graphite powder are mixed in step (3) of Solution 1, the mass content of the conductive plastic is 5 - 30% of the graphite powder; the temperature of the hot pressing molding is: 210 - 300 °C, the pressure is: 5 - 10 Mpa, and the pressure holding time is 1 min - 3 min.

[0015] Preferably, when the conductive plastic and graphite powder are mixed in step (2) of Solution 2, the mass content of the conductive plastic is 10 - 50% of the graphite powder; in step (3), the temperature of the hot pressing molding is: 210 - 300 °C, the pressure is: 1 - 3 Mpa, and the pressure holding time is 20 S - 1 min.

[0016] In Solution 1, the main purpose of adding the conductive plastic is to prepare the bipolar plate. At this time, the integral formation of the copper plate and the bipolar plate is mainly achieved through the pressure and holding time of hot pressing; in Solution 2, the conductive plastic is mainly used as a conductive adhesive between the copper plate and the bipolar plate. The minimum dosage is relatively a little more, and the viscosity will be better, but it should not be too much to prevent too poor conductivity; at this time, the hot pressing molding is assisted by the binder, and both the pressure and the holding time are relatively small, and it is enough to make the conductive plastic and graphite melt and combine into a whole.

[0017] Under the same technical concept, this application also provides an application of the above-mentioned integrated side plate for a flow battery, and the integrated side plate is used for a flow battery.

[0018] Preferably, the structure of the flow battery includes a first end plate, a first integrated side plate, a first flow frame, an intermediate single cell stack, a second flow frame, a second integrated side plate, and a second end plate arranged in sequence.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The integrated side plate of the flow battery provided by the present invention changes the existing method of assembling the side bipolar plate and the copper plate as separate components in a flow battery, so as to solve the problem of low charge and discharge efficiency often caused by poor contact between the side plate and the copper plate during the charge and discharge process of the battery or the stack; the thickness of the copper plate of the present invention can reach 0.3 - 5.0 mm, and it is integrally formed with the bipolar plate stably and uniformly, further avoiding the sealing problem caused by uneven plating and the problem of increased resistance caused by too thin copper layer; experimental data shows that after using the integrated side plate of the present invention, the energy efficiency of the flow battery is significantly improved, and the discharge capacity and the utilization rate of the electrolyte are also improved to a certain extent; (2) The preparation method of the integrated side plate of the flow battery provided by the present invention is simple and flexible. First, the copper plate is activated, which is beneficial to improving the bonding effect with the bipolar plate during subsequent hot pressing forming. The preheating step can increase the bonding force between the bipolar plate and the copper plate and reduce the deformation after forming. Description of the Drawings

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0021] Figure 1 It is a schematic structural diagram of the integrated side plate of the flow battery in Embodiment 1 of the present application; Figure 2 It is a schematic structural diagram of the flow battery in Embodiment 1 of the present application; Figure 3 It is a comparison chart of the energy efficiency of 50 charge and discharge cycles of the flow batteries in Embodiment 1 of the present application and Comparative Example 1; Figure 4 It is a comparison chart of the discharge capacity of 50 charge and discharge cycles of the flow batteries in Embodiment 1 of the present application and Comparative Example 1; Figure 5 It is a schematic structural diagram of the integrated side plate of the flow battery in Embodiment 2 of the present application; Figure 6 It is a comparison chart of the energy efficiency of 50 charge and discharge cycles of the flow batteries in Embodiment 2 of the present application and Comparative Example 1; Figure 7It is a comparison chart of the discharge capacities of the flow battery in Example 2 and Comparative Example 1 during 50 charge-discharge cycles; Figure 8 It is a comparison chart of the energy efficiencies of the flow battery in Example 1 and Comparative Example 2 during 50 charge-discharge cycles; Figure 9 It is a comparison chart of the discharge capacities of the flow battery in Example 1 and Comparative Example 2 during 50 charge-discharge cycles; Figure 10 It is a comparison chart of the energy efficiencies of the flow battery in Example 1 and Comparative Example 3 during 50 charge-discharge cycles; Figure 11 It is a comparison chart of the discharge capacities of the flow battery in Example 1 and Comparative Example 3 during 50 charge-discharge cycles; Figure 12 Side physical diagram of the integrated side plate of the flow battery in Example 1 of the present application; Figure 13 Side physical diagram of the integrated side plate of the flow battery in Example 2 of the present application. Detailed implementation manners

[0022] To facilitate the understanding of the present invention, the following will describe the present invention more comprehensively and meticulously in conjunction with the accompanying drawings of the specification and preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0023] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0024] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0025] Example 1: This example provides an integrated side plate for a flow battery, and its structural schematic diagram is as Figure 1 shown, and the side physical diagram is as Figure 12 shown, including a copper plate and a bipolar plate. The thickness of the copper plate is 0.5 mm, the thickness of the bipolar plate is 0.8 mm, the mass ratio of the bipolar plate to the copper plate is 1:2.5, and the copper plate and the bipolar plate are integrally formed by hot pressing.

[0026] The raw materials of the bipolar plate include graphite powder and conductive plastic. Among them, the mass of the conductive plastic is 54 g, and the mass of the graphite powder is 181 g; the conductive plastic is a composite additive type conductive plastic, among which the mass of the carbon black material is 28 g and the mass of the epoxy resin is 26 g.

[0027] The preparation method of the integrated side plate for the flow battery provided in this embodiment is specifically the following steps: (1) Perform surface treatment on the copper plate; the specific scheme of the surface treatment is: first perform pretreatment to remove the contaminants on the surface, and then use the etching solution to etch the pretreated copper plate; perform post-treatment and drying on the copper plate after the etching treatment; (2) Put the copper plate after surface treatment into the mold for preheating, the preheating temperature is 238 °C, and the time is 90 s; (3) Mix the conductive plastic and graphite powder to obtain a mixed powder, pour the mixed powder into the mold, and perform hot pressing to form. The temperature of the hot pressing is: 232 °C, the pressure is: 6.2 Mpa, and the pressure holding time is 90 s to obtain the integrated side plate for the flow battery; Assemble the integrated side plate for the flow battery in this embodiment into a flow battery, and its structural schematic diagram is as Figure 2 shown. The structure of the flow battery includes a first end plate, a first integrated side plate, a first flow frame, an intermediate single cell stack, a second flow frame, a second integrated side plate, and a second end plate arranged in sequence. Perform performance testing on this flow battery according to NBT42081-2016. The testing method is: select 1.7 mol / L trivalent vanadium electrolyte for both the positive and negative electrodes, and the dosage is uniformly 450 ml / side. After setting the constant current and the charging cut-off voltage of 1.6 V / cell and the discharging cut-off condition of 1.0 V / cell in the constant current charge and discharge mode, and setting the current density to 180 mA / cm², turn on the electrolyte pump and the charge and discharge tester to perform charge and discharge testing, and record the charge and discharge capacity, charge and discharge energy, and energy efficiency of the battery.

[0028] The test results are as Figure 3 、 4 shown. The energy efficiency of the flow battery using the integrated side plate in Example 1 is 83.5%, and the energy efficiency of the flow battery using the split bipolar plate in Comparative Example 1 is 80.9%. The former has an energy efficiency improvement of 2.6 percentage points compared to the latter. In the test of the discharge capacity, the discharge capacity of the flow battery using the integrated side plate in Example 1 is 13 Ah, and the discharge capacity of the flow battery using the split bipolar plate in Comparative Example 1 is 12.1 Ah. The former has a 7% increase in the discharge capacity compared to the latter, and the improvement effect is very significant.

[0029] Example 2: This embodiment provides an integrated side plate for a flow battery, and its structural schematic diagram is as Figure 5 shown, and the side physical diagram is as Figure 13 shown, including a copper plate and a bipolar plate. The thickness of the copper plate is 0.5 mm, the thickness of the bipolar plate is 0.8 mm, the thickness of the bonding layer is 0.1 mm, the mass ratio of the bipolar plate to the copper plate is 1:1.5, and the copper plate and the bipolar plate are integrally formed by hot pressing.

[0030] The existing bipolar plate used is a bipolar plate containing 84% graphite by mass; the graphite powder and conductive plastic coated on the bipolar plate, where the mass of the conductive plastic is 5.2 g and the mass of the graphite powder is 23.5 g; the conductive plastic is a composite additive conductive plastic, where the mass of acetylene black is 2.8 g and the mass of epoxy resin is 2.4 g.

[0031] The preparation method of the integrated side plate for the flow battery provided in this embodiment is specifically the following steps: (1) Perform surface treatment on the copper plate; the specific scheme of the surface treatment is: first perform pretreatment to remove the contaminants on the surface, and then use the etching solution to etch the copper plate that has undergone the pretreatment; perform post-treatment and drying on the copper plate that has undergone the etching treatment; prepare the existing bipolar plate; (2) Mix the conductive plastic and graphite powder to obtain a mixed powder, and coat the mixed powder on the surface of the existing bipolar plate, and the coating thickness is 0.6 mm; (3) Place the coated bipolar plate into the mold, and then place the copper plate, and perform hot pressing to form. The temperature of the hot pressing is: 225 °C, the pressure is: 2.6 Mpa, and the pressure holding time is 75 s to obtain the integrated side plate for the flow battery.

[0032] Assemble the integrated side plate for the flow battery in this embodiment into a flow battery, and its structural schematic diagram is as Figure 2 shown. The structure of the flow battery includes a first end plate, a first integrated side plate, a first flow frame, an intermediate single cell stack, a second flow frame, a second integrated side plate, and a second end plate arranged in sequence. Perform performance testing on this flow battery according to NBT42081-2016, and the testing method is the same as that in Example 1.

[0033] The test results are as Figure 6 , 7 shown. The energy efficiency of the flow battery using the integrated side plate in Example 2 is 83%, and the energy efficiency of the flow battery using the split bipolar plate in Comparative Example 1 is 80.9%. The former has an energy efficiency increase of 2.1 percentage points compared to the latter. In the test of the discharge capacity, the discharge capacity of the flow battery using the integrated side plate in Example 2 is 12.73 Ah, and the discharge capacity of the flow battery using the split bipolar plate in Comparative Example 1 is 12.1 Ah. The former has a 5% increase in discharge capacity compared to the latter, and the improvement effect is very significant.

[0034] Comparative Example 1: This comparative example provides a common split bipolar plate, the structure of which is a separated copper plate and a bipolar plate, with thicknesses of 0.5 mm and 0.8 mm respectively. The split bipolar plate is assembled into a flow battery, and the structure of the flow battery includes a first end plate, a first copper plate, a first side plate, a first flow frame, a middle single cell stack, a second flow frame, a second side plate, a second copper plate, and a second end plate arranged in sequence. The performance of this flow battery was tested according to NBT42081-2016, and the test method was the same as that in Example 1. The test results are as Figure 1 , 2 shown.

[0035] Comparative Example 2: This comparative example provides an integrated side plate for a flow battery, which is prepared by plating metal copper; its preparation method is: mixing graphite raw materials and a binder and then molding to obtain a graphite plate, and electroplating copper on the graphite plate after plasma treatment to obtain the bipolar plate.

[0036] For the integrated side plate of this comparative example, the thickness of the copper layer is 0.1 mm, the thickness of the bipolar plate is 0.8 mm, and the copper layer is unevenly plated on the surface of the bipolar plate. The integrated side plate is assembled into a flow battery, and the structure of the flow battery includes a first end plate, a first integrated side plate, a first flow frame, a middle single cell stack, a second flow frame, a second integrated side plate, and a second end plate arranged in sequence.

[0037] The performance of this flow battery was tested, and the test method was the same as that in Example 1. The test results are as Figure 8 , 9 shown. It can be seen from the figure that the energy efficiency of Example 1 is 6 percentage points higher than that of this comparative example. The discharge capacity of Example 1 remains stable, while the capacity of this comparative example shows a gradually decreasing trend, and Example 1 is about 26% higher at the end of 50 cycles.

[0038] Comparative Example 3: This comparative example provides an integrated side plate for a flow battery, which is not prepared by hot pressing; its preparation method is: coating a single-component inorganic silicoaluminate graphite conductive adhesive with a thickness of about 0.1 mm on the surface of the graphite bipolar plate, then fitting and pressing it tightly with a copper plate, putting it into an oven and heating it to 80-120 °C for drying to carry out fixed connection.

[0039] For the integrated side plate of this comparative example, the thickness of the copper layer is 0.5 mm, the thickness of the bipolar plate is 0.8 mm, the copper layer is not firmly bonded to the bipolar plate after bonding, and the contact resistance is large. The integrated side plate is assembled into a flow battery, and the structure of the flow battery includes a first end plate, a first integrated side plate, a first flow frame, a middle single cell stack, a second flow frame, a second integrated side plate, and a second end plate arranged in sequence Performance testing was carried out on this flow battery, and the testing method was the same as that in Example 1. The test results are as Figure 10 , 11 shown. It can be seen from the figure that the energy efficiency of Example 1 is 9 percentage points higher than that of this comparative example, and the capacity of Example 1 is 28% higher than the capacity of this comparative example.

Claims

1. An integrated side plate for a liquid flow battery, characterized in that: The integrated side plate includes a copper plate and a bipolar plate, the copper plate has a thickness of 0.3 mm-5.0 mm, the bipolar plate has a thickness of 0.5 mm-1.5 mm, the mass ratio of the bipolar plate to the copper plate is 1:0.8-40, and the copper plate and the bipolar plate are hot-pressed into one piece.

2. The integrated side plate according to claim 1, characterized in that: The integrated side plate for the liquid flow battery comprises a copper plate layer and a bipolar plate layer, and is formed by hot pressing a bipolar plate raw material and a copper plate into one piece. The bipolar plate raw material comprises graphite powder and conductive plastic, wherein the mass content of the conductive plastic is 5-30% of the graphite powder, and the conductive plastic is a composite additive conductive plastic.

3. The integrated side plate according to claim 1, characterized in that: The integrated side plate for the liquid flow battery comprises a copper plate layer, an adhesive layer and a bipolar plate layer, and is formed by hot pressing the bipolar plate and the copper plate into one piece, and the thickness of the adhesive layer is 0.05-0.5 mm; the raw materials of the bipolar plate include graphite powder and conductive plastic, wherein the mass content of the graphite powder is 75-95% of the raw materials of the bipolar plate, and the conductive plastic is a composite additive conductive plastic.

4. A method for preparing an integrated side plate for a flow battery, characterized in that: There are two preparation schemes: Solution 1: (1) Surface treatment of copper plate; (2) Place the surface treated copper plate into the mold for preheating; (3) mixing the conductive plastic and graphite powder to obtain a mixed powder, pouring the mixed powder into a mold, and hot pressing to obtain an integrated side plate for a liquid flow battery; Option 2: (1) Surface treatment of copper plates and preparation of finished bipolar plates; (2) mixing the conductive plastic and graphite powder to obtain a mixed powder, and coating the mixed powder on the surface of the bipolar plate in step (1) to a coating thickness of 0.2-1 mm; (3) The coated bipolar plate is placed in a mold, and then a copper plate is placed in the mold, and hot pressing is performed to obtain an integrated side plate for a liquid flow battery.

5. The preparation method according to claim 4, characterized in that: The surface treatment specifically includes: firstly performing corrosion treatment on one side of the copper plate, and then performing chemical cleaning.

6. The preparation method according to claim 4, characterized in that: The preheating temperature in step (2) of scheme 1 is 200-260° C. and the time is 1-3 min.

7. The preparation method according to claim 4, characterized in that: In step (3) of scheme 1, when the conductive plastic and graphite powder are mixed, the mass content of the conductive plastic is 5-30% of the graphite powder; the temperature of the hot pressing molding is: 210-300°C, the pressure is: 5-10Mpa, and the pressure holding time is 1min-3min.

8. The preparation method according to claim 4, characterized in that: When the conductive plastic and graphite powder are mixed in step (2) of scheme 2, the mass content of the conductive plastic is 10-50% of the graphite powder; the temperature of the hot pressing molding in step (3) is: 210-300°C, the pressure is: 1-3Mpa, and the pressure holding time is 20S-1min.

9. An application of the integrated side plate for a flow battery according to any one of claims 1 to 3 or the method for preparing the integrated side plate for a flow battery according to claims 4 to 8, characterized in that: The integrated side plate is used in a liquid flow battery.

10. The use according to claim 9, characterized in that The structure of the liquid flow battery includes a first end plate, a first integrated side plate, a first liquid flow frame, an intermediate single cell stack, a second liquid flow frame, a second integrated side plate and a second end plate which are arranged in sequence.

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