An integrated structure of electrode frame and bipolar plate and battery stack for liquid flow battery

Abstract

The present invention relates to an integrated structure of an electrode frame and a bipolar plate and a battery stack for a liquid flow battery. The bipolar plate is sealed inside the electrode frame by an injection molding or molding process. An electrolyte guide groove and an electrolyte inlet and outlet blind holes are provided on both sides of the bipolar plate at the inner edge of the electrode frame. A long platform for accommodating electrode materials extends from the electrolyte guide groove to allow the electrode material to fit seamlessly with the electrode frame. The electrode frame and the diaphragm are bonded by welding. When the liquid flow battery battery stack is assembled, two adjacent electrode frames are connected by welding. The battery stack is formed by stacking more than two groups of the above-mentioned combinations. By adopting the integrated structure of the liquid flow battery electrode frame and the bipolar plate and the battery stack of the present invention, the sealing of the liquid flow battery battery stack will be greatly improved, the battery structure will be significantly simplified, and the volume of the battery stack will be significantly reduced, the energy storage cost will be significantly reduced, the battery leakage will be significantly improved, and the battery operation stability will be significantly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic redox flow batteries, and in particular relates to an integrated structure of an electrode frame and a bipolar plate and a battery stack applied to a flow battery. Background Art

[0002] The 26th United Nations Climate Change Conference released the 2021 Global Climate Status Report. According to the statistical data in the report, the global average temperature continued to rise in 2021; the ocean continued to warm up and reached a new record; the sea ice range reached a historical low and the melting rate doubled; the worsening climate situation led to frequent extreme weather around the world. Faced with the impact of extreme weather and climate change, countries around the world have set carbon peak and carbon neutrality climate goals. Accelerating the clean and low-carbon transformation of energy and actively responding to climate change have become common global issues.

[0003] To achieve the goals of carbon peak and carbon neutrality, we must vigorously develop renewable energy, and the development of renewable energy power generation requires the simultaneous development of energy storage. Because renewable energy power generation has the disadvantages of intermittency, volatility, and uncontrollability, energy storage must be used to improve the quality of power supply and eliminate the phenomenon of wind and solar power abandonment. Safe and cheap energy storage methods are the central link of energy transformation and the key area of ​​carbon emission reduction. Organic redox flow batteries are one of the most promising electrochemical energy storage technologies for large-scale energy storage due to their unique liquid energy storage methods and characteristics. They can use water as an electrolyte solvent, which greatly improves the safety, ease of maintenance and site selection flexibility of the energy storage system. The battery energy density is adjustable, and organic flow batteries have the advantages of a wide range of electrolyte active substances, low cost and easy control of performance. They meet the energy storage requirements in large-scale scenarios and are an ideal technology for large-scale energy storage in the future.

[0004] The battery stack is the core component of the liquid flow battery, which is mainly composed of bipolar plates, electrode materials, diaphragms and electrode frames. In the liquid flow battery stack, the bipolar plate is one of the key components that affect the battery performance and cost. The bipolar plate prevents the mixing between the positive electrode electrolyte and the negative electrode electrolyte, conducts electrons, and provides mechanical support for the electrode materials in the liquid flow battery stack to a certain extent. The optimization of the battery stack assembly process is a necessary condition for the large-scale safe, efficient and low-cost use of liquid flow batteries in the future. At present, the two major bottlenecks faced by liquid flow batteries are low current density and easy leakage and cross-liquid problems of the battery stack. The use of an integrated structure of an electrode frame and a bipolar plate and a battery stack applied to a liquid flow battery of the present invention can effectively solve the problems of easy leakage and cross-liquid problems of the battery stack, thereby improving battery performance, simplifying the battery stack assembly process, reducing production costs, and thus reducing energy storage costs. Summary of the invention

[0005] In view of the bottlenecks currently faced by liquid flow batteries and the shortcomings of existing technologies, the present invention proposes an integrated structure of electrode frame and bipolar plate and a battery stack applied to liquid flow batteries. By improving the shortcomings of the existing technology, the battery sealing will be greatly improved, the battery structure will be significantly simplified, and the volume of the battery stack will be significantly reduced, the energy storage cost will be significantly reduced, and the battery operation stability will be significantly improved.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] An object of the present invention is to provide an integrated structure of an electrode frame and a bipolar plate for a liquid flow battery, comprising an integrally formed electrode frame and a bipolar plate, wherein the outer edge of the bipolar plate is sealed in the electrode frame, and electrolyte guide grooves, positive electrode electrolyte inlet blind holes, positive electrode electrolyte outlet blind holes, negative electrode electrolyte inlet blind holes and negative electrode electrolyte outlet blind holes are provided on both sides of the inner edge of the electrode frame. A long strip platform for accommodating electrode materials is extended from the electrolyte guide groove to enable the electrode materials to fit seamlessly with the electrode frame.

[0008] Furthermore, the outer edge of the bipolar plate is sealed in the electrode frame by injection molding, compression molding or moldless turning.

[0009] Furthermore, the positive electrode electrolyte inlet blind hole, the positive electrode electrolyte outlet blind hole, the negative electrode electrolyte inlet blind hole and the negative electrode electrolyte outlet blind hole are on the inner edge of the electrode frame; the positive electrode electrolyte inlet blind hole and the positive electrode electrolyte outlet blind hole are located on one side of the bipolar plate, and the negative electrode electrolyte inlet blind hole and the negative electrode electrolyte outlet blind hole are located on the other side of the bipolar plate.

[0010] Furthermore, the number of the positive electrode electrolyte inlet blind holes and the negative electrode electrolyte inlet blind holes are 2-8 respectively, and the number of the positive electrode electrolyte outlet blind holes and the negative electrode electrolyte outlet blind holes are 1-7 respectively.

[0011] Furthermore, the depth of the electrolyte guide groove is 0.3mm-10mm, and the distance between the electrolyte guide groove and the inner edge of the electrode frame is 1mm-10mm; a long platform with a width of 1mm-10mm for accommodating electrode materials extends from the electrolyte guide groove.

[0012] Furthermore, the electrolyte guide grooves are located at the inner edge of the electrode frame and on both sides of the bipolar plate, forming a symmetrical distribution structure. The electrolyte guide grooves on one side are connected to the positive electrode electrolyte inlet blind hole and the negative electrode electrolyte inlet blind hole, and the electrolyte guide grooves on the other side are connected to the negative electrode electrolyte outlet blind hole and the positive electrode electrolyte outlet blind hole.

[0013] Furthermore, the bipolar plate is a carbon composite material plate or a graphite plate with a thickness of 2-10 mm.

[0014] Another object of the present invention is to provide a battery stack for use in a liquid flow battery, the battery stack comprising the above-mentioned integrated structure of an electrode frame and a bipolar plate.

[0015] Furthermore, the battery stack includes a combination of n groups of electrode frames and a double-body structure, electrode materials, diaphragm materials, and electrode materials that are cycled in sequence, wherein n≥2.

[0016] Furthermore, the electrode frames are sealed by laser welding or ultrasonic welding; the electrode frames and the diaphragm are sealed by laser welding, ultrasonic welding or glue bonding.

[0017] The beneficial effects of the present invention are:

[0018] The requirements for bipolar plates for liquid flow batteries include strong mechanical strength to support the battery structure and withstand assembly stress, high compactness to prevent electrolyte leakage, and low resistance to reduce ohmic loss. The present invention proposes an integrated structure of an electrode frame and a bipolar plate for liquid flow batteries, which is to fix the bipolar plate inside the electrode frame by injection molding, molding or moldless turning to form a sealed integrated structure, and then weld or bond the electrode material and the diaphragm to the electrode frame. This arrangement solves the problem of thick adhesion between the bipolar plate and the electrode frame in conventional liquid flow battery stacks and the risk of leakage and cross-linking, thereby improving the stability of the liquid flow battery, eliminating sealing components, reducing processing procedures and processing difficulty, and reducing the volume of the stack.

[0019] Blind holes for the inlet and outlet channels of the positive and negative electrolytes are arranged on both sides of the bipolar plate at the inner edge of the electrode frame. The number of the positive electrolyte inlet blind holes and the negative electrolyte inlet blind holes are 2-8 respectively, and the number of the positive electrolyte outlet blind holes and the negative electrolyte outlet blind holes are 1-7 respectively. The number of the electrolyte outlet blind holes is set to be smaller than the number of the electrolyte inlet blind holes. Such a setting increases the reaction time of the electrolyte active substances on the electrodes, reduces the internal polarization and distribution uniformity of the battery, and thus increases the performance of the liquid flow battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The electrode frame and bipolar plate are integrated into one structure.

[0021] Figure 2 It is a schematic diagram of the battery stack assembly of the present invention applied to a liquid flow battery;

[0022] List of Figure Symbols:

[0023] Bipolar plate 1; electrode frame 2; positive electrode electrolyte inlet blind hole 3; positive electrode electrolyte outlet blind hole 4; negative electrode electrolyte inlet blind hole 5; negative electrode electrolyte outlet blind hole 6; electrolyte guide groove 7; long strip platform 8; electrode material 9; diaphragm 10; current collecting plate 11; end plate 12. DETAILED DESCRIPTION

[0024] The present invention will be further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0025] Example 1

[0026] like Figure 1 The present invention is shown as an integrated structure of an electrode frame and a bipolar plate applied to a liquid flow battery. The bipolar plate 1 is made of natural graphite, carbon black, carbon fiber and polypropylene as raw materials and is made by injection molding. The electrode frame 2 is made of polyethylene as raw material and is made into an integrated structure of an electrode frame and a bipolar plate by injection molding and compression molding. The electrode frame is provided with three positive electrolyte inlet blind holes 3, two positive electrolyte outlet blind holes 4, three negative electrolyte inlet blind holes 5, and two negative electrolyte outlet blind holes 6. Among them, the positive electrolyte inlet blind holes 3 and the positive electrolyte outlet blind holes 4 are located on one side of the inner edge bipolar plate 1 of the electrode frame, and the negative electrolyte inlet blind holes 5 and the negative electrolyte outlet blind holes 6 are located on the other side of the inner edge bipolar plate 1 of the electrode frame. Symmetrical electrolyte guide grooves 7 are provided on both sides of the inner edge bipolar plate of the electrode frame, and a long strip platform 8 extends from the electrolyte guide groove 7 for the electrode material to be attached.

[0027] The thickness of the bipolar plate 1 is 4 mm; the thickness of the electrode frame is 20 mm; the diameters of the positive electrolyte inlet blind hole 3, the positive electrolyte outlet blind hole 4, the negative electrolyte inlet blind hole 5 and the negative electrolyte outlet blind hole 6 are 6 mm; the depth of the electrolyte diversion groove 7 is 5 mm; the distance between the electrolyte diversion groove 7 and the electrolyte inlet and outlet blind holes 3-6 is 2 mm; the width of a long strip platform 8 for accommodating the electrode extending from the electrolyte diversion groove 7 is 3 mm away from the electrolyte diversion groove 7.

[0028] The electrolyte enters from the bottom and exits from the top. The positive electrolyte flows in from the positive electrolyte inlet blind hole 3, flows along the electrolyte guide groove 7, flows into the bipolar plate 1, then to the long platform 8, and finally flows out from the positive electrolyte outlet blind hole 4. The corresponding negative electrolyte flows in from the negative electrolyte inlet blind hole 5, flows along the back guide groove (the back of 7), flows into the bipolar plate (the back of 1), then to the long platform (the back of 8), and finally flows out from the positive electrolyte outlet blind hole 6. That is, the positive and negative electrolytes enter the two sides of the electrode frame from the blind holes 3 and 5 respectively, flow through the two sides of the bipolar plate through the front and rear guide grooves respectively, and then flow out through another set of guide grooves respectively, without the possibility of cross-liquid leakage, so that the battery can be charged and discharged.

[0029] Example 2

[0030] like Figure 2The figure shows the assembly schematic diagram of the integrated structure of the electrode frame and bipolar plate of the liquid flow battery of the present invention applied to the liquid flow battery stack, including the battery end plate 12, the current collecting plate 11, the electrode material 9, Figure 1 The electrode frame and the bipolar plate are integrated into a structure, and the diaphragm 10, wherein the electrode material 9 is attached to Figure 1 The electrolyte guide groove 7 of the structure shown in the figure extends out of a long strip platform 8 for accommodating the electrode, and the diaphragm 10 is welded to the electrode material by laser welding. Figure 1 On the electrode frame of the structure shown, the current collecting plate 11 is a copper plate with a thickness of 1 mm; the electrode material 9 is a carbon felt with a thickness of 4 mm; and the diaphragm 10 is an ion conducting membrane with a thickness of 100 μm.

[0031] The performance of the assembled battery stack was tested at current densities of 80, 110 and 160 mA / cm 2 The stack flow rate is 0.95m 3 / h. The charging cut-off voltage of the battery stack is 7.85V, and the discharging cut-off voltage is 5V. The performance test results of the battery stack are shown in Table 1 below.

[0032] Table 1

[0033]

[0034] From the performance comparison of the flow battery stacks in the embodiments, it can be seen that under the same conditions of current density and materials for making the stack, various performance indicators of the flow battery stack of the present invention are higher than those of conventional flow battery stacks.

[0035] It is proved that the integrated structure of the electrode frame and bipolar plate of the liquid flow battery proposed by the present invention avoids the possibility of electrolyte leakage and cross-linking from the perspective of the battery stack structure. Breaking through the sealing method of the electrode frame and the bipolar plate in the conventional liquid flow battery stack, the present invention injects or molds the bipolar plate and the electrode frame into an integrated structure, and a long platform that completely fits the size of the electrode material is provided on the electrode frame to form a seamless seal, and an electrolyte inlet and outlet blind hole is provided inside the electrode frame. Such a setting completely eliminates the chance of electrolyte leakage and the problem of cross-linking between the positive and negative electrolytes. The use of the integrated structure of the liquid flow battery electrode frame and bipolar plate of the present invention avoids the problems of complex battery structure, manufacturing and assembly difficulties in the past, can effectively improve the energy efficiency of the battery charging / discharging process, reduce the cost of the battery stack, and lay the foundation for the development of chemical power source technology for large-scale electric energy conversion and storage.

[0036] It should be noted that the above content only illustrates the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications all fall within the protection scope of the claims of the present invention.

Claims

1. An integrated structure of an electrode frame and a bipolar plate for a flow battery, characterized in that: It includes an integrally formed polymer material electrode frame and a bipolar plate, the outer edge of the bipolar plate is sealed in the electrode frame, and the inner edge of the electrode frame is provided with an electrolyte guide groove, a positive electrode electrolyte inlet blind hole, a positive electrode electrolyte outlet blind hole, a negative electrode electrolyte inlet blind hole and a negative electrode electrolyte outlet blind hole on both sides of the bipolar plate, and a long strip platform for accommodating the electrode material is extended from the electrolyte guide groove to make the electrode material and the electrode frame seamlessly fit; The number of the positive electrode electrolyte inlet blind holes and the number of the negative electrode electrolyte inlet blind holes are 3 respectively, and the number of the positive electrode electrolyte outlet blind holes and the number of the negative electrode electrolyte outlet blind holes are 2 respectively; The positive electrode electrolyte inlet blind hole, the positive electrode electrolyte outlet blind hole, the negative electrode electrolyte inlet blind hole and the negative electrode electrolyte outlet blind hole are on the inner edge of the electrode frame; the positive electrode electrolyte inlet blind hole and the positive electrode electrolyte outlet blind hole are located on one side of the bipolar plate, and the negative electrode electrolyte inlet blind hole and the negative electrode electrolyte outlet blind hole are located on the other side of the bipolar plate; The depth of the electrolyte guide groove is 0.3mm-10mm, and the distance between the electrolyte guide groove and the inner edge of the electrode frame is 1mm-10mm; a long strip platform for accommodating the electrode material is extended from the electrolyte guide groove, and the width of the long strip platform is 1mm-10mm; The bipolar plate is a carbon composite material plate or a graphite plate with a thickness of 2-10 mm.

2. The integrated structure of electrode frame and bipolar plate for liquid flow battery according to claim 1, characterized in that: The outer edge of the bipolar plate is sealed in the electrode frame by injection molding, compression molding or moldless turning molding.

3. According to the integrated structure of an electrode frame and bipolar plate for a liquid flow battery according to claim 1, the electrode frame is selected from one or a blend of two or more of PE, PP, PS, PVC, CPVC, PA, PET, CPE, EVA, ABS, AS, EVOH, EPR, PC, TPE, TPR, TPV, and TPO.

4. A battery stack for a liquid flow battery, characterized in that: The battery stack comprises an integrated structure of an electrode frame and a bipolar plate as claimed in any one of claims 1 to 3; The battery stack includes n groups of electrode frames and bipolar plate integrated structures, electrode materials, diaphragm materials, and a combination of electrode materials in a sequential cycle, wherein n≥2.

5. The battery stack for liquid flow battery according to claim 4, characterized in that: The electrode frames are sealed by laser welding or ultrasonic welding; the electrode frames and the diaphragm are sealed by laser welding, ultrasonic welding or glue bonding.

Images