An integrated electrode frame and bipolar plate structure for all-vanadium redox flow batteries

Abstract

The present invention discloses an integrated electrode frame and bipolar plate structure, a preparation method and an application for an all-vanadium liquid flow battery. Specifically, the electrode frame and the bipolar plate are sealed by welding to form an integrated battery frame structure. The electrode frame is an electrode frame made of a transparent material; the bipolar plate is a conductive composite plate made of a non-transparent material. The technology disclosed in the present invention can combine the key components of the all-vanadium liquid flow battery, such as the electrode frame and bipolar plate, into a whole. The integrated battery structure components prepared by this method will bring many advantages: it can ensure the many advantages of the integrated battery structure: it can be used as an independent integrated unit to assemble the battery stack, greatly improving the assembly efficiency of the battery stack, and at the same time greatly improving the sealing reliability of the battery stack, greatly reducing the sealing cost, reducing the thickness of the battery, and greatly reducing the volume of the battery, thereby improving the volume energy density of the all-vanadium liquid flow battery; at the same time, it can improve the disadvantage that the battery stack assembled with the early integrated battery structure cannot measure the voltage of a single battery cell.

Description

Technical Field

[0001] The present invention relates to the technical field of all-vanadium redox flow batteries, and in particular to an integrated battery structure and a preparation method for an all-vanadium redox flow battery. Background Art

[0002] The inherent randomness, intermittency, volatility, and difficulty in connecting directly to the grid of renewable energy sources like wind and solar have, to a certain extent, limited their development and utilization. Therefore, the development of energy storage technologies that complement them has become crucial.

[0003] Energy storage technologies fall into two categories: physical and chemical. Physical energy storage includes pumped hydro, compressed air, and flywheel storage. Chemical energy storage primarily includes lead-acid batteries, sodium-sulfur batteries, flow batteries, and lithium-ion batteries. While each energy storage technology has its own suitable application areas, chemical energy storage technologies suitable for large-scale energy storage primarily include flow batteries, sodium-sulfur batteries, lead-acid batteries, and lithium-ion batteries.

[0004] Among liquid flow batteries, all-vanadium liquid flow batteries have independent design capabilities for output power and energy storage capacity, and contain only vanadium ions as electrolyte ions. Therefore, there is no phase change common in other batteries during charging and discharging. The battery has a long service life, good charging and discharging performance, can be deeply discharged without damaging the battery, has low self-discharge, and has a large degree of freedom in site selection for vanadium batteries. The system can operate in a fully automatic and closed manner, is pollution-free, simple to maintain, and has low operating costs. The battery system has no potential explosion or fire hazards, is highly safe, and battery components are mostly made of cheap carbon materials and engineering plastics. The material sources are abundant and easy to recycle, no precious metals are required as electrode catalysts, the energy efficiency is high, reaching 75% to 80%, and the startup speed is fast. These advantages have attracted more attention.

[0005] The traditional all-vanadium redox flow battery stack structure consists of, in order: a current collector plate, bipolar plate, gasket, electrode frame, gasket, electrode, diaphragm, electrode, gasket, electrode frame, gasket, bipolar plate, and current collector plate. The diaphragm separates the positive and negative electrodes, preventing internal leakage, while the gaskets between components prevent external leakage. The extensive use of gaskets increases the stack size, reduces its volume-to-energy ratio, complicates the stack assembly process, increases the risk of leakage, and increases stack cost.

[0006] There is a drawback in the early integrated structural design and assembly of battery stacks. After the battery stack is assembled, the voltage of a single battery cell cannot be measured. This voltage value can intuitively reflect the uniformity of each battery cell in the battery stack and is of great significance. Summary of the Invention

[0007] To solve the above technical problems, the present invention redesigns a new integrated electrode frame and bipolar plate structure on the basis of ensuring improved sealing reliability of all-vanadium redox flow batteries, reducing the thickness of the batteries, reducing the volume of the batteries, and thus improving the volume energy density of the all-vanadium redox flow batteries.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] An integrated electrode frame and bipolar plate structure for an all-vanadium redox flow battery, wherein the electrode frame is a flat plate with a through hole in the middle;

[0010] The electrode frame is made of a transparent material; the bipolar plate is a flat plate made of a non-transparent material;

[0011] A protrusion serving as a pole ear is extended from the edge of the bipolar plate in a direction away from the bipolar plate and parallel to the surface of the bipolar plate; an annular step is etched on the surface of one side of the electrode frame and at the edges around the opening end face of the middle through hole in a direction away from the through hole, and a through hole A parallel to the surface of the flat plate is opened on the flat plate body between the annular step and the edges around the electrode frame; the edges around the bipolar plate are placed on the annular step of the electrode frame, the edges around the surface of one side of the bipolar plate are in contact with the annular step, and the pole ear extends through the through hole A to the outside of the electrode frame.

[0012] The thickness of the tab perpendicular to the surface of the bipolar plate is the same as the thickness of the bipolar plate, and the tab and the bipolar plate are made of the same material;

[0013] The thickness of the tab is the same as or equivalent to the thickness of the through hole A in the direction perpendicular to the surface of the electrode frame. The width of the tab is the direction parallel to the edge of the bipolar plate where it is located. The width of the tab is the same as or equivalent to the width of the through hole A (in the direction parallel to the opening end face of the through hole).

[0014] The through-hole A corresponds to the position of the bipolar plate tab, ensuring that when the bipolar plate is placed in the through-hole of the electrode frame, the tab of the bipolar plate can pass through the through-hole A of the electrode frame, and ensuring that the length of the tab exposed at the edge of the electrode frame is not less than 2 mm, preferably 5 mm-20 mm; the minimum width of the bipolar plate tab is 2 mm, and the preferred value is 5 mm-50 mm.

[0015] The constituent materials of the sealed connection between the bipolar plate and the electrode frame contain at least one same substance; the at least one same substance includes any one or more of PP, PE, PS, PC, ABS, PMMA, and PET.

[0016] Two opposite sides of the surface of one side of the flat plate of the electrode frame are provided with fluid distribution channels near the edges; the other side is a plane without channels.

[0017] The edges of the bipolar plate are located on the annular step of the electrode frame, and the edges of one side surface of the bipolar plate overlap with the annular step.

[0018] The laser transmittance of the transparent electrode frame is above 20%, preferably above 40%;

[0019] The difference in laser transmittance between the transparent electrode frame and the non-transparent bipolar plate is 15-100%, preferably 35-100%;

[0020] The non-transparent material is a combination of one or more of PP, PE, PS, PC, ABS, PMMA, and PET and a colorant, and the colorant is one or more of black, yellow, brown, tan, and dark blue;

[0021] The transparent material is one or more of PP, PE, PS, PC, ABS, PMMA, and PET;

[0022] The bipolar plate and the electrode frame contain at least one substance in their constituent materials, and the mass content of the same substance in their constituent materials should be greater than or equal to 10% of their respective masses, preferably greater than or equal to 40% of their respective masses;

[0023] The bipolar plate is a carbon-plastic composite plate composed of conductive carbon black and / or graphite.

[0024] This technology is prepared through the following process:

[0025] A protrusion serving as a tab extends from the edge of the bipolar plate in a direction away from the bipolar plate and parallel to the surface of the bipolar plate; an annular step is etched on the surface of one side of the electrode frame at the edges surrounding the end face of the central through hole in a direction away from the through hole; a through hole A parallel to the surface of the plate is opened on the plate between the annular step and the edges of the electrode frame; the edges of the bipolar plate are placed on the annular step of the electrode frame, the edges of one side of the bipolar plate are in contact with the annular step, and the tab extends through the through hole A to the outside of the electrode frame;

[0026] The edges of the bipolar plate are sealed and fixed to the annular steps of the electrode frame by welding. At the same time, the electrode ears are sealed and fixed to the through-hole A of the electrode frame on both sides of the transverse electrode frame by welding again, so that the bipolar plate and the electrode frame are combined into one.

[0027] The welding method is laser welding, and the welding power between the electrode frame and the bipolar plate is preferably 10-250W; the welding speed is 0.2-50mm / s.

[0028] The battery frame structure is used in an all-vanadium redox flow battery stack, which is composed of one or more single cells connected in series. The stack power is 0.5-100kW.

[0029] Beneficial effects of the present invention:

[0030] 1. The present invention optimizes the structure and materials of the electrode frame and bipolar plate to achieve direct welding and sealing of the bipolar plate and the electrode frame, forming a two-in-one integrated battery assembly. The integrated battery structure significantly improves the reliability of the all-vanadium liquid flow battery seal; in particular, the reliability of high-power liquid flow battery stacks suitable for large-scale energy storage technology is significantly increased.

[0031] 2. By further optimizing the electrode frame and bipolar plate structure, the battery stack assembled using the integrated structure described in the present invention can measure the voltage of a single battery cell in real time, monitor the uniformity of the battery stack operation, and ensure the efficient operation of the battery stack.

[0032] 3. The present invention reduces the use of sealing gaskets, reduces the thickness of the battery and improves the volume-to-energy ratio of the battery;

[0033] 4. Improved the utilization rate of bipolar plates. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 and Figure 2 Schematic diagram of a transparent material electrode frame, 1-transparent material electrode frame; 2-step; 3-through hole, 4-through hole A;

[0035] Figure 3 Schematic diagram of a bipolar plate made of non-transparent material, 5-bipolar plate; 6-ear;

[0036] Figure 4 Schematic diagram of the integrated electrode frame and bipolar plate structure. DETAILED DESCRIPTION

[0037] The following examples are provided to further illustrate the present invention but are not intended to limit the scope of the present invention.

[0038] Example 1

[0039] The electrode frame is made of 100% polyethylene by weight with a light transmittance of 95%. The bipolar plates are made of carbon-plastic composite plates with a polyethylene content of 30-50% (50% here) and a graphite content of 70-50% (50% here), with a light transmittance of 0.8%. The electrode frame is 40cm long, 50cm wide, and 4.4mm thick, respectively. The bipolar plates are 37cm long, 46cm wide, and 0.8mm thick, respectively. Lugs measuring 2cm wide and 2.5cm long, with a thickness of 0.8mm, are located 22-24cm across the width of the bipolar plates. The central through-hole in the electrode frame is 36cm long and 45cm wide. A 5mm wide, 1mm thick, annular step is etched around the edges of the central through-hole, away from the through-hole. A 2cm wide through-hole A is etched between 21.5cm and 23.5cm across the electrode frame. The hole height (i.e., thickness, perpendicular to the electrode frame surface) is 0.8mm. The hole is centered on the circular step, and along the thickness of the electrode frame, the distances from the two side edges of the through-hole A are 1mm and 2.6mm, respectively.

[0040] The bipolar plate is placed in the electrode frame through-hole, and the bipolar plate tab is inserted into electrode frame through-hole A. The bipolar plate is welded to a 5mm-wide circular step etched around the edge of the electrode frame through-hole in the center. The bipolar plate tab is then welded to electrode frame through-hole A at a welding power of 50W and a welding speed of 11mm / s, forming a "two-in-one" bipolar plate and electrode frame assembly. Ten sets of these "two-in-one" components were welded sequentially using this method and then assembled with other battery materials (diaphragms, electrodes, etc.) into a 10-cell 2kW all-vanadium redox flow battery stack.

[0041] The assembled 10-cell all-vanadium redox flow battery stack was tested for external leakage. The maximum internal leakage test pressure was 0.03MPa, and the external leakage test pressure was 0.26MPa. No leakage was found. The thickness of the stack was 95mm after measurement with a ruler. At a constant current of 100mA / cm 2 Battery performance tests under these conditions revealed a coulombic efficiency of 98.5%, a voltage efficiency of 87.9%, and an energy efficiency of 86.6%. During battery operation, the voltage of a single cell at a specific moment could be measured using the exposed tabs: 1.451V, 1.449V, 1.448V, 1.449V, 1.449V, 1.450V, 1.448V, 1.449V, 1.448V, and 1.450V, respectively.

[0042] Example 2

[0043] The electrode frame is made of 100% polyethylene by weight with a light transmittance of 90%. The bipolar plates are carbon-plastic composite plates with a polyethylene content of 30-50% (50% here) and a graphite content of 70-50% (50% here) by weight, and a light transmittance of 0.5%. The electrode frame is 40 cm long, 30 cm wide, and 4.4 mm thick, respectively, while the bipolar plates are 37 cm long, 26 cm wide, and 0.8 mm thick, respectively. Tabs measuring 4 cm wide and 3 cm long, with a thickness of 0.8 mm, are located 16.5-20.5 cm along the length of the bipolar plates. The central through-hole in the electrode frame is 36 cm long and 25 cm wide. A 5 mm wide, 1 mm thick, circular step is etched around the edges of the central through-hole, away from the through-hole. A 4 cm wide through-hole A is etched 16-20 cm along the length of the electrode frame through-hole, with a height (i.e., thickness, perpendicular to the electrode frame surface) of 0.8 mm. The hole takes the annular step as the plane, and in the thickness direction of the electrode frame, the distance between the through hole A and the two side edges is 1 mm and 2.6 mm respectively.

[0044] The bipolar plate is placed in the electrode frame through-hole, and the bipolar plate tab is inserted into electrode frame through-hole A. The bipolar plate is welded to a 5mm-wide circular step etched around the edge of the electrode frame through-hole in the center. The bipolar plate tab is then welded to electrode frame through-hole A at a welding power of 50W and a welding speed of 11mm / s, forming a "two-in-one" bipolar plate and electrode frame assembly. Ten sets of these "two-in-one" components were welded sequentially using this method and then assembled with other battery materials (diaphragms, electrodes, etc.) into a 10-cell 2kW all-vanadium redox flow battery stack.

[0045] The assembled 10-cell all-vanadium redox flow battery stack was tested for external leakage. The maximum internal leakage test pressure was 0.03MPa, and the external leakage test pressure was 0.26MPa. No leakage was found. The thickness of the stack was 95mm after measurement with a ruler. At a constant current of 100mA / cm 2 Battery performance tests under these conditions revealed a coulombic efficiency of 98.8%, a voltage efficiency of 87.4%, and an energy efficiency of 86.4%. During battery operation, the voltages of individual cells at specific moments were measured using the exposed tabs: 1.333V, 1.329V, 1.331V, 1.329V, 1.328V, 1.330V, 1.329V, 1.329V, 1.330V, and 1.331V.

[0046] Comparative Example 1

[0047] The electrode frame is made of 100% polyethylene by weight with a light transmittance of 95%. The bipolar plates are made of carbon-plastic composite plates with a polyethylene content of 30-50% (50% here) and a graphite content of 70-50% (50% here), with a light transmittance of 0.8%. The electrode frame is 40cm long, 50cm wide, and 4.4mm thick, respectively. The bipolar plates are 37cm long, 46cm wide, and 0.8mm thick, respectively. The electrode frame through-hole is 36cm long and 45cm wide. A 5mm-wide, 1mm-thick annular step is etched around the edge of the through-hole in the center of the electrode frame, moving away from the through-hole.

[0048] The bipolar plate was placed in the electrode frame through-hole and welded to a 5mm-wide circular step etched around the edge of the central through-hole in the electrode frame. The welding power was 50W and the welding speed was 11mm / s, forming a "two-in-one" bipolar plate and electrode frame component. Ten sets of these "two-in-one" components were welded sequentially using this method and then assembled with other battery materials (diaphragms, electrodes, etc.) into a 10-cell 2kW all-vanadium redox flow battery stack.

[0049] The assembled 10-cell all-vanadium redox flow battery stack was tested for external leakage. The maximum internal leakage test pressure was 0.03MPa, and the external leakage test pressure was 0.26MPa. No leakage was found. The thickness of the stack was 95mm after measurement with a ruler. At a constant current of 100mA / cm 2 The battery performance test was carried out under the following conditions: the battery coulombic efficiency was 98.4%, the voltage efficiency was 87.9%, and the energy efficiency was 86.5%.

[0050] It can be seen from Example 1 and Comparative Example 1 that, under the same conditions, the battery stack with external leakage tabs on the bipolar plates can achieve real-time monitoring of the voltage of a single cell without any impact on the sealing of the battery.

Claims

1. An integrated electrode frame and bipolar plate structure for an all-vanadium redox flow battery, characterized in that: The electrode frame is a flat plate with a through hole in the middle; The electrode frame is made of a transparent material; the bipolar plate is a flat plate made of a non-transparent material; A protrusion as a pole ear is extended from the edge of the bipolar plate in a direction away from the bipolar plate and parallel to the surface of the bipolar plate; an annular step is etched on the surface of one side of the electrode frame at the edges around the end face of the middle through hole in a direction away from the through hole, and a through hole A parallel to the surface of the flat plate is opened on the flat plate body between the annular step and the edges around the electrode frame; the edges around the bipolar plate are placed on the annular step of the electrode frame, the edges around the surface of one side of the bipolar plate are in contact with the annular step, and the pole ear extends through the through hole A to the outside of the electrode frame. The constituent materials of the sealed connection between the bipolar plate and the electrode frame contain at least one same substance; at least one same substance includes any one or more of PP, PE, PS, PC, ABS, PMMA, and PET, and the edges of the bipolar plate are sealed and fixed to the annular step of the electrode frame by welding. At the same time, at the front and back sides of the transverse electrode frame at the through-hole A of the electrode frame, the electrode ear is again sealed and fixed to the through-hole A of the electrode frame by welding, so that the bipolar plate and the electrode frame are combined into one.

2. The integrated electrode frame and bipolar plate structure for an all-vanadium redox flow battery according to claim 1, characterized in that: The thickness of the tab perpendicular to the surface of the bipolar plate is the same as the thickness of the bipolar plate, and the tab and the bipolar plate are made of the same material; The thickness of the electrode tab is the same as or equivalent to the thickness of the through hole A in the direction perpendicular to the surface of the electrode frame. The width of the electrode tab is the direction extending parallel to the edge of the bipolar plate on which it is located. The width of the electrode tab is the same as or equivalent to the width of the through hole A. The direction of the width of the through hole A is the direction parallel to the opening end face of the through hole.

3. The integrated electrode frame and bipolar plate structure for an all-vanadium redox flow battery according to claim 1, characterized in that: The through-hole A corresponds to the position of the bipolar plate tab, ensuring that when the bipolar plate is placed in the through-hole of the electrode frame, the tab of the bipolar plate can pass through the through-hole A of the electrode frame, and ensuring that the length of the tab exposed at the edge of the electrode frame is not less than 2 mm; the minimum width of the bipolar plate tab is 2 mm.

4. The integrated electrode frame and bipolar plate structure for an all-vanadium redox flow battery according to claim 3, characterized in that: The length of the tab exposed at the edge of the electrode frame is 5mm-20mm; the minimum width of the bipolar plate tab is 5mm-50mm.

5. The integrated electrode frame and bipolar plate structure for all-vanadium redox flow battery according to claim 1, characterized in that: Two opposite sides of the surface of one side of the flat plate of the electrode frame are provided with fluid distribution channels near the edges; the other side is a plane without channels.

6. The integrated electrode frame and bipolar plate structure for all-vanadium redox flow battery according to claim 1, characterized in that: The edges of the bipolar plate are located on the annular step of the electrode frame, and the edges of one side surface of the bipolar plate overlap with the annular step.

7. The integrated electrode frame and bipolar plate structure for an all-vanadium redox flow battery according to claim 1, characterized in that: The laser transmittance of the transparent electrode frame is above 20%; The laser transmittance difference between the transparent electrode frame and the non-transparent bipolar plate is 15-100%; The non-transparent material is a combination of one or more of PP, PE, PS, PC, ABS, PMMA, and PET and a colorant, and the colorant is one or more of black, yellow, brown, tan, and dark blue; The transparent material is one or more of PP, PE, PS, PC, ABS, PMMA, and PET.

8. The integrated electrode frame and bipolar plate structure for an all-vanadium redox flow battery according to claim 7, characterized in that: The laser transmittance of the transparent electrode frame is above 40%; The laser transmittance difference between the transparent material electrode frame and the non-transparent material bipolar plate is 35-100%.

9. The integrated electrode frame and bipolar plate structure for an all-vanadium redox flow battery according to claim 1, characterized in that: The bipolar plate and the electrode frame contain at least one substance in their constituent materials, and the mass content of the same substance in their constituent materials should be greater than or equal to 10% of their respective masses; The bipolar plate is a carbon-plastic composite plate composed of conductive carbon black and / or graphite.

10. The integrated electrode frame and bipolar plate structure for an all-vanadium redox flow battery according to claim 9, characterized in that: The constituent materials of the bipolar plate and the electrode frame contain at least one same substance, and the mass content of the same substance in their constituent materials should be greater than or equal to 40% of their respective masses.

11. A method for preparing an integrated electrode frame and bipolar plate structure for an all-vanadium redox flow battery according to any one of claims 1 to 10, characterized in that: Prepared by the following process: A protrusion serving as a tab extends from the edge of the bipolar plate in a direction away from the bipolar plate and parallel to the surface of the bipolar plate; an annular step is etched on the surface of one side of the electrode frame at the edges surrounding the end face of the central through hole in a direction away from the through hole; a through hole A parallel to the surface of the plate is opened on the plate between the annular step and the edges of the electrode frame; the edges of the bipolar plate are placed on the annular step of the electrode frame, the edges of one side of the bipolar plate are in contact with the annular step, and the tab extends through the through hole A to the outside of the electrode frame; The edges of the bipolar plate are sealed and fixed to the annular steps of the electrode frame by welding. At the same time, the electrode ears are sealed and fixed to the through-hole A of the electrode frame on both sides of the transverse electrode frame by welding again, so that the bipolar plate and the electrode frame are combined into one.

12. The preparation method according to claim 11, characterized in that: The welding method is laser welding, the welding power between the electrode frame and the bipolar plate is 10-250W; the welding speed is 0.2-50mm / s.

13. An application of the integrated electrode frame and bipolar plate structure for an all-vanadium redox flow battery as claimed in any one of claims 1 to 10, wherein the battery stack is formed by one or more single batteries connected in series.

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