Flow cell stack using laser welding bipolar plate

Abstract

The utility model discloses a flow cell stack applying a laser welding bipolar plate. The flow cell stack comprises a cell unit, a plug laser welding bipolar plate, a double-tap collector plate and a confluence plate, the bus plate, the double-tap collector plate, the plurality of battery units, the plug laser welding bipolar plate, the plurality of battery units, the double-tap collector plate and the bus plate are arranged in sequence; the battery unit comprises a laser welding bipolar plate; the laser welding bipolar plate comprises a bipolar plate body, a first dark-color plastic plate and a first light-transmitting plastic plate. A first hollow cavity is formed in the middle of the first dark plastic plate, and through holes are formed in four corners; the bipolar plate is arranged in a first hollow cavity of the first deep-color plastic plate; a second hollow cavity is formed in the middle of the first light-transmitting plastic plate; through holes are formed in four corners of the first light-transmitting plastic plate; first light-transmitting plastic plates are welded to the two surfaces of the first dark-color plastic plate. According to the laser welding bipolar plate structure, the use amount of conductive plastics is reduced, and the material cost is reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of flow batteries, and particularly relates to a flow battery stack applying a laser-welded bipolar plate. Background Technique

[0002] A flow battery unit is composed of positive / negative electrode frames, positive / negative electrodes, a membrane and a bipolar plate. The membrane is used to separate the positive and negative side electrodes of the battery. The electrodes are embedded in the central chambers of the frames. The battery units are separated by the bipolar plate, and the current generated by each battery is led out of the battery stack through a current path formed by the conductive bipolar plate.

[0003] The battery stack is the core component of the flow battery system. The design and improvement of the stack body mainly focus on performance improvement, reduction of material cost, improvement of assembly stability and efficiency, reduction of assembly difficulty, improvement of stack body sealing performance, etc.

[0004] In the early stage, the frames of flow battery stacks were produced by machining. Sealing grooves were designed on the surface, and the frames were processed and sealed by installing gaskets through fixed structures or pasting gaskets with back glue.

[0005] In order to save production costs, improve sealing reliability and reduce assembly difficulty, new frame processes have emerged, such as injection molding or compression molding to produce flow battery frames, and gaskets are produced by dispensing and curing on their surfaces. The disadvantage is that the components of the cured adhesive may affect the electrolyte, and the adhesive gradually denatures and deactivates, resulting in leakage after the stack has been operating for a period of time.

[0006] Other sealing methods also include bonding with a sealing film, designing an insertion structure on the flow channel plate surface to form a locking seal, using a laser-welded wire as a gasket, etc.

[0007] There are mainly the following three types of bipolar plates used in flow batteries: a bipolar plate with conductive whole surface, an ABA component bipolar plate, and a bipolar plate with conductive center but insulated outer frame.

[0008] The bipolar plate with conductive whole surface can be divided into two types: with holes and without holes on the surface. If the cut holes of the perforated bipolar plate pass through the electrolyte, it acts as the main inlet and outlet liquid channels of the frame. However, the uninsulated cut will conduct the current collected by the bipolar plate to the electrolyte in the main channel, and the current is carried out of the battery stack through the circulation of the pump, resulting in a very low Coulomb efficiency.

[0009] Another source of current loss is electrochemical corrosion. Except for the area in the center that contacts the electrodes, a large area of the bipolar plate directly contacts the electrolyte. If the contact area is covered with an insulating material, it can prevent the leakage current in the flow channels of the plate frame from reacting with substances such as carbon powder in the conductive bipolar plate. In addition, there is a potential difference between the series-connected flow batteries. If there are scratches or other defects on the surface of the bipolar plate, the current generated by the potential difference will cause obvious corrosion locally at the defects, reducing the material life. Therefore, both the perforated bipolar plate and the non-perforated bipolar plate need to be insulated in the non-electrode contact area.

[0010] A kind of bipolar plate is simply called the ABA component bipolar plate. Component A is an insulating plastic, and component B is a conductive plastic. If holes are drilled on the surface of component A, even if the surface of component A directly contacts the electrolyte, there will be no corrosion and Coulomb loss problems that occur in the bipolar plate with a conductive plastic surface on the whole. The extrusion process can be used for mass production, but the fluidities of the two components are different, and there are certain difficulties in formula research and development. The equipment investment for the initial extrusion production line is high, and it is difficult to achieve mass production of the ABA component bipolar plate, while the production efficiency of the molding process is low.

[0011] Another kind of bipolar plate has a conductive component B plastic in the center and an insulating component A plastic in the outer frame. This kind of bipolar plate can only be produced by molding, cannot be batch extruded, and has low production efficiency and high cost. Utility Model Content

[0012] In view of the above problems, the present utility model discloses a flow battery stack applying a laser-welded bipolar plate, including: a battery unit, a plug laser-welded bipolar plate, a double-tap current collector plate, and a bus bar plate;

[0013] The bus bar plate, the double-tap current collector plate, multiple battery units, the plug laser-welded bipolar plate, the double-tap current collector plate, and the bus bar plate are arranged in sequence;

[0014] The battery unit includes a laser-welded bipolar plate;

[0015] The laser-welded bipolar plate includes a bipolar plate, a first dark plastic plate, and a first light-transmitting plastic plate;

[0016] A first hollow cavity is arranged in the middle of the first dark plastic plate, and through holes are arranged at the four corners;

[0017] The bipolar plate is arranged in the first hollow cavity of the first dark plastic plate;

[0018] A second hollow cavity is arranged in the middle of the first light-transmitting plastic plate, and through holes are arranged at the four corners;

[0019] The first light-transmitting plastic plate is welded to both surfaces of the first dark plastic plate;

[0020] The first hollow cavity is larger in size than the second hollow cavity.

[0021] Furthermore, the battery cell further includes: an electrode, a plate frame, and an ion membrane;

[0022] The electrode, the laser-welded bipolar plate, the plate frame, the electrode, and the ion membrane are arranged in sequence.

[0023] Furthermore, a fourth hollow cavity is provided in the middle of the plate frame, and through holes are provided at the four corners;

[0024] Symmetrical flow channels are provided on one surface of the plate frame, and the flow channels are located on both sides of the fourth hollow cavity;

[0025] The flow channels communicate with the fourth hollow cavity;

[0026] The flow channels are in an S shape, multiple S-shaped ribs are provided in the flow channels, and short ribs are provided at the flow channel inlet and the turning points.

[0027] Furthermore, the plug laser-welded bipolar plate includes a bipolar plate, a first dark plastic plate, a steel plate, and a second light-transmitting plastic plate;

[0028] A third hollow cavity is provided in the middle of the second light-transmitting plastic plate;

[0029] The steel plate is arranged in the through hole of the first dark plastic plate;

[0030] The second light-transmitting plastic plate is welded to both surfaces of the first dark plastic plate.

[0031] Furthermore, the first hollow cavity is larger in size than the third hollow cavity.

[0032] Furthermore, the double-tap current collector plate includes a bipolar plate, a first light-transmitting plastic plate, a second dark plastic plate, a third light-transmitting plastic plate, and a double-tap copper plate;

[0033] The second dark plastic plates are respectively arranged on the long side of the bipolar plate;

[0034] The third light-transmitting plastic plate is welded to one surface of the second dark plastic plate, and the first light-transmitting plastic plate is welded to the other surface;

[0035] The double-tap copper plate abuts against the bipolar plate and is located between the two third light-transmitting plastic plates.

[0036] Furthermore, a double tap is provided at one end of the double-tap copper plate.

[0037] Furthermore, the double-tap copper plate is connected to the bipolar plate through a conductive adhesive.

[0038] Furthermore, the bipolar plate and the second dark plastic plate have the same thickness;

[0039] The third light-transmitting plastic plate has the same thickness as the double-tap copper plate.

[0040] Furthermore, the bipolar plate has the same thickness as the first dark plastic plate.

[0041] Compared with the prior art, the beneficial effects of the present utility model are as follows: The designs of the positive and negative plate frames of the battery stack are the same, reducing the types of parts; the laser-welded bipolar plate structure reduces the usage amount of conductive plastic and lowers the material cost; the laser-welded bipolar plate "sandwich" structure can reduce corrosion in the non-electrode contact area, and the welding wires designed on the welding surface meet the requirements of improving the structural strength, sealing, and exhausting air after the sheet is pressed; the same outer dimensions of the laser-welded bipolar plate and the plate frame can reduce the difficulty of assembly and positioning; the Coulomb loss of the mirror-image two-part stack is significantly less than that of the whole stack with the same number of cells, improving the energy efficiency of the battery; the method of covering the metal plate with a film in the plug laser-welded bipolar plate not only meets the strength requirement for the thin-wall structure to resist the impact of large-flow liquid but also meets the anti-corrosion requirement in high-concentration acid solution.

[0042] Other features and advantages of the present utility model will be described in the subsequent description, and some of them will be obvious from the description or can be understood by implementing the present utility model. The objectives and other advantages of the present utility model can be achieved and obtained through the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present utility model. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0044] Figure 1 Shows a schematic structural diagram of a flow battery stack according to an embodiment of the present utility model;

[0045] Figure 2 Shows an exploded view of a laser-welded bipolar plate according to an embodiment of the present utility model;

[0046] Figure 3 Shows a schematic diagram of a laser-welded bipolar plate according to an embodiment of the present utility model;

[0047] Figure 4 Shows a perspective view of a flow battery stack according to an embodiment of the present utility model;

[0048] Figure 5 Shows a tap schematic diagram of a flow battery stack according to an embodiment of the present utility model;

[0049] Figure 6 Shows an exploded view of a battery cell according to an embodiment of the present invention;

[0050] Figure 7 Shows a front view schematic diagram of a plate frame according to an embodiment of the present invention;

[0051] Figure 8 Shows a back view schematic diagram of a plate frame according to an embodiment of the present invention;

[0052] Figure 9 Shows an exploded view of a plug laser-welded bipolar plate according to an embodiment of the present invention;

[0053] Figure 10 Shows a schematic diagram of a plug laser-welded bipolar plate according to an embodiment of the present invention;

[0054] Figure 11 Shows an exploded view of a double-tap current collector plate according to an embodiment of the present invention;

[0055] Figure 12 Shows a schematic diagram of a double-tap current collector plate according to an embodiment of the present invention.

[0056] Reference numerals: 1, bipolar plate; 2, first dark plastic plate; 3, first light-transmitting plastic plate; 4, steel plate; 5, second light-transmitting plastic plate; 6, second dark plastic plate; 7, third light-transmitting plastic plate; 8, double-tap copper plate; 9, laser-welded bipolar plate; 10, plug laser-welded bipolar plate; 11, double-tap current collector plate; 12, plate frame. Detailed implementation manners

[0057] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0058] Figure 1 Shows a schematic diagram of the structure of a flow battery according to an embodiment of the present invention. As Figure 1 shown, a flow battery stack applying a laser-welded bipolar plate proposed by the present invention includes: a battery cell, a plug laser-welded bipolar plate 10, a double-tap current collector plate 11, and a bus bar;

[0059] The bus bar (the grid-filled area in the figure), the double-tap current collector 11, multiple battery cells (constituting a sub-stack), the plug laser-welded bipolar plate 10, another sub-stack, the double-tap current collector 11, and the bus bar are arranged in sequence;

[0060] The battery cell includes a laser-welded bipolar plate 9;

[0061] As Figure 2 shown, the laser-welded bipolar plate 9 includes a bipolar plate 1, a first dark plastic plate 2, and a first light-transmitting plastic plate 3;

[0062] A first hollow cavity is provided in the middle of the first dark plastic plate 2, and through holes are provided at the four corners;

[0063] The bipolar plate 1 is arranged in the first hollow cavity of the first dark plastic plate 2;

[0064] A second hollow cavity is provided in the middle of the first light-transmitting plastic plate 3, and through holes are provided at the four corners;

[0065] Both surfaces (the upper surface and the lower surface) of the first dark plastic plate 2 (with the bipolar plate 1 arranged in the middle) are welded with the first light-transmitting plastic plate 3;

[0066] The first hollow cavity is larger in size than the second hollow cavity. Both the first hollow cavity and the second hollow cavity are rectangular.

[0067] Among them, the dark plastic plate is a light-absorbing material. If a light-transmitting material is used, an absorbent coating needs to be applied on the surface or the area to be laser-welded on the surface of the light-transmitting material needs to be locally blackened by laser or other processes. Both the dark plastic plate and the light-transmitting plastic plate are insulating materials.

[0068] The bipolar plate 1 is used to separate the positive electrode side ( Figure 1 the horizontally-striped filled rectangular area) and the negative electrode side ( Figure 1 the non-filled rectangular area) of adjacent battery cells, and is in contact with the electrodes to collect the current generated by the electrochemical reaction;

[0069] The first dark plastic plate 2 is used to embed the bipolar plate 1 into the first hollow cavity; the first dark plastic plate 2 is an inexpensive insulating material that replaces part of the material of the bipolar plate 1, and the 4 through holes are used for the inflow and outflow of the electrolyte, and the cut is non-conductive; the first dark plastic plate 2 is an insulating material and is welded with the first light-transmitting plastic plate 3 for light absorption;

[0070] The first light-transmitting plastic plate 3 is used to cover the bipolar plate 1 and the first dark plastic plate 2, and is fixed and sealed with welding wires respectively to form the laser-welded bipolar plate 9;

[0071] The laser-welded bipolar plate 9 is used to separate the positive and negative sides of adjacent battery cells; the through holes at the four corners are the main channels for the electrode liquid;

[0072] The plug laser-welded bipolar plate 10 is used to separate the liquid flow cycles of two sub-stacks of the flow battery stack. The function of the bipolar plate 1 in the center is to connect in series the circuits in the electrode areas of the two sub-stacks;

[0073] The double-tap current collector plate 11 is used to collect the total current of the flow battery stack.

[0074] Among them, the bipolar plate 1 and the first dark plastic plate 2 have the same thickness. This ensures the flatness of the laser-welded bipolar plate 9 after laser welding. Exemplarily, the thickness of the bipolar plate 1 is between 0.5 mm and 5 mm; the thickness of the first light-transmitting plastic plate 3 is between 0.05 mm and 5 mm. The external dimensions of the laser-welded bipolar plate 9 do not exceed the table size of the laser welding machine.

[0075] The way to insulate the laser-welded bipolar plate 9 structurally is to embed the conductive bipolar plate 1 into the first dark plastic plate 2. There are 4 through holes on the first dark plastic plate 2, and then sandwich it with two insulating first light-transmitting plastic plates 3. Use the laser welding method to composite the three-layer plates, a total of 4 parts, into one component. The specific welding steps are as follows:

[0076] Step 1: First, embed the bipolar plate 1 into the first dark plastic plate 2;

[0077] Step 2: Cover the first light-transmitting plastic plate 3 on the surfaces of the bipolar plate 1 and the first dark plastic plate 2, and align the peripheries;

[0078] Step 3: Laser-weld the bipolar plate 1 and the first light-transmitting plastic plate 3, and the first dark plastic plate 2 and the first light-transmitting plastic plate 3;

[0079] Step 4: Turn it over;

[0080] Step 5: Take another first light-transmitting plastic plate 3 and cover it on the lower surfaces of the bipolar plate 1 and the first dark plastic plate 2, and align the peripheries;

[0081] Step 6: Laser-weld the bipolar plate 1 and the first light-transmitting plastic plate 3, and the first dark plastic plate 2 and the first light-transmitting plastic plate 3.

[0082] Such as Figure 3As shown, there are two wire bonding positions which mainly play a sealing role to prevent the electrolyte in the battery stack from leaking out through the sheet gaps. There is no wire bonding at the bipolar plate taps of the component, and the purpose is to exhaust gas. This is because the plastic sheet is welded under pressure, and the material deforms due to heat. The exhaust holes can ensure that the surface of the welded component is flat without bulges and wrinkles. In the figure, 3 discontinuous wire bonds that extend from the plate surface to the electrode cavity are symmetrically distributed. The purpose is to increase the connection strength between large-sized sheets, and at the same time, a connected exhaust channel is reserved on the surface to prevent the gas existing between the sheets from accumulating and discharging from the taps.

[0083] The flow battery stack with a laser-welded bipolar plate of the present utility model adopts a locally insulated laser-welded bipolar plate 9; adopts laser welding technology to weld the central conductive plastic plate (bipolar plate 1) and the insulating plastic plates (light-transmitting plastic plate and dark plastic plate) into a component; it not only avoids the current loss of the electrolyte at the liquid inlet cut, but also can relieve the electrochemical corrosion caused by the direct contact between the electrolyte and the conductive bipolar plate 1, and also saves the usage area of the conductive plastic and reduces the raw material cost.

[0084] When mass-producing by injection molding process, the mold cost can be reduced, and the types of battery parts can be reduced. The "mirror image two-part stack" is separated by a plug laser-welded bipolar plate 10 in the center, reducing the usage of the liquid inlet plate and the current collector copper plate, reducing the part cost, and significantly reducing the stack thickness and the product volume. In the plug laser-welded bipolar plate 10, the method of covering the metal plate with a film not only meets the strength requirement for the thin-wall structure to resist the impact of large-flow liquid, but also meets the anti-corrosion requirement in high-concentration acid solution. In addition, the Coulomb loss of the mirror image two-part stack is significantly less than that of the whole stack with the same number of cells, improving the energy efficiency of the battery.

[0085] The laser-welded bipolar plate 9, the plug laser-welded bipolar plate 10, and the double-tap current collector plate 11 in the present utility model are all prepared by laser welding, and the laser welding equipment is mature. The track welding machine or the quasi-synchronous welding machine can quickly complete the formation of the designed wire bonds. The process meets the requirements of mass production, and the initial equipment investment is lower than that of the ABA component bipolar plate production line, and the product performance is the same as that of the two-component bipolar plate made by the molding process.

[0086] The flow battery stack with a laser-welded bipolar plate of the present utility model reduces the number of parts of the flow battery stack, reduces the assembly difficulty, and thins the total thickness of the battery stack. Each sub-stack is also an independent U-shaped flow field, canceling 2 bus bars and 2 copper plates. The structure that separates the two sub-stacks in the center is 1 plug laser-welded bipolar plate 10. The center of the plug laser-welded bipolar plate 10 is a carbon-containing conductive plastic plate, which connects the battery units of the two sub-stacks in series to form a whole set of circuit systems. The meaning of the plug is to block the main liquid inlet channel of the battery stack, so that the two sub-stacks have independent flow fields, and the purpose is to suppress the leakage current of the battery stack.

[0087] The flow fields of the two sub-stacks of the flow battery stack are independent of each other because the plug laser-welded bipolar plate 10 is blocked by the steel plate 4 at the four through-hole positions, but the steel plate 4 is covered by the second light-transmitting plastic plate 5 and will not come into contact with the acidic electrolyte, and the material strength can withstand the impact of the fluid.

[0088] The current is transferred section by section through the bipolar plate 1 at the central position of the laser-welded bipolar plate 9 and directly passes through the bipolar plate 1 at the central position of the plug laser-welded bipolar plate 10. Therefore, the two battery stacks with independent flow fields have only one pair of current collector plates.

[0089] The thickness of the plug laser-welded bipolar plate 10 does not exceed 3 mm. The traditional design is that the two sub-stacks use independent liquid inlet plates and a pair of current collector plates. The new design significantly reduces the stack thickness at this point compared to the conventional structure (as Figure 4 shown), making the structure of the entire battery stack more compact and saving the cost of 2 copper plates and 2 busbars.

[0090] In order to minimize the types of parts as much as possible, the design of the positive and negative electrode plate frames 12 used in the battery stack is exactly the same. Assume that the front side of the plate frame 12 is the surface in contact with the laser-welded bipolar plate 9, and the back side is the surface in contact with the membrane. The structure of each cell is that the front sides of two plate frames 12 face each other, with a laser-welded bipolar plate 9 sandwiched in the middle, and adjacent cells are separated by the membrane.

[0091] In order to reduce the problem of seal failure caused by misalignment of the plates during the assembly process, the outer dimensions of the laser-welded bipolar plate 9 are the same as those of the plate frame 12. Since the charging and discharging current of the battery stack is relatively large, in order to reduce the thickness of the main body of the copper plate, reduce the material cost and the weight of the parts, the battery stack uses a double-tap copper plate 8 to introduce and export the total current from the battery stack. The design premise of the double-tap copper plate 8 is that the total cross-sectional area is the same as or larger than that of the original single-tap copper plate. Therefore, the total thickness of the copper plate is saved by at least 50%, and the material cost and types are reduced proportionally, but it can still conduct the charging and discharging current safely without problems such as overheating.

[0092] The battery stack implements a completely symmetric design concept. Therefore, the designs of the 2 insulation plates and 2 end plates are also exactly the same, and the positive and negative electrode plate frames 12 are not distinguished, minimizing the types of parts to the greatest extent. The laser-welded bipolar plate 9 has the same outer dimensions as the plate frame 12, reducing the assembly difficulty and the precision requirements for the relative positions of different layers of plates, which is conducive to implementing mechanical stacking.

[0093] As Figure 5As shown, the bipolar plate taps of the battery stack unit are used to connect a voltage inspection instrument to detect the voltage status of each battery during charging and discharging. Since the battery unit is designed to be very thin, it is difficult to wire the bipolar plate taps on one side. Therefore, the bipolar plate taps adopt an alternating arrangement method to provide more space for wiring operations for each battery. A piece of plastic is put on the battery stack double tap current collector plate 11 to prevent personnel from accidentally touching the exposed cut surface of the current collector plate and the contact between the cut surface and the metal screw.

[0094] As Figure 6 shown, in some embodiments, the battery unit further includes: an electrode, a plate frame 12, and an ion membrane;

[0095] The electrodes (not shown in the figure), the laser-welded bipolar plate 9, the plate frame 12, the electrodes (not shown in the figure), and the ion membrane (not shown in the figure) are arranged in sequence. Among them, the electrodes are arranged inside the plate frame 12.

[0096] For the battery stack plate frame 12 using this laser-welded bipolar plate 9, the positive and negative plate frames 12 are the same. Using the same type of plate frame 12 can reduce the types of parts of the stack body, and the completely symmetric and mirror-image design reduces the assembly difficulty. Since the plug laser-welded bipolar plate 10 is adopted, the volume of the battery with a two-part stack configuration is significantly reduced.

[0097] As Figure 6 shown, for this battery unit that does not distinguish between the positive and negative plate frames 12, the fronts of the two plate frames 12 face each other, and the laser-welded bipolar plate 9 is sandwiched in the middle. To prevent the wrong rotation direction of the plate frame 12 during face-to-face assembly, a semi-circular notch is added at a corner of the short side of the plate frame 12, as Figure 7 shown by the feature in the upper right corner. For the assembled battery unit, one notch is in the upper right corner of the laser-welded bipolar plate 9, and one notch is in the lower right corner of the laser-welded bipolar plate 9, which proves that the relative alignment of the battery unit plate frames 12 is correct.

[0098] As Figure 7 shown, in some embodiments, a fourth hollow cavity is provided in the middle of the plate frame 12, and through holes are provided at the four corners;

[0099] Symmetric flow channels are provided on one surface of the plate frame 12, and the flow channels are located on both sides of the fourth hollow cavity;

[0100] The flow channels are respectively communicated with the fourth hollow cavity and the through holes on the plate frame 12;

[0101] The flow channels are in an S shape, and multiple S-shaped ribs are provided in the flow channels. Short ribs are provided at the flow channel inlet and the turning points.

[0102] The plate frame 12, the closed frame body of the electrochemical reaction site, is used to place the electrodes and the membrane, and enable the electrolyte in the S-shaped bend on its surface to flow into and out of the electrodes evenly.

[0103] The plate frame 12 can be processed by machining, molding or injection molding. The gasket on the plate frame 12 can be processed by slicing after molding, pasting after cutting, curing after dispensing, and secondary injection molding and encapsulation.

[0104] The S-shaped ribs and short ribs are provided because the flow channels are shallow and wide. Without the support of the ribs, the laser-welded bipolar plates 9 laid flat on the front will deform during the heating operation of the battery stack and collapse into the flow channels, resulting in excessive flow resistance or even blockage. The outer sides of the flow channels and through holes are gaskets.

[0105] As Figure 7 shown, there are dense short ribs for support at the local parts of the inlet and turning of the flow channels. This is because after the front of the plate frame 12 is assembled face to face, the gasket partially crosses the flow channels. The designed flow channels are wide. Without additional ribs for support, when the gasket is compressed during press-fitting, the bipolar plate material will be pressed into the flow channels by the gasket, causing blockage.

[0106] Figure 8 Shown is the back of the plate frame 12, featuring a membrane sealing groove, a membrane gasket, and a shared channel sealing groove. The round holes at the four corners of the plate frame 12 are used to insert positioning posts, which serve as a reference and control misalignment during the assembly and press-fitting of the battery stack.

[0107] In order to control the leakage current, the flow battery stack adopts a multi-stack configuration. If a relatively thick bus bar is not used for stack separation, it can be Figure 9 replaced by the plug laser-welded bipolar plate 10 shown.

[0108] As Figure 9 shown, in some embodiments, the plug laser-welded bipolar plate 10 includes a bipolar plate 1, a first dark plastic plate 2, a steel plate 4, and a second light-transmitting plastic plate 5;

[0109] A third hollow cavity is provided in the middle of the second light-transmitting plastic plate 5;

[0110] The steel plate 4 is arranged in the through hole of the first dark plastic plate 2;

[0111] The second light-transmitting plastic plates 5 are welded to both surfaces (the upper surface and the lower surface) of the first dark plastic plate 2.

[0112] In some embodiments, the size of the first hollow cavity is larger than that of the third hollow cavity. The third hollow cavity is rectangular.

[0113] Among them, the outer dimension of the steel plate 4 is larger than that of the shared channel gasket of the plate frame 12. The purpose is to compact the steel plate 4 with the gasket and enclose the welding wire of the steel plate 4 outside the shared channel sealing ring. The impact force of the electrolyte acting on the steel plate 4 can be absorbed by the frame of the battery stack, and there is no risk of cracking of the enclosed welding wire of the steel plate 4.

[0114] The steel plate 4 is used to separate the liquid flow circulation of the two sub-stacks of the battery stack and block the four through-holes of the sealing plate frame 12. Since the fluid pressure in the through-holes of the battery stack is relatively large, the steel plate 4 is required to bear the pressure to prevent the blocked through-holes from being penetrated by the hydraulic pressure;

[0115] The second light-transmitting plastic plate 5 is used to cover the first dark plastic plate 2, the steel plate 4 and the bipolar plate 1. Sealing and fixing are completed by welding wires, and the steel plate 4 is prevented from contacting the electrolyte.

[0116] The structure of the plug laser-welded bipolar plate 10 is the same as that of Figure 2 which is to compound three layers of plates into one component by laser welding. Differences: 1) Steel plates 4 of equal thickness are embedded in the four through-holes of the first dark plastic plate 2; 2) Four through-holes of the second light-transmitting plastic plate 5 are cancelled. As Figure 10 shown, the specific welding steps are as follows:

[0117] Step 1: Embed the bipolar plate 1 into the first dark plastic plate 2;

[0118] Step 2: Cover the second light-transmitting plastic plate 5 on the surfaces of the bipolar plate 1 and the first dark plastic plate 2, and align the peripheries;

[0119] Step 3: According to the legend, laser-weld the bipolar plate 1 and the second light-transmitting plastic plate 5, and the welding wire is 0.5 mm away from the edge line of the second light-transmitting plastic plate 5. Laser-weld the second light-transmitting plastic plate 5 and the first dark plastic plate 2, and the welding wire is 2 mm away from the edge line of the steel plate 4, and the welding wire width is 3 mm.

[0120] Step 4: Turn it over;

[0121] Step 5: Embed the steel plate 4 into the through-holes of the first dark plastic plate 2;

[0122] Step 6: Cover another second light-transmitting plastic plate 5 on the lower surfaces of the bipolar plate 1 and the first dark plastic plate 2, and align the peripheries;

[0123] Step 7: According to the legend, use a continuous welding wire to laser-weld the second light-transmitting plastic plate 5 with the bipolar plate 1 and the first dark plastic plate 2, and the line is 2 mm away from the edge line of the steel plate 4, and the welding wire width is 3 mm.

[0124] Exemplarily, the thickness of the bipolar plate 1 is between 0.5 mm and 5 mm; the first dark plastic plate 2, the steel plate 4 and the bipolar plate 1 have the same thickness; the thickness of the second light-transmitting plastic plate 5 is between 0.05 mm and 5 mm. The external dimensions of the plug laser-welded bipolar plate 10 do not exceed the table size of the laser welding machine.

[0125] There will be two current collector plates at both ends of the flow battery stack to collect the total current of the flow battery stack. In order to save the usage area of the conductive bipolar plate 1 and copper, the flow battery stack uses Figure 11The double-tap current collector plate 11 shown.

[0126] As Figure 11 shown, in some embodiments, the double-tap current collector plate 11 includes a bipolar plate 1, a first transparent plastic plate 3, a second dark plastic plate 6, a third transparent plastic plate 7, and a double-tap copper plate 8;

[0127] The second dark plastic plates 6 are respectively arranged on the long side of the bipolar plate 1;

[0128] One surface of the second dark plastic plate 6 is welded with the third transparent plastic plate 7, and the other surface is welded with the first transparent plastic plate 3;

[0129] The double-tap copper plate 8 abuts against the bipolar plate 1 and is located between two third transparent plastic plates 7.

[0130] Among them, the bipolar plate 1 and the second dark plastic plate 6 have the same thickness;

[0131] The third transparent plastic plate 7 and the double-tap copper plate 8 have the same thickness.

[0132] The third transparent plastic plate 7 is wider than the second dark plastic plate 6.

[0133] The second dark plastic plate 6 has the same thickness as the bipolar plate 1 on the surface of the double-tap current collector plate 11. The second dark plastic plate 6 is an inexpensive insulating material, replacing a part of the bipolar plate material, and the four through holes are used for the inflow and outflow of the electrolyte. The cut is non-conductive and is welded with the third transparent plastic plate 7 for light absorption;

[0134] The third transparent plastic plate 7 is used to level the thickness of the double-tap copper plate 8, covers the surface of the second dark plastic plate 6, and is sealed and fixed by welding wires;

[0135] The double-tap copper plate 8 is used to introduce and export the total current of the battery stack.

[0136] As Figure 11 shown, the structure of the double-tap current collector plate 11 is the Figure 2 same, and three layers of plates are compounded into a component by laser welding. Differences: 1) The thickness of the third transparent plastic plate 7 is the same as that of the double-tap copper plate 8; 2) The second dark plastic plate 6 and the third transparent plastic plate 7 change from a frame to a rectangular strip; 3) The length of the bipolar plate 1 on the surface of the double-tap current collector plate 11 is the same as the length of the double-tap copper plate 8 (excluding the tap length). As Figure 12 shown, the specific welding steps are as follows:

[0137] Step 1: First, fix two second dark plastic plates 6 and the bipolar plate 1 on the same plane;

[0138] Step 2: Cover the first transparent plastic plate 3 on the surfaces of the bipolar plate 1 and the second dark plastic plate 6, and align the peripheries.

[0139] Step 3: According to the legend, laser-weld the bipolar plate 1 and the first transparent plastic plate 3, and the second dark plastic plate 6 and the first transparent plastic plate 3.

[0140] Step 4: Turn it over.

[0141] Step 5: Cover the third transparent plastic plate 7 on the upper surface of the second dark plastic plate 6, and align the peripheries.

[0142] Step 6: According to the legend, laser-weld the third transparent plastic plate 7 and the second dark plastic plate 6.

[0143] Exemplarily, the thickness of the bipolar plate 1 is between 0.5 mm and 5 mm; the second dark plastic plate 6 has the same thickness as the bipolar plate 1; the thickness of the first transparent plastic plate 3 is between 0.05 mm and 5 mm. The thickness of the third transparent plastic plate 7 is the same as that of the double-tap copper plate 8, and the thickness is between 0.5 mm and 5 mm. The outer dimensions of the double-tap current collector plate 11 do not exceed the table size of the laser welding machine.

[0144] In some embodiments, one end of the double-tap copper plate 8 is provided with a double tap.

[0145] In order to further reduce the usage amount of copper, a double-tap copper plate 8 with double taps is used to conduct current. The purpose is to reduce the thickness of the plate under the premise of ensuring the cross-sectional area of the tap, thereby reducing the material usage amount, controlling the cost and weight. In addition, the thickness of the third transparent plastic plate 7 in the welding assembly should be the same as that of the double-tap copper plate 8. If the material of the third transparent plastic plate 7 is too thick, it will affect the laser welding effect. Therefore, using the double-tap method to conduct current is also to reduce the thickness of the matching transparent plastic plate to meet the laser penetration requirement.

[0146] In some embodiments, the double-tap copper plate 8 is connected to the bipolar plate 1 through a conductive adhesive.

[0147] After the double-tap current collector plate 11 is welded, a layer of conductive adhesive is brushed on the surface of the bipolar plate 1, and the double-tap copper plate 8 and the bipolar plate 1 are compounded by a hot pressing method. The double-tap copper plate 8 is embedded in the space formed by two third transparent plastic plates 7, and the length of the double-tap copper plate 8 (excluding the tap length) is the same as that of the bipolar plate 1.

[0148] Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A flow battery stack using laser welding of bipolar plates, characterized in that: include: Battery unit, plug laser welded bipolar plate (10), double tap current collecting plate (11) and busbar; The busbar, the double-tap current collecting plate (11), a plurality of battery cells, the plug laser welded bipolar plate (10), the double-tap current collecting plate (11) and the busbar are arranged in sequence; The battery cell comprises a laser welded bipolar plate (9); The laser welded bipolar plate (9) comprises a bipolar plate (1), a first dark plastic plate (2) and a first light-transmitting plastic plate (3); The first dark plastic plate (2) is provided with a first hollow cavity in the middle and through holes at four corners; The bipolar plate (1) is arranged in a first hollow cavity of a first dark plastic plate (2); The first light-transmitting plastic plate (3) is provided with a second hollow cavity in the middle and through holes at the four corners; First light-transmitting plastic plates (3) are welded to both surfaces of the first dark-colored plastic plate (2); The first hollow cavity is larger in size than the second hollow cavity.

2. The flow battery stack using laser welding of bipolar plates according to claim 1, characterized in that: The battery unit also includes: electrodes, a plate frame (12) and an ion membrane; The electrode, the laser welded bipolar plate (9), the plate frame (12), the electrode and the ion membrane are arranged in sequence.

3. The liquid flow battery stack using laser welding of bipolar plates according to claim 2, characterized in that: The plate frame (12) is provided with a fourth hollow cavity in the middle and through holes at four corners; A surface of the plate frame (12) is provided with symmetrical flow channels, the flow channels being located on both sides of the fourth hollow cavity; The flow channel is communicated with the fourth hollow cavity; The flow channel is S-shaped, a plurality of S-shaped ribs are arranged in the flow channel, and short ribs are arranged at the inlet and the turning part of the flow channel.

4. The liquid flow battery stack using laser welding of bipolar plates according to claim 1, characterized in that: The plug laser welded bipolar plate (10) comprises a bipolar plate (1), a first dark plastic plate (2), a steel plate (4) and a second light-transmitting plastic plate (5); A third hollow cavity is arranged in the middle of the second light-transmitting plastic plate (5); The steel plate (4) is arranged in the through hole of the first dark-colored plastic plate (2); Second light-transmitting plastic plates (5) are welded to both surfaces of the first dark-colored plastic plate (2).

5. The flow battery stack using laser welding of bipolar plates according to claim 4, characterized in that: The first hollow cavity is larger in size than the third hollow cavity.

6. The flow battery stack using laser welding of bipolar plates according to claim 1, characterized in that: The double-tap current collecting plate (11) comprises a bipolar plate (1), a first light-transmitting plastic plate (3), a second dark-colored plastic plate (6), a third light-transmitting plastic plate (7) and a double-tap copper plate (8); A second dark-colored plastic plate (6) is respectively provided on the long sides of the bipolar plate (1); The second dark plastic plate (6) has a third light-transmitting plastic plate (7) welded to one surface thereof and a first light-transmitting plastic plate (3) welded to the other surface thereof; The double-tap copper plate (8) is in contact with the bipolar plate (1) and is located between two third light-transmitting plastic plates (7).

7. The liquid flow battery stack using laser welding of bipolar plates according to claim 6, characterized in that: One end of the double-tap copper plate (8) is provided with a double tap.

8. The liquid flow battery stack using laser welding of bipolar plates according to claim 6, characterized in that: The double-tap copper plate (8) is connected to the bipolar plate (1) via conductive glue.

9. The liquid flow battery stack using laser welding of bipolar plates according to claim 6, characterized in that: The bipolar plate (1) and the second dark plastic plate (6) have the same thickness; The third light-transmitting plastic plate (7) has the same thickness as the double-tap copper plate (8).

10. The liquid flow battery stack using laser welding of bipolar plates according to claim 1, characterized in that: The bipolar plate (1) has the same thickness as the first dark plastic plate (2).

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