A new type of all-vanadium liquid flow battery without electrode frame

Abstract

This invention provides a novel vanadium redox flow battery without an electrode frame, comprising two outer end plates, two insulating plates and two current collectors sequentially disposed between the two end plates, and at least one integrated bipolar plate disposed between the two current collectors. A pair of electrodes and a proton exchange membrane are sequentially disposed on both sides of the integrated bipolar plate. The integrated bipolar plate includes a bipolar plate body, electrolyte flow channels disposed in the middle of both sides of the bipolar plate body, and electrode grooves for embedding electrodes on both sides of the integrated bipolar plate. Two electrodes are respectively disposed outside the positive and negative electrolyte flow channels. In this invention, the electrode frame, electrode grooves, bipolar plate, and reaction flow channel regions of the flow battery are all integrally formed, resulting in high integration. Furthermore, the bipolar plate exhibits high conductivity and excellent mechanical properties, thus improving the stack performance of the flow battery.

Description

Technical Field

[0001] The invention belongs to the technical field of energy storage liquid flow batteries, and in particular relates to a novel all-vanadium liquid flow battery without an electrode frame. Background Art

[0002] As a new type of electrochemical energy storage technology, flow batteries have significant advantages in the field of large-scale energy storage, especially in terms of safety, environmental adaptability, long life and flexibility. The most prominent advantage is scalability, that is, the power and energy density of flow batteries can be improved by increasing the amount of electrode materials or electrolyte solutions without major changes to the battery structure. This makes flow batteries an ideal choice for large-scale energy storage applications.

[0003] All-vanadium liquid flow batteries are applied in large-scale stacks, including multiple battery cells. The mainstream all-vanadium liquid flow battery stack structure includes end plates, current collectors, bipolar plates, electrode frames, electrodes, diaphragms, electrodes, electrode frames, bipolar plates, current collectors and end plates. The stack assembly process is very cumbersome and complicated due to the large number of components; and the large number of components leads to a large volume and low power density.

[0004] The electrode frame of a flow battery is usually composed of a hollow flat frame, and a centrally symmetrical liquid flow structure is arranged at its four corners, including an electrolyte inlet and outlet and a shunt flow channel, so that the electrolyte can flow smoothly into and out of the electrode frame. And because the electrolyte in the flow battery is conductive, the traditional design of the flow battery plate requires the electrode frame to achieve edge insulation. Therefore, the electrode frame is an indispensable component in the traditional flow battery. Bipolar plates are also key components of flow batteries. Most of the commercial flow battery bipolar plates are bare plates without flow channels. The electrolyte distribution of the all-vanadium flow battery without flow channels is uneven, which will cause the electrode overpotential to be too high, the concentration polarization loss is large, and the electrolyte utilization rate is low, thereby affecting the battery efficiency. The all-vanadium flow battery with flow channels has bipolar plates with flow channels glued on both sides of the bipolar plate bare plate. The bipolar plates are composed of many parts and have a large overall internal resistance, which greatly increases the ohmic loss and total cost of the battery stack and reduces the performance of the battery stack. Therefore, it is very necessary to design an integrated liquid flow battery bipolar plate with high integration and high conductivity.

[0005] CN112928295A discloses an integrated structure and application of an electrode frame and a bipolar plate, which is achieved by arranging staggered orthogonal electrolyte distribution channels (non-reaction zone channels) at the electrode frames on both sides of the bipolar plate to achieve an integrated structure with electrode frames on both sides of the bipolar plate. However, the application document simply discloses the structure after the electrode frame and the bipolar plate are integrated, and does not achieve the integrated molding of the bipolar plate flow channel structure and the electrode frame structure on the same material.

[0006] In order to realize continuous batch production of integrated liquid flow battery bipolar plates, considering the production process and cost comprehensively, the flexible graphite blank is formed and then impregnated with resin, which is a cost-effective technical route. CN102569834A discloses a high-strength flexible graphite bipolar plate, which is to directly form the graphite bipolar plate first, and then impregnate it with phenolic resin to obtain a bipolar plate with a flow field and inlet, outlet and water holes. Although its preparation method discloses a preparation idea of ​​an integrally formed bipolar plate with a flow channel structure, it is a bipolar plate for fuel cells, and the molding structure of the bipolar plate of the fuel cell and the bipolar plate of the liquid flow battery is very different. The polar plate of a fuel cell is a double-plate structure, consisting of an anode plate and a cathode plate, which are used to transport hydrogen and oxygen respectively; the contents of paragraphs

[0004] -

[0005] and

[0058] in CN112959725A disclose the flow field structure molding range of the fuel cell bipolar plate, which is specifically manifested as follows: the fuel cell reaction zone is fed with gas, and its flow field design usually has a ridge width of no more than 0.8mm, a flow channel depth of no more than 0.5mm, and a ridge center distance of no more than 1.5mm; and its corresponding mechanical performance requirements are not high. The bipolar plate of a liquid flow battery is a single-plate structure, with reaction flow channel areas on both sides for the electrolyte to be passed through, and its flow field depth needs to be greater than 1mm, the ridge width needs to be several millimeters to tens of millimeters, and the center distance is also several millimeters to tens of millimeters. This kind of structural design has very high requirements for the mechanical properties of the bipolar plate, and also brings great difficulty to its integrated molding. The obvious difference in the design magnitude of the bipolar plate flow field of liquid flow batteries and fuel cells has seriously affected the formability of flexible graphite plates in the liquid flow field, that is, the existing preparation method of fuel cell bipolar plates is not suitable for directly preparing bipolar plates with flow channel structures for liquid flow batteries. Therefore, existing liquid flow batteries usually still use bipolar plates with flow channels bonded to them, or first prepare qualified bipolar plate flat plates and then perform subsequent forming; there has been no relevant report on liquid flow batteries with electrode frames, bipolar plates, and reaction zone flow channels formed in one.

[0007] Therefore, designing a more streamlined all-vanadium flow battery is still very meaningful for the production and manufacturing of flow batteries. Summary of the invention

[0008] In view of this, the present invention provides a novel all-vanadium liquid flow battery without an electrode frame.

[0009] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0010] A novel all-vanadium liquid flow battery without an electrode frame comprises two outer end plates, two insulating plates and two current collecting plates arranged in sequence between the two end plates, and at least one integrated bipolar plate arranged between the two current collecting plates, wherein a pair of electrodes and a proton exchange membrane are arranged in sequence on both sides of each of the integrated bipolar plates; wherein:

[0011] The integrated bipolar plate comprises a bipolar plate body, a positive electrode electrolyte flow channel area and a negative electrode electrolyte flow channel area respectively arranged in the middle of two side surfaces of the bipolar plate body, a positive electrode electrolyte outlet, a positive electrode electrolyte inlet, a negative electrode electrolyte outlet and a negative electrode electrolyte inlet arranged at four diagonal positions of the bipolar plate body, and a positive electrode electrolyte outlet distribution area, a positive electrode electrolyte inlet distribution area, a negative electrode electrolyte inlet distribution area and a negative electrode electrolyte outlet distribution area arranged on the bipolar plate body; electrode grooves for embedding electrodes are arranged on two side surfaces of the integrated bipolar plate, and two electrodes are respectively arranged on the outside of the positive electrode electrolyte flow channel area and the negative electrode electrolyte flow channel area;

[0012] The thickness of the integrated bipolar plate is 1.8-8mm, the depth of the electrode groove is 0.5-2.5mm, the ridge width of the reaction zone flow channel is 1-8mm, the flow channel width is 1-3mm, the ridge center distance length is 2-11mm, the flow channel depth is 1-3mm, the electrode thickness is 0.5-3mm, and the length and width dimensions are consistent with the electrode groove dimensions; the proton exchange membrane thickness is 10-50μm;

[0013] The method for preparing the integrated bipolar plate comprises the following steps:

[0014] (1) Using flexible graphite worms with an expansion ratio of 100-500 mL / g as raw materials, 25 mg / cm 2 ~90mg / cm 2 Flexible graphite sheet blanks;

[0015] (2) performing vibration needle punching treatment on the front and back sides of the flexible graphite sheet blank, with the single-side needle punching depth being 1 / 4 to 1 / 3 of the thickness of the flexible graphite sheet, the vibration frequency being 5 to 10 times / s, and the step length being 0.1 to 1 mm / s;

[0016] (3) forming the needle-punched flexible graphite sheet blank into an integrated shape by rolling or molding to prepare an integrated flexible graphite bipolar plate profile with required dimensions;

[0017] (4) The integrated flexible graphite bipolar plate profile is subjected to a process including resin filling, cleaning, curing, and oven drying to obtain a semi-finished product of a flow battery bipolar plate, wherein the resin is selected from at least one of thermosetting resins, and the weight proportion of the resin in the semi-finished product of the flow battery bipolar plate is 10-52%;

[0018] (5) The semi-finished product of the flow battery bipolar plate is subjected to edge insulation treatment on the portion other than the electrode groove to obtain the integrated bipolar plate.

[0019] The present invention is further configured such that a positive electrode sealing plate and a negative electrode sealing plate are respectively provided between the two outermost proton exchange membranes on both sides and the current collecting plates on both sides, and corresponding positive electrodes and negative electrodes are respectively embedded on the side of the positive electrode sealing plate and the negative electrode sealing plate close to the proton exchange membrane.

[0020] The present invention is further configured as a single-sided integrated bipolar plate in which the positive electrode sealing plate and the negative electrode sealing plate are integrally formed and a reaction flow channel region is provided on the side close to one electrode. Compared with the integrated bipolar plate, the positive electrode sealing plate and the negative electrode sealing plate only need to form the reaction flow channel region on one side when integrally formed, while the integrated bipolar plate needs to form the reaction flow channel regions of the positive electrode and the negative electrode on both sides at the same time.

[0021] The present invention is further configured such that the electrode is selected from carbon paper, carbon cloth or carbon felt.

[0022] The present invention is further configured such that the thickness of the electrode is 1.0-1.5 mm.

[0023] The present invention is further configured that, in step (4), the filling resin is performed by placing the integrated flexible graphite bipolar plate profile in a dipping system for filling the resin, wherein the dipping process includes vacuuming and pressurizing, the vacuuming pressure is 0-100 PaA, the vacuum time is 3-360 min; the pressurizing pressure is 0.5-50 MPa, and the pressurizing time is 3-240 min. The vacuuming pressure value is an absolute pressure value.

[0024] The present invention is further configured such that the thermosetting resin is selected from one or more of epoxy resin, phenolic resin and acrylic resin.

[0025] The present invention is further configured such that the weight proportion of the resin in the semi-finished bipolar plate of the flow battery is 20-50%.

[0026] The present invention is further configured such that, in step (4), the drying temperature is 100-200° C. and the drying time is 20-90 min.

[0027] The present invention is further configured such that, in step (4), the curing condition is to immerse in water at 80-100° C. for 150-200 min.

[0028] The present invention is further configured such that, in step (5), the insulation treatment is selected from one or more combinations of spraying resin, powder coating, electrophoresis, and chemical deposition.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The electrode frame-free all-vanadium liquid flow battery provided by the present invention achieves the omission of the electrode frame components in the traditional liquid flow battery by designing a new bipolar plate preparation method and battery structure, and integrates the electrode frame (including the inlet and outlet of the electrolyte and the electrode slot) and the structural design of the flow field into the bipolar plate, thereby improving the integration of the battery, significantly reducing the assembly parts of the battery stack, and saving the production cost of the battery stack.

[0031] (2) The integrated bipolar plate provided by the present invention has high electrical conductivity and excellent mechanical properties, thereby improving the stack performance of the liquid flow battery.

[0032] (3) The design of the present invention reduces the internal resistance of the battery, increases the flow channel, uniformly distributes the electrolyte, and reduces concentration polarization, thereby improving the energy efficiency of the liquid flow battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the composition of the all-vanadium liquid flow battery of the present invention;

[0034] Figure 2 for Figure 1 Schematic diagram of the structure of the integrated bipolar plate.

[0035] Figure 3 for Figure 2 A schematic cross-sectional view of the integrated bipolar plate in the left and right directions is shown.

[0036] Among them, 1, end plate, 2, insulating plate, 3, current collecting plate, 4, integrated bipolar plate, 5, electrode, 6, proton exchange membrane, 7', positive electrode sealing plate, 7", negative electrode sealing plate; 4-1, bipolar plate body, 4-2, positive electrode electrolyte outlet, 4-3, positive electrode electrolyte outlet distribution area, 4-4, positive electrode electrolyte flow channel area, 4-5, negative electrode electrolyte outlet, 4-6, positive electrode electrolyte inlet, 4-7, positive electrode electrolyte inlet distribution area, 4-8, negative electrode electrolyte inlet, 4-9, electrode slot.

[0037] D1-electrode groove depth, D2-channel depth, D3-channel wall thickness, D4-ridge center distance length, D5-channel width, D6-reaction zone channel ridge width. DETAILED DESCRIPTION

[0038] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the present invention is not limited to the following embodiments.

[0039] In the following examples, if no specific technology or conditions are specified, the technology or conditions described in the literature in the field or the product instructions are used; if the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased. Among them, the acrylic resin used in the examples was purchased from Heneng Company.

[0040] refer to Figure 1~Figure 3 The present invention provides a novel all-vanadium liquid flow battery without an electrode frame, comprising two outer end plates 1, two insulating plates 2 and two current collecting plates 3 arranged in sequence between the two end plates 1, and at least one integrated bipolar plate 4 arranged between the two current collecting plates 3, wherein a pair of electrodes 5 and a pair of proton exchange membranes 6 are arranged in sequence on both sides of each of the integrated bipolar plates 4; wherein,

[0041] The integrated bipolar plate 4 includes a bipolar plate body 4-1, a positive electrolyte flow channel area 4-4 and a negative electrolyte flow channel area (not shown in the figure) arranged in the middle of the two sides of the bipolar plate body 4-1, a positive electrolyte outlet 4-2, a positive electrolyte inlet 4-6, a negative electrolyte outlet 4-5 and a negative electrolyte inlet 4-8 arranged at four diagonal positions of the bipolar plate body 4-1, and a positive electrolyte outlet distribution area 4-3, a positive electrolyte inlet distribution area 4-7, a negative electrolyte inlet distribution area (not shown in the figure) and a negative electrolyte outlet distribution area (not shown in the figure) arranged on the bipolar plate body 4-1. The positive electrolyte outlet 4-2 and the positive electrolyte inlet 4-6 are arranged at two opposite diagonal positions of the bipolar plate body 4-1, and the negative electrolyte outlet 4-5 and the negative electrolyte inlet 4-8 are arranged at two opposite diagonal positions of the bipolar plate body 4-1. The positive electrode electrolyte outlet distribution area 4-3 is connected to the positive electrode electrolyte outlet 4-2 and the positive electrode electrolyte flow channel area 4-4, and the positive electrode electrolyte inlet distribution area 4-7 is connected to the positive electrode electrolyte flow channel area 4-4 and the positive electrode electrolyte inlet 4-6. The two sides of the integrated bipolar plate 4 are provided with electrode grooves 4-9 for embedding electrodes 5, and the two electrodes 5 are respectively arranged on the outside of the positive electrode electrolyte flow channel area and the negative electrode electrolyte flow channel area.

[0042] The thickness of the integrated bipolar plate is 1.8-8mm, the electrode groove depth D1 is 0.5-2.5mm, the reaction zone flow channel ridge width D6 is 1-8mm, the flow channel width D5 is 1-3mm, the ridge center distance length D4 is 2-11mm, the flow channel depth D2 is 1-3mm, the electrode groove thickness is 0.5-3mm, and the length and width dimensions are consistent with the electrode groove dimensions; the proton exchange membrane thickness is 10-50μm;

[0043] The method for preparing the integrated bipolar plate comprises the following steps:

[0044] (1) Using flexible graphite worms with an expansion ratio of 100-500 mL / g as raw materials, 25 mg / cm 2 ~90mg / cm 2 Flexible graphite sheet blanks;

[0045] (2) performing vibration needle punching treatment on the front and back sides of the flexible graphite sheet blank, with the single-side needle punching depth being 1 / 4 to 1 / 3 of the thickness of the flexible graphite sheet, the vibration frequency being 5 to 10 times / s, and the step length being 0.1 to 1 mm / s;

[0046] (3) forming the needle-punched flexible graphite sheet blank into an integrated shape by rolling or molding to prepare an integrated flexible graphite bipolar plate profile with required dimensions;

[0047] (4) The integrated flexible graphite bipolar plate profile is subjected to a process including resin filling, cleaning, curing, and oven drying to obtain a semi-finished product of a flow battery bipolar plate, wherein the resin is selected from at least one of thermosetting resins, and the weight proportion of the resin in the semi-finished product of the flow battery bipolar plate is 10-52%;

[0048] (5) The semi-finished product of the bipolar plate for the liquid flow battery is subjected to edge insulation treatment on the portion other than the electrode groove to obtain an integrated bipolar plate with a desired structure.

[0049] It should be noted that the technical solution of the present invention is to integrate the electrode frame, electrolyte inlet and outlet and its distribution flow channel and reaction zone electrolyte flow channel in the traditional liquid flow battery into a bipolar plate. For the specific structure of the bipolar plate flow field, those skilled in the art can design or adjust it according to actual needs. In one embodiment of the present invention, the structural design of the flow channel area adopts the following method: Figure 2 The return flow channel shown.

[0050] In one embodiment of the present invention, a positive electrode sealing plate 7' and a negative electrode sealing plate 7" are respectively provided between the two outermost proton exchange membranes 6 on both sides and the current collecting plates 3 on both sides, and the positive electrode sealing plate 7' and the negative electrode sealing plate 7" are respectively embedded with corresponding positive and negative electrodes on one side close to the proton exchange membrane 6.

[0051] In one embodiment of the present invention, the positive electrode sealing plate 7' and the negative electrode sealing plate 7" are integrally formed and a single-sided integrated bipolar plate having a reaction channel region on the side close to one side of the electrode. Compared with the integrated bipolar plate, the positive electrode sealing plate and the negative electrode sealing plate only need to form the reaction channel region on one side when integrally formed, while the integrated bipolar plate needs to integrally form the reaction channel regions of the positive and negative electrodes on both sides at the same time.

[0052] In one embodiment of the present invention, the electrode is selected from carbon paper, carbon cloth or carbon felt.

[0053] In one embodiment of the present invention, the thickness of the electrode is 1.0-1.5 mm.

[0054] In one embodiment of the present invention, the raw material of the integrated bipolar plate is 150-300 mL / g of flexible graphite worms.

[0055] In one embodiment of the present invention, in step (4), the filling resin is performed by placing the integrated flexible graphite bipolar plate profile in a dipping system for filling the resin, wherein the dipping process includes vacuuming and pressurizing, the vacuuming pressure is 0-100 PaA, the vacuum time is 3-360 min; the pressurizing pressure is 0.5-50 MPa, and the pressurizing time is 3-240 min.

[0056] In one embodiment of the present invention, the thermosetting resin is selected from one or more of epoxy resin, phenolic resin and acrylic resin.

[0057] In one embodiment of the present invention, the weight proportion of the resin in the semi-finished bipolar plate of the flow battery is 20-50%, for example, 25%, 30%, 35%, 40% or 45%.

[0058] In one embodiment of the present invention, in step (4), the drying temperature is 100-200° C. and the drying time is 20-90 min.

[0059] In one embodiment of the present invention, in step (4), the curing temperature is immersed in 80-100° C. water for 150-200 min.

[0060] Since in the technical solution of the present invention, the structure of the electrode frame is also formed in one piece at the same time, it is necessary to perform edge insulation treatment on the semi-finished bipolar plate of the liquid flow battery.

[0061] In one embodiment of the present invention, in step (5), the insulation treatment is selected from one or more combinations of spraying resin, powder coating, electrophoresis, and chemical deposition. In this process, those skilled in the art can use conventional insulation processes to perform edge insulation treatment on the semi-finished bipolar plate of the flow battery.

[0062] Example 1

[0063] This embodiment provides a novel all-vanadium liquid flow battery without an electrode frame, and its battery composition and bipolar plate structure are as follows: Figure 1~Figure 3 As shown, it includes two outer end plates 1, two insulating plates 2 and two current collecting plates 3 arranged between the two end plates 1 in sequence, and an integrated bipolar plate 4 arranged between the two current collecting plates 3, and a pair of electrodes 5 and a pair of proton exchange membranes 6 are arranged on both sides of the integrated bipolar plate 4 in sequence; a positive electrode sealing plate 7′ and a negative electrode sealing plate 7″ are respectively arranged between the two outermost proton exchange membranes 6 on both sides and the current collecting plates 3 on both sides, and the positive electrode sealing plate 7′ and the negative electrode sealing plate 7″ are respectively embedded with corresponding positive and negative electrodes on one side close to the proton exchange membrane 6.

[0064] The integrated bipolar plate 4 includes a bipolar plate body 4-1, a positive electrolyte flow channel area 4-4 and a negative electrolyte flow channel area (not shown in the figure) arranged in the middle of the two sides of the bipolar plate body 4-1, a positive electrolyte outlet 4-2, a positive electrolyte inlet 4-6, a negative electrolyte outlet 4-5 and a negative electrolyte inlet 4-8 arranged at four diagonal positions of the bipolar plate body 4-1, and a positive electrolyte outlet distribution area 4-3, a positive electrolyte inlet distribution area 4-7, a negative electrolyte inlet distribution area (not shown in the figure) and a negative electrolyte outlet distribution area (not shown in the figure) arranged on the bipolar plate body 4-1. The positive electrolyte outlet 4-2 and the positive electrolyte inlet 4-6 are arranged at two opposite diagonal positions of the bipolar plate body 4-1, and the negative electrolyte outlet 4-5 and the negative electrolyte inlet 4-8 are arranged at two opposite diagonal positions of the bipolar plate body 4-1. The positive electrode electrolyte outlet distribution area 4-3 is connected to the positive electrode electrolyte outlet 4-2 and the positive electrode electrolyte flow channel area 4-4, and the positive electrode electrolyte inlet distribution area 4-7 is connected to the positive electrode electrolyte flow channel area 4-4 and the positive electrode electrolyte inlet 4-6. The two sides of the integrated bipolar plate 4 are provided with electrode grooves 4-9 for embedding electrodes 5, and the two electrodes 5 are respectively arranged on the outside of the positive electrode electrolyte flow channel area and the negative electrode electrolyte flow channel area.

[0065] In this embodiment, the thickness of the integrated bipolar plate 4 is 2.8 mm; the electrode groove depth is D1=0.8 mm; the reaction zone flow channel ridge width D6=1.5 mm; the flow channel width D5=1.2 mm, the ridge center distance length D4=2.7 mm; the flow channel depth D2=1.0 mm; the flow channel wall thickness D3=0.2 mm, and the reaction zone thickness D2+D3=1.2 mm.

[0066] The electrode is carbon cloth with a thickness of 1.2 mm, and the proton exchange membrane has a thickness of 10 μm.

[0067] The integrated bipolar plate 4 is prepared by the following preparation method, including the following steps:

[0068] (1) Using expandable graphite as raw material, flexible graphite worms with an expansion ratio of 150mL / g-200mL / g were prepared;

[0069] (2) The flexible graphite worms are prepared to have a surface density of 30 mg / cm 2 Flexible graphite sheet blanks;

[0070] (3) performing vibration needle punching treatment on the front and back sides of the flexible graphite sheet blank, with the single-side needle punching depth being 1 / 3 of the thickness of the flexible graphite sheet, the vibration frequency being 10 times / s, and the step length being 0.5 mm / s;

[0071] (4) The flexible graphite sheet blank is formed by roller pressing to prepare an integrated flexible graphite bipolar plate profile with an electrode frame, a flow field and a plate;

[0072] (5) The integrated flexible graphite bipolar plate profile is placed in a resin impregnation system to be filled with resin, wherein the impregnation process includes vacuuming and pressurizing, wherein the vacuuming pressure is 20PaA, the vacuum time is 60min; the pressurizing pressure is 1MPa, and the pressurizing time is 60min; the filled resin is acrylic resin. After the resin filling is completed, the integrated flexible graphite bipolar plate profile is washed, and then the washed flexible graphite bipolar plate profile is placed in 90°C water and immersed for 180min, and then the cured flexible graphite bipolar plate profile is placed in a 130°C oven and dried for 60min and then taken out to obtain an integrated liquid flow battery bipolar plate semi-finished product; the test shows that the resin in the liquid flow battery bipolar plate semi-finished product accounts for 45% of the weight of the bipolar plate.

[0073] (6) The semi-finished integrated liquid flow battery bipolar plate is sprayed with insulating epoxy resin to perform edge insulation treatment to obtain an integrated bipolar plate.

[0074] Example 2

[0075] A novel all-vanadium liquid flow battery without an electrode frame, the composition of which is substantially the same as that of Example 1, except that the preparation method of the bipolar plate is different.

[0076] In this embodiment, the method for preparing the integrated bipolar plate includes the following steps:

[0077] (1) Using expandable graphite as raw material, flexible graphite worms with an expansion ratio of 150mL / g-200mL / g were prepared;

[0078] (2) The flexible graphite worms are prepared to have a surface density of 40 mg / cm 2 Flexible graphite sheet blanks;

[0079] (3) performing vibration needle punching treatment on the front and back sides of the flexible graphite sheet blank, with the single-side needle punching depth being 1 / 3 of the thickness of the flexible graphite sheet, the vibration frequency being 10 times / s, and the step length being 0.5 mm / s;

[0080] (4) The flexible graphite sheet blank is formed by roller pressing to prepare an integrated flexible graphite bipolar plate profile with an electrode frame, a flow field and a plate;

[0081] (5) The integrated flexible graphite bipolar plate profile is placed in a resin impregnation system to be filled with resin, wherein the impregnation process includes vacuuming and pressurizing, wherein the vacuuming pressure is 20PaA, the vacuum time is 60min; the pressurizing pressure is 1MPa, and the pressurizing time is 60min; the filled resin is acrylic resin. After the resin filling is completed, the integrated flexible graphite bipolar plate profile is washed, and then the washed flexible graphite bipolar plate profile is placed in an oven at 130°C and dried for 60min and then taken out to obtain an integrated liquid flow battery bipolar plate semi-finished product; the test shows that the weight ratio of the resin in the bipolar plate semi-finished product is 40%.

[0082] (6) The semi-finished integrated liquid flow battery bipolar plate is sprayed with insulating epoxy resin to perform edge insulation treatment to obtain an integrated bipolar plate.

[0083] Example 3

[0084] A novel all-vanadium liquid flow battery without an electrode frame, the composition of which is basically the same as that of Example 1, except that the preparation method of the bipolar plate is different. In this embodiment, the electrode is a carbon cloth with a thickness of 1.2 mm, and the preparation method of the integrated bipolar plate includes the following steps:

[0085] (1) Using expandable graphite as raw material, flexible graphite worms with an expansion ratio of 150mL / g-200mL / g were prepared;

[0086] (2) The flexible graphite worms are prepared to have a surface density of 60 mg / cm 2 Flexible graphite sheet blanks;

[0087] (3) performing vibration needle punching treatment on the front and back sides of the flexible graphite sheet blank, with the single-side needle punching depth being 1 / 3 of the thickness of the flexible graphite sheet, the vibration frequency being 10 times / s, and the step length being 0.5 mm / s;

[0088] (4) The flexible graphite sheet blank is formed by roller pressing to prepare an integrated flexible graphite bipolar plate profile with an electrode frame, a flow field and a plate;

[0089] (5) The integrated flexible graphite bipolar plate profile is placed in a resin impregnation system to be filled with resin, wherein the impregnation process includes vacuuming and pressurizing, wherein the vacuuming pressure is 20PaA, the vacuum time is 60min; the pressurizing pressure is 1MPa, and the pressurizing time is 60min; the filled resin is acrylic resin. After the resin filling is completed, the integrated flexible graphite bipolar plate profile is washed, and then the washed flexible graphite bipolar plate profile is placed in an oven at 130°C and dried for 60min and then taken out to obtain an integrated liquid flow battery bipolar plate semi-finished product; the test shows that the weight ratio of the resin in the liquid flow battery bipolar plate semi-finished product is 36%.

[0090] (6) The semi-finished integrated liquid flow battery bipolar plate is sprayed with insulating epoxy resin to perform edge insulation treatment to obtain an integrated bipolar plate.

[0091] Example 4

[0092] A novel all-vanadium liquid flow battery without an electrode frame, the composition of which is substantially the same as that of Example 3, except that the preparation method of the bipolar plate is different.

[0093] In this embodiment, the method for preparing the integrated bipolar plate includes the following steps:

[0094] (1) Using expandable graphite as raw material, flexible graphite worms with an expansion ratio of 150mL / g-200mL / g were prepared;

[0095] (2) The flexible graphite worms are prepared to have a surface density of 80 mg / cm 2 Flexible graphite sheet blanks;

[0096] (3) performing vibration needle punching treatment on the front and back sides of the flexible graphite sheet blank, with the single-side needle punching depth being 1 / 3 of the thickness of the flexible graphite sheet, the vibration frequency being 10 times / s, and the step length being 0.5 mm / s;

[0097] (4) The flexible graphite sheet blank is formed by roller pressing to prepare an integrated flexible graphite bipolar plate profile with an electrode frame, a flow field and a plate;

[0098] (5) The integrated flexible graphite bipolar plate profile is placed in a resin impregnation system to be filled with resin, wherein the impregnation process includes vacuuming and pressurizing, wherein the vacuuming pressure is 20PaA, the vacuum time is 60min; the pressurizing pressure is 1MPa, and the pressurizing time is 60min; the filled resin is acrylic resin. After the resin filling is completed, the integrated flexible graphite bipolar plate profile is washed, and then the washed flexible graphite bipolar plate profile is placed in an oven at 130°C and dried for 60min and then taken out to obtain an integrated liquid flow battery bipolar plate semi-finished product; the test shows that the weight ratio of the resin in the liquid flow battery bipolar plate semi-finished product is 30%.

[0099] (6) The semi-finished integrated liquid flow battery bipolar plate is sprayed with insulating epoxy resin to perform edge insulation treatment to obtain an integrated bipolar plate.

[0100] Example 5

[0101] A novel all-vanadium liquid flow battery without an electrode frame, the composition of which is substantially the same as that of Example 3, except that the preparation method of the bipolar plate is different.

[0102] In this embodiment, the method for preparing the integrated bipolar plate includes the following steps:

[0103] (1) Using expandable graphite as raw material, flexible graphite worms with an expansion ratio of 150mL / g-200mL / g were prepared;

[0104] (2) The flexible graphite worms are prepared to have a surface density of 100 mg / cm 2 Flexible graphite sheet blanks;

[0105] (3) performing vibration needle punching treatment on the front and back sides of the flexible graphite sheet blank, with the single-side needle punching depth being 1 / 3 of the thickness of the flexible graphite sheet, the vibration frequency being 10 times / s, and the step length being 0.5 mm / s;

[0106] (4) The flexible graphite sheet blank is prepared by roller-pressing integrated molding to form an integrated flexible graphite bipolar plate profile with an electrode frame, a flow field and an electrode plate. However, in this embodiment, it was found during the integrated molding process that it was impossible to obtain a qualified integrated flexible graphite bipolar plate profile with a thickness of 2.8 mm, an electrode groove depth of 0.8 mm, a reaction zone flow channel ridge width of 1.5 mm, a flow channel width of 1.2 mm, a center distance length of 2.7 mm, a flow channel depth of 1.0 mm and a flow channel wall thickness of 0.2 mm when the designed structure was used for molding. The main reason for this was that the local body density was too high, resulting in the wall thickness being unable to be compressed to 0.2 mm, and there were crack defects on the surface, resulting in preparation failure and inability to carry out subsequent processing.

[0107] Comparative Example 1

[0108] A novel all-vanadium liquid flow battery without an electrode frame, the composition of which is basically the same as that of Example 3, except that the structure of the integrated bipolar plate is different, the reaction zone of the bipolar plate is a flat plate, and the preparation method of the bipolar plate is the same as that of Example 3. In this embodiment, the bipolar plate is 2.8 mm thick; the electrode groove is 0.8 mm deep; the reaction zone is a flat plate with a thickness of 1.2 mm; the electrode is a carbon cloth with a thickness of 1.2 mm; and the proton exchange membrane is 10 μm thick.

[0109] Comparative Example 2

[0110] A novel all-vanadium liquid flow battery without an electrode frame, which is different from Example 3 in that the structure of the bipolar plate is different, specifically:

[0111] In this comparative example, the reaction zone flow channel is a flow channel bonded on both sides of the bipolar plate, rather than being formed integrally during the preparation of the integrated bipolar plate. The parameters of the bipolar plate are: the thickness of the bipolar plate is 2.8 mm; the electrode groove depth is D1 = 0.8 mm; the ridge width of the reaction zone flow channel is D6 = 1.5 mm; the flow channel width is D5 = 1.2 mm, the ridge center distance length is D4 = 2.7 mm; the flow channel depth is D2 = 1.0 mm, the flow channel wall thickness is D3 = 0.2 mm, and the reaction zone thickness is D2 + D3 = 1.2 mm. The electrode is a carbon cloth with a thickness of 1.2 mm, and the proton exchange membrane thickness is 10 μm.

[0112] Comparative Example 3

[0113] This comparative example provides a traditional all-vanadium liquid flow battery with an electrode frame, which adopts the currently mainstream carbon-plastic composite plate, with flow channels bonded on both sides, a ridge width of 1.5mm; a flow channel width of 1.2mm, a center distance length of 2.7mm; a flow channel depth of 1.0mm; a flow channel wall thickness of 0.2mm; a bipolar plate thickness of 2.8mm; the electrode is a carbon cloth with a thickness of 1.2mm; and a proton exchange membrane thickness of 10μm.

[0114] Comparative Example 4

[0115] Compared with Example 1, the difference is that the preparation method of the bipolar plate is different. The integrated bipolar plate is prepared by the following preparation method, including the following steps:

[0116] (1) Using expandable graphite as raw material, flexible graphite worms with an expansion ratio of 150mL / g-200mL / g were prepared;

[0117] (2) The flexible graphite worms are prepared to have a surface density of 30 mg / cm 2 Flexible graphite sheet blanks;

[0118] (3) The flexible graphite sheet blank is prepared by roller-pressing integrated molding to form an integrated flexible graphite bipolar plate profile with an electrode frame, flow field, and plate. During the integrated molding process, it was found that the sheet blank that had not been treated with vibration needle puncture was directly roller-pressed, and the back filling defects were serious, with a large number of creases, holes and other surface defects, and the plate could not meet the molding standards.

[0119] Comparative Example 5

[0120] Compared with Example 1, the difference is that the preparation method of the bipolar plate is different. The integrated bipolar plate is prepared by the following preparation method, including the following steps:

[0121] (1) Using expandable graphite as raw material, flexible graphite worms with an expansion ratio of 150mL / g-200mL / g were prepared;

[0122] (2) The flexible graphite worms are prepared to have a surface density of 30 mg / cm 2 Flexible graphite sheet blanks;

[0123] (3) performing vibration needle punching treatment on the front and back sides of the flexible graphite sheet blank, with the single-side needle punching depth being 1 / 5 of the thickness of the flexible graphite sheet, the vibration frequency being 10 times / s, and the step length being 0.5 mm / s;

[0124] (4) The flexible graphite sheet blank was prepared by roller pressing to form an integrated flexible graphite bipolar plate profile with an electrode frame, flow field, and plate. However, it was found through molding that when the needle puncture depth was only 1 / 5 of the thickness of the flexible graphite sheet blank, there were some creases on the spine, and the target surface quality could not be achieved, resulting in molding failure.

[0125] Comparative Example 6

[0126] Compared with Example 1, the difference is that the preparation method of the bipolar plate is different. The bipolar plate is prepared by the following preparation method, including the following steps:

[0127] (1) Using expandable graphite as raw material, flexible graphite worms with an expansion ratio of 150mL / g-200mL / g were prepared;

[0128] (2) The flexible graphite worms are prepared to have a surface density of 30 mg / cm 2 Flexible graphite sheet blanks;

[0129] (3) performing vibration needle punching treatment on the front and back sides of the flexible graphite sheet blank, with the single-side needle punching depth being 1 / 2 of the thickness of the flexible graphite sheet, the vibration frequency being 10 times / s, and the step length being 0.5 mm / s;

[0130] (4) The flexible graphite sheet blank was prepared by roller pressing to form an integrated flexible graphite bipolar plate profile with an electrode frame, flow field, and plate. The surface quality of the plate was intact and free of defects. However, after the air tightness test, the air tightness of the plate was far below the target requirement; after cross-sectional sampling, it was found that there were some through cracks inside the flexible graphite plate, which was due to the failure of the plate preparation due to the excessive depth of needle puncture.

[0131] Performance Testing

[0132] The semi-finished integrated liquid flow battery bipolar plates prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were subjected to room temperature mechanical property tests, electrical property tests, and battery stack performance tests. The test methods were based on the standard NB / T 42007-2013 all-vanadium liquid flow battery bipolar plate test method and the standard NB / T 42081-2016 all-vanadium liquid flow single cell performance test method. The test results are shown in Table 1 below.

[0133] Table 1 Performance test of flow battery bipolar plate and flow battery

[0134]

[0135] It should be noted that the above-described embodiments should be understood as illustrative rather than limiting the scope of protection of the present invention, and the scope of protection of the present invention shall be subject to the claims. For those skilled in the art, some non-essential improvements and adjustments made to the present invention still fall within the scope of protection of the present invention without departing from the essence and scope of the present invention.

Claims

1. An electrode frame-free all-vanadium liquid flow battery, characterized in that: It includes two outer end plates, two insulating plates and two current collecting plates arranged in sequence between the two end plates, and at least one integrated bipolar plate arranged between the two current collecting plates, and each of the integrated bipolar plates is provided with a pair of electrodes and a proton exchange membrane on both sides in sequence; wherein, The integrated bipolar plate comprises a bipolar plate body, a positive electrode electrolyte flow channel area and a negative electrode electrolyte flow channel area respectively arranged in the middle of two side surfaces of the bipolar plate body, a positive electrode electrolyte outlet, a positive electrode electrolyte inlet, a negative electrode electrolyte outlet and a negative electrode electrolyte inlet arranged at four diagonal positions of the bipolar plate body, and a positive electrode electrolyte outlet distribution area, a positive electrode electrolyte inlet distribution area, a negative electrode electrolyte inlet distribution area and a negative electrode electrolyte outlet distribution area arranged on the bipolar plate body; electrode grooves for embedding electrodes are arranged on two side surfaces of the integrated bipolar plate, and two electrodes are respectively arranged on the outside of the positive electrode electrolyte flow channel area and the negative electrode electrolyte flow channel area; The thickness of the integrated bipolar plate is 1.8-8mm, the depth of the electrode groove is 0.5-2.5mm, the width of the flow channel ridge in the flow channel area is 1-8mm, the flow channel width is 1-3mm, the length of the ridge center distance is 2-11mm, the flow channel depth is 1-3mm, the electrode thickness is 0.5-3mm, and the length and width dimensions are consistent with the electrode groove dimensions; the thickness of the proton exchange membrane is 10-50μm; The method for preparing the integrated bipolar plate comprises the following steps: (1) Using flexible graphite worms with an expansion ratio of 100-500 mL / g as raw materials, 25 mg / cm 2 ~90mg / cm 2 Flexible graphite sheet blanks; (2) performing vibration needle punching treatment on the front and back sides of the flexible graphite sheet blank, with the single-side needle punching depth being 1 / 4 to 1 / 3 of the thickness of the flexible graphite sheet, the vibration frequency being 5 to 10 times / s, and the step length being 0.1 to 1 mm / s; (3) The needle-punched flexible graphite sheet blank is integrally formed by rolling or molding to prepare an integrated flexible graphite bipolar plate profile having an electrode frame, a flow field, and a plate of required dimensions; (4) The integrated flexible graphite bipolar plate profile is subjected to a process including resin filling, cleaning, curing, and oven drying to obtain a semi-finished product of a flow battery bipolar plate, wherein the resin is selected from at least one of thermosetting resins, and the weight proportion of the resin in the semi-finished product of the flow battery bipolar plate is 10-52%; (5) The semi-finished product of the flow battery bipolar plate is subjected to edge insulation treatment on the portion other than the electrode groove to obtain the integrated bipolar plate.

2. The electrode frame-less all-vanadium liquid flow battery according to claim 1, characterized in that: A positive electrode sealing plate and a negative electrode sealing plate are respectively provided between the two outermost proton exchange membranes and the current collecting plates on both sides, and the positive electrode sealing plate and the negative electrode sealing plate are respectively embedded with corresponding positive electrodes and negative electrodes on one side close to the proton exchange membrane.

3. The electrode frame-less all-vanadium liquid flow battery according to claim 2, characterized in that: The positive electrode sealing plate and the negative electrode sealing plate are integrally formed and a single-sided integrated bipolar plate with a flow channel area on the side close to the electrode.

4. The electrode frame-less all-vanadium redox flow battery according to claim 1, characterized in that: The electrode is selected from carbon paper, carbon cloth or carbon felt.

5. The electrode frame-less all-vanadium liquid flow battery according to claim 4, characterized in that: The thickness of the electrode is 1.0-1.5 mm.

6. The electrode frame-less all-vanadium liquid flow battery according to claim 1, characterized in that: In step (4), the filling resin is performed by placing the integrated flexible graphite bipolar plate profile in a dipping system for filling the resin, wherein the dipping process includes vacuuming and pressurizing, the vacuuming pressure is 0-100 PaA, the vacuum time is 3-360 min; the pressurizing pressure is 0.5-50 MPa, and the pressurizing time is 3-240 min.

7. The electrode frame-less all-vanadium redox flow battery according to claim 1, characterized in that: The thermosetting resin is selected from one or more of epoxy resin, phenolic resin and acrylic resin.

8. The electrode frame-less all-vanadium redox flow battery according to claim 1, characterized in that: In step (4), the drying temperature is 100-200°C and the drying time is 20-90 minutes.

9. The electrode frame-less all-vanadium redox flow battery according to claim 1, characterized in that: In step (4), the curing condition is to immerse in water at 80-100° C. for 150-200 min.

10. The electrode frame-less all-vanadium redox flow battery according to claim 1, characterized in that: In step (5), the insulation treatment is selected from one or more combinations of spraying resin, powder coating, electrophoresis, and chemical deposition.

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