INTEGRATED ELECTRODE FRAME AND PREPARATION METHOD AND USE THEREOF

Abstract

An integrated electrode frame and preparation method and use thereof is provided. The integrated electrode frame includes a positive electrode frame, a negative electrode frame, and a membrane. Each of the positive electrode frame and the negative electrode frame is a flat plate with a central through-hole. The membrane is placed between the positive electrode frame and the negative electrode frame, and the membrane is located at the through-hole and hermetically connected to a peripheral edge of the through-hole. A peripheral edge of the positive electrode frame is hermetically connected to a peripheral edge of the negative electrode frame. A material composition of a connecting part of the positive electrode frame and the negative electrode frame contains at least one material which is the same as that of the positive electrode frame or the negative electrode frame. The structures and materials of the electrode frames and the membrane are optimized.

Claims

1. An integrated electrode frame, comprising a positive electrode frame, a negative electrode frame, and a membrane, wherein each of the positive electrode frame and the negative electrode frame is a flat plate with a central through-hole; the membrane is placed between the positive electrode frame and the negative electrode frame, and the membrane is located at the central through-hole and hermetically connected to a peripheral edge of the central through-hole; and a peripheral edge of the positive electrode frame is hermetically connected to a peripheral edge of the negative electrode frame; and a material composition of a connecting part of the positive electrode frame and the negative electrode frame contains at least one material which is the same as that of the positive electrode frame or the negative electrode frame.

2. The integrated electrode frame according to claim 1, wherein the same material is at least one selected from the group consisting of polypropylene (PP), polyethylene (PE), polystyrene (PS), polycarbonate (PC), acrylonitrile butadiene styrene (ABS), polymethyl methacrylate (PMMA), and polyethylene terephthalate (PET).

3. The integrated electrode frame according to claim 1, wherein the positive electrode frame and the negative electrode frame have same shape and size; and a size of the membrane is smaller than a size of the positive electrode frame and a size of the negative electrode frame.

4. The integrated electrode frame according to claim 3, wherein the positive electrode frame or the negative electrode frame has an encircling step around the central through-hole; and the membrane is located on the encircling step, and the membrane is hermetically connected to the encircling step.

5. The integrated electrode frame according to claim 1, wherein the membrane is non-transparent or transparent; and one of the positive electrode frame and the negative electrode frame is transparent, and the other of the positive electrode frame and the negative electrode frame is non-transparent.

6. The integrated electrode frame according to claim 5, wherein when the membrane hermetically connected to the positive electrode frame is non-transparent, the positive electrode frame is transparent, and the negative electrode frame is non-transparent; when the membrane hermetically connected to the positive electrode frame is transparent, the positive electrode frame is non-transparent, and the negative electrode frame is transparent; a material composition of a connecting part of the membrane and the positive electrode frame contains at least one material which is the same as that of the membrane or the positive electrode frame; and the same material is at least one selected from the group consisting of PP, PE, PS, PC, ABS, PMMA, and PET.

7. The integrated electrode frame according to claim 5, wherein a laser transmittance of the transparent electrode frame is 20% or above; a laser transmittance of the non-transparent electrode frame is 5% or below; and a difference of the laser transmittance between the transparent electrode frame and the non-transparent electrode frame is 15-100%.

8. The integrated electrode frame according to claim 7, wherein the laser transmittance of the transparent electrode frame is 40% or above; the laser transmittance of the non-transparent electrode frame is 1% or below; and the difference of the laser transmittance between the transparent electrode frame and the non-transparent electrode frame is 35-100%.

9. The integrated electrode frame according to claim 5, wherein the transparent material comprises at least one selected from the group consisting of PP, PE, PS, PC, ABS, PMMA, and PET; and the non-transparent material comprises the transparent material and a toner.

10. The integrated electrode frame according to claim 9, wherein the toner is at least one selected from the group consisting of a black toner, a yellow toner, a tan toner, a brown toner, and a dark blue toner; and the transparent material further comprises a white toner.

11. The integrated electrode frame according to claim 1, wherein the membrane has a thickness of 100 μm to 3 mm, a porosity of 40-90%, and a pore size of 1-300 nm.

12. The integrated electrode frame according to claim 1, wherein a content of the same material accounts for 10% or more of a total weight of the material composition of respective structure.

13. The integrated electrode frame according to claim 1, wherein a content of the same material accounts for 40% or more of a total weight of the material composition of respective structure.

14. The integrated electrode frame according to claim 1, wherein the flat plate has a fluid distribution channel.

15. A method for preparing the integrated electrode frame according to claim 1, comprising at least the following steps: covering the membrane on a surface of one of the positive electrode frame and the negative electrode frame where the central through-hole is formed, and hermetically connecting the membrane with the peripheral edge of the central through-hole to form a membrane-bonded electrode frame; and laminating the other of the positive electrode frame and the negative electrode frame with the membrane-bonded electrode frame, and hermetically connecting a peripheral edge of the other of the positive electrode frame and the negative electrode frame with a peripheral edge of the membrane-bonded electrode frame, wherein the membrane is located between the positive electrode frame and the negative electrode frame to form the integrated electrode frame.

16. The method according to claim 15, wherein when the membrane is transparent, the method comprises: covering the membrane on a surface of a non-transparent electrode frame where the central through-hole is formed, and hermetically connecting the membrane with the peripheral edge of the central through-hole to form a membrane-bonded non-transparent electrode frame; and laminating a transparent electrode frame with the membrane-bonded non-transparent electrode frame, and fixedly connecting a peripheral edge of the transparent electrode frame with a peripheral edge of the membrane-bonded non-transparent electrode frame, wherein the membrane is located between the transparent electrode frame and the non-transparent electrode frame to form the integrated electrode frame; and alternatively, when the membrane is non-transparent, the method comprises: covering the membrane on a surface of the transparent electrode frame where the central through-hole is formed, and hermetically connecting the membrane with the peripheral edge of the central through-hole to form a membrane-bonded transparent electrode frame; and laminating the non-transparent electrode frame with the membrane-bonded transparent electrode frame, and fixedly connecting a peripheral edge of the non-transparent electrode frame with a peripheral edge of the membrane-bonded transparent electrode frame, wherein the membrane is located between the non-transparent electrode frame and the transparent electrode frame to form the integrated electrode frame.

17. The method according to claim 15, wherein hermetical connection is implemented by laser welding.

18. The method according to claim 17, wherein the membrane is hermetically connected to the peripheral edge of the central through-hole by laser welding with a welding power of 2-50 W and a welding speed of 2-20 mm/s.

19. The method according to claim 17, wherein the peripheral edge of the positive electrode frame and the peripheral edge of the negative electrode frame are hermetically connected by laser welding with a welding power of 15-300 W and a welding speed of 5-50 mm/s.

20. A method of a use of the integrated electrode frame according to claim 1 for a stack of all-vanadium flow batteries, wherein the stack comprises one cell or a plurality of cells connected in series; and the method comprises: arranging the integrated electrode frame in each of the one cell or the plurality of cells connected in series.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0078] FIG. 1 is a structural diagram of a membrane and a positive electrode frame that are welded together according to Embodiment 1 of the present application;

[0079] FIG. 2 is a structural diagram of an integrated electrode frame according to Embodiment 1 of the present application; and

[0080] FIG. 3 is a structural diagram of a conventional stack of all-vanadium flow batteries.

REFERENCE NUMERALS

[0081] 1. positive electrode frame; 2. membrane; 3. through-hole; 4. encircling step; 5. negative electrode frame; and 6. sealing gasket.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0082] The present disclosure will be described in detail below with reference to embodiments, but the present disclosure is not limited to these embodiments.

Embodiment 1

[0083] A positive electrode frame is made of 100 wt % polyethylene (PE), and has a transmittance of 95%. A negative electrode frame is made of a non-transparent material including 99 wt % PE and 1 wt % black masterbatch (PLASBLAK PE2718 by Cabot), and has a transmittance of 1%. A membrane is made of a non-transparent material including 99 wt % PE and 1 wt % black masterbatch (PLASBLAK PE2718 by Cabot), and has a transmittance of 1%. The positive electrode frame 1 is 30 cm long, 40 cm wide, and 4.4 mm thick, while the negative electrode frame 5 is 30 cm long, 40 cm wide, and 2.7 mm thick. Central through-hole 3 of each of the positive electrode frame and the negative electrode frame is 23.5 cm long and 32.5 cm wide. The membrane 2 is 26 cm long and 35 cm wide. Encircling step 4 with a width of 5 mm and a thickness of 1 mm is etched at a peripheral edge of the central through-hole 3 of the positive electrode frame 1 in a direction away from the through-hole. The membrane has a thickness of 500 μm, a porosity of 70%, and a pore size of 1-300 nm.

[0084] As shown in FIGS. 1 and 2, the membrane 2 is welded to the encircling step 4 of the positive electrode frame 1 by laser welding, with a welding power of 10 W and a welding speed of 8 mm/s. The positive electrode frame 1 and the negative electrode frame 5 are welded together, with a welding power of 60 W and a welding speed of 18 mm/s, to form an integrated electrode frame of the positive electrode frame 1, the membrane 2, and the negative electrode frame 5. In this way, 10 integrated electrode frames are sequentially welded, and are assembled into a 10-cell 2 kW stack for an all-vanadium flow battery.

[0085] Leakage testing is performed on the assembled 10-cell stack for the all-vanadium flow battery, with a maximum internal leakage testing pressure of 0.03 MPa and an external leakage testing pressure of 0.26 MPa. No air leakage is observed, and the stack is 103 mm thick, measured by a scale. The battery performance is tested at a constant current of 120 mA/cm.sup.2, and the battery has a coulomb efficiency of 99.3%.

Embodiments 2 to 13

[0086] In these embodiments, the test conditions and process of the stack are the same (with the same parameter units) as those in Embodiment 1, except for the following aspects.

[0087] The material composition of the positive electrode frame and the negative electrode frame is shown in Table 1. PLASWITER PE7606 by Cabot is selected as a white toner. The membrane is made of a non-transparent material including 80 wt % PE, 19 wt % of PP, and 1 wt % black masterbatch (PLASBLAK PE2718 by Cabot), and has a transmittance of 1%. The positive electrode frame is 30 cm long, 40 cm wide, and 4.4 mm thick, while the negative electrode frame is 30 cm long, 40 cm wide, and 2.7 mm thick. The central through-hole of each of the positive electrode frame and the negative electrode frame is 23.5 cm long and 32.5 cm wide. The membrane is 26 cm long and 35 cm wide. The encircling step with a width of 5 mm and a thickness of 1 mm is etched at a peripheral edge of the central through-hole of the positive electrode frame in a direction away from the through-hole. The assembled stack is 103 mm thick. In Embodiments 2 to 12, an integrated electrode frame of the membrane, the positive electrode frame, and the negative electrode frame is formed. Multiple integrated electrode frames are assembled into a 10-cell 2 kW stack for an all-vanadium flow battery.

TABLE-US-00001 TABLE 1 Material composition Material composition of positive electrode of negative electrode Transmittance Transmittance frame (by weight) frame (by weight) of positive of negative White Black electrode electrode Embodiments Polyethylene % PP % masterbatch, % PE, % PP, % masterbatch, % frame, % frame, % 2 10 89.7 0.3 10 89 1 90 1 3 10 89.7 0.3 20 79 1 90 1 4 20 79.2 0.8 10 89 1 75 1 5 20 79.2 0.8 30 69 1 75 1 6 30 68.8 1.2 10 89 1 60 1 7 30 68.8 1.2 40 59 0.8 60 3 8 40 58.3 1.7 20 79.2 0.8 40 3 9 40 58.3 1.7 50 49.5 0.5 40 5 10 50 47 3 10 89.5 0.5 20 5 11 50 47 3 50 49.5 0.5 20 5 12 15 84.5 0.5 15 84 1 80 1 13 100 — — 10 89 1 95 1 Positive and Membrane and negative Transmittance electrode electrode External and difference frame frame internal of positive welding welding leakage Coulomb and negative power and power and testing efficiency electrode speed speed pressures of stack Embodiments frames, % Power Speed Power Speed of stack % 2 89 15 8 70 18 0.029 0.25 98.9 3 89 13 8 70 18 0.027 0.25 98.8 4 74 20 8 80 17 0.025 0.24 98.9 5 74 15 8 70 17 0.025 0.23 99.0 6 59 25 7 140 15 0.023 0.22 99.5 7 57 22 6 130 13 0.023 0.22 99.3 8 37 30 6 170 10 0.020 0.20 99.1 9 35 25 5 150 10 0.020 0.20 99.5 10 15 35 5 300 10 0.018 0.17 99.1 11 15 33 5 260 10 0.018 0.17 98.9 12 79 17 8 75 17 0.026 0.24 98.2 13 94 10 8 60 18 0.030 0.26 98.7

Embodiment 14

[0088] The positive electrode frame is made of 100 wt % PE, and has a transmittance of 95%. The negative electrode frame is made of a non-transparent material including 99 wt % PE and 1 wt % black masterbatch (PLASBLAK PE2718 by Cabot), and has a transmittance of 1%. The membrane is made of a non-transparent material including 99 wt % PE and 1 wt % black masterbatch (PLASBLAK PE2718 by Cabot), and has a transmittance of 1%. The positive electrode frame 1 is 30 cm long, 40 cm wide, and 4.4 mm thick, while the negative electrode frame 5 is 30 cm long, 40 cm wide, and 2.7 mm thick. The central through-hole 3 of each of the positive electrode frame and the negative electrode frame is 23.5 cm long and 32.5 cm wide. The membrane 2 is 26 cm long and 35 cm wide. The membrane has a thickness of 500 μm, a porosity of 70%, and a pore size of 1-300 nm.

[0089] The membrane 2 is welded to the peripheral edge of the central through-hole of the positive electrode frame 1, with a welding power of 30 W and a welding speed of 5 mm/s. The positive electrode frame 1 and the negative electrode frame 5 are welded together, with a welding power of 60 W and a welding speed of 18 mm/s, to form an integrated electrode frame of the positive electrode frame 1, the membrane 2, and the negative electrode frame 5. In this way, 10 integrated electrode frames are sequentially welded, and are assembled into a 10-cell 2 kW stack for an all-vanadium flow battery.

[0090] Leakage testing is performed on the assembled 10-cell stack for the all-vanadium flow battery, with a maximum internal leakage testing pressure of 0.025 MPa and an external leakage testing pressure of 0.26 MPa. No air leakage is observed, and the stack is 108 mm thick, measured by a scale. The battery performance is tested at a constant current of 120 mA/cm.sup.2, and the battery has a coulomb efficiency of 99.0%.

[0091] The test results of the above embodiments show that:

[0092] 1. When the content of the same material in the welded material reaches 10% or more of the welded material, both the internal and external leakage testing of the assembled stack meet the requirements (the internal leakage testing pressure is at least 0.018 MPa, and the external leakage testing pressure is at least 0.17 MPa).

[0093] 2. When the content of the same material in the welded material increases, the ability of the stack to resist both internal and external leakage testing pressures is improved.

[0094] 3. When the transmittance of the positive electrode frame is not lower than 20% and the transmittance of the negative electrode frame is not higher than 5%, effective welding can be achieved, thereby ensuring the air tightness of the stack.

[0095] 4. As the transmittance difference between the positive electrode frame and the negative electrode frame continues to increase, the ability of the finally assembled stack to resist internal and external leakage testing pressures continues to improve, and the laser welding power continues to decrease, saving energy. In addition, under the condition that the transmittance difference between the positive electrode frame and the negative electrode frame remains unchanged, the laser welding power is increased, thereby increasing the welding speed.

[0096] All other conditions not mentioned in the following Comparative Examples 1 to 4 are the same as those in Embodiment 1.

Comparative Example 1

[0097] The positive electrode frame is made of 100 wt % PE, and has a transmittance of 95%. The negative electrode frame is made of a non-transparent material including 99 wt % PE and 1 wt % black masterbatch (PLASBLAK PE2718 by Cabot), and has a transmittance of 1%. The membrane is made of a non-transparent material including 99 wt % PE and 1 wt % black masterbatch (PLASBLAK PE2718 by Cabot), and has a transmittance of 1%. Each of the positive electrode frame and the negative electrode frame is 30 cm long, 40 cm wide, and 3.55 mm thick. The central through-hole of each of the positive electrode frame and the negative electrode frame is 23.5 cm long and 32.5 cm wide. The membrane is 30 cm long and 40 cm wide. The membrane has a thickness of 500 μm, a porosity of 70%, and a pore size of 1-300 nm.

[0098] As shown in FIG. 3, a conventional stack structure is used, and the membrane and the electrode frame are sealed through sealing gasket 6. With the same assembly process, a 10-cell stack is assembled for an all-vanadium flow battery.

[0099] Leakage testing is performed on the assembled 10-cell 2 kW stack for the all-vanadium flow battery. A longitudinal surface of the membrane 2 is directly exposed, which can easily lead to small longitudinal leakage. For this reason, the maximum internal leakage testing pressure is 0.012 MPa, and the external leakage testing pressure of 0.08 MPa. The stack is 130 mm thick, measured by a scale. The battery performance is tested at a constant current of 120 mA/cm.sup.2, and the battery has a coulomb efficiency of 93.5%.

[0100] Embodiment 1 and Comparative Example 1 use the same assembly process. The membrane is welded with the positive electrode frame and the negative electrode frame, improving the sealing reliability of the stack. The maximum internal leakage testing pressure is 0.03 MPa, and the external leakage testing pressure is 0.26 MPa. The reliability of the stack is improved, the long-term cycling stability of the battery is significantly improved, and the life of the battery is extended. The stack in Embodiment 1 is 103 mm thick, and the stack in Comparative Example 1 is 130 mm thick. Compared with Comparative Example 1, in Embodiment 1, the volumetric energy density of the stack is increased by 26.2%.

Comparative Example 2

[0101] The positive electrode frame is made of a non-transparent material including 99 wt % PE and 1 wt % black masterbatch (PLASBLAK PE2718 by Cabot), and has a transmittance of 1%. The negative electrode frame is made of a transparent material including 100 wt % PP, and has a transmittance of 95%. The membrane is made of a non-transparent material including 99 wt % PE and 1 wt % black masterbatch (PLASBLAK PE2718 by Cabot), and has a transmittance of 1%. The positive electrode frame is 30 cm long, 40 cm wide, and 4.4 mm thick, while the negative electrode frame is 30 cm long, 40 cm wide, and 2.7 mm thick. The central through-hole of each of the positive electrode frame and the negative electrode frame is 23.5 cm long and 32.5 cm wide. The membrane is 26 cm long and 35 cm wide. An encircling step with a width of 5 mm and a thickness of 1 mm is etched at a peripheral edge of the central through-hole of the positive electrode frame. The membrane has a thickness of 500 μm, a porosity of 70%, and a pore size of 1-300 nm.

[0102] The membrane is welded to the encircling step with a width of 5 mm at the peripheral edge of the central through-hole of the negative electrode frame, with a welding power of 1 W and a welding speed of 5 mm/s. The positive electrode frame and the negative electrode frame are welded together, with a welding power of 14 W and a welding speed of 10 mm/s, to form an integrated electrode frame of the positive electrode frame, the membrane, and the negative electrode frame. In this way, 10 integrated electrode frames are sequentially welded.

[0103] The integrated electrode frames are assembled into a 10-cell 2 kW stack for an all-vanadium flow battery. Leakage testing is performed on the assembled 10-cell stack for the all-vanadium flow battery, with a maximum internal leakage testing pressure of 0.015 MPa and an external leakage testing pressure of 0.08 MPa. The stack is 103 mm thick, measured by a scale. The battery performance is tested at a constant current of 120 mA/cm.sup.2, and the battery has a coulomb efficiency of 96.2%.

[0104] The comparison of the data of Embodiment 1 and Comparative Example 2 shows that although the two materials without the same material can be welded together, their sealing reliability is poor, and they cannot meet the pressure performance requirements of a high-power stack.

Comparative Examples 3 to 4

[0105] The testing conditions of Comparative Examples 3 to 4 differing from Embodiment 1 are shown in Table 2, and those the same as Embodiment 1 can be referred to Embodiment 1.

TABLE-US-00002 TABLE 2 Material Material composition of composition of positive electrode negative electrode Transmittance Transmittance frame frame of positive of negative Comparative White Black electrode electrode Example Polyethylene % PP % toner % Polyethylene % PP % toner % frame % frame, % 3 10 89.7 3.5 10 89 0.5 15 5 4 100 — — 5 94 1 95 1 Positive and Membrane and negative Transmittance electrode electrode External and difference of frame frame internal positive and welding welding leakage Coulomb negative power and power and testing efficiency Comparative electrode speed speed pressures of stack Example frames, % Power Speed Power Speed of stack % 3 10 55 5 400 10 0.008 0.056 91 4 94 10 8 60 18 0.01 0.06 92

[0106] The comparison of the comparative examples with the embodiment shows that:

[0107] 1. The same assembly process is used, and the membrane is welded with the positive electrode frame and the negative electrode frame. The design improves the ability of the stack to resist the leakage testing pressures, improves the coulomb efficiency of the battery, and improves the operational reliability of the stack.

[0108] 2. When the same material accounts for more than 10 wt % of the welded material, the welding reliability is guaranteed, and the withstand pressure increases with the increase of the content.

[0109] 3. The membrane is welded with the positive electrode frame and the negative electrode frame, and the positive electrode frame and the negative electrode frame are directly welded to form the integrated electrode frame. There is no need to drill a flow channel hole on the membrane, improving the reliability of the membrane and extending the service life of the battery.

[0110] 4. The present application reduces the use of the sealing gasket, reduces the thickness of the battery, reduces the volume of the stack, and improves the volumetric energy density of the battery.

[0111] 5. Compared with traditional structures, the present application reduces the use of the sealing material, and reduces the area of the membrane by about 30%, greatly reducing the material cost of the stack.

[0112] The above embodiments are merely some of the embodiments of the present application, and do not limit the present application in any form. Although the present application is disclosed above with the preferred embodiments, the present application is not limited thereto. Some changes or modifications made by any technical personnel familiar with the profession using the technical content disclosed above without departing from the scope of the technical solutions of the present application are equivalent to equivalent implementation cases and fall within the scope of the technical solutions.