Frame body, cell frame, battery cell, cell stack, and redox flow battery system

Abstract

A frame body according to the present disclosure is used in a cell frame of a battery cell. The frame body according to the present disclosure comprises a first surface, a second surface that is on the opposite side from the first surface, an outer peripheral surface, and an inner peripheral surface. The outer peripheral surface is provided with a first outer peripheral surface that is connected to the first surface by a first corner portion, a second outer peripheral surface that is connected to the second surface by a second corner portion, and a connection surface that connects the first outer peripheral surface and the second outer peripheral surface. The connection surface has a first connection surface that is connected to the first outer peripheral surface. The interior angle formed by the first connection surface and the first outer peripheral surface is less than 180°.

Description

Frame, cell frame, battery cell, cell stack, and redox flow battery system

[0001] The present disclosure relates to a frame, a cell frame, a battery cell, a cell stack, and a redox flow battery system. This application claims priority to Japanese Patent Application No. 2024-006884, filed on January 19, 2024, and incorporates by reference all of the contents of said Japanese application.

[0002] Patent Literature 1 discloses a frame used in a redox flow battery system. The redox flow battery system includes a battery cell, and a frame supports the outer periphery of a bipolar plate in the cell frame of the battery cell. The redox flow battery system includes a stack in which a cell frame, a positive electrode, a diaphragm, a negative electrode, and another cell frame are stacked in this order.

[0003] International Publication No. 2018 / 066094

[0004] The frame body of the present disclosure is a plate-shaped frame body used in a cell frame of a battery cell. The frame body of the present disclosure includes a first surface, a second surface opposite the first surface, an outer peripheral surface, and an inner peripheral surface. The outer peripheral surface includes a first outer peripheral surface that connects to the first surface via a first corner portion, a second outer peripheral surface that connects to the second surface via a second corner portion, and a connecting surface that connects the first outer peripheral surface and the second outer peripheral surface. The connecting surface includes a first connecting surface that connects to the first outer peripheral surface. The interior angle formed by the first connecting surface and the first outer peripheral surface is less than 180°.

[0005] FIG. 1A is a plan view of a cell frame according to an embodiment. FIG. 1B is a schematic plan view of a frame according to an embodiment. FIG. 1C is a cross-sectional view taken along line II of FIG. 1B. FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1A. FIG. 3 is a cross-sectional view showing an enlarged view of a portion of the outer peripheral surface of the frame shown in FIG. 2. FIG. 4 is a cross-sectional view showing the vicinity of the outer peripheral surface of a frame according to Modification 1. FIG. 5 is a cross-sectional view showing the vicinity of the outer peripheral surface of a frame according to Modification 2. FIG. 6 is a cross-sectional view showing a portion of a cell frame according to Modification 3. FIG. 7 is a cross-sectional view showing a portion of a frame according to Modification 4. FIG. 8 is a schematic configuration diagram of a redox flow battery system according to an embodiment. FIG. 9 is a schematic configuration diagram of a cell stack according to an embodiment.

[0006] It is desirable to improve the ease of assembly of the cell frame and the laminate.

[0007] One object of the present disclosure is to provide a frame that allows for excellent assembly of components of a redox flow battery system.

[0008] The frame of the present disclosure provides excellent assembly properties for the components of the redox flow battery system.

[0009] First, embodiments of the present disclosure will be listed and described.

[0010] (1) A frame body according to the present disclosure is a frame body used in a cell frame of a battery cell. The frame body according to the present disclosure includes a first surface, a second surface opposite the first surface, an outer peripheral surface, and an inner peripheral surface. The outer peripheral surface includes a first outer peripheral surface connected to the first surface via a first corner portion, a second outer peripheral surface connected to the second surface via a second corner portion, and a connecting surface connecting the first outer peripheral surface and the second outer peripheral surface. The connecting surface includes a first connecting surface connected to the first outer peripheral surface. The interior angle formed by the first connecting surface and the first outer peripheral surface is less than 180°.

[0011] The first connecting surface provided on the outer peripheral surface of the frame body has a non-slip function when the frame body is handled. The non-slip function includes allowing a human finger or a robot's claw to hook onto the first connecting surface. A frame body having the first connecting surface makes it easy to assemble a cell frame composed of the frame body and a bipolar plate. A frame body having the first connecting surface makes it easy to assemble a stack in which a cell frame, a positive electrode, a diaphragm, a negative electrode, and another cell frame are stacked in this order.

[0012] (2) In the frame of (1) above, the second outer peripheral surface may be located farther from the inner peripheral surface than the first outer peripheral surface.

[0013] In the frame of (2) above, a step is formed between the first outer peripheral surface, the second outer peripheral surface, and the first connecting surface, and the first connecting surface is likely to catch a human finger or a robot's nail.

[0014] (3) In the frame body of (1) or (2) above, in a cross section of the frame body perpendicular to the first surface and the first outer peripheral surface, the point on the connecting surface that is closest to the inner peripheral surface is a first point, the point that is farthest from the inner peripheral surface is a second point, and the distance between the first point and the second point may be 1% or more of the maximum thickness of the frame body.

[0015] If the distance is 1% or more of the maximum thickness of the frame body, it is easy to increase the area of ​​the first connecting surface. If the area of ​​the first connecting surface is large, it is easy for a human finger or a robot's claw to get caught on the first connecting surface. In this specification, the "cross section of the frame body perpendicular to the first surface and the first outer peripheral surface" may be simply referred to as the "cross section of the frame body." This "cross section of the frame body" is the cross section of one of the frame body pieces on both sides of the through hole.

[0016] (4) In any of the frames described in (1) to (3), the width of the second outer peripheral surface may be smaller than the width of the first outer peripheral surface.

[0017] In the frame of (4) above, the width of the first outer peripheral surface is different from the width of the second outer peripheral surface. When the width of the first outer peripheral surface is different from the width of the second outer peripheral surface, it is easy to distinguish the front and back of the frame.

[0018] (5) In the frame of (4) above, the width of the second outer peripheral surface may be 5% or more and 20% or less of the maximum thickness of the frame.

[0019] If the width of the second outer peripheral surface is 5% or more of the maximum thickness of the frame body, the first connecting surface is less likely to be biased toward the second surface. For example, if a step is formed between the first outer peripheral surface, the second outer peripheral surface, and the first connecting surface, if the width of the second outer peripheral surface is 5% or more of the maximum thickness of the frame body, the protruding portion formed by the second outer peripheral surface, the first connecting surface, and the second surface will not be too thin. A protruding portion with a certain thickness is less likely to break. If the width of the second outer peripheral surface is 20% or less of the maximum thickness of the frame body, it is easy to distinguish between the front and back of the frame body.

[0020] (6) In any of the frame bodies described in (1) to (5) above, the first outer peripheral surface may be inclined so as to gradually approach the inner peripheral surface from the point where the first outer peripheral surface and the first connecting surface intersect toward the first surface.

[0021] When the first outer peripheral surface is inclined, a human finger or a robot claw can be easily caught on the first connecting surface. When the first outer peripheral surface is inclined, a space for placing a human finger or a robot claw on the first connecting surface can be easily formed.

[0022] (7) In the frame body according to any one of (1) to (6) above, the first corner may be rounded.

[0023] If the first corners are rounded, the frame bodies are less likely to be damaged even if they come into contact with each other when assembling the cell frame or the laminate.

[0024] (8) In the frame body according to any one of (1) to (7) above, the second corners may be rounded.

[0025] If the second corners are rounded, the frame bodies are less likely to be damaged even if they come into contact with each other when assembling the cell frame or the laminate.

[0026] (9) In the frame body of any one of (1) to (8) above, the first connecting surface may be provided continuously around the entire circumference of the first outer peripheral surface.

[0027] When the first connecting surface is provided continuously around the entire circumference of the first outer peripheral surface, a human finger or a robot's claw can be hooked onto the first connecting surface at any position on the outer periphery of the frame. When the first connecting surface is provided continuously around the entire circumference of the first outer peripheral surface, stress is less likely to concentrate at the intersection between the first outer peripheral surface and the first connecting surface compared to when the first connecting surface is provided only on a portion of the entire circumference of the first outer peripheral surface. Therefore, the protruding portion formed by the first connecting surface is less likely to break.

[0028] (10) The frame of any one of (1) to (9) above may have a notched surface. The inner circumferential surface may be connected to the first surface via the notched surface and a corner portion.

[0029] The frame supports the bipolar plate at the notched surface. When the frame has the notched surface, the bipolar plate can be positioned only at the position of the notched surface.

[0030] (11) A cell frame according to an embodiment of the present disclosure includes a frame body according to any one of (1) to (10) above, and a bipolar plate supported by the frame body.

[0031] The cell frame has excellent assembly properties due to the inclusion of the frame body.

[0032] (12) A battery cell according to an embodiment of the present disclosure includes the cell frame described above in (11).

[0033] The battery cell is excellent in assembling ability due to the cell frame.

[0034] (13) A cell stack according to an embodiment of the present disclosure includes the battery cell according to (12) above.

[0035] The cell stack is easy to assemble because it includes the battery cells.

[0036] (14) A redox flow battery system according to an embodiment of the present disclosure includes the battery cell of (12) above or the cell stack of (13) above.

[0037] The redox flow battery system is easy to assemble because it includes the battery cell or the cell stack.

[0038] [Details of the embodiments of the present disclosure] Specific examples of the frame, cell frame, battery cell, cell stack, and redox flow battery system of the present disclosure will be described with reference to the drawings. The same reference numerals in the drawings indicate the same or equivalent parts. In the drawings, some components may be exaggerated or simplified for ease of explanation. The dimensional ratios of the various parts in the drawings may differ from the actual dimensional ratios. The present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. Hereinafter, redox flow batteries may be referred to as "RF batteries."

[0039] <Frame> The frame 2 of the embodiment will be described with reference to Figures 1A, 1B, 1C, 2, and 3. The frame 2 is a component of the cell frame 1. With reference to Figures 8 and 9, the cell frame 1 is a component of the RF battery system 6, which will be described later. One of the features of the frame 2 is that, as shown in Figure 2, the outer peripheral surface 23 of the frame 2 is provided with a connecting surface 233. Note that the connecting surface 233, the connecting surface 243, and the protrusion 4 are not shown in Figures 1A to 1C. The liquid supply manifolds 25 and 26, the liquid supply slits 25s and 26s, the liquid drain manifolds 27 and 28, the liquid drain slits 27s and 28s, and the seal groove 29 are not shown in Figure 1C.

[0040] The frame 2 has a first surface 21 , a second surface 22 , an outer peripheral surface 23 , and an inner peripheral surface 24 .

[0041] The first surface 21 is the front surface of the frame body 2, and the second surface 22 is the rear surface of the frame body 2, or the first surface 21 is the rear surface of the frame body 2 and the second surface 22 is the front surface of the frame body 2. The battery cell 7, which will be described later, comprises a stack, and the frame body 2 is one of the components of the stack. The first surface 21 and the second surface 22 are each a surface of the stack that faces another frame body that is arranged adjacent to the frame body 2. A through hole 20 is formed in the frame body 2. In this embodiment, the cutout surface 35 has an opening edge of the through hole 20. A portion of the bipolar plate 5, which will be described later, is arranged in the through hole 20. The first surface 21 and the second surface 22 are each flat. The first surface 21 and the second surface 22 are parallel to each other. Adjacent frame bodies 2 are stacked so that the first surface 21 and the second surface 22 face each other.

[0042] The outer peripheral surface 23 forms the outer shape of the frame 2. The outer peripheral surface 23 is connected to the first surface 21 via a first corner 31, and is connected to the second surface 22 via a second corner 32. The inner peripheral surface 24 forms the through hole 20. In this embodiment, the inner peripheral surface 24 is connected to the first surface 21 via a corner and a notched surface 35. The inner peripheral surface 24 is connected to the second surface 22 via the corner. The frame 2 shown in FIG. 1A has a rectangular outer shape, and the shape of the through hole 20 is also rectangular. The outer shape of the frame 2 and the shape of the through hole 20 can be selected as appropriate.

[0043] The frame 2 includes a supply piece 2s and a discharge piece 2d that face each other among the four pieces that make up the rectangular frame 2. In the frame 2 shown in Fig. 1A, the supply piece 2s is located at the bottom and the discharge piece 2d is located at the top.

[0044] The first surface 21 is provided with a supply path and a discharge path for the electrolyte. The supply path is provided in the supply piece 2s, and the discharge path is provided in the discharge piece 2d.

[0045] The supply path of the first surface 21 includes a liquid supply manifold 25 and a liquid supply slit 25s. The liquid supply manifold 25 is a supply port for the electrolyte. The liquid supply manifold 25 penetrates the frame 2 from the first surface 21 to the second surface 22. The liquid supply slit 25s connects the liquid supply manifold 25 to the through-hole 20. The supply path of the first surface 21 may further include a liquid supply rectification unit (not shown). When the liquid supply rectification unit is provided along the inner edge of the first surface 21, the liquid supply slit 25s connects the liquid supply manifold 25 and the liquid supply rectification unit. The liquid supply rectification unit diffuses the electrolyte flowing from the liquid supply slit 25s along the inner edge of the first surface 21. The liquid supply rectification unit may be provided in the bipolar plate 5.

[0046] The discharge path on the first surface 21 includes a discharge manifold 27 and a discharge slit 27s. The discharge manifold 27 is a discharge port for the electrolyte. The discharge manifold 27 penetrates the frame 2 from the first surface 21 to the second surface 22. The discharge slit 27s connects the discharge manifold 27 to the through-hole 20. The discharge path on the first surface 21 may further include a discharge rectification unit (not shown). When the discharge rectification unit is provided along the inner edge of the first surface 21, the discharge slit 27s connects the discharge manifold 27 to the supply rectification unit. The discharge rectification unit collects the electrolyte flowing from the positive electrode 72 or the negative electrode 73 (described later) arranged on the bipolar plate 5 along the inner edge of the first surface 21 and distributes it through the discharge slit 27s. The discharge rectification unit may be provided on the bipolar plate 5.

[0047] The frame 2 further includes a seal groove 29 on the first surface 21. The seal groove 29 is provided continuously around the entire periphery of the frame 2 so as to surround the supply path and discharge path of the electrolyte.

[0048] The second surface 22, like the first surface 21, has a supply path and a discharge path for the electrolyte. The supply path of the second surface 22 includes a liquid supply manifold 26 and a liquid supply slit 26s. The supply path of the second surface 22 may also further include a liquid supply rectification unit (not shown). The discharge path of the second surface 22 includes a liquid drainage manifold 28 and a liquid drainage slit 28s. The discharge path of the second surface 22 may also further include a liquid drainage rectification unit (not shown). In FIG. 1A , the liquid supply slit 26s and the liquid drainage slit 28s are indicated by dashed lines. If the electrolyte flowing through the supply path and the discharge path of the first surface 21 is a positive electrode electrolyte, the electrolyte flowing through the supply path and the discharge path of the second surface 22 is a negative electrode electrolyte. If the electrolyte flowing through the supply path and the discharge path of the first surface 21 is a negative electrode electrolyte, the electrolyte flowing through the supply path and the discharge path of the second surface 22 is a positive electrode electrolyte. The second surface 22 may or may not include a seal groove (not shown).

[0049] The maximum thickness T2 of the frame body 2 is, for example, 3 mm or more and 15 mm or less. The maximum thickness T2 is the maximum length between the first surface 21 and the second surface 22 along a direction perpendicular to the first surface 21. If the maximum thickness T2 is 3 mm or more, the mechanical strength of the frame body 2 is high. If the maximum thickness T2 is 15 mm or less, the battery cell 7 including the frame body 2 (see the upper diagram in FIG. 9 ) and the cell stack 9 including the battery cell 7 (see the lower diagrams in FIGS. 8 and 9 ) are less likely to become large. The maximum thickness T2 may be 4 mm or more and 14 mm or less, or 5 mm or more and 13 mm or less.

[0050] As shown in FIG. 2 , the outer peripheral surface 23 includes a first outer peripheral surface 231, a second outer peripheral surface 232, and a connecting surface 233. The first outer peripheral surface 231 is connected to the first surface 21 via a first corner 31. The second outer peripheral surface 232 is connected to the second surface 22 via a second corner 32. The connecting surface 233 connects the first outer peripheral surface 231 and the second outer peripheral surface 232. The connecting surface 233 has a first connecting surface connected to the first outer peripheral surface 231. The interior angle α1 (see FIG. 3 ) formed between the first connecting surface and the first outer peripheral surface 231 is less than 180°. In this embodiment, the entire connecting surface 233 is the first connecting surface. Therefore, the first connecting surface will be simply referred to as the connecting surface 233.

[0051] The interior angle α1 is the angle between the first outer peripheral surface 231 and the connecting surface 233. As shown in FIG. 3 , the interior angle α1 is an angle formed on the outside of the frame body 2, not on the inside of the frame body 2. FIG. 2 illustrates an example in which the interior angle α1 is an obtuse angle, more specifically, an angle obtained by adding 90° to the inclination angle β1 described below. When the interior angle α1 is an obtuse angle, the connecting surface 233 may be an inclined surface such that the outer peripheral edge of the connecting surface 233 is farther from the first surface 21 than the inner peripheral edge. The interior angle α1 may be an angle other than an obtuse angle, i.e., a right angle or an acute angle. When the interior angle α1 is an acute angle, the connecting surface 233 may be an inclined surface such that, for example, the outer peripheral edge of the connecting surface 233 is closer to the first surface 21 than the inner peripheral edge. The outer peripheral edge of the connecting surface 233 connects the second outer peripheral surface 232 and the connecting surface 233. The inner peripheral edge of the connecting surface 233 connects the first outer peripheral surface 231 and the connecting surface 233. The interior angle α1 may be greater than or equal to 60° and less than or equal to 120°, or greater than or equal to 70° and less than or equal to 110°.

[0052] The connecting surface 233 has an anti-slip function when handling the frame body 2. For example, when assembling the cell frame 1 described below or the laminated body described below, a human finger or a robot's nail can be hooked onto the connecting surface 233. The connecting surface 233 is, for example, a flat surface. If the connecting surface 233 is flat, it is easier to hook a human finger or a robot's nail onto the connecting surface 233 compared to when the connecting surface 233 is a curved surface. The connecting surface 233 is provided so as to form a protruding portion 4 that partially protrudes from the first outer peripheral surface 231.

[0053] The connecting surface 233 is, for example, provided continuously around the entire circumference of the first outer peripheral surface 231. When the connecting surface 233 is provided continuously around the entire circumference of the first outer peripheral surface 231, a human finger or a robot's claw can be hooked onto the connecting surface 233 at any position on the outer circumference of the frame body 2. When the connecting surface 233 is provided continuously around the entire circumference of the first outer peripheral surface 231, stress is less likely to concentrate at the intersection between the first outer peripheral surface 231 and the connecting surface 233 than when the connecting surface 233 is provided only on a portion of the entire circumference of the first outer peripheral surface 231. Therefore, the protruding portion 4 formed by the connecting surface 233 is less likely to break. The connecting surface 233 may be provided only on a portion of the first outer peripheral surface 231. The connecting surface 233 may be provided discontinuously around the entire circumference of the first outer peripheral surface 231. In this case, the protruding portion 4 is provided on a portion of the entire circumference of the first outer peripheral surface 231.

[0054] The second outer peripheral surface 232 is located farther from the inner peripheral surface 24 than the first outer peripheral surface 231. The outer peripheral surface 23 has a step formed between the first outer peripheral surface 231, the second outer peripheral surface 232, and the connecting surface 233. In FIG. 2 , the second outer peripheral surface 232 is higher than the first outer peripheral surface 231, and the first outer peripheral surface 231 is lower than the second outer peripheral surface 232. The protruding portion 4 is formed between the extension of the first outer peripheral surface 231 and the second outer peripheral surface 232. The corners connecting the second outer peripheral surface 232 and the connecting surface 233 may be rounded or may not be rounded as shown in FIG. 2 . The connecting surface 233 is prone to catching a human finger or a robot's nail. Because stress is less likely to concentrate on the connecting surface 233, the protruding portion 4 is less likely to break.

[0055] In FIG. 2 (i.e., in the cross section of the frame 2), the first point P1 is the point on the connecting surface 233 that is closest to the inner circumferential surface 24. The second point P2 is the point on the connecting surface 233 that is farthest from the inner circumferential surface 24. The distance H3 between the first point P1 and the second point P2 is, for example, 1% or more of the maximum thickness T2. In this embodiment, the first point P1 is the point where the first outer circumferential surface 231 and the connecting surface 233 intersect in FIG. 2. In this embodiment, the second point P2 is the point where the second outer circumferential surface 232 and the connecting surface 233 intersect in FIG. 2. If the distance H3 is 1% or more of the maximum thickness T2, it is easy to increase the area of ​​the connecting surface 233. If the area of ​​the connecting surface 233 is large, it is easy for a human finger or a robot's nail to get caught on the connecting surface 233. If the distance H3 is large, it is easy for a human finger or a robot's nail to get caught on the connecting surface 233. The distance H3 may be 1.5% or more, 2% or more, 3% or more, or 4% or more of the maximum thickness T2. When the distance H3 is not constant over the entire outer periphery of the frame body 2, the maximum distance H3 (Max) is simply referred to as the distance H3 in this specification. The distance H3 (Max) is, for example, the maximum distance H3 among the distances H3 in any 10 cross sections of the frame body 2.

[0056] The distance H3 is, for example, 35% or less of the maximum thickness T2. If the distance H3 is 35% or less of the maximum thickness T2, the protruding portion 4 formed by the connecting surface 233 is less likely to break even if a large stress acts on the protruding portion 4. The distance H3 may be 30% or less, 25% or less, or 20% or less of the maximum thickness T2. The distance H3 may be 1% to 35%, 1.5% to 35%, 2% to 30%, 3% to 25%, or 4% to 20% of the maximum thickness T2.

[0057] Distance H3 is, for example, 0.06 mm or more and 2 mm or less. If distance H3 is 0.06 mm or more, a human finger or a robot's nail can easily get caught on connecting surface 233. If distance H3 is 2 mm or less, protruding portion 4 formed by connecting surface 233 is less likely to break even if a large stress acts on protruding portion 4. Distance H3 may be 0.08 mm or more and 1.8 mm or less, 0.10 mm or more and 1.6 mm or less, 0.15 mm or more and 1.5 mm or less, or 0.20 mm or more and 1.5 mm or less.

[0058] In this embodiment, the width W1 of the first outer peripheral surface 231 and the width W2 of the second outer peripheral surface 232 are different. The width W1 is the maximum length from the point where the first outer peripheral surface 231 and the connecting surface 233 intersect to the first surface 21, along a direction perpendicular to the first surface 21. The width W2 is the maximum length from the point where the second outer peripheral surface 232 and the connecting surface 233 intersect to the second surface 22, along a direction perpendicular to the second surface 22. When the widths W1 and W2 are different, it is easy to distinguish between the front and back of the frame body 2. In this embodiment, the width W2 is smaller than the width W1.

[0059] The width W2 is, for example, 5% to 20% of the maximum thickness T2. If the width W2 is 5% or more of the maximum thickness T2, the connecting surface 233 is less likely to be biased toward the second surface 22. If the connecting surface 233 forms a step, if the width W2 is 5% or more of the maximum thickness T2, the protruding portion 4 will not be too thin. A protruding portion 4 with a certain thickness is less likely to break. If the width W2 is 20% or less of the maximum thickness T2, it is easy to distinguish between the front and back of the frame body 2. The width W2 may be 6% to 19%, 6% to 18%, 7% to 16%, or 8% to 15% of the maximum thickness T2.

[0060] The first outer peripheral surface 231 may be inclined so as to gradually approach the inner peripheral surface 24 from the point where the first outer peripheral surface 231 and the connecting surface 233 intersect toward the first surface 21. When the first outer peripheral surface 231 is inclined, a human finger or a robot's claw can easily be caught on the connecting surface 233. When the first outer peripheral surface 231 is inclined, a space for placing a human finger or a robot's claw can easily be formed on the connecting surface 233. The inclination angle β1 of the first outer peripheral surface 231 is, for example, 1° or more and 45° or less. The inclination angle β1 is the angle between the first outer peripheral surface 231 and a plane that is perpendicular to the first surface 21 and perpendicular to the cross section of the frame 2. In this specification, a plane that is perpendicular to the first surface 21 and perpendicular to the cross section of the frame 2 may be simply referred to as a "plane perpendicular to the first surface 21." When the inclination angle β1 is 1° or more, a human finger or a robot's claw can easily be caught on the connecting surface 233. If the inclination angle β1 is 45° or less, the area of ​​the first outer peripheral surface 231 will not become too large, that is, the area of ​​the first surface 21 will not become too small. The inclination angle β1 may be 1.5° or more and 40° or less, 2° or more and 35° or less, or 3° or more and 35° or less.

[0061] The second outer peripheral surface 232 may be inclined so as to gradually become farther away from the inner peripheral surface 24 from the point where the second outer peripheral surface 232 and the connecting surface 233 intersect toward the second surface 22. In this embodiment, the second outer peripheral surface 232 is not parallel to a plane perpendicular to the first surface 21. In this embodiment, the connecting surface 233 is parallel to the first surface 21. The connecting surface 233 does not have to be parallel to the first surface 21.

[0062] In this embodiment, the first corner 31 is rounded. When the first corner 31 is rounded, the frame bodies 2 are less likely to be damaged when they come into contact with each other when assembling the cell frame 1 described below or the laminate described below. The radius of curvature of the first corner 31 is, for example, 0.2 mm or more and 5 mm or less. If the radius of curvature of the first corner 31 is 0.2 mm or more, the frame bodies 2 are less likely to be damaged when they come into contact with each other. If the radius of curvature of the first corner 31 is 5 mm or less, the area of ​​the first surface 21 is likely to be large, and the contact area between the frame bodies 2 is likely to be large. The radius of curvature of the first corner 31 may be 0.3 mm or more and 4 mm or less, or 0.4 mm or more and 3 mm or less.

[0063] The radius of curvature of the first corner 31 is, for example, 1% to 60% of the maximum thickness T2. If the radius of curvature of the first corner 31 is 1% or more of the maximum thickness T2, the frames 2 are less likely to be damaged when they come into contact with each other. If the radius of curvature of the first corner 31 is 60% or less of the maximum thickness T2, the area of ​​the first surface 21 is likely to be large, and the contact area between the frames 2 is likely to be large. The radius of curvature of the first corner 31 may be 2% to 55% or less, or 3% to 50% of the maximum thickness T2.

[0064] In this embodiment, the second corners 32 are rounded. When the second corners 32 are rounded, the frame bodies 2 are less likely to be damaged when they come into contact with each other during assembly of the cell frame 1 or the stack. The radius of curvature of the second corners 32 is, for example, 0.2 mm or more and 5 mm or less. If the radius of curvature of the second corners 32 is 0.2 mm or more, the frame bodies 2 are less likely to be damaged when they come into contact with each other. If the radius of curvature of the second corners 32 is 5 mm or less, the area of ​​the second surface 22 is likely to be large, and the contact area between the frame bodies 2 is likely to be large. The radius of curvature of the second corners 32 may be 0.3 mm or more and 4 mm or less, or 0.4 mm or more and 3 mm or less. Depending on the radius of curvature of the second corners 32, the entire second outer peripheral surface 232 may be the second corners 32.

[0065] The radius of curvature of the second corner portion 32 is, for example, 1% to 60% of the maximum thickness T2. If the radius of curvature of the second corner portion 32 is 1% or more of the maximum thickness T2, the frames 2 are less likely to be damaged when they come into contact with each other. If the radius of curvature of the second corner portion 32 is 60% or less of the maximum thickness T2, the area of ​​the second surface 22 is likely to be large, and the contact area between the frames 2 is likely to be large. The radius of curvature of the second corner portion 32 may be 2% to 55% or 3% to 50% of the maximum thickness T2.

[0066] Like the outer peripheral surface 23, the inner peripheral surface 24 of this embodiment includes a first inner peripheral surface 241, a second inner peripheral surface 242, and a connecting surface 243. The frame 2 of this embodiment includes a cutout surface 35, which will be described later. In this embodiment, the cutout surface 35 is composed of a surface parallel to the first surface 21 and a surface perpendicular to the first surface 21. In other words, a step portion is formed in the frame 2. The first inner peripheral surface 241 is connected to the first main surface 21 via the cutout surface 35 and a corner. The second inner peripheral surface 242 is connected to the second surface 22 via a corner. The connecting surface 243 connects the first inner peripheral surface 241 and the second inner peripheral surface 242. The connecting surface 243 has a first inner peripheral connecting surface that is connected to the first inner peripheral surface 241. The interior angle formed by the first inner peripheral connecting surface and the first inner peripheral surface 241 is less than 180°. In this embodiment, the entire connecting surface 243 is the first inner connecting surface. Therefore, the first inner connecting surface is simply referred to as the connecting surface 243. When the frame 2 does not have the notched surface 35, the first inner connecting surface 241 is connected to the first surface 21 via the corner.

[0067] FIG. 2 illustrates an example in which the interior angle between the first inner circumferential surface 241 and the connecting surface 243 is an obtuse angle, specifically, an angle obtained by adding the inclination angle of the first inner circumferential surface 241 to 90°. When this interior angle is an obtuse angle, the connecting surface 243 may be an inclined surface such that the inner circumferential edge of the connecting surface 243 is farther from the first surface 21 than the outer circumferential edge. The interior angle between the first inner circumferential surface 241 and the connecting surface 243 may be other than an obtuse angle, i.e., a right angle or an acute angle. When this interior angle is an acute angle, for example, the connecting surface 243 may be an inclined surface such that the inner circumferential edge of the connecting surface 243 is closer to the first surface 21 than the outer circumferential edge. The inner circumferential edge of the connecting surface 243 connects the second inner circumferential surface 242 and the connecting surface 243. The outer circumferential edge of the connecting surface 243 connects the first inner circumferential surface 241 and the connecting surface 243. The interior angle formed between the first inner circumferential surface 241 and the connecting surface 243 may be equal to or greater than 60° and equal to or less than 120°, or may be equal to or greater than 70° and equal to or less than 110°. The interior angle formed between the first inner circumferential surface 241 and the connecting surface 243 may be the same as or different from the interior angle α1 (see FIG. 3 ) formed between the first outer circumferential surface 231 and the connecting surface 233.

[0068] Like the connecting surface 233, the connecting surface 243 also functions as an anti-slip surface when handling the frame body 2. The connecting surface 243 is, for example, a flat surface. If the connecting surface 243 is a flat surface, it is easier for a human finger or a robot's claw to catch on the connecting surface 243 compared to a curved surface. The connecting surface 243 is provided so as to form a protruding portion 4 that partially protrudes from the first inner circumferential surface 241.

[0069] The coupling surface 243 may be provided continuously around the entire circumference of the first inner circumferential surface 241. When the coupling surface 243 is provided continuously around the entire circumference of the first inner circumferential surface 241, a non-slip surface is provided around the entire circumference of the inner circumferential surface 24. Therefore, a human finger or a robot's claw can hook onto the coupling surface 243 at any position on the inner circumferential surface 24. The coupling surface 243 may be provided only on a portion of the entire circumference of the first inner circumferential surface 241. The coupling surface 243 may be provided discontinuously around the entire circumference of the first inner circumferential surface 241.

[0070] The second inner circumferential surface 242 is located farther from the outer circumferential surface 23 than the first inner circumferential surface 241. A step is formed on the inner circumferential surface 24 between the first inner circumferential surface 241, the second inner circumferential surface 242, and the connecting surface 243. A protruding portion 4 is formed in the portion between the extension surface of the first inner circumferential surface 241 and the second inner circumferential surface 242. The corner connecting the second inner circumferential surface 242 and the connecting surface 243 may be rounded or may not be rounded as shown in FIG. 2 .

[0071] In FIG. 2 (i.e., in the cross section of the frame 2), the third point P3 is the point on the connecting surface 243 that is closest to the outer peripheral surface 23. The fourth point P4 is the point that is farthest from the outer peripheral surface 23. The distance between the third point P3 and the fourth point P4 is, for example, 1% to 35% of the maximum thickness T2. The distance may be 1.5% to 35%, 2% to 30%, 3% to 25%, or 4% to 20% of the maximum thickness T2. If the distance H4 is not constant throughout the entire inner circumference of the frame 2, the maximum distance H4(Max) among the distances H4 in any 10 cross sections of the frame 2 is simply referred to as the distance H4 in this specification. The distance H4(Max) is, for example, the maximum distance H4 among the distances H4 in any 10 cross sections of the frame.

[0072] The width of the second inner circumferential surface 242 is, for example, 5% to 20% of the maximum thickness T2. The width of the second inner circumferential surface 242 may be 6% to 19%, 6% to 18%, 7% to 16%, or 8% to 15% of the maximum thickness T2.

[0073] 2 , the first inner circumferential surface 241 may be inclined so as to gradually approach the outer circumferential surface 23 from the point where the first inner circumferential surface 241 and the connecting surface 243 intersect toward the first surface 21. The second inner circumferential surface 242 may be inclined so as to gradually move away from the outer circumferential surface 23 from the point where the second inner circumferential surface 242 and the connecting surface 243 intersect toward the second surface 22.

[0074] When the inner circumferential surface 24 includes the connecting surface 243, the distance from the second surface to the connecting surface 233 along the thickness direction of the frame body 2 may be the same as the distance from the second surface to the connecting surface 243. In Figure 2, the line connecting the connecting surface 233 and the connecting surface 243 is indicated by a dashed line. Unlike Figure 2, the distance from the second surface to the connecting surface 233 along the thickness direction of the frame body 2 may be different from the distance from the second surface to the connecting surface 243.

[0075] In this embodiment, the frame 2 has a notched surface 35 between the first surface 21 and the inner circumferential surface 24. The frame 2 supports the bipolar plate 5, which will be described later, at the notched surface 35. The notched surface 35 forms a stepped portion into which the bipolar plate 5 is fitted. By fitting the bipolar plate 5 into this stepped portion, the bipolar plate 5 can be positioned only at the position of the notched surface 35 of the frame 2.

[0076] The corners connecting the first inner circumferential surface 241 and the cutout surface 35 may be rounded. The corners connecting the second inner circumferential surface 242 and the second surface 22 may be rounded.

[0077] The frame 2 is made of an electrically insulating material, such as a resin such as a thermoplastic resin. Specific examples of the electrically insulating material include vinyl chloride, polypropylene, polyethylene, fluororesin, epoxy, acrylonitrile butadiene styrene, vinylidene chloride, polyamide, polyester, polystyrene, acrylic, polyvinyl alcohol, diacetate, triacetate, and polycarbonate. The frame 2 is, for example, an injection-molded product.

[0078] <<Modification 1>> As shown in Figure 4, the width W1 of the first outer peripheral surface 231 may be the same as the width W2 of the second outer peripheral surface 232. The basic configuration of Modification 1 is the same as the basic configuration of the above-described embodiment, except that the width W1 is the same as the width W2. The connecting surface 233 is located at a position that bisects the maximum thickness T2 of the frame body 2, and the width W2 of the second outer peripheral surface 232 is larger than in the above-described embodiment. Therefore, the width W2 of the protruding portion 4 is larger. Therefore, in the frame body 2 of Modification 1, the protruding portion 4 is less likely to break even if a large stress acts on the protruding portion 4.

[0079] <<Modification 2>> As shown in Fig. 5, the first outer peripheral surface 231 may not be inclined, but may be a plane perpendicular to the first surface 21. The basic configuration of Modification 2 is the same as the basic configuration of the above-described embodiment, except that the inclination angle β1 is zero. The interior angle α1 (see Fig. 3) formed between the first outer peripheral surface 231 and the connecting surface 233 in Modification 2 is smaller than the interior angle α1 in the embodiment. The interior angle α1 in Modification 2 is a right angle. The first outer peripheral surface 231 may be a plane perpendicular to the first surface 21, and the width W1 and width W2 may be the same, as shown in Fig. 4.

[0080] <<Modification 3>> As shown in Fig. 6 , the inner circumferential surface 24 does not have to include the connecting surface 243. The basic configuration of Modification 3 is the same as the basic configuration of the above-described embodiment, except that the inner circumferential surface 24 does not include the connecting surface 243. The inner circumferential surface 24 of Modification 3 is a flat surface perpendicular to the first surface 21. If the inner circumferential surface 24 does not include the connecting surface 243, the entire surface of the inner circumferential surface 24 is likely to come into contact with the bipolar plate 5.

[0081] <<Modification 4>> As shown in FIG. 7 , the first outer peripheral surface 231 and the second outer peripheral surface 232 may be planes extending in the thickness direction of the frame body 2 and arranged side by side on the same plane. In this case, the first outer peripheral surface 231 is connected to the second outer peripheral surface 232 via a plurality of connecting surfaces 233. The connecting surfaces 233 include a first connecting surface 233a, a second connecting surface 233b, and a third connecting surface 233c. The first connecting surface 233a is connected to the first outer peripheral surface 231. The interior angle α1 between the first connecting surface 233a and the first outer peripheral surface 231 is less than 180°. The second connecting surface 233b is connected to the second outer peripheral surface 232. The interior angle between the second connecting surface 233b and the second outer peripheral surface 232 is also less than 180°. The third connecting surface 233c connects the first connecting surface 233a and the second connecting surface 233b.

[0082] The first connecting surface 233a, the second connecting surface 233b, and the third connecting surface 233c constitute the protruding portion 4. The protruding portion 4 in FIG. 7 is exaggerated for clarity. In Modification 4, the distance H3 is, for example, 1% or more of the maximum thickness T2. The method for calculating the distance H3 is the same as that in the above-described embodiment. In Modification 4, in FIG. 7, the first point P1 is the point where the first outer peripheral surface 231 intersects with the first connecting surface 233a, and the second point P2 is the point where the first connecting surface 233a intersects with the third connecting surface 233c. Alternatively, in FIG. 7, the first point P1 is the point where the second outer peripheral surface 232 intersects with the second connecting surface 233b, and the second point P2 is the point where the third connecting surface 233c intersects with the second connecting surface 233b. If the distance H3 is 1% or more of the maximum thickness T2, it is easy to increase the area of ​​the first connecting surface 233a and the second connecting surface 233b. If the areas of the first connecting surface 233a and the second connecting surface 233b are large, a human finger or a robot's nail is easily caught on the first connecting surface 233a or the second connecting surface 233b. If the distance H3 is large, a human finger or a robot's nail is easily caught on the first connecting surface 233a or the second connecting surface 233b. The range of the distance H3 in the fourth modification may be the same as the range of the distance H3 in the above-described embodiment. Each of the first connecting surface 233a, the second connecting surface 233b, and the third connecting surface 233c is flat. The cross-sectional shape of the protruding portion 4 is rectangular. The first connecting surface 233a and the second connecting surface 233b may be directly connected. In this case, the third connecting surface 233c is absent, and the cross-sectional shape of the protruding portion 4 is triangular. The protruding portion 4 is provided at a position spaced apart from both the first surface 21 and the second surface 22 .

[0083] 7, the protruding portion 4 is disposed at a position that bisects the maximum thickness T2 of the frame 2. In other words, the width of the first outer peripheral surface 231 is the same as the width of the second outer peripheral surface 232. The width of the protruding portion 4 is smaller than the width of the first outer peripheral surface 231 and the width of the second outer peripheral surface 232. The width of the protruding portion 4 may be within the range of the width W2 of the second outer peripheral surface 232 in the above-described embodiment.

[0084] The basic configuration of Modification 4 is the same as that of the above-described embodiment, except for the shape of the protruding portion 4 and the fact that the inclination angle β1 is zero. The inner circumferential surface may have a protruding portion 4 similar to that of the outer circumferential surface 23, or the protruding portion 4 of the inner circumferential surface 24 shown in FIG. 2, or may have no protruding portion 4 as shown in FIG. 6. The frame 2 of Modification 4 has multiple connecting surfaces 233, particularly a first connecting surface 233a and a second connecting surface 233b. Therefore, a human finger or a robot's claw can be hooked on either the front or back of the frame 2.

[0085] <Cell Frame> As shown in FIGS. 1A and 2 , the cell frame 1 includes a frame 2 and a bipolar plate 5. The frame 2 supports the outer peripheral edge of the bipolar plate 5. The bipolar plate 5 is arranged to cover the through-hole 20 of the frame 2. In this embodiment, a portion of the bipolar plate 5 is fitted into the through-hole 20. In this embodiment, the bipolar plate 5 includes a thin-walled portion 51. The thin-walled portion 51 is arranged on the cutout surface 35, and the frame 2 supports the thin-walled portion 51. The thin-walled portion 51 is thinner than the other portions of the bipolar plate 5. The cell frame 1 may be formed by injection molding the frame 2 around the outer periphery of the bipolar plate 5.

[0086] The thickness of the bipolar plate 5 is thinner than the maximum thickness T2 of the frame 2. When the bipolar plate 5 is placed in the through-hole 20 of the frame 2, a space is formed between a portion of the notched surface 35 of the frame 2 and the surface of the bipolar plate 5, and a space is also formed between a portion of the inner circumferential surface 24 of the frame 2 and the surface of the bipolar plate 5. That is, a space is formed between a portion of the notched surface 35 and the first surface of the bipolar plate 5, and a space is also formed between a portion of the inner circumferential surface 24 and the second surface of the bipolar plate 5. A positive electrode 72 is placed in the space formed by the notched surface 35 and the first surface of the bipolar plate 5. A negative electrode 73 is placed in the space formed by the inner circumferential surface 24 of the frame 2 and the second surface of the bipolar plate 5. In FIG. 2 , the positive electrode 72 and the negative electrode 73 are indicated by two-dot chain lines. A negative electrode 73 may be arranged in the space formed by the cutout surface 35 and the first surface of the bipolar plate 5, and a positive electrode 72 may be arranged in the space formed by the inner surface 24 and the second surface of the bipolar plate 5.

[0087] <RF Battery System> An RF battery system 6 according to an embodiment will be described with reference to Figures 8 and 9. The RF battery system 6 is one type of electrolyte circulation type storage battery system. The RF battery system 6 includes battery cells 7 and a circulation mechanism 8 that circulates electrolyte through the battery cells 7. The RF battery system 6 charges and discharges while supplying electrolyte to the battery cells 7. For ease of explanation, the connecting surface 233 of the frame 2 is not shown in Figures 8 and 9.

[0088] Typically, the RF battery system 6 is connected to an AC / DC converter 100, which is connected to a substation 120, which is connected to a power generation unit 110 and a load 130. The RF battery system 6 charges the power generation unit 110 as a power supply source and discharges the power from the load 130. The power generation unit 110 is, for example, a solar power generator, a wind power generator, or other generators installed in a general power plant. The load 130 is, for example, a power grid or a power consumer. The RF battery system 6 is used, for example, for load leveling, voltage drop compensation, or output smoothing of natural energy power generation. The RF battery system 6 can also be used as an emergency power source.

[0089] <Battery Cell> As shown in Fig. 8 , the battery cell 7 is separated into a positive electrode cell 7P and a negative electrode cell 7N by a diaphragm 71. A positive electrode 72 is built into the positive electrode cell 7P. A positive electrode electrolyte is circulated through the positive electrode cell 7P. The positive electrode 72 is a reaction field where the active material contained in the positive electrode electrolyte undergoes a battery reaction. A negative electrode 73 is built into the negative electrode cell 7N. A negative electrode electrolyte is circulated through the negative electrode cell 7N. The negative electrode 73 is a reaction field where the active material contained in the negative electrode electrolyte undergoes a battery reaction. The diaphragm 71 is, for example, an ion exchange membrane.

[0090] As shown in the upper diagrams of Figures 8 and 9 , the battery cell 7 comprises a stack of a cell frame 1, a positive electrode 72, a diaphragm 71, a negative electrode 73, and another cell frame 1 stacked in this order. In each cell frame 1, the positive electrode 72 is disposed on a first surface of the bipolar plate 5, and the negative electrode 73 is disposed on a second surface of the bipolar plate 5. One battery cell 7 is formed between the bipolar plates 5 of two adjacent cell frames 1. An annular sealing member 75 is disposed between the frames 2. The sealing member 75 is disposed in a sealing groove 29 provided in the first surface 21. The sealing member 75 makes it difficult for electrolyte to leak from the battery cell 7.

[0091] <Cell Stack> Battery cells 7 are typically arranged inside a structure called a cell stack 9. As shown in the lower diagram of FIG. 9 , the cell stack 9 includes a substack 9S, two end plates 92, and a clamping mechanism 93. The cell stack 9 includes, for example, multiple substacks 9S. Each substack 9S includes a stack and two supply / discharge plates 91. As shown in the upper diagrams of FIGS. 8 and 9 , the stack includes a cell frame 1, a positive electrode 72, a diaphragm 71, a negative electrode 73, and another cell frame 1 stacked in this order. As shown in the lower diagram of FIG. 9 , the supply / discharge plates 91 are disposed at both ends of the stack. A supply pipe 84 and a discharge pipe 86 of a positive electrode circulation mechanism 8P, and a supply pipe 85 and a discharge pipe 87 of a negative electrode circulation mechanism 8N, which will be described later, are connected to the supply / discharge plates 91. The multiple substacks 9S are sandwiched between the two end plates 92. The clamping mechanism 93 clamps the two end plates 92 so that they approach each other.

[0092] 8, the circulation mechanism 8 includes a positive electrode circulation mechanism 8P and a negative electrode circulation mechanism 8N. The positive electrode circulation mechanism 8P circulates the positive electrode electrolyte through the positive electrode cell 7P. The negative electrode circulation mechanism 8N circulates the negative electrode electrolyte through the negative electrode cell 7N.

[0093] The positive electrode circulation mechanism 8P includes a positive electrode electrolyte tank 82, a supply pipe 84, a discharge pipe 86, and a pump 88. The positive electrode electrolyte tank 82 stores positive electrode electrolyte. The supply pipe 84 and the discharge pipe 86 connect the positive electrode electrolyte tank 82 and the positive electrode cell 7P. The pump 88 is provided midway along the supply pipe 84 and pressure-feeds the positive electrode electrolyte in the positive electrode electrolyte tank 82 to the positive electrode cell 7P. The positive electrode electrolyte is supplied from the positive electrode electrolyte tank 82 through the supply pipe 84 to the positive electrode cell 7P and is returned from the positive electrode cell 7P through the discharge pipe 86 to the positive electrode electrolyte tank 82. Specifically, the positive electrode electrolyte that has passed through the supply pipe 84 is supplied to the positive electrode 72 from the liquid supply manifold 25 shown in the upper diagram of FIG. 9 through the liquid supply slit 25s. The positive electrode electrolyte supplied to the positive electrode 72 flows from the bottom to the top of the positive electrode 72, as indicated by the arrows in the upper diagram of FIG. 9 . The positive electrode electrolyte that has flowed through the positive electrode 72 passes through the drain slit 27 s and is discharged from the drain manifold 27 to the discharge pipe 86 .

[0094] The anode circulation mechanism 8N includes an anode electrolyte tank 83, a supply pipe 85, a discharge pipe 87, and a pump 89. The anode electrolyte tank 83 stores the anode electrolyte. The supply pipe 85 and the discharge pipe 87 connect the anode electrolyte tank 83 and the anode cell 7N. The pump 89 is provided midway through the supply pipe 85 and pressure-feeds the anode electrolyte in the anode electrolyte tank 83 to the anode cell 7N. The anode electrolyte is supplied from the anode electrolyte tank 83 through the supply pipe 85 to the anode cell 7N and is returned from the anode cell 7N through the discharge pipe 87 to the anode electrolyte tank 83. Specifically, the anode electrolyte that has passed through the supply pipe 85 is supplied to the anode electrode 73 from the liquid supply manifold 26 and through the liquid supply slit 26s shown in the upper diagram of FIG. 9 . The negative electrode electrolyte supplied to the negative electrode 73 flows from the lower end to the upper end of the negative electrode 73 as shown by the arrows in the upper diagram of Fig. 9. The negative electrode electrolyte that has flowed through the negative electrode 73 passes through the drainage slit 28s and is discharged from the drainage manifold 28 to the discharge pipe 87.

[0095] The positive electrode electrolyte is circulated to the positive electrode cell 7 P, and the negative electrode electrolyte is circulated to the negative electrode cell 7 N. The battery cell 7 is charged and discharged in accordance with the valence change reaction of the active material ions in the positive electrode electrolyte and the negative electrode electrolyte.

[0096] The active material contained in the positive electrode electrolyte, the solvent for the positive electrode electrolyte, the active material contained in the negative electrode electrolyte, and the solvent for the negative electrode electrolyte are not particularly limited. The active material for the positive electrode electrolyte is, for example, one or more selected from the group consisting of vanadium ions, manganese ions, iron ions, polyacids, quinone derivatives, amines, and organometallic complexes. The active material for the negative electrode electrolyte is, for example, one or more selected from the group consisting of vanadium ions, titanium ions, chromium ions, polyacids, quinone derivatives, amines, and organometallic complexes. Both the positive electrode electrolyte and the negative electrode electrolyte may contain vanadium ions. The solvent for the positive electrode electrolyte and the negative electrode electrolyte is, for example, an aqueous solution containing one or more acids or acid salts selected from the group consisting of sulfuric acid, phosphoric acid, nitric acid, and hydrochloric acid.

[0097] DESCRIPTION OF SYMBOLS 1 Cell frame 2 Frame body 2s Supply piece 2d Discharge piece 20 Through hole 21 First surface 22 Second surface 23 Outer peripheral surface 231 First outer peripheral surface 232 Second outer peripheral surface 233 Connecting surface 233a First connecting surface 233b Second connecting surface 233c Third connecting surface 24 Inner peripheral surface 241 First inner peripheral surface 242 Second inner peripheral surface 243 Connecting surface 25, 26 Liquid supply manifold 25s, 26s Liquid supply slit 27, 28 Liquid discharge manifold 27s, 28s Liquid discharge slit 29 Seal groove 31 First corner portion 32 Second corner portion 35 Notched surface 4 Protruding portion 5 Bipolar plate 51 Thin portion 6 RF battery system (redox flow battery system) 7 Battery cell 7P Positive electrode cell 7N Negative electrode cell 71 Diaphragm 72 Positive electrode 73 Negative electrode 75 Seal member 8 Circulation mechanism 8P Positive electrode circulation mechanism 8N Negative electrode circulation mechanism 82 Positive electrode electrolyte tank 83 Negative electrode electrolyte tank 84, 85 Supply pipe 86, 87 Discharge pipe 88, 89 Pump 9 Cell stack 9S Substack 91 Supply and discharge plate 92 End plate 93 Fastening mechanism 100 AC / DC converter 110 Power generation unit 120 Substation equipment 130 Load T2 Maximum thickness W1, W2 Width H3 Distance H4 Distance α1 Interior angle β1 Tilt angle P1 First point P2 Second point P3 Third point P4 Fourth point

Claims

1. A frame used for the self-frame of a battery cell, comprising a first surface, a second surface opposite to the first surface, an outer peripheral surface, and an inner peripheral surface, wherein the outer peripheral surface comprises a first outer peripheral surface extending to the first surface through a first corner, a second outer peripheral surface extending to the second surface through a second corner, and a connecting surface connecting the first outer peripheral surface and the second outer peripheral surface, the connecting surface has a first connecting surface extending to the first outer peripheral surface, and an inner angle formed by the first connecting surface and the first outer peripheral surface is less than 180°, the frame.

2. The frame according to claim 1, wherein the second outer peripheral surface is located farther from the inner peripheral surface than the first outer peripheral surface.

3. In a cross-section of the frame perpendicular to the first surface and the first outer peripheral surface, at the connecting surface, a point closest to the inner peripheral surface is a first point, a point farthest from the inner peripheral surface is a second point, and a distance between the first point and the second point is 1% or more of the maximum thickness of the frame, the frame according to claim 1 or claim 2.

4. The frame according to any one of claims 1 to 3, wherein a width of the second outer peripheral surface is smaller than a width of the first outer peripheral surface.

5. The frame according to claim 4, wherein the width of the second outer peripheral surface is 5% or more and 20% or less of the maximum thickness of the frame.

6. The frame according to any one of claims 1 to 5, wherein the first outer peripheral surface is inclined so as to gradually approach the inner peripheral surface as it extends from a point where the first outer peripheral surface intersects the first connecting surface toward the first surface.

7. The frame according to any one of claims 1 to 6, wherein the first corner is rounded.

8. The frame according to any one of claims 1 to 7, wherein the second corner is rounded.

9. The frame according to any one of claims 1 to 8, wherein the first connecting surface is continuously provided over the entire circumference of the first outer peripheral surface.

10. Comprising a notch surface, wherein the inner peripheral surface extends to the first surface through the notch surface and a corner, the frame according to any one of claims 1 to 9.

11. A self-frame comprising the frame according to any one of claims 1 to 10 and a bipolar plate supported by the frame.

12. A battery cell comprising the self-frame according to claim 11.

13. A cell stack comprising the battery cell according to claim 12.

14. A redox flow battery system comprising the battery cell according to claim 12, or the cell stack according to claim 13.

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