CN113574706B

CN113574706B - Bipolar plate, battery cell, battery pack and redox flow battery

Info

Publication number: CN113574706B
Application number: CN202080021101.0A
Authority: CN
Inventors: 中石博之; 桑原雅裕; 津岛荣树
Original assignee: Sumitomo Electric Industries Ltd
Current assignee: Sumitomo Electric Industries Ltd
Priority date: 2019-04-24
Filing date: 2020-04-23
Publication date: 2024-03-29
Anticipated expiration: 2040-04-23
Also published as: WO2021215030A1; WO2020218418A1; CN115443563A; JPWO2021215030A1; TW202109958A; CN113574706A

Abstract

A bipolar plate for a redox flow battery, wherein the bipolar plate comprises a conductive material and a resin, and the bipolar plate has a distribution in which the resin content is different in at least one of a direction along a surface of the bipolar plate and a thickness direction of the bipolar plate.

Description

Bipolar plate, battery cell, battery pack and redox flow battery

Technical Field

The present disclosure relates to a bipolar plate, a battery cell, a battery pack, and a redox flow battery.

The present application claims priority from japanese patent application publication No. 2019-082517 on 24 th 2019 04 month and priority from japanese patent application publication No. 2019-082518 on 24 th 2019 04 month, and the entire contents of the descriptions of the japanese applications are incorporated by reference.

Background

As one of the secondary batteries, there is a redox flow battery. Redox flow batteries typically include a stack of one or more positive electrode, separator, and negative electrode arranged in that order. As illustrated in fig. 10 of patent document 1 and fig. 8 of patent document 2, one of the above-mentioned laminates is sandwiched by a group of battery cell frames. The cell frames sandwiching the laminate are fastened at a predetermined pressure. The laminate is maintained in a laminated state by the fastening force.

The battery cell frame includes a bipolar plate and a frame body. In a redox flow battery including a plurality of the above-described laminates, a positive electrode to which a positive electrolyte is supplied is disposed on a first surface of two surfaces of a bipolar plate. A negative electrode to which a negative electrolyte is supplied is disposed on the second surface of the bipolar plate. The frame is supported in a region of the bipolar plate on the outer edge side where the positive electrode and the negative electrode are not arranged. The frame is also used to supply an electrolyte solution or the like to each of the positive electrode and the negative electrode.

For example, a molded body made of a composite material as described in patent documents 1 to 4 is used as the bipolar plate. The composite material is a material obtained by mixing a thermoplastic resin with a powder made of a carbon-based material such as graphite.

Prior art literature

Patent literature

Patent document 1: international publication No. 2016/072192

Patent document 2: japanese patent laid-open No. 2002-367558

Patent document 3: japanese patent laid-open publication No. 2011-228059

Patent document 4: japanese patent application laid-open No. 2012-221775

Disclosure of Invention

The bipolar plate of the present disclosure is used for a redox flow battery, wherein the bipolar plate includes a conductive material and a resin, and the bipolar plate has a distribution in which the resin content is different in at least one of a direction along a surface of the bipolar plate and a thickness direction of the bipolar plate.

The battery cell of the present disclosure is provided with the bipolar plate of the present disclosure.

The battery pack of the present disclosure is provided with a plurality of battery cells of the present disclosure.

The redox flow battery of the present disclosure is provided with the battery cell of the present disclosure or the battery pack of the present disclosure.

Drawings

Fig. 1 is an explanatory diagram schematically showing the basic structure of a redox flow battery of the embodiment.

Fig. 2 is a perspective view schematically showing a battery cell according to an embodiment and a battery pack according to an embodiment.

Fig. 3 is a perspective view schematically showing a bipolar plate according to embodiment 1.

Fig. 4A is a cross-sectional view showing an example of a state in which the bipolar plate shown in fig. 3 is cut at an IV-IV cut line.

Fig. 4B is a cross-sectional view showing another example of the state of cutting the bipolar plate shown in fig. 3 at an IV-IV cut line.

Fig. 5 is a perspective view schematically showing a bipolar plate according to embodiment 2.

Fig. 6 is a perspective view schematically showing a bipolar plate according to embodiment 3.

Fig. 7 is a perspective view schematically showing a bipolar plate according to embodiment 4.

Fig. 8 is a perspective view schematically showing a bipolar plate according to embodiment 5.

Fig. 9 is a perspective view schematically showing a bipolar plate according to embodiment 6.

Fig. 10 is a partial cross-sectional view schematically showing a state of the bipolar plate of embodiment 7 in a plane parallel to the thickness direction of the bipolar plate.

Fig. 11 is a plan view showing a bipolar plate according to embodiment 1.

Fig. 12 is a plan view showing a battery cell frame including the bipolar plate according to embodiment 1.

Fig. 13 is a partial sectional view showing a state in which the battery cell frame shown in fig. 12 is cut at a XIII-XIII cut line.

Fig. 14 is a graph showing an example of a spectrum of fourier transform infrared spectroscopy (FT-IR) for the surface of the surface layer portion and the first region in the bipolar plate of the embodiment having the surface layer portion.

Fig. 15 is a plan view showing an example of a battery cell frame provided with a bipolar plate according to an embodiment, the bipolar plate having a surface layer portion.

Fig. 16 is a plan view illustrating the battery cell frame shown in fig. 15 as being decomposed into a bipolar plate and a frame body.

Fig. 17A is a partial cross-sectional view showing an example of a state in which the battery cell frame shown in fig. 15 is cut at a section line XVII-XVII.

Fig. 17B is a partial sectional view showing another example of the state in which the battery cell frame shown in fig. 15 is cut at the section line XVII-XVII.

Fig. 18 is a partial cross-sectional view showing a state in which a portion near the outer edge is cut in a plane parallel to the thickness direction of a bipolar plate in a cell frame including still another example of the bipolar plate of the embodiment, the bipolar plate including a surface layer portion.

Fig. 19 is a plan view showing an example of a bipolar plate according to an embodiment and including flow channels.

Fig. 20 is a plan view showing another example of the bipolar plate according to the embodiment, in which the bipolar plate is provided with flow channels.

Fig. 21 is a plan view showing still another example of the bipolar plate according to the embodiment, in which the bipolar plate is provided with flow channels.

Fig. 22 is a diagram schematically showing a first step in the method for manufacturing the bipolar plate.

Fig. 23 is a diagram showing a second step in the method for manufacturing a bipolar plate.

Fig. 24 is a diagram showing a third step and a fourth step in the method for manufacturing a bipolar plate.

Fig. 25 is a diagram showing an example of a fifth step in the method for manufacturing a bipolar plate.

Fig. 26 is a diagram showing a third step and a fourth step in the case of manufacturing a bipolar plate having a surface layer portion in the method of manufacturing a bipolar plate.

Detailed Description

[ problem to be solved by the present disclosure ]

A bipolar plate excellent in mechanical strength is desired.

For example, in the battery cell frame described in patent document 1, a sealing member such as an O-ring is provided between the frame and a region on the outer edge side of the bipolar plate. The tightening force is adjusted so that the sealing member generates a predetermined pressure, i.e., a sealing pressure.

If the tightening force is large, a predetermined sealing pressure can be satisfied. However, if the tightening force is large, the stress carried by the region on the outer edge side of the bipolar plate also becomes large. If the stress is large, a case is considered in which cracking occurs in the region on the outer edge side of the bipolar plate. When the number of the laminated products, that is, the number of laminated products is large, the tightening force tends to be large. Therefore, the occurrence of the above-mentioned cracking is more of a concern. If the mechanical strength of the bipolar plate is high, cracking is less likely to occur in the bipolar plate even if the tightening force is large. The redox flow battery is excellent in sealability if the bipolar plate is not cracked.

Further, a bipolar plate having a low contact resistance with the electrode is desired.

Accordingly, it is an object of the present disclosure to provide a bipolar plate having excellent mechanical strength. Another object of the present disclosure is to provide a battery cell, a battery pack, and a redox flow battery each including a bipolar plate having excellent mechanical strength.

[ Effect of the present disclosure ]

The bipolar plate of the present disclosure is excellent in mechanical strength. In the battery cell, the battery pack and the redox flow battery of the present disclosure, the mechanical strength of the bipolar plate is excellent.

[ description of embodiments of the present disclosure ]

First, embodiments of the present disclosure will be described.

(1) One aspect of the present disclosure relates to a bipolar plate for a redox flow battery, wherein the bipolar plate includes a conductive material and a resin, and the bipolar plate has a distribution in which the resin content is different in at least one of a direction along a surface of the bipolar plate and a thickness direction of the bipolar plate.

Hereinafter, the redox flow battery may be referred to as an RF battery.

Here, when the bipolar plate is made of the composite material, a conductive material such as carbon powder in the composite material is uniformly mixed to form a molded body having uniform conductivity. In a conventional bipolar plate made of such a composite material, the resin content is the same in both directions along the surface of the bipolar plate and in the thickness direction of the bipolar plate. That is, in the above-described conventional bipolar plate, the resin content in the region where the electrode is disposed at the center is the same as the resin content in the region where the electrode is not disposed at the outer edge side. As a result, the central region and the outer edge region have no difference in mechanical strength. Therefore, when an external force such as a large tightening force is applied to the region on the outer edge side, a crack may occur in the region on the outer edge side.

As a typical embodiment of the bipolar plate of the present disclosure, there is an embodiment in which the resin content in the region on the outer edge side of the bipolar plate is higher than the resin content in the region in the center where the electrode is arranged. In the bipolar plate of the present disclosure, the mechanical strength of the region on the outer edge side is superior to that of the conventional bipolar plate. Even if an external force such as a large fastening force is applied to the region on the outer edge side as described above, occurrence of cracking in the region on the outer edge side is suppressed.

If the region on the outer edge side is less likely to crack, the positive electrode electrolyte flowing through the first surface side of the bipolar plate is typically prevented from being mixed with the negative electrode electrolyte flowing through the second surface side of the bipolar plate via the crack. Such a bipolar plate of the present disclosure can construct an RF battery excellent in sealability.

As another embodiment of the bipolar plate of the present disclosure, a multilayer structure in which a plurality of layers are laminated in the thickness direction of the bipolar plate as described below is given. For example, a bipolar plate is a three-layer structure having two surface layers and one intermediate layer sandwiched between the two surface layers. The resin content in the intermediate layer is higher than the resin content in the surface layer. In other words, the content of the conductive material in the surface layer is higher than the content of the conductive material in the intermediate layer. Such a bipolar plate of the present disclosure improves mechanical strength by the above-described intermediate layer including a relatively large resin, as compared to the above-described conventional bipolar plate. In addition, the bipolar plate of the present disclosure can reduce the contact resistance with the electrode by the above-described surface layer. Such bipolar plates of the present disclosure are capable of constructing RF batteries with relatively small cell resistances.

(2) As an example of the bipolar plate of the present disclosure, the following can be given: the bipolar plate is provided with: a first region configured with an electrode; and a second region located on the outer edge side of the first region, wherein the second region includes a reinforcing portion, and the resin content of the reinforcing portion is higher than the resin content of the first region in a direction along the surface.

In the state where the bipolar plate is assembled in the RF battery, the second region includes a portion that is more likely to receive an external force such as stress due to the tightening force than the first region. The second region has a reinforcing portion containing a relatively large amount of resin, and thus has excellent mechanical strength as compared with a case where the reinforcing portion is not provided. Therefore, the second region is less prone to cracking.

(3) An example of the bipolar plate of the above (2) is as follows: the resin content in the reinforcement portion is 1.2 times or more the resin content in the first region.

The reinforcement portion contains more resin than the first region, and the conductive material that may become the starting point of cracking contains little or substantially no conductive material. The second region including such a reinforcement is less prone to cracking.

(4) An example of the bipolar plate of the above (3) is as follows: the reinforcing portion is made of the resin without containing the conductive material.

The second region having the reinforcing portion is more excellent in mechanical strength than the case where the reinforcing portion includes the conductive material.

(5) As an example of any one of the bipolar plates (2) to (4), the following can be given: the reinforcement portion includes an annular region in plan view from the thickness direction of the bipolar plate.

The reinforcement portion may be said to be continuously provided in the circumferential direction of the outer edge of the bipolar plate. The second region having such a reinforcing portion is more excellent in mechanical strength.

(6) As an example of any one of the bipolar plates (2) to (4), the following can be given: the reinforcement portion includes two band-shaped regions facing each other across the first region when viewed in plan from the thickness direction of the bipolar plate.

The second region has the reinforcing portion in a region where the external force is easily applied, and thus has excellent mechanical strength. In the above embodiment, the bipolar plate having a structure in which two regions constituting the reinforcing portion are arranged to sandwich the first region as viewed in a direction perpendicular to the thickness direction of the bipolar plate, and a structure of three stripes is said to be less likely to warp, as compared with the case in which the reinforcing portion is a surface layer portion described later. Such bipolar plates are easily stacked. The three-striped bipolar plate is excellent in manufacturability as described later.

(7) As an example of the bipolar plate of the above (5) or (6), the following can be given: the reinforcement portion includes a surface layer portion that is provided in a layer shape so as to constitute a part of the surface of the second region among the surfaces of the bipolar plate.

The above-described method can suppress occurrence of cracking in which the surface of the second region serves as a starting point.

(8) An example of the bipolar plate of the above (7) is as follows: the thickness of the surface layer part is 10 μm or more and 2mm or less.

In the above aspect, the surface layer portion is properly present, and therefore the second region is less prone to cracking. The above-described method is also excellent in manufacturability in that the surface layer portion is easily formed as described later.

(9) As an example of the bipolar plate of the above (7) or (8), the following can be given: the second region has stepped portions having different thicknesses, and the surface layer portion is provided on a lower step surface of the stepped portions.

The above-described method is typically used for a battery cell frame in which the bipolar plate and the frame are not integrally formed and are independent. As an example of the battery cell frame, there is a battery cell frame having a stepped structure in which the thickness of the outer peripheral side of the frame body is different from the thickness of the inner peripheral side. The battery cell frame is constructed by placing the stepped portion of the bipolar plate on the stepped portion of the frame. With the battery cell frame being easily constructed, the above-described manner contributes to improvement in the manufacturability of the RF battery. In addition, in the battery cell frame, a gap of a certain size can be ensured between the frame body and the outer edge of the bipolar plate. Therefore, the stress from the frame is not easily carried by the bipolar plate. With this, the second region is less prone to cracking. Details of the battery cell frame will be described later.

(10) As an example of any one of the bipolar plates (7) to (9), the following can be given: the width of the surface layer part is 3mm or more.

In the above aspect, the surface layer portion is properly present, and therefore the second region is less prone to cracking. In the case where the above-described embodiment is applied to a battery cell frame in which the bipolar plate and the frame are independent of each other, the surface layer portion tends to have a width larger than that of the sealing member provided between the bipolar plate and the frame. With this, the second region is less prone to cracking.

(11) As an example of any one of the bipolar plates (7) to (10), the following can be given: the elongation at break of the portion of the first region adjacent to the surface layer portion is 0.5% or more.

The first region has an excellent elongation. Therefore, the surface layer portion is less likely to be peeled from the first region on the boundary surface between the first region and the surface layer portion. Therefore, in the above manner, the bipolar plate as a whole is less prone to cracking.

(12) As an example of any one of the bipolar plates (2) to (11), the following can be given: the resin included in the first region and the resin included in the reinforcement include one or more thermoplastic resins selected from the group consisting of polyethylene, polypropylene, and polyphenylene sulfide.

The above-described aspect is excellent in manufacturability in terms of ease of molding the first region and the reinforcing portion as described later.

(13) An example of the bipolar plate of the above (12) is as follows: the resin contained in the first region and the resin contained in the reinforcing portion include the same kind of thermoplastic resin.

In the above aspect, the region near the boundary surface between the first region and the reinforcing portion may be a region in which the same kind of resin diffuses from one direction to the other or diffuses with each other. In the above-described mode including the diffusion region of such resin, cracking and deformation caused by stress carried in the region in the vicinity of the boundary surface are alleviated. Therefore, the second region is less prone to cracking.

(14) One embodiment of the present disclosure relates to a battery cell including any one of the bipolar plates (1) to (13) described above.

By having the bipolar plate of the present disclosure, the bipolar plate is less prone to cracking in the battery cell of the present disclosure. Such a battery cell of the present disclosure can construct an RF battery excellent in sealability.

(15) One embodiment of the present disclosure relates to a battery pack including a plurality of the battery cells of (14) above.

By having the bipolar plate of the present disclosure, in the battery of the present disclosure, the bipolar plate is less prone to cracking. In particular, even when the tightening force is large due to the large number of stacked battery cells, the bipolar plate is less likely to crack. Such a battery pack of the present disclosure can construct an RF battery excellent in sealability. In the case where the bipolar plate of the present disclosure has a structure with a small contact resistance with the electrode as described above, the battery pack of the present disclosure can construct an RF battery with a small cell resistance.

(16) One embodiment of the present disclosure relates to a redox flow battery (RF battery) including the battery cell of (14) above or the battery pack of (15) above.

By having the bipolar plates of the present disclosure, the bipolar plates are less prone to cracking in the RF battery of the present disclosure. Such an RF battery of the present disclosure is excellent in sealability. In the case where the bipolar plate of the present disclosure has a structure in which the contact resistance with the electrode is small as described above, the RF battery of the present disclosure can reduce the cell resistance.

[ details of embodiments of the present disclosure ]

Hereinafter, a bipolar plate, a battery cell, a battery pack, and a redox flow battery (RF battery) according to embodiments of the present disclosure will be described with reference to the accompanying drawings. Like reference numerals refer to like designations in the drawings.

Embodiment(s)

First, with reference mainly to fig. 1 and 2, an outline of the RF battery 1, the battery cell 10, the battery cell frame 3, and the battery pack 100 will be described in order. The bipolar plate 4 according to the embodiment will be described in detail below.

(summary)

RF battery

The RF battery 1 is one of the secondary batteries of the electrolyte circulation type. The RF battery 1 includes a battery cell 10 or a battery pack 100 described later, and a circulation mechanism for supplying an electrolyte to the battery cell 10. The RF battery 1 is charged and discharged while supplying an electrolyte to the battery cell 10.

Typically, the RF battery 1 is connected to the power generation unit 7 and the load 8 via the power transformation device 61 and the ac/dc converter 6. The RF battery 1 charges the power generation unit 7 as a power supply source, and discharges the load 8 as a power supply target. The power generation unit 7 includes, for example, a solar power generator, a wind power generator, and other common power generation stations. Examples of the load 8 include a power system and a power consumer. The RF battery 1 is used for output smoothing of natural energy power generation such as load averaging, instantaneous low compensation, emergency power supply, solar power generation, wind power generation, and the like. The RF battery 1 is a secondary battery that generates electrification by a redox reaction of vanadium ion plasma in an electrolyte, and is particularly expected to be used for storage of large electric power. The RF battery 1 has the advantages of long charge/discharge cycle life, high responsiveness, low environmental load, and the like.

Battery cell

The battery cell 10 typically includes a positive electrode 13, a negative electrode 14, and a separator 11, and is constructed using a battery cell frame 3 described below. The separator 11 is disposed between the positive electrode 13 and the negative electrode 14. Examples of the positive electrode 13 and the negative electrode 14 include fibrous assemblies of carbon materials, porous metal members, and the like. Examples of the fiber aggregate of the carbon-based material include carbon felt, carbon paper, and carbon cloth. The separator 11 may be, for example, an ion exchange membrane. In the following description, the electrode 12 may be simply referred to as "electrode 12" to represent one of the positive electrode 13 and the negative electrode 14.

When the RF battery 1 is a single cell including one cell 10, the RF battery 1 includes a laminate in which the cell frame 3, the positive electrode 13, the separator 11, the negative electrode 14, and the cell frame 3 are laminated in this order. The laminate is shown in an exploded view in fig. 2. When the RF battery 1 is a multi-cell battery including a plurality of battery cells 10, the RF battery 1 includes a laminate in which the battery cell frame 3, the positive electrode 13, the separator 11, and the negative electrode 14 are sequentially stacked (fig. 1). The laminate is a battery pack 100. In order to obtain a predetermined output voltage, the battery pack 100 is configured such that the battery cells 10 having the above-described structure are stacked and connected in series.

Battery cell frame

The cell frame 3 includes a bipolar plate 4 and a frame body 30.

The bipolar plate 4 is a conductive plate through which current flows. The region where the electrode 12 is disposed on the surface of the bipolar plate 4 is also a region through which the electrolyte flows. However, the bipolar plate 4 does not transmit the electrolyte. In the battery pack 100, the bipolar plates 4 separate adjacent battery cells 10 from each other.

The bipolar plate 4 may also include a flow path 5 for an electrolyte (fig. 19 to 21 described later). The bipolar plate 4 having the flow channels 5 in the first region 41 (fig. 2) which is the region where the electrodes 12 are arranged is excellent in the flow-through property of the electrolyte.

The frame 30 is supported in a region of the bipolar plate 4 where the electrode 12 is not disposed, typically in a region on the outer edge 44 (fig. 11 and the like described later). The housing 30 is used to supply and discharge the electrolyte to and from the electrode 12 disposed on the bipolar plate 4.

As shown in fig. 2, the housing 30 includes a window 31, and a supply path and a discharge path for the electrolyte. The window 31 is provided in the central portion of the frame 30, and exposes the first region 41 of the bipolar plate 4. Fig. 2 illustrates a case where the outer shape and the shape of the window 31 are rectangular as the housing 30. The outer shape of the housing 30 and the shape of the window 31 can be changed as appropriate. The frame 30 is made of an electrically insulating material. Examples of the electric insulating material include various resins such as thermoplastic resins. Examples of the thermoplastic resin include vinyl chloride.

Typically, the housing 30 includes a supply path and a discharge path on the positive side on the first surface, and a supply path and a discharge path on the negative side on the second surface. The supply path on the positive electrode side includes a liquid supply manifold 33, a slit extending from the liquid supply manifold 33 to the window 31, and the like. The discharge path on the positive electrode side includes a discharge manifold 35, a slit continuous from the window 31 to the discharge manifold 35, and the like. The negative electrode side supply path and the negative electrode side discharge path are provided with a liquid supply manifold 34, a slit, and the like, and a liquid discharge manifold 36, a slit, and the like, as well. The lower edge in fig. 2 is used as the supply edge 5i of the electrolyte at a portion including the opening of the slit of the supply path on the inner peripheral edge of the window 31. The upper edge in fig. 2 serves as the discharge edge 5o of the electrolyte at a portion including the opening of the slit of the discharge path on the inner peripheral edge of the window 31. In addition, a seal member 39 is disposed in the housing 30. The adjacent cell frames 3 are kept liquid-tight by the sealing member 39 (fig. 1).

In the cell frame 3 for the end portion of the single cell or the multiple cell, the electrode 12 is arranged on the first surface of the bipolar plate 4. The electrode 12 is not disposed on the second surface. In the cell frame 3 for the middle portion of the multi-cell, a positive electrode 13 is arranged on the first surface of one bipolar plate 4. A negative electrode 14 is disposed on the second surface of the bipolar plate 4. That is, the positive electrode 13 and the negative electrode 14 are disposed so as to sandwich both surfaces of one bipolar plate 4 (see fig. 1, fig. 13, etc., which will be described later).

Battery pack

The battery pack 100 typically includes the above-described laminate including a plurality of battery cells 10, a pair of end plates 101, and a coupling member 102. The coupling member 102 may be a coupling member such as a long bolt or a nut. The pair of end plates 101 are fastened by the coupling member 102. The stacked body is held in a stacked state by the fastening force, that is, the fastening force in the stacking direction of the stacked body.

As illustrated in fig. 2, the battery pack 100 may include a plurality of sub-battery packs 110. The sub-battery pack 110 includes a laminate of a predetermined number of battery cells 10 and a pair of supply/discharge plates 103 sandwiching the laminate. Pipes 160 and 170 (fig. 1) described later are connected to the supply/discharge plate 103.

Circulation mechanism

As shown in fig. 1, the circulation mechanism includes tanks 16 and 17, pipes 160 and 170, and pumps 18 and 19. The pipes 160 and 170 include forward pipes 161 and 171 and return pipes 162 and 172. The tank 16 stores the positive electrode electrolyte which is circulated and supplied to the positive electrode 13. The forward pipe 161 and the backward pipe 162 are connected to the tank 16, the battery cell 10, or the battery pack 100. The tank 17 stores the negative electrode electrolyte which is circulated and supplied to the negative electrode 14. The forward pipe 171 and the backward pipe 172 are connected to the tank 17 and the battery cell 10 or the battery pack 100. Pumps 18 and 19 are connected to the forward pipes 161 and 171, respectively, and pressure-feed the electrolyte to the battery cells 10. In the assembled battery 100, the common positive electrode electrolyte and negative electrode electrolyte are circulated through all the battery cells 10. The black arrows of fig. 1 illustrate the flow of electrolyte.

Electrolyte solution

The electrolyte may be a solution containing ions as an active material. Representative electrolytes include aqueous solutions comprising the above-described ions and acids. As the electrolyte, an electrolyte having a known composition such as an all-vanadium RF battery including vanadium ions as positive and negative active materials, and an mn—ti RF battery including manganese ions as positive active material and titanium ions as negative active material can be used.

Bipolar plate

First, the structure of the bipolar plate 4 of the embodiment will be described with reference to fig. 3 to 10.

Fig. 4A and 4B show cross sections of the bipolar plate 4 shown in fig. 3, respectively, taken along a plane parallel to the thickness direction of the bipolar plate 4. Hereinafter, a cross section obtained by cutting the bipolar plate 4 in a plane parallel to the thickness direction of the bipolar plate 4 will be referred to as a vertical cross section.

Hereinafter, the plan view refers to a state in which the first surface 4a and the like of the bipolar plate 4 are viewed from the thickness direction of the bipolar plate 4. The side view is a state in which the side surface 4c of the bipolar plate 4 is viewed from a direction orthogonal to the thickness direction of the bipolar plate 4.

In fig. 3 to 10 and fig. 11 and subsequent drawings described later, the dimensions of the bipolar plates 4 and 4A, the preform 90, and the like are different from the actual dimensions for the purpose of highlighting the structure. The ratio between the dimension in the up-down direction in these figures and the dimension in the left-right direction in the figures is also different from the actual ratio.

Summary

The bipolar plate 4 of the embodiment is a member for the RF battery 1.

The bipolar plate 4 of the embodiment includes a conductive material and a resin. In particular, the bipolar plate 4 of the embodiment has a distribution in which the resin content varies in at least one of the direction along the surface of the bipolar plate 4 and the thickness direction of the bipolar plate 4. Fig. 3 and 5 to 8 illustrate bipolar plates 4 having a distribution of different resin contents in a direction along the surface of bipolar plates 4. Fig. 5, 6, and 8 illustrate a bipolar plate 4 having a distribution in which the resin content is different in both the direction along the surface of the bipolar plate 4 and the thickness direction of the bipolar plate 4.

Specifically, the bipolar plate 4 is a plate-shaped molded body. The bipolar plate 4 includes a first surface 4A, a second surface 4b, and a side surface 4c (fig. 3, 4A, and the like) that connects the first surface 4A and the second surface 4 b. The first surface 4a and the second surface 4b are main surfaces of the surface of the bipolar plate 4 in the region where the electrodes 12 are arranged. The first surface 4a and the second surface 4b are surfaces that are typically arranged in a direction along the surface of the bipolar plate 4. The side surface 4c is a surface typically along the thickness direction of the bipolar plate 4.

In the bipolar plate 4 shown in fig. 3 and 5 to 8, the first surface 4a includes regions adjacent to each other in a direction along the surface of the first surface 4a in a plan view, and the resin content is different. The bipolar plate 4 having such a first surface 4a has a distribution in which the resin content varies in a direction along the surface of the bipolar plate 4.

Fig. 10 shows a vertical cross section of a portion of the bipolar plate 4 having grooves 50 and ridges 55 where the grooves 50 and ridges 55 are provided. In the vertical cross section, the resin content at the portions constituting the ridge portions 55 is different from the resin content at the portions constituting the grooves 50. Such bipolar plate 4 also has a distribution in which the resin content varies in the direction along the surface of the bipolar plate 4.

In the bipolar plate 4 shown in fig. 5, 6, 8, and 9, the side surface 4c includes regions adjacent to each other in the thickness direction of the bipolar plate 4 and having different resin contents in a side view. The bipolar plate 4 shown in fig. 4A includes regions adjacent to each other in the thickness direction of the bipolar plate 4 in a vertical cross section and having different resin contents. The bipolar plate 4 having such a side surface 4c and at least one of the vertical cross sections has a distribution in which the resin content varies in the thickness direction of the bipolar plate 4.

That is, the bipolar plate 4 of the embodiment includes a plurality of regions having different resin contents. The plurality of regions satisfy at least one of the case of being adjacent in the direction along the surface of the bipolar plate 4 and the case of being adjacent in the thickness direction of the bipolar plate 4. The resin content in the bipolar plate 4 of the embodiment may be different stepwise or continuously.

Next, details of the structure of the bipolar plate 4 according to the embodiment and main effects of each structure will be described.

Embodiment 1

The bipolar plate 4 according to embodiment 1 will be described with reference to fig. 3, 4A, and 4B.

Structure

The bipolar plate 4 of embodiment 1 includes a first region 41 and a second region 42 (fig. 3). The first region 41 and the second region 42 are virtual regions in a state of looking down the first surface 4a or the second surface 4b of the bipolar plate 4. The first region 41 is a region where the electrode 12 is arranged. The second region 42 is a region located closer to the outer edge 44 than the first region 41. The bipolar plate 4 of embodiment 1 includes both the first region 41 and the second region 42 on both the first surface 4a and the second surface 4 b. In this case, the second region 42 is the entire region on the outer edge 44 side of the bipolar plate 4.

The first region 41 is a virtual region surrounded by the outer edge of the electrode 12 in a state where the electrode 12 is arranged in the bipolar plate 4. Accordingly, the shape and size of the first region 41 correspond to the shape of the electrode 12 and the size of the electrode 12. Typically, the first region 41 is a central region spaced apart to some extent from the outer edge 44 of the bipolar plate 4. Fig. 3 illustrates a case where the planar shape of the first region 41 is rectangular corresponding to the electrode 12 having a rectangular planar shape. The planar shape and the planar size of the first region 41 can be appropriately changed in accordance with the planar shape and the planar size of the electrode 12. The planar shape herein refers to the shape in the plane view. The dimensions in the plane here refer to the flat area, length, width, etc.

The bipolar plate 4 of embodiment 1 includes a plate-like portion formed of the same material, that is, a uniform material, from the first surface 4a through the inside in the thickness direction of the bipolar plate 4 to the second surface 4b as a whole. The first region 41 is provided in the plate-like portion. The plate-like portion is typically composed of a composite material including a conductive material and a resin. In the above composite material, the conductive material is dispersed in the resin.

The first region 41 made of the composite material described above flows the current as described above by containing the conductive material. The more the content of the conductive material is, the more easily the contact resistance between the first region 41 and the electrode 12 is reduced. In addition, the first region 41 prevents the electrolyte from passing between the first surface 4a and the second surface 4b of the bipolar plate 4 by containing the resin. In addition, the first region 41 is made of the same material, so that the bipolar plate 4 is excellent in manufacturability.

The second region 42 is a virtual region in which the electrode 12 is not disposed in the bipolar plate 4 in which the electrode 12 is disposed. The planar shape of the second region 42 is annular, i.e., frame-like, corresponding to the shape of the outer edge 44 of the bipolar plate 4. Fig. 3 illustrates a case where the planar shape of the second region 42 is a rectangular frame shape similar to the shape of the outer edge 44 and has substantially the same width W (fig. 4A, 4B). The planar shape of the second region 42 may be similar to the shape of the electrode 12 as in the present example, or may be dissimilar.

The second region 42 is provided with a reinforcing portion 43. The resin content of the reinforcement portion 43 is higher than the resin content of the first region 41 in the direction along the surface of the bipolar plate 4. The reinforcing portion 43 contains at least a resin. For example, in the case where the reinforcing portion 43 is composed of a composite material including a conductive material and a resin, the reinforcing portion 43 contains more resin than the first region 41. Alternatively, the reinforcing portion 43 does not include a conductive material, but is substantially composed of a resin.

The second region 42 may include at least a portion including the reinforcing portion 43. When the second region 42 is substantially constituted by the reinforcing portion 43, the boundary between the first region 41 and the second region 42 substantially coincides with the boundary between the first region 41 and the reinforcing portion 43. In the case where the second region 42 includes a portion other than the reinforcing portion 43, the two boundaries do not necessarily coincide. Fig. 3 to 4B, and two-dot chain lines of fig. 5 to 7 described later virtually show boundaries of the first region 41 and the second region 42. The boundary between the first region 41 and the second region 42 varies according to the size in the plane of the electrode 12. In the case where the electrode 12 is relatively small, i.e., in the case where the distance between the outer edge of the electrode 12 and the outer edge 44 of the bipolar plate 4 is relatively large, the bipolar plate 4 has a boundary 41A. In the case where the electrode 12 is relatively large, that is, in the case where the distance is relatively small, the bipolar plate 4 has a boundary 41C. When the distance is the intermediate value between the two cases, the bipolar plate 4 has the boundary 41B.

In the bipolar plate 4 of fig. 4A and the bipolar plate 4 of fig. 4B having the boundary 41A, the second region 42 includes the reinforcing portion 43 and a portion other than the reinforcing portion 43 in a plan view or in a vertical cross section. In the bipolar plate 4 having the boundary 41B or the boundary 41C in fig. 4B, the second region 42 is substantially constituted by the reinforcing portion 43 in a plan view and in a vertical cross section, and does not include a portion other than the reinforcing portion 43. In the bipolar plate 4 provided with the boundary 41C, the first region 41 includes a part of the reinforcing portion 43, and the second region 42 includes the remaining part of the reinforcing portion 43. That is, the case where the first region 41 includes a part of the reinforcing portion 43 is allowed. In the case where the first region 41 includes the reinforcing portion 43, if the reinforcing portion 43 is composed of a composite material including a conductive material and a resin, it is easy to reduce the contact resistance of the bipolar plate 4 with the electrode 12.

In the bipolar plate 4 of embodiment 1, the reinforcing portion 43 includes an annular region in plan view. As an example of the reinforcement portion 43 having such a planar shape, fig. 4A shows that the reinforcement portion 43 includesThe surface layer 430. The surface layer portion 430 is provided in a layered manner so as to constitute a part of the surface of the second region 42 out of the surfaces of the bipolar plates 4. In the bipolar plate 4 shown in fig. 4A, the second region 42 has a surface layer portion 430 on the surface side, and has a base portion 420 inside the surface layer portion 430 in the thickness direction of the bipolar plate 4. The thickness t of the surface layer portion 430 is smaller than the thickness t of the first region 41 ₄₁ The thin layer is typically a layer or film of the surface layer 430. The base 420 is covered with the surface layer portion 430. The base 420 can be said to support the surface layer portion 430.

The planar shape of the surface layer portion 430 in this example is a rectangular frame shape. The surface layer 430 of this example is a frame-shaped region having a predetermined width W from the outer edge 44 toward the inside. The planar shape, the width W, and the like can be appropriately selected. The planar shape and size are typically selected according to the shape, size, etc. of the seal member 39. For example, the planar shape may be a frame shape, a circular ring shape, an elliptical ring shape, or the like, which is a polygon other than a rectangle. The width W of the surface layer portion 430 is described in detail below. The surface layer 430 of this example includes the outer edge 44 of the bipolar plate 4, and forms the entire surface of the region on the outer edge 44 side of the bipolar plate 4. The surface layer 430 may not include the outer edge 44.

In the bipolar plate 4 shown in fig. 4A, the reinforcement portion 43 includes a surface layer portion 430 on the first surface 4A, the second surface 4b, and the side surface 4c of the bipolar plate 4. The vertical cross-sectional shape of the surface layer portion 430 is a gate shape. The surface layer portion 430 continues from the region on the outer edge 44 side of the first surface 4a of the bipolar plate 4 to the region on the outer edge 44 side of the second surface 4b of the bipolar plate 4 through the side surface 4c of the bipolar plate 4 constituting the outer edge 44. The surface layer portion 430 constitutes a part of the first surface 4a, a part of the second surface 4b, and the entire side surface 4 c. The base 420 is surrounded by a door-shaped reinforcement 43.

The base 420 of this example is a portion on the outer edge side of the plate-like portion including the first region 41. Thus, the base 420 is composed of the same composite material as the composite material constituting the first region 41. In addition, the composite material comprising the first region 41 may also be different from the composite material comprising the base 420. For example, the composite material constituting the base 420 may contain more resin than the composite material constituting the first region 41, and may contain less resin than the composite material constituting the surface layer portion 430.

The bipolar plate 4 including the surface layer portion 430 and the base portion 420 as described above includes, in a vertical section, portions in which portions composed of different materials are adjacently arranged in the thickness direction of the bipolar plate 4.

In the bipolar plate 4 shown in fig. 4B, the reinforcing portion 43 is a frame-shaped molded body. The first region 41 is a plate-shaped molded body. The reinforcement 43 surrounds the plate-like first region 41. The thickness t of the reinforcing part 43 and the thickness t of the first region 41 ₄₁ Substantially the same. The bipolar plate 4 including such a reinforcing portion 43 in the second region 42 includes a portion composed of the same material in the thickness direction of the bipolar plate 4.

In the case where the reinforcing portion 43 provided in the second region 42 constitutes a part of the surface of the bipolar plate 4, it is preferable that the surface 43f of the reinforcing portion 43 is continuous with the surface 41f of the first region 41 without steps (see also fig. 3 to 8, fig. 13 and the like described later). The term "continuous without steps" here means that the steps generated in the thickness direction of the bipolar plate 4 are smaller than 500 μm for the boundary between the reinforcing portion 43 and the first region 41 and the vicinity thereof on the surface of the bipolar plate 4. The smaller the step is, the less stress is concentrated on the reinforcing portion 43 even if the reinforcing portion 43 bears the external force, and therefore, it is preferable. For example, it is preferable that the above-mentioned step is less than 200. Mu.m. More preferably, the step is 100 μm or less, 50 μm or less, or 10 μm or less. It is further preferable that the step is substantially 0 μm. That is, it is preferable that the boundary between the reinforcing portion 43 and the first region 41 and the vicinity thereof and the surface 43f of the reinforcing portion 43 are substantially flush with the surface 41f of the first region 41. Cracking is less likely to occur in such second regions 42. Further, the bipolar plate 4 is less prone to cracking.

Effect

The second region 42 has superior mechanical strength to the region on the outer edge side of the conventional bipolar plate in which the conductive material and the resin are uniformly mixed, by providing the reinforcing portion 43. Therefore, even if the second region 42 bears an external force such as stress due to the fastening force, pressure due to the electrolyte, or force due to a thermal expansion difference due to a temperature change, the second region 42 is less likely to crack.

In the case where the reinforcing portion 43 includes the annular surface layer portion 430 (fig. 4A), the surface layer portion 430 increases the mechanical strength of the surface side of the second region 42. Since the surface layer portion 430 is continuously provided in the circumferential direction of the outer edge 44, the second region 42 is also excellent in mechanical strength. In the surface layer portion 430 of this example, the contact area with the base portion 420 integral with the first region 41 is wider and the number of contact surfaces with the base portion 420 is larger than that of the bipolar plate 4 shown in fig. 4B. In this regard, the bonding strength of the reinforcing portion 43 to the first region 41 is easily improved as compared with the bipolar plate 4 shown in fig. 4B. Based on these, the surface of the second region 42 is a portion of the bipolar plate 4 that is likely to bear the external force, but cracking is unlikely to occur starting from the surface of the second region 42. In the case where the surface layer portion 430 is substantially made of resin, the conductive material does not become a starting point of cracking. The second region 42 including such a surface layer portion 430 is less prone to cracking. In the case where the surface layer portion 430 is made of a composite material including a conductive material and a resin, the surface layer portion 430 contains the conductive material in a range smaller than the content of the conductive material in the first region 41. The surface layer 430 has a certain degree of conductivity. Therefore, the occurrence of cracking of the second region 42 can be reduced by the surface layer portion 430, and a certain degree of conductivity can be ensured.

In the case where the reinforcing portion 43 is a ring-shaped molded body (fig. 4B), the second region 42 has an increased mechanical strength over the entire region from the first surface 4a to the second surface 4B by the reinforcing portion 43. Since the reinforcing portion 43 is continuously provided in the circumferential direction of the outer edge 44, the second region 42 is also excellent in mechanical strength. In such a second region 42, cracking is less likely to occur even if the above-described external force is borne. In the case where the reinforcing portion 43 is substantially composed of resin, the second region 42 is less likely to crack. In the case where the reinforcing portion 43 is composed of a composite material including a conductive material and a resin, occurrence of cracking can be reduced as described above, and a certain degree of conductivity can be ensured.

The first region 41 contains more conductive material than the reinforcing portion 43. By such a first region 41, the bipolar plate 4 can reduce the contact resistance with the electrode 12.

The bipolar plate 4 shown in fig. 4A includes a surface layer portion 430 so that the first surface 4A and the second surface 4b have a symmetrical shape. When the first surface 4a and the second surface 4b each include the surface layer 430, at least one of the shape and the size may be different between the surface layer 430 on the first surface 4a side and the surface layer 430 on the second surface 4b side. Alternatively, the bipolar plate 4 may have only the surface layer portion 430 on the first surface 4a and may not have the surface layer portion 430 on the second surface 4b (see fig. 17A described later). The description matters in this paragraph are also applicable to embodiment 2 and the like described later, which includes the surface layer portion 430.

Embodiment 2

The bipolar plate 4 of embodiment 2 will be described with reference to fig. 5.

In the bipolar plate 4 of embodiment 2, the reinforcement portion 43 includes a surface layer portion 430 that is annular in a plan view, as in embodiment 1. In addition, like the bipolar plate 4 shown in fig. 4A, the reinforcement portion 43 includes an annular surface layer portion 430 on both the first surface 4A and the second surface 4b of the bipolar plate 4. However, unlike embodiment 1, the surface layer 430 is only partially formed on the side surface 4 c. Each of the four side surfaces 4c is composed of an outer edge side portion including the plate-like portion of the first region 41 and two surface layer portions 430 which sandwich the outer edge side portion. The bipolar plate 4 of embodiment 2 includes portions made of different materials on the first surface 4a and the second surface 4b, which are adjacently arranged in a direction along the surface of the bipolar plate 4. The bipolar plate 4 of embodiment 2 includes portions made of different materials on the side surface 4c and the vertical cross section, and the portions are arranged adjacently in the thickness direction of the bipolar plate 4. The bipolar plate 4 according to embodiment 2 has the same effect as the bipolar plate 4 shown in fig. 4A.

Embodiment 3

The bipolar plate 4 of embodiment 3 will be described with reference to fig. 6.

In the bipolar plate 4 of embodiment 3, the reinforcement portion 43 includes the surface layer portion 430 on both the first surface 4a and the second surface 4b of the bipolar plate 4, as in embodiment 2. However, the reinforcing portion 43 is not annular. Specifically, the reinforcing portion 43 includes two belt-like regions in plan view. The two band-shaped regions are opposed to each other across the first region 41. The bipolar plate 4 of this example is rectangular flat plate-like. The reinforcement portion 43 of the present example includes an elongated rectangular strip-shaped surface layer portion 430 extending in the longitudinal direction of the rectangle in plan view. The two surface layer portions 430 and the first region 41 are arranged in three stripes in a plan view. Two side surfaces 4c among the four side surfaces 4c are each composed of the above-described plate-like portion including the first region 41 and four surface layer portions 430 provided at four corners of the portion on the outer edge side. The remaining two side surfaces 4c are the same as in embodiment 2. Like embodiment 2, the bipolar plate 4 of embodiment 3 includes portions formed of different materials that are adjacently arranged.

The second region 42 has superior mechanical strength to the conventional bipolar plate by providing the reinforcing portion 43 continuous along the outer edge 44. In particular, the reinforcing portion 43 includes a band-shaped surface layer portion 430 across the first region 41. Therefore, the mechanical strength of the second region 42 is easily uniform across the first region 41. Such second region 42 uniformly receives the external force even if the external force is received. Therefore, cracking is less likely to occur in the second region 42.

The planar shape of the surface layer portion 430 may be other than rectangular. For example, the planar shape may be a wave shape, a saw tooth shape, or the like. The surface layer 430 of the present embodiment includes a part of the outer edge 44 of the bipolar plate 4, but may not include the outer edge 44. Further, in this example, the shape of the boundary between the surface layer portion 430 and the first region 41 and the shape of the outer edge 44 included in the surface layer portion 430 are linear and have the same shape, but may be different shapes. For example, the outer edge 44 may have a linear shape, and the boundary may have a wave shape. The matters described in this paragraph are also applicable to embodiment 4 described below.

Embodiment 4

The bipolar plate 4 of embodiment 4 will be described with reference to fig. 7.

As in embodiment 3, in the bipolar plate 4 of embodiment 4, the reinforcing portion 43 includes two band-shaped regions in plan view. The two band-shaped regions are opposed to each other across the first region 41. However, the reinforcing portion 43 is not a layer or a film, but is formed of a plate-like molded body or a rod-like molded body. The two band-plate-shaped reinforcing portions 43 are provided so as to sandwich the plate-shaped first region 41. Like the bipolar plate 4 shown in fig. 4B, the bipolar plate 4 of this embodiment 4 includes a portion made of the same material in the thickness direction of the bipolar plate 4. The bipolar plate 4 of embodiment 4 has a vertical cross section shown in fig. 4B.

The first region 41 in this example is a rectangular plate-shaped molded body. The reinforcing portion 43 of this example is a molded body having a rectangular elongated plate shape in a plan view. The reinforcing portions 43 are arranged along the longitudinal direction of the first region 41. The bipolar plate 4 of embodiment 4 has three stripes in a plan view. In addition, the two side surfaces 4c out of the four side surfaces 4c are arranged in three stripes in a side view, including the outer edge side portion of the plate-like portion of the first region 41 and the two reinforcing portions 43. The remaining two side surfaces 4c are constituted by the reinforcing portions 43. Like embodiment 3, the bipolar plate 4 of embodiment 4 includes portions made of different materials that are adjacently aligned in a direction along the surface of the bipolar plate 4. In addition, like the bipolar plate 4 shown in fig. 4B, the bipolar plate 4 of embodiment 4 includes a portion made of the same material in the thickness direction of the bipolar plate 4.

As in embodiment 3, the bipolar plate 4 of embodiment 4 has two reinforcing portions 43 continuous along the outer edge 44, and thus has excellent mechanical strength and uniformly receives the external force. In particular, the reinforcing portion 43 is a molded body having a band plate shape. Therefore, as in the bipolar plate 4 shown in fig. 4B, the second region 42 has an increased mechanical strength over the entire region from the first surface 4a to the second surface 4B by the reinforcing portion 43. Thus, cracking is less likely to occur in the second region 42. In the case where the reinforcing portion 43 is substantially composed of resin, the second region 42 is less likely to crack as described above.

In addition, bipolar plate 4 of embodiment 4 is less likely to warp than embodiment 3 having surface layer 430. Therefore, the battery cell frame 3 including the bipolar plate 4 of embodiment 4 is easily laminated. Further, if a continuous process described later is used, the bipolar plate 4 of embodiment 4 can be mass-produced. From this point of view, the bipolar plate 4 of embodiment 4 is excellent in manufacturability.

Embodiment 5

The bipolar plate 4 of embodiment 5 will be described with reference to fig. 8.

The planar shape of the reinforcing portion 43 is not limited to the annular shape and the belt shape. For example, as shown in fig. 8, the reinforcing portion 43 may have a lattice shape in plan view. Fig. 8 illustrates a case where the reinforcement portion 43 includes a lattice-like surface layer portion 430 on both the first surface 4a and the second surface 4b of the bipolar plate 4. Width W of lattice ₅ The length of the long side and the length of the short side of the rectangle in the lattice can be appropriately selected.

Like embodiment 2, the bipolar plate 4 of embodiment 5 includes portions formed of different materials that are adjacently arranged. In addition, like the bipolar plate 4 shown in fig. 4B, the bipolar plate 4 of embodiment 5 includes a portion made of the same material in the thickness direction of the bipolar plate 4.

The lattice-shaped reinforcing portion 43 includes a larger amount of resin than the portion constituting the rectangular region arranged in each lattice, thereby improving the mechanical strength of the second region 42. The portions constituting the rectangular regions and the portions of the lattices constituted by the reinforcing portions 43 are alternately arranged on the first surface 4a and the second surface 4b of the bipolar plate 4. Such second region 42 is expected to be easily and uniformly subjected to the above-described external force. Further, by forming the rectangular regions disposed in each lattice from a composite material containing more conductive material than the reinforcing portion 43, the first region 41 is easy to ensure a predetermined conductivity. In the bipolar plate 4 of embodiment 5, the first region 41 in which the electrode 12 is disposed includes a part of the reinforcement portion 43. Therefore, the reinforcing portion 43 is preferably composed of a composite material including a conductive material and a resin. In embodiment 5 and modification 5-1 described later, the width W of the lattice ₅ The larger the second region 42, the easier it is to increase the mechanical strength. Width W of lattice ₅ The smaller the conductivity of the first region 41 is, the more excellent. Therefore, the contact resistance with the electrode 12 is easily reduced.

As modification 5-1, the reinforcing portion 43 may be a lattice-shaped molded body. In embodiment 5 described above, the two surface layer portions 430 are separated in the thickness direction of the bipolar plate 4. In contrast, in modification 5-1, the molded body constituting the reinforcing portion 43 is continuous over the entire region in the thickness direction of the bipolar plate 4. By this reinforcement portion 43, the second region 42 is more likely to have higher mechanical strength than embodiment 5.

As modification 5-2, the reinforcement portion 43 may have a rectangular surface layer portion 430 disposed in each lattice, contrary to embodiment 5. That is, the reinforcing portion 43 includes a plurality of rectangular surface layer portions 430. The lattice portion is composed of a composite material containing more conductive material than the surface layer portion 430. In this case, the plurality of surface layer portions 430 makes it easier to increase the mechanical strength of the second region 42 than in embodiment 5. In modification 5-2 and modification 5-3 described later, the width W of the lattice ₅ The smaller the second region 42, the easier it is to increase mechanical strength. Width W of lattice ₅ The larger the first region 41 is, the more excellent the conductivity is.

As modification 5-3, the reinforcing portion 43 may be a cube-shaped molded body filled in each lattice. That is, the reinforcing portion 43 includes a plurality of cube-shaped regions. In modification 5-2 described above, the two surface layer portions 430 are separated in the thickness direction of the bipolar plate 4. In contrast, in modification 5-3, the molded body constituting the reinforcing portion 43 is continuous over the entire region in the thickness direction of the bipolar plate 4. By this reinforcement portion 43, the second region 42 is more likely to have higher mechanical strength than embodiment 5.

In addition, the planar shape of the reinforcement portion 43 may be a mesh shape other than a lattice. The reinforcing portion 43 may include a plurality of regions that are arranged in an island shape or in a dot shape in a plan view. Specifically, the reinforcing portion 43 may include an island-like or dot-like surface layer portion 430, and may include a plurality of columnar molded bodies continuous in the thickness direction of the bipolar plate 4. Each columnar molded body has an end surface constituting a part of the first surface 4a and an end surface constituting a part of the second surface 4b of the bipolar plate 4.

Embodiment 6

The bipolar plate 4 of embodiment 6 will be described with reference to fig. 9.

As shown in fig. 9, the bipolar plate 4 may be a laminate in which a plurality of molded bodies are stacked. The bipolar plate 4 of embodiment 6 is a laminate, and at least one layer is a reinforcing portion 43. Fig. 9 includes two layered base portions 432 and a layered reinforcing portion 43. The two base portions 432 are disposed so as to sandwich the reinforcing portion 43. The base portion 432 is made of a composite material containing more conductive material than the reinforcing portion 43. The base portion 432 forms the first surface 4a and the second surface 4b and the surface of the first region 41. By such a base portion 432, the bipolar plate 4 of embodiment 6 can reduce the contact resistance with the electrode 12. In the bipolar plate 4 according to embodiment 6, the second region 42 has the reinforcing portion 43 at the intermediate position in the thickness direction, and the mechanical strength is improved as compared with the conventional bipolar plate. Therefore, even if the external force is carried, the second region 42 is less prone to cracking.

As a modification, the bipolar plate 4 may include two surface layer portions 430 and one base portion 432. The two surface layer portions 430 are disposed so as to sandwich the base portion 432. In this modification, the surface of the bipolar plate 4 is excellent in mechanical strength. Therefore, cracking starting from the surface of the second region 42 is less likely to occur.

The number of layers constituting the laminate may be two or four or more. In this example, the reinforcing portion 43 and the base portion 432 are provided so that the boundary surfaces between the adjacent reinforcing portions 43 and base portion 432 are planar. The reinforcing portion 43 and the base portion 432 may be provided so that the boundary surface is a curved surface such as a wave shape or an arc shape.

Embodiment 7

The bipolar plate 4 of embodiment 7 will be described with reference to fig. 10.

The bipolar plate 4 may have a plurality of grooves 50 and ridge portions 55 that separate adjacent grooves 50 in the first region 41 (see fig. 19 and the like described later). In the bipolar plate 4 of embodiment 7, the resin content is different in the portion including the bottom surface of the groove 50 and the portion including the surface of the ridge portion 55. In detail, the reinforcement 43 constitutes a portion including the bottom surface of the groove 50. The portion including the surface of the ridge portion 55 is composed of a composite material containing more conductive material than the reinforcing portion 43. The surface of the ridge 55 forms the first surface 4a and the second surface 4b.

Fig. 10 illustrates a bipolar plate 4 having grooves 50 provided at the same positions along the direction of the surface on the first surface 4a and the second surface 4b. That is, the bottom surface of the groove 50 on the first surface 4a side and the bottom surface of the groove 50 on the second surface 4b side face each other. The portion including the surface of the ridge portion 55 is constituted by the above-described composite material in the entire region in the thickness direction of the bipolar plate 4. The reinforcing portion 43 is a relatively thin portion sandwiched between the bottom surface of the groove 50 opened on the first surface 4a side and the bottom surface of the groove 50 opened on the second surface 4b side. The reinforcing portion 43 includes a plurality of the relatively thin portions. A portion including the surface of the ridge portion 55 is disposed between the adjacent relatively thin portions. That is, the reinforcing portion 43 is discontinuously provided in a direction along the surface of the bipolar plate 4.

In the bipolar plate 4 of embodiment 7, the portion including the bottom surface of the groove 50 is thinner than the portion including the surface of the ridge portion 55, but is constituted by the reinforcing portion 43 containing a large amount of resin. The portion including the surface of the ridge portion 55 is made of a composite material containing more resin than the reinforcing portion 43, but is thicker than the reinforcing portion 43. According to these, the bipolar plate 4 of embodiment 7 is excellent in mechanical strength.

The surface of the ridge portion 55 in contact with the electrode 12 is made of a composite material containing a large amount of conductive material as described above. Therefore, the bipolar plate 4 of embodiment 7 can reduce the contact resistance with the electrode 12.

As a modification, the reinforcing portion 43 may be a flat plate continuously provided in a direction along the surface. The ridge 55 protrudes from the surface of the flat plate-like reinforcement 43. The bipolar plate 4 of this modification further improves mechanical strength by continuing the reinforcing portion 43 in the surface direction of the bipolar plate 4.

Next, details of constituent materials and the like of the bipolar plate 4 of the embodiment and the relationship between the bipolar plate 4 and the cell frame 3 will be described with reference to fig. 11 to 14.

Fig. 11 is a plan view of the bipolar plate 4 of embodiment 1 from the thickness direction of the bipolar plate 4. The thickness direction is a direction perpendicular to the paper surface in fig. 11.

Fig. 12 is a top view of the battery cell frame 3 including the bipolar plate 4 according to embodiment 1.

Fig. 13 is a cross section of the cell frame 3 shown in fig. 12, in which a portion near the outer edge 44 of the bipolar plate 4 is cut in a plane parallel to the thickness direction of the bipolar plate 4.

Summary of bipolar plate and Battery cell frame

The bipolar plate 4 of the embodiment includes the first region 41 and the second region 42 as described above. For ease of understanding, fig. 11 marks the second region 42 with a cross-hatching. In this example, the second region 42 includes a surface layer portion 430 as the reinforcing portion 43. The surface-side region of the second region 42 is substantially entirely constituted by the surface layer portion 430. The resin content in the surface layer portion 430 is higher than the resin content in the surface 41f (fig. 13) of the first region 41. That is, the surface layer portion 430 contains more resin than the surface 41f of the first region 41. In addition, the surface layer portion 430 contains less conductive material or no conductive material at all than the surface 41f of the first region 41.

The bipolar plate 4 of the present example is a separate member from the housing 30 (fig. 12). The bipolar plate 4 is not integrally formed with the frame 30. As will be described later, the bipolar plate 4 is mounted on the housing 30 via a seal member 39 (fig. 13) disposed on the inner peripheral side of the housing 30. By this placement, the cell frame 3 is constructed (fig. 12). The second region 42 is covered with a recess (fig. 13) of the housing 30, and is disposed opposite to the seal member 39.

Constituent Material

As a constituent material of the first region 41, a composite material including a conductive material and a resin is mentioned as described above. Alternatively, the constituent material of the first region 41 may be a substantially conductive material. In the bipolar plate 4 of the embodiment, if a predetermined mechanical strength can be ensured by the reinforcing portion 43, the first region 41 can contain more conductive material than the above-described conventional bipolar plate. By providing the first region 41 containing a large amount of conductive material, the contact resistance between the bipolar plate 4 and the electrode 12 can be reduced more easily.

The reinforcing portion 43 in the second region 42 is formed of a composite material including a conductive material and a resin as described above and contains more resin than the first region 41. The content of the conductive material in the reinforcing portion 43 is, for example, 5 mass% or more and 40 mass% or less, assuming that the reinforcing portion 43 is 100 mass%. Alternatively, the constituent material of the reinforcing portion 43 may be substantially resin as described above.

The portion other than the reinforcing portion 43 in the second region 42 is made of a composite material including a conductive material and a resin. The base 420 may be, for example, the above-mentioned portion. In the bipolar plate 4 having the boundary 41A (fig. 3), examples of the above-mentioned portion include a portion sandwiched between the boundary 41A and the reinforcing portion 43 in a plan view.

The composite material constituting the second region 42 at a portion other than the reinforcing portion 43 is preferably the same as the composite material constituting the first region 41. More preferably, the portion other than the reinforcing portion 43 is integrally formed with the first region 41. In this case, the characteristics such as the coefficient of thermal expansion of the portion other than the reinforcing portion 43 are substantially equal to the characteristics of the first region 41. Therefore, even when the portions other than the reinforcing portion 43 and the first region 41 thermally expand and contract, the state where the portions are integrated with each other is well maintained when the RF battery 1 is used or the like. If the portions other than the reinforcing portions 43 are integrally formed with the first region 41, the bipolar plate 4 is also excellent in manufacturability. The composite material constituting the portion other than the reinforcing portion 43 may be different from the composite material constituting the first region 41.

Resin

The resin included in the first region 41 and the resin included in the reinforcing portion 43 include various resins. Examples thereof include thermoplastic resins and thermosetting resins.

The resin contained in the first region 41 and the resin contained in the reinforcing portion 43 include thermoplastic resins. In the case where the first region 41 and the reinforcing portion 43 are made of a composite material including a conductive material and a thermoplastic resin, the bipolar plate 4 can be easily manufactured by injection molding, press molding, or the like, which will be described later. The surface layer portion 430 made of a resin can be easily formed by using a film made of a thermoplastic resin or the like as described later. According to these, the manufacturability of the manner in which both the resin in the first region 41 and the resin in the reinforcing portion 43 include thermoplastic resin is excellent.

Examples of the thermoplastic resin include an olefin-based resin having corrosion resistance against strong acids and strong bases, a fluororesin having similar corrosion resistance, and a resin having heat resistance, which are suitable for use in the bipolar plate 4. Examples of the olefin-based resin include Polyethylene (PE) and polypropylene (PP). Examples of the fluororesin include PTFE (polytetrafluoroethylene), PFA (perfluoropropyl perfluorovinyl ether), and FEP (fluorinated ethylene propylene copolymer). Examples of the resin having heat resistance include polyphenylene sulfide (PPS).

In particular, if the thermoplastic resin is one or more resins selected from the group consisting of PE, PP and PPs, not only the electrical insulation property but also the resistance to the electrolytic solution is excellent. Accordingly, the thermoplastic resins listed above can be suitably used as constituent materials of the bipolar plate 4 that may contact the electrolyte. Further, since the thermoplastic resin listed above is excellent in moldability, it is advantageous in that it is easy to manufacture a blank such as a frame-like material or a film as a raw material of the reinforcing portion 43. The first region 41 and the reinforcing portion 43 may include one of the resins listed above or a resin obtained by chemically or otherwise denaturing a plurality of resins.

The resin contained in the first region 41 and the resin contained in the reinforcing portion 43 preferably contain the same kind of thermoplastic resin. For example, PE is preferably contained. One of the reasons for this is that the bipolar plate 4 is less likely to crack as will be described below. For another reason, the ease of manufacturing the first region 41 and the reinforcing portion 43 in the manufacturing process leads to excellent joining properties of the blanks and the two blanks, and thus, the bipolar plate 4 can be manufactured with excellent productivity. The excellent manufacturability will be described in terms of the manufacturing method described later.

When the first region 41 and the reinforcing portion 43 include the same kind of thermoplastic resin, the region near the boundary surface between the first region 41 and the reinforcing portion 43 is a diffusion region of the following resin. The diffusion region of the resin is a region in which the same kind of resin as described above diffuses from the reinforcement portion 43 toward the first region 41, or from the first region 41 toward the reinforcement portion 43, or mutually. By including the diffusion region of the resin in the region near the boundary surface, occurrence of cracking and deformation due to stress carried in the region are alleviated. With this, occurrence of cracking in the bipolar plate 4 is reduced. In the case where the base 420 and the surface layer 430 include the same type of thermoplastic resin, if the region near the boundary surface between the base 420 and the surface layer 430 includes a diffusion region of the resin, it is also possible to expect to alleviate the occurrence of the crack and the deformation. Thus, the bipolar plate 4 is less prone to cracking.

Composite material

The composite material is typically an organic composite material, or a so-called conductive plastic. Examples of the constituent material of the conductive material include a non-metallic inorganic material such as a carbon-based material, and various metals. Examples of the carbon-based material include graphite and carbon black. Examples of the metal include aluminum. Examples of the form of the conductive material include powder and fiber.

Content of resin >

The higher the resin content in the reinforcement portion 43, the more preferable the resin content in the first region 41. The reason for this is that by making the conductive material in the reinforcing portion 43 that may become the starting point of cracking less or substantially not include the conductive material, the second region 42 including the reinforcing portion 43 is less likely to crack. For example, the resin content in the reinforcement portion 43 is 1.2 times or more the resin content in the first region 41. In this case, in the reinforcing portion 43, it can be said that the resin is relatively more and the conductive material is relatively less. When it is desired to further reduce the occurrence of cracking, the resin content in the reinforcement portion 43 is preferably 1.5 times or more, 2 times or more, or even 2.5 times or more the resin content in the first region 41.

The resin content in the reinforcement portion 43 is, for example, 20 times or less the resin content in the first region 41. In this case, the reinforcing portion 43 is also excellent in conductivity by containing a conductive material to some extent. The resin content in the reinforcing portion 43 may be 1.2 times or more and 20 times or less, and may be 1.5 times or more and 15 times or less, from the viewpoint of reduction in occurrence of cracking and securing of conductivity. The resin content in the reinforcing portion 43 may be adjusted in a range where the resin content is greater than that in the first region 41 and the portion other than the reinforcing portion 43. For example, the content of the resin in the reinforcing portion 43 may be 5 mass% or more and 100 mass% or less, assuming that the reinforcing portion 43 is 100 mass%. When the resin content in the reinforcing portion 43 is 15 mass% or more and 30 mass% or more, the mechanical strength of the second region 42 is improved. When the resin content in the reinforcing portion 43 is more than 50 mass% or more and 60 mass% or more, the mechanical strength of the second region 42 is further improved.

The content of the resin in the reinforcing portion 43 may be 100% by mass, assuming that the reinforcing portion 43 is 100% by mass. Since the reinforcing portion 43 is substantially composed of resin, the second region 42 including the reinforcing portion 43 is less prone to cracking. When the surface layer portion 430 is manufactured using a film made of resin, the second region 42 is less likely to crack because the film has excellent bonding strength. Further, the bipolar plate 4 is excellent in manufacturability in terms of ease of manufacturing the thin film and ease of bonding the thin film.

The content of the resin in the portion other than the reinforcing portion 43 in the second region 42, for example, the portion such as the base portion 420, is set to 100 mass%, and examples thereof include 0.5 mass% or more and less than 100 mass%. As described above, the base 420 is excellent in manufacturability when it is made of the same composite material as the composite material constituting the first region 41. Accordingly, the content rate of the resin in the base 420 may be the same as the content rate of the resin in the first region 41.

When the first region 41 is made of the composite material, the content of the resin in the first region 41 is, for example, 0.5 mass% or more and 50 mass% or less, assuming that the first region 41 is 100 mass%. The remainder of the first region 41 is a conductive material. That is, the content of the conductive material in the first region 41 is 50% by mass or more and 95.5% by mass or less. The content of the resin in the first region 41 can be adjusted within a range where the first region 41 has a predetermined conductivity. For example, the content of the resin in the first region 41 may be 5 mass% or more and 50 mass% or less, and may be 15 mass% or more and 50 mass% or less.

In the case where the reinforcement portion 43 constitutes a part of the surface of the second region 42 of the surface of the bipolar plate 4, the following method is exemplified as a method for discriminating the level between the resin content in the reinforcement portion 43 and the resin content in the first region 41. The method uses a total reflection measurement (ATR) which is one of infrared spectroscopic analysis (IR) to analyze the surface of the bipolar plate 4, and fourier transform infrared spectroscopic (FT-IR) spectroscopy is used. The ATR method can acquire an FT-IR spectrum for an extremely thin region of about several μm from the surface of a sample to be measured in the thickness direction. Therefore, it is considered that the FT-IR spectrum by the ATR method is suitable as an index for comparing the content of the resin in the surface portion with respect to the member containing the resin.

If the resin content is large, the absorption peak due to the structure of the resin appears at the specific wave number (cm ^-1 ). The amount of the resin contained can be determined from the wave number. If the resin content is small, the absorption peak is small or does not occur at all.

Fig. 14 is a graph showing an example of the FT-IR spectrum in the surface layer portion 430 and an example of the FT-IR spectrum in the first region 41. In the graph of FIG. 14, the horizontal axis represents wave number (cm ^-1 ). The vertical axis represents absorbance. The samples analyzed are shown below.

(sample)

The sample includes a surface layer portion 430 as the reinforcing portion 43. The surface layer portion 430 is made of polyethylene. The resin content in the surface layer portion 430 is 100 mass% and is about 5 times the resin content in the first region 41. The surface layer portion 430 exists only on the surface side of the second region 42 in the surface of the bipolar plate 4. The thickness t of the surface layer portion 430 is about 200 μm or more and 400 μm or less.

The base 420 constituting the interior at a distance from the surface of the second region 42 is composed of the same composite material as that constituting the first region 41.

The first region 41 contains about 80 mass% graphite with the remainder being polyethylene. The content of the resin in the first region 41 was about 20 mass%.

As illustrated in fig. 14, in the surface layer portion 430 containing relatively large amounts of resin, a plurality of wave numbers indicating absorption peaks appear. The absorption peak is here a convex waveform. On the other hand, in the first region 41 where the resin is relatively small, the wave number of the absorption peak is not shown, and the waveform of the broad peak is shown. The wide-peak waveform here is a waveform representing a straight line parallel to the horizontal axis. The difference in the spectra, that is, the presence or absence of the absorption peak or the number of waves indicating the absorption peak, allows the difference between the resin content of the top layer 430 and the resin content of the first region 41 to be determined.

In addition, it was confirmed that the same FT-IR spectrum was obtained even when the thermoplastic resin was polypropylene or polyphenylene sulfide instead of polyethylene. Specifically, a plurality of wave numbers indicating absorption peaks appear in the top sheet portion 430, and no wave number indicating absorption peaks appears in the first region 41.

The FT-IR spectrum by the ATR method is measured by a commercially available analyzer. An example of the analyzer is IRTracer-100 attached to ATR8000A, manufactured by Shimadzu corporation. The measurement conditions include, for example, a wave number resolution of 4cm ^-1 And the cumulative number of times was 16.

The content of the resin is measured by using the absorption peak of the FT-IR spectrum. In addition, as a method for measuring the content of the resin, for example, specific gravity is used. Samples were cut out from the first region 41 and the reinforcing portion 43, and specific gravity of each sample was measured. The content of the resin can be estimated from the measured specific gravity.

Thickness of reinforcing portion

It is possible to give the reinforcing portion 43 a thickness t smaller than or equal to the thickness t of the first region 41 ₄₁ . The thickness t of the reinforcing portion 43 is equal to the thickness t of the first region 41 as illustrated in fig. 4B and 7 ₄₁ Is provided.In the layered reinforcing part 43 shown in fig. 9, the thickness t of the reinforcing part 43 may be smaller than the thickness t of the first region 41 ₄₁ Is appropriately selected within the range of (2). The thickness t of the reinforcing portion 43 constituting one layer may be, for example, the thickness t ₄₁ More than 2% and less than 100%. The thickness t of the reinforcing portion 43 constituting one layer may be the thickness t ₄₁ More preferably, the ratio of (2) is 5% to 80%, and still more preferably 10% to 50%. Further, the thickness t of the first region 41 ₄₁ Examples thereof include 0.5mm to 20 mm.

In the case where the reinforcing portion 43 includes the surface layer portion 430, it can be said that the thicker the thickness t of the surface layer portion 430 is, the more the portion having a relatively large resin content is located at a deeper position from the surface of the second region 42 toward the inside. The second region 42 having such a surface layer portion 430 is less likely to crack. For example, the thickness t of the surface layer 430 may be 10 μm or more. If the thickness t of the surface layer portion 430 is 10 μm or more, it can be said that the surface layer portion 430 is properly present. Therefore, the second region 42 is less prone to cracking. In the case where it is desired to further reduce the occurrence of cracking, the thickness t of the surface layer portion 430 is preferably 50 μm or more. The thickness t of the surface layer portion 430 is more preferably 80 μm or more and 100 μm or more, 150 μm or more and 200 μm or more.

The thickness t of the surface layer portion 430 may be, for example, 2mm or less. If the thickness t of the surface layer portion 430 is 2mm or less, the surface layer portion 430 can be formed using the film or the like described above. In this case, the thickness t of the surface layer portion 430 depends on the thickness of the film. When the thickness of the film is, for example, 1mm or less and 500 μm or less, the film is favorably bonded to the material used as the base 420. Therefore, the surface layer portion 430 is less likely to peel from the base portion 420. With this, the second region 42 is less prone to cracking. Further, the bipolar plate 4 is excellent in manufacturability by utilizing the fact that the bonding operation of the thin film and the preform is easy. The thickness t of the surface layer portion 430 may be about 450 μm or less to about 400 μm or less based on the thickness of the film.

The thickness t of the surface layer portion 430 may be 10 μm or more and 2mm or less and 50 μm or more and less than 500 μm from the viewpoint of reducing the occurrence of cracking and good manufacturability of the bipolar plate 4.

The thickness t of the surface layer portion 430 is measured as follows, for example. When the surface layer portion 430 is substantially made of resin and the base portion 420 of the second region 42 is made of the composite material, a vertical cross section of the bipolar plate 4 is used. First, in the bipolar plate 4, a vertical cross section of the second region 42 is employed. Then, the vertical cross section is observed by a microscope or the like. In the vertical cross section, a boundary between a portion made of a resin and a portion made of the composite material, which substantially does not contain a conductive material, can be distinguished. In the vertical cross section, the distance from the surface 43f of the surface layer 430 to the boundary is measured. The distance is measured at a plurality of places, for example, at 50 or more places. Alternatively, the distance to the boundary is measured within a range of 100mm or more along the boundary. The measured distances are averaged. The average value is set to the thickness t of the surface layer portion 430. The thickness t of the layered surface layer portion 430 may be measured in the same manner, and the distance between the boundaries of different materials may be measured by using the vertical cross section and the average value may be obtained.

Width of reinforcing portion

The width W of the reinforcing portion 43 may be selected within a range of less than or equal to the width of the second region 42. It can be said that the wider the width W, the wider the portion where the content of the resin is relatively large is present in the second region 42. The second region 42 provided with such a reinforcing portion 43 is less prone to cracking. For example, the width W may be 3mm or more. If the width W is 3mm or more, it can be said that the reinforcing portion 43 is properly present and the second region 42 is less likely to crack. Since the bipolar plate 4 of this example is disposed in the housing 30 via the seal member 39, the width W is preferably larger than the width of the seal member 39. In particular, the width W is preferably larger than the width of the seal member 39 in a state where the seal member 39 is compressed by the above-described tightening force.

In a state where the bipolar plate 4, the seal member 39, and the housing 30 are stacked, the portion of the second region 42 facing the seal member 39 is particularly susceptible to stress caused by the fastening force when viewed from above in the stacking direction. Therefore, it is desirable to provide the reinforcing portion 43 at least at this portion. If the width W of the reinforcing portion 43 is wider than the width of the seal member 39, preferably wider than the width of the seal member 39 in the compressed state, the reinforcing portion 43 receives the stress satisfactorily. As a result, the second region 42 is less prone to cracking. In addition, if the width of the sealing member 39 is 3mm or more, the RF battery 1 excellent in sealability can be constructed.

In the case where it is desired to further reduce the occurrence of cracking and the improvement of the sealing property, the width W of the reinforcing portion 43 is preferably 3.5mm or more and 4.0mm or more, 4.5mm or more and 5.0mm or more. As illustrated in fig. 13, 17A to 18, the width W may be substantially the same as the width of the second region 42. That is, the entire surface of the second region 42 and the vicinity of the surface in the thickness direction of the bipolar plate 4 may be the surface layer portion 430. In this case, the surface layer 430 is also easily formed using the film. The width W may be, for example, 10mm or less.

When the reinforcing portion 43 includes the outer edge 44, the width W of the reinforcing portion 43 is a distance from the outer edge 44 to a boundary between the first region 41 and the reinforcing portion 43 in the above-described plan view. When the reinforcing portion 43 does not include the outer edge 44, the second region 42 includes, for example, edge portions of two reinforcing portions 43 arranged at predetermined intervals in the planar view. In this case, the width W is the distance between the two edge portions. Even in the case where the first region 41 and the reinforcing portion 43 are flush with each other as described above, the textures of the surfaces 41f, 43f are different due to the difference in the content of the resin. Therefore, the boundary between the first region 41 and the reinforcing portion 43 and the edge portion of the reinforcing portion 43 can be discriminated in the above-described plan view.

The width W of the reinforcement portion 43 is measured as follows, for example. 10 or more measurement sites are provided at equal intervals in the extending direction of the reinforcing portion 43 or in the circumferential direction of the reinforcing portion 43. The width was measured at each measurement site. The measured widths were averaged. The average value is set to the width W of the reinforcing portion 43.

The width W of the reinforcing portion 43 may be uniform in the extending direction of the reinforcing portion 43 or the circumferential direction of the reinforcing portion 43, or may be locally thin or locally thick. In the manufacturing process, if a blank of a frame-like material, a film, or the like having a uniform width is used, the reinforcing portion 43 having a ring shape, a belt shape, or the like having a uniform width W can be easily manufactured. In the case where the width W is uneven in the extending direction or the circumferential direction, the minimum width of the reinforcing portion 43 is preferably larger than the width of the seal member 39 in the compressed state.

Width W and thickness t of this example

The width W of the surface layer portion 430 in this example is larger than the width of the seal member 39 in the compressed state described above (fig. 13). Such a surface layer portion 430 can be said to exist widely on the surface side of the second region 42. The thickness t of the surface layer portion 430 in this example is uniform over substantially the entire surface layer portion 430 (fig. 13). The bipolar plate 4 of this example has a surface layer portion 430 having a thickness t in a region on the outer edge 44 side thereof and has a surface layer portion (t) ₄₁ -t x 2) thickness of the base 420. The shape and size of the surface layer portion 430 in the vertical cross section of this example are symmetrical about the central axis in the thickness direction of the bipolar plate 4. These are examples, and the width W, the thickness t, and the like can be appropriately changed.

Mechanical Properties

When the reinforcing portion 43 includes the surface layer portion 430, the elongation at break of the portion adjacent to the surface layer portion 430 in the first region 41 is 0.5% or more. Here, the first region 41 includes a conductive material. Therefore, the elongation in the first region 41 is easily reduced as compared with the surface layer portion 430 containing a relatively large amount of resin. If the elongation at break is 0.5% or more, the elongation of the first region 41 is excellent. By making the elongation of the portion of the first region 41 adjacent to the surface layer portion 430 excellent, the surface layer portion 430 is less likely to peel off at the boundary surface between the first region 41 and the surface layer portion 430. Such bipolar plate 4 is not prone to cracking as a whole. The elongation at break is preferably 0.8% or more, and more preferably 1.0% or more. The greater the content of the resin in the first region 41, the more easily the elongation at break increases. That is, if the content of the conductive material in the first region 41 is small, the above-mentioned elongation at break is liable to be increased.

In the case of measuring the elongation at break, a test piece is selected from a portion of the first region 41 adjacent to the surface layer portion 430, that is, a portion near a boundary between the first region 41 and the surface layer portion 430 in a plan view. In the case where the entire first region 41 is made of a uniform material, the measurement results are substantially equal even when the elongation at break is measured by selecting a test piece from a portion distant from the boundary. Therefore, in the case where it is difficult to select a test piece from the boundary portion in the first region 41, it is allowed to select a test piece from a portion distant from the boundary.

Battery cell frame

The bipolar plate 4 of embodiment 1 includes the surface layer portion 430 as the reinforcing portion 43 on both the first surface and the second surface. As shown in fig. 13, such a bipolar plate 4 is used in the following cases: for example, the housing 30 includes a pair of divided pieces 301 and 302, and is supported by the housing 30 by being sandwiched between the two divided pieces 301 and 302. This utilization method can also be applied to embodiments 2 to 7.

Each of the divided pieces 301 and 302 has a notch 305. By combining the two divided pieces 301 and 302, the cutout 305 forms a space having a rectangular cross section. This space serves as a recess into which the second region 42 of the bipolar plate 4 is embedded. The second region 42 is accommodated in this space. The inner peripheral surface of the cutout 305 is provided with a groove 309 at a position facing the second region 42. The sealing member 39 is fitted into the groove 309. The bipolar plate 4 may also have grooves into which the seal members 39 are fitted. The sealing member 39 may be, for example, a seal, an O-ring, or the like.

The battery cell frame 3 is constructed by sandwiching the second region 42 of the bipolar plate 4 with the split pieces 301, 302 having the sealing member 39 embedded in the groove 309. In this example, as shown in fig. 12, in the assembled state of the battery cell frame 3, the second region 42 including the surface layer portion 430 is covered or blocked by the frame body 30, and is substantially invisible. Substantially only the first region 41 is exposed from the window 31 of the housing 30.

In the cell frame 3, the seal member 39 is sandwiched between the inner peripheral surfaces of the divided pieces 301 and 302 and the reinforcing portion 43, here, the surface layer portion 430, provided in the second region 42 of the bipolar plate 4. The second region 42 receives stress from the frame 30 by being sandwiched between the divided pieces 301 and 302 constituting the frame 30. However, the bipolar plate 4 according to embodiment 1 and the like is less likely to crack by being provided on the surface layer 430 of the second region 42 on both the first surface and the second surface. The bipolar plate 4 of embodiment 4 and the like is less likely to crack due to the reinforcement portion 43 provided over the entire region in the thickness direction of the bipolar plate 4. Further, the bipolar plate 4 is not easily detached from the housing 30 because it is sandwiched by the divided pieces 301 and 302. The bipolar plate 4 of this embodiment contributes to improvement in the manufacturability of the RF battery 1 by making use of the ease of construction and lamination of the battery cell frame 3.

Next, another example of the bipolar plate 4 according to the embodiment including the surface layer portion 430 will be described with reference to fig. 15 to 18.

Fig. 15 is a top view of a cell frame 3 including another bipolar plate 4.

Fig. 16 is a top view of the bipolar plate 4 and the housing 30 of another example.

Fig. 17A and 17B are cross-sections of the cell frame 3 shown in fig. 15, each of which is a section of the vicinity of the outer edge 44 of the bipolar plate 4 taken in a plane parallel to the thickness direction of the bipolar plate 4.

As shown in fig. 16 to 18, the bipolar plate 4 of the present example is used in the following cases: the frame 30 includes a flange 303 on the inner peripheral side, and is supported by the frame 30 by being placed on the flange 303.

First, the housing 30 will be described. As shown in fig. 17A and the like, the housing 30 has a stepped structure in which the thickness of the outer peripheral side of the housing 30 is different from the thickness of the inner peripheral side of the housing 30. The frame 30 includes an outer frame portion having a relatively large thickness and a flange portion 303 having a relatively small thickness. The flange portion 303 is provided along an inner peripheral wall of the window portion 31 formed in the outer frame portion. As shown in fig. 17A, the flange 303 is provided to be offset to the first surface side of the outer frame. The first surface of the outer frame portion forms the surface of the frame body 30. The first surface of the flange 303 is continuous with and flush with the first surface of the outer frame. The first surface here is the surface on the left side of the paper surface in fig. 17A to 18. A recess 306 into which the bipolar plate 4 is fitted is formed by the second surface of the flange portion 303 and the inner peripheral wall. The second surface here is a surface near the front orthogonal to the paper surface in fig. 16, and is a surface on the right side of the paper surface in fig. 17A to 18. Hereinafter, the second surface of the flange 303 is referred to as a base surface. The base surface of the flange 303 includes a groove 309 into which the seal member 39 is fitted. The groove 309 is omitted in fig. 16. The seating surface supports a second region 42 (fig. 15) of the bipolar plate 4.

The battery cell frame 3 including the frame body 30 having the flange portion 303 is easily formed by placing the second region 42 of the bipolar plate 4 on the base surface of the groove portion 309 in which the seal member 39 is fitted. With this, the battery cell frame 3 contributes to improvement in manufacturability of the RF battery 1. In the cell frame 3, as illustrated in fig. 15, a gap of a certain size can be secured between the window 31 of the frame body 30 and the outer edge 44 of the bipolar plate 4 (see fig. 17A, etc.). The bipolar plate 4 is less likely to bear stress from the frame 30 due to the gaps. Therefore, the bipolar plate 4 of the present example is less prone to cracking. In addition, in this cell frame 3, the flange portion 303 and the surface layer portion 430 of the second region 42 of the bipolar plate 4 sandwich the sealing member 39.

As an example of the bipolar plate 4 used for the cell frame 3 having the flange 303, the following can be given: the first surface of the bipolar plate 4 includes a first region 41 and a second region 42, and the second surface of the bipolar plate 4 includes only the first region 41 (fig. 16 to 17B). In fig. 16, the first surface of the bipolar plate 4 is a surface facing the deep side of the paper.

As shown in fig. 16, the surface layer portion 430 of the present example is a frame-shaped region having a predetermined width W from the outer edge 44 toward the inside in a state in which the bipolar plate 4 is seen in a plan view. The entire surface of the second region 42, which is the region on the outer edge 44 side, on the first surface of the bipolar plate 4 is a surface layer portion 430 (see fig. 17A, etc.). For ease of understanding, fig. 16 is a hatched line of a broken line to the surface layer portion 430.

Manner of bipolar plate without step

In the bipolar plate 4 shown in fig. 17A, the thickness t of the first region 41 ₄₁ Is substantially equal to the thickness of the region on the outer edge 44 side provided with the surface layer portion 430. If the width W of the surface layer portion 430 is smaller than the compressed state of the seal member 39 as illustrated in fig. 17A also in the bipolar plate 4 having the surface layer portion 430 on only the first surface of the bipolar plate 4The second region 42 is less prone to cracking if the width is large.

In addition, in the bipolar plate 4 shown in fig. 17A, the thickness t of the surface layer portion 430 is uniform over substantially the entire surface layer portion 430. The region on the outer edge 44 side of the bipolar plate 4 includes a surface layer portion 430 having a thickness t and a region having (t) ₄₁ -t) a base 420 of thickness. These are examples, and the width W, the thickness t, and the like can be appropriately changed.

Mode with step of bipolar plate 1

The bipolar plate 4 shown in fig. 17B has a thickness t at a portion closer to the outer edge 44 than the outer edge 44 of the first region 41 in a region closer to the outer edge 44 than the surface layer 430 ₄₁ Thin portions. The bipolar plate 4 includes a surface layer portion 430 at the thin portion. Specifically, the second region 42 has a stepped portion 45 having a different thickness. At least the lower step surface 450 of the step 45 includes the surface layer 430.

The region of the bipolar plate 4 on the outer edge 44 side has a predetermined thickness t ₁ And has a thickness t ₂ Is a part of the same. Thickness t ₁ Specific thickness t ₂ Is small. Thickness t ₂ And thickness t ₄₁ Substantially equal. The step 45 has the thickness t ₁ Is provided with a lower step surface 450. The lower step surface 450 of the step 45 is placed on the flange 303 of the housing 30. The upper step surface of the step portion 45 is continuous substantially flush with the first region 41.

As shown in fig. 17B, the surface layer portion 430 of the present example continues from the lower step surface 450 of the step portion 45 to a portion near the first region 41 in the first surface of the bipolar plate 4 via a connection surface connecting the lower step surface 450 and the upper step surface. In this example, the surface 43f of the surface layer portion 430 is continuous with the surface 41f of the first region 41 without steps in the first surface of the bipolar plate 4. If the width of the portion of the surface layer portion 430 provided at the lower step surface 450 is larger than the width of the sealing member 39 in the compressed state, the second region 42 is less likely to crack.

In addition, in the bipolar plate 4 shown in fig. 17B, the thickness t of the surface layer portion 430 is uniform over substantially the entire surface layer portion 430. The region of the bipolar plate 4 on the outer edge 44 side has a surface layer portion 430 having a thickness t and a base belowAnd a portion 420. The base 420 includes a base having (t) ₁ -a relatively thin portion of thickness of t) and having a thickness (t) ₂ -t) a relatively thick portion of the thickness. These are examples, and the width W, the thickness t, and the like can be appropriately changed.

When the bipolar plate 4 having the stepped portion 45 is placed on the base surface of the flange portion 303 in the frame body 30 as described above in the process of constructing the cell frame 3, the stepped portion 45 is less likely to be displaced from the frame body 30. The step portion 45 and the flange portion 303 can be said to function as positioning portions with each other. In addition, since the misalignment is less likely to occur, stacking work and the like can be easily performed even when a multi-cell is constructed. Such bipolar plate 4 and battery cell frame 3 contribute to improvement in the manufacturability of RF battery 1. Further, in the cell frame 3, the locally thin step portion 45 in the bipolar plate 4 receives an external force such as stress due to the tightening force, but since the step portion 45 includes the surface layer portion 430, the bipolar plate 4 is less likely to crack.

Bipolar plate stepped mode 2

In the case where the second region 42 has the step 45, as shown in fig. 18, the surface layer 430 may be formed on the entire surface of the step 45. Like the bipolar plate 4 of embodiment 1, the bipolar plate 4 includes the surface layer portion 430 on both the first surface and the second surface. By providing the surface layer portion 430 on the entire surface of the step portion 45, the bipolar plate 4 of embodiment 2 is less likely to crack than the bipolar plate of embodiment 1 (fig. 17B).

The surface layer 430 of this example continues from a portion near the first region 41 of the first surface of the bipolar plate 4, that is, an upper step surface, to a region on the outer edge 44 side of the second surface of the bipolar plate 4 via a connection surface connecting the upper step surface and the lower step surface 450, and an end surface constituting the outer edge 44. In this example, the surface 43f of the surface layer portion 430 and the surface 41f of the first region 41 are substantially flush-continuous without steps on each of the first surface and the second surface of the bipolar plate 4.

In addition, in the bipolar plate 4 shown in fig. 18, the width of the portion of the surface layer portion 430 provided on the lower step surface 450 is larger than the width of the seal member 39 in the compressed state. The outer edge of the bipolar plate 4The region 44 includes a surface layer portion 430 having a thickness t and a base portion 420 below. The base 420 includes a base having (t) ₁ -t x 2) and a relatively thin portion having a thickness (t) ₄₁ -t x 2) a relatively thick portion of the thickness. These are examples, and the width W, the thickness t, and the like can be appropriately changed.

Flow passage

A specific example of the flow path 5 will be described below with reference to fig. 19 to 21. The flow paths 5 described below are examples, and the shape, size, number, and the like of the flow paths 5 can be appropriately changed. The bipolar plate 4 may not have the flow passage 5.

Fig. 19 to 21 are views of the bipolar plate 4 from the thickness direction of the bipolar plate 4. The thickness direction is the direction perpendicular to the paper surface in fig. 19 to 21.

Fig. 19 shows a case where a plurality of linear grooves 51 extending in the flow direction of the electrolyte are provided as the flow paths 5. Each groove 51 has a first end portion open at the supply edge 5i (fig. 2) and a second end portion open at the discharge edge 5o (fig. 2). In addition, each of the grooves 51 has a length equal to the distance between the supply edge 5i of the electrolyte and the discharge edge 5o of the electrolyte. The grooves 51 are arranged at predetermined intervals in the extending direction of the supply edge 5i or the discharge edge 5 o. The direction of flow of the electrolyte is the up-down direction of the paper in fig. 19 to 21. The cross-sectional shape of the groove 51 may be, for example, rectangular (see fig. 10 and fig. 26 described later).

Fig. 20 shows a case where a meandering groove 52 is provided as the flow path 5. The groove 52 has a first end portion open at the supply edge 5i and a second end portion open at the discharge edge 5 o. The intermediate portion of the groove 52 swings between the supply edge 5i and the discharge edge 5 o. The length of the groove 52 is longer than the length of the linear groove 51 shown in fig. 19.

Fig. 21 shows another example of the case where a linear groove extending in the flow direction of the electrolyte is provided as the flow path 5. The flow path 5 includes linear grooves 53 and 54 shorter than the groove 51. The groove 53 has a first end portion open at the supply edge 5i and a second end portion closed at the discharge edge 5o side. The groove 54 has a first end portion closed at the supply edge 5i side and a second end portion opened at the discharge edge 5 o. The grooves 53 and the grooves 54 are alternately arranged at predetermined intervals in the extending direction of the supply edge 5i or the discharge edge 5 o.

Method of manufacturing

Hereinafter, a method for manufacturing the bipolar plate 4 according to the embodiment will be described.

The bipolar plate 4 of the embodiment is manufactured as follows, for example.

(1) A first blank is prepared as the first region 41.

(2) A second blank is prepared as the reinforcing portion 43.

(3) Heating and pressurizing are performed in a state where the two blanks are overlapped or in a state where the two blanks are combined.

The first material may be, for example, a plate material made of a composite material including a conductive material and a resin. The sheet material may be produced by various molding methods, for example. Examples of the molding method include injection molding, press molding, and vacuum molding. In the case where the first region 41 includes the flow channel 5, the flow channel 5 may be formed at the same time when the first material is formed into a plate shape. Alternatively, the flow path 5 may be formed by manufacturing a flat plate material and cutting the plate material. The sheet material may be manufactured by a known manufacturing method of a bipolar plate.

In the case of manufacturing the bipolar plate 4 including the surface layer portion 430, a blank in which at least a part of the region on the outer edge side of the first blank is used as the base portion 420 in the second region 42 may be used. In this case, the second material is heated and pressed in a state where a film, for example, to be described later, is disposed in the region on the outer edge side. The region of the first blank remote from the inner side of the outer rim constitutes a first region 41. There is no need to provide a groove or step for placing the second material in the region on the outer edge side of the first material.

The second material may be, for example, a frame-like material, a plate material, a foil-like material, or the like, which is made of a composite material including a conductive material and a resin. The method for manufacturing the second material made of the composite material is the same as the method for manufacturing the first material. Alternatively, the second material may be a frame-like material made of resin, a plate material, a film, or the like. The bipolar plate 4 having the surface layer portion 430 is manufactured by using a thin second blank of a foil-like material, a film, or the like. The film made of the resin may be a commercially available product. The thickness of the film may be, for example, 50 μm or more and 1mm or less. The thickness of the film may be 100 μm or more and less than 500 μm, 480 μm or less, 450 μm or less, 400 μm or less.

The second blank preferably comprises the thermoplastic resin described above. More preferably, the first and second blanks comprise the same thermoplastic resin. The thermoplastic resin is softened by heating, and the first material and the second material are excellent in bonding property. Therefore, the bipolar plate 4 in which the reinforcing portion 43 is not easily peeled off from the first region 41 is easily manufactured.

The heating and pressurizing may be performed by, for example, hot stamping. By heating, the resin is softened or melted in the second preform containing at least the resin. The first and second blanks are integrated by pressurizing the second blank containing the resin in a softened or molten state. If the two blanks contain resin, the two blanks are more reliably integrated. In addition, in a case where the reinforcing portion 43 constitutes a part of the surface of the second region 42, the bipolar plate 4 is manufactured by hot stamping using a die, the surface of the reinforcing portion 43 and the surface of the first region 41 being continuous without steps.

The heating temperature may be adjusted according to the type of resin contained in the first and second blanks. The heating temperature is preferably equal to or higher than the glass transition point of the resin. The pressure is, for example, 5MPa to 10MPa based on the heating temperature, the thickness of the second material, the composition of the first material and the second material, and the like. The holding time of the pressurized state may be, for example, 30 seconds to 10 minutes.

When the holding time has elapsed, the heating is stopped, and the temperature is cooled from the heating temperature to room temperature. The pressurized state may be released during the cooling process, or the pressurized state may be maintained. It is considered that, by maintaining the pressurized state, it is easy to prevent the occurrence of a step between the surface 43f of the reinforcing portion 43 and the surface 41f of the first region 41 due to deformation caused by thermal contraction at the time of cooling. In the case where the pressurized state is maintained during the cooling, for example, the pressurized state is obtained from the heating temperature to 180 ℃. When the temperature reaches 80 ℃ during cooling, the pressurized state is released and only cooling is performed.

In manufacturing the bipolar plate 4 having the surface layer portion 430, the second material such as a film is heated and pressed in a state where the second material is placed on the outer edge side of at least one of the first surface and the second surface of the first material. The integration of the two blanks is performed along the inner peripheral surface of the die. The mold molds the two blanks so that the surface of the second blank and the surface of the portion other than the position on which the second blank is placed in the first blank form a uniform plane. As a result, the bipolar plate 4 is formed such that the surface 43f of the surface layer portion 430 is continuous with the surface 41f of the first region 41 without steps. The width W of the surface layer portion 430 is substantially equal to the width of the second material such as a film. In addition, according to this manufacturing method, if the resins contained in the first and second blanks are thermoplastic resins of the same type, the regions near the boundary surface between the surface layer portion 430 and the first region 41 and the regions near the boundary surface between the surface layer portion 430 and the base portion 420 become regions where the resins diffuse.

The surface layer portion 430 shown in fig. 4A, 13, and 18 is formed using the thin film described above, for example, as follows. A film is placed on a region from the outer edge side of the first surface of the first material through the end surface of the first material to the outer edge side of the second surface of the first material, and hot stamping is performed. In this case, the region where the thin film is disposed is wider for the first blank than for the bipolar plate 4 shown in fig. 17A, for example. The bipolar plate 4 shown in fig. 4A and the like is excellent in manufacturability by virtue of the fact that the thin film is easily arranged on the first blank. The bipolar plate 4 shown in fig. 17A can reduce the amount of thin films used. When a plurality of plate-like blanks having different resin contents are laminated and subjected to hot stamping or the like, the bipolar plate 4 shown in fig. 9 can be manufactured. Further, if a plurality of blanks having different resin contents are used, it is possible to manufacture the bipolar plate 4 having regions in which the resin contents are different stepwise or continuously in the thickness direction of the bipolar plate 4.

The bipolar plate 4 shown in fig. 17B can be manufactured, for example, as follows. As the first blank, a first blank having a stepped portion 45 is prepared. A thin film is placed on a region from the lower step surface 450 of the step 45 to the outer edge 44 side of the first surface of the bipolar plate 4 through the connecting surface, and hot stamping or the like is performed. The bipolar plate 4 is also excellent in manufacturability because of the wide arrangement area of the thin film.

As in the three-striped bipolar plate 4 described in embodiment 4, a bipolar plate 4 in which a plurality of plate-like molded bodies are arranged in a striped manner is produced by the following continuous production method. As a blank, a plurality of continuous long plates are prepared. In embodiment 4, three plates are prepared, one plate is used as a first material, and two plates are used as a second material. By arranging two second blanks in such a manner as to sandwich the first blank, an intermediate blank arranged in three stripes is produced. The intermediate material is supplied to the rollers and heated and pressurized by the rollers, thereby integrating the intermediate material. By continuously feeding the intermediate material to the roller, three striped molded bodies are continuously produced. The bipolar plate 4 is manufactured by cutting the manufactured integrated molded body into an appropriate length. It is expected that the continuous process can be used for mass production of the bipolar plate 4.

Alternatively, the three-striped bipolar plate 4 and the bipolar plate 4 having the reinforcing portion 43 formed of the frame-shaped molded body shown in fig. 4B may be formed by injection molding or the like of a resin molded body having a band plate shape or a frame shape or a molded body of the composite material on the outer periphery of the first material. The resin molded body or the composite molded body is a reinforcing portion 43. In particular, the resin molded body can be easily molded.

Multistage preparation method

As another example of the method for manufacturing the bipolar plate 4 of the embodiment, a manufacturing method using the following bipolar plate is given. The following method for manufacturing a bipolar plate is a method for manufacturing a bipolar plate containing carbon powder as a conductive material, and a bipolar plate having a large content of carbon powder can be manufactured. Therefore, if the following method for manufacturing a bipolar plate is used, the bipolar plate 4 including the first region 41 containing a large amount of carbon powder, that is, the bipolar plate 4 having a high conductivity and a low volume resistivity can be manufactured.

A method for manufacturing a bipolar plate, which comprises a first powder composed of carbon and a second powder composed of a thermoplastic resin as raw materials, comprises the following steps:

a first step of obtaining a mixed powder obtained by stirring and mixing the first powder and the second powder at a temperature lower than the softening temperature of the thermoplastic resin;

a second step of heating the mixed powder to a first temperature and pressurizing the mixed powder, and then cooling the mixed powder to obtain a precursor;

a third step of heating the precursor or a precursor processed body obtained by mechanically processing the precursor to a second temperature which is higher than the first temperature and is equal to or higher than the softening temperature of the thermoplastic resin; and

And a fourth step of pressurizing the heated precursor or the precursor processed body by a mold and then cooling the precursor or the precursor processed body, thereby obtaining the bipolar plate having a higher density than the precursor.

Hereinafter, the method of manufacturing the bipolar plate is referred to as a multi-stage manufacturing method.

The multi-stage recipe may be set as follows.

Mode with fifth step

After a first mixed powder, which is the mixed powder obtained by setting the mixing ratio of the first powder and the second powder to a first mixing ratio, is obtained in the first step, a first precursor is produced by performing the second step using the first mixed powder.

In the first step, a second mixed powder, which is the mixed powder obtained by setting the mixing ratio of the first powder and the second powder to a second mixing ratio different from the first mixing ratio, is obtained, and then the second precursor is produced by performing the second step using the second mixed powder.

The multi-stage process includes a fifth step of manufacturing the precursor processed body by mechanically processing and combining the first precursor and the second precursor.

And performing the third step and the fourth step on the precursor processed body to obtain the bipolar plate.

In the fifth step, an opening may be formed in one of the plate-shaped first precursor and the plate-shaped second precursor, and the other precursor may be machined and then fitted into the opening to manufacture the precursor processed body.

Mode of using resin-made blank

And forming the precursor processed body by locally abutting and disposing a blank made of thermoplastic resin in a direction along the surface of the precursor.

In the multistage process, the main materials are carbon powder and a thermoplastic resin in a powder state, and finally, a bipolar plate having a final shape is produced by mold molding at a temperature equal to or higher than the softening temperature of the thermoplastic resin, which is the same as the techniques described in patent documents 3 and 4. However, the multistage production method differs from the techniques described in patent documents 3 and 4 in the production steps until a molded article of a final shape is obtained. The multistage process increases the carbon powder content by performing two-stage heating until a final molded article is obtained. In addition, the multi-stage manufacturing method can easily manufacture bipolar plates 4 of various structures by forming a plate-like precursor having a shaping property in the middle of manufacturing and appropriately processing the precursor.

Further, a conventional bipolar plate, which is a plate-shaped molded body obtained by mixing carbon powder and thermoplastic resin and has a molded body with uniform conductivity by uniformly mixing carbon powder, is manufactured as follows.

First, the thermoplastic resin formed into particles and the carbon powder are uniformly mixed by a stirrer. After this mixing, the thermoplastic resin and the carbon powder are uniformly mixed in a state heated to a temperature equal to or higher than the melting point of the thermoplastic resin. By cooling the mixture after this mixing, a solidified mixture, i.e., a composite, is obtained. The composite is, for example, granular, powdery having a larger particle diameter than the raw material, and is not a bipolar plate having a predetermined shape, for example, a bipolar plate formed with grooves or the like. After the composite is put into a mold, the composite is reheated to a temperature equal to or higher than the melting point of the thermoplastic resin, and a bipolar plate having a predetermined shape is formed.

In order to uniformly disperse carbon powder in the composite when the composite is produced, fluidity of the thermoplastic resin after heating is required. Therefore, it is necessary to contain a thermoplastic resin in a certain proportion or more. On the other hand, in order for the bipolar plate to have high conductivity, a large content of carbon powder is required. In the above conventional production method, it is necessary to increase the content of the thermoplastic resin in order to ensure fluidity, and therefore it is difficult to reduce the content of the thermoplastic resin. Therefore, in the above conventional manufacturing method, the content of carbon powder is large, and it is difficult to manufacture a bipolar plate having uniformly high conductivity.

The multistage recipe is described in detail below with reference to fig. 22 to 26.

First procedure ]

First powder

The carbon powder used as the raw material is, for example, graphite particles. The graphite may be artificial or natural. The density of the carbon powder was set to 2.2g/cm ³ Left and right. The average particle diameter of the first powder will be described later.

Second powder

The thermoplastic resin used as the raw material may be a resin described in the above item of "resin". The relationship between the average particle diameter of the second powder composed of the thermoplastic resin, the average particle diameter of the second powder, and the average particle diameter of the first powder will be described later.

Details of the procedure

In the first step, the first powder and the second powder are mixed in a predetermined ratio. The mixing is performed at a temperature less than the softening temperature of the thermoplastic resin. Typically, the mixing is performed without heating, for example, at room temperature. As shown in fig. 22, for example, a first powder 901 and a second powder 902 are charged in a predetermined ratio in a rotary mixer 20. The mixed powder 900 is obtained after uniformly stirring and mixing the powders 901 and 902 in the stirrer 20.

< second procedure >

In the second step, the mixed powder 900 is press-molded at a low temperature and a low pressure, which will be described later, to obtain a precursor. Hereinafter, the precursor is referred to as a preform 90. The preform 90 obtained here is a flat plate-shaped molded body. The press molding uses a box-shaped precursor die 21 and a plate-shaped precursor die 22, which are open at the upper part. The inner peripheral shape of the precursor mold 21 and the surface shape of the precursor mold 22 have shapes corresponding to the preform 90.

As shown in the upper part of fig. 23, the mixed powder 900 is put into the precursor die 21. Next, as shown in the second part of fig. 23, the amount of the mixed powder 900 is adjusted. After the adjustment, as shown in the third part of fig. 23, a plate-shaped precursor die 22 is combined with the precursor die 21. The preform 90 is formed by pressurizing the precursor die 22 to a predetermined pressure, for example, 0.5MPa or more, and further about 1MPa to 4MPa, as shown in the lower part of fig. 23.

The first temperature at which the preform 90 is formed may be a temperature close to the melting point of the thermoplastic resin constituting the second powder 902. The first pressure at which the preform 90 is formed may be set such that the density of the preform 90 is 70% or more and less than 90% of the theoretical density at the time of the closest packing. Such a preform 90 has fine voids. Thus, the density of the preform 90 is lower than that of the finally fabricated bipolar plate. Due to the lower density, the mechanical strength of the preform 90 is not high. The density in the above range is a density at which it is assumed that the grooves having a predetermined shape are formed in the preform 90, and the preform 90 cannot be used as a bipolar plate. If the first pressure is higher, a high density, high strength preform 90 is formed. However, although the plate-like shape is maintained, the first temperature and the first pressure in the state shown in the lower part of fig. 23 are set so as to form the preform 90 having a low density.

The temperature close to the melting point of the thermoplastic resin may be, for example, about ±50 ℃ of the melting point. In a temperature range close to the above melting point, if the first temperature is relatively low, the first pressure is set higher. If the first temperature is relatively high, the first pressure is set lower. At a first temperature higher than the above melting point, the second powder 902 tends to soften. For example, the first temperature may be about 70℃higher than the melting point.

In the above conventional production method, the thermoplastic resin is sufficiently softened to form the composite. Thus, the density of the above-mentioned composite is high. That is, the composite is in the form of particles having a high density, and the like. In contrast, the preform 90 is a low-density plate.

< third procedure >

In a third process step, the preform 90 is placed on the mold 23, 24 (fig. 24) corresponding to the final shape of the bipolar plate and heated. Thereafter, in the fourth step, the preform 90 is densified and molded so as to form a bipolar plate having a predetermined surface shape. Fig. 24 illustrates a bipolar plate 4A provided with a plurality of grooves 50 as a bipolar plate. The groove 50 is formed to extend in the direction perpendicular to the paper surface of fig. 24.

As shown in the upper part of fig. 24, in the third step, the plate-shaped preform 90 is heated while being sandwiched between the lower mold 23 and the upper mold 24. The second temperature, which is the heating temperature at this time, is set higher than the first temperature in the second step, and the thermoplastic resin is sufficiently softened.

< fourth procedure >

As shown in the middle part of fig. 24, the fourth process is performed by pressurizing the mold 23 or the mold 24 in a direction perpendicular to the direction along the surface of the preform 90 immediately after the third process. This step is performed using a cold press. Therefore, at least the temperature at the end of this step is room temperature. The preform 90 is pressurized and compressed in the thickness direction to thereby increase the density, and the bipolar plate 4A having a final shape is manufactured. Here, as shown in the lower part of fig. 24, a bipolar plate 4A in which grooves 50 and the like are formed is obtained. The third step and the fourth step are performed as described above in order to densify the preform 90 and form the surface structure of the bipolar plate 4A. In the fourth step, unlike the second step, the groove 50 and the like are formed. Accordingly, the pressure applied to the preform 90, i.e., the second pressure, is not uniform. The second pressure may be, for example, about 5MPa or more. The second pressure may be 7MPa or more, for example.

In the multi-stage process, if the preform 90 is compared with the finally manufactured bipolar plate 4A, the density or porosity is different. However, the ratio of the first powder to the second powder is substantially the same. In the multi-stage production method, the proportion of the first powder in the preform 90, that is, the proportion of the carbon powder can be increased as compared with the composite formed in the above-described conventional production method. For example, the volume ratio of carbon powder in the finally produced bipolar plate 4A can be increased to 70% or more. By containing a large amount of carbon powder, the bipolar plate 4A is excellent in conductivity. In addition, as the voids in the bipolar plate 4A, the volume ratio of the fine voids can be reduced to typically less than 10%. The bipolar plate 4A having fewer voids has a high density, and thus has excellent mechanical strength.

Average particle diameter of powder

The average particle diameter of the carbon powder as the first powder is preferably 1mm Φ or less. The average particle diameter of the thermoplastic resin powder as the second powder is preferably 2 times or less the average particle diameter of the first powder. By satisfying these two conditions, a plate-shaped preform 90 having a shape-formability is produced in the first step and the second step. In the third and fourth steps thereafter, a bipolar plate 4A in which carbon powder is uniformly dispersed is produced. If the average particle diameter of the first powder is 1mm Φ or less, the first powder is easily and uniformly dispersed in the bipolar plate 4A. If the average particle diameter of the second powder is 2 times or less the average particle diameter of the first powder, gaps in the bipolar plate 4A where the first powder is dispersed are sufficiently filled with the second powder. Such bipolar plate 4A has a high density. When the average particle diameter of the second powder exceeds 2 times the average particle diameter of the first powder, the above-mentioned filling becomes difficult. The average particle diameter of the first powder may be 500 μm or less and 250 μm or less, and more preferably 150 μm or less. The average particle diameter herein may be calculated by using a sieving method using arithmetic average based on a number basis. Further, the average particle diameter of the carbon powder in the bipolar plates 4, 4A is substantially maintained at the average particle diameter of the first powder used in the manufacturing process. The average particle diameter of the carbon powder in the bipolar plates 4, 4A is measured by the following method: the resin is removed from the bipolar plates 4, 4A to extract carbon powder, and a sieving method is used for the extracted carbon powder as described above. Even if the carbon powder of the raw material is extracted and sieved during the manufacturing process of the bipolar plates 4, 4A, the average particle diameter of the carbon powder is not substantially changed.

< fifth procedure >

As described above, the plate-shaped preform 90 has a shaping property, and thus is easy to machine. In the fifth step, a precursor processed body, which is a processed body obtained by applying non-thermal processing to the preform 90, is manufactured. Hereinafter, the precursor processed body will be referred to as a preform processed body. If the high-pressure and high-temperature treatment is not applied to the preform 90, the preform processed body maintains the same composition and density as the original preform 90. That is, the ratio of the first powder to the second powder in the preform processed body is substantially the same as the ratio of the first powder to the second powder in the preform 90. If the third step and the fourth step are performed by replacing the preform 90 with such a preform processed body, a bipolar plate having the above-described composition and density is obtained.

For example, a first precursor and a second precursor having different presence ratios of the first powder to the second powder are used. The first preform 91 as the first precursor and the second preform 92 as the second precursor are manufactured through the first and second steps. The mixing ratio of the first powder and the second powder in the first step is different. For example, the proportion of the first powder in the first mixed powder used for the production of the first preform 91 is set to be larger than the proportion of the first powder in the second mixed powder used for the production of the second preform 92. The temperature, pressure, precursor dies 21, 22 in the second process may be different for the preforms 91, 92. Here, the thicknesses of the preforms 91 and 92 are set to be the same.

As shown in fig. 25, the rectangular plate-like first preform 91 is mechanically cut to form a smaller preform processed body 91A. The rectangular plate-shaped second preform 92 is formed into a preform processed body 92A having an opening 92B by cutting through a central region in a plan view. The shape of the opening 92B is rectangular like the preform processed body 91A. The preform processed body 91A is fitted into the opening 92B of the frame-shaped preform processed body 92A, thereby forming a new preform processed body 93. In this case, an adhesive or the like is not required. In the third step, the position of the preform processed body 91A with respect to the preform processed body 92A may be defined.

The third and fourth steps can be performed on the preform 93 in the same manner as in fig. 24. The preform processed body 91A is integrated with the preform processed body 92A by heating and pressurizing in the third step and the fourth step. The structure of the bipolar plate thus manufactured is the same as that of the preform processing body 93 shown in the lower part of fig. 25. In the bipolar plate manufactured as described above, the carbon powder content in the region corresponding to the preform 91A, that is, the region in the center in plan view, is greater than the carbon powder content in the region on the outer edge side of the bipolar plate. That is, in the central region, the ratio of the first powder to the second powder is higher than the ratio of the first powder to the carbon powder.

In general, the higher the ratio of the first powder, i.e., the carbon powder, in the presence ratio of the first powder to the second powder, the higher the conductivity of the bipolar plate and the lower the mechanical strength. The lower the proportion of the carbon powder, the lower the conductivity of the bipolar plate and the higher the mechanical strength. In the bipolar plate obtained by using the preform 93, the electric conductivity is high in the central region and the mechanical strength is high in the outer edge region. The above-mentioned central region in the bipolar plate can be used as the first region 41. The region on the outer edge side of the bipolar plate can be used as the reinforcing portion 43. In addition, the surface of the reinforcing portion 43 is continuous with the surface of the first region 41 without steps by the molds 23, 24. Therefore, the preform processed body 91A is suitable as the first blank of the first region 41. The preform 92A is suitable as a second blank for the reinforcing portion 43. By using such a preform processing body 93, the bipolar plate 4 of embodiment 1 shown in fig. 3 and 4B, for example, is manufactured.

As described above, the multi-stage method can use a new preform processed body obtained by applying mechanical processing such as cutting to a plurality of preforms having different compositions as raw materials of the bipolar plate and combining the processed preform processed bodies. In the above example, a bipolar plate having two regions corresponding to the respective preform processed bodies used was manufactured. If three or more preform processing bodies are used, a bipolar plate having three or more regions can be manufactured. The shape of each region is arbitrary as long as the third step and the fourth step can be performed on a new preform. For example, the bipolar plate 4 of embodiment 4 can be manufactured by using a preform processed body in which three plate-shaped preform processed bodies are arranged (fig. 7). Further, for example, a striped preform processed body obtained by combining a plurality of rod-shaped preform processed bodies having the same thickness can be used to manufacture the bipolar plate 4 (fig. 10) of embodiment 7. Rod-shaped preform processed bodies having different thicknesses may be combined. The groove 50 may also be formed by cutting after the fourth process.

As long as the third and fourth steps can be performed, a preform processed body other than a flat plate-shaped structure in which a plurality of preform processed bodies are fitted as in the preform processed body 93 described above can be used. For example, a preform processed body in which a blank 95 such as a film as the reinforcing portion 43 is disposed on the preform 90 can be used.

Fig. 26 shows a case in which the bipolar plate 4 is manufactured by using the preform processed body 96 obtained by combining the blanks 95, in the third step and the fourth step, corresponding to fig. 24. The preform processing body 96 shown in the upper part of fig. 26 has blanks 95 placed on the left and right end portions of the upper and lower surfaces of the preform 90, respectively. In a state where the preform 95 is laminated on the preform 90, the preform processed body 96 is placed between the dies 23, 24. As shown in the middle part of fig. 26, the preform processed body 96 is subjected to the fourth step in a state where the blanks 95 are laminated to the preform 90.

In the fourth step, the preform 90 is compressed together with the blank 95 to increase the density, thereby obtaining the bipolar plate 4 shown in the lower part of fig. 26. In the bipolar plate 4, as in the case of fig. 25, the conductivity is high in the central region, and the mechanical strength is high in the end-side region. The majority of the bipolar plate 4 is composed of a composite material corresponding to the preform 90. The central region of the bipolar plate 4 in plan view can be used as the first region 41. In the bipolar plate 4, the regions on the upper and lower and left and right end sides in fig. 26 are representatively used as the second regions 42. The second region 42 includes a reinforcing portion 43 substantially composed only of a thermoplastic resin corresponding to the blank 95. The reinforcing portion 43 here is a surface layer portion 430. This bipolar plate 4 corresponds to, for example, embodiments 2 and 3 (fig. 5 and 6).

In order to perform the manufacturing process shown in fig. 26, the preform processing body 96 is preferably shaped to approximate a simple flat plate shape. The blank 95 is preferably thin compared to the thickness of the preform 90. The thickness of the blank 95 is preferably set to a range of 0.01mm to 2mm as described above. The effect of reinforcement is small when the thickness is less than 0.01 mm. When the thickness exceeds 2mm, it is difficult to properly set the blank 95 at a predetermined position in the fourth step.

Examples of the preform 95 include a film, a sheet, and a platelet made of a thermoplastic resin. The shape of the blank 9 may be a frame shape, a belt shape, or the like as described above. In the case where the blank 95 is made of a thermoplastic resin, it is not necessary that the blank 95 and the second powder 902 are the same material. The material of each of the blank 95 and the second powder 902 can be a material that can realize each mode at low cost. The material of which the blank 95 is made is particularly required to have high mechanical strength. As described in the item of the reinforcing portion 43, a thermoplastic resin having high mechanical strength is PE, PP, PPS. The blank 9 may be the preform processed body described above.

The form of the preform and the preform processed body is not limited to a flat plate. Even if the preform or the like is not flat, the bipolar plate 4 or the like can be manufactured by heating the preform or the like and then pressurizing the same. In addition, a flat bipolar plate 4 without grooves 50 can also be manufactured. In the case of manufacturing the bipolar plate 4 using the preform processed body, the form of the preform can be appropriately set so that a predetermined preform processed body can be easily manufactured.

Hereinafter, a preform, a bipolar plate, and the like manufactured by the multi-stage manufacturing method will be described.

(sample No. 1)

In the first step, 3kg of artificial graphite particles as a first powder, namely carbon powder, and 500g of PE (polyethylene) particles as a second powder, namely powder of a thermoplastic resin, were mixed. The average particle diameter of the artificial graphite particles was 20. Mu.m. The density of the artificial graphite particles was 2.2g/cm ³ . The average particle diameter of the PE particles was 10. Mu.m. The PE particles had a density of 0.92g/cm ³ . The theoretical density at the time of the most dense packing in this case was 1.83g/cm ³ 。

The first step is performed by putting the powder into a stirrer and rotating it at a high speed for one minute. The mixer was designated as AC-50S, manufactured by Kagaku Kogyo Co., ltd. The second step was performed using an aluminum mold having internal dimensions of 880mm×440mm×20mm as the precursor mold 21. The first temperature in the second step is a temperature higher than the softening temperature of PE. Specifically, the softening temperature of PE was 80 ℃, whereas the first temperature was 150 ℃. By applying a pressure of 2MPa to the mixed powder 900 using the upper-side precursor die 22, a flat plate-shaped preform 90 having the above-described dimensions was formed. The density of the preform 90 is 1.50g/cm ³ And the ratio to the theoretical density at the time of the above-mentioned closest packing was 0.82. The preform 90 has a shape-fixing property that can be handled.

Thereafter, as shown in fig. 24, as a third step, the preform 90 is heated at 180 ℃ while being sandwiched between the molds 23 and 24. Thereafter, as a fourth step, a load of 300 tons (a pressure of 7.7 MPa) was applied to the molds 23, 24 to produce the bipolar plate 4A. Double-pieceThe density of the polar plate 4A is 1.80g/cm ³ And the ratio to the theoretical density at the time of the above-mentioned closest packing was 0.98. The volume resistance value of the bipolar plate 4A was measured to obtain a value as low as 10mΩ·cm. The reason for this is considered to be that the proportion of the carbon powder contained in the bipolar plate 4A is high. From these, it was confirmed that the bipolar plate 4A of sample No.1 was high-density and high-conductivity.

(sample No. 101)

A preform and a bipolar plate were produced in the same manner as in sample No.1, except that the average particle diameter of the thermoplastic resin powder as the second powder was 500. Mu.m. The theoretical density at the time of the closest packing is the same as that of sample No. 1. The density of the obtained bipolar plate was 1.52g/cm ³ The ratio to the theoretical density was 0.83, which significantly reduced. The above ratio means that the porosity in the bipolar plate of sample No.101 is 17%. This means that the thermoplastic resin is not sufficiently filled between the carbon powders in such a bipolar plate.

In sample No.101, the ratio of the first powder to the second powder was the same as sample No.1, but the volume resistivity of the bipolar plate was as high as 65mΩ·cm due to the high porosity. In the bipolar plate of sample No.101, it was confirmed that the liquid barrier property and the gas tightness were also inferior to those of the bipolar plate of sample No. 1.

The average particle diameter of the thermoplastic resin powder as the second powder was gradually reduced from 500 μm under the same production conditions as in sample No. 1. As a result, when the average particle diameter of the second powder reached 40 μm, that is, when it reached 2 times the average particle diameter of the first powder, a bipolar plate having characteristics equivalent to those of sample No.1 was obtained.

(sample No. 102)

In sample No.1, the average particle diameter of the carbon powder as the first powder was increased to 200. Mu.m, and the average particle diameter of the thermoplastic resin powder as the second powder was changed in the same manner as in sample No. 101. As a result, when the average particle diameter of the second powder was 400 μm or less, a bipolar plate having characteristics equivalent to those of sample No.1 was obtained. That is, it was confirmed that it was difficult to obtain a fine bipolar plate when the average particle diameter of the second powder exceeded 2 times the average particle diameter of the first powder.

(sample No. 2)

Except that the second powder was set to have an average particle diameter of 10 μm and a density of 0.92g/cm ³ Except for the powder of PP (polypropylene), the first powder and 500g of the second powder were mixed in the first step in the same manner as in sample No. 1. The theoretical density at the time of the most dense packing in this case was 1.83g/cm ³ 。

By performing the first step and the second step in the same manner as in sample No.1, a preform 90 having the same size as sample No.1 was obtained. The first temperature and pressure in the second step were also set to be the same as those of sample No. 1. The softening temperature of the PP was 120 ℃. The density of the preform 90 is 1.50g/cm ³ The above ratio was 0.82.

Thereafter, the third step and the fourth step in fig. 24 are performed in the same manner as in sample No.1, whereby the bipolar plate 4A is produced. The second temperature in the third step and the pressure in the fourth step are also set to be the same as those of sample No. 1. The density of the obtained bipolar plate 4A was 1.82g/cm ³ And the ratio to the theoretical density at the time of the above-mentioned closest packing is 0.99. The volume resistance value of the bipolar plate 4A was measured to obtain a value as low as 5mΩ·cm. From these, it was confirmed that the multistage process was effective similarly even when PP was used as the thermoplastic resin.

(sample No. 3)

Using such a preform 93 shown in fig. 25, a bipolar plate 4 of sample No.3 having a reinforcing portion 43 was produced. Specifically, the first powder and the second powder, which are the same as sample No.2 and have the first mixing ratio, are mixed in the first step and used in the same amount as sample No. 2. Using this first mixed powder, a preform 91 having the same size as sample No.2 was produced in the same manner as sample No. 2.

On the other hand, 1.5kg of the carbon powder, which is the first powder identical to sample No.2, and 1.22kg of the thermoplastic resin powder, which is the second powder identical to sample No.2, were mixed in the first step. Using the second mixed powder having the second mixing ratio, the preform 92 having the same size as that of sample No.2 was produced in the same manner as sample No. 2. The mass ratio of the carbon powder in the preform 92 is smaller than that of the carbon powder in the preform 91.

Thereafter, as shown in fig. 25, the preform processed body 91A is cut from the preform 91. The preform processed body 91A has a rectangular plate shape of 680mm×240 mm. The preform 92A is formed by forming an opening 92B in a central region of the preform 92. The size of the opening 92B is the same as the size of the preform processed body 91A. The preform processed body 93 is formed by fitting the preform processed body 91A into the opening 92B of the preform processed body 92A.

The bipolar plate 4 is produced by performing the third step and the fourth step in the same manner as in the samples nos. 1 and 2 using the preform processing body 93. In the bipolar plate 4 of sample No.3, the volume resistivity of the central region in plan view was 5mΩ·cm. The central region is manufactured by the preform processing body 91A. In the bipolar plate 4 of sample No.3, the volume resistivity of the region on the outer edge side, which is the peripheral portion of the bipolar plate 4 in plan view, is 120mΩ·cm, which is higher than that of the central region. The peripheral portion is manufactured by the preform processed body 92A. On the other hand, the bending strength of the peripheral portion was 40MPa, which was about 1.5 times that of the central region. According to these, by performing the fifth step shown in fig. 25, it is possible to manufacture bipolar plates 4 having different characteristics in the direction along the surface of the bipolar plate 4. Here, the bending strength was evaluated by three-point bending by cutting out sample pieces from the central region and the peripheral region, respectively, according to ISO178 jis k 7171. Regarding the dimensions of the test piece, the width was 10mm, the thickness was 3mm, and the length was about 100mm.

(sample No. 4)

The bipolar plate 4 having the reinforcing portion 43 is manufactured by the manufacturing method shown in fig. 26. Here, the same preform 90 as that of sample No.1 was produced. Thereafter, a preform processed body was prepared in which PE sheet materials were placed on the upper and lower surfaces of the four sides of the preform 90 shown in the upper part of fig. 26 as a blank 95. The preform product was placed between the dies 23 and 24, and the third and fourth steps were performed in the same manner as in sample No. 1. In the PE sheet, the upper portion in FIG. 26 has a width of 100mm in the horizontal direction and a thickness of 0.5mm.

In the bipolar plate 4 of the obtained sample No.4, the central region has the same volume resistivity and bending strength as those of the sample No.1 in a plan view. In the bipolar plate 4 of sample No.4, the bending strength was 1.5 times that of the central region in the region of about 100mm outward from the outer edge of the bipolar plate 4. Such an area on the outer edge side is provided with a reinforcing portion 43, here a surface layer portion 430. Thus, by using a PE sheet as the preform 95 and performing the manufacturing method shown in fig. 26, it is possible to manufacture bipolar plates 4 having different characteristics in the direction along the surface of the bipolar plate 4. The bending strength was measured in the same manner as in sample No. 3. In the sampling for bending strength, the sample piece cut from the region on the outer edge side described above includes a surface layer portion having a thickness of about 0.5mm.

(sample No. 5)

Instead of the PE sheet used in sample No.4, a PP sheet of the same size was used to produce a bipolar plate 4 under the same conditions. The central region of the bipolar plate 4 of sample No.5 obtained has the same characteristics as sample No. 4. In the region of about 100mm outward from the outer edge of the bipolar plate 4 of sample No.5, the bending strength was 1.8 times that of the central region. Such an area on the outer edge side is provided with a reinforcing portion 43, here a surface layer portion 430. Thus, by using a PP sheet as the preform 95 and performing the manufacturing method shown in fig. 26, it is possible to manufacture bipolar plates 4 having different characteristics in the direction along the surface of the bipolar plate 4.

(sample No. 6)

The first powder and the second powder were mixed in the same manner as in sample No.1 by the first step except that 730g of PPS (polyphenylene sulfide) powder having an average particle diameter of 20 μm was used as the second powder. The density of the PPS resin was 1.35g/cm ³ . The first temperature in the second step was 340℃and the pressure was 0.5MPa, whereby a preform 90 having the same dimensions as those of sample No.1 was produced. A bipolar plate was produced in the same manner as in sample No.1, using the same mold as in sample No.1, with the second temperature in the third step set at 360 ℃ and the pressure in the fourth step set at 25 MPa. The density of the bipolar plate of sample No.6 obtained was 1.95g/cm ³ And is in closest packing with the aboveThe ratio of the theoretical density of (2) is 0.99 or more.

Thermoplastic resins having a softening temperature of 300 ℃ or higher, such as PPS (polyphenylene sulfide), PTFE (polytetrafluoroethylene) and PFA (perfluoropropyl perfluorovinyl ether), have high heat resistance and high mechanical strength. Therefore, the above thermoplastic resin is preferable as a material for constituting the bipolar plate. On the other hand, it has been difficult to obtain a composite material having a high proportion of carbon powder in the composition using the thermoplastic resin and the carbon powder, since the softening temperature is high. In contrast, in the multistage process, a fine bipolar plate is obtained using PPS or the like as in the case of using PE or PP. Even when a thermoplastic resin having a relatively high softening temperature is used, a bipolar plate having good characteristics can be obtained by increasing the first temperature of the second step and the second temperature of the third step in accordance with the softening temperature.

Thermoplastic resins other than the above-described sample nos. 1 to 6 may be used for the second powder, the blank 95, and the like. In this case, the preform and the bipolar plate can be obtained in the same manner by setting the conditions (first temperature and pressure) of the second step, the conditions (second temperature) of the third step, and the fourth step (pressure) in accordance with the thermoplastic resin. In the above-mentioned sample nos. 1 to 6, the raw materials were two components of the first powder and the second powder, namely, two components of the carbon powder and the thermoplastic resin powder. The raw material may suitably contain other components in addition to the two components. For example, the second powder may be two or more components. In this case, the multistage process can be similarly applied as long as the bipolar plate can be similarly formed through the precursor or the precursor processed body as described above.

The precursor processed body having a structure other than those shown in fig. 25 and 26 can be appropriately manufactured according to the required structure of the bipolar plate. The multistage process described above can be applied to a bipolar plate for a redox flow battery as long as it is a plate-like member molded using a thermoplastic resin powder with carbon powder added for conductivity.

(Main Effect)

The bipolar plate 4 according to the embodiment is provided with the reinforcing portion 43 in the second region 42, so that the bipolar plate is less likely to be broken even when an external force such as stress due to the tightening force is applied thereto in the assembled state of the RF battery 1. The reinforcing portion 43 is substantially made of resin, and the second region 42 is more excellent in mechanical strength, so that it is less likely to crack. In the case where the reinforcing portion 43 contains a conductive material and a resin, contact resistance with the electrode 12 is liable to be reduced even if the first region 41 includes a part of the reinforcing portion 43.

The battery cell 10 of the embodiment includes the bipolar plate 4 of the embodiment. Therefore, in the RF battery 1 including the battery cell 10 according to the embodiment, the bipolar plate 4 is less likely to be broken by the external force. Therefore, the battery cell 10 according to the embodiment can prevent the deterioration of the sealability caused by the cracking of the bipolar plate 4, and construct the RF battery 1 excellent in sealability.

Further, the bipolar plate 4 of the cell frame 3 provided on the positive electrode side and the bipolar plate 4 of the cell frame 3 provided on the negative electrode side in the cell 10 are only one of the bipolar plates 4 of the embodiment. However, the bipolar plate 4 on both the positive electrode side and the negative electrode side is preferably the bipolar plate 4 of the embodiment.

The assembled battery 100 of the embodiment includes a plurality of battery cells 10 of the embodiment. Therefore, in the RF battery 1 including the battery pack 100 according to the embodiment, the bipolar plate 4 is less likely to be broken by the external force. Therefore, the assembled battery 100 according to the embodiment can prevent the deterioration of the sealability caused by the cracking of the bipolar plate 4, and can construct the RF battery 1 excellent in sealability.

In addition, at least one bipolar plate 4 provided on the cell frame 3 in the assembled battery 100 is the bipolar plate 4 of the embodiment. However, it is preferable that the bipolar plate 4 constituting both the positive electrode side and the negative electrode side of at least one cell 10 out of the plurality of cells 10 constituting the battery pack 100 is the bipolar plate 4 of the embodiment. More preferably, the bipolar plate 4 provided in all the cell frames 3 constituting the battery pack 100 is the bipolar plate 4 of the embodiment.

The RF battery 1 of the embodiment includes the battery cell 10 of the embodiment or the battery pack 100 of the embodiment. Therefore, the RF battery 1 of the embodiment is excellent in sealability as described above.

The present invention is not limited to these examples, but is set forth in the claims, and is intended to include all modifications equivalent in meaning and scope to the claims.

For example, the cell frame 3 may be an integrally molded product of the bipolar plate 4 and the frame body 30. That is, the frame 30 may be integrally molded on the outer edge 44 side of the bipolar plate 4. The battery cell frame 3 is manufactured by molding the frame body 30 in a region on the outer edge 44 side of the bipolar plate 4 by injection molding or the like, for example. The bipolar plate 4 has a reinforcing portion 43 in the second region 42. At least a part of the second region 42 of the bipolar plate 4 is covered with a resin constituting the frame 30. The second region 42 and the frame 30 are firmly joined by the injection molding or the like. According to these, the bipolar plate 4 is less prone to cracking.

Description of the reference numerals

1. Redox flow battery (RF battery)

10. Battery cell

11. A diaphragm; 12. an electrode; 13. a positive electrode; 14. negative electrode

16. 17 cans; 160, a step of detecting a position of the base; 170. piping arrangement

161. 171 forward piping; 162. 172 return piping

18. 19 pump

100. A battery pack; 110. sub-battery pack

101. An end plate; 102. a coupling member; 103. supply and discharge plate

3. Battery cell frame

30. A frame; 31. a window portion; 33. 34 fluid supply manifold

35. A 36 drain manifold; 39. sealing member

301. 302 dividing the sheet; 303. flange part

305. Cutting; 306. a concave portion; 309. groove part

4. 4A bipolar plate

4a first side; 4b second side; 4c side

41f, 43f surface

41A, 41B;41C boundary

41. A first region; 42. a second region; 43. reinforcing part

420. A base; 430. a surface layer portion; 432. base body part

44. An outer edge; 45. a step portion; 450. lower step surface

5. A flow path; 50. 51, 52, 53, 54 slots; 55. ridge part

5i supply edges; 5o discharge edge

6. An ac/dc converter; 61. a power transformation device; 7. a power generation unit; 8. load(s)

900. Mixing the powder; 901. a first powder; 902. second powder

90. Preformed body (precursor)

91. First preform (first precursor)

91A, 92A, 93, 96 preform processed body (precursor processed body)

92. A second preform (second precursor); 92B opening part

95. Blank material

20. Mixer

21. 22 precursor die; 23. 24 mould

t、t ₁ 、t ₂ 、t ₄₁ Thickness of (L)

W、W ₅ Width of (L)

Claims

1. A bipolar plate for a redox flow battery, wherein,

The bipolar plate comprises a conductive material and a resin,

the bipolar plate has a distribution in which the resin content is different in at least one of a direction along a surface of the bipolar plate and a thickness direction of the bipolar plate,

the bipolar plate is provided with:

a first region configured with an electrode; and

a second region located on the outer edge side of the first region,

the first region is composed of a composite material in which the conductive material is dispersed in the resin,

the second region is provided with a reinforcing portion,

the resin content of the reinforcing portion is higher than the resin content of the first region in a direction along the surface,

the reinforcement portion includes an annular region in plan view from the thickness direction of the bipolar plate,

the reinforcing portion has surface layer portions on both surfaces of the bipolar plate,

the surface layer portion is provided in a layered manner so as to constitute a part of the surface of the second region among the surfaces of the bipolar plate,

the reinforcement portion is composed of a composite material including a conductive material and a resin.

2. A bipolar plate for a redox flow battery, wherein,

the bipolar plate comprises a conductive material and a resin,

the bipolar plate is provided with:

a first region configured with an electrode; and

a second region located on the outer edge side of the first region,

the second region is provided with a reinforcing portion,

the reinforcement portion includes two strip-shaped regions when viewed in plan from the thickness direction of the bipolar plate,

the two strip-shaped regions are opposite to each other across the first region,

3. The bipolar plate according to claim 1 or 2, wherein,

The resin content in the reinforcement portion is 1.2 times or more the resin content in the first region.

4. The bipolar plate according to claim 1 or 2, wherein,

the thickness of the surface layer part is 10 μm or more and 2mm or less.

5. The bipolar plate according to claim 1 or 2, wherein,

the second region has a stepped portion having a different thickness,

the surface layer portion is provided on a lower step surface in the step portion.

6. The bipolar plate according to claim 1 or 2, wherein,

the width of the surface layer part is 3mm or more.

7. The bipolar plate according to claim 1 or 2, wherein,

the elongation at break of the portion of the first region adjacent to the surface layer portion is 0.5% or more.

8. The bipolar plate according to claim 1 or 2, wherein,

the resin included in the first region and the resin included in the reinforcement include one or more thermoplastic resins selected from the group consisting of polyethylene, polypropylene, and polyphenylene sulfide.

9. The bipolar plate of claim 8, wherein,

the resin contained in the first region and the resin contained in the reinforcing portion include the same kind of thermoplastic resin.

10. A battery cell provided with a bipolar plate according to any one of claims 1 to 9.

11. A battery pack provided with a plurality of the battery cells according to claim 10.

12. A redox flow battery provided with the battery cell of claim 10 or the battery pack of claim 11.