Separator and method for manufacturing the same

Abstract

To provide a separator that is highly conductive and capable of suppressing metal elution, and a manufacturing method thereof.SOLUTION: A separator 1 for a power storage device or a fuel cell includes a plate 2 containing graphite, resin, and metal fibers, the plate 2 has grooves 30, 32 as flow paths on its surface and containing aramid fibers, the metal fibers are made of at least one of copper, titanium, and stainless steel, and there is also provided a manufacturing method thereof.SELECTED DRAWING: Figure 2A

Description

Technical Field

[0001] The present invention relates to a separator and a method for manufacturing the same.

Background Art

[0002] A fuel cell is a battery that extracts energy by utilizing the reaction between hydrogen and oxygen. Since water is generated by this reaction, fuel cells are known as environmentally friendly batteries. In particular, solid polymer fuel cells are considered promising as batteries for automobiles, communication devices, electronic devices, etc. because they enable high power density and are small and lightweight, and some have been put into practical use. A fuel cell is a cell stack composed of a plurality of cells stacked together. A plate-like member called a separator is disposed between adjacent cells. The separator is a partition plate that separates the passages for hydrogen and oxygen adjacent to each other, and plays a role of allowing hydrogen and oxygen to flow uniformly in contact with the entire surface of the ion exchange membrane. For this reason, grooves serving as flow paths are formed in the separator.

[0003] Separators are roughly classified into a metal material type and a carbon material type from the viewpoint of their constituent materials. Generally, stainless steel, aluminum or its alloy, or titanium or its alloy is used for the metal material type separator. The metal material type separator is excellent in workability and can be thinned due to the strength and ductility peculiar to metals. However, the metal material type separator has a larger specific gravity than the carbon material type separator described later, which is contrary to the weight reduction of the fuel cell. Furthermore, the metal material type separator has low corrosion resistance and has a drawback of forming a passive film depending on the material. Corrosion of the metal material or the passive film leads to an increase in the electrical resistance of the separator, which is not preferable. When a noble metal is plated or coated by sputtering or the like to improve the corrosion resistance of the metal material type separator, the cost increases. In order to prevent such an increase in cost, a method of forming the convex portions of the flow paths formed on the surface of the separator with a photoresist film is known (see Patent Document 1).

[0004] On the other hand, carbon-based separators have the advantages of lower specific gravity and superior corrosion resistance compared to metal-based separators. However, carbon-based separators are inferior in processability and mechanical strength. There is also a demand for further reduction in electrical resistance (i.e., further improvement in conductivity). As a method for improving mechanical strength, for example, a separator in which graphite particles are dispersed in a thermoplastic resin is known (see Patent Document 2). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2011-090937 [Patent Document 2] Japanese Patent Publication No. 2006-294407 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Such carbon-based separators can be made even more conductive by incorporating metal materials. However, carbon-based separators containing metal materials may be susceptible to ionization and leaching of the metal due to the influence of corrosive substances such as strong acids generated in the operating environment of fuel cells.

[0007] The present invention aims to provide a separator that is highly conductive and capable of suppressing metal elution, and a method for manufacturing the same. [Means for solving the problem]

[0008] (1) A separator according to one embodiment for achieving the above objective is a separator for an energy storage device comprising a plate containing graphite, resin, and metal fibers, wherein the plate has grooves on its surface as flow channels, and the metal fibers consist of at least one of copper, titanium, and stainless steel. (2) In a separator according to another embodiment, preferably the metal fibers may be contained in an amount of 40 parts by mass or more and 1000 parts by mass or less per 100 parts by mass of the resin. (3) A separator according to another embodiment may further include a barrier layer having better gas barrier properties than the plate, which is formed on both surfaces in the thickness direction of the plate and includes the grooves and the surface of the plate other than the grooves. (4) In a separator according to another embodiment, preferably the barrier layer may be a film-like coating layer different from the plate. (5) In a separator according to another embodiment, preferably the barrier layer is a filling layer in which resin or rubber fills the spaces between the particles or fibers constituting the plate. (6) In a separator according to another embodiment, preferably the barrier layer may include the filling layer and a film-like coating layer different from the plate. (7) In a separator according to another embodiment, preferably the barrier layer may contain at least one of polyetheretherketone and polyphenylene sulfide. (8) In a separator according to another embodiment, preferably the resin constituting the plate and the resin constituting the barrier layer may be the same type of thermoplastic resin. (9) In a separator according to another embodiment, preferably, at least one of the resin constituting the plate and the resin constituting the barrier layer may be made primarily of polyphenylene sulfide. (10) Separators according to another embodiment may preferably be fuel cell separators used between fuel cell cells. (11) A method for manufacturing a separator according to one embodiment for achieving the above objective is a method for manufacturing a separator as described in any of the above, comprising: a workpiece placement step of placing a workpiece containing at least the graphite, the resin, and the metal fibers in a mold; and a molding step of closing the mold with the workpiece in place and performing molding. (12) In a method for manufacturing a separator according to another embodiment, preferably the mold is provided with irregularities on its inside for transferring the groove, and the molding step may be performed using the mold provided with the irregularities to form the workpiece and form the groove. (13) A method for manufacturing a separator according to another embodiment preferably further includes a pre-molding step prior to the workpiece placement step, in which a semi-cured workpiece is obtained from a mixture containing at least the graphite, the resin, and the metal fibers, and the workpiece placement step may involve placing the semi-cured workpiece in the mold. (14) A method for manufacturing a separator according to another embodiment preferably further includes, prior to the workpiece placement step, a first film placement step of placing a film for forming a barrier layer having better gas barrier properties than the plate on one surface in the thickness direction of the plate inside the mold, and a second film placement step of placing a film for forming the barrier layer on the other surface in the thickness direction of the plate on the workpiece placed inside the mold in the workpiece placement step, wherein the workpiece placement step involves placing the workpiece on the film placed inside the mold in the first film placement step, and the molding step involves closing the mold with the workpiece sandwiched between the films to perform molding, thereby forming the barrier layer on both surfaces in the thickness direction of the plate. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a separator that is highly conductive and can suppress metal elution, and a method for manufacturing the same. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 shows a plan view of a separator according to the first embodiment of the present invention. [Figure 2A] Figure 2A shows a cross-sectional view of the separator in Figure 1 along line AA, and an enlarged view of a part of it, B. [Figure 2B]FIG. 2B shows enlarged views of variations a, b, and c of part C in part B of FIG. 2A. [Figure 3] FIG. 3 shows an example of the flow of the main steps of the method for manufacturing a separator according to the first embodiment. [Figure 4] FIG. 4 shows the situation of each step of the manufacturing method of FIG. 3 in a cross-sectional view. [Figure 5] FIG. 5 shows in a cross-sectional view the situation when grooves are formed in a prepreg in a semi-cured state in the method for manufacturing a separator according to a modified example. [Figure 6] FIG. 6 shows a cross-sectional view taken along line A-A similar to FIG. 2A of the separator according to the second embodiment and an enlarged view of a part B thereof. [Figure 7] FIG. 7 shows an example of the flow of the main steps of the method for manufacturing a separator according to the second embodiment.

MODE FOR CARRYING OUT THE INVENTION

[0011] Next, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below do not limit the invention according to the claims, and not all of the elements and combinations thereof described in the embodiments are essential for the solution means of the present invention.

[0012] <First Embodiment> 1. Separator FIG. 1 shows a plan view of a separator according to the first embodiment of the present invention. FIG. 2A shows a cross-sectional view taken along line A-A of the separator of FIG. 1 and an enlarged view of a part B thereof, respectively.

[0013] The separator 1 according to this embodiment is a plate-like body that is substantially rectangular in plan view. The separator 1 is a plate-like body that sandwiches both sides of a membrane / electrode assembly (MEA) in which an electrolyte membrane is sandwiched between an air electrode and a hydrogen electrode, for example, in a fuel cell. In this embodiment, the separator 1 is broadly interpreted to include an anode-side separator arranged on the hydrogen electrode (also called the "anode electrode") side and a cathode-side separator arranged on the air electrode (also called the "cathode electrode") side. In this embodiment, the separator 1 is a carbon material-based separator. Furthermore, the separator 1 is not limited to fuel cells and can also be used as a plate-like member arranged between cells in other batteries (preferably storage batteries).

[0014] The separator 1 is provided with through holes 11, 12, 21, and 22 that penetrate in the thickness direction. Through holes 11 and 21 are located on one end of the separator 1. Through hole 12 is located on the other end of the separator 1, opposite to the one end, when the separator 1 is viewed from above, and facing through hole 21. Through hole 22 is located on the other end of the separator 1, opposite to the one end, when the separator 1 is viewed from above, and facing through hole 11. A groove 30 is formed on one side (front side) of the separator 1 as a flow path. Surfaces 31 other than the groove 30 are convex with respect to the groove 30. Also, a groove 32 is formed on the opposite side (back side) of the separator 1 as a flow path. Surfaces 31 other than the groove 32 are convex with respect to the groove 32.

[0015] When separator 1 is the cathode-side separator, through-hole 11 is the supply port for oxidizing gas. Through-hole 12 is the outlet for oxidizing gas. Through-hole 21 is the outlet for hydrogen gas. Through-hole 22 is the supply port for hydrogen gas. The oxidizing gas is, for example, air, but oxygen may also be used. The groove 30 on the surface side of separator 1 is a passage for the flow of oxidizing gas. The groove 32 on the back side of separator 1 is a passage for the flow of cooling water. In Figure 1, the flow of oxidizing gas is indicated by white arrows.

[0016] When separator 1 is the anode-side separator, through-hole 11 is the hydrogen gas supply port. Through-hole 12 is the hydrogen gas outlet. Through-hole 21 is the oxidizing gas outlet. Through-hole 22 is the oxidizing gas supply port. The groove 30 on the surface side of separator 1 is a flow path for hydrogen gas. The groove 32 on the back side of separator 1 is a flow path for cooling water.

[0017] The separator 1 comprises at least a plate 2. In this embodiment, the separator 1 preferably comprises a plate 2 and optionally a barrier layer 3 on both surfaces of the plate 2 in the thickness direction.

[0018] (plate) Plate 2 is a plate comprising graphite, resin, and metal fibers, and has grooves 30 and 32 on its surface as flow channels. Plate 2 is a molded body comprising graphite, resin, and metal fibers, and has a microstructure in which graphite is dispersed in the resin and metal fibers after melting and solidification. In addition to graphite, resin, and metal fibers, Plate 2 may also contain fibers other than those of the resin. These fibers may be any type of non-metallic fiber, such as resin fibers, carbon fibers, or ceramic fibers, but are preferably resin fibers, and more preferably aramid fibers. The fiber diameter of the aramid fibers is preferably 5 to 20 μm, more preferably 9 to 15 μm. The fiber length of the aramid fibers is preferably 1 to 15 mm, more preferably 3 to 9 mm. The fiber diameter and fiber length refer to the fiber diameter and fiber length measured from the field of view of 20 independent fibers selected using a microscope (optical microscopes and scanning electron microscopes are used depending on the size). To determine the average fiber diameter or average fiber length, average the diameter or length of 20 fibers. The same applies to the following fiber diameter, fiber length, average fiber diameter, and average fiber length. By adding fibers to plate 2, the strength of plate 2 can be increased. The area of ​​plate 2 in plan view is preferably 10 to 1000 cm². 2 more preferably 100-750cm 2The thickness of plate 2 is preferably 0.1 to 2.0 mm, more preferably 0.2 to 1.5 mm.

[0019] The resin constituting plate 2 is not particularly restricted, but is preferably a thermoplastic resin. More suitable resins for plate 2 are those with excellent heat resistance, specifically, polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyamide (PA), polyether ketone ether ketone ketone (PEKEKK), polyether ketone (PEK), liquid crystal polymer (LCP), polytetrafluoroethylene (PTFE), tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), polyimide (PI), polyamide-imide (PAI), polyethersulfone (PES), polyphenylsulfone (PPSU), polyetherimide (PEI), and polysulfone (PSU). Among these, PPS or PEEK are particularly preferred. Examples of PPS include M2888 and E2180 from Toray Industries, Inc., and FZ-2140 and FZ-6600 from Dainippon Ink and Chemicals, Inc.

[0020] The average particle size of the resin used before molding plate 2 is preferably 1 μm to 300 μm, more preferably 5 μm to 150 μm, and even more preferably 10 μm to 100 μm. Here, the average particle size refers to the particle size measured by laser diffraction / scattering particle size distribution measurement. The same applies to the subsequent methods for measuring the average particle size.

[0021] The graphite constituting plate 2 may be any of the following: artificial graphite, expanded graphite, natural graphite, etc. Here, expanded graphite refers to graphite or graphite intercalation compounds in which the intercalation between graphite layers is expanded by intercalation (insertion of another material layer into a specific surface of a structure in which regular hexagonal planes of graphite are superimposed). For example, expanded graphite can be BSP-60A (average particle size 60 μm) or EXP-50SM manufactured by Fuji Graphite Industry Co., Ltd. For artificial graphite, for example, 1707SJ (average particle size 125 μm), AT-No.5S (average particle size 52 μm), AT-No.10S (average particle size 26 μm), AT-No.20S (average particle size 10 μm) manufactured by Oriental Industry Co., Ltd., or PAG, HAG manufactured by Nippon Graphite Industry Co., Ltd. For natural graphite, CNG-75N (average particle size 43 μm) manufactured by Fuji Graphite Industry Co., Ltd. or CPB (scaly graphite powder, average particle size 19 μm) manufactured by Nippon Graphite Industry Co., Ltd. can be used. Furthermore, there are no particular restrictions on the shape of the graphite particles, and they can be appropriately selected as flaky, scaly, spherical, etc. Furthermore, graphite may contain some amorphous carbon.

[0022] The average particle size of the graphite used before forming plate 2 is preferably 1 μm to 500 μm, more preferably 3 μm to 300 μm, and even more preferably 10 μm to 150 μm.

[0023] Graphite and resin may be mixed after adjusting their particle sizes separately and then used for molding plate 2, or they may be kneaded first, then ground, and then used for molding plate 2 after adjusting their particle size. When kneading graphite and resin and then grinding to adjust the particle size, the average particle size of the mixed powder is preferably 1 μm to 500 μm, more preferably 3 μm to 300 μm, and even more preferably 10 μm to 150 μm.

[0024] The mass ratio of graphite to resin constituting plate 2 is graphite:resin = 70-95 parts by mass:30-5 parts by mass. For example, 70 to 95 parts by mass of graphite can be mixed with 5 parts by mass of resin to form the constituent material of separator 1. Similarly, 70 to 95 parts by mass of graphite can be mixed with 30 parts by mass of resin to form the constituent material of separator 1. It is preferable that separator 1 contains more graphite by mass than resin. A more preferable mass ratio of graphite to resin is 10 parts by mass of graphite, or 10.1 to 20 parts by mass of graphite, per 1 part by mass of resin. As described above, if the mass of graphite is greater than the mass of resin, the contact area between graphite particles increases compared to conventional separators, thereby lowering the electrical resistance of separator 1 (i.e., increasing its conductivity). In a typical sample of separator 1, the volume resistivity is 3 mΩ·cm or less.

[0025] The metal fibers constituting plate 2 are made of at least one of copper, titanium, and stainless steel, i.e., fibers made of copper, titanium, stainless steel, or alloys thereof. As copper fibers, for example, metal fibers (grade: copper) manufactured by Kogyo Co., Ltd. (average fiber diameter 52.08 μm, average fiber length 1.88 mm) can be used. As titanium fibers, for example, metal fibers (grade: titanium) manufactured by Kogyo Co., Ltd. (average fiber diameter 51.82 μm, average fiber length 1.72 mm) can be used. As stainless steel fibers, for example, metal fibers (grade: SUS316L) manufactured by Kogyo Co., Ltd. (average fiber diameter 32.23 μm, average fiber length 1.29 mm) can be used. The fiber diameter of the metal fibers is preferably 5 to 80 μm, more preferably 20 to 60 μm. The fiber length of the metal fibers is preferably 0.5 to 3.5 mm, more preferably 1.5 to 2.5 mm.

[0026] By incorporating metal fibers into plate 2, conductivity is increased, and thus the volume resistivity can be lowered. In a typical sample of separator 1 consisting of such a plate 2 with metal fibers, the volume resistivity is 1.8 mΩ·cm or less.

[0027] The metal fibers constituting plate 2 preferably amount to 40 parts by mass or more and 1000 parts by mass per 100 parts by mass of resin. By including 40 parts by mass or more of metal fibers per 100 parts by mass of resin, plate 2 can lower the electrical resistance of separator 1 (i.e., increase its conductivity). On the other hand, by including 1000 parts by mass or less of metal fibers per 100 parts by mass of resin, plate 2 can suppress mold damage caused by metal fibers during the manufacturing of separator 1.

[0028] (Barrier layer) The barrier layer 3 is not an essential component, but in this embodiment, it includes the grooves 30, 32 and the surface 31 of the plate 2 other than the grooves 30, 32, and covers at least the front and back surfaces of the plate 2. That is, the barrier layer 3 covers both the front and back surfaces of the plate 2, including the inner surfaces of the grooves 30, 32. The barrier layer 3 is, for example, a film-like covering layer different from the plate 2, and is formed by separating or fusing two types of films: a film 4, which is an example of a barrier layer covering the front surface, and a film 5, which is an example of a barrier layer covering the back surface. In this embodiment, the barrier layer 3 is divided into film 4 and film 5, which are attached to both sides of the plate 2 in the thickness direction, respectively. However, the barrier layer 3 may also be in the shape of a bag that encloses the outer surface of the plate 2 with film 4 and film 5 joined together.

[0029] Figure 2B shows enlarged views of variations a, b, and c of part C within part B of Figure 2A.

[0030] Embodiment a is a form in which a film, preferably made mainly of resin or rubber, is provided on the surface of the plate 2. In embodiment a, the barrier layer 3 is a film-like coating layer F different from that of the plate 2. Embodiment b is a form in which a barrier layer 3 impregnated with resin or rubber is provided near the surface of the plate 2. In embodiment b, the barrier layer 3 is a filling layer M in which resin or rubber fills the spaces between the particles or fibers constituting the plate 2. Furthermore, in embodiment c, the barrier layer 3 includes both the filling layer M and the coating layer F. Thus, the barrier layer 3 preferably takes the form of a, b, or c. However, the barrier layer 3 may take a form other than embodiments a, b, or c, as long as it has superior gas barrier properties compared to the plate 2. In this application, "gas barrier properties" or "gas barrier performance" means the property of preventing gas permeation. The following description will mainly focus on the barrier layer 3 of embodiment a.

[0031] The barrier layer 3 is preferably a resin or rubber. The barrier layer 3 mainly consists of one or more of the above preferred options of resins constituting the plate 2, and more preferably at least one of PEEK and PPS. Here, "main material" means a material that accounts for more than 50% by mass of the barrier layer 3. The main material may be, for example, 51%, 60%, 70%, 80%, 90%, 95%, or 100% by mass, as long as it exceeds 50% by mass of the mass of the barrier layer 3.

[0032] The thickness of the barrier layer 3 is preferably 2 μm to 50 μm, more preferably 4 μm to 35 μm. A barrier layer thickness of 2 μm or more, and even more preferably 4 μm or more, allows for higher gas barrier properties and greater strength (flexural strength) of the separator 1, improving ease of handling. On the other hand, a barrier layer thickness of 50 μm or less, and even more preferably 35 μm or less, allows for lower volume resistivity (i.e., higher conductivity) of the separator 1. In this embodiment, strength refers to the flexural strength measured according to JIS K7171.

[0033] The resin constituting plate 2 and the resin constituting barrier layer 3 can also be the same type of thermoplastic resin. In this case, the resin near the surface of plate 2 and the barrier layer 3 covering plate 2 can be partially integrated, thereby further improving the strength of separator 1. The thermoplastic resin is preferably PEEK or PPS.

[0034] 2. Method for manufacturing separators Next, a method for manufacturing a separator according to an embodiment of the present invention will be described.

[0035] A method for manufacturing separator 1 (hereinafter also simply referred to as "manufacturing method") includes a workpiece placement step of placing a workpiece containing at least graphite, resin, and metal fibers into a mold, and a molding step of closing the mold with the workpiece in place and performing molding. Preferably, the method for manufacturing separator 1 further includes a pre-molding step prior to the workpiece placement step of obtaining a semi-cured workpiece from a mixture containing at least graphite, resin, and metal fibers. Preferably, the method for manufacturing separator 1 further includes a first film placement step of placing a film 4 into the mold prior to the workpiece placement step, and a second film placement step of placing a film 5 on the workpiece placed in the mold during the workpiece placement step. In the following embodiments, the method for manufacturing separator is preferably a method for manufacturing a fuel cell separator used between cells of a fuel cell. Preferably, separator 1 is a carbon material-based separator. However, the separator 1 is not limited to fuel cells and can also be used as a plate-shaped member placed between cells of other batteries (preferably storage batteries).

[0036] Figure 3 shows an example of the main steps in the manufacturing method of the separator according to the first embodiment. Figure 4 shows a cross-sectional view of each step in the manufacturing method shown in Figure 3.

[0037] Separator 1 can be manufactured through a mixture formation step (S100), a pre-molding step (S110), a first film placement step (S200), a workpiece placement step (S210), a second film placement step (S220), and a molding step (S230). Steps S100 to S230 will be described in detail below with reference to Figures 3 and 4.

[0038] (1)Mixture formation process (S100) This process involves forming a mixture containing at least graphite, resin, and metal fibers. Specifically, graphite, resin, and metal fibers are mixed and dispersed in water or an aqueous alcohol solution to produce a slurry. In this process, additional fibers other than the resin may be added to the graphite, resin, and metal fibers to produce the slurry.

[0039] (2) Preforming process (S110) This process is for obtaining a semi-cured molded product from a mixture. Specifically, the mixture is formed into a wet sheet by filtering and separating the liquid using a mesh sheet machine, and this wet sheet is heated and pressurized in a press machine. This allows a semi-cured molded product (hereinafter also referred to as "pre-plate") to be obtained. If a plate containing at least graphite, resin, and metal fibers can be obtained by means of purchase or other means, the mixture formation process (S100) and the pre-molding process (S110) can be omitted.

[0040] (3) First film placement process (S200) This step involves placing a film 4 for forming a barrier layer 3 inside a mold 60. Specifically, a lower mold 40, which constitutes the mold 60, is prepared, and the film 4 is laid in the recess 41 of the lower mold 40 (see Figure 4(a)). The lower mold 40 has irregularities 42 on the inner bottom surface of the recess 41 that can transfer and form grooves 32.

[0041] (4) Molding object placement process (S210) This step involves placing the pre-plate 70, which is a semi-cured molded product, onto the film 4. Specifically, the pre-plate 70 is placed on the film 4 laid on the lower mold 40 (see Figure 4(b)).

[0042] (5) Second film placement process (S220) This step, which follows the workpiece placement step (S210), involves placing a film 5 on the pre-plate 70 inside the mold 60 to form a barrier layer 3. Specifically, the film 5 is placed on the pre-plate 70 positioned in the recess 41 of the lower mold 40 (see Figure 4(c)).

[0043] (6) Molding process (S230) This process involves closing the mold 60 with the pre-plate 70 sandwiched between films 4 and 5 to perform molding. Specifically, an upper mold 50, which constitutes the mold 60, is prepared and placed on the recessed side 41 of the lower mold 40, and the lower mold 40 and upper mold 50 are closed (see Figures 4(d) and (e)). The upper mold 50 has a recess 51 on the surface facing the recess 41 of the lower mold 40. The recess 51 has irregularities 52 on its inner bottom surface that can transfer and form grooves 30. After the mold 60 is clamped, it is heated to mold the pre-plate 70. As a result, the pre-plate 70 hardens to form plate 2. In addition, grooves 30 and 32 covered with barrier layers 3 (films 4 and 5) are formed by the transfer of irregularities 41 and 51 (see Figure 4(f)).

[0044] After the molding process (S230), the mold 60 is opened and the separator 1 is completed. In the manufacturing method of the separator 1, it is not necessary to perform either the first film placement process (S100) or the second film placement process (S120).

[0045] Figure 5 shows a cross-sectional view of the situation when grooves are formed in the semi-cured pre-plate in the separator manufacturing method according to a modified example.

[0046] In this modified example, the separator 1 is manufactured using a preplate 70a, which has grooves formed on both surfaces in the thickness direction, instead of the preplate 70. Specifically, in the pre-molding process (S110), a preplate 70a with grooves formed on both surfaces in the thickness direction is obtained from the mixture formed in the mixture forming process (S100). More specifically, the mixture is formed into a wet sheet by filtering and separating the liquid using a mesh sheet machine, and the wet sheet is placed in a mold with irregularities formed on its inner bottom surface and then heated and pressurized in a press machine. This makes it possible to obtain a preplate 70a with grooves formed on both surfaces in the thickness direction. Then, in the workpiece placement process (S210), the preplate 70a is placed on the film 4 so that the grooves of the preplate 70a match the irregularities 42 (see Figure 5). After that, the irregularities 52 of the upper mold 50 are aligned with the grooves of the preplate 70a, the upper mold 50 and the lower mold 40 are closed, and the mold 60 is clamped. Subsequently, the molding process (S230) of the manufacturing method described above is performed, and separator 1 is completed (see Figures 4(e) and (f)).

[0047] <Second Embodiment> Next, a second embodiment of the present invention will be described. In the separator and its manufacturing method according to the second embodiment, parts common to the first embodiment will be omitted from the description and the description in the first embodiment will be used instead.

[0048] 1. Separator Figure 6 shows a cross-sectional view of the separator according to the second embodiment, similar to Figure 2A, along with an enlarged view of a part of it, B.

[0049] The separator 1a according to this embodiment includes a plate 2. Unlike the separator 1 according to the first embodiment, the separator 1a according to this embodiment does not include a barrier layer 3 (film 4 and film 5). The separator 1a is identical to the separator 1 except that it does not include a barrier layer 3.

[0050] 2. Method for manufacturing separators Figure 7 shows an example of the main steps in the manufacturing method of the separator according to the second embodiment.

[0051] The separator 1a includes a mixture forming step (S300) of forming a mixture containing at least graphite, resin, and metal fibers; a pre-molding step (S310) of obtaining a semi-cured molded object from the mixture; a molded object placement step (S400) of placing the molded object in a mold; and a molding step (S410) of closing the mold with the molded object in place and performing molding. The mixture forming step (S300) and the pre-molding step (S310) are common to the mixture forming step (S100) and the pre-molding step (S110). The molded object placement step (S400) is common to the molded object placement step (S210), except that the film 4 is not placed in the mold 60. The molding step (S410) is common to the molding step (S230), except that the films 4 and 5 are not placed. Therefore, here we will omit explanations that overlap with the manufacturing method of the separator 1 according to the first embodiment described above.

[0052] <Other Embodiments> As described above, preferred embodiments of the present invention have been explained, but the present invention is not limited to these and can be implemented in various modified forms.

[0053] The groove 30 of the separators 1,1a may be a groove that forms a flow path other than the gas flow path indicated by the white arrow in Figure 1. Also, the groove 32 may be a groove that forms any form of flow path. For example, groove 30 may be a groove that forms a straight flow path from one end to the other of the separators 1,1a, and groove 32 may be a groove that forms a straight flow path in a direction approximately perpendicular to groove 30. Furthermore, the separators 1,1a may not have at least one of grooves 30 and 32.

[0054] After the molding process, a trimming process may be performed to trim off any excess areas of film 4 and / or film 5.

[0055] The separator 1 has barrier layers 3 on both surfaces in the thickness direction of the plate 2, but the barrier layer 3 may be provided on only one surface in the thickness direction. If the barrier layer 3 is formed on only one surface, the second film placement step (S220) or the first film placement step (S200) may be omitted.

[0056] In the first embodiment, the manufacturing method is for a fuel cell separator in which the barrier layer 3 is a layer of resin or rubber, but the manufacturing method may also be for a fuel cell separator in which the barrier layer 3 is a layer of form b or form c in Figure 2B. [Examples]

[0057] Next, embodiments of the present invention will be described in comparison with comparative examples. However, the present invention is not limited to the following embodiments.

[0058] 1. Main ingredients of the plate (1) Graphite Two types of graphite powder were used as constituent materials for the separator plates: Oriental Kogyo Co., Ltd.'s product code: 1707SJ (artificial graphite, average particle size 125 μm) and Oriental Kogyo Co., Ltd.'s product code: AT-No.5S (artificial graphite, average particle size 52 μm). (2) Resin Polyphenylene Fluorine (PPS) powder was used as the resin component of the separator plate. For the PPS, we used fine PPS powder, which was prepared by freeze-grinding Toray Industries, Inc.'s Torelina M2888 flake-type PPS powder to an average particle size of 50 μm. (3) Aramid fiber Two types of aramid fibers were used as constituent materials for the separator plates: Technora T32PNW 3-12 (average fiber length 3.2 mm, average fiber diameter 18 μm) and Twaron® D8016 (average fiber length 0.8 mm), both manufactured by Teijin Limited. (4) Metal fibers Copper fibers, titanium fibers, stainless steel fibers, and aluminum fibers were used as the metal fibers that make up the separator plates. For the copper fibers, metal fibers (grade: copper) manufactured by Kogyo Co., Ltd. (average fiber length 1.88 mm, average fiber diameter 52.08 μm) were used. For the titanium fibers, metal fibers (grade: titanium) manufactured by Kogyo Co., Ltd. (average fiber length 1.72 mm, average fiber diameter 51.82 μm) were used. For the stainless steel fibers, metal fibers (grade: SUS316L) manufactured by Kogyo Co., Ltd. (average fiber length 1.29 mm, average fiber diameter 32.23 μm) were used. For the aluminum fibers, metal fibers (grade: aluminum) manufactured by Kogyo Co., Ltd. (average fiber length 1.73 mm, average fiber diameter 61.83 μm) were used. (5) Metal particles Copper particles, titanium particles, and stainless steel particles were used as the constituent materials for the separator plates. For the copper particles, Cu-At-100 At2 (average particle size 97.98 μm) manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd. was used. For the titanium particles, TC-150 (average particle size 103.13 μm) manufactured by Toho Tech Co., Ltd. was used. For the stainless steel particles, SUS316L powder (average particle size 127.51 μm) manufactured by Nicola Co., Ltd. was used.

[0059] 2. Film For the separator film, a PPS film was used. The PPS film used was a 9μm thick film (product number: Torelina 9-3071) manufactured by Toray Industries, Inc.

[0060] 3. Mold As for the mold, a mold made of pre-hardened steel NAK80 manufactured by Daido Steel Co., Ltd., with an upper and lower split design, was used. Inside the closed mold, there is a space (approximately 63 cm) in which the separator can be formed. 3 ) is formed. In addition, irregularities are formed on the inner bottom of each of the upper and lower molds to form the grooves for the separator.

[0061] 4. Evaluation Method (1) Volume resistivity The volume resistivity of the separator was measured using a device (Loresta-GX T-700) manufactured by Mitsubishi Chemical Analytec Co., Ltd., in accordance with JIS K7194. A volume resistivity of 1.8 mΩ·cm or less was evaluated as pass B (indicated as "〇" in the table), and a volume resistivity of 0.5 mΩ·cm or less was evaluated as pass A (indicated as "◎" in the table). (2) Dissolution test The separator elution test involved placing the separator in a flask, adding 400 ml of dilute sulfuric acid adjusted to pH 3, covering it, and immersing it at 80°C for 10 days. After immersion, the separator was removed, and the eluted and precipitated substances were dissolved in the solution by acid decomposition. The eluted substances were then quantitatively analyzed using an ICP analyzer. A metal ion concentration of 200 ppm or higher was marked as a failure (indicated by "×" in the table), 100 ppm to less than 200 ppm was marked as a pass C (indicated by "△" in the table), 1 ppm to less than 100 ppm was marked as a pass B (indicated by "〇" in the table), and less than 1 ppm was marked as a pass A (indicated by "◎" in the table). For example, in the case of titanium fibers, the ion concentration of dissolved titanium was used as the measured value for the elution test. In the case of stainless steel fibers, the total ion concentration of iron, manganese, etc. derived from the stainless steel fibers was used as the measured value for the elution test. In other words, in the elution test, the total ion concentration of ions derived from the metal fiber or metal particle was used as the measured value for the elution test, depending on the type of metal fiber or metal particle. (3) Overall evaluation A rating of "Pass" (indicated as "○" in the table) was given if all of the characteristic value evaluations were rated as "Pass." Conversely, a rating of "Fail" (indicated as "×" in the table) was given if at least one of the characteristic value evaluations was rated as "Fail."

[0062] 5. Manufacturing of separators <Examples> (1) Example 1 977.8 parts by mass of artificial graphite particles (product code: AT-No.5S), 100 parts by mass of PPS powder, 62.5 parts by mass of aramid fiber (product code: T32PNW 3-12), 4.17 parts by mass of aramid fiber (product code: Twaron® D8016), and 244.4 parts by mass of titanium fiber were prepared and mixed and dispersed in water to make a slurry with a solid content of 1%. Here, 1 part by mass corresponds to 0.1 g. The same applies to the following examples. This slurry was put into a filter equipped with a 25 cm square inlet, and a sheet-like wet sheet was formed from the residue obtained by filtration. The wet sheet was set in a press heated to 150°C and pressurized and heated at a surface pressure of 13.4 MPa for about 20 minutes to dry the wet sheet and remove moisture, thereby producing a sheet with a thickness of 2.0 mm and a basis weight of 1435 g / m² in which the artificial graphite particles, PPS particles, aramid fibers, and titanium fibers were dispersed. 2 We manufactured the pre-plates. Next, the pre-plate was placed in the recess on the inside of the lower mold, which constitutes the split mold. Then, the upper mold and the lower mold, which constitute the split mold, were closed and molding was performed. Molding was carried out by pressurizing the mold at a surface pressure of 13.4 MPa until the mold temperature rose to 340°C, then increasing the surface pressure to 53.7 MPa and holding it for 1 minute. After that, the mold was cooled under pressure until it reached 30°C while maintaining the same pressure. After molding was completed, the mold was opened, the molded body was removed, and the manufacturing of the separator was completed. This separator has a single-layer structure consisting only of a plate. The separator was evaluated using the evaluation method described above. (2) Example 2 A pre-plate was manufactured under the same conditions as in Example 1, except that 244.4 parts by mass of stainless steel fiber were used instead of 244.4 parts by mass of titanium fiber. Next, a PPS film was laid in the recess on the inside of the lower mold, which constitutes a split mold, and the pre-plate was placed on the film. Then, a PPS film was placed on top of the pre-plate. Next, the upper mold and the lower mold, which constitute the split mold, were closed and molding was performed. Molding was carried out by pressurizing the mold at a surface pressure of 13.4 MPa until the mold temperature rose to 340°C, then increasing the surface pressure to 53.7 MPa and holding it for 1 minute. After that, the mold was cooled under pressure until it reached 30°C while maintaining the same pressure. After the molding was completed, the mold was opened, the molded body was removed, and the production of the separator was completed. This separator has a three-layer structure of film, plate, and film. The separator was evaluated using the evaluation method described above. (3) Example 3 A separator was manufactured and evaluated under the same conditions as in Example 1, except that 244.4 parts by mass of copper fiber were used instead of 244.4 parts by mass of titanium fiber. This separator has a single-layer structure consisting only of a plate. (4) Example 4 A preplate was manufactured under the same conditions as in Example 1, except that 1102.22 parts by mass of artificial graphite particles (product code: AT-No.5S) and 120 parts by mass of titanium fibers were used instead of 977.8 parts by mass of artificial graphite particles (product code: AT-No.5S) and 244.4 parts by mass of titanium fibers. Then, a separator was manufactured and evaluated using this preplate under the same conditions as in Example 2. This separator has a three-layer structure consisting of film, plate, and film. (5) Example 5 A separator was manufactured and evaluated under the same conditions as in Example 4, except that 742.22 parts by mass of artificial graphite particles (product code: AT-No.5S) and 480 parts by mass of titanium fibers were used instead of 1102.22 parts by mass of artificial graphite particles (product code: AT-No.5S) and 120 parts by mass of titanium fibers. This separator has a three-layer structure consisting of film, plate, and film. (6) Example 6 A separator was manufactured and evaluated under the same conditions as in Example 4, except that 1173.611 parts by mass of artificial graphite particles (product code: AT-No.5S) and 48 parts by mass of titanium fibers were used instead of 1102.22 parts by mass of artificial graphite particles (product code: AT-No.5S) and 120 parts by mass of titanium fibers. This separator has a three-layer structure consisting of film, plate, and film. (7) Example 7 A separator was manufactured and evaluated under the same conditions as in Example 4, except that 502.22 parts by mass of artificial graphite particles (product code: AT-No.5S) and 720 parts by mass of titanium fibers were used instead of 1102.22 parts by mass of artificial graphite particles (product code: AT-No.5S) and 120 parts by mass of titanium fibers. This separator has a three-layer structure consisting of film, plate, and film. (8) Example 8 A separator was manufactured and evaluated under the same conditions as in Example 2, except that 122.2 parts by mass of titanium fiber and 122.2 parts by mass of stainless steel fiber were used instead of 244.4 parts by mass of stainless steel fiber. This separator has a three-layer structure consisting of film, plate, and film.

[0063] <Comparative Example> (1) Comparative Example 1 A separator was manufactured and evaluated under the same conditions as in Example 2, except that 244.4 parts by mass of copper particles were used instead of 244.4 parts by mass of stainless steel fibers. Comparative Example 1 was carried out using copper particles, which are an example of metal particles, instead of metal fibers. The separator of Comparative Example 1 has a three-layer structure of film, plate, and film. (2) Comparative Example 2 A separator was manufactured and evaluated under the same conditions as in Example 2, except that 977.8 parts by mass of artificial graphite particles (product number: 1707SJ) and 244.4 parts by mass of artificial graphite particles (product number: AT-No.5S) were used instead of 977.8 parts by mass of artificial graphite particles (product number: AT-No.5S) and 244.4 parts by mass of stainless steel fibers. Comparative Example 2 was carried out without using metal fibers. The separator in Comparative Example 2 has a single-layer structure consisting only of plates. (3) Comparative Example 3 A separator was manufactured and evaluated under the same conditions as in Example 1, except that 244.4 parts by mass of aluminum fiber were used instead of 244.4 parts by mass of titanium fiber. Comparative Example 3 was carried out without using metal fibers consisting of at least one of copper, titanium, and stainless steel. The separator of Comparative Example 3 has a single-layer structure consisting only of plates. (4) Comparative Example 4 A separator was manufactured and evaluated under the same conditions as in Example 2, except that 244.4 parts by mass of titanium particles were used instead of 244.4 parts by mass of stainless steel fibers. Comparative Example 4 was carried out using titanium particles, an example of metal particles, instead of metal fibers. The separator of Comparative Example 4 has a three-layer structure of film, plate, and film. (5) Comparative Example 5 A separator was manufactured and evaluated under the same conditions as in Example 2, except that 244.4 parts by mass of stainless steel particles were used instead of 244.4 parts by mass of stainless steel fibers. Comparative Example 5 was carried out using stainless steel particles, which are an example of metal particles, instead of metal fibers. The separator of Comparative Example 5 has a three-layer structure of film, plate, and film.

[0064] 7.Results Tables 1-4 show the manufacturing conditions and evaluation results for the examples and each comparative example.

[0065] [Table 1]

[0066] [Table 2]

[0067] [Table 3]

[0068] [Table 4]

[0069] Comparative Examples 1-5 failed at least one of the volume resistivity and dissolution tests. In contrast, Examples 1-8 passed all of the characteristic tests.

[0070] From the above results, a comparison between Examples 1-8 and Comparative Example 2 confirmed the effect of including metal fibers as a constituent material of the plate. Furthermore, a comparison between Examples 2, 4-8 and Comparative Examples 1, 4, and 5 confirmed the effect of including metal fibers, rather than metal particles, as a constituent material of the plate. Additionally, a comparison between Examples 1-8 and Comparative Example 3 confirmed the effect of including metal fibers made of at least one of copper, titanium, and stainless steel, rather than metal fibers made of other metals, as a constituent material of the plate. Finally, a comparison between Example 2 and Example 8 confirmed that including two or more types of metal fibers from copper, titanium, and stainless steel produced the same effect as including one type of metal fiber from copper, titanium, and stainless steel. [Industrial applicability]

[0071] The separator according to the present invention can be used as a separator between cells in batteries, particularly storage batteries. [Explanation of Symbols]

[0072] 1,1a...Separator, 2...Plate, 3...Barrier layer, 4,5...Film, 30,32...Groove, 31...Surface, 40...Lower mold (a component of the mold), 41,51...Concave, 42,52...Rubber, 50...Upper mold (a component of the mold), 60...Mold, 70,70a...Pre-plate (an example of a molded object), F...Coating layer, M...Filling layer.

Claims

1. A separator for an energy storage device or fuel cell, comprising a plate containing graphite, resin, and metal fibers, The plate has grooves on its surface that serve as flow channels, and contains aramid fibers as resin fibers separate from the resin. The separator is characterized in that the metal fiber consists of at least one of copper, titanium, and stainless steel.

2. The separator according to claim 1, characterized in that the metal fibers are contained in an amount of 40 parts by mass or more and 1000 parts by mass or less per 100 parts by mass of the resin.

3. The separator according to claim 1 or 2, further comprising a barrier layer having superior gas barrier properties compared to the plate, which is formed on both surfaces in the thickness direction of the plate, including the groove and the surface of the plate other than the groove.

4. The separator according to claim 3, characterized in that the barrier layer is a film-like coating layer different from the plate.

5. The separator according to claim 3 or 4, characterized in that the barrier layer comprises at least one of polyetheretherketone and polyphenylene sulfide.

6. The separator according to any one of claims 3 to 5, characterized in that at least one of the resin constituting the plate and the resin constituting the barrier layer is mainly made of polyphenylene sulfide.

7. A method for manufacturing a separator according to any one of claims 1 to 6, A molded object placement step involves placing a molded object containing at least the graphite, the resin, the metal fibers, and the aramid fibers inside a mold. A molding process in which the mold is closed and molded with the workpiece in place, A method for manufacturing a separator containing [a specific component].

8. The mold is provided with irregularities on its inside for transferring the groove, The method for manufacturing a separator according to claim 7, characterized in that the molding step involves using the mold having the irregularities to mold the workpiece and form the grooves.

9. Prior to the workpiece arrangement step, the process further includes a pre-molding step of obtaining a semi-cured workpiece from a mixture containing at least the graphite, the resin, the metal fibers, and the aramid fibers, The method for manufacturing a separator according to claim 7 or 8, characterized in that the step of arranging the molded object is arranging the semi-cured molded object in the mold.

10. Prior to the molded object placement step, a first film placement step is performed in which a film is placed in the mold on one surface in the thickness direction of the plate to form a barrier layer having better gas barrier properties than the plate, A second film placement step involves placing a film for forming the barrier layer on the other surface of the plate in the thickness direction, on the molded object that is placed in the mold during the molded object placement step. It further includes, The aforementioned workpiece placement step involves placing the workpiece on the film that was placed in the mold in the first film placement step, The method for manufacturing a separator according to any one of claims 7 to 9, characterized in that the molding step involves closing the mold with the object to be molded sandwiched between the films and forming the barrier layer on both surfaces in the thickness direction of the plate.

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