Separator and manufacturing method thereof

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 producing the same. [Background technology]

[0002] A fuel cell is a battery that extracts energy by utilizing the reaction between hydrogen and oxygen. Since the reaction produces only water, 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 to practical use. A fuel cell is a cell stack composed of multiple cells stacked on top of each other. A plate-shaped member called a separator is placed between the cells. The separator is a partition plate that separates the passages of hydrogen and oxygen that are adjacent to each other, and plays a role in allowing hydrogen and oxygen to flow in contact with each other uniformly over the entire surface of the ion exchange membrane. For this reason, grooves that serve as the flow paths are formed in the separator.

[0003] Separators are broadly classified into metallic and carbon-based separators based on the material of which they are made. Stainless steel, aluminum or its alloy, or titanium or its alloy are generally used for metallic separators. Metallic separators have excellent workability and can be thinned due to the strength and ductility inherent to metals. However, metallic separators have a higher specific gravity than carbon separators described below, which is contrary to the weight reduction of fuel cells. Furthermore, metallic separators have the disadvantage of low corrosion resistance and forming a passivation film depending on the material. Corrosion of metallic materials or a passivation film is undesirable because it leads to an increase in the electrical resistance of the separator. Coating metallic separators with precious metals by plating or sputtering, etc., leads to high costs, but in order to prevent such high costs, a method is known in which the convex parts of the flow paths formed on the surface of the separator are formed with a photoresist film (see Patent Document 1).

[0004] On the other hand, carbon material-based separators have the advantage of being smaller in specific gravity and more corrosion resistant than metal material-based separators. However, carbon material-based separators are inferior in processability and mechanical strength. There is also a demand for further lower electrical resistance (i.e., further higher electrical 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] JP 2011-090937 A [Patent Document 2] JP 2006-294407 A Summary of the Invention [Problem to be solved by the invention]

[0006] Such carbonaceous separators can be effectively made more conductive by incorporating a metal material, but there is a risk that the metal in the carbonaceous separator containing the metal material may be ionized and eluted due to the influence of corrosive substances such as strong acids that are generated in the operating environment of the fuel cell.

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

[0008] (1) In order to achieve the above object, one embodiment of a separator is a separator for an electricity storage device having a plate containing graphite, resin, and metal fibers, the plate having grooves on a surface thereof as flow paths, and the metal fibers being made of at least one of copper, titanium, and stainless steel. (2) In the separator according to another embodiment, the metal fibers may be contained in an amount of 40 parts by mass or more and 1000 parts by mass or less with respect to 100 parts by mass of the resin. (3) A separator according to another embodiment may further include a barrier layer, which is preferably a layer including the groove and the surface of the plate other than the groove and is formed on both surfaces of the plate in the thickness direction, and which has better gas barrier properties than the plate. (4) In the separator according to another embodiment, the barrier layer may preferably be a film-like coating layer different from the plate. (5) In the separator according to another embodiment, the barrier layer may preferably be a filled layer in which resin or rubber fills spaces between particles or fibers that constitute the plate. (6) In the separator according to another embodiment, the barrier layer may preferably include the filling layer and a film-like covering layer different from the plate. (7) In the separator according to another embodiment, the barrier layer may preferably contain at least one of polyether ether ketone and polyphenylene sulfide. (8) In the separator according to another embodiment, the resin constituting the plate and the resin constituting the barrier layer may preferably be the same type of thermoplastic resin. (9) In the separator according to another embodiment, preferably, at least one of the resin constituting the plate and the resin constituting the barrier layer may be mainly made of polyphenylene sulfide. (10) A separator according to another embodiment may preferably be a separator for a fuel cell used between cells of a fuel cell. (11) A method for producing a separator according to one embodiment for achieving the above object is a method for producing any of the separators described above, comprising: a molded object placement step of placing a molded object containing at least the graphite, the resin, and the metal fibers in a die; and a molding step of closing the die with the molded object placed therein to perform molding. (12) In another embodiment of the method for manufacturing a separator, the mold may have an inner surface provided with projections and recesses for transferring the grooves, and the molding step may involve molding the molded object and forming the grooves using the mold having the projections and recesses. (13) In another embodiment, the method for manufacturing a separator preferably further includes a pre-molding step of obtaining the molded object in a semi-cured state from a mixture containing at least the graphite, the resin, and the metal fibers prior to the molded object placing step, and the molded object placing step may include placing the molded object in the semi-cured state in the die. (14) In another embodiment, the method for manufacturing a separator preferably further includes, prior to the object to be molded arranging step, a first film arranging step of arranging 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 in the mold, and a second film arranging step of arranging a film for forming the barrier layer on the other surface in the thickness direction of the plate on the object to be molded that was arranged in the mold in the object to be molded in the object to be molded in the first film arranging step, and the molding step may include closing the mold with the object to be molded sandwiched between the films to perform molding, and forming the barrier layer on both surfaces in the thickness direction of the plate. Effect of the Invention

[0009] According to the present invention, it is possible to provide a separator that is highly conductive and capable of suppressing metal elution, and a method for producing the same. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 shows a plan view of a separator according to a first embodiment of the present invention. [Figure 2A] FIG. 2A shows a cross-sectional view of the separator taken along line AA in FIG. 1 and an enlarged view of a part B thereof. [Figure 2B]FIG. 2B shows enlarged views of variations a, b, and c of part C in part B of FIG. 2A. [Diagram 3] FIG. 3 shows an example of a flow of main steps in the method for producing the separator according to the first embodiment. [Figure 4] FIG. 4 shows cross-sectional views of the respective steps of the manufacturing method shown in FIG. [Diagram 5] FIG. 5 is a cross-sectional view showing a state in which grooves are formed in a semi-cured preplate in a manufacturing method for a separator according to a modified example. [Figure 6] FIG. 6 shows a cross-sectional view of the separator according to the second embodiment taken along line AA similar to FIG. 2A and an enlarged view of a part B thereof. [Figure 7] FIG. 7 shows an example of a flow of main steps in the method for producing a separator according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

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

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

[0014] The separator 1 has through holes 11, 12, 21, and 22 penetrating in the thickness direction. The through holes 11 and 21 are arranged on one end side of the separator 1. The through hole 12 is arranged on the other end side opposite the one end side of the separator 1, facing the through hole 21 when the separator 1 is viewed in plan. The through hole 22 is arranged on the other end side opposite the one end side of the separator 1 so as to face the through hole 11 when the separator 1 is viewed in plan. A groove 30 is formed as a flow path on one surface side (front surface side) of the separator 1. The surface 31 other than the groove 30 is convex with respect to the groove 30. In addition, a groove 32 is formed as a flow path on the surface (rear surface side) opposite the one surface side of the separator 1. The surface 31 other than the groove 32 is convex with respect to the groove 32.

[0015] When the separator 1 is a cathode separator, the through hole 11 is an oxidizing gas supply port. The through hole 12 is an oxidizing gas exhaust port. The through hole 21 is a hydrogen gas exhaust port. The through hole 22 is a hydrogen gas supply port. The oxidizing gas is, for example, air, but may be oxygen. The groove 30 on the front side of the separator 1 is a flow path for the oxidizing gas to flow. The groove 32 on the back side of the separator 1 is a flow path for the cooling water to flow. In FIG. 1, the flow of the oxidizing gas is indicated by white arrows.

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

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

[0018] (plate) The plate 2 is a plate containing graphite, resin, and metal fibers, and has grooves 30, 32 as flow paths on the surface of the plate. The plate 2 is a molded body containing graphite, resin, and metal fibers, and has a microstructure in which graphite is dispersed in the resin and metal fibers that have solidified after melting. The plate 2 may also contain fibers other than the resin, in addition to the graphite, resin, and metal fibers. The fibers may be any type of non-metallic fibers such as resin fibers, carbon fibers, and 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). When determining the average fiber diameter or average fiber length, 20 fiber diameters or fiber lengths are averaged. The same applies to the following fiber diameter, fiber length, average fiber diameter, and average fiber length. By adding fibers to the plate 2, the strength of the plate 2 can be increased. The area of ​​the plate 2 in a plan view is preferably 10 to 1000 cm. 2 , more preferably 100 to 750 cm 2The thickness of the plate 2 is preferably 0.1 to 2.0 mm, and more preferably 0.2 to 1.5 mm.

[0019] The resin constituting the plate 2 is not particularly limited, but is preferably a thermoplastic resin. A resin more suitable for the plate 2 is a resin having excellent heat resistance, and specific examples thereof include 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), polyether sulfone (PES), polyphenyl sulfone (PPSU), polyether imide (PEI) and polysulfone (PSU). Among these, PPS or PEEK is particularly suitable. Examples of PPS include M2888 and E2180 manufactured by Toray Industries, Inc., and FZ-2140 and FZ-6600 manufactured by Dainippon Ink and Chemicals, Inc.

[0020] The average particle size of the resin used before molding the plate 2 is preferably 1 μm or more and 300 μm or less, more preferably 5 μm or more and 150 μm or less, and even more preferably 10 μm or more and 100 μm or less. Here, the average particle size refers to a particle size measured by a laser diffraction / scattering type particle size distribution measurement method. The measurement method of the average particle size hereinafter is the same.

[0021] The graphite constituting the plate 2 may be any of artificial graphite, expanded graphite, natural graphite, etc. Here, expanded graphite refers to graphite or graphite intercalation compound in which the graphite layers are expanded by inserting another material layer (=intercalation) into a specific surface of a structure in which regular hexagonal planes of graphite (graphite) are stacked. Examples of the expanded graphite include BSP-60A (average particle size 60 μm) and EXP-50SM manufactured by Fuji Graphite Industries Co., Ltd. Examples of the artificial graphite include 1707SJ (average particle size 125 μm), AT-No.5S (average particle size 52 μm), AT-No.10S (average particle size 26 μm), and AT-No.20S (average particle size 10 μm) manufactured by Oriental Sangyo Co., Ltd., or PAG and HAG manufactured by Nippon Graphite Industries Co., Ltd. Examples of the natural graphite include CNG-75N (average particle size 43 μm) manufactured by Fuji Graphite Industries Co., Ltd., and CPB (scale graphite powder, average particle size 19 μm) manufactured by Nippon Graphite Industries Co., Ltd. The shape of the graphite particles is not particularly limited, and can be appropriately selected from flaky, scaly, spherical, and the like. Furthermore, the graphite may partially contain non-crystalline carbon (amorphous carbon).

[0022] The average particle size of the graphite used before forming the 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] The graphite and the resin may be mixed together after adjusting the particle size separately and then used to form the plate 2, or may be kneaded together first, pulverized, and the particle size adjusted before being used to form the plate 2. When the graphite and the resin are kneaded together and then pulverized to adjust the particle size, the average particle size of the mixed powder is preferably 1 μm or more and 500 μm or less, more preferably 3 μm or more and 300 μm or less, and even more preferably 10 μm or more and 150 μm or less.

[0024] The mass ratio of graphite and resin constituting the plate 2 is graphite:resin=70-95 parts by mass:30-5 parts by mass. For example, 5 parts by mass of resin can be mixed with 70 parts by mass or more and 95 parts by mass or less to form the constituent material of the separator 1. Similarly, for example, 30 parts by mass of resin can be mixed with 70 parts by mass or more and 95 parts by mass or less to form the constituent material of the separator 1. The separator 1 preferably contains more graphite than resin in terms of mass ratio. A more suitable mass ratio of graphite to resin is 10 parts by mass of graphite or 10.1 parts by mass or more and 20 parts by mass or less of graphite per 1 part by mass of resin. As described above, when the parts by mass of graphite are more than the parts by mass of resin, the number of contact points between the graphite particles is more than that of conventional separators, and thus the electrical resistance of the separator 1 can be lowered (i.e., the electrical conductivity can be increased). A representative sample of separator 1 has a volume resistivity of 3 mΩ·cm or less.

[0025] The metal fibers constituting the plate 2 are fibers made of at least one of copper, titanium, and stainless steel, that is, fibers made of copper, titanium, stainless steel, or an alloy thereof. As the copper fibers, for example, metal fiber (type: copper) (average fiber diameter 52.08 μm, average fiber length 1.88 mm) manufactured by Kogi Co., Ltd. can be used. As the titanium fibers, for example, metal fiber (type: titanium) (average fiber diameter 51.82 μm, average fiber length 1.72 mm) manufactured by Kogi Co., Ltd. can be used. As the stainless steel fibers, for example, metal fiber (type: SUS316L) (average fiber diameter 32.23 μm, average fiber length 1.29 mm) manufactured by Kogi Co., Ltd. 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 providing metal fibers in the plate 2, the electrical conductivity can be increased, i.e., the volume resistance can be reduced. In a representative sample of the separator 1 made of the plate 2 provided with such metal fibers, the volume resistance is 1.8 mΩ·cm or less.

[0027] The metal fibers constituting the plate 2 are preferably 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. By containing 40 parts by mass or more of metal fibers per 100 parts by mass of the resin, the electrical resistance of the separator 1 can be lowered (i.e., the conductivity can be increased). On the other hand, by containing 1000 parts by mass or less of metal fibers per 100 parts by mass of the resin, the plate 2 can suppress damage to the mold caused by the metal fibers during the production of the separator 1.

[0028] (Barrier layer) Although the barrier layer 3 is not an essential component, 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 a film 4 and a film 5, which are attached to both sides of the plate 2 in the thickness direction. However, the barrier layer 3 may be in a bag shape that wraps the outer surface of the plate 2 with the film 4 and the film 5 joined together.

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

[0030] In the form a, a film mainly made of resin or rubber is provided on the surface of the plate 2. In the form a, the barrier layer 3 is a film-like covering layer F different from the plate 2. In the form b, the barrier layer 3 is impregnated with resin or rubber near the surface of the plate 2. In the form b, the barrier layer 3 is a filling layer M in which the resin or rubber fills the spaces between the particles or fibers that constitute the plate 2. In the form c, the barrier layer 3 includes the filling layer M and the covering layer F. Thus, the barrier layer 3 preferably takes the form a, b, or c. However, the barrier layer 3 may take a form other than the form a, b, or c as long as it has a gas barrier property superior to the plate 2. In the present application, "gas barrier property" or "gas barrier performance" means a property of preventing gas permeation. Hereinafter, the barrier layer 3 of the form a will be mainly described.

[0031] The barrier layer 3 is preferably made of resin or rubber. The barrier layer 3 is mainly made of one or more of the above-mentioned preferred resin choices for the plate 2, and more preferably at least one of PEEK and PPS. Here, the "main material" means a material that occupies 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 with respect to the mass of the barrier layer 3.

[0032] The thickness of the barrier layer 3 is preferably 2 μm or more and 50 μm or less, more preferably 4 μm or more and 35 μm or less. When the thickness of the barrier layer 3 is 2 μm or more, or even 4 μm or more, the separator 1 can have higher gas barrier properties and higher strength (bending strength), and can be made easier to handle. On the other hand, when the thickness of the barrier layer 3 is 50 μm or less, or even 35 μm or less, the volume resistance value of the separator 1 can be made lower (i.e., the conductivity can be made higher). In this embodiment, the strength means the bending strength measured according to JIS K7171.

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

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

[0035] The method for producing the separator 1 (hereinafter, simply referred to as the "production method") includes a step of arranging a molding object containing at least graphite, resin, and metal fiber in a mold, and a molding step of closing the mold with the molding object placed therein to perform molding. The method for producing the separator 1 preferably further includes a pre-molding step of obtaining a molding object in a semi-hardened state from a mixture containing at least graphite, resin, and metal fiber prior to the molding object placement step. The method for producing the separator 1 preferably further includes a first film placement step of arranging a film 4 in the mold, and a second film placement step of arranging a film 5 on the molding object placed in the mold in the molding object placement step prior to the molding object placement step. In the following embodiment, the method for producing a separator is preferably a method for producing a fuel cell separator used between cells of a fuel cell. The separator 1 is preferably a carbon material-based separator. However, the separator 1 is not limited to use in fuel cells, and can also be used as a plate-like member disposed between cells of other batteries (preferably storage batteries).

[0036] Fig. 3 shows an example of a flow of main steps of the method for producing a separator according to the first embodiment. Fig. 4 shows cross-sectional views of the status of each step of the production method shown in Fig. 3.

[0037] The separator 1 can be manufactured through a mixture forming step (S100), a pre-molding step (S110), a first film arranging step (S200), a molding target arranging step (S210), a second film arranging step (S220), and a molding step (S230). S100 to S230 will be described in detail below with reference to Figs. 3 and 4.

[0038] (1)Mixture formation process (S100) This step is a step of 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 alcohol aqueous solution to prepare a slurry. In this step, a fiber other than the resin may be further added to the graphite, resin, and metal fibers to prepare a slurry.

[0039] (2) Preforming process (S110) This step is a step of obtaining a semi-cured molded object from the mixture. Specifically, the mixture is formed into a wet sheet by filtering and separating the liquid using a mesh-structured sheet machine, and the wet sheet is heated and pressed using a press machine. This allows a semi-cured molded object (hereinafter also referred to as a "pre-plate") to be obtained. When a plate containing at least graphite, resin, and metal fibers is not manufactured but can be obtained by purchasing or other methods, the mixture formation step (S100) and pre-molding step (S110) can be omitted.

[0040] (3) First film placement process (S200) This step is a step of placing the film 4 for forming the barrier layer 3 in a mold 60. Specifically, a lower mold 40 constituting the mold 60 is prepared, and the film 4 is placed in a recess 41 of the lower mold 40 (see FIG. 4(a)). The lower mold 40 has an inner bottom surface of the recess 41 with projections and recesses 42 capable of transferring and forming the grooves 32.

[0041] (4) Molding object placement process (S210) This step is a step of placing a preplate 70, which is a molding target in a semi-cured state, on the film 4. Specifically, the preplate 70 is placed on the film 4 placed on the lower mold 40 (see FIG. 4(b)).

[0042] (5) Second film placement process (S220) This step is a step of placing a film 5 for forming a barrier layer 3 on a preplate 70 in the mold 60 after the molding target placement step (S210). Specifically, the film 5 is placed on the preplate 70 placed in the recess 41 of the lower mold 40 (see FIG. 4(c)).

[0043] (6) Molding process (S230) In this step, the mold 60 is closed while the preplate 70 is sandwiched between the films 4 and 5 to perform molding. Specifically, the upper mold 50 constituting the mold 60 is prepared and placed on the recessed portion 41 side of the lower mold 40, and the lower mold 40 and the upper mold 50 are closed (see Figs. 4(d) and (e)). The upper mold 50 has a recess 51 on the surface facing the recessed portion 41 of the lower mold 40. The recess 51 has an irregularity 52 on its inner bottom surface that can transfer and form the groove 30. After the mold 60 is clamped, it is heated to form the preplate 70. As a result, the preplate 70 hardens to form the plate 2. In addition, the transfer of the irregularities 41 and 51 forms the grooves 30 and 32 covered with the barrier layer 3 (film 4 and film 5) (see Fig. 4(f)).

[0044] After the molding step (S230), the mold 60 is opened to complete the separator 1. In the method for manufacturing the separator 1, it is not necessary to perform either the first film positioning step (S100) or the second film positioning step (S120).

[0045] FIG. 5 is a cross-sectional view showing a state in which grooves are formed in a semi-cured preplate in a manufacturing method for a separator according to a modified example.

[0046] In this modification, the separator 1 is manufactured using a preplate 70a having grooves formed on both surfaces in the thickness direction instead of the preplate 70. Specifically, in the preforming step (S110), the preplate 70a having grooves formed on both surfaces in the thickness direction is obtained from the mixture formed in the mixture forming step (S100). More specifically, the mixture is formed into a wet sheet by filtering and separating the liquid using a sheet machine with a mesh structure, and the wet sheet is placed in a mold having an inner bottom surface formed with irregularities and pressurized while being heated by a press machine. This makes it possible to obtain the preplate 70a having grooves formed on both surfaces in the thickness direction. Then, in the molding target placement step (S210), the preplate 70a is placed on the film 4 so that the grooves of the preplate 70a match the irregularities 42 (see FIG. 5). Thereafter, the irregularities 52 of the upper mold 50 are matched to the grooves of the preplate 70a, the upper mold 50 and the lower mold 40 are closed, and the mold 60 is clamped. Thereafter, the molding step (S230) of the above-mentioned manufacturing method is carried out, and the separator 1 is completed (see FIGS. 4(e) and (f)).

[0047] <Second embodiment> Next, a second embodiment of the present invention will be described. In the separator and the manufacturing method thereof according to the second embodiment, the overlapping descriptions of the portions common to the first embodiment will be omitted and the descriptions in the first embodiment will be used instead.

[0048] 1. Separator FIG. 6 shows a cross-sectional view of the separator according to the second embodiment taken along line AA similar to FIG. 2A and an enlarged view of a part B thereof.

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

[0050] 2. Separator manufacturing method FIG. 7 shows an example of a flow of main steps in the method for producing a 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 fiber, a preforming step (S310) of obtaining a semi-hardened molded object from the mixture, a molded object arranging step (S400) of arranging the molded object in a die, and a molding step (S410) of closing the die with the molded object arranged therein to perform molding. The mixture forming step (S300) and the preforming step (S310) are common to the mixture forming step (S100) and the preforming step (S110). The molded object arranging step (S400) is common to the molded object arranging step (S210) except that the film 4 is not arranged in the die 60. The molding step (S410) is common to the molding step (S230) except that the films 4 and 5 are not arranged. Therefore, here, a description that overlaps with the manufacturing method of the separator 1 according to the first embodiment described above will be omitted.

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

[0053] The grooves 30 of the separators 1, 1a may be grooves that form flow paths other than the flow paths that allow gas to flow in the direction indicated by the white arrows in Fig. 1. The grooves 32 may be grooves that form any type of flow path. For example, the grooves 30 may be grooves that form linear flow paths from one end of the separators 1, 1a to the other end, and the grooves 32 may be grooves that form linear flow paths in a direction approximately perpendicular to the grooves 30. The separators 1, 1a may not have at least one of the grooves 30 and 32.

[0054] The shaping step may be followed by a trimming step in which excess areas of film 4 and / or film 5 are trimmed.

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

[0056] The manufacturing method of the first embodiment is a method for manufacturing a fuel cell separator in which the barrier layer 3 is a layer of resin or rubber, but it may also be a method for manufacturing 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, examples of the present invention will be described in comparison with comparative examples. Note that the present invention is not limited to the following examples.

[0058] 1. Main ingredients of the plate (1) Graphite For the graphite powder used as the constituent material of the separator plates, two types of graphite powder were used: Oriental Kogyo Co., Ltd. product number: 1707SJ (artificial graphite, average particle size 125 μm) and Oriental Kogyo Co., Ltd. product number: AT-No. 5S (artificial graphite, average particle size 52 μm). (2) Resin The resin used to make the separator plates was polyphenylene sulfide (PPS) powder. The PPS used was fine PPS powder made by freezing and crushing flake-shaped PPS powder of Toray Industries, Inc.'s Torelina M2888 to an average particle size of 50 μm. (3) Aramid fiber Two types of aramid fibers were used as the constituent material of the separator plates: Technora T32PNW 3-12 (average fiber length 3.2 mm, average fiber diameter 18 μm) manufactured by Teijin Limited, and Twaron (registered trademark) D8016 (average fiber length 0.8 mm) manufactured by Teijin Limited. (4) Metal fibers Copper fibers, titanium fibers, stainless steel fibers, and aluminum fibers were used as metal fibers that are constituent materials of the separator plates. Metal fiber (type: copper) (average fiber length 1.88 mm, average fiber diameter 52.08 μm) manufactured by Kogi Co., Ltd. was used as the copper fiber. Metal fiber (type: titanium) (average fiber length 1.72 mm, average fiber diameter 51.82 μm) manufactured by Kogi Co., Ltd. was used as the titanium fiber. Metal fiber (type: SUS316L) (average fiber length 1.29 mm, average fiber diameter 32.23 μm) manufactured by Kogi Co., Ltd. was used as the stainless steel fiber. Metal fiber (type: aluminum) (average fiber length 1.73 mm, average fiber diameter 61.83 μm) manufactured by Kogi Co., Ltd. was used as the aluminum fiber. (5) Metal particles Copper particles, titanium particles, and stainless steel particles were used as metal particles that were the constituent materials of the separator plates. The copper particles were Cu-At-100 At2 (average particle size 97.98 μm) manufactured by Fukuda Metal Foil and Powder Co., Ltd. The titanium particles were TC-150 (average particle size 103.13 μm) manufactured by Toho Tech Co., Ltd. The stainless steel particles were SUS316L powder (average particle size 127.51 μm) manufactured by Nikola Co., Ltd.

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

[0060] 3.Mold The mold used was a top-bottom split mold made of prehardened steel NAK80 manufactured by Daido Steel Co., Ltd. When closed, there was a space (approximately 63 cm2) inside the mold that was large enough to mold the separator. 3 In addition, the bottom of the inside of each of the upper and lower dies has projections and recesses for forming the grooves of the separator.

[0061] 4. Evaluation Methodology (1) Volume resistivity The volume resistivity of the separator was measured in accordance with JIS K7194 using a device (Loresta-GX T-700) manufactured by Mitsubishi Chemical Analytech Co., Ltd. A volume resistivity of 1.8 mΩ·cm or less was rated as Pass B (in the table, "O"), and a volume resistivity of 0.5 mΩ·cm or less was rated as Pass A (in the table, "◎"). (2) Dissolution test The separator elution test was carried out by placing the separator in a flask, adding 400 ml of dilute sulfuric acid adjusted to pH 3, closing the flask, and immersing the separator at 80°C for 10 days. The separator was then removed, and the entire amount of the eluted and precipitated material in the solution was dissolved by acid decomposition, and the eluted material was quantitatively analyzed using an ICP analyzer. Metal ion concentrations of 200 ppm or more were evaluated as failure ("x" in the table), 100 ppm or more but less than 200 ppm as pass C ("△" in the table), 1 ppm or more but less than 100 ppm as pass B ("〇" in the table), and less than 1 ppm as pass A ("◎" in the table). For example, in the case of titanium fibers, the ion concentration of the eluted titanium was used as the measured value of the elution test. In addition, in the case of stainless steel fibers, the total ion concentration of iron, manganese, and other ions derived from the stainless steel fibers was used as the measured value of the elution test. In other words, in the elution test, the total ion concentration of ions derived from the metal fibers or metal particles was used as the measured value of the elution test depending on the type of metal fibers or metal particles. (3) Overall evaluation When all of the characteristic evaluations were evaluated as "pass," the sample was evaluated as "pass" (in the table, "○"). When at least one of the characteristic evaluations was evaluated as "fail," the sample was evaluated as "fail" (in the table, "×").

[0062] 5. Manufacturing of separators <Example> (1) Example 1 977.8 parts by mass of artificial graphite particles (product number: AT-No.5S), 100 parts by mass of PPS powder, 62.5 parts by mass of aramid fiber (product number: T32PNW 3-12), 4.17 parts by mass of aramid fiber (product number: Twaron (registered trademark) D8016), and 244.4 parts by mass of titanium fiber were prepared, and these were mixed and dispersed in water to prepare 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 fed into a filter equipped with a 25 cm square inlet, and a sheet-like wet sheet, which is the residue obtained by filtration, was formed. The wet sheet was set in a press machine heated to 150°C and pressurized and heated at a surface pressure of 13.4 MPa for about 20 minutes, and the wet sheet was dried to remove moisture, resulting in a 2.0 mm thick, 1435 g / m2 wet sheet in which artificial graphite particles, PPS particles, aramid fibers, and titanium fibers were dispersed. 2 A preplate of 100 mm was produced. Next, the preplate was placed in the recess on the inside of the lower die constituting the split die. Next, the upper die and the lower die constituting the split die were closed to perform molding. The molding was performed by applying pressure at a surface pressure of 13.4 MPa until the temperature of the die rose to 340°C, then increasing the surface pressure to 53.7 MPa and holding for 1 minute. Thereafter, the die was pressurized and cooled to 30°C while maintaining the pressure. After molding was completed, the die was opened, the molded body was removed, and the production of the separator was completed. This separator had a single-layer structure consisting of only a plate. The separator was evaluated by the above evaluation method. (2) Example 2 A preplate was manufactured under the same conditions as in Example 1, except that 244.4 parts by mass of stainless steel fiber was used instead of 244.4 parts by mass of titanium fiber. Next, a PPS film was laid in the recess inside the lower mold constituting the split mold, and the preplate was provided on the film. Then, a PPS film was placed on the preplate. Next, the upper mold constituting the split mold and the lower mold were closed to perform molding. The molding was performed by applying pressure at a surface pressure of 13.4 MPa until the temperature of the mold rose to 340°C, then increasing the surface pressure to 53.7 MPa and holding for 1 minute. Thereafter, the mold was pressurized and cooled to 30°C while maintaining the pressure. After the molding was completed, the mold was opened, the molded body was removed, and the manufacturing of the separator was completed. This separator has a three-layer structure of a film, a plate, and a film. The separator was evaluated by the above evaluation method. (3) Example 3 Except for using 244.4 parts by mass of copper fibers instead of 244.4 parts by mass of titanium fibers, a separator was produced and evaluated under the same conditions as in Example 1. This separator has a single-layer structure consisting of only a plate. (4) Example 4 A preplate was produced under the same conditions as in Example 1, except that 1102.22 parts by mass of artificial graphite particles (product number: 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 number: AT-No.5S) and 244.4 parts by mass of titanium fibers. Then, a separator was produced and evaluated using the preplate under the same conditions as in Example 2. This separator has a three-layer structure of a film, a plate, and a film. (5) Example 5 A separator was produced and evaluated under the same conditions as in Example 4, except that 742.22 parts by mass of artificial graphite particles (product number: 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 number: AT-No. 5S) and 120 parts by mass of titanium fibers. This separator has a three-layer structure of a film, a plate, and a film. (6) Example 6 A separator was produced and evaluated under the same conditions as in Example 4, except that 1173.611 parts by mass of artificial graphite particles (product number: 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 number: AT-No.5S) and 120 parts by mass of titanium fibers. This separator has a three-layer structure of a film, a plate, and a film. (7) Example 7 A separator was produced and evaluated under the same conditions as in Example 4, except that 502.22 parts by mass of artificial graphite particles (product number: 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 number: AT-No. 5S) and 120 parts by mass of titanium fibers. This separator has a three-layer structure of a film, a plate, and a film. (8) Example 8 Except for using 122.2 parts by mass of titanium fiber and 122.2 parts by mass of stainless steel fiber instead of 244.4 parts by mass of stainless steel fiber, a separator was produced and evaluated under the same conditions as in Example 2. This separator has a three-layer structure of a film, a plate, and a film.

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

[0064] 7.Results Tables 1 to 4 show the production conditions and evaluation results of the examples and comparative examples.

[0065] [Table 1]

[0066] [Table 2]

[0067] [Table 3]

[0068] [Table 4]

[0069] At least one of the volume resistivity and elution tests was unsuccessful for Comparative Examples 1 to 5. In contrast, all properties were passed for Examples 1 to 8.

[0070] From the above results, the effect of including metal fibers as the constituent material of the plate was confirmed by comparing Examples 1 to 8 with Comparative Example 2. Also, the effect of including metal fibers as the constituent material of the plate, instead of metal particles, was confirmed by comparing Examples 2, 4 to 8 with Comparative Examples 1, 4, and 5. Also, the effect of including metal fibers as the constituent material of the plate, instead of metal fibers made of other metals, was confirmed by comparing Examples 1 to 8 with Comparative Example 3. Also, the effect of including metal fibers made of at least one of copper, titanium, and stainless steel as the constituent material of the plate, instead of metal fibers made of other metals, was confirmed by comparing Example 2 with Example 8. Also, the effect of including two or more types of metal fibers of copper, titanium, and stainless steel was confirmed to be the same as that of including one type of metal fiber of copper, titanium, and stainless steel. [Industrial Applicability]

[0071] The separator according to the present invention can be used as a separator between cells in a battery, particularly in a storage battery. [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...recess, 42,52...irregularities, 50...upper mold (a component of the mold), 60...mold, 70,70a...preplate (an example of an object to be molded), F...coating layer, M...filling layer.

Claims

1. A separator for an electric storage device or a fuel cell, comprising a plate including graphite, a resin, and metal fibers, The plate has a groove on its surface as a flow path and contains aramid fibers. The separator is characterized in that the metal fibers are made of at least one of copper, titanium, and stainless steel.

2. 2. The separator according to claim 1, wherein the metal fibers are contained in an amount of 40 parts by mass to 1000 parts by mass relative to 100 parts by mass of the resin.

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

4. 4. The separator according to claim 3, wherein the barrier layer is a film-like covering layer different from the plate.

5. 5. The separator according to claim 3, wherein the barrier layer comprises at least one of polyether ether ketone and polyphenylene sulfide.

6. 6. The separator according to claim 3, wherein 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 producing the separator according to any one of claims 1 to 6, comprising the steps of: a molding object placement step of placing a molding object including at least the graphite, the resin, and the metal fibers in a die; a molding step of closing the die with the object to be molded placed therein and performing molding; A method for producing a separator comprising the steps of:

8. the die has an inner surface provided with projections and recesses for transferring the grooves; 8. The method for producing a separator according to claim 7, wherein the molding step comprises molding the molding object and forming the grooves using the die having the projections and recesses.

9. The method further includes a pre-molding step of obtaining the molding object in a semi-cured state from a mixture containing at least the graphite, the resin, and the metal fibers, prior to the molding object placement step, 9. The method for producing a separator according to claim 7, wherein the molding target placement step includes placing the molding target in a semi-cured state in the mold.

10. a first film arranging step, prior to the molding target arranging step, in the mold, arranging a film on one surface in a thickness direction of the plate to form a barrier layer having a gas barrier property superior to that of the plate; 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 molding object placed in the mold in the molding object placement step; Further comprising: The molding target placement step includes placing the molding target on the film that was placed in the mold in the first film placement step, 10. The method for manufacturing a separator according to claim 7, characterized in that the molding step comprises closing the mold while the molded object is sandwiched between the film, and molding is performed to form the barrier layer on both sides of the plate in the thickness direction.

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