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`Primary document | PAI
`*
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`NOTICE
`
`:
`
`JPO and INPIT are not responsible for any damages caused by the use of this
`translation.
`
`1. This document has been translated by computer. So the translation may not reflect
`the original precisely.
`****
`shows a word which cannot be transiated.
`2.
`3. In the drawings, any words are not translated.
`
`
`
`(19) [Publication country] JP
`(12) [Kind of official gazette]
`(11) [Publication number] 2008103164
`(43) [Date of publication of application] 20080501
`(54) [Title of the invention] COMPOSITE MATERIAL OF CARBON AND WATER-REP
`ELLENT MATERIAL
`
`A
`
`(51) [International Patent Classification]
`HO1M 4/86
`HO1M 4/88
`
`(2006.01)
`
`(2006.01)
`
`HO1M 8/1
`
`https://www j-platpat.inpit.¢o.jp/p0200
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`Page 2 of 62
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`0
`
`(2006.01)
`
`Cc
`
`M
`
`[FI]
`HO1M 4/86
`HO1M 4/88
`HOiM 8/10
`(21) [Application number] 2006284113
`(22) [Filing date] 20061018
`(Patent Office notes: The following registered trademark)
`1. Bubble Jet
`
`(71) [Applicant]
`[Name] NISSAN MOTOR CO LTD
`[Name] UNIV OF YAMANASHI
`
`(72) [Inventor]
`[Full name} FURUYA CHOICHI
`[Full name] MINEO TOKUICHI
`{Theme code (reference)]
`5HO18
`
`5HO26
`
`[F-term (reference) }
`5HO18AA06
`
`5HOL8ASO1
`
`5SHOI8BBOL
`
`5HO18BB03
`
`5HO18BB08
`
`5HO18BB12
`
`5HO18DD05
`
`5HOL8DD06
`
`5HOL8DDO8
`
`5HOL8EE05
`
`5HOL8EE06
`
`5HOL8EE0O7
`
`5HOL8SEEO8
`
`S5HOL8EE19
`
`5HOLBSHHOI
`
`SHOLI8HHO4
`
`5HOL8HHO5
`
`5HOLSHHO8
`
`5HO26AA06
`
`5HO26BBOL
`
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`5HO26CX02
`
`5HO26CX04
`
`5HO26EE05
`
`5HO26EE19
`
`5HO26GHHO1
`
`5HO26HHO04
`
`5HO26HHO5
`
`5HO26GHHO8
`
`(57) [Overview]
`a porous composite material, hardly genera
`PROBLEM TO BE SOLVED: To provide
`a
`a
`structuring member of aG
`problem of penetrating through electrades by
`ting
`DL such as carbon fiber, and useful for a
`catalyst layer forming material or a GDL
`case the GDL is of a
`two-layered structure with a base mater
`forming material (in
`ial and a carbon particle layer (MIL), the forming material is for at least one of th
`ose
`(a base material/MIL)) capable of being used for a solid polymer fuel cell exc
`ellent in a gas diffusion property.
`11 anda
`SOLUTION: The porous composite material containing carbon particles
`water-repellent material 12, has a distribution width of a pore diameter 13 to be
`nm or more.
`
`1,000
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` {Patent Claims]
`
`[Claim 1]
`This porous composite material contains carbon particles and a water repellent
`aterial, and has a pore diameter distribution width of 1000 nm or more.
`
`m
`
`[Claim 2]
`The porous composite material according to claim 1, comprising the pore diamete
`r of 40 nm or more and 2000 nm or less.
`
`[Claim 3]
`to claim 1 or
`The porous composite material according
`frequency of the pore diameter is 15%or less.
`
`{Claim 4}
`
`2, wherein the distribution
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`to any one of claims 1 to 3, wherein the
`The porous composite material according
`an average particle dia
`porous composite material comprises fine particles having
`meter of 0.7 to 50 pm.
`
`[Claim 5]
`The porous composite material according to any one of claims 1 to 4, wherein the
`water-repellent material is polytetrafluoroethylene.
`
`[Claim 6]
`A porous composite material according
`a conductive material.
`
`sing
`
`to any one of claims 1 to 5, further compri
`
`[Claim 7]
`The porous composite material of claim 6, wherein the conductive material is a ca
`rbon nanotube,
`
`[Claim 8]
`: a porous composite material acco
`A gas diffusion layer for a fuel cell, comprising
`rding to any one of claims 1 to 7 ; and a carbon fiber sintered porous sheet.
`
`[Claim 9]
`a porous composite material
`An electrode catalyst layer for a fuel cell comprising
`to any one of claims i to 7,
`an electrode catalyst, and an
`
`electrolyte.
`
`according
`
`{Claim 10]
`An electrode for a fuel cell, comprising at least one of the gas diffusion layer
`to claim 9.
`to claim 8 and the electrode catalyst layer according
`
`rding
`
`acco
`
`{Claim 11]
`A membrane electrode assembly for a fuel cell comprising
`16 ; and an
`electrolyte membrane.
`
`: an electrode of claim
`
`{Claim 12]
`a porous composite material is characterized in th
`The method for manufacturing
`at a
`dispersion liquid in which carbon particles and a water repellent materia! are
`in a solvent is formed into a
`in a gas phase space, desolv
`dispersed
`droplet shape
`entized as it is, and is further baked at a
`temperature higher than the melting poi
`nt of the water repellent material.
`
`[Claim 13]
`a porous composite material according to claim 12, wh
`The method for producing
`erein a
`droplet formation and a desolvation are
`in a vapor phase space
`of said dispersion liquid by dry spraying.
`
`performed
`
`
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`[Detailed description of the invention]
`
`[Technical field]
`
`f[O0001}
`a method of manuf
`The present invention relates to a porous composite material,
`acturing the same, a gas diffusion layer for a fuel cell using the porous composite
`a
`material (hereinafter, simply referred to as
`catalyst layer and an electro
`"GDL"),
`de, and a membrane electrode assembly (hereinafter, simply referred to as "ME
`A"} for a fuel cell using the electrode.
`[Background of the Invention]
`
`{0002}
`In recent years, in response to social demands and trends on the basis of energy
`and environmental problems, attention has been paid attention as a power supply
`for a mobile unit and a
`as a fuel cell that operates at roo
`stationary power supply
`a
`temperature and provides
`
`high output density.
`
`m
`
`env
`
`an el
`A fuel cell is a clean power generation system in which a
`product caused by
`water and has little adverse effect on the global
`ectrode reaction is principally
`a solid polymer electrolyte fue! cell using
`a solid polymer
`ironment. In particular,
`to operate at a
`electrolyte is expected
`relatively low temperature, and thus is exp
`ected as a power source for a mobile body in a wide range of fields from a fuel cel
`a
`i vehicle to a
`a cellular phone,
`portable information termi
`portable device (e.g.,
`a notebook personal computer, etc.).
`portable music player,
`
`a
`
`nal,
`
`0003}
`Such a GDL of a
`polymer electrolyte fuel cell has a role of supplying and dischargi
`ng gas to and from the reaction layer (electrode catalyst layer). For this reason, i
`n the GDL of a solid polymer electrolyte fuel cell,
`a carbon paper or a carbon cloth
`a thickness of about 150 up m which is suitable for achieving such a role is
`having
`normally used (see, for example, Patent Document 1).
`[Patent document 1]JP S 60-140668A
`{Disclosure of invention]
`[Problem to be solved by the invention]
`
`[0004]
`However, a conventional carbon paper or carbon cloth material for GDL as describ
`ed in Patent Document 1 is a material obtained by processing carbon fibers into p
`aper or cloth. Since the diameter of the carbon fiber is about 10 u m and the fiber
`is hard and tough, there is a drawback that the anode electrode (the fuel electrod
`are short-circuited through
`t
`e) and the cathode electrode (the oxidant electrode)
`
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`he solid electrolyte. Further, in order to reduce the contact resistance between th
`e GDL and a
`separator such as a
`bipolar plate, when fastening pressure (= cell fa
`stening pressure) due to
`fastening of the end plate of the fuel cell stack is increas
`ed, it is difficult to break the fiber.
`
`[0005]
`As a GDL which Its free from such punch-through, it can be constituted of carbon
`black particles and polytetrafluoroethylene (hereinafter, also referred to as
`PTFE)
`as used in an oxygen cathode of salt electrolysis. However, when an
`fine particles
`as a
`oxygen cathode of this salt electrolyte electrolysis is intended to be applied
`an average pore (pores) of about 0.1 p m, and since the distribut
`GDL, it has only
`ion width of the pore diameter (about 0.1 up m) is very narrow, the pore diameter
`(pore diameter) is too small for a solid polymer electrolyte fuel cell and the gas di
`to a fuel cell, there is
`ffusivity is too low. As a
`result, when such a GDL is applied
`a
`problem that the battery performance is lowered.
`
`[0006]
`
`an
`
`a material for forming
`object of the present invention is to
`Therefore,
`provide
`a GDL (2 layer structure of a substrate and a
`layer of carbon particles (MIL)) whic
`h is capable of being used in a solid polymer fuel cell having good gas diffusibility
`a compone
`and hardly causing the problem of penetration between electrodes by
`a
`nt of GDL such as carbon fiber. There is provided
`molding material of at least o
`ne of these (also referred to as a substrate / MIL),
`a porous composite material a
`S a
`a method for manufacturing the same, a GDL
`catalyst layer molding material,
`a
`electrode, and an M
`catalyst layer and an
`using the porous composite material,
`EA using the electrode.
`{Means for solving the problem]
`
`{0007}
`As a result of extensive studies to achieve the above object, the present inventor
`s obtain a porous composite material in which a carbon particle and a
`water-repel
`lent material such as a fluororesin are formed into a
`in a gas phase
`liquid droplet
`as it is, a solid state is obtained, and
`space, a solvent is removed in a gas phase
`a solid is sintered at a
`temperature higher than or
`to a
`melting point of the
`equal
`water repellent material to obtain a porous composite material in which a carbon
`particle and a water
`repellent material are bonded. It has been found that the ab
`ove
`can be solved by using this porous composite material for GDL moldi
`problem
`ng material (in the case of a 2 layer structure, substrate / MIL molding material),
`to the present invention.
`
`leading
`
`[0008]
`a porous composite mater
`object of the present invention is to
`That is,
`provide
`ial comprising carbon particles and a
`water-repellent material, wherein the pore d
`
`an
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`iameter distribution width is 1000 nm or more.
`
`{0009}
`Further, it is another object of the present invention to
`provide
`a
`in which carbon particles and a water
`
`ucing
`liquid dispersion
`rsed in a solvent.
`
`a method for prod
`are
`
`repellent
`
`dispe
`
`This method for producing the porous composite material is characterized in that
`it is formed into a
`in space, desolventized as it is, and is formed by
`droplet shape
`mat
`temperature higher than the melting point of the water-repellent
`
`baking
`
`at a
`
`erial.
`
`[Effect of the Invention]
`
`{0010}
`Although the porous composite material of the present invention has a
`plurality of
`a pore size distribution width of 1000 nm or more,
`it is hard to defor
`pores having
`mina spherical shape and hard to deform, and it is possible to have a
`porosity of
`preferably 50% or more in terms of porosity. In addition, in the method for produ
`m
`a porous composite material of the present invention, a porous composite
`cing
`a
`a narrow
`particle size distribution, and a uniform
`aterial having
`spherical shape,
`distribution width distribution of a pore diameter of 1000 nm or more can be easil
`y obtained. Further, according to the manufacturing method of the present invent
`a
`to
`ion, by changing the droplet size of the dispersion liquid, it is possible
`adjust
`n
`a porous composite material havi
`arbitrary average particle size and to provide
`to the intended use.
`ng a size corresponding
`
`[0011]
`Therefore, in the GDL (in the case of a 2 layer structure, base material / MIL) for
`med by hot-pressing the porous composite material of the present invention and
`binding the particles of the porous composite material to each other, pores existin
`g in the interior of the porous composite material and pores formed between the
`porous composite materials can be provided. As a
`result, in such GDL (in the case
`of a 2 layer structure, substrate / MIL), since pores of pores having
`a pore diamet
`er of several 10 nm
`to several pp m have numerous pores, diffusion
`(about 40 nm)
`use of GDL (in the case of a 2 layer structure, sub
`of gas greatly increases. Thus,
`can
`greatly enhance performance. Further, by adding the porous co
`strate / MIL)
`mposite material to the catalyst layer coating liquid (catalyst ink), gas diffusion of
`the obtained catalyst layer becomes easy and performance is improved.
`
`[0012]
`Further, in the GDL (in the case of a 2 layer structure, substrate / MIL) of the pre
`sent invention, by making the particle diameter of the porous composite material
`to or
`of the present invention to be equal
`larger than, for example, 10 um, pores
`
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`a
`
`large diameter of 1 ym or more can be also present, and water can easi
`having
`iy pass through, and thus water can be easily discharged. By forming the catalyst
`on the GDL (in the case of a 2
`layer structure, MIL) by coating with a
`layer
`cataly
`an electrode and an MEA can be easily manufactured. When the MEAis inc
`st ink,
`orporated in a fuel cell, it is not deformed over a
`long period of time under a
`so that the durability of the fuel cell is improved.
`pressure condition,
`[Best mode for carrying out the invention]
`
`high
`
`{0013}
`
`a porous composite material of the present invention,
`Hereinafter,
`a
`manufacturing the same, a fuel cell (GDL,
`catalyst layer and an
`electrode, and
`an MEA using the electrode) using the porous composite material will be describe
`d respectively.
`
`a method for
`
`[0014]
`(1) Porous composite material
`A porous composite material according to the present invention is a porous comp
`osite material comprising carbon particles and a
`water-repellent material, and has
`a distribution width of 1000 nm or more.
`
`[0015]
`
`a porous composite material of the present invention will be describe
`Hereinafter,
`d with reference to the drawings.
`
`[0016]
`FIG. 1 is a schematic diagram schematically showing, in an
`enlarged scale, 1 part
`a
`icles of a porous composite material having
`spherical shape and in a
`powder (p
`article) form so as to be abie to know the state of the carbon particles, the water
`repellent material, and the pores present in the porous composite material which
`constitute the porous composite material of the present invention.
`
`[0017]
`As shown in FIG. 1, the porous composite materia! 10 is formed using carbon part
`a
`icles 11 and a
`water-repellent material 12. Then,
`large number of pores (throug
`a distribution width of a pore diameter of 1000 nm or more ar
`h-holes} 13 having
`e
`11 and the water
`provided mainly between the carbon particles
`al 12 in the porous composite material 10.
`
`repellent materi
`
`[0018]
`Here, the porous composite material 10 is a sintered body, and has a structure in
`which, when the water repellent material 12 is baked at a
`temperature higher tha
`n or
`repellent material 12 in the manufact
`to the melting point of the water
`equal
`uring process as described later, the water repellent material 11 is melted to act
`as a
`repellent material are bon
`12 and the water
`binder, and the carbon particles
`ded to each other. And the carbon particle
`
`11
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`an infinite number of pores 13 are formed in which the distribution wi
`in addition,
`repellent materials 1
`dth of pore diameters of pores generated between the water
`larger than 1000 nm. That is, the porous compasite material 10 h
`to or
`2 is equal
`aS a porous structure having
`a pore diamet
`an infinite number of pores 13 having
`er distribution width of 1000 nm or more.
`
`[0019]
`It is desirable that the pore size of the pores 13 be small so that it is possible
`orm a pore region which is impermeabie
`to gas. The p
`to moisture and permeable
`ores 13 having the distribution width of the pore diameter of 1000 nm or more ca
`n be formed by preventing the shearing
`so that the wat
`stress from being applied
`er
`repellent 12 does not become fibrillated at the time of firing (more specifically,
`refer to the manufacturing method and the like described later).
`
`to f
`
`{0020}
`(I) Average particle size of porous composite material 10 ;
`It is desirable that the average particle diameter of the porous composite materia
`110 is 0.7um-50pum, preferably 2 to 20 p m, more
`preferably 5 to 10 um. Whent
`he average particle diameter of the porous composite material is 0.7 4 mor mor
`e, GDL (2 layer structure) is used. When used in a substrate / MIL, it is suitable f
`or
`a pore diameter of 0.5 um or
`forming relatively large pores (more specifically,
`more
`capable of permeating moisture and gas ; see 30 in FIG. 3 b) capable of diff
`using gas through gaps between particles of a porous composite material and allo
`water to pass easily. Further, when the catalyst layer is added to the c
`wing liquid
`can be facilitated through relativel
`atalyst layer, gas diffusion in the catalyst layer
`y small pores 13 in the inside of the porous composite material dispersed in the c
`atalyst layer, thereby improving performance. When the average particle diamete
`r of the porous composite material is 50 pm or
`tess, film formation such as GDL i
`s facilitated. The average particle diameter of the porous composite material can
`a
`particle size distribution apparatus for powder.
`be measured by
`
`[0021]
`to the difference in the average particle diameter o
`As described above, according
`f the porous composite material, the average pore diameter and the pore distribu
`tion of the pores (through holes ; reference numeral 30 in FIG. 3 b) between the
`ex
`so as to
`particles of the porous composite material can be adjusted
`effectively
`hibit the effect of the present invention. By changing the average pore diameter a
`nd pore distribution of pores (through holes) between particles of such a porous c
`omposite material, for example, it is possible to effectively and effectively control
`water.
`the permeability of liquid
`
`[0022]
`
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`(ii) Tensile strength and deformation rate of the porous composite material 10 ;
`Preferably, the porous composite 10 has a tensile strength of 20 kgf / cm 2 or mo
`a
`20-40kgf/cm2, and a fracture deformation rate of 20%or
`re, preferably
`less, pr
`eferably 15%or
`more
`preferably 5%to 10%.
`
`less,
`
`[0023}
`Here, when the tensile strength of the porous composite material 10 is 20 kgf /c
`m 2 or more, when the porous composite material 10 is used, the GDL (substrat
`e
`/ MIL in the case of a 2
`layer structure) is manufactured by hot press molding.
`The gaps between the porous composite materials 10 and (pores) and the poresi
`nside the porous composite material 10 are hard to be crushed,
`so that a GDL (2
`a desired size can be provided. It is possible
`an
`to
`layer structure) having
`provide
`inter-particle structure of a porous composite material w
`internal structure and an
`hich is formed by connecting such porous composite materials 10 with an appropr
`iate gap, and which is hardly crushed even when a small pore 13 and a
`large pore
`are
`placed in a
`manufacturing process or ah
`(a reference numeral 30 in FIG. 3 b)
`eating and pressurizing state in a fuel cell.
`
`[0024]
`Further, when the fracture deformation rate of the porous composite material 10 i
`or
`S not more than 20%, it is excellent in
`shape stability of a sheet (GDL
`MIL) aft
`er
`molding, and is excellent in handleability. The tensile strength of the porous co
`mposite material can be measured by
`a tensile tester manufactured by Shimadzu
`Corporation. The fracture deformation rate of the porous composite material can
`a tensile tester manufactured by Shimadzu Corporation. These a
`be measured by
`re measured using
`a
`a porous composite
`sample obtained by hot-press-molding
`material in the form of a
`powder {particie) in the following condition, rather than i
`:.
`n the form of powder (particle)
`
`[0025]
`Hot pressing conditions
`
`:
`
`a porous composite material in the form of a
`Material for hot press moiding
`Only
`to the invention is used.
`
`powder according
`: 360°C.
`Hot press temperature
`Hot press pressure : 5 MPa.
`Hot press time : 1 min.
`: 5 cm x 5 cm = 0.1 nm thickness
`Shape of a
`compact
`Porosity of porous composite material 10
`Further, the porosity of the porous composite material 10 is preferably 50 to 8
`0%, and more
`preferably 60 to 70%. When the porosity is 80%or
`less, it is possi
`ble to obtain a fine and hard to deform particle
`structure. When the porosity is 5
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`
`a size of liquid impermeabilit
`0% or more, a
`large number of pore regions having
`y and capable of transmitting water vapor can be formed, and the diffusion ability
`repellent pores can be increased. Therefore, in the GDL
`of the gas by the water
`(2 layer structure} using the porous composite material 10 having pores 13 havin
`g such porosity, water can be supplied and drained quickly through relatively larg
`e pores formed in gaps between the porous composite materials 10. In addition,
`even when the gas passes through relatively large pores (through holes) in the w
`ater or the water
`an infinite
`supply, the gas can be diffused (transmitted) through
`number of relatively small pores (through holes) 13 existing inside the porous co
`a structure in which the g
`mposite material 10. Therefore, it is possible to provide
`as diffusion path (through hole) is hardly blocked by the supply and drain of the g
`as. AS a
`result, the gas diffusion greatly increases the performance of the fuel cell
`using the GDL (substrate / MIL in the case of 2
`layer structure). Porosity of the p
`orous
`composite material 10 can be measured by
`or a wat
`a mercury porosimeter
`
`er
`
`porosimeter.
`
`[0026]
`{v) each component of the porous composite material 10 ;
`Next, the distribution width of the pore diameter which exists in the carbon particl
`e 11 which is the component member and the repellent 12, and also porous comp
`osite describes each constituent features, such as the fine pores 13 which are 100
`0 nm or more, about the porous composite of the present invention.
`
`[0027]
`-
`i1
`1) Carbon particles
`(v
`(a) The material of a carbon particle
`a porous composi
`a material (type) of a carbon particle 11 constituting
`To provide
`a
`te material 10, which is capable of imparting conductivity (electric conductivity)
`nd porosity to a GDL (a substrate / MIL in the case of a 2 layer structure). In addi
`tion, the same conductive carbon material as that used for carbon paper or carbo
`n
`cloth, which is a
`can be used to impart por
`conventionally known GDL material,
`a conventional one such as g
`osity to the catalyst layer. Specifically, for example,
`or
`expanded graphite may be used. Among them, carbon blacks such as o
`raphite
`if furnace black, channel black, lamp black, thermal black, and cetylene black are
`s
`preferred because they have excellent electronic conductivity and large specific
`or in combination of 1 or more kinds of 2
`urface area. These may be used singly
`or more thereof.
`
`{0028}
`{b) carbon particles.
`particulate form so as
`It is desirable that the shape of the carbon particles be in a
`to prevent short circuiting between the anode electrode (fuel electrode) and the c
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`athode electrode (oxidant electrode or cathode electrode). Specifically, the aspect
`ratio (aspect ratio) of the carbon particles is in the range of 1 to 3, preferably 1 t
`o 2. Here, it is assumed that the aspect ratio is expressed by the long axis lengt
`or
`h / short axis length (cross-sectional diameter) of the sample (carbon particles
`water repellent particles to be described later), and an average value of 100 orm
`ore
`particles selected at random is used. The shape and aspect ratio can be meas
`ured by SEM (Scanning Electron Microscope) observation, TEM (Transmission Elec
`or the like.
`tron
`
`Microscope) observation,
`
`[0029]
`Average 2 particle size of carbon particles and average 1 order particle size
`AS an average secondary particle size of the carbon particles 11, moisture imper
`meable is contained in the porous composite material 10. 2
`
`It is desirable to be able to form pores 13 of a size which can be gas permeable,
`200-1000nm, preferably in the range from 300 to 600 nm.
`with a
`Here, the avera
`11 mean an average particle size of
`ge secondary particles of the carbon particles
`an
`or a
`lump (= 2 particle) in which individual carbon particles {= 1 pa
`aggregate
`are
`aggregated (= 2). When the average secondary particle diameter of t
`rticles)
`to or
`11 is equal
`to the parti
`larger than 200 nm, almost equal
`he carbon particles
`cle diameter of the water repellent material (e.g., PTFE fine particles), the gap be
`repellent material, and a p
`tween the carbon particles is not blocked by the water
`a
`ore formation having
`predetermined pore diameter distribution width is enabled
`in a
`an av
`2. If the secondary [
`relatively small pore region of the carbon particles
`11 is LOO00 nm or less on the ot
`erage of | particle diameter of the carbon particle
`her hand, the problem of the dispersibility of ink (dispersion liquid which made th
`e solvent distribute a carbon particle and a
`repellent) is preferable few.
`
`[0030]
`can be measured, for example, by SEM (s
`The particle size of the carbon particles
`canning electron microscope) observation, TEM
`(transmission electron microscop
`or the like (see FIG. 9 a). In some cases, the carbon particles incl
`e) observation,
`ude particles having different aspect ratios as described above. Therefore, the par
`ticle size and the like described above are
`as an absolute maximum len
`
`expressed
`gth because the shape of the particles is not uniform. This is also true of the parti
`cle diameter of water
`repellent particles described later. Here, the absolute maxi
`length is assumed to be a maximum length among distances between arbitr
`on a contour line of particles (e.g., carbon particles,
`water
`ary 2 points
`particles, and the like).
`
`mum
`
`repellent
`
`{0031}
`(d) blending ratio of carbon particles ;
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`From the viewpoint of effectively exhibiting the above-mentioned conductivity (el
`ectric conductivity), the mixing ratio of the carbon particles 11 is in a range of 40
`to 80% by mass, preferably 50 to 70% by mass, based on the total amount of th
`m
`e€ porous composite. When the blending ratio of the carbon particles is 40% by
`ass or more, a structure (durability),
`a structure (durability} which is difficuit to b
`e crushed and which is difficult to be crushed can be secured. On the other hand,
`mass or
`less, desired co
`when the blending ratio of the carbon particles is 80% by
`can be exhibited without impairing the electr
`nductivity and gas diffusion property
`to obtain a structure
`In addition, it is possible
`in wh
`ode performance.
`(durability)
`ich a necessary strength is obtained by the binding action of the water repellent
`material and which does not deform for a
`long time under a
`high pressure state.
`
`{0032}
`-
`2) Water repellent materia! 12
`{v
`Material of water
`repellent material
`The material (kind) of the water repellant material 12 constituting the porous co
`a w
`mposite material 10 will be described. In the case of GDL (2 layer structure),
`a
`water-repellent material or a material subjected to
`ater repelient material (e.g.,
`repellent treatment) conventionally used in GDL can be used so that water
`water
`as well a
`can be increased and flooding phenomenon
`can be prevented
`repellency
`Ss
`catalyst layer. The material {type} of such a
`water-repellent material is not parti
`cularly limited, but polytetrafluoroethylene (PTFE) is used. Examples thereof inclu
`de fluorine-based polymeric materiais such as
`polyvinylidene fluoride (PVDF), pol
`
`yhexafluoropropylene, tetrafluoroethylene-hexafluoro propylen copolymer (FEP),
`and tetrafluoroethylene-perfluoroalkyl viny! ether copolymer (PFA), polypropyilen
`a fluorine-based polymer material is preferabl
`e, and polyethylene. Among them,
`y used because of excellent water
`repellency, corrosion resistance at the time of
`as shown in FIG. 1, since the ca
`electrode reaction, and the like. More preferably,
`11 can be bonded and a
`water-repellent surface can be formed, a fl
`rbon particles
`uorine-based polymer material of a
`PTFE,PFA,FEP is particularly desirable. Particul
`arly preferred is PTFE from the viewpoint of durability. Further, by using suchas
`a function of reducing th
`to
`uitable water-repellent material, it is possible
`provide
`e electric resistance, and preventing the permeation of water by the water repelle
`nt pores into the interior of the porous composite material 10.
`
`[0033]
`a water repellent material ;
`(b)
`As shown in FIG. 1, it is desirable that the shape of the water
`12 is parti
`repellent
`culate so that the anode electrode (fuel electrode) and the cathode electrode (air
`are not short-circuited by penetrating between the electrodes like a co
`electrode)
`nventional carbon fiber. In other words, it is desirable that the granular water-rep
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`ellent material 12 added during the manufacturing process is not fibrillated (fiberi
`zed). Specifically, it is an
`aspect ratio of the form of the repellent i2.
`
`1 to 2. It can be said that the
`The aspect ratio is in the range of 1 to 4, preferably
`particulate water repellent 12 does not need to be spherical, but rather has a sha
`as shown in F
`11 to each other,
`pe suitable for firmly binding the carbon particles
`IG. 1, within an unfibrillated range (the range of the aspect ratio). In other word
`m
`s, it can be said that a
`shape is desirable in which the spherical water-repellent
`11 and crushed and deform
`aterial 12 is sandwiched between the carbon particles
`ed so as to be closely adhered to the surface of the carbon particles 10.
`
`[0034}
`a ratio of non-fibrillation of the water repellent material ;
`(c)
`In other words, it is desirable that the water
`repellent material 12 has not less th
`an
`not more than
`not less than 80%, and particularly preferably
`60%, preferably
`100%(total water repellent material} of the water repellent material. Therefore, i
`{ can be said that, when a water
`repellent material (e.g., PTFE) is not fibrillated,
`a water repellent material exists in a
`a small aspect ratio, e.g., a gr
`shape having
`or a
`PTFE)
`layered shape. Since the water-repellent material (e.g.,
`anular shape
`i
`S not fibrillated in this way, it is excellent in that the porous composite material 1
`can be strengt
`0 and the GDL (in the case of a 2 layer structure, substrate / MIL)
`hened, and a
`problem such as a short circuit between electrodes can be prevente
`ca
`d. Further, it is excellent in that the gas diffusion property of the catalyst layer
`n be secured and that the performance
`can be improved.
`
`[0035]
`Fibrillation of the water-repellent material can be observed by, for example,
`nning electron microscope (SEM image) (see FIG. 15), and a
`water-repellent
`erial (PTFE) which is fibrillated and becomes fibrous is observed in FIG. 15. }.
`
`a sca
`
`mat
`
`[0036]
`Tensile strength of water
`repellent material
`It is assumed that the tensile strength of the water repellent material is measure
`d as a sintered body with 100%of particulate
`water
`repellent particles. It is desir
`able that the tensile strength of the water repellent particles is 10 MPa or more, p
`referably 10 to 30 MPa. When the tensile strength of the water-repellent particles
`is LO MPa or more, a
`strong porous composite material can be obtained. Further,
`the upper limit of the tensile strength of the water-repellent particles is not partic
`ularly limited, but if the upper limit is 30 MPa or
`less, the structure of the porous
`composite material 10 and the GDL (substrate / MIL in the case of a 2 layer struc
`can be sufficiently strengthened, and the problem of short-circuiting betwee
`ture)
`n electrodes can be prevented.
`even when it exceeds 30 MPa, there i
`In addition,
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