EP4233108A1 - Electrode material - Google Patents

Electrode material

Info

Publication number
EP4233108A1
EP4233108A1 EP21805397.3A EP21805397A EP4233108A1 EP 4233108 A1 EP4233108 A1 EP 4233108A1 EP 21805397 A EP21805397 A EP 21805397A EP 4233108 A1 EP4233108 A1 EP 4233108A1
Authority
EP
European Patent Office
Prior art keywords
layer
resins
electrode material
carbon
thermoplastic material
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP21805397.3A
Other languages
German (de)
French (fr)
Inventor
Rüdiger-Bernd SCHWEISS
Christian MEISER
Dana Cazimir
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
SGL Carbon SE
Original Assignee
SGL Carbon SE
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by SGL Carbon SE filed Critical SGL Carbon SE
Publication of EP4233108A1 publication Critical patent/EP4233108A1/en
Pending legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/8605—Porous electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/04—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of carbon-silicon compounds, carbon or silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
    • H01B13/0016—Apparatus or processes specially adapted for manufacturing conductors or cables for heat treatment
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the present invention relates to a method for producing an electrode material for gas diffusion layers, the electrode material produced using this method and its use.
  • GDLs Gas diffusion layers
  • PEMFCs polymer electrolyte fuel cells
  • metal-air batteries metal-air batteries
  • electrochemical reactors electrolyzers
  • GDLs which additionally contain electrocatalytically active components, are referred to as gas diffusion electrodes (GDEs).
  • the core task of the GDL is the supply of the electrochemically active layers with gaseous or liquid fuels (hydrogen, methanol) and with oxidants (oxygen) as well as the dissipation of electricity and heat or the removal of reaction products.
  • Gaseous or liquid fuels hydrogen, methanol
  • oxidants oxygen
  • Carbon-based GDLs usually have a macroporous electrode material comprising carbon fibers, which is made hydrophobic with fluoropolymers and has a micro-porous layer (MPL) made of carbon particles and fluoropolymers (usually polytetrafluoroethylene, PTFE) on one side .
  • MPL micro-porous layer
  • the macroporous electrode materials are manufactured either by weaving carbon fibers or by non-woven processes (dry or wet non-woven technology).
  • Today's GDLs are based almost exclusively on nonwovens made from carbon fibers, while woven fabrics only play a subordinate role.
  • a primary fleece is made from carbon fibers and binders, or a primary fleece is made from carbon fiber precursors and this fleece is then carbonized.
  • a primary fleece is made from carbon fiber precursors and this fleece is then carbonized.
  • A) Dry laying of nonwovens made of precursor fibers Here, webs are produced from crimped staple fibers made from polyacrylonitrile (PAN) or oxidized polyacrylonitrile with a typical fiber titre of 0.8 to 4 dtex and a fiber length of 30 to 70 mm using water jet bonding (spunlace technology). These fleeces are then further carbonized into carbon fiber fleeces, with prior thermal stabilization taking place when PAN is used as a precursor fiber. The carbonization causes the fleece to shrink by around 10 to 15%.
  • PAN polyacrylonitrile
  • oxidized polyacrylonitrile with a typical fiber titre of 0.8 to 4 dtex and a fiber length of 30 to 70 mm using water jet bonding (spunlace technology).
  • These fleeces are then further carbonized into carbon fiber fleeces, with prior thermal stabilization taking place when PAN is used as a precursor fiber. The carbonization causes the fleece to shrink by around 10 to 15%.
  • short-cut carbon fibers made of polyacrylonitrile (PAN) with a typical fiber length of 3 to 15 mm are dispersed and applied using an inclined wire paper machine with the aid of binder fibers or aqueous dispersions of binder polymers fleece processed. This is followed by optional impregnation with carbonizable resins and hardening of the resin matrix with subsequent carbonization.
  • PAN polyacrylonitrile
  • EP1328947B1 describes a process based on method A with crimped, preoxidized polyacrylonitrile staple fibers having a length of 40 to 80 mm with the addition of binding fibers based on polyvinyl alcohol. The latter flow as a result of the effects of temperature and moisture (hydroentanglement). These primary fleeces are compacted using calenders and then carbonized.
  • Routes according to Method B are based on short-cut carbon fibers with a length of 6 to 12 mm, which are processed into paper using thermoplastic binders.
  • These primary fleeces usually have a low grammage ( ⁇ 30 g/m 2 ) and are mechanically less stable.
  • carbonizable resins eg phenolic resins and carbonized again (US7144476B2).
  • EP1502992A1 describes a method based on method B (paper process) with short-cut carbon fibers and using fibrillated or ground lenen polyacrylonitrile fibers as a binding substance. The latter are added to the pulp suspension. After the formation of the non-woven fabric, the web is compressed under the influence of heat using double-belt presses.
  • Production methods according to EP 2089925B1 use dry or wet laying processes in which the binder is introduced in the form of uncured phenolic resin fibers (for example Novoloid® (uncured phenolic resin fibers)).
  • An electrode material is obtained by thermal crosslinking under the action of pressure with subsequent carbonization.
  • fuel cells for automotive use increasingly require thinner gas diffusion layers ( ⁇ 200 ⁇ m) with high requirements in terms of thickness tolerances and homogeneity. This has to do with the fact that these fuel cell stacks consist of up to 400 individual cells, and problems with regard to uniform compression and stack dimensioning can therefore arise with relatively large fluctuations in thickness of the GDL (compared to the other components).
  • the disadvantage of method B is that, especially in the case of carbon fiber papers, impregnation processes are required after the paper production process, which require additional process steps and cost factors. This relates in particular to the effort involved in dispersing and drying and the longer process cycles.
  • the impregnation processes can sometimes lead to inhomogeneities if the impregnation with fillers or binder resins is uneven.
  • classic manufacturing processes without compression of the impregnated material do not allow the production of thin substrates with sufficient mechanical stability, since the fiber volume fraction is too low.
  • a high proportion of fibers or a low proportion of binder is desirable, since during fuel cell operation water accumulation can occur preferentially on the binder matrix, which is disadvantageous since this reduces the performance of the cell.
  • the object of the present invention is therefore to provide an alternative method for producing an electrode material for gas diffusion layers with a small thickness provide, which prevents the disadvantages of additional process steps and thus costs.
  • this object was achieved by providing a method for producing an electrode material for gas diffusion layers, which comprises the following steps: a) providing at least one layer of fiber structures, b) providing at least one layer of thermoplastic material, c) stacking the at least one layer Fibrous structure from step a) with at least one layer of thermoplastic material from step b) d) connecting the stacked layers from step c) by applying a pressure of 2 to 80 bar and a temperature of 70 to 280 °C to form a composite material, and e) carbonization of the composite material from step d) at temperatures of 1400 to 2500° C. under a protective gas atmosphere.
  • the advantage of the method according to the invention is that no impregnation steps of the fiber structure are necessary in the further production of the electrode material, so that a simpler and more cost-effective method is made available.
  • the reason for this is that by forming a composite of at least one layer of fiber structure and at least one layer of thermoplastic material, by connecting the layers under the influence of temperature and pressure to form a composite material, the thermoplastic material penetrates into the fiber structure, making impregnation superfluous will.
  • the thermoplastic material is equipped with carbonizable resins and/or carbon-based fillers, as a result of which the porosity of the carbonized material can be adjusted.
  • the electrode material described is more stable and has a higher fiber volume content.
  • the method according to the invention can be carried out either as a continuous or batch process.
  • continuous process roll-to-roll process
  • sheet material is used in the batch process.
  • the continuous process is preferred because it reduces process times.
  • Stacking of the tiers can be in any order, with no limit to the number of tiers. However, two and three layers are preferred.
  • the composite is obtained by the action of heat and pressure in step d), which is done by means of double stamp presses, laminating systems, double belt presses or calendering.
  • Any protective gas, such as argon or nitrogen, can be used for the protective gas used in step e).
  • fiber structures are understood to mean nonwovens made from short fibers or staple fibers, with fiber fabrics also counting among the fiber structures.
  • Short fibers have a length of 1 mm - 20 mm and staple fibers have a length of 30-80 mm.
  • Woven fabrics are textile fabrics that have at least two thread systems that do not run parallel and thus intersect.
  • a non-woven fabric is a structure made of short fibers or staple fibers that are produced by wet laying or dry laying.
  • the at least one layer of fiber structure from step a) is a carbon fiber fleece or a carbon fiber fabric.
  • the carbon fiber nonwovens can be obtained using various processes such as meltblown, spunlace or wet-laid processes.
  • the at least one layer of the fiber structure has a thickness of 50 ⁇ m to 400 ⁇ m, preferably 100 ⁇ m to 250 ⁇ m. With a thickness of less than 50 ⁇ m, the fibrous structure is too unstable, so that handling is made more difficult, and with a thickness of the fibrous structure greater than 400 ⁇ m, compaction is difficult.
  • the thickness range from 100 ⁇ m to 200 ⁇ m is preferred, since the relationship between stability and the possibility of compression is particularly favorable here.
  • the at least one layer of thermoplastic material from step b) is selected from the group consisting of polyethylene (low-density polyethylene (LDPE), high-density polyethylene (HDPE)), polypropylene (PP), ethylene-vinyl acetate copolymers (EVA), polyvinyl butyral (PVB), cellulose acetate (CA), polyvinyl alcohol (PVA), vinylpyrrolidone-vinyl acetate copolymers, styrene-maleic anhydride copolymers (styrene-maleic anhydride (SMA)) or thermoplastic elastomers (thermoplastic polyolefins (TPO ), Styrene block copolymers (TPS)), preferably selected polyvinyl butyral, cellulose acetate or polyvinyl alcohol.
  • Polymers with hydroxyl or anhydride groups are preferred, since these enter into condensation reactions with resins or are themselves capable of crosslinking reactions.
  • thermoplastic material is advantageously in the form of a film or textile structure.
  • Foil and textile structures are preferred because the material is in the form of a web, so that the process can be carried out as a continuous process.
  • the thermoplastic material has a thickness of 10 ⁇ m to 300 ⁇ m, preferably 20 ⁇ m to 75 ⁇ m.
  • Thermoplastic material with a thickness smaller than 10 ⁇ m is not commercially available and thicker than 300 ⁇ m reduces the stability of the substrate and densification is deteriorated.
  • the range from 50 ⁇ m to 250 ⁇ m is preferred, since this results in a preferred ratio of fiber structure to thermoplastic material.
  • the at least one layer of thermoplastic material is coated with carbonizable resins and/or carbon materials. The coating increases the carbon yield, because the carbonizable resins convert to carbon during carbonization.
  • the resins and carbon materials can be in the form of powders, suspensions, dispersions or solutions.
  • Suspensions, dispersions or solutions can be applied by dip coating, spraying, screen printing, knife coating, curtain coating, roller application, prepreg technology or inkjet printing. Powdery substances can be applied by sprinkling.
  • the mechanical properties of the electrode material can be controlled by the coating and the coating also contributes to the fact that an impregnation step is not necessary in the further production of the electrode material.
  • the resins are advantageously selected from the group consisting of phenolic resins, melamine resins, resorcinol resins, cyanoester resins, and vinylester resins
  • the carbon materials are advantageously selected from the group consisting of molasses, bitumen, graphite, soot, activated carbon, ground carbon fibers, coal tar pitch or coke particles.
  • the coating comprises crosslinking additives (1-5% based on the proportion of thermoplastic material).
  • the carbon yield of the thermoplastic components is increased by the crosslinking additives and an electrode material with improved stability and conductivity is thereby obtained.
  • the crosslinking additives are advantageously selected from the group consisting of organic peroxides, dialdehydes, diamines and UV-curable polymers.
  • crosslinking additives have a particularly high carbon yield.
  • the assembly is additionally irradiated with ionizing radiation or UV radiation in step d).
  • the carbon yield can be increased, which creates a higher conductivity of the electrode material.
  • a further object of the present invention is an electrode material which has been produced using the method according to the invention.
  • the advantage of the electrode material is that it has a particularly smooth surface, so that contact resistances within the cell are reduced.
  • the high fiber volume content of the electrode material significantly reduces the accumulation of water, so that the cell has a higher output and, on the other hand, increases the thermal and electrical conductivity, which also leads to a higher conductivity of the cell.
  • the higher fiber volume content also causes a higher rigidity or a higher shear modulus of the material. This results in less intrusion of the electrode material into the flow channels of the bipolar plate in the cell. This has the advantage that in turn contact resistances are reduced and there is less accumulation of liquid water in the flow channels of the bipolar plates.
  • the electrode material has a thickness of 50 ⁇ m to 500 ⁇ m, preferably 70 ⁇ m to 200 ⁇ m. According to an even more preferred embodiment, the electrode material has a density of 0.1 g/cm 3 to 0.6 g/cm 3 , preferably 0.15 g/cm 3 to 0.40 g/cm 3 .
  • the selected thicknesses of the electrode material determine the desired stability and the selected densities of the electrode material ensure a pore space that is important for the GDL.
  • Yet another object of the present invention is the use of the electrode material in polymer electrolyte fuel cells, in phosphoric acid fuel cells, microbial fuel cells, electrochemical reactors, oxygen-consuming cathodes, metal-air batteries, PEM electrolyzers or batteries.
  • FIG. 1 shows the method according to the invention
  • FIG. 2 shows the method according to the invention
  • Figure 3 shows a thermoplastic material with a coating
  • FIG. 4 shows a substrate with two layers
  • FIG. 5 shows a substrate with three layers
  • FIG. 6 shows a substrate with three layers
  • FIG. 1 shows the method according to the invention.
  • a thermoplastic film (1) is coated with a dispersion (2), thereby obtaining a film web with a coating (4).
  • Two webs of film with a coating (4) are combined with a carbon fiber fleece (6) to form a composite (9) using a number of hot calenders or belt presses (7, 8).
  • the composite (9) then carbonized in a continuous furnace (10) under a protective gas atmosphere to form an electrode material (11).
  • FIG. 2 additionally shows the crosslinking of the thermoplastic polymer by ionizing or UV radiation (12).
  • FIG. 3 shows a thermoplastic material (4) coated according to the invention, the coating (5) being applied to the thermoplastic material (1).
  • FIG. 4 shows a two-layer electrode material according to the invention, the coating (5) of the thermoplastic material (1) adjoining the layer of carbon fiber fleece (6).
  • Figure 5 shows a 3-layer electrode material according to the invention, the layer sequence being thermoplastic material (1) with a coating (5), carbon fiber fleece (6), thermoplastic material (1) with a coating (5) and the coating (5th ) in each case adjoins the carbon fiber fleece (6).
  • FIG. 6 shows a 3-layer electrode material according to the invention, the sequence of layers being carbon fiber fleece (6), thermoplastic material with coating (5), carbon fiber fleece (6).
  • a prosthesis component can be produced as described below.
  • novolak phenolic resin (Bakelit PF0227 SP, Hexion), 100 g ground carbon fibers (Sigrafil® CM80, SGL Carbon) and 100 g phenol-modified indene coumarone resin (Novares CA80, Rütgers) are dissolved or suspended in 150 g acetone. died This viscous dispersion is coated onto a polyvinyl butyral film (Trosifol®, Kuraray, 50 ⁇ m) using a doctor blade method (wet film thickness 50 ⁇ m).
  • a composite of 2 layers of the coated polyvinyl butyral film and a carbon fiber structure (23 g/m 2 ) is then produced using a hot press (layer sequence film I carbon fiber structure I film). This composite is then carbonized in a protective gas atmosphere at a temperature of 1400°C.
  • a polyethylene film (HDPE, 50 ⁇ m, Folienwerk Lahr) is coated with a dispersion of phenolic resin (10 parts), acetylene black (5 parts) in isopropanol (18.5 parts) in a desk coater and dried at 80.degree. The amount applied was 10 g/m 2 .
  • a hot calender 180° C., 10 bar
  • a composite is produced from one layer of carbon fiber structure (23 g/m 2 ) between 2 layers of the coated film, with the coating being oriented towards the carbon fiber structure in each case. This is followed by carbonization at 1700 °C in a protective gas atmosphere.
  • a layer of carbon fiber fleece (18 g/m 2 ) is laminated on both sides with a film based on ethylene-vinyl acetate copolymer (TecWeb®, 20). This is followed by electron irradiation (dose 150 Gy) to crosslink the polymer. The composite is then carbonized in a protective gas atmosphere at a temperature of 1750 °C.
  • Electrode materials according to the invention have properties comparable to those of the reference materials with a smaller thickness.
  • the area-specific resistance was measured according to DIN 51911-1997 and the longitudinal and transverse bending stiffness according to ISO 5628-2019

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  • Chemical & Material Sciences (AREA)
  • General Chemical & Material Sciences (AREA)
  • Electrochemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Thermal Sciences (AREA)
  • Inert Electrodes (AREA)
  • Electrodes For Compound Or Non-Metal Manufacture (AREA)
  • Manufacture Of Metal Powder And Suspensions Thereof (AREA)
  • Powder Metallurgy (AREA)
  • Hybrid Cells (AREA)
  • Fuel Cell (AREA)

Abstract

The present invention relates to a method for producing an electrode material for gas diffusion layers, to the electrode material thereby produced and to its use.

Description

ELEKTRODENMATERIAL ELECTRODE MATERIAL
Die vorliegende Erfindung betrifft ein Verfahren zur Herstellung eines Elektrodenma- terials für Gasdiffusionsschichten, das mit diesem Verfahren hergestellte Elektroden- material sowie dessen Verwendung. The present invention relates to a method for producing an electrode material for gas diffusion layers, the electrode material produced using this method and its use.
Gasdiffusionsschichten (englisch: Gas Diffusion Layers, GDLs) sind hochporöse, leitfähige Materialien auf Basis von Kohlenstoff oder Metallen und werden vor- nehmlich in Polymerelektrolytbrennstoffzellen (PEMFCs), Metall-Luft-Batterien, elektrochemischen Reaktoren und Elektrolyseuren eingesetzt. Als Gasdiffusions- elektroden (GDEs) werden GDLs bezeichnet, welche zusätzlich elektrokatalytisch wirksame Bestandteile enthalten. Gas diffusion layers (GDLs) are highly porous, conductive materials based on carbon or metals and are primarily used in polymer electrolyte fuel cells (PEMFCs), metal-air batteries, electrochemical reactors and electrolyzers. GDLs, which additionally contain electrocatalytically active components, are referred to as gas diffusion electrodes (GDEs).
Kernaufgabe der GDL ist die Versorgung der elektrochemisch aktiven Schichten mit gasförmigen bzw. flüssigen Brennstoffen (Wasserstoff, Methanol) und mit Oxi- danten (Sauerstoff) sowie die Ableitung von Strom und Wärme bzw. der Abtrans- port von Reaktionsprodukten. Kohlenstoffbasierte GDLs weisen in der Regel ein makroporöses, Carbonfasern umfassendes Elektrodenmaterial auf, welches mit Fluorpolymeren hydrophobiert und einseitig mit einer mikroporösen Schicht (engl. micro-porous layer, MPL) aus Kohlenstoffpartikeln und Fluorpolymeren (in der Re- gel Polytetrafluorethylen, PTFE) versehen ist. Die MPL penetriert zum Teil in das makroporöse Elektrodenmaterial. The core task of the GDL is the supply of the electrochemically active layers with gaseous or liquid fuels (hydrogen, methanol) and with oxidants (oxygen) as well as the dissipation of electricity and heat or the removal of reaction products. Carbon-based GDLs usually have a macroporous electrode material comprising carbon fibers, which is made hydrophobic with fluoropolymers and has a micro-porous layer (MPL) made of carbon particles and fluoropolymers (usually polytetrafluoroethylene, PTFE) on one side . The MPL partly penetrates into the macroporous electrode material.
Die makroporösen Elektrodenmaterialien werden entweder durch Weben von Koh- lenstoffasern oder durch Vliesstoffprozesse (Trocken- bzw. Nassvliestechnologie) hergestellt. Heutige GDLs basieren fast ausschließlich auf Vliesstoffen aus Carbon- fasern, während die Gewebe nur noch eine untergeordnete Rolle spielen. The macroporous electrode materials are manufactured either by weaving carbon fibers or by non-woven processes (dry or wet non-woven technology). Today's GDLs are based almost exclusively on nonwovens made from carbon fibers, while woven fabrics only play a subordinate role.
Zur Herstellung von GDL-Elektrodenmaterialien wird entweder ein Primärvlies aus Carbonfasern und Bindern erzeugt oder es wird ein Primärvlies aus Carbonfaser- prekursoren erzeugt und dieses Vlies wird anschließend karbonisiert. In der industri- ellen Praxis verwendet man im Wesentlichen folgende 2 unterschiedliche Verfahren zur Herstellung von Primärvliesen: To produce GDL electrode materials, either a primary fleece is made from carbon fibers and binders, or a primary fleece is made from carbon fiber precursors and this fleece is then carbonized. In industrial practice, the following 2 different processes are essentially used to produce primary nonwovens:
A) Trockenlegen von Vliesen aus Prekursorfasern: Hier werden Vliese aus gekräuselten Stapelfasern aus Polyacrylnitril (PAN) bzw. aus oxidiertem Polyacrylnitril mit einem typischen Fasertiter von 0.8 bis 4 dtex und einer Faserlänge von 30 bis 70 mm unter Anwendung der Wasser- strahlverfestigung (Spunlace-Technologie) hergestellt. Diese Vliese werden dann weiter zu Carbonfaservliesen karbonisiert, wobei bei Verwendung von PAN als Prekursorfaser eine vorherige thermische Stabilisierung erfolgt. Die Karbonisierung bewirkt einen Schrumpf des Vlieses um ca. 10 bis 15 %. A) Dry laying of nonwovens made of precursor fibers: Here, webs are produced from crimped staple fibers made from polyacrylonitrile (PAN) or oxidized polyacrylonitrile with a typical fiber titre of 0.8 to 4 dtex and a fiber length of 30 to 70 mm using water jet bonding (spunlace technology). These fleeces are then further carbonized into carbon fiber fleeces, with prior thermal stabilization taking place when PAN is used as a precursor fiber. The carbonization causes the fleece to shrink by around 10 to 15%.
B) Nassvliestechnologie (Papierherstellung) mit Kurzschnitt-Carbonfasern Hier werden Kurzschnitt-Carbonfasern aus Polyacrylnitril (PAN) mit einer typi- schen Faserlänge von 3 bis 15 mm dispergiert und mittels einer Schrägsieb- Papiermaschine unter Zuhilfenahme von Bindefasern bzw. von wässrigen Dispersionen von Binderpolymeren zu Vliesen verarbeitet. Anschließend er- folgt optional eine Imprägnierung mit karbonisierbaren Harzen und eine Här- tung der Harzmatrix mit anschließender Karbonisierung. B) Wet web technology (paper production) with short-cut carbon fibers Here, short-cut carbon fibers made of polyacrylonitrile (PAN) with a typical fiber length of 3 to 15 mm are dispersed and applied using an inclined wire paper machine with the aid of binder fibers or aqueous dispersions of binder polymers fleece processed. This is followed by optional impregnation with carbonizable resins and hardening of the resin matrix with subsequent carbonization.
EP1328947B1 beschreibt einen Prozess auf Basis von Verfahren A mit gekräusel- ten, präoxidierten Polyacrylnitril-Stapelfasern aufweisend eine Länge von 40 bis 80 mm unter Zusatz von Bindefasern auf Basis von Polyvinylalkohol. Letztere verfließen durch die Einwirkung von Temperatur und Feuchtigkeit (Wasserstrahl- verfestigung). Diese Primärvliese werden mittels Kalander verdichtet und an- schließend karbonisiert. EP1328947B1 describes a process based on method A with crimped, preoxidized polyacrylonitrile staple fibers having a length of 40 to 80 mm with the addition of binding fibers based on polyvinyl alcohol. The latter flow as a result of the effects of temperature and moisture (hydroentanglement). These primary fleeces are compacted using calenders and then carbonized.
Routen nach Verfahren B basieren auf Kurzschnitt-Carbonfasern aufweisend eine Länge von 6 bis 12 mm, welche mittels thermoplastischen Bindern zu einem Papier verarbeitet werden. Diese Primärvliese („Papiere") haben in der Regel eine niedrige Grammatur (< 30 g/m2) und sind mechanisch weniger stabil. Zur Verbesserung der elektrischen und thermischen Leitfähigkeit und zur Erhöhung der Festigkeit werden diese mit karbonisierbaren Harzen, z.B. Phenolharzen, imprägniert und nochmals karbonisiert (US7144476B2). Routes according to Method B are based on short-cut carbon fibers with a length of 6 to 12 mm, which are processed into paper using thermoplastic binders. These primary fleeces ("papers") usually have a low grammage (<30 g/m 2 ) and are mechanically less stable. To improve the electrical and thermal conductivity and to increase the strength, they are impregnated with carbonizable resins, eg phenolic resins and carbonized again (US7144476B2).
EP1502992A1 beschreibt eine Methode auf Basis von Verfahren B (Papierprozess) mit Kurzschnitt-Carbonfasern und unter Verwendung von fibrillierten bzw. gemah- lenen Polyacrylnitrilfasern als Bindesubstanz. Letztere werden in die Faserstoff- suspension zudosiert. Nach der Bildung des Vliesstoffes erfolgt eine Verdichtung der Bahn unter Wärmeeinwirkung mittels Doppelbandpressen. EP1502992A1 describes a method based on method B (paper process) with short-cut carbon fibers and using fibrillated or ground lenen polyacrylonitrile fibers as a binding substance. The latter are added to the pulp suspension. After the formation of the non-woven fabric, the web is compressed under the influence of heat using double-belt presses.
Herstellungsverfahren gemäß EP 2089925B1 nutzen Trocken- bzw. Nasslegepro- zesse, bei welchen der Binder in unter anderem Form von ungehärteten Phenol- harzfasern (beispielsweise Novoloid® (ungehärtete Phenolharzfasern)) eingebracht wird. Durch thermische Vernetzung unter Druckeinwirkung mit anschließender Kar- bonisierung wird ein Elektrodenmatenal erhalten. Production methods according to EP 2089925B1 use dry or wet laying processes in which the binder is introduced in the form of uncured phenolic resin fibers (for example Novoloid® (uncured phenolic resin fibers)). An electrode material is obtained by thermal crosslinking under the action of pressure with subsequent carbonization.
Brennstoffzellen für den automobilen Einsatz erfordern aufgrund des beschränkten Bauraums und der hohen Stromdichten zunehmend dünnere Gasdiffusionsschichten (< 200 μm) mit hohen Anforderungen bezüglich Dickentoleranzen und Homogenität. Dies hat damit zu tun, dass diese Brennstoffzellenstapel aus bis zu 400 Einzelzellen bestehen, und damit bei relativ hohen Dickenschwankungen der GDL (im Vergleich zu den restlichen Komponenten) Probleme bezüglich gleichmäßiger Kompression und Stapeldimensionierung auftreten können. Due to the limited installation space and the high current densities, fuel cells for automotive use increasingly require thinner gas diffusion layers (< 200 μm) with high requirements in terms of thickness tolerances and homogeneity. This has to do with the fact that these fuel cell stacks consist of up to 400 individual cells, and problems with regard to uniform compression and stack dimensioning can therefore arise with relatively large fluctuations in thickness of the GDL (compared to the other components).
Nachteilig an dem Verfahren B ist, dass vor allem bei Carbonfaser-Papieren Impräg- nierprozesse im Anschluss an den Papierherstellungsprozess erforderlich sind, wel- che zusätzliche Prozessschritte und Kostenfaktoren erfordern. Dies betrifft insbeson- dere den Aufwand für das Dispergieren und die Trocknung und die längeren Pro- zesszyklen. Zudem könnend die Imprägnierprozesse zum Teil zu Inhomogenitäten führen, falls die Imprägnierung mit Füllstoffen oder Binderharzen ungleichmäßig er- folgt. Darüber hinaus ermöglichen klassische Herstellverfahren ohne Verdichtung des imprägnierten Materials keine Herstellung von dünnen Substraten mit ausreichender mechanischer Stabilität, da der Faservolumenanteil zu gering ausfällt. Ein hoher Fa- seranteil bzw. ein geringer Binderanteil ist erwünscht, da im Brennstoffzellenbetrieb bevorzugt an der Bindermatrix eine Wasserakkumulation erfolgen kann, welche nach- teilig ist, da diese die Leistung der Zelle herabsetzt. The disadvantage of method B is that, especially in the case of carbon fiber papers, impregnation processes are required after the paper production process, which require additional process steps and cost factors. This relates in particular to the effort involved in dispersing and drying and the longer process cycles. In addition, the impregnation processes can sometimes lead to inhomogeneities if the impregnation with fillers or binder resins is uneven. In addition, classic manufacturing processes without compression of the impregnated material do not allow the production of thin substrates with sufficient mechanical stability, since the fiber volume fraction is too low. A high proportion of fibers or a low proportion of binder is desirable, since during fuel cell operation water accumulation can occur preferentially on the binder matrix, which is disadvantageous since this reduces the performance of the cell.
Die Aufgabe der vorliegenden Erfindung ist es daher, ein alternatives Verfahren zur Herstellung eines Elektrodenmaterials für Gasdiffusionsschichten mit geringer Dicke bereitzustellen, welches die Nachteile, von zusätzlichen Prozessschritten und somit Kosten verhindert. The object of the present invention is therefore to provide an alternative method for producing an electrode material for gas diffusion layers with a small thickness provide, which prevents the disadvantages of additional process steps and thus costs.
Erfindungsgemäß wurde diese Aufgabe durch die Bereitstellung eines Verfahrens zur Herstellung eines Elektrodenmatenals für Gasdiffusionsschichten gelöst, wel- ches folgende Schritte umfasst: a) Bereitstellen von mindestens einer Lage Fasergebilde, b) Bereitstellen von mindestens einer Lage thermoplastischen Materials, c) Stapeln der mindestens einen Lage Fasergebilde aus Schritt a) mit der min- destens einer Lage thermoplastischen Materials aus Schritt b) d) Verbinden der gestapelten Lagen aus Schritt c) durch Anwenden eines Drucks von 2 bis 80 bar und einer Temperatur von 70 bis 280 °C zu einem Verbundmaterial, und e) Karbonisieren des Verbundmaterials aus Schritt d) bei Temperaturen von 1400 bis 2500 °C unter Schutzgasatmosphäre. According to the invention, this object was achieved by providing a method for producing an electrode material for gas diffusion layers, which comprises the following steps: a) providing at least one layer of fiber structures, b) providing at least one layer of thermoplastic material, c) stacking the at least one layer Fibrous structure from step a) with at least one layer of thermoplastic material from step b) d) connecting the stacked layers from step c) by applying a pressure of 2 to 80 bar and a temperature of 70 to 280 °C to form a composite material, and e) carbonization of the composite material from step d) at temperatures of 1400 to 2500° C. under a protective gas atmosphere.
Der Vorteil des erfindungsgemäßen Verfahrens liegt darin, dass keine Imprägnie- rungsschritte des Fasergebildes in der weiteren Herstellung des Elektrodenmate- rials notwendig sind, so dass ein einfacheres und kostengünstigeres Verfahren zur Verfügung gestellt wird. Der Grund hierfür liegt darin, dass durch die Bildung eines Verbundes aus mindestens einer Lage Fasergebilde und mindestens einer Lage thermoplastischen Materials, durch das Verbinden der Lagen unter Temperatur- und Druckeinwirkung zu einem Verbundmaterial, das thermoplastische Material in das Fasergebilde eindringt und so eine Imprägnierung überflüssig wird. Weiterhin wird das thermoplastische Material mit karbonisierbaren Harzen und/oder kohlen- stoffbasierten Füllstoffen ausgerüstet, wodurch die Porosität des karbonisierten Material eingestellt werden kann. Darüber hinaus ist das beschriebene Elektroden- material stabiler und weist einen höheren Faservolumengehalt auf. Das erfindungs- gemäße Verfahren kann sowohl als kontinuierlicher oder Batch-Prozess ausgeführt werden. Im kontinuierlichen Verfahren (Rolle-zu Rolle-Verfahren) werden Bahnen von Fasergebilden und thermoplastischen Materialien verwendet. Im Batch-Pro- zess wird hingegen Plattenware verwendet. Bevorzugt wird der kontinuierliche Prozess, da so Prozesszeiten verringert werden. Das in Schritt c) beschriebene Stapeln der Lagen kann in jeglicher Reihenfolge erfolgen, wobei die Anzahl der La- gen nicht begrenzt ist. Bevorzugt werden jedoch zwei und drei-Lagen. Durch die Hitze und Druckeinwirkung in Schritt d), welche mittels Doppelstempelpressen, Ka- schieranlagen, Doppelbandpressen oder Kalandrieren wird der Verbund erhalten. Bei dem in Schritt e) verwendeten Schutzgas kann jedes beliebige Schutzgas, wie beispielsweise Argon oder Stickstoff verwendet werden. The advantage of the method according to the invention is that no impregnation steps of the fiber structure are necessary in the further production of the electrode material, so that a simpler and more cost-effective method is made available. The reason for this is that by forming a composite of at least one layer of fiber structure and at least one layer of thermoplastic material, by connecting the layers under the influence of temperature and pressure to form a composite material, the thermoplastic material penetrates into the fiber structure, making impregnation superfluous will. Furthermore, the thermoplastic material is equipped with carbonizable resins and/or carbon-based fillers, as a result of which the porosity of the carbonized material can be adjusted. In addition, the electrode material described is more stable and has a higher fiber volume content. The method according to the invention can be carried out either as a continuous or batch process. In the continuous process (roll-to-roll process), webs of fibrous structures and thermoplastic materials are used. In the batch process, on the other hand, sheet material is used. The continuous process is preferred because it reduces process times. The one described in step c). Stacking of the tiers can be in any order, with no limit to the number of tiers. However, two and three layers are preferred. The composite is obtained by the action of heat and pressure in step d), which is done by means of double stamp presses, laminating systems, double belt presses or calendering. Any protective gas, such as argon or nitrogen, can be used for the protective gas used in step e).
Im Rahmen der Erfindung werden unter Fasergebilden Vliesstoffe aus Kurzfasern oder Stapelfasern verstanden, wobei auch, Fasergewebe zu den Fasergebilden zählen. Kurzfasern weisen eine Länge von 1 mm - 20 mm und Stapelfasern eine Länge von 30-80 mm auf. Bei Geweben handelt es sich um textile Flächengebilde, wobei diese mindestens zwei Fadensysteme aufweisen, die nicht parallel verlaufen und sich somit kreuzen. Unter einem Vliesstoff versteht man ein Gebilde aus Kurz- fasern oder Stapelfasern, welche durch Nasslegen bzw. Trockenlegen hergestellt werden. In the context of the invention, fiber structures are understood to mean nonwovens made from short fibers or staple fibers, with fiber fabrics also counting among the fiber structures. Short fibers have a length of 1 mm - 20 mm and staple fibers have a length of 30-80 mm. Woven fabrics are textile fabrics that have at least two thread systems that do not run parallel and thus intersect. A non-woven fabric is a structure made of short fibers or staple fibers that are produced by wet laying or dry laying.
In einer vorteilhaften Ausführungsform sind die mindestens eine Lage Fasergebilde aus Schritt a) ein Carbonfaservlies oder ein Carbonfasergewebe. Die Carbonfaser- vliese können mittels verschiedener Verfahren, wie Meltblown, Spunlace oder Nasslegeverfahren, erhalten werden. In an advantageous embodiment, the at least one layer of fiber structure from step a) is a carbon fiber fleece or a carbon fiber fabric. The carbon fiber nonwovens can be obtained using various processes such as meltblown, spunlace or wet-laid processes.
In einer vorteilhaften Ausführungsform weist die mindestens eine Lage des Faser- gebildes eine Dicke von 50 μm bis 400 μm, bevorzugt 100 μm bis 250 μm auf. Bei einer Dicke von kleiner als 50 μm ist das Fasergebilde zu instabil, so dass das Handling erschwert wird und bei größer als 400 μm Dicke des Fasergebildes ist die Verdichtung erschwert. Der Dickenbereich von 100 μm bis 200 μm ist bevorzugt, da hier das Verhältnis von Stabilität und Verdichtungsmöglichkeit besonders günstig ist. In an advantageous embodiment, the at least one layer of the fiber structure has a thickness of 50 μm to 400 μm, preferably 100 μm to 250 μm. With a thickness of less than 50 μm, the fibrous structure is too unstable, so that handling is made more difficult, and with a thickness of the fibrous structure greater than 400 μm, compaction is difficult. The thickness range from 100 μm to 200 μm is preferred, since the relationship between stability and the possibility of compression is particularly favorable here.
Erfindungsgemäß wird die mindestens eine Lage thermoplastischen Materials aus Schritt b) aus der Gruppe Polyethylen (Low Density Polyethylen (LDPE), High Density Polyethylen (HDPE)), Polypropylen (PP), Ethylen-Vinylacetat-Copolymere (EVA), Polyvinylbutyral (PVB), Celluloseacetat (CA), Polyvinylalkohol (PVA), Vi- nylpyrrolidon-vinylacetat-Copolymere, Styrol-Maleinsäureanhydrid-Copolymere (Styrol-Maleinsäureanhydrid (SMA)) oder thermoplastische Elastomere (thermo- plastische Polyolefine (TPO), Styrolblockcopolymere (TPS)), bevorzugt Polyvinyl- butyral, Celluloseacetat oder Polyvinylalkohol ausgewählt. Bevorzugt sind Poly- mere mit Hydroxyl- oder Anhydridgruppen, da diese Kondensationsreaktionen mit Harzen eingehen oder selbst zu Vernetzungsreaktionen befähigt sind. According to the invention, the at least one layer of thermoplastic material from step b) is selected from the group consisting of polyethylene (low-density polyethylene (LDPE), high-density polyethylene (HDPE)), polypropylene (PP), ethylene-vinyl acetate copolymers (EVA), polyvinyl butyral (PVB), cellulose acetate (CA), polyvinyl alcohol (PVA), vinylpyrrolidone-vinyl acetate copolymers, styrene-maleic anhydride copolymers (styrene-maleic anhydride (SMA)) or thermoplastic elastomers (thermoplastic polyolefins (TPO ), Styrene block copolymers (TPS)), preferably selected polyvinyl butyral, cellulose acetate or polyvinyl alcohol. Polymers with hydroxyl or anhydride groups are preferred, since these enter into condensation reactions with resins or are themselves capable of crosslinking reactions.
Vorteilhafterweise ist das thermoplastische Material als Folie oder textiles Gebilde ausgebildet. Folie und textiles Gebilde werden bevorzugt, da es sich um bahnförmi- ges Material handelt, so dass das Verfahren als kontinuierliches Verfahren ausge- führt werden kann. The thermoplastic material is advantageously in the form of a film or textile structure. Foil and textile structures are preferred because the material is in the form of a web, so that the process can be carried out as a continuous process.
Vorteilhafterweise weist das thermoplastische Material eine Dicke von 10 μm bis 300 μm auf, bevorzugt von 20 μm bis 75 μm. Thermoplastisches Material mit einer Dicke kleiner als 10 μm ist kommerziell nicht verfügbar und dicker als 300 μm ver- ringert die Stabilität des Substrates und die Verdichtung wird verschlechtert. Der Bereich 50 μm bis 250 μm ist bevorzugt, da sich hier ein bevorzugtes Verhältnis von Fasergebilde zu thermoplastischem Material ergibt. In einer weiteren vorteilhaf- ten Ausführungsform ist die mindestens eine Lage thermoplastischen Materials mit karbonisierbaren Harzen und/oder Kohlenstoffmatenalien beschichtet. Durch die Beschichtung wird die Kohlenstoffausbeute erhöht., denn die karbonisierbaren Harze wandeln sich bei der Karbonisierung in Kohlenstoff um. Die Harze und Koh- lenstoffmatenalien können in Form von Pulvern, Suspensionen, Dispersionen oder Lösungen vorliegen. Suspensionen, Dispersionen oder Lösungen können durch Tauchbeschichtung, Besprühen, Siebdruck, Rakeln, Curtain-Coating, Walzenauf- trag, Prepreg-Technologie oder Inkjet-Drucken aufgebracht werden. Pulverförmige Stoffe können durch Aufstreuen aufgetragen werden. Durch die Beschichtung kön- nen die mechanischen Eigenschaften des Elektrodenmatenals gesteuert werden und auch die Beschichtung trägt dazu bei, dass ein Imprägnierungsschritt in der weiteren Herstellung des Elektrodenmaterial nicht erforderlich ist. Vorteilhafterweise werden die Harze aus der Gruppe Phenolharze, Melaminharze, Resorcinolharze, Cyanesterharze, Vinylesterharze ausgewählt Advantageously, the thermoplastic material has a thickness of 10 μm to 300 μm, preferably 20 μm to 75 μm. Thermoplastic material with a thickness smaller than 10 μm is not commercially available and thicker than 300 μm reduces the stability of the substrate and densification is deteriorated. The range from 50 μm to 250 μm is preferred, since this results in a preferred ratio of fiber structure to thermoplastic material. In a further advantageous embodiment, the at least one layer of thermoplastic material is coated with carbonizable resins and/or carbon materials. The coating increases the carbon yield, because the carbonizable resins convert to carbon during carbonization. The resins and carbon materials can be in the form of powders, suspensions, dispersions or solutions. Suspensions, dispersions or solutions can be applied by dip coating, spraying, screen printing, knife coating, curtain coating, roller application, prepreg technology or inkjet printing. Powdery substances can be applied by sprinkling. The mechanical properties of the electrode material can be controlled by the coating and the coating also contributes to the fact that an impregnation step is not necessary in the further production of the electrode material. The resins are advantageously selected from the group consisting of phenolic resins, melamine resins, resorcinol resins, cyanoester resins, and vinylester resins
Diese Harze weisen eine besonders hohe Kohlenstoffausbeute auf. These resins have a particularly high carbon yield.
Vorteilhafterweise werden die Kohlenstoffmaterialen aus der Gruppe Melasse, Bitu- men, Graphit, Ruß, Aktivkohle, gemahlene Carbonfasern, Steinkohlenteerpech oder Kokspartikel ausgewählt. The carbon materials are advantageously selected from the group consisting of molasses, bitumen, graphite, soot, activated carbon, ground carbon fibers, coal tar pitch or coke particles.
In einer weiteren vorteilhaften Ausführungsform umfasst die Beschichtung Vernet- zungsadditive (1 -5% bezogen auf den Anteil an thermoplastischem Material). Durch die Vernetzungsadditive wird die Kohlenstoffausbeute der thermoplastischen Kom- ponenten erhöht und dadurch wird ein Elektrodenmaterial mit verbesserter Stabilität und Leitfähigkeit erhalten. In a further advantageous embodiment, the coating comprises crosslinking additives (1-5% based on the proportion of thermoplastic material). The carbon yield of the thermoplastic components is increased by the crosslinking additives and an electrode material with improved stability and conductivity is thereby obtained.
Vorteilhafterweise werden die Vernetzungsadditive aus der Gruppe organische Per- oxide, Dialdehyde, Diamine oder UV- härtbare Polymere ausgewählt. The crosslinking additives are advantageously selected from the group consisting of organic peroxides, dialdehydes, diamines and UV-curable polymers.
Diese Vernetzungsadditive weisen eine besonders hohe Kohlenstoffausbeute auf. These crosslinking additives have a particularly high carbon yield.
In einer weiteren vorteilhaften Ausführungsform wird der Verbund in Schritt d) zu- sätzlich mit ionisierender Strahlung oder UV-Strahlung bestrahlt. In a further advantageous embodiment, the assembly is additionally irradiated with ionizing radiation or UV radiation in step d).
Hierdurch kann die Kohlenstoffausbeute erhöht werden, was eine höhere Leitfähig- keit des Elektrodenmaterials erzeugt. As a result, the carbon yield can be increased, which creates a higher conductivity of the electrode material.
Ein weiterer Gegenstand der vorliegenden Erfindung ist ein Elektrodenmaterial, wel- ches nach dem erfindungsgemäßen Verfahren hergestellt worden ist. A further object of the present invention is an electrode material which has been produced using the method according to the invention.
Der Vorteil des Elektrodenmatenals ist, dass dieses eine besonders glatte Oberflä- che aufweist, so dass Kontaktwiderstände innerhalb der Zelle verringert werden. Darüber hinaus wird durch den hohen Faservolumengehalt des Elektrodenmatenals zum einen die Wasserakkumulation deutlich verringert, so dass die Zelle eine hö- here Leistung aufweist und zum anderen die thermische und elektrische Leitfähigkeit erhöht, was ebenfalls zu einer höheren Leitung der Zelle führt. Der höhere Faservo- lumengehalt bewirkt zusätzlich eine höhere Steifigkeit bzw. einen höheren Schermo- dul des Materials. Daraus resultiert eine geringere Intrusion des Elektrodenmatenals in die Flußkanäle der Bipolarplatte in der Zelle. Dies hat den Vorteil, dass wiederum Kontaktwiderstände reduziert werden und weniger Flüssigwasseranreicherung in den Flußkanälen der Bipolarplatten erfolgt. The advantage of the electrode material is that it has a particularly smooth surface, so that contact resistances within the cell are reduced. In addition, the high fiber volume content of the electrode material significantly reduces the accumulation of water, so that the cell has a higher output and, on the other hand, increases the thermal and electrical conductivity, which also leads to a higher conductivity of the cell. The higher fiber volume content also causes a higher rigidity or a higher shear modulus of the material. This results in less intrusion of the electrode material into the flow channels of the bipolar plate in the cell. This has the advantage that in turn contact resistances are reduced and there is less accumulation of liquid water in the flow channels of the bipolar plates.
Gemäß einer bevorzugten Ausführungsform weist das Elektrodenmaterial eine Dicke von 50 μm bis 500 μm, bevorzugt von 70μm bis 200 μm auf. Gemäß ei- ner noch weiter bevorzugten Ausführungsform weist das Elektrodenmatenal eine Dichte von 0,1 g/cm3 bis 0,6 g/cm3, bevorzugt 0,15 g/cm3 bis 0,40 g/cm3 auf. Die ge- wählten Dicken des Elektrodenmatenals bedingen die gewünschte Stabilität und die gewählten Dichten des Elektrodenmatenals sorgen für einen Porenraum, der für die GDL von Bedeutung ist. According to a preferred embodiment, the electrode material has a thickness of 50 μm to 500 μm, preferably 70 μm to 200 μm. According to an even more preferred embodiment, the electrode material has a density of 0.1 g/cm 3 to 0.6 g/cm 3 , preferably 0.15 g/cm 3 to 0.40 g/cm 3 . The selected thicknesses of the electrode material determine the desired stability and the selected densities of the electrode material ensure a pore space that is important for the GDL.
Ein noch weiterer Gegenstand der vorliegenden Erfindung ist die Verwendung des Elektrodenmaterials in Polymerelektrolytbrennstoffzellen, in Phosphorsäurebrenn- stoffzellen, mikrobiellen Brennstoffzellen, elektrochemischen Reaktoren, Sauer- stoffverzehrkatoden, Metall-Luft-Batterien, PEM-Elektrolyseuren oder Batterien. Yet another object of the present invention is the use of the electrode material in polymer electrolyte fuel cells, in phosphoric acid fuel cells, microbial fuel cells, electrochemical reactors, oxygen-consuming cathodes, metal-air batteries, PEM electrolyzers or batteries.
Nachfolgend wird die vorliegende Erfindung rein beispielhaft anhand vorteilhafter Ausführungsformen und unter Bezugnahme auf die beigefügten Zeichnungen be- schrieben. The present invention is described below purely by way of example using advantageous embodiments and with reference to the accompanying drawings.
Figur 1 zeigt das erfindungsgemäße Verfahren FIG. 1 shows the method according to the invention
Figur 2 zeigt das erfindungsgemäße Verfahren FIG. 2 shows the method according to the invention
Figur 3 zeigt ein thermoplastisches Material mit Beschichtung Figure 3 shows a thermoplastic material with a coating
Figur 4 zeigt ein Substrat mit zwei Lagen FIG. 4 shows a substrate with two layers
Figur 5 zeigt ein Substrat mit drei Lagen FIG. 5 shows a substrate with three layers
Figur 6: zeigt ein Substrat mit drei Lagen FIG. 6 shows a substrate with three layers
Figur 1 zeigt das erfindungsgemäße Verfahren. Zunächst wird eine thermoplastische Folie (1 ) mit einer Dispersion (2) beschichtet und dadurch eine Folienbahn mit einer Beschichtung (4) erhalten. Zwei Folienbahnen mit Beschichtung (4) werden mit einem Carbonfaservlies (6) zu einem Verbund (9) mittels mehrerer Heißkalander oder Bandpressen (7,8) vereinigt. In einem folgenden Schritt wird der Verbund (9) anschließend in einem kontinuierlichen Ofen (10) unter Schutzgasatmosphäre zu einem Elektrodenmaterial (11 ) karbonisiert. FIG. 1 shows the method according to the invention. First, a thermoplastic film (1) is coated with a dispersion (2), thereby obtaining a film web with a coating (4). Two webs of film with a coating (4) are combined with a carbon fiber fleece (6) to form a composite (9) using a number of hot calenders or belt presses (7, 8). In a subsequent step, the composite (9) then carbonized in a continuous furnace (10) under a protective gas atmosphere to form an electrode material (11).
Figur 2 zeigt zusätzlich die Vernetzung des thermoplastischen Polymers durch ioni- sierende oder UV-Strahlung (12). FIG. 2 additionally shows the crosslinking of the thermoplastic polymer by ionizing or UV radiation (12).
Figur 3 zeigt ein erfindungsgemäßes beschichtetes thermoplastisches Material (4), wobei die Beschichtung (5) auf dem thermoplastischen Material (1 ) aufgebracht ist. FIG. 3 shows a thermoplastic material (4) coated according to the invention, the coating (5) being applied to the thermoplastic material (1).
Figur 4 zeigt ein erfindungsgemäßes zwei-lagiges Elektrodenmaterial, wobei die Be- schichtung (5) des thermoplastischen Materials (1 ) an die Lage Carbonfaservlies (6) angrenzt. FIG. 4 shows a two-layer electrode material according to the invention, the coating (5) of the thermoplastic material (1) adjoining the layer of carbon fiber fleece (6).
Figur 5 zeigt ein erfindungsgemäßes, 3-lagiges Elektrodenmaterial, wobei die Schichtreihenfolge thermoplastisches Material (1 ) mit einer Beschichtung (5), Car- bonfaservlies (6), thermoplastisches Material (1 ) mit einer Beschichtung (5) ist und die Beschichtung (5) jeweils an das Carbonfaservlies (6) angrenzt. Figure 5 shows a 3-layer electrode material according to the invention, the layer sequence being thermoplastic material (1) with a coating (5), carbon fiber fleece (6), thermoplastic material (1) with a coating (5) and the coating (5th ) in each case adjoins the carbon fiber fleece (6).
Figur 6 zeigt ein erfindungsgemäßes, 3-lagiges Elektrodenmaterial, wobei die Schichtreihenfolge Carbonfaservlies(6), thermoplastisches Material mit Beschichtung (5) , Carbonfaservlies (6) ist. FIG. 6 shows a 3-layer electrode material according to the invention, the sequence of layers being carbon fiber fleece (6), thermoplastic material with coating (5), carbon fiber fleece (6).
Nachfolgend wird die vorliegende Erfindung anhand von Ausführungsbeispielen er- läutert, wobei die Ausführungsbeispiele keine Einschränkung der Erfindung darstel- len. The present invention is explained below using exemplary embodiments, with the exemplary embodiments not representing any restriction of the invention.
Die Herstellung eines Prothesenbauteils kann wie unten beschrieben erfolgen. A prosthesis component can be produced as described below.
Ausführungsbeispiel 1 Example 1
1 ,5 Teile Novolak-Phenolharz (Bakelit, Hexion) und 1 Teil synthetischer Graphit (d50 =4 μm) werden in 1 ,5 Teilen Ethanol gelöst bzw. suspendiert. Mittels Rakelverfahren wird diese viskose Dispersion auf eine Polyvinylbutyralfolie (Trosifol®,Kuraray, 50μm) beschichtet (Nassfilmdicke 40 μm). Anschließend wird mittels einer Heißpresse (160°C, 5 bar) ein Verbund aus 2 Lagen der beschichteten Polyvinylbutyralfolie und einem Carbonfaservlies (23 g/m2) hergestellt (Schichtfolge: Folie I Carbonfaservlies I Folie). Dieser Verbund wird anschließend in Schutzgasatmosphäre bei einer Tem- peratur von 1400°C karbonisiert. 1.5 parts of novolak phenolic resin (bakelite, hexion) and 1 part of synthetic graphite (d50=4 μm) are dissolved or suspended in 1.5 parts of ethanol. This viscous dispersion is coated onto a polyvinyl butyral film (Trosifol®, Kuraray, 50 μm) using a doctor blade method (wet film thickness 40 μm). Then, using a hot press (160° C., 5 bar), a composite of 2 layers of the coated polyvinyl butyral film and a carbon fiber fleece (23 g/m 2 ) (layer sequence: film I carbon fiber fleece I film). This composite is then carbonized in a protective gas atmosphere at a temperature of 1400°C.
Ausführungsbeispiel 2 Example 2
150 g Novolak-Phenolharz (Bakelit PF0227 SP, Hexion), 100 g gemahlene Kohlen- stofffasern (Sigrafil® CM80, SGL Carbon) und 100 g phenolmodifiziertes Inden- Cumaronharz (Novares CA80, Rütgers) werden in 150 g Aceton gelöst bzw. suspen- diert. Mittels Rakelverfahren wird diese viskose Dispersion auf eine Polyvinylbutyral- folie (Trosifol®, Kuraray, 50 μm) beschichtet (Nassfilmdicke 50 μm). Anschließend wird mittels einer Heißpresse ein Verbund aus 2 Lagen der beschichteten Polyvinyl- butyralfolie und einem Carbonfasergebilde (23 g/m2) hergestellt (Schichtfolge Folie I Carbonfasergebilde I Folie). Dieser Verbund wird anschließend in Schutzgas- atmosphäre bei einer Temperatur von 1400°C karbonisiert. 150 g novolak phenolic resin (Bakelit PF0227 SP, Hexion), 100 g ground carbon fibers (Sigrafil® CM80, SGL Carbon) and 100 g phenol-modified indene coumarone resin (Novares CA80, Rütgers) are dissolved or suspended in 150 g acetone. died This viscous dispersion is coated onto a polyvinyl butyral film (Trosifol®, Kuraray, 50 μm) using a doctor blade method (wet film thickness 50 μm). A composite of 2 layers of the coated polyvinyl butyral film and a carbon fiber structure (23 g/m 2 ) is then produced using a hot press (layer sequence film I carbon fiber structure I film). This composite is then carbonized in a protective gas atmosphere at a temperature of 1400°C.
Ausführungsbeispiel 3 Example 3
Auf einem Deskcoater wird eine Polyethylenfolie (HDPE, 50 μm, Folienwerk Lahr) mit einer Dispersion aus Phenolharz (10 Teile), Azetylenruß (5 Teile) in Isopropanol (18,5 Teile) beschichtet und bei 80 °C getrocknet. Die Auftragsmenge betrug 10 g/m2. Mittels eines Heißkalanders (180 °C, 10 bar) wird ein Verbund aus einer Lage Carbonfasergebilde (23 g/m2) zwischen 2 Lagen der beschichteten Folie herge- stellt, wobei die Beschichtung jeweils zum Carbonfasergebilde orientiert ist. An- schließend erfolgt eine Karbonisierung bei 1700 °C in Schutzgasatmosphäre. A polyethylene film (HDPE, 50 μm, Folienwerk Lahr) is coated with a dispersion of phenolic resin (10 parts), acetylene black (5 parts) in isopropanol (18.5 parts) in a desk coater and dried at 80.degree. The amount applied was 10 g/m 2 . Using a hot calender (180° C., 10 bar), a composite is produced from one layer of carbon fiber structure (23 g/m 2 ) between 2 layers of the coated film, with the coating being oriented towards the carbon fiber structure in each case. This is followed by carbonization at 1700 °C in a protective gas atmosphere.
Ausführungsbeispiel 4 Example 4
Mittels einer kontinuierlichen Presse (140 °C, 5 bar) wird eine Lage Carbonfaservlies (18 g/m2) und beidseitig mit je einer Folie auf Basis von Ethylen-Vinylacetat-Copoly- mer (TecWeb®, 20) kaschiert. Anschließend erfolgt eine Elektronenbestrahlung (Do- sis 150 Gy) zur Vernetzung des Polymers. Der Verbund wird anschließend in Schutzgasatmosphäre bei einer Temperatur von 1750 °C karbonisiert. Using a continuous press (140 °C, 5 bar), a layer of carbon fiber fleece (18 g/m 2 ) is laminated on both sides with a film based on ethylene-vinyl acetate copolymer (TecWeb®, 20). This is followed by electron irradiation (dose 150 Gy) to crosslink the polymer. The composite is then carbonized in a protective gas atmosphere at a temperature of 1750 °C.
Die folgende Tabelle zeigt eine Zusammenfassung der Ausfahrungsbeispiele. The table below shows a summary of the exemplary embodiments.
Folgende Tabelle zeigt die physikalischen Eigenschaften der Ausführungsbeispiele im Vergleich zu kommerziellen Referenzmatenalien auf Basis von etablierter Tech- nologie (Sigracet® GDL 29 AA und Sigracet® GDL 28 AA). Es zeigt sich, dass dieThe table below shows the physical properties of the exemplary embodiments in comparison to commercial reference materials based on established technology (Sigracet® GDL 29 AA and Sigracet® GDL 28 AA). It turns out that the
Elektrodenmaterialen gemäß der Erfindung bei geringerer Dicke vergleichbare Ei- genschaften wie die Referenzmaterialien aufweisen. Der flächenspezifische Wider- stand wurde gemäß DIN 51911 -1997 gemessen und die Biegesteifigkeit längs und quer gemäß ISO 5628- 2019 Electrode materials according to the invention have properties comparable to those of the reference materials with a smaller thickness. The area-specific resistance was measured according to DIN 51911-1997 and the longitudinal and transverse bending stiffness according to ISO 5628-2019
*DIN 51911 *DIN 51911
**ISO 5628 **ISO 5628
Bezugszeichenliste Reference List
(1 ) Thermoplastische Folie (1) Thermoplastic film
(2) Dispersion (2) Dispersion
(3) Rolle (3) role
(4) Thermoplastisches Material mit Beschichtung(4) Thermoplastic material with coating
(5) Beschichtung (5) Coating
(6) Carbonfaservlies (6) Carbon fiber fleece
(7) Heißkalander oder Bandpressen (7) Hot calenders or belt presses
(8) Heißkalander oder Bandpressen (8) Hot calenders or belt presses
(9) Verbund (9) Composite
(10) Ofen (10) Furnace
(11 ) Elektrodenmaterial (11) Electrode material
(12) Ionisierende oder UV-Strahlung (12) Ionizing or UV radiation

Claims

Patentansprüche patent claims
1 . Verfahren zur Herstellung eines Elektrodenmatenals für Gasdiffusionsschich- ten umfassend folgende Schritte: a) Bereitstellen von mindestens einer Lage Fasergebilde, b) Bereitstellen von mindestens einer Lage thermoplastischen Materials, c) Stapeln der mindestens einen Lage Fasergebilde aus Schritt a) mit der mindestens einer Lage thermoplastischen Materials aus Schritt b), d) Verbinden der gestapelten Lagen aus Schritt c) durch Anwenden eines Drucks von 2 bis 80 bar und einer Temperatur von 70 bis 280 °C zu einem Verbundmaterial, und e) Karbonisieren des Verbundmaterials aus Schritt d) bei Temperaturen von 1400 bis 2500 °C unter Schutzgasatmosphäre. 1 . Method for producing an electrode material for gas diffusion layers, comprising the following steps: a) providing at least one layer of fiber structure, b) providing at least one layer of thermoplastic material, c) stacking the at least one layer of fiber structure from step a) with the at least one layer of thermoplastic Material from step b), d) connecting the stacked layers from step c) by applying a pressure of 2 to 80 bar and a temperature of 70 to 280 °C to form a composite material, and e) carbonizing the composite material from step d) at temperatures from 1400 to 2500 °C under protective gas atmosphere.
2. Verfahren nach Anspruchl , wobei die mindestens eine Lage Fasergebilde aus Schritt a) ein Carbonfaservlies oder Carbonfasergewebe ist. 2. The method according to claim 1, wherein the at least one layer of fiber structure from step a) is a carbon fiber fleece or carbon fiber fabric.
3. Verfahren nach Anspruch 1 oder 2, wobei die mindestens eine Lage Faserge- bilde aus Schritt a) eine Dicke von 50 bis 400 μm aufweist. 3. The method according to claim 1 or 2, wherein the at least one layer of fiber structures from step a) has a thickness of 50 to 400 μm.
4. Verfahren nach Anspruch 1 , wobei das thermoplastische Material der min- destens einen Lage aus der Schritt b) aus der Gruppe Polyethylen Polypro- pylen, Ethylen-Vinylacetat- Copolymere, Polyvinylbutyral, Celluloseacetat, Polyvinylalkohol, Vinylpyrrolidon-vinylacetat-Copolymere, Styrol-Maleinsäure- anhydrid-Copolymere oder thermoplastische Elastomere, bevorzugt Polyethy- len, Polyvinylbutyral oder Celluloseacetat ausgewählt ist. 4. The method according to claim 1, wherein the thermoplastic material of the at least one layer from step b) from the group polyethylene, polypropylene, ethylene-vinyl acetate copolymers, polyvinyl butyral, cellulose acetate, polyvinyl alcohol, vinylpyrrolidone-vinyl acetate copolymers, styrene Maleic anhydride copolymers or thermoplastic elastomers, preferably polyethylene, polyvinyl butyral or cellulose acetate is selected.
5. Verfahren nach Anspruch 1 oder 4, wobei die mindestens eine Lage des ther- moplastischen Materials aus Schritt b) als Folie oder textiles Gebilde ausge- bildet ist. 5. The method according to claim 1 or 4, wherein the at least one layer of the thermoplastic material from step b) is designed as a film or textile structure.
6. Verfahren nach Anspruch 5, wobei die mindestens eine Lage des thermo- plastisches Materials eine Dicke von 10 bis 300 μm aufweist. Verfahren nach Anspruch 6, wobei die mindestens eine Lage des thermo- plastischen Materials mit karbonisierbaren Harzen und/oder Kohlenstoffma- terialien beschichtet ist. Verfahren nach Anspruch 7, wobei die karbonisierbaren Harze aus der Gruppe Phenolharze, Melaminharze, Resorcinol-Formaldehydharze, Phenol- modifizierte Kohlenwasserstoffharze, Benzoxazinharze, Cyanesterharze, Vinylesterharze, Furanharze, Polyimide, Polyoxadiazol, oder Polyacrylnitrile ausgewählt sind. Verfahren nach Anspruch 7, wobei die Kohlenstoffmaterialen aus der Gruppe Melasse, Bitumen, Steinkohlenteerpech, Graphit, Ruß, Aktivkohle, gemahlene bzw. geschnittene Carbonfasern oder Kokspartikel ausgewählt sind. Verfahren nach Anspruch 7, wobei die mindestens eine Lage des thermo- plastischen Materials zusätzlich mit Vernetzungsadditiven beschichtet ist. Verfahren nach Anspruch 10, wobei die Vernetzungsadditive aus der Gruppe organische Peroxide, Dialdehyde, Diamine oder UV- vernetzende Polymere ausgewählt sind. Verfahren nach Anspruch 1 , wobei in Schritt d) der Verbund zusätzlich mit ionisierender Strahlung oder UV-Strahlung bestrahlt wird. Elektrodenmatenal hergestellt nach einem der Ansprüche 1 bis 12. Elektrodenmaterial nach Anspruch 12, wobei das Elektrodenmatenal eine Dicke von 50 bis 500 μm aufweist. 16 Verwendung des Elektrodenmaterials gemäß Anspruch 13 oder 14 in Poly- merelektrolytbrennstoffzellen, in Phosphorsäurebrennstoffzellen, mikrobiellen Brennstoffzellen, elektrochemischen Reaktoren, Sauerstoffverzehrkatoden, Metall-Luft-Batterien, PEM-Elektrolyseuren oder Batterien. 6. The method according to claim 5, wherein the at least one layer of the thermoplastic material has a thickness of 10 to 300 μm. A method according to claim 6, wherein the at least one layer of thermoplastic material is coated with carbonisable resins and/or carbon materials. The method according to claim 7, wherein the carbonizable resins are selected from the group consisting of phenolic resins, melamine resins, resorcinol-formaldehyde resins, phenol-modified hydrocarbon resins, benzoxazine resins, cyanate ester resins, vinyl ester resins, furan resins, polyimides, polyoxadiazole, or polyacrylonitriles. A method according to claim 7, wherein the carbon materials are selected from the group consisting of molasses, bitumen, coal tar pitch, graphite, carbon black, activated carbon, chopped carbon fibers or coke particles. The method according to claim 7, wherein the at least one layer of thermoplastic material is additionally coated with crosslinking additives. Method according to claim 10, wherein the crosslinking additives are selected from the group consisting of organic peroxides, dialdehydes, diamines or UV-crosslinking polymers. Method according to claim 1, wherein in step d) the composite is additionally irradiated with ionizing radiation or UV radiation. Electrode material produced according to any one of claims 1 to 12. Electrode material according to claim 12, wherein the electrode material has a thickness of 50 to 500 µm. 16 Use of the electrode material according to claim 13 or 14 in polymer electrolyte fuel cells, in phosphoric acid fuel cells, microbial fuel cells, electrochemical reactors, oxygen-consuming cathodes, metal-air batteries, PEM electrolyzers or batteries.
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RU2450403C2 (en) * 2006-01-24 2012-05-10 Фишер Контролз Интернешнел Ллс Explosion-proof device with ungrounded voltage limiter

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