Electrode substrate made of carbon fibers and method of producing the electrode substrate

Abstract

A porous electrode substrate has a form of a tape material and contains a structure made of carbon fibers and a carbon matrix. A specific surface area, porosity, and pore distribution are determined by the carbon matrix. The carbon matrix contains carbon particles including activated carbon with a high specific surface area and a carbonized or graphitized residue of a carbonizable or graphitizable binder.

Claims

1. A porous electrode substrate formed as a tape material, comprising: a structure of carbon fibers; and a carbon matrix, wherein the carbon matrix comprises carbon particles including activated carbon with a specific surface area of more than 1000 m.sup.2/g and a carbonized or graphitized residue of a carbonizable or graphitizable binder, and that at least a part of interstices in the structure of carbon fibers and the carbon matrix is filled with the activated carbon, as well as with the carbonized or graphitized residue of a carbonizable or graphitizable binder, further wherein specific surface area, porosity and pore distribution are determined by the carbon matrix.

2. The porous electrode substrate according to claim 1, wherein: a mass ratio between said carbonized or graphitized residue and said carbon particles is between 1:10 and 10:1, including said activated carbon having a specific surface area greater than 1000 m.sup.2/g; and said carbonized or graphitized residue, together with said carbon particles, constitute a mass proportion between 25 and 75% of the porous electrode substrate, a substrate BET is 5 to 250 m.sup.2/g, the porous electrode substrate has a thickness between 0.1 and 0.4 mm and an electrical resistance in a z-direction is below 25 mOhm/cm.sup.2.

3. The porous electrode substrate according to claim 1, wherein said structure of carbon fibers is selected from the group consisting of non-crimp fabrics, paper, woven fabrics and nonwovens.

4. The porous electrode substrate according to claim 1, wherein said carbon particles contain at least one of acetylene black, furnace black, gas black, graphitized carbon black, milled carbon fibers, carbon nanotubes (CNT's), carbon nano-fibers, carbon aerogels, meso-porous carbon, fine-grain graphite, glassy carbon powder, expanded graphite, ground expanded graphite, graphite oxide, flake graphite, activated carbon, graphene, graphene oxide, N-doped CNT's, boron-doped CNT's, fullerenes, petcoke, acetylene coke, anthracite coke, carbonized meso-phase pitches, or doped diamond.

5. The porous electrode substrate according to claim 1, wherein said carbonizable or graphitizable binder contains at least one of coal tar pitches, phenolic resins, benzoxazine resins, epoxide resins, furane resins, furfuryl alcohols, vinyl ester resins, melamine-formaldehyde resins (MF), urea-formaldehyde resins (UF), resorcinol formaldehyde (RF) resins, acrylonitrile butadiene rubber, cyanate-ester resins, bismaleimide resins, polyurethane resins, or polyacrylo nitrile.

6. The porous electrode substrate according to claim 1, wherein a carbon proportion in a form of said carbon fibers, said carbonized or graphitized residue and said carbon particles including said activated carbon, is at least 95% by weight and a heteroatom proportion is at least 1% by weight.

7. The porous electrode substrate according to claim 1, wherein the porosity is between 15 and 97% by weight, expressed as a proportion of an open volume to a sum of open volume, volume of carbon fibers, and a volume formed by all solid materials, containing said carbonized or graphitized residue and said carbon particles including said activated carbon.

8. The porous electrode substrate according to claim 1, wherein the porous electrode substrate is at least one of impregnated with at least one impregnation agent or doped with at least one doping agent.

9. An apparatus selected from the group consisting of redox flow batteries, lithium sulfur batteries, sodium sulfur batteries, zinc bromine batteries, zinc air batteries, vanadium air batteries, fuel cells, microbial fuel cells, H.sub.2/Cl.sub.2 fuel cells, H.sub.2/Br.sub.2 fuel cells, and PEM electrolyzers, the apparatus comprising: a porous electrode substrate formed as a tape material, said porous electrode containing a structure of carbon fibers and a carbon matrix, wherein the carbon matrix comprises carbon particles including activated carbon with a specific surface area of more than 1000 m.sup.2/g and a carbonized or graphitized residue of a carbonizable or graphitizable binder, and that at least a part of interstices in the structure of carbon fibers and the carbon matrix is filled with the activated carbon, as well as with the carbonized or graphitized residue of a carbonizable or graphitizable binder, further wherein specific surface area, porosity and pore distribution are determined by the carbon matrix.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) The following examples explain the invention.

Example 1

(2) A line of carbon fiber raw paper (square measures 20 g/m.sup.2), produced in wet fluid processing with short cut carbon fibers (3-12 mm), is impregnated by a foulard in an aqueous dispersion consisting of 50 kg water, 0.75 kg polyvinyl pyrrolidone, 6.75 kg acetylene soot, 0.75 kg activated carbon (BET>1,000 m.sup.2/g), 0.75 kg 2-aminopropanole, 0.1 kg ammonium hydrogen carbonate, and 18.75 kg resorcinol formaldehyde resin dispersion and dried and/or hardened in a continuous furnace. Carbonization subsequently takes place under inert gas atmosphere in a continuous furnace at 1,400 C.

Example 2

(3) A roll of carbon fiber fleece (40 g/m.sup.2), produced by carbonizing a water-jet hardened fleece on the basis of polyacryl nitrile or oxidized polyacryl nitrile staple fibers (20 to 80 mm), is impregnated on a foulard in an aqueous dispersion consisting of 56 kg water, 0.95 kg polyvinyl alcohol, 7.5 kg acetylene soot (BET surface 60 m.sup.2/g), and 20.65 kg melamine formaldehyde resin (40%) and dried and/or hardened in a continuous furnace. Carbonization subsequently takes place under inert gas atmosphere in a continuous furnace at 1,400 C.

(4) The following table shows the material parameters for examples 1 and 2, with a reference sample for comparison. A 2-point measurement at a load of 100 N/cm.sup.2 was conducted to measure the resistance.

(5) TABLE-US-00001 Resistance Element analysis Thickness Porosity (mOhm/ C BET (m) (%) cm.sup.2) O N (m.sup.2/g) Reference 370 87.8 4.2 98.5 0.3 0.8 GDL 0.1 10AA Example 210 91.2 6.2 97.8 0.9 70 1 0.6 Example 380 88.7 9.8 97.5 1.4 34 2 0.1

(6) In order to assess electrochemical activity, cyclic voltammetry measurements of untreated electrode materials were conducted in 1 mM Fe(CN).sub.6.sup.3/4 in 0.1 M potassium chloride solution.

(7) An ideally reversible redox pair results in a separation of 60 mV between the oxidation (E.sub.p.sup.ox) and reduction peak (E.sub.p.sup.red) (A. J. Bard, L. M. Faulkner (eds.), Electrochemical Methods: Fundamentals and Applications, Wiley, 2001). The considerably smaller peak separations for the materials in examples 1 and 2, compared to the reference material, confirm the significantly improved electrochemical kinetics of the materials from embodiment examples 1 and 2.

(8) TABLE-US-00002 E.sub.p.sup.ox - E.sub.p.sup.red Reference GDL 10AA 322 mV Example 1 70 mV Example 2 100 mV