Stainless steel material for a separator of a solid polymer fuel cell and a solid polymer fuel cell using the separator

Patent metadata

Field	Value
Publication number	US-9312546-B2
Application number	US-97560810-A
Country	US
Kind code	B2
Filing date	Dec 22, 2010
Priority date	Jun 26, 2008
Publication date	Apr 12, 2016
Grant date	Apr 12, 2016

Abstract

A stainless steel member comprising a stainless steel base metal; an oxide film located on the surface of the stainless steel base metal; an electroconductive layer located on the surface of the oxide film and comprising a nonmetallic electroconductive material; and an electroconductive material which is located so as to penetrate the oxide film and which electrically contacts the stainless steel base metal and the electroconductive layer is provided as a stainless steel member for a separator of a solid polymer fuel cell having excellent properties such that a degradation in performance is low even after prolonged operation. A solid polymer fuel cell using the stainless steel member is also provided.

First claim

The invention claimed is:

1. A stainless steel member for a separator of a solid polymer fuel cell, the member comprising:
a stainless steel base metal;
an oxide film located on a surface of the stainless steel base metal;
an electroconductive layer located on a surface of the oxide film opposite to the oxide film surface located on the stainless steel base metal, and comprising a nonmetallic electroconductive material, wherein the nonmetallic electroconductive material comprises graphite and the value of a lattice spacing of d002 of the graphite is at most 3.390 angstroms; and
an electroconductive material which is located so as to penetrate the oxide film and which electrically contacts the stainless steel base metal and the electroconductive layer;
wherein when comparing peak intensities of diffraction lines of atomic planes of a crystal of the graphite located on the surface of the oxide film as measured by wide-angle X-ray diffraction, the ratio of a peak intensity of a diffraction line of a (110) atomic plane to a peak intensity of a diffraction line of a (004) atomic plane is less than 0.1,
wherein the electroconductive material is formed of a boride-type metallic inclusion which has a M 2 B-type structure and which is partly embedded in the stainless steel base metal, wherein M is a metal.

2. The stainless steel member according to claim 1 , wherein the electroconductive layer is located on a surface of the electroconductive material.

3. The stainless steel member according to claim 1 , wherein the boride-type metallic inclusion contains a chromium boride.

4. The stainless steel member according to claim 1 , wherein the electroconductive layer is prepared by sliding a member containing graphite on a surface consisting of the surface of the oxide film and a surface of the boride-type metallic inclusion exposed on the stainless steel base metal.

5. The stainless steel member according to claim 4 , wherein the surface consisting of the surface of the oxide film and the surface of the boride-type metallic inclusion exposed on the stainless steel base metal has an Ra roughness of at least 0.10 micrometers.

6. The stainless steel member according to claim 1 , wherein the electroconductive layer is prepared by coating a composition comprising the graphite and an adhesive agent on a surface consisting of the surface of the oxide film and an exposed surface of the boride-type metallic inclusion, the content of the adhesive agent in the composition being at most 2% by weight of the content of the graphite in the composition.

7. The stainless steel member according to claim 6 , wherein the adhesive agent contains at least one of PVDF (polyvinylidene difluoride) and PTFE (polytetrafluoroethylene).

8. A solid polymer fuel cell having a stack of unit cells with individual separators disposed between them, each of the unit cells being prepared by laminating a fuel electrode film, a proton-exchange membrane, and an oxidant electrode film in this order, DC power being generated by supplying a fuel gas and an oxidant gas to the stack of unit cells, wherein each separator is obtained from the stainless steel member described in claim 1 .

Assignees

• Kaminaka Hideya
• Imamura Junko
• Higashida Yasuto
• Nippon Steel & Sumitomo Metal Corp

Inventors

• Kaminaka Hideya
• Imamura Junko
• Higashida Yasuto

Classifications

• C22C38/001

  containing N · CPC title

• H01M2008/1095

  Fuel cells with polymeric electrolytes · CPC title

• C22C38/42

  with copper · CPC title

• C23C28/048

  with layers graded in composition or physical properties · CPC title

• C23C28/00

  Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D · CPC title