Fuel cell

Abstract

The present invention provides a fuel cell having a layered structure, including: a membrane electrode assembly having a fuel electrode, an oxidation electrode, and an electrolyte membrane held between the fuel electrode and the oxidation electrode; and stainless steel separators holding the membrane electrode assembly therebetween. The stainless steel separator contains Cr and Fe; the Cr concentration by mass % by mass ratio of Cr to Fe at the separator surface facing the fuel electrode is from 0.7 to 1.3; and the Cr concentration by mass % by mass ratio of Cr to Fe at the separator surface facing the oxidation electrode is less than 0.7.

1 . A fuel cell having a layered structure, comprising: 
 a membrane electrode assembly having a fuel electrode, an oxidation electrode, and an electrolyte membrane held between the fuel electrode and the oxidation electrode; and    stainless steel separators holding the membrane electrode assembly therebetween;    wherein the stainless steel separator contains Cr and Fe,    the Cr concentration by mass % by mass ratio of Cr to Fe at the separator surface facing the fuel electrode is from 0.7 to 1.3, and    the Cr concentration by mass % by mass ratio of Cr to Fe at the separator surface facing the oxidation electrode is less than 0.7.    
   
   
       2 . A fuel cell comprising: 
 a layered structure having:    anode separators and cathode separators having groove passages on front and back surfaces thereof and being made of a stainless steel, steel anode separators and cathode separators being alternately layered, so that groove passages form a fuel gas passage, an oxidation gas passage, and a cooling medium passage; and    a cooling medium inlet and a cooling medium outlet which penetrate the layered structure in a layering direction of the separators, thereby a cooling medium supplied from the cooling medium inlet being discharged from the cooling medium outlet via the cooling medium passage,    insulating coatings formed on inner surfaces of the cooling medium inlet and the cooling medium outlet; and    insulating coatings formed on the cooling medium passage in the vicinities of the cooling medium inlet and the cooling medium outlet,    wherein the separator contains Cr and Fe, the Cr concentration of portions except for the vicinities of the cooling medium inlet and the cooling medium outlet is from 12 to 25 mass %.    
   
   
       3 . The fuel cell according to  claim 2 , wherein the cooling medium has a conductivity of not more than 20 μS/cm.  
   
   
       4 . A fuel cell comprising: 
 a unit power generation cell having a separator with a cooling medium passage formed on a surface of the separator;    cooling medium communicating holes for supplying a cooling medium and for discharging a cooling medium, the cooling medium communicating holes penetrating the unit power generation cell and having an insulating coating formed inside the cooling medium communicating holes;    a cooling medium supply portion for supplying a cooling medium from the cooling medium communicating hole for supplying a cooling medium to the cooling medium passage;    a cooling medium discharge portion for discharging a cooling medium from the cooling medium passage to the cooling medium communicating hole for discharging a cooling medium; and    an insulating portion provided between the cooling medium supply portion and the cooling medium discharge portion and having an insulating coating formed thereinside,    wherein the cooling medium communicating hole for supplying a cooling medium has a liquid resistance from 1.5 to 30 kΩ per unit power generation cell, and the insulating portion has a liquid resistance of from 0.2 to 15 MΩ.    
   
   
       5 . A fuel cell comprising: 
 a unit power generation cell having a separator with a cooling medium passage formed on a surface of the separator;    cooling medium communicating holes for supplying a cooling medium and for discharging a cooling medium, the cooling medium communicating holes penetrating the unit power generation cell and having an insulating coating formed inside of the cooling medium communicating holes;    a cooling medium supply portion for supplying a cooling medium from the cooling medium communicating hole for supplying a cooling medium to the cooling medium passage;    a cooling medium discharge portion for discharging a cooling medium from the cooling medium passage to the cooling medium communicating hole for discharging a cooling medium; and    an insulating portion provided between the cooling medium supply portion and the cooling medium discharge portion and having an insulating coating formed thereinside,    wherein a liquid resistance R 1  between both ends of the cooling medium communicating hole for supplying a cooling medium and a liquid resistance R 2  at the insulating portion satisfy the relationship      ( R   1 / R   2 )=0.1 to 3.    
   
   
       6 . The fuel cell according to  claim 4 , wherein the insulating portion is provided at at least one of the cooling medium supply portion and the cooling medium discharge portion.  
   
   
       7 . The fuel cell according to  claim 5 , wherein the insulating portion is provided at at least one of the cooling medium supply portion and the cooling medium discharge portion.  
   
   
       8 . The fuel cell according to  claim 4 , wherein the cooling medium has a conductivity of not more than 10 μS/cm.  
   
   
       9 . The fuel cell according to  claim 5 , wherein the cooling medium has a conductivity of not more than 10 μS/cm.  
   
   
       10 . The fuel cell according to  claim 4 , wherein not less than 50 power generation cell units are layered.  
   
   
       11 . The fuel cell according to  claim 5 , wherein not less than 50 power generation cell units are layered.