Fuel cell separator. production method, and solid polymer fuel cells

#The present invention relates to a method of making fuel cell separators having excellent hydrophilic properties. The invention also relates to fuel cell separators obtained by such a method, and to solid polymer fuel cells in which such separators are used.

#Fuel cells are devices which, when supplied with a fuel such as hydrogen and with atmospheric oxygen, cause the fuel and oxygen to react electrochemically, producing water and directly generating electricity. Because fuel cells are capable of achieving a high fuel-to-energy conversion efficiency and are environmentally friendly, they are being developed for a variety of applications, including small-scale local power generation, household power generation, simple power sources for isolated facilities such as campgrounds, mobile power sources such as for automobiles and small boats, and power sources for satellites and space development.

#As shown in FIG. 1, such fuel cells, and particularly solid polymer fuel cells, are built in the form of modules composed of a stack of at least several tens of unit cells. Each unit cell has a pair of plate-like separators 1, 1 with a plurality of ribs 1a on either side thereof that define channels for the flow of gases such as hydrogen and oxygen. Disposed between the pair of separators 1, 1 in the unit cell are a solid polymer electrolyte membrane 2 and gas diffusing electrodes 3 made of carbon paper.

#FIG. 1 is a perspective view showing the unit cell construction in a typical fuel cell.

#FIG. 2 shows a perspective view of a fuel cell separator according to one embodiment of the invention.

#The inventive method of producing fuel cell separators includes the steps of shaping a composition primarily comprising a metal oxide, an electrically conductive powder and a binder to form a shaped body, coating and impregnating the shaped body with a hydrophilic resin, then curing the hydrophilic resin.

#The metal oxide used herein may be any that is both hydrophilic and stable in water, including hot water, that is, not subject to dissolution, exothermic reaction or degradation in water. Illustrative examples of suitable metal oxides include activated alumina, tin oxide and ruthenium oxide. Of these, the use of one or more selected from among activated alumina, and tin oxide is preferred.

#No particular limitation is imposed on the average particle size of the metal oxide, although an average particle size of 0.1 to 500 μm is preferred. An average particle size of 10 to 100 μm is especially preferred for activated alumina, and an average particle size of 0.1 to 10 μm is especially preferred for tin oxide and ruthenium oxide.