An electrode used for oxygen reactions, the electrode being excellent in catalytic activity and stability, a method of producing the electrode, and an electrochemical device using the electrode are provided. This electrode includes, as an oxygen catalyst, an oxide that has peaks at positions of 2=34.881.00, 50.201.00, and 59.651.00 in an X-ray diffraction measurement using a CuK ray and has constituent elements of bismuth, ruthenium, sodium, and oxygen.

A method of producing a lithium ion secondary battery includes the following (A) to (E). (A) A negative electrode active material powder having a BET specific surface area of 2.2 m.sup.2/g or more and 5.2 m.sup.2/g or less is prepared. (B) Fluorine is incorporated into the negative electrode active material powder. (C) Wet granules are prepared by mixing the negative electrode active material powder, a water-soluble binder powder, and water. (D) A negative electrode is produced by forming the wet granules into a film form. (E) A lithium ion secondary battery including the negative electrode, a positive electrode, and an electrolytic solution is produced. When the negative electrode active material powder is formed into a pellet having a density of 1.5 g/m.sup.3, fluorine is incorporated into the negative electrode active material powder so that the pellet has a water contact angle of 96 or more and 138 or less.

The present invention provides a micro-porous layer which provides a fuel battery having high productivity, high power generation performance, and high durability. The present invention provides a micro-porous layer including fibrous carbohydrate having a fiber diameter of 5 nm-10 m and an aspect ratio of 10 or more. The carbohydrate has an oxygen/carbon element ratio of 0.02 or more.

Provided are a method of forming a gas diffusion layer on carbon paper, the method being capable of balancing smoothness with air permeability and water drainage ability in the gas diffusion layer as an underlayer, as well as the carbon paper having the gas diffusion layer formed thereon used in fuel cells. The method of forming a gas diffusion layer (L2) on carbon paper (CP) used in fuel cells includes the steps of: forming a water-repellent layer (L1) on the surface of the carbon paper (CP), forming a crack (CR) in the water-repellent layer (L1), and forming the gas diffusion layer (L2) on the water-repellent layer (L1) having the crack (CR) formed therein.

A gas diffusion layer, a preparation method therefor, a membrane electrode assembly and a fuel cell. The gas diffusion layer comprises gas diffusion layer substrates (41, 42) and a microporous layer slurry coated on the gas diffusion layer substrates (41, 42). An additive that contains catechol or contains a catechol structure compound is specifically added into the microporous layer slurry, and the additive is specifically dopamine hydrochloride.

The present invention provides a gas diffusion electrode including a microporous layer, characterized in that the microporous layer includes at least a first microporous layer and a second microporous layer, wherein the first microporous layer contains a first hydrophobic polymer and is located on the outermost surface on one side of the microporous layer; wherein the second microporous layer contains a second hydrophobic polymer and is located on the outermost surface of the microporous layer on the side opposite to the first microporous layer, and is located on an outermost surface of the gas diffusion electrode; and wherein the first hydrophobic polymer is a resin having a melting point lower than the melting point of the second hydrophobic polymer. The present invention provides a gas diffusion electrode for a fuel cell, in which both high performance and durability are achieved.

A multilayer structure, of use as composite diffusion layer in a proton-exchange membrane fuel cell, including at least one mat of carbon nanotubes having a unit diameter of less than or equal to 20 nm, defining at least one face of the structure, the mat of carbon nanotubes being superposed on a support based on carbon fibres. It also relates to a process for preparing such a multilayer structure and to the use thereof for an electrode of a PEMFC.

A method of treating a carbon substrate, includes the successive steps of impregnating the carbon substrate with an aqueous solution containing an amorphous fluorinated copolymer of tetrafluoroethylene and of perfluoromethoxy dioxole, drying the carbon substrate at a pressure lower than the atmospheric pressure, and obtaining a carbon substrate impregnated with a fluorinated copolymer. Such a carbon substrate may be used as a gas diffusion layer in a fuel cell.

The present invention provides a substrate film that has a catalyst coating liquid having good coating properties when producing a membrane electrode assembly, has a catalyst layer and support film having good release properties after the catalyst layer is transferred to an electrolyte membrane using a catalyst transfer sheet, and does not contaminate the catalyst layer. Provided is a substrate film for a catalyst transfer sheet, said substrate film being formed by introducing fluorine atoms to at least one surface of a base film formed from one or more types of polymers selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene napthalate, polyphenylene sulfide, polysulf ones, polyether ketone, polyether ether ketone, polyimides, polyetherimide, polyamides, polyamide-imides, polybenzimidazoles, polycarbonates, polyarylates, and polyvinyl chloride, wherein the ratio, measured by X-ray photoelectron spectroscopy, of the number of fluorine atoms/the number of carbon atoms in the surface to which the fluorine atoms are introduced, i.e. the modified surface, is 0.02-1.9, inclusive.

A method of producing a lithium ion secondary battery includes the following (A) to (E). (A) A negative electrode active material powder having a BET specific surface area of 2.2 m.sup.2/g or more and 5.2 m.sup.2/g or less is prepared. (B) Fluorine is incorporated into the negative electrode active material powder. (C) Wet granules are prepared by mixing the negative electrode active material powder, a water-soluble binder powder, and water. (D) A negative electrode is produced by forming the wet granules into a film form. (E) A lithium ion secondary battery including the negative electrode, a positive electrode, and an electrolytic solution is produced. When the negative electrode active material powder is formed into a pellet having a density of 1.5 g/m.sup.3, fluorine is incorporated into the negative electrode active material powder so that the pellet has a water contact angle of 96 or more and 138 or less.