A gas diffusion layer for an electrolyser or for a fuel cell comprises a first nonwoven layer of metal fibers provided for contacting a proton exchange membrane, a second nonwoven layer of metal fibers, and a third porous metal layer. The first nonwoven layer of metal fibers comprises metal fibers of a first equivalent diameter. The second nonwoven layer of metal fibers comprises metal fibers of a second equivalent diameter. The second equivalent diameter is larger than the first equivalent diameter. The third porous metal layer comprises open pores. The open pores of the third porous metal layer are larger than the open pores of the second nonwoven layer of metal fibers. The second nonwoven layer is provided in between and contacting the first nonwoven layer and the third porous metal layer. The second nonwoven layer is metallurgically bonded to the first nonwoven layer and to the third porous metal layer. The thickness of the third porous metal layer is at least two timesand preferably at least three timesthe thickness of the first nonwoven layer.

An electrolyte of a redox flow battery, including a negative electrolyte and a positive electrolyte, is provided. The negative electrolyte includes a negative active material and a negative solvent, and the positive electrolyte includes a positive active material and a positive solvent. An initial volume of the negative electrolyte is greater than an initial volume of the positive electrolyte. A redox flow battery including the electrolyte is also provided.

A process for making a catalyst and gas diffusion hybrid electrode member (or members) adapted for use in a fuel cell by integrally bonding a plurality of catalyst and gas diffusion layers to be a catalyst and gas diffusion hybrid electrode member to be inserted between two bipolar plates of the fuel cell for simplifying the production and decreasing the cost.

A process for making a catalyst and gas diffusion hybrid electrode member (or members) adapted for use in a fuel cell by integrally bonding a plurality of catalyst and gas diffusion layers to be a catalyst and gas diffusion hybrid electrode member to be inserted between two bipolar plates of the fuel cell for simplifying the production and decreasing the cost.

A gas diffusion electrode substrate that is used in a fuel cell and is constituted by an electrode substrate and microporous parts, in which a microporous part (A) is formed on one surface of the electrode substrate, and a microporous part (B) is formed in a part of the inside of the electrode substrate, the gas diffusion electrode substrate having a part in which the microporous part (B) is continuously present from the electrode substrate surface on the side on which the microporous part (A) is formed to a position near the electrode substrate surface on the opposite side, and a part in which pores are continuously distributed from the electrode substrate surface on the side on which the microporous part A is formed to the electrode substrate surface on the opposite side.

An electrode for redox flow batteries, the electrode being formed of a carbon fiber aggregate including a plurality of carbon fibers. Each of the carbon fibers has a plurality of pleats formed in the surface thereof. The ratio of L.sub.1 to L.sub.2, that is, L.sub.1/L.sub.2, is more than 1, where L.sub.1 is the peripheral length of a cross section of the carbon fibers and L.sub.2 is the peripheral length of a virtual rectangle circumscribing the cross section of the carbon fibers.

An electrode and a method of manufacturing an electrode for a flowing electrolyte battery enable improved robustness and reduced manufacturing costs of bipolar electrodes for flowing electrolyte batteries. The electrode includes a polymer sheet having a first side and a second side; a graphite layer on the first side; and an activated carbon layer on the second side.

A redox flow battery including an electrode assembly, the electrode assembly including a carbon block having pores and a flow frame having a first and a second surface, wherein the carbon block is accommodated on one or both of the first and second surfaces.

An object of the present invention is to provide a carbon sheet to be used suitably for a gas diffusion electrode, in which the carbon sheet does not worsen the electrical resistance in the through-plane direction, and can be prevented from the deflection into the gas flow channels provided in the bipolar plate, although such characteristics. A carbon sheet according to the present invention, provided to achieve the above-described object, is a carbon sheet including a first surface and a second surface located at the opposite side to the first surface; wherein, assuming that a specific section is equally divided into 20 portions in the thickness direction to form 20 layers, the degree of fiber orientation of the first surface side outermost layer of the 20 layers is 1.20 or more and 3.00 or less; and wherein, assuming that a region composed of consecutive layers that are included in the 20 layers, and satisfy specific conditions is a first surface side region, and that a region composed of a layer(s) included in the 20 layers but not included in the first surface side region is a second surface side region, the thickness of the first surface side region is 40% or less of the thickness of the whole carbon sheet, and a difference between the average degree of fiber orientation of the second surface side region and the degree of fiber orientation of the first surface side outermost layer is larger than 0.10.

A bipolar plate for a fuel cell stack or for an electrolyzer stack, having an anode plate and a cathode plate which are joined to face-to-face. Wherein the face of the anode plate that faces the face of the cathode plate delimits an internal space that forms a circuit for the distribution of a first fluid, thereby forming a bipolar plate. Wherein the first opening and the second opening facing one another thereby forming a collector configured to enable the passage of the first fluid or a second fluid through the bipolar plate. Wherein the first opening and the second opening have distinct dimensions such the peripheral end of the first opening and the peripheral end of the second opening are offset in relation to one another in the plane of the bipolar plate, forming a shoulder at the peripheral end of the collector.