The invention relates to a bipolar plate (10) for a fuel cell (100), comprising—an internal coolant flow field (33), which comprises a coolant channel (43), and—a first and a second flat side (11, 12) with a first and second reactant flow field (31, 32) respectively, which has at least one first and second channel structure (41, 42) respectively, wherein—the first and the second channel structure (41, 42) each form a trunk channel (44) and branch channels (46), wherein the branch channels (46) branch off in a branching region (48) from the respective trunk channel (44), and a first intermediate region (51) is formed between the branch channels (46) of the first channel structure (31), and a second intermediate region (52) is formed between the branch channels (46) of the second channel structure (32), wherein normal projections of the first and second intermediate region (51, 52) onto a center plane (56) of the bipolar plate (10), which center plane is arranged between the two flat sides (11, 12) of the bipolar plate (10), partially overlap so that an overlapping region (53) is formed. It is provided that the coolant channel (43) extends from an outer region (54), which is located outside the first and second intermediate region (51, 52), into the overlapping region (53), crossing a transit region (55) in the process, wherein the transit region (55) is a subregion of the normal projection of the first intermediate region (51) onto the center plane, which projects from the overlapping region (53).

The invention relates to a bipolar plate (10) for a fuel cell (100), comprising—an internal coolant flow field (33), which comprises a coolant channel (43), and—a first and a second flat side (11, 12) with a first and second reactant flow field (31, 32) respectively, which has at least one first and second channel structure (41, 42) respectively, wherein—the first and the second channel structure (41, 42) each form a trunk channel (44) and branch channels (46), wherein the branch channels (46) branch off in a branching region (48) from the respective trunk channel (44), and a first intermediate region (51) is formed between the branch channels (46) of the first channel structure (31), and a second intermediate region (52) is formed between the branch channels (46) of the second channel structure (32), wherein normal projections of the first and second intermediate region (51, 52) onto a center plane (56) of the bipolar plate (10), which center plane is arranged between the two flat sides (11, 12) of the bipolar plate (10), partially overlap so that an overlapping region (53) is formed. It is provided that the coolant channel (43) extends from an outer region (54), which is located outside the first and second intermediate region (51, 52), into the overlapping region (53), crossing a transit region (55) in the process, wherein the transit region (55) is a subregion of the normal projection of the first intermediate region (51) onto the center plane, which projects from the overlapping region (53).

A fuel cell system includes a fuel cell, a cathode off-gas discharge channel, a gas-liquid separator, and a cover member. The gas-liquid separator includes a body, a first discharge channel including a first valve seat at an end, and a first valve device including a first valve element and a first driver. The cover member covers at least the first discharge channel and the first valve seat in the gas-liquid separator, and includes a gas channel defining portion that defines a gas channel communicating with the cathode off-gas discharge channel between the cover member and the gas-liquid separator. The gas channel is configured such that a cathode off-gas flowing into the cover member comes into contact with the first discharge channel and the first valve seat and does not come into contact with the first driver.

A SOC stack has interconnects with a maximum distance between the contact points which are designed to compensate for pressure difference between one side of the interconnect to the other side.

Systems and methods for separator plates, bipolar plates, stacks of plates, and electrochemical systems, comprising at least one through-opening for the passage of a fluid and a rim that delimits the through-opening. The rim having a curved course and a rectilinear course that adjoins the curved course. A bead arrangement extends around the curved course and the rectilinear course. An edge portion spans the bead arrangement and the rim, so that the bead arrangement is situated at a distance from the rim. A cutout formed in the curved course, so that a minimum distance of the bead arrangement from the rim is smaller in the curved course than in the rectilinear course.

Systems and methods for separator plates, bipolar plates, stacks of plates, and electrochemical systems, comprising at least one through-opening for the passage of a fluid and a rim that delimits the through-opening. The rim having a curved course and a rectilinear course that adjoins the curved course. A bead arrangement extends around the curved course and the rectilinear course. An edge portion spans the bead arrangement and the rim, so that the bead arrangement is situated at a distance from the rim. A cutout formed in the curved course, so that a minimum distance of the bead arrangement from the rim is smaller in the curved course than in the rectilinear course.

A method for welding between two metallic plates, including: (a) fitting a solid plate without openings, configured to be transparent at at least one emission wavelength of a laser beam (F) emitted by a laser (L), between the laser (L) and at least one contact zone between the metallic plates to be welded; (a1) inerting of the contact zone via a netural gas, where the neutral gas circulates in channels delimited by the contact zone between the metallic plates and by the solid plate; (a2) exerting pressure on the two metallic plates to apply them against one another in the contact zone to be welded, where the application pressure is exerted by the solid plate directly in contact with one of the two metallic plates to be welded; and (b) emission of a laser beam, through the solid plate, to perform welding of the metallic plates in the contact zone.

A method for welding between two metallic plates, including: (a) fitting a solid plate without openings, configured to be transparent at at least one emission wavelength of a laser beam (F) emitted by a laser (L), between the laser (L) and at least one contact zone between the metallic plates to be welded; (a1) inerting of the contact zone via a netural gas, where the neutral gas circulates in channels delimited by the contact zone between the metallic plates and by the solid plate; (a2) exerting pressure on the two metallic plates to apply them against one another in the contact zone to be welded, where the application pressure is exerted by the solid plate directly in contact with one of the two metallic plates to be welded; and (b) emission of a laser beam, through the solid plate, to perform welding of the metallic plates in the contact zone.

A gas diffusion layer includes a laminate made up of sheets each having a plurality of through-holes through which gas passes. One or a plurality of the sheets in the laminate includes communication paths to communicate the through-holes in another sheet adjacent to the one sheet or one of the plurality of sheets with each other or to communicate the through-holes in another sheet adjacent to the one sheet or one of the plurality of sheets with the through-holes in the other adjacent sheet, the through-holes being separated from and being not communicated with the other through-holes in the same sheet.

A separator for a fuel cell includes a plurality of channels; and an inlet hole and an outlet hole formed in a first side and a second side of the plurality of channels, respectively, such that a reaction gas flows into and out from the separator to be exposed to a reaction surface including a membrane electrode assembly. The inlet hole is larger in size than the outlet hole.