Composite carbon sheet, and electrochemical cells made therewith

Abstract

Cathode assembly precursor cathode assembly (,) and elongate air depolarized electrochemical cells (,) made therewith. Cathode assembly precursor comprises a closed-loop elongate cathode current collector (,), and perforations (,) from outer to inner surfaces, and catalystically active carbon extending into the perforations (,). The current collector (,) can be cylindrical and can be free from longitudinal jointing, or can have a longitudinal joint (,), preferably free from overlap of the side wall. The current collector (,) can comprise an imperforate edge region at the top (,) and/or bottom (,), left (,) and/or right (,) edge. The perforations (,) define an open traction of the wall, of about 45 to about 70 percent. Typical cathode assemblies (,) have air diffusion member (,) on the outer surface of the cathode assembly (,). Such air diffusion member (,) typically has thickness of about 0.0025 to 0.005 inch (about 0.06 to about 0.13 mm.), and comprises a reduced thickness endless wrap extending at least 1.5 times, preferably 2 times, or 3 times, about the current collector (,), discouraging transfer of moisture vapor into or out of a cell, discouraging leakage, and controlling air diffusion rate. The diffusion member (,) extends beyond the top edge (,) of the current collector, and is folded in and down about the top edge (,) and inner surface (,) of the cathode assembly (,). The cathode current collector (,) can be mounted on a mandrel (,), the carbon sheet (,) passing through a nip defined between (i) support structure (,) having greater arc radius than the mandrel (,) and (ii) the mandrel (,), and applying force at the nip to consolidate the carbon (,) onto the side wall (,), passing air diffusion material (,) through the nip, and applying force to consolidate the air diffusion material (,) onto the carbon (,). The invention contemplates fabricating an air cathode assembly (,) comprising mounting the current collector (,) on a mandrel (,), defining an arc having a radius smaller than the arc of the cathode current collector (,), mounting the combination mandrel (,) and cathode current collector (,) in a stack (,) of assembly rolls (,A,,B,,C,,D), making a sheet stack of carbon sheets (,B,,C,,D), passing the sheet stack through a nip, and applying force to the stack, reducing thickness of the stack, and passing air diffusion material (,) through the nips and applying force to consolidate the diffusion material (,) onto the carbon (,).