Patent EP-0940870-A2 (EP)
Inventor: DOPP ROBERT B
IPC: H01M4/02
Filed: 1999-03-08
Abstract: The invention relates to seals, and electrochemical cells made therewith. An elongate, generally tubular, air depolarized electrochemical cell (10) comprising a cathode (14), including an air cathode assembly (26), extending about the tubular circumference, and along the tubular length, of the cell (10), an anode (12), a separator (16) between the anode (12) and the cathode (14), electrolyte, a top closure member (177, 200), and a bottom closure member (114, 202). The cathode assembly (26) is fixedly held, by a friction fit, in a slot (116) at the bottom of the cell. The slot can be developed, for example, by inner (110) and outer (114) walls of a cathode can (28), by inner (226) and outer (224) walls of a bottom closure member (202), or by an outer wall (114) of a cathode can (28) and an opposing outer wall of a plug (128) on the interior of the cell. Preferably, bottom closure structure of the cell (10) and receives a bottom edge portion (44) of the cathode current collector (32), and makes electrical contact with the bottom edge portion (44), preferably at an inner surface (60) of the cathode current collector. A diffusion member (36) of the cathode assembly (26) is preferably compressed as a seal, at the bottom of the cell (10), between an outer side wall (39) of the cell and the remainder of the cathode assembly (26). The diffusion member (36) is also used at least as an assist in sealing the cell (10) against electrolyte leakage from the anode cavity (137) and past the cathode assembly (26).A grommet (18) closes the top of the cell (10). A seal (36) can extend upwardly into a slot (174) between the grommet (18) and a top closure member (177) such as at the top of a cathode can (28), or a separate top closure member (200). Cathode assembly (26) and separator (16) can extend into the slot (174). The seal is between the grommet (18) and cathode assembly (26), or between grommet (18) and separator (16), or both. The seal can extend upwardly into the slot (174) from an outer surface of the cathode assembly (26), can extend about respective upper edges of the cathode current collector (57), catalyst, and separator (16), and downwardly toward, preferably against or along the inner surface of, the separator (16). The top closure member (200) can be crimped against the grommet (18) at the slot (174), with the cathode assembly (26), and optionally the separator (16), in the slot (174) between the grommet (18) and the top closure (200), thus to provide a liquid-tight crimp seal. The top closure (200) can be crimped first against the grommet (18) at the slot (174), and further crimped against the grommet (18) at a second locus (178) displaced longitudinally from the first crimp. Composition of the seal comprises a microporous polymer (36), preferably polytetrafluoroethylene. Preferred embodiments comprise at least two, preferably at least three, layers of air permeable microporous sheet material, useful for diffusion of air therethrough to the cathode reaction surface (63). The layers are wrapped continuously and without intervening end, to form an outer surface of the cathode assembly (26). Another expression of the invention is a cathode assembly (26), or cathode-separator combination, for use in an elongate air depolarized cell (10). The air permeable sheet material (36), as wrapped about the tubular cathode assembly, is compressed so as to have a compressed thickness less than the uncompressed thickness.