Closure Assembly with Low Vapor Transmission for Electrochemical Cell

Abstract

A closure assembly for an electrochemical cell including a container and an end assembly sealing an open end of the container in order to minimize mass or weight loss of the cell due to electrolyte vapor transmission is disclosed. The end assembly is provided with a vent member capable of venting a fluid when the pressure within the cell exceeds a predetermined limit; a contact member operatively in electrical contact with a conductive contact of the end assembly and a current collector of an electrode of the cell; and an insulating, polymeric seal member disposed at least between conductive components of the closure assembly having different polarities. In a preferred embodiment, the seal member has a selected dimensional ratio in order to minimize vapor transmission of the electrolyte through the seal member.

1 . A method for forming an electrochemical cell, comprising the steps of:
 providing a cylindrical container having a closed bottom end, a sidewall and an open end;   forming an initial bead in the sidewall of the container after insertion of an electrode assembly into the container, wherein the initial bead is located at a cell axial height above the electrode assembly;   inserting an end assembly into the container so that a peripheral portion of the end assembly is seated on an upper wall of the initial bead;   providing support to a) the bottom end of the container, b) the initial bead with a bead support, and c) the open end of the container and tapering the upper wall upward towards the radial center of the cell; and   crimping the open end of the container sidewall and securing the end assembly between the crimped end and a portion of the upwardly tapered upper wall to form a sealed cell, wherein the bead upwardly tapered upper wall is spaced from a lower wall of the bead in the sealed cell.   
     
     
         2 . The method according to  claim 1 , wherein the bead support extends around the circumference of the cell during formation of the upwardly tapered upper wall. 
     
     
         3 . The method according to  claim 2 , wherein forming the initial bead includes pressing a forming wheel against the sidewall of the container while the can is rotated around its axial axis. 
     
     
         4 . The method according to  claim 1 , wherein during the crimping process, the container is also supported at the bottom of the container. 
     
     
         5 . The method according to  claim 1 , wherein an upper sidewall located above the bead is subjected to diameter reduction. 
     
     
         6 . The method according to  claim 5 , wherein radial compression is maintained on at least the upper sidewall during crimping of the upper end of the container.