Battery cell with improved pressure relief vent

An electrochemical cell with a pressure relief vent formed in a metal plate disposed in at least one of the closed end and the open end of the container. The pressure relief vent has an annular ring that includes a reduced thickness groove, interrupted in at least two places by unthinned sections of the plate. When the vent opens to relieve pressure from within the cell, the area of the plate within the annular ring remains attached to the remainder of the plate by at least one of the unthinned sections. A can with such a pressure relief vent formed in the can bottom is useful as an electrochemical cell container.