An alkali metal secondary electrochemical cell, and preferably a lithium ion cell, provided with a removable gas relief valve, is described. The gas release valve is positioned on the casing, in fluid flow communication between the inside thereof and the exterior. This gas release valve serves to eliminate cell gases that build up inside the casing during the cell's formation stage. Once the lithium-ion cell has completed formation, the gas release valve is removed and replaced with a hermetic closure. Removal of the gas release valve and sealing of the cell takes place in an environment in which no outside gas is capable of being introduced inside the casing. The cell can also be provided in a tank filled with inert gas and a filter which separates the cell gas from the inert gas. When cell formation is completed, the cell hermetically sealed.