A method is disclosed for making a lithium-ion electrochemical cell comprising elements of the lithium-ion electrochemical cell contained within an aluminum alloy or magnesium alloy single-cell container. External surfaces of the container are coated for resistance to water-based corrosion. Rolled or folded layers of anode, cathode, and separator elements of the lithium-ion cell are placed in the aluminum or magnesium alloy container. And, with the placed elements of the lithium-ion cell in the container, and during one or more following steps of a manufacturing assembly process of the lithium-ion cell, an atmospheric pressure plasma stream, initially comprising hexamethyldisiloxane, is applied to external surfaces of the aluminum alloy or magnesium alloy container to form a silicone polymer coating on the surfaces that protects the container from water-based corrosion. The method is useful in forming batteries for automotive vehicles exposed to salt water environments.