A prismatic battery cell and a method of making such a cell. The cell includes one or more anode regions, cathode regions, and electrolyte regions to facilitate ion flow between the anode and cathode regions. Electrically-conductive tabs are attached to the corresponding anode and cathode regions, and a pouch-like containment is formed around the regions. The containment includes facing substantially planar surfaces sealingly joined to one another. A barrier layer coating includes at least one low-permeability material and is placed over at least a portion of the cell edge defined by the joined surfaces such that the barrier layer coating blocks ambient gases or vapors from passing through the heat seal region that is used to join the pouch surfaces. The barrier layer coating may also include one or more hydrophobic surface treatments or enhancements, including an additional layer of surface treatments or, in another form, by surface roughening.