A battery case including: a container configured to house an electrode assembly, wherein the container includes a bottom wall and a plurality of side walls, the bottom wall and the plurality of side walls are integrated to define a space for housing the electrode assembly and to provide a top opening opposite the bottom wall, the container includes a polymeric composition including a polymer and an inorganic moisture absorbent dispersed in the polymer, and the battery case has a water vapor transmission rate (WVTR) of less than about 0.05 grams per square meter per day, when measured at 38° C. and a relative humidity of 100% according to ISO 15106 or ASTM F1249.