Outer package material for lithium-ion battery and method for producing lithium-ion battery using the outer package material

A method for producing an outer package material for a lithium-ion battery, the method comprising:

• forming a base layer by biaxially stretching a film in a sequential manner to obtain a sequentially biaxially stretched film;
• layering a first adhesive layer, a metallic foil layer, a corrosion prevention treatment layer, a second adhesive layer and a sealant layer sequentially on one of surfaces of the base layer;
• wherein
• under tensile testing conditions that a test specimen of the base layer is stored at 23° C. and 40% relative humidity (RH) for 24 hours prior to tensile testing, and the tensile testing is carried out at 23° C. and 40% RH, and the test specimen is 15 mm in width, a distance between gauge points is 50 mm, and a tensile rate is 100 mm/minute, tensile elongation being measured in a first direction and in a second direction of the specimen of the base layer relative to the length of the specimen, the first direction being a machine direction of the specimen of the base layer and the second direction being a transverse direction perpendicular to the first direction,
• a ratio of tensile elongation measured in the first direction to tensile elongation measured in the second direction is 140:75, and
• a ratio of tensile stress measured in the first direction to tensile stress measured in the second direction is 200:229.