Cable-type secondary battery

A cable-type secondary battery, comprising:

• an inner electrode having an open-structured inner current collector and an inner electrode active material layer coated on the surface of the inner current collector;
• an electrolyte layer surrounding the inner electrode, the electrolyte layer being a polymer electrolyte film;
• an outer electrode having an outer electrode active material layer surrounding the outer surface of the electrolyte layer and an outer current collector surrounding the outer electrode active material layer;
• and
• a protection coating disposed to surround the outer electrode,
• wherein the polymer electrolyte film has a first electrolyte layer comprising a mixture of a first polymer and a first organic electrolyte solution in a weight ratio of 50:50 and 80:20;
• and a second electrolyte layer formed on at least one surface of the first electrolyte layer and comprising a mixture of a second polymer and a second organic electrolyte solution in a weight ratio of 20:80 and 50:50.
• wherein the first electrolyte layer has the tensile strength from 0.3 MPa to 6.0 MPa at 200% strain and the ionic conductivity from 2.0×10−6 S/cm to 2.0×10−3 S/cm, and
• the second electrolyte layer has the tensile strength from 003 MPa to 0.011 MPa at 50% strain and the ionic conductivity from 3.0×10−4 S/cm to 2.8×10−3 S/cm.