Electrode for secondary battery, preparation thereof, and secondary battery and cable-type secondary battery comprising the same

A cable-type secondary battery, comprising:

• two or more cores for supplying lithium ions, which comprise an electrolyte;
• two or more inner electrodes arranged in parallel to each other, each inner electrode surrounding an outer surface of one of the two or more cores for supplying lithium ions and comprising a current collector and an electrode active material layer;
• a separation layer surrounding outer surfaces of the two or more inner electrodes to prevent a short circuit between electrodes;
• and
• an outer electrode helically wound to surround an outer surface of the separation layer and comprising a current collector and an electrode active material layer,
• wherein at least one of the two or more inner electrodes and the outer electrode is a sheet-form electrode comprising the respective current collector, the respective electrode active material layer on one surface of the respective current collector, and a first porous supporting layer on the respective electrode active material layer.