Patent ID: 8530097

Claim:
A secondary battery comprising: an electrode assembly comprising a positive electrode including a positive electrode active material layer, a negative electrode including a negative electrode active material layer, and a separator separating the positive and negative electrodes from each other; and an electrolyte, wherein the separator includes a porous layer comprising a ceramic material and a binder, and a polyolefin-based resin layer, wherein the ceramic material includes at least one selected from the group consisting of silica (SiO 2 ), alumina (Al 2 O 3 ), zirconium oxide (ZrO 2 ), and titanium oxide (TiO 2 ), and wherein the sol olefin-based resin layer is a polyethylene (PE) single layer, a polypropylene (PP) single layer, or a polypropylene-polyethylene-polypropylene multilayer, wherein the porous layer has a centerline average roughness (Ra) of 0.3 μm to 1.5 μm, the polyolefin-based resin layer has a porosity of 30% to 60%, and the polyolefin-based resin layer has a compressibility of 4% to 10%.