A multi-layer polyolefin porous membrane is disclosed. The membrane includes first and second layers, and a plurality of protrusions including polyolefin. The protrusions have a protrusion width (W) satisfying 5 μm≤W≤50 μm and have a protrusion height (H) satisfying 0.5 μm≤H. The protrusions are randomly disposed on a first side of the membrane, and the protrusions are disposed with a density of not less than 3 protrusions/cm2 and not greater than 200 protrusions/cm2. A meltdown temperature of the membrane is not lower than 165° C., an air permeation resistance of the membrane is not greater than 300 sec/100 cc Air, and a thickness of the membrane is not greater than 20 μm.