Patent ID: 8404377

Claim:
A separator for use in a non-aqueous electrolyte secondary battery comprising a first porous layer (layer A) having a shutdown function which becomes substantially a non-porous layer at a high temperature, and a second porous layer (layer B) including an aramid resin and an inorganic material, said layer A and said layer B being laminated together, said inorganic material being immobilized in said layer B, wherein a ratio (T A /T B ) of a thickness (T A ) of said layer A relative to a thickness (T B ) of said layer B is 2.5 or more and 13 or less, a total (T A +T B ) of the thickness of said layer A and the thickness of said layer B is 11 μm or more and 22 μm or less, a content of said aramid resin included in said layer B is 20 wt % or more and 45 wt % or less, a content of said inorganic material included in said layer B is 120 parts by weight or more and 400 parts by weight or less, with respect to 100 parts by weight of said aramid resin a particle size of said inorganic material is 0.01 to 1 μm, and an air permeability is 150 sec/100 mL or more and 400 sec/10 mL or less.