Patent ID: 8841031

Claim:
A battery separator, comprising: (a) a porous substrate having pores; and (b) a styrene-butadiene layer formed on at least one region selected from the group consisting of a surface of the substrate and a part of the pores present in the substrate, wherein the styrene-butadiene layer comprises styrene-butadiene rubber; wherein the porous substrate having pores is selected from the group consisting of: (i) an organic/inorganic composite porous film, which comprises a porous film having pores, coated with a coating layer comprising a mixture of inorganic particles with a binder polymer, on a surface of the porous film and on a part of the pores present in the porous film, the inorganic particles linked and fixed among themselves by the binder polymer, and having a pore structure formed by interstitial volumes of the inorganic particles throughout the coating layer, wherein the coating layer restrains the thermal shrinkage of the porous film; and (ii) an organic/inorganic composite porous free-standing film comprising inorganic particles and a binder polymer, the inorganic particles linked and fixed among themselves by the binder polymer, and having a pore structure formed by interstitial volumes of the inorganic particles throughout the organic/inorganic composite porous free-standing film; wherein the inorganic particles are present in an amount of 50-99 wt % based on 100 wt % of the mixture of the inorganic particles and the binder polymer.