Patent ID: 8277981

Claim:
A secondary battery comprising an electrode, an electrolyte, and a separator, wherein the separator is an organic/inorganic composite separator comprising: an organic layer selected from the group consisting of a polyethylene layer, a polypropylene layer, a polyethylene/polypropylene bilayer, a polyethylene/polypropylene/polyethylene trilayer, a polypropylene/polyethylene/polypropylene trilayer, and an organic fiber filter paper layer; and an inorganic layer comprising inorganic particles and an inorganic modifying agent, wherein the inorganic particles comprise an OH group and at least one selected from the group consisting of alumina, titanium oxide, zirconium oxide, zinc oxide, silicon dioxide, and magnesium oxide; the inorganic modifying agent comprises at least one functional group selected from the group consisting of phosphonate, phosphate, and phosphonic acid; and a molar ratio of the OH group of the inorganic particles and the functional group of the inorganic modifying agent is from 5:1 to 10:1.