Patent ID: 8822074

Claim:
An electrode for a lithium-ion secondary battery comprising an electrode active material layer including an electrode active material, a thickener and a binder, and a porous membrane layer including inorganic filler, wherein the electrode active material layer is bound to at least one surface of a collector, and the porous membrane layer is applied onto the electrode active material layer, wherein said binder is unsaturated carboxylic ester based polymer in which a content rate of an acrylic acid alkyl ester monomer unit is 85 mass % to 99 mass %, wherein said thickener is carboxymethyl cellulose having a degree of polymerization of 1,000 to 3,000, and wherein said binder forms a spherical island phase having an average diameter of 0.5 μm or more in a cross-section of a composite membrane obtained by preparing a solution in which the binder and 1% aqueous solution of the thickener are mixed in the ratio of 1:10 (ratio in solid content) so as to be adjusted solid content concentration of the solution to have 1 to 1.5 mass % and then coating the solution on the collector followed by drying.