A non-aqueous electrolyte secondary battery capable of withstanding a reflow temperature has a positive electrode having a conductive material, a binder, and an electrode active material selected from the group consisting of LiCoO.sub.2, LiNiO.sub.2 and LiMn.sub.2 O.sub.4. A negative electrode has a conductive material, a binder and an electrode active material selected from the group consisting of a titanium oxide having an anatase structure, lithium titanate having a spinel structure and a molybdenum oxide. An electrolyte has a supporting salt and a non-aqueous solvent having a boiling point greater than 200.degree. C. A gasket is comprised of a material having a heat deformation temperature greater than 230.degree. C. A separator is disposed between the positive electrode and the negative electrode and is comprised of a material having a heat deformation temperature greater than 230.degree. C. At least one of the positive electrode and the negative electrode comprises an electrode heat-treated to a temperature of 250.degree. C. to 450.degree. C. for deactivating a thermally active portion of each of the conductive material, the binder and the electrode active material thereof.