Abstract: A non-aqueous electrolyte secondary cell excellent in cycle characteristics is provided. This purpose is achieved by the following structure. A non-aqueous electrolyte secondary cell has a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a non-aqueous electrolyte having a non-aqueous solvent and an electrolytic salt. The positive electrode active material has a lithium-cobalt compound oxide having added therein at least zirconium. The non-aqueous electrolyte has LiBF4 at from 0.05 to 1.0 mass % of a total mass of the non-aqueous electrolyte and unsaturated cyclic carbonate at from 1.0 to 4.0 mass %. The true density ratio of the positive electrode is 0.72 or greater, the true density ratio being represented by formula 1 shown below: (Formula 1) True density ratio=active material apparent density of electrode active material layer÷true density of active material.

Abstract: A nonaqueous electrolyte secondary battery comprising a negative electrode constituted of a carbonaceous material permitting reversible insertion and desorption of lithium, a positive electrode permitting reversible insertion and desorption of lithium, a separator separating these positive electrode and negative electrode from each other and a nonaqueous electrolyte composed of an organic solvent and, dissolved therein, a solute of lithium salt, wherein the nonaqueous electrolyte contains vinylene carbonate and di(2-propynyl) oxalate, these vinylene carbonate and di(2-propynyl) oxalate added in an amount of 0.1 to 3.0% by mass and 0.1 to 2.0% by mass, respectively, based on the mass of the nonaqueous electrolyte. Thus, there can be provided a nonaqueous electrolyte secondary battery wherein a stable SEI surface coating is formed to thereby exhibit a large initial capacity and excel in cycle characteristics at high temperature and wherein any cell swelling is slight.

Abstract: A non-aqueous electrolyte secondary cell excellent in cycle characteristics is provided. This purpose is achieved by the following structure. A non-aqueous electrolyte secondary cell has a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a non-aqueous electrolyte having a non-aqueous solvent and an electrolytic salt. The positive electrode active material has a lithium-cobalt compound oxide having added therein at least zirconium. The non-aqueous electrolyte has LiBF4 at from 0.05 to 1.0 mass % of a total mass of the non-aqueous electrolyte and unsaturated cyclic carbonate at from 1.0 to 4.0 mass %. The true density ratio of the positive electrode is 0.72 or greater, the true density ratio being represented by formula 1 shown below: (Formula 1) True density ratio=active material apparent density of electrode active material layer÷true density of active material.