Lithium-ion secondary battery

Abstract

A lithium-ion secondary battery of the present invention includes a positive electrode, a negative electrode, a non-aqueous electrolytic solution, and a separator. The positive electrode includes, as a positive electrode active material, a lithium-containing oxide that contains at least one element selected from Co and Mn. The negative electrode includes, as a negative electrode active material, graphite having a d002 in X-ray diffraction of 0.338 nm or less and a carbonaceous material having a d002 in X-ray diffraction of 0.340 to 0.380 nm. The negative electrode active material contains the carbonaceous material in an amount of 5 to 15 mass %. The non-aqueous electrolytic solution contains LiBF4, a nitrile compound having one or more cyano groups, and LiPF6. The non-aqueous electrolytic solution contains the LiBF4 in an amount of 0.05 to 2.5 mass % and the nitrile compound in an amount of 0.05 to 5.0 mass %.

Dependencies are inferred from the claim text.