Abstract: A secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution. The negative electrode includes a film covering a negative electrode active material layer. The electrolytic solution includes a chain carboxylic acid ester. According to an analysis of the film by inductively coupled plasma optical emission spectroscopy, a content of boron in the film is greater than or equal to 10 ?mol/m2 and less than or equal to 30 ?mol/m2, a content of sulfur in the film is greater than or equal to 20 ?mol/m2 and less than or equal to 70 ?mol/m2, and a ratio of the content of sulfur to the content of boron is greater than or equal to 1.0 and less than or equal to 3.0.

Abstract: A lithium-ion secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution that includes an alkoxy compound represented by CmX2m+1—O—(CX2)n—OH. Each X represents hydrogen (H) or a halogen, m is an integer of 1 or greater, n is an integer of 1 or greater, and (m+n) is 4 or greater.