| abstract |
【Task】 To provide a lithium ion secondary battery capable of improving cycle characteristics. [Solution means] A lithium ion secondary battery comprising a positive electrode, a negative electrode, a separator positioned between the positive electrode and the negative electrode, and an electrolytic solution, The negative electrode contains silicon or a compound of silicon, and the porosity of the negative electrode is 25% to 38%. The electrolytic solution contains 0.1% by volume or more and 5.0% by volume or less of a fluorinated carbonate, and a carboxylic acid ester, The mass of the said electrolyte solution is 30 mass% or more and 45 mass% or less with respect to the total mass of the said positive electrode and the said negative electrode, The lithium ion secondary battery characterized by the above-mentioned. [Selected figure] Figure 1 |