Abstract: A lithium ion secondary battery including a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte, the positive electrode including a positive electrode current collector and a positive electrode active material held on the positive electrode current collector, the positive electrode active material including a lithium-containing transition metal oxide, the negative electrode including a negative electrode current collector and a negative electrode active material held on the negative electrode current collector, the negative electrode active material including at least one selected from the group consisting of lithium metal, lithium alloys, carbon materials, lithium-containing titanium compounds, silicon oxides, silicon alloys, zinc, zinc alloys, tin oxides and tin alloys, the nonaqueous electrolyte including a first salt formed between an organic cation and a first anion and a second salt formed between a lithiu