| 摘要 |
PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery having excellent cycle characteristics.SOLUTION: The lithium ion secondary battery comprises a positive electrode having a positive electrode active material capable of storing and releasing lithium ions; a negative electrode having negative electrode active material particles each comprising a core capable of storing and releasing lithium ions and composed of silicon or/and a silicon compound, and a coating covering the surface of the core, allowing lithium ions to pass through, and containing lithium fluoride; and an electrolyte containing a fluoride salt. In a spectrum obtained by X-ray photoelectron spectroscopy (XPS) using the AlKα (monochromatic) ray radiated at a voltage of 15 kV and a current of 10 mA, the integrated intensity ratio of the peak arising from the 1s orbit of fluorine to the peak arising from the 2p orbit of silicon at the surface of the negative electrode active material particles is 70 or lower. |
