| abstract |
A lithium ion secondary battery having a positive electrode, a negative electrode, and a nonaqueous electrolyte is provided. The positive electrode has a lithium transition metal composite oxide having a layered structure as a positive electrode active material. The positive electrode active material contains at least one metal element M 0 of Ni, Co, and Mn, further contains at least one metal element M ′ of Zr, Nb, and Al, and further contains W. When 2 g of the positive electrode active material and 100 g of pure water are stirred to prepare a suspension, and the suspension is filtered, the suspension per 1 g of the filtrate obtained by inductively coupled plasma mass spectrometry with respect to the filtrate obtained by the filtration. W elution amount is 0.025 mmol or less. |