A purpose of the present invention is to provide a lithium ion secondary battery which has further improved life characteristics. The lithium ion secondary battery of the present invention is characterized by comprising a positive electrode comprising a positive electrode active material that operates at 4.5 V or more with respect to lithium, and an electrolyte solution comprising an electrolyte solvent comprising a fluorinated ether, a cyclic sulfonic acid ester and LiN(FSO
2
)
2
.
Gubanov,V.A. et al., Journal of general chemistry of the USSR, 1965, vol. 35, p. 399 - 400