NOVELTY - Secondary battery (I) comprises a cathode (21), an anode (22) and an electrolytic solution, where: the anode includes an anode active material layer (22B) including many anode active material particles, which include silicon as a constituent element, and at least one of an oxide-containing film and a metal material as a constituent element; and the electrolytic solution includes a solvent including isocyanate compounds (A).    USE - The electrolytic solution is useful in secondary battery (claimed). (I) is useful as lithium-ion secondary battery.    ADVANTAGE - The electrolytic solution has improved chemical stability, so decomposition reaction of the electrolytic solution during charge and discharge is prevented, hence improves cycle characteristics while securing initial charge-discharge characteristics, and storage characteristics.    DETAILED DESCRIPTION - Secondary battery (I) comprises a cathode (21), an anode (22) and an electrolytic solution, where: the anode includes an anode active material layer (22B) including many anode active material particles, which include silicon as a constituent element, and at least one of an oxide-containing film and a metal material as a constituent element; the oxide-containing film covers the surfaces of the anode active material particles; the metal material includes a metal element, which is not alloyed with an electrode reactant, and being arranged in a gap in the anode active material layer; and the electrolytic solution includes a solvent including isocyanate compounds (A) of formulae (R1-X-N=C=O) and/or (R2-(N=C=O)z).    R1 = univalent organic group;    X = C(=O), -O-C(=O)-, -S(=O)-, -O-S(=O)-, -S(=O)2- or -O-S(=O)2-, where X is bonded to C in R1;    R2 = z-valent organic group; and    z = 2 or more, where N in an isocyanate group is bonded to C in R2.    An INDEPENDENT CLAIM is included for an electrolytic solution comprising a solvent including an isocyanate compound of formula (R1-(C(=O)-N=C=O)z) (17a).    DESCRIPTION OF DRAWING(S) - The figure shows a sectional view of the configuration of a secondary battery.    Cathode (21)    Anode (22)    Anode current collector (22B) Anode active material layer (22A)    Separator. (23)