NOVELTY - Secondary battery comprises a cathode (21), an anode (22), and an electrolytic solution including a cyano compound.    USE - The secondary battery such as a lithium secondary battery is useful in a battery pack, an electric vehicle, an electric power storage system, an electric power tool and an electronic apparatus (all claimed) including mobile phones and personal digital assistants, where the electric vehicles include electric automobiles, the electric power storage systems include home electric power servers, and the electric power tools include electric drills.    ADVANTAGE - The light-weight secondary battery is compact with improved battery characteristics thus providing high electric power source and prolonged lifetime to the electronic apparatuses and vehicles.    DETAILED DESCRIPTION - Secondary battery comprises a cathode (21), an anode (22), and an electrolytic solution including a cyano compound of formula (R1-O-C(=O)-O-R2) (I) and/or (R3-C(=O)-O-R4) (II).    R1, R2 = optionally saturated hydrocarbyl, oxygen-containing saturated hydrocarbyl, cyano-group-containing group or halogenated groups, where each group is obtained by bonding two or more of the foregoing groups to one another, and R1 and R2 includes the cyano-group-containing group in which a cyano group is bonded to oxygen atom (O) at terminal of -O-C(=O)-O- bond with one or more carbon atoms in between, provided that (A) when one of the R1 and the R2 does not include the cyano-group-containing group but includes an unsaturated carbon bond and the other of the R1 and the R2 includes the cyano-group-containing group, then the number of the cyano group in the other of the R1 and the R2 is greater than or equal to 1, (B) when one of the R1 and the R2 include neither the cyano-group-containing group nor the unsaturated carbon bond and the other of the R1 and the R2 includes the cyano-group-containing group and the unsaturated carbon bond, then the number of the cyano group in the other of the R1 and the R2 is greater than or equal to 1, or (C) when one of the R1 and the R2 include neither the cyano-group-containing group nor the unsaturated carbon bond and the other of the R1 and the R2 includes the cyano-group-containing group but does not include the unsaturated carbon bond, then the number of the cyano group in the other of the R1 and the R2 is greater than or equal to 2;    R3 = optionally saturated hydrocarbyl, oxygen-containing saturated hydrocarbyl, halogenated groups of the foregoing groups, where each group is obtained by bonding two or more of the foregoing groups to one another; and    R4 = one of a cyano-group-containing group or its halogenated groups, where each group is obtained by bonding two or more of the foregoing groups to one another, and a cyano group in the cyano-group-containing group is bonded to an oxygen atom at a terminal of a -C(=O)-O- bond with one or more carbon atoms in between, provided that (D) when the R3 includes an unsaturated carbon bond, then the number of the cyano group in the R4 is greater than or equal to 1, (E) when the R3 does not include the unsaturated carbon bond and the R4 includes the unsaturated carbon bond, then the number of the cyano group in the R4 is greater than or equal to 1 and (F) when the R3 does not include the unsaturated carbon bond and the R4 does not include the unsaturated carbon bond, then the number of the cyano group in the R4 is greater than or equal to 2.    INDEPENDENT CLAIMS are included for:    (1) an electrolytic solution comprising the cyano compound;    (2) a battery pack comprising a secondary battery, a control section controlling a used state of the secondary battery, and a switch section switching the used state of the secondary battery according to an instruction of the control section, where the secondary battery includes a cathode, an anode, and the electrolytic solution;    (3) an electric vehicle comprising the secondary battery, a conversion section converting electric power supplied from the secondary battery into drive power, a drive section operating according to the drive power, and a control section controlling a used state of the secondary battery;    (4) an electric power storage system comprising the secondary battery, one or more electric devices supplied with electric power from the secondary battery, and a control section controlling the supplying of the electric power from the secondary battery to the one or more electric devices;    (5) an electric power tool comprising the secondary battery, and a movable section supplied with electric power from the secondary battery; and    (6) an electronic apparatus comprising the secondary battery as an electric power supply source.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-sectional view of a secondary battery.    Battery can (11)    Insulating plate (12)    Electrode body (20)    Cathode (21)    Anode. (22)