Secondary battery and vehicle including secondary battery

A secondary battery comprising a positive electrode, a nonaqueous solvent, and a negative electrode,

• wherein the nonaqueous solvent comprises an ionic liquid at greater than or equal to 50 vol % and less than or equal to 95 vol % and an organic solvent comprising a fluorinated cyclic carbonate,
• wherein the ionic liquid comprises a lithium salt, an imidazolium, and a bis(fluorosulfonyl) imide anion, and
• wherein a viscosity of the nonaqueous solvent at −15° C. is lower than a viscosity of the ionic liquid at −15° C.

A nonaqueous solvent comprising

• an ionic liquid at greater than or equal to 50 vol % and less than or equal to 95 vol % and an organic solvent comprising a fluorinated cyclic carbonate represented by Structural Formula (H15),
• wherein the ionic liquid comprises a lithium salt, an imidazolium cation represented by Structural Formula (111), and a bis(fluorosulfonyl) imide anion represented by Structural Formula (H11), and
• wherein a viscosity of the nonaqueous solvent at 20° C. is lower than a viscosity of the ionic liquid at 20° C.

A secondary battery comprising a positive electrode, a nonaqueous solvent, and a negative electrode,

• wherein the nonaqueous solvent comprises an ionic liquid at greater than or equal to 50 vol % and less than or equal to 95 vol % and an organic solvent comprising a fluorinated cyclic carbonate,
• wherein the ionic liquid comprises a lithium salt, an imidazolium cation, and a bis(fluorosulfonyl) imide anion, and
• wherein a viscosity of the nonaqueous solvent at 20° C. is lower than a viscosity of the ionic liquid at 20° C.