| abstract |
Disclosed is a highly safe secondary battery. In the secondary battery, a positive electrode is composed of an oxide which adsorbs/desorbs lithium ions; a negative electrode is composed of a carbon material which adsorbs/desorbs lithium ions; and an electrolyte solution is composed of an ionic liquid and a phosphate ester derivative. Consequently, the secondary battery can be highly safe. Since a phosphate ester and an ionic liquid are contained at the same time, high discharge capacity can be maintained even when the phosphate ester is used at a high concentration. |