| abstract |
A lithium ion capacitor includes a positive electrode, a negative electrode, and a non-protonic organic solvent electrolytic solution of a lithium salt. A positive electrode active material is a material capable of reversibly doping a lithium ion and/or an anion. A negative electrode active material is a material capable of reversibly doping a lithium ion. The lithium ion is doped in advance to either one or both of the negative electrode and the positive electrode so that a positive electrode potential after the positive electrode and the negative electrode are short-circuited is 2.0 V (relative to Li/Li + ) or less when capacitance per unit weight of the positive electrode is C + (F/g), weight of the positive electrode active material is W + (g), capacitance per unit weight of negative electrode is C − (F/g), and weight of the negative electrode active material is W − (g), a value of (C − ×W − )/(C + ×W + ) is 5 or more. |