Hybrid capacitor and separator for hybrid capacitors

Provided is a hybrid capacitor with an excellent long-term stability. A hybrid capacitor includes a positive electrode 1 including a positive-electrode active material layer 1a containing a carbon material employing a porous structure or a fibrous structure with an electric double layer capacity, and a negative electrode 2 including a negative-electrode active material 2a containing a material capable of adsorbing and releasing lithium ions. A lithium compound that traps protons is disposed between the positive-electrode active material layer 1a and the negative-electrode active material layer 2a. This hybrid capacitor further includes a separator 3 disposed between the positive-electrode active material layer 1a and the negative-electrode active material layer 2a, and the separator contains the lithium compound.