Nonaqueous electrolytic capacitor element

A nonaqueous electrolytic capacitor element, comprising:

• a positive electrode comprising a positive electrode active material capable of intercalating or deintercalating anions,
• a negative electrode comprising carbon powder as a negative electrode active material, wherein the carbon powder of the negative electrode active material has a BET specific surface area by nitrogen adsorption of 4,600 m2/g, and
• a nonaqueous electrolyte, which comprises a nonaqueous solvent, an electrolyte salt consisting of LiPF6, and a compound comprising a site capable of bonding to a halogen-containing anion, wherein the compound comprising a site capable of bonding to a halogen-containing anion is at least one member selected from the group consisting of a compound represented by formula (1), and a compound represented by formula (2):
• where R1, R2 and R3 are independently an alkyl group, an aryl group, or a heteroaryl group, each of which is optionally substituted with a halogen atom, an alkyl group, an alkoxide group, a thiol group, a thioalkoxide group, an aryl group, an ether group, or a thioether group,
• where R4, R5 and R6 are independently an alkyl group, an aryl group, or a heteroaryl group, each of which is optionally substituted with a halogen atom, an alkyl group, an alkoxide group, a thiol group, a thioalkoxide group, an aryl group, an ether group, or a thioether group;
• and wherein an amount of the compound comprising a site capable of bonding to an a halogen containing anion comprising a halogen atom is 0.5% by mass or greater and 5% by mass or less relative to an amount of the nonaqueous electrolyte;
• wherein the electrolyte salt is present in an amount higher than 2 mol/L, and wherein the capacitor element has a maximum voltage during charging that is higher than 4.5 V.