| 摘要 |
An additive with which a nonaqueous-electrolyte secondary battery or nonaqueous-electrolyte electric-double-layer capacitor having excellent low- temperature properties while retaining necessary battery properties, etc. ca n be produced; and a nonaqueous-electrolyte secondary battery and a nonaqueous - electrolyte electric-double-layer capacitor both containing the additive. Th e additive is characterized by containing at least tautomers of a phosphazene derivative which are represrnted by general formulae (1) and (2), wherein R1 , R2, and R3 each represents a monovalent substituent or a halogen element; X represents a substituent containing at least one of carbon, silicon, germanium, tin, nitrogen, phosphorus, arsenic, antimony, bismuth, oxygen, sulfur, selenium, tellurium, and polonium; and Y1 and Y2 each represents a divalent connecting group, divalent element, or single bond. |
