Synthesis of Aromatic and Aliphatic N-Heterocyclic Salts and Their Application as Organic Electrolyte Supporters in Electrochemical Capacitor

Abstract

Aromatic and aliphatic N-heterocyclic chemical salts were synthesized by counter-anion-exchange reactions after substitution reactions in order to apply them as organic electrolyte supporters in an electrochemical capacitor (super capacitor). The aromatic N-heterocyclic salts were N-methylpyridinium tetrafluoroborate ([MPy]+[BF4]−), N-methylpyridinium hexafluorophosphate ([MPy]+[PF6]−), 1,3-dibuthylimidazolium tetrafluoroborate ([DI]+[BF4]−), 1,3-dibuthylimidazolium hexafluorophosphate ([DI]+[PF6]−), 1-buthyl-4-methyl-1,2,4-triazolium tetrafluoroborate ([BMTA]+[BF4]−), and 1-buthyl-4-methyl-1,2,4-triazolium hexafluorophosphate ([BMTA]+[PF6]−). The aliphatic N-heterocyclic salts were N,N-dimethylpiperilidium tetrafluoroborate ([DMP]+[BF4]−), N,N-dimethylpiperilidium hexafluorophosphate ([DMPy]+[PF6]−), N,N-dimethylpyrrolidium tetrafluoroborate ([DMPy]+[BF4]−) and N,N-dimethylpyrrolidium hexafluorophosphate ([DMPy]+[PF6]−), 1-ethyltriethamine tetrafluoroborate ([E-TEDA]+[BF4]−), and 1-ethyltriethamine hexafluorophosphate ([E-TEDA]+[PF6]−), respectively. We confirmed the successful synthesis of the aromatic and aliphatic N-heterocyclic chemical salts by 1H-NMR, FT-IR, and GC/MS analysis before conducting the counter-anion-exchange reactions. Then, we determined the electrochemical potential of vanadium acetylacetonate (V(acac)3) under acetonitrile in the presence of the N-heterocyclic chemical salts as energy-storage chemicals. By cyclic voltammetry, the maximum voltages with the N-heterocyclic chemical salts in acetonitrile reached 2.2 V under a fixed current value. Charge-discharge experiments were performed in the electrochemical capacitor with an anion-exchange membrane using a non-aqueous electrolyte prepared with a synthesized N-heterocyclic salt in acetonitrile.