TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The electrolyte solution further contains a non-aqueous solvent. The non-aqueous solvent is chosen from propylene carbonate, ethylene carbonate, butylene carbonate, sulfolane, methyl sulfolane, acetonitrile, (gamma )-butyrolactone, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, xylene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene and 1,4-dichlorobenzene. Preferred Definitions:    R4,R5=H, methyl or ethyl;    X-=BF4-, PF6-, AsF6-, SbF6-, N(RfSO3)2-, C(RfSO3)3- or RfSO3-;and    Rf=1-12C fluoroalkyl.    EXAMPLE - 70% aqueous solution of ethylamine (in weight parts) (152), 25% aqueous solution of phosphine (160) and sulfuric acid (12) were added to the reaction flask. A mixture of 40% aqueous solution of glyoxal (172) and acetaldehyde (102) was dripped at 40-50degrees C, for 4 hours in nitrogen atmosphere. After dripping, the mixture was aged at 45degrees C for 1 hour to obtain reaction mixture. Then, the moisture content of the reaction mixture was removed by evaporating and distilling the mixture, to obtain 1-ethyl-2-methyl-phosphazole. 1-Ethyl-2-methyl-phosphazole (127), methyl iodide (142) and tetrahydrofuran (1000) were mixed and dissolved uniformly. Then, the mixture was heated at 100degrees C and cooled at 30degrees C, to obtain an iodide salt of phosphazole cation. Silver oxide (232), ion exchange water (200) and 42 wt.% fluoroboric-acid aqueous solution (209) were mixed with the obtained iodide salt (269). The mixture was washed using methanol, and solvent was removed, to obtain electrolyte (243) which was tetrafluoroborate salt of phosphazole cation of formula (I). The obtained electrolyte had purity of 99%. The obtained electrolyte (20) and propylene carbonate (80) were uniformly mixed at 25degrees C. Molecular sieves (3) were added to the mixed solution (100), reacted at 25degrees C for 60 hours, dried and electrolyte solution was obtained. The obtained electrolyte solution had a moisture content of 35 ppm. The winding type electric-double-layer capacitor was produced using the obtained electrolyte solution. The electric-double-layer capacitor had withstand voltage of 2.46 V and capacitance retention rate of 95%.