TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: Compound (I) is Li+((PF(CN)5)-), Mg2+((PF(CN)5)-)2, Zn2+((PF(CN)5)-)2, Ca2+((PF(CN)5)-)2, (N(n-Bu)4)+((PF(CN)5)-), (P(n-Bu)4)+((PF(CN)5)-), compound of formula (aa), 1,3-dimethylimidazolium ((PF(CN)5)-), 1-ethyl-3-methylimidazolium ((PF(CN)5)-), and/or 1-propyl-3-methylimidazolium ((PF(CN)5)-). Compound (I) is compound of formula ((n-Bu)4N)(PF5(CN)) (13), compound of formula ((n-Bu)4N)(cis-PF4(CN)2) (14), compound of formula ((n-Bu)4N)(PF4(CN)2) (mixture of cis and trans) (14a), compound of formula ((n-Bu)4N)(trans-PF4(CN)2) (14b), compound of formula ((n-Bu)4N)(mer-PF3(CN)3) (15), compound of formula ((n-Bu)4N)(PF3(CN)3) (mixture of fac and mer) (15a), compound of formula ((n-Bu)4N)(fac-PF3(CN)3) (15b), compound of formula ((n-Bu)4N)(trans-PCl2(CN)4) (17), compound of formula ((n-Bu)4N)(PCl3(CN)3) (mixture of fac and mer) (18), compound of formula ((n-Bu)4N)(fac-PCl3(CN)3) (18a), compound of formula ((n-Bu)4N)(mer-PCl3(CN)3) (18b), compound of formula ((n-Bu)4N)(trans-PCl4(CN)2) (19), compound of formula ((n-Bu)4N)(cis-PCl4(CN)2) (20), and compound of formula ((n-Bu)4N)(PF(CN)5) (21). Electrolyte formulation comprises solvent selected from ethylene carbonate, propylene carbonate, gamma -butyrolactone, gamma -valerolactone, delta -valerolactone, 1,2-dimethoxyethane, diethoxyethane, ethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, 1,4-dioxane, ethanol, ethylene glycol monomethyl ether, polyethylene glycol monoalkyl ether, ethylene glycol, propylene glycol, polyethylene glycol, tetrahydrofuran, 2-methyltetrahydrofuran, acetonitrile, glutarodinitrile, propionitrile, valeronitrile, methoxyacetonitrile, benzonitrile, methyl acetate, ethyl acetate, ethyl propionate, trimethyl phosphate, triethyl phosphate, N-methylpyrrolidone, 2-methyl-1,3-dioxolane, N-butylbenzimidazole, sulfolane, dimethyl sulfoxide, formamide, N,N-dimethylformamide, and/or nitromethane. Electrolyte formulation comprises salt e.g. iodide of group 1 metal ion and ionic compound of formula (I-Cat-n). Ionic compound is compound of formula (CatORGn+)t1(AnINORGq-)t2 (I-IonLiqu) or compound of formula (CatINORGn+)t1(AnINORGq-)t2 (II-IonLiqu). Electrolyte formulation comprises redox couple selected from Br-/Br2, I-/I3, SCN-/SCN2, SeCN-/SeCN2, and bipyridine cobalt (III/II).AnINORGq-=Br-, I-, SCN-, BF4-, PF6-, CF3SO3-, (CF3SO2)2N-, (FSO2)2N-, anion of 1-20C monocarboxylic aliphatic acid, N(CN)2-, C(CN)3-, and/or B(CN)4-;Catn+=formula (bb), 1,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium, 1-propyl-3-methylimidazolium, 1-allyl-3-methylimidazolium, 1-methyl-3-hexylimidazolium, 1-ethylimidazolium, and/or 1-butyl-2,3-dimethylimidazolium;n, q, t1, t2=1; andCatINORGn+=Li+, Na+, K+, Ag+, Mg2+, Zn2+, Ca2+, Ba2+, H3O+, and/or H5O2+. Preferred Definitions:    CatINORGn+=Li+, Na+, K+, Mg2+, Ca2+, Ti4+, V4+, v3+ v2+ Cr3+, Fe4+, Fe3+, Fe2+, Co4+, Co3+, Co2+, Cu4+, Cu3+, Cu2+, Cu+, Ag2+, Ag+, Zn2+, Zn+, Al3+, Sn4+, Sn2+, Pb4+, Pb2+, Sb3+, Eu3+, Gd3+, NH4+, H3O+, or H5O2+;    CatORGn+=cyclopropenylium, 1,2,3-triphenylcyclopropenylium, tri-tert.-butylcyclopropenylium, 1,2,3-tris(diethylamino)cyclopropenylium, 1,2,3-tris(trimethylsilyl)cyclopropenylium, tropylium, or 1,2,3,4,5,6,7-heptaphenylcyclohepta-2,4,6-trien-1-ylium; and    Catn+=CatORG-B+, formula (cc), Li+, Na+, K+, Mg2+, or Zn2+.