TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Compositions: Phosphonium salts are liquid or solid at less than or equal to 100 degrees C and are additives. Phosphonium ionic liquids and/or phosphonium salts contain 1 cation and 1 anion pair, 1 anion and multiple cations, 1 cation and multiple anions, or multiple cations and multiple anions. Phosphonium-based cation is represented by formulae (CH3CH2CH2)2(CH3CH2)(CH3)P+, (CH3CH2CH2)(CH3CH2)(CH3)2P+, (CH3CH2)3(CH3)P+, (CH3CH2CH2)(CH3CH2)3P+, (CH3CH2)4P+, (CH3CH2CH2)3(CH3)P+, (CH3CH2CH2)3(CH3CH2)P+, (CH3CH2CH2)(CH3)3P+, (CF3CH2CH2)(CH3CH2)3P+, (CF3CH2CH2)3(CH3CH2)P+, (CF3CH2CH2)3(CH3)P+, or (CF3CH2CH2)4P+. Anions are represented by formulae PF6, (CF3)3PF3, (CF3)4PF2, (CF3CF2)4PF2, (CF3CF2CF2)4PF2, (-OC(=O)C(=O)O-)PF4, (-OC(=O)C(=O)O)(CF3)3PF, (-OC(=O)C(=O)O)3P, BF4, CF3BF3, (CF3)2BF2, (CF3)3BF, (CF3)4B, (-OC(=O)C(=O)O)BF2, (-OC(=O)C(=O)O)BF(CF3), (-OC(=O)C(=O)O)(CF3)2B, (-OS(=O)CH2S(=O)O-)BF2, (-OS(=O)CF2S(=O)O)BF2, (-OS(=O)CH2S(=O)O-)BF(CF3), (-OS(=O)CF2S(=O)O-)BF(CF3), (-OS(=O)CH2S(=O)O-)B(CF3)2, (-OS(=O)CF2S(=O)O-)B(CF3)2, CF3SO3, (CF3SO2)2N, (-OC(=O)C(=O)O)PF2, (CF3CF2)3PF3, (CF3CF2CF2)3PF3, (-OC(=O)C(=O)O)2B, (-OC(=O)(CH2)nC(=O)O-)BF(CF3), (-OC(=O)CR2C(=O)O-)BF(CF3), (-OC(=O)CR2C(=O)O-)B(CF3)2, (-OC(=O)CR2C(=O)O-)2B, CF3BF(-OOR)2, CF3B(-OOR)3, CF3B(-OOR)F2, (-OC(=O)C(=O)C(=O)O-)BF(CF3), (-OC(=O)C(=O)C(=O)O-)B(CF3)2, (-OC(=O)C(=O)C(=O)O-)2B, (-OC(=O)CR1R2CR1R2C(=O)O-)BF(CF3), (-OC(=O)CR1R2CR1R2C(=O)O-)B(CF3)2, -O3SCF3, -O2CCF3, -O2CCF2CF2CF3, CF3BF3-, C(CN)3-, PF6, NO3-, -O3SCH3, BF4-, -O3SCF2CF2CF3, -O2CCF2CF3, -O2CH, -O2CC6H5, -OCN, CO32-, (-OC(=O)C(=O)O-)BF2-, (-OC(=O)C(=O)O-)(CF3)2B-, (-OC(=O)C(=O)O-)2B-, (CF3SO2)2N-, (CF3)2BF2-, (CF3)3BF-, CF3CF2BF3-, or -N(CN)2. Solvent is acetonitrile, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), methylethyl carbonate (MEC), methyl propionate (MP), fluoroethylene carbonate (FEC), fluorobenzene (FB), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), phenylethylene carbonate (PhEC), propylmethyl carbonate (PMC), diethoxyethane (DEE), dimethoxyethane (DME), tetrahydrofuran (THF), gamma -butyrolactone (GBL), and/or gamma -valerolactone (GVL). Electrolyte composition contains greater than or equal to 1 conventional non-phosphonium salts e.g. tetraethylammonium tetrafluoroborate (TEABF4), triethylmethylammonium tetrafluoroborate (TEMABF4), 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4), 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIIm), and/or 1-ethyl-3-methylimidazolium hexafluorophosphate (EMIPF6). Mole ratio of phosphonium ionic liquids or phosphonium salts and conventional salts is 1:100-1:1. Conventional salts are lithium-based salts e.g. lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonyl)imide (Li(CF3SO2)2N), and/or lithium bis(pentafluoromethanesulfonyl)imide (Li(CF3CF2SO2)2N).R, R1, R2=H or F. Preferred Definitions:    R1-R4=1-4C alkyl optionally substituted by F provided that greater than or equal to 2 groups are the same and none of the groups contain oxygen.