TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Composition: The concentration is greater than a molecular ratio of 0.2, 0.3, or 0.4. The electrolyte has a lithium ion transference number greater than 0.4, greater than 0.75, greater than 0.4, or greater than 0.6. Molar fraction or molecular ratio of the lithium salt in the electrolyte is greater than 0.2, greater than 0.3, or greater than 0.4. The electrolyte further contains an ionic liquid solvent and a first organic liquid solvent-to-ionic liquid solvent ratio is greater than 1/1. Preferred Components: The first organic liquid solvent is selected from 1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME), tetraethylene glycol dimethylether (TEGDME), poly(ethylene glycol) dimethyl ether (PEGDME), diethylene glycol dibutyl ether (DEGDBE), 2-ethoxyethyl ether (EEE), sulfone, sulfolane, ethylene carbonate (EC), dimethyl carbonate (DMC), methylethyl carbonate (MEC), diethyl carbonate (DEC), ethyl propionate, methyl propionate, propylene carbonate (PC), gamma-butyrolactone ( gamma -BL), acetonitrile (AN), ethyl acetate (EA), propyl formate (PF), methyl formate (MF), toluene, xylene, methyl acetate (MA), fluoroethylene carbonate (FEC), vinylene carbonate (VC), allyl ethyl carbonate (AEC), a hydrofloroether, and its combinations. The lithium salt is selected from lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium borofluoride (LiBF4), lithium hexafluoroarsenide (LiAsF6), lithium trifluoro-metasulfonate (LiCF3SO3), bis-trifluoromethyl sulfonylimide lithium (LiN(CF3SO2)2), lithium bis(oxalato)borate (LiBOB), lithium oxalyldifluoroborate (LiBF2C2O4), lithium oxalyldifluoroborate (LiBF2C2O4), lithium nitrate (LiNO3), lithium-fluoroalkyl-phosphates (LiPF3(CF2CF3)3), lithium bisperfluoro-ethysulfonylimide (LiBETI), lithium bis(trifluoromethanesulphonyl)imide, lithium bis(fluorosulphonyl)imide, lithium trifluoromethanesulfonimide (LiTFSI), an ionic liquid lithium salt, or its combination. The cathode active material is selected from a metal oxide, a metal oxide-free and sulfur-free inorganic material, an organic material, a polymeric material, its combination, or a combination with sulfur or lithium polysulfide. Metal oxide-free and sulfur-free inorganic material is selected from a transition metal dichalcogenide, a transition metal trichalcogenide, or its combination. The cathode active material is selected from titanium disulfide (TiS2), tantalum disulfide (TaS2), molybdenum disulfide (MoS2), niobium triselenide (NbSe3), manganese dioxide (MnO2), cobalt dioxide (CoO2), an iron oxide, a vanadium oxide, or its combination. It contains a vanadium oxide selected from vanadium dioxide (VO2), lithium vanadium oxide (LixVO2), vanadium pentoxide (V2O5), lithium vanadium pentoxide (LixV2O5), vanadate (V3O8), lithium vanadate (LixV34O8), LixV3O7, ternary vanadium oxide (V4O9), LixV4O9, V6O13, LixV6O13, their doped versions, their derivatives, and its combinations, where 0.1 not less than x not less than 5. It contains a layered compound LiMO2, spinel compound LiM2O4, olivine compound LiMPO4, silicate compound Li2MSiO4, Tavorite compound LiMPO4F, borate compound LiMBO3, or its combination, where M is a transition metal or a mixture of multiple transition metals. It contains an inorganic material selected from: (a) bismuth selenide or bismuth telluride, (b) transition metal dichalcogenide or trichalcogenide, (c) sulfide, selenide, or telluride of niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt, manganese, iron, nickel, or a transition metal; (d) boron nitride, or (e) its combination. The organic material or polymeric material is selected from poly(anthraquinonyl sulfide) (PAQS), a lithium oxocarbon, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), poly(anthraquinonyl sulfide), pyrene-4,5,9,10-tetraone (PYT), polymer-bound PYT, Quino(triazene), redox-active organic material, Tetracyanoquinodimethane (TCNQ), tetracyanoethylene (TCNE), 2,3,6,7,10,11-hexamethoxytriphenylene (HMTP), poly(5-amino-1,4-dyhydroxy anthraquinone) (PADAQ), phosphazene disulfide polymer (((NPS2)3)n), lithiated 1,4,5,8-naphthalenetetraol formaldehyde polymer, Hexaazatrinaphtylene (HATN), Hexaazatriphenylene hexacarbonitrile (HAT(CN)6), 5-Benzylidene hydantoin, Isatine lithium salt, Pyromellitic diimide lithium salt, tetrahydroxy-p-benzoquinone derivatives (THQLi4), N,N'-diphenyl-2,3,5,6-tetraketopiperazine (PHP), N,N'-diallyl-2,3,5,6-tetraketopiperazine (AP), N,N'-dipropyl-2,3,5,6-tetraketopiperazine (PRP), a thioether polymer, a quinone compound, 1,4-benzoquinone, 5,7,12,14-pentacenetetrone (PT), 5-amino-2,3-dihydro-1,4-dyhydroxy anthraquinone (ADDAQ), 5-amino-1,4-dyhydroxy anthraquinone (ADAQ), calixquinone, Li4C6O6, Li2C6O6, Li6C6O6, or its combination. The thioether polymer is selected from poly(methanetetryl-tetra(thiomethylene)) (PMTTM), poly(2,4-dithiopentanylene) (PDTP), a polymer containing poly(ethene-1,1,2,2-tetrathiol) (PETT) as a main-chain thioether polymers, a side-chain thioether polymer having a main-chain consisting of conjugating aromatic moieties, and having a thioether side chain as a pendant, poly(2-phenyl-1,3-dithiolane) (PPDT), poly(1,4-di(1,3-dithiolan-2-yl)benzene) (PDDTB), poly(tetrahydrobenzodithiophene) (PTHBDT), poly(1,2,4,5-tetrakis(propylthio)benzene) (PTKPTB), or poly(3,4(ethylenedithio)thiophene) (PEDTT). It contains a phthalocyanine compound selected from copper phthalocyanine, zinc phthalocyanine, tin phthalocyanine, iron phthalocyanine, lead phthalocyanine, nickel phthalocyanine, vanadyl phthalocyanine, fluorochromium phthalocyanine, magnesium phthalocyanine, manganous phthalocyanine, dilithium phthalocyanine, aluminum phthalocyanine chloride, cadmium phthalocyanine, chlorogallium phthalocyanine, cobalt phthalocyanine, silver phthalocyanine, a metal-free phthalocyanine, its chemical derivative, or its combination. The ionic liquid solvent is selected from a room temperature ionic liquid having a cation selected from tetraalkylammonium, di-, tri-, or tetra-alkylimidazolium, alkylpyridinium, dialkyl-pyrrolidinium, dialkylpiperidinium, tetraalkylphosphonium, trialkylsulfonium, or its combination. It is selected from a room temperature ionic liquid having an anion selected from (BF4)-, (B(CN)4)-, (CH3BF3)-, (CH2CHBF3)-, (CF3BF3)-, (C2F5BF3)-, (n-C3F7BF3)-, (n-C4F9BF3)-, (PF6)-, (CF3CO2)-, (CF3SO3)-, (N(SO2CF3)2)-, (N(COCF3)(SO2CF3))-, (N(SO2F)2)-, (N(CN)2)-, (C(CN)3)-, SCN-, SeCN-, (CuCl2)-, (AlCl4)-, (F(HF)2.3)-, or its combination. The anode contains an anode active material selected from lithium metal, a lithium metal alloy, a mixture of lithium metal or lithium alloy with a lithium intercalation compound, a lithiated compound, lithiated titanium dioxide, lithium titanate, lithium manganate, a lithium transition metal oxide, Li4T15O12, or its combination. It contains an anode active material selected from: (a) silicon (Si), germanium (Ge), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), zinc (Zn), aluminum (Al), nickel (Ni), cobalt (Co), manganese (Mn), titanium (Ti), iron (Fe), and cadmium (Cd), and its lithiated versions; (b) alloys or intermetallic compounds of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, or Cd with other elements, and its lithiated versions, where the alloys or compounds are stoichiometric or non-stoichiometric; (c) oxides, carbides, nitrides, sulfides, phosphides, selenides, and tellurides of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, Fe, Ni, Co, Ti, Mn, or Cd, and their mixtures or composites, and its lithiated versions; (d) salts and hydroxides of Sn and its lithiated versions; (e) carbon or graphite materials and its prelithiated versions; and its combinations. Preferred Device: The rechargeable lithium cell is a lithium-sulfur cell or lithium-ion sulfur cell containing a sulfur cathode having sulfur or lithium polysulfide as a cathode active material. It is a lithium metal secondary cell or a lithium-ion cell, excluding lithium-sulfur cell. The rechargeable lithium cell further comprises a layer of protective material disposed between the anode and the electrolyte where the protective material is a lithium ion conductor.