TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The lithium salt is lithium hexafluorophosphate.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Solution: The organic electrolytic solution comprises the phosphate compound (I) (0.5 - 20, preferably 1 - 15 wt.%); and lithium salt (0.5 - 2.0 M).Preferred Components: The first solvent having high permittivity is ethylene carbonate, butylene carbonate and/or gamma-butyrolactone (preferably ethylene carbonate). The second solvent having low boiling point is dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, dipropyl carbonate, dimethoxyethane, diethoxyethane and/or aliphatic ester derivatives (preferably diethyl carbonate). The phosphate compound is heterocyclic compound of formula (Ia) or of formula P(OCH2R4)(OCH2R5)(OCH2R6).R4 - R6 = H or 1-20C alkyl (optionally substituted by halogen).    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The first solvent having high permittivity is polypropylene carbonate. SPECIFIC COMPOUNDS - 4-Methyl-2-(2,2,3,3-tetrafluoropropoxy)-1,3,2-dioxaphosphorane, 4,5-dimethyl-2-(2,2,3,3-tetrafluoropropoxy)-1,3,2-dioxaphosphorane and tris(2,2,3,3-tetrafluoropropoxy)phosphate are specifically claimed as compound (I).    EXAMPLE - Graphite based powder (96 wt.%) as an anode active material, poly(vinylidene fluoride) (4 wt.%) as a binder, and N-methyl pyrrolidone (NMP) (100 ml) were mixed and a ceramic ball was added to the mixture. The mixture was stirred for 10 hours. The mixture was coated on a copper film having a thickness of 19 microns and dried for 10 hours at 90degreesC. The dried film was roll pressed to produce an anode having a thickness of 120 microns. A 100 microns-thick lithium metal layer was pressed on a 20 microns-thick copper foil to give an electrode having a thickness of 120 microns. A battery cell (test) was prepared using the anode having a size of 2x3 cm2, a polytetrafluoroethylene separator, lithium electrode as a counter electrode, and organic electrolytic solution (S1) (prepared by organic solvent containing ethylene carbonate (30 vol.%), diethyl carbonate (70 vol.%), 4-methyl-2-(2,2,3,3-tetrafluoropropoxy)-1,3,2-dioxaphosphorane (1 wt.%) as an additive, and lithium hexafluorophosphate (1.3M)). Another battery cell (control) was prepared similarly but using electrolytic solution without containing 4-methyl-2-(2,2,3,3-tetrafluoropropoxy)-1,3,2-dioxaphospholane. The cells were charged with a constant current of 60 mA per 1 g of the active material until a voltage of 0.001 V with respect to the lithium electrode was reached. The cells were then continuously charged with a constant voltage of 0.001 V until the current decreased to 5 mA per 1 g of the active material. Subsequently, the cells were discharged with a constant current of 60 mA per 1 g of the active material until a voltage of 1.5 V was reached. As a result, the charge/discharge capacity was obtained and the charge/discharge efficiency was measured. The charge/discharge efficiency (%) after first cycle for test/control was found to be 90/87. The test cells had irreversible capacities of 13 - 23 mAh/g, but control cells had irreversible capacities of 28 - 29 mAh/g. The improvement in the charge/discharge properties results from improved electrochemical stability at the surface of the anode due to bulky functional groups and fluorine in the phosphate compound, which improves the properties of the solid electrolyte interface (SEI) membrane.