TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The lithium salt is lithium hexafluorophosphate.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Solution: The organic electrolytic solution comprises the phosphine oxide compound (I) (0.5 - 20, preferably 1 - 10 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).    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The first solvent having high permittivity is polypropylene carbonate. Preferred Definitions:    R1 - R3=CH2 or -(CH2)m;    m=0 - 5;and    n=1.    SPECIFIC COMPOUNDS - Tris(trimethylsilyloxymethyl)phosphine oxide and tris(trimethylsilyloxy)phosphine oxide 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-tris(trimethylsilyloxymethyl)phosphine oxide (1 wt.%) as an additive, and lithium hexafluorophosphate (1.3M)). Another battery cell (control) was prepared similarly but using electrolytic solution without containing 4-tris(trimethylsilyloxymethyl)phosphine oxide. 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 95/91. The improvement in the charge/discharge properties results from improved electrochemical stability at the surface of the anode due to the phosphine oxide compound, which improves the properties of the solid electrolyte interface (SEI) membrane.