TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The lithium manganese oxide is of formula LiMnO2, LiMnO3, LiMn2O3, Li1+xMn2-xO4, composite oxide of formula LiMn2-x1Mx1O2, Li2Mn3M'O8 or LiMn2O4 (in which a portion Li is substituted by alkaline earth metal ions) (preferably LiMn2O4, LiNi0.5Mn0.5O2 or LiNi1/3Mn1/3Co1/3O, especially LiNi1/3Mn1/3Co1/3O).x=0 - 0.33;x1=0.01 - 0.1;M=Co, Ni, Fe, Cr, Zn and/or Ta;M'=Fe, Co, Ni, Cu and/or Zn.The non-graphitic carbon material is hard carbon. Propylene carbonate (PC) or a mixed solvent of PC and a linear carbonate is used as a solvent of the electrolyte. Preferred Definitions:    R=butyl.    SPECIFIC COMPOUNDS - Tetrabutylammonium tetrabutylborate (Ia); tetrabutylammonium tetrafluoroborate, tetrabutylammonium tetraphenylborate, tetrabutylammonium hexafluorophosphate and tetrabutylphosphonium tetrafluoroborate are specifically claimed as the salt (I).    EXAMPLE - LiNi1/3Mn1/3Co1/3O2 as a cathode active material, Super-P as a conductive material and polyvinylidene fluoride (PVDF) as a binder in a weight ratio of 85:10:5 were mixed in a solvent (N-methylpyrrolidone) to prepare a slurry. The resulting slurry was uniformly applied to aluminum foil, dried in a convection oven at 130degreesC, and pressed under predetermined pressure to fabricate a cathode. Amorphous carbon as an anode active material and polyvinylidene fluoride (PVDF) as a binder in a weight ratio of 95:5 were mixed in a solvent (N-methylpyrrolidone) to prepare a slurry. The resulting slurry was uniformly applied to copper foil, dried in a convection oven at 130degreesC, and pressed under predetermined pressure to fabricate an anode. A lithium salt-containing non-aqueous electrolyte was prepared by adding 1M LiPF6 to a mixed solvent of polycarbonate/dimethyl carbonate (ratio 70:30), followed by addition of (C4H9)4NB(C4H9)4 (3 wt.%). Then, Celgard (RTM: porous polyethylene film) as a separator was interposed between the anode and cathode prepared as above, and the above-prepared lithium salt-containing non-aqueous electrolyte was added to the resulting electrode assembly in a dry box under argon atmosphere, thus fabricating a lithium-ion polymer battery (test). A lithium-ion polymer battery (comparative) was fabricated in the same manner as in except that (C4H9)4NB(C4H9)4 was not added to the electrolyte. Power output of the battery at -20degreesC was measured for both the batteries. The power output was 113/100% respectively for the test/comparative battery. Thus the test battery exhibited superior power output at a low temperature, as compared to the comparative battery which had no salt.