NOVELTY - A lithium battery electrolyte (26) contains non-aqueous organic solvent, lithium salt, and additive comprising compound (I) and sulfone-based compound and/or poly(ester)(meth)acrylate. Compound (I) is 3-fluoroanisole, 3-chloroanisole, 3-bromoanisole, 4-fluoroanisole, 4-chloroanisole, 4-bromoanisole, 2,4-difluoroanisole, 3,5-difluoroanisole, and/or 3-chloro-5-fluoroanisole.    USE - For lithium battery.    ADVANTAGE - The electrolyte improves the safety of a battery during overcharge and inhibits swelling of battery resulting from gas generation by using an additive comprising compound (I) and sulfone-based compound and/or poly(ester)(meth)acrylate. The additive consumes the overcurrent by forming a polymerization coating layer with ionic/electric conductivity and inhibits an increase of battery potential. The electrolyte reduces overcharge and improves electrochemical characteristics of the battery.    DETAILED DESCRIPTION - A lithium battery electrolyte contains non-aqueous organic solvent, lithium salt, and additive comprising compound of formula (I) and sulfone-based compound and/or poly(ester)(meth)acrylate.    R1=1-10C alkyl, 1-10C alkoxy, or 6-10C aryl, preferably Me, Et, or OMe;    X=halo;    m, n=1-5; and    m+n=less than or equal to6.    Compound (I) is 3-fluoroanisole, 3-chloroanisole, 3-bromoanisole, 4-fluoroanisole, 4-chloroanisole, 4-bromoanisole, 2,4-difluoroanisole, 3,5-difluoroanisole, and/or 3-chloro-5-fluoroanisole. INDEPENDENT CLAIMS are included for:    (1) preparation of electrolyte by adding compound (I) and sulfone-based compound and/or poly(ester)(meth)acrylate to lithium salt-containing organic solution to prepare a composition for polymer electrolyte, and impregnating or coating the composition on a current collector to prepare a solid polymer electrolyte; and    (2) a lithium battery comprising the electrolyte.    DESCRIPTION OF DRAWING(S) - The figure is a cross-sectional view of a lithium secondary battery cell.    Positive and negative electrodes (2, 4)    Separator (6)    Electrode assembly (8)    Battery case (10)    Cap plate (12)    Sealing gasket (14)    Safety vent (16)    Positive and negative electrode tabs (18, 20)    Insulators (22, 24)    Electrolyte (26)