NOVELTY - A rechargeable lithium battery (100) comprises a positive electrode; a negative electrode; a separator interposed between the positive and negative electrodes and including a porous substrate having a coating layer formed on at least one side of the porous substrate; and an electrolyte including a lithium salt, a non-aqueous organic solvent, and an additive. The coating layer comprises a fluorine-based polymer and/or a ceramic.    USE - As rechargeable lithium battery (claimed) used in a smart phone, tablet personal computer, and a net book.    ADVANTAGE - In the present rechargeable lithium battery, when the fluorine-based polymer is coated on at least one side of the porous substrate to manufacture a separator, the fluorine-based polymer is physically cross-linked with binders that are respectively present in the positive and negative electrodes, which further improves adherence between the separator and the electrodes. When the ceramic is coated on at least one side of the porous substrate of a separator, the porous substrate can be structurally prevented from directly contacting active material layers that are respectively present on the positive and negative electrodes. When the porous substrate directly contacts the active material layers, active materials work as an oxidizing catalyst and thus, oxidizes the porous substrate and elutes metal ions, but, the elution of metal ions can be suppressed by coating the porous substrate with the ceramic. In this way, a separator having the coating layer on at least one side of the porous substrate has excellent adherence to an electrode and thus, realize a rechargeable lithium battery having excellent safety and cycle-life characteristic. The coating layer has a thickness of 1-10 mu m, preferably 1-8 mu m. When the coating layer has a thickness within this range, the coating layer can accomplish excellent heat resistance and suppress thermal shrinkage and elution of metal ions. Thus, the present battery has high adherence between an electrode and a separator and improved safety.    DETAILED DESCRIPTION - A rechargeable lithium battery (100), either comprises a positive electrode, a negative electrode, a separator interposed between the positive and negative electrodes and including a porous substrate having a coating layer formed on at least one side of the porous substrate, and an electrolyte including a lithium salt, a non-aqueous organic solvent, and an additive of formula (I), where the coating layer comprises a fluorine-based polymer and/or a ceramic; or comprises a positive electrode, negative electrode, a separator interposed between the positive and negative electrodes and including a porous substrate and a coating layer formed on at least one side of the porous substrate, and an electrolyte including a lithium salt and a non-aqueous organic solvent, where the coating layer comprises a fluorine-based polymer, and/or a ceramic, and an additive of formula (I).    R1-R3=H, or T1;    T1=1-20C alkyl, 2-20C alkenyl, 2-20C alkynyl, 1-20C alkoxy, 3-20C cycloalkyl, 3-20C cycloalkenyl, 3-20C cycloalkynyl, 6-30C aryl, or epoxy (all optionally substituted).    At least one of the R1-R3 is optionally substituted epoxy group. An INDEPENDENT CLAIM is included for fabricating a rechargeable lithium battery, either involving coating at least one side of a porous substrate with a coating layer material to fabricate a separator; preparing an electrode assembly (10) including the separator, a positive electrode, and a negative electrode; putting the electrode assembly into a battery case (20); mixing a lithium salt, a non-aqueous organic solvent, and the additive (I) to prepare an electrolyte; injecting the electrolyte into the battery case; and heating and pressing the battery case including the electrolyte, where the coating layer material comprises a fluorine-based polymer, and/or a ceramic; or involving coating at least one side of a porous substrate with a coating layer material to fabricate a separator; preparing an electrode assembly including the separator, a positive electrode, and a negative electrode; putting the electrode assembly into a battery case; mixing a lithium salt, and a non-aqueous organic solvent to prepare an electrolyte; injecting the electrolyte into the battery case; and heating and pressing the battery case including the electrolyte, where the coating layer material comprises a fluorine-based polymer, and/or a ceramic, and the additive (I).    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a rechargeable lithium battery.    Electrode assembly (10)    Electrode tab (13)    Battery case (20)    Rechargeable lithium battery (100)