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Electrolyte for a lithium battery and a lithium battery comprising the sameRelated Patent Categories: Chemistry: Electrical Current Producing Apparatus, Product, And Process, Current Producing Cell, Elements, Subcombinations And Compositions For Use Therewith And Adjuncts, Include Electrolyte Chemically Specified And Method, Chemically Specified Organic Solvent Containing, Plural Organic Solvents (i.e., Solvent Mixture)Electrolyte for a lithium battery and a lithium battery comprising the same description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060194118, Electrolyte for a lithium battery and a lithium battery comprising the same. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATION [0001] This application claims priority to and the benefit of Korean Patent Application No. 110-2005-0016691 filed in the Korean Intellectual Property Office on Feb. 28, 2005, the entire content of which is incorporated herein by reference. FIELD OF THE INVENTION [0002] The present invention relates to an electrolyte for a lithium battery and a lithium battery comprising the same, and more particularly, to an electrolyte which improves battery safety. BACKGROUND OF THE INVENTION [0003] Portable electronic devices are becoming smaller and lighter due to advancements in the high-tech electronic industry. As a result, portable electronic devices are increasingly being used. The increased need for batteries having high energy density for use as power sources for these portable electronic devices has led to recent research into lithium secondary batteries. [0004] Lithium secondary batteries have average discharge potentials of about 4 V, and more particularly 3.7 V. These lithium secondary batteries are essential to the digital generation because they are indispensable energy sources for portable digital devices such as the "3C" devices, i.e. cellular telephones, notebook computers, and camcorders, as well as other portable electronic devices. [0005] Research has also been conducted on batteries to develop effective safety characteristics such as the prevention of overcharge. When a battery is overcharged, excess lithium ions are deposited on the positive electrode, and excess lithium ions are inserted into the negative electrode, making the positive and negative electrodes thermally unstable. An explosion may occur due to the decomposition of the electrolytic organic solvent causing thermal runaway which can seriously decrease battery safety. [0006] To overcome these problems, an aromatic compound, such as an oxidation-reduction agent, or "redox shuttle additive," has been added to the electrolyte. For example, U.S. Pat. No. 5,709,968 to Shimizu discloses the use of a benzene compound, such as 2,4-difluoroanisole, in a non-aqueous lithium ion secondary battery to prevent thermal runaway resulting from overcharge current. Also, U.S. Pat. No. 5,879,834 to Mao discloses the use of electrochemically polymerized aromatic compounds, such as biphenyl, 3-chlorothiophene, furan, etc., to improve battery safety by increasing the internal resistance of the battery during unusual overvoltage conditions. [0007] Redox shuttle additives quickly increase the temperature inside the battery by the heat produced by the oxidation-reduction reaction. In addition, the additive closes the pores of the separator by quickly and uniformly fusing the separator to inhibit overcharge reactions. The polymerization reaction of these redox shuttle additives consumes the overcharge current, thereby improving battery safety. [0008] However, the need for high capacity batteries is increasing, and these redox shuttle additives cannot provide the high level of safety required of such high capacity batteries. Therefore, a need exists for an electrolyte capable of preventing overcharge and ensuring battery safety. SUMMARY OF THE INVENTION [0009] In one embodiment of the present invention, a lithium battery electrolyte imparts improved battery safety. [0010] In another embodiment of the present invention, a lithium battery comprises an electrolyte which imparts improved battery safety. [0011] One embodiment of the electrolyte for a lithium battery includes a non-aqueous organic solvent, a lithium salt, and an additive which is stable at voltages ranging from about 2.5 to about 4.8 V. The additive is capable of forming a chelating complex with a transition metal. [0012] In another embodiment of the present invention, a lithium battery includes an electrolyte having a non-aqueous organic solvent, a lithium salt, and an additive which is stable at voltages ranging from about 2.5 to about 4.8 V. The electrolyte additive is capable of forming a chelating complex with a transition metal. The battery further comprises a positive electrode and a negative electrode. The positive electrode comprises a positive active material capable of intercalating and deintercalating lithium ions. The negative electrode comprises an active material selected from the group consisting of materials capable of intercalating/deintercalating lithium ions, lithium metals, lithium-containing alloys, and materials capable of forming lithium-containing compounds by reversibly reacting lithium. BRIEF DESCRIPTION OF THE DRAWINGS [0013] These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which: [0014] FIG. 1 is a cross-sectional view of a lithium battery according to one embodiment of the present invention; [0015] FIG. 2 is a graph of the voltammetry measurements of a lithium secondary battery prepared according to Experimental Example 1; and [0016] FIG. 3 is a graph of the current, temperature, and voltage characteristics, measured at 1.5 C, during overcharging of lithium batteries prepared according to Example 2 and Comparative Example 2. DETAILED DESCRIPTION OF THE PRESENT INVENTION [0017] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. However, one of ordinary skill in the art understands that various modifications may be made to the described embodiments, and that the invention is not limited to the described embodiments. Rather, the embodiments are described for illustrative purposes only. [0018] The present invention relates to an electrolyte for a lithium battery. FIG. 1 is a cross-sectional view of a non-aqueous lithium secondary battery according to one embodiment of the present invention. The battery 1 comprises an electrode assembly 8 contained within a battery case 10. The electrode assembly 8 includes a positive electrode 2, a negative electrode 4 and a separator 6 positioned between the positive and negative electrodes 2 and 4, respectively. The positive and negative electrodes 2 and 4, respectively, comprise active materials capable of intercalating and deintercalating lithium ions. The separator can comprise polyethylene, polypropylene, or a combination thereof. 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