Lithium secondary battery and a method for preparing the same

A lithium secondary battery, comprising:

• a positive electrode including a material that is capable of reversible intercalation/deintercalation of lithium ions as a positive active material;
• a negative electrode including a lithium metal, a lithium-containing alloy, a material that is capable of reversible intercalation/deintercalation of lithium ions as a negative active material or a material that is capable of reversibly forming a lithium-containing compound;
• a separator interposed between the positive and negative electrodes;
• and
• an electrolyte on the separator, wherein the electrolyte includes a non-aqueous organic solvent, a lithium salt, and a linear polymer having P═O bonds,
• wherein the linear polymer having P═O bonds is present in an amount ranging from about 0.005 to less than 5 wt % based on the total amount of the electrolyte,
• wherein the non-aqueous organic solvent comprises a mixed solvent of a carbonate solvent and an aromatic hydrocarbon solvent,
• wherein the aromatic hydrocarbon solvent is at least one selected from the group consisting of fluorobenzene, fluorotoluene, trifluorotoluene, and a compound of Formula (1):
• where R is a halogen, or a C1 to C10 alkyl, and p is an integer of 1 to 6,
• wherein the linear polymer having P═O bonds is formed of a polymerized phosphonate compound with a polymerizable functional unsaturated hydrocarbon group, and
• wherein the phosphonate compound with the unsaturated hydrocarbon group is at least one selected from the group consisting of allyl diethylphosphonoacetate (C2H50)2P(O)CH2CO2CH2CH═CH2), triethyl 3-methyl-4-phosphonocrotonate (C2H50)2P(O)CH2C(CH3)—CHCO2C2H5), and allyl tetraisopropylphosphonodiamidite ([[CH3)2CH]2N]2POCH2CH═CH2).