NOVELTY - An electrolyte (E1) for a rechargeable lithium battery, comprises: phosphite-based or borate-based compound; lithium salt; and non-aqueous organic solvent.    USE - As an electrolyte for a rechargeable lithium battery (e.g. lithium ion battery and lithium polymer battery) (claimed).    ADVANTAGE - The electrolyte for a rechargeable lithium battery shows excellent output characteristics due to a resistance reduction at a low temperature. The electrolyte solution of the rechargeable lithium battery includes an additive of a phosphite-based or borate-based compound, it decreases the low temperature resistance at the low temperature of an solid electrolyte interphase (SEI) layer formed on the surface of the electrode plate to provide a high capacity battery. The electrolyte affects surface chemical characteristics of an electrode at high rate discharging at a low temperature and can thereby reduce resistance at the interface between a positive electrode and the electrolyte, and at the interface between a negative electrode and the electrolyte, and internal resistance of a cell, resultantly, a reduction of lithium ion conductivity in accordance with a cell thickness increase can be suppressed and thereby battery output at a low temperature can be improved. The electrolyte is not deteriorated even if the battery cell is stored at a high temperature for a long time, in addition, the charge and discharge efficiency and the cycle characteristics are not deteriorated. The rechargeable lithium battery including the electrolyte has an excellent cycle-life characteristic, temperature characteristic, and high rate discharge characteristic as well as charge and discharge characteristic.    DETAILED DESCRIPTION - An electrolyte (E1) for a rechargeable lithium battery, comprises: a phosphite-based or borate-based compound of formula A(OSi(CmH2m+1)3)3 (I); a lithium salt; and a non-aqueous organic solvent.    A=P or B;and    m=0-6.    An INDEPENDENT CLAIM is included for the rechargeable lithium battery, comprising a positive electrode including a positive active material capable of reversibly intercalating and deintercalating lithium ions; a negative electrode including a negative active material capable of reversibly intercalating and deintercalating lithium ions; and the electrolyte (E1).