NOVELTY - A polymer electrolyte composition comprises: a pre-gel composition including a first monomer (I), a second monomer (II) and a third monomer (III); a lithium salt; and a non-aqueous organic solvent.    USE - In a lithium rechargeable battery (claimed).    ADVANTAGE - The polymer electrolyte have improved reliability and safety by increasing thermal stability of a polymer of the polymer electrolyte and crosslinking density of a matrix of the polymer while improving electrode impregnation capability by inducing low viscosity in a pre-gel composition. The polymer electrolyte rechargeable lithium battery has advantages such as a reduced likelihood of leaking, improved safety, improved high-temperature stability, and it may be more resistant to external physical impact. The polymer electrolyte composition (e.g. the polymer electrolyte in the pre-gel state) is injected into the battery and then polymerized, the resultant polymer electrolyte has leak prevention (or a reduction of the likelihood that a leak will occur), safety, high temperature stability, and durability against external physical impact. The polymer electrolyte provides a rechargeable battery having excellent cycle-life and safety characteristics.    DETAILED DESCRIPTION - A polymer electrolyte composition comprises: a pre-gel composition including a first monomer of formula (I), a second monomer of formula (II) and a third monomer of formula (III); a lithium salt; and a non-aqueous organic solvent.    X, Y' and Z'=repeating units of divalent or higher valence alkylene oxides or its repeating units, alkylene groups or its repeating units;    x, y and z=1-20;    l=0-5;    m=0-5;    n=0-5;    R1=H, 1-10C hydrocarbons or 1-10C aromatic hydrocarbons;    A=1-20C hydrocarbons, or 1-20C halogenated hydrocarbons;    R2=H, 1-10C hydrocarbons or 1-10C aromatic hydrocarbons;    B'=5-20C hydrocarbons, 5-20C aromatic hydrocarbons, or 5-20C halogenated aromatic hydrocarbons.    INDEPENDENT CLAIMS are included for the following:    (1) a polymer electrolyte comprising a cured product of the polymer electrolyte composition; and    (2) a lithium rechargeable battery comprising: a positive electrode; a negative electrode; a separator interposed between the positive electrode and the negative electrode; and the polymer electrolyte.