NOVELTY - A binder composition comprises a semi-interpenetrating polymer network including a copolymer having an ester group-containing repeating unit (I) and an alkoxy group-containing repeating unit (II), and polyacrylamide, and polyalkylene glycol.    USE - Binder composition is used for rechargeable lithium battery (claimed).    ADVANTAGE - The binder composition contains semi-interpenetrating polymer network having strong and tough characteristics and excellent flexibility, has improved adhesiveness and excellent stability with an electrolyte solution, and can be prepared by environmentally-friendly process. The rechargeable lithium battery using the binder composition has high capacity, excellent initial efficiency and charging/discharging cycle characteristics.    DETAILED DESCRIPTION - A binder composition comprises a semi-interpenetrating polymer network including a copolymer (a) having an ester group-containing repeating unit of formula (I) and an alkoxy group-containing repeating unit of formula (II), and polyacrylamide, and polyalkylene glycol.    R1,R2=H, or optionally substituted 1-10C alkyl;    R3,R4=alkali metal;and    R5-R8=H, or 1-30C alkyl, 6-30C aryl or 1-30C alkoxy (all optionally substituted).    INDEPENDENT CLAIMS are included for the following:    (1) rechargeable lithium battery (100), which comprises an electrode (112) including the binder composition, an electrode active material and an electrolyte; and    (2) preparation of binder composition, which involves adding a copolymer of at least one monomer chosen from olefin-based monomer, aromatic vinyl monomer and alkyl vinyl ether monomer, cyclic unsaturated acid anhydride monomer, and polyalkylene glycol to a solvent, adding an alkali metal-containing compound to the resultant solution, and adding an acrylamide monomer to the resultant solution to form polyacrylamide by polymerization and form a semi-interpenetrating network structure of copolymer and polyacrylamide.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a structure of the rechargeable lithium battery.    Rechargeable lithium battery (100)    Negative electrode (112)    Separator (113)    Positive electrode (114)    Battery case (120)    Sealing component (140)