An oligomer-polymer and a lithium battery are provided. The oligomer-polymer is obtained from the polymerization reaction of a polymerizable compound having one ethylenically unsaturated group and one active hydrogen atom in the same molecule. In addition, the oligomer-polymer is obtained from the polymerization reaction of a compound containing an ethylenically unsaturated group and a nucleophile compound, wherein the nucleophile compound includes maleimide, trithiocyanuric acid, hydantoin, hydantoin derivatives, thiohydantoin, thiohydantoin derivetaives. The compound containing an ethylenically unsaturated group comprises a maleimide-based, acrylate ester-based, acrylamide-based or vinylamide-based structure. The lithium battery including an anode, a cathode, an isolation film, an electrolyte solution and a package structure is also provided, wherein the cathode includes the oligomer-polymer.