TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Battery: The lithium polymer battery is obtained by joining the solid electrolyte cathode conjugant, and a solid electrolyte anode conjugant consisting of hardening film obtained by coating the lithium ion electroconductive composition (I) on composite anode and carrying out postcure, such that the solid electrolyte surfaces optionally contact, or by joining cathode consisting of lithium foil portion and solid electrolyte anode conjugant.    TECHNOLOGY FOCUS - POLYMERS - Preferred Component: The hardenable oligomer (A) is urethane (meth)acrylate-type compound (A1) having (meth)acryloyl group in molecule terminal, and/or polyisocyanate group derivative (A2) having hydrocarbon group and (meth)acryloyl group. Preferred Property: The thickness of the hardening film obtained from lithium ion electroconductive composition (I) is 5-100 microns. Preferred Composition: The lithium ion electroconductive composition (I) further contains electrolyte liquid (E), and does not contain solvent. EXAMPLE - Lithium nitrate salt (LiN(CF3SO2)2) (in parts) (5) and lithium boron fluoride (LiBF4) (10) were dissolved in methoxy polyethylene glycol monoacrylate (37). R202 (silicon oxide with particle size of 14 nm surface-treated by silicone oil) (10), urethane acrylate (80) having solid content of 98.8% and number average molecular weight of 4300 and Irgacure 184 (1-hydroxy-cyclohexyl-phenyl-ketone as photoinitiator) (3) were add-mixed to the resulting mixture, to obtain a lithium ion electroconductive composition. The obtained composition was applied on lithium foil portion having thickness of 100 microns, and irradiated by irradiation amount of 500 mJ/cm2, to obtain a solid electrolyte cathode conjugant having hardening film with thickness of 10 microns. Lithium manganese oxide (Li0.03MnO2) powder (1 g) and carbon black (0.15 g) were mixed. Lithium nitrate salt (LiN(CF3SO2)2) (0.033 g) and copolymer (0.1 g) of ethylene oxide (88 mmol%) and 2-(2-methoxy ethoxy)ethylglycidyl ether (12 mol%), were dissolved in acetonitrile. The acetonitrile solution was added to the resulting mixture and mixed, to obtain an anode slurry. The obtained slurry was applied on aluminum foil portion having thickness of 20 microns, and dried at 10degreesC for 15 minutes, to obtain a composite anode having film thickness of 30 microns. The obtained composite anode and solid electrolyte cathode conjugant were subjected to thermocompression bonding, to obtain a lithium polymer battery. The obtained battery had excellent electroconductivity and charging-and-discharging characteristics and mechanical strength.