TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - In the step of performing the electroless copper plating, the plating is performed at 20-30 degrees C for 10-30 seconds under a current density of 10-20 A/cm2 using a mixture of 60 g/l CuSO4-H2O, 150 g/l H2SO4 and 50 ppm HCl. In the step of removing the polymer pattern, the micropolymer pattern is removed by immersing the current collector in a solvent, where the solvent is chloroform. In the step of forming of electrode active material, the electrode active material is a phosphorus-doped silicon thick film comprising silane and phosphine. In the step of modifying the surface of the electrode active material, the surface modification involves connecting a copper plate to a positive electrode and an electrode to a negative electrode in a plating solution and flowing electrical current or placing the electrode active material in a vacuum chamber and coating copper on the electrode active material under vacuum to a thickness of 0.1-20 nm.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - The solvent is at least one selected from acetone, acetic acid, aniline, allylamine, benzene, bromobenzene, chloroform, chloroethane, chlorobenzene, chlorohexanol, ethylbenzene, ethoxyethane and hexane. In the step of preparing the mixture solvent, the non-solvent is at least one selected from butanol, 1-butoxybutane, 1,3-butanediol, cyclohexanol, ethanol, ethylene glycol, formamide, 1-pentanol, 2-isopropoxypropane, isopropyl alcohol, methanol and water. In the step of preparing the mixture solvent, the mixture solvent is prepared by diluting the solvent which is acetone, acetic acid, aniline, allylamine, benzene, bromobenzene, chloroform, chloroethane, chlorobenzene, chlorohexanol, ethylbenzene, ethoxyethane or hexane with the non-solvent which is butanol, 1-butoxybutane, 1,3-butanediol, cyclohexanol, ethanol, ethylene glycol, formamide, 1-pentanol, 2-isopropoxypropane, isopropyl alcohol, methanol or water to 1-100 vol.%.    TECHNOLOGY FOCUS - POLYMERS - In the step of preparing the polymer solution, the polymer resin is at least one selected from polyethylene, polystyrene, polypropylene and poly(methyl methacrylate). In the step of preparing the polymer solution, a solvent is used. In the step of preparing the polymer solution, the polymer resin is included in the polymer solution in an amount of 0.01-50 wt.%. In the step of preparing the polymer solution, the current collector is a porous copper current collector. In the step of coating the polymer solution, the coating is doctor blade coating, bar coating, dip coating or spin coating.