TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: One of the positive electrode and the negative electrode has porosity of 5-30 vol.%.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The binder composition further comprises at least one additive comprising a dispersant, a viscosity agent, a conductive agent or a filler. The additive is present at 0.1-10 wt.% based on the weight of binder composition excluding the solvent.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The solvent soluble polymer is pyrolyzed in an amount of less than 10 wt.% and the solvent-insoluble pore forming material is pyrolyzed in an amount of greater than 90 wt.%, based on the initial weight of the binder at an initial reaction stage. The solvent soluble polymer and the solvent-insoluble pore forming material are mixed in a weight ratio of 50:50-95:5 based on a total weight of solid matter. The solvent soluble polymer is poly(acrylether ketones), poly(aryl amides), aromatic polyamides, aromatic poly(amide-imides), aromatic polyurethanes, aromatic polyesters, polybenzimidazoles, polybenzoxazoles, polybenzothiazoles, aromatic polysulfones, aromatic poly(ether sulfones), aromatic poly phenylene sulfides or aromatic polyphosphazene. The polymer includes one or more components comprising a polymer having a fluoride substituted, a polymer including a sulfone group in a main chain, and a block copolymer having another polymer added in the form of a block to the polymer. The solvent insoluble pore forming material is: a polymer or an organic-inorganic hybrid; dispersed in a solution; nanoparticles having a size of 10-200 nm; spherically shaped; and a mixture of two or more kinds of materials having different pyrolysis characteristics. The solvent insoluble binder and the solvent-insoluble pore forming material are dispersed in a same solvent. The solvent insoluble pore forming material is pyrolyzed at less than 400 degrees C under vacuum. The solvent soluble polymer is not pyrolyzed at less than 400 degrees C under vacuum. EXAMPLE - Water (70 g) as a solvent, methyl methacrylate (6.42 g) and styrene (3.21 g) as monomers, sodium dioctyl sulfosuccinate (0.36 g) as an emulsifier, potassium persulfonate (6 mg) as a polymerization initiator and sodium bisulfite (4 mg) as a molecular weight adjusting agent were added to a flask, and the resulting mixture was stirred. Methyl methacrylate (12 g), styrene (6 g), and trimethylolpropane triacrylate (2 g) as a crosslinking agent were added to the injection vessel, and then mixed by stirring for 0.5 hour, and then nitrogen gas was injected into the stirred reaction vessel and the temperature of the reaction vessel was elevated to 80 degrees C followed by slowly injecting the monomers in the injection vessel for 2 hours, after the injection was completed, the temperature of the reaction vessel was maintained at 80 degrees C for 30 minutes, followed by polymerization. The reaction vessel was cooled to room temperature, and the emulsified polymer was filtered to remove some lumps, thus preparing a single-phase solution of the solvent-insoluble pore forming material having 30% of solid matter (A). Organic solvent-soluble polyamic acid binder (100 g) dissolved in N-methylpyrrolidone, and 1M ammonium hydroxide solution (40 ml) was slowly injected to a reaction vessel with a stirrer. The resultant mixture was stirred at room temperature for 6 hours and slowly poured into a vessel containing acetone (2l) with stifling to afford a precipitate. The precipitate was filtered, washed and dried in a vacuum oven at 60 degrees C for 3 hours, to obtain powder. The obtained powder (10 g) was dissolved in pure water (90 g), to prepare an aqueous binder solution having solid matter (10%) (B). (A) (4 g), and (B) (48 g) were added to a stirrer vessel, and then pure water was added while slowly stirring for 1 hour and worked up to afford binder composition.