TECHNOLOGY FOCUS - POLYMERS - Preferred Compound: The polymerizable gelatinizer is polyfunctional (meth)acrylate. EXAMPLE - Ethylene-methacrylic copolymer (in weight parts) (5) which had melting point of 95degreesC as hot melt adhesive and polyethylene glycol dimethacrylate (95) as polymerizable gelatinizer were uniformly mixed and applied to whole front and back surfaces of porous film made of polyethylene resin at ratio of 5 g/m2. The porous film had thickness of 25 mum, porosity of 50% and average pore size of 0.1 mum. The mixture of hot melt adhesive and polymerizable gelatinizer was supported on the porous film, and an adhesive agent/gelatinizer supported porous film was obtained. An anode consisting of polyvinylidene fluoride resin and lithium cobaltate, and a cathode consisting of polyvinylidene fluoride resin and graphite powder, were adhered on two surfaces of the adhesive agent/gelatinizer supported porous film, respectively by heating at 95degreesC under pressure of 5 kg/cm2. The whole structure was cooled, and a porous film/electrode joint structure was obtained. An electrolyte liquid consisting of lithium hexafluoro phosphate dissolved in mixed solvent of ethylene carbonate and ethylmethyl carbonate, was prepared. 2,2'-azobisisobutyronitrile (1) as polymerization initiator, was dissolved in the electrolyte liquid with respect to polyethylene dimethacrylate (100). The porous film/electrode joint structure was arranged in a battery container. The electrolyte liquid mixture was poured into the battery container at ratio of 90 g/m2 with respect to the porous film. The battery container was sealed, heated at 80degreesC, and the gelatinizer from the porous film was eluted into the electrolyte liquid, and the electrolyte liquid was gelatinized by the gelatinizer. The entire structure was cooled to room temperature, and coin-shaped rechargeable lithium ion battery was assembled. The battery had discharge capacitance of 95%, and had firm adhesion between the porous film and electrode.