TECHNOLOGY FOCUS - POLYMERS - Preferred materials: The pore-closing initiating temperature is 100 - 150 degreesC. The separator material is selected from polyolefins, cellulose and/or polyvinylidene fluoride. The separator has air permeability 600 sec/100 cm3 or less and thickness 5 - 30 micron. The thermoplastic resin layer has melting point at least 120 degreesC. It is preferably a polyolefin. The positive and negative electrodes and separator are made integral by adhesive polymer present in at least a portion of the boundary between them; or the positive and negative electrodes contain a binder and the electrodes and separator are made integral by thermally curing the binder.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred materials: The electrolyte is selected from liquid, gel and solid nonaqueous electrolytes. It preferably comprises a lithium salt dissolved in a nonaqueous solvent containing 40 - 95 vol.% gamma-butyrolactone. EXAMPLE - A slurry was prepared by adding 91 wt.% lithium-containing cobalt oxide powder, 2.5 wt.% acetylene black, 3 wt.% graphite and 4 wt.% polyvinylidene fluoride to N-methylpyrrolidone then stirring. Both surfaces of a 10 micron thick aluminum foil collector were coated with the slurry, followed by drying and pressing the collector to form a positive electrode having a 48 micron thick positive electrode layer on each surface of the collector and electrode density 3.0 g/cm3. A slurry was prepared by adding 93 wt.% mesophase pitch based carbon fiber powder subjected to heat treatment at 3000 degreesC (fiber diameter 8 micron, average fiber length 20 micron, average interplanar spacing d002 0.3360 nm) and 7 wt.% polyvinylidene fluoride binder to N-methylpyrrolidone then stirring. Both surfaces of a 10 micron thick copper foil collector were coated with the slurry, followed by drying and pressing the collector to form a negative electrode having a 45 micron thick negative electrode layer on each surface of the collector and electrode density 1.3 g/cm3. A separator was prepared comprising 20 micron thick polyethylene porous film having porosity 40% and pore closing initiating temperature 120 degreesC. An electrode group having thickness 2.5 mm, width 30 mm and height 50 mm was prepared by spirally winding a structure consisting of the positive and negative electrodes with the separator interposed between them, followed by flattening the spiral structure. The nonaqueous electrolyte comprised 1.5 mol/l lithium borofluoride in ethylene carbonate/gamma-butyrolactone (volume ratio 25:75). A 100 micron thick laminate film, comprising a polypropylene thermoplastic resin layer (melting point 160 degreesC) on each surface of an aluminum foil, was heat sealed using a hot press (190 degreesC) to form a bag. The electrode group was housed in the bag and both surfaces of the bag held such that the bag had thickness 2.7 mm. 0.3 wt.% polyvinylidene fluoride adhesive polymer in dimethylformamide (boiling point 153 degreesC) was poured into the electrode group housed in the bag in an amount of 0.6 ml/100 mAh battery capacity to permit the solution to permeate the inner region of the electrode group and be attached to the entire surface of the electrode group. Vacuum drying (80 degreesC, 12 hrs.) was applied to the electrode group housed in the bag so as to evaporate the organic solvent and permit the adhesive polymer to be retained within the cavities of the electrodes and separator to form a porous bonding portion on the electrode group surface. The electrolyte was poured into the electrode group housed in the jacket, then the open portion of the jacket was sealed by hot pressing (190 degreesC) to form a nonaqueous electrolyte secondary battery of thickness 2.7 mm, width 32 mm and height 55 mm. Heat generation did not occur when the battery was stored at 140 degreesC resulting in excellent safety and no liquid leakage. Reduction in battery capacity when the battery was discharged at a high rate was small.