TECHNOLOGY FOCUS - POLYMERS - Preferred Materials: The polymer is in sheet-form, particle form or powder form. The separator (5) of a battery internal part comprises a polyolefin and is a porous sheet in which ultrahigh molecular weight polyethylene powder is fired. The battery is formed where the polymer coats at least part of the separator surface. The battery has a nonwoven sheet comprising polyolefin fibers where at least part of the separator surface is coated with the polymer. The battery has a separator which a porous sheet comprising the polymer.A porous fired sheet is used as a separator which is obtained by firing the polymer powder at a temperature of at least the melting point. The separator is a porous fired sheet obtained by firing the polymer and polyolefin particles at least the melting point of the polyolefin particles. The separator is a porous sheet in which a porous fired body is cut. The separator is a porous sheet comprising coated polymer particles in which a coating layer of polycarbodiimide is provided on the surface of core particles e.g. of polyolefin.In the cathode and/or anode of the battery, a polymer is used in the surface and/or internal part. The polymer particles or powder is used between the separator and electrodes. The polymer is arranged in cavities in the separator. EXAMPLE - A mixture (100g) of 2,4-tolylene-diisocyanate and 2,6-tolylene-diisocyanate is introduced into toluene (500g) along with carbodiimidation catalyst (0.06g) such as 3-methyl-1-phenyl phosphorene-1-oxide and isopropylphenyl isocyanate (10g). A reaction is carried out at 100degreesC for 6 hours to obtain a polycarbodiimide solution. The solution is formed into a film on a glass plate. A nonwoven fabric of polypropylene and polyethylene fibers is immersed in a 2.5 weight% aqueous solution of sodium dodecyl benzene sulfonate and dried to produce a separator.    A positive electrode is formed from a mixture of 100 weight parts nickel hydroxide powder, 10 weight parts cobalt powder, 10 weight parts polytetrafluoroethylene (PTFE) powder and 20 weight parts water which is injected into foam nickel plate. A negative electrode is formed from a mixture of 100 weight parts hydrogen absorbing alloy such as mischmetal, 10 weight parts PTFE powder and 20 weight parts water which is injected into a foam nickel plate. These components are used to produce a battery.