TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The metal ion comprises maximum valence state ion and/or average valence state ion of tungsten, zirconium, iridium, yttrium, manganese, ruthenium, cerium, vanadium, zinc, titanium, and lanthanum. The total concentration of metal ion in the solution containing metal ion is 0.0001-0.5 mol/L.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: The group with ion exchange function is sulfur dioxide, sulfur trioxide, perfluorosulfonic acid monomer of formula CF2=CFO(CF2C(CF3)FO)h(CF2)iSO2A, perfluorocarboxylic acid monomer of formula CF2=CFO(CF2C(CF3)FO)j(CF2)kCO2B', and/or perfluorophosphoric acid monomer of formula CF2=CFO(CF2)l(O=)P(OD)-OD.h=0-1;i=1-5;A=F, Cl, Br, OH, methoxy, or ONa;j=0-1;k=1-5;B'=methyl, H, or ethyl;andD=H, methyl, or ethyl.    TECHNOLOGY FOCUS - POLYMERS - Preferred Component: The fluorine-containing polymer thin film is PTFE, hexafluoropropylene copolymer, polyvinylidene fluoride, polytrifluorochloroethylene, and/or tetrafluoroethylene-ethylene copolymer. The ion exchange resin is perfluorinated sulfonic acid resin of formula -((CF2CF2)x-CF2C(O(CF2C(CF3)FO)m(CF2)pSO3H)F)y-, -((CF2-CF2)a-(C(O-CF2-CF2-SO3H)F-CF2)a')x'-((CF2-CF2)b-(C(O-CF2-CF2-CF2-CF2-SO3H)F-CF2)b')y-, -((CF2-CF2)c-(C(O-CF2-CF2-SO3H)F-CF2)c')x''-((CF2-CF2)d-(C(O-CF2-CF2-CF2-CF2-SO3H)F-CF2)d')y''-((CF2-CF2)g-(C(O(CF2-C(CF3)F-O)n-CF2-CF2-(O=)P(OM)-OM')F-CF2))z''-, or -((CF2-CF2)r-(C(O-CF2-CF2-SO3H)F-CF2)r')x'''-((CF2-CF2)s-(C(O-CF2-CF2-CF2-CF2-SO3H)F-CF2)s')y'''-((CF2-CF2)t-(C(O-(CF2-C(CF3)F-O)q-CF2-CF2-Q)F-CF2)t')z'''; and/or perfluorinated phosphoric acid resin of formula -(CF2-CF2)e-(CF2-C(O-(CF2)3-(O=)P(OH)-OH)F)f-.m=0-2;p=2-5;x, y, a-d, g, r-t=3-15;a', b', c', d', r', s', t', f=1-3;x'/(x'+y'), y'/(x'+y')=0.2-0.8, preferably 0.4-0.6;M, M'=H, K, Na, or NH4;x''/(x''+y''+z''), x'''/(x'''+y'''+z''')=0.2-0.7, preferably 0.4-0.6;ory''/(x''+y''+z''), y'''/(x'''+y'''+z''')=0.2-0.79, preferably 0.34-0.58;orz''/(x''+y''+z''), z'''/(x'''+y'''+z''')=0.01-0.1, preferably 0.02-0.06;Q=CN or Br;q=0-3;ory'''/(x'''+y'''+z''')=0.35-0.58;orz'''/(x'''+y'''+z''')=0.02-0.05;ande=2-20.The fluorine-containing polymer thin film with microcellular structure has thickness of not greater than 100, preferably 5-20 mu m, voidage of 60-97%, and aperture of 0.2-5 mu m. Preferred Method: The soaking time of thin film obtained in step (A) in the solution containing metal ion is 5-100, preferably 30-100 minutes.