TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composite: The composite is ion-conducting at -40 to 300 degrees C, especially -10 to 200 degrees C. The ion-conductor is mixed in the structure of the composite, a layer (preferably 0.0001-1, especially 0.001-0.05 mum thick) on the inside and/or outside of particles in the composite or in the interstices between the particles of the composite. The composite is flexible and especially can be bent round a radius as small as 1 mm.Preferred Production: The composite is made by treating a composite without ion-conducting properties with ion conductor(s) or precursor(s). For composites with a pore size of 0.001-5 mum, this can be carried out by impregnation or by coating by dipping, brushing, rolling, spreading, spraying or other coating techniques. The ion conductor (precursor) is applied as a solution containing 1-99% solvent. Suitable precursors are converted to ion conductors by thermal treatment, more especially at 100-700 degrees C. Alternatively, ion conductor(s) or precursor(s) is/are incorporated during composite production, preferably by treating the sol with ion conductor or precursor or material forming ion-conducting layers on the inside and/or outside of the particles. The original composite is produced by adding water- and/or alcohol-soluble acid(s) or base(s) to a sol. The sol is obtained by hydrolyzing metal, metalloid and/or mixed metal compound(s) with a liquid, gas and/or solid. A compound containing both hydrolyzable and unhydrolyzable groups may be used. These compounds may be added to an alcohol and/or acid before hydrolysis. The sol especially comprises non-stoichiometric metal, metalloid or nonmetal oxides or hydroxides obtained by changing the oxidation stage of the element, especially by oxidation with (in)organic compounds or electrochemical oxidation and may be treated with substances causing the formation of inorganic ion-conducting structures. SPECIFIC COMPOUNDS - Specific examples of the ion conductors are inorganic and/or organic materials, preferably with sulfonic, phosphonic, carboxylic, tetra-organylammonium and/or tetraorganylphosphonium groups, especially on organic compounds, bound chemically and/or chemically to the inorganic particles, especially through aryl and/or alkyl chains. Specific examples of inorganic ion conductors are oxides, phosphates, phosphides, phosphonates, sulfates, sulfonates, vanadates, stannates, plumbates, chromates, tungstates, molybdates, manganates, titanates, silicates, aluminosilicates and/or aluminates of aluminum (Al), potassium, sodium, titanium (Ti), iron (Fe), zirconium (Zr), yttrium (Y), vanadium (V), tungsten (W), molybdenum (Mo), calcium, magnesium, lithium, chromium (Cr), manganese (Mn), cobalt, nickel, copper and/or zinc and their (partial) hydrolyzates, preferably amorphous and/or crystalline compounds of Zr, silicon (Si), Ti, Al, Y and/or V with (some) unhydrolyzable groups. Specific examples of the precursors are Broensted acids or bases, especially solutions or suspensions of trialkoxysilanes containing acid and/or basic groups, especially quaternary ammonium, phosphonium, alkylsulfonic acid, carboxylic acid or phosphonic acid groups, which may also contain water and an acid or basic compound, especially a Broensted or Lewis acid or base. Specific examples of precursors added to the sol used during composite production are materials forming inorganic ion-conducting layers on the inside and/or outside surface of particles in the composite. Specific examples of the liquid, base and/or solid used for hydrolysis are water, water vapor, ice, alcohol and/or acid. Specific examples of the starting compounds for the sol are nitrates, chlorides, carbonates and alcoholates of metals and metalloids, preferably of Ti, Zr, V, Mn, W, Mo, Cr, Al, Si, tin (Sn) and/or Y. Specific examples of the sol are non-stoichiometric metal, metalloid or nonmetal oxides or hydroxides, especially of Cr, Mn, V, Ti, Sn, Fe, Mo, W or lead. Specific examples of the additives for forming inorganic ion-conducting structures are zeolite and beta-aluminosilicate particles. Specific examples of compounds with hydrolyzable and unhydrolyzable groups are alkyl-trialkoxy, dialkyl-dialkoxy and trialkyl-alkoxy-silicon compounds.    Specific examples of organic ion conductors are polymers (I), preferably sulfonated or aminolyzed polytetrafluoroethylene, polyvinylidene fluoride, polysulfone and/or polyether-imide. Specific examples of the precursors are polyorganylsiloxanes with ionic constituent(s), especially polyalkyl and/or polyarylsiloxanes. Specific examples of ion conductors and precursors incorporated during composite production are polymer-bound Broensted acids or bases, preferably a sol of polymer particles with fixed charges or polyelectrolyte, especially with a melting or softening point below 500 degrees C, more especially preferred polymers (I) in a concentration of 0.001-50.0, preferably 0.01-25% in the sol, which can be changed chemically and/or physically during processing.    EXAMPLE - 120 g Ti tetraisopropylate were stirred with 140 g deionized ice until the precipitate was very finely divided. After adding 100 g 25% hydrochloric acid, stirring was continued until the phase was clear, then 280 g alpha-alumina (CT3000SG; RTM) were added and the mixture was stirred for several days. A thin film of the suspension was then applied to a wire mesh and consolidated as quickly as possible at 550 degrees C. 20 g Al ethanolate and 17 g V chloride were hydrolyzed with 20 g water and the resultant precipitate was peptized with 120 g 25% nitric acid. The solution was stirred until it became clear, then 40 g T dioxide (P25; RTM) were added and de-agglomerated by stirring. After adjusting to pH 6, a very thin film of the suspension was applied to the porous membrane and heated at 450 degrees C. Tests with (A) the resultant proton-conducting membrane and (B) a commercially-available membrane (Nafion 117; RTM) were carried out at various temperatures and an applied potential of 2.0 V in a proton exchange membrane (PEM) fuel cell. The current was (A) 105, (B) 124 mA/cm2 at 60 degrees C; (A) 101, (B) 107 mA/cm2 at 80 degrees C; (A) 98, (B) 41 mA/cm2 at 110 degrees C; (A) 71, (B) 5 mA/cm2 at 130 degrees C; and (A) 64, (B) less than 2 mA/cm2 at 150 degrees C.