NOVELTY - Composite body production comprises applying separator and cathode and/or anode layers onto substrate foils by a wet-in-wet coating process.    USE - The composite body is used for production of an electrochemical cell, in a sensor, an electrochromic window, a display, a capacitor or an ion conductive foil and the cell is used in automobile batteries, appliance batteries, flat batteries, on-board batteries, batteries for static applications, electro traction batteries or polymer batteries (claimed), the battery being especially a lithium ion battery.    ADVANTAGE - The process produces mechanically stable composite bodies in a simpler manner than conventional processes and eliminates the need for additional steps such as extraction of plasticizers and for expensive equipment.    DETAILED DESCRIPTION - A process is claimed for production of a composite body comprising one or more substrate foils (A) bearing (a) a separator layer (B) which is free from electronically conductive electrochemically active compounds and which consists of (i) a combination (I) containing 1-100 wt.% of a mixture (II) of (by wt.) 1-95% preferably basic solids (III) of 5 nm to 20 microns primary particle size and 5-99% polymeric material (IV) obtained by polymerizing (a) 5-100 wt.% condensation product (V) of a compound (VI) capable of reacting with carboxylic and/or sulfonic acids or their derivatives and a molar equivalent quantity of carboxylic and/or sulfonic acid (derivative) having one or more functional groups capable of radical polymerization and (b) 0-95 wt.% further compound (VIII) of number average molecular weight at least 5000 with main or side chain polyether segments or (ii) a polymer or copolymer of vinyl chloride, acrylonitrile, vinylidene fluoride, vinyl chloride + vinylidene chloride, vinyl chloride + acrylonitrile, vinylidene chloride + hexafluoropropylene, vinylidene fluoride + hexafluoropropylene and one of vinyl fluoride, tetrafluoroethylene and tri fluoroethylene; and (b) a cathode layer (C) containing an electronically conductive electrochemically active compound capable of releasing lithium ions during charging and/or an anode layer (D) containing an electronically conductive electrochemically active compound capable of accepting lithium ions during charging. The process comprises applying the separator (B) and the cathode (C) and/or anode (D) layers by a wet-in-wet coating process. An INDEPENDENT CLAIM is also included for an electrochemical cell comprising a composite body produced by the above process.