NOVELTY - Forming ion-permeable web-reinforced separator involves transporting elongated porous web having two outermost surfaces, downwards between two impregnating heads (6 and 6') comprising two slots each with upper and lower slot faces parallel to the web providing simultaneously to both surfaces of the web metered quantities of shear-thinning dope (7) comprising membrane polymer(s) and solvent(s); impregnating the web completely with dope; subjecting dope to phase inversion with non-solvent(s) to form a membrane; and removing solvent residues for membrane polymer from the membrane.    USE - In electrochemical applications, particularly in batteries e.g. in non-aqueous secondary batteries that employ a lithium-containing transition metal oxide as the positive electrode, a lithium dopable/dedopable carbon-based material as the negative electrode and a non-aqueous electrolyte solution as the electrolyte solution (lithium ion secondary batteries); in fuel cells; and in electrolytic or electrochemical cells e.g. in local hydrogen generators in which the hydrogen is produced by the electrolysis of water.    ADVANTAGE - The use of shear-thinning dopes enables the cockling (waviness) of the ion-permeable web-reinforced separator to be reduced without having to use viscosities which adversely affect the dope-penetration of the elongated porous web. The ion-permeable web-reinforced separator is macroscopically flat at a tensile force of less than 100N/m, this enables compact stacking in electrolytic cells; has a crimp after 120 minutes at 100 degrees C of less than 10%, with a crimp of less than 5% being preferred; and has a ratio of total thickness to thickness of the elongated porous web of less than 2.1. The amplitude of the cocking of the ion-permeable web-reinforced separator is preferably at most ten-times the thickness of the elongated porous web.    DETAILED DESCRIPTION - Production of an ion-permeable web-reinforced separator involves providing an elongated porous web comprising two outermost surfaces; transporting the elongated porous web downwards between two impregnating heads (6 and 6') comprising two slots each with upper and lower slot faces having a vertical orientation or an orientation which may deviate from vertical by not greater than 10 degrees , parallel to the elongated porous web providing simultaneously to both surfaces of the elongated porous web metered quantities of a shear-thinning dope (7) comprising at least one membrane polymer and at least one solvent, where the quantities on both surfaces are identical or may deviate from identical by not greater than 5%; impregnating the elongated porous web completely with the dope and providing dope layers on each surface of the outermost surfaces of the elongated porous web with an equally thickness or a thickness which may deviate from equally by not greater than 5%, the thickness is independent of the gap between one of the lower slot faces and the surface of the elongated porous web nearest to it; subjecting the dope associated with the elongated porous web immediately after dope-impregnation to phase inversion with at least one non-solvent (preferably an organic solvent) where the phase inversion of the dope layer is symmetrical on each surface of the web, thus forming a membrane; and removing residues of the solvent for the membrane polymer from the membrane. The dope further contains an inorganic material. The impregnation is performed using extrusion or slot coating techniques; and is performed intermittently.    DESCRIPTION OF DRAWING(S) - The figure shows schematically impregnation heads providing identical quantities of dope to elongated porous web.    Two parts of 3D spacer fabric (3) Monofilament spacer threads (1 and 1')    Impregnating heads (6 and 6')    Dope (7)