Patent ID: 8016896

Claim:
A process for producing a separator for an electrochemical cell, the separator comprising (A) a flexible perforate support, (B) a porous first ceramic material which fills the perforations in the support and which (i) has a pore structure having an average pore size, and (ii) is suitable for receiving an ion-conducting electrolyte, wherein (C) an electrolyte-contactable pore surface of the first porous ceramic material is covered with fine particles of a further material to extend the use life, the average size of the fine particles being in the range from 0.5 to 30% of the average pore size of the ceramic material, wherein the process comprises: (a) applying a dispersion as a thin layer onto and into a woven and/or nonwoven, the dispersion comprising: (a1) large ceramic particles whose average particle size provides a pore structure to the thin layer having an average pore diameter, (a2) fine particles whose average particle size is in the range from 0.5 to 30%, of the average particle size of the ceramic material, and (a3) optionally, ceramic particles having an average primary particle size which is substantially less than the average particle size of the ceramic particles as per (a1) and (a2); and (b) solidifying the dispersion at a temperature from 100° C. to 680° C. to form the separator.