Patent ID: 8597819

Claim:
A process for producing a separator for an electrochemical cell comprising (A) a flexible perforated support having perforations, and (B) a porous ceramic material which fills the perforations in the flexible perforate support and is suitable for receiving an ion-conducting electrolyte, wherein the porous ceramic material comprises a first porous layer having an average pore size and at least one second porous layer for contacting with an electrode, the second porous layer having an average pore size which is smaller than the average pore size of the first porous layer the process, comprising the steps of: (a) applying a first dispersion as a thin layer onto and into at least one flexible perforate support selected from the group consisting of a woven perforate support and a nonwoven perforate support, the dispersion comprising (a1) large ceramic particles whose average particle size provides a pore structure to the thin layer that is characterized by an average pore diameter, and also (a2) first ceramic particles having an average primary particle size which is less than the average particle size of the large ceramic particles as per (a1), (b) solidifying the first dispersion at a temperature from 100° C. to 680° C. to form a first layer of porous ceramic material, (c) applying a further dispersion to at least one side of the first porous layer of porous ceramic material, the further dispersion comprising: (c1) second ceramic particles whose particle size provides a pore structure whose average pore size is less than the average pore size of the first porous layer of porous ceramic material that is coated with the further dispersion, and (d) solidifying at a temperature from about 100° C. to 680° C. to form a further layer of porous ceramic material.