The present invention relates to electrical separators and to a process for making them. An electrical separator is a separator used in batteries and other arrangements in which electrodes have to be separated from each other while maintaining ion conductivity for example. The separator is preferably a thin porous insulating material possessing high ion permeability, good mechanical strength and long-term stability to the chemicals and solvents used in the system, for example in the electrolyte of the battery. In batteries, the separator should fully electrically insulate the cathode from the anode. Moreover, the separator has to be permanently elastic and to follow movements in the system, for example in the electrode pack in the course of charging and discharging. This object is achieved by an electrical separator according to the invention, comprising a sheetlike flexible substrate having a multiplicity of openings and having a coating on and in said substrate, said substrate being a polymeric nonwoven and said coating being a porous electrically insulting ceramic coating, said separator being characterized by a thickness of less than 80 μm.