NOVELTY - Composite material comprises (a) at least one base body composed of nonwoven, (b) at least one nanocomposite material, (c) at least one polyether or at least one polyether-containing residue and (d) optionally at least one lithium salt, where (b) comprises (b1) at least one inorganic (semi) metal-organic phase containing at least one metal or semimetal and (b2) at least one organic polymer phase, (b2) and (b1) are form substantially co-continuous phase domain, and the polyether-containing residue is covalently bonded to (b1) or (b2).    USE - The composite material is useful as separator, or as part of a separator in electrochemical cells, fuel cells or supercapacitors. The electrochemical cell is useful in lithium ion batteries, motor vehicles, electric motor-driven bicycles, airplanes, ships and stationary energy storage materials (all claimed). The lithium ion batteries are useful in computers, preferably laptops, phones or electric-hand tools in the field of construction e.g. drill, cordless screw driver or cordless stapler.    ADVANTAGE - The composite material provides separators with small thickness, low basis weight, good mechanical stability during processing, such as high flexibility and low abrasion strength, good temperature resistance, low shrinkage, high porosity, high lithium ion conductivity and good wettability with electrolyte fluids.    DETAILED DESCRIPTION - Composite material comprises (a) at least one base body composed of nonwoven, (b) at least one nanocomposite material, (c) at least one polyether or at least one polyether-containing residue and (d) optionally at least one lithium salt, where (b) comprises (b1) at least one inorganic (semi) metal-organic phase containing at least one metal or semimetal and (b2) at least one organic polymer phase, (b2) and (b1) are form substantially co-continuous phase domain, the average distance between two neighboring domains of identical phases is maximum 100 nm and the polyether-containing residue is covalently bonded to (b1) or (b2). INDEPENDENT CLAIMS are included for:    (1) preparing composite materials comprising cationically polymerizing at least one monomer AB, which comprises at least one first cationically polymerizable monomer unit A containing metal or semimetal and at least one second cationically polymerizable organic monomer unit B, which is covalently chemically bonded to the monomer unit A, where during the polymerization, the polymerizable monomers A and B are polymerized by breaking the bond between the monomers A and B, where the monomer AB is polymerized in the presence of (a), (c) and optionally (d);    (2) a separator for an electrochemical cell containing the composite material; and    (3) the monomer AB of formula (IIIA), which contains a polyether containing group.    R = halo, CN, 1-6C-alkyl, 1-6C-alkoxy or phenyl;    m = 0-2;    Raa, Rbb = H or CH3;    R1a = 1-6C-alkyl, 3-6C-cycloalkyl, a polyether-containing group containing monomer units consisting of ethylene oxide and propylene oxide, aryl or Ar2-C(R2aa,R2bb)-;    Ar2 = (hetero)aryl ring optionally having 1 or 2 halo, CN, 1-6C-alkyl, 1-6C-alkoxy or phenyl;    R2aa, R2bb = H or CH3;    R2a = polyether containing group containing monomer units of ethylene oxide and propylene oxide bonded over carbon, where polyether containing group containing units is of formula (-CH2-(CH2)o-CH2-(O-CH2-CH2)n-O-CH3);    o = 0-18; and    n = 1-100.