NOVELTY - Separator comprises: a porous substrate having multiple pores; a porous coating layer formed on at least one surface of the porous substrate comprising a mixture of inorganic particles and a binder comprising at least one vinylidene fluoride compound (I) and at least one vinylidene fluoride compound (II); and a binder layer comprising at least one (I) and at least one (II).    USE - The separator is useful in electrochemical device including lithium secondary battery (all claimed).    ADVANTAGE - The separator has improved adhesiveness with electrodes and inhibits resistance increase in interfaces between the electrodes and the binder layer, thus enhancing cycle characteristics.    DETAILED DESCRIPTION - Separator comprises: a porous substrate having multiple pores; a porous coating layer formed on at least one surface of the porous substrate comprising a mixture of inorganic particles and a binder comprising at least one vinylidene fluoride compound of formula (-(VDF)a-(HFP)b-) (I) and at least one vinylidene fluoride compound of formula (-(VDF)c-(HFP)d-) (II) so that a content difference between hexafluoropropylene (HFP) in (I) and that in (II) is greater than or equal to 3 wt.%; and a binder layer comprising at least one (I) and at least one (II), where a fraction of (II) in both of the porous coating layer and the binder layer is greater than 10% and less than 99%, the fraction is calculated by dividing the content of the (II) with the total content of the (I) and the (II), and a fraction of the (II) in the binder layer is 50-99%.    VDF = vinylidene fluoride;    HFP = hexafluoropropylene; and    a-d = wt.%.    Provided that: a+b is 100; c+d is 100, b is greater than 0, d is greater than 0 and d-b is greater than 3. INDEPENDENT CLAIMS are also included for    (1) an electrochemical device comprising a cathode, an anode, and the separator interposed between the cathode and the anode; and    (2) preparing a separator, comprising (a) dissolving a binder in a polar solvent to obtain a binder solution, (b) adding inorganic particles to the binder solution, followed by stirring, to obtain a slurry containing the inorganic particles dispersed in it, and (c) coating the slurry on at least one surface of a porous substrate, followed by drying, to form a porous coating layer on at least one surface of the porous substrate or on at least one pore-bearing area in the porous substrate, where the porous coating layer comprises a binder layer in the outermost part of it in the thickness direction of the porous substrate, the binder layer has (II) in a fraction of 50-99%, the fraction is calculated by dividing the content of (II) with the total content of the (I) and (II).