The present invention pertains to a process for manufacturing a solid composite separator, said process comprising the following steps: (i) providing a liquid composition [composition (L)] comprising, preferably consisting of: at least one fluoro-polymer [polymer (F)] comprising one or more backbone chains, said backbone chains comprising recurring units derived from at least one fluorinated monomer [monomer (F)], and one or more side functional groups selected from the group consisting of —O—Rx and —C(O)O—Rx groups, wherein Rx is a hydrogen atom or a C1-C5 hydrocarbon group comprising at least one hydroxyl group, optionally, at least one metal compound of formula (I) [compound (M)]: X4-mAYm wherein X is a hydrocarbon group, optionally comprising one or more functional groups, m is an integer from 1 to 4, A is a metal selected from the group consisting of Si, Ti and Zr, and Y is a hydrolysable group selected from the group consisting of an alkoxy group, an acyloxy group and a hydroxyl group, at least one inorganic filler [filler (I)], and a liquid medium [medium (L)]; (ii) providing a porous substrate layer made from one or more sets of polymer fibres [substrate (P)]; (iii) applying the composition (L) onto the substrate (P) thereby providing a wet substrate (P) [substrate (P-W)]; (iv) drying and then, optionally, curing the substrate (P-W) provided in step (iii) thereby providing a solid composite separator; and (v) optionally, submitting to compression the solid composite separator provided in step (iv). The present invention also pertains to the solid composite separator obtainable by said process and to use of the solid composite separator in electrochemical devices.