A separator comprising: a porous substrate, and a coating layer on one side or both sides of the porous substrate, wherein the coating layer comprises: a filler being an inorganic compound having a number average particle diameter of from 0.3 μm to 2 μm; and a binder comprising: an organic polymer being a diene-based polymer; and an inorganic particle having a number average particle diameter of from 5 nm to 200 nm, an organic particle having a number average particle diameter of from 5 nm to 200 nm, or a combination thereof; wherein, in the binder, the inorganic particle, the organic particle or the combination thereof is included in an amount of from 10 parts by weight to 100 parts by weight based on 100 parts by weight of the organic polymer; wherein the filler is included in an amount of from 70 wt% to 99 wt% based on a total amount of the coating layer; wherein the number average particle diameters are measured by a laser-scattering particle distribution system; characterised in that: the separator further comprises an adhesion layer positioned on the coating layer, further wherein the adhesion layer comprises: the binder; an acrylate-based binder; a rubber-based binder; a diene-based binder; a styrene-based binder; or a combination thereof. a porous substrate, and a coating layer on one side or both sides of the porous substrate, wherein the coating layer comprises: a filler being an inorganic compound having a number average particle diameter of from 0.3 μm to 2 μm; and a binder comprising: an organic polymer being a diene-based polymer; and an inorganic particle having a number average particle diameter of from 5 nm to 200 nm, an organic particle having a number average particle diameter of from 5 nm to 200 nm, or a combination thereof; wherein, in the binder, the inorganic particle, the organic particle or the combination thereof is included in an amount of from 10 parts by weight to 100 parts by weight based on 100 parts by weight of the organic polymer; wherein the filler is included in an amount of from 70 wt% to 99 wt% based on a total amount of the coating layer; wherein the number average particle diameters are measured by a laser-scattering particle distribution system; characterised in that: the separator further comprises an adhesion layer positioned on the coating layer, further wherein the adhesion layer comprises: the binder; an acrylate-based binder; a rubber-based binder; a diene-based binder; a styrene-based binder; or a combination thereof. a filler being an inorganic compound having a number average particle diameter of from 0.3 μm to 2 μm; and a binder comprising: an organic polymer being a diene-based polymer; and an inorganic particle having a number average particle diameter of from 5 nm to 200 nm, an organic particle having a number average particle diameter of from 5 nm to 200 nm, or a combination thereof; wherein, in the binder, the inorganic particle, the organic particle or the combination thereof is included in an amount of from 10 parts by weight to 100 parts by weight based on 100 parts by weight of the organic polymer; wherein the filler is included in an amount of from 70 wt% to 99 wt% based on a total amount of the coating layer; wherein the number average particle diameters are measured by a laser-scattering particle distribution system; characterised in that: the separator further comprises an adhesion layer positioned on the coating layer, further wherein the adhesion layer comprises: the binder; an acrylate-based binder; a rubber-based binder; a diene-based binder; a styrene-based binder; or a combination thereof. the separator further comprises an adhesion layer positioned on the coating layer, further wherein the adhesion layer comprises: the binder; an acrylate-based binder; a rubber-based binder; a diene-based binder; a styrene-based binder; or a combination thereof.