Separator for an electrochemical device including a porous organic/inorganic composite coating layer and an electrochemical device including same

An electrochemical device separator comprising

• a porous polymer substrate;
• and
• an organic/inorganic composite porous coating layer on at least one side of the porous polymer substrate, said organic/inorganic composite porous coating layer comprising particulate binder polymers, first inorganic particles and second inorganic particles, which second inorganic particles are different from the first inorganic particles,
• wherein the particulate binder polymers comprise:
• (a) hybrid polymer particles comprising a fluorine-containing polymer and an acrylic-containing polymer;
• and
• (b) acrylic-containing polymer particles, wherein the acrylic-containing polymer particles have an average particle diameter D50 “a” in a range of 1 μm to 7.5 μm,
• the first inorganic particles have an average particle diameter D50 “b” in a range of 200 nm to 800 nm,
• a/b is in a range of 2 to 15,
• the hybrid polymer particles have an average particle diameter D50 smaller than the average particle diameter D50 of the acrylic-containing polymer particles, and
• the second inorganic particles have an average particle diameter D50 smaller than or equal to the average particle diameter D50 of the first inorganic particles.