In this study, an eco-friendly and inexpensive cellulose acetate (CA) separator was fabricated and a method of making a single film by combining a polypropylene (PP) film and cellulose was proposed. The CA solution was coated on the PP film with a doctor blade and water treatment was applied to the bonded polymer to create interconnected pores and completely bond the CA onto the PP. In addition, lactic acid was added to CA to induce a plasticizing effect for abundant pore formation. The binding was confirmed using FT-IR and SEM, and the pore size generated from the CA side was found to be less than 1 μm on average. TGA was used to measure the thermal stability of the connected polymers.