Safety issue for Li-ion batteries have attained great attention as increasing the capacity and power of battery. In particular, development of functional separator which can retard flame generation or have shut-down properties has been focused steadily in recent years. One of method will be addition of functional microparticles or capsules on separator. Herein we attempted to prepare smart microcapsules and the capsules were coat on Li-ion battery separator in order to enhance Li-battery safety. The shell polymer can melt down under certain condition, so that induce shut-down of Li-ion battery operation. In addition, frame retardant materials can be inserted into core materials to prevent unexpected fire generation.