Thermal shutdown characteristics of insulating materials used in lithium ion batteries

The lithium ion (Li-ion) battery market has undergone tremendous growth since its conception in 1990. Projections have indicated that the Li-ion battery market in the United States will top $9 billion in the next 3 years. Several factors including technical innovation, increased use of sophisticated consumer electronic gadgets and surge in high efficiency power sources for industrial applications have been the key in propelling the market demand for these products. Despite the positive trends, safety concerns related to the use of Li-ion batteries remain and may impact the market growth in future. Product recalls due to rechargeable batteries overheating and thereby posing a fire hazard to consumers have occurred as recently as April 2010. Research efforts have been undertaken to develop new separator materials with increased dimensional and thermal stability at high temperatures to make the Li-ion batteries safer for use. The separator is an electrically insulating polymer material that is engineered to have pores that allow lithium ions to shuttle back and forth between the battery's electrodes during the charge and discharge cycles. This paper presents an introduction to separator materials used in commercially available Li-ion batteries and a discussion of their thermal shutdown characteristics.