ExxonMobil Chemical and its Japanese affiliate, Tonen Chemical Corporation, are developing a prototype microporous film for lithium-ion battery (LIB) separators that it expects will dramatically improve lithium-ion battery power and safety performance in hybrid-electric vehicle (HEV) applications.
The researchers describe their progress in a paper presented at the sixth International Advanced Automotive Battery and Ultracapacitor Conference (AABC-06) in Baltimore May 15-19, 2006.
The film offers the potential to reduce the size and weight of HEV batteries, according to ExxonMobil Chemical, thereby contributing to HEV system cost reduction and to improvements in design flexibility and durability.
Tonen Chemical commercialized and produces a thin, polyethylene-based, porous film that is used as a separator in many rechargeable LIB applications. The film is thin, yet strong, helping to increase the stability and reliability of lithium ion batteries.
A homogeneous pore structure provides exceptional performance that maximizes battery safety. The film closes its pores if excessive heat is generated during the chemical reaction in the battery, minimizing the potential for short circuits and battery rupture.
The prototypes of the new film separators offer higher permeability as well as good strength and thermal integrity. The high permeability of the separator strongly enhances the power-related performance, which potentially reduces the size and weight of a battery system.
|A comparison of the surface structure between the standard grade and LIB prototype separator materials for HEV applications. Click to enlarge.|
In April, ExxonMobil Chemical and Tonen Chemical announced increased production capacity for separator film at the Nasu Plant in Japan to satisfy strong demand and high growth in the lithium-ion battery separator market.
The added film lines at the Nasu production facilities enable us to pursue potential demand growth for customers developing new-generation lithium ion batteries for hybrid vehicles.—Jim Harris, Polymers senior vice president
Tonen Chemical’s product was adopted for the world’s first commercial lithium ion battery in 1991.
Battery Separators for HEV Application (Word document)