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2009-10 Seminars

Polymer Separator Film for Lithium Ion Batteries: Past, Present, and Future

Patrick Brant
Global R&D
ExxonMobil Chemical Company

Abstract
Due to their excellent energy and power-to-weight ratios, as well as (benefit/cost), lithium ion batteries (LIB) are the power source of choice for portable electronics such as cell phones, cameras, and notebook computers. LIB's and lithium batteries (LB’s) are also used extensively in biomedical and military applications. More recently, LIB's are driving rapid growth in portable power tools and e bikes. Due to their key role in so many markets, LIB's have enjoyed robust growth since their commercial launch 18 years ago. Now, combined market, political, and environmental forces suggest that prospects are bright for widespread use of LIB's in transportation - hybrid electric vehicles (HEV), plug-in hybrids (pHEV), as well as electric vehicles (EV). In order to meet the market demands for increased energy, power, safety, longevity, and reduced cost, research and development on all aspects of LIB materials, design, and function have accelerated. LIB's have three critical solid components - cathode, anode, and a thin (typically 7-30 micron) microporous polyolefin separator film – along with liquid or gel electrolyte. EM Chemical pioneered separator design and commericialization for LIB and continue to improve separator performance for the evolving array of applications.

In this talk, we review:

(1) genesis of the LIB separator and focus on its roles in LIB as well as the increasing demands put upon it. Briefly, separators must be: (a) chemically inert and separate the anode and cathode electrically (b) flexible, tough, and dimensionally stable (c) microporous to allow ion transport between cathode and anode yet prevent particulate transport (d) act as a safety device that maintains separation between anode and cathode in the event of an exotherm from abuse or a potential battery flaw and, in most cases, helps shut down the battery through designed pore closure.

(2) Prospects for LIBs in transportation, with attention to some of the key factors involved in wider deployment.

SLIDES