Lithium ion batteries and supercapacitors for HEV

Electrochemical energy storage/conversion systems for the high energy conversion efficiency are playing a key role for a sustainable transportation by hybrid electric vehicles (HEVs). A short overview of the basic differences between batteries and supercapacitors and of the various HEVs with implemented electric functions is given; the operation modes and performance targets for the electrochemical systems stated by the United States Advanced Battery Consortium (USABC) and the U.S. Department of Energy (DOE) for HEVs are pointed out. Research efforts have much increased in the last years to develop safe, high power lithium ion batteries of large size and high energy supercapacitors for application in HEVs. Achievements in lithium ion batteries based on different chemistries are reported and the performance of these batteries (some already on the market) are compared on the basis of benchmark tests stated by USABC and DOE to simulate the dynamic functioning in power assist HEVs. Strategies to enhance specific energy of supercapacitors, without sacrificing power and safety, in order to meet the targets for power assist HEVs are even discussed, and recent findings by our laboratory in the frame of the ILHYPOS European Project are presented.