Note that the writing was on the wall in 2001:
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TH1-449V2XG-6&_user=681878&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000037398&_version=1&_urlVersion=0&_userid=681878&md5=6304411428dcbc5dbc312f494599bca9 High performance nickel-metal hydride and lithium-ion batteries
U. Köhler uwe.koehler@varta.com , J. Kümpers and M. Ullrich
NBT GmbH, Am Leineufer 51, D-30419, Hannover, Germany
Available online 30 October 2001.Abstract
In comparison to pure electric vehicles (EV) the opportunities for hybrid electric vehicles (HEV) are much better, since range restrictions no longer apply and the interaction of the internal combustion engine and electrical drive bring increased energy efficiency and environmental friendliness. The batteries used in such applications must meet very high standards in terms of performance and service life. Although the battery capacity is smaller than for a purely EV, it needs to be able to generate far higher levels of power. The technical challenges of hybrid applications have led to the development of high-performance batteries. At the forefront of these is the nickel-metal hydride system (NiMH). With specific power and energy data in the range from 300 to 900 W/kg, 55 to 37 Wh/kg, respectively (based on cell weight), excellent charge efficiency and energy throughput levels of more than 10,000 times the nominal energy, the NiMH system comes very close to satisfying the needs of the HEV. Parallel developments with the lithium-ion system based on manganese spinel as cathode material show that, with specific power and energy levels above 1000 W/kg, 50 Wh/kg, respectively, this technology will also be able to play an important role in the future. Service life figures in terms of calendar life have been improved tremendously to about three years, but there is still a need for further improvement in order to meet the specifications of car manufacturers. For this reason, an increase of life span is the subject of intensive development work.
...4. Conclusion
Efforts over recent years have seen considerable progress being made in NiMH systems in terms of performance. Specific power which comes close to the 1000 W/kg level signifies an increasing degree of competition for capacitor systems since, in addition to comparable power levels, they also offer an energy storage capacity which is around twenty times higher. Use in electric and hybrid vehicle prototypes demonstrates that the NiMH system can have a particularly interesting role to play in the future of vehicle construction. Its particular strengths are to be found in its high gravimetric and volumetric power data. This makes this battery particularly attractive wherever small, powerful, quick-charge batteries are required.
The results achieved with the NiMH–UHP–technology not only support use of NiMH power assist batteries for future hybrid vehicles, but also open up additional fields of application for the NiMH system. Such applications include supply batteries for new 42 V-vehicle electrical systems.
In the field of development and production engineering, the lithium-ion high-power battery still lies several years behind the corresponding NiMH system for applications in the automotive sector. The results achieved to date nevertheless show that considerable potential exists in terms of power levels which it will be important to exploit in the future. Specific power levels up to 1500 W/kg with specific energy levels of up to 80 Wh/kg appear feasible. The main problem at the current time is the calendar service life, particularly under temperature conditions such as those that can be expected in automotive applications. It will be necessary to double the current service life in order to satisfy the needs of the vehicle industry.
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