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| Prototype of a Fraunhofer lithium-polymer cell for use in hybrid vehicles. |
The Fraunhofer Institutes for Silicon Technology (ISIT) in Itzehoe, Integrated Circuits (IIS) in Nuremberg, and Integrated Systems and Device Technology (IISB) in Erlangen are collaborating on the development of a new lithium-ion polymer cell and pack as part of the German project “Fleet test: electric drive vehicles” (“Flottenversuch Elektromobilität”).
Volkswagen AG is leading the project, with E.ON (energy provider) and LTC/GAIA and Evonik/Li-Tec (lithium-ion battery providers) as principal partners. Also contributing from the research side are the Fraunhofer-Gesellschaft, Heidelberg Institute for Energy and Environmental Research (Ifeu), the German Center for Aerospace Technology (DLR), and the Westphalian Wilhelms University at Münster.
Fraunhofer will use a chemistry that is “significantly different from current mainstream technologies,” according to Dr. Gerold Neumann of Fraunhofer ISIT and the co-ordinator of the Fraunhofer activities for the project.
Fraunhofer ISIT has been optimizing and testing new cell chemistries for use in HEV- and/or EV-storage devices for a number of years. The Institute has put a special focus on systems using lithium titanate (Li4Ti5O12) as the anode material. ISIT is exploring the combination of titanate-based systems with conventional electrolytes for standard Li-ion cells or with new electrolytes to further extend the temperature range of operation or improve safety and durability. In its annual report for 2007, ISIT notes that:
High current capability (charging and discharging) in such cells can be achieved by using fine sized or even nanocrystallinic Lithium titanate particles in the anode. One challenge left is the improvement of energy density in this system. Projects addressing this aspect are on the way.
For the VW PHEV project, the researchers will use an internally-developed polymer matrix separator containing a ceramic filler. The electrolyte material is not ORMOCER, said Dr. Neumann. Other Fraunhofer researchers have developed a lithium-ion polymer electrolyte derived from ORMOCER (ORganically MOdified CERamics) materials—inorganic-organic hybrid polymers also developed at Fraunhofer.
A polymer electrolyte in lithium-ion batteries can offer a number of advantages such as design flexibility and stability under abusive conditions, but it can also be a less efficient conductor of the lithium ions. Groups at Fraunhofer have been working with ORMOCER materials over the last 10 years to optimize its properties for use in Li-ion cells (among other applications).
Work on the new energy storage system for the PHEV project will also incorporate a specially developed battery management system to deliver better durability and reliability and new packaging concepts.
This module has to be able to withstand the harsh environmental conditions it will encounter in a hybrid vehicle, and above all it must guarantee high operational reliability and a long service life.
—Dr. Gerold Neumann
The tasks involved are distributed between the three Fraunhofer Institutes according to their expertise: ISIT is manufacturing the cells; IIS is responsible for battery management and monitoring; and IISB is contributing its know-how on power electronics components to configure the modules. The development and configuration of the new energy storage module is expected to be finished by mid-2010.
Volkswagen AG will then carry out field trials to test the modules’ suitability for everyday use in the vehicles.
The Fraunhofer-Gesellschaft is the largest organization for applied research in Europe and comprises more than 80 research units, including 56 Fraunhofer Institutes at 40 different locations in Germany. It has an annual research budget totalling € 1.3 billion (US$1.9 billion). Of this, more than €1 billion is generated through contract research. Two thirds of the research revenue is derived from contracts with industry and from publicly financed research projects.
Resources
Fraunhofer ISIT Achievements and Results Annual Report 2007
# Glossary: PHEV - Plug-in Hybrid Electric Vehicles
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