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Wednesday - February 13, 2008

Carbon nanotubes for lithium-ion battery packs

High purity for optimum charge flow

The strength of Baytubes® C150 HP is their exceptional purity, which is essential for the manufacture of lithium-ion batteries.

Leverkusen, February 13, 2008 – Because of their high energy density, long service life and low weight, rechargeable lithium-ion batteries are becoming increasingly popular in today's mobile world. They are particularly suitable for powering devices that have high energy consumption and also have to be light in weight, such as laptops, cameras, model airplanes and tools. Another important field of application for the future is car batteries, with the first Li-ion car batteries due to come off the production line very soon. One of the keys to their service life and performance is that the lithium ions are able to move unhindered in the graphite matrix that serves as the anode, so that there is no decrease in capacity even after several charge/discharge cycles. “Under the name Baytubes® C150 HP, we market carbon nanotubes that could be used as a battery additive to help safeguard this unhindered charge flow over a long period. The advantage of our product is that it complies with the extreme purity requirements specified by manufacturers of Li-ion batteries,” explains Dr. Heiko Hocke, a Baytubes® expert at Bayer MaterialScience AG.

When a lithium-ion battery is charged, lithium ions migrate from a lithium metal oxide to the anodic graphite layers and become embedded there (intercalation). When the battery discharged, the process is reversed. Through these charge/discharge processes, cyclical volume changes occur in the graphite matrix which, in the long term, cause changes in the matrix and result in a loss of power and a shortening of the battery's service life. Because of their structure, Baytubes® C150 HP are able to counter the negative effects of the volume changes and, in this way, ensure consistently high capacities and a long service life for the battery. “The high purity of our carbon nanotubes contributes to this. They contain no molybdenum and no iron. In addition, the concentration of soluble impurities that could contaminate the electrolyte of the Li-ion batteries is extremely low and is only in the ppm range,” says Hocke.
Further details on the applications and properties of Baytubes®, together with contact data for Baytubes® experts and information on ordering sample quantities can be found at www.baytubes.com.

About Bayer MaterialScience:
With 2006 sales of EUR 10.2 billion (continuing operations), Bayer MaterialScience is among the world’s largest polymer companies. Business activities are focused on the manufacture of high-tech polymer materials and the development of innovative solutions for products used in many areas of daily life. The main segments served are the automotive, electrical and electronics, construction and sports and leisure industries. Bayer MaterialScience has 30 production sites around the globe and employed approximately 14,900 people at the end of 2006. Bayer MaterialScience is a Bayer Group company.

Find more information at www.bayermaterialscience.com.

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This release may contain forward-looking statements based on current assumptions and forecasts made by Bayer Group or subgroup management. Various known and unknown risks, uncertainties and other factors could lead to material differences between the actual future results, financial situation, development or performance of the company and the estimates given here. These factors include those discussed in Bayer’s public reports which are available on the Bayer website at www.bayer.com. The company assumes no liability whatsoever to update these forward-looking statements or to conform them to future events or developments.