17 May 2007
On a charge!
US researchers may have discovered a technique that greatly improves the performance of lithium ion batteries, although the development is unlikely to be mature enough for inclusion in the forthcoming revision of an important IEEE standard.
A team from the Argonne National Laboratory, part of the US Department of Energy, has unveiled laptop type batteries with storage capacities of 250mAh/g and better – more than twice the capacity of comparable batteries available today.
The performance boost was primarily achieved by simply changing the material for the positive electrode to a proprietary nano crystalline, layered composite rich in manganese. These electrodes are also cheaper to produce than the cobalt and nickel based versions currently used.
However, in presenting the research, Chris Johnson from the Argonne team, cautioned that the performance was ‘anomalous’ in that it exceeded expectations for reasons that could not yet be fully explained.
He further noted that the capacity of the current prototype batteries fell too rapidly for the technology to be available for short term commercial deployment. A decline from 311mAh/g to 261mAh/g occurred in just nine charge/discharge/recharge cycles, followed by further decreases for subsequent cycles.
Finally, extra innovation is required to control the impact of decay in the manganese rich layers over a battery’s lifetime.
Argonne will continue its work, but these issues mean the new battery is unlikely to influence the next version of IEEE1625, the ‘Standard for Rechargeable Batteries for Portable Computing’.
The IEEE fast tracked the update to 1625 late last year following a series of Li-ion battery recalls. The revised standard is due before the end of the year.
Author
Paul Dempsey
Supporting Information
Websites
http://www.anl.gov
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