Green Car Congress  
Go to GCC Discussions forum About GCC Contact  RSS Subscribe Twitter headlines

« Western China to Rebuild 37 Airports Between 2006-10 | Main | Thune Pushes for E20 Approval by US EPA »

Print this post

Researchers Explore “Molecular Wiring” to Enhance Li-Ion Battery Performance

12 March 2007

Ja066260jf00002
Cyclic voltammograms (CV) of BMABP-derivatized LiFePO4 (red, blue) and mesoscopic Al2O3 (green) electrodes. The black line shows the curve of a bare LiFePO4 electrode. Click to enlarge.

Michael Grätzel (of the Grätzel Cell, a dye-sensitized photoelectrochemical cell) and colleagues at the Swiss Federal Institute of Technology in Lausanne (École Polytechnique Fédérale de Lausanne, EPFL), are researching the use of a molecular charge transport layer to reduce the amount of carbon required in lithium-ion battery cathodes and open up the possibility of much improved energy storage density.

Their work will be published in the 4 April print issue of the Journal of the American Chemical Society, and is currently published online.

he cathodes (positive electrodes) in lithium-ion batteries usually contain large amounts of carbon, graphite or other conductive material to improve conductivity. In some cells, the conductive additives occupy practically half the volume of the active materials, greatly decreasing the energy density of the cell.

This situation is even more severe for the new generation cathodic materials, olivine-type LiMPO4 (M = Fe, Co, Ni, Mn), because of their extremely low electronic conductivity (s, ~10-9 S cm-1). For this reason, great endeavors are being made to increase the conductivity of the cathode materials, for example, carbon coating and supervalent cation doping. However, so far the success of these strategies has been very limited, a large amount of carbon still being needed to afford reasonable battery performance.

The EPFL team had been working with self-assembled molecular charge transport layers on mesoscopic oxide films. In this work, they applied such molecular charge transport layers to electrochemically address insulating battery materials.

The EPFL team took a lithium iron phosphate cathode material (LiFePO4)—one of the most thermally stable li-ion cathode materials, but hampered by lower voltage and lower energy—and created a derivative material with a monolayer of 4-[bis(4-methoxyphenyl)amino]benzylphosphonic acid (BMABP).

The findings demonstrated that a single molecular layer of a suitable redox-active molecule alone can provide the desired electronic charge transport while still permitting lithium-ion exchange to occur rapidly across the solid/electrolyte interface.

As compared to the total electrode size, the space occupied by the molecular charge transport layer is negligibly small, which greatly reduces the volume of conductive additive, opening up the possibility to increase substantially the energy storage density and rate capability at equal amounts of loading of conductive additives.

Resources:

March 12, 2007 in Batteries | Permalink | Comments (0) | TrackBack (0)

TrackBack

TrackBack URL for this entry:
http://www.typepad.com/services/trackback/6a00d8341c4fbe53ef00d83576838e69e2

Listed below are links to weblogs that reference Researchers Explore “Molecular Wiring” to Enhance Li-Ion Battery Performance:

Comments

Verify your Comment

Previewing your Comment

This is only a preview. Your comment has not yet been posted.

Working...
Your comment could not be posted. Error type:
Your comment has been posted. Post another comment

The letters and numbers you entered did not match the image. Please try again.

As a final step before posting your comment, enter the letters and numbers you see in the image below. This prevents automated programs from posting comments.

Having trouble reading this image? View an alternate.

Working...

Post a comment

Green Car Congress © 2013 BioAge Group, LLC. All Rights Reserved. | Home | BioAge Group