11-09 :: September 2011

nanotimes News in Brief

37

At left, the traditional approach to composite anodes using silicon (blue spheres) for higher energy capacity has a polymer binder such as PVDF (light brown) plus added particles of carbon to conduct electricity (dark brown spheres).

Silicon swells and shrinks while acquiring and relea- sing lithium ions, and repeated swelling and shrinking eventually break contacts among the conducting carbon particles.

At right, the new Berkeley Lab polymer (purple) is itself conductive and continues to bind tightly to the silicon particles despite repeated swelling and shrin- king. © LBL

At top, spectra of a series of polymers obtained with soft x-ray absorption spectroscopy at ALS beamline 8.0.1 show a lower “lowest unoccupied molecular orbital” for the new Berkeley Lab polymer, PFFOMB (red), than other polymers (purple), indicating better potential conductivity.

Here the peak on the absorption curve reveals the lower key electronic state. At bottom, simulations disclose the virtually complete, two-stage electron charge transfer when lithium ions bind to the new polymer. © LBL