Boffins build bionic battery Ten times' Li-ion capacity, charges
in a tenth of the time Researchers have devised an electrode
material that allows lithium-ion batteries to hold ten times the
charge they do today - and recharge ten times as quickly. The
trick, uncovered by scientists at Northwestern University in
Evanston, Illinois led by Professor Harold Kung, is to build the
battery's positive electrode, the anode, out of graphene, a form
of carbon comprised of atom-thick sheets. The anode is formed
from a "flexible, self-supporting three-dimensional conducting
graphenic scaffold" with clusters of silicon nanoparticles held
between each sheet of graphene. Silicon has been proposed before
as a material for lithium-ion battery anodes as it can hold more
lithium ions than carbon can: four lithium ions for every
silicon atom, compared to one lithium ion for every six carbon
atoms. Replacing carbon with silicon is hard, however, because
silicon expands and contracts during the charging process,
causing the materi