็High capacity alloying anode materials for lithium ion
batteries, such as silicon and germanium, have generated
significant research interest in the last 10 years. Silicon, which has
a lithium storage specific capacity of 4200 mAh/g,1 has been the
topic of over 500 research papers in the last 3 years.2 Although
silicon is a promising anode active material due to its extremely
high specific capacity, one of its primary disadvantages is that
large volume changes (>400%)3 can lead to rapid pulverization
of Si particles and loss of capacity during cycling. A common
approach to improving the cycling performance of silicon-based
anodes is to use nanostructured silicon,1,4−7 but a drawback to
this approach is that the high surface area of nanostructured
materials significantly increases solid electrolyte interphase
(SEI) formation on the first cycle.8 SEI formation on silicon
anodes during the first cycle causes a high irreversible capacity
loss and can result in low Coulombic efficiency (CE) values
such as 25−75%, depending on the structure of the silicon and
the composition of the anode composite.1 In addition to using
high capacity active materials like silicon, free-standing
electrodes have generated significant interest due to their
potential to eliminate electrochemically inactive mass from
metal foil current collectors.8−22 Similar to composite electrodes
based on nanostructured silicon, free-standing electrodes
often incorporate high surface area nanomaterials like CNTs or
graphene, which causes low CE values (