  Silicon is one of the most promising anode materials for Lithium-ion
batteries. Silicon endures volume changes upon cycling, which leads to
subsequent pulverization and capacity fading. These drawbacks lead to a poor
lifespan and hamper the commercialization of silicon anodes. In this work, a
hybrid nanostructured anode based on silicon nanoparticles (SiNPs) anchored on
vertically aligned carbon nanotubes (VACNTs) with defined spacing to
accommodate volumetric changes is synthesized on commercial macroscopic current
collector. Achieving electrodes with good stability and excellent
electrochemical properties remain a challenge. Therefore, we herein tune the
active silicon areal loading either through the modulation of the SiNPs volume
by changing the silicon deposition time at a fixed VACNTs carpet length or
through the variation of the VACNT length at a fixed SiNPs volume. The low
areal loading of SiNPs improves capacity stability during cycling but triggers
large irreversible capacity losses due to the formation of the solid
electrolyte interphase (SEI) layer. By contrast, higher areal loading electrode
reduces the quantity of the SEI formed, but negatively impacts the capacity
stability of the electrode during the subsequent cycles. A higher gravimetric
capacity and higher areal loading mass of silicon is achieved via an increase
of VACNTs carpet length without compromising cycling stability. This hybrid
nanostructured electrode shows an excellent stability with reversible capacity
of 1330 mAh g-1 after 2000 cycles.
