jp7b05919_si_001.pdf (847.32 kB)
Cycling Behavior of Silicon-Containing Graphite Electrodes, Part A: Effect of the Lithiation Protocol
journal contribution
posted on 2017-08-08, 00:00 authored by Tiphaine Schott, Rosa Robert, Pirmin A. Ulmann, Patrick Lanz, Simone Zürcher, Michael E. Spahr, Petr Novák, Sigita TrabesingerSilicon (Si) is a promising additive
for enhancing the specific charge of graphite negative electrodes
in Li-ion batteries. However, Si alloying with lithium leads to an
extreme volume expansion and in turn to rapid performance decline.
Here we present how controlling the lithiation depth affects the performance
of graphite/Si electrodes when different lithiation cutoff potentials
are applied. The relationship between Si particle size and cutoff
potential was investigated to clarify the interdependence of these
two parameters and their impact on the performance of Si-containing
graphite electrodes. For Si with a particle size of 30–50 nm,
Li15Si4 is only formed for the potential cutoff
of 5 mV vs Li+/Li, whereas using a higher cutoff of 50
mV has no impact on the performance. For larger Si nanoparticles,
70–130 nm in size, Li15Si4 is already
formed at 50 mV. However, in these larger particles only 70% of the
Si initially participates in the lithiation, independent of the cutoff
potential (5 or 50 mV), and the performance fades rapidly. For the
highest tested cutoff potential of 120 mV, the contribution of larger
Si particles to the specific charge of the electrodes was negligible,
but for the smaller particles a stable and still significant Si specific
charge was obtained.