Simultaneous Purification and Perforation of Low-Grade
Si Sources for Lithium-Ion Battery Anode
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Abstract
Silicon is regarded as one of the
most promising candidates for lithium-ion battery anodes because of
its abundance and high theoretical capacity. Various silicon nanostructures
have been heavily investigated to improve electrochemical performance
by addressing issues related to structure fracture and unstable solid–electrolyte
interphase (SEI). However, to further enable widespread applications,
scalable and cost-effective processes need to be developed to produce
these nanostructures at large quantity with finely controlled structures
and morphologies. In this study, we develop a scalable and low cost
process to produce porous silicon directly from low grade silicon
through ball-milling and modified metal-assisted chemical etching.
The morphology of porous silicon can be drastically changed from porous-network
to nanowire-array by adjusting the component in reaction solutions.
Meanwhile, this perforation process can also effectively remove the
impurities and, therefore, increase Si purity (up to 99.4%) significantly
from low-grade and low-cost ferrosilicon (purity of 83.4%) sources.
The electrochemical examinations indicate that these porous silicon
structures with carbon treatment can deliver a stable capacity of
1287 mAh g<sup>–1</sup> over 100 cycles at a current density
of 2 A g<sup>–1</sup>. This type of purified porous silicon
with finely controlled morphology, produced by a scalable and cost-effective
fabrication process, can also serve as promising candidates for many
other energy applications, such as thermoelectrics and solar energy
conversion devices