Si-Ni Composite from Recycled Solar-Grade Kerf-Loss Silicon and Its Application in Lithium-ion Batteries
Date Issued
2015
Date
2015
Author(s)
Huang, Tzu-Yang
Abstract
Turning the recycled waste into high-value products is of strategic importance for industrial processes. Despite the fact that most of the high-purity Si is wasted during wafer slicing in fabricating photovoltaic (PV) modules, the applications of recycled kerf-loss Si (K-Si) still remain limited and may not meet the cost of purification from slurry containing abrasive silicon carbide (SiC). K-Si was found to be ragged-edge particles in nano-size, while micro-sized SiC single-crystallites featured sharp edge. A simple and facile method was developed to synthesize structurally robust Si-SiC-Ni composite microparticles (SSNs) from processed kerf-loss powder with the addition of metal Ni. Owing to their mechanically robust and conductive nature, the SSN electrodes exhibited suppressed expansion and stable cycling performance as lithium-ion battery (LiB) anodes. Adjustment in milling time with addition of carbon black (CB) resulted in different amount of amorphous silicon oxide (a-SiO2) formed during high-energy ball-mill. Analysis from X-ray absorption spectroscopy (XAS) combined with X-ray diffraction (XRD) led to the proposed mechanism of solid-phase reaction facilitated by ball-mill: 2 NiO + 3 Si → 2 a-NiSi + a-SiO2. Temperature programmed reduction (TPR) analysis further underlined the fact that part of NiO has been irreversibly reduced by Si particles in the milling step. As a result from process analysis and optimization, composite milled with 1 wt.% CB for 4 hours and calcined at 700°C was found to exhibit the most promising electrochemical behavior, suggesting a reversible capacity up to 769 mAh/g. Cycling stability was further improved by modifying the acidity of electrode-slurry and cut-off voltage for lithiation. Modified SSN anodes retained 85% retention of capacity after 100 cycles of full lithiation/delithiation at 300 mA/g and no capacity decay was observed for electrode cut off at 40 mV for lithiation in the first 100 cycles, which is expected to meet the requirement of practical applications in LiB and suggests an alternative for the usage of Si recovered from kerf loss.
Subjects
Li-ion batteries
Anodes
Silicon
Nickel
Kerf loss
Recycling
Type
thesis
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