Effective Strategies for Improving Electrochemical Properties of Highly Porous Si Foam Anodes in Lithium-Ion Batteries

Transcription

1 Electronic Supplementary Material (ESI for Journal of Materials Chemistry A. This journal is The Royal Society of Chemistry 214 Supplementary Information Effective Strategies for Improving Electrochemical Properties of Highly Porous Si Foam Anodes in Lithium-Ion Batteries Taesoo Bok, a Sinho Choi, a Jeongchan Lee, b and Soojin Park* a a Interdisciplinary School of Green Energy, Ulsan National Institute of Science and Technology (UNIST, Ulsan , Korea b Duksan Hi-metal company, Yeonam-Dong, Buk-gu,Ulsan , Korea 1

2 a b c Vol. Adsorbed (cm 3 g nm 8 8 d 7 e 7 f Relative Pressure (P/P Vol. Adsorbed (cm 3 g Relative Pressure (P/P Vol. Adsorbed (cm 3 g Relative Pressure (P/P Fig. S1 TEM images of (a no-calcined SiO 2 foam, (b air-calcined SiO 2 foam, and (c oxygen-calcined SiO 2 foam. BET plots of (d no-calcined SiO 2 foam, (e air-calcined SiO 2 foam, and (f oxygen-calcined SiO 2 foam. SEM images of three samples show a similar sponge-like morphology. However, the surface areas of no-calcined SiO 2, air-calcined SiO 2 and oxygen-calcined SiO 2 foam are.13 m 2 /g, m 2 /g, and m 2 /g, respectively. 2

3 2 Intensity (a. u Si-foam Carbon-coated Si D-band G-band Raman shift (cm -1 Fig. S2 Raman spectra of as-synthesized Si foam (black line and carbon-coated Si foam (red line. D/G ratio of 2.21 indicates that amorphous carbon was coated on the Si surface. 3

4 a b c Fig. S3 TEM images of (a carbon-coated ncsi foam, (b carbon-coated acsi foam, and (c carbon-coated ocsi foam. Quantity Adsorbed (cm 3 /g STP dv/dlog(d cm 3 /g Quantity Adsorbed (cm 3 /g STP 2 a b c Relative Pressure (P/P Relative Pressure (P/P.4.6 d e f.5.3 dv/dlog(d cm 3 /g Quantity Adsorbed (cm 3 /g STP dv/dlog(d cm 3 /g Relative Pressure (P/P Pore diameter (nm Pore diameter (nm Pore diameter (nm Fig. S4 Surface area and pore size distribution of (a carbon-coated ncsi foam, (b carboncoated acsi foam, and (c carbon-coated ocsi foam. The surface areas of carbon-coated ncsi, acsi, and ocsi particles are m 2 /g, 63.2 m 2 /g, and 51.8 m 2 /g, respectively. 4

5 Si SiC Intensity (a.u. ocsi acsi ncsi (Degree Fig. S5 XRD patterns of ocsi (top, acsi (middle, and ncsi (bottom particles. In particular, ncsi particles show an existence of SiC layer that was formed during magnesiothermic reaction. 5

6 a b 22 μm 14 μm 1 μm 1 μm c d 37 μm 47 μm 2 μm 2 μm Fig. S6 Cross-sectional SEM images showing volume expansion of two Si electrodes (with and without NaCl before and after 1 cycles. Electrode thicknesses of Si with NaCl (a: before, c: after cycle and Si without NaCl (b: before, d: after cycle. The Si electrodes synthesized in the presence of NaCl showed volume expansion of 12% after 1 cycles, while Si electrode without NaCl exhibited 16%. 6

7 -Z'' ( a Z'' ( b Z' ( Z' ( Fig. S7 Nyquist plots of the electrochemical impedance spectra of (a Ag-loaded ocsi and (b ocsi electrodes after 5 cycles at a rate of.2 C. 7

8 a b Voltage (V Vs. Li/Li nm 2 nm c Specific Capacity (mah g -1 Charge Capacity (mah g d Cycle Number Coulombic Efficiency (% Fig. S8 TEM images of (a Cu-loaded SiO 2 foam and (b Cu-doped Si particles. (c First cycle voltage profile of the Cu-doped Si anode was obtained at.5 C rate between.5 and 1.2 V. (d Cycling retention of the Cu-doped Si was obtained at.2 C rate (dischargecharge until 5 cycles. After 5 cycles, a high reversible capacity of 141 mah g -1 was seen with good capacity retention of 84.2%, compared to initial capacity. 8