Electronic Supplementary Information (ESI) for

Novel hybrid Si film/carbon nanofiber for anode materials in lithium-ion batteries

Haejune Kim, Xingkang Huang, Zhenhai Wen, Shumao Cui, Xiaoru Guo, and Junhong Chen

Department of Mechanical Engineering,University of Wisconsin-Milwaukee,Milwaukee, Wisconsin 53211, USAJunhong Chen, email:jhchen@uwm.edu; Fax: +1-414-229-6958; Tel: +1-414-229-2615

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Co

un

ts

Energy (keV)

C

O AlSi

Cr Fe

a b

c d

Fig. S1. (a) SEM secondary electron image, (b) and(c) Elemental maps of Si and C in Si/CNF, respectively, (d) EDS spectra of Si /CNF.

Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A.This journal is © The Royal Society of Chemistry 2014

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0

Inte

nsity

(a.u

.)

Cu K 2 (degree)

111

Fig. S2. XRD pattern of the Si/CNF electrode. No detectable peak for Si was observed. The

two peaks can be indexed to the stainless steel (JCPDS no. 33-397).

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nsity

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.)

2θ (degree)

Cu

Si on Cu

Fig. S3. X-ray diffraction patterns of Si film on Cu substrate (red line) and Cu substrate alone (black line).

Si

SiO2

D G

Fig. S4. Raman spectra of CNFs before and after the Si film deposition (red line: Si/CNF,

black line: CNF).

Fig. S5. TEM images of the Si/CNF composite anode after 200 cycles.

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ific

capa

city

/ mAh

g-1

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Charge Discharge Coulumbic efficiency

020406080100

Cou

lom

bic

effic

ienc

y/ %

Fig. S6. Cycle performance of CNF alone electrode between 0.01 and 2.0 V at a current rate

of 0.5 C (or 150 mA g-1) in the first 3 cycles, and 1 C (or 300 mA g-1) for the rest of the

cycles.

Fig. S7. Cyclic voltammetry (CV) of the Si/CNF anode. The initial 3 cycles were limited in

the potential range between 0.01 and 1.5 V, while at the 4th cycle, the potential limit was

extended to 3.0 V. The solid electrolyte interphase formation was observed at 0.5 V during

the initial cathodic scan. The CV curves are typical for Si anodes, showing two cathodic

peaks at 0.23 and 0.06 V and two anodic peaks at 0.33 and 0.49 V; the cathodic shoulder

peak at 0.09 V and the anodic peak at 1.7 V are very likely due to the lithiation and

delithiation of the CNF, a poorly crystalized carbon.

a b

Fig. S8. CNFs grown on stainless steel foil. (a) CNF-grown stainless steel foil in CVD

reactor. (b) CNFs are totally covered on both sides of stainless steel foil size of 15 ⨯ 150 mm.