Download Supporting Information Spindle-like Mesoporous α

Supporting Information
Spindle-like Mesoporous α-Fe2O3 Anode Material Prepared from MOF Template
for High Rate Lithium Batteries
Xiaodong Xu, Ruiguo Cao, Sookyung Jeong and Jaephil Cho*
Interdisciplinary School of Green Energy,
Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Korea
*E-mail: [email protected]
Experimental Section
Synthesis of MIL-88-Fe: Typically, FeCl3·6H2O (0.748 g) and 1,4benzenedicarboxylate (0.460 g) were dissolved in 120 mL DMF. After thorough mixing,
the solution was transferred into a Teflon-lined stainless steel autoclave and placed in an
o
oven at 150 C for 7 days. After cooling down to room temperature, the product was
collected by centrifugation, washed with DMF and ethanol for three times, respectively.
At last, the orange powder of MIL-88-Fe was obtained after drying in a vacuum oven at
60 oC for 12 h.
Preparation of the spindle-like porous α-Fe2O3.: The powder of MIL-88-Fe was placed
in a tube furnace under N2 gas flow (1 L/min), heated to 500 oC (5 oC/min), and
maintained at 500 oC for 1h. The obtained black powder was FeOx-C composite. Then it
was placed in a box furnace, heated to 380 oC (5 oC/min) in air, and maintained at 380 oC
for 1 h to remove the carbon residue. This two-step calcination resulted in the final
spindle-like porous α-Fe2O3. For comparison, MIL-88-Fe was also directly heated to 380
o
C (5 oC /min) in air, and maintained at 380 oC for 2 h, to obtain another different α-Fe2O3.
Characterization of materials: Powder X-ray diffraction (PXRD) patterns were
obtained on D/MAX-2200 diffractometer (Rigaku) in step mode by using Cu-Ka
radiation. The adsorption-desorption isotherms for N2 (77 K) were recorded by using
Autosorb-1 (ATI Korea). The SEM images were obtained by using NanoSEM230
scanning electron microscopy (FEI). The TEM and EDS mapping images were taken on
JEM2100 transmission electron microscopy (JEOL) operated at 200kV. The TGA curves
were performed on thermogravimetric analyzer TGA-50 (Shimadzu). Elemental analysis
was performed on Flash2000 element analyzer (Thermo Scientific).
Fabrication of electrochemical cells: The anodes were made of Fe2O3, Ketjen Black,
and polyvinylidone fluoride (PVDF) binder (LG Chem.) in a weight ratio of 80:10:10.
The coin-type half cells (2016R) were assembled in an Ar-filled glove box, using lithium
metal foil as the counter electrode, microporous polyethylene as the separator, and 1.1 M
LiPF6 in ethylene carbonate/diethylene carbonate (EC/DEC, 1:1 in volume ratio, Panax
Starlyte, Korea) as the electrolyte. The loading amount of the electrode material was
measured as ~1 mg cm-2. The cell tests were performed by using a WBCS3000 automatic
battery cycler system, and the capacity was estimated based only on α-Fe2O3.
Figure S1. (A) PXRD pattern of as-prepared MIL-88-Fe.
Figure S2. (A) PXRD pattern of the FeOx-C composite. (B) TGA curve of the FeOx-C
composite in air at a heating rate of 5 oC/min. The increasing of weight starts at 150 oC should be
o
attributed to the transformation from FeOx to Fe2O3. The weight loss after 300 C corresponds to
the removal of carbon residue.
Figure S3. TGA curve of the final spindle-like α-Fe2O3 in air at a heating rate of 5 oC/min.
Figure S4. N2 adsorption-desorption isotherm of the spindle-like α-Fe2O3. Inset: poresize distribution based on the BJH method.
Figure S5. EDS mapping images of elemental distribution in the spindle-like α-Fe2O3.
Figure S6. Coloumbic efficiencies of the spindle-like α-Fe2O3 anode when cycling at 0.2
C rate.
Figure S7. Voltage profiles of bulk α-Fe2O3 at different charge rates. The discharge rate
is fixed at 0.1 C (1 C=1000 mA g-1).
Figure S8. (A) PXRD pattern (B) N2 adsorption-desorption isotherm (C) SEM image (D)
cell performance of α-Fe2O3 obtained by heating MIL-88-Fe directly in air at 380 oC.