Supporting Information
Understanding structure-function relationship in hybrid Co3O4-Fe2O3/C lithium-ion
battery electrodes
Irin Sultanaa, Md Mokhlesur Rahmana*, Thrinathreddy Ramireddya, Neeraj Sharmab, Debasis
Poddara, Abbas Khalidc, Hongzhou Zhangc, Ying Chena, Alexey M. Glushenkov a,d*
a
Institute for Frontier Materials, Deakin University, Waurn Ponds, VIC 3216, Australia.
b
c
School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia.
School of Physics and Centre for Research on Adaptive Nanostructures and Nano devices
(CRANN), Trinity College Dublin, Dublin 2, Ireland.
d
Melbourne Centre for Nanofabrication, 151 Wellington Rd, Clayton, VIC 3168, Australia.
Corresponding authors: [email protected]; [email protected]
Fax:+61352271103; Phone:+61352272642
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Molten salt method
The molten salt synthesis method is very simple, effective, inexpensive and practical for largescale application. The method can result in a very fine morphology due to the large viscosity and
dielectric behaviour of the eutectic system. Furthermore, molten salt compositions with their low
melting points could be very helpful in preventing the excessive growth of particles in such a
eutectic environment. The method itself is characterized by an accelerated reaction rate and
controllable particle morphology, because the salt melt acts as a strong solvent and exhibits a
high ionic diffusion rate. The molten salt method could also be used to produce other metal
oxides, such as nanosized magnetic or electrode materials. Please refer to additional references
on page S-7.
Figure S1
Figure S1a. (a) TEM bright-field image of Co3O4-Fe2O3 sample and (b) an overlay of the
energy-filtered elemental maps of Co and Fe (color scheme: iron-green; iron-red) of region (a).
The bright-field image reveals a duplex crystallite size of fine Co3O4 and coarser Fe2O3
nanoparticles.
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Figure S1b. TEM images (a, b) of the composite Co3O4/C sample: (a) a bright-field image and
(b) an energy-filtered elemental map of Co of region (a). TEM images (c, d) of the composite
Fe2O3/C sample: (c) a bright-field image and (d) an energy-filtered elemental map of Fe of
region (c).
Method of expected theoretical capacity calculations:
Co3O4-Fe2O3 sample:
In the Co3O4-Fe2O3 sample, the refined relative phase fractions of Co3O4 and Fe2O3 were
approximately 42 and 58 wt. %, respectively. It was confirmed by Rietveld-refined fit of the
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Co3O4 and Fe2O3 structural models to the XRD data as shown in Figure 1b. Therefore, traditional
theoretical capacity of Co3O4-Fe2O3 mixture as follows:
Theoretical capacity of Co3O4-Fe2O3 = theoretical capacity of Co3O4* % mass of Co3O4 +
theoretical capacity of Fe2O3 * % mass of Fe2O3 = 890*0.42 + 1007*0.58 = ~374 + ~584 =
~ 958 mAh g-1
(1)
Therefore, 1C = 958 mA current
Hybrid Co3O4-Fe2O3/C sample:
Co3O4-Fe2O3 and super P LiTM carbon black powders were mixed in a 2:1 weight ratio. i.e.,
hybrid Co3O4-Fe2O3 = ~ 67 wt. %, where phase fractions of Co3O4 = 28 wt. % and Fe2O3 = 39
wt. %, respectively.
Super P LiTM carbon black = ~ 33 wt. %.
Therefore, theoretical capacity of hybrid Co3O4-Fe2O3/C = theoretical capacity of Co3O4* %
mass of Co3O4 + theoretical capacity of Fe2O3 * % mass of Fe2O3 + experimental capacity of
super P LiTM carbon black * % mass of super P LiTM carbon black = 890*0.28 + 1007*0.39 +
270*0.33 = ~ 249.2 + ~ 392.73 + ~ 89.1 = ~ 731mAh g-1
(2)
Therefore, 1C = 731 mA current
It is important to note that we have considered capacity of super P LiTM carbon black around 270
mAh g-1 according to our experimental data as below:
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Figure S2. Cyclic performance of super P LiTM carbon black in the voltage range of 0.01-2.0V at
a current density of 150 mA g-1.
Fe2O3/C sample:
Fe2O3 nanoparticles and super P LiTM carbon black powder were mixed in a 2:1 weight ratio.
i.e., Fe2O3 nanoparticles = ~ 67 wt. %.
Super P LiTM carbon black = ~ 33 wt. %.
Therefore, theoretical capacity of Fe2O3/C = theoretical capacity of Fe2O3 * % mass of Fe2O3 +
experimental capacity of super P LiTM carbon black * % mass of super P LiTM carbon black =
1007*0.67 + 270*0.33 = ~ 674.69 + ~ 89.1 = ~ 764 mAh g-1
(3)
Therefore, 1C = 764 mA current
Co3O4/C sample:
Co3O4 nanoparticles and super P LiTM carbon black powder were mixed in a 2:1 weight ratio.
i.e., Co3O4 nanoparticles = ~ 67 wt. %.
Super P LiTM carbon black = ~ 33 wt. %.
Therefore, theoretical capacity of Co3O4/C = theoretical capacity of Co3O4* % mass of Co3O4 +
experimental capacity of super P LiTM carbon black * % mass of super P LiTM carbon black =
890*0.67 + 270*0.33 = ~ 596.3 + ~ 89.1 = ~ 685 mAh g-1
(4)
Therefore, 1C = 685 mA current
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Figure S3
Figure S3. Galvanostatic discharge/charge voltage profiles of (a) Co3O4-Fe2O3; (b) Co3O4/C;
and (c) Fe2O3/C samples measured in the voltage range of 0.01-3.0V at a current rate of 0.5C.
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Figure S4
Figure S4. Coulombic efficiency at 0.5C up to 150 cycles.
References:
Tang, W.; Yang, X.; Liu, Z.; Kasaishi, S.; Ooi, K. Preparation of Fine Single Crystals of
Spinel-Type Lithium Manganese Oxide by LiCl Flux Method for Rechargeable Lithium
Batteries. Part 1. LiMn2O4. J. Mater. Chem. 2002, 12, 2991-2997.
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Guo, Z.P.; Du, G.D.; Nuli, Y.; Hassan, M.F.; Liu, H.K. Ultra-Fine Porous SnO2 Nanopowder
Prepared via a Molten Salt Process: A Highly Efficient Anode Material for Lithium-Ion
Batteries. J. Mater. Chem. 2009, 19, 3253-3257.
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