A well-crystallized and nano-sized Metal oxide/reduced graphene oxide composite material for lithium
ion batteries has been successfully synthesized. The nano-sized metal oxide particles were evenly dispersed
on the reduced graphene oxide template without any agglomeration, which allows the inherent high active
surface area of individual metal oxide nano-particles in the composite. These unique structural and morphological
properties of metal oxide on the highly conductive reduced graphene oxide sheets in the composite
enable achieving the high specific capacity, and excellent high rate capability and stable cycling performance.
an analysis of the cyclic voltammogram data revealed that a large surface charge storage contribution
of the metal oxide/reduced graphene oxide nanocomposite plays an important role in achieving faster
charge/discharge.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3526

Jegal, J.-P.

Kim, H.-K.

Kim, J.-G.

Kim, J.-Y.

Kim, K.-B.

Kim, K.-H.

Park, S.-H.

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 1 No 4, 04NEA07(3pp) (2012)   2304-1862/2012/1(4)04NEA07(3) 04NEA07-1  2012 Yonsei University Nanocomposites of Reduced Graphene Oxide for Energy Storage Applications  J.G. Kim, H.K. Kim, J.P. Jegal, K.H. Kim, J.Y. Kim, S.H. Park and K.B. Kim*  Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul, 120-749, South Korea  (Received 19 June; revised manuscript received 28 June 2012; published online 23 August 2012)  A well-crystallized and nano-sized Metal oxide/reduced graphene oxide composite material for lithium ion batteries has been successfully synthesized. The nano-sized metal oxide particles were evenly dispersed on the reduced graphene oxide template without any agglomeration, which allows the inherent high active surface area of individual metal oxide nano-particles in the composite. These unique structural and mor-phological properties of metal oxide on the highly conductive reduced graphene oxide sheets in the compo-site enable achieving the high specific capacity, and excellent high rate capability and stable cycling per-formance. an analysis of the cyclic voltammogram data revealed that a large surface charge storage contri-bution of the metal oxide/reduced graphene oxide nanocomposite plays an important role in achieving fast-er charge/discharge.  Keywords: Lithium Ion Battery, Metal Oxide, Reduced Graphene Oxide, Nanocomposite.   PACS numbers: 61.05.cp, 68.37.Lp                                                             * kbkim@yonsei.ac.kr 1. INTRODUCTION  Reduced graphene oxide (RGO) is expected to bring about a breakthrough in many applications including electrochemical energy storage devices due to its large specific surface area, high electrical conductivity, its chemical and mechanical properties. One obvious chal-lenge would be to utilize the 2D carbon nanostructure with regard to its large specific surface area and edge sites for the potential application in energy storage devices. RGO would be an excellent electrode materials and templates for the preparation of nanocomposites with metal oxides for electrochemical capacitor(EC) and Li ion battery applications [1, 2, 3].  Metal oxide/RGO nanocomposites are also of con-siderable interest for electrochemical energy storage applications owing to their unique electrical, chemical, and electrochemical properties. These excellent proper-ties of metal oxide/RGO nanocomposites are generated from synergistic combination of RGO with metal oxide on the nanometer scale. Pseudocapacitive reaction of metal oxide is likely to occur only at the surface or a very thin surface layer of the oxide. Therefore, metal oxide/RGO nanocomposites, where metal oxide forms only on the surface of RGO on the nanometer scale with a control over particle size, particle size distribu-tion, coating layer thickness, thickness uniformity and loading amount of metal oxide on RGOs, are expected to improve both high power and high energy properties for energy storage applications.  2. EXPERIMENTAL  2.1 Material preparation  A MnO2/RGO nanocomposite was first prepared by a direct redox reaction between RGO and MnO4- in aqueous solution. RGO nanosheets were used as a high surface area template for the selective heterogeneous nucleation and growth of MnO2.1 This MnO2/RGO nanocomposite was then allowed to react with LiOH aqueous solution for conversion to the LiMn2O4/RGO nanocomposite under MAH conditions. 2.2 Material Charaterizations  X-Ray diffraction (XRD) patterns of the LMO/RGO nanocomposite were measured at the beamline X7B of the National Synchrotron Light Source at Brookhaven National Laboratory. The wavelength used was 0.3184 Å. The sample (5–10 mg) was loaded into a glass capillary with a diameter of 0.5 mm. Two-dimensional powder patterns were collected with an image plate detector and the powder rings were integrated using the FIT2D code. The lattice parameter was determined by a Rietveld analysis using the general structure analysis system (GSAS) program The instrumental parameters (Thompson–Cox–Hastings profile coefficients) were derived from the fit of a LaB6 reference pattern. Trans-mission electron microscopy (TEM) imaging was per-formed on a JEOL JEM2100F TEM operated at 200 kV. The electrochemical properties were investigated using a three-electrode electrochemical cell , with two lithium foils as counter and reference electrodes at room temperature. The working electrode was prepared by mixing 85 wt % active material (LiMn2O4/RGO nanocomposite, LiMn2O4), 10 wt % acetylene black and 5 wt % polyvinylidene fluoride dissolved in N-methylpyrrolidone as a binder. The slurry mixture was coated on a titanium foil (99.7 % purity, Aldrich) and then dried at 100 C for 24 h. Each working electrode with a 1  1 cm2 area contained 1–2 mg of the dried slurry. The charge–discharge tests and cyclic voltam-metry were carried out at between 3.5 and 4.5 V (vs. Li/Li+) using a potentiostat/galvanostat (VMP2, Prince-ton Applied Research). The electrolyte used was 1 M LiPF6 dissolved in a mixture of ethyl carbonate (EC) and diethyl carbonate (DEC) at a volume ratio of 1 : 1. The specific capacity was calculated based on the weight of the LiMn2O4 in the LiMn2O4/RGO nanocom-posite electrode . (A 1 C rate corresponds to a current rate of 148 mA g − 1, which in the ideal case gives com-plete discharge in 1 h, based on the 73 wt% LiMn2O4 in the LiMn2O4/RGO nanocomposite).   J. G. KIM, H. K. KIM, J. P. JEGAL, ET AL. PROC. NAP 1, 04NEA07 (2012)   04NEA07-2 3. RESULT AND DISCUSSION  Fig. 1 shows the X-ray diffraction (XRD) pattern of the LiMn2O4/RGO nanocomposite (73 wt. % of LiMn2O4 in the LiMn2O4/RGO nanocomposite). All peaks could be indexed based on the cubic spinel LiMn2O4 structure (space group:Fd-3m). Rietvelt refinement was performed using this structure and afforded an excellent fit, indi-cating the formation of well-crystallized spinel LiMn2O4 phase on the RGO template without any impurity phase. The refined lattice constant a (8.2134  0.0002 Å) was slightly smaller than that of bulk stoichiometric LiMn2O4 (a   8.235 Å), which was attributed to either the slightly lithium-rich stoichiometry or the nano-size effect of the LiMn2O4 formed on the RGO template. The (002) peak of RGO was very weak, implying that the LiMn2O4 nanoparticles deposited on the RGO surface might prevent the restacking of the RGO sheets.     Fig. 1 – The Rietveld refinement of the spinel LiMn2O4/RGO nanocomposite materials    Fig. 2 – Low high-magnification TEM images of the spinel LiMn2O4/RGO nanocomposite materials  Transmission electron microscopy was used to inves-tigate the morphology of the LiMn2O4/RGO nanocompo-site material. Fig. 2 clearly shows the good dispersion and uniform coverage on the RGO nanosheets of the LiMn2O4 nanoparticles of size 10-40 nm.  Fig. 3 shows a cyclic voltammogram (CV) of the LiMn2O4/RGO nanocomposite electrode in an EC/DEC electrolyte of 1M LiPF6 at increasing potential scan rate from 1 mVs – 1 to 10 mVs – 1. The electrodes were fabri-cated by slurry casting of 85 wt. % active material (LiMn2O4/RGO nanocomposite), 10 wt. % acetylene black, and 5 wt. % PVDF binder dissolved in NMP sol-vent. The CV plot showed the typical shape of spinel LiMn2O4 with two pairs of well-separated current peaks in the 4V region. The two pairs of current peaks in the CV suggest that the lithium ions were extracted from and inserted into the spinel structure by a two-step pro-cess, which was in good agreement with those of typical well-crystallized spinel LiMn2O4    Fig. 3 – Cyclic voltammogram of the LiMn2O4/RGO nano-composite electrode (CV; scan rate: 1 mVs – 1  10 mVs – 1)  The two initial current peaks of the CV at 0.1 mVs – 1 were well distinguishable with increasing potential scan rate up to 10 mVs – 1, suggesting a good high rate capa-bility for the LiMn2O4/RGO nanocomposite. This result is further verified by the charge/discharge curves at dif-ferent C-rates. The rate performance of LiMn2O4/RGO was excellent, showing a capacity retention of 85  at 50 C-rate and 74  at 100 C-rate, compared with the specif-ic capacity of 137 mAhg – 1 at 1 C-rate. A comparison of the rate performance of the LiMn2O4/RGO nanocompo-site with data from the literature further supported its excellent rate capability.   4. CONCLUSION  A well-crystallized and nano-sized spinel LiMn2O4/RGO nanocomposite cathode material for high rate lithium ion batteries was successfully synthesized by a MAH method. Combined use of microwave irradia-tion and graphene as a template enabled the quick syn-thesis of a spinel LiMn2O4/RGO nanocomposite material with high crystallinity and ordered structure while maintaining a well-dispersed, nano-particular shape at very low temperature. This unique structural property of the LiMn2O4 in the nanocomposite supported a high spe-cific capacity of 137 mAhg – 1 at 1 C-rate and an excellent rate performance.     NANOCOMPOSITES OF REDUCED GRAPHENE OXIDE … Proc. NAP 1, 04NEA07 (2012)   04NEA07-3 AKNOWLEDGEMENTS  This work was supported by the National Research Laboratory Program through the National Research Foundation of Korea (NRF) grant funded by the Minis-try of Education, Science and Technology (MEST) (Grant No.: 2007-0055835). The work done at BNL was sup-ported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy under Contract Number DE-AC02-98CH10886.    REFERENCES  1. H.K. Kim, S.M. Bak, and K.B. Kim, Electrochem. Commun. 12, 1768 (2010). 2. S.H. Park, S.M. Bak, K.H. Kim, J.P. Jegal, S.I. Lee, J.H. Lee, and K.B. Kim, J. Mater. Chem. 21, 680 (2011). 3. S.M. Bak, K.W. Nam, C.W. Lee, K.H. Kim, H.C. Jung, X.Q. Yang and K.B. Kim, J. Mater. Chem. 21, 17309 (2011).  

Nanocomposites of Reduced Graphene Oxide for Energy Storage Applications

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 1 No 4, 04NEA07(3pp) (2012) 
 
 
2304-1862/2012/1(4)04NEA07(3) 04NEA07-1  2012 Yonsei University 
Nanocomposites of Reduced Graphene Oxide for Energy Storage Applications 
 
J.G. Kim, H.K. Kim, J.P. Jegal, K.H. Kim, J.Y. Kim, S.H. Park and K.B. Kim* 
 
Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul, 120-749, South Korea 
 
(Received 19 June; revised manuscript received 28 June 2012; published online 23 August 2012) 
 
A well-crystallized and nano-sized Metal oxide/reduced graphene oxide composite material for lithium 
ion batteries has been successfully synthesized. The nano-sized metal oxide particles were evenly dispersed 
on the reduced graphene oxide template without any agglomeration, which allows the inherent high active 
surface area of individual metal oxide nano-particles in the composite. These unique structural and mor-
phological properties of metal oxide on the highly conductive reduced graphene oxide sheets in the compo-
site enable achieving the high specific capacity, and excellent high rate capability and stable cycling per-
formance. an analysis of the cyclic voltammogram data revealed that a large surface charge storage contri-
bution of the metal oxide/reduced graphene oxide nanocomposite plays an important role in achieving fast-
er charge/discharge. 
 
Keywords: Lithium Ion Battery, Metal Oxide, Reduced Graphene Oxide, Nanocomposite. 
 
 PACS numbers: 61.05.cp, 68.37.Lp 
 
 
                                                          
* kbkim@yonsei.ac.kr 
1. INTRODUCTION 
 
Reduced graphene oxide (RGO) is expected to bring 
about a breakthrough in many applications including 
electrochemical energy storage devices due to its large 
specific surface area, high electrical conductivity, its 
chemical and mechanical properties. One obvious chal-
lenge would be to utilize the 2D carbon nanostructure 
with regard to its large specific surface area and edge 
sites for the potential application in energy storage 
devices. RGO would be an excellent electrode materials 
and templates for the preparation of nanocomposites 
with metal oxides for electrochemical capacitor(EC) 
and Li ion battery applications [1, 2, 3].  
Metal oxide/RGO nanocomposites are also of con-
siderable interest for electrochemical energy storage 
applications owing to their unique electrical, chemical, 
and electrochemical properties. These excellent proper-
ties of metal oxide/RGO nanocomposites are generated 
from synergistic combination of RGO with metal oxide 
on the nanometer scale. Pseudocapacitive reaction of 
metal oxide is likely to occur only at the surface or a 
very thin surface layer of the oxide. Therefore, metal 
oxide/RGO nanocomposites, where metal oxide forms 
only on the surface of RGO on the nanometer scale 
with a control over particle size, particle size distribu-
tion, coating layer thickness, thickness uniformity and 
loading amount of metal oxide on RGOs, are expected 
to improve both high power and high energy properties 
for energy storage applications. 
 
2. EXPERIMENTAL 
 
2.1 Material preparation 
 
A MnO2/RGO nanocomposite was first prepared by 
a direct redox reaction between RGO and MnO4- in 
aqueous solution. RGO nanosheets were used as a high 
surface area template for the selective heterogeneous 
nucleation and growth of MnO2.1 This MnO2/RGO 
nanocomposite was then allowed to react with LiOH 
aqueous solution for conversion to the LiMn2O4/RGO 
nanocomposite under MAH conditions. 
2.2 Material Charaterizations 
 
X-Ray diffraction (XRD) patterns of the LMO/RGO 
nanocomposite were measured at the beamline X7B of 
the National Synchrotron Light Source at Brookhaven 
National Laboratory. The wavelength used was 
0.3184 Å. The sample (5–10 mg) was loaded into a glass 
capillary with a diameter of 0.5 mm. Two-dimensional 
powder patterns were collected with an image plate 
detector and the powder rings were integrated using the 
FIT2D code. The lattice parameter was determined by a 
Rietveld analysis using the general structure analysis 
system (GSAS) program The instrumental parameters 
(Thompson–Cox–Hastings profile coefficients) were 
derived from the fit of a LaB6 reference pattern. Trans-
mission electron microscopy (TEM) imaging was per-
formed on a JEOL JEM2100F TEM operated at 200 kV. 
The electrochemical properties were investigated 
using a three-electrode electrochemical cell , with two 
lithium foils as counter and reference electrodes at 
room temperature. The working electrode was prepared 
by mixing 85 wt % active material (LiMn2O4/RGO 
nanocomposite, LiMn2O4), 10 wt % acetylene black and 
5 wt % polyvinylidene fluoride dissolved in N-
methylpyrrolidone as a binder. The slurry mixture was 
coated on a titanium foil (99.7 % purity, Aldrich) and 
then dried at 100 C for 24 h. Each working electrode 
with a 1  1 cm2 area contained 1–2 mg of the dried 
slurry. The charge–discharge tests and cyclic voltam-
metry were carried out at between 3.5 and 4.5 V (vs. 
Li/Li+) using a potentiostat/galvanostat (VMP2, Prince-
ton Applied Research). The electrolyte used was 1 M 
LiPF6 dissolved in a mixture of ethyl carbonate (EC) 
and diethyl carbonate (DEC) at a volume ratio of 1 : 1. 
The specific capacity was calculated based on the 
weight of the LiMn2O4 in the LiMn2O4/RGO nanocom-
posite electrode . (A 1 C rate corresponds to a current 
rate of 148 mA g − 1, which in the ideal case gives com-
plete discharge in 1 h, based on the 73 wt% LiMn2O4 in 
the LiMn2O4/RGO nanocomposite). 
 
 J. G. KIM, H. K. KIM, J. P. JEGAL, ET AL. PROC. NAP 1, 04NEA07 (2012) 
 
 
04NEA07-2 
3. RESULT AND DISCUSSION 
 
Fig. 1 shows the X-ray diffraction (XRD) pattern of 
the LiMn2O4/RGO nanocomposite (73 wt. % of LiMn2O4 
in the LiMn2O4/RGO nanocomposite). All peaks could be 
indexed based on the cubic spinel LiMn2O4 structure 
(space group:Fd-3m). Rietvelt refinement was performed 
using this structure and afforded an excellent fit, indi-
cating the formation of well-crystallized spinel LiMn2O4 
phase on the RGO template without any impurity phase. 
The refined lattice constant a (8.2134  0.0002 Å) was 
slightly smaller than that of bulk stoichiometric 
LiMn2O4 (a   8.235 Å), which was attributed to either 
the slightly lithium-rich stoichiometry or the nano-size 
effect of the LiMn2O4 formed on the RGO template. The 
(002) peak of RGO was very weak, implying that the 
LiMn2O4 nanoparticles deposited on the RGO surface 
might prevent the restacking of the RGO sheets.  
 
 
 
Fig. 1 – The Rietveld refinement of the spinel LiMn2O4/RGO 
nanocomposite materials 
 
 
 
Fig. 2 – Low high-magnification TEM images of the spinel 
LiMn2O4/RGO nanocomposite materials 
 
Transmission electron microscopy was used to inves-
tigate the morphology of the LiMn2O4/RGO nanocompo-
site material. Fig. 2 clearly shows the good dispersion 
and uniform coverage on the RGO nanosheets of the 
LiMn2O4 nanoparticles of size 10-40 nm.  
Fig. 3 shows a cyclic voltammogram (CV) of the 
LiMn2O4/RGO nanocomposite electrode in an EC/DEC 
electrolyte of 1M LiPF6 at increasing potential scan rate 
from 1 mVs – 1 to 10 mVs – 1. The electrodes were fabri-
cated by slurry casting of 85 wt. % active material 
(LiMn2O4/RGO nanocomposite), 10 wt. % acetylene 
black, and 5 wt. % PVDF binder dissolved in NMP sol-
vent. The CV plot showed the typical shape of spinel 
LiMn2O4 with two pairs of well-separated current peaks 
in the 4V region. The two pairs of current peaks in the 
CV suggest that the lithium ions were extracted from 
and inserted into the spinel structure by a two-step pro-
cess, which was in good agreement with those of typical 
well-crystallized spinel LiMn2O4 
 
 
 
Fig. 3 – Cyclic voltammogram of the LiMn2O4/RGO nano-
composite electrode (CV; scan rate: 1 mVs – 1  10 mVs – 1) 
 
The two initial current peaks of the CV at 0.1 mVs – 1 
were well distinguishable with increasing potential scan 
rate up to 10 mVs – 1, suggesting a good high rate capa-
bility for the LiMn2O4/RGO nanocomposite. This result 
is further verified by the charge/discharge curves at dif-
ferent C-rates. The rate performance of LiMn2O4/RGO 
was excellent, showing a capacity retention of 85  at 50 
C-rate and 74  at 100 C-rate, compared with the specif-
ic capacity of 137 mAhg – 1 at 1 C-rate. A comparison of 
the rate performance of the LiMn2O4/RGO nanocompo-
site with data from the literature further supported its 
excellent rate capability.  
 
4. CONCLUSION 
 
A well-crystallized and nano-sized spinel 
LiMn2O4/RGO nanocomposite cathode material for high 
rate lithium ion batteries was successfully synthesized 
by a MAH method. Combined use of microwave irradia-
tion and graphene as a template enabled the quick syn-
thesis of a spinel LiMn2O4/RGO nanocomposite material 
with high crystallinity and ordered structure while 
maintaining a well-dispersed, nano-particular shape at 
very low temperature. This unique structural property of 
the LiMn2O4 in the nanocomposite supported a high spe-
cific capacity of 137 mAhg – 1 at 1 C-rate and an excellent 
rate performance. 
 
 
 
 NANOCOMPOSITES OF REDUCED GRAPHENE OXIDE … Proc. NAP 1, 04NEA07 (2012) 
 
 
04NEA07-3 
AKNOWLEDGEMENTS 
 
This work was supported by the National Research 
Laboratory Program through the National Research 
Foundation of Korea (NRF) grant funded by the Minis-
try of Education, Science and Technology (MEST) (Grant 
No.: 2007-0055835). The work done at BNL was sup-
ported by the Assistant Secretary for Energy Efficiency 
and Renewable Energy, Office of Vehicle Technologies of 
the U.S. Department of Energy under Contract Number 
DE-AC02-98CH10886. 
 
 
 
REFERENCES 
 
1. H.K. Kim, S.M. Bak, and K.B. Kim, Electrochem. Commun. 
12, 1768 (2010). 
2. S.H. Park, S.M. Bak, K.H. Kim, J.P. Jegal, S.I. Lee, 
J.H. Lee, and K.B. Kim, J. Mater. Chem. 21, 680 (2011). 
3. S.M. Bak, K.W. Nam, C.W. Lee, K.H. Kim, H.C. Jung, 
X.Q. Yang and K.B. Kim, J. Mater. Chem. 21, 17309 
(2011). 
 


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Nanocomposites of Reduced Graphene Oxide for Energy Storage Applications

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