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Cite this: J. Mater. Chem., 2012, 22, 17429

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Self-supporting Co3O4 with lemongrass-like morphology as ahigh-performance anode material for lithium ion batteries†

Yujun Fu, Xiuwan Li, Xiaolei Sun, Xinghui Wang, Dequan Liu and Deyan He*

Received 8th June 2012, Accepted 3rd July 2012

DOI: 10.1039/c2jm33704e

Self-supporting Co3O4 with lemongrass-like morphology exhibits

excellent rate capability and cyclic stability for high-performance Li

ion batteries as electrodes. It retains a high reversible capacity of up

to 981 mA h g�1 after 100 cycles at a rate of 0.5 C and a capacity

higher than 381 mA h g�1 even at a rate as high as 10 C.

Recently, Co3O4 has attractedmuch attention and become one of the

most promising anodematerials for the next generation of lithium ion

batteries (LIBs) due to its superior specific capacity (890 mA h g�1 intheory), low cost, and environmental friendliness.1–5 Until recently,

Co3O4 powders with various morphologies have been synthesized as

anode materials, including hollow spheres,6 nanofibers,7 nanobelts,8

nanotubes,9 nanocapsules,10 nanocages,11 and so on. Despite the high

capacities in the first few cycles, most of the powder materials display

unsatisfactory cycling stability mainly owing to the poor electronic

conduction. Several strategies have been proposed to solve the

problems, in which self-supporting Co3O4 nanostructures grown

directly on current-collecting substrates represent an attractive

approach. Li et al. have prepared mesoporous Co3O4 nanowire

arrays on Ti foil by a template-free method, which deliver a capacity

of 700 mA h g�1 after 20 cycles at a current of 111 mA g�1.12 Fanet al. have synthesized freestanding Co3O4 porous nanosheets on

nickel foil and found that, when the architecture is used as an anode

for LIBs, the capacity maintains 631 mA h g�1 after 50 cycles at a

constant current of 150 mA g�1.13 Wang et al. have prepared the

Co3O4 nanobelt arrays on Ti foil, which retain a specific capacity of

770 mA h g�1 over 25 cycles at a current density of 177 mA g�1.14 Liet al. have fabricated Co3O4 nanowire arrays directly on steel coins

coated by gold nanoparticles, which show a capacity of 743mAh g�1

after 50 cycles at a current density of 100 mA g�1, but the capacitiesgradually fade at higher discharge rates.15 It is clear that, as a qualified

anode material for LIBs for high-power applications, further

School of Physical Science and Technology, Key Laboratory forMagnetism and Magnetic Materials of MOE, Lanzhou University,Lanzhou, 730000, China. E-mail: hedy@lzu.edu.cn; Fax: +86-931-8913554; Tel: +86-931-8912546

† Electronic supplementary information (ESI) available: Experimentaldetails; XRD pattern and SEM images of the as-synthesized precursor;XRD pattern, Raman spectrum, and schematic diagram of Li+

insertion/extraction for self-supporting Co3O4 electrodes; SEM imagesof the self-supporting Co3O4 electrode after 100 discharge–chargecycles at a rate of 0.5 C. See DOI: 10.1039/c2jm33704e

This journal is ª The Royal Society of Chemistry 2012

investigations are essential to improve the rate capacity and cycling

stability of Co3O4 materials.

In this letter, we report a self-supporting Co3O4 with lemongrass-

like morphology grown on a Ni foam substrate by a simple

hydrothermal synthesis with subsequent calcination. The unique

architecture exhibits high capacity, excellent rate capability and cyclic

stability when used as an anode in LIBs. The experimental results

indicate that such a nanostructure of Co3O4 might be a qualified

anode material for LIBs.

Self-supporting Co3O4 with lemongrass-like morphology was

fabricated by a facile hydrothermal growth with subsequent calci-

nation (see ESI† for more experimental details). Fig. 1 shows typical

SEMandTEM images of the obtainedCo3O4. It reveals that the self-

supporting Co3O4 (Fig. 1a and b) still retains the morphology of the

as-synthesized precursor (see ESI, Fig. S1†). The low-magnification

SEM image (Fig. 1a) shows that Co3O4 with lemongrass-like

morphologywas growndirectly on the substrate ofNi foam in a large

area. The architectures are homogeneously aligned and intensively

adhered to Ni foam (inset in Fig. 1a) with an average thickness of

about 2 mm. The detailed morphology of the unique architecture is

Fig. 1 Morphology and structure characterization of the sample. (a)

Low-magnification SEM image, the inset is a side view. (b) High-

magnification SEM image. (c) TEM image of a single blade, the inset

shows its SAED pattern. (d) HRTEM image of the area indicated by the

white rectangle in (c).

J. Mater. Chem., 2012, 22, 17429–17431 | 17429

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displayed in Fig. 1b. It can be observed that the architecture is

composed of small blades. The typical TEM image for a single blade

shown in Fig. 1c indicates that it is porous and rough. The blade is

made up of crystalline particles, as confirmed by the selected area

electron diffraction (SAED) pattern (inset of Fig. 1c). All the SAED

rings can be indexed to the spinel phase of Co3O4. The HRTEM

image (Fig. 1d) exhibits clear lattice fringes with spacings of 0.46 nm

and 0.28 nm, which correspond to the (111) and (220) planes of spinel

Co3O4, respectively. The structure and composition of the samples

were further confirmed by XRD and Raman spectrum measure-

ments (see ESI, Fig. S3 and S4†).

Coin-type cells were assembled to investigate the electrochemical

performance of the obtained self-supporting Co3O4 as an anode for

LIBs. Fig. 2a shows the cyclic voltammetric (CV) curves which were

tested at a scan rate of 0.1 mV s�1 over a voltage range from 0.02 to

3.0 V. Three cathodic peaks were observed at 0.50, 0.86, and 1.22V in

the first cycle, which correspond to the electrochemical reduction

reaction of Co3O4 and the formation of the solid electrolyte inter-

phase (SEI).12,16 One anodic peak was recorded at around 2.20 V,

which corresponds to the oxidation reaction of Co3O4. In the

subsequent cycles, only one cathodic peak can be observed around

1.15 V, and the position of the anodic peak shifts to 2.23 V. Theo-

retically, the formation of Co and Li2O and the re-formation of

Co3O4 can be described by the following electrochemical conversion

reaction:12,17

Fig. 2 Electrochemical performances of the self-supporting Co3O4

electrodes. (a) CV curves at a scan rate of 0.1 mV s�1. (b) Cycling

performance and coulombic efficiency at a rate of 0.5 C. The inset shows

the discharge–charge curves for the 1st, 2nd, 10th, and 100th cycles.

17430 | J. Mater. Chem., 2012, 22, 17429–17431

Co3O4 þ 8Liþ þ 8e�discharge�������!charge �������

3Coþ 4Li2O (1)

It is found that both the peak current and the integrated area of the

cathodic/anodic peak are almost constant after the 2nd cycle, indi-

cating that both the formed SEI layer and the electrode material are

highly stable.

Galvanostatic discharge–charge cyclings were measured with a

voltage cut-off window of 0.02–3.0 V. Fig. 2b shows the voltage

profile, cycling behavior and coulombic efficiency of the self-sup-

porting Co3O4 electrode under 100 cycles at a rate of 0.5 C (1 C ¼890 mA g�1). From the first discharge curve in the inset of Fig. 2b, it

can be seen that there are a fine plateau located at 0.95 V and a

distinct long plateau at 0.62 V, which are ascribed to the reduction

processes from Co3O4 to CoO and CoO to Co, respectively.4,12 The

discharge and charge plateaus shift to higher voltages in the subse-

quent cycles, which is consistent with the CV results. The initial

discharge and charge capacities are 1221 and 893 mA h g�1,respectively, corresponding to a coulombic efficiency of 73.2%. The

large irreversible capacity, which is almost inevitable for most anode

materials,18–21 can be mainly attributed to the possible irreversible

processes such as electrolyte decomposition and formation of the SEI

layer.12,22 Nevertheless, the discharge–charge capacity is well retained

during the following cycling, and the coulombic efficiency is increased

to above 97.4%, suggesting excellent capacity retention of the self-

supporting Co3O4 electrode with lemongrass-like morphology.

Despite the large irreversible loss in the first cycling, a very high

charge capacity of 981 mA h g�1 is attained after 100 cycles. The

value is substantially higher than those of the previous Co3O4

nanostructures.10–17,23,24

To obtain further evidence of the high power performance of the

lemongrass-like Co3O4 electrodes, the rate capability was also

investigated. Fig. 3a shows the representative discharge–charge

voltage profiles of the Co3O4 electrode at various rates ranging from

0.5 C to 10 C. The discharge potential decreases and the charge

potential increases with increasing discharge–charge rate, which are

due to kinetic effects of the material.25 The excellent rate capability

and cycling stability of the electrode are explicitly demonstrated in

Fig. 3b. It can be seen that the discharge capacity reaches to about

901mAh g�1 after the first 11 cycles at a low rate of 0.5 C, and then it

slightly reduces to 852, 760, and 610 mA h g�1 at rates of 1 C, 2 C,

and 5 C, respectively. Even at the rate as high as 10 C, the electrode

can deliver a capacity higher than 381 mA h g�1. More importantly,

when the current rate is returned to the initial value of 0.5 C after

51 cycles, the electrode recovers its original capacity or even a little

higher (905 mA h g�1 in the 70th cycle).

The superior rate capability and reversibility capacity of the

obtained Co3O4 electrode could be ascribed to the following reasons:

(1) the lemongrass-like morphology of Co3O4 nanoparticles can limit

the mobility and agglomeration of the particles during cycling, which

may endure the volume expansion/contraction during lithiation/

delithiation. The SEM images of the self-supporting Co3O4 electrode

after 100 discharge–charge cycles at a rate of 0.5 C are shown in

Fig. S5 (see ESI†). It is obvious that the lemongrass-like morphology

of the self-supporting Co3O4 is perfectly retained after 100 cycles; (2)

the small nanoparticles of nanoblades shorten the diffusion length for

lithium ions insertion/extraction, hence benefiting the structural

stability and rate capability. A schematic diagram for Li+ insertion/

This journal is ª The Royal Society of Chemistry 2012

Fig. 3 Rate capability of the self-supporting Co3O4 electrodes. (a)

Representative discharge–charge curves at various current rates. (b)

Cycling at various current rates from 0.5 to 10 C.

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extraction of the self-supporting Co3O4 electrode is shown in Fig. S6

(see ESI†); (3) the self-supporting Co3O4 morphology grown directly

on Ni foam can improve electrical contact between Co3O4 and

current-collecting substrate; (4) the three-dimensional architecture

with high surface-to-volume ratio and open space between nano-

blades can enhance the electrolyte/Co3O4 contact area and provide

fast transport channels.

Conclusions

In summary, self-supporting Co3O4 with lemongrass-like

morphology has been fabricated on Ni foam by a facile hydro-

thermal growth with subsequent calcination. As an anode for

LIBs, the unique architecture of Co3O4 exhibits high capacity,

excellent rate capability and cyclic stability. A high reversible

This journal is ª The Royal Society of Chemistry 2012

capacity of 981 mA h g�1 after 100 cycles at a rate of 0.5 C and a

high capacity of 381 mA h g�1 at a rate as high as 10 C made the

material a promising candidate for anode materials of high-power

LIBs. Also, it is envisaged that such a self-supporting Co3O4 with

lemongrass-like morphology could find its interesting applications in

other fields.

The project was financially supported by the National Natural

Science Foundation of China (grant nos. 10974073 and 11179038).

Notes and references

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3 Z. Y. Wang, L. Zhou and X. W. Lou, Adv. Mater., 2012, 24, 1903.4 M. W. Xu, F. Wang, M. S. Zhao, S. Yang and X. P. Song,Electrochim. Acta, 2011, 56, 4876.

5 J. H. Liu and X. W. Liu, Adv. Mater., 2012, DOI: 10.1002/adma.201104993.

6 Y. Sun, X. Y. Feng and C. H. Chen, J. Power Sources, 2011, 196, 784.7 Y. H. Ding, P. Zhang, Z. L. Long, Y. Jiang, J. N. Huang, W. J. Yanand G. Liu, Mater. Lett., 2008, 62, 3410.

8 L. Tian, H. L Zou, J. X. Fu, X. F. Yang, Y. Wang, H. L. Guo,X. H. Fu, C. L. Liang, M. M. Wu, P. K. Shen and Q. M. Gao,Adv. Funct. Mater., 2010, 20, 617.

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10 J. Liu, H. Xia, L. Lu and D. F. Xue, J. Mater. Chem., 2010, 20, 1506.11 N. Yan, L. Hu, Y. Li, Y. Wang, H. Zhong, X. Y. Hu, X. K. Kong and

Q. W. Chen, J. Phys. Chem. C, 2012, 116, 7227.12 Y. G. Li, B. Tan and Y. Y. Wu, Nano Lett., 2008, 8, 265.13 Y. Q. Fan, H. B. Shao, J. M. Wang, L. Liu, J. Q. Zhang and

C. N. Cao, Chem. Commun., 2011, 47, 3469.14 Y. Wang, H. Xia, L. Lu and J. Y. Lin, ACS Nano, 2010, 4, 1425.15 C. C. Li, Q. H. Li, L. B. Chen and T. H.Wang, J. Mater. Chem., 2011,

21, 11867.16 C. Wang, D. L. Wang, Q. M. Wang and L. Wang, Electrochim. Acta,

2010, 55, 6420.17 J. Q. Wang, G. D. Du, R. Zeng, B. Niu, Z. X. Chen, Z. P. Guo and

S. X. Dou, Electrochim. Acta, 2010, 55, 4805.18 X. W. Li, D. Li, L. Qiao, X. H. Wang, X. L. Sun, P. Wang and

D. Y. He, J. Mater. Chem., 2012, 22, 9189.19 X. H. Wang, X. W. Li, X. L. Sun, F. Li, Q. M. Liu, Q. Wang and

D. Y. He, J. Mater. Chem., 2011, 21, 3571.20 L. M. Li, X. M. Yin, S. Liu, Y. G. Wang, L. B. Chen and T. H. Wang,

Electrochem. Commun., 2010, 12, 1383.21 X. H. Wang, Z. B. Yang, X. L. Sun, X. W. Li, D. S. Wang, P. Wang

and D. Y. He, J. Mater. Chem., 2011, 21, 9988.22 H. Wu, G. Chan, J. W. Choi, I. Ryu, Y. Yao, M. T. McDowell,

S. W. Lee, A. Jackson, Y. Yang, L. B. Hu and Y. Cui, Nat.Nanotechnol., 2012, 7, 310.

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24 R. Tummala, R. K. Guduru and P. S. Mohanty, J. Power Sources,2012, 199, 270.

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J. Mater. Chem., 2012, 22, 17429–17431 | 17431

Supporting Information

Self-supporting Co3O4 with lemongrass-like morphology as a

high-performance anode material for lithium ion batteries

Yujun Fu, Xiuwan Li, Xiaolei Sun, Xinghui Wang, Dequan Liu, Deyan He*

School of Physical Science and Technology, and Key Laboratory for Magnetism and Magnetic

Materials of MOE, Lanzhou University, Lanzhou, 730000, P. R. China

Experimental details

Sample preparation: For in-situ growth of Co3O4 on Ni foam, 1 mmol of

Co(NO3)2•6H2O and 10 mmol of CO(NH2)2 were dissolved into 50 mL deionized

water under vigorous stirring. After stirring for 20 min, the homogeneous solution was

transferred into a Teflon-lined stainless steel autoclave with a volume of 80 mL, and

then a piece of cleaned Ni foam (with an area of 2×3 cm2) was immersed into it. The

autoclave was tightly sealed and heated at 90 °C for 6 h in an oven, then cooled down

to room temperature naturally. The Ni foam with purple precursors grown was fetched

out and rinsed with deionized water several times. Finally, the as-synthesized

precursors were annealed at 350 °C for 1 h in air.

Structural characterization: The crystalline structures and morphologies of the

samples were characterized by X-ray diffraction (XRD, X’ Pert PRO PHILIPS, Cu Kα

radiation, λ=1.54056 Å), micro-Raman spectrometer (Raman, Jobin-Yvon LabRAM

HR800) with a radiation of 532 nm, field emission scan electron microscopy

                                                              * Corresponding author. Tel.: +86 931 8912546; fax: +86 931 8913554. E-mail address: hedy@lzu.edu.cn 

Electronic Supplementary Material (ESI) for Journal of Materials ChemistryThis journal is © The Royal Society of Chemistry 2012

(FE-SEM, Hitachi S-4800), and high-resolution transmission electron microscopy

(HRTEM, FEI, Tecnai G2 F30).

Electrochemical characterizations: Electrochemical characterizations were carried

out with CR2032 coin type half cells by using the grown Co3O4 on Ni foam as the

working electrode and lithium foil as the counter and reference electrodes. The cell

preparation process has been described in our previous paper.[1] Celgard 2320 was

used as the separator membrane. The electrolyte was 1 M lithium

hexafluorophosphate (LiPF6) dissolved in ethylene carbonate: dimethyl carbonate:

ethyl methyl carbonate in a 1:1:1 volume ratio. The cyclic voltammetry and

galvanostatic discharge-charge cycling were carried out at room temperature by using

an electrochemical workstation (CHI 660C) and a multichannel battery tester (Neware

BTS-610), respectively.

Supporting figures

Figure S1. Low-magnification and high-magnification images of the precursor on Ni

foam. The lemongrass-like morphologies of the samples before and after annealing in

air are similar, which were grown directly on the substrate of Ni foam in a large area.

Electronic Supplementary Material (ESI) for Journal of Materials ChemistryThis journal is © The Royal Society of Chemistry 2012

Figure S2. XRD pattern of the precursor on Ni foam. Besides the diffraction peaks

marked “#” from the Ni foam substrate, the other obvious diffraction peaks can be

indexed to the orthorhombic Co(CO3)0.5(OH)·0.11H2O (JCPDS card No. 48-0083),

showing that the cobalt carbonate hydroxide hydrate precursor has been grown on Ni

foam.

 

Figure S3. XRD patterns of the sample after annealing in air. Besides the diffraction

peaks marked “#” from the Ni foam substrate, the other diffraction peaks can be

indexed to (111), (220), (311), (222), (422), (511) and (440) lattice planes of spinel

Co3O4, respectively (JCPDS Card No. 42-1467), indicating that the cobalt carbonate

Electronic Supplementary Material (ESI) for Journal of Materials ChemistryThis journal is © The Royal Society of Chemistry 2012

hydroxide hydrate precursor was turned into crystalline Co3O4 completely. 

 

Figure S4. Raman spectrum of the sample after annealing in air. The peaks centered

at 187, 466, 512, 609, and 674 cm-1, can be attributed to the F2g, Eg, F2g, F2g, and A1g

vibration modes of spinel Co3O4 phase,[2] respectively, which is consistent with the

results of SAED, HRTEM and XRD examinations.

Figure S5 SEM images of the self-supporting Co3O4 electrode after 100

discharge/charge cycles at a rate of 0.5 C. It can be seen that no obvious exfoliation

can be found and the lemongrass-like morphology was remained perfectly.

Electronic Supplementary Material (ESI) for Journal of Materials ChemistryThis journal is © The Royal Society of Chemistry 2012

Figure S6. A schematic diagram for Li+ insertion/extraction of self-supporting Co3O4

with lemongrass-like morphology on Ni foam electrode.

References

[1] X.W. Li, D. Li, L. Qiao, X.H. Wang, X.L. Sun, P. Wang, D.Y. He, J. Mater.

Chem. 22 (2012) 9189.

[2] V.G. Hadjiev, M.N. Iliev, I.V. Vergilov, J. Phys. C: Solid State Phys. 21 (1988)

L199.

Electronic Supplementary Material (ESI) for Journal of Materials ChemistryThis journal is © The Royal Society of Chemistry 2012