Electrochemically deposited interconnected
porous Co
3
O
4
nanoflakes as anodes with excellent
rate capability for lithium ion batteries
Yunxian Zheng, Li Qiao, Jun Tang, Zhibo Yang, Hongwei Yue and Deyan He
*
Interconnected porous Co
3
O
4
nanoflakes were prepared on nickel foam by a simple electrochemical
deposition combined with a subsequent heat treatment. The featured nanoflakes consisted of
interconnected primary nanoparticles and nanopores resulting in a large specific surface area. As an
anode material of lithium ion batteries, the as-prepared samples exhibited superior cyclic performance
and excellent rate capacity. The discharge capacity remained at 1211 mA h g
1
after 100 cycles at a
current density of 1 A g
1
. Notably, after cycling at various current densities up to 5 A g
1
, the capacity
recovered to 1266 mA h g
1
at 0.1 A g
1
.
Introduction
As the most important energy storage device, lithium ion
batteries (LIBs) have received considerable attention in the eld
of consumer electronics and electric vehicles because of their
high power density, fast rechargeable capability and long cycle
life.
1–3
It is essential to develop alternative anode materials for
commercial LIBs because the state-of-the-art graphite anodes
always show low capacity and poor rate capability. Numerous
efforts have been made to investigate transition metal oxides
with higher theoretical capacities.
4–8
Among the transition
metal oxides, Co
3
O
4
is particularly attractive due to its low cost,
environmental friendliness, and high redox activity and theo-
retical capacity (890 mA h g
1
).
9,10
However, similar to the other
transition metal oxides, poor electrical conductivity and large
volume change of the Co
3
O
4
based materials during lithiation
and de-lithiation commonly lead to an unsatised reversible
capacity and fast capacity fading.
11–13
In this work, we report an architecture of interconnected
porous Co
3
O
4
nanoakes prepared on nickel foam by a elec-
trochemical deposition and its electrochemical performance as
an anode for LIBs. The Co
3
O
4
nanoakes are composed of
primary nanoparticles and nanopores, which can give rise to a
high surface-to-volume ratio and short path length for lithium
ion transport.
17
Besides, directly depositing Co
3
O
4
on Ni foam
current collector can improve electrical contact and make the
anode preparation much easier.
6,10,14,16
The obtained anodes
exhibited superior cyclic performance and excellent rate
capability.
Experimental
Firstly, Ni foam substrates with an area of 1 1 cm
2
were
ultrasonically treated for 10 min in 1 M hydrochloric acid,
degreased with acetone and rinsed with deionized water and
ethanol. Then Co(OH)
2
precursor was cathodically deposited on
the cleaned Ni foam substrate at 10 mA cm
2
for 150 s in an
aqueous bath solution of 0.1 M Co(NO
3
)
2
. The deposition was
carried out at room temperature with a three-electrode system.
Aer a subsequent heating treatment at 350
C in air for 2 h,
Co(OH)
2
was transformed into Co
3
O
4
. The active mass of the
electrodes was 0.89 mg cm
2
for capacity retention test and
0.92 mg cm
2
for rate capability test.
The morphology and structure of the samples were charac-
terized by eld-emission scanning electron microscopy
(FE-SEM, Hitachi, S-4800), transmission electron microscopy
(TEM, FEI, Tecnai G
2
F30), micro-Raman spectroscopy (Jobin-
Yvon LabRAM HR800 UV, with an excitation light of 532 nm),
and X-ray photoelectron spectroscopy (XPS, ESCA MK II, MgKa
source).
The electrochemical measurements were performed using
CR-2032 coin cells which were assembled in an argon-lled
glovebox (H
2
O, O
2
< 0.5 ppm, MBraun). The sample of the
interconnected porous Co
3
O
4
nanoakes on Ni foam was served
as the working electrode while lithium foil as the counter and
reference electrode. The electrolyte was 1 M LiPF
6
dissolved in a
mixture of ethylene carbonate (EC) and diethyl carbonate (DEC)
in a volume ratio of 1 : 1.
18
Celgard 2320 microporous poly-
propylene lm was used as separator.
19
The galvanostatic
charge–discharge cycle and cyclic voltammetry (CV) were
implemented at room temperature with a multichannel battery
tester (Neware BTS-610) and an electrochemical workstation
(CHI 660C), respectively.
School of Physics Science and Technology, Key Laboratory for Magnetism and Magnetic
Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000, China.
E-mail: hedy@lzu.edu.cn; Fax: +86 931 8913554; Tel: +86 931 8912546
Cite this: RSC Adv. , 2015, 5, 36117
Received 13th March 2015
Accepted 13th April 2015
DOI: 10.1039/c5ra04447b
www.rsc.org/advances
This journal is © The Royal Society of Chemistry 2015 RSC Adv. , 2015, 5, 36117–36121 | 36117
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