Dynamic Article LinksC<Journal ofMaterials Chemistry
Cite this: J. Mater. Chem., 2012, 22, 13328
www.rsc.org/materials PAPER
Publ
ishe
d on
10
May
201
2. D
ownl
oade
d on
12/
05/2
014
13:4
0:42
. View Article Online / Journal Homepage / Table of Contents for this issue
Spinel ZnMn2O4 nanoplate assemblies fabricated via‘‘escape-by-crafty-scheme’’ strategy†
Jiao Zhao,ab Fuqing Wang,bc Panpan Su,ab Mingrun Li,a Jian Chen,c Qihua Yang*a and Can Li*a
Received 11th April 2012, Accepted 10th May 2012
DOI: 10.1039/c2jm32261g
A two-step process that differs in important details from previous methods used to prepare ZnMn2O4
nanoplate assemblies has been reported. This material was prepared by thermal transformation of
metal–organic nanoparticles into metal–oxide nanoparticles based on the ‘‘escape-by-crafty-scheme’’
strategy. Firstly, the nanoscale mixed-metal–organic frameworks (MMOFs) precursor, ZnMn2–ptcda
(ptcda ¼ perylene-3,4,9,10-tetracarboxylic dianhydride), containing Zn2+ and Mn2+, was prepared by
the designed soft chemical assembly of mixed metal ions and organic ligands at a molecular scale. In
a second step, the MMOFs are thermally transformed into spinel structured ZnMn2O4 with
morphology inherited from the MMOFs precursors. The well-crystallized spinel structure can be
formed by thermal treatment of ZnMn2–ptcda at 350�C, and is formed at temperatures$450 �C using
the co-precipitation method. This ‘‘escape-by-crafty-scheme’’ strategy can be extended to the
preparation of other spinel metal–oxide nanoparticles, e.g. CoMn2O4, and NiMn2O4, with well-defined
morphology inherited from the metal–organic precursors. The ZnMn2O4 nanoplate assemblies
thermally treated at 450 �C have potential application in lithium ion batteries as anode materials, which
show high specific capacity and good cyclability.
Introduction
Rechargeable lithium ion batteries have become the dominant
power source for portable electronic devices, such as notebook
PCs, mobile phones, and camcorders. The ever-growing
demands for new electrode materials with high capacity and/or
high energy density for upcoming large-scale applications have
prompted numerous research efforts, in particular in electric
vehicles and hybrid electric vehicles.1–5 Transition metal oxides,
which can react with Li reversibly via the conversion reaction:
MxOy + 2yLi+ + 2ye� 4 xM + yLi2O, exhibit high reversible
capacities at a relatively low potential as anode materials.6,7 A
combination of two metal oxides in a spinel-like structure has
shown good capacity on cycling compared with single metal
oxides.8–12 Among various candidates, ZnMn2O4 is regarded as
a potential high-performance anode material because of its low
aState Key Laboratory of Catalysis, Dalian Institute of Chemical Physics,Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023,China. E-mail: [email protected]; [email protected]; Web: http://www.hmm.dicp.ac.cn; http://www.canli.dicp.ac.cn. Fax: +86-411-84694447;Tel: +86-411-84379552; +86-411-84379070bGraduate School of the Chinese Academy of Sciences, Beijing 100049,ChinacLaboratory of Advanced Rechargeable Batteries, Dalian Institute ofChemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road,Dalian 116023, China
† Electronic supplementary information (ESI) available: Fullinformation about EDX spectrum, XRD patterns, SEM images, andN2 adsorption–desorption isotherm. See DOI: 10.1039/c2jm32261g
13328 | J. Mater. Chem., 2012, 22, 13328–13333
cost, environmental benignancy, low operating voltages and high
energy density. Abu-Lebdeh’s group reported that ZnMn2O4
showed better performance compared to its single metal oxides,
Mn2O3 or ZnO.13 However, this material shows significant
volume change during lithiation and delithiation and severe
electron conduction restriction during the electrochemical reac-
tion. Therefore, the discharge capacity and cycling stability for
ZnMn2O4 should be improved. It was reported that metal oxides
with novel nanostructure have the advantages of high surface-
to-volume ratio and short path length for Li+ transport.14–26
ZnMn2O4 nanostructures with specific morphology have been
prepared. Zhang’s group developed a solvothermal method to
synthesize flower-like ZnMn2O4 superstructures which exhibit
higher stable capacity than nanocrystalline ZnMn2O4 synthe-
sized by a polymer-pyrolysis method.27,28 Kim and co-workers
fabricated one-dimensional ZnMn2O4 nanowires by a solid-state
method and the mechanism research reveals that there is an
additional electrochemical activity, possibly due to the enhanced
kinetics of the nanowire.29 Lou’s group reported the preparation
of ZnMn2O4 hollow microspheres from ZnCO3–MnCO3
microspheres and this material exhibits high specific discharge
capacity and cycling stability, which is attributed to the unique
hollow structure.30
Although there are several successful examples of the synthesis
of ZnMn2O4 nanomaterials as electrodes for lithium ion
batteries, a general method for the preparation of spinel struc-
tured metal oxides with well-defined composition and
morphology is still lacking. Recently, our group and others have
This journal is ª The Royal Society of Chemistry 2012
Publ
ishe
d on
10
May
201
2. D
ownl
oade
d on
12/
05/2
014
13:4
0:42
. View Article Online
reported the synthesis of metal oxides by a thermal trans-
formation method using nanoscale metal–organic frameworks
(MOFs) as precursors.31–39 Through a simple thermal treatment
process, the metal oxides with morphology similar to the nano-
scale MOFs could be facilely synthesized. The separated
morphology and composition control step of this method
provides more possibility for precisely controlling the structure
and morphology of the metal oxides. However, the thermal
transformation of MOFs to metal oxides has mainly focused on
MxOy, and the preparation of mixed-metal oxides using this
method is seldom reported.40,41 Herein, we present a general
method for the synthesis of spinel structured mixed-metal oxides,
such as ZnMn2O4, CoMn2O4, and NiMn2O4, with well defined
morphology and composition, by thermal treatment of nano-
scale mixed-metal–organic frameworks (MMOFs) via an
‘‘escape-by-crafty-scheme’’ strategy, as shown in Fig. 1. The key
issue for this method is to prepare MMOFs precursors with
homogeneous mixing of different metal ions in a crystal structure
with well-controlled morphology. After simple thermal treat-
ment process, the spinel structured metal oxides with
morphology similar to the MMOFs precursors could be
successfully prepared. The potential of ZnMn2O4 nanoplate
assemblies as anode materials for lithium ion batteries was also
investigated.
Experimental
Synthesis of ZnMn2–ptcda MMOFs
In a typical synthesis,39 Zn(OAc)2$2H2O (0.133 mmol) and
Mn(OAc)2$4H2O (0.267 mmol) were dissolved in 22.5 mL
deionized water, and ptcda (0.2 mmol) was dissolved in 12.5 mL
NaOH solution (0.8 mmol NaOH). The ptcda solution was
added dropwise to the mixture solution of metal acetates with
stirring. The immediate formation of a precipitate was observed.
The reaction mixture was stirred at room temperature for 30 min,
and then transferred to a Teflon-lined stainless steel vessel
(45 mL) and heated at 100 �C for 4 h. After cooling down to
room temperature, the precipitate was collected by centrifuga-
tion, washed with water and dried. ZnMn6–ptcda MMOFs were
prepared in a similar way to ZnMn2–ptcda MMOFs except
a Zn : Mn molar ratio of 1 : 6 was used. For other MMn2–ptcda
MMOFs, the synthesis process was similar to that described for
ZnMn2–ptcda except using M(II) acetate instead of zinc(II)
acetate.
Fig. 1 Illustration of the two step process for the preparation of spinel
ZnMn2O4 using ZnMn2–ptcda as a precursor by an ‘‘escape-by-crafty-
scheme’’ strategy.
This journal is ª The Royal Society of Chemistry 2012
Formation of ZnMn2O4 nanomaterials
ZnMn2–ptcda MMOFs were thermally treated in air at 450 �Cfor 1 h with a ramp of 5 �C min�1. CoMn2O4 and NiMn2O4 were
formed from CoMn2–ptcda and NiMn2–ptcda respectively,
under the same thermal treatment process.
Characterization
The thermogravimetric (TG) analysis was performed in air with
a heating rate of 5 �C min�1 by using a NETZSCH STA-449F3
thermogravimetric analyzer. The powder X-ray diffraction data
(PXRD) were collected on a Rigaku D/Max2500 PC diffrac-
tometer with Cu Ka radiation (l ¼ 1.5418 �A) in the 2q range of
3–70� with a scan speed of 5� min�1 at room temperature.
Scanning electron microscopy (SEM) was undertaken on a FEI
QUANTA 200F scanning electron microscope operating at an
acceleration voltage of 20 kV. The samples were sputtered with
gold prior to imaging. Selected-area electron-diffraction (SAED)
and high-resolution transmission electron microscopy
(HRTEM) images were recorded on a FEI Tecnai F30 micro-
scope with a point resolution of 0.20 nm operated at 300 kV. The
nitrogen sorption experiments were performed at �196 �C on
a Micromeritics ASAP 2020 system. Prior to measurement, the
samples were out-gassed at 120 �C for 6 h. The BET (Brunauer–
Emmett–Teller) specific surface areas were calculated using
adsorption data in a relative pressure range of P/P0 ¼ 0.05–0.25.
The pore size distribution curve was calculated from the
adsorption branch using the BJH (Barrett–Joyner–Halenda)
method.
Electrode fabrication and performance measurements
The ZnMn2O4 electrode slurry was prepared by mixing 75 wt%
active material, 15 wt% acetylene carbon black, 10 wt% poly-
vinylidene fluoride (PVDF) binder and an adequate amount of
N-methyl-2-pyrrolidone (NMP). The slurry was coated onto
copper foil and dried under vacuum at 85 �C overnight. The
electrode was cut into a shape with an area of 1 cm2. The loading
weight of the active materials in the electrode was about 2.0 mg
cm�2. The electrochemical performance of the ZnMn2O4 elec-
trode was evaluated in a 2016 coin-type ZnMn2O4–Li cell, in
which the lithium electrode was used as the counter electrode as
well as the reference electrode. The electrolyte was 1 M LiPF6 in
ethylene carbonate (EC) and diethyl carbonate (DEC) (1 : 1 by
volume). A Celgard 2400 (polypropylene) was used as the sepa-
rator. All the cells were assembled in an argon-filled glove box
maintaining the moisture and oxygen levels below 1.0 ppm. All
electrochemical measurements were evaluated galvanostatically
between 0.01 and 3.0 V using a Neware instrument (China). The
charge–discharge measurements were tested under a current
density of 60 mA g�1. For the rate capability measurements, the
cells were both charged and discharged at a current density of
60–3600 mA g�1.
Results and discussion
ZnMn2–ptcda, containing Zn2+ and Mn2+ ions, was prepared by
reaction of Zn2+ and Mn2+ (the molar ratio of Zn : Mn is 1 : 2)
with perylene-3,4,9,10-tetracarboxylic dianhydride (ptcda) in
J. Mater. Chem., 2012, 22, 13328–13333 | 13329
Fig. 3 PXRD patterns of ZnMn2–ptcda precursor and spinel ZnMn2O4
prepared by ‘‘escape-by-crafty-scheme’’ strategy using ZnMn2–ptcda as
a precursor and by co-precipitation method (450 �C, 1 h, air atmosphere).
Publ
ishe
d on
10
May
201
2. D
ownl
oade
d on
12/
05/2
014
13:4
0:42
. View Article Online
NaOH solution under hydrothermal conditions. The scanning
electron microscopy (SEM) image of ZnMn2–ptcda clearly
shows that the sample is composed of flower-like assemblies
(particle size of ca. 4 mm) constructed of nanoplates with thick-
ness of ca. 60 nm (Fig. 2a). Energy-dispersive X-ray spectroscopy
(EDX) analysis shows that ZnMn2–ptcda is composed of carbon,
oxygen, manganese and zinc elements, and the Mn : Zn molar
ratio is�2 (Fig. S1†). The EDXmappings reveal that manganese
and zinc elements are homogeneously distributed in the whole
ZnMn2–ptcda sample (Fig. 2b). Furthermore, the elemental
distribution analysis on the selected region confirms the uniform
distribution of Zn and Mn elements (Fig. 2d). This proves that
both elements are distributed homogeneously in the ZnMn2–
ptcda particle. The transmission electron microscopy (TEM) and
selected area electron diffraction (SAED) analysis of an isolated
particle display single crystal properties with periodic diffraction
spots (Fig. 2c). The powder X-ray diffraction (PXRD) pattern of
ZnMn2–ptcda is shown in Fig. 3. ZnMn2–ptcda displays strong
diffraction peaks, exhibiting a three-dimensional framework
which is isostructural with Zn–ptcda MOFs.39 The sample has
(001) crystallographic texture, a crystalline structure with an
orthorhombic crystal system and Pbam space group. All of the
diffraction peaks can be well indexed, which indicates that
ZnMn2–ptcda is a pure phase complex. The above results show
that ZnMn2–ptcda is a pure MMOFs phase with homogeneous
distribution of Zn and Mn ions. The fabrication of nanoscale
MMOFs with mixed metal ions has not been reported previ-
ously, although the post-synthesis ion-exchange method has been
used to prepare nanoscale MMOFs.34,42 Our results indicate that
nanoscale MMOFs with controllable composition, morphology
and crystal phase can be successfully synthesized by using mixed
metal ions in the initial synthesis mixture.
By thermal treatment of ZnMn2–ptcda in air at 450 �C for 1 h,
brown powders and yellow crystals were obtained. The yellow
crystal is perylene, formed by the decarboxylation of ptcda,
Fig. 2 (a) SEM image, (b) EDX mapping SEM images, (c) TEM image
of a selected particle (inset is the SAED pattern), and (d) STEM image of
a selected region and the elemental mapping of Zn and Mn of ZnMn2–
ptcda.
13330 | J. Mater. Chem., 2012, 22, 13328–13333
showing that the thermal treatment involves the ‘‘escape-by-
crafty-scheme’’ of perylene as we previously reported.41 The
brown powders can be ascertained to be tetragonal spinel struc-
tured ZnMn2O4 with I41/amd space group (JCPDS card no. 07-
0354) by XRD characterization (Fig. 3). All the diffraction peaks
can be assigned to the spinel structure phase, indicating that high
purity spinel ZnMn2O4 has been synthesized. ZnMn2O4 has
a normal spinel structurewithZn2+ occupying the tetrahedral sites
and Mn3+ occupying the octahedral sites, forming ZnO4 groups
andMnO6 groups respectively. ZnMn2O4 is isostructural with the
spinel Mn3O4. This clearly indicates that zinc is well incorporated
into the Mn3O4 lattice without phase segregation, forming
ZnMn2O4 with the replacement of Mn2+ by Zn2+.
The SEM image reveals that the resulting ZnMn2O4 material is
composed of nanoplate assemblies inherited from the ZnMn2–
ptcda precursor with flower-like morphology (Fig. 4a). The
particle size of the resulting ZnMn2O4 is about 1.6 mm, which is
smaller than that of the ZnMn2–ptcda precursor because of the
escape of the organic portion. The nanoplates, which assemble to
form the flower-like morphology, are porous under observation
of the TEM image (Fig. 4b). Furthermore, the nanoplates are
composed of nanoparticles with a particle size of about 12 nm
(Fig. 4c). Fig. 4d displays a representative HRTEM image of the
ZnMn2O4 nanoparticles. They are well-crystallized in the
tetragonal phase with the (101), (112), and (211) crystal lattices
having interplane spacings of 0.48 nm, 0.30 nm, and 0.24 nm,
respectively. ZnMn2O4 nanoplate assemblies show the uniform
distribution of Zn and Mn in the particle with a Mn : Zn molar
ratio of �2 (Fig. 4e and S1†). The porous structure of the
ZnMn2O4 nanoplate assemblies can be further confirmed by N2
sorption analysis (Fig. 4f–g). The sample exhibits a typical type
IV isotherm with a type H3 hysteresis loop, showing that this
material has a mesoporous structure. The sample has a BET
surface area of 42 m2 g�1 and uniform distribution of the meso-
pores with a pore diameter of 17.4 nm. It should be mentioned
that the spinel structured ZnMn2O4 could also be formed even at
a treatment temperature as low as 350 �C. For comparison
This journal is ª The Royal Society of Chemistry 2012
Fig. 4 (a) SEM, (b) TEM, and (c–d) HRTEM images of ZnMn2O4, (e)
STEM image of a selected region of a ZnMn2O4 particle and the
elemental mapping of Zn andMn, (f) N2 adsorption–desorption isotherm
and (g) pore size distribution of ZnMn2O4.
Fig. 5 (a) TG curve and (b) PXRD pattern of ZnMn2–ptcda before and
after thermal treatment at different temperatures for 1 h in air.
Publ
ishe
d on
10
May
201
2. D
ownl
oade
d on
12/
05/2
014
13:4
0:42
. View Article Online
purposes, ZnMn2O4 was also prepared using the conventional
co-precipitation method, which is a general method for the
preparation of mixed-metal oxides.13 The spinel structure could
not be formed at treatment temperatures below 450 �C. TheXRD results show that ZnMn2O4 prepared by co-precipitation
method is not as well crystallized as that prepared using ZnMn2–
ptcda as a precursor at the same thermal treatment conditions
(Fig. 3 and S2†). This is probably due to the uniform distribution
of Zn and Mn ions in a well-defined coordination state in the
crystalline ZnMn2–ptcda precursor. This suggests the advantages
of this transformation method using MMOFs as a precursor
compared with the conventional co-precipitation method.
Through varying the Zn : Mn molar ratio in the initial
mixture, ZnMn6–ptcda MMOFs (Zn : Mn molar ratio of 1 : 6)
with a nanoplate morphology could also be prepared (Fig. S3†).
However, the nanoplates with diameter about 2 mm are
uniformly distributed with only a limited amount of flower-like
assemblies. The EDX result confirms the uniform distribution of
Zn and Mn in the nanoparticles. After thermal treatment of
This journal is ª The Royal Society of Chemistry 2012
ZnMn6–ptcda in a similar way to ZnMn2–ptcda, off-stoichio-
metric Zn0.43Mn2.57O4, with the nanoplate morphology inherited
from ZnMn6–ptcda, was formed. The XRD and N2 sorption
isotherm show that Zn0.43Mn2.57O4 has a well-crystallized spinel
structure and mesoporous textural features similar to those of
ZnMn2O4 (Fig. S4†).
The thermal transformation process from MMOFs to spinel
structured mixed-metal oxide was investigated by thermogravi-
metric (TG) analysis using ZnMn2–ptcda as a model (Fig. 5a).
ZnMn2–ptcda has two consecutive weight loss steps. The
preliminary weight loss at 150 �C corresponds to the release of
coordinated water molecules. There is a well-defined weight loss
due to the escape of perylene by decarboxylation above 345 �C.Thermal treatment of ZnMn2–ptcda at temperatures below
345 �C results in the obvious {00h} diffraction peaks in its XRD
pattern, although loss of fine structure and a lattice contraction
are observed. When the temperature reaches 350 �C, ZnMn2–
ptcda is converted into spinel structured ZnMn2O4 immediately
by perylene escaping from the MMOFs through decarboxylation
(Fig. 5b). The structural and TG results suggest that ZnMn2–
ptcda, with its robust lamellar structure, acts as a precursor for
the formation of ZnMn2O4 nanoparticles with similar
morphology. Due to the complex structure of the ZnMn2–ptcda
precursor, the exact mechanism responsible for this trans-
formation from original single crystalline ZnMn2–ptcda
MMOFs to polycrystalline ZnMn2O4 is not completely under-
stood yet, though a template-engaged quasi-topotactic trans-
formation process might be plausible.39
This ‘‘escape-by-crafty-scheme’’ strategy could be extended for
the formation of various spinel structured mixed-metal oxides
J. Mater. Chem., 2012, 22, 13328–13333 | 13331
Publ
ishe
d on
10
May
201
2. D
ownl
oade
d on
12/
05/2
014
13:4
0:42
. View Article Online
using MMOFs as precursors. Fig. 6 displays the SEM images of
CoMn2–ptcda andNiMn2–ptcda synthesized by a similarmethod
to ZnMn2–ptcda with a Co (or Ni) : Mn molar ratio of 1 : 2.
CoMn2–ptcda has a flower-like morphology composed of nano-
plates similar to ZnMn2–ptcda (Fig. 6a) and NiMn2–ptcda is
irregular nanolamella (Fig. 6d). EDX analyses confirmed the
uniform distribution of Co (or Ni) and Mn in the MMOFs
(Fig. S5†). CoMn2–ptcda and NiMn2–ptcda were respectively
converted into CoMn2O4 and NiMn2O4 by thermal treatment at
450 �C in air. As shown in the SEM images, the resultingmaterials
maintain the morphology of the corresponding MMOFs precur-
sors (Fig. 6b and e). The Co (or Ni) signals are observed in the
EDX spectra, confirming the presence of Co (or Ni) in the spinel
structuredCoMn2O4orNiMn2O4 (Fig. S5†). ThePXRDpatterns
only show the spinel structured diffractions without cobalt oxide
or nickel oxide impurities, suggesting that the cobalt and nickel
ions are completely doped into the Mn3O4 lattice. CoMn2O4
exhibits the typical I41/amd tetragonal spinel structure, similar to
ZnMn2O4 (Fig. 6c), and NiMn2O4 shows a cubic spinel structure
in the Fd�3 m space group (Fig. 6f).
The above results suggest that the spinel structured mixed-
metal oxides could be readily synthesized using thermal trans-
formation of MMOFs via the ‘‘escape-by-crafty-scheme’’
strategy, and the morphology of the MMOFs precursors could
be precisely transferred to the resulting spinel structured mixed-
metal oxides.
The spinel structured ZnMn2O4 nanomaterials were tested as
anode materials for rechargeable lithium ion batteries. The
discharge–charge profiles of the ZnMn2O4 nanoplate assemblies
Fig. 6 (a) SEM image of CoMn2–ptcda with a Co : Mn molar ratio of
1 : 2, (b) SEM image and (c) PXRD pattern of CoMn2O4, (d) SEM image
of NiMn2–ptcda with a Ni : Mn molar ratio of 1 : 2, (e) SEM image and
(f) PXRD pattern of NiMn2O4.
13332 | J. Mater. Chem., 2012, 22, 13328–13333
for the first two cycles were recorded at a current density of 60mA
g�1 at room temperature in the potential range between 0.01 and
3.00 V. As shown in Fig. 7a, the first discharge profile comprises
a steep line above 1.50 V, a small plateau at about 1.40 V, a wide
and steady plateau at about 0.50V, and a gradual voltage decrease
in sequence. The overall capacity for the first discharge and charge
are as high as 1277 mAh g�1 and 730 mAh g�1, respectively. An
irreversible capacity of 547 mAh g�1 was measured between the
first charge and discharge, which mainly corresponds to the
formation of the solid-electrolyte interphase (SEI) layers at
the ZnMn2O4/electrolyte interface above 1.50V and the reduction
of Mn(III) to Mn(II) at about 1.40 V.29 For the second discharge,
the potential plateau shifts upward to near 0.57 V (vs.Li+/Li) with
a more sloping profile accompanied by the disappearance of the
steep line above 1.50 V and the small plateau at about 1.40 V.
Nevertheless, the overall discharge capacity of 752mAh g�1 in the
second discharge process is retained. The coulombic efficiency of
the seconddischarge–charge process is 91%and stabilizes at>97%
after eight cycles, indicating the good reversibility of the
ZnMn2O4 anode after the first discharge–charge process. Fig. 7b
shows the cycle performance of ZnMn2O4. After 30 cycles, the
capacity decays at a slower and slower rate andmaintains a nearly
constant value of about 502 mAh g�1, demonstrating the high
reversible specific capacity and long cycle life of the anode. The
excellent electrochemical performance of ZnMn2O4might benefit
from its unique architecture of assemblies of nanoplates consist-
ing of well-crystallized agglomerated nanoparticles. The porosity
of the material will enhance the electrolyte/ZnMn2O4 contact
area, shorten the Li+ ion diffusion length, and accommodate the
strain induced by the volume change during the charge and
discharge cycles.
Fig. 7 (a) Discharge–charge curves of ZnMn2O4 nanoplate assemblies,
(b) plots of discharge capacity versus cycle number for ZnMn2O4 in the
voltage range of 0.01–3.00 V at a current rate of 60 mA g�1, and (c) rate
performances of the electrode made using ZnMn2O4.
This journal is ª The Royal Society of Chemistry 2012
Publ
ishe
d on
10
May
201
2. D
ownl
oade
d on
12/
05/2
014
13:4
0:42
. View Article Online
Besides the high specific capacity and good cyclability, the rate
capability is also a very important property for electrode mate-
rials. To evaluate the rate capability, the ZnMn2O4 electrode was
tested at various current densities (60–3600mA g�1) in the voltage
range of 0.01–3.0 V (Fig. 7c). The discharge capacities are grad-
ually reduced with the gradual increase of the current rate. The
capacities are 488 mAh g�1 for 600 mA g�1, 426 mAh g�1 for 900
mA g�1, and 324 mAh g�1 for 1800mA g�1. Even at the rigorously
high charge–discharge rate (3600 mA g�1), the discharge capacity
is still maintained at 187 mAh g�1. After the high rate charge–
discharge cycles, the current density is reduced to 60 mA g�1 and
a discharge capacity of as high as 578 mAh g�1 could be resumed.
Conclusions
In summary, we presented a general method via ‘‘escape-by-
crafty-scheme’’ for the preparation of spinel mixed-metal oxides
MMn2O4 (M ¼ Co, Ni, Zn) using nanoscale mixed-metal–
organic frameworks (MMOFs) as precursor. The morphology
of the MMOFs precursors could be transferred precisely to the
spinel metal oxides by a simple thermal treatment process. The
MMOFs with different kinds of metal ions distributed
uniformly and with high crystallinity favor the formation of
a highly crystallized spinel structure compared with the tradi-
tional co-precipitation method. Phase pure CoMn2O4,
NiMn2O4, and ZnMn2O4 were readily synthesized using this
method, showing the wide generality of the method. ZnMn2O4,
with a unique flower-like morphology, uniform mesopores and
high crystallinity shows high reversible capacity and good
cyclability as an anode for lithium ion batteries. This work
offers exciting possibilities for the development of new func-
tional materials for lithium ion batteries.
Acknowledgements
This work was supported by the Program Strategic Scientific
Alliances between China and The Netherlands (Grant
2008DFB50130) and the National Basic Research Program of
China (Grant 2009CB623503).
References
1 J. M. Tarascon and M. Armand, Nature, 2001, 414, 359.2 Y. Idota, T. Kubota, A. Matsufuji, Y. Maekawa and T. Miyasaka,Science, 1997, 276, 1395.
3 M. Armand and J. M. Tarascon, Nature, 2008, 451, 652.4 Y. G. Guo, J. S. Hu and L. J. Wan, Adv. Mater., 2008, 20, 2878.5 P. G. Bruce, B. Scrosati and J. M. Tarascon, Angew. Chem., Int. Ed.,2008, 47, 2930.
6 P. Poizot, S. Laruelle, S. Grugeon, L. Dupont and J. M. Tarascon,Nature, 2000, 407, 496.
7 H. Li, P. Balaya and J. Maier, J. Electrochem. Soc., 2004, 151,A1878.
8 Y. Sharma, N. Sharma, G. V. S. Rao and B. V. R. Chowdari,Electrochim. Acta, 2008, 53, 2380.
This journal is ª The Royal Society of Chemistry 2012
9 P. Lavela and J. L. Tirado, J. Power Sources, 2007, 172, 379.10 Y. Sharma, N. Sharma, G. V. S. Rao and B. V. R. Chowdari, Adv.
Funct. Mater., 2007, 17, 2855.11 Y. C. Qiu, S. H. Yang, H. Deng, L. M. Jin and W. S. Li, J. Mater.
Chem., 2010, 20, 4439.12 Y. Sharma, N. Sharma, G. V. S. Rao and B. V. R. Chowdari, J. Power
Sources, 2007, 173, 495.13 F. M. Courtel, H. Duncan, Y. Abu-Lebdeh and I. J. Davidson, J.
Mater. Chem., 2011, 21, 10206.14 K. T. Nam, D. W. Kim, P. J. Yoo, C. Y. Chiang, N. Meethong,
P. T. Hammond, Y. M. Chiang and A. M. Belcher, Science, 2006,312, 885.
15 J. Hassoun, S. Panero, P. Simon, P. L. Taberna and B. Scrosati, Adv.Mater., 2007, 19, 1632.
16 Y. G. Li, B. Tan and Y. Y. Wu, Nano Lett., 2008, 8, 265.17 S. Mitra, P. Poizot, A. Finke and J. M. Tarascon, Adv. Funct. Mater.,
2006, 16, 2281.18 S. J. Han, B. C. Jang, T. Kim, S. M. Oh and T. Hyeon, Adv. Funct.
Mater., 2005, 15, 1845.19 L. Taberna, S. Mitra, P. Poizot, P. Simon and J. M. Tarascon, Nat.
Mater., 2006, 5, 567.20 Y. Yu, C. H. Chen and Y. Shi, Adv. Mater., 2007, 19, 993.21 J. Chen, L. N. Xu, W. Y. Li and X. L. Gou, Adv. Mater., 2005, 17,
582.22 X.W. Lou, D. Deng, J. Y. Lee, J. Feng and L. A. Archer,Adv.Mater.,
2008, 20, 258.23 Y. Wang and G. Z. Cao, Adv. Mater., 2008, 20, 2251.24 Y. Wang, K. Takahashi, K. Lee and G. Z. Cao, Adv. Funct. Mater.,
2006, 16, 1133.25 X. W. Lou, Y. Wang, C. L. Yuan, J. Y. Lee and L. A. Archer,
Adv.Mater., 2006, 18, 2325.26 J. S. Chen, Y. L. Tan, C.M. Li, Y. L. Cheah, D. Y. Luan, S.Madhavi,
F. Y. C. Boey, L. A. Archer and X. W. Lou, J. Am. Chem. Soc., 2010,132, 6124.
27 L. F. Xiao, Y. Y. Yang, J. Yin, Q. Li and L. Z. Zhang, J. PowerSources, 2009, 194, 1089.
28 Y. Y. Yang, Y. Q. Zhao, L. F. Xiao and L. Z. Zhang, Electrochem.Commun., 2008, 10, 1117.
29 S. W. Kim, H. W. Lee, P. Muralidharan, D. H. Seo, W. S. Yoon,D. K. Kim and K. Kang, Nano Res., 2011, 4, 505.
30 L. Zhou, H. B.Wu, T. Zhu and X.W. Lou, J. Mater. Chem., 2012, 22,827.
31 W. Cho, Y. H. Lee, H. J. Lee and M. Oh, Chem. Commun., 2009,4756.
32 W. Cho, S. Park and M. Oh, Chem. Commun., 2011, 47, 4138.33 S. Jung, W. Cho, H. J. Lee and M. Oh, Angew. Chem., Int. Ed., 2009,
48, 1459.34 W. Cho, Y. H. Lee, H. J. Lee and M. Oh, Adv. Mater., 2011, 23,
1720.35 C. C. Li, X. M. Yin, L. B. Chen, Q. H. Li and T. H. Wang, Chem.–
Eur. J., 2010, 16, 5215.36 B. Liu, X. B. Zhang, H. Shioyama, T. Mukai, T. Sakai and Q. Xu, J.
Power Sources, 2010, 195, 857.37 H. Y. Shi, B. Deng, S. L. Zhong, L. Wang and A. W. Xu, J. Mater.
Chem., 2011, 21, 12309.38 Y. X. Lu, H. Q. Cao, S. C. Zhang and X. R. Zhang, J. Mater. Chem.,
2011, 21, 8633.39 J. Zhao,M. R. Li, J. L. Sun, L. F. Liu, P. P. Su, Q. H. Yang and C. Li,
Chem.–Eur. J., 2012, 18, 3168.40 P. Mahata, D. Sarma, C. Madhu, A. Sundaresen and S. Natarajan,
Dalton Trans., 2011, 40, 1952.41 P. Mahata, T. Aarthi, G. Madras and S. Natarajan, J. Phys. Chem. C,
2007, 111, 1665.42 M. Oh and C. A. Mirkin, Angew. Chem., Int. Ed., 2006, 45,
5492.
J. Mater. Chem., 2012, 22, 13328–13333 | 13333
