Nb2O5 nanoparticles encapsulated in ordered mesoporous carbon matrix as advanced anode materials for Li ion capacitors

Article abstract of DOI:10.1039/c6ra11460a

Lithium ion capacitors (LICs), which have high energy density and power density and benefit from the combination of the merits of batteries and supercapacitors, have been attracted tremendous attention. The sluggish faradaic battery anode is a big challenge for the development of high-performance LICs. In this study, an Nb₂O₅/ordered mesoporous carbon (CMK-3) nanocomposite has been synthesized via the nanocasting technology using CMK-3 as the hard template and NbCl₅ as the precursor. The Nb₂O₅/CMK-3 electrode exhibits significantly enhanced electrochemical performance in terms of specific capacity, rate capability and cyclic stability when compared with bulk Nb₂O₅. Furthermore, a high performance LIC composed of the Nb₂O₅/CMK-3 nanocomposite as the anode and activated carbon derived from peanut shell as the cathode was constructed, which exhibits a high energy density of 43.9 W h kg^-1 (at a power density of 87.5 W kg^-1) and high power density of 8750 W kg^-1 (at an energy density of 24.4 W h kg^-1). Such outstanding performance mainly stems from the synergic effects between the mesoporous carbon matrices and the well-dispersed active material nanoparticles, which increase electronic conductivity and the reactivity of Nb₂O₅.

Full text of DOI:10.1039/c6ra11460a

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PAPER
Nb2O5 nanoparticles encapsulated into ordered mesoporous
carbon matrix as advanced anode materials for Li ion capacitors
Received 00th January 20xx,
Accepted 00th January 20xx
Jingjie Wang, Hongsen Li, Laifa Shen, Shengyang Dong, and Xiaogang Zhang*
Benefit from the combination of the merits of batteries and supercapacitors, lithium ion capacitors (LICs) with high energy
density and power density have been attracted tremendous attentions. The sluggish Faradaic battery anode is a big
challenge for developing high-performance LICs. In this work, Nb2O5/ordered mesoporous carbon (CMK-3)
nanocomposites have been synthesized by a nanocasting technology using the CMK-3 as hard template and NbCl5 as
precursor. The Nb2O5/CMK-3 electrode exhibits significantly enhanced electrochemical performance in terms of specific
capacity, rate capability and cyclic stability when compared with bulk Nb2O5. Furthermore, a high performance LIC
composed of Nb2O5/CMK-3 nanocomposites as anode and activated carbon derived from peanut shell as cathode was
constructed, which exhibits a high energy density of 43.9 Wh kg-1 (at a power density of 87.5 W kg-1) and a high power
density of 8750 W kg-1 (at a energy density of 24.4 Wh kg-1). Such outstanding performance mainly stemming from the
synergic effects between the mesoporous carbon matrices and the well-dispersed active materials nanoparticles that
increase the electronic conductivity and the reactivity of Nb2O5.
DOI: 10.1039/x0xx00000x
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physical adsorption/desorption type cathode. Hence, to
develop a type of advanced high-power anode materials are
essential to narrow the kinetics gap between anodes and
Introduction
With the growing concerns regarding energy storage devices in
recent years, lithium ion batteries (LIBs) and supercapacitors
(SCs) have attracted tremendous attention. Typically, LIBs
deliver high energy density through faradaic insertion reaction
mechanism, whereas its power density and cycle life are
relatively poor.1, 2 On the contrary, SCs provide high power
density and long cycle life due to fast non-faradaic
adsorption/desorption occur in the electrode-electrolyte
interface but with fairly low energy density.3-7 Therefore, in
order to bridge the gap between LIBs and SCs, it is urgent to
seek a new type of energy storage devices that possess high
energy density, high power density and long cycle life. In this
regard, lithium ion capacitors (LICs) stand out by using battery-
type electrode as anode and capacitor-type carbon electrode
as cathode in organic electrolyte.8-13 The battery-type anode
undergoes a faradaic redox reaction that providing high energy
density, while the capacitor-type cathode involves the
formation of anionic double layer at the electrode/electrolyte
interface, supplying high power density. Nevertheless, the
cathodes.
In previous studies, nanostructure anode materials, such as
V2O5, TiO2 and Li4Ti5O12, have received the widespread
attention due to their potential high reversible capacity, rapid
rate capability and stable cycle performance.10, 16-21 Wang et al
developed a hybrid Li-ion capacitor based TiO2 nanobelt array
anode and graphene hydrogels cathode with a high energy of
82 Wh kg-1 at a power density of 570 W kg-1.13 Furthermore,
nano-sized structural electrode material is attractive owing to
an increased surface contact area between the electrode and
the electrolyte and shorten diffusion path for both electrons
and ions. However, because of the sluggish redox reaction
mechanism of these materials, the rate capability is still
unsatisfactory.22 Thus, seeking a kind of novel anode materials
with high-power performance is another effective way. Among
the potential candidates, niobium pentoxide (Nb2O5) has been
regarded as a promising anode material for lithium ion
supercapacitor because of its several unique advantages.
Nb2O5 possess high theoretical capacity (~200 mAh g-1), which
is higher than that of Li4Ti5O12 (~175 mAh g-1).23-29 This feature
can result in an enhanced energy density of LICs according to
the following equation: E=1/2CV2, where C is the specific
capacitance and V is the working potential. Kong et al.
imbalance of reaction kinetics between these two electrodes is
the major problem needs to be solved.14,
15
The faradaic
intercalation type anode is far more sluggish than non-faradaic
constructed
a series of nanoarchitectured intercalation
Jiangsu Key Laboratory of Materials and Technology for Energy Conversion,
College of Material Science & Engineering, Nanjing University of Aeronautics and
Astronautics, Nanjing, 210016, P.R. China.
materials including orthorhombic Nb2O5 hollow microspheres,
orthorhombic Nb2O5/carbon core-shell microspheres and
tetragonal NbO2/C core-shell microspheres for ultrahigh-rate
Li+ intercalation pseudocapacitors.29 Besides, orthorhombic
Corresponding author: azhangxg@nuaa.edu.cn
†Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
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Nb2O5 can deliver a pseudocapacitive mechanism on the (near) novel LICs can be ascribed to the synergistic and cooperative
surface of the electrode when an intercalation reaction occurs, effects between the mesoporous CMK-3 structure and
which can leads to an enhanced reaction kinetics.30, 31 The pseudocapacitive property of orthorhombic Nb2O5.
unique property of orthorhombic Nb2O5 can be attributed to
crystalline structure that offers two-dimensional transport way
Experimental
and with slight structural change during intercalation
process.30 Thereby, the Nb2O5 anode with pseudocapacitive
property could exhibits excellent power performance which
may maintain the balance of sluggish faradaic anode and
instant electric double-layer type cathode. Furthermore, the
low working voltage of Nb2O5 make the LICs far from safety
problems related to the electrolyte decomposition, which can
be helpful to improve the cycle life.32-36 Nevertheless, the
intrinsic low electric conductivity (3×10-6 S cm-1) of Nb2O5 has
limited its application. To date, many strategies such as the
incorporate with carbon materials have been proposed to
overcome this issue. For example, Wang et al. reported
Nb2O5/carbon nanotubes nanocomposites for LICs, which
exhibits a power density of 4000 W kg-1 at an energy density of
4 Wh kg-1.23 Xu et al. synthesized binder-free Nb2O5/graphene
that delivered a energy density of 29 Wh kg-1 and a power
density of 2.9 kW kg-1.25 Moreover, Lee et al. developed
Nb2O5/carbon core-shell nanostructures and shows
outstanding electrochemical performance that can achieved a
power density of 16528 W kg-1 at 5 Wh kg-1.37 It should be note
that pure phase orthorhombic Nb2O5 is generally formed at
Synthesis of CMK-3
Mesoporous CMK-3 was synthesized using SBA-15 as template and
sucrose as the carbon source.49 The SBA-15 was synthesized using
triblock copolymer (Pluronic P123, EO20PO70EO20) as the surfactant
and tetraethylorthosilicate (TEOS) as the silica source, reported by
Zhao et al.50 For a typical synthesis, 1 g of prepared SBA-15 was
added to the solution containing 1.25 g sucrose, 014 g of H2SO4, and
5 g H2O. The mixture was heated at 100 °C for 6 h and then at 160
°C for another 6 h. Subsequently, the impregnation and baking
processes were repeated again after the addition of 0.75 g of
sucrose, 0.08 g of H2SO4 and 5 g of H2O. Afterwards, the dried
mixture was placed in the furnace and carbonized at 900 °C for 5 h
under nitrogen atmosphere. The resulting carbonized powder was
washed with 2M hot NaOH solution to remove silica.
Synthesis of Nb2O5/CMK-3
Firstly, 0.2 g CMK-3 was refluxed in concentrated HNO3 with
magnetic stirring at 80 °C for 1 h to increase the powders
dispersibility in ethanol. In a typical procedure, 0.1 g treated CMK-3
and 0.82 g NbCl5 were dispersed in 10 mL ethanol with the help of
ultrasonic, then the mixture was stirred for 48 h to assure complete
permeation and dried under vacuum at 35 °C. Afterwards, the
prepared composite was preheated at 300 °C for 2 h in air and
further sintered at 700 °C with a heating rate of 2 °C min-1 for 2 h
under nitrogen to obtain the final product. For comparison, bulk
Nb2O5 was prepared using the same way without the participation
of CMK-3.
high calcination temperature (>600
℃). However,
nanostructure materials can be easily aggregated at high
temperature, resulting in the decreased ion-accessible surface
and increased ion transfer path.38 Therefore, nanostructure
orthorhombic Nb2O5 material is highly desired to achieve high-
power performance in LICs systems.
CMK-3 is an ordered mesoporous carbon material with
fascinating features such as ordered pore distribution, large
pore volume, high specific surface areas, and intrinsic high
conductivity, which improve the electrode-electrolyte
interfacial area and support efficient transport for both
electrons and ions.39-45 Additional, the special structure of
CMK-3 suppresses the volume change in the process of Li-ion
insertion and extraction.46-48 Our group synthesized
Li4Ti5O12/CMK-3 nanocomposite as anode material for lithium
ion batteries that delivered exceptional rate capability (73.4
mAh g-1 at 80C) and excellent cycling performance (5.6%
capacity loss after 1000 cycles at 20 C), such superior
electrochemical performance can be attributed to abundant
conductive carbon network and CMK-3 effectively suppress
Li4Ti5O12 agglomeration during calcination process.46
Preparation of Peanut shell carbon (PSC)
Peanut shell carbon (PSC) as the cathode material was prepared as
before,51,52 a ratio of 1.5 g pretreated outer peanut shell, 3 mL
concentrated sulfuric acid and 60 mL distilled water were sealed in
a 100 mL Teflon-lined stainless-steel autoclave. The autoclave was
kept in an electric oven at 180 °C for two days and then cooled
down to room temperature naturally. The precipitate was collected
by filtration, washed with distilled water and dried at 60 °C
overnight. Afterwards, the as-prepared products and KOH, in a
mass ratio of 1:3, were thoroughly ground using an agate mortar
and then the mixtures were heated at 800 °C for 1 h in an argon
flow. Furthermore, the final product was washed thoroughly with 2
M diluted hydrochloric acid and distilled water, and then dried at
100 °C overnight.
In this work, for the first time, Nb2O5/CMK-3
nanocomposites have been prepared by
a nanocasting
Materials characterization
technology, which achieves a high specific capacity of 215 mAh
g-1 at 0.5 C and a good rate capability with 95 mAh g-1
retention at 10 C. Furthermore, the LICs constructed by using
Nb2O5/CMK-3 nanocomposite as anode and activated carbon
derived from peanut shell (PSC) as cathode delivers a high
energy density of 43.9 Wh kg-1 at a power density of 87.5 W kg-
1, and it can maintain 24.4 Wh kg-1 at a high power density of
8750 W kg-1. The exceptional electrochemical properties of the
The crystal structure of the obtainde samples was characterized by
Powder X-ray diffraction (XRD) (Bruker D8 advance) with Cu Kα
radiation and Raman spectroscopy (LABRAM HR-800).
Microstructural properties were determined using field-emission
scanning electron microscopy (FESEM, HITACHI S-4800) and
transmission electron microscopy (TEM, JEOL JEM-2100). The N2
adsorption/desorption isotherms were determined by Brunauer-
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Emmett-Teller (BET) measurements using an ASAP-2010 surface
area analyzer. The carbon content in the samples was collected
form thermogravimetry (TG, NETZSCH STA 409 PC) curves.
Electrochemical measurement
Electrochemical characterization was carried out by
galvanostatic cycling in
a CR2016-type coin cell. The
mesoporous Nb2O5/CMK-3 nanocomposite electrode was
prepared by mixing 80 wt% active materials, 10 wt% acetylene
carbon black, and 10 wt% polyvinylidene fluoride (PVDF)
dissolved in N-methyl pyrrolidinone (NMP). The resulting
slurries were coated uniformly on a piece of copper foil and
dried at 110 °C for 12 h in a vacuum oven. The mass loading of
Nb2O5/CMK-3 nanocomposite was controlled to be about 0.8
mg cm-2. The PSC electrode was prepared in the same way
except using the aluminium foil as the current collector. The
half-cells were assembled in an argon-filled glove box using Li
metal as both counter and reference electrodes and the
polypropylene (PP) film as the separator. 1 mol L-1 LiPF6
solution in ethylene carbonate (EC) and dimethyl carbonate
(DMC) (1:1 volume ratio) as electrolyte. For full-cell
electrochemical tests of the LICs, the Nb2O5/CMK-3 electrode
and PSC electrode were used as anode and cathode, respectively,
using the same electrolyte. All the electrochemical tests were
performed at different current densities using a CT2001A cell test
instrument (LAND Electronic Co.).
Fig. 2 SEM images of (a, b) CMK-3 mesoporous carbon template. (c) Nb2O5/CMK-3
nanocomposite. (d) Nb2O5 sample synthesized under same condition without CMK-3
and TEM images of (e) CMK-3 mesoporous carbon template. (f) Nb2O5/CMK-3
nanocomposite.
nitrogen atmosphere to obtain the final products.
Results and discussion
The morphology of the CMK-3 and mesoporous Nb2O5/CMK-
The synthesis process of mesoporous Nb2O5/CMK-3
nanocomposite is schematically illustrated in Fig. 1. Firstly, the
mesoporous carbon CMK-3 was prepared through using
mesoporous silica SBA-15 as template and sucrose as carbon
source as previously reported.49 In order to increase the
dispersion of CMK-3 in aqueous solution, the CMK-3 was
treated with concentrated nitric acid at 80 °C for 1 h to
introduce hydroxyl groups on its surface, which can increase
its hydrophilcity and further benefit to the following
penetration process.46 Then the modified CMK-3 was soaked in
3
nanocomposite were characterized by field emission
scanning electron microscopy (FESEM) and transmission
electron microscopy (TEM). As seen from Fig. 2 (a, b), CMK-3
has worm-like mesoporous structure, which is consisted of a
lot of micrometer-sized rod-like particles. The corresponding
TEM image (Fig. 2e) clearly demonstrates that the channel
structure is ordered, parallel and uniform. Additional, the
presence of strong diffraction peak at low angle region further
identify the ordered structure (Fig. S1), suggesting the
successful synthesis of CMK-3. Such
a special structure
Nb2O5 precursor solution under stirring for
2 days.
indicates that CMK-3 can act as a desired template, which can
provide an effective way for both the electrons and ions to
contact with the active materials. After embedded with Nb2O5
nanoparticles, the Nb2O5/CMK-3 nanocomposite displays a
rod-like shape similar with the CMK-3, indicating that the
Nb2O5 nanoparticles are almost inserted into the pores of
CMK-3, as observed in Fig. 2c. TEM image of Nb2O5/CMK-3
nanocomposite (Fig. 2f) exhibits the Nb2O5 nanoparticles with
a size about several nanometres were uniformly dispersed in
the CMK-3, further identified the successful insertion of Nb2O5
nanoparticles into the pores. In addition, SEM and TEM images
of Nb2O5/CMK-3 nanocomposite also reveal the mesoporous
structures were almost maintained after filling with Nb2O5
nanoparticles, which benefits to the penetration of electrolyte
and transportation for lithium ion. For comparison, the bulk
Nb2O5 was also synthesized using the same procedure without
the participation of CMK-3. As clearly shown in Fig. 2d, the size
Subsequently the sample was calcined at 700 °C for 2 h in
Fig. 1 Schematic illustration of the formation of Nb2O5/CMK-3 nanocomposite.
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Fig. 3 (a) X-ray diffraction pattern and (b) TG profile of Nb2O5/CMK-3 nanocomposite.
and morphology of the bulk Nb2O5 is irregular and random, which
may result in a poor electrochemical performance.
Fig. 3a shows X-ray diffraction patterns of mesoporous
Nb2O5/CMK-3 nanocomposite and bulk Nb2O5, the sharp
diffraction peaks suggest the obtained sample were well
crystallized and their major diffraction peaks are well matched
with the orthorhombic phase (JCPDS No. 30-0873) of Nb2O5.
The absence of diffraction peak corresponding to CMK-3 may
be attributed to low diffraction intensity of CMK-3 compared
to Nb2O5. This point is further confirmed by the Raman
spectroscopy (Fig. S2), the two bands around 1360 (disordered
carbon) and 1595 cm-1 (graphitic carbon) confirms the
presence of low graphitization degree of CMK-3. Meanwhile,
the similar diffraction peaks of Nb2O5/CMK-3 compared with
bulk Nb2O5 demonstrate the CMK-3 templates did not
influence the formation of orthorhombic Nb2O5. The weight
percentage of carbon in the Nb2O5/CMK-3 nanocomposite is
further analyzed by thermogravimetric test in air with a ramp
rate of 10 °C min-1. The as-prepared sample shows a large
weight loss in the temperature range of 440-530 °C, which is
attributed to the combustion of the CMK-3 in air. The mass
was estimated to be about 20% (Fig. 3b). It was concluded that
the final product is consists of Nb2O5 nanocrystals and carbon.
The porous structure of the CMK-3 templates, the
mesoporous Nb2O5/CMK-3 nanocomposite and the bulk Nb2O5
are characterized by nitrogen sorption measurement.
Compared to CMK-3, Nb2O5/CMK-3 shows no clear hysteresis
loop in the P/P0 range, demonstrating most of the
nanochannels of CMK-3 are occupied by the Nb2O5
nanoparticles, as shown in Fig. 4.53 After the impregnation
process, the BET surface area decreases from 979 m2 g-1 for
CMK-3 to 353 m2 g-1 for Nb2O5/CMK-3 nanocomposite.
However, the BET surface area of bulk Nb2O5 is 8 m2 g-1, which
is much less than that of mesoporous Nb2O5/CMK-3
nanocomposites. As a result, the greatly improved specific
capacity of the Nb2O5/CMK-3 nanocomposite can be excepted
since more active sites for lithium ion. The pore size
Fig. 5 (a) Cyclic voltammetry curves of Nb2O5/CMK-3 at various sweep rates from 0.1 to
2.0 mV s-1. (b) charge-discharge curves of Nb2O5/CMK-3 at difference current densities.
(c) charge-discharge curves of bulk Nb2O5 at difference current densities and (d) the
rate and cycling performances of Nb2O5/CMK-3 nanocomposite and bulk Nb2O5.
distributions of the as-prepared products were calculated by
the Barrett-Joyner-Halenda (BJH) method.54,55 Fig. 4b shows
the corresponding pore size distributions of the CMK-3
template, the Nb2O5/CMK-3 nanocomposite and the bulk
Nb2O5. The average pore size of CMK-3 centred at 5.1 nm and
decreased to 1.2 nm for the Nb2O5/CMK-3 nanocomposite,
further demonstrating the Nb2O5 nanocrystals embedded in
the pores of the CMK-3 templates.
To study the electrochemical performance of the
Nb2O5/CMK-3 and bulk Nb2O5, half cells were assembled by
using Li foil as both counter and reference electrode and active
material as working electrode. Fig. 5a shows the cyclic
voltammetry (CV) curves of the mesoporous Nb2O5/CMK-3
nanocomposite electrode at scan rates ranging from 0.1 to 2
mV s-1 in the potential window between 1.0 and 3.0 V (vs.
Li/Li+). The CV curves show broad cathodic and anodic peaks,
which are the characteristic peaks of Nb2O5, demonstrating its
pseudocapacitive property that provides two-dimensional
transport for the insertion of Li+. Furthermore, the similar
shape of CV curves from low scan rate (0.1 mV s-1) to high scan
rate (2 mV s-1) indicates its high rate capability, which can be
ascribed to the unique mesoporous structure and enhanced
conductivity that contributes to the ion and electronic
transfer.31,56 The galvanostatic charge-discharge profiles at
various rates of mesoporous Nb2O5/CMK-3 and bulk Nb2O5 are
shown in Fig. 5(b, c). The mesoporous Nb2O5/CMK-3
nanocomposite delivers 243.6 mAh g-1 at a rate of 0.2 C, higher
than that of bulk Nb2O5 (214.9 mAh g-1), which can be owing to
the enhanced utilization of active materials. More importantly,
when at a high rate of 20 C, the reversible capacity of
Nb2O5/CMK-3 (75.5 mAh g-1) is significantly higher than bulk
Nb2O5 (43.7 mAh g-1), indicating an excellent rate capability.
Furthermore, the rate performance of the mesoporous
Nb2O5/CMK-3 and bulk Nb2O5 at various charge-discharge
rates of 0.2-20 C is revealed in Fig. 5d. It is evident that
mesoporous Nb2O5/CMK-3 nanocomposite exhibits higher
discharge and charge capacities compared to bulk Nb2O5 at the
Fig. 4 (a) Nitrogen adsorption-desorption isotherms for Nb2O5 nanocomposite and (b)
same
rate.
In
detail,
mesoporous
Nb2O5/CMK-3
the corresponding pore size distribution.
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nanocomposite delivers a discharge capacity of 215.6, 118.4,
96.6 and 75.5 mAh g-1 at a rate of 0.5, 2, 10 and 20 C,
respectively. However, bulk Nb2O5 has a discharge capacity of
151.4, 90.4, 71.6 and 43.7 mAh g-1 at corresponding current
rates. The outstanding rate performance of Nb2O5/CMK-3
nanocomposite can be attributed to its unique mesoporous
structure and enhance electronic conductivity that contributes
to the transportation of lithium ion and electronic.
Furthermore, to examine the robust of our materials, the half-
cell was proceeded immediately at a low rate of 0.2 C after a
rate-step testing process. As seen in Fig. 5d, the reversible
capacity of the mesoporous Nb2O5/CMK-3 nanocomposites
recovered to 235.6 mAh g-1 when the charge rate was returned
to 0.2 C after 35 cycles, only slightly lower than the initial
value, suggesting the reliability of the material. The cycle life
measurement was conducted in order to evaluate its practical
application. As seen in Fig. S4, the discharge capacity of the
mesoporous Nb2O5/CMK-3 nanocomposite remains 167 mAh
g-1 at the rate of 1 C after 50 cycles with nearly no capacity
loss, indicative of the superior cyclic stability. By comparison,
the bulk Nb2O5 suffers from terrible capacity fading that only
remains 79.6 mAh g-1 at the same rate after 50 cycles. Clearly,
the great enhanced electrochemical property of the
mesoporous Nb2O5/CMK-3 can be ascribed to the particular
mesoporous structure, interpenetrating conductive carbon
network and small Nb2O5 nanoparticles, which effectively
improves the electronic conductivity, the utilization of active
material, and prevent the volume expansion during the Li+
intercalation process.
Fig. 6 (a) Galvanostatic charge-discharge profiles of the Nb2O5/CMK-3//PSC hybrid
device at various current densities. (b) rate capability of the Nb2O5/CMK-3//PSC hybrid
device at various current densities from 0.05 to 5 A g-1. (c) relationship between cycle
number and capacitance retention at 1 A g-1. (d) Ragone plots of the Nb2O5/CMK-
3//PSC in comparison with other dates.
P=E/t
(2)
Where V is the working potential, t is the discharge time and C
is the specific capacitance of the LICs which can be calculated
based on equation:
C=I
△
t/M
△
Where I is the discharge current,
V
(3)
△t is the discharge time, M is
the total mass of the active material used in both electrodes,
and △V is the potential window of device. Appealingly, the
hybrid device of Nb2O5/CMK-3//PSC achieves a high energy
density of 43.9 Wh kg-1 at a current density of 0.05 A g-1, and
the corresponding power density is 87.5 W kg-1, as shown in
Fig. 6b. Furthermore, when performed at high current density
of 5 A g-1 (8750 W kg-1), the energy density of LICs remains
24.4 Wh kg-1, indicative of an excellent rate capability. In
addition, the cyclic performance was tested by conducting a
constant current charge/discharge at 1 A g-1. As seen in Fig. 6c,
the capacitance retention of the LICs could be able to maintain
87.3% after 1000 cycles, indicating an excellent
electrochemical stability. We compared this work with some
previously reported LICs. As seen in Fig. 6d, the performance
of our work is significant better than some previously reported
LICs regardless of energy density and power density, such as
Nb2O5/CNT//AC23, V2O5/CNT//AC16, Li4Ti5O12-C//AC17, TiO2-
B//CNT10. As a whole, the outstanding performance of the LICs
using Nb2O5/CMK-3 as anode can be attributed to the several
factors. Firstly, the orthorhombic phase is beneficial to high
rate Li+ intercalation/deintercalation. Secondly, CMK-3 as hard
template to construct three dimensional conductive network
structures that offers ordered channels not only shorten the
diffusion pathways for Li+ but also effectively enhance the
electronic conductivity of the composite. Thirdly, CMK-3
served as a rigid support for Nb2O5 nanoparticles that prevents
agglomeration and growth of Nb2O5 nanoparticles during the
calcination process. As a result, the synergic effect between
the mesoporous carbon matrices and the well-dispersed Nb2O5
To further investigate the feasibility of Nb2O5/CMK-3 for LICs
applications, we designed
a coin cell device based on
Nb2O5/CMK-3 as anode and PSC (Peanut shell carbon) as
cathode. At first, we explored the electrochemical
performance of PSC in half-cells. As shown in Fig. S5, the PSC
exhibits a specific capacity of 70 mAh g-1 at 0.2 A g-1 in the
potential range from 2.5 to 4.5 V (vs. Li/Li+). Thus, the
optimum mass ratio of Nb2O5/CMK-3 and PSC was calculated
to be 1: 2.5 in the potential window between 0.5 and 3.0 V to
balance the charge between positive and negative electrodes.
The galvanostatic charge-discharge profiles of the LICs at
various current densities (the current density was based on the
total mass of active material used in both anode and cathode)
were shown in Fig. 6a. The charge-discharge curves of the LICs
were differential from the well-symmetric triangle shapes of
SCs, indicative of a capacitive response and further evidence
that the energy storage mechanism is a combination of surface
adsorption/desorption processes at the cathode and redox
reactions at the anode. Fig. S6 shows the cyclic voltammetry
curves of the Nb2O5/CMK-3//PSC hybrid device at various scan
rates from 2 to 20 mV s-1 between 0.5 and 3 V. The quasi-
rectangular shape suggests the fast intercalation
pseudocapacitive reactions and electrolyte ion transport. The
energy and power density of LICs is calculated respectively by
using galvanostatic measurements and the following equations:
E=1/2CV2
(1)
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13 H. Wang, C. Guan, X. Wang and H. J. Fan, Small, 2015, 11
1470-1477.
14 K. Naoi, Fuel Cells, 2010, 10, 825-833.
,
active materials nanoparticles that greatly improve the
electrochemical performance.
15 X. Wang, C. Yan, J. Yan, A. Sumboja and P. S. Lee, Nano
Energy, 2015, 11, 765-772.
16 Z. Chen, V. Augustyn, J. Wen, Y. Zhang, M. Shen, B. Dunn and
Y. Lu, Adv. Mater., 2011, 23, 791-795.
Conclusions
In summary, we have successfully developed a simple method
to synthesis mesoporous Nb2O5/CMK-3 nanocomposites as
high-performance anode materials for LICs. CMK-3 not only
affords a three dimensional conductive network structure to
improve electronic conductivity, but also hinder the
agglomeration of Nb2O5 nanoparticles during heat treatment
process. The Nb2O5/CMK-3 exhibited excellent lithium storage
performance, which is attributed to the special mesoporous
structure, the formation of conductive carbon matrix and
nanometer particles. Furthermore, the LICs composed of
Nb2O5/CMK-3 as anode and PSC as cathode demonstrated high
energy density, power density and excellent cyclic stability,
suggesting the Nb2O5/CMK-3 is a promising anode material for
high-performance LIC.
17 H.-G. Jung, N. Venugopal, B. Scrosati and Y.-K. Sun, J. Power
Sources, 2013, 221, 266-271.
18 Q. Qu, Y. Zhu, X. Gao and Y. Wu, Adv. Energy Mater., 2012, 2,
950-955.
19 K. Naoi, S. Ishimoto, Y. Isobe and S. Aoyagi, J. Power Sources,
2010, 195, 6250-6254.
20 H. Liu, G. Wen, S. Bi and P. Gao, Electrochim. Acta, 2015, 171
114-120.
,
21 J. Shu, L. Hou, R. Ma, M. Shui, L. Shao, D. Wang, Y. Ren and
W. Zheng, RSC Adv., 2012, , 10306-10309.
22 H. Kim, M. Y. Cho, M. H. Kim, K. Y. Park, H. Gwon, Y. Lee, K. C.
Roh and K. Kang, Adv. Energy Mater., 2013, , 1500-1506.
23 X. Wang, G. Li, Z. Chen, V. Augustyn, X. Ma, G. Wang, B. Dunn
and Y. Lu, Adv. Energy Mater., 2011, , 1089-1093.
24 E. Lim, H. Kim, C. Jo, J. Chun, K. Ku, S. Kim, H. I. Lee, I.-S. Nam,
S. Yoon and K. Kang, ACS nano, 2014, , 8968-8978.
25 L. P. Wang, L. Yu, R. Satish, J. Zhu, Q. Yan, M. Srinivasan and
Z. Xu, RSC Adv., 2014, , 37389-37394.
2
3
1
8
4
26 S. H. Kang, S.-Y. Lee, M. G. Gang, K.-S. Ahn and J. H. Kim,
Electrochim. Acta, 2014, 133, 262-267.
27 L. Kong, C. Zhang, J. Wang, W. Qiao, L. Ling and D. Long, ACS
Acknowledgements
This work was supported by the National Basic Research Program of
China (973 Program) (No. 2014CB239701), Natural Science
Foundation of Jiangsu Province (BK2011030, BK20151468), National
Natural Science Foundation of China (Grant Nos. 51372116 and
51504139), Natural Science Foundations of Jiangsu Province (Grant
nano, 2015, 9, 11200-11208.
28 H. Luo, W. Song, P. G. Hoertz, K. Hanson, R. Ghosh, S.
Rangan, M. K. Brennaman, J. J. Concepcion, R. A. Binstead
and R. A. Bartynski, Chem. Mater., 2012, 25, 122-131.
29 L. Kong, C. Zhang, J. Wang, W. Qiao, L. Ling and D. Long, Sci.
rep., 2016, 6, 21177.
30 V. Augustyn, J. Come, M. A. Lowe, J. W. Kim, P.-L. Taberna, S.
H. Tolbert, H. D. Abruña, P. Simon and B. Dunn, Nature
materials, 2013, 12, 518-522.
Nos. BK20150739)
, the Funding for Outstanding Doctoral
Dissertation in NUAA (BCXJ14-10; BCXJ16-07), the Funding of
Jiangsu Innovation Program for Graduate Education (KYLX_0255),
Fundamental Research Funds for the Central Universities and the
Priority Academic Program Development of Jiangsu Higher
Education Institutions (PAPD).
31 J. W. Kim, V. Augustyn and B. Dunn, Adv. Energy Mater.,
2012,
32 K. Naoi, S. Ishimoto, J.-i. Miyamoto and W. Naoi, Energy
Environ. Sci., 2012, , 9363-9373.
2, 141-148.
5
33 C. Decaux, G. Lota, E. Raymundo-Piñero, E. Frackowiak and F.
Béguin, Electrochim. Acta, 2012, 86, 282-286.
34 M. S. Park, Y. G. Lim, S. M. Hwang, J. H. Kim, J. S. Kim, S. X.
Notes and references
Dou, J. Cho and Y. J. Kim, ChemSusChem, 2014,
35 E. Lim, C. Jo, H. Kim, M.-H. Kim, Y. Mun, J. Chun, Y. Ye, J.
Hwang, K.-S. Ha and K. C. Roh, ACS nano, 2015, , 7497-7505.
36 L. Kong, C. Zhang, S. Zhang, J. Wang, R. Cai, C. Lv, W. Qiao, L.
Ling and D. Long, J. Mater. Chem. A, 2014, , 17962-17970.
7, 3138-3144.
1
2
J.-M. Tarascon and M. Armand, Nature, 2001, 414, 359-367.
J. B. Goodenough and Y. Kim, Chem. Mater., 2009, 22, 587-
603.
9
3
4
E. Frackowiak, Phys. Chem. Chem. Phys., 2007,
Y. Luo, D. Kong, Y. Jia, J. Luo, Y. Lu, D. Zhang, K. Qiu, C. M. Li
and T. Yu, Rsc Adv., 2013, , 5851-5859.
X. Lu, M. Yu, G. Wang, Y. Tong and Y. Li, Energy Environ. Sci.,
2014, , 2160-2181.
P. Zhang, Y. Yang, Z. Ma, Y. Wang, Y. Pan and C. Lu, Mater.
Lett., 2016, 164, 421-424.
Y. Xu, J. Wang, B. Ding, L. Shen, H. Dou and X. Zhang,
ChemElectroChem, 2015, 2, 2020-2026.
G. G. Amatucci, F. Badway, A. Du Pasquier and T. Zheng, J.
Electrochem. Soc., 2001, 148, A930-A939.
T. Cottineau, M. Toupin, T. Delahaye, T. Brousse and D.
Belanger, Appl. Phys. A, 2006, 82, 599-606.
9, 1774-1785.
2
37 N. Kumagai, Y. Koishikawa, S. Komaba and N. Koshiba, J.
Electrochem. Soc., 1999, 146, 3203-3210.
38 C. J. Zhang, R. Maloney, M. R. Lukatskaya, M. Beidaghi, B.
Dyatkin, E. Perre, D. Long, W. Qiao, B. Dunn and Y. Gogotsi, J.
Power Sources, 2015, 274, 121-129.
39 H. Zhou, S. Zhu, M. Hibino, I. Honma and M. Ichihara, Adv.
Mater., 2003, 15, 2107-2111.
40 L. Ji, Z. Lin, M. Alcoutlabi and X. Zhang, Energy Environ. Sci.,
2011, 4, 2682-2699.
41 C. Liang, N. J. Dudney and J. Y. Howe, Chem. Mater., 2009,
21, 4724-4730.
42 I. Grigoriants, L. Sominski, H. Li, I. Ifargan, D. Aurbach and A.
Gedanken, Chem. Commun., 2005, 921-923.
43 K. Xia, Q. Gao, J. Jiang and J. Hu, Carbon, 2008, 46, 1718-
1726.
44 J. Roggenbuck and M. Tiemann, J. Am. Chem. Soc., 2005,
127, 1096-1097.
45 Y. Jiang, Z. Yang, W. Li, L. Zeng, F. Pan, M. Wang, X. Wei, G.
3
5
6
7
8
9
7
10 Q. Wang, Z. Wen and J. Li, Adv. Funct. Mater., 2006, 16
2141-2146.
11 J. H. Park and O. O. Park, J. Power Sources, 2002, 111, 185-
190.
12 H. Li, L. Shen, J. Wang, S. Fang, Y. Zhang, H. Dou and X.
,
Zhang, J. Mater. Chem. A, 2015, 3, 16785-16790.
Hu, L. Gu and Y. Yu, Adv. Energy Mater., 2015, 5, 1402104.
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
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Please do not adjust margins
RSC Advances
Page 7 of 7
View Article Online
DOI: 10.1039/C6RA11460A
Journal Name
ARTICLE
46 L. Shen, X. Zhang, E. Uchaker, C. Yuan and G. Cao, Adv.
Energy Mater., 2012, , 691-698.
2
47 X. Zhou, L.-J. Wan and Y.-G. Guo, Nanoscale, 2012,
5871.
48 H. Huwe and M. Fröba, Carbon, 2007, 45, 304-314.
4, 5868-
49 S. Jun, S. H. Joo, R. Ryoo, M. Kruk, M. Jaroniec, Z. Liu, T.
Ohsuna and O. Terasaki, J. Am. Chem. Soc., 2000, 122,
10712-10713.
50 D. Zhao, J. Feng, Q. Huo, N. Melosh, G. H. Fredrickson, B. F.
Chmelka and G. D. Stucky, science, 1998, 279, 548-552.
51 J. Ding, H. Wang, Z. Li, K. Cui, D. Karpuzov, X. Tan, A.
Kohandehghan and D. Mitlin, Energy Environ. Sci., 2015, 8,
941-955.
52 S. Dong, L. Shen, H. Li, P. Nie, Y. Zhu, Q. Sheng and X. Zhang, J.
Mater. Chem. A, 2015, , 21277-21283.
53 R. Ryoo, S. H. Joo, M. Kruk and M. Jaroniec, 2001.
3
54 E. Kang, Y. S. Jung, A. S. Cavanagh, G. H. Kim, S. M. George, A.
C. Dillon, J. K. Kim and J. Lee, Adv. Funct. Mater., 2011, 21,
2430-2438.
55 W.-M. Zhang, X.-L. Wu, J.-S. Hu, Y.-G. Guo and L.-J. Wan, Adv.
Funct. Mater, 2008, 18, 3941-3946.
56 J. Come, V. Augustyn, J. W. Kim, P. Rozier, P.-L. Taberna, P.
Gogotsi, J. W. Long, B. Dunn and P. Simon, J. Electrochem.
Soc., 2014, 161, A718-A725.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
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