Hierarchical LiMnPO4 assembled from nanosheets via a solvothermal method as a high performance cathode material

Article abstract of DOI:10.1039/c5ra14040d

A series of LiMnPO₄ nanoparticles with different morphologies have been successfully synthesized via a solvothermal method. The samples have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM). The results show that the morphology, particle size and crystal orientation are controllably synthesized by various precursor composite tailoring with various Li:Mn:P molar ratios. At 3:1:1, a Li⁺-containing precursor Li₃PO₄ is obtained while at 2:1:1, only a Mn²⁺-containing precursor involving Mn₅(PO₄)₂[(PO₃)OH]₂·4H₂O and MnHPO₄·2.25H₂O is detected. Especially, at 2.5:1:1, the precursor consists predominantly of a Mn²⁺-containing precursor with a minor amount of Li₃PO₄. From 2:1:1 to 3:1:1, the particle morphology evolves from sheet to spherical texture accompanied with the particle size reducing. In the presence of urea, highly uniform LiMnPO₄ with a hierarchical micro-nanostructure is obtained, which is composed of nanosheets with a thickness of several tens of nanometers. Thus, these unique hierarchical nanoparticles with an open porous structure play an important role in the LiMnPO₄ cathode material. At a concentration of 0.16 mol L^-1 for urea, the hierarchical LiMnPO₄/C sample assembled from nanosheets with the (010) facet exposed shows the best electrochemical performance, delivering higher reversible capacity of 150.4, 142.1, 138.5, 125.5, 118.6 mA h g^-1 at 0.1, 0.2, 0.5, 1.0, 2.0C, respectively. Moreover, the composites show long cycle stability at high rate, displaying a capacity retention up to 92.4% with no apparent voltage fading after 600 cycles at 2.0C.

Full text of DOI:10.1039/c5ra14040d

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Hierarchical LiMnPO assembled from nanosheets via
4
solvothermal method as high performance cathode material
Received 00th January 20xx,
Accepted 00th January 20xx
1
1
1*
1
1
1
Zhijian Zhang , Guorong Hu , Yanbing Cao , Jianguo Duan , Ke Du , Zhongdong Peng
4
A series of LiMnPO nanoparticles with different morphology have been successfully synthesized via solvothermal method.
DOI: 10.1039/x0xx00000x
The samples have been characterized by Xꢀray diffraction (XRD), Scanning electron microscope (SEM), Transmission
electron microscopy (TEM). The results show that morphology, particle size and crystal orientation are controllable
www.rsc.org/
+
synthesized by various precursor composite tailoring with various Li:Mn:P molar ratio. At 3:1:1, Li ꢀcontaining precursor
2
+
Li
MnHPO
minor amount of Li
with the particle size reduced. In the presence of urea, highly uniform LiMnPO
obtained, which is composed of nanosheets with the thickness of several tens of nanometers. Thus, those unique hierarchical
nanopartilces with open porous structure play an important role in LiMnPO cathode material. At the concentration of 0.16
/C sample assembled from nanosheets with (010) facet exposed shows the best
3
PO
4
is obtained while at 2:1:1, only Mn ꢀcontaining precursor involving Mn
·2.25H O is detected. Specially, at 2.5:1:1, the precursor consists predominantly of Mn ꢀcontaining precursor with
PO . From 2:1:1 to 3:1:1, the particle morphology evolves from sheet to spherical texture accompanied
with hierarchical microꢀnanostructure is
5 4 2 3 2 2
(PO ) [(PO )OH] ·4H O and
2
+
4
2
3
4
4
4
ꢀ1
mol L for urea, the hierarchical LiMnPO
electrochemical performance, delivering higher reversible capacity of 150.4, 142.1, 138.5, 125.5, 118.6 mAh g at 0.1, 0.2,
.5, 1.0, 2.0C, respectively. Moreover, the composites show long cycle stability at high rate, displaying a capacity retention
up to 92.4% with no apparent voltage fading after 600 cycles at 2.0 C.
4
ꢀ1
0
LiMnPO4 via a solvothermal method, showing a reversible
ꢀ
1
1
. Introduction
capacity of 153.4 mAh g at 0.1 C, which is ascribed to the
nanostructure with the average length and diameter of
LiMnPO is one of the most promising cathode material for
4
1
0
approximately 100 and 60 nm, respectively. In this sense, the
nanostructure is key to synthesizing LiMnPO cathode material
with excellent electrochemical performance. Since the
solvothermal process is
nanostructure and high crystalline materials with the notable
virtues such as simple and straight ward operations, costꢀ
effectiveness, and scalable production, it has been widely used
to prepare the LiMnPO4 cathode material. So far,
nanostructured LiMnPO4 cathode material has been
successfully prepared via the solvothermal process, in which
the expensive chemicals was used.
traditional hydrothermal/solvothermal method, to prepare the
nanostructured LiMnPO , excess Li is used with the Li:Mn:P
molar ratio of 3:1:1 or even more.
solvent has been successfully used to prepare microꢀ and nanoꢀ
structure LiMPO (M=Fe, Mn, Ni) for lithium ionꢀbatteries, and
the morphology could be easily tuned by altering the synthesis
condition or selecting different raw materials, such as the
concentration, solvent, temperature and time, pH valve, feeding
lithium ionꢀbatteries, due to its high specific capacity, low
toxicity, low cost, and excellent thermal stability, and has been
expected to be applied in a wideꢀscale use in plugꢀin hybrid
electric vehicles (PHEVs), electric vehicles (EVs) and smart
grid storage that fast electronic transfer and superior ionic
migration are demanded.
suffers from poor electronic conductivity and slow Li
diffusion, leading to low specific capacity, poor rate capacity,
4
a facile approach to prepare
1
, 2
However, the bulk LiMnPO4
+
3
ꢀ5
and inferior cycle stability. Up to now, the electrochemical
performance of LiMnPO cathode material has been improved
4
1
1, 12
What’s more, in a
by controlling the particle size and morphology. It has been
demonstrated that the particles with dimensionally modulated
nanostructure such as nanorod, nanosheets and nanosphere can
enhance the electrochemical performance due to a shortening of
both the electron and lithium ion diffusion path lengths within
4
1
2, 13
Up to now, EG based
6
ꢀ8
4
the particles.
The clusterꢀlike LiMnPO4 composed of
nanoplates with a thickness of ca. 35 nm and a width of ca. 400
nm via a solvothermal method exhibited a discharge capacity of
ꢀ1
9
147 mAh g at 0.05 C. Xu et.al. reported the rodꢀlike
6, 8, 14ꢀ18
sequence and the surfactant.
However, It is rarely
reported the effect of the phase composition in the precursor
solution or Li:Mn:P molar ratio on the morphology and
1
School of Metallurgy and Environment, Central South University, Changsha
10083, China. Eꢀmail address: cybcsu@csu.edu.cn; Tel: +86ꢀ13875868540; Fax:
4
+
86ꢀ0731ꢀ88830474.
structure of LiMnPO
reveal the role that phase composition or Li:Mn:P molar ratio
play in the preparation of LiMnPO . With this perspective, we
4
. Thus, it deserves further research to
†Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
4
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report the morphology controllable synthesis of LiMnPO
4
Li:Mn:P was controlled at 2:1:1, 2.5:1:1 and 3:1:1 by adjusting
tailoring with the molar ratio of Li:Mn:P by solvothermal the added amount of LiOH, and the product was named sꢀ1, sꢀ2
method, using ethanol as green solvent, LiH PO , LiOH and sꢀ3. During the series experiments in the presence of urea,
O as the starting material, as illustrated in the molar ratio of Li:Mn:P was 2:1:1, while the concentration
2
4
2
·H O
and MnSO
Scheme 1.
4 2
·H
ꢀ1
of urea was controlled at 0.08, 0.12, 0.16, 0.2 mol L , namely
On the other hand, it is hard to control the morphology, sꢀ4, sꢀ5, sꢀ6, and sꢀ7, respectively.
especially for highly uniform particles with nanostructure.
Generally, the nanoparticles prefer to agglomerate together, 2.2 Characterization
which in turn constantly limits the demonstration of its intrinsic
performance. In this regard, LiMnPO nanoparticles with a examined by Xꢀray diffraction (XRD) (Haoyuan DXꢀ2500,
novel hierarchical microꢀnanostructure are expected as a new Dandong Instrument Co., Ltd., China) analysis with nickelꢀ
prototype to minimize the selfꢀagglomeration and reꢀstacking filtered Cu Kα radiation ( = 1.5418 Å) over the 2 range from
and also facilitate physical properties at macroscale. 10 to 90 . The morphology was investigated with a field
Herein, a urea assisted solvothermal method was proposed for emission scan electron microscope (SEM, JEOL JSMꢀ6360LV,
the growth of hierarchical microꢀnanostructured LiMnPO by and Japan) and a transmission electron microscope (TEM,
The crystal structures of the synthesized powers were
4
λ
θ
°
°
4
controlling the molar ratio of Li:Mn:P at 2:1:1. To fully Tecnai G2 F20).
demonstrate the effect of urea, the concentration of urea was
optimized. With the morphology and composition advantages, 2.3 Electrochemical measurement
the asꢀprepared LiMnPO
4
/C is expected to manifest superior
The electrochemical performance of the samples as cathode
electrochemical performance, especially, the high rate capacity material was evaluated using CR2025 coin cells assembled in
and long cycle stability.
an argonꢀfilled glove box. For the cathode preparation, a
mixture of LiMnPO /C, Super P carbon, and poly(vinyl
4
difluoride) (PVDF) with a weight ratio of 75:15:10 was pasted
on an Al foil, which works as a current collector. A Celgard
2
340 microporous membrane was used as the separator and
lithium foil was used as the counter electrode. The nonꢀaqueous
electrolyte was 1 M LiPF solution in ethylene carbonate,
6
dimethyl carbonate, and methylꢀethyl carbonate with a volume
ratio of 1:1:1 (LIB 315, Guotai Huarong Chem. Co.,
Ltd., Zhangjiagang, China). The electrochemical tests were
carried out at room temperature on a Land Test System
Scheme. 1 the morphology controllable solvothermal process
by tailoring with the Li:Mn:P molar ratio
(
CT2001A, Wuhan Jinnuo Eletronic Co., Ltd., Wuhan China)
+
setting the cut off voltages of 2.50~4.50 V versus Li /Li (1
ꢀ1
C=160 mA g ).
2
. Experimental
2
.1 preparation
3
. Results and discussion
The LiMnPO
4
samples were prepared by solvothermal
3
.1 effect of Li:Mn:P molar ratio
approach in ethylene glycol (EG) and deꢀionized water mixing
solvent (volume ratio of 9:1) as follows: various amount of
The structure and morphology of the product are highly dependent
on the Li:Mn:P molar ratio. The XRD pattern of the product
obtained from various molar ratio are presented in Fig. 1. It can be
clearly seen that all samples are single phase which can be indexed
to the orthorhombic olivine structure with a Pmnb space group
LiOH aqueous solution was added dropꢀwise into the LiH
EGꢀH O solution under vigorous stirring, and then CTAB
hexadecyl trimethyl ammonium bromide, 0.015 mol L ) was
dissolved in the above white suspension followed by MnSO
2 4
PO
2
ꢀ1
(
4
(
JCPDS card no.74ꢀ0375). Upon closer observation, the relative
aqueous solution introduced into the mixture. The final mixture
was transferred to a 300 mL stainless steel autoclave. The
peak intensities change with the molar ratio variation of Li:Mn:P.
The diffraction intensity from the (020) facet is strongest at 2:1:1,
while the highest intensity at 3:1:1 comes from the (311) facet. This
may indicate that the asꢀobtained sample at 2:1:1 has a preferential
2
+
concentration of Mn in the precursor solution was controlled
ꢀ1
to be 0.1 mol L . The solvothermal reaction was carried out at
20 for 4 h to form a white precipitation. After that, white
2
℃
crystal orientation along the [010] direction, which is favorable to
particles were collected via centrifugation, washed with
distilled water three times, absolute ethanol twice. After dried
+
the Li diffusion due to the fact that LiMnPO has a oneꢀdimension
4
9
, 19
migration path along the b axis.
Fig. 2 shows the SEM images of
in a vacuum oven at 60
was mixed and ground with PVA (20 wt%), and then annealed
at 670 for 4 h (3 /min) under an Ar atmosphere to
carbonize glucose and increase the crystallinity of the LiMnPO
℃ for 12 h, the asꢀprepared LiMnPO
4
the samples tailoring with different Li:Mn:P molar ratio. At 2:1:1, a
novel morphology was obtained. As shown in Fig. 2a, the sample
consists of sheetꢀlike crystals with the thickness of several tens of
nanometers, a mean length of ~450 nm, an average width of ~300
nm, in which the small crystals attach together irregularly to
assemble into hierarchical structure with open porousness. But
℃
℃
4
material. The mass percentage of carbon was determined by
carbon sulfur analyzer to be about 3.4 wt%. The molar ratio of
2
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unfortunately, the hierarchical structure is not open enough, thus we
To further understand the evolution of morphology and the
carried out the urea assisted solvothermal method to effectively take diversity of particle size. The structure and morphology of the
advantage of those novel morphology which will be discussed later precursors from the mother solution before solvothermal treatment
in detail. When the molar ratio is prolonged to 2.5:1:1, LiMnPO
4
were characterized. The XRD patterns of the dried precursors
composed of sheetꢀlike crystals similar to 2:1:1 is obtained. It is synthesized at room temperature are presented in Fig.3. The phase
clearly seen that the obtained sample was randomly dispersed with composition of the precursor is strongly affected by the molar ratio
2
+
wellꢀdefined shape, in which the sheetꢀlike crystals have a uniform of Li:Mn:P. From the XRD patterns, obviously, Mn ꢀcontaining
particle size distribution. For instance, the length is varied from 250 precursor involving Mn (PO [(PO )OH] ·4H (JCPDS card
nm to 500 nm, while the width from 150 nm to 450 nm. When the no.34ꢀ0146) and MnHPO ·2.25H O (JCPDS card no.47ꢀ0199) is
molar ratio increased to 3:1:1, the particles are nearꢀspherical with stable at the offꢀstoichiometry, leaving Li freely existing in the
an average diameter of several tens of nanometers. Obviously, the mother solution, as the molar ratio of Li:Mn:P increased, Li PO
particles are seriously agglomerated, which will bring negative phase (JCPDS card no.25ꢀ1030) is detected. When increased to 3:1:1,
5
4
)
2
3
2
2
O
4
2
+
3
4
+
3 4
effects on the electrochemical performance. It is worth noting that, no other phase but Li ꢀcontaining precursor Li PO is identified,
when increasing the molar ratio of Li:Mn:P, a smaller particle size is while the manganese salt phases cannot be detected. Fig. S1 shows
achieved, indicating that excess Li was favorable for attaining small the SEM images of the dried precursors, clearly, at 3:1:1, the
particle size for LiMnPO
study.
4
, in well agreement with the previous particles exhibit spherical texture similar to that of the resultant
product LiMnPO , indicating that LiMnPO is most likely formed by
an in situ evolution from the precursor Li PO in the solvothermal
20, 21
4
4
3
4
22
method, in agreement with previous research. In the EG based
solvothermal condition in which water is almost highly deficient is
not likely able to dissolve the starting material Li
intermediate phases such as Mn (PO , MnHPO , which are known
as the dissolutionꢀreprecipitation process in the hydrothermal
3 4
PO to form the
3
4
)
2
4
23, 24
method similar to LiFePO
4
,
3 4
Thus, the Li PO may plays as an
hard template to form LiMnPO
4
directly. At 2:1:1, the precursor also
presents the spherical texture different with the subsequent product,
which may due to the multiꢀphases in the precursor solution, in
which case the crystal units may contain more than one nucleus with
different orientation and growth rates. In addition, such remarkable
divergence in precursor solution results in different released ions
from the precursor with various types or priority orders, leading to
the different nucleation or growth rates. In this regard, the distinction
in morphology is caused by the different solution composition
generated by adjusting the molar ratio of Li:Mn:P.
Fig. 1 the XRD pattern of the sample tailoring with different
Li:Mn:P molar ratio: (a) 2:1:1; (b)2.5:1:1; (c) 3:1:1.
Fig. 2 the SEM images of samples tailoring with different
Li:Mn:P molar ratio: (a) 2:1:1; (b)2.5:1:1; (c) 3:1:1.
Fig. 3 the XRD pattern of the precursors tailoring with different
Li:Mn:P molar ratio: (a) 2:1:1; (b)2.5:1:1; (c) 3:1:1.
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Based on the above results, it can be reasonably understood that the
According to the SEM images in Fig. 5, the morphologies are
molar ratio of Li:Mn:P has a great effect on the phase composition of not obviously changed by varying the concentration of urea,
the precursor, which will control the morphology and particle size of and all the samples are composed of sheetꢀlike crystals, which
the LiMnPO
confirm the roles of molar ratio of Li:Mn:P, also, taking advantage formation of LiMnPO
of the sheetꢀlike crystals with preferred orientation of [010] direction, changing the shape of the LiMnPO
a set of independent experiments were carried out where urea was believed that the phase composition of the precursor has a great
mainly used as the alkaline reagent. effect on the morphology of LiMnPO instead of the pH when
tailoring with the molar ratio of Li:Mn:P. In addition, the
LiMnPO crystals assemble regularly to form the flowerꢀlike
Crystal structure is significantly important for cathode materials, structure with more open porousness gradually, as increasing
including the phase composition, crystallinity, and crystal orientation. the concentration of urea. For the closed observation in Fig. 5,
To characterize the crystal structure of LiMnPO , the series samples we can see that the particle size become smaller with the
4
crystals in the solvothermal process. To further indicates that urea can act as an alkaline reagent for the
phase and has no obvious role in
crystals. Therefore, it is
4
4
4
3.2 effect of urea addition
4
4
were tested by XRD after thermal treatment. Fig. 4 shows the XRD increasing amount of urea, as well as less agglomeration,
pattern of the series samples. Among the samples after thermal indicating that urea is useful to reduce agglomeration and
treatment, the diffraction peaks can be well indexed to the inhibit particles from growing. Importantly, when the
ꢀ1
orthorhombic olivine type LiMnPO
no other impurity phase is found except that of the sample sꢀ7, in consists of nanosheets with flowerꢀlike texture. As shown in
which the impurity phase Mn (JCPDS card no.24ꢀ0734) is Fig. 6aꢀc, the flowerꢀlike sample is uniformly dispersed with
observed. In addition, the sample sꢀ7 before thermal treatment, the wellꢀdefined microꢀnanostructure. Obviously, the nanosheets
impurity phase MnO (JCPDS card no.12ꢀ0141) is detected. Thus, crosslink together forming an open porous structure with an
the formation of Mn(IV) impurity may be caused by the oxidation of average thickness of several tens of nanometers, which further
4
(JCPDS card no.74ꢀ0375), and concentration of urea is increased to 0.16 mol L , the sample
3 4
O
2
2
+
Mn with oxygen from the solution and air in the dissolving and demonstrates their looseꢀpacked flowery architecture. From the
2+
feeding processes, because Mn is strongly sensitive to the oxygen Fig. 6d, it is clear that the hierarchical structure can be
in a strong alkaline environment due to the increasing amount of maintained after the thermal treatment, which may be due to the
urea. Also, the similar results are found in LiFePO
4
under the fact that the relative low calcination temperature and short
Under the thermal calcination time was employed during the thermal treatment,
was further reduced by the decomposed carbon also the decomposed carbon can hinder agglomeration. Thus,
4
O . Therefore, excess urea would cause the side reaction, those highly hierarchical structure constructed from the
2
5ꢀ27
hydrothermal/solvothermal condition.
treatment, the MnO
to form Mn
2
3
leading to impurity phase. It is worth noting that all the samples are attached sheetꢀlike crystals is beneficial to reduce the transport
well crystallized with the strongest peak (020), indicating an lengths for both electron and ion for the large surface areas
enlarged (010) facet exposed is expected.
readily accessible to electrolyte compared with the bulk
material. Furthermore, the microꢀnanostructure enables easy
operation in terms of electrode fabrication and high tap density,
compared with the nanoparticles. In addition, from the HRTEM
image in Fig. 6e, the sample exhibits a set of lattice fringe with
the d spacing value of 0.43 nm, which is indexed to the (101)
facet of LiMnPO
perfect carbon coating on the surface of LiMnPO
4
. Importantly, the sample has a uniform and
with a
4
thickness of around 2 nm, which is beneficial to the electron
transfer. It also reveals that the flowerꢀlike sample is a single
crystal from the clear lattice fringe, which is further confirmed
by the FFT pattern with regular spots. A more detailed analysis
of FFT pattern reveals that the sample exhibits an exposed
(
010) as shown in Fig. 6f. Combination the XRD,TEM,
HRTEM and FFT pattern, we could further confirm that the b
axis of the sheetꢀlike crystals are parallel to the electron beam
direction [010], indicating that the product of the flowerꢀlike
sample exposes a large (010) facet and the [010] direction is the
thinnest direction of the particle, which is an optimal situation
for LiMPO
4
(M=Mn, Fe) cathode material with favorable
lithium ion migration owing to the known fact that lithium
Fig.
4 the XRD pattern of the samples with various
2
8, 29
ꢀ1
(
4
de)insertion in LiMPO (M=Mn, Fe) is along the bꢀaxis.
concentration of urea under thermal treatment: (a) 0 mol L ; (b)
ꢀ1
ꢀ1
ꢀ1
ꢀ1
0.08 mol L ; (c) 0.12 mol L ; (d) 0.16 mol L ; (e) 0.2 mol L ;
ꢀ1
(f) 0.2 mol L without thermal treatment
4
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ꢀ1
ꢀ1
ꢀ1
Fig. 5 the SEM images of the samples with various concentration of urea: (a) 0 mol L ; (b) 0.08 mol L ; (c) 0.12 mol L ; (d)
ꢀ1
ꢀ1
0.16 mol L ; (e) 0.2 mol L
Fig. 6 the morphology of the flowerꢀlike LiMnPO
LiMnPO
4
4
: (a), (b), (c) the SEM images of LiMnPO ; (d) the TEM images of
4
/C; (e) the HRTEM images from the red region of (d); (f) the FFT of the offꢀgreen region of (e)
The electrochemical performance of the asꢀprepared LiMnPO
.3 electrochemical performance cathode materials with various morphology and particle size
4
3
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was studied for its potential as a cathode material for lithiumꢀ contact between electrolyte and active material, as well as
ion batteries. Fig. 7a shows the typical discharge profiles of additive Super P carbon between nanoparticles during the
LiMnPO
LiMnPO
4
4
/C at 0.1 C, in the voltage range of 2.5~4.5 V. All the fabrication of the composite electrodes. In addition, the mainly
/C exhibits a single discharge plateau around 4.0~4.1 exposed facet is different with the (010). In a word, the
3
+
2+
V, corresponding to the redox couple of Mn /Mn , in well electrochemical performance of LiMnPO
agreement with the typical lithium extractionꢀinsertion reaction affected by the morphology and structure.
4
is significantly
in pure olivine LiMnPO
discharge process, the flowerꢀlike LiMnPO
4
phase. During the initial chargeꢀ
/C demonstrates a
reversible capacity of 150.4 mAh g , while 126.3, 128.0, 130.0,
4
ꢀ1
ꢀ
1
1
10.2 mAh g for sꢀ1, sꢀ2, sꢀ3, sꢀ7, respectively. Obviously, the
flowerꢀlike LiMnPO /C exhibits the longest and the most stable
plateau with a highest discharge potential of about 4.1 V vs
4
+
4
Li /Li, which indicates that the flowerꢀlike LiMnPO /C has the
best reversibility of electrode reaction by reducing electrode
polarization owing to the novel morphology with (010) facet
exposed. In particular, the sample sꢀ7 shows the shortest
plateau with a discharge potential of about 4.0 V, while no
other plateau related to the impurity phase is observed. The rate
performance of the typical samples are presented in Fig. 7b.
The cells are tested at various rate from 0.1 C to 2.0 C. It is
noted that the flowerꢀlike sample shows a superior rate
capacity, in particular at high rate, for example, it exhibits
Fig.
LiMnPO
7
the electrochemical performance of the typical
/C samples: (a) the initial discharge curve at 0.1 C; (b)
4
the rate capacity from 0.1 C to 2.0 C
ꢀ1
125.5, 118.6 mAh g at 1.0 C, 2.0 C, respectively. As for sꢀ7,
the sample shows the worst electrochemical performance,
ꢀ1
showing a capacity of 65.2, 50.9 mAh g at 1.0 C, 2.0 C,
respectively, which is significantly influenced by the
manganese oxide impurity phase. Thus, the amount of urea is a
crucial parameter to control the electrochemical properties of
4
LiMnPO in terms of controllable impurity phase. As shown
Fig. 8 the cycle performance of the flowerꢀlike LiMnPO /C: (a)
4
above, these samples excluding sꢀ7 do not contain any impurity
phases and differ only in their morphology, particle size and
crystal orientation. Therefore, we can imply that the
morphology, particle size and crystal orientation play an
important role in the electrochemical performance. In terms of
the flowerꢀlike sample, it has such advantages listed below: (1)
the asꢀprepared porous nanoparticles with the 3D hierarchical
the cycle curve at 2.0 C for 600th; (b) the chargeꢀdischarge
profile after 1st and 600th
Long cycle performance is one of the significant
electrochemical aspects of lithiumꢀion batteries for high power
applications. The cycle performance of the flowerꢀlike
LiMnPO
4
/C is shown in Fig. 8a. The cells were cycled at 2.0 C
+
structure are beneficial to reduce the Li diffusion pathway, and
in the voltage range of 2.5~4.5 V. As shown in Fig. 8b, the
favorable to the full permeability and infiltration between
electrolyte and active material; also, it can decrease the
agglomeration, which has been a rather severe challenge to
maintain the excellent performance; (2) the flowerꢀlike sample
is composed of sheetꢀlike nanocrystals with mainly (010) facet
exposed, which has large facet in the aꢀc plane and is thin in the
b axis, resulting in an increase in the electrochemical reaction
ꢀ1
4
initial discharge capacities of LiMnPO sample is 109.6 mA g
with a potential plateau of about 4.0 V. As usual, upon
increasing the cycle number, the samples exhibit slight
polarization, which is reflected in the term of potential
difference between the chargeꢀdischarge plateaus, thereby
declining the storage capacity of the electrode. However, the
flowerꢀlike sample displays excellent cycle stability with a
negligible voltage fading after 600 cycles at 2.0 C, showing a
capacity retention up to 92.4%, which indicates that those novel
morphology can obviously improve the cycle behaviour,
especially at high rate.
+
surface area, and enhancement in electrical conductivity and Li
diffusion. (3) The well decorated carbon coating provides easy
electron transfer, which is beneficial to improve the kinetic
process. Thus, it is selfꢀevident that the flowerꢀlike LiMnPO /C
4
behaves superior electrochemical performance. The samples
including sꢀ1, sꢀ2 and sꢀ3 exhibit almost the same
electrochemical performance due to the various morphology
and structure. For example, sꢀ1 has a desired exposed facet
Conclusions
In summary, we successfully synthesized the LiMnPO
4
(010) with a relative thick nanosheets, while sꢀ2 shows a less
nanoparticle with different morphology and particle size via
solvothermal method. The results show that morphology and
particle size was controllable synthesized with various
precursor composite tailoring with the molar ratio of Li:Mn:P.
uniform particle size distribution. As the Li:Mn:P molar ratio
increased further, the sample sꢀ3 exhibits the spherical
nanoparticles with smaller particle size. However, it exhibits
agglomeration to some degree, which is adverse to the effective
6
| J. Name., 2012, 00, 1ꢀ3
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From 2:1:1 to 3:1:1, the particle morphology evolves from 10.
sheetꢀlike to spherical texture while the particle size reduced,
L.ꢀe. Li, J. Liu, L. Chen, H. Xu, J. Yang and Y. Qian, RSC
Adv., 2013, 3, 6847ꢀ6852.
2
+
accompanied with the phase composition from Mn ꢀcontaining
precursor to Li ꢀcontaining precursor. In addition, the urea is
1
1.
J. Liu, X. Liu, T. Huang and A. Yu, J. Power. Sources,
+
2
013, 229, 203ꢀ209.
used to further confirm the conclusions, in which the urea has
no obvious effect on the morphology, but prevent crystals from 12.
growing and reduce the agglomeration. At the concentration of
J. Su, B.ꢀQ. Wei, J.ꢀP. Rong, W.ꢀY. Yin, Z.ꢀX. Ye, X.ꢀQ.
Tian, L. Ren, M.ꢀH. Cao and C.ꢀW. Hu, J. Solid State
Chem., 2011, 184, 2909ꢀ2919.
ꢀ1
0.16 mol L , the sample consists of small sheetꢀlike crystals
with flowerꢀlike texture, delivering excellent reversible
capacity of 150.4, 125.5, 118.6 mAh g at 0.1, 1.0, 2.0 C,
respectively. The composites show long cycle stability at high
1
3.
X.ꢀL. Pan, C.ꢀY. Xu, D. Hong, H.ꢀT. Fang and L. Zhen,
Electrochim. Acta, 2013, 87, 303ꢀ308.
ꢀ1
rate, displaying a capacity retention up to 92.4% with no 14.
apparent voltage fading after 600 cycles at 2.0 C. The attracting
electrochemical performance of the flowerꢀlike LiMnPO /C
4
Z. Dai, L. Wang, F. Ye, C. Huang, J. Wang, X. Huang, J.
Wang, G. Tian, X. He and M. Ouyang, Electrochim. Acta,
2
014, 134, 13ꢀ17.
composites suggests that the unique 3D hierarchical structure
with (010) facet exposed and well carbon decorated is a
promising way for high power Liꢀion batteries electrode
1
5.
K. Dokko, S. Koizumi, H. Nakano and K. Kanamura, J.
Mater. Chem., 2007, 17, 4803ꢀ4810.
materials. Combination of the simple and facile synthesis 16.
method, it may also be applicable for the other olive type
L. Hu, B. Qiu, Y. Xia, Z. Qin, L. Qin, X. Zhou and Z. Liu,
J. Power. Sources, 2014, 248, 246ꢀ252.
4 4
cathode materials such as LiFePO , LiCoPO that require
electrodes with high electronic and ionic conductivity.
1
7.
Z. Dai, L. Wang, X. He, F. Ye, C. Huang, J. Li, J. Gao, J.
Wang, G. Tian and M. Ouyang, Electrochim Acta, 2013,
1
12, 144ꢀ148.
Acknowledgements
1
1
8.
9.
D. Fujimoto, Y. Lei, Z.ꢀH. Huang, F. Kang and J.
Kawamura, Int. J. Electrochem., 2014, 2014, 1ꢀ9.
This work was supported by the Nature Science Foundation of
Hunan province (Grant No.2015JJ3152), Fundamental
Research Funds for the Central Universities (2012QNZT018),
and China Postdoctoral Science Foundation (2012M521546).
D. Wang, H. Buqa, M. Crouzet, G. Deghenghi, T. Drezen,
I. Exnar, N.ꢀH. Kwon, J. H. Miners, L. Poletto and M.
Grätzel, J. Power. Sources, 2009, 189, 624ꢀ628.
2
2
2
2
2
2
2
2
2
2
0.
1.
2.
3.
4.
5.
6.
7.
8.
9.
K. Dokko, S. Koizumi, K. Sharaishi and K. Kanamura, J.
Power. Sources, 2007, 165, 656ꢀ659.
Notes and references
1.
2.
3.
A. K. Padhi, K. S. Nanjundaswamy and J. B. Goodenough,
J. Electrochem. Soc., 1997, 144, 1188ꢀ1194.
K. Dokko, T. Hachida and M. Watanabe, J. Electrochem.
Soc., 2011, 158, A1275ꢀA1281.
M. Yonemura, A. Yamada, Y. Takei, N. Sonoyama and R.
Kanno, J. Electrochem. Soc., 2004, 151, A1352ꢀA1356.
Z. Li, K. Zhu, J. Li and X. Wang, CrystEngComm, 2014,
1
6, 10112ꢀ10122.
C. Delacourt, L. Laffont, R. Bouchet, C. Wurm, J. B.
Leriche, M. Morcrette, J. M. Tarascon and C. Masquelier,
J. Electrochem. Soc., 2005, 152, A913ꢀA921.
B. Ellis, W. H. Kan, W. R. M. Makahnouk and L. F.
Nazar, J. Mater. Chem., 2007, 17, 3248ꢀ3254.
J. Chen, J. Bai, H. Chen and J. Graetz, J. Phys. Chem.
Lett., 2011, 2, 1874ꢀ1878.
4.
5.
D. Arčon, A. Zorko, P. Cevc, R. Dominko, M. Bele, J.
Jamnik, Z. Jagličić and I. Golosovsky, J. Phys. Chem.
Solids, 2004, 65, 1773ꢀ1777.
K. Dokko, K. Shiraishi and K. Kanamura, J. Electrochem.
Soc., 2005, 152, A2199ꢀA2202.
A. Yamada, M. Hosoya, S.ꢀC. Chung, Y. Kudo, K.
Hinokuma, K.ꢀY. Liu and Y. Nishi, J. Power. Sources,
K. Shiraishi, K. Dokko and K. Kanamura, J. Power.
Sources, 2005, 146, 555ꢀ558.
2003, 119-121, 232ꢀ238.
6.
7.
8.
9.
N. H. Kwon and K. M. Fromm, Electrochim. Acta, 2012,
9, 38ꢀ44.
C. M. Burba and R. Frech, J. Electrochem. Soc., 2004,
6
1
51, A1032ꢀA1038.
A. Vadivel Murugan, T. Muraliganth, P. J. Ferreira and A.
Manthiram, Inorg Chem, 2009, 48, 946ꢀ952.
M. S. Islam, D. J. Driscoll, C. A. J. Fisher and P. R. Slater,
Chem. Mat., 2005, 17, 5085ꢀ5092.
Y. Wang, Y. Yang, Y. Yang and H. Shao, Solid State
Commun., 2010, 150, 81ꢀ85.
C. Ouyang, S. Shi, Z. Wang, X. Huang and L. Chen, Phys.
Rev. B, 2004, 69, 104303.
F. Wang, J. Yang, P. Gao, Y. NuLi and J. Wang, J. Power.
Sources, 2011, 196, 10258ꢀ10262.
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Table of content entry
The hierarchical flowerꢀlike LiMnPO
provide a superior Li migration and electron transfer via the solvothermal method with the assisted of urea. The asꢀprepared
4
/C microꢀnanostructures with (010) exposed and uniform carbon coated were prepared to
+
material showed excellent high rate capacity, and behaved long cycle performance.
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