Enhancement of electrochemical performance of LiNi1/3Co1/3Mn1/3O2 by surface modification with MnO2

Article abstract of DOI:10.1016/j.jallcom.2015.06.270

LiNi_1/3Co_1/3Mn_1/3O₂ is successfully coated with MnO₂ by a chemical deposition method. The X-ray diffraction (XRD), scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM) results demonstrate that MnO₂ forms a thin layer on the surface of LiNi_1/3Co_1/3Mn_1/3O₂ without destroying the crystal structure of the core material. Compared with pristine LiNi_1/3Co_1/3Mn_1/3O₂, the MnO₂-coated sample shows enhanced electrochemical performance especially the rate capability. Even at a current density of 750 mA g^-1, the discharge capacity of MnO₂-coated LiNi_1/3Co_1/3Mn_1/3O₂ is 155.15 mAh g^-1, while that of the pristine electrode is only 132.84 mAh g^-1 in the range of 2.5-4.5 V. The cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS) curves show that the MnO₂ coating layer reacts with Li⁺ during cycling, which is responsible for the higher discharge capacity of MnO₂-coated LiNi_1/3Co_1/3Mn_1/3O₂. Electrochemical impedance spectroscopy (EIS) results confirmed that the MnO₂ coating layer plays an important role in reducing the charge transfer resistance on the electrolyte-electrode interfaces.

Full text of DOI:10.1016/j.jallcom.2015.06.270

Accepted Manuscript
Enhancement of electrochemical performance of LiNi Co Mn O by surface
/3 1/3 1/3 2
1
modification with MnO
2
Xin Guo, Li-Na Cong, Qin Zhao, Ling-Hua Tai, Xing-Long Wu, Jing-Ping Zhang,
Rong-Shun Wang, Hai-Ming Xie, Li-Qun Sun
PII:
S0925-8388(15)30389-3
10.1016/j.jallcom.2015.06.270
JALCOM 34678
DOI:
Reference:
To appear in: Journal of Alloys and Compounds
Received Date: 29 April 2015
Revised Date: 26 June 2015
Accepted Date: 30 June 2015
Please cite this article as: X. Guo, L.-N. Cong, Q. Zhao, L.-H. Tai, X.-L. Wu, J.-P. Zhang, R.-S.
Wang, H.-M. Xie, L.-Q. Sun , Enhancement of electrochemical performance of LiNi Co Mn
O
1
/3 1/3 1/3 2
by surface modification with MnO , Journal of Alloys and Compounds (2015), doi: 10.1016/
2
j.jallcom.2015.06.270.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to
our customers we are providing this early version of the manuscript. The manuscript will undergo
copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please
note that during the production process errors may be discovered which could affect the content, and all
legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Enhancement of electrochemical performance of
LiNi Co Mn O by surface modification with MnO
1/3
1/3
1/3
2
2
a,b
a,b
a,b
a,b
a,b
a,b
Xin Guo , Li-Na Cong , Qin Zhao , Ling-Hua Tai , Xing-Long Wu , Jing-Ping Zhang
,
a,b
a,b,
a,b,
Rong-Shun Wang , Hai-Ming Xie *, Li-Qun Sun
*
a
Institute of Functional Materials Chemistry, Faculty of Chemistry, Northeast Normal University,
Changchun, P. R. China
b
National & Local United Engineering Lab for Power Battery, Northeast Normal University;
Changchun, P. R. China
*E-mail: xiehm136@nenu.edu.cn, sunlq446@nenu.edu.cn.
Tel.: +86-431-85099511; fax: +86-431-85099511.
Abstract
LiNi Co Mn O is successfully coated with MnO by a chemical deposition method. The
1/3
1/3
1/3
2
2
X-ray diffraction (XRD), scanning electron microscope (SEM) and high resolution transmission
electron microscope (HRTEM) results demonstrate that MnO forms a thin layer on the surface of
2
LiNi Co Mn O without destroying the crystal structure of the core material. Compared with
1
/3
1/3
1/3
2
pristine LiNi Co Mn O , the MnO -coated sample shows enhanced electrochemical
1
/3
1/3
1/3
2
2
-1
performance especially the rate capability. Even at a current density of 750 mA g , the discharge
-1
capacity of MnO -coated LiNi Co Mn O is 155.15 mAh g , while that of the pristine
2
1/3
1/3
1/3
2
-1
electrode is only 132.84 mAh g in the range of 2.5-4.5 V. The cyclic voltammetry (CV) and
+
X-ray photoelectron spectroscopy (XPS) curves show that the MnO coating layer reacts with Li
2
during cycling, which is responsible for the higher discharge capacity of MnO -coated
2
LiNi Co Mn O . Electrochemical impedance spectroscopy (EIS) results confirmed that the
1
/3
1/3
1/3
2
MnO coating layer plays an important role in reducing the charge transfer resistance on the
2
electrolyte-electrode interfaces.
Keywords: Lithium ion battery; Cathode material; LiNi Co Mn O ; Surface modification
1
/3
1/3
1/3
2

ACCEPTED MANUSCRIPT
1
. Introduction
Nowadays, rechargeable lithium ion batteries are the leading power sources for portable
electronic devices and show great prospect in application of electric vehicles and hybrid electric
vehicles, by virtue of their high energy density and power capability [1-9]. One of the principal
cathode materials for such lithium ion batteries, LiCoO , has been investigated intensely in the
2
past few years. Despite of its stability and high rate capability, LiCoO is plagued by issues such
2
as the toxicity and high cost of cobalt. Recently, a variety of materials have been developed to
substitute all or some of the cobalt with other transition metals [10-13]. One viable LiCoO2
replacement material is layered LiNi Co Mn O due to its high reversible capacity, superior
1
/3
1/3
1/3
2
safety, less toxicity and low cost [14-16]. Unfortunately, there are still two serious shortcomings
hindering its further applications. One is the degradation of the reversible capacity upon prolonged
cycling. Such phenomenon is attributed to the instability of the electrode surface, leading to severe
side reactions between the electrode and electrolyte. The other is the inferior rate capability due to
its intrinsic low lithium ion mobility and electronic conductivity.
Surface coating of cathode materials is an effective way to protect the electrode surface from
directly contact with the electrolyte, and thus suppress the side-reactions which lead to the
deterioration of the cell properties. As coating materials, carbon composites [17-19], metal oxides
[20-24], fluorides [25, 26], and phosphates [27, 28] have been shown to improve the cycling
stability and rate capability. Nevertheless, all the coated materials used above also lead to the
reversible capacity loss because of their inactive characteristics for the lithium insertion/extraction.
+
It is suppose that some electro-active materials, which can provide the conduction path for Li ion
transportation from the electrode to electrolyte, should be more favorable for enhancing the
electrochemical performance of LiNi Co Mn O . Precisely, MnO is a promising
1
/3
1/3
1/3
2
2
electrochemical active oxide which has been used in catalytic [29-31], supercapacitor [32-34] and
-1
especially in lithium ion batteries [35, 36]. It features high theoretical capacity of 1230 mAh g ,
low cost, low toxicity and earth abundance, and there are numerous methods for synthesizing
different types of MnO . In this work, with the aim to highly improve the electrochemical
2
properties of layered LiNi Co Mn O , MnO is introduced as a coating material which can
1
/3
1/3
1/3
2
2
+
provide Li intercalating sites. Meanwhile, the MnO coating layer can stabilize the bulk particles
2

ACCEPTED MANUSCRIPT
as well. The structure, surface character and electrochemical performance of MnO -coated
2
LiNi Co Mn O are systematically investigated. The difference between LiNi Co Mn O
2
1
/3
1/3
1/3
2
1/3
1/3
1/3
and MnO -coated LiNi Co Mn O is also discussed.
2
1/3
1/3
1/3
2
2
. Experimental
2
.1. Synthesis of MnO -coated LiNi Co Mn O
2 1/3 1/3 1/3 2
All reagents used in the experiment were of analytical grade (purchased from Aladdin) without
further purification. The Ni Co Mn CO precursor was prepared via co-precipitation. An
1
/3
1/3
1/3
3
aqueous solution containing NiSO ·6H O, CoSO ·7H O, and MnSO ·H O with a concentration of
4
2
4
2
4
2
-
1
2
.0 mol L was pumped into a continuously stirred tank reactor. At the same time, a Na CO
2 3
-1
solution of 2.0 mol L and a desired amount of NH HCO solution were separately fed into the
4
3
o
reactor. The reaction temperature was kept at 50 C and pH was controlled by Na CO solution to
2
3
8
.5. After vigorous stirring for 12 h, the homogenously precipitated carbonate powders were
o
filtered, washed and dried at 110 C overnight. To prepare LiNi Co Mn O powders,
1
/3
1/3
1/3
2
stoichiometric amounts of the Ni Co Mn CO precursor and 5 wt% excess Li CO (molar ratio
1
/3
1/3
1/3
3
2
3
of Li/(Ni + Co + Mn) = 1.05:1) were mixed thoroughly by ball milling, calcined and sintered at
o
o
5
00 C for 5 h and then 900 C for 12 h in air.
The surface modification of the synthesized layered oxides was carried out by dispersing 2.0 g
LiNi Co Mn O powders in MnSO ·H O (0.117 g) solution under ultrasound conditions for 1
1
/3
1/3
1/3
2
4
2
-1
h, and then the suspension was stirred mechanically while Na CO solution of 1.0 mol L slowly
2
3
dropped into it. After a certain reaction time, the precipitated product was filtered and washed with
o
o
distilled water, dried at 120 C for 10 h and finally heated at 400 C for 4 h in air to form
LiNi Co Mn O sample coated with 3 wt% MnO .
1
/3
1/3
1/3
2
2
2
.2. Structural and morphological characterization
X-ray diffractometry (XRD, Rigaku-Dmax2500) was employed to characterize the crystal
structure of the sample. XRD data were obtained with Cu-Kα radiation (λ = 0.15406 nm) in the 2θ
-1
range of 10-80° at a continuous scan mode with a step size of 0.02° and a scan rate of 3° min .
The morphology of the samples were observed by scanning electron microscope (SEM, quanta250

ACCEPTED MANUSCRIPT
FEG) and high resolution transmission electron microscope (HRTEM, JEOL 2100F). The
electronic states of Ni, Co, Mn and O for the samples were analyzed using X-ray photoelectron
spectroscopy (XPS, PHI 5500 system) with Al-Kα radiation under ultrahigh vacuum.
2
.3. Electrochemical measurements
For fabrication of the positive electrodes, the as-prepared samples were mixed with acetylene
black and polyvinylidene fluoride (80:10:10) in N-methyl-2-pyrrolidone to obtain a slurry, which
o
was coated onto aluminum foil and dried at 120 C for 12 hours in a vacuum oven. The
electrochemical characterizations were performed using R2025 coin-type cells with Li metal as
the negative electrode. The electrolyte solution was a 1M LiPF in ethylene carbonate/dimethyl
6
carbonate (EC/DMC = 1:1, volume ratio). All the cells were assembled in an argon-filled glove
box with water and oxygen contents below 0.5 ppm. The cells were galvanostatically charged and
-1
discharged at various current densities (1 C = 150mA g ) on a Neware battery tester in the voltage
ranges of 2.5-4.3 V and 2.5-4.6 V at room temperature. The cyclic voltammetry (CV) and
electrochemical impedance spectroscopy (EIS) of the cells were determined with CHI660A
-
1
electrochemical workstation. The sweep rate of CV was 0.1 mV s in the potential window of
.0-5.0 V. The amplitude of the AC signal was 10 mV over the frequency range of 100 kHz to 0.1
Hz.
2
3
. Results and discussion
A variety of manganese oxides can be obtained when MnCO is heat-treated at different
3
temperature. It can be confirmed from the XRD patterns (Fig. 1a) that MnCO is converted to
3
o
MnO at 400 C. The reaction can be written:
2
2
MnCO + O ꢀ 2MnO + 2CO
(1)
3
2
2
2
Thus, the MnO -coated LiNi Co Mn O is obtained by heat treatment at the same temperature.
2
1/3
1/3
1/3
2
Fig. 1b shows the XRD patterns of LiNi Co Mn O and MnO -coated LiNi Co Mn O .
1
/3
1/3
1/3
2
2
1/3
1/3
1/3
2
The synthesized materials exhibit a well-defined layered structure based on a hexagonal α-NaFeO2
ꢀ
with space group R3m without any impurity phases. The crystal lattice constants are summarized
in Table 1. The results of the coated material show no significant change in the ɑ and c lattice

ACCEPTED MANUSCRIPT
parameters and the 2θ values of the peaks. Furthermore, the lattice parameters (ɑ, c) of the two
samples show consistency with that of the theoretical and experimental parameter of
LiNi Co Mn O reported [9]. That is, a well layered structure is maintained completely after
1
/3
1/3
1/3
2
MnO coating, which ensures the lithium ions migration smoothly.
2
The morphologies of the LiNi Co Mn O before and after MnO coating are presented in
1/3
1/3
1/3
2
2
Fig. 2. It is clearly seen from the SEM and TEM images that the surface morphology of the
pristine LiNi Co Mn O is smooth and clean without any heterophase particles (Fig. 2a, 2c).
1
/3
1/3
1/3
2
By comparison, the surface of the coated sample is rough and covered with nanoparticles, which
appeared to be the MnO coating layer (Fig. 2b, 2d). In order to observe the detailed existence of
2
MnO on the surface, HRTEM analysis is also performed. As shown in Fig. 2f, a distinguishable
2
and compact layer can be obviously observed on the surface of the coated sample. The interplanar
distances of the parallel lattice is 4.7 Å, which corresponds to the distance of the closely packed
ꢀ
003) plane of the R3m-layered structure. Thus, a MnO film is successful growth on the surface
(
2
of LiNi Co Mn O particles. The coating layer could reduce the contact area between the
1/3
1/3
1/3
2
electrode and electrolyte, and then it could protect the cathode material from dissolving into the
electrolyte.
To explore the composition of the coating layer, XPS measurement is employed, and the
partial XPS spectrum of Ni2p, Co2p, Mn2p and O1s are presented in Fig. 3. All of the binding
energies in the XPS analysis are corrected for specimen charging by referencing them to the C 1s
peak (set at 284.6 eV). No other element peak is detected, indicating that the pristine
LiNi Co Mn O and MnO -coated LiNi Co Mn O are high purity. Both pristine and
1
/3
1/3
1/3
2
2
1/3
1/3
1/3
2
coated samples have Ni2p , Co2p and Mn2p3/2 peaks without remarkable chemical shift of
3
/2
3/2
binding energy, indicating that the Ni, Co and Mn ion environment in the structure are not
changed. In contrast, the shape of O1s spectra has little changed. The chemical shift of the binding
energy of O1s implies that the surface of the LiNi Co Mn O is altered by MnO coating. As
1
/3
1/3
1/3
2
2
shown in Fig. 3d, two peaks are observed in the pristine sample. The dominating one is located at
30.17 eV, which can be assigned lattice oxygen in the layered LiNi Co Mn O . Another small
5
1
/3
1/3
1/3
2
and broad peak located at the higher binding energy of 532.05 eV is likely due to the active
oxygen species on the surface or the impurity of adsorbed species, such as Li CO . However, the
2
3

ACCEPTED MANUSCRIPT
peak at high binding energy disappears after the coating treatment, suggesting the adsorbed
species Li CO is consumed by MnO layer during the process of heat-treatment. And then, the
2
3
2
nonstoichiometric Li MnO oxides are formed on the surface of LiNi Co Mn O . Accordingly,
x
2
1/3
1/3
1/3
2
the coating layer is likely to be partly Li MnO instead of the nominal MnO , which can be further
x
2
2
confirmed by the testing of the initial charge/discharge performance.
Fig. 4a illustrates the initial voltage versus capacity curves of the pristine and MnO -coated
2
-1
LiNi Co Mn O at the constant current density of 15 mA g in the range of 2.5-4.3 V. It is
1
/3
1/3
1/3
2
worthwhile to note that a small plateau appears at 3.0 V in the charge curve of MnO -coated
2
LiNi Co Mn O sample, which is due to the electrochemical delithiated process of
1
/3
1/3
1/3
2
nonstoichiometric Li MnO oxides. Correspondingly, a small plateau belonging to the inserted
x
2
+
progress of Li to the MnO layer at 2.8 V is also observed in the discharge curve, which will
2
deliver more discharge capacities. It can be seen that the pristine LiNi Co Mn O electrode
1
/3
1/3
1/3
2
-1
delivers a discharge capacity of 161.99 mAh g , whereas the coated electrode exhibits a discharge
-1
capacity of 166.65 mAh g . Significantly, as shown in Fig. 4b, the coated electrode delivers a
-1
-1
discharge capacity of 153.66 mAh g even at a high rate of 300 mA g , whereas only 141.07 mAh
-1
g specific capacities can be obtained for the pristine LiNi Co Mn O electrode at the same
1
/3
1/3
1/3
2
rate. Moreover, the MnO -coated electrode can still have a very stable capacity delivery with a
2
-1
capacity retention of 88.23 % over 100 cycles at 300 mA g (vs. to the initial discharge capacity),
while only 71.62 % capacity retention for the pristine LiNi Co Mn O electrode can be
1
/3
1/3
1/3
2
obtained. Discharge capacity and capacity retention of a cathode are controlled by surface property.
So the enhanced electrochemical properties of the MnO -coated LiNi Co Mn O should be
2
1/3
1/3
1/3
2
attributed to the stabilization of cathode surface by MnO coating. It can also be confirmed in Fig.
2
4
c and 4d that the coated electrode shows much better voltage platforms at the following cycles.
To further evaluate the superiority of the MnO -coated LiNi Co Mn O material, the cells
2
1/3
1/3
1/3
2
are tested in a high voltage range of 2.5-4.5 V. Fig. 5a displays the initial charge/discharge profiles
-1
of the as-prepared materials at 15 mA g . As expected, the initial discharge capacity of the
-1
MnO -coated electrode is up to 195.86 mAh g , while the pristine electrode presents a lower
2
-1
discharge capacity of 189.86 mAh g . Fig. 5b shows the rate capability of the pristine and
MnO -coated LiNi Co Mn O electrodes between 2.5 V and 4.5 V. At the same current density,
2
1/3
1/3
1/3
2

ACCEPTED MANUSCRIPT
the MnO -coated electrode shows a higher discharge capacity than that of the pristine. The
2
discharge capacity gap between the pristine and coated materials is more remarkable with the rate
increasing. For example, the reversible capacity of the MnO -coated LiNi Co Mn O electrode
2
1/3
1/3
1/3
2
-1
-1
has been measured as high as 155.15 mAh g at 750 mA g , while that of the pristine electrode
-1
merely is 132.84 mAh g . Moreover, the coated sample shows excellent capacity retention at each
rate step. The stable film layer facilitates the electron transfer at the surface of electrode, which
leads to an enhanced rate capability of the MnO -coated LiNi Co Mn O .
2
1/3
1/3
1/3
2
Cyclic voltammetry (CV) is a useful technique to study the electrochemical performance and
electrode kinetics of oxide materials. Fig. 6 shows the CV curves of the cells with the pristine
LiNi Co Mn O and MnO -coated LiNi Co Mn O samples as the working electrodes.
1
/3
1/3
1/3
2
2
1/3
1/3
1/3
2
-1
The cells are tested at a scan rate of 0.1 mV s in the range of 2.0-5.0 V. As for the pristine
LiNi Co Mn O electrode, the main peak at 3.9 V and another low-intensity peak at 4.6 V are
1
/3
1/3
1/3
2
2
+
4+
3+
4+
corresponding to the redox couples of Ni /Ni and Co /Co , respectively. In the case of
4
+
3+
MnO -coated electrode, the peaks belonging to the redox reaction of Mn to Mn at around 3.0 V
2
are observed. The CV of the MnO -coated LiNi Co Mn O at low anodic and cathodic peaks
2
1/3
1/3
1/3
2
around 3.0 V can be attributed to the oxidation and reduction of MnO during electrochemical
2
reaction. This result is well consistent with the charge/discharge profiles. Overall, the MnO layer
2
+
reacts with Li and converts to nonstoichiometric Li MnO oxides, which should be the reason for
x
2
the higher discharge capacity of the MnO -coated LiNi Co Mn O electrode. Besides, the CV
2
1/3
1/3
1/3
2
curves of MnO -coated electrode overlap much better, also suggesting the superior
2
electrochemical cycle stability.
To understand the electron transfer process of the pristine LiNi Co Mn O and
1
/3
1/3
1/3
2
MnO -coated LiNi Co Mn O electrodes, electrochemical impedance spectroscopy (EIS) has
2
1/3
1/3
1/3
2
been performed. Fig. 7 shows the impedance spectrum measured using the coin cells after the
00th charge-discharge cycles. Both Nyquist plots have the high frequency semicircles and low
1
frequency tails. Generally, an intercept at the Zreal-axis in high frequency region corresponded to
ohmic resistance (R ) of the battery, which contains the resistance of electrolyte, separator,
e
electrode, etc. The semicircle in the high frequency is related to charge transfer resistance (Rct)
and the double layer capacitance (CPE). The low frequency tail represents the Warburg impedance

ACCEPTED MANUSCRIPT
+
(
Z ), which is associated with Li ion diffusion process in the solid phase of electrode. All the
w
sections correspond to the partitions in the equivalent circuit, which is used to fit the EIS data to
give a quantitative result to further understand the effect of MnO coating. It directly demonstrates
2
that the MnO -coatedelectrode has much lower charge resistance (R = 235 ꢀ) than the pristine
2
ct
LiNi Co Mn O (R = 592 ꢀ). This result clearly indicates that the improvement of the
1
/3
1/3
1/3
2
ct
electrochemical performance is due to the presence of MnO coating layer, which effectively
2
suppresses the chemical instability ascribed to surface reaction between electrode and electrolyte.
4
. Conclusions
In summary, the MnO -coated LiNi Co Mn O cathode material is successfully
2
1/3
1/3
1/3
2
synthesized via a simple chemical deposition method. Compared with the pristine
LiNi Co Mn O , the coated electrode shows higher discharge capacity, longer cycle life and
1
/3
1/3
1/3
2
better rate capability. These improvements are mainly attributed to the electrochemical activity
MnO coating layer, which could not only provide more lithium ions insertion/extraction sites, but
2
also act as a protective layer to avoid the directly contact between the cathode materials and the
electrolyte and further minimize the side reactions.
Acknowledgements
This work was supported by National High Technology Research and Development Program
of China (2012AA110103).
Reference
[
[
[
[
[
1] J.B. Goodenough, Y. Kim, Chem Mater, 22 (2010) 587-603.
2] J. Jiang, Y. Li, J. Liu, X. Huang, C. Yuan, X.W. Lou, Adv Mater, 24 (2012) 5166-5180.
3] J.B. Goodenough, K.S. Park, J Am Chem Soc, 135 (2013) 1167-1176.
4] S.M. Rezvanizaniani, Z. Liu, Y. Chen, J. Lee, J Power Sources, 256 (2014) 110-124.
5] W. Hu, X.B. Zhang, Y.L. Cheng, C.Y. Wu, F. Cao, L.M. Wang, ChemSusChem, 4 (2011)

ACCEPTED MANUSCRIPT
1
091-1094.
6] W. Hu, X.B. Zhang, Y.L. Cheng, Y.M. Wu, L.M. Wang, Chem Commun (Camb), 47 (2011)
250-5252.
7] D.L. Ma, Z.Y. Cao, H.G. Wang, X.L. Huang, L.M. Wang, X.B. Zhang, Energy &
Environmental Science, 5 (2012) 8538.
[
5
[
[
[
[
[
[
8] H.G. Wang, D.L. Ma, Y. Huang, X.B. Zhang, Chemistry, 18 (2012) 8987-8993.
9] Z.L. Wang, D. Xu, L.M. Wang, X.B. Zhang, ChemPlusChem, 77 (2012) 124-128.
10] Y. Zhang, C.Y. Wang, J Electrochem Soc, 156 (2009) A527.
11] Y. Lee, M.G. Kim, J. Cho, Nano Lett, 8 (2008) 957-961.
12] J. Xiao, X. Chen, P.V. Sushko, M.L. Sushko, L. Kovarik, J. Feng, Z. Deng, J. Zheng, G.L.
Graff, Z. Nie, D. Choi, J. Liu, J.G. Zhang, M.S. Whittingham, Adv Mater, 24 (2012) 2109-2116.
[
[
[
13] Y. Sun, C. Ouyang, Z. Wang, X. Huang, L. Chen, J Electrochem Soc, 151 (2004) A504.
14] T. Ohzuku, Y. Makimura, Chem Lett, 30 (2001) 642-643.
15] H. Sclar, D. Kovacheva, E. Zhecheva, R. Stoyanova, R. Lavi, G. Kimmel, J. Grinblat, O.
Girshevitz, F. Amalraj, O. Haik, E. Zinigrad, B. Markovsky, D. Aurbach, J Electrochem Soc, 156
(
[
[
[
[
[
2009) A938.
16] W. Xiong, Y. Jiang, Z. Yang, D. Li, Y. Huang, J Alloy Compd, 589 (2014) 615-621.
17] S. Niketic, M. Couillard, D. MacNeil, Y. Abu-Lebdeh, J Power Sources, 271 (2014) 285-290.
18] X. Zhi, G. Liang, L. Wang, X. Ou, L. Gao, X. Jie, J Alloy Compd, 503 (2010) 370-374.
19] J.R. He, Y.F. Chen, P.J. Li, Z.G. Wang, F. Qi, J.B. Liu, RSC Adv., 4 (2014) 2568-2572.
20] S.T. Myung, K. Izumi, S. Komaba, H. Yashiro, H.J. Bang, Y.K. Sun, N. Kumagai, J Phys
Chem C, 111 (2007) 4061-4067.
[21] J. Gao, J. Kim, A. Manthiram, Electrochem Commun, 11 (2009) 84-86.
[22] G.Q. Liu, H.T. Kuo, R.S. Liu, C.H. Shen, D.S. Shy, X.K. Xing, J.M. Chen, J Alloy Compd,
4
96 (2010) 512-516.
[23] Y.D. Chen, Y. Zhao, Q.Y. Lai, N.N. Wei, J.Z. Lu, X.G. Hu, X.Y. Ji, Ionics, 14 (2007) 53-58.
[24] F. Wu, M. Wang, Y. Su, L. Bao, S. Chen, Electrochim Acta, 54 (2009) 6803-6807.
[25] Y.K. Sun, M.J. Lee, C.S. Yoon, J. Hassoun, K. Amine, B. Scrosati, Adv Mater, 24 (2012)
1192-1196.
[26] J. Li, L. Wang, Q. Zhang, X. He, J Power Sources, 190 (2009) 149-153.

ACCEPTED MANUSCRIPT
[
[
[
(
[
[
[
[
27] Y. Wu, A. Vadivel Murugan, A. Manthiram, J Electrochem Soc, 155 (2008) A635.
28] G.R. Hu, X.R. Deng, Z.D. Peng, K. Du, Electrochim Acta, 53 (2008) 2567-2573.
29] Z. Yang, Y. Zhang, W. Zhang, X. Wang, Y. Qian, X. Wen, S. Yang, J Solid State Chem, 179
2006) 679-684.
30] F. Cheng, Y. Su, J. Liang, Z. Tao, J. Chen, Chem Mater, 22 (2010) 898-905.
31] N. Sui, Y. Duan, X. Jiao, D. Chen, J Phys Chem C, 113 (2009) 8560-8565.
32] X. Li, G. Wang, X. Wang, X. Li, J. Ji, J Mater Chem A, 1 (2013) 10103.
33] A. Bahloul, B. Nessark, E. Briot, H. Groult, A. Mauger, K. Zaghib, C.M. Julien, J Power
Sources, 240 (2013) 267-272.
[
[
[
34] R.K. Sharma, L. Zhai, Electrochim Acta, 54 (2009) 7148-7155.
35] H. Xia, M. Lai, L. Lu, J Mater Chem, 20 (2010) 6896.
36] F. Tu, T. Wu, S. Liu, G. Jin, C. Pan, Electrochim Acta, 106 (2013) 406-410.
Figure Captions
Fig.1. XRD patterns of (a) the thermal decomposition products of MnCO at different
3
temperatures and (b) LiNi Co Mn O and MnO -coated LiNi Co Mn O powders.
1/3
1/3
1/3
2
2
1/3
1/3
1/3
2
Fig.2. SEM, TEM and HRTEM morphologies of (a, c, e) LiNi Co Mn O and (b, d, f)
1
/3
1/3
1/3
2
MnO -coated LiNi Co Mn O powders.
2
1/3
1/3
1/3
2
Fig.3. XPS spectra of the pristine LiNi Co Mn O and MnO -coated LiNi Co Mn O (a)
1
/3
1/3
1/3
2
2
1/3
1/3
1/3
2
Ni 2p; (b) Co 2p; (c) Mn 2p and (d) O 1s.
Fig.4. (a) The initial charge-discharge curves of LiNi Co Mn O and MnO -coated
1
/3
1/3
1/3
2
2
-1
LiNi Co Mn O electrodes at 15 mA g from 2.5 to 4.3 V; (b) cycle performance upon 100
1
/3
1/3
1/3
2
-1
cycles at a rate of 300 mA g ; (c) and (d) corresponding discharge curves at different cycles of the
pristine LiNi Co Mn O and MnO -coated LiNi Co Mn O .
1
/3
1/3
1/3
2
2
1/3
1/3
1/3
2
Fig.5. (a) The initial charge-discharge curves of LiNi Co Mn O and MnO -coated
1
/3
1/3
1/3
2
2
-1
LiNi Co Mn O electrodes at 15 mA g from 2.5 to 4.5 V; (b) rate properties at the current
1
/3
1/3
1/3
2
-1
density of 15, 30, 75, 150, 300 and 750 mA g , respectively; (c) and (d) corresponding the first
discharge profiles at various current densities of the pristine LiNi Co Mn O and
1
/3
1/3
1/3
2

ACCEPTED MANUSCRIPT
MnO -coated LiNi Co Mn O .
2
1/3
1/3
1/3
2
Fig.6. Cyclic voltammograms of (a) LiNi Co Mn O and (b) MnO -coated
1
/3
1/3
1/3
2
2
LiNi Co Mn O electrodes between 2.0 and 5.0 V.
1
/3
1/3
1/3
2
Fig.7. Nyquist plots of LiNi Co Mn O and MnO -coated LiNi Co Mn O electrodes at
1
/3
1/3
1/3
2
2
1/3
1/3
1/3
2
1
00th cycle. Inset shows the equivalent circuit.

ACCEPTED MANUSCRIPT
Table 1:
Crystal cell parameters of the pristine and MnO -coated LiNi Co Mn O .
2
1/3
1/3
1/3
2
3
Sample
ɑ-Axis(Å)
c-Axis(Å)
c/ɑ
Unit volume(Å )
Pristine
2.871
2.865
14.250
14.246
4.96
4.97
101.76
101.24
3
% MnO2

ACCEPTED MANUSCRIPT
Fig.1

ACCEPTED MANUSCRIPT
Fig.2

ACCEPTED MANUSCRIPT
Fig.3

ACCEPTED MANUSCRIPT
Fig.4

ACCEPTED MANUSCRIPT
Fig.5

ACCEPTED MANUSCRIPT
Fig.6

ACCEPTED MANUSCRIPT
Fig.7

ACCEPTED MANUSCRIPT
Highlights
ꢀ
ꢀ
ꢀ
MnO coated LiNi Co Mn O cathode material is synthesized for the first time.
2 1/3 1/3 1/3 2
MnO offers available sites for insertion of extracted lithium.
2
The preserved surface and crystal structures results in the improved kinetics.