Solid State Phenomena
ISSN: 1662-9779, Vol. 301, pp 195-201
© 2020 Trans Tech Publications Ltd, Switzerland
Submitted: 2019-08-21
Revised: 2019-11-13
Accepted: 2019-11-13
Online: 2020-03-10
Electrochemical Performance of Mn and Fe Substitution in LiCo0.9X0.1O2
Cathode Materials
Nor Syamilah Syamimi Mohd Abdillih1,2,a*, Norlida Kamarulzaman1,3,
Kelimah Elong1,2,b*, Nurhanna Badar1 and Mohd Sufri Mastuli1,2
1Centre
of Nanomaterials Research, Institute of Science, Universiti Teknoloogi MARA, 40450 Shah
Alam Malaysıa
2School
3School
of Chemistry and Environment, Faculty of Applied Sciences, Universiti Teknologi MARA,
40450 Shah Alam Malaysıa
of Physics and Materials, Faculty of Applied Sciences, Universiti Teknologi MARA, 40450
Shah Alam Malaysıa
asyamilahsyamimi23@yahoo.com.my, bkelimah0907@salam.uitm.edu.my
Keywords: Cathode, LiCoO2, Self-propagating combustion, electrochemical performance
Abstract. LiCo0.9X0.1O2 (where X=Mn and Fe) were synthesized using self-propagating combustion
(SPC) method using citric acid as a combustion agent. The precursors of LiCo0.9X0.1O2 were
annealed at a temperature of 800 ˚C at 24 h. The phase and crystalinity of the materials were
characterized using X-Ray Diffraction (XRD). All the materials were observed to be single and
pure phase with no impurity peaks detected. The morphology and particle sizes of the materials
were also analyzed using Field Emission Scanning Electron Microcopy (FESEM). Finally, the
electrochemical performance of the materials was studied using charge-discharge cycling in the
voltage range of 2.5 to 4.3 V. Based on the results from charge-discharge studies, Mn substituted
cathode materials exhibit better specific discharge capacity compared with Fe substituted cathode
materials.
Introduction
LiCoO2 introduced by Goodenough and Mizushima et al. in 1976 is the first and the most
commercially successful form of layered transition metal oxide cathodes which originally
commercialized by SONY [1, 2]. This material possesses several desirable characteristics such as
high discharge potential, low molecular weight, high energy capacity, great charge-discharge
performance, easy to synthesis, stable and high discharge voltage [2, 3, 4]. The theoretical capacity
of LiCoO2 is 274 mA h/g, unfortunately the practical reversible specific capacity of LiCoO2 is
limited to only 160 mA h/g or less when cycled between 3.0 and 4.3 V (vs. Li/Li+) in order to
maintain a reasonable cycling stability [5, 6, 7].
However, LiCoO2 does have some limitations such as low thermal stability and fast capacity
fading at high current rates or during deep cycling. Besides, LiCoO2 also expensive and toxic due to
the high amount of cobalt content [7, 8, 9]. Many approaches have been done to overcome the
limitations thus improving the performance of LiCoO2 cathode material. Theoretical studies state
that doping of LiCoO2 with transition metal ions resulting the increasing in capacity and doping
with non transition metal can increase the voltage [10, 11].
In this paper, we report the synthesis and electrochemical performance of LiCo0.9X0.1O2 (X=
Mn and Fe) prepared by self-propagating combustion (SPC) method using citric acid as a reduction
agent. The doped LiCoO2 materials are further characterized by X-Ray Diffraction (XRD) and Field
Emission Scanning Electron Microscopy (FESEM). In addition, the electrochemical performance of
LiCo0.9X0.1O2 (X=Mn and Fe) cathode materials are studied.
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans
Tech Publications Ltd, www.scientific.net. (#535340277-18/02/20,11:28:08)
196
Semiconductor Materials and Technology
Methodology
The LiCoO2, LiCo0.9Mn0.1O2 and LiCo0.9Fe0.1O2 LiCo0.9X0.1O2 materials were prepared by
self-propagating combustion (SPC) method [12]. The starting materials used were lithium nitrate,
LiNO3, cobalt (II) nitrate hexahydrate, Co(NO3)2.6H2O, manganese (II) nitrate hexahydrate,
Mn(NO3)2.xH2O and iron (III) nitrate nanohydrate, Fe(NO3)3.9H2O The stoichiometric amounts of
starting materials were dissolved in deionized water and then mixed with citric acid C6H8O7 as a
fuel.The mixture was heated slowly at 350 ˚C. The precursors obtained were in black powder and
then annealed at 800 ˚C for 24 h in a furnace.
The phase purity and crystallographic structure of the materials were obtained by using X-Ray
Diffraction (XRD) with Cu Kα radiation. The XRD instrument used was PANalytical Xpert Pro
powder diffraction with potential and current measured at 45 kV and 40 mA. The morphology and
particle size of materials were determined by FESEM instrument, ZEISS SUPRA 40VP Field
Emission Scanning Electron Microscope.
The fabrication of cathode was prepared using 80 wt% of active material, 10 wt% of Super P
as conducting agent and 10 wt% of granular polytetrafluoroethylene (PTFE) as a binder. All the
compositions were mixed in an agate mortar and pressed onto metal grids. Thus prepared cathode
was dried in oven at 200 ˚C for 24 h before assembling in a glove box (Unilab Mbraun) filled with
argon gas. The lithium metal was used as anode and the Celguard 2400 microporous polyethylene
film as a separator was soaked in the electrolyte. The electrolyte used was 1.0 M LiPF4 in 1:1
volume ratio of ethylene carbonate (EC) and dimethylcarbonate (DMC). Charge-discharge cycling
performance was characterized using WonATech (WBCS 3000) by applying 1.0 mA current within
a voltage range of 4.3 to 2.5 V.
Results and Discussion
Fig. 1 shows the XRD patterns for LiCo0.9X0.1O2 (X=Mn and Fe) cathode materials annealed
at 800 ˚C for 24 h. It can be observed that the single and pure phase of LiCo0.9X0.1O2 (X=Mn and
Fe) were obtained with no impurity peaks detected which indicated that the transition metal ions are
successfully substituted in the LiCoO2 structure. The materials obtained have a layered hexagonal
α-NaFeO2 structure with R3m space group. The XRD patterns can be indexed according to ICDD
00-050-0653 pattern as all the fingerprint peak viz. (003), (101), (006), (012), (104), (015), (017),
(018), (110), (113), (116), (024) where all the peaks can be easily identifiable.
Solid State Phenomena Vol. 301
197
Figure 1. XRD patterns of (a) LiCoO2 (b) LiCo0.9Mn0.1O2 and (c) LiCo0.9Fe0.1O2 and enlargement of
XRD patterns at 30˚ and 50˚ for (d) LiCoO2 (e) LiCo0.9Mn0.1O2 and (f) LiCo0.9Fe0.1O2
The morphology of LiCoO2, LiCo0.9Mn0.1O2 and LiCo0.9Fe0.1O2 cathode materials annealed
at 800 ˚C for 24 h are displayed in Fig. 2. Based on the FESEM results, it can be observed that both
LiCo0.9Mn0.1O2 and LiCo0.9Fe0.1O2 materials have a roughly polyhedral-type crystal. The range of
particle size of the sample is summarized in Table 1. The LiCo0.9Mn0.1O2 material appeared to has
particle size in range of 140-220 nm and the particle size of LiCo0.9Fe0.1O2 is 280-550 nm. The
introduction of Mn decrease the particle size in LiCoO2 lattice but the other way around with Fe
substitution in LiCoO2 lattice which increase the particle size of the materials. The changes of
particle size in LiCoO2 lattice will affected the performance of the cells which will be further
explain using charge-discharge cycling profile.
Energy Disperssive X-Ray Spectroscopy of the substituted materials was carried out to verify
the amount of transition metal content in the materials. Table 2 summerized the comparison
between calculated synthesis value of LiCo0.9Mn0.1O2 and LiCo0.9Fe0.1O2 materials and EDX results.
198
Semiconductor Materials and Technology
Figure 2. FESEM images for (a) LiCoO2 (b) LiCo0.9Mn0.1O2 and (c) LiCo0.9Fe0.1O2 annealed at
800 ˚C for 24 h
Table 1. The particle size of LiCoO2, LiCo0.9Mn0.1O2 and LiCo0.9Fe0.1O2 materials
Material
Range of particle size
(nm)
Average particle size
(nm)
LiCoO2
LiCo0.9Mn0.1O2 LiCo0.9Fe0.1O2
180-350
140-220
280-550
244
180
432
Table 2. Comparison between calculated synthesis value of LiCo0.9Mn0.1O2 and LiCo0.9Fe0.1O2
materials and EDX results
Material
(chemical formula)
Atomic %
Synthesis
EDX
Chemical formula from
EDX
Co
TM
Co
TM
LiCo0.9Mn0.1O2
90
10
90.75
9.25
LiCo0.9075Mn0.0925O2
LiCo0.9Fe0.1O2
90
10
89.93
10.07
LiCo0.8993Fe0.1007O2
The first discharge cycle of LiCoO2, LiCo0.9Mn0.1O2 and LiCo0.9Fe0.1O2 are shown in Fig. 3
with a discharge current of 1.0 mA and the specific capacity of cells up to 40 cycles are shown in
Fig. 4. The initial discharge capacity of LiCoO2, LiCo0.9Mn0.1O2 and LiCo0.9Fe0.1O2 are
128.16 mAh/ g, 136.60 mAh/ g and 57.35 mAh/ g, respectively.
Solid State Phenomena Vol. 301
199
4.5
(a)
Voltage (V)
4.0
(b)
(c )
3.5
3.0
2.5
2.0
0
20
40
60
80
100
120
Specific Discharge Capacity (mAh/ g)
140
Figure 3. Initial specific discharge capacity of (a) LiCoO2 (b) LiCo0.9Mn0.1O2 and
(c) LiCo0.9Fe0.1O2 cathode materials
Specific Discharge Capacity
(mAh/ g)
160
(a)
(b)
(c)
140
120
100
80
60
40
20
0
0
10
20
Number of Cycle
30
40
Figure 4. Cycling data of (a) LiCoO2 (b) LiCo0.9Mn0.1O2 and (c) LiCo0.9Fe0.1O2 cathode materials
Table 3. Electrochemical performance of LiCoO2, LiCo0.9Mn0.1O2 and LiCo0.9Fe0.1O2 materials
annealed at 800 ˚C for 24 h
Material
800 ˚C, 24 h
1st specific discharge
capacity (mAh/ g)
40th specific discharge
capacity (mAh/ g)
Capacity loss after
40th cycle (%)
LiCoO2
LiCo0.9Mn0.1O2
LiCo0.9Fe0.1O2
128.16
136.60
57.35
49.52
37.92
14.39
61.36
72.24
74.91
200
Semiconductor Materials and Technology
The electrochemical performance of all the materials are summerized in Table 3. The initial
discharge capacity of Mn substituted sample is about 6-7 % more than LiCoO2 sample and the
initial discharge capacity of Fe substituted sample is 55-56 % less than LiCoO2 sample. However,
the capacity fading of LiCo0.9Mn0.1O2 is higher compared with capacity fading of LiCoO2 after
40 cycles. Both LiCo0.9Mn0.1O2 and LiCo0.9Fe0.1O2 gives a higher degree of capacity loss which are
72.24 % and 74.91 % respectively. It can be observed that Mn substituted sample gives much better
performance than Fe substituted sample although the capacity fading is not really favourable. The
better performance of LiCo0.9Mn0.1O2 can be explained as smaller particle size deliver good
electrochemical performance as surface area over volume ratio is increasing thus reducing the
structural degradation during charge discharge process [13].
Conclusion
LiCo0.9X0.1O2 (where X=Mn and Fe) materials prepared by self-popagating combustion (SPC)
method have been successfully synthesized. The substitution of Mn in LiCoO2 increase the initial
discharge capacity which 136.60 mAh/ g , meanwhile the substitution of Fe in LiCoO2 gives lower
intial discharge capacity, 57.35 mAh/ g. Although the substitution of Mn does gives higher intial
discharge capacity but the fading capacity is higher than LiCoO2. The electrochemical performance
of the material can be improve by using different stoichiometry of doped metal.
Acknowledgement
The authors would like to thank Institute of Research Management & Innovation (IRMI) for
the grant 600-IRMI/FRGS 5/3 (044/2017), 600-IRMI/DANA 5/3 BESTARI (0026/2016) and
Institute of Science, Universiti Teknologi Mara Shah Alam, Malaysia for financially funding this
project.
References
[1]
A. Ullah, A. Majid, N. Rani, A review on first principles based studies for improvement of
cathode material of lithium ion batteries, J. Energy Chem. 27 (2018) 219–237.
[2]
N. Nitta, F. Wu, J. T. Lee, G. Yushin, Li-ion battery materials:present and future, Mater.
Today. 18 (2015) 252–264.
[3]
N. Bensalah, H. Dawood, Review on Synthesis, Characterizations, and Electrochemical
Properties of Cathode Materials for Lithium Ion Batteries, Journal of Material Science &
Engineering. 5 (2016).
[4]
B. Xu, D. Qian, Z. Wang, Y. S. Meng, Recent progress in cathode materials research for
advanced lithium ion batteries, Mater. Sci. Eng. R Reports. 73 (2012) 51–65.
[5]
Z. Wang, Z. Wang, H. Guo, W. Peng, X. Li, Improving the cycling stability of LiCoO2 at 4.5
V through co-modification by Mg doping and zirconium oxyfluoride coating, Ceram. Int. 41
(2015) 469–474.
[6]
M. Zhang, M. Tan, H. Zhao, S. Liu, X. Shu, Y. Hu, Applied Surface Science Enhanced highvoltage cycling stability and rate capability of magnesium and titanium co-doped lithium
cobalt oxides for lithium-ion batteries, Appl. Surf. Sci. 458 (2018) 111–118.
[7]
M. Eilers-rethwisch, M. Winter, F. Mark Schappcher, Synthesis, electrochemical
investigation and structural analysis of doped Li, J. Power Sources. 387 (2018) 101–107.
[8]
X. Dai, L. Wang, J. Xu, Y. Wang, A. Zhou, J. Li, Improved electrochemical performance of
LiCoO2 electrodes with ZnO coating by radio frequency magnetron sputtering, ACS Appl.
Mater. Interfaces. 6 (2014) 15853–15859.
Solid State Phenomena Vol. 301
[9]
201
A. Azahidi, K. Elong, N. Badar, N. A. Mohd Mokhtar, R. Rusdi, N. Kamarulzaman, Mn
Substitution with Co in LiCo(1-X)MnxO2 Cathode Materials and their Charge-Discharge
Characteristic, Adv. Mater. Res. 50 (2012) 133–137.
[10] J. P. Yu, Z. H. Han, X. H. Hu, H. Zhan, Y. H. Zhou, X. J. Liu, The investigation of LiCo1xSbxO2 as a promising cathode material for lithium-ion batteries, Electrochim. Acta. 121
(2014) 301–306.
[11] E. Oz, S. Demirel, S. Altin, Fabrication and electrochemical properties of LiCo1-xRuxO2
cathode materials for Li-ion battery, J. Alloys Compd. 671 (2016) 24–33.
[12] K. Elong, N. Kamarulzaman, R. Rusdi, Ti Doped LiMn1/3Co1/3Ni1/3O2 for Li-ion Battery
Application, Mater. Sci. 846 (2016) 493–496.
[13] K. Elong, N. Kamarulzaman, R. Rusdi, Effect of Different Stoichiometry on the
Electrochemical Behaviour of LiCoxNi1-xO2 Cathode Materials, J. Phys. (2018) 1–6.