Characterization of Li1-x Ni1+x O2 prepared by the thermal-assisted precipitation process

Article abstract of DOI:10.1134/S0036023608040050

Li_1-x Ni_1+x O₂ was prepared by the thermal-assisted precipitation process of LiOH ? H₂O and Ni(CH₃COO)₂ ? 4H₂O at a pH of 6-13 followed by the high temperature calcination for a variety of prolonged times. Phases, morphologies and constituents were characterized using an x-ray diffractometer (XRD), a scanning electron microscope (SEM), an energy dispersive x-ray (EDX) analyzer an atomic absorption spectrophotometer (AAS) and titration. Maximum [I₍₀₀₃₎/I₍₁₀₄₎] and minimum [I _(006+102)/I₍₁₀₁₎] intensity ratios were used to determine the preparation conditions. In addition, possible formation reactions of the precursors and calcined products were proposed.

Full text of DOI:10.1134/S0036023608040050

ISSN 0036-0236, Russian Journal of Inorganic Chemistry, 2008, Vol. 53, No. 4, pp. 515–519. © Pleiades Publishing, Ltd., 2008.
SYNTHESIS AND PROPERTIES
OF INORGANIC COMPOUNDS
Characterization of Li Ni O Prepared
by the Thermal-Assisted Precipitation Process
1
– x
1 + x
2
1
Titipun Thongtem*, Russamee Sitthikhankaew, Somchai Thongtem
Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand
Abstract—Li1 – xNi1 + xO was prepared by the thermal-assisted precipitation process of LiOH · H O and
2
2
Ni(CH COO) · 4H O at a pH of 6–13 followed by the high temperature calcination for a variety of prolonged
3
2
2
times. Phases, morphologies and constituents were characterized using an x-ray diffractometer (XRD), a scan-
ning electron microscope (SEM), an energy dispersive x-ray (EDX) analyzer an atomic absorption spectropho-
tometer (AAS) and titration. Maximum [I(003)/I(104)] and minimum [I(006 + 102)/I(101)] intensity ratios were used
to determine the preparation conditions. In addition, possible formation reactions of the precursors and calcined
products were proposed.
DOI: 10.1134/S0036023608040050
1
mine Ni3+ ions. Ni3+ was reduced to Ni2+ by excess
ammonium iron(II) sulphate and titrated back with
standard potassium permanganate solution.
INTRODUCTION
LiNiO has been very attractive for use as a cathode
2
material of Li-ion batteries due to its large discharge
capacity, environmental advantages, and low cost [1–3].
To prepare the stoichiometric oxide has proved diffi-
RESULTS AND DISCUSSION
cult. Li1 – xNi1 + xO can be prepared by solid state and
2
chemical solution methods. Conventionally, the solid
state reaction produces the oxide with irregular mor-
phology, broader particle size distribution, inhomoge-
neous phase, and other problems [4–5]. Chemical solu-
tion methods have been shown to solve the problems.
They are sol-gel [6], the Pechini method [7], hydroxide
precipitation [8], coprecipitation [9], and others. The
purpose of this study is to determine the best conditions
Comparing the XRD spectra of the products pre-
pared using a variety of pH values followed by 750°C
calcination for 24 h (Fig. 1a) to those of the JCPDS
standard [10], they correspond to Li1 – xNi1 + xO . No
2
impurities were detected. The (006) and (102) peaks
overlap each other. The strongest intensity (I) peak is at
2
θ = 44.2 degrees. It diffracts from the (104) plane of
the products. I(003)/I(104) and I(006 + 102)/I(101) intensity
ratios were calculated and plotted (Fig. 2a). The
I(003)/I(104) ratio increased to its maximum at a pH of 8.5.
The I(006 + 102)/I(101) ratio decreased to its minimum at a
pH of 9.5. At the maximum and minimum intensity
ratios, cations are the most ordering and least mixing,
for use in preparing Li1 – xNi1 + xO by the thermal-
2
assisted precipitation process followed by high temper-
ature calcination.
EXPERIMENT
LiOH · H O and Ni(CH COO) · 4H O (1 : 1 mole resulting in the good rechargeable capacity and electro-
2
3
2
2
ratio of Li : Ni) were separately dissolved in water and chemical reversibility [11,12]. The pH values play a
mixed. A variety of pH values were adjusted using role in the composition of the precursors, which were
HNO and NH OH. The mixtures were heated at 110°C subsequently calcined to form the products. For the
3
4
until they were dry. The dried solid precursors were present research, the best conditions were in the pH
subsequently calcined to form powders, which were range of 8.5–9.5. XRD spectra of the precursors pre-
intensively analyzed using an x-ray diffractometer pared at the selected pH value, with and without high
(
XRD) operating at 20 kV, 15 mA, and CuK as the tar-
α
temperature calcination, are shown in Figs. 1b and 3,
get, a scanning electron microscope (SEM), and an respectively. Before calcination, LiOH, Ni(OH)2,
energy dispersive x-ray (EDX) analyzer operating at
5 kV, an atomic absorption spectrophotometer (AAS)
Ni(CH COO) · 4H O, and Li(CH COO) were detected.
They are crystalline phases to a certain degree. After
00–800°C calcination, the spectra are very sharp, show-
3
2
2
3
1
to determine Li and Ni content, and titration to deter-
3
1
ing that the products are composed of crystals. A variety
of phases was detected. Among them are NiO and
Li CO at 300–500°C, Li CO and Li Ni O at 600°C,
The article was submitted by the authors in English.
Corresponding Author; email: ttpthongtem@yahoo.com and ttp-
thongtem@hotmail.com
*
2
3
2
3
2
8
10
5
15

5
16
THONGTEM et al.
(
a)
(b)
Li1– xNi1+ xO2
Li CO
Li1– xNi1+ xO2
2
3
Li Ni O
2
8
10
NiO
1
1
1
1
3.0
2.0
1.0
0.0
8
00°C
7
50°C
9
.5
.0
.5
.0
.0
.0
7
00°C
9
6
75°C
8
8
7
6
6
50°C
6
00°C
5
00°C
(
c)
Li1– xNi1+ xO2
400°C
3
00°C
30
4
6 h
2
0
40
θ (degree)
50
60
2
4
4 h
4
3
2 h
4 h
2
8 h
2
4 h
0 h
2
1
4 h
1
0 h
Fig. 1. XRD spectra of the products prepared using
a) a variety of pH values followed by 750°C calci-
(
nation for 24 h, (b) pH of 8.5 followed by 300–800°C
calcination for 24 h, and (c) pH of 8.5 followed by
700°C calcination for 10–46 h.
2
0
30
40
50
60
2
θ (degree)
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 53 No. 4 2008

CHARACTERIZATION OF Li1 – xNi1 + xO2
517
I(003)/I(104)
I(006 + 102)/I(101)
(
‡)
0
0
0
0
0
.9
.8
.7
.6
.5
1.8
LiOH
Ni(OH)2
I(003)/I(104)
Ni(CH COO) · 4H O
1.6
1.4
1.2
1.0
3
2
2
Li(CH COO)
3
I(006 + 102)/I(101)
1
0
20
30
40
50
2
60
θ (degree)
5
6
7
8
9
10 11 12 13 14
pH
Fig. 3. XRD spectra of the precursors prepared using a pH
of 8.5.
1
0
0
0
0
.0
.9
.8
.7
.6
(b)
I(003)/I(104)
1.5
1
1
1
.4
.3
.2
The reaction of the starting reagents proceeds for
several steps to form the precursors.
Starting Reagents - - -
LiOH + Ni(OH)2
+ Ni(CH COO) · 4H O + Li(CH COO).
3
2
2
3
Calcination at 300–500°C:
1.1
Ni(OH)2
NiO + H O
2
1
0
.0
.9
Ni(CH COO) · 4H O + 4O
NiO + 4CO + 7H O
2 2
3
2
2
2
I(006 + 102)/I(101)
2
Li(CH COO) + 4O
Li CO + 3CO + 3H O,
2 3 2 2
3
2
6
50 675 700 725 750 775 800
Temperature, °C
and
2
LiOH + CO2
Li CO + H O
2 3 2
Calcination at 600°C:
1
0
0
0
0
0
0
.00
.95
.90
.85
.80
.75
.70
(c)
1.3
1
6NiO + 2Li CO (excess) + O
2Li Ni O +
2 8 10
I(006 + 102)/I(101)
2
3
2
2
CO2.
1
1
1
0
.2
.1
.0
.9
Calcination at 650–800°C:
Li CO + 2Li Ni O + 3O
6
16LiNiO + 6CO .
2 2
2
3
2
8
10
2
During high temperature calcination, crystallinity
of the product is improved. Lithium ions evaporate
and vacancies form on Li sites. The rate of Li evapo-
ration is increased with an increase in the calcination
temperature. This leads to an increase in the Ni per-
cent as well. Therefore, the chemical formula is writ-
ten as Li1 – xNi1 + xO2.
I(003)/I(104)
0.8
Evaporation reaction: 2(1 + x)LiNiO2
8
12 16 20 24 28 32 36 40 44 48 52
Time, h
2
Li1 − xNi1 + xO + 2xLi O (g) + xO .
2 2 2
The I(003)/I(104) and I(006 + 102)/I(101) intensity ratios
were plotted on Fig. 2b. The extreme values are both
at a temperature of 700°C. The products, prepared at
a pH of 8.5, were calcined at 700°C for 10–46 h. Their
XRD spectra (Fig. 1c) revealed the presence of only
Fig. 2. Intensity ratios for the products prepared using (a) a
variety of pH values followed by 750°C calcination for 24 h,
(
b) pH of 8.5 followed by 650–800°C calcination for 24 h,
and (c) pH of 8.5 followed by 700°C calcination for 10–46 h.
Li1 − xNi1 + xO . No impurities were detected, showing
2
that the prolonged time did not play a significant role in
the phase formation. The intensity ratios are shown on
Fig. 2c. The maximum and minimum intensity ratios
are at 42 and 44 h, respectively. By using AAS and a
and Li1 − xNi1 + xO at 650–800°C. Several reactions are
proposed on according to the following.
2
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 53 No. 4 2008

5
18
THONGTEM et al.
ONi
Ni
C
Au
7
00°C 42h
Ni
8
7
00°C 24h
50°C 24h
1
1
1
00 nm
(
‡)
7
6
6
00°C 24h
75°C 24h
50°C 24h
0
1
2
3
4
5
6
7
8
9
10
Energy (keV)
Fig. 5. EDX spectra of the products prepared using a variety
of the calcination temperatures and times.
00 nm
(
b)
SEM images (Fig. 4) show that the products are
composed of facet grains of crystals. The analysis is in
accord with the sharp peaks shown on the XRD spectra.
The calcination temperatures and times play a role in
the sizes of the crystals as well. After 700°C calcination
for 42 h, the average size is 375 nm.
EDX spectra (Fig. 5) revealed the presence of Ni and
O contained in the products. Li is the lightest metallic
element and was not detected. To improve electrical
conductivity for the analysis, Au was sputtered on top
of the products and was detected. C was detected as
well. This is from the carbon tape used for sticking the
powder on a copper stub.
00 nm
(
c)
CONCLUSIONS
Fig. 4. SEM images of the products prepared using the pH
of 8.5 and followed by a variety of the calcination tempera-
tures and times. (a) 650°C for 24 h, (b) 700°C for 24 h, and
Li1 – xNi1 + xO was successfully prepared by the
thermal-assisted precipitation process using a pH of
2
(
c) 700°C for 42 h.
6
−13 and subsequent calcination at 650–800°C for the
prolonged times. The best conditions used for the prep-
aration are at a pH of 8.5 followed by 700°C calcination
for 42–44 h. Possible formation reactions of the precur-
sors and calcined products were proposed according to
the XRD results. At a pH of 8.5 followed by 700°C cal-
cination for 42 h, the product is composed of 5.95 wt %
titration, the product prepared at a pH of 8.5 followed by
7
00°C calcination for 42 h was found to be composed of
3
+
5
.95 wt % Li, 70.43 wt % Ni and 65.86 wt % Ni of the
total nickel. The mean oxidation state of nickel in
Li1 − xNi1 + xO was calculated using the equation
2
3
+
Mean Oxidation State of Nickel = 2 + N, where N is Li, 70.43 wt % Ni and 65.86 wt % Ni of the total
3
+
the mole fraction of Ni of a total mole of nickel. The nickel. Its chemical formula is Li0.86Ni1.20
O and the
2
calculated oxidation state of nickel is 2.66 and the mean oxidation state of nickel is 2.66. It is composed of
chemical formula is Li0.86Ni1.20O2.
375 nm crystalline particles.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 53 No. 4 2008

CHARACTERIZATION OF Li1 – xNi1 + xO2
519
ACKNOWLEDGMENTS
5. Y. S. Lee, Y. K. Sun, S. Ota et al , Electrochem. Com-
mun. 4, 989 (2002).
We would like to thank the Faculty of Science and
the Institute for Science and Technology Research and
Development, Chiang Mai University, Chiang Mai,
Thailand, for funding the research.
6
7
8
9
. L. J. Fu, H. Liu, C. Li, et al., Prog. Mater. Sci. 50, 881
2005).
. S. P. Lin, K. Z. Fung,Y. M. Hon, and M. H. Hon, J. Cryst.
Growth 226, 148 (2001).
. V. Bianchi, D. Caurant, N. Baffier, et al., Solid State Ion-
ics 140, 1 (2001).
(
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