Chapter 3
Optimization of the Synthesis
of Combinatorial Samples
3.1 Experimental Design
Though combinatorial samples were synthesized along each of the single-phase regions I, II, III and IV shown in Fig. 3.1, only the Li x Ni 2−x O 2 samples (line IV) are
reported here in order to describe the mechanisms for lithium loss in the small samples. The methods used to make the samples were closely based on the synthesis done
by Carey [10], but several variables were controlled in order to find the conditions
that minimize the lithium loss. These included the choice of substrate, the chemical
used to cause precipitation (called “precipitator” here), the heating temperature and
the atmosphere during heating.
Three substrates were tested: Al 2 O 3 , MgO and Al 2 O 3 treated with LiOH. The
main concern with respect to alumina is that it reacts with lithium carbonate to
form LiAlO 2 , a process which has been observed to go to completion at 700
◦ C
[67]. Magnesia shows no such reaction, but it is hygroscopic and porous, thereby
requiring large quantities of stearic acid to prevent the water in the solutions from
entering the substrate before the co-precipitation reaction takes place. The LiOH
treatments were done by spraying 3 M LiOH onto the surface, drying at 55
◦ C and
then heating to 900
◦ C for an hour in a box furnace. This was repeated three times.
Figure 3.2 (d) shows that after the treatments, the substrate had a layer of LiAlO 2
(JCPDS #73-1338) on the surface. A fourth treatment typically resulted in cracking
and flaking of this layer.
The primary objective here was to synthesize LiNiO 2 at 800
◦ C, the temperature
required to make the spinel samples in the Li–Mn–Ni–O system. Since stearic acid
has been found to react with lithium to form lithium stearate [68, 69], this chapter also
deals with identifying the role of stearic acid in the samples, especially on magnesia
where more was required. The precipitators tested were ammonium bicarbonate and
ammonium hydroxide, these being the two most commonly used to synthesize metal
carbonates or hydroxides from solution. The atmospheres used were either air in a
box furnace or oxygen flowing in a tube furnace. The heating temperature was varied
Data in this chapter are reprinted from Ref. [66] with permission from Elsevier.
35
E. McCalla, Consequences of Combinatorial Studies of Positive Electrodes
for Li-ion Batteries, Springer Theses, DOI 10.1007/978-3-319-05849-8_3,
© Springer International Publishing Switzerland 2014
Optimization of the Synthesis
of Combinatorial Samples
3.1 Experimental Design
Though combinatorial samples were synthesized along each of the single-phase regions I, II, III and IV shown in Fig. 3.1, only the Li x Ni 2−x O 2 samples (line IV) are
reported here in order to describe the mechanisms for lithium loss in the small samples. The methods used to make the samples were closely based on the synthesis done
by Carey [10], but several variables were controlled in order to find the conditions
that minimize the lithium loss. These included the choice of substrate, the chemical
used to cause precipitation (called “precipitator” here), the heating temperature and
the atmosphere during heating.
Three substrates were tested: Al 2 O 3 , MgO and Al 2 O 3 treated with LiOH. The
main concern with respect to alumina is that it reacts with lithium carbonate to
form LiAlO 2 , a process which has been observed to go to completion at 700
◦ C
[67]. Magnesia shows no such reaction, but it is hygroscopic and porous, thereby
requiring large quantities of stearic acid to prevent the water in the solutions from
entering the substrate before the co-precipitation reaction takes place. The LiOH
treatments were done by spraying 3 M LiOH onto the surface, drying at 55
◦ C and
then heating to 900
◦ C for an hour in a box furnace. This was repeated three times.
Figure 3.2 (d) shows that after the treatments, the substrate had a layer of LiAlO 2
(JCPDS #73-1338) on the surface. A fourth treatment typically resulted in cracking
and flaking of this layer.
The primary objective here was to synthesize LiNiO 2 at 800
◦ C, the temperature
required to make the spinel samples in the Li–Mn–Ni–O system. Since stearic acid
has been found to react with lithium to form lithium stearate [68, 69], this chapter also
deals with identifying the role of stearic acid in the samples, especially on magnesia
where more was required. The precipitators tested were ammonium bicarbonate and
ammonium hydroxide, these being the two most commonly used to synthesize metal
carbonates or hydroxides from solution. The atmospheres used were either air in a
box furnace or oxygen flowing in a tube furnace. The heating temperature was varied
Data in this chapter are reprinted from Ref. [66] with permission from Elsevier.
35
E. McCalla, Consequences of Combinatorial Studies of Positive Electrodes
for Li-ion Batteries, Springer Theses, DOI 10.1007/978-3-319-05849-8_3,
© Springer International Publishing Switzerland 2014