Chapter 4
Combinatorial Studies in the Li–Co–Mn–O
System
4.1 Experimental Design
Figure 4.1 shows the results of the current project for the Li–Co–Mn oxide pseudoternary system obtained in air at 800
◦ C. The two single-phase regions that lie solely
on the Co–Mn line are a tetragonal spinel phase (including CoMn 2 O 4 ) and a bixbyite
phase (including Mn 2 O 3 ). Once again, there are two solid solution regions of significance to the Li-ion research community: the cubic spinel and layered regions.
The coexistence region between them is relatively simple with two-phase coexistence only. The layered single-phase region and the coexistence between the layered
structures and Co 3 O 4 are the focus of this chapter. The entire spinel region was also
determined [76]. Much of the work for the spinel region was done by Colby Brown
and evidence for this will be part of his Master’s thesis.
Each combinatorial sample, with an approximate mass of 2 mg, was made using
the method described in Sect. 2.1.1. Samples were made for 11 compositions, evenly
spaced along each of the three lines: LiCoO 2 – Li 2 MnO 3 , LiCoO 2 – sample A 4 , and
Li 2 MnO 3 – sample A 4 (using the labels in Fig. 4.1). In this system, lithium loss
is less severe than in the case of the Li–Mn–Ni–O layered materials such that 3 h
heating in air (P O 2 = 0.21 atm) was possible. In the vast majority of studies found in
the literature, the samples were made by cooling from high temperature at roughly
5–10
◦ C/min, e.g., [18, 23] . However, the cooling rate can have a significant impact
on the phases obtained, so one important feature of the current study was to vary the
cooling rate to see the effect on the layered region. The objective was to understand
how and at which compositions, the layered–layered nano-composites form in order
to determine if the phase diagrams produced with combinatorial samples can be used
to predict nano-composite formation. Three cooling rates (quenched, regular cooling
and slow cooling) were therefore used.
It was found that lithium loss occurred in all samples at 900
◦ C when nonquenched,
as well as in a few samples heated to 800
◦ C when slow cooled. This loss resulted
in samples lying in the spinel–layered coexistence region (Fig. 4.1) such that Co 3 O 4
Data in this chapter are reprinted from Ref. [75] with permission from the American Chemical
Society.
49
E. McCalla, Consequences of Combinatorial Studies of Positive Electrodes
for Li-ion Batteries, Springer Theses, DOI 10.1007/978-3-319-05849-8_4,
© Springer International Publishing Switzerland 2014
Combinatorial Studies in the Li–Co–Mn–O
System
4.1 Experimental Design
Figure 4.1 shows the results of the current project for the Li–Co–Mn oxide pseudoternary system obtained in air at 800
◦ C. The two single-phase regions that lie solely
on the Co–Mn line are a tetragonal spinel phase (including CoMn 2 O 4 ) and a bixbyite
phase (including Mn 2 O 3 ). Once again, there are two solid solution regions of significance to the Li-ion research community: the cubic spinel and layered regions.
The coexistence region between them is relatively simple with two-phase coexistence only. The layered single-phase region and the coexistence between the layered
structures and Co 3 O 4 are the focus of this chapter. The entire spinel region was also
determined [76]. Much of the work for the spinel region was done by Colby Brown
and evidence for this will be part of his Master’s thesis.
Each combinatorial sample, with an approximate mass of 2 mg, was made using
the method described in Sect. 2.1.1. Samples were made for 11 compositions, evenly
spaced along each of the three lines: LiCoO 2 – Li 2 MnO 3 , LiCoO 2 – sample A 4 , and
Li 2 MnO 3 – sample A 4 (using the labels in Fig. 4.1). In this system, lithium loss
is less severe than in the case of the Li–Mn–Ni–O layered materials such that 3 h
heating in air (P O 2 = 0.21 atm) was possible. In the vast majority of studies found in
the literature, the samples were made by cooling from high temperature at roughly
5–10
◦ C/min, e.g., [18, 23] . However, the cooling rate can have a significant impact
on the phases obtained, so one important feature of the current study was to vary the
cooling rate to see the effect on the layered region. The objective was to understand
how and at which compositions, the layered–layered nano-composites form in order
to determine if the phase diagrams produced with combinatorial samples can be used
to predict nano-composite formation. Three cooling rates (quenched, regular cooling
and slow cooling) were therefore used.
It was found that lithium loss occurred in all samples at 900
◦ C when nonquenched,
as well as in a few samples heated to 800
◦ C when slow cooled. This loss resulted
in samples lying in the spinel–layered coexistence region (Fig. 4.1) such that Co 3 O 4
Data in this chapter are reprinted from Ref. [75] with permission from the American Chemical
Society.
49
E. McCalla, Consequences of Combinatorial Studies of Positive Electrodes
for Li-ion Batteries, Springer Theses, DOI 10.1007/978-3-319-05849-8_4,
© Springer International Publishing Switzerland 2014