Chapter 10
Conclusions and Future Works
10.1 The Li–Co–Mn–Ni–O Pseudo-Quaternary System
Figure 10.1 shows the Li–Co–Mn–Ni–O pseudo-quaternary system with the Li–Co–
Mn–O and Li–Mn–Ni–O faces shown, as determined with combinatorial samples
quenched from 800
◦ C. Some approximations were made to join the two faces since
the Li–Co–Mn–O face was synthesized in air while the nickel containing samples
were made in oxygen. Nonetheless, the two faces join quite well. The pyramid
strongly suggests that both single-phase regions of importance for battery materials,
spinel and layered, extend into the pyramid and form relatively large 3D shapes. On
the Li–Co–Mn–O system, the layered region is restricted to a single line showing
that cobalt is always synthesized in the 3+ state as it is in LiCoO 2 . By contrast, nickel
can be in the 2+ state as in NiO rocksalt or the 3+ state as in layered LiNiO 2 such that
a much larger and more complex layered region exists on the Li–Mn–Ni–O face. The
spinel-layered coexistence region is also simpler in the Li–Co–Mn–O triangle with
all tie-lines connecting to either the cobalt spinel, Co 3 O 4 , or the manganese layered
material, Li 2 MnO 3 , while in the Li–Mn–Ni–O system there are 2 three-phase regions.
The differences between the roles of cobalt and nickel should prove significant in
upcoming combinatorial work in the Li–Co–Mn–Ni–O pseudo-quaternary system
that is of extreme interest for battery materials as it includes commercial materials
such as Li[Ni 1/3 Mn 1/3 Co 1/3 ]O 2 [93] as well as promising spinel-layered core-shell
materials [88] and lithium-rich layered materials [3].
One of the main findings in this work is that the boundaries of the single-phase
region move dramatically with synthesis conditions. Most importantly, the layered
single-phase regions become smaller when cooled more slowly, and this occurred
in both faces of the pyramid. The consequences of this were discussed in detail
throughout the thesis and will be summarized here by showing how this work helps
resolve a number of points of confusion in the literature mentioned in Chap. 1. These
were listed with roman numerals and will be repeated and addressed here with the
same numerals in the next section.
133
E. McCalla, Consequences of Combinatorial Studies of Positive Electrodes
for Li-ion Batteries, Springer Theses, DOI 10.1007/978-3-319-05849-8_10,
© Springer International Publishing Switzerland 2014
Conclusions and Future Works
10.1 The Li–Co–Mn–Ni–O Pseudo-Quaternary System
Figure 10.1 shows the Li–Co–Mn–Ni–O pseudo-quaternary system with the Li–Co–
Mn–O and Li–Mn–Ni–O faces shown, as determined with combinatorial samples
quenched from 800
◦ C. Some approximations were made to join the two faces since
the Li–Co–Mn–O face was synthesized in air while the nickel containing samples
were made in oxygen. Nonetheless, the two faces join quite well. The pyramid
strongly suggests that both single-phase regions of importance for battery materials,
spinel and layered, extend into the pyramid and form relatively large 3D shapes. On
the Li–Co–Mn–O system, the layered region is restricted to a single line showing
that cobalt is always synthesized in the 3+ state as it is in LiCoO 2 . By contrast, nickel
can be in the 2+ state as in NiO rocksalt or the 3+ state as in layered LiNiO 2 such that
a much larger and more complex layered region exists on the Li–Mn–Ni–O face. The
spinel-layered coexistence region is also simpler in the Li–Co–Mn–O triangle with
all tie-lines connecting to either the cobalt spinel, Co 3 O 4 , or the manganese layered
material, Li 2 MnO 3 , while in the Li–Mn–Ni–O system there are 2 three-phase regions.
The differences between the roles of cobalt and nickel should prove significant in
upcoming combinatorial work in the Li–Co–Mn–Ni–O pseudo-quaternary system
that is of extreme interest for battery materials as it includes commercial materials
such as Li[Ni 1/3 Mn 1/3 Co 1/3 ]O 2 [93] as well as promising spinel-layered core-shell
materials [88] and lithium-rich layered materials [3].
One of the main findings in this work is that the boundaries of the single-phase
region move dramatically with synthesis conditions. Most importantly, the layered
single-phase regions become smaller when cooled more slowly, and this occurred
in both faces of the pyramid. The consequences of this were discussed in detail
throughout the thesis and will be summarized here by showing how this work helps
resolve a number of points of confusion in the literature mentioned in Chap. 1. These
were listed with roman numerals and will be repeated and addressed here with the
same numerals in the next section.
133
E. McCalla, Consequences of Combinatorial Studies of Positive Electrodes
for Li-ion Batteries, Springer Theses, DOI 10.1007/978-3-319-05849-8_10,
© Springer International Publishing Switzerland 2014