10.3 Future Work
137
triangle at high temperature such that the initial material synthesized at 1,000
◦ C
was single-phase. Upon annealing at 600
◦ C the boundary was lower in the Gibbs
triangle and the sample was then in the layered–layered rocksalt three-phase region
determined in Chap. 6. The XRD pattern of the 600
◦ C annealed sample shown in
the introduction is consistent with the R, N and M phases identified here. These
transformations were also shown to be reversible in Chap. 7 explaining the return to
single-phase upon re-heating to 1,000
◦ C.
XI Much work has been done in trying to develop layered-spinel composite electrodes in the Li–Mn–Ni–O system, but there was a poor understanding of the nature
of the coexistence region. The work here shows that the layered-spinel region is small
and ties to layered materials in the “bump” region discussed extensively in Chap. 8.
Slow cooling in the layered-spinel two-phase region may result in the presence of
some rocksalt material which grows rapidly as the three-phase regions transform.
The rest of the coexistence region contains three-phase materials. Layered–layered–
spinel materials can be made by quenching, though one of the layered materials
is the disordered N phase discussed in Chap. 6. The N-material has poor electrochemistry and as such should be avoided. Kim et al. [94] have recently claimed to
make a layered–layered spinel material under regular cooling conditions. This cannot be done as rocksalt will always be present in the three-phase samples that are not
quenched. Instead the materials made by Kim were near enough to the Li–Mn line
to be layered–spinel composites.
10.3 Future Work
There are now a wide variety of studies that can be performed using the PixSys
solution-processing robot to synthesize combinatorial positive electrode materials.
The first opportunity for continued research in combinatorial positive electrode materials is to adapt the combinatorial electrochemical method used by Fleischauer [95]
for negative electrode materials. The primary challenge here is that the combinatorial positive electrodes are synthesized as powders and cannot be readily made by
sputtering. The project of adapting the 64 channel combinatorial electrochemistry
method for powders made using the PixSys robot is underway. Having both structural and electrochemical information for the combinatorial samples would be very
useful in the search for promising new electrode materials.
Even without the electrochemical information, there are now a number of composition spaces that are worth studying with XRD of combinatorial samples. The
first is to map out the single-phase regions in the Li–Co–Mn–Ni–O system. The
main challenge with respect to mapping out the entire pseudo-quaternary system
involves the coexistence regions. Since the layered boundaries are surfaces, it will
be extremely difficult to determine directions of tie-lines. Nonetheless, it should be
possible to identify approximate boundaries using the visual inspection of XRD patterns in a very large array of samples spanning hundreds of compositions. Mapping
137
triangle at high temperature such that the initial material synthesized at 1,000
◦ C
was single-phase. Upon annealing at 600
◦ C the boundary was lower in the Gibbs
triangle and the sample was then in the layered–layered rocksalt three-phase region
determined in Chap. 6. The XRD pattern of the 600
◦ C annealed sample shown in
the introduction is consistent with the R, N and M phases identified here. These
transformations were also shown to be reversible in Chap. 7 explaining the return to
single-phase upon re-heating to 1,000
◦ C.
XI Much work has been done in trying to develop layered-spinel composite electrodes in the Li–Mn–Ni–O system, but there was a poor understanding of the nature
of the coexistence region. The work here shows that the layered-spinel region is small
and ties to layered materials in the “bump” region discussed extensively in Chap. 8.
Slow cooling in the layered-spinel two-phase region may result in the presence of
some rocksalt material which grows rapidly as the three-phase regions transform.
The rest of the coexistence region contains three-phase materials. Layered–layered–
spinel materials can be made by quenching, though one of the layered materials
is the disordered N phase discussed in Chap. 6. The N-material has poor electrochemistry and as such should be avoided. Kim et al. [94] have recently claimed to
make a layered–layered spinel material under regular cooling conditions. This cannot be done as rocksalt will always be present in the three-phase samples that are not
quenched. Instead the materials made by Kim were near enough to the Li–Mn line
to be layered–spinel composites.
10.3 Future Work
There are now a wide variety of studies that can be performed using the PixSys
solution-processing robot to synthesize combinatorial positive electrode materials.
The first opportunity for continued research in combinatorial positive electrode materials is to adapt the combinatorial electrochemical method used by Fleischauer [95]
for negative electrode materials. The primary challenge here is that the combinatorial positive electrodes are synthesized as powders and cannot be readily made by
sputtering. The project of adapting the 64 channel combinatorial electrochemistry
method for powders made using the PixSys robot is underway. Having both structural and electrochemical information for the combinatorial samples would be very
useful in the search for promising new electrode materials.
Even without the electrochemical information, there are now a number of composition spaces that are worth studying with XRD of combinatorial samples. The
first is to map out the single-phase regions in the Li–Co–Mn–Ni–O system. The
main challenge with respect to mapping out the entire pseudo-quaternary system
involves the coexistence regions. Since the layered boundaries are surfaces, it will
be extremely difficult to determine directions of tie-lines. Nonetheless, it should be
possible to identify approximate boundaries using the visual inspection of XRD patterns in a very large array of samples spanning hundreds of compositions. Mapping