Chapter 2
Experimental and Theoretical Considerations
2.1 Sample Preparation
2.1.1 Synthesis of Combinatorial Samples
The method used to synthesize hundreds of samples across the pseudo-ternary systems was to make combinatorial arrays of milligram-scale oxides. Throughout this
section, the method used to make samples in the Li–Mn–Ni–O system will be described. The only variation needed to make samples in the Li–Co–Mn–O system is to
replace the nickel starting solution with a cobalt solution (both were nitrates in these
studies). This method, developed by Carey and Dahn [10], was closely based on that
typically used for large scale samples made in a tank reactor. Carey [10] mixed a
total of 10 μL of roughly 2 M lithium nitrate (Aldrich, 98 %), manganese nitrate
(Sigma-Aldrich, 97 %) and nickel nitrate (Sigma-Aldrich, 97 %) using a Cartesian
Pixsys solution-processing robot shown in Fig. 2.1. Figure 2.2 (a) shows how these
solutions were dispensed onto an alumina plate (Pi-Kem, 96 %) coated with stearic
acid (Aldrich, 96 %) which served to bead the solutions. Carey then added ammonium bicarbonate (Alfa Aesar, 98 %) in excess to cause co-precipitation of Li, Mn
and Ni carbonates. After drying at 55
◦ C, the sample was made up of the mixed
carbonate and any other products of the reaction (in Chap. 3, this will be shown to
be primarily ammonium carbonate). Carey then heated the samples to 800
◦ C for 3 h
in air to form the oxides. Silicon (100) wafers were then covered in a tacky mixture
of Trilene-65 (a polymer mixture made by Lion Copolymer) and cyclohexane. The
wafer was placed over the alumina plates and flipped in order to transfer the samples
onto the silicon wafer. The final products were shown to be the expected spinel oxides
by XRD.
By contrast, for bulk samples, a precursor is made over the course of several
hours by mixing manganese and nickel solutions in a tank reactor in the presence of
a precipitator such as ammonium bicarbonate or ammonium hydroxide. The results of
this co-precipitation reaction, after rinsing, is a mixed manganese–nickel compound
(either hydroxide or carbonate) which is then mixed with a lithium salt (typically
Li 2 CO 3 or LiOH) and heated to high temperature to make the oxide material. The
main differences between the combinatorial approach and the tank reactor method
19
E. McCalla, Consequences of Combinatorial Studies of Positive Electrodes
for Li-ion Batteries, Springer Theses, DOI 10.1007/978-3-319-05849-8_2,
© Springer International Publishing Switzerland 2014
Experimental and Theoretical Considerations
2.1 Sample Preparation
2.1.1 Synthesis of Combinatorial Samples
The method used to synthesize hundreds of samples across the pseudo-ternary systems was to make combinatorial arrays of milligram-scale oxides. Throughout this
section, the method used to make samples in the Li–Mn–Ni–O system will be described. The only variation needed to make samples in the Li–Co–Mn–O system is to
replace the nickel starting solution with a cobalt solution (both were nitrates in these
studies). This method, developed by Carey and Dahn [10], was closely based on that
typically used for large scale samples made in a tank reactor. Carey [10] mixed a
total of 10 μL of roughly 2 M lithium nitrate (Aldrich, 98 %), manganese nitrate
(Sigma-Aldrich, 97 %) and nickel nitrate (Sigma-Aldrich, 97 %) using a Cartesian
Pixsys solution-processing robot shown in Fig. 2.1. Figure 2.2 (a) shows how these
solutions were dispensed onto an alumina plate (Pi-Kem, 96 %) coated with stearic
acid (Aldrich, 96 %) which served to bead the solutions. Carey then added ammonium bicarbonate (Alfa Aesar, 98 %) in excess to cause co-precipitation of Li, Mn
and Ni carbonates. After drying at 55
◦ C, the sample was made up of the mixed
carbonate and any other products of the reaction (in Chap. 3, this will be shown to
be primarily ammonium carbonate). Carey then heated the samples to 800
◦ C for 3 h
in air to form the oxides. Silicon (100) wafers were then covered in a tacky mixture
of Trilene-65 (a polymer mixture made by Lion Copolymer) and cyclohexane. The
wafer was placed over the alumina plates and flipped in order to transfer the samples
onto the silicon wafer. The final products were shown to be the expected spinel oxides
by XRD.
By contrast, for bulk samples, a precursor is made over the course of several
hours by mixing manganese and nickel solutions in a tank reactor in the presence of
a precipitator such as ammonium bicarbonate or ammonium hydroxide. The results of
this co-precipitation reaction, after rinsing, is a mixed manganese–nickel compound
(either hydroxide or carbonate) which is then mixed with a lithium salt (typically
Li 2 CO 3 or LiOH) and heated to high temperature to make the oxide material. The
main differences between the combinatorial approach and the tank reactor method
19
E. McCalla, Consequences of Combinatorial Studies of Positive Electrodes
for Li-ion Batteries, Springer Theses, DOI 10.1007/978-3-319-05849-8_2,
© Springer International Publishing Switzerland 2014