Solution-based combinatorial samples of lithium cobalt manganese oxide were synthesized and studied by X-ray diffraction in order to map out the pseudoternary phase diagram over the entire metal composition ranges. This report focuses on the single-phase layered region found to be made up of a single composition line joining LiCoO2 to Li2MnO3. The solid solution was found to phase separate during slow cooling (1 °C/min). The end points of this coexistence are not LiCoO2 and Li2MnO3: instead the Co-rich phase contains some Mn and the Mn-rich phase contains some Co. This phase separation occurs at compositions where previous studies showed nanodomain phase separation when an intermediate cooling rate was used. The nanoscale composites are therefore an intermediate structure that forms when there is insufficient time during cooling for large scale crystallites of the new phases to form. A simple Monte Carlo simulation was used to illustrate this phase separation and study the impact of cooling rate.

The Li-Mn-Ni-O system has received much attention for potential positive electrode materials in lithium ion batteries. This article is an executive summary of a large project that used combinatorial samples synthesized at over 500 compositions to determine the entire Li-Mn-Ni-O and Li-Co-Mn-O pseudo-ternary systems under various synthesis conditions. During slow cooling, the boundaries of the single phase layered region in the Li-Mn-Ni-O system move significantly making the solid-solution area smaller, while the complex co-existence region, made up of two 3-phase regions, transforms dramatically. The impact of these phase transformations on battery performance is presented here for the first time. The electrochemical data for three new materials present in the co-existence region demonstrates why efforts to design a spinel-layered composite electrode have been so difficult. Furthermore, the layered region is considerably larger than previously discussed in the literature implying that a portion of the region remains unexplored. Additionally, matching published lattice parameters with contour plots obtained from the combinatorial studies shows that the common practice of using excess lithium during synthesis may result in single phase compounds with more lithium than the target stoichiometry, which helps explain the large variation in electrochemical performance seen in the literature. This study is therefore a significant contribution toward a complete understanding of how synthesis conditions affect Li-Mn-Ni-O structures and their electrochemistry.

Combinatorial synthesis has proven extremely effective in screening for new battery materials for Li-ion battery electrodes. Here, a study in the Li-Ni-Mn-Co-O system is presented, wherein samples with nearly 800 distinct compositions were prepared using a combinatorial and high-throughput method to screen for single-phase materials of high interest as next generation positive electrode materials. X-ray diffraction is used to determine the crystal structure of each sample. The Gibbs' pyramid representing the pseudoquaternary system was studied by making samples within three distinct pseudoternary planes defined at fractional cobalt metal contents of 10%, 20%, and 30% within the Li-Ni-Mn-Co-O system. Two large single-phase regions were observed in the system: the layered region (ordered rocksalt) and cubic spinel region; both of which are of interest for next-generation positive electrodes in lithium-ion batteries. These regions were each found to stretch over a wide range of compositions within the Li-Ni-Mn-Co-O pseudoquaternary system and had complex coexistence regions existing between them. The sample cooling rate was found to have a significant effect on the position of the phase boundaries of the single-phase regions. The results of this work are intended to guide further research by narrowing the composition ranges worthy of study and to illustrate the broad range of applications where solution-based combinatorial synthesis can have significant impact.

Titanium-boron pyrotechnic reactions are essentially gasless, are very exothermic, and are known to initiate only at extremely high temperatures. The reactants are stable in normal laboratory environments and require no special sample handling, such as inert storage. These factors make the titaniundboron mixture ideal for one-shot thermal heat source applications. Mound has been investigating energetic material ignition properties for a number of years. Pyrotechnic mixtures of TiH,/KCIO, have revealed that the surface composition of the titanium fuel was TiO, and its presence on the fuel's surface controls the TiH, + KCIO, reaction. In the present study the surface chemistry of titanium and of boron have been examined before ignition. To understand the effect of temperature on the reactants and the mixture, titanium powder, boron powder, and blends were analyzed at ambient and elevated temperatures. XPS, TG and DTA results presented will show that the oxide on boron is the controlling factor in the ignition mechanism of the titanium-boron pyrotechnic reaction.

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