Establishment of Reaction Phase Diagrams of Pseudo Quaternary Li-Ni-Co-Ti Oxides Library
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Establishment of Reaction Phase Diagrams of Pseudo Quaternary Li-Ni-Co-Ti Oxides Library Kenjiro Fujimoto, Kazuhiro Onoda, and Shigeru Ito Department of Pure and Applied Chemistry, Tokyo University of Science, 2641 Yamazaki, Noda, 278-8510, Japan ABSTRACT A reaction phase diagram for pseudo quaternary Li-Ni-Co-Ti oxides has been developed for finding new chemical compositions and functional materials using the combinatorial highthroughput preparation system, “M-ist Combi,” which is based on the electrostatic spray deposition process and a combinatorial powder x-ray diffraction apparatus. New layered compounds were found in a composition region that was wider than the LiNi0.8-yCo0.2TiyO2 (0≤y≤0.1) composition region that had been described in a previous report. Furthermore, new composition regions of single-phase compounds for spinel and rock-salt were soon found in a pseudo four-component Li-Ni-Co-Ti oxide system.
INTRODUCTION Researchers are increasingly seeking new functional materials with multi-component compounds. For example, in ternary compounds, changing the composition ratio in steps of 5 and 10% leads to 231 and 66 combinations, respectively. When a fourth component is added, changing the composition ratio in the same steps of 5 and 10% leads to 1771 and 286 combinations, respectively, which considerably increases both the synthesis parameter and the time needed to prepare samples using conventional methods. Therefore, when exploring multicomponent compounds, many researchers generally determine a candidate material by considering not only references but also the ion valence, ionic radius, and so on, and prepare several kinds of materials. However, new functional materials may also contain having different composition ratios except for the limited candidate materials. In order to explore a wider composition region, it is necessary to adopt a high-throughput screening method such as our “Mist Combi,” which is based on the wet/dry and electrostatic spray deposition methods. In the electrostatic spray deposition method, the materials to be deposited on a grounded substrate are atomized by applying a high voltage to the solution. Kobayashi [1] and Taniguchi [2] have used the electrostatic spray deposition method to prepare electrode materials for lithium ion secondary batteries and solid oxide fuel cells. The materials were fed from a syringe pump containing a solution of the starting materials. On the other hand, the “M-ist Combi” system uses multiple syringe pumps, each of which contains a starting material. The “M-ist Combi” system consists of a high-voltage power supply, a unit for feeding multiple solutions of the starting materials, a robot system for controlling the atomizing position, and a temperature control unit attached to the thermo-plate that is used for drying the atomized mixed solution. This system is fully controlled by conventional PC hardware running a control program written in Visual Basic 6.0 (Microsoft Corp.). The control system is designed to provide an easy-to-use enviro
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