NMR and Phonon-Echo Study on the Ionic Operation of Electrode Materials of Lithium Ion Batteries

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Research results are summarized as follows. 1. Experiments(1) Sample preparation : Positive electrode material, LiCu0_2 was synthesized from Li_2O, LiOH and CuO powders. The powder of LiV_2O_5 was supplied by Bharathiar Univ. (India), LiGa by Hosei Univ. and Aomori Univ. Group, and Carbon powder by Matsushita Battery Industrial Co.,Ltd.(2) Measurements : The temperature dependence of the spin-lattice relaxation time T_1 and the line width ΔH have been measured for ^7Li in LiCoO_2, LiNiO_2, LiCuO_2 and LiV_2O_5. The chemical shift has been measured in LiCuO_2 and LiV_2O_5 by MAS-NMR. The electrical conductivity has been measured in LiCoO_2 and LiNiO_2 as a function of temperature by a four-terminal method. NMR measurement has been done for ^7Li and ^<71>Ga in β -LiGa over the temperature range of 77K〜500K.2. Results and Summary(1) We discussed about using LiNiO_2 instead of LiCoO_2 from NMR and conductivity data of both samples. Four oral presentations were given and one paper was published.(2) From the discussion about the possibility of the practical use of LiCuO_2 as the positive electrode from NMR Line width, we gave one oral report and one paper.(3) We investigated the behavior of Li^+ defects in β -LiGa by NMR measurements and discussed about the efficiency as the negative electrode. Six oral presentations were given in addition to three papers.(4) We could not observe the phonon echoes for the carbon powder. Further investigations are now being performed.