Lithium-Ion Conductors of the System LiCo_(1-x)Fe_xO_2, Preparation and Structural Investigation

摘要

Layered structure oxides of the system NaCo,_xFexO_2 were prepared for 0<= x ,= 1by solid-state reaction. Vegard-Iike be- havior was proved for these compounds by X-ray analysis, indic- ating mixed transition metal layers and sodium layers without cation disorder. By ion-exchange of these compounds In a molten eutectic mixture of LiCI and LiNOJ at 260°C the system LiCol-xFexO_2 was prepared for the whole composition range and characterized by chemical analysis, X-ray diffraction and FTIR spectroscopy. Atomic absorption spectroscopy showed almost complete ion-exchange from sodium to lithium. The members of this system are shown to crystallize, as the sodium compounds, in the rhombohedral space group Rjm (IX-NaFeO_2-tYJK!). X-ray diffraction, considerations based on the intensity ratio R1o1 = I]oPJ04 and Rietveld refinement give evidence for increasing cation disorder with increasing iron content, that reaches the value of LiFeO2 (4.5% ) already at an iron content of x = 0.4.