Preparation and Electrical Properties of MgO-M x O y (M=Fe, Ni) Solid Solution for Magnesium Secondary Battery Cathode

Abstract

MgO-M x O y (M=Fe, Ni) oxide powders were prepared by a direct drying technique and a co-precipitation method for comparing their physical properties. These dried nitrate precursors or hydroxide precipitates were subsequently calcined at 550 o C to transform themselves into oxides, respectively. Calcined oxide powders were sintered at 1100 o C to determine their crystal structures, microstructures, and electrical properties at room temperature. As to crystal structures, sintered Mg 1-x Fe x O 1+y and Mg 1-x Ni x O (x=1/3, 1/2, 2/3) specimens contained spinel and rock salt (NaCl or MgO) crystal structures separately. Electrical resistances of these sintered specimens decrease as the measuring frequency of LCR increases. Sintered specimens obtained from the co-precipitated powders had slightly lower electrical conductivities. At a low measuring frequency of 30-3000Hz, these polycrystalline grains have a grain electrical conductivity of 1.0-9.0*10 -4 S/m -1 in the semiconductor range. As to microstructures, grain size of these sintered specimens was 0.1-1.0 μm. Relationships between crystal structure, microstructure, and electrical properties were discussed. From this preliminary investigation, these magnesium-containing oxides were a possible cathode material for the secondary magnesium battery.