Synthesis and electrochemical properties of LiyM1-xCaxMnO3 (M = Pr, Eu) solid solutions

Abstract

New Li-containing solid solutions LiyM1-xCaxMnO3 (M = Pr and Eu) were synthesized by electrochemical lithiation of the ceramics with perovskite structure. The qualitative and quantitative composition of the initial and Li-containing ceramics was determined by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The M/Ca/Mn cation ratio was confirmed by X-ray fluorescence spectroscopy. The crystal structure of theM1-xCaxMnO3solid solutions before lithiation (GdFeO3-type structure, space group Pnma, Pearson code oP20) and after lithiation (filled-up GdFeO3-type) was determined by the Rietveld method. X-ray structural analysis showed the formation of phases with increased unit cell parameters after lithiation process. In the case of Eu and Pr-containing samples X-rays diffraction patterns illustrate the amorphous halo based on the by-products of reaction between of ceramics surface and components from electrolyte. Under experimental conditions (Li-metal anode) the quantity of intercalated Li increases for ceramics: Li0.084Eu0.5Ca0.5MnO3, Li0.113Pr0.5Ca0.5MnO3, and Li0.134Pr0.7Ca0.3MnO3. Scanning electron microscopy method revealed the formation of Li-containing aggregates with dimension of 200-900 nm. The grains demonstrate block-like or irregular shape morphology with developed area surface.