Electrochemical lithiation of the CeNiC2 compound

Abstract

Electrochemical lithiation of CeNiC 2 was carried out in a Swagelok-type cell with a positive electrode containing LiCoO 2 over 51/50 cycles of lithiation/delithiation. The crystal structure of CeNiC 2 (structure type CeNiC 2 , Pearson symbol oS8, space group Amm2) before and after lithiation was investigated by X-ray diffraction. The electrodes containing the ternary carbide were examined by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The crystal structure of CeNiC 2 remained very stable toward electrochemical lithiation. The volume of the unit cell after 51/50 lithiation/delithiation cycles decreased by only 0.06 %. A small amount of lithium, up to 0.115 Li per formula unit, was reversibly incorporated into CeNiC 2. The electrochemical lithiation process included two reactions: 1) insertion of Li into suitable voids and channels of near-surface layers of CeNiC 2 , and 2) partial decarbonization of the electrode. The composition and morphology of the grains of the electrode material changed only slightly. Small amounts of Li z C y , Ce 22.7 Ni 21.6 O 55.7 and Li 2 O were detected as by-products of the lithiation. The lithiation mechanism of ternary carbides containing a rare earth and a 3d-element depends on the stoichiometry and peculiarities of the crystal structure. Ternary carbides / X-ray diffraction / Crystal structure / Electrochemical lithiation