Electrochemical lithiation of the CeNiC₂ compound

Chem. Met. Alloys 12 (2019) 9-15

https://doi.org/10.30970/cma12.0384

Vasyl KORDAN, Mykola HEMBARA, Volodymyr PAVLYUK, Bogdan KOTUR

Electrochemical lithiation of CeNiC₂ was carried out in a Swagelok-type cell with a positive electrode containing LiCoO₂ over 51/50 cycles of lithiation/delithiation. The crystal structure of CeNiC₂ (structure type CeNiC₂, 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 CeNiC₂ 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 CeNiC₂. The electrochemical lithiation process included two reactions: 1) insertion of Li into suitable voids and channels of near-surface layers of CeNiC₂, 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_zC_y, Ce_22.7Ni_21.6O_55.7 and Li₂O 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.

Crystal structure of CeNiC₂.

Keywords

Ternary carbides / X-ray diffraction / Crystal structure / Electrochemical lithiation