Lithium and sodium intercalation into VTe2

Abstract

Lithium intercalation into monoclinic VTe₂ has been carried out by the n-butyllithium technique and in Li|LiClO₄(PC)|telluride test cells. Step potential electrochemical spectroscopy revealed several successive reduction peaks corresponding to lithium intercalation processes that occur by partial filling of the distorted octahedral sites in the interlayer space. For LiVTe₂, an expansion of the c_h parameter normal to the layers of 0.35 Å was observed. Sodium intercalation was carried out in Na|NaClO₄(PC)|telluride cells. Lower cell voltages and a higher expansion of the lattice (Δc_h≈ 1.06 Å) were observed. The incremental capacity vs. composition curve is consistent with a maximum intercalation of 0.9 Na atoms per formula unit. The structural changes throughout intercalation and the alkali-metal ion diffusion coefficients are explained on the basis of the interlayer Te–Te interactions and V–V bonding in the structure of the solid.