V. Sánchez

Temperature effects on the diffusion of lithium in MoS2

The diffusion coefficients of lithium in Li x MoS 2 (0 < x < 0.43) compounds were determined at different temperatures by the galvanostatic-pulse relaxation technique. In the temperature range studied, the diffusion rate increases with increasing temperature but it decreases while lithium intercalation degree increases. The enthalpy contribution to the activation energy was evaluated.

Molybdenum Disulfide Intercalates with Special Transport Properties

Abstract Chemical modification of molybdenum disulfide based either in the restacking of the layered solid or the intercalation of lithium or organic donors as poly(ethylene oxide) or dialkylamines leads to products with improved transport properties. The products are mixed electronic-ionic conductors. Electrical conductivity, which in pressure compacted samples shows a clear anisotropic behavior, depends on the nature of the intercalated phase. For some dialkylamines [sgrave]-values of about 10−2 S cm−1 are reached. Electrode potentials available from charge/discharge curves in lithium electrochemical cells are mainly determined by both the trigonal prismatic-octahedral phase equilibrium in the matrix and the capacity of the guest for stabilizing Li+ ions in the interlaminar spaces. MoS2 phase change during lithium intercalation is also detected in the analysis of the 7Li-NMR linewidths of the LixMoS2 intercalates. Lithium diffusion coefficient analysis indicates that the mass transport of modified MoS2 is in general better than in the pristine compound.

Structure-Property Relationships in Molybdenum Disulfide Intercalates

The effects of host-guest and guest-guest interactions on the structure and electric inductivity of the products of the intercalation of electron pair donors as poly(ethylene oxyde), short chain (n=2-5) secondary amines, and long chain (n=12-18) amines into molybdenum disulfide are discussed. Although in most of the intercalates MoS 2 presents an octahedral conformation, induced principally by a host-guest charge transfer, in those with long chain amines predominate the hydrophobic intermolecular interactions bearing to products with different structural and transport properties.

Lithium dynamics in molybdenum disulfide intercalation compounds studied by nuclear magnetic resonance

Cluster architecture and lithium motion dynamics are investigated in nanocomposites formed by the intercalation of lithium and a dialkylamine (diethylamine, dibutylamine and dipentylamine) in molybdenum disulfide by means of 7Li Nuclear Magnetic Resonance (NMR) technique. The present contribution illustrates the potential of the NMR techniques in the study of both the short range atomic structure and the local dynamics of ions in these intercalation compounds. Structural information is gained through measurements of the various interactions (such as dipolar and quadrupolar) that affect the lineshapes of the NMR spectra, while ion dynamics information is gained through the study of the effects that ionic motion has on the nuclear relaxation times, which are modulated by these interactions. The formation of lithium clusters in these nanocomposites is suggested by the Li-Li dipolar interaction strength calculated from the 7Li NMR data. The lithium spin-lattice relaxation is mainly due to the interaction between the quadrupolar moment of the 7Li nuclei and the fluctuating electric field gradient at the site of the nucleus, produced by the surrounding charge distribution. The relaxation mechanism is consistent with a fast exchange motion of lithium ions between the coordination sites within the aggregates.

Dialkylamines—Molybdenum Disulfide. Intercalates. Synthesis, Characterization, and Electrical Properties

Abstract The synthesis and characterization of secondary amine-molybdenum disulfide intercalation compounds are described. Products which are layered organic-inorganic nanocomposites behave as mixed ionic electronic conductors with electrical conductivities depending on the nature ofthe amine of about 10−2 S cm−1

NMR Study of Lithium Dybutilamine Molybdenum Disulfide Nanocomposite

Measurements of 1 H and 7 Li Nuclear Magnetic Resonance (NMR) are reported for the nanocomposite formed by the intercalation of lithium and dibutylamine in molybdenum disulfide, Li 0.1 [(C 4 H 9 ) 2 NH] y MoS 2 . The temperature dependence NMR lineshapes and spin-lattice relaxation times ( T l ) measured exhibit the qualitative features associated with the lithium motions, namely the presence of a line narrowing at 230 K. The 1 H and the 7 Li longitudinal magnetization recovery was found to be non exponential. The T l values at each temperature was determined from the fit of a stretched exponential function. An activation energy for the lithium motion E a ≈0.18 eV was extracted from the 7 Li relaxation data. The dynamical parameters obtained from the 7 Li temperature dependence relaxation data indicate the mobility of the lithium in the nanocompositeis of the same order of magnitude as those obtained in other lithium intercalation compounds.