R.R. Haering

Structure and electrochemistry of the spinel oxides LiTi2O4 and Li43Ti53O4

Abstract LiTi2O4 is metallic, has the cubic spinel structure and is known to react with one further lithium atom to form Li2Ti2O4. We find that the related spinel Li 4 3 Ti 5 3 O4, which is electrically insulating, also reacts reversibly with one lithium atom. Both Li/LiTi2O4 and Li/Li 4 3 Ti 5 3 O4 cells cycle reversibly with little capacity loss for over 100 cycles, but have subtle differences in their voltage profiles. We interpret the differences in cell behaviour using arguments based on the band structure of Li1+xTi2−xO4

Theory of lithium ordering in LixTiS2

Abstract Real space renormalization group and Monte Carlo techniques are used to study the statistical mechanics of a lattice gas model of Li ordering in an intercalation battery. The dependence of the voltage on the state of charge of the battery is related to the number and types of sites available to the Li ions and to the strength and distance dependence of the Li-Li interaction. Several models are discussed and compared with the observed behaviour of LixTiS2.

Elastic energy and staging in intercalation compounds

Abstract We present a simple model for the elastic energy associated with the intercalation of a layered host lattice. The model accounts for the staging phenomena observed in many intercalation systems and is compared with Safrans theory of staging. The model is used to discuss the thermodynamic behaviour of Li x TiS 2 and is shown to give a good account of the experimental observations.

Anomalous Bragg Peak Widths in Lixtis2

Abstract We have performed X ray diffraction experiments on LixTiS2 and have found an experimental correlation between features observed in the (00l) peak width and -δx/δV data. (00l) peak broadening is indicative of imperfect order in the c direction of the lattice. This suggests that three dimensional models for lithium intercalation in TiS2 should be investigated.

Phase mixtures and staging in intercalated LixNbSe2

Abstract We present experimental evidence for the existence at room temperature of staged compounds in the Li x NbSe 2 system. For x in the range .27 ⩽ × ⩽ 1, a stage 1 structure is observed. For × ≅ .14 and × ≅ .08, stage 2 and stage 3 structures, respectively, are seen. For other values of x in the range 0 ⩽ × ⩽ .27, coexisting phase mixtures are observed.

Temperature dependence of sound velocities in TTF-TCNQ

Abstract Measurements of a and b axis sound velocities in TTF-TCNQ single crystals are presented from 0–300K. The Youngs modulus is larger in the a than in the b direction. The temperature dependence of the velocity is compared with heat capacity and thermal expansion data. A 1.5% increase in the velocity below 52K is attributed to the freezing out of the conduction electrons.

The Role of Kinetic Effects in Voltammetry Studies of Intercalation Systems

The techniques of electrochemical potential spectroscopy [1,2] and linear sweep voltammetry [3,4] have recently been shown to be of value in studying electrochemical cells based on the intercalation of lithium in transition metal dichalcogenides. Fine structure in the voltage (V) versus charge (Q) relation is best seen when the dependence of -dQ/dV on V or Q is examined. It has been shown [4,5] that such structure can be caused by phase transitions, including those arising from lithium ordering. Thus linear sweep voltammetry can in principle be used to yield the phase diagram of an intercalation system such as LixMX2. Earlier studies of such phase systems [6,7,8] usually employed the techniques of X-ray or neutron diffraction.

The 3R phase of LixTiS2

Abstract When Li x TiS 2 (0 ⩽ x ⩽ 1) is synthesized at elevated temperature (500°C ⩽ T ⩽ 900°C), a new polytype, 3R-Li x TiS 2 , is found for some values of x . Here we discuss the structure of the new phase and present a preliminary phase diagram which shows the regions of stability of the 3R polytype and the well known 1T polytype. Lithium can be intercalated or de-intercalated from both polytypes at room temperature. Ambient temperature Li/3R-Li x TiS 2 cells have higher average voltages than Li/1T-Li x TiS 2 cells.

Nanosecond acoustic strain pulses from CdS phonon masers

Abstract Observations of nanosecond strain pulses generated by a mode-locked CdS phonon maser are reported. Peak strains exceeding 5 × 10-5 have been measured. An analogy is drawn between the observed mode-locked operation and a repetitive pulse generator.

Observation of acoustically induced space charge gratings in CdS

Abstract Static space charge gratings, produced via a nonlinear acoustoelectric interaction, have been directly observed in CdS by means of laser diffraction. Spatial and temporal filtering techniques were used to separate the required optical information from extraneous signals due to background and acoustic diffraction effects.