W.R. McKinnon

Hysteresis during Lithium Insertion in Hydrogen‐Containing Carbons

The authors studied lithium insertion in hydrogen-containing carbons heated at temperatures near 700 C. High capacities with large hysteresis (lithium insertion into these carbons at nearly 0 V and removal at nearly 1 V) were shown to be proportional to the hydrogen content of the samples. It is believed that the lithium atoms may bind on hydrogen-terminated edges of hexagonal carbon fragments, causing a change in the bond from sp{sup 2} to sp{sup 3}. The authors have carefully studied the electrochemical insertion of lithium in hydrogen-containing carbons using a variety of charge-discharge rates and cycling temperatures. These measurements allow the hysteresis to be quantified. A simple model, which treats the bonding change as an activated process, is used to model the hysteresis in the cells qualitatively.

Structure and electrochemistry of LixMoO2

The structure and phase diagram of LixMoO2 for 0<x<1 is determined using in situ X-ray diffraction and electrochemical methods. The phase diagram consists of three single phase regions and regions where these phases coexist. In two of the single phase regions (0<x<12and 0.98<x<1.0), LixMoO2 has a monoclinic unit cell with Mo-Mo pairing along the Mo atom chains. In the other single phase region (0.45<x<0.78), LixMoO2 is orthorhombic with no Mo-Mo pairing along the Mo atom chains. The transitions between these phases show hysteresis in x and in V, the voltage of Li/LixMoO2 cells. We correlate the features in V(x) with the phase diagram.

Lithium electrochemical cells at low voltage: Decomposition of Mo and W dichalcogenides

Abstract Results are presented for low voltage discharges of lithium electrochemical cells containing layered dichalcogenides of molybdenum and tungsten. Reversible intercalation of Li at high voltages occurs only for phases with octahedrally-coordinated metal atoms but all phases decompose irreversibly at low voltages to a mixture of Mo or W and Li2X, where X is S, Se, or Te. Lithium can be removed electrochemically from these mixtures at a voltage that correlates with the free energies of formation of Li2X.

Thermodynamics of Lithium Intercalation from High Resolution Electrochemical Measurements

We discuss the importance of high resolution measurements of d/chi//dV, the inverse derivative of the voltage (V) vs. intercalant concentration (/chi/) relation for intercalation-based electrochemical cells. The resul of experiments on Li/2HLi /SUB x/ TaS/sub 2/ cells demonstrate the use of high resolution measurements of d/chi//dV to determin a partial phase diagram for the lithium order-disorder transition near /chi/ = 2/3. We stress the reproducibility of our results, which were obtained using derivative constant current chronopotentiometry.

Salting-out in intercalation compounds: Removing copper from Cu3Mo6S8 by intercalating lithium

Abstract We study the removal of the copper in Cu 3 Mo 6 S 8 by the intercalation of lithium. For 0 x Cu 3 Mo 6 S 8 is a single phase compound. For x ⩾1, the copper atoms are forced out of the Mo 6 S 8 host. We present a lattice-gas model which shows how the intercalation of Li can force the Cu out of the host.

Lithium intercalation in 2H-LixTaS2

The authors describe electrochemical, X-ray diffraction and theoretical studies of 2H-LixTaS2. At room temperature this compound shows lithium order-disorder transitions near x=1/3 and x=2/3 and a stage-2 structure near x=0.12. Calculations using a lattice gas model of intercalation are in good agreement with results from electrochemical and X-ray measurements. They also compare intercalation in LixTiS2 and 2H-LxTaS2.

Lithium insertion into the layered perovskites LiCa2Nb3O10 and LiLaNb2O7

Abstract We have studied the intercalation of lithium into the layered niobates LiCa 2 Nb 3 O 10 and LiLaNb 2 O 7 using an electrochemical cell. Several new phases with varying were isolated and thier lattice parameters were measured in situ by X-ray diffraction. Preliminary measurements of the susceptibility for those new compounds showed no anomalous magnetisation, and no evidence of superconductivity was delected to 10 K.

Galvanomagnetic measurements in Fe3O4

Resistance, DC Hall effect and transverse magnetoresistance (TMR) measurements were attempted on a synthetic monocrystal of magnetite over the range 60-280K in fields up to 47*105 A m-1. The conductivity below Tv is described by a model which incorporates the temperature-dependent overlap of the wavefunctions. Systematic tendencies in the Hall and TMR effects above Tv suggest two components: one that is sensitive to the relative orientation of current flow and the domain walls and the other that arises from an interaction at the Fe ions. The former makes the current distribution very sensitive to the magnetic state and so accounts for some improbable results reported previously for the range below Tv.

Structure and electrochemistry of LixWO2

Abstract Using in situ X-ray diffraction and electrochemical techniques the structure and phase diagram of LixWO2 for 0

Lithium intercalation in LixZrSe2

Abstract We report electrochemical and X-ray diffraction studies of Li x ZrSe 2 . We have measured the variation of the lattice parameters of Li x ZrSe 2 with x and show that the lattice expands as soon as Li is intercalated. The results of our electrochemical experiments which measure V( x ) of Li/Li x ZrSe 2 cells are presented and compared to previously published data. We also explain several of the inconsistencies in the published literature on Li x ZrSe 2 .