Lithium Intercalation into Graphite during Direct Contact and Anodic Polarization

Values of the diffusion coefficient for lithium in thermoexpanded graphite (TEG) are measured during cathodic intercalation from an aprotic electrolyte and during the TEG plate in contact with metallic lithium without electrolyte. In the course of cathodic intercalation, the diffusion coefficient is measured by method of galvanostatic switching-on curves. During TEG contact with lithium, the variation of x-ray diffraction pattern of TEG with time is recorded. It is established that during TEG contact with lithium the lattice spacing decreases and the characteristic size of TEG particles increases with time until the lithiation is complete and intercalate LiC₆ forms. Values of the diffusion coefficient determined by either method coincide and amount to 10^–10 cm² s^–1.     

Mechanism of growth of ZnO single crystals from hydrothermal alkali solutions

The results obtained in experiments on the growth of zinc oxide, ZnO, under hydrothermal conditions are generalized. The polar growth and nonstoichiometry of ZnO crystals are analyzed in terms of crystal chemistry with due regard for the physicochemical conditions of the growth medium. The effect of the Li⁺ and of di-and trivalent metal (Co²⁺, Fe²⁺, Mn²⁺, Fe³⁺, Mn³⁺, Sc³⁺, In³⁺) impurities on the kinetics and some physical characteristics of ZnO crystals are studied, and the chemical reactions occurring on the surfaces of the (0001) and \((000\bar 1)\) faces are considered.     

Relaxation nature of a current settling upon the application of an electric voltage in LaMnO3 crystals

The electrical conductivity of LaMnO₃ crystals was measured at room temperature to determine that the transition to a stable magnitude of electric current corresponding to the applied voltage has a relaxational nature with a characteristic time of about 10 min. The steady-state value of the current depends on the preceding voltage applied to the sample. The effect was observed in both dc and ac measurements. Detailed characterization of the crystals was performed using magnetic and x-ray methods.     

Reversibility of the lithium—vanadium bronze structure when cycled

Positive electrodes of secondary lithium batteries, based on Li^{1 + x}V₃O₈ obtained by the alcoxytechnology, are studied. As lithium intercalates, the initial crystalline bronze turns amorphous, remaining single-phase. An increase in the lithiation degreex leads to an almost linear decrease in parametera and increase in parametersb andc of the bronze crystal lattice; the changes are quite reversible when cycling. A noticeable degradation of electric characteristics of electrodes is unrelated to irreversible structural changes and may be explained by the formation of passive films on the bronze surface.     

Structure and properties of hydrogen bonded complexes of pyridine-N-oxide and its derivatives

Molar Kerr constants and electric dipole moments of hydrogen bonded complexes that pyridine-N-oxide and its derivatives form with phenols are studied (a) experimentally, (b) by the vector/tensor addition scheme, and (c) by AM1 and PM3 semi-empirical quantum chemical methods. The data are used to establish the geometry of the complexes. It is shown that for a series of pyridine-N-oxide derivatives, the logarithm of the complex formation equilibrium constant correlates with the charge on the oxygen atom of the N–O group. A method to calculate the first and second complex formation constants based on the electric properties of the individual components of the complex is proposed. A relationship between the polarity of the hydrogen bond and the sum of the charges on the hydrogen and oxygen atoms forming the bond is established for the complexes under study.