卷 59, 编号 7 (2023)

Solid solutions Na3V2 − xScx(PO4)3 (0 < x < 2) are synthesized by the sol-gel method followed by annealing in inert atmosphere. The structure of Na3V2 − xScx(PO4)3 (x = 0.5, 1.2) compounds is studied by the method of powder X-ray diffraction. As the degree of substitution increases, the unit cell parameters and volume tend to increase on retention of the NASICON-type structure. The electrochemical properties of Na3V2 − xScx(PO4)3/C materials as the cathodes for sodium-ion batteries are studied in sodium half-cells in different potential intervals: 2.5−3.8, 2.5−4.5, and 1.0−4.5 V vs. Na/Na+. The charging curves of all materials demonstrate two plateaus: at ≈3.5 and ≈4 V vs. Na/Na+, corresponding to the successive transitions V3+/V4+ and V4+/V5+. However, the high-voltage plateau is reversible at the subsequent discharge only for the Na3V1.5Sc0.5(PO4)3/C material. This allows one to carry out the stable reversible cycling of this material in the potential interval of 1.0−4.5 V vs. Na/Na+ with the capacity higher than 170 mA h g−1, which corresponds to (de)intercalation of three Na+ per formula unit.

A phenomenological model describing the change in the structural characteristics of loose zinc deposits obtained in pulsed current modes is presented. Comparison of experimental data on the structural properties of deposits with the results of model calculations indicates the adequacy of the model. To describe the features of the dendritic deposit growth and to determine the duration of the homogeneous structure formation in pulsed modes, the concept of critical thickness is introduced, at which a sharp change in the loose deposit density occurs. The dependence of the zinc deposit critical thickness on the pulse duty ratio under pulsed current modes is determined. The increasing of the pulse duty ratio leads to denser deposits with rounded dendrite shapes and fewer growth points, as compared with the deposit obtained in galvanostatic mode.

The possibility of analyzing the electrochemical impedance spectra of lithium–lithium cells using the Distribution of Relaxation Times (DRT) function is studied. A comparative analysis of the electrochemical impedance spectra of lithium–lithium cells obtained during long-term storage at a constant temperature and at different temperatures was performed using the method of either equivalent electrical circuits or the DRT function. The analysis of the impedance of lithium–lithium cells by the DRT function is shown to allow estimating the number of layers in the surface film on the lithium electrodes and evaluating their physical parameters—the resistance and capacitance. It has been established that with a long exposure of lithium–lithium cells at the temperature of 30°C, the number of layers in the surface film and its resistance decreased. With the increase in the temperature, the physical properties of the layers of the surface film are differentiated and its total resistance decreased. The analysis of the electrochemical impedance spectra of lithium–lithium cells by the DRT functions is more informative than the method of equivalent electrical circuits.