The pulsed method of measuring impedance is described. The cell is galvanostatically stimulated by a bipolar current signal of square shape. The cell response is registered by sampling U+i, U−i with ...selected period Δt. The impedance spectra are calculated by direct Fourier transform. The internal resistance of the lithium sulphur cell is characteristically minimum in the calculated impedance diagrams in the frequency range of 0.035–5 Hz. It is shown that the lithium sulphur cells have maximum internal resistance at the transient between high and low voltage plateaus of charge and discharge curves. The internal resistance increases significantly during the initial stages of cycling because of the formation of passivation layers at the electrodes. It was found that the internal resistance of the lithium sulphur cell in the same charge state is governed by the way in which it is achieved. This is explained by differences in molar volumes of products generated in the sulphur electrode by electrochemical reaction during charging and discharging.
•The pulsed method as a way to determine the internal resistance of batteries.•The internal resistance of Li–S cells depends on the depth of charge and discharge.•The polarization direction of lithium sulphur cell governs the internal resistance.
We have studied the interaction of polycrystalline samples of lithium nitride with metallic lithium. We have found that upon contact, metallic lithium spontaneously dissolves into polycrystalline ...lithium nitride samples. Spontaneous penetration of metallic lithium into polycrystalline samples of lithium nitride leads to the appearance of electronic conductivity and the formation of mixed ion-electronic conductors.
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•Interaction of metallic lithium and polycrystalline lithium nitride is studied.•Metallic lithium spontaneously penetrates in a pellet of Li3N.•Penetration of lithium in Li3N leads to short circuit of the cell Li │ Li3N │ Li.•Penetration of Li in Li3N leads to the formation of mixed ion-electronic conductors.
The effect of lithium polysulfides on the amount and ratio of electrochemically active metallic lithium, electrochemically inactive metallic lithium, and chemically formed lithium compounds in the ...cathodic deposits formed on a stainless-steel electrode during galvanostatic cycling in 1 М LiClO
4
solution in sulfolane at 15, 30, 45, and 60°C is studied using the method we have developed earlier. It is shown that the increase in temperature leads to increase in the Coulomb efficiency of cycling and the amount of electrochemically active metallic lithium; a decrease in the amount of electrochemically inactive metallic lithium, regardless of the presence of lithium polysulfides in the electrolyte. When lithium polysulfides have been introduced into the electrolyte, an increase in the Coulomb efficiency of the metallic lithium cycling and a change in the ratio of various forms of lithium in the cathodic deposits toward an increase in electrochemically active lithium by about 1.5 times are observed. The lithium polysulfides are assumed to contribute to the dissolution of electrochemically inactive metallic lithium, forming an interfacial “sulfide” film at the electrode, which possessed high ionic conductivity and good protective properties, the more so, at elevated temperatures.
The changes in the properties of lithium–sulphur cell components (electrolyte, sulphur and lithium electrodes) during cycling are studied by AC impedance spectroscopy. It is shown that during the ...charge and discharge of lithium–sulphur cells the conductivity of the electrolyte is changed. We believe that the observed changes in the electrolyte conductivity can be explained by the formation of soluble lithium polysulphides by electrochemical reactions. The properties of the electrolyte significantly influence the rate of the electrochemical processes which occur both on the sulphur and lithium electrodes in lithium–sulphur cells.
A simple and convenient method has been developed for the quantitative determination of various forms of lithium in cathodic deposits formed on a stainless steel electrode during cycling, based on ...measuring the amount of hydrogen released during their interaction with protic solvents. The amount and ratio of electrochemically active metallic lithium, electrochemically inactive metallic lithium, and chemically bound lithium in the composition of cathode deposits formed on a steel electrode during galvanostatic cycling in sulfolane and propylene carbonate solutions of LiClO
4
were determined. A method is proposed for determining the amount of an electrolyte solvent chemically reacted with metallic lithium. It has been found that, regardless of the solvent nature, the molar ratio of the reacted solvent to freshly formed lithium lies in the range of 0.84–0.85. It is assumed that the interaction of freshly formed metallic lithium with an electrolyte solvent occurs in a molar ratio of 1 : 1. The underestimated value of the reacted solvent–freshly formed lithium ratio is explained by the interaction of freshly precipitated lithium with a salt anion, which results in the formation of lithium oxide. It has been shown that the rate of destruction of sulfolane during cycling of the lithium electrode is approximately 1.5 times higher than the rate of destruction of propylene carbonate. Propylene carbonate, when interacting with freshly formed metallic lithium, forms surface films with better protective properties than sulfolane, which leads to a decrease in the rate of its interaction with metallic lithium and an increase in the Coulomb efficiency and the duration of the lithium electrode cycling.
A nonideal helium plasma has been compressed to a density of ρ ≈ 14 g/cm
3
at a pressure of
TPa (200 Mbar) in a spherical two-cascade device. The design of the device has been presented and the ...thermodynamic parameters of the helium plasma reached in it have been estimated. Data on the dynamics of the external and internal cascades in the device used to choose the calculation method have been obtained in a preliminary experiment with a hemispherical prototype. The experiment has been performed on the X-ray complex at the Russian Federal Nuclear Center All-Russian Research Institute of Experimental Physics, which includes BIM 234.3000 betatrons with a boundary energy of 60 MeV used in the multipulse bremsstrahlung generation regime with a multichannel optoelectronic system of recording X-ray images. A high-current linear accelerator LIU-R-T and an image detector assembly consisting of photochromic ADC screens have been used in addition to betatrons to detect the compressed shell cavity.
The results of
190
Pt–
4
He dating of placer-forming minerals of platinum (PMP) from the Baimka gold placer cluster (Western Chukotka, Russia) are reported. PMPs are represented by isoferroplatinum ...with a composition of Pt
3 +
x
Fe
1 –
x
and Pt
3
Fe. The concentrations of
190
Pt and
4
He in 14 PMP samples were obtained. The results of
190
Pt–
4
He dating showed the existence of two age clusters of PMP (148 ± 6 and 188 ± 4 Ma) for the first time. The primary sources of PMP, which are similar in their genetic type, but have different ages, are assumed: (1) later, 148 ± 6 Ma of the Baimka Complex (J
3
b) and (2) earlier, 188 ± 4 Ma. PMPs enter alluvial gold placers mainly from the intermediate PGM reservoir, which is composed of rocks of the Volgian stage J
3
v
2–3
(Tithonian). Thus, sedimentary rocks or explosive breccia of andesite–basalt of the Volgian stage could be the PMP source reservoir.
The effect of temperature (40, 50, 60, and 70°C) on the composition of solvate complexes of lithium perchlorate with sulfolane was studied by the method of automated vacuum gravimetry during ...isothermal evaporation of the solvent. It is found that the composition of the solvate complexes of lithium perchlorate with sulfolane is determined by the temperature of their formation. Raising the temperature lowers the number of sulfolane molecules in the solvate complex. A tetrasolvate of lithium perchlorate with sulfolane forms at 40°C, and disolvates form at 50, 60, and 70°C. The composition of solvate complexes of lithium perchlorate with sulfolane is also confirmed via thermogravimetry. It is assumed that the differences between the compositions of the solvate complexes in the lithium perchlorate–sulfolane system at different temperatures are due to differences in their structure.
—
A multichannel hardware and software complex for studying electrochemical cells during charge–discharge cycling is described. The complex consists of 16 identical channel modules controlled by an ...on-board computer. Each channel is a four-band potentiostat/galvanostat that allows the performance of independent experiments. The modules can be hot-swapped during operation. Means are provided for connecting external sensors with an analog output to each channel. Owing to the client–server architecture, it is possible to manage the experiment, obtain measurement results, and remotely administer the device from client computers over a local-area network (LAN) or the Internet. Advanced software for numerical processing and visualization of experimental data is a part of the complex.
The thermodynamic parameters of a strongly nonideal helium plasma obtained in experimental devices of hemispherical and spherical geometries are presented. Under shock-wave loading in the ...hemispherical device, the helium plasma was compressed to a density ρ ≈ 0.76 g cm
–3
by a pressure
P
≈ 83 GPa at a temperature
T
≈ 51000 K. Two-cascade spherical experimental devices of two types were used under quasi-isentropic helium plasma compression. In the devices of the first type at the same initial gas pressure in both cavities of the shells, the helium plasma was compressed approximately by a factor of 200 to a density ρ ≈ 8 g cm
–3
by a pressure
P
≈ 4800 GPa. In the devices of the second type at a ratio of the initial gas pressures in the cavities of about 9: 1, the thermodynamic parameters of a nonideal helium plasma compressed by a factor of 900 to a density ρ ≈ 5 g cm
–3
by a pressure
P
≈ 3700 GPa were determined. The compressed-plasma pressure was determined from the results of gasdynamic computations. An X-ray radiograph consisting of three betatrons and a multichannel optoelectronic X-ray imaging system was used to determine the positions of the boundaries of the gaseous-helium-compressing steel shell.
