Oleg A. Drozhzhin

Sr0.75Y0.25Co0.5Mn0.5O3 − y Perovskite Cathode for Solid Oxide Fuel Cells

The Sr 0.75 Y 0 . 25 Co 0.5 Mn 0.5 O 3-y , (SYCM) oxide with a cubic perovskite structure was examined as a promising cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). The electrical conductivity, thermal expansion coefficient (TEC), and reactivity with gadolinia-doped ceria (GDC) or yttria-stabilized zirconia (YSZ) were studied. Reflections from SrZrO 3 (~6 wt %) after heat-treatment of the SYCM:YSZ mixture at 900°C for 48 h and no reaction after heat-treatment with GDC were observed. In the low and intermediate temperature region (473-873 K), the TEC value is 13.3 ppm K -1 and most closely matches the common IT-SOFC electrolyte material GDC, but the TEC value increases to 19.6 ppm K -1 at 873-1073 K. The investigations of the electrochemical properties of the model SOFCs at 900°C with the SYCM cathode show that substituting the SYCM cathode for the standard (La,Sr)Mn03 cathode improves the cell performance.

Neutron scattering for analysis of processes in lithium-ion batteries

The review is concerned with analysis and generalization of information on application of neutron scattering for elucidation of the structure of materials for rechargeable energy sources (mainly lithium-ion batteries) and on structural rearrangements in these materials occurring in the course of electrochemical processes. Applications of the main methods including neutron diffraction, small-angle neutron scattering, inelastic neutron scattering, neutron reflectometry and neutron introscopy are considered. Information on advanced neutron sources is presented and a number of typical experiments are outlined. The results of some studies of lithium-containing materials for lithium-ion batteries, carried out at IBR-2 pulsed reactor, are discussed. The bibliography includes 50 references.

Synthesis and electrochemical performance of Li2Co1−xMxPO4F (M = Fe, Mn) cathode materials

Summary In the search for high-energy materials, novel 3D-fluorophosphates, Li2Co1− xFexPO4F and Li2Co1− xMnxPO4F, have been synthesized. X-ray diffraction and scanning electron microscopy have been applied to analyze the structural and morphological features of the prepared materials. Both systems, Li2Co1− xFexPO4F and Li2Co1− xMnxPO4F, exhibited narrow ranges of solid solutions: x ≤ 0.3 and x ≤ 0.1, respectively. The Li2Co0.9Mn0.1PO4F material demonstrated a reversible electrochemical performance with an initial discharge capacity of 75 mA·h·g−1 (current rate of C/5) upon cycling between 2.5 and 5.5 V in 1 M LiBF4/TMS electrolyte. Galvanostatic measurements along with cyclic voltammetry supported a single-phase de/intercalation mechanism in the Li2Co0.9Mn0.1PO4F material.

New superconductor LixFe1+δSe (x ≤ 0.07, Tc up to 44 K) by an electrochemical route

The superconducting transition temperature (Tc) of tetragonal Fe1+δSe was enhanced from 8.5 K to 44 K by chemical structure modification. While insertion of large alkaline cations like K or solvated lithium and iron cations in the interlayer space, the [Fe2Se2] interlayer separation increases significantly from 5.5 Å in native Fe1+δSe to >7 Å in KxFe1−ySe and to >9 Å in Li1−xFex(OH)Fe1−ySe, we report on an electrochemical route to modify the superconducting properties of Fe1+δSe. In contrast to conventional chemical (solution) techniques, the electrochemical approach allows to insert non-solvated Li+ into the Fe1+δSe structure which preserves the native arrangement of [Fe2Se2] layers and their small separation. The amount of intercalated lithium is extremely small (about 0.07 Li+ per f.u.), however, its incorporation results in the enhancement of Tc up to ∼44 K. The quantum-mechanical calculations show that Li occupies the octahedrally coordinated position, while the [Fe2Se2] layers remain basically unmodified. The obtained enhancement of the electronic density of states at the Fermi level clearly exceeds the effect expected on basis of rigid band behavior.

The effect of LiFeBO3/C composite synthetic conditions on the quality of the cathodic material for lithium-ion batteries

Composite electrode materials based on LiFeBO3 are synthesized under different conditions and studied as the cathodic materials for lithiumion batteries. Composites with different degrees of iron oxidation are synthesized by annealing in a closed system with the use of metal-oxide getters. Based on the results of cyclic voltammetry and galvanostatic cycling of samples with different Fe(II) contents, it is concluded that the surface composition is the determining factor for applicability of materials to reversible processes of inter-calation-deintercalation.

Synthesis and crystal structure of the new complex cobalt and nickel oxide Sr2.25Y0.75Co1.25Ni0.75O6.84

The complex cobalt and nickel oxide Sr2.25Y0.75Co1.25Ni0.75O6.84 has been synthesized by the citrate method. The oxygen content of the oxide has been determined by iodometric titration. The crystal structure of the compound has been refined using X-ray powder diffraction data (a = 3.7951(2) Å, c = 19.700(1) Å, χ2 = 1.15, RF2 = 0.0586, Rp = 0.0365, Rwp = 0.0462). Sr2.25Y0.75Co1.25Ni0.75O6.84 has the structure of the second member of the Ruddlesden-Popper series An + 1BnO3n + 1.

Neutron diffraction analysis of structural transformations in lithium-Ion batteries

The possibilities of using neutron diffraction in real-time studies of structural transformations occurring in crystalline functional materials during the action of external factors are discussed. As an example, the diffraction patterns are directly collected with 5-min resolution in the course of three charge–discharge cycles of a commercial lithium-ion battery (operando mode). It is shown that the analysis of spectrum evolution allows the main processes occurring in electrode materials to be characterized, namely, to identify the structural transformations, assess the fraction of material involved in the process, follow the kinetics and the degree of symmetry of charge–discharge processes, compare the structural transformations with the charge–discharge characteristic of the battery. The high-resolution neutron diffraction in combination with X-ray diffraction and X-ray spectral elemental analysis makes it possible to elucidate the structural type and composition of the working electrode and determine its microsctructural characteristics. Neutron diffraction is shown to be a powerful method often sufficient for studying structural transformations in complex multi-component objects.

An electrochemical cell with sapphire windows for operando synchrotron X-ray powder diffraction and spectroscopy studies of high-power and high-voltage electrodes for metal-ion batteries

A new multi-purpose operando electrochemical cell was designed, constructed and tested on the Swiss-Norwegian Beamlines BM01 and BM31 at the European Synchrotron Radiation Facility. Single-crystal sapphire X-ray windows provide a good signal-to-noise ratio, excellent electrochemical contact because of the constant pressure between the electrodes, and perfect electrochemical stability at high potentials due to the inert and non-conductive nature of sapphire. Examination of the phase transformations in the Li1-xFe0.5Mn0.5PO4 positive electrode (cathode) material at C/2 and 10C charge and discharge rates, and a study of the valence state of the Ni cations in the Li1-xNi0.5Mn1.5O4 cathode material for Li-ion batteries, revealed the applicability of this novel cell design to diffraction and spectroscopic investigations of high-power/high-voltage electrodes for metal-ion batteries.

Tc-enhancement of Fe1+δSe by electrochemical lithium intercalation

Evgeny Antipov1, Anastasya Alekseeva2, Oleg Drozhzhin2, Olga Volkova1, Alexander Vasiliev3, Dmitry Chareev4, Juri Grin5 1Department of Chemistry, Lomonosov Moscow State University, Moscow, Russian Federation, 2MPG-MSU Partner Group, Department of Chemistry, Lomonosov Moscow State University, Moscow, Russian Federation, 3Department of Physics, Lomonosov Moscow State University, Moscow, Russian Federation, 4Institute of Experimental Mineralogy, Russian Academy of Sciences, Chernogolovka, Russian Federation, 5Max-Planck-Institut für Chemische Physik fester Stoffe, Dresden, Germany E-mail: evgeny.antipov@gmail.com

Electrodeposition of Fe x Se y films from acidic solutions

Iron selenide (FexSey) thin films were electrodeposited on a glassy carbon electrode (GCE) surface under constant potential and pulse potential modes. The deposition mechanism was investigated using cyclic voltammetry. Electrochemical processes at room temperature are accompanied by adsorption of selenium on the electrode surface and complicated by chemical reactions in the solution bulk. Several approaches to control the film stoichiometry were applied: varying of electrodeposition potential; the use of elevated temperatures (60–80°C) to decrease the electrode passivation and electrodissolution of interfering elements under pulse mode. The composition of FexSey thin films was analyzed using an energy dispersive X-rays (EDX) analysis.