Oleg Brylev
Moscow State University
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Featured researches published by Oleg Brylev.
Solid State Ionics | 2002
A. A. Burukhin; Oleg Brylev; Pascal Hany; B. R. Churagulov
Ultrafine powders of LiCoO2 were prepared under mild hydrothermal conditions. Reactant mixtures of aqueous solutions of cobalt (II) nitrate, lithium hydroxide and hydrogen peroxide with different Co/Li and Co/H2O2 ratios were hydrothermally treated at 150–250 °C for 0.5–24 h in a Teflon-lined autoclave. Only HT-LiCoO2 phase was observed by X-ray diffraction (XRD) analysis. Scanning (SEM) and transmission (TEM) electron microscopies revealed the formation of well-crystallized hexagonal platelike particles with average size 70–200 nm. The increase in LiOH concentration results in better crystallinity. Annealing of hydrothermally prepared LiCoO2 at 230 °C leads to decreasing initial capacity from 130 down to 120 mA h/g, but improves cyclability (fade rate drops from 3.1 to 1.6 mA h/g per cycle). Submicrometric particle size and high surface area results in good electrochemical properties for high discharge rate.
Solid State Ionics | 2003
Oleg Brylev; O. A. Shlyakhtin; T. L. Kulova; A. M. Skundin; Yu. D. Tret'yakov
Abstract Thermal decomposition of freeze-dried salt precursors leads to the formation of low-temperature (LT) modification of LiCoO 2 at 350–450 °C. The conversion rate of LT into high-temperature (HT) modification at 850 °C depends greatly on the anion composition of salt precursors and correlates quite well with the appearance of second step at thermogravimetric curves of their thermal decomposition related to the solid-state reaction between Li 2 CO 3 and Co 3 O 4 . Relationship between the appearance of Co 3 O 4 and preferential formation of LT/HT polymorphs at reduced temperatures is discussed. The consecutive formation of LT and HT modifications during solid-state reaction between Li 2 CO 3 and Co 3 O 4 at T >800 °C was observed. LiCoO 2 cathode materials with the domination of LT polymorph demonstrated a better initial discharge capacity while a greater amount of HT modification is accompanied by better reversibility of charge–discharge processes.
Electrochimica Acta | 2003
Oleg Brylev; Fannie Alloin; M. Duclot; J.-L. Souquet; J.-Y. Sanchez
Abstract Single-anion conducting polyether networks have been synthesized and investigated. They have been prepared by cross-linking a quaternary ammonium salt with an unsaturated prepolymer. Anion conducting networks have been prepared with various anions such as F − , Cl − , Br − , I − , BF 4 − and (CF 3 SO 2 ) 2 N − by cross-linking appropriate diallyldimethylammonium salts with an unsaturated polyether. The conductivity measurements revealed that anionic conductivity increases, in the halide serie, with the anion size and more generally with the nucleophilicity decrease. This is mainly related to an increase in charge carriers due to an easier dissociation. The Arrhenius plots are not linear suggesting, as in salt–polymer complexes, a VTF behavior.
Ionics | 1998
Jean Louis Souquet; Fannie Alloin; Oleg Brylev; Michel Duclot; Jean Yves Sanchez
Accurate conductivity measurements as a function of hydrostatic pressure (1 – 5000 bars) and temperature (20 – 150 °C) have been performed on a cationic inorganic glass and a cationic conducting polymer.In both cases, the conductivity decreases with increasing pressure and the variation of Inσ at constant temperature as a function of pressure gives straight lines with slopes which allow an “activation volume”, ΔV*, to be obtained by the relationship (∂lnσ/∂P)T=− (ΔV*/RT). In the case of silver metaphosphate glass, studied below its glass transition temperature, the activation volume (5 cm3⋅mol−1) is temperature independent and equal to the molar volume of the silver cation. Since the transport mechanism implies a free energy barrier, this volume is a real activation volume, corresponding to the difference in volume between a mole of the moving species in its activated transition state and its volume at normal equilibrium.In the case of the sodium conductive polymer, studied above its glass transition temperature, the previous thermodynamic definition does not hold any more because the ionic transport follows a V.T.F. behaviour rather than an Arrhenius law. Consequently, ΔV* is an “apparent activation volume” without a simple physical meaning. Experimental values are higher (20 to 30 cm3⋅mol−1) and decrease with temperature. In this polymer, the mobility of the charge carriers is interpreted in terms of free volume mechanism. From the variations of the apparent activation volume with temperature, the critical free volume Vf* for an elementary displacement is estimated. For the Na+ conductive ionomer Vf* is estimated to be equal to 13 cm3⋅mol−1. This large value would indicate the participation of macromolecular chain segments in the ionic transport.
Russian Journal of Inorganic Chemistry | 2010
S. V. Makaev; V. K. Ivanov; T. L. Kulova; O. S. Polezhaeva; Oleg Brylev; A. M. Skundin; Yu. D. Tret’yakov
The specifics of electrochemical lithium intercalation into nanocrystalline ceria were studied. The lithium capacity of CeO2 − x is discovered to increase systematically as the nanoparticle size shifts down, indicating the potential of nanocrystalline ceria for use in electrochromic applications.
Materials | 2018
Ofok Normakhmedov; Oleg Brylev; Dmitrii Petukhov; Konstantin A. Kurilenko; T. L. Kulova; Elena Tuseeva; A. M. Skundin
A new route for the preparation of nickel and cobalt substituted spinel cathode materials (LiMn1.95Co0.025Ni0.025O4 and Li1.1Mn1.95Co0.025Ni0.025O4) by freeze-drying of acetate precursors followed by heat treatment was suggested in the present work. The experimental conditions for the preparation single-phase material with small particle size were optimized. Single-phase spinel was formed by low-temperature annealing at 700 °C. For discharge rate 0.2 C, the reversible capacities 109 and 112 mAh g−1 were obtained for LiMn1.95Co0.025Ni0.025O4 and Li1.1Mn1.95Co0.025Ni0.025O4, respectively. A good cycle performance and capacity retention about 90% after 30 cycles at discharge rate 0.2–4 C were observed for the materials cycled from 3 to 4.6 V vs. Li/Li+. Under the same conditions pure LiMn2O4 cathode materials represent a reversible capacity 94 mAh g−1 and a capacity retention about 80%. Two independent experimental techniques (cyclic voltammetry at different scan rates and electrochemical impedance spectroscopy) were used in order to investigate the diffusion kinetics of lithium. This study shows that the partial substitution of Mn in LiMn2O4 with small amounts of Ni and Co allows the cyclability and the performance of LiMn2O4-based cathode materials to be improved.
Beilstein Journal of Nanotechnology | 2016
Konstantin A. Kurilenko; O. A. Shlyakhtin; Oleg Brylev; Dmitry I. Petukhov; A.V. Garshev
Nanocomposites of Li1.4Ni0.5Mn0.5O2+ x and amorphous carbon were obtained by the pyrolysis of linear and cross-linked poly(vinyl alcohol) (PVA) in presence of Li1.4Ni0.5Mn0.5O2+ x. In the case of linear PVA, the formation of nanostructured carbon coatings on Li1.4Ni0.5Mn0.5O2+ x particles is observed, while for cross-linked PVA islands of mesoporous carbon are located on the boundaries of Li1.4Ni0.5Mn0.5O2+ x particles. The presence of the carbon framework leads to a decrease of the polarization upon cycling and of the charge transfer resistance and to an increase in the apparent Li+ diffusion coefficient from 10−16 cm2·s−1 (pure Li1.4Ni0.5Mn0.5O2+ x) to 10−13 cm2·s−1. The nanosized carbon coatings also reduce the deep electrochemical degradation of Li1.4Ni0.5Mn0.5O2+ x during electrochemical cycling. The nanocomposite obtained by the pyrolysis of linear PVA demonstrates higher values of the apparent lithium diffusion coefficient, a higher specific capacity and lower values of charge transfer resistance, which can be related to the more uniform carbon coatings and to the significant content of sp2-hybridized carbon detected by XPS and by Raman spectroscopy.
Archive | 2000
Oleg Brylev; M. Duclot; Fannie Alloin; J.-Y. Sanchez; J.-L. Souquet
High pressure studies of solid electrolytes [1] or molten salts mixtures [2] have been a very valuable tool in order to determine the nature of charge carriers and to investigate ionic transport mechanisms. More recently, such studies have concerned polymer electrolytes [3–5]. In that case, ionic transport occurs concurrently by anionic and cationic migrations. This simultaneous transport of anions and cations makes difficult the interpretation of electrical conductivity measurements with temperature and pressure. During this work, we have used a new family of polymer electrolytes in which the transport number of alkali cation is unity because the counter anion is fixed on polymeric chains.
Archive | 2002
A. V. Egorov; Oleg Brylev; O. A. Shlyakhtin; T. L. Kulova; A. M. Skundin; Yury D. Tretyakov
Recent works demonstrated the growing interest to lithium cuprates as cathode materials for secondary lithium batteries. Li2CuO2, having orthorhombic structure (a=3,654 A, b=2,859 A, c=9,374 A) (Arai et al., 1998), is often considered as one of the most perspective among them, though many features of the phase formation mechanism and its relation to electrochemical properties remain underestimated.
Archive | 2002
Oleg Brylev; O. A. Shlyakhtin; A. V. Egorov; T. L. Kulova; A. M. Skundin; S. V. Pouchko
LiCoO2 and LiV3O8 are perspective cathode materials for lithium-ion batteries. Their electrochemical behavior depends on applied synthesis technique. According to West et al. (1996), LiV3O8 prepared by sol-gel technique can accommodate up to 3.5 additional lithium atoms per formula unit contrary to LiV3O8 prepared by slow cooling of the melt (3 lithium atoms). Generally soft chemistry techniques allow to improve the electrochemical performance of cathode materials, giving the reasons for the application of freeze drying technique (Tretyakov et al., 1997) to the preparation of aforementioned materials.