Large Li-Ion Insertion Capacity of Thin-Wall Anatase TiO 2 Nanotubes at 25 °C–55 °C

Anatase TiO2 was prepared in the form of nanotube arrays by anodic oxidation of Ti foil followed by annealing at 400 °C. Electrochemical experiments, which included cyclic voltammetry (CV), galvanostatic (GS) cycling and electrochemical impedance spectroscopy (EIS) were conducted in 1 M solution of LiClO4 in propylene carbonate (PC) at temperatures 25 °C–55 °C. CV experiments, at scan rates 5–50 mV·s−1 , demonstrated with increasing temperature a large increase in the intensity of the redox peaks along with a decrease in the peak-to-peak separation. GS cycling showed large increase of capacity of thin-wall TiO2 nanotubes with increasing temperature, which attains 357 mAh·g−1 at 55 °C during lithiation at current rate 5.3 C, with capacity retention of 98.5% and Coulombic efficiency of 97.5%. Surface storage and development of secondary voltage plateau strongly contribute to such a large capacity value. EIS showed a multiple decrease in solid electrolyte interphase (SEI) layer resistance and charge transfer resistance with temperature rising up to 55 °C

Electrochemical properties of LiFePO4/C composites obtained by ultrasound assisted synthesis at different calcination temperatures

Olivine structure LiFePO4/C composite powders were prepared by combining sonochemical precipitation and calcination at three different temperatures. A polyvinyl alcohol solution was used as the source of an in situ formed carbon. The crystal structures of the powders were revealed by X-ray powder diffraction. Electrochemical properties of the powders calcined at different temperatures were discussed. It was shown that optimal electrochemical performance may be attained by using both slightly reductive atmosphere and moderate temperature of 600 °C.Physical chemistry 2008 : 9th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 200

The crystal structure, microstructure, and dielectric properties of BaTi1-xSnxO3 (x = 0,0.05 and 0.1) ceramics sintered in different atmospheres (air and Ar)

Due to specific dielectric and ferroelectric properties, functional ceramics based on barium titanate (BaTiO3) have found application in semiconductor industries. Appropriate electrical properties of barium titanate-based materials, such as magnitude of relative dielectric permittivity and the Curie temperature, could be achieved by varying the sintering conditions (which influenced ceramics’ microstructure) and/or by doping with various cations. Here, we investigated an influence of sintering atmosphere (air and argon) on the crystal structure, microstructure, and dielectric properties of barium titanate-stannate (BTS; BaTi1-xSnxO3) ceramics. The BTS powders (with x = 0, 0.05 and 0.1; denoted BT, BTS5 and BTS 10, respectively) were synthesized by solid-state reaction technique. In the following, the powders were uniaxially pressed (P = 240 MPa) into cylindrical compacts (Ø6 mm and h approx. 2 mm) and sintered in SETSYS TMA (Setaram Instrumentation, Caluire, France) by heating rate of 10 °/min up 1420 °C and with dwell time of 2 hours. To establish the influence of a sintering atmosphere two sets of experiments were performed: (1) in air, and (2) in Ar. During sintering, the shrinkage was recorded in axial (h) direction. The crystal structure of BTS ceramics were studied at room temperature by X-ray diffractometry and Raman spectroscopy. The microstructure and chemical (Ti/Sn) composition were examined by SEM–EDS methods. The electrical measurements were made in air, at 1 kHz using a Wayne Kerr Universal Bridge B224; the measurements were done in cooling, from 160 to 20 °C. A profound effect of argon atmosphere on the magnitude of relative dielectric permittivity of sintered BTS ceramics has been found

Lithium-ion insertion into anatase TiO2 nanotube arrays at room temperature

High demand for efficient storage devices has set a goal of improving the efficiency of lithium-ion batteries (LIBs), which currently represent the most promising energy storage devices . Most of the commercial LIBs today are composed of graphitic-based anodes, which are not suitable for high performance applications, such as electric vehicles. In this context, there is an increased interest in the development of novel anode materials, with enhanced kinetics. Such an electrode with enhanced capabilities could be TiO2 nanotube arrays (NTAs). In this paper, anatase TiO2 NTAs were prepared by anodization of a Ti foil in the solution of NH4F in glycerol at the voltage of 45 V and subsequent annealing at 400oC. The presence of anatase TiO2 was confirmed by Raman spectroscopy and the morphology was observed by scanning electron microscopy (SEM), while the electrochemical insertion of Liion in nanotubes was studied by means of cyclic voltammetry (CV) and galvanostatic (GS) charge-discharge experiments by exposing the electrode to the 1M solution of LiClO4 in propylene carbonate. The CV response was fast at all scan rates, up to 50 mV·s-1 , with characteristic Ti4+/Ti3+ redox peaks. The Ti/TiO2 NTAs electrode was GC cycled at different current densities (in orders 100, 50, 25 and again 100 µA·cm-2 ) at room temperature. After the initial 50 cycles the insertion/extraction capacity amounted 191.1/170.1 mAh·g-1 . By decreasing the current density, capacity significantly rises to 268.4/243.3 and 347.8/312.3 mAh·g-1 at 50 and 25 µA·cm-2 , respectively. After the last cycle at 100 µA·cm-2 , capacity amounts 188.9/168.1 mAh·g-1 , which is about 99% of the initial capacity. The diffusion coefficient of Li-ion was calculated to be 7.06·10-16 cm2 ·s-1 during deintercalation and 8.16·10-16 cm2 ·s-1 during intercalation.Twentieth Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 30 – December 2, 2022, Belgrade, Serbi

Nanostructured materials for sensing Pb(II) and Cd(II) ions: Manganese oxohydroxide versus carbonized polyanilines?

Nanostructured materials including three different carbonized polyanilines and manganese oxyhydroxide were prepared and evaluated as electrode materials for sensing of lead and cadmium ions in aqueous media. Anodic stripping voltammetry results indicated that all prepared materials could be successfully used for determination of these two heavy metal ions. Carbonized polyaniline-based electrodes have higher signal and lower limits of detection (10-7 М) compared to manganese oxyhydroxide-based electrode. Among the three studied carbonized polyanilines, the one that was derived from polyaniline precursor produced in the presence of 3,5-dinitrosalicyclic acid showed the highest electrocatalytic activity towards the lead and cadmium oxidation. [Projekat Ministarstva nauke Republike Srbije, br. OI172043 i br. III45014

Structure and dielectric caracteristics of BaTi1-xSnxO3 ceramic powders

BaTi1-xSnxO3 (BTS) ceramic powders, with different tin content (x = 0-1) were prepared. The BTS powders were calcined at 1370 °C for 4 hours. The structure of these powders was characterized by XRPD method, tetragonal and cubic crystal structures were noticed. Powders were pressed in pellets and sintered at 1370 °C for 1 hour. The dielectric properties of BTS ceramics were measured and the results were reported.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200

Influence of dimensionality on phase transition in VO2 nanocrystals

Hydrothermally synthesized one-dimensional and two-dimensional nanocrystals of VO2 undergo phase transition around 65°C, where temperature and mechanism of phase transition are dependent on dimensionality of nanocrystals. Both nanocrystalline samples exhibit depression of phase transition temperature compared to the bulk material, the magnitude of which depends on the dimensionality of the nanocrystal. One-dimensional nanoribbons exhibit lower phase transition temperature and higher values of apparent activation energy than two-dimensional nanosheets. The phase transition exhibits as a complex process with somewhat lower value of enthalpy than the phase transition in the bulk, probably due to higher proportion of surface atoms in the nanocrystals. High values of apparent activation energy indicate that individual steps of the phase transition involve simultaneous movement of large groups of atoms, as expected for single-domain nanocrystalline materials. [Projekat Ministarstva nauke Republike Srbije, br. 142015

Synthesis And Structure Of LiMn2-XZnxO4 Through Ultrasonic Spray Pyrolysis

Poster presented at the VIII Conference on Fundamental and. Applied Aspects of Physical Chemistry 2006, Beograd, 26-29. septembar 2006

Synthesis and structure of LiMn2-xZnxO4 through ultrasonic spray pyrolysis

Ultrasonic spray pyrolysis method was used for the synthesis of quaternary spinel oxide LiMn2-xZnxO4 (x ≈ 0.08) powder, without additional annealing. Aqueous solutions of metal nitrates were atomized at a frequency of 1.7 MHz by the ultrasonic nebulizer. Aerosol was introduced in the horizontal electric furnace at the temperature of 1073 K. The crystal structure of the as-prepared powder was revealed by Xray powder diffraction and identified as a single spinel phase with Fd3m space group. Particle morphology was determined by scanning electron microscopy (SEM).Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

Structural and Electrochemical Properties of LiFePo4/C Composites Obtained through Ultrasound Assisted Synthesis

Poster presented at PHYSICAL CHEMISTRY 2008. 9th International Conference on Fundamental and Applied Aspects of Physical Chemistry, Belgrade, September 24-26, 200