Synthesis and characterization of LiNi1/3Co1/3Mn1/3O2 cathode material for rechargeable lithium batteries by polyacrylic acid-assisted sol–gel method

Nanocrystalline LiNi_1/3Co_1/3Mn_1/3O₂ cathode materials are synthesized by sol–gel method using polyacrylic acid as a chelating agent. The effects of the calcination temperature and calcination time on the structure, morphology, and electrochemical performances of the LiNi_1/3Co_1/3Mn_1/3O₂ electrode materials are investigated by X-ray diffraction, scanning electron microscopy and charge–discharge cycling test, respectively. All experiments show that the microscopic structural features and the morphology properties are deeply related with the electrochemical performance. The results show that the nanocrystalline LiNi_1/3Co_1/3Mn_1/3O₂ with a particle size of 80 nm sintered at 700 °C for 2 h presents good α-NaFeO₂ layer structure and the best electrochemical performance. When it is discharged between 4.4 and 2.8 V at 20 mAg^?1, the initial specific capacity of the LiNi_1/3Co_1/3Mn_1/3O₂ obtained at 700 °C for 2 h is 169.2 mAhg^?1. The investigated electrode materials retain 151 mAhg^?1 after 30 cycles when cycled at 20 mAg^?1.     

Synthesis and electrochemical performance of LiNi0.475Mn0.475Al0.05O2 as cathode material for lithium-ion battery from Ni–Mn–Al–O precursor

LiNi_0.475Mn_0.475Al_0.05O₂ cathode material was prepared by solid-state reaction using Ni–Mn–Al–O solid solution as precursor. The solid solution is of spinel structure, in which nickel, manganese, and aluminum are sufficiently mixed at atomic level. Rietveld refinement of X-ray diffraction data revealed that Al doping in LiNi_0.5Mn_0.5O₂ was significantly effective to decrease the degree of Li/Ni cation mixing. XPS analysis showed that the valence states of nickel and manganese were mainly +2 and +4, respectively. LiNi_0.475Mn_0.475Al_0.05O₂ delivered a stable capacity of about 206 mAh g⁻¹ with high reversibility. High-rate capability test was also performed.     

Preparation of BaFe12O19 as anode material for lithium-ion batteries through sol–gel method

The BaFe₁₂O₁₉ nanocrystalline was prepared via a sol–gel process. The structure, morphology and electrochemical properties of the nanocrystallines were detected by means of XRD, TEM, TGA and electrochemical measurements. This BaFe₁₂O₁₉ is firstly used as anode electrode material for lithium-ion batteries. The mechanism of BaFe₁₂O₁₉ with Li will also be discussed. The reversible specific capacity of BaFe₁₂O₁₉ is 959.5 mAh/g. A capacity of 358.3 mAh/g can be retained after 50 cycles which will have a broad space for improvement with modifying.     

Synthesis of SnO2 nanostructures by ultrasonic-assisted sol–gel method

Fluorine doped SnO₂ nanostructures were grown using ultrasonic assisted sol–gel method. The gel was obtained by dissolving stannous chloride in methanol with ammonium fluoride as dopant followed by irradiation with ultrasonic vibrations. Obtained samples were characterized by structural, morphological and optical studies. All the peaks in the X-ray diffractograms are identified and indexed as tetragonal cassiterite structure. Negative slope of Williamson–Hall plots indicates compressive strain. Particle size of SnO₂ nanostructures is decreases with increases in concentration of fluorine doping. Atomic force microscopy, scanning electron microscopy and transmission electron microscopy studies confirm the formation of ring like porous structures and then hollow tube like growth with increase in the fluorine concentration. Peaks in Raman spectra also indicate strong confinement in SnO₂ particles. Distinct peaks in the PL spectra make the structure suitable for photovoltaic applications.     

V2O3/C composite fabricated by carboxylic acid-assisted sol–gel synthesis as anode material for lithium-ion batteries

Journal of Sol-Gel Science and Technology - The potential battery electrode material V2O3/C has been prepared using a sol–gel thermolysis technique, employing vanadyl hydroxide as precursor...     

Synthesis of polyferromethylsiloxane sorbents using a sol–gel method

Trivalent iron complexes which could be easily converted into materials are formed by the reaction of FeCl₃ with K₃[O₃SiMe] in a highly concentrated aqueous alkaline solution. The presence of the liquid glass as an additive and decreasing the pH results in solutions that give rise to homogeneous gels. Polycondensation proceeds very rapidly in the higher pH range (viz. pH 9–10) and substantially slower in an acidic medium (pH 2–3). Xerogels were obtained having microporous structure after treatment of polyferromethylsiloxane gels obtained from acidic medium or mesoporous structure when obtained from alkaline medium.     

Synthesis of novel ZnAl2O4/Al2O3 nanocomposite by sol–gel method and its application as adsorbent

Journal of Sol-Gel Science and Technology - In this research, ZnAl2O4/Al2O3 nanocomposites with different ZnAl2O4 (30, 50, and 70?wt.%) were successfully prepared in one step by sol–gel...     

Mössbauer study of LiFeVPO x as a new cathode material for lithium-ion battery

The Mössbauer spectrum of LiFeVPO _x , LiFeV_0.5PO _x and LiFePO _x glasses prepared by conventional melt-quenching method for cathode active material is composed of a doublet due to distorted Fe^IIIO₄ tetrahedra. The Mössbauer spectrum of LiFePO _x glass has an additional doublet due to distorted Fe^IIO₆ octahedra. Heat treatment of LiFeVPO _x and LiFeV_0.5PO _x glasses at a given temperature close to each crystallization temperature causes a marked decrease in the value of Δ, reflecting a decrease in the distortion or an increase in the local symmetry of distorted Fe^IIIO₄ tetrahedra. Heat treatment of LiFeVPO _x glass causes an increase in the electric conductivity from the order of 10^?7 to 10^?3 S·cm^?1, together with an increase in the specific discharge-and charge-capacity of a coin-type Li-ion cell from 50 to 150 mAh·g^?1. These results prove that structural relaxation of the glass network causes an increase in the electric conductivity and an increase in the energy density of the Li-ion cell.     

Preparation and characterization of magnetic TiO2/ZnFe2O4 photocatalysts by a sol–gel method

A magnetic TiO₂/ZnFe₂O₄ photocatalyst was prepared by a sol-gel method, and X-ray diffraction (XRD), magnetic and photocatalytic properties analysis were employed to characterize this photocatalyst. The XRD results show that ZnFe₂O₄ can prevent the transformation of titania from anatase to rutile. The magnetic properties analysis indicates that TiO₂/ZnFe₂O₄ is of large saturation magnetization value and low coercivity. The photocatalytic experimental results show that TiO₂/ZnFe₂O₄=3 and 4 are superior in photocatalytic reactivity to other proportions. TEM shows that TiO₂/ZnFe₂O₄ has a fine core-shell fabric. After being used for four times during the photocatalytic reaction, the TiO₂/ZnFe₂O₄ nanoparticles have good photocatalytic stability.     

Preparation and electrochemical characterization of Ruddlesden–Popper oxide La4Ni3O10 cathode for IT-SOFCs by sol–gel method

La₄Ni₃O₁₀ oxide was synthesized as a cathode material for intermediate-temperature solid oxide fuel cells by a facile sol–gel method using a nonionic surfactant (EO)106(PO)70(EO)106 tri-block copolymer (F127) as the chelating agent. The crystal structure, electrical conductivity, and electrochemical properties of La₄Ni₃O₁₀ were investigated by X-ray diffraction, DC four-probe method, electrochemical impedance spectra, and I–V measurements. The La₄Ni₃O₁₀ cathode showed a significantly low polarization resistance (0.26 Ω cm²) and cathodic overpotential value (0.037 V at the current density of 0.1 A cm^?2) at 750 °C. The results measured suggest that the diffusion process was the rate-limiting step for the oxygen reduction reaction. The La₄Ni₃O₁₀ cathode revealed a high exchange current density value of 62.4 mA cm^?2 at 750 °C. Furthermore, an anode-supported single cell with La₄Ni₃O₁₀ cathode was fabricated and tested from 650 to 800 °C with humidified hydrogen (～3 vol% H₂O) as the fuel and the static air as the oxidant. The maximum power density of 900 mW cm^?2 was achieved at 750 °C.     

Synthesis and characterization of lead oxide nano-powders by sol–gel method

Our goal in this research was to obtain lead oxide nano-powders by sol–gel method. In this method, lead oxide nano-powders were synthesized through the reaction of citric acid (C₆H₇O₈·H₂O) solution and lead acetate [Pb(C₂H₃O₂)₂] solution as stabilizer and precursor, respectively. The effect of different parameters including calcination temperature, (molar ratio of citric acid to lead acetate) and drying conditions were investigated. The prepared lead oxide nano-powders were characterized by FT-IR spectroscopy, X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. The prepared PbO samples consist of the particles in the range of 50–120 nm or the thick plate like structures with thickness of 53 nm depending on the drying conditions.     

Synthesis and characterization of nanostructured aluminum borate by sol–gel method

Nanostructured aluminum borate was synthesized using sol?Cgel technique. X-ray diffraction study revealed that the synthesized aluminum borate was single crystal. These nanorods have very uniform diameter. High-resolution transmission electron microscope images indicate that aluminum borate is well crystallized. The alternating current (AC) conductivity of the aluminum borate was studied as a function of temperature and frequency. The AC conductivity mechanism of the aluminum borate was found to be proportional to ??^s. The exponent s is almost independent with temperature. This suggests that AC conductivity mechanism of the aluminum borate can be interpreted by localized hopping model.     

Synthesis and characterization of nitrogen-doped TiO2 nanoparticles prepared by sol–gel method

The N-doped TiO₂ has been synthesized by sol?Cgel method, using titanium isopropoxide, isopropanol and an aqueous solution of ammonia with ratio 2:1:10. The concentrations used for the NH₃ aqueous solution were 3, 7, 10 and 15?%. The samples have been analysed by X-ray diffraction, electron microscopy (SEM and TEM) thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), micro-Raman spectroscopy and diffuse reflectivity. TEM, SEM, DSC and TGA showed that the morphology is influenced by the presence of N^3? ions but not by the concentration of the solution. Instead reflectance gave us a relation between values of the energy gap and the concentration of N^3? ions: the gap between valence and conduction band lowers as the concentration of NH₃ in the starting solution increases. From these results we can say that the properties of the material have been tuned by doping with nitrogen ions because the particles absorb more light in the visible range, and this is important for photovoltaic and photocatalytic applications.     

Synthesis and characterization of nanocrystalline tin oxide by sol–gel method

Nanocrystalline SnO₂ particles have been synthesized by a sol–gel method from the very simple starting material granulated tin. The synthesis leads a sol–gel process when citric acid is introduced in the solution obtained by dissolving granulated tin in HNO₃. Citric acid has a great effect on stabilizing the precursor solution, and slows down the hydrolysis and condensation processes. The obtained SnO₂ particles range from 2.8 to 5.1 nm in size and 289–143 m² g⁻¹ in specific surface area when the gel is heat treated at different temperatures. The particles show a lattice expansion with the reduction in particle size. With the absence of citric acid, the precursor hydrolyzes and condenses in an uncontrollable manner and the obtained SnO₂ nanocrystallites are comparatively larger in size and broader in size distribution. The nanocrystallites have been characterized by means of TG-DSC, FT-IR, XRD, BET and TEM.     

Synthesis and characteristics of nanostructured Li(Co1/3Ni1/3Mn1/3)O2 cathode material prepared at 0 °C

Special synthetic conditions at 0 °C were used to prepare nanostructured Li[Ni_1/3Co_1/3Mn_1/3]O₂ via chemical coprecipitation synthesis. The precursor preparation shows platelet shape with thickness of 10 nm and width of 100 nm. After calcination, the particles change to spherical or rectangle shape with a size of 100~200 nm. The nanostructured Li[Ni_1/3Co_1/3Mn_1/3]O₂ shows a well-ordered layered hexagonal lattice with low cation mixing. Galvanostatic testing showed good electrochemical properties and high rate capability, which may be due to its unique morphological and structural characteristics. Synthesis at 0 °C effectively prevented growth of the precursor particles and produced nanosize Li[Ni_1/3Co_1/3Mn_1/3]O₂, which gave improvement in high rate performance and favoring the future use of this cathode material for high power applications.     

Synthesis of a dysprosium aluminum garnet nanopowder via sol–gel method

A dysprosium aluminum garnet (DAG) nanopowder was synthesized by aqueous sol–gel method using Al powder, HCl and Dy(CH₃COO)₃·4H₂O as raw materials. The dried amorphous gel was heat treated in the range of 800–1,200 °C. The influence of heat treatment on crystallization and phase transformation of the dried gel was investigated using X-ray diffractometery, scanning electron microscopy, thermogravimetry and differential thermal analysis and Fourier transform infrared spectroscopy. It was shown that the gel calcined from 900 to 1,200 °C resulted in the formation of a crystalline DAG nanopowder with particle size distribution ranges from 26 to 98 nm.