Molten-salt decomposition synthesis of SnO2 nanoparticles as anode materials for lithium ion batteries

SnO₂ nanoparticles were synthesized by a simple, easily scaled-up molten-salt decomposition method with SnSO₄ as the molten salt and the reactive phase. During the synthesis process, the undecomposed molten SnSO₄ makes it possible to obtain SnO₂ nanoparticles by serving as the dispersion medium and keeping the particles from aggregation. The as-prepared SnO₂ had a tetragonal rutile structure with an average particle size of 50 nm. When used as anode materials for lithium ion battery, SnO₂ nanoparticles retained the charge capacity still as high as 402 mAh g^? 1 at a current density of 156 mA g^? 1 after 40 cycles. Moreover, cyclic voltammograms tests showed the formation/deformation of Li₂O was partially reversible.     

Surfactant-assisted synthesis of Sn nanoparticles via solution plasma technique

We have adopted a solution plasma synthesis for preparing Sn nanoparticles (Sn-NPs) directly from metallic Sn electrode. The Sn-NPs were synthesized in the presence of the surfactant, cetyltrimethylammonium bromide (CTAB), and the effect of the concentration of CTAB on the Sn-NPs was investigated. Without CTAB addition, SnO plates were precipitated. Sn-NPs with less than 200 nm were synthesized at a high concentration of 200 × 10⁻⁶ g ml⁻¹ of CTAB. Electrochemical properties of SnO plates and Sn-NPs were analyzed for use as an anode material in Li-ion batteries. A composite of Sn-NPs and graphite enhanced the cyclic stability owing to the buffer space provided by the graphite for volume expansion. In the case of the 30 wt% loaded Sn-NPs, the capacity was measured to be 414 mA h g⁻¹ after 20 cycles.     

Lithium storage capability of CuGeO3 nanorods

Copper metagermanate (CuGeO₃) nanorods were synthesized through a low temperature hydrothermal method at 180 °C. The as-synthesized CuGeO₃ nanorods show a well crystallined nanostructure with diameters in the range from 40 to 70 nm, and a length from 250 to 350 nm. Electrochemical measurements demonstrate that the CuGeO₃ nanorods exhibit a first charge capacity of 924 mAh g^?1 and 690 mAh g^?1 after 50 cycles, which is remarkably improved than the pure nanosize GeO₂ electrode. This investigation indicates that CuGeO₃ nanorods could be utilized as a high capacity anode material in lithium-ion batteries by reducing particle size and metal oxide addition. The lithium storage mechanisms for the improved capacity retention were also studied.     

Synthesis of SnO2 nanoparticles inside mesoporous carbon via a sonochemical method for highly reversible lithium batteries

A sonochemical method was introduced to synthesize SnO₂ nanoparticles in the pores of mesoporous carbon without any other agents. The nitrogen adsorption measurement and transmission electron microscopy results revealed that the SnO₂ nanoparticles with the average particle size of around 10 nm were homogeneous distribution in the matrix. The aggregation of SnO₂ was hindered by the three-dimensioned porous frameworks, resulting in a relatively large surface area of 362 m² g^? 1, which is beneficial for lithium-ion storage in batteries. The resultant composites with 43% SnO₂ exhibited a high reversible capacity of 200 mAh g^? 1 even after 300 cycles, which is 186% higher than that of the initial mesoporous carbon matrix. This strategy is expected to incorporate other functional nanoparticles inside mesoporous carbon for many applications.     

Nb2O5 hollow nanospheres as anode material for enhanced performance in lithium ion batteries

Nb₂O₅ hollow nanospheres of average diameter ca. ～29 nm and hollow cavity size ca. 17 nm were synthesized using polymeric micelles with core–shell–corona architecture under mild conditions. The hollow particles were thoroughly characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), infrared spectroscopy (FTIR), thermal (TG/DTA) and nitrogen adsorption analyses. Thus obtained Nb₂O₅ hollow nanospheres were investigated as anode materials for lithium ion rechargeable batteries for the first time. The nanostructured electrode delivers high capacity of 172 mAh g^?1 after 250 cycles of charge/discharge at a rate of 0.5 C. More importantly, the hollow particles based electrodes maintains the structural integrity and excellent cycling stability even after exposing to high current density 6.25 A g^?1. The enhanced electrochemical behavior is ascribed to hollow cavity coupled with nanosized Nb₂O₅ shell domain that facilitates fast lithium intercalation/deintercalation kinetics.     

Low temperature growth of SnO2 nanowires by electron beam evaporation and their application in UV light detection

For the first time, high quality tin oxide (SnO₂) nanowires have been synthesized at a low substrate temperature of 450 °C via vapor–liquid–solid mechanism using an electron beam evaporation technique. The grown nanowires have shown length of 2–4 μm and diameter of 20–60 nm. High resolution transmission electron microscope studies on the grown nanowires have shown the single crystalline nature of the SnO₂ nanowires. We investigated the effect of growth temperature and oxygen partial pressure on SnO₂ nanowires growth. Variation of substrate temperature at a constant oxygen partial pressure of 4 × 10⁻⁴ mbar suggested that a temperature equal to or greater than 450 °C was the best condition for phase pure SnO₂ nanowires growth. The SnO₂ nanowires grown on a SiO₂ substrate were subjected to UV photo detection. The responsivity and quantum efficiency of SnO₂ NWs photo detector (at 10V applied bias) was 12 A/W and 45, respectively, for 12 μW/cm² UV lamp (330 nm) intensity on the photo detector..     

The AMWCNTs supported porous nanocarbon composites for high-performance supercapacitor

The porous nanocarbons supported by acid-treated multiwall carbon nanotubes (PC@ACNTs) were prepared by the combination of the hydrothermal polymerization of glucose on ACNTs, carbonization under N₂ protection and final activation with ZnCl₂. The materials were characterized by transmission electron microscopy, X-ray powder diffraction and Raman spectra. The results indicated that the ACNTs distributed uniformly into the framework of the porous carbon. The composites showed the high BET specific surface area up to 1712 m² g⁻¹ and good conductivity. The electrochemical measurements indicated that the composites processed good performances for electrochemical energy storage (210 F g⁻¹ at 0.5 A g⁻¹), and high stability (>99.9%), much higher than the corresponding ACNTs, porous carbons and the samples prepared by using raw MWCNTs as source. The good performance of PC@ACNTs composites was relative with the synergy of good conductivity of ACNTs and large specific surface areas of PC.     

Structural,optical and morphological properties of La,Cu co-doped SnO2 nanocrystals by co-precipitation method

Sn_0.96−xLa_0.04Cu_xO₂ (0 ⩽ x ⩽ 0.03) nanocrystals have been successfully synthesized by employing a simple co-precipitation method. The crystal structure of the synthesized nanocrystals was found to be tetragonal rutile of tin oxide by using X-ray diffraction technique and was not affected by doping. The change in lattice parameters was discussed based on the secondary phase formation and presence of Cu²⁺/Cu³⁺ in LaSnO₂ lattice. The variation in size and shape of the nanocrystals by Cu-doping was discussed using scanning electron microscope. The chemical stoichiometry of Sn, Cu, La and O was confirmed by energy dispersive X-ray spectra. The best optical transparency and lower absorption observed at Sn_0.97La_0.02Cu_0.01O₂ nanocrystals seems to be optimal for industrial applications especially as transparent electrode. The initial blue shift of energy gap from 3.65 eV (Cu = 0%) to 3.78 eV (Cu = 1%) (ΔE_g ≈ 0.13 eV) is due to the distortion in the crystal structure of the host compound and generation of defects. The red shift of energy gap after Cu = 1% is due to the charge-transfer transitions between the metal ions d-electrons and the SnO₂ conduction or valence band. Lattice mode of SnO₂ at 686 cm⁻¹ in Sn_0.98La_0.02O₂ nanocrystals and anti-symmetric SnOSn stretching mode of the surface bridging oxide around 634–642 cm⁻¹ in Cu doped Sn_0.98La_0.02O₂ nanocrystals was confirmed by Fourier transform infrared spectra.     

Study on the behaviour of ZnCoCu alloy electroplating

Ternary zinc–cobalt–copper alloys of wide range composition were deposited on to steel substrates from dilute metal sulphate bath. The bath consisted of 1–20 g dm⁻³ CuSO₄·5H₂O, 1–30 g dm⁻³ CoSO₄·7H₂O, 1–50 g dm⁻³ ZnSO₄·7H₂O, 20 g dm⁻³ Na₂SO₄ and 150–200 g dm⁻³ NH₂CH₂COOH. The effect of bath composition, current density and temperature on the cathodic potential, cathodic current efficiency and composition of the deposits were investigated. The codeposition of ZnCoCu alloys from these solutions can be classified as regular. Increasing current density enhances the rate of Zn deposition but suppresses that of Cu deposition. However, increasing the bath temperature favours Cu deposition. Co content in the deposits is hardly affected by changing these variables. Increasing Cu content in the bath or increasing the applied current density greatly improves the cathodic efficiency for the alloy deposition. X-ray diffraction studies showed that the deposits obtained at high current density (Zn-rich alloy) consisted of a cubic CuZn₂ phase, while that obtained at high temperature (Cu-rich alloy) consisted of a face, centred cubic CuCo phase. The structure and morphology of the deposited alloys were characterised by anodic stripping and SEM.     

Non-hydrothermal synthesis of mesoporous materials using sodium silicate from coal fly ash

Siliceous mesoporous materials with pores of ordered 2-D hexagonal structure were successfully prepared without hydrothermal treatment from condensation–polymerization of various concentration of quaternary ammonium salt as structure directing agents and silica precursor from the supernatant of coal fly ash (CFA) in the presence of catalyst. The synthesized materials had high surface area of ca. 740 m² g⁻¹ and pore volume of ca. 0.42 mL g⁻¹. The synthesized material exhibited a narrow size pore distribution and the mean pore diameter as measured by Dollimore–Heal method was about 2.3 nm. The formation of ammonium salt that act as precipitant during the synthesis enable the hydrolysis and co-condensation of the sodium silicate at room temperature.     

Extremely high surface area of ordered mesoporous MCM-41 by atrane route

Silatrane synthesized from inexpensive oxide precursor, silica and TEA was used as the precursor for MCM-41 synthesis at low temperature because of its stability in aqueous solutions. Using cationic surfactant hexadecyltrimethyl ammonium bromide (CTAB) as a template, the resulting meso-structure mimics the liquid crystal phase. Varying the surfactant concentration, ion concentration and temperature of the system, changes the structure of the liquid crystal phase, resulting in different pore structures and surface area. After heat treatment, very high surface area mesoporous silica was obtained and characterized using XRD, BET and TEM. XRD and TEM results show a clear picture of hexagonal structure. The surface area is extraordinarily high, up to more than 2400 m² g⁻¹ at a pore volume of 1.29 cm³ g⁻¹. However, the pore volume is up to 1.72 cm³ g⁻¹ when the surface area is greater than 2100 m² g⁻¹.     

Enhanced H2S gas sensing properties of multiple-networked Pd-doped SnO2-core/ZnO-shell nanorod sensors

Pd-doped SnO₂-core/ZnO-shell nanorods were synthesized by using a three-step process: thermal evaporation of Sn powders in an oxygen atmosphere, atomic layer deposition of ZnO, and Pd diffusion followed by annealing. The sensitivity of the multiple networked SnO₂-core/ZnO-shell nanorod sensor to H₂S gas was found to be improved further significantly by Pd doping. The Pd-doped SnO₂-core/ZnO-shell nanorod sensor showed sensitivities of 6.4, 15.4, and 36.2% at H₂S concentrations of 20, 50, and 100 ppm at room temperature. The sensitivity of the nanorods was improved by more than 10 times at a H₂S concentration of 100 ppm. The sensitivity enhancement of the SnO₂-core/ZnO-shell nanorods by Pd doping may be attributed to the spillover effect, active reaction site generation, and the enhancement of chemisorption and dissociation of gas.     

Effect of solvent ratio on the properties of highly oriented sprayed fluorine-doped tin oxide thin films

Transparent conducting thin films of F:SnO₂ have been deposited onto preheated glass substrates by a spray pyrolysis technique using pentahydrate stannic chloride (SnCl₄·5H₂O) and ammonium fluoride (NH₄F) as precursors and mixture of water and propane-2-ol as solvent. The concentration of SnCl₄·5H₂O and NH₄F is kept fixed and the ratio of water and propane-2-ol solvent in the spraying solution is varied. A fine spray of the source solution using air as a carrier gas has grown films of thickness up to 995 nm. Optical absorption, X-ray diffraction, Van der Pauw technique for measurement of a sheet resistance and Hall effect measurements at room temperature for determination of carrier density and conductivity have been used. The as-deposited films are of polycrystalline SnO₂ with a tetragonal crystal structure and are preferentially having orientation along the (200) direction with texture coefficient as high as 6.16. The average grain size for the as-deposited sample is found to be of the order of 44 nm. The films have moderate optical transmission (up to 70–85% at 550 nm). The figure of merit (ϕ) values vary from 1.95 · 10^− 3 to 35.68 · 10^− 3 Ω^− 1. The films are heavily doped, degenerate and exhibit n-type electrical conductivity. The lowest sheet resistance (R_s) for the optimized sample is 5.1 Ω. The films have a resistivity of 5.43 · 10^− 4 Ω cm and mobility around 7.38 cm² V^− 1 s^− 1.     

Synthesis and electrochemical performance of a simple and low-cost sulfur/porous carbon composite cathode for rechargeable lithium sulfur battery

The sugar and phenolic resin were used as source materials to prepare porous carbons labeled as PC1 and PC2 respectively, which were activated by chemical methods with CaCO₃ as active agent. Sulfur/porous carbon composites were synthesized by thermally treating a mixture of sublimed sulfur and porous carbon. The morphology, structure, and electrochemical performance of the composite were investigated by scanning electron microscopy, Brunauer–Emmett–Teller, and a variety of electrochemical techniques. The electrochemical measurements show that the SPC2 electrode presents a more favorable electrochemical kinetics than the SPC1 electrode. In comparison with SPC1, it is shown that the rate of Li⁺ diffusion with SPC2 is significantly higher and the charge transfer resistance is much lower. The PC2 with high surface area (735.2 m² g⁻¹) and large pore volume (1.56 cm³ g⁻¹) not only increases the electronic conductivity of composites, but also facilitates transfer of the Li ion in the composite electrode.     

Improvement of cycle stability at elevated temperature and high rate for LiNi0.5−xCuxMn1.5O4 cathode material after Cu substitution

A series of Cu-substituted LiNi_0.5−xCu_xMn_1.5O₄ (x = 0, 0.03, 0.05 and 0.08) spinels have been synthesized using a sol–gel method. The results demonstrate that when x = 0.05, the sample (LiNi_0.45Cu_0.05Mn_1.5O₄) exhibits the best electrochemical performance, achieving 124.5 mAh g⁻¹ and 115.0 mAh g⁻¹ at the discharge rates of 5 C and 20 C with the capacity retention of 97.7% and 95.7% after 150 cycles, respectively. Besides, the excellent cycle stability at 55 °C has been demonstrated to retain 96.8% of the maximum attainable discharge capacity (127.3 mAh g⁻¹) at the discharge rate of 5 C after 100 cycles. These data indicate that the LiNi_0.45Cu_0.05Mn_1.5O₄ cathode material has the real potential to be used for high power and high energy lithium ion battery in electric vehicle applications.     

Synthesis of SnO2 nanoparticles through the controlled precipitation route

The controlled precipitation method allowed to the synthesis of SnO₂ with advantageous specific properties, such as size and shape employing an aqueous SnCl₂·2H₂O solution as precursor. Through XRD analyses, the optimum pH value of the solution that yielded the desired product was found to be 6.25. After a thermal treatment at 600 °C, the final powder presented an average particle size below 50 nm with a surface area of 19 m² g⁻¹ and a large reactivity. The evolution of the most important functional groups during the steps involved in this synthesis route is explained in view of the results obtained with FTIR and XRD. A thorough discussion on the different intermediates involved in the whole process is presented on the basis of hydrolysis and condensation reactions. The conclusions are supported with a complete characterization through differential and gravimetric thermal analysis (DTA/TGA), electron microscopies (SEM/TEM) and surface area determinations (BET).     

Controlled synthesis of mesoporous α-Fe2O3 nanorods and visible light photocatalytic property

Porous α-Fe₂O₃ nanorods with typical pore size of 2–4 nm were controlled prepared by a facile hydrothermal process of Fe(NO₃)₃·9H₂O aqueous solution in the presence of NaOH, followed by a calcination treatment. Contrast experiments indicate that the morphology and crystalline structure of the hydrothermal products depend greatly on the quantity of NaOH. Hematite nanoparticles and microplates were respectively obtained under conditions without or with excess NaOH. The porous α-Fe₂O₃ nanorods exhibit a high BET surface area of 105.1 m² g^?1 and a pore volume of 0.13 m³ g^?1. UV–vis measurement shows wide absorption to visible light and an obvious blue-shift of the adsorption edge due to the quantum size effect. The visible-light photocatalytic performances of the as-prepared samples were evaluated by photocatalytic decolorization of methylene blue at ambient temperature. The results indicate that the photocatalytic activity of the porous α-Fe₂O₃ nanorods is superior to hematite nanoparticles and platelets and exhibit good reusable feature. The photocatalytic process of porous structure is determined to be pseudo-first-order reaction with apparent reaction rate constant of 1.04 × 10^?2 min^?1. And the optimum photocatalyst dosage is 20 mg per 100 mL of dye solution. The porous α-Fe₂O₃ nanorods are considered potential photocatalyst for practical application due to the excellent photocatalytic behavior and good reusability.     

Multifunctional CuO nanowire embodied structural supercapacitor based on woven carbon fiber/ionic liquid–polyester resin

Novel structural supercapacitors based on CuO nanowires and woven carbon fiber (WCF) has been developed for the first time employing vacuum assisted resin transfer molding (VARTM) process. The growth of CuO nanowires on WCF is an efficient process and can be used in structural capacitors which can trigger the electric vehicle industries toward a new direction. The specific surface area of the carbon fiber was enhanced by NaOH etching (41.36 m² g⁻¹) and by growing CuO nanowires (132.85 m² g⁻¹) on the surface of the WCF. The specific capacitance of the CuO–WCF based supercapacitor was 2.48 F g⁻¹, compared with 0.16 F g⁻¹ for the bare WCF-based supercapacitor. The usage of ionic liquid and lithium salt improved the capacitance to 5.40 and 6.75 F g⁻¹ with lowest ESR and R_p values of 133 and 1240 Ω along with improving mechanical properties within an acceptable range. The energy and power densities were also increased up to 106.04 mW h kg⁻¹ and 12.57 W kg⁻¹. Thus, this study demonstrated that growing CuO nanowires on the surface of WCF is a novel approach to improve multifunctionality that could be exploited in diverse applications such as electric cars, unmanned aerial vehicles (UAVs), and portable electronic devices.     

Solution combustion synthesis of LiMn2O4 fine powders for lithium ion batteries

In this work, fine powders of spinel-type LiMn₂O₄ as cathode materials for lithium ion batteries (LIBs) were produced by a facile solution combustion synthesis using glycine as fuel and metal nitrates as oxidizers. Single phase of LiMn₂O₄ products were successfully prepared by SCS with a subsequent calcination treatment at 600–1000 °C. The structure and morphology of the powders were studied in detail by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The electrochemical properties were characterized by galvanostatic charge–discharge cycling and cyclic voltammetry. The crystallinity, morphology, and size of the products were greatly influenced by the calcination temperature. The sample calcined at 900 °C had good crystallinity and particle sizes between 500 and 1000 nm. It showed the best performance with an initial discharge capacity of 115.6 mAh g⁻¹ and a capacity retention of 93% after 50 cycles at a 1 C rate. In comparison, the LiMn₂O₄ sample prepared by the solid-state reaction showed a lower capacity of around 80 mAh g⁻¹.     

Synthesis and electrochemical properties of nanosized LiFeO2 particles with a layered rocksalt structure for lithium batteries

Layered rocksalt-type LiFeO₂ particles (O3-LiFeO₂) with average particle sizes of ca. 40 and 400 nm were synthesized by an ion exchange reaction from α-NaFeO₂ precursors. X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images confirmed the formation of nanosized O3-LiFeO₂. 40-nm LiFeO₂ exhibited a higher discharge capacity (115 mAh g^?1) than 400-nm LiFeO₂ (80 mAh g^?1), and also had better rate characteristics. The downsizing effect and cation disorder between the lithium and iron layers may have improved the electrochemical activity of the LiFeO₂ particles. Transmission electron microscopy (TEM) observation indicated a phase transition from O3-LiFeO₂ to a cubic lattice system during the electrochemical process. The cubic lithium iron oxide exhibited stable electrochemical reactions based on the Fe²⁺/Fe³⁺ and Fe²⁺/Fe⁰ redox couples at voltages between 4.5 and 1.0 V. The discharge capacities of 40-nm LiFeO₂ were ca. 115, 210, and 390 mAh g^?1 under cutoff voltages of 4.5–2.0 V, 4.5–1.5 V, and 4.5–1.0 V, respectively.