Structural and electrochemical properties of a porous nanostructured SnO2 film electrode for lithium-ion batteries

A B₂O₃-doped SnO₂ thin film was prepared by a novel experimental procedure combining the electrodeposition and the hydrothermal treatment, and its structure and electrochemical properties were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, energy dispersive X-ray (EDX) spectroscopy and galvanostatic charge–discharge tests. It was found that the as-prepared modified SnO₂ film shows a porous network structure with large specific surface area and high crystallinity. The results of electrochemical tests showed that the modified SnO₂ electrode presents the largest reversible capacity of 676 mAh g^?1 at the fourth cycle, close to the theoretical capacity of SnO₂ (790 mAh g^?1); and it still delivers a reversible Li storage capacity of 524 mAh g^?1 after 50 cycles. The reasons that the modified SnO₂ film electrode shows excellent electrochemical properties were also discussed.     

ZIF-8 derived nano-SnO2@ZnO as anode for Zn/Ni secondary batteries

SnO₂@ZnO was synthesized by a new method involving the immobilization of Sn onto zeolitic imidazolate framework-8 (ZIF-8) followed by calcination. The synthesized nanoparticles were characterized as 20–30 nm spherical ZnO particles uniformly dotted with SnO₂. When SnO₂@ZnO were used as anode material for Zn/Ni batteries, the average specific capacity was approximately 600 mAh g^− 1 and remained stable after 150 cycles at a rate of 1 C.     

Partially reduced SnO2 nanoparticles anchored on carbon nanofibers for high performance sodium-ion batteries

One-dimensional (1-D) carbon nanofibers anchored with partially reduced SnO₂ nanoparticles (SnO₂/Sn@C) were successfully synthesized through a simple electrospinning method followed by carbon coating and thermal reduction processes. The partially reduced Sn frameworks, combined with the carbon fibers, provide a more favorable mechanism for sodiation/desodiation than SnO₂. As a result, SnO₂/Sn@C exhibits a high reversible capacity (536 mAh g^− 1 after 50 cycles) and an excellent rate capability (396 mAh g^− 1 even at 2 C rate) when evaluated as an anode material for sodium-ion batteries (SIBs).     

Fe-doped SnO2 transparent semi-conducting thin films deposited by spray pyrolysis technique: Thermoelectric and p-type conductivity properties

In this paper, we report structural, electrical, optical, and especially thermoelectrical characterization of iron (Fe) doped tin oxide films, which have been deposited by spray pyrolysis technique. The doping level has changed from 0 to 10 wt% in solution ([Fe]/[Sn] = 0–40 at% in solution). The thermoelectric response versus temperature difference has exhibited a nonlinear behavior, and the Seebeck coefficient has been calculated from its slope in temperature range of 300–500 K. The Hall effect and thermoelectric measurements have shown p-type conductivity in SnO₂:Fe films with [Fe]/[Sn] ≥ 7.8 at%. In doping levels lower than 7.8 at%, SnO₂:Fe films have been n-type with a negative thermoelectric coefficient. The Seebeck coefficient for SnO₂:Fe films with 7.8 at% doping level has been obtained to be as high as +1850 μV/K. The analysis of as-deposited samples with thicknesses ～350 nm by X-ray diffraction (XRD) and scanning electron microscopy (SEM) has shown polycrystalline structure with clear characteristic peak of SnO₂ cassiterite phase in all films. The optical transparency (T%) of SnO₂:Fe films in visible spectra decreases from 90% to 75% and electrical resistivity (ρ) increases from 1.2 × 10^?2 to 3 × 10³ Ω cm for Fe-doping in the range 0–40 at%.     

Optical and electrical conducting properties of Polyaniline/Tin oxide nanocomposite

Polyaniline(PANI)/Tin oxide (SnO₂) hybrid nanocomposite with a diameter 20–30 nm was prepared by co-precipitation process of SnO₂ through in situ chemical polymerization of aniline using ammonium persulphate as an oxidizing agent. The resulting nanocomposite material was characterized by different techniques, such as X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Fourier Transform Infrared spectroscopy (FT-IR) and Ultraviolet–Visible spectroscopy (UV–Vis), which offered the information about the chemical structure of polymer, whereas electron microscopy images provided information regarding the morphology of the nanocomposite materials and the distribution of the metal particles in the nanocomposite material. SEM observation showed that the prepared SnO₂ nanoparticles were uniformly dispersed and highly stabilized throughout the macromolecular chain that formed a uniform metal-polymer nanocomposite material. UV–Vis absorption spectra of PANI/SnO₂ nanocomposites were studied to explore the optical behavior after doping of nanoparticles into PANI matrix. The incorporation of SnO₂ nanoparticles gives rise to the red shift of π–π¹ transition of polyaniline. Thermal stability of PANI and PANI/SnO₂ nanocomposite was investigated by thermogravimetric analysis (TGA). PANI/SnO₂ nanocomposite observed maximum conductivity (6.4 × 10^?3 scm^?1) was found 9 wt% loading of PANI in SnO₂.     

SnO2@MWCNT nanocomposite as a high capacity anode material for sodium-ion batteries

We report the synthesis and characterization of SnO₂@multiwalled carbon nanotubes (MWCNTs) nanocomposite as a high capacity anode material for sodium-ion battery. SnO₂@MWCNT nanocomposite was synthesized by a solvothermal method. SEM and TEM analyses show the uniform distribution of SnO₂ nanoparticles on carbon nanotubes. When applied as anode materials in Na-ion batteries, SnO₂@MWCNT nanocomposite exhibited a high sodium storage capacity of 839 mAh g^− 1 in the first cycle. SnO₂@MWCNT nanocomposite also demonstrated much better cycling performance than that of bare SnO₂ nanoparticles and bare MWCNTs. Furthermore, the nanocomposite electrode also showed a good cyclability and an enhanced Coulombic efficiency on cycling.     

Efficient passivation of SnO2 nano crystallites by Indoline D-149 via dual chelation

For the first time in SnO₂ based dye solar cells, here we report, efficiency exceeding 3% of the cells consisting with Indoline D-149 dye with unmodified SnO₂ nano-crystallites. The cells sensitized with metal free D-149 dye together with liquid electrolyte comprising with 0.5 M tetrapropyl ammonium iodide and 0.05 M iodine in a mixture of acetonitrile and ethylene carbonate (1:4 by volume) delivered a short circuit current density of 10.4 mA cm^?2 with an open circuit voltage of 530 mV under the illumination of 100 mW cm^?2 (AM1.5) having an efficiency of 3.1%. As evident from the FTIR measurement, strong surface passivation of recombination centers of SnO₂ crystallites due to the dual mode of attachment of dye molecules to the surface of SnO₂ via both COOH and S–O direct bond might be the possible reason for this enhancement in these SnO₂ based cells.     

Polyol-mediated synthesis of ultrafine tin oxide nanoparticles for reversible Li-ion storage

A simple, cheap and versatile, polyol-mediated fabrication method has been extended to the synthesis of tin oxide nanoparticles on a large scale. Ultrafine SnO₂ nanoparticles with crystallite sizes of less than 5 nm were realized by refluxing SnCl₂ · 2H₂O in ethylene glycol at 195 °C for 4 h under vigorous stirring in air. The as-prepared SnO₂ nanoparticles exhibited enhanced Li-ion storage capability and cyclability, demonstrating a specific capacity of 400 mAh g⁻¹ beyond 100 cycles.     

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.     

Electrospun porous SnO2 nanotubes as high capacity anode materials for lithium ion batteries

Porous SnO₂ nanotubes were prepared via electrospinning followed by calcination in air. As anode materials for lithium ion batteries, the porous nanotubes delivered a high discharge capacity of 807 mAh g^? 1 after 50 cycles. Even after cycled at high rates, the electrode still retained a high fraction of its theoretical capacity. Such excellent performances of porous SnO₂ nanotubes could be attributed to the porous and hollow structure which facilitated liquid electrolyte diffusion into the bulk materials and buffered large volume changes during lithium ions insertion/extraction. Furthermore, the nanoparticles of nanotubes provided the shorter diffusion length for lithium ions insertion which benefited in retaining the structural stability and good rate performance. Our results demonstrated that this simple method could be extended for the synthesis of porous metal oxide nanotubes with high performances in the applications of lithium ion batteries and other fields.     

Microstructures and electrochemical hydrogen storage properties of novel Mg–Al–Ni amorphous composites

The amorphous Mg–Al–Ni composites were prepared by mechanical ball-milling of Mg₁₇Al₁₂ with x wt.% Ni (x = 0, 50, 100, 150, 200). The effects of Ni addition and ball-milling parameters on the electrochemical hydrogen storage properties and microstructures of the prepared composites have been investigated systematically. For the Mg₁₇Al₁₂ ball-milled without Ni powder, its particle size decreases but the crystal structure does not change even the ball-milling time extending to 120 h, and its discharge capacity is less than 15 mAh g^?1. The Ni addition is advantageous for the formation of Mg–Al–Ni amorphous structure and for the improvement of the electrochemical characteristics of the composites. With the Ni content x increasing, the composites exhibit higher degree of amorphorization. Moreover, the discharge capacity of the composite increases from 41.3 mAh g^?1 (x = 50) to 658.2 mAh g^?1 (x = 200) gradually, and the exchange current density I₀ increases from 67.1 mA g^?1 (x = 50) to 263.8 mA g^?1 (x = 200), which is consistent with the variation of high-rate dischargeability (HRD). The ball-milled Mg₁₇Al₁₂ + 200 wt.% Ni composite has the highest cycling discharge capacity in the first 50 cycles.     

A novel process to prepare porous membranes comprising SnO2 nanoparticles and P(MMA-AN) as polymer electrolyte

We have successfully developed a new process to prepare porous poly(methyl methacrylate-co-acrylonitrile) (P(MMA-AN)) copolymer based gel electrolyte. The porous structure in the polymer matrix is achieved by adding SnO₂ nanoparticles which are mostly used as gas sensor materials. The quasi-aromatic solvent, NMP, has an electron-repulsion effect with the space charge layer on the surface of SnO₂ nanoparticles and forms a special gas–liquid phase interface. Once the cast polymer solution is stored at an elevated temperature to evaporate the solvent, gas–liquid phase separation happens and spherical pores are obtained. The ionic conductivity at room temperature of the prepared gel polymer electrolyte based on the porous membrane is as high as 1.54 × 10⁻³ S cm⁻¹ with the electrochemical stability up to 5.10 V (vs. Li/Li⁺). This method presents another promising way to prepare porous polymer electrolyte for practical use.     

NiCo2O4 nanosheets supported on Ni foam for rechargeable nonaqueous sodium–air batteries

NiCo₂O₄ nanosheets supported on Ni foam were synthesized by a solvothermal method. A composite of NiCo₂O₄ nanosheets/Ni as a carbon-free and binder-free air cathode exhibited an initial discharge capacity of 1762 mAh g^− 1 with a low polarization of 0.96 V at 20 mA g^− 1 for sodium–air batteries. Na₂O₂ nanosheets were firstly observed as the discharged product in sodium–air battery. High electrocatalytic activity of NiCo₂O₄ nanosheets/Ni made it a promising air electrode for rechargeable sodium–air batteries.     

Synthesis,characterization and electrocatalytic activity for ethanol oxidation of carbon supported Pt,Pt–Rh,Pt–SnO2 and Pt–Rh–SnO2 nanoclusters

Nanoclusters of Pt, Pt–Rh, Pt–SnO₂ and Pt–Rh–SnO₂ were successfully synthesized by polyol method and deposited on high-area carbon. HRTEM and XRD analysis revealed two phases in the ternary Pt–Rh–SnO₂/C catalyst: solid solution of Rh in Pt and SnO₂. The activity of Pt–Rh–SnO₂/C for ethanol oxidation was found to be much higher than Pt/C and Pt–Rh/C and also superior to Pt–SnO₂/C. Quasi steady-state measurements at various temperatures (30–60 °C), ethanol concentrations (0.01–1 M) and H₂SO₄ concentrations (0.02–0.5 M) showed that Pt–Rh–SnO₂/C is about 20 times more active than Pt/C in the potential range of interest for the fuel cell application.     

Improved electrochemical performance of SrCo0.8Fe0.2O3−δ–La0.45Ce0.55O2−δ composite cathodes for IT-SOFC

The performance of the SrCo_0.8Fe_0.2O_3−δ(SCF)–La_0.45Ce_0.55O_2−δ(LDC) composite cathodes was studied in this paper. The composite cathodes were prepared by screen-printing, and then sintered at 1200 °C for 2 h. Electrochemical impedance spectroscopy (EIS) and cathodic polarization test were carried out to investigate the electrochemical properties of the composite cathodes. The results showed that the composite cathodes had superior electrochemical performance compared to that of the pure SCF cathodes. Through optimizing the structures of composite cathodes, the cathodic overpotential of triple-layer SCF–LDC composite cathodes was only 23 mV at 0.3 A cm⁻². The specific ohmic resistance, charge transfer resistance and gas phase diffusion resistance of the triple-layer SCF–LDC cathodes were the lowest for the SCF–LDC composite cathodes, and they were 0.1 Ω cm², 0.01 Ω cm² and 0.1 Ω cm² respectively at 800 °C. The changes were attributable to the enlargement of triple phases boundary (tpb) and enhancement of the adhesion between electrode and electrolyte by adding LDC to the cathode material.     

Si–AB5 composites as anode materials for lithium ion batteries

The Si–AB₅ (MmNi_3.6Co_0.7Al_0.3Mn_0.4 alloy) composites with a high tap density as anode materials for lithium-ion batteries were synthesized by ball-milling. Si nanoparticles are distributed homogeneously on the surface of the AB₅ matrix. The electrochemical performance of the Si–AB₅ composites as a function of Si content was investigated. It is demonstrated that the Si–AB₅ composite delivers a larger reversible capacity and better cycle ability because the inactive AB₅ alloy can accommodate the large volume changes of Si nanoparticles distributed on the surface of the Si–AB₅ composite during cycling. In particular, the Si–AB₅ composite containing 20 wt% Si with the high tap density of 2.8 g/cm³ obtained after ball-milling for 11 h exhibits an initial and maximum reversible (charge) capacity of 370 and 385 mAh/g. The high capacity retention can be achieved after 50 cycles in the potential range from 0.02 to 1.5 V.     

Development of novel low-temperature SOFCs with co-ionic conducting SDC-carbonate composite electrolytes

A series of ceria-based composite materials consisting of samaria doped ceria (SDC) and binary carbonates(Li₂CO₃–Na₂CO₃) were examined as functional electrolytes for low-temperature solid oxide fuel cells (SOFCs). DTA and SEM techniques were applied to characterize the phase- and micro-structural properties of the composite materials. Conductivity measurements were carried on the composite electrolytes with a.c. impedance in air. A transition of ionic conductivity with temperature was occurred among all samples with different carbonate content, which related to the interface phase. Single cells based on the composite electrolytes, NiO as anode and lithiated NiO as cathode, were fabricated by a simple dry-pressing process and tested at 400–600 °C. The maximum output power at 600 °C increased with the carbonate content in the composite electrolytes, and reached the maximum at 25 wt.%, then decreased. Similar trend has also shown at 500 °C, but the maximum was obtained at 20wt.%. The best performances of 1085 mW cm⁻² at 600 °C and 690 mW cm⁻² at 500 °C were achieved for the composite electrolytes containing 25 and 20 wt.% carbonates, respectively. During fuel cell operation, it found that the SDC-carbonate composites are co-ionic (O²⁻/H⁺) conductors. At lower carbonate contents, both oxide–ion and proton conductions were significant, when the content increased to 20–35 wt.%, proton conduction dominated. The detailed conduction mechanism in these composites needs further investigation.     

Composite cathode for IT-SOFC: Sr-doped lanthanum cuprate and Gd-doped ceria

Composite cathodes were synthesized via a citrate combustion method followed by an organic precipitation method. The cathodes were of K₂NiF₄-type crystal structure with x wt.% Ce_0.9Gd_0.1O_1.95 (CGO)–(100 ? x) wt.% La_1.96Sr_0.04CuO_4 + δ (LSC), where x = 0, 10, 20 and 30. The individual structural phases of the composite cathodes were characterized using a third-generation synchrotron source beamline powder X-ray diffractometer (XRD). The porous grain morphology of the CGO–LSC cathode composite for a symmetrical half-cell was determined from cross-sectional scanning electron microscopy images and elemental line profiles. The composite cathode was made of 20 wt.% CGO–80 wt.% LSC (CL20–80) and was coated onto a Ce_0.9Gd_0.1O_1.95 electrolyte. It showed the lowest area specific resistance (ASR) of 0.07 Ω cm² at 750 °C. An electrolyte-supported (300 μm thick) single-cell configuration of CL20–80/CGO/Ni-CGO attained a maximum power density of 626 mW cm^? 2 at 700 °C. The unique composite composition of CL20–80 demonstrates enhanced electrochemical performance and good chemical compatibility with the CGO electrolyte, as compared with the pure LSC (CL0–100) cathode for IT-SOFCs.     

Fabrication of metal-shelled coaxial nanowires and annealing-induced formation of metal nanoparticles for catalytic applications: Growth and characteristics of SnO2-branched nanostructures

We have fabricated SnO₂ branches on SiO_x stem nanowires, via a novel multi-step process. With the SnO₂ branches having diameters in the range 20–80 nm, X-ray diffraction, transmission electron microscopy and selected area diffraction pattern coincidentally revealed that the branches were crystalline rutile SnO₂ structures. We suggested that a Ag-catalyzed base-growth vapor–liquid–solid growth mechanism was responsible for the growth of SnO₂ branches. Photoluminescence analysis indicated that the Ag-coated SiO_x nanowires exhibited emission bands centered at 2.6 eV and 3.1 eV, presumably from the SiO_x core nanowires. Subsequent annealing induced 2.4-eV band, whereas the growth of SnO₂ branches induced 2.1-eV band. For the branched product, we have investigated the O₂ and NO₂ sensing properties. A linear relationship between sensitivity and the O₂ gas concentration was observed, which demonstrates its potential application to chemical sensors.     

Microstructure,magnetic properties and exchange–coupling interactions for one-dimensional hard/soft ferrite nanofibers

SrFe₁₂O₁₉ (SFO)/Ni_0.5Zn_0.5Fe₂O₄ (NZFO) composite ferrite nanofibers with diameters about 120 nm have been prepared by the electrospinning and calcination process. The SFO/NZFO composite ferrites are formed after calcined at 700 °C for 2 h and the composite nanofibers with various mass ratios obtained at 900 °C are fabricated from NZFO grains about 16–40 nm and SFO grains of 19–45 nm with a uniform phase distribution. With the SFO ferrite content increasing, the coercivity (H_c) and remanence (M_r) for the composite ferrite nanofibers initially increase, reaching maximum values of 379.8 kA/m (297 K) and 242.2 kA/m (77 K), 39.1 Am²/kg (297 K) and 53.5 Am²/kg (77 K), respectively, at a mass ratio (SFO:NZFO) of 4, and then show a reduction tendency with a further increase of the mass ratio. This enhancement in magnetic properties is attributed to the competition of the exchange–coupling interaction and the dipolar interaction in the composite nanofibers.