Sodium chloride template synthesis of cubic tin dioxide hollow particles for lithium ion battery applications

A sandwich nanocomposite composed of commercially available SnO and reduced graphene oxide as advanced anode materials for sodium-ion full batteries

A sandwich structure with SnO and reduced graphene oxide (SnO/rGO) is designed via freeze drying. It delivers a specific capacity of 109.5 mA h g⁻¹ with a retention of 70.62% after 1200 cycles at 4 A g⁻¹, revealing its stable cycling performance.

Dual Immobilization of SnOx Nanoparticles by N-Doped Carbon and TiO2 for High-Performance Lithium-Ion Battery Anodes

The grain aggregation engendered kinetics failure is regarded as the main reason for the electrochemical decay of nanosized anode materials. Herein, we proposed a dual immobilization strategy to suppress the migration and aggregation of SnO_x nanoparticles and corresponding lithiation products through constructing SnO_x/TiO₂@PC composites. The N-doped carbon could anchor the tin oxide particles and inhibit their aggregation during the preparation process, leading to a uniform distribution of ultrafine SnO_x nanoparticles in the matrix. Meanwhile, the incorporated TiO₂ component works as parclose to suppress the migration and coarsening of SnO_x and corresponding lithiation products. In addition, the N-doped carbon and TiO₂/Li_xTiO₂ can significantly improve the electrical and ionic conductivities of the composites, enabling a good diffusion and charge-transfer dynamics. Owing to the dual immobilization from the "synergistic effect" of N-doped carbon and the "parclose effect" of TiO₂, the conversion reaction of SnO_x remains fully reversible throughout the cycling. Thereby, the composites exhibit excellent cycling performance in half cells and can be fully utilized in full cells. This work may provide an inspiration for the rational design of tin-based anodes for high-performance lithium-ion batteries.

Two-Dimensional Ga2O3/C Nanosheets as Durable and High-Rate Anode Material for Lithium Ion Batteries

The self-healing feature of gallium (Ga) is unique, making Ga-based materials attract attention for their potential to solve the anode pulverization issue of lithium ion batteries. In this work, a hierarchical two-dimensional (2D) Ga₂O₃/C structure has been synthesized by a facile NaCl template method. Ga₂O₃ nanoparticles (3.8 nm) are uniformly embedded in 2D carbon nanosheets. The long horizontal length of the carbon nanosheets (10 μm) provides long-range electron conductivity, and the thin vertical thickness (75 nm) shortens the Li ion diffusion path. Benefited from the integrated 2D structure and the high electron conductivity, the obtained 2D Ga₂O₃/C nanosheets exhibit excellent overall performance, including high lithium storage capacity (1026 mAh g^-1 at 0.5 A g^-1), high rate capability (378 mAh g^-1 at 10.0 A g^-1), and high cyclability (500 cycles at 0.5 A g^-1). The lithiation/delithiation mechanism of 2D Ga₂O₃/C has been further studied with combined electrochemical and ex situ X-ray diffraction methods.

Lithium-ion storage performances of sunflower-like and nano-sized hollow SnO2 spheres by spray pyrolysis and the nanoscale Kirkendall effect

Nanostructured metal selenides with a variety of morphologies are crucial for fabricating porous, hollow metal-oxide nanomaterials by nanoscale Kirkendall diffusion. Herein, SnSe-SnO2 composite powders and SnSe nanospheres were synthesized via one-pot spray pyrolysis by optimizing the concentration of the Se precursor in the spray solution; these were then used to fabricate sunflower-like SnO2 and hollow SnO2 nanospheres, respectively, via nanoscale Kirkendall diffusion. Post-treatment of the SnSe-decorated SnO2 under air produced sunflower-like SnO2, in which ray and disk florets consisting of hollow nanoplates and dense nanospheres, respectively, were present. The mean diameter of the homogeneous hollow SnO2 nanospheres was 150 nm. The hollow morphology shortens the diffusion length, increasing the contact area between the electrolyte and voids and buffering large volume changes during repeated cycling. As anode materials for lithium-ion batteries, the hollow SnO2 nanospheres showed excellent cycling and rate performances. The discharge capacity of the hollow SnO2 nanospheres, after 500 cycles from 0.001 V to 3.0 V, was 1043 mA h g-1, at a current density of 3.0 A g-1. The hollow SnO2 nanospheres showed a high reversible capacity of 638 mA h g-1, even at current density as high as 10 A g-1.

Large-Scale Fabrication of Core-Shell Structured C/SnO2 Hollow Spheres as Anode Materials with Improved Lithium Storage Performance

Due to the high theoretical capacity as high as 1494 mAh g^-1 , SnO₂ is considered as a potential anode material for high-capacity lithium-ion batteries (LIBs). Therefore, the simple but effective method focused on fabrication of SnO₂ is imperative. To meet this, a facile and efficient strategy to fabricate core-shell structured C/SnO₂ hollow spheres by a solvothermal method is reported. Herein, the solid and hollow structure as well as the carbon content can be controlled. Very importantly, high-yield C/SnO₂ spheres can be produced by this method, which suggest potential business applications in LIBs field. Owing to the dual buffer effect of the carbon layer and hollow structures, the core-shell structured C/SnO₂ hollow spheres deliver a high reversible discharge capacity of 1007 mAh g^-1 at a current density of 100 mA g^-1 after 300 cycles and a superior discharge capacity of 915 mAh g^-1 at 500 mA g^-1 after 500 cycles. Even at a high current density of 1 and 2 A g^-1 , the core-shell structured C/SnO₂ hollow spheres electrode still exhibits excellent discharge capacity in the long life cycles. Consideration of the superior performance and high yield, the core-shell structured C/SnO₂ hollow spheres are of great interest for the next-generation LIBs.

Versatile Solution-Processed Synthesis of Two-Dimensional Ultrathin Metal Chalcogenides Following Frank-van der Merwe Growth

Two-dimensional (2D) ultrathin metal chalcogenides represent a class of promising materials for various applications thanks to attractive physicochemical properties. However, a reliable pathway for fabricating ultrathin metal chalcogenides nanosheets, regardless of the bulk crystals of their 3D counterparts, still remains a challenge. Herein, we present a versatile solution-processed template synthesis strategy, in which a single molecular-level precursor anneals to ultrathin single-crystal nanosheets with the aid of lattice-matching templates, following the Frank-van der Merwe growth mode and featuring high quality, low cost, scalability, and processability. Following this strategy, Sb₂S₃, MoS₂, and ZnS nanosheets are successfully prepared as representatives for materials whose bulk counterparts possess 1D, 2D, and 3D crystal structures, respectively, and the growth mechanism is confirmed by crystal mode analysis. As a proof-of-concept application, MoS₂ and Sb₂S₃ nanosheets are used for gas sensor and flexible photodetector applications, respectively, which exhibit excellent performance. The method can also be easily extended to other ultrathin nanosheets like single metals, metal oxide, metal nitride, and heterostructures.

Control of Mechanical Stability of Hollow Silica Particles, and Its Measurement by Mercury Intrusion Porosimetry

Hollow silica particles (HSPs) have become the focus of interest in many laboratories recently, because of their versatility, stemming from the ability to control their size and shape, as well as surface functionalization. Determining the mechanical stability of hollow particles is essential for their use, both in applications in which they need to retain their structure, as well as those in which they need to break down. We have synthesized a series of HSPs (inner diameter of 231 nm) with increasing wall thickness (7-25 nm), using a template approach. Their mechanical stability was measured using mercury intrusion porosimetry (MIP), which represents the novel application of the technique for these materials. The samples with complete shells break at progressively higher pressures, and samples with wall thickness ≥21 nm remain stable to the highest pressure applied (414 MPa). Other characterization methods, namely microscopy, gas adsorption, and small-angle X-ray scattering, shed light on the size parameters of the particles, as well as the porosity of the silica walls. By varying the amount of silica precursor used in the template coating step, we were able to produce hollow silicas with variable stability, thereby allowing for control of their mechanical properties.

Highly sensitive SnO2 sensor via reactive laser-induced transfer

Gas sensors based on tin oxide (SnO₂) and palladium doped SnO₂ (Pd:SnO₂) active materials are fabricated by a laser printing method, i.e. reactive laser-induced forward transfer (rLIFT). Thin films from tin based metal-complex precursors are prepared by spin coating and then laser transferred with high resolution onto sensor structures. The devices fabricated by rLIFT exhibit low ppm sensitivity towards ethanol and methane as well as good stability with respect to air, moisture, and time. Promising results are obtained by applying rLIFT to transfer metal-complex precursors onto uncoated commercial gas sensors. We could show that rLIFT onto commercial sensors is possible if the sensor structures are reinforced prior to printing. The rLIFT fabricated sensors show up to 4 times higher sensitivities then the commercial sensors (with inkjet printed SnO₂). In addition, the selectivity towards CH₄ of the Pd:SnO₂ sensors is significantly enhanced compared to the pure SnO₂ sensors. Our results indicate that the reactive laser transfer technique applied here represents an important technical step for the realization of improved gas detection systems with wide-ranging applications in environmental and health monitoring control.

Scalable salt-templated synthesis of two-dimensional transition metal oxides

Two-dimensional atomic crystals, such as two-dimensional oxides, have attracted much attention in energy storage because nearly all of the atoms can be exposed to the electrolyte and involved in redox reactions. However, current strategies are largely limited to intrinsically layered compounds. Here we report a general strategy that uses the surfaces of water-soluble salt crystals as growth templates and is applicable to not only layered compounds but also various transition metal oxides, such as hexagonal-MoO3, MoO2, MnO and hexagonal-WO3. The planar growth is hypothesized to occur via a match between the crystal lattices of the salt and the growing oxide. Restacked two-dimensional hexagonal-MoO3 exhibits high pseudocapacitive performances (for example, 300 F cm(-3) in an Al2(SO4)3 electrolyte). The synthesis of various two-dimensional transition metal oxides and the demonstration of high capacitance are expected to enable fundamental studies of dimensionality effects on their properties and facilitate their use in energy storage and other applications.

High Efficiency Dye-sensitized Solar Cells Constructed with Composites of TiO2 and the Hot-bubbling Synthesized Ultra-Small SnO2 Nanocrystals

An efficient photo-anode for the dye-sensitized solar cells (DSSCs) should have features of high loading of dye molecules, favorable band alignments and good efficiency in electron transport. Herein, the 3.4 nm-sized SnO₂ nanocrystals (NCs) of high crystallinity, synthesized via the hot-bubbling method, were incorporated with the commercial TiO₂ (P25) particles to fabricate the photo-anodes. The optimal percentage of the doped SnO₂ NCs was found at ~7.5% (SnO₂/TiO₂, w/w), and the fabricated DSSC delivers a power conversion efficiency up to 6.7%, which is 1.52 times of the P25 based DSSCs. The ultra-small SnO₂ NCs offer three benefits, (1) the incorporation of SnO₂ NCs enlarges surface areas of the photo-anode films, and higher dye-loading amounts were achieved; (2) the high charge mobility provided by SnO₂ was confirmed to accelerate the electron transport, and the photo-electron recombination was suppressed by the highly-crystallized NCs; (3) the conduction band minimum (CBM) of the SnO₂ NCs was uplifted due to the quantum size effects, and this was found to alleviate the decrement in the open-circuit voltage. This work highlights great contributions of the SnO₂ NCs to the improvement of the photovoltaic performances in the DSSCs.

Nanofibers Comprising Yolk-Shell Sn@void@SnO/SnO₂ and Hollow SnO/SnO₂ and SnO₂ Nanospheres via the Kirkendall Diffusion Effect and Their Electrochemical Properties

Nanofibers with a unique structure comprising Sn@void@SnO/SnO2 yolk-shell nanospheres and hollow SnO/SnO2 and SnO2 nanospheres are prepared by applying the nanoscale Kirkendall diffusion process in conventional electrospinning process. Under a reducing atmosphere, post-treatment of tin 2-ethylhexanoate-polyvinylpyrrolidone electrospun nanofibers produce carbon nanofibers with embedded spherical Sn nanopowders. The Sn nanopowders are linearly aligned along the carbon nanofiber axis without aggregation of the nanopowders. Under an air atmosphere, oxidation of the Sn-C composite nanofibers produce nanofibers comprising Sn@void@SnO/SnO2 yolk-shell nanospheres and hollow SnO/SnO2 and SnO2 nanospheres, depending on the post-treatment temperature. The mean sizes of the hollow nanospheres embedded within tin oxide nanofibers post-treated at 500 °C and 600 °C are 146 and 117 nm, respectively. For the 250th cycle, the discharge capacities of the nanofibers prepared by the nanoscale Kirkendall diffusion process post-treated at 400 °C, 500 °C, and 600 °C at a high current density of 2 A g(-1) are 663, 630, and 567 mA h g(-1), respectively. The corresponding capacity retentions are 77%, 84%, and 78%, as calculated from the second cycle. The nanofibers prepared by applying the nanoscale Kirkendall diffusion process exhibit superior electrochemical properties compared with those of the porous-structured SnO2 nanofibers prepared by the conventional post-treatment process.

Study of the photocatalytic properties of bio-mimicked hollow SnO2 microstructures synthesized with Ceiba pentandra (L.) Gaertn. (kapok) as a natural template

Hollow SnO₂ microstructures have been simply fabricated via a template impregnation technique using Ceiba pentandra (L.) Gaertn. as a natural template.

Facile synthesis of SnO2 nanocrystals anchored onto graphene nanosheets as anode materials for lithium-ion batteries

A SnO₂/graphene nanocomposite was prepared via a facile solvothermal process using stannous octoate as a Sn source, which exhibited excellent electrochemical behavior with a high reversible capacity, a long cycle life and a good rate capability when used as an anode material for lithium-ion batteries.

A scalable formation of nano-SnO2 anode derived from tin metal–organic frameworks for lithium-ion battery

In this work, for the first time, we synthesize a SnO₂ nanomaterial through the calcination of tin metal–organic framework (MOF) precursors.

Synthesis of NaCl single crystals with defined morphologies as templates for fabricating hollow nano/micro-structures

Hollow structured SiO₂, TiO₂ and related XRD patterns before and after removal of the NaCl template.

Ultrasmall SnO₂ nanocrystals: hot-bubbling synthesis, encapsulation in carbon layers and applications in high capacity Li-ion storage

Ultrasmall SnO₂ nanocrystals as anode materials for lithium-ion batteries (LIBs) have been synthesized by bubbling an oxidizing gas into hot surfactant solutions containing Sn-oleate complexes. Annealing of the particles in N₂ carbonifies the densely packed surface capping ligands resulting in carbon encapsulated SnO₂ nanoparticles (SnO₂/C). Carbon encapsulation can effectively buffer the volume changes during the lithiation/delithiation process. The assembled SnO₂/C thus deliver extraordinarily high reversible capacity of 908 mA·h·g⁻¹ at 0.5 C as well as excellent cycling performance in the LIBs. This method demonstrates the great potential of SnO₂/C nanoparticles for the design of high power LIBs.

Ultrafast synthesis of yolk-shell and cubic NiO Nanopowders and application in lithium ion batteries

A continuous one-pot method was employed to synthesize yolk-shell and single-crystalline cubic NiO powders in a few seconds. Submicrometer-sized NiO yolk-shell particles were prepared by spray pyrolysis at 900 °C. Single-crystalline cubic NiO nanopowders were prepared by one-pot flame spray pyrolysis from NiO vapors. Particle surface areas of the yolk-shell and single-crystalline cubic NiO powders as obtained using the Brunauer-Emmett-Teller method were 8 and 5 m(2) g(-1), respectively. The mean crystallite sizes of the yolk-shell-structured and cubic NiO powders were 50 and 80 nm, respectively. The yolk-shell and single-crystalline cubic NiO powders delivered discharge capacities of 951 and 416 mA h g(-1), respectively, after 150 cycles, and the corresponding capacity retentions measured after the first cycle were 106 and 66%, respectively. The yolk-shell-structured NiO powders showed rate performance better than that of the single-crystalline cubic NiO nanopowders. Even at a high current density of 1 A g(-1), the discharge capacity of the yolk-shell-structured NiO powders was as high as 824 mA h g(-1) after 50 cycles, in which the current densities were increased stepwise.

Electrospun hollow cage-like α-Fe2O3 microspheres: synthesis, formation mechanism, and morphology-preserved conversion to Fe nanostructures

Novel 3D hollow cage-like α-Fe₂O₃ and Fe microspheres were fabricated by electrospinning followed by an annealing process for the first time.

Molten salt synthesis of tin doped hematite nanodiscs and their enhanced electrochemical performance for Li-ion batteries

Sn⁴⁺ doped α-Fe₂O₃ nanodiscs with good lithium storage properties have been prepared by a molten salt method.

In situ growth of hierarchical SnO(2) nanosheet arrays on 3D macroporous substrates as high-performance electrodes

Finding out how to overcome the self-aggregation of nanostructured electrode materials is a very important issue in lithium-ion battery technology. Herein, by an in situ construction strategy, hierarchical SnO2 nanosheet architectures have been fabricated on a three-dimensional macroporous substrate, and thus the aggregation of the SnO2 nanosheets was effectively prevented. The as-prepared hierarchical SnO2 nanoarchitectures on the nickel foam can be directly used as an integrated anode for lithium-ion batteries without the addition of other ancillary materials such as carbon black or binder. In view of their apparent advantages, such as high electroactive surface area, ultrathin sheet, robust mechanical strength, shorter ion and electron transport path, and the specific macroporous structure, the hierarchical SnO2 nanosheets exhibit excellent lithium-storage performance. Our present growth approach offers a new technique for the design and synthesis of metal oxide hierarchical nanoarrays that are promising for electrochemical energy-storage electrodes without carbon black and binder.

Ni and p-Cu2O nanocubes with a small size distribution by templated electrodeposition and their characterization by photocurrent measurement

A method for the reproducible formation of Ni and Cu2O nanocubes with dimensions of 200-500 nm and a small size distribution is introduced. For this, the well-known templated electrodeposition technique was extended to cubic PMMA templates made by nanoimprint lithography. When making cubic templates in larger quantities, this method has the potential to become simple and cost-effective. This method was successfully used for the formation of Ni and p-Cu2O nanocubes as well as for the formation of segmented nanobars containing both phases. The lateral dimensions of the nanocubes exactly resembled the dimensions of the template, and the height could be varied by adjusting the deposition time. Nanocubes formed via this method can remain attached to the substrate or can be dispersed in solution. p-Cu2O is considered to be one of the most promising photocathode materials for solar water splitting. It is demonstrated that the activity of the p-Cu2O nanocubes for photocatalytic water splitting can be measured, and it was found that the nanocube morphology enhances the photocatalytic activity compared to thin films.

SnO₂ tube-in-tube nanostructures: Cu@C nanocable templated synthesis and their mutual interferences between heavy metal ions revealed by stripping voltammetry

SnO2 tube-in-tube nanostructures are synthesized using Cu@C nanocables as effective sacrificial templates. It is revealed by stripping voltammetry that SnO2 tube-in-tube nanostructures show excellent performances in the determination of heavy metal ions, which might be related to the extraordinary adsorbing capacities of the hollow structure to metal ions, i.e., metal ions could diffuse into the interior of tubular structure.

Controllable low-temperature chemical vapor deposition growth and morphology dependent field emission property of SnO2 nanocone arrays with different morphologies

Vertically aligned SnO2 nanocones with different morphologies have been directly grown on fluorine-doped tin oxide (FTO) glass substrates in a large area by heating a mixture of stannous chloride dihydrate (SnCl2·2H2O) and anhydrous zinc chloride (ZnCl2) at 600 °C in air. Control over the SnO2 nanocone arrays with different morphologies is achieved by adjusting the heat treatment time. The SnO2 nanocones are single crystalline with the tetragonal structure. A single-layer SnO2 nanoparticle film is first formed via the vapor-solid (VS) process due to the decentralization function of ZnCl2 vapor, and the SnO2 nanoparticles served as seeds and grew into nanocone arrays via the VS process. The sharp-tipped nanostructure formation may originate from a concentration gradient of reactant in the growth process. The as-obtained whiskerlike nanocone arrays exhibit enhanced field emission properties in comparison with typical nanoconelike structure arrays and other SnO2 nanostructured materials reported previously, and the turn-on field and field-enhancement factor is 1.19 V/μm and 3110, respectively. The experimental result is consistent with the Utsumi's relative figure of merit for pillar-shaped emitters.