High-rate amorphous SnO2 nanomembrane anodes for Li-ion batteries with a long cycling life

Boron Dopant Modulated Electron Localization of Tin Oxide for Efficient Electrochemical CO2 Reduction to Formate

Sn-based electrocatalysts have great economic potential in the reduction of CO2 to HCOOH, while they still suffer from low current density, dissatisfactory selectivity, and poor stability. Inspired by electronic modification engineering, boron-doped SnO2 nanospheres (B-SnO2 ) are successfully synthesized to achieve high-efficiency CO2 reduction reaction (CO2 RR). It is found that the introduction of boron dopants can increase the number of active sites and facilitate the formation of the electron-rich Sn sites in its structure, thus enhancing the activation of CO2 molecules and reducing the energy barrier of *OCHO intermediates on the SnO2 surface. Thus, the B-doped SnO2 electrocatalyst exhibits a remarkable FEHCOOH above 90% within a broad potential window of -0.7 to -1.3 V versus reversible hydrogen electrode (RHE) (600 mV) and obtains the maximum value of 95.1% (the partial current density of HCOOH is 42.35 mA cm-2 ) at -1 V versus RHE. In conclusion, this work provides a novel strategy for optimizing the intrinsic properties of electrocatalysts for CO2 RR by the method of tuning the electronic structure.

Engineering amorphous SnO2 nanoparticles integrated into porous N-doped carbon matrix as high-performance anode for lithium-ion batteries

A facile in-situ preparation strategy is proposed to anchor amorphous SnO₂ nanoparticles into the porous N-doped carbon (NC) matrix to fabricate amorphous composite powders (am-SnO₂@p-NC), which feature the hierarchically interconnected and well interlaced porous configurations by employing polyvinylpyrrolidone as the soft template. The morphology regulation of the porous structure is precisely realized by adjusting the content of the template and the relationship between structural evolution and electrochemical performance of composite powders is accurately described to explore the optimal template dosage. The results indicate that the am-SnO₂@p-NC-50 % composite electrode can deliver the improved lithium storage capacity and cycling performance when the content of the template is controlled at 0.500 g, in which the initial discharge specific capacity is about 1557.6 mAh/g and the reversible value retains at 841.5 mAh/g after 100 cycles at 100 mA/g. Meanwhile, the discharge specific capacity of 869.8 mAh/g is exhibited for the am-SnO₂@p-NC-50 % composite electrode after 60 cycles when the current density is recovered from 2000 to 100 mA/g. Moreover, the Li⁺ ions diffusion coefficient up to about 5.5 × 10^-12 cm²/s is calculated from galvanostatic intermittent titration technique tests, which can be partly ascribed to the conductive NC substrate that provides the high electronic conductivity, and partly to the highly porous structure that shortens Li⁺ ions transfer pathways and guarantees the fast reaction kinetics. Therefore, the hierarchically porous engineering of carbon networks to confine amorphous transition metal oxide nanoparticles is of great significance in the development of high-performance anode materials for lithium-ion batteries.

Insight into Reversible Conversion Reactions in SnO2 -Based Anodes for Lithium Storage: A Review

Various anode materials have been widely studied to pursue higher performance for next generation lithium ion batteries (LIBs). Metal oxides hold the promise for high energy density of LIBs through conversion reactions. Among these, tin dioxide (SnO₂ ) has been typically investigated after the reversible lithium storage of tin-based oxides is reported by Idota and co-workers in 1997. Numerous in/ex situ studies suggest that SnO₂ stores Li⁺ through a conversion reaction and an alloying reaction. The difficulty of reversible conversion between Li₂ O and SnO₂ is a great obstacle limiting the utilization of SnO₂ with high theoretical capacity of 1494 mA h g^-1 . Thus, enhancing the reversibility of the conversion reaction has become the research emphasis in recent years. Here, taking SnO₂ as a typical representative, the recent progress is summarized and insight into the reverse conversion reaction is elaborated. Promoting Li₂ O decomposition and maintaining high Sn/Li₂ O interface density are two effective approaches, which also provide implications for designing other metal oxide anodes. In addition, some in/ex situ characterizations focusing on the conversion reaction are emphatically introduced. This review, from the viewpoint of material design and advanced characterizations, aims to provide a comprehensive understanding and shed light on the development of reversible metal oxide electrodes.

MoS2 nanoflowers encapsulated into carbon nanofibers containing amorphous SnO2 as an anode for lithium-ion batteries

SnO₂ with high abundance, large theoretical capacity, and nontoxicity is considered to be a promising candidate for use as advanced electrodes. However, the poor electronic conductivity and large volume variations hinder the practical applications of SnO₂-based electrodes for use in lithium-ion batteries (LIBs). Herein, the MoS₂-SnO₂ heterostructures were encapsulated into carbon nanofibers (CNFs) via facile solvothermal and electrospinning methods. Remarkably, when the binder-free and robust MoS₂-SnO₂@CNF is employed as the anode for LIBs, such a clever structure yields a discharge capacity of 983 mA h g^-1 at a current density of 200 mA g^-1 after 100 cycles and a capacity of 710 mA h g^-1 after 800 cycles at a current density of 2000 mA g^-1. Moreover, full cells and flexible full cells were constructed, which exhibited high flexibility and delivered a high reversible capacity of 463 mA h g^-1 after 100 cycles at 500 mA g^-1. The exceptional performance of MoS₂-SnO₂@CNF could be attributed to the rational design of the electrode structure. On one hand, the robust structure of the amorphous SnO₂ and MoS₂ nanoflowers in the conductive carbon network not only provides direct current pathways, but also enhances electron transfer. On the other hand, the abundance of p-n heterogeneous interfaces considerably reduces the charge transfer resistance and enhances the surface reaction kinetics. This work proposes a feasible strategy to enhance the capacity and stability of SnO₂-based electrodes and opens up a new avenue for the potential applications of SnO₂ anode materials.

Difference in Electrochemical Mechanism of SnO2 Conversion in Lithium-Ion and Sodium-Ion Batteries: Combined in Operando and Ex Situ XAS Investigations

Conversion and alloying type negative electrodes attracted huge attention in the present research on lithium/sodium-ion batteries (LIBs/SIBs) due to the high capacity delivered. Among these, SnO₂ is investigated intensively in LIBs due to high cyclability, low reaction potential, cost-effectiveness, and environmental friendliness. Most of the LIB electrodes are explored in SIBs too due to expected similar electrochemical performance. Though several LIB negative electrode materials successfully worked in SIBs, bare SnO₂ shows very poor electrochemical performance in SIB. The reason for this difference is investigated here through combined in operando and ex situ X-ray absorption spectroscopy (XAS). For this, the electrodes of SnO₂ (space group P4₂/mnm synthesized via one-pot hydrothermal method) were cycled in Na-ion and Li-ion half-cells. The Na/SnO₂ half-cell delivered a much lower discharge capacity than the Li/SnO₂ half-cell. In addition, higher irreversibility was observed for Na/SnO₂ half-cell during electrochemical investigations compared to that for Li/SnO₂ half-cell. In operando XAS investigations on the Na/SnO₂ half-cell confirms incomplete conversion and alloying reactions in the Na/SnO₂ half-cell, resulting in poor electrochemical performance. The difference in the lithiation and sodiation mechanisms of SnO₂ is discussed in detail.

Research Advances of Amorphous Metal Oxides in Electrochemical Energy Storage and Conversion

Amorphous metal oxides (AMOs) have aroused great enthusiasm across multiple energy areas over recent years due to their unique properties, such as the intrinsic isotropy, versatility in compositions, absence of grain boundaries, defect distribution, flexible nature, etc. Here, the materials engineering of AMOs is systematically reviewed in different electrochemical applications and recent advances in understanding and developing AMO-based high-performance electrodes are highlighted. Attention is focused on the important roles that AMOs play in various energy storage and conversion technologies, such as active materials in metal-ion batteries and supercapacitors as well as active catalysts in water splitting, metal-air batteries, and fuel cells. The improvements of electrochemical performance in metal-ion batteries and supercapacitors are reviewed regarding the enhancement in active sites, mechanical strength, and defect distribution of amorphous structures. Furthermore, the high electrochemical activities boosted by AMOs in various fundamental reactions are elaborated on and they are related to the electrocatalytic behaviors in water splitting, metal-air batteries, and fuel cells. The applications in electrochromism and high-conducting sensors are also briefly discussed. Finally, perspectives on the existing challenges of AMOs for electrochemical applications are proposed, together with several promising future research directions.

Scalable Fabrication of Nanostructured Tin Oxide Anodes for High-Energy Lithium-Ion Batteries

Although tin and tin oxides have been considered very promising anode materials for future high-energy lithium-ion batteries due to high theoretical capacity and low cost, the development of commercial anodes falls short of expectations. This is due to several challenging issues related to a massive volume expansion during operation. Nanostructured electrodes can accommodate the volume expansion but typically suffer from cumbersome synthesis routes and associated problems regarding scalability and cost efficiency, preventing their commercialization. Herein, a facile, easily scalable, and highly cost-efficient fabrication route is proposed based on electroplating and subsequent electrolytic oxidation of tin, resulting in additive-free tin oxide anodes for lithium-ion batteries. The electrodes prepared accordingly exhibit excellent performance in terms of gravimetric and volumetric capacity as well as promising cycle life and rate capability, making them suitable for future high-energy lithium-ion batteries.

Enhancing the Lithium Storage Performance of Graphene/SnO2 Nanorods by a Carbon-Riveting Strategy

Graphene/metal oxide (MO) nanocomposites hold great promise for application as anodes in lithium-ion batteries (LIBs). However, the restacking of graphene during subsequent processing remains a challenge to overcome for enhanced lithium storage properties. Herein, the fabrication of sandwich-architecture carbon-riveted graphene/SnO₂ nanorods, in which the SnO₂ nanorods are confined in the nanospaces formed by the carbon layers on graphene, by a two-step hydrothermal process followed by thermal treatment, is reported. Electrochemical tests show that the carbon-riveted nanolayers significantly improve the lithium storage performance of graphene/SnO₂ . The nanocomposite displays a high reversible capacity of 815 mAh g^-1 after 150 cycles at 100 mA g^-1 and high cycling stability at 1000 mA g^-1 . This work provides an efficient way to manipulate graphene/MO-based nanocomposites for LIBs with improved performance.

Assembly and Self-Assembly of Nanomembrane Materials-From 2D to 3D

Nanoscience and nanotechnology offer great opportunities and challenges in both fundamental research and practical applications, which require precise control of building blocks with micro/nanoscale resolution in both individual and mass-production ways. The recent and intensive nanotechnology development gives birth to a new focus on nanomembrane materials, which are defined as structures with thickness limited to about one to several hundred nanometers and with much larger (typically at least two orders of magnitude larger, or even macroscopic scale) lateral dimensions. Nanomembranes can be readily processed in an accurate manner and integrated into functional devices and systems. In this Review, a nanotechnology perspective of nanomembranes is provided, with examples of science and applications in semiconductor, metal, insulator, polymer, and composite materials. Assisted assembly of nanomembranes leads to wrinkled/buckled geometries for flexible electronics and stacked structures for applications in photonics and thermoelectrics. Inspired by kirigami/origami, self-assembled 3D structures are constructed via strain engineering. Many advanced materials have begun to be explored in the format of nanomembranes and extend to biomimetic and 2D materials for various applications. Nanomembranes, as a new type of nanomaterials, allow nanotechnology in a controllable and precise way for practical applications and promise great potential for future nanorelated products.

Porous and Low-Crystalline Manganese Silicate Hollow Spheres Wired by Graphene Oxide for High-Performance Lithium and Sodium Storage

Herein, a graphene oxide (GO)-wired manganese silicate (MS) hollow sphere (MS/GO) composite is successfully synthesized. Such an architecture possesses multiple advantages in lithium and sodium storage. The hollow MS structure provides a sufficient free space for volume variation accommodation; the porous and low-crystalline features facilitate the diffusion of lithium ions; meanwhile, the flexible GO sheets enhance the electronic conductivity of the composite to a certain degree. When applied as the anode material for lithium-ion batteries (LIBs), the as-obtained MS/GO composite exhibits a high reversible capacity, ultrastable cyclability, and good rate performance. Particularly, the MS/GO composite delivers a high capacity of 699 mA h g^-1 even after 1000 cycles at 1 A g^-1. The sodium-storage performance of MS/GO has been studied for the first time, and it delivers a stable capacity of 268 mA h g^-1 after 300 cycles at 0.2 A g^-1. This study suggests that the rational design of metal silicates would render them promising anode materials for LIBs and SIBs.

Efficient mass-fabrication of amorphous MnSiO3/C with high stability through a simple water-boiling treatment and its Li-ion storage performance

Amorphous manganese silicate with high stability up to 700 °C was prepared by simply water-boiling a mixture of Na₂SiO₃·9H₂O and MnCl₂·4H₂O and subsequently coating with carbon. The amorphous silicate reveals stable cycling performance even at 500 mA g⁻¹.

Engineered nanomembranes for smart energy storage devices

This review presents recent progress in engineered tubular and planar nanomembranes for smart energy storage applications, especially related to the investigation of fundamental electrochemical kinetics.

XANES, EXAFS and photocatalytic investigations on copper oxide nanoparticles and nanocomposites

CuO nanoparticles, Cu₂O/CuO and CuO/TiO₂ nanocomposites exhibit excellent photocatalyst properties toward the degradation of methyl-orange and potassium-dichromate under the visible light irradiation.