Carbon coated SnO2 nanoparticles anchored on CNT as a superior anode material for lithium-ion batteries

Carbon Nanotubes Connecting and Encapsulating MoS2-Doped SnO2 Nanoparticles as an Excellent Lithium Storage Performance Anode Material

Doping and carbon encapsulation modifications have been proven to be effective methods for enhancing the lithium storage performance of batteries. The hydrothermal method and ball milling are commonly used methods for material synthesis. In this study, a composite anode material rich in carbon nanotubes (CNTs) conductive tubular network connection and encapsulation of SnO2-MoS2@CNTs (SMC) was synthesized by combining these two methods. In this highly conductive network, nano-SnO2 particles are uniformly dispersed and embedded in MoS2 with a layered structure, and the obtained SnO2-MoS2 composite material is tightly connected and encapsulated by the tubular network of CNTs. It is worth noting that the incorporation of layered MoS2 not only effectively anchors the SnO2 nanoparticles, but also provides a broader space for lithium-ion movement due to the larger interlayer spacing. The conductive network of CNTs shortens the diffusion path of electrons and Li+ and provides more diffusion channels. The reversible capacity of the SnO2-MoS2@CNTs nanocomposite material remains at 1069.3 mA h g-1 after 320 cycles at 0.2 A g-1, and it exhibits excellent long-term cycling stability, maintaining 904.5 mA h g-1 after 1000 cycles at 1.0 A g-1. The composite material demonstrates excellent pseudocapacitive contribution rate performance, with a contribution rate of 87% at 2.0 mV s-1. The results indicate that SnO2-MoS2@CNTs has excellent electrochemical lithium storage performance and is a promising anode material for lithium-ion batteries.

Hydrogen spillover effects in the Fischer–Tropsch reaction over carbon nanotube supported cobalt catalysts

Support (CNTs) surface defect-induced hydrogen spillover significantly impacted the catalytic activity (turnover frequency, TOF) and methane selectivity evolution in cobalt-based Fischer–Tropsch synthesis.

Nano-Confined Tin Oxide in Carbon Nanotube Electrodes via Electrostatic Spray Deposition for Lithium-Ion Batteries

The development of novel materials is essential for the next generation of electric vehicles and portable devices. Tin oxide (SnO2), with its relatively high theoretical capacity, has been considered as a promising anode material for applications in energy storage devices. However, the SnO2 anode material suffers from poor conductivity and huge volume expansion during charge/discharge cycles. In this study, we evaluated an approach to control the conductivity and volume change of SnO2 through a controllable and effective method by confining different percentages of SnO2 nanoparticles into carbon nanotubes (CNTs). The binder-free confined SnO2 in CNT composite was deposited via an electrostatic spray deposition technique. The morphology of the synthesized and deposited composite was evaluated by scanning electron microscopy and high-resolution transmission electron spectroscopy. The binder-free 20% confined SnO2 in CNT anode delivered a high reversible capacity of 770.6 mAh g-1. The specific capacity of the anode increased to 1069.7 mAh g-1 after 200 cycles, owing to the electrochemical milling effect. The delivered specific capacity after 200 cycles shows that developed novel anode material is suitable for lithium-ion batteries (LIBs).

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.

Boosting Reversibility and Stability of Li Storage in SnO2 -Mo Multilayers: Introduction of Interfacial Oxygen Redistribution

Among the promising high-capacity anode materials, SnO₂ represents a classic and important candidate that involves both conversion and alloying reactions toward Li storage. However, the inferior reversibility of conversion reactions usually results in low initial Coulombic efficiency (ICE, ≈60%), small reversible capacity, and poor cycling stability. Here, it is demonstrated that by carefully designing the interface structure of SnO₂ -Mo, a breakthrough comprehensive performance with ultrahigh average ICE of 92.6%, large capacity of 1067 mA h g^-1 , and 100% capacity retention after 700 cycles can be realized in a multilayer Mo/SnO₂ /Mo electrode. Furthermore, high capacity retentions are also achieved in pouch-type Mo/SnO₂ /Mo||Li half cells and Mo/SnO₂ /Mo||LiFePO₄ full cells. The amorphous SnO₂ /Mo interfaces, which are induced by redistribution of oxygen between SnO₂ and Mo, can precisely adjust the reversible capacity and cycling stability of the multilayers, while the stable capacities are parabolic with the interfacial density. Theoretical calculations and in/ex situ investigation reveal that oxygen redistribution in SnO₂ /Mo heterointerfaces boosts Li-ion transport kinetics by inducing a built-in electric field and improves the reaction reversibility of SnO₂ . This work provides a new understanding of interface-performance relationship of metal-oxide hybrid electrodes and pivotal guidance for creating high-performance Li-ion batteries.

Tin oxide based nanostructured materials: synthesis and potential applications

In view of their inimitable characteristics and properties, SnO₂ nanomaterials and nanocomposites have been used not only in the field of diverse advanced catalytic technologies and sensors but also in the field of energy storage such as lithium-ion batteries and supercapacitors, and in the field of energy production such as solar cells and water splitting. This review discusses the various synthesis techniques such as traditional methods, including processes like thermal decomposition, chemical vapor deposition, electrospinning, sol-gel, hydrothermal, solvothermal, and template-mediated methods and green methods, which include synthesis through plant-mediated, microbe-mediated, and biomolecule-mediated processes. Moreover, the advantages and limitations of these synthesis procedures and how to overcome them that would lead to future research are also discussed. This literature also focuses on various applications such as environmental remediation, energy production, energy storage, and removal of biological contaminants. Therefore, the rise and journey of SnO₂-based nanocomposites will motivate the modern generation of chemists to modify and design robust nanoparticles and nanocomposites that can effectively tackle significant environmental challenges. This overview concludes by providing future perspectives on research into tin oxide in synthesis and its various applications.

Unlocking Rapid Charging and Extended Lifetimes for Li-Ion Batteries Using Freestanding Quantum Conversion-Type Aerofilm Anode

Batteries capable of quick charging as fast as fossil fuel vehicles are becoming a vital issue in the electric vehicle market. However, conversion-type materials promising as a next-generation anode have many problems to satisfy fast charging and long-term cycles due to their low conductivity and large irreversibility despite a high theoretical capacity. Here, we report effective strategies for a SnO₂-based anode to enable rapid-charging, long-cycle, and high reversible capacity. The quantum size of SnO₂ nanoparticles uniformly embedded within a 3D conductive carbon matrix as a prerequisite for high reversible capacity increases the interdiffusion layer and facilitates a highly reversible conversion reaction between Li₂O/Sn and SnO₂. In particular, the Sn-C chemical bond achieves ion-site control and direct electron transfer, enabling boost charging. Further, the robust and porous structure of the binder-free three-dimensional electrode buffers the massive volume expansion during Li insertion/desertion and allows for multidimensional rapid-ion diffusion. As a result, our quantum SnO₂ anode delivers a high reversible capacity of about 753 mAh g^-1 with a 468% capacity increase after 4000 cycles at 10 C. It also presents a gradually increasing capacity up to 548 mAh g^-1 even at 20 C and superior cyclability over 20 000 cycles in capacity stabilization. This study will contribute to designing aerofilm-based conversion-type electrodes for fast charging devices.

Boosting the lithium storage performance of tin dioxide by carbon nanotubes supporting and surface engineering

In order to reduce the negative impact of the extra carbon coating on the electrochemical properties of the commonly sandwiched carbon nanotubes@tin dioxide@carbon (CNT@SnO₂@C) composites, the external C coating has been designed as a porous carbon in this work. The well-designed porous carbon coating offers an attractive advantage compared to the common carbon coatings, namely, it can not only better mitigate the volumetric variation of SnO₂ by means of its spongy structure with better flexibility and rich free space, but also accelerate the lithium-ions diffusion by virtue of its open tunnel-like architecture. For this reason, this composite prepared here shows outstanding electrochemical performance stemming from the cooperative effect of inner CNT supporting and externally porous carbon coating, displaying 819.3 and 576.0 mAh g^-1 at 200 and even 1000 mA g^-1 after even 500 cycles, respectively. This surface engineering strategy may be valuable for enhancing the cyclical durability of other metal oxides with higher theoretical specific capacities.

Carbon coating on metal oxide materials for electrochemical energy storage

During the past decades, nano-structured metal oxide electrode materials have received growing attention due to their low development cost and high theoretical specific capacity, accordingly, quite a lot of metal oxide electrode materials are being used in electrochemical energy storage devices. However, the further development was limited by the relatively low electrical conductivity and the volume expansion during electrochemical reactions. Thus, many approaches have been proposed to obtain high-efficiency metal oxide electrode materials, such as designing nanomaterials with ideal morphology and high specific surface area, optimizing with carbon-based materials (such as graphene and glucose) to prepare nanocomposites, combining with conductive substrates to enhance the conductivity of electrodes, etc. Owning to the advantages of low cost and high chemical stability of carbon materials, core-shell structure formed by carbon-coated metal oxides is considered to be a promising solution to solve these problems. Therefore, this review mainly focuses on recent research advances in the field of carbon-coated metal oxides for energy storage, summarizing the advantages and disadvantages of common metal oxides and different types of carbon sources, and proposing methods to optimize the material properties in terms of structure and morphology, carbon layer thickness, coating method, specific surface area and pore size distribution, as well as improving electrical conductivity. In addition, the double or multi-layer coating strategy is also a reflection of the continuous development of carbon coating method. Hopefully, this rereview may provide a new direction for the renewal and development of future energy storage electrode materials.

Highly conductive triple-layered hollow MnO2@SnO2@NHCS nanospheres with excellent lithium storage capacity for high performance lithium-ion batteries

Multilayered hollow MnO2@SnO2@NHCS nanospheres incorporate the merits of highly conductive N-doping and the synergistic effect of metal oxides.

ZIF-67-derived NiCo2O4@Co2P/Ni2P honeycomb nanosheets on carbon cloth for high-performance asymmetric supercapacitors

NiCo2O4@Co2P/Ni2P-CC, for the first time, was prepared using ZIF-67 as sacrificial templates through 4 steps procedure. Based on honeycomb structures, NiCo2O4@Co2P/Ni2P-CC electrode shows high areal capacitance and excellent cycle stability.

Tin dioxide-based nanomaterials as anodes for lithium-ion batteries

The development of new electrode materials for lithium-ion batteries (LIBs) has attracted significant attention because commercial anode materials in LIBs, like graphite, may not be able to meet the increasing energy demand of new electronic devices. Tin dioxide (SnO2) is considered as a promising alternative to graphite due to its high specific capacity. However, the large volume changes of SnO2 during the lithiation/delithiation process lead to capacity fading and poor cycling performance. In this review, we have summarized the synthesis of SnO2-based nanomaterials with various structures and chemical compositions, and their electrochemical performance as LIB anodes. This review addresses pure SnO2 nanomaterials, the composites of SnO2 and carbonaceous materials, the composites of SnO2 and transition metal oxides, and other hybrid SnO2-based materials. By providing a discussion on the synthesis methods and electrochemistry of some representative SnO2-based nanomaterials, we aim to demonstrate that electrochemical properties can be significantly improved by modifying chemical composition and morphology. By analyzing and summarizing the recent progress in SnO2 anode materials, we hope to show that there is still a long way to go for SnO2 to become a commercial LIB electrode and more research has to be focused on how to enhance the cycling stability.

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.

Ultrafine Re/Pd nanoparticles on polydopamine modified carbon nanotubes for efficient perchlorate reduction and reusability

This study synthesized nanocomposite catalysts via a modification of Re/Pd codoped carbon nanotubes (CNTs) with different concentrations of polydopamine (PDA), which were used for perchlorate (ClO₄^-) reduction. The loads, dispersion and reducibility of Re/Pd nanoparticles increased yet their particle sizes significantly decreased with the increase of PDA concentrations. The average diameter of Re/Pd codoped D₂CNT (CNT modified by 2 mg/mL PDA) with a narrow size distribution was measured to be 2 nm. The ultrafine Re/Pd codoped D₂CNT catalysts represented outstanding catalytic reduction activity for the conversion of ClO₄^- to Cl^- with TOF of 17.34 h^-1 under the room H₂ atmospheric pressure, which was about 8 times than that of the unmodified catalysts. Furthermore, PDA modification minimized the dissociation of Re by chemical bonding between Re and CNTs carrier and maintained good stability of nanocomposite. This study inspires us to apply green bionic methods to enhance the catalytic reduction of perchlorate by changing the physical properties of Re/Pd nanoparticles.

Facile synthesis of SnO2@carbon nanocomposites for lithium-ion batteries

SnO₂@C nanocomposite nanostructure approach is demonstrated, which confers shielding for volume expansion because of carbon. The SnO₂@C nanocomposite anode exhibits superior cycling stability and rate capability due to the stable electrode structure.

The Sn–C bond at the interface of a Sn2Nb2O7–Super P nanocomposite for enhanced electrochemical performance

A Sn₂Nb₂O₇–Super P nanocomposite (SNO–SP) as an anode material for lithium ion batteries is successfully synthesized through a simple hydrothermal method.

Photon management properties of Yb-doped SnO2 nanoparticles synthesized by the sol-gel technique

SnO2 is a transparent large band gap semiconductor, particularly interesting for optoelectronic and photovoltaic devices, mainly because its conduction can be easily tuned by doping or by modulating the amount of oxygen vacancies. Besides, rare earth doping was successfully exploited for up conversion properties. Here we report on the functionalization of SnO2 nanoparticles with optically active Yb3+ ions using the sol-gel method, which allows UV to NIR spectral (down) conversion. As starting solutions we used stable non-alkoxide metal-organic compounds, which is rather uncommon. Transmission electron microscopy analysis demonstrated the formation of small well-crystallized nanoparticles while X-ray photoelectron spectroscopy measurements have revealed that the Yb is well inserted in the host matrix and has a 3+ valence state. All nanoparticles present large absorption in the UV-visible range (250 to 550 nm) and a band gap that decreases down to 2.72 eV upon doping. The UV energy converted into NIR on the basis of efficient energy transfer from SnO2 to the Yb3+ ions ranges between 250 and 400 nm. Reference undoped SnO2 nanoparticles with a mean size of 20 nm allow converting UV light into broad visible emission centered at 650 nm. The incorporation of up to 3.5 at% of Yb3+ ions into the SnO2 host matrix results in a spectacular decrease of the nanoparticle size down to 6.6 nm. This allowed also the shift of the photoluminescence to NIR in the 970-1050 nm range. The energy level structure of Yb3+ in SnO2 was successfully determined from the deconvolution of the Yb emission. This emission is significantly enhanced by increasing the doping level. All optical measurements suggest that these nanoparticles can be efficiently used as down-shifting converters.

Tin Oxide Based Nanomaterials and Their Application as Anodes in Lithium-Ion Batteries and Beyond

Herein, recent progress in the field of tin oxide (SnO2 )-based nanosized and nanostructured materials as conversion and alloying/dealloying-type anodes in lithium-ion batteries and beyond (sodium- and potassium-ion batteries) is briefly discussed. The first section addresses the importance of the initial SnO2 micro- and nanostructure on the conversion and alloying/dealloying reaction upon lithiation and its impact on the microstructure and cyclability of the anodes. A further section is dedicated to recent advances in the fabrication of diverse 0D to 3D nanostructures to overcome stability issues induced by large volume changes during cycling. Additionally, the role of doping on conductivity and synergistic effects of redox-active and -inactive dopants on the reversible lithium-storage capacity and rate capability are discussed. Furthermore, the synthesis and electrochemical properties of nanostructured SnO2 /C composites are reviewed. The broad research spectrum of SnO2 anode materials is finally reflected in a brief overview of recent work published on Na- and K-ion batteries.

Self-limiting electrode with double-carbon layers as walls for efficient sodium storage performance

As a promising energy storage device, sodium ion batteries (SIBs) have attracted more and more attention. Nevertheless, the radius of a sodium ion is much larger than that of a lithium ion, and it is still a significant challenge to solve the problem of volume expansion. In order to solve the problem of volume expansion, a rational nanostructure consisting of CNTs as a carbon matrix, and were sequentially coated with mesoporous SnO2 and N-doped porous carbon tube (NCT). Mesoporous SnO2 can alleviate the volume expansion caused by charge and discharge, and the N-doped porous carbon layer can further inhibit the volume expansion of SnO2. When used as an anode material in sodium ion batteries, the CNT@SnO2@NCT heterostructure achieves efficient capabilities (350 and 150 mA h g-1 at current densities of 0.1 and 2 A g-1, respectively).

Steam Selective Etching: A Strategy to Effectively Enhance the Flexibility and Suppress the Volume Change of Carbonized Paper-Supported Electrodes

Paper-supported electrodes with high flexibility have attracted much attention in flexible Li-ion batteries. However, they are restricted by the heavy inactive paper substrate and large volume change during the lithiation-delithiation process, which will lead to low capacity and poor rate capability and cyclability. Converting the paper substrate to carbon fiber by carbonization can substantially eliminate the "dead mass", but it becomes very brittle. This study reports a water-steam selective etching strategy that successfully addresses these problems. With the help of steam etching, pores are created, and transition-metal oxides are embedded into the fiber. These effectively accommodate the volume change and enhances the kinetics of ion and electron transport. The pores release the mechanical stress from bending, ensuring the sufficient bendability of carbonized paper. Benefiting from these merits, the steam-etched samples show high flexibility and possess outstanding electrochemical performance, including ultra-high capacity and superior cycling stability with capacity retention over 100% after 1500 cycles at 2 A g^-1. Furthermore, a flexible Li-ion full battery using the steam-etched Fe₂O₃@CNF anode and LiFePO₄/steam-etched CNF cathode delivers a high capacity of 623 mAh g^-1 at 100 mA g^-1 and stable electrochemical performances under the bent state, holding great promise for next-generation wearable devices.

Electrochemical Reduction of CO2 by SnOx Nanosheets Anchored on Multiwalled Carbon Nanotubes with Tunable Functional Groups

Sn-based electrocatalysts are promising for the electrochemical CO₂ reduction reaction (CO2RR), but suffer from poor activity and selectivity. A hierarchical structure composed of ultrathin SnO_x nanosheets anchored on the surface of the commercial multiwalled carbon nanotubes (MWCNTs) is synthesized by a simple hydrothermal process. The electrocatalytic performance can be further tuned by functionalization of the MWCNTs with COOH, NH₂ , and OH groups. Both SnO_x @MWCNTs-COOH and SnO_x @MWCNTs-NH₂ show excellent catalytic activity for CO₂ RR with nearly 100 % selectivity for C₁ products (formate and CO). SnO_x @MWCNTs-COOH has favorable formate selectivity with a remarkably high faradaic efficiency (FE) of 77 % at -1.25 V versus standard hydrogen electrode (SHE) and a low overpotential of 246 mV. However, SnO_x @MWCNTs-NH₂ manifests increased selectivity for CO with higher current density. Density functional theory calculations and experimental studies demonstrate that the interaction between Sn species and functional groups play an important role in the tuning of the catalytic activity and selectivity of these functionalized electrocatalysts. SnO_x @MWCNTs-COOH and SnO_x @MWCNTs-NH₂ both effectively inhibit the hydrogen evolution reaction and prove stable without any significant degradation over 20 h of continuous electrolysis at -1.25 V versus SHE.

Coaxial Carbon Nanotube Supported TiO2@MoO2@Carbon Core-Shell Anode for Ultrafast and High-Capacity Sodium Ion Storage

The sluggish kinetic in electrode materials is one of the critical challenges in achieving high-power sodium ion storage. We report a coaxial core-shell nanostructure composed of carbon nanotube (CNT) as the core and TiO₂@MoO₂@C as shells for a hierarchically nanoarchitectured anode for improved electrode kinetics. The 1D tubular nanostructure can effectively reduce ion diffusion path, increase electrical conductivity, accommodate the stress due to volume change upon cycling, and provide additional interfacial active sites for enhanced charge storage and transport properties. Significantly, a synergistic effect between TiO₂ and MoO₂ nanostructures is investigated through ex situ solid-state nuclear magnetic resonance. The electrode exhibits a good rate capability (150 mAh g^-1 at 20 A g^-1) and superior cycling stability with a reversibly capacity of 175 mAh g^-1 at 10 A g^-1 for over 8000 cycles.

Efficient photocatalytic reactions of Cr(vi) reduction and ciprofloxacin and RhB oxidation with Sn(ii)-doped BiOBr

Efficient photocatalytic reactions of Cr(VI) reduction, ciprofloxacin and RhB oxidation with Sn(II) doped BiOBr.

Self-Adaptive Electrode with SWCNT Bundles as Elastic Substrate for High-Rate and Long-Cycle-Life Lithium/Sodium Ion Batteries

Massive volume change of active materials in lithium/sodium ion batteries (LIB/SIB) causes severe structural collapse of electrodes and fast capacity decay of batteries. Here, a coaxial composite of single-wall carbon nanotube bundle (SWCNTB/SnO₂ ) nanoparticles (NPs)/N-doped carbon shell (SWCNTB@SnO₂ @C) is constructed, where SWCNTBs with exceptional elasticity are explored as a self-adaptive substrate to supply a highly resilient conductive network. Within the confinement of hard carbon shells, SWCNTB can produce radially elastic deformation to accommodate the volume change of SnO₂ during Li⁺ /Na⁺ insertion/extraction. This overcomes the problem of strain fracturing of the outer carbon shell, as well as maintains close electrical contact between SnO₂ and the conductive network. The LIB/SIB with the self-adaptive SWCNTB@SnO₂ @C electrode presents a series of superior battery performances, for example, a high specific capacity of 608 mAh g^-1 at 10 A g^-1 and 600 cycles in LIB without capacity decay.

Sandwiched spherical tin dioxide/graphene with a three-dimensional interconnected closed pore structure for lithium storage

Low reversion of lithium oxide (Li2O) and the tin (Sn) coarsening causing irreversible capacity loss is the main reason for the poor cycle performance in tin dioxide (SnO2) based composites. In this research, a novel sandwiched spherical tin dioxide/graphene with a three-dimensional interconnected closed pore structure is synthesized. The microstructural characterization shows that the spherical graphene with submicron sized diameters interconnects with each other forming an interconnected flexible conductive network, whereas a large number of SnO2 nanoparticles (approximately 5 nm) are limited homogeneously in between the interlayers of the sphere-like graphene shell. The sandwich structure of the SnO2/graphene and the closed graphene sphere can provide double protection for the SnO2. When it is used as an anode material for energy storage, the generated Li2O can remain in close contact with Sn to make the conversion reaction (SnO2 + 4Li+ + 2e- ↔ Sn + Li2O) highly reversible in situ and the reversibility even does not diminish markedly after 100 cycles. A high reversible specific capacity of 914.8 mA h g-1 is expressed in the sandwiched spherical SnO2/graphene composite at 100 mA g-1 after 100 cycles, which is significantly higher than that of a SnO2/graphene aerogel with an open pore structure.

MOF-Derived Metal Oxide Composites for Advanced Electrochemical Energy Storage

Over the past two decades, metal-organic frameworks (MOFs), a type of porous material, have aroused great interest as precursors or templates for the derivation of metal oxides and composites for the next generation of electrochemical energy storage applications owing to their high specific surface areas, controllable structures, and adjustable pore sizes. The electrode materials, which affect the performance in practical applications, are pivotal components of batteries and supercapacitors. Metal oxide composites derived from metal-organic frameworks possessing high reversible capacity and superior rate and cycle performance are excellent electrode materials. In this Review, potential applications for MOF-derived metal oxide composites for lithium-ion batteries, sodium-ion batteries, lithium-oxygen batteries, and supercapacitors are studied and summarized. Finally, the challenges and opportunities for future research on MOF-derived metal oxide composites are proposed on the basis of academic knowledge from the reported literature as well as from experimental experience.

A tin(iv) oxides/carbon nanotubes composite with core-tubule structure as an anode material for high electrochemistry performance LIBs

SnO2/CNTs composites with core-tubule structure are prepared by a facile wet chemical method. The investigation of electrochemical characteristics of the SnO2/CNTs composites shows that the composites exhibit some advantages, such as stable core-tubule structure, small particle size of SnO2, low electron-transfer resistance and faster lithium ion migration speed. The final product synthesized under optimized conditions can release a stable capacity of about 743 mA h g-1 after 100 cycles at the current density of 0.4 A g-1, 598 mA h g-1 after 500 cycles at the current density of 4 A g-1. Even at a super high current density of 8 A g-1, the composite can still deliver a steady capacity of 457 mA h g-1, and the discharge capacity can be restored to 998 mA h g-1 when current density is decreased to 0.4 A g-1.

Atomically Intercalating Tin Ions into the Interlayer of Molybdenum Oxide Nanobelt toward Long-Cycling Lithium Battery

Atomic intercalation of different agents into 2D layered materials can engineer the intrinsic structure on the atomic scale and thus tune the physical and chemical properties for specific applications. Here we successfully introduce tin (Sn) atoms into the interlayer of α-MoO₃ nanobelts forming a new MoO₃-Sn intercalation with ultrastable structure. Combining with theoretical calculations, our synchrotron radiation-based characterizations and electron microscope observations clearly reveal that the intercalated Sn atoms could bond with five O atoms, forming a pentahedral structure. Subsequently, the Sn-O bonds induce a less distorted [MoO₆] octahedral structure, resulting in a unique structure that is distinct with pristine α-MoO₃ or any other molybdenum oxides. Employed as anode for lithium-ion battery, the as-prepared MoO₃-Sn nanobelts display a much higher capacity of 520 mAhg^-1 at 500 mAg^-1 than α-MoO₃ nanobelts (291 mAhg^-1), with a Coulombic efficiency of 99.5%. Moreover, owing to the strong intercalation from Sn ions, the MoO₃-Sn nanobelts pose superior cyclability, durability, and reliability.

A critical role of catalyst morphology in low-temperature synthesis of carbon nanotube-transition metal oxide nanocomposite

The effect of the catalyst morphology on the growth of carbon nanotubes (CNT) on nanostructured transition metal oxides was investigated to study a novel low-temperature synthetic route to functional CNT-transition metal oxide nanocomposites. Among several nanostructured manganese oxides with various morphologies and structures, only exfoliated 2D nanosheets of layered MnO₂ acted as an effective catalyst for the chemical vapor deposition of CNT at low temperatures of 400-500 °C, which emphasizes the critical role of the catalyst morphology in CNT growth. Heat treatment of the MnO₂ nanosheets under a C₂H₂ flow induced the deposition of CNT, as well as a phase transition to a 2D ordered assembly of MnO nanoparticles. The resulting CNT-MnO nanocomposites displayed excellent functionalities in Li-ion electrodes with huge discharge capacities and good rate characteristics, which highlights the usefulness of the present method for studying functional CNT-metal oxide nanocomposites. Electron microscopy and density functional theory calculations propose a formation mechanism via the efficient adsorption of carbon on the MnO₂ nanosheets followed by the surface diffusion of carbon. It is of prime importance that the substitution of Fe for layered MnO₂ nanosheets remarkably improved the efficiency of the formation of CNT by enhancing the surface adsorption of carbon species. This is the first report of the efficient growth of CNT at a very low temperature of 400 °C. The universal merit of the 2D nanosheet morphology was confirmed by the successful synthesis of a CNT-TiO₂ nanocomposite with exfoliated titanate nanosheets. The present study demonstrates that employing exfoliated transition metal oxide nanosheets as catalysts provides an efficient low-temperature synthetic route to functional CNT-transition metal oxide nanocomposites.

One-Step Self-Assembly Synthesis α-Fe2O3 with Carbon-Coated Nanoparticles for Stabilized and Enhanced Supercapacitors Electrode

A cocoon-like α-Fe2O3 nanocomposite with a novel carbon-coated structure was synthesized via a simple one-step hydrothermal self-assembly method and employed as supercapacitor electrode material. It was observed from electrochemical measurements that the obtained α-Fe2O3@C electrode showed a good specific capacitance (406.9 Fg−1 at 0.5 Ag−1) and excellent cycling stability, with 90.7% specific capacitance retained after 2000 cycles at high current density of 10 Ag−1. These impressive results, presented here, demonstrated that α-Fe2O3@C could be a promising alternative material for application in high energy density storage.

One-Pot Hybrid SnO2 /Poly(methyl methacrylate) Nanocomposite Formation through Pulsed Laser Irradiation

The localized in situ formation of tin dioxide (SnO₂ ) nanoparticles embedded in poly(methyl methacrylate) (PMMA) films is presented. This is achieved by the photoinduced conversion of the tin acetate precursor included in polymeric films, through controlled UV or visible pulsed laser irradiation at λ=355 and 532 nm, respectively. The evolution of the formation of nanoparticles is followed by UV/Vis spectroscopy and shows that their growth is affected in different ways by the laser pulses at the two applied wavelengths. This, in combination with electron microscopy analysis, reveals that, depending on the irradiation wavelength, the size of the nanoparticles in the final nanocomposites differs. This difference is attributed to distinct mechanistic pathways that lead to the synthesis of small nanoparticles (from 1.5 to 4.5 nm) at λ=355 nm, whereas bigger ones (from 5 to 16 nm) are formed at λ=532 nm. At the same time, structural studies with both X-ray and electron diffraction measurements demonstrate the crystallinity of SnO₂ nanoparticles in both cases, whereas XPS analysis confirms the light-induced oxidation of tin acetate into SnO₂ . Taken all together, it is demonstrated that the pulsed laser irradiation at λ=355 and 532 nm leads to the formation of SnO₂ nanoparticles with defined features highly dispersed in PMMA solid matrices.

Hierarchical architecture for flexible energy storage

The introduction of hierarchy and chirality into structure is of great interest, and can result in new optical and electronic properties due to the synergistic effect of helical and anisotropic structures. Herein, we demonstrate a simple and straightforward route toward the fabrication of hierarchical chiral materials based on the assembly of two-dimensional graphene oxide nanosheets (GO) and one-dimensional cellulose nanocrystals (CNCs). The unique layered structure of CNC/GO could be preserved in the solid state, allowing electrode active SnO₂ to be loaded for potential applications in energy storage. The resultant SnO₂/CNC/reduced GO (SnO₂/CNC/rGO) composite could be processed into film, fiber, and textile with an extremely high tensile strength of 100 MPa. The free-standing SnO₂/CNC/rGO electrodes exhibit highly improved energy storage performance, with a reversible capacity of ∼500 mA h g^-1 maintained for 1500 cycles in the film and ∼800 mA h g^-1 maintained for 150 cycles in the textile at a current density of 500 mA g^-1. This is attributed to the prepared hierarchical chiral structures. The presented technique provides an effective approach to producing hierarchical functional materials from nanoparticles as building blocks, which might open an avenue for the creation of new flexible energy storage devices.

Nitrogen-doped-carbon-coated SnO2 nanoparticles derived from a SnO2@MOF composite as a lithium ion battery anode material

A facile method was developed to combine MOF-derived N-doped carbon with SnO₂ nanoparticles, which can cushion the volume change. The optimized SOC-3 composite achieved a reversible specific capacity of 1032 mA h g⁻¹ after 150 cycles at 100 mA g⁻¹.