Bowl-like SnO2@Carbon Hollow Particles as an Advanced Anode Material for Lithium-Ion Batteries

In Situ Encapsulation of SnS2/MoS2 Heterojunctions by Amphiphilic Graphene for High-Energy and Ultrastable Lithium-Ion Anodes

Lithium-ion batteries with transition metal sulfides (TMSs) anodes promise a high capacity, abundant resources, and environmental friendliness, yet they suffer from fast degradation and low Coulombic efficiency. Here, a heterostructured bimetallic TMS anode is fabricated by in situ encapsulating SnS2/MoS2 nanoparticles within an amphiphilic hollow double-graphene sheet (DGS). The hierarchically porous DGS consists of inner hydrophilic graphene and outer hydrophobic graphene, which can accelerate electron/ion migration and strongly hold the integrity of alloy microparticles during expansion and/or shrinkage. Moreover, catalytic Mo converted from lithiated MoS2 can promote the reaction kinetics and suppress heterointerface passivation by forming a building-in-electric field, thereby enhancing the reversible conversion of Sn to SnS2. Consequently, the SnS2/MoS2/DGS anode with high gravimetric and high volumetric capacities achieves 200 cycles with a high initial Coulombic efficiency of >90%, as well as excellent low-temperature performance. When the commercial Li(Ni0.8Co0.1Mn0.1)O2 (NCM811) cathode is paired with the prelithiated SnS2/MoS2/DGS anode, the full cells deliver high gravimetric and volumetric energy densities of 577 Wh kg-1 and 853 Wh L-1, respectively. This work highlights the significance of integrating spatial confinement and atomic heterointerface engineering to solve the shortcomings of conversion-/alloying typed TMS-based anodes to construct outstanding high-energy LIBs.

Janus nanoplates, -bowls, and -cups: controlling size and curvature via terpolymer/homopolymer blending in 3D confinement

The synthesis and properties of Janus nanoparticles with spherical, cylindrical, and disk-like shapes are nowadays rather well understood. Other topologies such as nanorings and bowl-shaped Janus nanoparticles are believed to show distinctly different solution behavior and interaction with interfaces, but limitations in their synthesis currently prevents a proper investigation of these properties. Especially the combination of shape- and surface-anisotropy of bowl-shaped Janus nanoparticles could result in enhanced selectivity in uptake of cargo and enhanced directional diffusion. We here produce bowl-shaped Janus nanoparticles without noticeable side products through evaporation-induced confinement assembly (EICA) of triblock terpolymers blended with high molecular weight homopolymer. The triblock terpolymer phase separates from the homopolymer into spherical domes, where the terpolymer adopts a hemispherical lamella-lamella morphology (ll). Selective cross-linking, removal of the homopolymer, and disassembly of the microparticles releases the bowl-shaped Janus nanoparticles. The amount of blended homopolymer determines the size of the spherical dome, allowing to control particle curvature into flat Janus nanoplates, hemispherical Janus nanobowls, and deep Janus nanocups. The use of Shirasu Porous Glass (SPG) membranes with pore sizes in the range of dpore = 0.2-2.0 μm further provides control of particle diameter. Size and shape were analyzed with electron microscopy and the Janus character through selective surface decoration. The diffusion behavior of bowl-shaped Janus nanoparticles was investigated depending on particle curvature and anisotropy using angle-dependent dynamic light scattering.

Electrostatic Adsorption Enables Layer Stacking Thickness-Dependent Hollow Ti3 C2 Tx MXene Bowls for Superior Electromagnetic Wave Absorption

Although transition metal carbides/carbonitrides (MXenes) exhibit immense potential for electromagnetic wave (EMW) absorption, their absorbing ability is hindered by facile stacking and high permittivity. Layer stacking and geometric structures are expected to significantly affect the conductivity and permittivity of MXenes. However, it is still a formidable task to simultaneously regulate layer stacking and microstructure of MXenes to realize high-performance EMW absorption. Herein, a simple and viable strategy using electrostatic adsorption is developed to integrate 2D Ti₃ C₂ T_x MXene nanosheets into 3D hollow bowl-like structures with tunable layer stacking thickness. Density functional theory calculations indicate an increase in the density of states of the d orbital from the Ti atom near the Fermi level and the generation of additional electrical dipoles in the MXene nanosheets constituting the bowl walls upon reducing the layer stacking thickness. The hollow MXene bowls exhibit a minimum reflection loss (RL_min ) of -53.8 dB at 1.8 mm. The specific absorbing performance, defined as RL_min (dB)/thickness (mm)/filler loading (wt%), exceeds 598 dB mm^-1 , far surpassing that of the most current MXene and bowl-like materials reported in the literature. This work can guide future exploration on designing high-performance MXenes with "lightweight" and "thinness" characteristics for superior EMW absorption.

Facile Synthesis of Hybrid Anodes with Enhanced Lithium-Storage Performance Realized by a "Synergistic Effect"

Alloying-type anodes including Si- and Sn-based materials are considered the most exploitable anodes for high-performance lithium-ion batteries. However, problems of poor kinetics properties and structural failures such as grain pulverization and coarsening hinder their large-scale application. Herein, SnO₂/Si@graphite hybrid anodes, with nano-SnO₂ and nano-Si thoroughly mixed with each other and loaded onto graphite flakes, have been prepared by a facile ball milling method. Attributed to the "synergistic effect" between SnO₂ and Si, the mechanical stability and kinetics properties can be remarkably enhanced. Furthermore, graphite substrate supplies a fast electrically conductive path and buffers the volume expansion of active particles. Accordingly, SnO₂/Si@graphite delivers 798.9 mAh g^-1 at 200 mA g^-1 and maintains 550.8 mAh g^-1 after 1000 cycles at 1 A g^-1 in half cells. Impressively, a high energy density of 431.4 Wh kg^-1 (based on the mass of anode and cathode) can be obtained in full cells when paired with the NCM622 cathode. This work presents an effective strategy to exploit high-performance alloying-type anodes for LIBs by designing hybrid materials with multiple active components.

In situ anchor of Na2Ti3O7 in nitrogen-rich carbon hollow red blood cell-like structure as a 0D-3D hierarchical electrode material for efficient electrochemical desalination

Reasonable design of the structure and complementary compounding of electrode materials is helpful to enhance capacitive deionization (CDI) performance. Herein, a novel 0D-3D hierarchical electrode material containing Na2Ti3O7 nanoparticles anchored at hollow red blood cell (HRBC)-like nitrogen-rich carbon (HRBC-NTO/N-C-60) was prepared via selective protection, pyrolysis, and alkalization. Specifically, a HRBC-like NH2-MIL-125-based material (HRBC-MOF-60) was first constructed by a selective protection approach of tannic acid (TN), which addresses the shortcomings of using sacrificial templates or corrosive agents. Afterwards, HRBC-NTO/N-C-60 was obtained in situ by annealing and alkalization of HRBC-MOF-60. The nitrogen-rich carbon with a HRBC-like structure has the ability to rapidly transport electrons, and its porous structure enables remarkable charge transfer. Benefiting from the grafted 3D N-doped porous carbon with a HRBC-like structure, well-dispersed 0D Na2Ti3O7 nanoparticles, and satisfactory bonding effects, HRBC-NTO/N-C-60 exhibited high specific capacitance and fast ionic and electronic diffusion kinetics. Moreover, HRBC-NTO/N-C-60 was well-suited for desalination by functioning as a cathode material for capacitive deionization (CDI), and delivering a high desalination capacity of 66.8 mg g-1 in 200 mg L-1 NaCl solution at 1.4 V. This work introduces an excellent high-performance candidate for electrochemical deionization as well as affording afflatus for accurately inventing OD-3D hierarchical materials with hollow structures.

Boosting the Electrochemical Performance of V2 O3 by Anchoring on Carbon Nanotube Microspheres with Macrovoids for Ultrafast and Long-Life Aqueous Zinc-Ion Batteries

Zinc-ion batteries (ZIBs) are next-generation energy storage systems with high safety and environmental friendliness because they can be operated in aqueous systems. However, the search for electrode materials with ideal nanostructures and compositions for aqueous ZIBs is in progress. Herein, the synthesis of porous microspheres, consisting of V₂ O₃ anchored on entangled carbon nanotubes (p-V₂ O₃ -CNT) and their application as cathode for ZIBs is reported. From various analyses, it is revealed that V₂ O₃ phase disappears after the initial charge process, and Zn_{3+ x} (OH)_{2+3 x} V_{2- x} O_{7-3 x} ∙2H₂ O and zinc vanadate (Zn_y VO_z ) phases undergo zinc-ion intercalation/deintercalation processes from the second cycle. Additionally, the electrochemical performances of p-V₂ O₃ -CNT, V₂ O₃ -CNT (without macrovoids), and porous V₂ O₃ (without CNTs) microspheres are compared to determine the effects of nanostructures and conductive carbonaceous matrix on the zinc-ion storage performance. p-V₂ O₃ -CNT exhibits a high reversible capacity of 237 mA h g^-1 after 5000 cycles at 10 A g^-1 . Furthermore, a reversible capacity of 211 mA h g^-1 is obtained at an extremely high current density of 50 A g^-1 . The macrovoids in V₂ O₃ nanostructure effectively alleviate the volume changes during cycling, and the entangled CNTs with high electrical conductivity assist in achieving fast electrochemical kinetics.

Enhanced Diffusion Kinetics of Li Ions in Double-Shell Hollow Carbon Fibers

The rational design and preparation of hierarchical hollow structures have promising potential in electrochemical energy storage systems. In this paper, double-shell hollow carbon fibers (DSHCFs) with tunable thickness and shell spacing are prepared using hollow electrospun polystyrene fibers as the hard template and in situ coated polypyrrole as the carbon source. The as-prepared DSHCFs with an optimized structure exhibit a submicrometer shell spacing and a nanoscaled shell thickness, which guarantees sufficient contact area with the electrolyte and provides abundant electrochemical active sites for Li⁺ storage. Owing to the unique structural advantages, a DSHCF-based anode shows favorable transport kinetics for both Li⁺ ions and electrons during the lithiation/delithiation process, and a high reversible capacity of 348 mAh g^-1 at 5.0 A g^-1 is well maintained even after 500 cycles with no obvious capacity attenuation. Particular emphasis is given to kinetic Li⁺ storage mechanisms in DSHCFs that are discussed in detail, providing a new avenue for developing high-performance carbon materials for the practical application of energy storage devices.

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.

In Situ Synthesis of Mn3 O4 Nanoparticles on Hollow Carbon Nanofiber as High-Performance Lithium-Ion Battery Anode

The practical applications of Mn₃ O₄ in lithium-ion batteries are greatly hindered by fast capacity decay and poor rate performance as a result of significant volume changes and low electrical conductivity. It is believed that the synthesis of nanoscale Mn₃ O₄ combined with carbonaceous matrix will lead to a better electrochemical performance. Herein, a convenient route for the synthesis of Mn₃ O₄ nanoparticles grown in situ on hollow carbon nanofiber (denoted as HCF/Mn₃ O₄ ) is reported. The small size of Mn₃ O₄ particles combined with HCF can significantly alleviate volume changes and electrical conductivity; the strong chemical interactions between HCF and Mn₃ O₄ would improve the reversibility of the conversion reaction for MnO into Mn₃ O₄ and accelerate charge transfer. These features endow the HCF/Mn₃ O₄ composite with superior cycling stability and rate performance if used as the anode for lithium-ion batteries. The composite delivers a high discharge capacity of 835 mA h g^-1 after 100 cycles at 200 mA g^-1 , and 652 mA h g^-1 after 240 cycles at 1000 mA g^-1 . Even at 2000 mA g^-1 , it still shows a high capacity of 528 mA h g^-1 . The facile synthetic method and outstanding electrochemical performance of the as-prepared HCF/Mn₃ O₄ composite make it a promising candidate for a potential anode material for lithium-ion batteries.

Robust SnO2-x Nanoparticle-Impregnated Carbon Nanofibers with Outstanding Electrochemical Performance for Advanced Sodium-Ion Batteries

The sluggish sodium reaction kinetics, unstable Sn/Na₂ O interface, and large volume expansion are major obstacles that impede practical applications of SnO₂ -based electrodes for sodium-ion batteries (SIBs). Herein, we report the crafting of homogeneously confined oxygen-vacancy-containing SnO_2-x nanoparticles with well-defined void space in porous carbon nanofibers (denoted SnO_2-x /C composites) that address the issues noted above for advanced SIBs. Notably, SnO_2-x /C composites can be readily exploited as the working electrode, without need for binders and conductive additives. In contrast to past work, SnO_2-x /C composites-based SIBs show remarkable electrochemical performance, offering high reversible capacity, ultralong cyclic stability, and excellent rate capability. A discharge capacity of 565 mAh g^-1 at 1 A g^-1 is retained after 2000 cycles.

Colloidal Rings by Site-Selective Growth on Patchy Colloidal Disc Templates

Anisotropic colloidal building blocks are quite attractive as they enable the self-assembly towards new materials with designated hierarchical structures. Although many advances have been achieved in colloidal synthetic methodology, synthesis of colloidal rings with low polydispersity and on a large scale remains a challenge. To address this issue we introduce a new site-selective growth strategy, which relies on using patchy particles. For example, by using patchy discs as templates, silica can selectively be grown on only side surfaces, resulting in formation of silica rings. We demonstrate that shape parameters are tunable and find that these silica rings can be used as secondary template to synthesize other types of rings. This method for synthesizing ring-like colloids provides possibilities for studying their self-assembly and associated phase transitions, and this patchy particles template strategy paves a new route for fabricating other new colloidal particles.

Precise Formation of a Hollow Carbon Nitride Structure with a Janus Surface To Promote Water Splitting by Photoredox Catalysis

The precise modification of redox species on the inner and outer surfaces of hollow nanostructures is relevant in catalysis, surface science, and nanotechnology, but has proven difficult to achieve. Herein, we develop a facile approach to specifically fabricate Pt and Co₃O₄ nanoparticles (NPs) onto the interior and exterior surface of hollow carbon nitride spheres (HCNS), respectively, to promote the surface redox functions of the polymer semiconductors. The photocatalytic water splitting activities of HCNS with spatially separated oxidation and reduction centers at their nanodomains were enhanced. The origin of the enhanced activity was attributed to the spatially separated reactive sites for the evolution of H₂ and O₂ and also to the unidirectional migration of the electron and hole on the Janus surfaces, thereby preventing the unwanted reverse reaction of water splitting and decreasing charge recombination.

High-rate and long-life of Li-ion batteries using reduced graphene oxide/Co3O4 as anode materials

A new one-step microwave method was designed for synthesis of rGO/Co₃O₄, and the Li-ion battery showed high capacity and long life.

Reserving Interior Void Space for Volume Change Accommodation: An Example of Cable-Like MWNTs@SnO2@C Composite for Superior Lithium and Sodium Storage

Reserving interior void space in the cable-like structure of multiwalled carbon nanotubes-in-SnO2-in-carbon layer (MWNTs@SnO2@C) is reported for the first time. Such a design enables the structure performing excellent for Li and Na storage, which benefit from the good electrical conductivity of MWNTs and carbon layer as well as the reserved void space to accommodate the volume changes of SnO2.

Iron triad (Fe, Co, Ni) nanomaterials: structural design, functionalization and their applications

Synthetic strategies and the functionalization of iron triad nanomaterials are summarized, applied mainly in the fields of energy and the environment.