Hollow Porous CoSnOx Nanocubes Encapsulated in One-Dimensional N-Doped Carbon Nanofibers as Anode Material for High-Performance Lithium Storage

Effectively coupling of SnSe2nanosheet with N, Se co-doped carbon nanofibers as self-standing anode for lithium-ion batteries

Tin selenides possess layered structure and high theoretical capacity, which is considered as desirable anode material for lithium-ion batteries. However, its further development is limited by the low intrinsic electrical conductivity and sluggish reaction kinetics. Herein, a well-designed structure of SnSe2nanosheet attached on N, Se co-doped carbon nanofibers (SnSe2@CNFs) is fabricated as self-standing anodes for lithium-ion batteries. The integration of structural engineering and heteroatom doping enables accelerated electrons transfer and rapid ion diffusion for boosting Li+storage performance. Impressively, the flexible SnSe2@CNFs anodes exhibit inspiring capacity of 837.7 mAh g-1after 800 cycles at 1.2 C with coulombic efficiency almost 100% and superior rate performance 419.5 mAh g-1at 2.4 C. The kinetics analysis demonstrates the pseudocapacitive characteristic of SnSe2@CNFs promotes the storage property. This work sheds light on the hierarchical electrode construction towards high-performance energy storage applications.

Multicomponent Nanoparticles Synergistic One-Dimensional Nanofibers as Heterostructure Absorbers for Tunable and Efficient Microwave Absorption

Application of novel radio technologies and equipment inevitably leads to electromagnetic pollution. One-dimensional polymer-based composite membrane structures have been shown to be an effective strategy to obtain high-performance microwave absorbers. Herein, we reported a one-dimensional N-doped carbon nanofibers material which encapsulated the hollow Co3SnC0.7 nanocubes in the fiber lumen by electrospinning. Space charge stacking formed between nanoparticles can be channeled by longitudinal fibrous structures. The dielectric constant of the fibers is highly related to the carbonization temperature, and the great impedance matching can be achieved by synergetic effect between Co3SnC0.7 and carbon network. At 800 °C, the necklace-like Co3SnC0.7/CNF with 5% low load achieves an excellent RL value of - 51.2 dB at 2.3 mm and the effective absorption bandwidth of 7.44 GHz with matching thickness of 2.5 mm. The multiple electromagnetic wave (EMW) reflections and interfacial polarization between the fibers and the fibers internal contribute a major effect to attenuating the EMW. These strategies for regulating electromagnetic performance can be expanded to other electromagnetic functional materials which facilitate the development of emerging absorbers.

Synthesis of MnO-Sn cubes embedding in nitrogen-doped carbon nanofibers with high lithium-ion storage performance

In this paper, a carbon nanofiber (CNF) hybrid nanomaterial composed of MnO-Sn cubes embedding in nitrogen-doped CNF (MnO-Sn@CNF) is synthesized through electrospinning and post-thermal reduction processes. It exhibits good electrochemical lithium-ion storage performance as the anode, such as high reversible capacity, outstanding cycle performance (754 mAh g^-1at 1 A g^-1after 1000 cycles), and good rate capability (447 mAh g^-1at 5 A g^-1). The excellent electrochemical properties are derived from a unique nanostructure design. MnO-Sn@CNF has a three-dimensional conductive network with a stable core-shell structure, which improves the electrical conductivity and mechanical stability of the materials. In addition, the mesopores on the surface of carbon fibers can shorten the diffusion distance of lithium ions and promote the combination of active sites of the material with lithium ions. The internal MnO and Sn form a heterostructure, which enhances the stability of the physical structure of the electrode material. This material design method provides a reference strategy for the development of high-performance lithium-ion batteries anode.

Influence of the Hollowness and Size Distribution on the Magnetic Properties of Fe3O4 Nanospheres

In this study, Fe₃O₄ nanospheres with different levels of hollowness were successfully prepared by the solvent thermal method. The synthesized Fe₃O₄ nanospheres were characterized by transmission electron microscopy, X-ray diffraction, and vibrating sample magnetometry, and Image-Pro software was used to analyze the hollowness of the Fe₃O₄ nanospheres for the first time. It was found that excess reactants could lead to the disappearance of the hollow structure of the Fe₃O₄ nanospheres, and the reason for this phenomenon was discussed as due to entropy increase theory. Furthermore, the influence of the hollowness and size distribution on the magnetic properties of the Fe₃O₄ nanospheres was evaluated. The magnetic properties of a Fe₃O₄ nanosphere with a hollowness of 10.48% showed a relatively high saturation magnetization of 103 emu/g and a rather low coercivity (54 Oe). The as-prepared Fe₃O₄ nanospheres are expected to be useful in a wide range of fields such as drug-delivery and energy applications.

Double-Shelled Hollow SiO2 @N-C Nanofiber Boosts the Lithium Storage Performance of [PMo12 O40 ]3

Polyoxometalates (POMs)-based materials, with high theoretical capacities and abundant reversible multi-electron redox properties, are considered as promising candidates in lithium-ion storage. However, the poor electronic conductivity, low specific surface area and high solubility in the electrolyte limited their practical applications. Herein, a double-shelled hollow PMo₁₂ -SiO₂ @N-C nanofiber (PMo₁₂ -SiO₂ @N-C, where PMo₁₂ is [PMo₁₂ O₄₀ ]^3- , N-C is nitrogen-doped carbon) was fabricated for the first time by combining coaxial electrospinning technique, thermal treatment and electrostatic adsorption. As an anode material for LIBs, the PMo₁₂ -SiO₂ @N-C delivered an excellent specific capacity of 1641 mA h g^-1 after 1000 cycles under 2 A g^-1 . The excellent electrochemical performance benefited from the unique double-shelled hollow structure of the material, in which the outermost N-C shell cannot only hinder the agglomeration of PMo₁₂ , but also improve its electronic conductivity. The SiO₂ inner shell can efficiently avoid the loss of active components. The hollow structure can buffer the volume expansion and accelerate Li⁺ diffusion during lithiation/delithiation process. Moreover, PMo₁₂ can greatly reduce charge-resistance and facilitate electron transfer of the entire composites, as evidenced by the EIS kinetics study and lithium-ion diffusion analysis. This work paves the way for the fabrication of novel POM-based LIBs anode materials with excellent lithium storage performance.