Yolk-Shell Nanostructures: Syntheses and Applications for Lithium-Ion Battery Anodes

A Selective Oxidation Strategy towards the Yolk-Shell Structured ZnS@C Material for Ultra-Stable Li-Ion Storage

Metal chalcogenides are attractive anode materials for lithium-ion batteries (LIBs) due to their high theoretical capacities. With the advantages of low cost and abundance reserves, ZnS is regarded as the prime candidate anode material for future generations, but its practical application is hindered by the large volume expansion during repeated cycling processes and inherent poor conductivity. Rational design of the microstructure with large pore volume and high specific surface area is of great significance to solve these problems. Here, a carbon-coated ZnS yolk-shell structure (YS-ZnS@C) has been prepared by selective partial oxidation of a core-shell structured ZnS@C precursor in air and subsequent acid etching. Studies show that the carbon wrapping and proper etching to bring cavities can not only improve the material's electrical conductivity, but can also effectively alleviate the volume expansion problem of ZnS during its cycles. As a LIB anode material, the YS-ZnS@C exhibits an obvious superiority in capacity and cycle life compared to ZnS@C. The YS-ZnS@C composite shows a discharge capacity of 910 mA h g^-1 at the current density of 100 mA g^-1 after 65 cycles, compared to only 604 mA h g^-1 for ZnS@C after 65 cycles. Notably, at a large current density of 3000 mA g^-1, a capacity of 206 mA h g^-1 can still be maintained after 1000 cycles (over three times of the capacity for ZnS@C). It is expected that the synthetic strategy developed here is applicable to designing various high-performance metal chalcogenide-based anode materials for LIBs.

Research progress of yolk-shell structured nanoparticles and their application in catalysis

Yolk-shell nanoparticles (YSNs) have attracted a broad interest in the field of catalysis due to their unique structure and properties. The hollow structure of YSNs brings high porosity and specific surface areas which is conducive to the catalytic reactions. The flexible tailorability and functionality of both the cores and shells allow a rational design of the catalyst and may have synergistic effect which will improve the catalytic performance. Herein, an overview of the research progress with respect to the synthesis and catalytic applications of YSNs is provided. The major strategies for the synthesis of YSNs are presented, including hard template method, soft template method, ship-in-a-bottle method, galvanic replacement method, Kirkendall diffusion method as well as the Ostwald ripening method. Moreover, we discuss in detail the recent progress of YSNs in catalytic applications including chemical catalysis, photocatalysis and electrocatalysis. Finally, the future research and development of YSNs are prospected.

Encapsulating Fe2 O3 Nanotubes into Carbon-Coated Co9 S8 Nanocages Derived from a MOFs-Directed Strategy for Efficient Oxygen Evolution Reactions and Li-Ions Storage

The development of high-efficiency, robust, and available electrode materials for oxygen evolution reaction (OER) and lithium-ion batteries (LIBs) is critical for clean and sustainable energy system but remains challenging. Herein, a unique yolk-shell structure of Fe₂ O₃ nanotube@hollow Co₉ S₈ nanocage@C is rationally prepared. In a prearranged sequence, the fabrication of Fe₂ O₃ nanotubes is followed by coating of zeolitic imidazolate framework (ZIF-67) layer, chemical etching of ZIF-67 by thioacetamide, and eventual annealing treatment. Benefiting from the hollow structures of Fe₂ O₃ nanotubes and Co₉ S₈ nanocages, the conductivity of carbon coating and the synergy effects between different components, the titled sample possesses abundant accessible active sites, favorable electron transfer rate, and exceptional reaction kinetics in the electrocatalysis. As a result, excellent electrocatalytic activity for alkaline OER is achieved, which delivers a low overpotential of 205 mV at the current density of 10 mA cm^-2 along with the Tafel slope of 55 mV dec^-1 . Moreover, this material exhibits excellent high-rate capability and excellent cycle life when employed as anode material of LIBs. This work provides a novel approach for the design and the construction of multifunctional electrode materials for energy conversion and storage.

Prospective of biosynthesized L.satiVum oil/PEG/Ag-MgO bionanocomposite film for its antibacterial and anticancer potential

A substantial interest has been manifested in utilizing oil/metal oxide hybrid bionanocomposite, especially organic/ inorganic to design different biomedical applications. The present study reports the synthesis, characterization, antibacterial and anticancer properties of biogenic silver nanoparticles (AgNPs) and L.satiVum oil/PEG/Ag-MgO bionanocomposite. The fabricated AgNPs and L.sativum oil/PEG/Ag-MgO bionanocomposite were characterized by employing different spectroscopic (UV, FTIR, XRD) and microscopic (TEM, SEM) techniques. The particle size analysis showed that the mean size of 16.32 nm for AgNPS and 13.45 nm L.satiVum oil/PEG/Ag-MgO, indicating the excellent dispersion of Ag-MgO nanoparticles in the PEG- L.satiVum oil matrix. The antimicrobial activity of AgNPs and polymeric bionanocomposite was investigated against two pathogenic bacteria. The highest antibacterial effect was observed for bionanocomposite towards Gram-positive Staphylococcus aureus (27 mm) and Gram-negative Escherichia coli (25 mm) at 40 µg/well. The bionanocomposite completely vanished the bacterial growth (100%) at 80 µgmL-1 concentrations. Moreover, the AgNPs and polymeric bionanocomposite was evaluated for anticancer activity against human cervical cancer cells (HeLa cells) at different doses (50, 250, 500, and 1000 µgmL-1). The results showed polymeric bionanocomposite was stronger in inducing the HeLa cancer cell death than AgNPs. Overall, the fabricated L.satiVum oil/PEG/Ag-MgO bionanocomposite serve as a potential antimicrobial and anticancer agent and could be used in the development of novel drugs and health care products in near future.

In Situ Reduced Multi-Core Yolk-Shell Co@C Nanospheres for Broadband Microwave Absorption

The preparation of yolk–shell microwave absorption materials with low density and excellent microwave absorption property requires reasonable design and economical manufacture. In this study, an efficient strategy without any templates or reducing gases has been designed to fabricate multi-core yolk–shell Co@C nanospheres by high temperature carbonization. The results showed that Co₃O₄ was completely reduced by the carbon shell to metal cobalt at temperatures above 750 °C. This unique multi-core yolk–shell structure with shell of 600 nm and multiple cores of tens of nanometers can provide sufficient interface and space to reflect and scatter electromagnetic waves. At the same time, the metal cobalt layer and carbon layer provide magnetic loss ability and dielectric loss ability, respectively, making the composite show good wave absorption performance. The minimal RL value of samples carbonized at 750 °C reaches −40 dB and the efficient absorption band reaches 9 GHz with the thickness ranges from 2–9 mm. Therefore, this is a facile, effective and economical strategy to prepare yolk–shell structure, which provides a new idea for the preparation of microwave absorption materials.

Recent Trends in Morphology-Controlled Synthesis and Application of Mesoporous Silica Nanoparticles

The outstanding journey towards the investigation of mesoporous materials commences with the discovery of high surface area porous silica materials, named MCM-41 (Mobil Composition of Matter-41) according to the inventors' name Mobile scientists in the United States. Based on a self-assembled supramolecular templating mechanism, the synthesis of mesoporous silica has extended to wide varieties of silica categories along with versatile applications of all these types in many fields. These silica families have some extraordinary structural features, like highly tunable nanoscale sized pore diameter, good Brunauer-Emmett-Teller (BET) surface areas, good flexibility to accommodate different organic and inorganic functional groups, metals etc., onto their surface. As a consequence, thousands of scientists and researchers throughout the world have reported numerous silica materials in the form of published articles, communication, reviews, etc. Beside this, attention is also given to the morphology-oriented synthesis of silica nanoparticles and their significant effects on the emerging fields of study like catalysis, energy applications, sensing, environmental, and biomedical research. This review highlights a consolidated overview of those morphology-based mesoporous silica particles, emphasizing their syntheses and potential role in many promising fields of research.

Onion-Structured Si Anode Constructed with Coating by Li4Ti5O12 and Cyclized-Polyacrylonitrile for Lithium-Ion Batteries

Low dimensional Si-based materials are very promising anode candidates for the next-generation lithium-ion batteries. However, to satisfy the ever-increasing demand in more powerful energy storage devices, electrodes based on Si materials should display high-power accompanied with low volume change upon operation. Thus far, there were no reports on the Si-based materials which satisfy the stated requirements. Hence, here, we report on modified onion-structured Si nanoparticles (SiNPs) co-coated with Li4Ti5O12 (LTO) and cyclized polyacrylonitrile (cPAN) to bring the synergistic effect enhancing the conductivity, tolerance to volume change and stable performance. Obtained results suggest that the nanoparticles were conformally coated with both materials simultaneously and the thicknesses of the films were in a range of a few nanometers. Electrochemical tests show that the modified SiNPs deliver a high initial capacity of 2443 mAh g-1 and stable capacity retention over 50 cycles with 95% Coulombic efficiency.