Hollow Silica Spheres Embedded in a Porous Carbon Matrix and Its Superior Performance as the Anode for Lithium‐Ion Batteries

Silica (SiO₂) is regarded as one of the most promising anode materials for lithium‐ion batteries due to the high theoretical specific capacity and extremely low cost. However, the low intrinsic electrical conductivity and the big volume change during charge/discharge cycles result in a poor electrochemical performance. Here, hollow silica spheres embedded in porous carbon (HSS–C) composites are synthesized and investigated as an anode material for lithium‐ion batteries. The HSS–C composites demonstrate a high specific capacity of about 910 mA h g^?1 at a rate of 200 mA g^?1 after 150 cycles and exhibit good rate capability. The porous carbon with a large surface area and void space filled both inside and outside of the hollow silica spheres acts as an excellent conductive layer to enhance the overall conductivity of the electrode, shortens the diffusion path length for the transport of lithium ions, and also buffers the volume change accompanied with lithium‐ion insertion/extraction processes.     

Sulfur Immobilized in Hierarchically Porous Structured Carbon as Cathodes for Lithium–Sulfur Battery with Improved Electrochemical Performance

In order to overcome the main obstacles for lithium–sulfur batteries, such as poor conductivity of sulfur, polysulfide intermediate dissolution, and large volume change generated during the cycle process, a hard‐template route is developed to synthesize large‐surface area carbon with abundant micropores and mesopores to immobilize sulfur species. The microstructures of the C/S hybrids are investigated using field emission scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, Raman spectroscopy, X‐ray photoelectron spectroscopy, nitrogen adsorption–desorption isotherms, and electrochemical impedance spectroscopy techniques. The large surface and porous structure can effectively alleviate large strain due to the lithiation/delithiation process. More importantly, the micropores can effectively confine small molecules of sulfur in the form of S_2–4, avoiding loss of active S species and dissolution of high‐order lithium polysulfides. The porous C/S hybrids show significantly enhanced electrochemical performance with good cycling stability, high specific capacity, and rate capability. The C/S‐39 hybrid with an optimal content of 39 wt% S shows a reversible capacity of 780 mA h g^?1 after 100 cycles at the current density of 100 mA g^?1. Even at a current density of 5 A g^?1, the reversible capacity of C/S‐39 can still maintain at 420 mA h g^?1 after 60 cycles. This strategy offers a new way for solving long‐term reversibility obstacle and designing new cathode electrode architectures.     

Towards Excellent Anodes for Li‐Ion Batteries with High Capacity and Super Long Lifespan: Confining Ultrasmall Sn Particles into N‐Rich Graphene‐Based Nanosheets

Sn is regarded as a promising anode material for Li‐ion batteries due to high capacity and cost effectiveness. Hitherto large‐scale fabrication of Sn‐based materials while achieving both high capacity and long cycle life remains challenging, but it is highly required for its realization in practical applications. Furthermore, low melting point always casts shadow over the morphology‐controllable preparation, and leads to multistep or high‐cost processes. Here, a facile and scalable method is devised for a 2D hybrid structure of Sn@graphene‐based nanosheets incorporating of optimized nitrogen species (≈13 wt%). Distinct from conventional Sn–C composites, the fairly N‐rich carbon nanosheets liberate limited potential of low N doping, induce massive extra Li‐storage sites, and encourage a high capacity significantly. In addition, these abundantly anchored heteroatoms also promote the homogeneous dispersion and robust confinement of ultrasmall Sn nanoparticles into the flexible graphene‐based nanosheets. This elastic encapsulation towards Sn nanoparticles admirably maintains structural integrity through effective remission of volume expansion, demonstrating a super long‐term cyclic stability for 1000 cycles. This structural and componential engineering offers a significant implication for rational design of materials in extended areas of energy conversion and storage.     

Template‐Free Fabrication of Mesoporous Hollow ZnMn2O4 Sub‐microspheres with Enhanced Lithium Storage Capability towards High‐Performance Li‐Ion Batteries

In this work, we rationally designed an efficient template‐free synthetic strategy to fabricate hierarchical mesoporous hollow ZnMn₂O₄ sub‐microspheres (HZSMs) constructed entirely from nanoparticle (NP) building blocks of size ≈15 nm. The well‐known inside‐out Ostwald ripening process was tentatively proposed to shed light on the formation mechanism of the mesoporous hollow nano‐/microarchitecture. In favor of the intrinsic structural advantages, these resulting HZSMs exhibited superior electrochemical lithium‐storage performance with high specific capacity, excellent cyclability, and good rate capability when evaluated as an anode material for advanced Li‐ion batteries (LIBs). The excellent electrochemical performance should be reasonably ascribed to the porous and hollow structure of the unique HZSMs with nanoscale subunits, which reduced the diffusion length for Li⁺ ions, improved the kinetic process and enhanced the structural integrity with sufficient void space for tolerating the volume variation during the Li⁺ insertion/extraction. These results further revealed that the as‐prepared mesoporous HZSMs would be a promising anode for high‐performance LIBs.     

Janus Particles: Metallic Janus and Patchy Particles (Part. Part. Syst. Charact. 1/2013)

The concepts of Janus and patchy particles are relatively new in nanoscience. Much effort has been made during recent years to devise and fabricate asymmetric particles with multiple compositions and functionalities due to their interesting properties and potential applications in a variety of fields such as catalysis, optical imaging, or drug delivery. Here, recent advances in the field of Janus particles are highlighted, focusing on nanoparticles comprising (at least) one metallic component, which is responsible for the most interesting properties of the particles. First, the main synthetic approaches are summarized, i.e., phase separation, masking, and self‐assembly techniques, and then the special properties, applications, and future prospects of metallic Janus particles are described.     

Colloidal Nanoparticles: Formation of Large 2D Arrays of Shape‐Controlled Colloidal Nanoparticles at Variable Interparticle Distances (Part. Part. Syst. Charact. 1/2013)

A method for the production of homogeneous layers of nanoparticles of arbitrary shape is presented. The method relies on a ligand exchange with a functionalized polymer and a subsequent self‐assembly of a thin film on the substrates. The interparticle distances in the layer can be adjusted by the length of the polymer. In the case of spherical particles, the approach yields quasi‐hexagonal structures; in the case of anisotropic particles, the minimum distance between adjacent particles is controlled. Regular arrangements of the nanoparticles covering areas of several square centimeters are achieved.     

A Facile Method for Synthesis of Porous NiCo2O4 Nanorods as a High‐Performance Anode Material for Li‐Ion Batteries

Porous electrode materials with large specific surface area, relatively short diffusion path, and higher electrical conductivity, which display both better rate capabilities and good cycle lives, have huge benefits for practical applications in lithium‐ion batteries. Here, uniform porous NiCo₂O₄ nanorods (PNNs) with pore‐size distribution in the range of 10–30 nm and lengths of up to several micrometers are synthesized through a convenient oxalate co‐precipitation method followed by a calcining process. The PNN electrode exhibits high reversible capacity and outstanding cycling stability (after 150 cycles still maintain about 650 mA h g^?1 at a current density of 100 mA g^?1), as well as high Coulombic efficiency (>98%). Moreover, the PNNs also exhibit an excellent rate performance, and deliver a stable reversible specific capacity of 450 mA h g^?1 even at 2000 mA g^?1. These results demonstrate that the PNNs are promising anode materials for high‐performance Li‐ion batteries.