Silicon‐Based Photonic Crystals

Photonic crystals can be thought of as optical analogues of semiconductors. Here recent advances in photonic crystals based on silicon are reviewed. After summarizing the theory of photonic bandgap materials, the preparation and linear optical properties of 1D, 2D, and 3D silicon‐based photonic crystals are discussed. Laterally structured porous silicon with a defect line is shown in the Figure.     

Localized Surface Plasmon Induced Position‐Sensitive Photodetection in Silicon‐Nanowire‐Modified Ag/Si

Surface plasmon‐based approaches are widely applied to improve the efficiency of photoelectric devices such as photosensors and photocells. In order to promote the light absorption and electron–hole pair generation in devices, metallodielectric nanostructures are used to boost the growth of surface plasmons. Here, silicon nanowires (SiNWs) are used to modify a metal–semiconductor structure; thus, Ag/SiNWs/Si is manufactured. In this system, a large increased lateral photovoltaic effect (LPE) is detected with a maximum positional sensitivity of 65.35 mV mm^?1, which is ≈53‐fold and 1000‐fold compared to the conventional Ag/Si (1.24 mV mm^?1) and SiNWs/Si (0.06 mV mm^?1), respectively. It is demonstrated that localized surface plasmons (LSPs) contribute a lot to the increment of LPE. Furthermore, through the surface‐enhanced Raman scattering spectra of rhodamine‐6G and finite‐difference time‐domain simulation, it is illustrated that silver‐coated SiNWs support strong LSPs. The results propose an enhancement mechanism based on LSPs to facilitate the photoelectric conversion in LPE and offer an effective way to improve the sensitivity of photodetectors.     

Silicon‐Based Anodes for Lithium‐Ion Batteries: From Fundamentals to Practical Applications

Silicon has been intensively studied as an anode material for lithium‐ion batteries (LIB) because of its exceptionally high specific capacity. However, silicon‐based anode materials usually suffer from large volume change during the charge and discharge process, leading to subsequent pulverization of silicon, loss of electric contact, and continuous side reactions. These transformations cause poor cycle life and hinder the wide commercialization of silicon for LIBs. The lithiation and delithiation behaviors, and the interphase reaction mechanisms, are progressively studied and understood. Various nanostructured silicon anodes are reported to exhibit both superior specific capacity and cycle life compared to commercial carbon‐based anodes. However, some practical issues with nanostructured silicon cannot be ignored, and must be addressed if it is to be widely used in commercial LIBs. This Review outlines major impactful work on silicon‐based anodes, and the most recent research directions in this field, specifically, the engineering of silicon architectures, the construction of silicon‐based composites, and other performance‐enhancement studies including electrolytes and binders. The burgeoning research efforts in the development of practical silicon electrodes, and full‐cell silicon‐based LIBs are specially stressed, which are key to the successful commercialization of silicon anodes, and large‐scale deployment of next‐generation high energy density LIBs.     

Self‐Supported and Flexible Sulfur Cathode Enabled via Synergistic Confinement for High‐Energy‐Density Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries have attracted much attention in the field of electrochemical energy storage due to their high energy density and low cost. However, the “shuttle effect” of the sulfur cathode, resulting in poor cyclic performance, is a big barrier for the development of Li–S batteries. Herein, a novel sulfur cathode integrating sulfur, flexible carbon cloth, and metal–organic framework (MOF)‐derived N‐doped carbon nanoarrays with embedded CoP (CC@CoP/C) is designed. These unique flexible nanoarrays with embedded polar CoP nanoparticles not only offer enough voids for volume expansion to maintain the structural stability during the electrochemical process, but also promote the physical encapsulation and chemical entrapment of all sulfur species. Such designed CC@CoP/C cathodes with synergistic confinement (physical adsorption and chemical interactions) for soluble intermediate lithium polysulfides possess high sulfur loadings (as high as 4.17 mg cm^–2) and exhibit large specific capacities at different C‐rates. Specially, an outstanding long‐term cycling performance can be reached. For example, an ultralow decay of 0.016% per cycle during the whole 600 cycles at a high current density of 2C is displayed. The current work provides a promising design strategy for high‐energy‐density Li–S batteries.