Piezo/triboelectric nanogenerators based on 2-dimensional layered structure materials

Recently, research on energy harvesting has attracted great attention as a solution to energy depletion and environmental problems due to the use of fossil fuels such as coal, natural gas, and oil. To be precise, harvesting technology converts the energy sources around us such as solar, heat, and mechanical energy into electrical energy. It has the advantage of being able to supply and sustain energy on a permanent basis, rather than being non-renewable, and it is also eco-friendly. Among the various energy harvesting techniques, nanogenerators based on piezoelectric and triboelectric phenomena can generate electrical energy based on mechanical energy sources, which are usually ubiquitous, there are no restrictions due to weather, time, or space, and this technology is also user-friendly. Recently, two-dimensional (2D) materials have been chosen for implementing piezo/triboelectric nanogenerators. The 2D materials have transparency, flexibility, and a high surface-to-volume ratio. Owing to the very low thickness of the atomic unit, a stacking structure using 2D materials can be also made to form a very thin device, which is applicable for insertion into the body or wearable electronic devices. In this review, we summarize the characteristics and research results on piezo/triboelectric energy harvesters based on 2D layered structure materials

Electrochemical properties of nonstoichiometric silicon suboxide anode materials with controlled oxygen concentration

Among the silicon (Si)-based anode materials, Si/SiOx is likely to be the best candidate for maintaining structural stability while taking advantage of the high capacity of Si as well as the compatible functionality between Si and SiOx. The oxygen content of SiOx is an especially significant factor for obtaining better performance, because it directly affects electrochemical properties such as reversible capacity, structural stability, and electrical conductivity. Herein, we have synthesized SiOx materials with different oxygen contents via magnesiothermic reduction of silica. The theoretical capacities of a series of Si/SiOx samples were estimated by using X-ray photoelectron spectroscopy, and then those results were compared with empirical results. This work paves the way to predicting the electrochemical performances of lithium-ion battery anodes based on oxygen content in the nonstoichiometric Si/SiOx structure

Biomolecular Piezoelectric Materials: From Amino Acids to Living Tissues

2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Biomolecular piezoelectric materials are considered a strong candidate material for biomedical applications due to their robust piezoelectricity, biocompatibility, and low dielectric property. The electric field has been found to affect tissue development and regeneration, and the piezoelectric properties of biological materials in the human body are known to provide electric fields by pressure. Therefore, great attention has been paid to the understanding of piezoelectricity in biological tissues and its building blocks. The aim herein is to describe the principle of piezoelectricity in biological materials from the very basic building blocks (i.e., amino acids, peptides, proteins, etc.) to highly organized tissues (i.e., bones, skin, etc.). Research progress on the piezoelectricity within various biological materials is summarized, including amino acids, peptides, proteins, and tissues. The mechanisms and origin of piezoelectricity within various biological materials are also covered

Patchable and Implantable 2D Nanogenerator

With the development of technology, electronic devices are becoming more miniaturized and multifunctional. With the development of small electronic devices, they are changing from the conventional accessory type, which is portable, to the patchable type, which can be attached to a person\u27s apparel or body, and the eatable/implantable type, which can be directly implanted into the human body. In this regard, it is necessary to address various technical issues, such as high-capacity/high-efficiency small-sized battery technology, component miniaturization, low power technology, flexible technology, and smart sensing technology. In addition, there is a demand for self-powered wireless systems in particular devices. A piezoelectric/triboelectric nanogenerator (PENG/TENG) can generate electric energy from small amounts of mechanical energy such as from blood flow and heartbeats in the human body as well as human movement, so it is expected that it will enable the development of self-powered wireless systems. Due to their unique properties, such as flexibility, transparency, mechanical stability, and nontoxicity, 2D materials are optimal materials for the development of implantable and patchable self-powered nanodevices in the human body. In this Review, the studies related to patchable and implantable devices for the human body using PENGs/TENGs based on 2D materials are discussed

Temperature-dependent piezotronic effect of MoS2 monolayer

Molybdenum disulfide (MoS 2 ) monolayer is one of the most promising materials for next-generation electronic/optoelectronic devices because of its prominent piezoelectric property that can modulate Schottky barrier height and control transport behaviors without applying any external gate bias. In this work, we systematically investigated temperature dependence of piezotronic effect of chemical vapor deposition grown MoS 2 monolayer by measuring transport behaviors under strains from 0% to 0.3% with various sample temperatures ranging from 270 K to 320 K. It was found that piezoelectric effect in MoS 2 monolayer significantly depends on sample temperature. Due to less screening effect of piezoelectric potential generated in MoS 2 with a mechanical strain at low temperature, the piezotronic effect is significantly enhanced when the sample temperature is decreased from 320 K to 270 K, revealing that the piezoelectric effect becomes stronger at lower temperature

Lithium metal storage in zeolitic imidazolate framework derived nanoarchitectures

© 2020 Elsevier B.V. Due to the increasing demands for energy storage devices with higher energy density, lithium (Li) metal is considered to be the ultimate choice as an anode material because it has a high theoretical capacity (3860 mAh g−1) and the lowest reduction potential (−3.04 V versus standard hydrogen electrode) among all the alkali metals. Despite these advantages, repeated Li plating/stripping during cell operation leads to dendritic Li and the formation of irreversible Li (dead Li), leading to internal short-circuits and capacity fading. These fundamental problems cause safety issues and cell failure, so they must be resolved to commercialize Li-metal anode. Many in-depth studies are ongoing to solve these drawbacks through a variety of approaches, such as the formation of artificial solid-electrolyte interphase (SEI), inserting an interfacial layer between the electrolyte and electrode, demonstrating three-dimensional structured electrodes, and using stable host structures to store Li-metal. In this Review, we focus on using host materials to store Li-metal among various strategies, which may be regarded as an alternative method but is very feasible. Also, we propose porous carbon materials derived from zeolitic imidazolate frameworks (ZIFs) as the host materials due to their suitable properties for Li-metal storage. To advance progress towards practical application, the Li-metal storage capacity of porous materials is mathematically inferred, and further strategies are discussed for improving the storage capacity in this regard. Finally, we presented a perspective that paves the way for applying host materials to anodes of practical Li-metal battery

Everlasting Living and Breathing Gyroid 3D Network in Si@SiOx/C Nanoarchitecture for Lithium Ion Battery

Silicon-based materials are the most promising candidates to surpass the capacity limitation of conventional graphite anode for lithium ion batteries. Unfortunately, Si-based materials suffer from poor cycling performance and dimensional instability induced by the large volume changes during cycling. To resolve such problems, nanostructured silicon-based materials with delicately controlled microstructure and interfaces have been intensively investigated. Nevertheless, they still face problems related to their high synthetic cost and their limited electrochemical properties and thermal stability. To overcome these drawbacks, we demonstrate the strategic design and synthesis of a gyroid three-dimensional network in a Si@SiOx/C nanoarchitecture (3D-Si@SiOx/C) with synergetic interaction between the computational prediction and the synthetic optimization. This 3D-Si@SiOx/C exhibits not only excellent electrochemical performance due to its structural stability and superior ion/electron transport but also enhanced thermal stability due to the presence of carbon, which was formed by a cost-effective one-pot synthetic route. We believe that our rationally designed 3D-Si@SiOx/C will lead to the development of anode materials for the next-generation lithium ion batteries

Different Effects of Ni and Mn on Thermodynamic and Mechanical Stabilities in Cr-Ni-Mn Austenitic Steels

Thermodynamic and mechanical stabilities of austenite were investigated in Cr-Ni-Mn austenitic steels by varying the contents of Ni and Mn. Mn was more beneficial to increasing thermodynamic stability against martensitic transformation than the equivalent amount of Ni. However, the tendency for strain-induced martensite transformation was governed not by the thermodynamic stability but by stacking fault energy (SFE) which was increased more effectively by Ni than by the equivalent amount of Mn. A modified SFE equation and experimentally determined Ni equivalents may suggest a criterion for austenite stability throughout tensile deformation.11Nsciescopu