Amorphous SiO2 coating layers with thicknesses of ca. 2, 7, 10, and 15 nm are introduced into bulk@nanowire core@shell Si particles via direct thermal oxidation at 650–850 °C. Of the coated samples, ...Si with a coating thickness of ca. 7 nm has the best electrochemical performance. This sample shows an initial discharge capacity of 2279 mA h g−1 with a Coulombic efficiency of 92% and displays 83% capacity retention after 50 cycles at 0.2C rate.
Two-dimensional Si nanosheets have been studied as a promising candidate for lithium-ion battery anode materials. However, Si nanosheets reported so far showed poor cycling performances and required ...further improvements. In this work, we utilize inexpensive natural clays for preparing high quality Si nanosheets via a one-step simultaneous molten salt-induced exfoliation and chemical reduction process. This approach produces high purity mesoporous Si nanosheets in high yield. As a control experiment, two-step process (pre-exfoliated silicate sheets and subsequent chemical reduction) cannot sustain their original two-dimensional structure. In contrast, one-step method results in a production of 5 nm-thick highly porous Si nanosheets. Carbon-coated Si nanosheet anodes exhibit a high reversible capacity of 865 mAh g–1 at 1.0 A g–1 with an outstanding capacity retention of 92.3% after 500 cycles. It also delivers high rate capability, corresponding to a capacity of 60% at 20 A g–1 compared to that of 2.0 A g–1. Furthermore, the Si nanosheet electrodes show volume expansion of only 42% after 200 cycles.
Three-dimensional (3D) hyperporous silicon flakes (HPSFs) are prepared via the chemical reduction of natural clay minerals bearing metal oxides. Natural clays generally have 2D flake-like structures ...with broad size distributions in the lateral dimension and varied thicknesses depending on the first processing condition from nature. They have repeating layers of silicate and metal oxides in various ratios. When the clay mineral is subjected to a reduction reaction, metal oxide layers can perform a negative catalyst for absorbing large amounts of exothermic heat from the reduction reaction of the silicate layers with metal reductant. Selectively etching out metal oxides shows a hyperporous nanoflake structure containing 100 nm macropores and meso-/micropores on its framework. The resultant HPSFs are demonstrated as anode materials for lithium-ion batteries. Compared to conventional micro-Si anodes, HPSFs exhibit exceptionally high initial Coulombic efficiency over 92%. Furthermore, HPSF anodes show outstanding cycling performance (reversible capacity of 1619 mAh g–1 at a rate of 0.5 C after 200 cycles, 95.2% retention) and rate performance (∼580 mAh g–1 at a rate of 10 C) owing to their distinctive structure.
The middleware framework for IoT collaboration services should provide efficient solutions to context awareness and uncertainty issues among multiple collaboration domains. However, existing ...middleware frameworks are mostly limited to a single system, and developing self-adaptive IoT collaboration services using existing frameworks requires developers to take considerable time and effort. Furthermore, the developed IoT collaboration services are often dependent on a particular domain, which cannot easily be referenced in other domains. This paper proposes a cloud-based middleware framework that provides a set of cloud services for self-adaptive IoT collaboration services. The proposed middleware framework is generic in the sense that it clearly separates domain-dependent components from the layers that leverage existing middleware frameworks. In addition, the proposed framework allows developers to upload domain-dependent components onto the cloud, search for registered components, and launch Virtual Machine (VM) running a new MAPE cycle via a convenient web-based interface. The feasibility of the proposed framework has been shown with a simulation of an IoT collaboration service that traces a criminal suspect. The performance evaluation shows that the proposed middleware framework runs with an overhead of only 6% compared to pure Java-based middleware and is scalable as the number of VMs increases up to 16.
Controlling the morphology of nanostructured silicon is critical to improving the structural stability and electrochemical performance in lithium-ion batteries. The use of removable or sacrificial ...templates is an effective and easy route to synthesize hollow materials. Herein, we demonstrate the synthesis of mesoporous silicon hollow nanocubes (m-Si HCs) derived from a metal–organic framework (MOF) as an anode material with outstanding electrochemical properties. The m-Si HC architecture with the mesoporous external shell (∼15 nm) and internal void (∼60 nm) can effectively accommodate volume variations and relieve diffusion-induced stress/strain during repeated cycling. In addition, this cube architecture provides a high electrolyte contact area because of the exposed active site, which can promote the transportation of Li ions. The well-designed m-Si HC with carbon coating delivers a high reversible capacity of 1728 mAhg–1 with an initial Coulombic efficiency of 80.1% after the first cycle and an excellent rate capability of >1050 mAhg–1 even at a 15 C-rate. In particular, the m-Si HC anode effectively suppresses electrode swelling to ∼47% after 100 cycles and exhibits outstanding cycle stability of 850 mAhg–1 after 800 cycles at a 1 C-rate. Moreover, a full cell (2.9 mAhcm–2) comprising a m-Si HC-graphite anode and LiCoO2 cathode exhibits remarkable cycle retention of 72% after 100 cycles at a 0.2 C-rate.
In a consecutive, single-center series of patients who were unable to follow commands after acute brain injury, 15% of patients had brain activation on EEG recorded at the bedside.
Using Si-based anodes in Li-ion batteries is one of the most feasible approaches to achieve high energy densities despite their disadvantages, such as low conductivity and massive volume expansion, ...which cause unstable solid electrolyte interphase layers with mechanical failure. The forefront in research and development to address the above challenges suggests the possibility of fully commercially viable cells using various structural and interfacial modifications. In particular, we present a discussion of each dimension of Si-based anodes in multiple controlled systems, including plain, hollow, porous, and uniquely engineered structures, which are further evaluated based on their anode performances, such as initial reversibility, capacity retention for extended cycles with its efficiency, degree of volume expansion tolerance, and rate capabilities, by several practical standards in half cells. With these practical considerations, multi-dimensional structures with uniform size distributions (micrometers, on average) are strongly desired to satisfy the rigorous requirements for widespread applications. Furthermore, we closely examined several full cells composed of Si-based multicomponent anodes coupled with suitable cathodes based on practical standards to propose future research directions for Si-based anodes to keep pace with the rapidly changing market demands for diverse energy storage systems.
With the development of flexible mobile devices, flexible Li-ion batteries have naturally received much attention. Previously, all reported flexible components have had shortcomings related to power ...and energy performance. In this research, in order to overcome these problems while maintaining the flexibility, honeycomb-patterned Cu and Al materials were used as current collectors to achieve maximum adhesion in the electrodes. In addition, to increase the energy and power multishelled LiNi0.75Co0.11Mn0.14O2 particles consisting of nanoscale V2O5 and Li x V2O5 coating layers and a LiδNi0.75–z Co0.11Mn0.14V z O2 doping layer were used as the cathode–anode composite (denoted as PNG-AES) consisting of amorphous Si nanoparticles (<20 nm) loaded on expanded graphite (10 wt %) and natural graphite (85 wt %). Li-ion cells with these three elements (cathode, anode, and current collector) exhibited excellent power and energy performance along with stable cycling stability up to 200 cycles in an in situ bending test.
Abstract This study aimed to determine whether there might be differences in masticatory performance and eating behaviors by gender and obesity status. Forty eight (24 males; 24 females) non-obese ...and pre-obese young adults were matched for age, gender, and dental health. Eating behaviors were assessed using the Three-Factor Eating Questionnaire (TFEQ), and chewing performance while eating 152 g of boiled rice was measured using electromyography (EMG). Compared with non-obese participants, pre-obese participants had significantly higher levels of disinhibition according to the TFEQ (P < 0.05 for males; P < 0.01 for females). Microstructures of chewing performance were significantly different by gender but not by obesity status. Males had a greater bite size (P < 0.05), greater chewing power (P < 0.001) and a faster eating rate (P < 0.05) than females. Females habitually chewed more (P < 0.05) and had a longer meal duration (P < 0.01) than males. Eating rate was positively associated with disinhibition ( r = 0.490, P < 0.05) score in males. Bite size ( r = − 0.449, P < 0.05 for non-obese) and chewing power ( r = − 0.581, P < 0.01 for non-obese and r = − 0.446, P < 0.05 for pre-obese) were negatively associated with disinhibition score. Results suggest that the effects of gender and, in part, obesity on eating responses may be explained as chewing performance. Therefore, gender-specific interventions and counseling aimed at slowing the rate of ingestion could be promising behavioral treatments for obese persons.
The imperative to electrify the transport sector in the past few decades has put millions of electric vehicles on the road worldwide with an extended mile range from critical technological ...breakthroughs in developing the rechargeable energy storage systems, which also covers electronic devices and smart grid applications. However, the available energy density of prevailing systems in the market (i.e., batteries) is reaching its boundaries due to the limited choice of electrochemical reactions that necessarily depend on the thermodynamics and kinetics of the components (e.g., cathode, anode, electrolyte, separator, and current collectors). Reaching the high energy density of batteries exploits new redox chemistry such as sensitive metal anodes, insulating and highly dissolving sulfur cathodes, etc., thus requiring novel designs of various multiscale functional materials to address the corresponding issues. Here, the recent achievements on the designs of smart functional materials for emerging problems in the whole range of systems are discussed: i) interfacial control/kinetic regulation of Li–S battery; ii) self‐healing‐driven structural stability in the electrode and electrolyte; iii) ion‐sieving functional membranes for selective scavenging capability; and iv) functional materials to ensure battery safety.
Smart, functional materials in the nano/microscale that are specially designed for rechargeable batteries are comprehensively discussed. The designed materials aim to address the issues in interfacial chemistry of Li metal anodes and sulfur cathodes, integration of electrodes or electrolytes during unusual deformations, selectivity of membranes, and safety of systems.
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