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We describe a facile single-step non-hydrothermal chemical route for the synthesis of N and S dual-doped reduced graphene oxide (SN-rGO) and the synergistic effect of N and S in oxygen reduction reaction (ORR). The reduction of graphene oxide (GO) and dual doping of rGO are achieved in one-step with a single doping agent in ethylene glycol. SN-rGO has pyridinic and pyrrolic nitrogen and thiophenic sulphur and it has N/C and S/C atomic ratio of 0.12 and 0.08, respectively. The atomic percentage of pyridinic N (66%) is significantly higher than pyrrolic N (34%). The electrocatalytic performance of SN-rGO towards ORR is examined in terms of onset potential, kinetic current density, number of electrons transferred, durability and methanol tolerance in alkaline solution. SN-rGO shows excellent electrocatalytic activity with an onset potential of −15mV (Hg/HgO) and it tends promotes the four electron pathway. The activity of SN-rGO is superior to that of rGO doped only with N and S (N-rGO and S-rGO) and undoped rGO. The comparison of the ORR activity of SN-rGO with N-rGO and S-rGO indicates the synergistic effect of heteroatoms of SN-rGO in the electrocatalytic reaction. SN-rGO is highly durable and completely silent towards the anode fuel methanol.
Sodium-ion batteries (SIBs) are considered to be a promising low-cost alternative to common lithium-ion batteries. Herein, we present a detailed electrochemical characterization of anatase TiO2 nanoparticles as anode material for Na-ion batteries, highlighting the substantial influence of the electrolyte composition (salt and solvent) on the obtainable specific capacity, cycling stability, and particularly the coulombic efficiency. TiO2-based electrodes cycled using a 1M solution of NaClO4 in a mixture of ethylene carbonate and propylene carbonate present excellent high rate capability, offering about 100 and 86 mAh g−1 at 5.5 and 11C, respectively, which is – to the best of our knowledge – the best high rate capability for all titanium-based sodium-ion anode materials reported so far. Setting the C rate to 5.5C (i.e., 1.85 A g−1), such electrodes can be cycled for more than 1000 cycles without significant capacity decay, confirming their outstanding durability at such high specific current. These results, in combination with its environmental friendliness and cost efficiency, render anatase TiO2 nanoparticles a promising anode material for high power sodium-ion batteries.
To solve the recycling challenge for aqueous binder based lithium-ion batteries (LIBs), a novel process for recycling and resynthesizing LiNi1/3Co1/3Mn1/3O2 from the cathode scraps generated during manufacturing process is proposed in this study. Trifluoroacetic acid (TFA) is employed to separate the cathode material from the aluminum foil. The effects of TFA concentration, liquid/solid (L/S) ratio, reaction temperature and time on the separation efficiencies of the cathode material and aluminum foil are investigated systematically. The cathode material can be separated completely under the optimal experimental condition of 15vol.% TFA solution, L/S ratio of 8.0mLg− 1, reacting at 40°C for 180min along with appropriate agitation. LiNi1/3Co1/3Mn1/3O2 is successfully resynthesized from the separated cathode material by solid state reaction method. Several kinds of characterizations are performed to verify the typical properties of the resynthesized LiNi1/3Co1/3Mn1/3O2 powder. Electrochemical tests show that the initial charge and discharge capacities of the resynthesized LiNi1/3Co1/3Mn1/3O2 are 201mAhg− 1 and 155.4mAhg−1 (2.8–4.5V, 0.1C), respectively. The discharge capacity remains at 129mAhg−1 even after 30 cycles with a capacity retention ratio of 83.01%.
This study evaluated the homework functioning of middle-school students with ADHD to determine what aspects are most predictive of school grades and the best source (e.g., parents or teachers) for obtaining this information. Students with ADHD in grades 5–8 (N = 57) and their parents and teachers completed the Children’s Organization Skills Scales (COSS) to measure materials organization, planning, and time management, and parents completed the Homework Problems Checklist (HPC) to examine homework completion and homework materials management behaviors. Regression analyses revealed that parent-rated homework materials management and teacher-rated memory and materials management were the best predictors of school grades. These findings suggest that organization of materials is a critical component of the homework completion process for students with ADHD and an important target for intervention. Teachers were the best source of information regarding materials organization and planning, whereas parents were a valuable source of information for specific homework materials management problems.
A flexible and free-collector-current of silicon-based anode is facilely prepared just by coating carbon black (CB) and silicon powders layer-by-layer. The resultant electrodes with a “sandwich” structure (CB/Si/CB) are assembled into half-cell and its electrochemical properties are tested. This type of anode exhibits excellent cycling and outstanding rate capability. The superior electrochemical performances are ascribed to both flexible CB-layers to offset the volume expansion of Si-particle. And, the CB-layer with high electric conductivity can provide efficient electron conductive pathways when Si particles react with lithium. More importantly, the CB/Si/CB electrodes without the collerctor (copper-foil) are exhibited high energy density, due to the weight proportion of copper foil is exceeded 60%. The CB/Si/CB electrode is used to assemble full-cell with the same structure as free-collector LCO/CB cathode material. It imposes the energy density of 200Whkg−1, and can keep stable charging-discharging capability at various deformations of shapes. And the flexible-cell of high performance is obtained to meet diverse applications in energy storage devices. Until now, many flexible batteries are put forward by researchers, but these product is faced with the complex production-process, high-cost material, low energy-density. This CB/Si/CB structure is produced with the matching current manufacturing industry and the common raw material, and to get a full-cell of the high energy density.
‘Active and intelligent’ (A&I) food packaging is based on a deliberate interaction of the packaging with the food and/or its direct environment. This article presents: (i) the main types of materials developed for food contact; (ii) the global market and the future trends of active and intelligent packaging with a special emphasis on safety concerns and assessment; and (iii) the EU Legislation and compliance testing of these novel food packaging technologies.
The compatibility of glutaronitrile (GLN) and its mixtures with dimethyl carbonate (DMC) containing lithium bis-(trifluoromethane sulfonyl) imide (LiTFSI) with graphite negative electrode was investigated. GLN/DMC/LiTFSI electrolytes’ mixtures were characterized in terms of their ionic conductivities and viscosities. Cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy were performed in order to study the performances of the graphite anode in the GLN-based electrolytes. Results clearly indicate that no significant Li intercalation occurs in graphite in pure GLN, but when GLN/DMC (1:1 and 1:3 w/w) mixtures were used, the cycling ability of the electrode was improved as the coulombic efficiency reaches 98 and 99 %, respectively. Moreover, SEM images of the graphite anode indicate that after being cycled in GLN-based electrolytes, the electrode surface was homogenously covered by a Solid Layer Interface which insures a reversible lithiation of graphite anode.
Surface-modified carbon nanotubes were utilized as a coating for LiNi0.5Mn1.5O4 (LNMO) via a mechano-fusion method as a strategy to prevent unfavorable carbothermal reduction. Two types of carbon nanotubes were investigated as coating materials: carbon nanotubes (CNTs) and oxidized carbon nanotubes (OCNTs), which were prepared by a simple re-oxidation process. The samples coated with CNTs or OCNTs were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning and transmission electron microscopy, Raman spectroscopy, and elemental analyses. The OCNT-coated LNMO presented a highly enhanced discharge capacity retention (95.5%) and a coulombic efficiency of 99.9% after 80 cycles between 3.5 and 4.9 V (versus Li/Li+), whereas the CNT-coated LNMO exhibited poor retention of 47.2% and a coulombic efficiency of 95.3%. In addition, post-mortem XPS and electrochemical impedance spectroscopy (EIS) analysis proved that the OCNT coating improved the surface electrochemical stability and rate capability, whereas the CNT coating formed a thick resistive solid electrolyte interphase (SEI) film by accelerating the surface side reactions.
Exploring the concept of soft energy unit with improved sustainability and flexibility is critically important for the development of wearable electronics that comes into direct contact with human tissues. Herein, a flexible and self-chargeable sodium-ion full battery was developed by coupling elastic piezo-films with the separator of flexible sodium-ion batteries. This new device achieves excellent flexibility and self-charging performance. It can not only be charged to about 0.65 V under mechanical bending in 150 s or palm patting within 300 s, but also demonstrates interesting self-charging behavior even with quasi-static pressing. In the latter case, the self-charging rate increases with the rising of the applied static forces, which can be ascribed to the sound elasticity of the piezo-film. This work contributes to the development of flexible and self-chargeable electrochemical power devices for soft wearable electronics.
Lithium-sulfur (Li-S) batteries with lithium sulfide (Li2S) as cathode have attracted great attention recently, because of high specific capacity (1166 mA h g−1) of Li2S and potential safety of using Li metal-free anode. Li2S cathode has lower volume expansion and higher thermal stability than the traditional sulfur cathode. However, the problems of “shuttle effect” and poor electrical conductivity of the cathode material still need to be overcome. In this work, multi-layered Ti3C2/Li2S (ML-Ti3C2/Li2S) composite has been prepared and applied as a cathode in advanced Li-S batteries. The unique multi-layer sheet structure of Ti3C2 provides space for the storage of Li2S, and its good conductivity greatly enhances the usage ratio of Li2S and improves the conductivity of the whole Li2S cathode. Compared with commonly used graphene, ML-Ti3C2 can trap polysulfides effectively by chemical adsorption and also activate the reaction of Li2S to polysulfides by forming Ti-S bond. As a result, during the cycling of the batteries with ML-Ti3C2/Li2S cathodes, the activation voltage barrier of the first cycle has decreased to 2.8 V, and the “shuttle effect” has been suppressed effectively. The cycling and rate performances of the ML-Ti3C2/Li2S cathodes have been significantly improved compared to that of graphene/Li2S cathodes. They maintain a capacity of 450 mA h g−1 at 0.2 C after 100 cycles, and deliver attractive rate performances of 750, 630, 540, 470 and 360 mA h g−1 at 0.1 C, 0.2 C, 0.5 C, 1 C, and 2 C, respectively.
NASICON-type Na3V2(PO4)2F3 is employed as a promising cathode for sodium-ion batteries in order to explore the ion-migration mechanism and diffusion capability. Two kinds of Na sites, namely Na(1) site and Na(2) site exist in the crystal structure per formula unit to accommodate a total of three sodium ions. The ion at Na(2) site with half occupation extracts first and inserts the last due to its high chemical potential, while the whole extraction/insertion of two ions between 1.6 and 4.6 V vs. Na+/Na can produce three plateaus in charge/discharge processes because of the reorganization of ions. The first discharge capacity of 111.6 mAh g−1 with retention of 97.6% after 50 cycles could be obtained by electrochemical testing at 0.091C. Electrochemical activation and/or structural reorganization of the system by cycling could improve the diffusion coefficient of sodium with a comparatively large magnitude of 10−12 cm2 s−1, though many influences on the resistance factors also can be attributed to the cycling process. Such work is of fundamental importance to the progression of sodium-based batteries to be fully realized and be implemented over existing Li-ion based batteries.
In this paper we provide new insights into the motives underlying insider participation in private investments in public equity (PIPEs) by considering the association among insider participation, pricing, and contractual terms. PIPEs are a financing choice that have become popular over the last decade and frequently involve insider participation. We find that board seats and weak pre-PIPE performance are important determinants of insider participation. We also find evidence in support of the certification motive for insider participation. In particular, we show that insider participation is associated with lower PIPE discounts and improved future firm operating performance. Announcement wealth effects are significantly higher when insiders participate than when they are absent both for single and repeated PIPE transactions. We extend the prior literature by documenting that the insider certification effect also exists for repeated PIPE transactions and that the granting of control mechanisms, such as board seats, is an important component of contractual arrangements in insider participation, potentially to achieve incentive alignment by mitigating moral hazard considerations.
Being easy, safe and reliable, non-invasive prenatal diagnosis (NIPD) has been greatly pursued in recent years. Holding the complete genetic information of the fetus, fetal nucleated red blood cells (fNRBCs) are viewed as a suitable target for NIPD application. However, effective separating fNRBCs from maternal peripheral blood for clinic use still faces great challenges, given that fNRBCs are extremely rare in maternal blood circulation. Here, by combining the high-throughput inertial microfluidic chip with multifunctional microspheres as size amplification, we develop a novel method to isolate fNRBCs with high performance. To enlarge the size difference between fNRBCs and normal blood cells, we use the gelatin coated microspheres to capture fNRBCs with anti-CD147 as specific recognizer at first. The size difference between fNRBCs captured by the microspheres and normal blood cells makes it easy to purify the captured fNRBCs through the spiral microfluidic chip. Finally, the purified fNRBCs are mildly released from the microspheres by enzymatically degrading the gelatin coating. Cell capture efficiency about 81%, high purity of 83%, as well as cell release viability over 80% were achieved using spiked samples by this approach. Additionally, fNRBCs were successfully detected from peripheral blood of pregnant women with an average of 24 fNRBCs per mL, suggesting the great potential of this method for clinical non-invasive prenatal diagnosis.
This study adopts an in-situ infrared (IR) sintering incorporated with carbonization technique to synthesize carbon-coated LiNi1/3Co1/3Mn1/3O2 (LNCM) cathode materials for Li-ion batteries. Compared with electric resistance heating, the in-situ IR sintering is capable of rapidly producing highly-crystalline LNCM powders at 900 °C within a short period, i.e., 3 h in this case. Glucose additive is employed to serve a carbon precursor, which is carbonized and coated over the surface of LNCM crystals during the IR sintering process. The electrochemical performance of LNCM cathodes is well examined by charge–discharge cycling at 0.1−5C. An appropriate carbon coating is capable of raising discharge capacity (i.e., 181.5 mAh g−1 at 0.1C), rate capability (i.e., 75.0 mAh g−1 at 5C), and cycling stability (i.e., capacity retention: 94.2% at 1C after 50 cycles) of LNCM cathodes. This enhanced performance can be ascribed to the carbon coating onto the external surface of LNCM powders, creating an outer circuit of charge-transfer pathway and preventing cathode corrosion from direct contact to the electrolyte. Accordingly, the in-situ IR sintering technique offers a potential feasibility for synthesizing cathode materials commercially in large scale.
The deployment of highly interactive, media-rich applications on mobile devices is hindered by the inherent limitations on compute power, memory and battery capacity of these hand-held platforms. The cloudlet concept, opportunistically offloading computation to nearby devices, has proven to be a viable solution in offering resource-intensive applications on mobile devices. In this paper, we propose to extend the cloudlet concept with collaborative scenarios, in which not only hardware resources for processing are shared between all cloudlet users, but also the data computed. In a cloudlet, the resource demand should be spread over all available cloudlet nodes. User mobility and fluctuations in wireless bandwidth will cause the optimal resource allocation to vary over time. The cloudlet middleware must continuously balance the performance gain of reallocating components with the operational costs in terms of user experience and management complexity. In this paper, we formulate this optimization problem based on a theoretical cloudlet model capturing the infrastructure, application structure and user behavior. In order to solve this problem, two heuristic allocation algorithms based on Steepest Descent (SD) and Simulated Annealing (SA) are described. Besides optimality of the found solution, it is also important to limit the number of reallocations at runtime. To evaluate the performance and stability of the algorithms, we propose a discrete-event model for cloudlet simulation. For multiple application scenarios, we observe that SD performs 4 times less reallocations than SA. By introducing hysteresis, the number of reallocations by SA can be nearly halved without any significant degradation of application performance.
In an increasingly aged population, sleep disturbances and neurodegenerative disorders have become a major public health concern. Poor sleep quality and cognitive changes are complex health problems in aging populations that are likely to be associated with increased frailty, morbidity, and mortality, and to be potential risk factors for further cognitive impairment. We aimed to evaluate whether sleep quality and excessive daytime sleepiness may be considered as early predictors of cognitive impairment. Study Objectives The objective of this study was to examine whether subjective sleep quality and daytime sleepiness are associated with cognition in middle-aged males. Participants A total of 189 healthy males born in 1953 were considered as participants for the study. Based on previous cognitive assessments, the participants were selected for the study as cognitively improved (N = 97) or cognitively impaired (N = 92). Methods The Pittsburgh Sleep Quality Index and Epworth Sleepiness Scale measured subjective sleep quality and daytime sleepiness, respectively. Depressive symptoms were determined using Beck's Depression Inventory (BDI-II). A neuropsychological battery was administered to confirm group differences in cognitive functioning at the time when sleep data were collected. Results Compared with cognitively improved males, the cognitively impaired group reported significantly lower subjective sleep quality (5.40 ± 3.81 vs. 4.39 ± 2.40, p = 0.03). Forty-one percent of the sample exhibited poor sleep quality and 15% experienced excessive daytime sleepiness. There were few correlations between sleep parameters and cognitive test performance in the combined sample. Conclusion Self-reported poor sleep quality was related to cognitive changes, whereas daytime sleepiness was not related. Our results suggest that sleep quality may be an early marker of cognitive decline in midlife.
The solid electrolyte interphase (SEI) is a layer that forms at the anode surface for all alkali metal ion batteries which utilize liquid electrolytes. It acts as an electronic insulator and ion conductor, but the formation of the SEI results in an irreversible capacity loss. For high capacity anodes in sodium ion batteries (NIBs), continued cycling of the battery ruptures the SEI and exposes new areas of the anode surface where the electrolyte will reduce. In this work, we utilize colloidal probe microscopy to investigate the mechanical properties of the SEI layer in NIBs for use in future anode designs. Our results indicate a lateral inhomogeneity in the Young's Modulus on the micron scale spanning 3 orders of magnitude. This technique can be used to investigate the differences in the SEI formed by different electrolytes and electrolyte additives and ultimately to determine the best liquid electrolyte for NIBs.
The low ionic conductivity and poor interfacial contact are the main obstacles restricting the practical application of all-solid-state polymer electrolyte in lithium metal batteries. Herein, four-armed and imidazolium cation-tethered polymeric ionic liquid (IMFPIL) is prepared through atom transfer radical polymerization of hydroxyethyl acrylate and subsequent functionalization. The branching architecture of the organic scaffold endows IMFPIL with high thermal stability, low glass transition temperature and loosely packed polymer backbones. The derived more free paths and volumes for Li-ion migration confer much enhanced ion conductivity on the as-prepared all-solid-state polymer electrolyte (IMFSPE), which is 22 times that of the linear counterpart with the same composition. High-temperature thermal integration of IMFSPE into the lithium metal battery effectively eliminates the gaps between the electrolyte and the two electrodes, rendering excellent interfacial contact and stability. The volume variation of the electrodes during the charge-discharge can be effectively mediated. As a result, in sharp contrast to the battery failure of the linear counterpart, such an integrated LiFePO4/IMFSPE/Li all-solid-state battery presents a high discharge capacity of 153 mAh g−1 at 0.2 C with 99% of coulombic efficiency, and the capacity retention ratio reaches 73% after 150 cycles. Compared with IMLSPE, IMFSPE-2 efficiently weakens the formation of dendritic lithium. The branching design combining with the thermal integration strategy and superior electrochemical features of imidazole make IMFSPE behave as an all-solid-state polymer electrolyte, which paves a new way for developing PILs as ideal SPEs in energy storage device.
Lithiated Nafion 112 ionomer was characterized by FT-IR spectroscopy, AC impedance, and cyclic voltammetry. The ionomer swollen with mixed solvents of propylene carbonate (PC) and ethylene carbonate shows ionic conductivity of 8.18×10−5Scm−1 at 25°C and good electrochemical stability to allow operation in Li/ionomer/LiCoO2 cells. The discharge capacity of the first cycle is 126mAhg−1. Significant capacity loss occurs during cycling due to the presence of PC. AC impedance shows that the passive layer formed at the Li/ionomer interface dominates the cycling performance of the cell.
Mesoporous FeF3(H2O)0.33 microspheres, hexagonal columns, and β-FeF3 ·3H2O square microrods have been prepared via facile solution methods using polyethylene glycol, oleic acid, and dodecyl trimethyl ammonium chloride as a surfactant, respectively. The as-prepared mesoporous FeF3(H2O)0.33 microspheres exhibits an enhanced lithium storage capacity and excellent cycling stability (159.2mAhg−1 at 142mAg−1 after 100 cycles). Even at a high current density of 474mAg−1, mesoporous FeF3(H2O)0.33 microspheres still deliver a discharge capacity as large as 95.9mAhg−1 after 100 cycles. This remarkable electrochemical performance can be attributed to the high specific surface area and mesoporous micro-spherical structure, which effectively increase the contact area between the active materials and the electrolyte, reducing the Li-ion diffusion pathway and buffering the volume change during cycling.