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The instability of the electrolyte is believed to be one of the reasons affecting the electrochemical performance of the today's Li–O2 batteries. Aim of this study is to give new insights about the stability of LiTFSI-Tetraglyme as electrolyte for Li–O2 batteries. Thus the electrochemical behavior of Li–O2 cells comprised of Super-P based cathode coated on gas diffusion layer, lithium anode and LiTFSI-Tetraglyme electrolyte is investigated by galvanostatic cycling and impedance spectroscopy. The reversibility of the formation/dissolution of Li2O2 in the carbon cathode upon discharge/charge is suggested by impedance outcomes and confirmed by ex situ XRD measurements. The chemical degradation of the liquid aprotic electrolyte is investigated via gas chromatography with headspace injection, which allows detecting decomposition products generated during the galvanostatic charge/discharge of Li–O2 batteries.
Data suggest that treatment with luteinizing hormone–releasing hormone (LHRH) agonists may be associated with reduced cognitive functioning. The purpose of the current study was to compare rates of clinically significant cognitive impairment in men treated with LHRH agonists to a matched sample of healthy men without cancer.
Porous carbon spheres (PCSs) were fabricated through a fast microwave-assisted approach using sucrose as the precursor in a microwave system and subsequent thermal treatment at 600, 800 and 1000°C. The morphology, structure and electrochemical performance of the PCSs were characterized by scanning electron microscopy, Raman spectroscopy, nitrogen adsorption-desorption, cyclic voltammetry and electrochemical impedance spectroscopy. Their electrosorption performance in NaCl solution was studied and compared with activated carbon, carbon nanotubes, reduced graphene and carbon aerogels. The results show that due to their high specific surface area and low charge transfer resistance, PCSs treated at 1000°C exhibit high electrosorption capacity of 5.81mgg−1 when the initial solution concentration is 500mg l−1, which is higher than those of other carbon materials.
The hollow mesoporous silicon nanobox dually encapsulated by tin oxide and carbon layers is successfully fabricated and used for anode active material of lithium ion battery. The effects of the double coating layers on the structure, morphology and features of nanocomposite are systematically investigated by transmission electron microscopy, field emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and galvanostatic charge-discharge tests. The results reveal that hollow mesoporous silicon/tin oxide/carbon nanobox has the adjustable void space and a rationally designed hierarchical structure, which permits the free expansion of Si core without breaking double coating layers and preserves the structural integrity of the electrode during the (de)lithiation processes, as well as significantly enhances the electronic conductivity of anode. As expected, the resultant hollow mesoporous silicon/tin oxide/carbon nanobox exhibits a high reversible capacity up to 1535 mAh g−1 at 0.5 A g−1 after 200 cycles of (dis)charging due to the unique nanostructure. Especially, the as-synthesized nanocomposite exhibits an excellent rate capacity as high as 858 mAh g−1 at 6 A g−1. This rational structure design and innovative approach can be of visible significance for the development of new anode active materials of next-generation lithium-ion battery.
We report on the synthesis of amphiphilic polymers with a composition shift of the hydrophobic block made by emulsion polymerization that is used as a water-based binder for LiFePO4 cathodes. The integrity of the electrode is sustained by using a unique chemical procedure for cross-linking the binder. This technique yields higher adhesion of the binder on aluminium collectors comparing with the state-of-the-art binders. Amphiphilic polymers are excellent for well-dispersed inorganic particles, and consequently demonstrate satisfactory electrochemical performances.
Sulfur nanocomposites are prepared by using graphene derived carbon (GDC), with controlled porosity characteristics, as confining matrix and are studied as efficient cathodes for lithium-sulfur (Li-S) batteries. To understand the effect of micro-/mesoporosity in porous carbon for the effective encapsulation of sulfur and polysulfides towards improved Li-S battery performance, two different GDC samples with controlled porosity characteristics, one with predominantly micropores (GDC-1) and a surface area of 1970m2g−1 and the other with a surface area of 3239m2g−1, having more or less equal contribution of micro- and mesopores (GDC-2), are used to synthesize nanocomposite sulfur electrodes following melt diffusion process. Electrochemical studies are carried out by using cyclic voltammetry, galvanostatic charge/discharge cycling and electrochemical impedance spectroscopy (EIS). EIS spectra collected at different depth of discharge (DOD) in the first cycle as well as upon cycling give valuable insights into the Li-S redox reactions and capacity fading phenomena in these electrodes. The impedance response of GDC-S electrodes suggests a detrimental effect of the mesopores, where insoluble reaction products can easily accumulate, resulting in the loss of active material leading to capacity fading of Li-S cells.
Recent high-energy lithium-ion batteries contain highly densified electrodes, but they are expected to endure fast charging without safety compromises or accelerated aging. To investigate fast charging strategies, we use a multi-dimensional model consisting of several newman-type electrochemical models (p2D) coupled to an electrical-thermal cell domain model. Open-circuit potential, infrared thermography and calorimetry experiments of a high-energy 18650 NMC-811/SiC lithium-ion cell are used for model parameterization and validation. First, a single p2D model is used to compare the charging rate capabilities of NMC-811/SiC and NMC-111/graphite cells. We assess the modeling error of the single p2D model relative to the multi-dimensional model as a function of tab design. The multi-dimensional model is then used to study different tab and electrode designs regarding their susceptibility to lithium plating, which is evaluated based on local anode overpotential and local temperature. High-rate charging current profiles that minimize the risk of lithium plating are derived by implementing an anode potential threshold. We show that a state of charge beyond 60% can be reached in less than 18 min.
A nano-sized ZnO-loaded/N-doped carbon composite (ZnO/N-CF) was prepared by anchoring the zeolitic imidazolate framework, ZIF-8, onto a porous carbon foam (CF) with water vapor-assisted method, followed by the controlled two-step heat treatments. Utilization of ZIF-8 as a Zn source facilitated the impregnation of Zn species into the mesopores of the CF matrix, establishing the beneficial conductive networks between ZnO particles and preventing the growth and aggregation of ZnO particles during the prolonged cycles. The ZnO/N-CF sample exhibited stable discharge capacities of more than 1177mA h g−1 after 100 cycles with a current density of 98mAg−1 between 0.01 and 3.0V. It also showed excellent rate capabilities compared to bare ZnO and previously reported other ZnO-based electrodes.
A major application of energy-harvesting technology is to power portable and wearable consumer electronics. We report a packaged power-generating insole with built-in flexible multi-layered triboelectric nanogenerators that enable harvesting mechanical pressure during normal walking. Using the insole as a direct power source, we develop a fully packaged self-lighting shoe that has broad applications for display and entertainment purposes. Furthermore, a prototype of a wearable charging gadget is introduced for charging portable consumer electronics, such as cellphones. This work presents a successful initial attempt in applying energy-harvesting technology for self-powered electronics in our daily life, which will have broad impact on people's living style in the near future.
For the first time, Cu(NO3)2·xH2O (x ≤ 2.5) is investigated as a new lithium storage anode material for lithium-ion batteries. The impressive characteristic of Cu(NO3)2·xH2O(x ≤ 2.5)/Li cell is the high initial discharge capacity reaching to around 2200 mAh g−1. To make a comparison, Cu(NO3)2·2.5H2O electrodes are used as raw materials and heat-treated at 80, 120 and 160 °C. Among all the three samples, Cu(NO3)2·xH2O (x < 2.5) obtained at 160 °C shows the highest reversible capacity of 597.6 mAh g−1 and the best cycling stability after 30 cycles. The difference in electrochemical behaviors is attributed to the variation of surface morphology, crystal water and particles size after heat-treatment at different temperatures. Besides, the thermal reaction results also show that Cu(NO3)2·xH2O (x < 2.5) obtained at 160 °C has the highest thermal stability among all the three samples after repeated cycles. The present findings can provide the fact that Cu(NO3)2·xH2O (≤2.5) may be a promising anode material for lithium-ion batteries.
Micro-combined heat and power (CHP) holds great potential for lowering energy cost and CO2 emissions in the residential housing sector. Of the various micro-CHP technologies, fuel cells, and in particular solid oxide fuel cells, show great promise due to their high electrical efficiency and resulting low heat-to-power ratio that is better suited to residential applications. However, fuel cells are still under development and the capital cost of units available today remains high. This paper looks at the technological aspects and operating modes of fuel cells relevant to micro-CHP as well as examining the state of commercial development, life cycle issues and the techno-economics of fuel cells for micro-CHP at the residential scale.
This paper aims to explore the relationship between the economic growth and the pressure on nature from the environmental sustainability perspective. The pressure on nature is measured by the natural disinvestment component of the Adjusted Net Savings data of the World Bank; which is the sum of energy, mineral, net forest depletions and carbon dioxide damage, all measured in US dollars. Our panel consists of 213 countries and spans the period between 1970 and 2008. We employ a panel Fixed-Effects Instrumental Variable (IV) methodology. Regression analysis reveals that there is a positive relationship between income and pressure on nature, yet the effect is much stronger in middle-income than in low and high-income countries, and also differs across subcomponents. While increase in income decreases the pressure on forests, CO2 damage and mineral extraction increase. We found that increasing trade, all else equal, increases the pressure on nature, hence our findings support Race-to-the-bottom hypothesis.
A nitroxyl radical, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), is known to be oxidized electrochemically at 3.5V versus lithium [4,5]. Since this reaction is reversible in the aprotic electrolyte, we can use it as a cathode reaction in lithium rechargeable battery. Some nitroxyl radical compounds which have different structures have been prepared and their electrochemical behavior and spectroscopic properties have been studied. The electrochemical measurements in aprotic electrolyte revealed that most nitroxyl radical compounds show reversible redox behavior similar to that of TEMPO independent of their structures in the range of −0.15–0.20V versus Ag/Ag+ (3.69–4.04V versus Li/Li+). The redox potentials for these materials were found to be predictable approximately by quantum calculations. Thus, various molecular designs tailored to desired redox potentials would be possible as active materials for lithium rechargeable batteries, and their specific capacities, mechanical properties and colors can be controlled within limits.
Si–Cu–Ti thin films with Cu3Si nanowires on the surface and voids in the Cu layer are fabricated for the first time by magnetron sputtering combined with atomic layer deposition (ALD) of alumina. The formation of the surface Cu3Si nanowires is strongly dependent on the thickness of the coated alumina and cooling rate of the thin films during annealing. The maximum coverage of the surface Cu3Si nanowires is obtained with an alumina thickness of 2 nm and a cooling rate of 1 °Cmin−1. The electrode based on this thin film shows an excellent capacity retention of more than 900 mAh g−1 and a high columbic efficiency of more than 99% after 100 cycles. The improvement of the electrochemical performance of Si–Cu–Ti thin film electrode is attributed to the surface Cu3Si nanowires which reduce the polarization and inhomogeneous lithiation by formation of a surface conductive network, in addition to the alleviation of volume expansion of Si by voids in the Cu layer during cycling.
The energy density and operational life of lithium-ion batteries (LIBs) depend sensitively on the properties of electrode materials. Transition metal oxide based electrodes attract much attention because of their potential to offer high energy density. In this study, we report a binder-free composite anode composed of CuO nanosheets and multi-wall carbon nanotubes for LIBs. This composite anode is fabricated by a cost-effective electrophoretic deposition process followed by facile solution immersion. When tested in a LIB, this composite anode delivers a high reversible capacity of 540 mAh g−1 and maintains its capacity retention of above 78% after 50 cycles at a current density of 100 mA g−1, which is much higher than the CuO anode without carbon nanotubes. The high capacity, enhanced rate capability, low resistance, and increased operational life are attributed to the unique architecture of the hybrid electrode. The carbon nanotubes facilitate the electron transfer, enhance the structural stability of CuO nanosheets, and improve the adhesion of the CuO nanosheets to current collector. Such highly porous cross-linked network based on CuO nanosheets and multi-wall carbon nanotubes has great potential as a binder-free anode for high-performance LIBs.
Redox shuttle electrolyte additives (RSAs) can be applied for reversible overcharge protection of batteries. Their successful operation involves their oxidation at the cathode and reduction at the anode. The most common anodes in lithium-ion batteries are graphite or amorphous carbon, which are normally covered with a solid electrolyte interphase (SEI). The reduction of RSAs at these anodes is in apparent contradiction with the common understanding of the SEI, which is thought to be electronically insulating. In this communication the reduction behaviour of ferrocene and 2,5-di-tert-butyl-1,4-dimethoxybenzene is studied at un-filmed and SEI-filmed electrodes. It is found that it depends strongly on the type of RSA and/or composition of the SEI. The rotating ring-disc electrode (RRDE) is introduced as a powerful diagnostic tool to study the reaction mechanism of RSAs in general and the influence of the SEI in particular.
In the early 21st century, Korean government issued a policy recommendation that Korean public research institutes should select strategic research fields to concentrate their resources, based on a careful review of the various strategic R&D factors. The government has emphasized the “selection and concentration” strategy for the efficient use of R&D resources and as a way to increase the national competitiveness of Korea. This paper suggests a method, a “Technology Cluster Analysis,” for selecting the strategic research areas, mainly targeting large, multi-disciplinary and long-term programs. The technology cluster analysis groups near technologies together based on key indicators. In this study, the method is applied to national R&D programs in the nano-technology field. Fifty-six nano-technologies are analyzed and grouped into three main clusters based on the survey data from 180 experts. Technological distances and correlations among individual technologies are depicted by hierarchical dendrogram. Three main clusters in nano-technology field are found and termed nano-materials, nano-devices, and nano-bio. These three clusters are expected to be the core technology clusters in nano-technology field in South Korea.
Organic materials with high natural abundance, low price as well as environmental friendliness have been considered as proper alternatives to replace inorganic electrodes. However, it is still challengeable for exploiting novel organic materials incorporating highly stable framework in electrolyte, optimized nanostructure and large lithium storage capacity. In the present work, hyper-crosslinked polystyrene (HPS) nanospheres are fabricated by combination of emulsion polymerization and subsequent Friedel-Crafts reaction. The obtained HPS has abundant oxygen-containing functional groups for reversible lithium ions storage reactions, uniform spherical morphology along with well-developed porous structure to minimize transfer distance of lithium ions, rigid macromolecular frameworks to resist the dissolution of electrolyte. Therefore, HPS presents promising potential as electrode in lithium ion battery. The initial discharge and charge capacities of HPS can reach 533 and 262 mAh g −1, respectively, and a stable capacity of 356 mAh g−1 is delivered after repeated charge-discharge for 100 times at 0.2 A g−1. Even cycled for 1000 times at 2 A g−1, the capacity remains 222 mAh g−1.
Multimorbidity affects up to one quarter of primary care populations. It is associated with reduced quality of life, an increased risk of mental health difficulties and increased healthcare utilisation. Functional decline is defined as developing difficulties with activities of daily living and is independently associated with poorer health outcomes. The aim of this systematic review was to examine the association between multimorbidity and functional decline and to what extent multimorbidity predicts future functional decline.
Summary This paper examines technology spillover from foreign direct investment (FDI) based on a cross-industry analysis of Thai manufacturing. The analysis is built around the hypothesis by Bhagwati that technology spillover is conditioned by the nature of the trade policy regime. The result, based on a two-equation model that allows for the two-way link between the foreign presence and productivity of locally owned industries, provides support for the hypothesis. A key policy implication is that liberalizing the foreign investment regime has to go hand in hand with liberalizing the trade policy regime to maximize gains from FDI technology spillover.
Due to the strong nonlinearity and complex time-variant property of batteries, the existing state of charge (SOC) estimation approaches based on a single equivalent circuit model (ECM) cannot provide the accurate SOC for the entire discharging period. This paper aims to present a novel SOC estimation approach based on a multiple ECMs fusion method for improving the practical application performance. In the proposed approach, three battery ECMs, namely the Thevenin model, the double polarization model and the 3rd order RC model, are selected to describe the dynamic voltage of lithium-ion batteries and the genetic algorithm is then used to determine the model parameters. The linear matrix inequality-based H-infinity technique is employed to estimate the SOC from the three models and the Bayes theorem-based probability method is employed to determine the optimal weights for synthesizing the SOCs estimated from the three models. Two types of lithium-ion batteries are used to verify the feasibility and robustness of the proposed approach. The results indicate that the proposed approach can improve the accuracy and reliability of the SOC estimation against uncertain battery materials and inaccurate initial states.
An in-depth study on the photovoltaic characteristics under indoor lights, i.e., light-emitting diode (LED), fluorescent lamps, and halogen lamps, was performed with varying the photoactive layer thickness (120–870 nm), by comparing those under 1-sun condition. The semi-crystalline mid-gap photoactive polymer, poly[(2,5-bis(2-hexyldecyloxy)phenylene)-alt-(5,6-difluoro-4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole)] (PPDT2FBT) and a fullerene derivative, [6,6]-phenyl C71 butyric acid methyl ester (PC70BM) were used as a photoactive layer. In the contrary to the measurements under 1-sun condition, the indoor devices show a clearly different behavior, showing the thickness tolerant short-circuit current density (J SC) and fill factor (FF) values with 280–870 nm thick photoactive layers. The retained J SC and FF values of thick indoor devices were discussed in terms of the parasitic resistance effects based on the single-diode equivalent circuit model. The much lower series/shunt resistance (Rs/R P) ratio was measured with thick photoactive layer (≥280 nm), resulting in negligible decreases in the J SC and FF values even with a 870-nm-thick active layer under the LED condition. Under 1000 lx LED light, the PPDT2FBT:PC70BM device showed an optimum power conversion efficiency (PCE) of 16% (max power density, 44.8 μW/cm2) with an open-circuit voltage of 587 mV, a J SC of 117 μA/cm2, and a FF of 65.2. The device with a 870-nm-thick active layer still exhibited an excellent performance with a PCE of 12.5%. These results clearly suggest that the critical parasitic resistance effects on the performance vary depending on the light illumination condition, and the large R P associated with the viable thick photoactive layer and the well-matched absorption (of photoactive layer) with the irradiance spectrum (of indoor light) are essential to realize efficient indoor photovoltaic cells with high J SC and FF.
Developing high capacity yet stable cathodes is key to advancing Li-ion battery technologies. Now, a new metal oxide cathode that is rich in Li with a gradient in Li concentration is shown to be stable to O2 release leading to long cycle life and high capacity.
Aim ng at improving the high rate capability of spinel lithium manganese oxide (LiMn2O4) cathode, ultralong LiMn2O4 nanofibers are prepared by combination of electrospinning and sol-gel techniques. The effect of processing parameters, including the weight ratio of polyvinylpyrrolidone (PVP) to Li and Mn precursor, calcination temperature and time, on the morphology and the resultant cathode performance of spinel LiMn2O4 nanofiber cathodes have been systematically investigated. Thermal behavior of LiMn2O4 precursor nanofibers is performed on a differential scanning calorimetry-differential thermal analysis (DSC-DTA), indicating the spinel LiMn2O4 began forming at 513°C. The cathode materials appear porous “network-like” morphology with nanosize in diameter (∼170nm), microsize in length (∼20μm) and pure spinel structure, confirmed by scanning electron microscopy (SEM) and X-ray diffractometer (XRD). The ultralong LiMn2O4 nanofiber cathode calcined at 700°C for 8h shows highest capacity and best rate capability. Its discharge capacity is 146mAhg−1 at 0.1C; more importantly, the discharge capacities are 112mAhg−1, 103mAhg−1 and 92mAhg−1 at high discharge rates of 10C, 20C and 30C, respectively.