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Lithium ion batteries (LIBs) with organic electrode materials have drawn considerable attentions with advantages of their flexibility, low cost, and green sustainability, but been limited by high solubility in aprotic electrolytes, leading to capacity decay and short cycling life. Herein, we focus on the co-effect of structural modification and the increase of conductive carbon in electrode composites to accommodate soluble quinonic materials and achieve a long cycling life. Here, 2,3-dichloro-5-hydroxy-6-cyano-1,4-benzoquinone (DHCQ) is synthesized through a simple chemical hydrolysis of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The increase of conductive additive not only enhances the electronic conductivity but also suppresses the dissolution of DHCQ. Benefiting from reasonable molecular design and appropriate control of conductive carbon, the as-prepared material demonstrates a high reversible capacity (921 mA h g−1 at 50 mA g−1), good rate capability (207 mA h g−1 at 5 A g−1) and long-term cycling stability (remaining retention of around 78% after 400 cycles at 500 mA g−1).
Multifunctional ionomers based on poly(oxyethylene)-co-poly(epichlorohydrin) random copolymers were blended with poly(oxyethylene) or cross-linked through urethane curing. Their conductivities, transference numbers and electrochemical stability were investigated. The cross-linked materials exhibited good mechanical properties. Gelled by liquid organic electrolytes they provided conductivities very close to that of the liquid electrolyte. A thorough comparative investigation of the cationic transference numbers of cross-linked and uncross-linked ionomers was performed. From these data it may be assumed that the cell electrical polarization is enough to induce chain disentanglements, which result in a significant anionic transference number.
A series of LiNi1/3Mn1/3Co1/3O2−x F x (0≤ x ≤1) compounds was prepared by a solid state reaction and their characteristics were investigated by XRD, SEM, XPS, EIS, and charge–discharge test. The substitution of oxygen by fluorine produces change in the valences of the transition metal ions, thereby induces a complex change in the lattice parameters. Moreover, the fluorine doping of the LiNi1/3Mn1/3Co1/3O2 can promote the grain size growth and improve its crystallinity. The substituted samples with a low fluorine content can stabilize the interface between the surface layer of the active particles and the electrolyte after cycling, which is probably related to the improvement of the cyclic performance. A high fluorine content introduction into LiNi1/3Mn1/3Co1/3O2 significantly decreases its electrochemical properties, which is probably due to the formation of a new unstable interface as well as a structural instability caused by the nonequivilent substitution.
The paper reviews different approaches, technologies, and strategies to manage large-scale schemes of variable renewable electricity such as solar and wind power. We consider both supply and demand side measures. In addition to presenting energy system flexibility measures, their importance to renewable electricity is discussed. The flexibility measures available range from traditional ones such as grid extension or pumped hydro storage to more advanced strategies such as demand side management and demand side linked approaches, e.g. the use of electric vehicles for storing excess electricity, but also providing grid support services. Advanced batteries may offer new solutions in the future, though the high costs associated with batteries may restrict their use to smaller scale applications. Different “P2Y”-type of strategies, where P stands for surplus renewable power and Y for the energy form or energy service to which this excess in converted to, e.g. thermal energy, hydrogen, gas or mobility are receiving much attention as potential flexibility solutions, making use of the energy system as a whole. To “functionalize” or to assess the value of the various energy system flexibility measures, these need often be put into an electricity/energy market or utility service context. Summarizing, the outlook for managing large amounts of RE power in terms of options available seems to be promising.
Anodic polarisation of a vanadium electrode has been studied in H3PO4 solutions and some phosphate solutions: LiH2PO4, NaH2PO4, KH2PO4 and NH4H2PO4. The anodic behaviour of a vanadium electrode showed similarities in weak concentrated H3PO4, in LiH2PO4 and NaH2PO4 solutions: the polarisation curve exhibited a current peak followed by current oscillations and then a current plateau. Concentrated H3PO4, 1M KH2PO4 and NH4H2PO4 solutions involved vanadium passivation with a very slight current density plateau. Yellow compound identified to VOPO4·2H2O was obtained after controlled potential oxidation of vanadium in 5–10M H3PO4. Green products were obtained in 1M phosphate solutions and in 1–3M H3PO4 on vanadium anode after controlled potential electrolysis. All these vanadophosphate compounds contained the monovalent cation which was present in the solution.
Depression is the most common negative reaction among family caregivers of terminal cancer patients, persisting to post-bereavement. A modifiable factor associated with depression is mortality communication (i.e., caregiver-relative communication about illness and impending death). The purpose of this study was to examine the impact that mortality communication has on family caregiver’s depression after bereavement, and to translate into Danish and examine the construct validity of the caregiver communication with patients about illness and death scale (CCID; Bachner et al. Omega 57(4):381-397, 2008).
X-ray diagnostics in today's high-energy density environments must contend with intense and energetic X-ray background levels. In this work, we address the issues of X-ray fluorescence and scattering in reflection-geometry X-ray crystal spectrometers. In this geometry, the detector can capture not only a dispersed X-ray spectrum but also fluorescence and/or scattered X-rays from the diffracting crystal and crystal mounts. Studies to optimally reduce these sources of spectral contamination have been performed using the HENEX spectrometer. Variables that mitigate such unwanted background include filtration, collimation and judicious selection of crystal and detector materials.
Ni and Ti sulfides are formed on the surface of a Ti50Ni50 alloy by annealing the alloy at 873K for 0.24–72ks under the sulfur pressure of 160kPa, and then microstructures, martensitic transformation behavior, shape memory characteristics, superelasticity and electrochemical properties are investigated by means of scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, thermal cycling tests under constant load and tensile tests. NiS2 particles are formed first on the surface of the alloy, and then are grown and coalesced with increasing annealing time. When annealing time is longer than 1.2ks, in addition to NiS2, Ti8.2S11 sulfide is formed, and therefore the surface sulfide layers is consisted of NiS2 and Ti8.2S11. A Ti50Ni50 alloy with the surface sulfide layers shows the shape memory effect and superelasticity clearly. A Ti50Ni50 alloy with the surface sulfide layers shows clear discharge behavior with an increase of annealing time. Multi-voltage plateaus of 1.89, 1.70 and 1.42V are observed at a cell with electrode annealed for 1.2ks and an additional plateau at 2.0V appeared at cells of 3.6 and 10.8ks. NiS2 is not transformed into pure Ni and Li2S during discharging process directly but is transformed by way of intermediate phases such as NiS and Ni3S2.
The complexity of modern mobile phones makes it difficult for developers to understand the power consumption of their applications. Our measurement framework produces fine-grained, annotated traces of a phone’s power consumption which we are using to develop an understanding of how particular aspects of an application drive energy use. We ran a large number of automated tests using Google Android G1, Magic, Hero and Nexus handsets and present results for the average energy consumption of connection and data transmission over 802.11 wireless networks. Our results show that the optimal choice of data transmission strategy is different between handsets, operating systems, and device context.
Carbon and aluminum oxide co-coated Na3V2(PO4)2F3 cathode material has been successfully prepared via a wet chemistry method. The effects of the hybrid layer coating of C and Al2O3 on crystalline structure, morphology and electrochemical performance have been investigated. It is found that C and Al2O3 co-coating can stabilize the structure and improve the conductivity of NVPF. As a cathode material for sodium-ion batteries, the co-coated NVPF electrode shows a significant enhancement in rate capability and cycling performance, i.e., compared with bare NVPF, C-coated NVPF and Al2O3-coated NVPF, the NVPF/C-Al electrode delivers the highest capacity of 122.8 mAh g−1 with a superior capacity retention ratio of 95.6% after 100 cycles at 1 C. This enhancement in cycling performance and rate capability can be ascribed to the protective effect of this hybrid coating layer of C and Al2O3 on NVPF from electrolyte attack and the facilitated electron/ion transmission caused by the hybrid coating layer. This modification method of co-coating with electronic conductor C and sodium ionic conductivity Al2O3 provides an effective way to improve the electrochemical properties of NVPF and other cathode materials with low electron/ion conductivity for sodium/lithium ion batteries.
The “capacitive mixing” (CAPMIX) technique is aimed at the extraction of energy from the salinity difference between the sea and rivers. It is based on the voltage rise that takes place at the electrodes when changing the salt concentration of the solution in which the two electrodes are dipped. In this paper, we focus on activated carbon electrodes, produced with various methods and treatments, and we measure their behaviour in CAPMIX experiments. We find that they behave as polarizable electrodes only on time scales of the order of minutes, while on longer time scales they tend to move to a specific “spontaneous” potential, likely due to chemical redox reactions. This analysis sheds light on the charge leakage, i.e. the loss of the stored charge due to undesired chemical reactions, which is one of the main hurdles of the CAPMIX technique when performed with activated carbon electrodes. We show that the leakage finds its origin in the tendency of the electrode to move to its spontaneous potential. Our investigation allows us to completely get rid of the leakage and demonstrates the striking result that CAPMIX cycles can be performed without an external power supply.
Despite recent advances in resuscitation algorithms, neurological injury after cardiac arrest due to cerebral ischemia and reperfusion is one of the reasons for poor neurological outcome. There is currently no adequate means of measuring cerebral perfusion during cardiac arrest. It was the aim of this study to investigate the feasibility of measuring near infrared spectroscopy (NIRS) as a potential surrogate parameter for cerebral perfusion in patients with out-of-hospital resuscitations in a physician-staffed emergency medical service.
The quantity of charge stored in transition metal oxide intercalation cathodes for Li or Na batteries is not limited by transition metal redox reactions but can also access redox reactions on O; examples include Li1.2Ni0.13Mn0.54Co0.13O2, Li2Ru0.75Sn0.25O3, Li1.2Nb0.3Mn0.4O2, Na2RuO3 and Na2/3Mg0.28Mn0.72O2. Here we show that oxyfluorides can also exhibit charge storage by O-redox. We report the discovery of lithium manganese oxyfluoride, specifically the composition, Li1.9Mn0.95O2.05F0.95, with a high capacity to store charge of 280 mA h g−1 (corresponding to 960 W h kg−1) of which almost half, 130 mA h g−1, arises from O-redox. This material has a disordered cubic rocksalt structure and the voltage–composition curve is significantly more reversible compared with ordered Li-rich layered cathodes. Unlike lithium manganese oxides such as the ordered layered rocksalt Li2MnO3, Li1.9Mn0.95O2.05F0.95 does not exhibit O loss from the lattice. The material is synthesised using a simple, one-pot mechanochemical procedure.
The fabrication of nano-network structures for enhancing specific surface area and electrical conductivity is very crucial to attain high specific capacitance and energy density, which are important parameters to investigate a material for supercapacitor applications. Graphene oxide (GO) supported Al2S3 with hierarchical nanorambutan like morphology was fabricated by employing hydrothermal method. The determined high electrical conductivity, surface area, as well as the mechanical support offered by GO make the Al2S3 nanorambutan electrochemically active. The CV curves with well-defined redox peaks confirm the pseudocapacitive behavior of GO based hierarchical Al2S3 nanorambutan in 1M NaOH electrolyte. The specific capacitance extracted from the CV curves is 1687.97 Fg−1 at the scan rate of 5 mVs−1. Moreover, a good galvanostatic discharge time of 903s and a huge specific capacitance of 2178.16 Fg−1 at the current density of 3mAcm−2 have been observed. The energy density calculated from the galvanostatic discharge is 108.91 WhKg−1 at the current density of 3mAcm−2, while a power density of 978.92 WKg−1 is observed at the current density of 15mAcm−2. The electrochemical impedance also confirms the pseudocapacitive nature of Al2S3 hierarchical nanorambutan electrode. The electrode stability test shows 57.84% retention of the specific capacitance up to 1000 cycles. The experimental results suggest that hierarchical Al2S3 nanorambutan is suitable electrode material for supercapacitor applications.
Resistive companion (RC) modeling is an easy-to-use approach for electric circuit simulations. With a RC numerical solver, simulations of complex electric systems can be achieved based on RC models. In this study, the construction of RC battery models is investigated. A general battery model and a nickel–metal hydride cell model have been built. Simulations of RC battery models on virtual test bed (VTB) are presented and analyzed. It is shown that RC modeling provides a flexible and powerful way for the simulation of battery systems.
The fuel cells have high potential and superiority in future green transportations. The hybridization of the fuel cells with other energy storage devices such as the lithium-ion batteries and supercapacitors provides an effective way to alleviate the burden and prolong the lifespan of the fuel cells. The designs of topology and management strategy are important for fuel cell vehicles. This paper presents an improved power splitting strategy for hybrid propulsion systems by using multiple-grained velocity prediction. In this paper, the dynamic programming strategy is presented to realize optimal power splitting for different power sources. Moreover, the Markov prediction method is employed for the multiple-grained vehicle velocity prediction. In order to verify the proposed method in the hybrid propulsion system, a semi-physical platform is established to realize the hardware-in-loop simulation. The case study of different hybrid electric propulsion structures is analyzed and discussed. The system hydrogen consumption cost and electricity price of different hybrid propulsion systems are compared under the urban dynamometer driving schedule. The paper systematically compares the power splitting strategy used in different hybrid propulsion structures, in hopes of providing some inspirations to the design and control of the hybrid propulsion system.
This paper investigates the empirical link between fiscal vulnerabilities and currency crashes in advanced economies over the last 130 years, building on a new data set of real effective exchange rates and fiscal balances for 21 countries since 1880. The paper finds evidence that crashes depend more on prospective fiscal deficits than on actual ones, and more on the composition of public debt (that is, rollover/sudden stop risk) than on its level. The paper also uncovers significant nonlinear effects at high levels of public debt as well as significantly negative risk premiums for major reserve currencies, which enjoy a lower probability of currency crash than other currencies ceteris paribus. Yet, the estimates indicate that such premiums remain small in size relative to the conditional probability of a currency crash if prospective fiscal deficits or rollover/sudden stop risk are high.
An asymmetric supercapacitor, exploiting nm-scale conformal coating of conducting polymer (CP) on aligned carbon nanotubes (A-CNTs) as the negative electrode and ultra-high density A-CNTs as the positive electrode, has been developed. The conformal CP coating on the A-CNTs enhances charge storage while the aligned nanotube morphology provides straight and fast ion transport pathways. The A-CNT electrode, densified using a unique mechanical method, possesses high volumetric capacitance while preserving the aligned morphology to maintain the high power, provides an ideal positive electrode for the asymmetric supercapacitor. By complementary tailoring of the asymmetric electrodes, the device exhibits a wide operation voltage of 4V with maximum energy and power densities of 82.8WhL−1 and 130.6kWL−1 in volumetric performance. In this paper, a new method was introduced which is simple but can determine directly the energy storage efficiency of a supercapacitor cell. An equivalent circuit was developed to model the performance of each electrode and investigate the asymmetric design of the cell.
One-dimensional (1D) cobalt acetate hydroxide (Co5(OH)2(CH3COO)8·2H2O) prisms has been obtained through a low temperature re-crystallization process in the dissolvant of ethanol and then transferred to cobalt oxide by calcining in the air. Cobalt oxide keeps the outside configuration of the 1D cobalt acetate hydroxide but turns to be boxes with hollow structure inside through the Kirkendall effect. The precursor prisms and polycrystalline boxes both have length of about 3 μm, width of 300 nm and height of 300 nm characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical measurement results show that the hollow Co3O4 structures exhibit wonderful capacitive properties with high capacitance and good cyclicity.
Distributed generation in the form of DC microgrids has recently attracted increasing research interest. For integrating renewable energy resources and energy storage devices, such as an ultracapacitor, to the DC bus of a DC microgrid and sustain the charging and discharging states of the ultracapacitor, a bidirectional DC–DC converter is required. For the fast dynamic response of the ultracapacitor, bidirectional voltage-fed topology is preferred. But for a wide input voltage variation of the ultracapacitor, this topology exhibits a higher circulating power flow and higher conduction losses as a consequence. In this paper a comprehensive overview on several modulation methods that employed to control the power flow of the bidirectional voltage-fed DC–DC converter for the ultracapacitor applications are presented. A detailed analysis of the bidirectional converter exploring the impact of the circulating power flow interval is developed in this study. Analytical methods have been applied to establish alternative modulation methods for the bidirectional converter to improve its performance and efficiency.
S0.87Se0.13/CPAN (carbonized polyacrylonitrile) composites material was synthesized by annealing the mixture of S (sulfur), Se (selenium) and PAN directly at 400 °C. The prepared composites was used as high capacity and stable cycling performance cathode for lithium sulfur battery. It delivers a specific capacity of 1210 mAh g−1 after 100 cycles at a constant current density of 120 mA g−1. In addition, it remains 989 mAh g−1 after 200 cycles at a current density of 300 mA g−1 with ultralow capacity fading of 0.025% per cycle. Meantime, the S0.87Se0.13/CPAN cathode exhibits extremely low self-discharge behavior. The superior electrochemical performance of S0.87Se0.13/CPAN composites should be ascribed to high S/Se ratio in S0.87Se0.13/CPAN composites and good conductivity brought by the addition of Se, which make full use of high capacity of S. Moreover, the chemical bonding between Se and S, as well as the chemical bonding between S0.87Se0.13 and CPAN decrease the loss of active material. This easy one-step synthesis procedure offers a feasible new route for the development of sulfide-based cathode material.
Amorphous Ru1−y CryO2/TiO2 nanotube composites were synthesized by loading different amount of Ru1−y CryO2 on TiO2 nanotubes via a reduction reaction of K2Cr2O7 with RuCl3·nH2O at pH 8, followed by drying in air at 150°C. Cyclic voltammetry and galvanostatic charge/discharge tests were applied to investigate the performance of the Ru1−y CryO2/TiO2 nanotube composite electrodes. For comparison, the performance of amorphous Ru1−y CryO2 was also studied. The results demonstrated that the three dimensional nanotube network of TiO2 offered a solid support structure for active materials Ru1−y CryO2, allowed the active material to be readily available for electrochemical reactions, and increased the utilization of active materials. A maximum specific capacitance 1272.5F/g was obtained with the proper amount of Ru1−y CryO2 loaded on the TiO2 nanotubes.
Layered materials provide good electrochemical performance, but insufficient rate capability, which is the main issue in energy storage. Herein, we propose a facile synthesis of Co2(CO3)(OH)2 nanoflakes and polyhedron flowers supported on Ni foam, a novel binder-free electrode. Power law revealed that Co2(CO3)(OH)2 stores charge by a battery-type mechanism at the peak potential. The nanoflakes store more internal surface charge than the polyhedron-flower, which was confirmed via Trasatti plot. Benefiting from amorphous nanostructure, unique morphology and high surface area, the nanoflakes shows good performance. The areal capacitance (2111 mF cm−2), rate capability (80%), and energy density (0.152 mWh cm−2) are comparable to recent reports. The results suggest that the amorphous Co2(CO3)(OH)2 nanoflakes are a suitable cathode candidate for the supercapattery. The assembled supercapattery (ASC) provides high specific capacitance (91 F g−1), high energy density (26.22 Wh kg−1 at power density 828 W kg−1), and long cycle life (specific capacitance retention of 85% over 4000 cycles). The ASC device shows good potential in the field of energy storage devices.
An isothermal reduced order physics-based Li ion battery model is developed by incorporating solution phase charge and material balances into single particle (SP) model. Li ion concentration and potential profiles in electrolyte phase are approximated by polynomial functions. A cubic polynomial is used for electrolyte concentration and potential inside electrodes, while separator liquid phase potential and concentration are estimated by parabolas. Diffusion inside solid particles is also simplified using an approximate solution based on analytical solution for the solid concentration. Applying the aforementioned reduction techniques decreases the degree of freedom of full order model by more than 100, while the cell voltage relative error of proposed model is less than 1% at different charge–discharge rates up to 5C.
The TMI-2 and Fukushima Daiichi accidents appear to be dissimilar because they involve different reactor types. However, the health physics related lessons learned from TMI-2 are applicable, and can enhance the Fukushima Daiichi recovery effort.