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A fully dense Ce0.8Gd0.2O1.9 (gadolinia doped ceria, GDC) is obtained by a novel using a sintering technique for several seconds at 545°C by applying a direct current (DC) electrical field of 70Vcm−1. The onset applied field value of this phenomenon is 20Vcm−1, and the volume specific power dissipation for the onset of flash sintering is about ∼10mWmm−3. Through contrast with the shrinkage strain of the conventional sintering as well as scanning electron microscopy (SEM) analysis, we conclude that GDC specimens are sintered to fully density under various applied fields. In addition, we demonstrate that the grain size of GDC is decreasing with the increase of applied field and the decrease of sintering temperature. Through calculation, we find that sintering of GDC can be explained by the Joule heating from the applied electrical field.
The optical and electrochemical properties of thin films of a nickel–vanadium mixed oxide have been investigated as a new Li+ intercalation compound, to be used as an optically passive counterelectrode in electrochromic switching devices. The thin film samples were prepared by radio frequency (RF) sputtering under different preparation conditions, using targets with different Ni/V ratios and a reactive (20% O2) or, alternatively, non-reactive (pure Ar) sputtering atmosphere. The optical properties of as-grown and Li+ inserted–extracted electrodes were determined by computer fitting of the UV–Vis–NIR transmittance and specular reflectance spectra. The electrochemical measurements of Li+ insertion and extraction consisted of cyclic voltammetry, chronopotentiometry and potentiostatic intermittent titration technique. The samples showed interesting electrochemical and optical properties, a good electrochemical reversibility and ion-storage capacity exceeding 40 mCcm−2, lasting for several hundreds cycles at a current of 50 μAcm−2. The electrodes displayed an almost passive electrochromic behavior during the electrochemical experiments.
Advances in secondary batteries are required for realization of many technologies. In particular, there remains a need for stable higher energy batteries. Here we suggest a new anode concept consisting of an ultrathin Co3O4 nanosheet-coated Ni inverse opal which provides high charge–discharge rate performance using a material system with potential for high energy densities. Via a hydrothermal process, about 4 nm thick Co3O4 nanosheets were grown throughout a three-dimensional Ni scaffold. This architecture provides efficient pathways for both lithium and electron transfer, enabling high charge–discharge rate performance. The scaffold also accommodates volume changes during cycling, which serves to reduce capacity fade. Because the scaffold has a low electrical resistance, and is three-dimensionally porous, it enables most of the electrochemically active nanomaterials to take part in lithiation–delithiation reactions, resulting in a near-theoretical capacity. On a Co3O4 basis, the Ni@Co3O4 electrode possesses a capacity of about 726 mAh g−1 at a current density of 500 mA g−1 after 50 cycles, which is about twice the theoretical capacity of graphite. The capacity is 487 mAh g−1, even at a current density of 1786 mA g−1.
Vagus nerve stimulation (VNS) is an increasingly used therapy for patients with treatment-refractory epilepsy and depression. Hypomanic and manic symptoms are a rare but recognized adverse effect of VNS treatment. Here we describe a case in which VNS treatment in a patient with epilepsy and unipolar depression was associated with the rapid development of manic symptoms. The patient's manic symptoms resolved with temporary discontinuation of the VNS current, and the patient was eventually able to resume VNS treatment with good effect and without further manic symptoms. Mania is a rare but serious side effect of VNS; however, in this case and in the majority of reported cases of VNS-associated mania, symptoms resolve and VNS can be safely administered.
This work reports a facile solution based chemical transformation of thin film of CdCO3 cuboids into Cd-based Prussian blue analogue structured thin film with controlled redox-state by manipulating the anion exchange reaction between the solid film and the aqueous solution of K3[Fe(CN)6] at 60°C. The progress of the transformation reaction is monitored via electron microscopy, X-ray difractometry and X-ray photoelectron spectroscopy. Based on the scenario of the reaction progress revealed by these analysis, the CdCO3 cuboids are first found to be transformed into the smaller cuboids of cadmium ferricyanide, which, on further reaction, are transformed into the cadmium ferrocyanide cuboids. Thus, by controlling the redox-state of the Fe-metal center on the frameworks, the electrocatalytic activity of the frameworks on oxygen reduction reaction (ORR) is studied. The electrocatalytically inert CdCO3 cuboids after transformation to the frameworks with Fe3+-centers demonstrate an enhanced catalytic activity on ORR, while the Fe2+-centers of the frameworks are found to relegate the catalytic activity, thereby manifesting the redox-sate modulated ORR activity of the frameworks. To the best of the authors' knowledge, this is the first report of this kind on redox-state specific ORR activity.
The physics-based single particle (SP) model was compared to the semi-empirical equivalent circuit analog (ECA) model to predict the cell voltage under constant current charge and discharge for different sets of Li-ion cell data. The parameters of the models were estimated for each set of data using nonlinear least squares regression. In order to enhance the probability of finding the global optima, a combination of the trust region method with a genetic algorithm was applied to minimize the objective function (the sum of squared residuals). Several statistical quantities such as sum of the squared errors, adjusted R 2, root mean squared error, confidence intervals of the parameters, and prediction bounds were included to compare the models. A significance test (t test) on the parameters and the analysis of the variances (F and χ 2 tests) were also performed to discriminate between the goodness of the fit obtained from the two models. The statistical results indicate that the SP model superiorly predicts all sets of data compared to the ECA model, while the computation times of both models are on the same order of magnitude.
A physics-based, reduced order model was developed to describe the capacity degradation in LiNiMnCoO2-graphite cells. By starting from fundamental principles, the model captures the effects of four degradation mechanisms: (i) SEI growth on the anode, (ii) electrolyte oxidation on the cathode, (iii) anode active material loss, and (iv) cathode active material loss, the last two due to chemomechanical fracture. The model is computationally efficient (∼1 ms/cycle) and enables physical, real-time, capacity loss calculations for automotive applications. Results demonstrate that under storage conditions, SEI growth and electrolyte oxidation are the major degradation mechanisms, in agreement with experiments. In contrast, batteries subjected to electric currents of a wide amplitude, close to the upper cutoff voltage, electrolyte oxidation contributes ∼50% of all the degradation mechanisms, consistent with recent experiments in the literature. Chemomechanically induced active material losses are maximal in the anode at high states of charge and maximal in the cathode at low states of charge. Results quantify the contribution to degradation from each individual mechanism, highlighting, for the first time, the need of physics-based, on-the-fly descriptions that go beyond traditional coulomb counting approaches. Finally, the identification of the individual degradation contributions enables the possibility of tailoring the charge/discharge sequence to extend battery life.
The mechanism of oxygen reduction at MnO2-catalyzed air cathode was investigated by measurements of polarization curves in wide OH− concentrations, oxygen pressures and using different crystalline MnO2 catalysts. It is found that the oxygen reduction at MnO2 catalyst is accompanied with the reduction of MnO2 and the catalytic activities of MnO2 is closely related to the electrochemical activities of MnO2. Based on the experimental determination of the reaction orders of OH−, O2 and the intermediate Mn3+ ion, we propose a chemical oxidation mechanism for the catalytic oxygen reduction, in which oxygen reduction proceeds through chemical oxidation of the discharge product of MnO2 rather than through a direct two-electron reduction. The rate expression derived from this mechanism can very well explain the observed polarization properties and the concentration dependence of oxygen reduction.
As an appealing storage system for electric vehicle application, the lithium-oxygen battery could theoretically provide ultrahigh energy density; however, its attractive implementation is overshadowed by unsatisfactory electrochemical characteristics of the poor rate capability and the short span life. Here, we put forward one kind of effective strategy to ameliorate these deficiencies. By embedding a novel air electrode, the utilization level of the electrochemically available active sites is effectively increased and meanwhile the mass transfer of oxygen is signally improved. The evaporation speed of the solvent is greatly slowed down to some degree. We demonstrate that a super P-based lithium-O2 battery could be operated over stable 50 cycles at the current density of 3000 mA g Carbon − 1 (equivalent to 2.4 mA cm−2), corresponding to a discharge time of about 20 min to 1000 mAh g Carbon − 1 . Based on the weight of the super P and the resultant Li2O2, the specific power density could reach 4040 W kg−1; even so, a substantial specific energy density of 1350 Wh kg−1 still could be achieved.
The degradation of LiNi0.8Co0.15Al0.05O2 (LNCAO), a cathode material in lithium-ion-batteries, was studied using in situ powder diffraction and in situ Ni K edge X-ray absorption spectroscopy (XAS). The fatigued material was taken from a 7 Ah battery which was cycled for 34 weeks under defined durability conditions. Meanwhile, a cell was stored, as reference, under controlled conditions without electrochemical treatment. The fatigued LNCAO used in this study showed a capacity loss of 26% ± 9% compared to the non-cycled material. During charge and discharge the local and the overall structure of LNCAO was investigated by X-ray near edge structure (XANES) analysis, the extended X-ray absorption fine structure (EXAFS) analysis and by using Rietveld refinement of in situ powder diffraction patterns. Both powder diffraction and XAS revealed additional, rhombohedral phases which do not change with electrochemical cycling. Moreover, a phase with the lattice parameters of fully lithiated LNCAO was still present in the fatigued material at high potentials, while it was absent in the non-fatigued reference material. The coexistence of these phases is described by domains within the LNCAO particles, in correlation with the observed fatigue.
Lithium-rich layered oxide materials are considered as one of the most promising cathodes for high-energy lithium-ion batteries. However, their practical applications are currently restricted by its low initial Coulombic efficiency and poor rate capability and cycling stability. In this study, we report the preparation of Li1.2Mn0.54Ni0.13Co0.13O2 nanowires that have porous structures with different contents of spinel phase via a co-precipitation method followed by carefully controlled calcination steps. Structural characterizations verify that the as-prepared nanowires are composed of interconnected nano-sized subunits with porous structures, and spinel phases are embedded inside the layered structure. The electrochemical measurements show that the Li1.2Mn0.54Ni0.13Co0.13O2 nanowires bearing moderate content of spinel phase exhibit a high capacity of 291 mAh g−1 at 0.1 C and excellent capacity retention of 91.8% after 200 cycles at 1 C. The results also demonstrate that electrochemical performance of the Li1.2Mn0.54Ni0.13Co0.13O2 nanowires is influenced by the content of spinel phase which can be readily tuned by changing the heating rate in the calcination step. The combination of one-dimension porous structures and built-in spinel domains in Li1.2Mn0.54Ni0.13Co0.13O2 nanowires improves the electrolyte contact and Li+ diffusion, and restrains structural degeneration.
This work demonstrates the first cyclic voltammetry in a perfluorocarbon solvent without use of a cosolvent. The novel electrolyte tetrabutylammonium tetrakis[3,5-bis(perfluorohexyl)phenyl]borate (NBu4BArF104; 80mM) allows for voltammetry of ferrocene in perfluoro(methylcyclohexane) by lowering the specific resistance to 268kΩcm at 20.8°C. Despite significant solution resistance, the resulting voltammograms can be fitted quantitatively without difficulty. The thus determined standard electron transfer rate constant, ko , for the oxidation of ferrocene in perfluoro(methylcyclohexane) is somewhat smaller than for many solvents commonly used in electrochemistry, but can be explained readily as the result of the viscosity and size of the solvent using Marcus theory. Dielectric dispersion spectroscopy verifies that addition of NBu4BArF104 does not significantly raise the overall polarity of the solution over that of neat perfluoro(methylcyclohexane).
Since Sifneos in 1973 introduced the term, “alexithymia” to describe the apparent incapacity of some of his patients to discern and verbally express their emotions, without finding a physical cause for it, this phenomenon has become the object of various studies and publications. In the pursuit of effective treatment methods, art therapy has been indicated as being among the possibly effective forms of treatment. But in the literature on art therapy alexithymia up to now has scarcely received the attention the authors believe it deserves. This paper focuses on the concept of alexithymia, especially in psychotrauma, and the usefulness of art therapy. A concise review of literature on the concept of alexithymia is included and an illustration of the use of art therapy by a detailed description of treatment of a case of alexithymia in a patient, Rita, with severe self-pathology, who had grown up in a traumatizing environment. The patient was able to recognize and name emotional reactions after the treatment with art therapy, and thus, art therapy seems to be a promising form of treatment for traumatized patients suffering from alexithymia, even in cases of severe self-pathology.
We demonstrated a sort of self-powered vibration sensor based on a triboelectric generator (TEG) using triboelectrification and electrostatic induction effects. The as-prepared TEG delivered an output voltage of 34.06V and short-circuit current density of 22.5mA/m2 corresponding to a maximum power density of 0.77W/m2, which was capable of driving five LEDs directly and continuously with working frequency of 50Hz without any rectification circuit or energy storage unit. The vibration sensor has a detection range of 0–500Hz, and high accuracy. Besides, it could realize detection under non-contact mode, which would protect the device and the detected object in operation. Moreover, the stability and repeatability could also be well retained. The TEG based vibration sensor possessed great potential in machines operation monitoring, process control, and security applications in unreachable and access-denied extreme environments.
Crystal and electronic structures of two model crystals for Li[Co1/3Ni1/3Mn1/3]O2 have been investigated using first principles calculations. One is so-called superlattice model of [√3×√3]R30°-type in triangular lattice of sites and the other is piled-up model among CoO2, NiO2 and MnO2 slabs. For both models, the formal charges of Co, Ni and Mn are, respectively, estimated to be +3, +2 and +4 from the interatomic distances and electronic structures. The formation energy for a superlattice model is −0.17eV while that for a piled-up model is +0.06eV, indicating that Li[Co1/3Ni1/3Mn1/3]O2 having a [√3×√3]R30°-type superlattice can be prepared when the processing method is exploited. The solid-state redox reactions in a superlattice model are also calculated and predicted that the reaction in the ranges of 0≤x≤1/3, 1/3≤x≤2/3 and 2/3≤x≤1 in Li1−x [Co1/3Ni1/3Mn1/3]O2 consists of Ni2+/Ni3+, Ni3+/Ni4+ and Co3+/Co4+, respectively, with smaller change in unit-cell volume associated with lithium insertion reaction than those of LiCoO2, LiNiO2 and LiMnO2.
A 3D mesoporous TiO2 material with well-developed mesostructure is prepared in the form of a binder-free thin (100nm) film and studied as potential candidate for the negative electrode in lithium microbatteries. By appropriate thermal treatments, the selected crystal structure (anatase, rutile, or amorphous), and micro-/mesostructure of the materials was obtained. The effects of voltage window and prelithiation treatment improved first cycle reversibility up to 86% and capacity retention of 90% over 100 cycles. After a prolonged intercalation of lithium ions in ordered mesoporous TiO2 appeared small particles assigned to Li2Ti2O4 with cubic structure as observed from ex-situ TEM micrographs. This study highlights the flexibility of the potential window to which the electrode can operate. Maximum capacity values over 100 cycles of 470μAhcm−2 μm−1 and 177μAhcm−2 μm−1 are obtained for voltage ranges of 0.1–2.6V and 1.0–2.6V, respectively. The observed values are between 6 and 2 times higher than those obtained for films with 600nm (80μAhcm−2 μm−1) and 900nm (92μAhcm−2 μm−1) lengths. This indicates that 100nm thin TiO2 films with high accessibility show finite-length type diffusion which is interesting for this particular application.
Rechargeable proton conducting polymeric solid-state batteries have been fabricated with the configuration Zn+ZnSO4·7H2O||PEO:NH4ClO4 +PC||V2O5 +PbO2 +C+E. The maximum cell voltage is ∼1.57V at full charge. The discharge characteristics of the cell have been studied at different loads. The cell remains stable for more than 180h for low current drain (∼μA) making it suitable for low current density application. The cell also showed a good rechargeability which was tested for nine cycles.
Low crystalline CoSx was fabricated by anion-exchange of 2-dimensional (2D) cobalt carbonate hydroxide (CoCH) using aqueous sodium sulfide solution at room temperature. It was proved that single crystalline CoCH nanoplates would transform into porous 2D CoSx with low crystallinity after the anion-exchange. When they were used as electrode materials for supercapacitor, the 2D CoSx material had a much higher specific capacitance than its precursor due to their different compositions and electroconductivities. CoSx had a high specific capacitance of 863 F g−1 at 1 A g−1 and a good stability during long time charge-discharge processes, about 64.7% of initial capacitance retention after 10000 cycles. Asymmetric hybrid devices using 2D CoSx as positive electrode and activated carbon as negative electrode were assembled, and the capacitor devices were able to achieve a high energy density of 33.56 Wh kg−1 at the power density of 400 W kg−1. The high performances of the porous CoSx make it a promising electrode material for energy storage.
This paper discusses the effects of a potential leachate leakage from a municipal solid waste landfill, situated at Mavallipura, Bangalore, India, on the surrounding water bodies. The landfill area is spread over an area of about 100 acres that began accepting waste from 2005. MSW was deposited in non-engineered manner that has resulting in steep and unstable slopes, leachate accumulation within the MSW mass, and leachate runoff into nearby water bodies such as ponds and open wells. The current study investigates the physicochemical characterization of landfill leachate and nearby water bodies. The batch leach tests were conducted to know the heavy metal concentrations in the contaminated soil. A series of column tests were also conducted to estimate the migration rates of different contaminants through the soil. Furthermore, these transport parameters were considered as input for fluidyn-POLLUSOL model to estimate the migration of leachate from the landfill site to the surrounding water bodies.
Carbon coated silicon (Si/C) dispersed in a carbon paper (CP) was examined as the anode for solid polymer lithium-ion batteries. The CP was prepared by pyrolysis of poly(acrylonitrile) fiber and Manila hemp non-woven cloth at 2600 °C under an inert atmosphere. The Si/C composite was formed by pyrolysis of a slurry consisting of Si power and a solution of polyvinyl chloride in tetrahydrofuran as the carbon source. Si/C:CP with a weight ratio of 20:100 had a high initial capacity of 980 mAh g−1 of Si/C and a high initial columbic efficiency of 77%, and also exhibited excellent capacity retention with a reversible capacity of 710 mAh g−1 of Si/C even after 250 cycles at a charge and discharge rate of 0.1 A g−1. The carbon fiber framework in the carbon paper could adsorb the volume change of Si during the lithium insertion and stripping processes.
This paper proposes a sophisticate application of redox flow batteries (RFB) coordinate with Interline Power Flow Controller (IPFC) for the improvement of Load Frequency Control (LFC) of a multiple units two- area power system. The Interline Power Flow Controller is to stabilize the frequency oscillations of the inter-area mode in the interconnected power system by the dynamic control of tie-line power flow. The redox flow batteries, which are not aged to the frequent charging and discharging, have a quick response and outstanding function during overload conditions. In addition to leveling load, the battery is advantageous for secondary control in the power system and maintenance of power quality of distributes power resources. The Bacterial Foraging Optimization (BFO) algorithm is use to optimize the parameters of the cost functions for designing the integral controller. Compliance with North American Electric Reliability Council (NERC) standards for Load Frequency Control has also been establishes in this work. Simulation studies reveal that the RFB coordinate with IPFC units has greater potential for improving the system dynamic performance.
Metal–organic frameworks (MOFs) are increasingly being investigated as electrocatalysts for the oxygen evolution reaction (OER). Despite their promising catalytic activity, many fundamental questions concerning their structure−performance relationships—especially those regarding the roles of active species—remain to be answered. Here we show the structural transformation of a Ni0.5Co0.5-MOF-74 during the OER by operando X-ray absorption spectroscopy analysis and high-resolution transmission electron microscopy imaging. We suggest that Ni0.5Co0.5OOH0.75, with abundant oxygen vacancies and high oxidation states, forms in situ and is responsible for the high OER activity observed. The ratio of Ni to Co in the bimetallic centres alters the geometric and electronic structure of as-formed active species and in turn the catalytic activity. Based on our understanding of this system, we fabricate a Ni0.9Fe0.1-MOF that delivers low overpotentials of 198 mV and 231 mV at 10 mA cm−2 and 20 mA cm−2, respectively.