batterydata/paper-abstracts huggingface dataset:
The dynamic performance is a very important evaluation index of proton exchange membrane (PEM) fuel cells used for real application, which is mostly related with water, heat and gas management. A commercial PEM fuel cell system of Nexa module is employed to experimentally investigate the dynamic behavior and transient response of a PEM fuel cell stack and reveal involved influential factors. Five groups of dynamic tests are conducted and divided into different stage such as start-up, shut-down, step-up load, regular load variation and irregular load variation. It is observed that the external load changes the current output proportionally and reverses stack voltage accordingly. The purge operation benefits performance recovery and enhancement during a constant load and its time strongly depends on the operational current level. Overshoot and undershoot behaviors are observed during transience. But the current undershoot does not appear due to charge double-layer effect. Additionally, magnitudes of the peaks of the voltage overshoot and undershoot vary at different current levels. The operating temperature responds fast to current load but changes slowly showing an arc-like profile without any overshoot and undershoot events. The air flow rate changes directly following the dynamic load demand. But the increased amount of air flow rate during different step-change is not identical, which depends on the requirement of internal reaction and flooding intensity. The results can be utilized for validation of dynamic fuel cell models, and regarded as reference for effective control and management strategies.
In this work we report the properties and electrochemical performance of composite electrodes containing lithium iron phosphate (LFP) and activated carbon (AC) as the active materials. These composite electrodes display high capacity during cycles carried out at specific current as high as 17.2Ag−1. Moreover, even after 500 cycles carried out at 8.6Ag−1, the electrodes display capacity retention higher than 98%. The high performance of these composite electrodes can be explained by a positive influence of AC on the LFP performance. The presence of AC increases the conductivity, reduces the density and modifies the porosity of the electrodes. The “dilution” of the LFP particles (with respect to the electrodes containing only LFP) results in exceptional high rate performance. During cycles carried out at specific current higher than 12Ag−1, LFP–AC electrodes display two times higher specific capacities compared to electrodes containing only LFP as active material.
The mild combustion synthesis of cobalt vanadate involving the reaction of V2O5, Co(NO3)2 and glycine as starting materials is reported. The synthesized material is annealed at 550°C and characterized by means of X-ray diffraction (XRD), cyclic voltammetry, and galvanostatic charge–discharge cycling techniques. XRD analysis indicates that the structure of the synthesized cobalt vanadate is amorphous. The initial delivered capacity is ∼275mAhg−1 in a Li//CoV2O5 cell at a current density of 0.05mAcm−2 when cycled between 2 and 4V using 1M LiClO4 in propylene carbonate as electrolyte. The capacity remains stable even after 10 cycles. The cobalt vanadate prepared by this new synthetic route is, therefore, a potential candidate for lithium secondary batteries.
Charge and discharge characteristics of lithium/polymer electrolyte/sulfur cells are presented. Three different electrolytes were studied, and cells were operated at temperatures ranging from ambient to about 100°C. The effects of the sulfur electrode composition and cycling regimen on both the potential profiles and the capacity fade rate were investigated. Cells prepared with poly(ethylene oxide) (PEO) and operated at 90–100°C could be discharged to nearly the full theoretical 1672 mA h/g active material but with a high rate of capacity fade. Reducing the depth of discharge to 30% or less increased the cell lifetime. Room-temperature cells with poly(ethylene glycol) dimethyl ether could be discharged to about 45% utilization of the sulfur and showed a much lower capacity fade rate after the second cycle. Several possible explanations for the high rate of capacity fade and the effect of the depth of discharge on this rate are presented.
Thermal energy harvesting technologies based on composite phase change materials (PCMs) are capable of harvesting tremendous amounts of thermal energy via isothermal phase transitions, thus showing enormous potential in the design of state-of-the-art renewable energy infrastructure. Great progress has been recently made in terms of enhancing the thermal energy storage capability, transfer rate, conversion efficiency and utilization of composite PCMs. Although there are some recent reviews on composite PCMs, they are mainly concentrated on the thermal transfer enhancement and conventional utilization of PCMs. There are few systematic reviews concerning optimization strategies of PCM for thermal energy conversion. In particular, advanced multifunctional utilization of PCMs is still in its infancy. Herein, we systematically summarize the optimization strategies and mechanisms of recently reported composite PCMs for thermal energy storage, thermal transfer, energy conversion (solar-to-thermal, electro-to-thermal and magnetic-to-thermal conversion) and advanced utilization (fluorescence emission, infrared stealth technologies, drug release systems, thermotherapy and thermal protection), including some novel supporting materials (BN nanosheets and metal organic frameworks (MOFs)). Simultaneously, we provide in-depth and constructive insights into the correlations between the structural optimization strategies and thermal performances of composite PCMs. Finally, future research trends, alternative strategies and prospects are also highlighted according to up-to-date optimization strategies.
The surface structure and material composition of current collectors significantly affect the electrochemical performances of lithium-ion batteries. This study forms array-pattern blind holes and creates a layer of copper oxide (CuO) on the surface of thin copper plates using the chemical etching method. This copper plate is made into a CuO/Cu composite current collector with array-pattern porous structures for lithium-ion batteries. Using mesocarbon microbead graphite powders as the anode material, this new composite current collector is assembled into CR2032 coin half-cells for electrochemical tests. Batteries with this porous current collector exhibit high reversible discharge capacities of 383.9mAhg−1 at 0.5mA and 374mAhg−1 even after 0.2C and 0.5C rate cycles, whereas batteries with a complanate current collector deliver only 309.6mAhg−1 and 296.7mAhg−1. It is believed that the array-pattern blind holes coupled with the morphological effects of the oatmeal-like CuO significantly enhance the electrochemical performances of batteries in terms of reversible capacity, cycling stability, electrical conductivity and coulombic efficiency.
We reported here on the synthesis, the crystal structure and the study of the structural changes during the electrochemical cycling of layered LiNi0.1Mn0.1Co0.8O2 positive electrode material. Rietveld refinement analysis shows that this material exhibits almost an ideal α-NaFeO2 structure with practically no lithium–nickel disorder. The SQUID measurements confirm this structural result and evidenced that this material consists of Ni2+, Mn4+ and Co3+ ions. Unlike LiNiO2 and LiCoO2 conventional electrode materials, there was no structural modification upon lithium removal in the whole 0.42≤ x ≤1.0 studied composition range. The peaks revealed in the incremental capacity curve were attributed to the successive oxidation of Ni2+ and Co3+ while Mn4+ remains electrochemically inactive.
In this work, three categories of advanced carbon materials coated on current collector are investigated. The results indicate that carbon coating has a positive influence on the depolarization effect and electrochemical performance of LiFePO4 cathode, different carbon coatings have drastically different influences, high rates in particular. The depolarization effect and rate performance show the following order: Graphene nanosheets (GNs)>Carbon nanotubes (CNTs)>Activated carbons (ACs), and the differences of rate capacities among them become more and more obvious with increasing rates. Especially for 5C, the discharge capacities values are 122mAhg−1, 114.8mAhg−1, 106.8mAhg−1 and 49.2mAhg−1 for LFP-GNs-Al, LFP-CNTs-Al, LFP-ACs-Al and LFP-Al, respectively. The enhancement is attributed to the carbon coating acting as a transport system of electron between cathode materials and current collector, resulting in reducing the contact impedance within the electrodes, thus providing a favorable balance between fast ion diffusion and increased electron transport.
A solid polymer electrolyte (SPE) based on polyethylene oxide (PEO) is prepared by photocuring of polyethylene glycol acrylates. The conductivity is greatly enhanced by adding low molecular weight poly(ethylene glycol) dimethylether (PEGDME). The maximum conducticity is 5.1×10−4 Scm−1 at 30°C. These electrolytes display oxidation stability up to 4.5V against a lithium reference electrode. Reversible electrochemical plating/stripping of lithium is observed on a stainless steel electrode. Li/SPE/LiMn2O4 as well as C(Li)/SPE/LiCoO2 cells have been fabricated and tested to demonstrate the applicability of the resulting polymer electrolytes in lithium–polymer batteries.
It is widely recognized that the presence of residual moisture has significant detrimental effects on the performance of lithium ion batteries. Studies have shown that the positive active material can be a major source of moisture contributors to the overall cell moisture. The aim of the present study is to understand the factors affecting moisture uptake by the doped-lithium nickel cobalt oxide material from the casting solvent, acetone, and the ambient environment. As-is and the air-dried powders under various conditions (300°C for 24h, 500°C for 8h, and 500°C for 24h) were exposed to ambient and humid air for various lengths of time. Similarly, all these powders were exposed to extra dry (47ppm) and wet (5789ppm) acetone. Karl Fisher measurements at 160°C and 290°C show that humidity levels (80–85% relative humidity versus 20–25%) and the exposure times are the critical factors. Acetone wetness and the length of exposure in it do not contribute significantly to the moisture uptake by the active material. Cathode powder drying helps in minimizing the amount of moisture uptake from the environment.
This work reports a simple and cost-effective synthesis path to fabricate manganese dioxide nanostructures with controlled morphologies. Herein, we have used oleylamine as a reducing, surfactant, and structure directing agent. The treatment of MnO2 precursor with the varying concentration of oleylamine led to the formation of different morphologies of MnO2 (nanorods, nanoflowers and three-dimensional MnO2 spheres). The as-synthesized nanostructures were characterized by various techniques and their electrochemical performances were studied. When used as an electrode material for supercapacitors, 3D-MnO2 exhibited a higher specific capacitance of 450 Fg−1 and admirable cyclic stability (~91.7%) after 5000cycles, which were higher than that of the other formulations. Moreover, an asymmetric supercapacitor was assembled by using as-prepared 3D-MnO2 and nitrogen-doped graphene hydrogels as the positive and negative electrodes, respectively. As-fabricated asymmetric device delivered specific capacitance of 49.44 Fg−1 at 1 Ag−1 an outstanding energy density of 20 Whkg−1 at 857.14 Wkg−1, and retained ~93.15% stability after 5000cycles. The obtained results showed that the as-synthesized 3D-MnO2 can be considered as the positive electrode material in supercapacitors.
Lithium metal anode is regarded as the "holy grail" due to its extremely high specific capacity, low density and low reduction potential. However, Li dendrite growth reduces coulombic efficiency and causes safety accidents synchronously. In this paper, a rational designed three-dimensional ordered macroporous Cu is used as current collector for Li metal anode with excellent electrochemical performance, which is prepared by colloidal template method combined with copper electrodeposition. The novel porous Cu/Li anode with the pore size of 450 nm can stably run for 750 h at 0.2 mA/cm2 with a small Li electroplating/stripping overpotential (<30 mV), and it exhibits a high coulombic efficiency of 93.3% over 120 cycles. The three-dimensional ordered macroporous structure with large specific surface area results in lower local current density and enhances electrochemical reaction kinetics, and benefits Li deposition inside pores. Especially, the Li layer on the arc area of outer pores acts as seed crystal for the subsequent Li deposition, which leads to Li uniform nucleation and dendrite suppression effectively.
Nowadays, 2D nanosheets or nanoplatelets have attracted great attention due to their wide applications. However, the synthesis of 2D α-Fe2O3 nanosheets with well-defined hexagonal shape is extremely challenging, because the selective growth along one specific facet is very hard to be realized. In our work, we studied the non-capping ligand mediated reaction within graphene layer chamber, and successfully synthesized α-Fe2O3 hexagonal nanoplatelets sandwiched between graphene layers (HP-Fe–G). These materials exhibit an improved electrochemical performance compared with the pre-existing α-Fe2O3 nanoparticles loaded graphene (G-Fe2O3) composites because of the uniqueness of such architectures: thin nanoplatelets, large enough sandwiched spaces to buffer the volume expansion and N-doped graphene. HP-Fe–G delivered an ultrahigh reversible capacity of 1100mAh/g after 50 cycles, thus higher than their theoretical value (926mAh/g); while G-Fe2O3 composites showed relatively low capacity retention even after only 20 cycles (582mAh/g). In addition, HP-Fe–G also reveal superior rate capability, 887mAh/g at 1C; in comparison, this value was only 135mAh/g at 1C for G-Fe2O3.
Objective To identify neuromuscular impairments most predictive of unfavorable mobility outcomes in late life. Design Longitudinal cohort study. Setting Research clinic. Participants Community-dwelling primary care patients aged ≥65 years (N=391) with self-reported mobility modifications, randomly selected from a research registry. Interventions Not applicable. Main Outcome Measures Categories of decline in and persistently poor mobility across baseline, 1 and 2 years of follow-up in the Lower-Extremity Function scales of the Late-Life Function and Disability Instrument. The following categories of impairment were assessed as potential predictors of mobility change: strength (leg strength), speed of movement (leg velocity, reaction time, rapid leg coordination), range of motion (ROM) (knee flexion/knee extension/ankle ROM), asymmetry (asymmetry of leg strength and knee flexion/extension ROM measures), and trunk stability (trunk extensor endurance, kyphosis). Results The largest effect sizes were found for baseline weaker leg strength (odds ratio [95% confidence interval]: 3.45 [1.72–6.95]), trunk extensor endurance (2.98 [1.56–5.70]), and slower leg velocity (2.35 [1.21–4.58]) predicting a greater likelihood of persistently poor function over 2 years. Baseline weaker leg strength, trunk extensor endurance, and restricted knee flexion motion also predicted a greater likelihood of decline in function (1.72 [1.10–2.70], 1.83 [1.13–2.95], and 2.03 [1.24–3.35], respectively). Conclusions Older adults exhibiting poor mobility may be prime candidates for rehabilitation focused on improving these impairments. These findings lay the groundwork for developing interventions aimed at optimizing rehabilitative care and disability prevention, and highlight the importance of both well-recognized (leg strength) and novel impairments (leg velocity, trunk extensor muscle endurance).
Due to their abundance and environmentally benign nature, iron and titanium present as the most attractive potential elements for use in rechargeable sodium-ion batteries (SIBs). Accordingly, two structurally different Fe and Ti based compounds, stoichiometric NaFeTiO4 and sodium deficient NaxFexTi2-xO4 (where x = 0.9, and 0.8), are explored as anode materials for SIBs. Their structure and sodium storage capacity are systematically investigated by using combined structural and electrochemical analysis. Rietveld refinement analysis reveals that the sodium deficiency leads to the structural transformation from a single-tunnel structure (NaFeTiO4) to a zigzag-type double-tunnel structure (Na0.9Fe0.9Ti1.1O4 and Na0.8Fe0.8Ti1.2O4). The series of sodium deficient compounds bears systematic sodium ion vacancies in their structure up to 20%. Sodium deficiency in the NaxFexTi2-xO4 logically provides additional space for accommodating the excess sodium ions as such the NaxFexTi2-xO4 compounds with higher level of sodium deficiency show higher specific capacities than the stoichiometric NaFeTiO4. All the compounds exhibited very good electrochemical cycling stability, with minimal capacity loss during cycling. The present approach is a model example of improvement in the sodium storage capacity of the anode materials by tuning the chemical composition, and could facilitate the performance improvement of known or new electrode materials for SIBs.
In this paper, α-Fe2O3 microdisks (~1.1μm in diameter, ~150nm in thickness) have been synthesized by a facile hydrothermal method using a novel NaNO3–Na2SO4 crystal salts solution (CSS) containing CNTs fragments as template. Interestingly, the synthesized α-Fe2O3 microdisks exhibit a unique axial compressive property. The small-sized CNTs fragments in α-Fe2O3 microdisks could act as a robust framework for such assemblies and endow them the axial compressive property. Owing to the existence of CNTs fragments, the α-Fe2O3 microdisks are not easily destroyed. AFM results indicate that the α-Fe2O3 microdisks could be compressed to 10–50 times than the original thickness. Electrochemical studies show that the synthesized α-Fe2O3 microdisks exhibited good cyclic stability and rate performance. The α-Fe2O3 microdisks electrode delivers a reversible specific capacity of 632mAhg31 even at a high rate of 800mAg31. When returning to the initial rate of 100mAg31, the α-Fe2O3 microdisks electrode returns to a higher capacity (968mAhg31). The unique axial compressive property of α-Fe2O3 microdisks endows that they could alleviate the pulverization and structural destruction of electrodes during the lithium ion insertion and extraction process.
Mechanically alloyed Mg2Ni and a single air (oxygen) electrode are used as the anode and cathode, respectively, in a Mg2Ni|6M KOH|O2 rechargeable metal-hydride–air (MH–air) battery. The battery is tested for self-discharge by measuring the open-circuit voltage (OCV) and cycling characteristics. Battery degradation after charge–discharge cycling is characterized by means of X-ray diffraction (XRD) and scanning electron microscopic (SEM) analyses.
Effect of surfactants present in alkaline solutions on the capacitance of carbon electrodes has been studied. Different types of surfactants, i.e., sodium and lithium dodecyl sulphate as anionic surfactants, tetrapropylammonium bromide and iodide as cationic surfactants and polymer of polyethylene glycol and p-t-octylophenol (commercially called Triton® X-100) as non-ionic one have been selected for this target. Concentration of these electrolyte additives was 0.005molL−1. Decreasing the surface tension in the electrode/electrolyte interface allows better penetration of electrolyte into the pores. However, surfactants played a different role depending on the electrode polarity. Detailed analysis of capacitance versus current load, frequency dependence as well as self-discharge, cyclability and behaviour in wider voltage range proved especially a profitable effect of Triton® X-100 on capacitor operating in alkaline solution. Influence of surfactant concentration on capacitance properties was also investigated.
Background The use of repetitive transcranial magnetic stimulation (rTMS) for the treatment of depression has been studied extensively over the last 15 years. In this time the vast majority of trials included assessment of cognition to determine whether the technique is cognitively safe. However, recent evidence suggests that the assessment of cognition could also have an important role to play in the prediction of antidepressant response. Objectives The current study conducted a post hoc analysis of the cognitive data from four clinical trials of rTMS for treatment resistant depression, with an aim to investigate the relationship between early cognitive changes and eventual depression improvement. Method Data from 137 patients were included in the analysis (62 male and 75 female, mean ages 41.86 ± 11.68 years). The primary outcome measure for all four studies was the Montgomery Asberg Depression Rating Scale (MADRS). Clinical and cognitive assessments were undertaken at baseline, a midtime point, and at endpoint after 4 or 6 weeks of treatment. Results There was no cognitive deterioration after a treatment course of rTMS across the four depression trials. Initial improvements in performance on immediate visuospatial memory were significantly related to eventual reduction of depression severity, with visuospatial improvement being a significant predictor of degree of eventual improvement in a near significant regression model. Conclusions Traditionally cognitive batteries in rTMS trials are designed to provide a broad assessment of neuropsychological functioning across numerous cognitive domains; however, there is growing evidence that cognition may have a very important role to play as an early indicator of antidepressant response.
A polymer carbonization route was designed to synthesis carbon network-supported Fe3O4@C composites. The Fe3O4 nanoparticles with an average of ∼200nm were uniformly wrapped up in this novel carbon network. As an anode material for rechargeable lithium-ion batteries, the Fe3O4@C composites present attractive properties with a high specific capacity of 730mAhg−1 at 2C after 300 cycles. The novel carbon network plays a key role in enhancing the electrochemical performance of the composites.
We investigated the effect of CO2 on layered Li1+z Ni1−x−y Co x M y O2 (M=Al, Mn) cathode materials for lithium ion batteries which were prepared by solid-state reactions. Li1+z Ni(1−x)/2Co x Mn(1−x)/2O2 (Ni/Mn mole ratio=1) singularly exhibited high storage stability. On the other hand, Li1+z Ni0.80Co0.15Al0.05O2 samples were very unstable due to CO2 absorption. XPS and XRD measurements showed the reduction of Ni3+ to Ni2+ and the formation of Li2CO3 for Li1+z Ni0.80Co0.15Al0.05O2 samples after CO2 exposure. SEM images also indicated that the surfaces of CO2-treated samples were covered with passivation films, which may contain Li2CO3. The relationship between CO2-exposure time and CO3 2− content suggests that there are two steps in the carbonation reactions; the first step occurs with the excess Li components, Li2O for example, and the second with LiNi0.80Co0.15Al0.05O2 itself. It is well consistent with the fact that the discharge capacity was not decreased and the capacity retention was improved until the excess lithium is consumed and then fast deterioration occurred.