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The electrochemical performance and the degradation mode of the zirconium doped cathode material, LiNi0.8Co0.18Zr0.02O2 were investigated and compared with the pristine cathode, LiNi0.8Co0.2O2. The cyclic performance of the doped cathode was superior to the pristine cathode, especially under the high voltage cutoff, although its rate capability remained unimproved. The trend in the graphs of the differential capacity showed that the impedance growth of the cell made of the pristine cathode was much faster than the doped. From the results of the XRD pattern changes between before and after the galvanostatic cycling, less cation mixing and more ordered hexagonal structure were observed for the doped cathode. The impedance spectra showed that the charge transfer resistance for the pristine cathode grew significantly with cycling, while that for the doped cathode increased just moderately. Considerable decrease in the impedance was observed when the new lithium was substituted with the cycled anode, which implied that the interfacial impedance growth on the anode accounted for about 20% of the total impedance measured. It is concluded that the fading mode for LiNi0.8Co0.2O2 is mainly due to the cation mixing, partially contributed by the impedance growth on the anode and by doping the pristine cathode with Zr, cation mixing can be efficiently suppressed.
Acquired Brain Injury (ABI) admissions have an incidence of 385 per 100,000 of the population in the UK, and as brain injury often involves the frontal networks, cognitive domains affected are likely to be executive control, working memory, and problem-solving deficits, resulting in difficulty with everyday activities. The above observations make working memory, and related constructs such as attention and executive functioning attractive targets for neurorehabilitation. We propose a combined home-based rehabilitation protocol involving the concurrent administration of a working memory training program (adaptive N-back task) with non-invasive transcranial direct current stimulation (tDCS) of the right dorsolateral prefrontal cortex to promote long-lasting modification of brain areas underlying working memory function.
We report the outstanding electrochemical performance of LiNi0.5Mn1.5O4 porous microellipsoids with a core–shell configuration synthesized by a simple self-template method. The structure and electrochemical properties of the products are investigated via X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller method and various electrochemical analysis techniques. LiNi0.5Mn1.5O4 porous microellipsoids have a discharge capacity of 110.3 mA h g−1 after 400 cycles at a rate of 5C (735 mA g−1). The capacity retention ratio is 93.7% of the maximum capacity (142.3 mA h g−1) after 150 cycles under 5C rate at elevated temperature (55 °C). The porous ellipsoidal product could be a promising cathode material for high-performance lithium ion batteries.
In this study we report on the temperature dependence of the initial coulombic efficiency (ICE) in Li-rich layered Li[Li0.144Ni0.136Co0.136Mn0.544]O2 oxide, consisting of rhombohedral LiNi1/3Co1/3Mn1/3O2 and monoclinic Li2MnO3 component confirmed by SXRD and SAED. The electrochemical result shows that the ICE increases from 74.6 to 91.5% with the applied charging/discharging temperature from 0 to 50 °C, and it reproducibly approaches 92% when discharged at 50 °C, regardless of the applied charging temperature. From the dQ/dV plots, it is observed that the discharging temperature significantly influences the lithium intercalation into the MnO2-like component derived from Li2MnO3 component, i.e. the discharge process determines the ICE. This phenomenon indicates that the lithium re-intercalation into the MnO2-like component appears to be the most important factor.
In this work, polyethyleneglycole (PEG) is introduced into polypyrrole (PPy) film coated on LiFePO4 powder particles to promote the properties of cathode material for lithium-ion batteries. The enhancement of the electrochemical activity by the substitution of a carbon with electrochemically active polymer is investigated. Films of the PPy doped with the PEG were prepared by the chemical oxidative polymerization of pyrrole (Py) monomer. PEG has been added as an additive during polymerization process to improve mechanical and structural properties of the PPy in final PPy/PEG–LiFePO4 cathode material. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge measurements were employed to characterize the electrochemical properties of PPy/PEG–LiFePO4 material. The electrochemical performance of PPy–LiFePO4 electrodes was greatly improved by introduction of PEG into the PPy films. Charge/discharge measurements confirmed the increase in capacity when applying PEG in PPy. The morphology and particle sizes of the prepared cathode powder material were investigated by scanning electron microscopy (SEM) and particle size analysis (PSA). Distribution of PPy and PPy/PEG films onto the LiFePO4 particles surface was studied by time of flight secondary ion mass spectrometry (TOF-SIMS). In addition to polymeric coating layer on the surface of PPy–LiFePO4 composite particles, some PPy unequally distributed between the particles was found. The median diameter value is 4.92μm for PPy–LiFePO4 sample. TOF-SIMS measurements and SEM images confirmed that thickness of polypyrrole coating on LiFePO4 particles is about 100nm.
Waste lead storage battery is the most important recyclable lead material not only in various European and other OECD countries but also in China. Pollution control of lead has become the focus of people’s attention in the world. A vacuum process for recycling waste lead storage battery was developed in this work. The experimental results showed that all the valuable materials in waste lead storage battery could be satisfactorily recycled by vacuum technologies. The vacuum melting of lead grids and the vacuum reduction of lead pastes produce the lead bullion with the direct recovery ratio of 96.29% and 98.98%, respectively. The vacuum pyrolysis of plastics can produce pyrolysis oil with yield of more than 93 wt.%. These vacuum recycling technologies offer improvements in metallurgical and environmental performance.
Nanostructured pyropolymers contain significant amounts of redox-active heteroatoms, have high specific surface areas, and a defective carbon microstructure, indicating good potential for pseudocapacitive charge storage. In this study, nitrogen-enriched pyropolymer nanoparticles (N-PNs-50) are fabricated from polyaniline nanotubes through rapid pyrolysis at 50 °C min−1. N-PNs-50 exhibit a nitrogen content of 9.8 wt%, a high specific surface area of 875.8 m2 g−1, and an amorphous carbon structure with an I D /I G intensity ratio of 0.95. These unique characteristics lead to good electrochemical performances, in which reversible capacities of 660 and 255 mAh g−1 are achieved for Li-ion and Na-ion storage, respectively, with favorable voltage characteristics (<1.5 V for Li-ions and <1.2 V for Na-ions). This study provides a more feasible production method for nitrogen-doped pyropolymers and their practicable electrochemical performances for use as an anode in energy storage devices.
Plantar heel pain (PHP) accounts for 11–15% of foot symptoms requiring professional care in adults. Recovery is variable, with no robust prognostic guides for sufferers, clinicians or researchers. Therefore, we aimed to determine the validity, reliability and feasibility of questionnaire, clinical and biomechanical measures selected to generate a prognostic model in a subsequent cohort study.
This study optimises and compares the operation of a conventional gas-fired power generation company with its operation in combination with wind power and compressed air energy storage (CAES). A mixed integer non-linear programming (MINLP) formulation is developed for the optimisation problem. Limits in ramp rate, capacity, and minimum on/off time, as well as start-up cost constraints, are considered for the modelling of conventional units. Injected and produced power constraints, storage, air balance and CAES-operation limits are considered in the CAES modelling. Two objective functions (profit maximisation and cost minimisation) are modelled. Without considering capital costs, it is found that the use of CAES results in 43% higher operational profits and 6.7% lower costs in a market environment.
“Chimie douce” based strategies allow, through the deep knowledge of materials chemistry and processing, the birth of the molecular engineering of nanomaterials. This feature article will highlight some of the main research accomplishments we have performed during the last years. We describe successively the design and properties of: sol–gel derived hybrids, Nano Building Blocks (NBBs) based hybrid materials, nanostructured porous materials proceeds as thin films and ultra-thin films, aerosol processed mesoporous powders and finally hierarchically structured materials. The importance of the control of the hybrid interfaces via the use of modern tools as DOSY NMR, SAXS, WAXS, Ellipsometry that are very useful to evaluate in situ the hybrid interfaces and the self-assembly processes is emphasized. Some examples of the optical, photocatalytic, electrochemical and mechanical properties of the resulting inorganic or hybrid nanomaterials are also presented.
Activated carbons were prepared via a pyrolysis of sucrose followed by activation in the stream of CO2 gas for 2–6h at 900°C to tune the pore size distribution (PSD) and increase the specific surface area (SSA). The porosity of the activated sucrose derived carbons (ASCs) has been characterized using N2 sorption measurements. Increasing activation time led to the significant increase in SSA and pore volume of ASCs, among which sucrose derived carbon with 6h activation time (ASC-6h) exhibited the highest SSA of 1941m2 g−1 and the highest micropore volume of 0.87cm3 g−1. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge–discharge cycle tests have been applied to investigate the capacitive performance of the ASC electrodes in ionic liquids (ILs) at room and elevated temperatures. The ASC-6h electrodes in ethyl-dimethyl-propyl-ammonium bis (trifluoromethylsulfonyl) imide (EdMPNTf2N) showed specific capacitance in excess of 170Fg−1 at 60°C, whereas the same electrodes in 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) showed slightly lower capacitance but significantly better rate performance.
Levels of Interleukin-6 (IL-6) and C-creative protein (CRP) indicating systemic inflammation are known to be elevated in chronic diseases including chronic obstructive pulmonary disease (COPD) and depression. Comorbid depression is common in patients with COPD, but no studies have investigated whether proinflammatory cytokines mediate the association between pulmonary function and depressive symptoms in healthy individuals with no known history of obstructive pulmonary diseases.
Addition of moderate contents (≤20wt%) of ionic liquids (ILs) to binary solid polymer electrolytes (SPEs) is made to alter the overall SPE properties, foremost to increase the room temperature ionic conductivity. Sodium conducting ternary electrolytes, based on sodium salts; NaTFSI and NaFSI, the polymer poly(ethylene oxide) (PEO), and pyrrolidinium ILs; Pyr13TFSI and Pyr13FSI, with different compositions: NaX(PEO)n – Pyr13X (X=TFSI, FSI), have been prepared. Raman and dielectric spectroscopy as well as differential scanning calorimetry have been used to evaluate the plasticizing effect of the Pyr13 IL cation and the accompanying TFSI and FSI IL anions via changes in ionic association, crystallinity, polymer chain dynamics, and total ionic conductivity. While all the TFSI based systems seem rather insensitive to the addition of IL with respect to speciation, the situation is much less clear for the FSI based systems. Furthermore, the addition of ILs seems beneficial for inhibiting PEO crystallization, especially for the FSI anion, and also for enhancing the polymer chain dynamics, but yet the FSI based ternary electrolytes show lower ion conductivities as compared to the analogous TFSI based systems.
Mesoporous materials have attracted increasing attention due to their wide application. In this paper, the Na4Ge9O20 microspheres were firstly prepared by solvothermal method. Then, the as-prepared Na4Ge9O20 microspheres were dispersed into Bi(NO3)3 solution, and the Bi4(GeO4)3 microspheres with mesoporous structure were formed due to the solid-state reaction between bismuth nitrate and Na4Ge9O20. The morphology, structure and optical properties were characterized by SEM, EDS, XRD, FITR, BET and UV–Vis diffuse reflectance analysis. The as-prepared products exhibited excellent photocatalytic performance for degradation of reactive brilliant red X-3B under the UV light irradiation. A possible photocatalytic mechanism was discussed as well.
Polyaniline (PAn) films were electrodeposited on stainless steel 304 (SS) from 0.5M H2SO4 solution containing 0.1M aniline (An) by using potentiodynamic and potentiostatic techniques. In particular, PAn films were prepared as follows: (i) by cyclic potential sweep (CPS) deposition upon varying the upper potential limit (E l) of the polymerization potential region between 0.8 and 1.1V, while the lower potential limit was equal to −0.2V; (ii) by potentiostatic deposition upon varying the applied potential (E appl) between 0.8 and 1.1V. The potential sweep rate (dE/dt) was also varied for the An polymerization during the CPS deposition. Variation of the E l, dE/dt and E appl affects the PAn growth leading to films of different electrochemical and structural properties. The electrochemical properties of the PAn were examined by using cyclic voltammetry. Scanning electron microscopy was used to reveal the structure and morphology of the PAn films. Monitoring the open circuit potential (E OC) of the PAn-coated SS electrode in 0.5M H2SO4 shows that the SS remains in the passive state. PAn films can also provide protection to SS in chloride-containing 0.5M H2SO4 for the studied period of time, although pits were detected during prolonged immersion. The protection efficiency seems to be related with the parameters E l, dE/dt and E appl varied during polymerization. The mechanism of the SS protection provided by the PAn coatings is discussed in terms of the active role of PAn in corrosive environments.
Direct methanol fuel cells (DMFCs) are a promising power source for mobile devices. However, DMFCs currently experience the technical shortcomings of high cost due to the use of noble metal catalysts and polymer electrolyte membranes (PEMs), low power density because of their low catalytic efficiency and cathode catalyst poisoning by methanol, which crosses through the PEM from anode to cathode. Here, we report a new DMFC structure utilizing a polymer fiber membrane (PFM), which is electrolyte-permeable, instead of a PEM. An inexpensive perovskite-type oxide, LaNiO3, is used as the cathode catalyst, which has shown excellent tolerance to methanol-poisoning and good catalytic activity for oxygen reduction reaction (ORR). The peak power density can reach 103 mW cm−2 at 65 °C. This improvement in performance is due to the lower electrical resistance of the PFM.
Developing advanced and reliable electrical energy storage systems is critical to fulfill global energy demands and stimulate the growth of renewable energy resources. Sodium metal halide batteries have been under serious consideration as a low cost alternative energy storage device for stationary energy storage systems. Yet, there are number of challenges to overcome for the successful market penetration, such as high operating temperature and hermetic sealing of batteries that trigger an expensive manufacturing process. Here we demonstrate simple, economical and practical sealing technologies for Na-NiCl2 batteries operated at an intermediate temperature of 190 °C. Conventional polymers are implemented in planar Na-NiCl2 batteries after a prescreening test, and their excellent compatibilities and durability are demonstrated by a stable performance of Na-NiCl2 battery for more than 300 cycles. The sealing methods developed in this work will be highly beneficial and feasible for prolonging battery cycle life and reducing manufacturing cost for Na-based batteries at elevated temperatures (<200 °C).
Recently, there has been an explosion of literature dedicated to organic electrodes for energy storage applications. While inorganic materials, especially oxides, have generally being explored for these applications, the guiding principles for successful electrical energy storage—maximizing capacity and energy density per unit mass and cost—have naturally led to the pursuit of organic materials. However, there has only been a modest focus on methods for systematic exploration, which could help establish rational design principles for their enhanced properties and performance. Here we focus on a specific class of pseudocapacitive cathodes based on conducting polymers with pendant redox sites. We have previously demonstrated that the addition of such a pendant charge storage component provides a significant increase in the capacity, in addition to well-defined voltage plateaus, all the while maintaining the superior rate capability of these materials. In this report, we present a computational screening study for downselection of pendant candidates and a systematic study of structure–electrochemical property relationships. From this study, a generalized approach for defining the formal potential of oxidation of “violene” organic pendants is presented. Surprisingly, many of the structural parameters with which the oxidations can be tuned are independently addressable. While the methods described here have only been applied to the violene system, it should be emphasized that similar formalisms can be applied to other systems where the ability to rationally tune redox active components is desirable. Notable examples include organic energy storage electrodes based on oxygen and sulfur redox couples, charge shuttles for Li-ion batteries, organic photovoltaics, synthetic metals and organic light-emitting diodes.
The SnO2-based anode with improved reversible capacity and cyclability was achieved by employing a protective layer composed of crosslinked polypyrrole nanowires. Scanning electron microscopy measurement was performed to characterize the surface and cross section morphology of electrodes before and after cycling. The crosslinked polypyrrole nanowire protective layer with good elasticity adhered to the SnO2 surface could form a network, leading to buffer the volumetric swelling of active materials during the lithiation/delithiation process. A good cycling stability and an excellent rate capability of the modified electrode were achieved.
A review of mathematical models of lithium and nickel battery systems developed at the University of South Carolina is presented. Models of Li/Li-ion batteries are reviewed that simulated the behavior of single electrode particles, single electrodes, full cells and batteries (sets of full cells) under a variety of operating conditions (e.g. constant current discharge, pulse discharge, impedance and cyclic voltammetry). Models of nickel battery systems are reviewed that simulate the performance of full cells, as well as the behavior of the nickel hydroxide active material. The ability of these models to predict reality is demonstrated by frequent comparisons with experimental data.
Lithium batteries suffer from a number of safety concerns which limits their use in some applications. Nail penetration tests are used by the battery industry to compare the safety of different batteries during an incursion by a metallic object through a battery that physically violates the containment and locally damages the internal structure. For most lithium chemistries, such as mixed metal oxide or lithium iron phosphate cathodes, these tests result in rapid and dangerous failure. Lithium sulfur is an important next generation ultra-high energy density battery chemistry which is also inherently safer. Results are reported for nail penetration tests on 16Ah lithium sulfur batteries showing how they heat up by less than 10°C during a 10min penetration and then cool down rapidly after removal of the nail. Results of a nail penetration test under load are also reported for the first time, showing how the battery was capable of continuing to provide 1.6A (C/10) of current to an external load, with only a 1% drop in voltage. The results should be of interest for applications requiring ultra-high energy densities, improved safety, and continuous provision of power for a short period after damage, particularly military, aviation, portable electronics and automotive industries.
A Si thin film of thickness 275 nm was deposited on rough Cu foil by magnetron sputtering for use as lithium ion battery anode material. X-ray diffraction (XRD) and TEM analysis revealed that the Si thin film was completely of amorphous structure. The electrochemical performance of the Si thin film was investigated by cyclic voltammetry and constant current charge/discharge test. The film exhibited a high capacity of 3,134 mAh g−1 at 0.025 C rate. The capacity retention was 61.3% at 0.5 C rate for 500 cycles. An island structure formed on the Cu foil substrate after cycling adhered to the substrate firmly and provided electrical connection. This is the possible reason for the long cycling life of Si thin film anode. Moreover, the cycling performance was further improved by annealing at 300 °C. The Li+ diffusion coefficients (D0) of Si thin film, measured by cyclic voltammetry, are 1.47 × 10−9 cm2 s−1 and 2.16 × 10−9 cm2 s−1 for different reduced peaks.
The electrode is the key part of the electrochemical capacitors, so the electrode material is the most important ingredient in determining their properties. In this study, a simple carbonization method has been presented to prepare porous carbons as electrode materials without activation process, in which inexpensive, reproducible calcium lignosulfonate serves as carbon source. The carbon products were characterized by means of thermogravimetric analysis, X-ray diffraction, field emission scanning electron microscopy and BET surface area measurement. It clearly reveals that the carbonization temperature involved has the crucial effect upon the porous structures as well as the resultant capacitive performances. Given the results from cyclic voltammetry and galvanostatic charge–discharge measurements in 6M KOH aqueous solution, the present carbons possess high specific capacitance and excellent cycle stability. The maximum specific capacitance reaches as much as 182Fg−1 at the current density of 1mAcm−2, corresponding to a BET surface area of 1362m2 g−1, and ca. 95% of the capacitance remains even after 1000 charge–discharge cycles. The present carbons are excellent electrodes candidates for high-rate electrochemical capacitors.