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The N-doped carbon coated ZnO nanorods (ZnO/NC-Z NRDs) are synthesized through a simple solvent-free method, in which the N-doped carbon is derived from thermal treatment of the in-situ grown zeolitic imidazolate framework-8 (ZIF-8) on the surface of ZnO NRDs. The in-situ coated N-doped carbon layer can not only enhance the electrical conductivity of ZnO NRDs and thus increasing the diffusion rate of Li ions, but also serve as a buffer layer to impede the volume expansion during the charge-discharge processes. When utilized as anodes for lithium-ion batteries (LIBs), the as-synthesized ZnO/NC-Z NRDs deliver a high capacity of 1011mAhg−1 at 200mAg−1 after 200 cycles and remain 544mAhg−1 at 1000mAg−1 after 850 cycles, holding a capacity retention of as high as 87.7%. In addition, the as-synthesized ZnO/NC-Z NRDs can also act as a precursor for the preparation of high performance N-doped carbon tube (1001.1mAhg−1 at 200mAg−1 with the retention of 99.1% after 100 cycles) with an ultrathin wall thickness. Such solvent-free synthetic method can not only simplify the synthesis process, but also pave a new strategy to synthesize Zn-based materials for the application of energy storage devices.
Hydrogen production from direct water electrolysis has long been pursued as a key that may revolutionize the hydrogen economy. With the rapid availability of electricity generated using renewable energy resources, this long-pursued target is now closer to reality than ever before. To date, most studies regarding electrocatalytic hydrogen evolution reaction (HER) are carried out in strong acidic/alkali electrolytes. However, hydrogen production from HER under extreme pH conditions has several drawbacks, including a corrosive working environment, the requirement of expensive anion/cation exchange membranes, and acidic/alkali withstanding electrocatalysts. The more sustainable approach to address these drawbacks is to deploy neutral/near-neutral electrolytes for HER. Regretfully, both theoretical discussions and practical applications regarding HER under neutral/near-neutral conditions are relatively rare and very elusive. In this review, we systematically discuss the current understandings of HER mechanisms under neutral conditions and analyze the influences of different types of neutral electrolytes. The most recent advances in the development of neutral HER electrocatalysts are summarized and exemplified, and general electrocatalyst design principles are highlighted. Lastly, we provide our perspective on the potential future research direction. We hope that this review inspires future endeavors to realize efficient HER for hydrogen production under neutral conditions.
Olivine type multi-walled carbon nanotube encrusted LiFePO4/C composites have been prepared using economic and energy efficient simple polyol technique without any subsequent heat treatment. The prepared material has an olivine type orthorhombic phase. Also, the iron oxidation state is 2+, which is identified by X-ray diffraction and X-ray photoelectron spectroscopy. It is possible to attain the discharge capacity almost close to theoretical capacity of LiFePO4 as in high temperature methods with ∼100% coulombic efficiency. The specific surface area has been increased upon encrusting multi walled carbon nano tube on LiFePO4/C, which results in enhanced reversible capacity upto 166 mAh g−1 at C/10. Also, it exhibits 89 mAh g−1 even at 30 C rate. This is due to the formation of conductive networks by carbon nanotube, and excellent attachment of LiFePO4/C composite particles on multi-walled carbon nanotube, which induced the kinetics during intercalation/deintercalation process. Multi-walled carbon nanotube acts as the electro-conductive filler on the LiFePO4 surface. The direct addition of MWCNT would result better performances than blending the MWCNT with LiFePO4/C.
Lithium titanate (Li4Ti5O12) and SiO2-incorporated Li4Ti5O12 are synthesized, using a facile cellulose-assisted combustion technique, as anodes for lithium-ion batteries tested under different conditions, i.e., discharge to an end potential of 1.0 V/0.01 V at room/elevated temperature (55 °C). The particles are characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), nitrogen adsorption–desorption isotherms, X-ray spectrometry (EDX) and transmission electron microscopy (TEM). The results show that silicon element is successfully incorporated with Li4Ti5O12 homogeneously in the forms of Si-doping and SiO2 separate phase. When discharged in the potential range of 0.01–3.0 V, initial discharge capacities of 260 mA h g−1 and 298 mA h g−1 are obtained for the Li4Ti5O12 and SiO2-incorporated Li4Ti5O12 electrodes, respectively. Both electrodes show stable cycling performance for 400 cycles (approximately 1.5 months) at room temperature between 0.01 and 3.0 V at a current density of 175 mA g−1. In addition, the stability of the electrodes under hurdle conditions (0.01–3.0 V at 55 °C) are explored and discussed, and a proposed mechanism for the “decrease–increase–decrease” cycling behavior is confirmed using electrochemical impedance spectroscopy (EIS) and TEM observations. The incorporation of SiO2 was found to improve the cycling stability under hurdle conditions.
AlPO4-coated LiCoO2 cathodes display improved cycle-life performance compared with bare LiCoO2. This is attributed to suppression of cobalt dissolution from the cathodes by the AlPO4-nanoparticle coating. Dissolution of cobalt during cycling with a charge cut-off voltage of 4.6V leads to structural degradation, and induces a non-uniform distribution of local strain in the cathodes. The strain in coated samples is significantly reduced after 50 cycles, and is correlated with the enhanced cycle-life performance.
Selected properties of commercial iron powders, standardised in the atmosphere of hydrogen, have been studied. The reactivity of iron oxides in the thermal decomposition of KClO4 in the solid-state mechanical mixture of Fe and KClO4 containing 9, 13, 17, 21 and 25wt.% of KClO4, respectively, has been tested by the differential thermal analysis (DTA) and thermogravimetric analysis (TG). It has been established that the Fe3O4 phase on the surface of the iron powder act as an effective catalysts in the thermal decomposition of KClO4.
1-Ethyl-1-methyl piperidinium bis(trifluoromethanesulfonyl)imide (EMP-TFSI) is an ionic liquid with a melting temperature of 85 °C. Although it is a solid salt, it shows good miscibility with carbonate solvents, which allows EMP-TFSI to be used as a co-solvent in these systems. Ethylene carbonate is another solid co-solvent used in Li-ion batteries. Due to its smaller cationic size, EMP-TFSI provides better conductivity as a co-solvent than 1-methyl-1-propyl piperidinium bis(trifluoromethanesulfonyl)imide (MPP-TFSI), which is the smallest room-temperature piperidinium liquid salt known. In cells with 50 wt% IL and 50 wt% carbonate electrolyte, an EMP-TFSI mixed electrolyte performs better than an MPP-TFSI mixed electrolyte. Additionally, the discharge capacity values obtained from rate capability tests carried out with mixed EMP-TFSI are as good as those conducted with a pure carbonate electrolyte.
Controlling nanoscale structure and morphology of LiNi1/3Co1/3Mn1/3O2 (NCM) cathode material is essential to optimizing their electrochemical performance in rechargeable lithium batteries owing to their anisotropic Li ion transport behavior. Here we report novel nanoarchitectured NCM cathodes composed of self-assembled nanosheet structures synthesized via a facile hydrothermal method and a stepwise calcination process. The as-obtained NCM cathodes showed different surface architectures with various degrees of packing and tap densities, leading to very different Li ion transport kinetics and thus variable rate capability. This study shows a promising material model for detailed investigation of the fundamental relationship between the structures/morphologies of battery electrodes and their Li ion transport kinetics.
In the present article, oxygen reduction reaction (ORR) at electrochemically fabricated tin-palladium (Sn-Pd) bimetallic electrocatalyst-modified glassy carbon (GC) electrode (Sn-Pd/GC electrode) in acidic media is addressed. Hydrodynamic voltammetric measurements were employed with a view to evaluating various kinetic parameters of the ORR at the Sn-Pd/GC electrode. The obtained results obviously demonstrated that the Sn-Pd bimetallic electrocatalyt substantially promoted the activity of the GC electrode and drove the ORR through an exclusive one-step four-electron pathway forming H2O as the final product.
Foot problems are likely to contribute to falls risk in older adults. Foot and ankle exercises may be beneficial, but uptake may be influenced by cultural factors. Few studies have explored the views of older adults from different cultural backgrounds about foot-specific falls risk factors, and foot and ankle falls prevention exercises.
Computer-assisted solutions are changing surgical practice continuously. One of the most disruptive technologies among the computer-integrated surgical techniques is Augmented Reality (AR). While Augmented Reality is increasingly used in several medical specialties, its potential benefit in orthopedic surgery is not yet clear. The purpose of this article is to provide a systematic review of the current state of knowledge and the applicability of AR in orthopedic surgery.
Halide perovskite solar cells containing a mixture of A-site cations are attracting considerable interest due to their improved stability and high power conversion efficiencies. Ionic transport is known to be an important predictor of perovskite behaviour, but the impact of partial A-site substitution on iodide ion diffusion is poorly understood. Here, we combine ab initio modelling, impedance spectroscopy and muon spin relaxation to investigate the effect on iodide ion transport of incorporating a low concentration of each of seven different sized cations (from small rubidium to large guanidinium) into methylammonium lead iodide. Experimental and simulation results are in good agreement, indicating that these cation substitutions increase the activation energy for iodide ion diffusion. We show for the first time that partial guanidinium substitution into methylammonium lead iodide strongly suppresses iodide ion transport. The insights gained from this multi-technique study are important for the future design of mixed-cation perovskite solar cells with enhanced performance.
Applications of lithium ion battery have been hampered by a lack of ideal anode materials in terms of capacity and stability. The emergence of metal chalcogenide as a candidate material has reinvigorated the search of a low cost and high capacity material system. However, debate about the underlying mechanisms and overall appraisal of its usage in lithium ion battery system remains. Here, a comprehensive study on the energy storage mechanism of copper zinc tin sulfide (CZTS) nanowalls possessing ultrahigh rate capability (500mAhg−1 charged within 60s) is reported. Structural evolutions along with the accompanying changes in the oxidation state upon charge/discharge were monitored by ex-situ X-ray diffraction and X-ray photoelectron spectroscopy. During lithiation, lithium ion reacted with CZTS to form lithium sulfides. At the same time, a sequential conversion reactions of copper, zinc and tin sulfides enabled the CZTS nanowalls to achieve excellent electrochemical performance (1400mAhg−1 at a current density of 1000mAg−1 over 400 cycles). Multi-element metal chalcogenides in conjunction with an adhesion-enhancing seed layer and a rational nanostructure design hold the key to such ultrahigh capacity and stable anode materials for next generation energy storage devices.
Four new Hofmann–3-phenylpropylamine (3PPA) type complexes with chemical formulae M(3PPA)2Ni(CN)4 (M=Ni, Co, Cd, and Pd) have been prepared and their vibrational spectra are reported in the region of 4000–60cm−1. The vibrational bands arising from 3PPA ligand molecule, the polymeric sheet and metal–ligand bands of the compounds are assigned. The thermal behaviour of these complexes is also provided using the DTA and TGA along with the magnetic susceptibility data. The results indicate that the monodentate 3PPA ligand molecule bonds to the metal atom of |M–Ni(CN)4|∞ polymeric layers and hence the compounds are similar in structure to Hofmann-type complexes.
Ni-rich layered lithium transition metal oxides (LTMO) are regarded as one of the most potential candidates to usher in a new stage of the ultra-high available energy density lithium-ion batteries (LIBs). However, the severe capacity and voltage fading remain a big challenge on the practical application, while lacking of atomic scale evidence makes the performance degradation mechanism of Ni-rich LTMO essentially ambiguous. Here we report a more accurate study on the detailed structural transformation and chemical evolution processes upon cycling to shed light on the performance decay from the perspective of variation on the nature of the stoichiometric Ni-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode. A novel continuous structural evolution mechanism at atomic scale based on the migration of transition metal cations into lithium ion diffusion channels has been proposed to acquire a new insight into the energy decay behaviour of Ni-rich cathode. It is demonstrated that Ni would migrate from bulk to surface along with the irreversible reduction by virtue of the low diffusion barrier and the Ni concerntration gradient in lattice, resulting in the growth of structural restruction layer (SRL) throughout the whole charge/discharge processes and the ongoing performance decay. Thus, the future works on achieving higher available energy and longer cycle life for Ni-rich layered cathodes should focus on how to prevent the migration of transition metal ions.
Nano-sized boron carbon oxynitride (BCNO) phosphors around 50nm containing no rare earth metal and free from color heterogeneity were synthesized from mixtures of boric acid, urea, and citric acid by microwave heating with substantially shorter reaction times and lower temperatures than in the conventional BCNO preparation method such as electric-furnace heating. The emission wavelength of the phosphors varied with the mixing ratio of raw materials and it was found that lowering the proportion of urea to boric acid or citric acid tended to increase the internal quantum yield and shorten the emission wavelength under excitation at 365nm. It was also found for the first time that a light-emitting polymer could be synthesized from a mixture of the prepared BCNO nanoparticles and a polyvinyl alcohol. This polymer composite exhibited uniform dispersion and stabilization of the luminescence and had a high internal quantum yield of 54%, which was higher than that of the phosphor alone.
Hard carbon is emerging as a highly promising material for power-demanded energy storage devices. Recently, introducing heteroatom such as oxygen is confirmed to be available to improve the capacity. However, it remains a significant challenge to achieve simultaneously superior high-rate capability and long-term cycling stability. Here we demonstrate that the surface oxo-funcitionalized hard carbon spheres (o-HCS, 4.2 m2 g−1) derived from mild oxidative approach enhance pseudocapacitance lithium-ion storage with improved Li-ion diffusivity and thus exhibit high-rate capacity and long cycle life in both Li-ion batteries and Li-ion capacitors. The o-HCS electrode delivers specific capacity of around 275 mAh g−1 at 744 mA g−1 (2C) and capacity retention of above 92.0% and about 86.5% after 1100 and 1700 cycles, respectively. Impressively, it delivers above 110 mAh g−1 at extreme high current density of 14.88 A g−1 (40C). As well, o-HCS electrode in Li-ion capacitor shows a capacitance of 34.8 F g−1 (corresponding to 48.5 Wh kg−1 and 3.6 kW kg−1) at the current density of 3720 mA g−1, and after 7000 cycles the capacity retention is 96% (∼0.057% decay per cycle).
Multilayered graphene/MnO2 nanocomposite electrode prepared by anodic electrodeposition and electrophoresis exhibited superior capacitive behavior compared to the bare MnO2 and graphene electrodes. The multilayered architecture provided both the horizontal and vertical channels for electrolyte access during fast charging and discharging. The graphene layer turned out to play an important role in enhancing the electron conduction in the multilayered architecture. Therefore, the improved electrochemical behavior might result from the significantly improved ion transport and electron conduction in the multilayered architecture of the graphene/MnO2 composite electrode. Furthermore, the MnO2 nanowire layer coated on the graphene layer could significantly suppress the oxygen evolution reaction, broadening the potential window of water stability.
For a good understanding of the aging and its prediction for Li ion cells, an identification of aging mechanisms, such as loss of mobile Li or loss of active material, is essential. The results of this identification might be used as input parameter or as validation for a Li ion cell aging model. In this publication, the changes of the open-circuit-voltage (OCV) characteristic are analyzed carefully to draw conclusions regarding the aging mechanisms that reduce cell capacity. For this, a model which calculates the OCV characteristic of the automotive scale full-cell (FC) based on the anode and cathode half-cell (HC) OCV characteristics is suggested. The resulting changes of the FC OCV due to anodic and cathodic side reactions as well as loss of active material (LAM) are simulated. The analysis of these simulation results shows that each aging mechanism effects the OCV characteristic in a unique way, like a fingerprint, which can help to identify the aging mechanisms if unknown. Finally, the reverse mode operation, in which the model is used to identify the aging mechanisms based on the changes in the OCV, is validated on FC level. For this, a cell is disassembled after significant aging and the storage capacities of anode and cathode are measured on HC level. Even though inhomogeneities must be expected for the large automotive scale FC with more than 30 Ah capacity, loss of mobile Li inventory (LLI) and LAM can be identified and quantified.
Extant research suggests that when marketers introduce products with functions that span multiple categories, consumers tend to generate beliefs in line with only a single category. This has been regarded as a major marketing challenge because it leads consumers to ignore key attributes from the product's supplementary category. Contrary to this prediction, the authors find that because consumers tend to classify new hybrid products by contrasting them against the competitive context, attributes from the supplementary category become more salient and thus contribute greater utility in choice. The authors pit the strength of this effect against several of the most dominant and favored category cues. The results confirm that classification inferences and attribute preference for new hybrid products are highly contextual, and as such, single category inferences need not translate directly into attribute preference.
Neuropsychological (NP) studies in schizophrenia often require data reduction to avoid statistical type I error from multiple comparisons. Typically, this involves grouping measures into domains defined by experts a priori based on delineations validated in brain-injured but not schizophrenia samples (e.g. attention, executive functioning, memory, language visuospatial, motor). Component measures are arbitrarily selected and validity may not generalize to different samples or within the same sample over time. One solution to these problems is illustrated using neurocognitive subdomains based on recent schizophrenia literature, and validated with data from a longitudinal study (156 subjects) involving repeated NP testing (baseline—within 6 months of hospital discharge—and 6 and 18 months later). A priori subdomains were grouped and submitted to principal component analysis (PCA) at each time point. Longitudinal stability of the resulting factors was tested by computing congruency coefficients. Six stable factors were extracted having good construct, divergent and predictive validity. Five neuropsychological measures frequently studied in schizophrenia were not correlated with these factors, suggesting that they should be maintained as independent neurocognitive subdomains. Distinct factors for executive functioning, verbal memory and motor functions could not be validated; this raises concerns about conclusions of previous studies regarding the pattern, severity and correlates of specific neurocognitive functions in schizophrenia.
To investigate the feasibility of scaling up bio-inspired organic materials as cathode materials in lithium ion batteries, large-sized pouch cells are successfully prepared via tape casting using lumichrome with an alloxazine structure and aqueous styrene butadiene rubber-carboxymethyl cellulose (SBR-CMC) binders. A battery module with a two-in-series, six-in-parallel (2S6P) configuration is also successfully fabricated and is able to power blue LEDs (850 mW). Lumichrome shows no structural changes during the fabrication processes used to produce the positive electrode. The large-sized pouch cells show two sets of cathodic and anodic peaks with average potentials of 2.58 V and 2.26 V vs. Li/Li+, respectively. The initial discharge capacities are 142 mAh g−1 and 148 mAh g−1 for ethylene carbonate-dimethyl carbonate (EC-DMC) and tetraethylene glycol dimethyl ether (TEGDME) electrolytes, respectively, similar to that of a coin cell (149 mAh g−1). The EC-DMC-injected pouch cells exhibit higher rate performance and cyclability than the TEGDME-injected ones. The TEGDME electrolyte is not suitable for lithium metal anodes because of electrolyte decomposition and subsequent cell swelling.
Lithium-ion capacitor is a hybrid electrochemical energy storage device, which combines the intercalation mechanism of lithium ion battery with the cathode of electric double-layer capacitor. To improve the energy density of hybrid Lithium-ion capacitor, a high-performance ion adsorption cathode is essential. Herein the porous activated carbon for using as cathode of hybrid Lithium-ion capacitor has been prepared through a two-step fabrication process in which naturally Chinese-chives are used as biomass carbon precursor. The biomass-derived porous carbon exhibits an extremely high specific surface area (3011 m2 g−1) and relatively applicable pore volume (2.6 m3 g−1). Besides, it displays excellent capacitive performance with specific capacity of 124 mAh g−1 at a current density of 0.3 A g−1, good rate capability and outstanding cycling stability in organic electrolyte. The hybrid Lithium-ion capacitor is assembled using biomass-derived porous carbon as cathode material and the silicon/flake graphite/carbon nanocomposite as anode material. The hybrid device shows a high energy density of 159 W h kg−1 at 945 W kg−1 and outstanding cycle stability (with 80% capacity retention rate after 8000 cycles at 1 A g−1).