High‐Capacity Concentration Gradient Li[Ni0.865Co0.120Al0.015]O2 Cathode for Lithium‐Ion Batteries

A Ni‐rich concentration‐gradient Li[Ni_0.865Co_0.120Al_0.015]O₂ (NCA) cathode is prepared with a Ni‐rich core to maximize the discharge capacity and a Co‐rich particle surface to provide structural and chemical stability. Compared to the conventional NCA cathode with a uniform composition, the gradient NCA cathode exhibits improved capacity retention and better thermal stability. Even more remarkably, the gradient NCA cathode maintains 90% of its initial capacity after 100 cycles when cycled at 60 °C, whereas the conventional cathode exhibits poor capacity retention and suffers severe structural deterioration. The superior cycling stability of the gradient NCA cathode largely stemmed from the gradient structure combines with the Co‐rich surface, which provides chemical stability against electrolyte attack and reduces the inherent internal strain observed in all Ni‐rich layered cathodes in their charged state, thus providing structural stability against the repeated anisotropic volume changes during cycling. The high discharge capacity of the proposed gradient NCA cathode extends the driving range of electric vehicles and reduces battery costs. Furthermore, its excellent capacity retention guarantees a long battery life. Therefore, gradient NCA cathodes represent one of the best classes of cathode materials for electric vehicle applications that should satisfy the demands of future electric vehicles.     

Tunable Free‐Standing Ultrathin Porous Nickel Film for High Performance Flexible Nickel–Metal Hydride Batteries

The nickel matrix has a significant impact on the structure and performance of a nickel–metal hydride (NiMH) battery. However, few studies have focused on the nickel matrix thus far due to the difficulty of fabricating controllable porous nickel materials. In addition, conventional nickel matrices show poor flexibility, making it difficult to fabricate flexible NiMH batteries. To achieve a high performance flexible NiMH battery, the fabrication of a thin, free‐standing, and flexible nickel matrix with an optimized pore structure is a key prerequisite. Here, a novel flexible porous nickel matrix with a controllable pore size, density, and distribution of pore position is developed by nickel electrodeposition on templates that are produced by silkscreen printing different insulating ink microarrays on stainless steel sheets. Benefitting from the excellent structure of the porous nickel matrix, flexible NiMH batteries are fabricated, which show excellent flexibility and very high energy densities of 151.8 W h kg^?1 and 508.5 W h L^?1 as well as high energy efficiencies of 87.9–98.5%. These batteries outperform conventional NiMH batteries and many other commercial batteries, holding great promise for their future practical application. The present strategy provides a new route to promote the development of nickel‐based alkaline rechargeable batteries.     

Nickel tolerance and copper - nickel co - tolerance in Mimulus guttatus from copper mine and serpentine habitats

Previous work on M. guttatus suggested that nickel tolerance in copper mine populations may also be given by the genes for copper tolerance. It has been shown that copper tolerance in M. guttatus is controlled by a single major gene, plus a number of minor genes (or modifiers) which elevate copper tolerance. Crosses between nickel tolerant individuals from three families and non - tolerants showed that nickel tolerance in M. guttatus is heritable. In order to study the effects of the major copper tolerance gene on copper - nickel co - tolerance in M. guttatus, homozygous copper tolerant and non - tolerant lines were screened against nickel. Significant differences occur between these lines for copper, but were not found when analysed for nickel, indicating that copper - nickel tolerance is not governed by the major gene for copper tolerance. To test whether the minor genes for copper have a pleiotropic effect on nickel tolerance, five selection lines derived from three copper mines (Copperopolis, Penn and Quail) in Calaveras county, California, which vary in degree of tolerance to copper, by the presence or absence of minor copper genes, were also screened against nickel. Two out of three of the lines from Copperopolis showed elevated tolerance to nickel, but two further selection lines derived from Penn and Quail copper mines gave no indication of increased nickel tolerance. These results suggest that the minor genes for copper do not give tolerance to nickel. This was confirmed by the screening of modifier lines, in which modifiers for differing degrees of copper tolerance were inserted into a non - tolerant background. Genotypes possessing fewer copper modifiers yielded higher nickel tolerance than those genotypes which have a greater number of modifiers. Thus nickel tolerance in this species is heritable and under the control of different genes to those producing copper tolerance.     

Variation in Nickel Content in the Nickel-Hyperaccumulating Shrub Psychotria douarrei (Rubiaceae) from New Caledonia1

Plants that hyperaccumulate Ni contain > 1000 ppm (dry wt.) in their tissues. Variation of Ni content within hyperaccumulating plant species is poorly explored. Using the Ni-hyperaccumulating shrub Psychotria douarrei, we documented variation of leaf Ni levels within individual shrubs, and variation with respect to plant size and leaf age. Plant size did not correlate significantly with leaf Ni content, and leaf Ni content did not correlate significantly with soil Ni content. Older leaves contained twice as much Ni as younger leaves. Older leaves also contained greater concentrations of Ca, Fe, and Cr but less K, P, and Cu. Five elements (Zn, Pb, Co, Mn, Mg) showed no significant variation due to leaf age. We also examined the effect of leaf age on epiphyll cover, finding increased epiphyll cover on the upper surface of older leaves. The dominant leafy liverwort epiphyll had a relatively high Ni content (400 ppm), suggesting that epiphylls of Ni hyperaccumulators obtain some Ni from host leaves. Individual shrubs differed in mean leaf Ni content almost two-fold (14,900-27,700 ppm). Variation among branches within individuals also ranged widely; however, this intraplant variability was not strongly correlated with the mean leaf Ni content of an individual shrub. We concluded that Ni contents in leaves of P. douarrei vary considerably due to leaf age, among individual shrubs, and among branches within a shrub.     

Experimental and Theoretical Assessment of Ni‐Based Binary Compounds for the Hydrogen Evolution Reaction

Metallic binary compounds have emerged in recent years as highly active and stable electrocatalysts toward the hydrogen evolution reaction. In this work, the origin of their high activity from a theoretical and experimental point of view is elucidated. Here, different metallic ceramics as Ni₃S₂, Ni₃N, or Ni₅P₄ are grown directly on Ni support in order to avoid any contaminations. The correlation of theoretical calculations with detailed material characterization and electrochemical testing paves the way to a deeper understanding of possible active adsorption sites for each material and the observed catalytic activity. It is shown that heteroatoms as P, S, and N actively take part in the reaction and do not act as simple spectator. Due to the anisotropic nature of the materials, a variety of adsorption sites with highly coverage‐dependent properties exists, leading to a general shift in hydrogen adsorption free energies ΔG _H close to zero. Extending the knowledge gained about the here described materials, a new catalyst is prepared by modifying a high surface Ni foam, for which current densities up to 100 mA cm^?2 at around 0.15 V (for Ni₃N) are obtained.     

Ames test evaluation of two commercially available zero-valent nickel compounds

Zero-valent nickel compounds are organometallic chemicals that are used in synthetic applications and may also occur as intermediates in nickel-catalyzed hydrogenation reactions used in food processing. Few studies have been performed on their possible genotoxic actions. We have tested two commercially available examples of this class of compounds. Solubility and stability were examined. Mutagenicity testing did not confirm a previous report that bis(1,5-cyclooctadiene)nickel is positive in the Ames assay. No stimulation of lipid peroxidation was observed in studies of bovine erythrocytes exposed in vitro. Our results do not indicate that zero-valent nickel compounds have genotoxic effects.     

DIFFERENT PHYSIOLOGICAL RESPONSES OF FOUR MARINE SYNECHOCOCCUS STRAINS (CYANOPHYCEAE) TO NICKEL STARVATION UNDER IRON‐REPLETE AND IRON‐DEPLETE CONDITIONS1

Synechococcus species are important primary producers in coastal and open‐ocean ecosystems. When nitrate was provided as the sole nitrogen source, nickel starvation inhibited the growth of strains WH8102 and WH7803, while it had little effect on two euryhaline strains, WH5701 and PCC 7002. Nickel was required for the acclimation of Synechococcus WH7803 to low iron and high light. In WH8102 and WH7803, nickel starvation decreased the linear electron transport activity, slowed down Q_A reoxidation, but increased the connectivity factor between individual photosynthetic units. Under such conditions, the reduction of their intersystem electron transport chains was expected to increase, and their cyclic electron transport around PSI would be favored. Nickel starvation decreased the total superoxide dismutase (SOD) activity of WH8102 and WH7803 by 30% and 15% of the control, respectively. The protein‐bound ⁶³Ni of the oceanic strain WH8102 comigrated with SOD activity on nondenaturing gels and thus provided additional evidence for the existence of active NiSOD in Synechococcus WH8102. In WH7803, it seems likely that nickel starvation affected other metabolic pathways and thus indirectly affected the total SOD activity.     

T-channels and Na<Superscript>+</Superscript>,Ca<Superscript>2+</Superscript>-exchangers as components of the Ca<Superscript>2+</Superscript>-system of regulation of activity of the heart myocardium of the frog <Emphasis Type="Italic">Rana temporaria</Emphasis>

Earlier we have shown that regulation of rhythm and strength of the frog heart contractions, mediated by transmitters of the autonomic nervous system, is of the Ca²⁺-dependent character. In the present work, we studied chronoand inotropic effect of verapamil—an inhibitor of Ca²⁺-channels of the L-type, of nickel chloride-an inhibitor of Ca²⁺—channels of the T-type and of Na⁺,Ca²⁺exchangers as well as of adrenaline and acetylcholine (ACh) after nickel chloride. It has been found that the intracardially administered NiCh₂ at a dose of 0.01 μg/kg produced a sharp fall of amplitude of action potential (AP) and an almost twofold deceleration of heart rate (HR). The intracardiac administration of NiCh₂ (0.01 μg/kg) on the background of action of verapamil (6 mg/kg, i/m) led as soon as after 3 min to even more prominent HR deceleration and to further fall of the AP amplitude by more than 50% as compared with norm. An intracardiac administration of adrenaline (0.5 mg/kg) partly restored the cardiac activity. However, preservation of the myocardium electrical activity in such animals was brief and its duration did not exceed several minutes. Administration of Ni²⁺ on the background of acetylcholine (3.6 mg/kg) led to almost complete cessation of cardiac activity. As soon as 3 min after injection of this agent the HR decreased to 2 contractions/min. On electrograms (EG), the 10-fold fall of the AP amplitude was recorded. To elucidate role of extraand intracellular Ca²⁺ in regulation of strength of heart contractions, isometric contraction of myocardium preparations was studied in response to action of NiCl₂ (10–200 μM), verapamil (70 μM), adrenaline (5 μM), and acetylcholine (0.2 μM) after NiCl₂. It has been found that Ni²⁺ causes a dose-dependent increase of the muscle contraction amplitude. Minimal change of the contraction amplitude (on average, by 14.9% as compared with control) was recorded at a Ni²⁺ concentration of 100 μM. An increase of Ni²⁺ in the sample to 200 μM increased the cardiac contraction strength, on average, by 41%. The negative inotropic action of verapamil was essentially reduced by 100 μM Ni²⁺. Adrenaline added to the sample after Ni²⁺ produced stimulating effect on the cardiac muscle, with an almost twofold rise of the contraction amplitude. ACh (0.2 μM) decreased the cardiac contraction amplitude, on average, by 56.3%, whereas Ni²⁺ (200 μM) administered after ACh not only restored, but also stimulated partly the myocardial work. Within several parts of percent there was an increase of such isometric contraction parameters as amplitude of the effort developed by muscle, maximal rate, maximal acceleration, time of semirise and semifall. The obtained experimental results indicate that the functional activity of the frog pacemaker and contractile cardiomyocytes is regulated by Ca²⁺-dependent mechanisms. Structure of these mechanisms includes the potential-controlled Land T-channels of the plasma membrane as well as Na⁺,Ca²-exchangers characteristic exclusively of contractile cardiomyocytes. The existence of these differences seems to be due to the cardiomyocyte morphological peculiarities that appeared in evolution at the stage of the functional cell specialization.