A facile method to transform pickled olive wastes into sulfur-doped carbon for sodium-ion battery electrode.

This work provides a novel, low-cost, and effective method to prepare disordered carbon materials for advanced sodium-ion batteries using biomass. A large amount of olive stone waste is yearly produced in the world, and it could be re-used for fine applications other than fuel for heat production. After treatment with sulfuric acid solution and carbonization process, wastes of olive stone are efficiently transformed into optimized carbon electrode material. XRD, XRF and XPS, electron microscopy, and physical gas adsorption are used for the compositional, microstructural, and textural characterization of the carbons. During the synthesis, impurities are removed, C-S links are formed and micropores pores are created. Sulfuric acid acts like S-dopant. The latent pores, or pores closed to nitrogen, can be found using CO2 adsorption, and are very suitable for accommodation for sodium. The results reveal that the reversible capacity is raised from ca. 200 mAh g-1 to ca. 250 mAh g-1 for the carbon obtained through treatment with sulfuric acid. The improved electrochemistry is the result of the s-doping and the porosity.

Review and New Perspectives on Non-Layered Manganese Compounds as Electrode Material for Sodium-Ion Batteries.

After more than 30 years of delay compared to lithium-ion batteries, sodium analogs are now emerging in the market. This is a result of the concerns regarding sustainability and production costs of the former, as well as issues related to safety and toxicity. Electrode materials for the new sodium-ion batteries may contain available and sustainable elements such as sodium itself, as well as iron or manganese, while eliminating the common cobalt cathode compounds and copper anode current collectors for lithium-ion batteries. The multiple oxidation states, abundance, and availability of manganese favor its use, as it was shown early on for primary batteries. Regarding structural considerations, an extraordinarily successful group of cathode materials are layered oxides of sodium, and transition metals, with manganese being the major component. However, other technologies point towards Prussian blue analogs, NASICON-related phosphates, and fluorophosphates. The role of manganese in these structural families and other oxide or halide compounds has until now not been fully explored. In this direction, the present review paper deals with the different Mn-containing solids with a non-layered structure already evaluated. The study aims to systematize the current knowledge on this topic and highlight new possibilities for further study, such as the concept of entatic state applied to electrodes.

Coping Strategies Among Undergraduates: Spanish Adaptation and Validation of the Brief-COPE Inventory.

Purpose: Different studies have highlighted the importance of coping strategies in stressful situations. The Coping Orientation to Problem Experienced (COPE) by Carver et al is one of the instruments that is frequently used for measuring this aspect. The aim of this study was to carry out the cross-cultural adaptation and validation of the Brief-COPE inventory to measure coping strategies in Spanish populations. Methods: The linguistic and cultural adaptation of the Brief-COPE was carried out using the back-translation method and, after considering the results of the pilot test, the Spanish version of the instrument was configured, and subsequently administered to a convenient sample of 2135 undergraduates. A confirmatory factor analysis was carried out to examine construct validity of the Spanish adaptation of the brief-COPE; likewise, reliability was analyzed from two approaches, internal consistency and composite reliability. Concurrent validity was also tested. Results: The results showed that the Spanish version of Brief-COPE has adequate reliability values, as well as satisfactory fit indexes for the proposed 14-factor first-order structural model. Likewise, external evidence of the validity of the inventory with the variables perceived stress, level of satisfaction with life, and academic performance is provided. Conclusion: The results suggest that this instrument presents a satisfactory metric quality and, therefore, it could be useful to evaluate coping strategies, which would allow further research on its incidence and consequences on health and psychological functioning.

Grit as a Predictor and Outcome of Educational, Professional, and Personal Success: A Systematic Review / La tenacidad como predictor y resultado del éxito educativo, profesional y personal: revisión sistemática

Given the recent relevance of non-cognitive skills for consequential outcomes in the educational, personal, and professional domains, the objective of this systematic review was to synthesize the quality of the evidences on grit as predictor and outcome of educational, professional, and personal success. A pre-specified systematic review protocol was designed and implemented to synthesize the qualitative finding. A systematic literature search was conducted across diverse platforms and databases. A narrative content analysis was adopted to analyze the results. The final sample of studies reviewed was 90. The following analytical themes were identified: grit as a predictor of educational, professional, and personal success, and grit as outcome of demographic, educational, professional, and personal success. The results suggest that the evidences of effectiveness of grit as a predictor are largely stronger than those of grit as outcome. Additionally, our findings unveil that research on this construct is off to a good start, even though higher-quality research is needed

Dada la reciente importancia de las habilidades no cognitivas para obtener resultados significativos en los ámbitos educativo, personal y profesional, el objetivo de esta revisión sistemática es sintetizar la calidad de la evidencia de la tenacidad como predictor y resultado del éxito educativo, profesional y personal. Se diseñó y aplicó un protocolo de revisión sistemática preespecificado para sintetizar los resultados cualitativos. Se llevó a cabo una búsqueda sistemática de literatura en diversas plataformas y bases de datos. Se adoptó un análisis del contenido narrativo para analizar los resultados. La muestra final de estudios revisados fue de 90. Se identificaron los siguientes temas analíticos: tenacidad como predictor del éxito educativo, profesional y personal y tenacidad como resultado del éxito demográfico, educativo, profesional y personal. Los resultados indican que la evidencia acerca de la eficacia de la tenacidad como predictor es en gran medida mayor que de la tenacidad como resultado. Además, nuestros hallazgos revelan que la investigación sobre este constructo es prometedora, aunque necesita mejorar su calidad

Sustainable and Environmentally Friendly Na and Mg Aqueous Hybrid Batteries Using Na and K Birnessites.

Sodium and magnesium batteries with intercalation electrodes are currently alternatives of great interest to lithium in stationary applications, such as distribution networks or renewable energies. Hydrated laminar oxides such as birnessites are an attractive cathode material for these batteries. Sodium and potassium birnessite samples have been synthesized by thermal and hydrothermal oxidation methods. Hybrid electrochemical cells have been built using potassium birnessite in aqueous sodium electrolyte, when starting in discharge and with a capacity slightly higher than 70 mA h g-1. Hydrothermal synthesis generally shows slightly poorer electrochemical behavior than their thermal counterparts in both sodium and potassium batteries. The study on hybrid electrolytes has resulted in the successful galvanostatic cycling of both sodium birnessite and potassium birnessite in aqueous magnesium electrolyte, with maximum capacities of 85 and 50 mA h g-1, respectively.

Morphological adaptability of graphitic carbon nanofibers to enhance sodium insertion in a diglyme-based electrolyte.

The recent introduction of glyme-based solvents has opened new opportunities to characterize graphitic materials as anodes for sodium-ion batteries. We evaluated the electrochemical behaviour of a graphitized carbon nanofiber for the first time. X-ray diffraction, electron paramagnetic resonance and nuclear magnetic resonance allowed the sodium insertion mechanism to be untangled, in which the occurrence of an activation process during the first discharge enhances sodium accessibility to active redox centres at the interlayer space. Morphological changes observed by electron microscopy could be responsible for this behaviour. A fully graphitized carbon nanofibers/NaPF6(diglyme)/Na3V2(PO4)3 sodium-ion battery was tested to probe the reliability of this graphitic nanostructure as a negative electrode.

Grit as Predictor of Entrepreneurship and Self-Employment in Spain.

Extending the growing literature on the role of grit in different life domains, this research explores the relationship between grit and involvement in entrepreneurship. The research highlights the role of personal income and satisfaction with one's current financial situation as moderators of the relationship between grit and entrepreneurial behavior. Using a large representative sample of Spanish young adults and controlling for a number of potential confounding variables, we find that grit is modestly negatively related to the probability of involvement in entrepreneurship. As predicted, however, this relationship is qualified by both income and satisfaction with current financial situation, though in opposite directions and more weakly for satisfaction with financial status. Gritty individuals with higher levels of income are more prone to become entrepreneurs than gritty individuals with lower levels of income. Gritty individuals with lower levels of satisfaction with their financial situation are more likely to set up a business or become self-employed.

On the Beneficial Effect of MgCl2 as Electrolyte Additive to Improve the Electrochemical Performance of Li4Ti5O12 as Cathode in Mg Batteries.

Magnesium batteries are a promising technology for a new generation of energy storage for portable devices. Attention should be paid to electrolyte and electrode material development in order to develop rechargeable Mg batteries. In this study, we report the use of the spinel lithium titanate or Li4Ti5O12 (LTO) as an active electrode for Mg2+-ion batteries. The theoretical capacity of LTO is 175 mA h g-1, which is equivalent to an insertion reaction with 1.5 Mg2+ ions. The ability to enhance the specific capacity of LTO is of practical importance. We have observed that it is possible to increase the capacity up to 290 mA h g-1 in first discharge, which corresponds to the reaction with 2.5 Mg2+ ions. The addition of MgCl2·6H2O to the electrolyte solutions significantly improves their electrochemical performance and enables reversible Mg deposition. Ex-situ X-ray diffraction (XRD) patterns reveal little structural changes, while X-ray photoelectron spectrometer (XPS) (XPS) measurements suggest Mg reacts with LTO. The Ti3+/Ti4+ ratio increases with the amount of inserted magnesium. The impedance spectra show the presence of a semicircle at medium-low frequencies, ascribable to Mg2+ ion diffusion between the surface film and LTO. Further experimental improvements with exhaustive control of electrodes and electrolytes are necessary to develop the Mg battery with practical application.

On the Mechanism of Magnesium Storage in Micro- and Nano-Particulate Tin Battery Electrodes.

This study reports on the electrochemical alloying-dealloying properties of Mg2Sn intermetallic compounds. 119Sn Mössbauer spectra of β-Sn powder, thermally alloyed cubic-Mg2Sn, and an intermediate MgSn nominal composition are used as references. The discharge of a Mg/micro-Sn half-cell led to significant changes in the spectra line shape, which is explained by a multiphase mechanism involving the coexistence of c-Mg2Sn, distorted Mg2−δSn, and Mg-doped β-Sn. Capacities and capacity retention were improved by using nanoparticulate tin electrodes. This material reduces significantly the diffusion lengths for magnesium and contains surface SnO and SnO2, which are partially electroactive. The half-cell potentials were suitable to be combined versus the MgMn2O4 cathodes. Energy density and cycling properties of the resulting full Mg-ion cells are also scrutinized.

Development and Validation of a Spanish Version of the Grit-S Scale.

This paper describes the development and initial validation of a Spanish version of the Short Grit (Grit-S) Scale. The Grit-S Scale was adapted and translated into Spanish using the Translation, Review, Adjudication, Pre-testing, and Documentation model and responses to a preliminary set of items from a large sample of university students (N = 1,129). The resultant measure was validated using data from a large stratified random sample of young adults (N = 1,826). Initial validation involved evaluating the internal consistency of the adapted scale and its subscales and comparing the factor structure of the adapted version to that of the original scale. The results were comparable to results from similar analyses of the English version of the scale. Although the internal consistency of the subscales was low, the internal consistency of the full scale was well-within the acceptable range. A two-factor model offered an acceptable account of the data; however, when a single correlated error involving two highly similar items was included, a single factor model fit the data very well. The results support the use of overall scores from the Spanish Grit-S Scale in future research.

Insight into the Electrochemical Sodium Insertion of Vanadium Superstoichiometric NASICON Phosphate.

A slight deviation of the stoichiometry has been introduced in Na3-3xV2+x(PO4)3 (0 ≤ x ≤ 0.1) samples to determine the effect on the structural and electrochemical behavior as a positive electrode in sodium-ion batteries. X-ray diffraction and XPS results provide evidence for the flexibility of the NASICON framework to allow a limited vanadium superstoichiometry. In particular, the Na2.94V2.02(PO4)3 formula reveals the best electrochemical performance at the highest rate (40C) and capacity retention upon long cycling. It is attributed to the excellent kinetic response and interphase chemical stability upon cycling. The electrochemical performance of this vanadium superstoichiometric sample in a full sodium-ion cell is also described.

Induced Rate Performance Enhancement in Off-Stoichiometric Na3+3x V2-x (PO4 )3 with Potential Applicability as the Cathode for Sodium-Ion Batteries.

Off-stoichiometric Na3+3x V2-x (PO4 )3 samples have been prepared by a sol-gel route. X-ray diffraction and XPS revealed the flexibility of the NASICON framework to accommodate these deviations of the stoichiometry; at least for low x values. X-ray photoelectron spectra evidenced the presence of Na4 P2 O7 impurities. The synergic combination of the structural deviations and the presence of Na4 P2 O7 impurities induce a significant improvement of the electrochemical performance and cycling stability at high rates, as compared to the stoichiometric Na3 V2 (PO4 )3 sample. The fast kinetic response provided by the induced off-stoichiometry involves a decrease of the cell resistance.

Improved Surface Stability of C+MxOy@Na3V2(PO4)3 Prepared by Ultrasonic Method as Cathode for Sodium-Ion Batteries.

Coated C+MxOy@Na3V2(PO4)3 samples containing 1.5% or 3.5% wt. of MxOy (Al2O3, MgO or ZnO) have been synthesized by a two-step method including first a citric based sol-gel method for preparing the active material and second an ultrasonic stirring technique to deposit MxOy. The presence of the metal oxides properly coating the surface of the active material is evidenced by XPS and electron microscopy. Galvanostatic cycling of sodium half-cells reveals a significant capacity enhancement for samples coated with 1.5% of metal oxides and an exceptional cycling stability as evidenced by Coulombic efficiencies as high as 95.9% for ZnO@ Na3V2(PO4)3. It is correlated to their low surface layer and charge transfer resistance values. The formation of metal fluorides that remove traces of corrosive HF from the electrolyte is checked by XPS spectroscopy. The feasibility of sodium-ion batteries assembled with C+MxOy@Na3V2(PO4)3 is further verified by evaluating the electrochemical performance of full cells. Particularly, a Graphite//Al2O3@ Na3V2(PO4)3 battery delivers an energy density as high as 260 W h kg-1 and exhibits a Coulombic efficiency of 89.3% after 115 cycles.

Enhancing the energy density of safer Li-ion batteries by combining high-voltage lithium cobalt fluorophosphate cathodes and nanostructured titania anodes.

Recently, Li-ion batteries have been heavily scrutinized because of the apparent incompatibility between safety and high energy density. This work report a high voltage full battery made with TiO2/Li3PO4/Li2CoPO4F. The Li2CoPO4F cathode and TiO2 anode materials are synthesized by a sol-gel and anodization methods, respectively. X-ray diffraction (XRD) analysis confirmed that Li2CoPO4F is well-crystallized in orthorhombic crystal structure with Pnma space group. The Li3PO4-coated anode was successfully deposited as shown by the (011) lattice fringes of anatase TiO2 and (200) of γ-Li3PO4, as detected by HRTEM. The charge profile of Li2CoPO4F versus lithium shows a plateau at 5.0 V, revealing its importance as potentially high-voltage cathode and could perfectly fit with the plateau of anatase anode (1.8-1.9 V). The full cell made with TiO2/Li3PO4/Li2CoPO4F delivered an initial reversible capacity of 150 mA h g(-1) at C rate with good cyclic performance at an average potential of 3.1-3.2 V. Thus, the full cell provides an energy density of 472 W h kg(-1). This full battery behaves better than TiO2/Li2CoPO4F. The introduction of Li3PO4 as buffer layer is expected to help the cyclability of the electrodes as it allows a rapid Li-ion transport.

Synthesis of Porous and Mechanically Compliant Carbon Aerogels Using Conductive and Structural Additives.

We report the synthesis of conductive and mechanically compliant monolithic carbon aerogels prepared by sol-gel polycondensation of melamine-resorcinol-formaldehyde (MRF) mixtures by incorporating diatomite and carbon black additives. The resulting aerogels composites displayed a well-developed porous structure, confirming that the polymerization of the precursors is not impeded in the presence of either additive. The aerogels retained the porous structure after etching off the siliceous additive, indicating adequate cross-linking of the MRF reactants. However, the presence of diatomite caused a significant fall in the pore volumes, accompanied by coarsening of the average pore size (predominance of large mesopores and macropores). The diatomite also prevented structural shrinkage and deformation of the as-prepared monoliths upon densification by carbonization, even after removal of the siliceous framework. The rigid pristine aerogels became more flexible upon incorporation of the diatomite, favoring implementation of binderless monolithic aerogel electrodes.

High Performance Full Sodium-Ion Cell Based on a Nanostructured Transition Metal Oxide as Negative Electrode.

A novel design of a sodium-ion cell is proposed based on the use of nanocrystalline thin films composed of transition metal oxides. X-ray diffraction, Raman spectroscopy and electron microscopy were helpful techniques to unveil the microstructural properties of the pristine nanostructured electrodes. Thus, Raman spectroscopy revealed the presence of amorphous NiO, α-Fe2 O3 (hematite) and γ-Fe2 O3 (maghemite). Also, this technique allowed the calculation of an average particle size of 23.4 Å in the amorphous carbon phase in situ generated on the positive electrode. The full sodium-ion cell performed with a reversible capacity of 100 mA h g(-1) at C/2 with an output voltage of about 1.8 V, corresponding to a specific energy density of about 180 W h kg(-1) . These promising electrochemical performances allow these transition metal thin films obtained by electrochemical deposition to be envisaged as serious competitors for future negative electrodes in sodium-ion batteries.

A fractal-like electrode based on double-wall nanotubes of anatase exhibiting improved electrochemical behaviour in both lithium and sodium batteries.

An anatase nanotube array has been prepared with a special morphology: two concentric walls and a very small central cavity. The method used here to achieve the double-wall structure is a single-step anodization process under a voltage ramp. Thanks to this nanostructure, which is equivalent to a fractal electrode, the electrochemical behaviour is improved, and the specific capacity is higher in both lithium and sodium cells due to pseudocapacitance. The double-wall structure of the nanotube enhances the surface of TiO2 being in contact with the electrolyte solution, thus allowing an easy penetration of the alkali ions into the electrode active material. The occurrence of sodium titanate in the electrode material after electrochemical reaction with sodium is studied by using EPR, HRTEM and NMR experiments.

P3-Type Layered Sodium-Deficient Nickel-Manganese Oxides: A Flexible Structural Matrix for Reversible Sodium and Lithium Intercalation.

Sodium-deficient nickel-manganese oxides exhibit a layered structure, which is flexible enough to acquire different layer stacking. The effect of layer stacking on the intercalation properties of P3-Nax Ni0.5 Mn0.5 O2 (x=0.50, 0.67) and P2-Na2/3 Ni1/3 Mn2/3 O2 , for use as cathodes in sodium- and lithium-ion batteries, is examined. For P3-Na0.67 Ni0.5 Mn0.5 O2 , a large trigonal superstructure with 2√3 a×2√3 a×2 c is observed, whereas for P2-Na2/3 Ni1/3 Mn2/3 O2 there is a superstructure with reduced lattice parameters. In sodium cells, P3 and P2 phases intercalate sodium reversibly at a well-expressed voltage plateau. Preservation of the P3-type structure during sodium intercalation determines improving cycling stability of the P3 phase within an extended potential range, in comparison with that for the P2 phase, for which a P2-O2 phase transformation has been found. Between 2.0 and 4.0 V, P3 and P2 phases display an excellent rate capability. In lithium cells, the P3 phase intercalates lithium, accompanied by a P3-O3 structural transformation. The in situ generated O3 phase, containing lithium and sodium simultaneously, determines the specific voltage profile of P3-Nax Ni0.5 Mn0.5 O2 . The P2 phase does not display any reversible lithium intercalation. The P3 phase demonstrates a higher capacity at lower rates in lithium cells, whereas in sodium cells P3-Nax Ni0.5 Mn0.5 O2 operates better at higher rates. These findings reveal the unique ability of sodium-deficient nickel-manganese oxides with a P3-type structure for application as low-cost electrode materials in both sodium- and lithium-ion batteries.

High-intensity ultrasonication as a way to prepare graphene/amorphous iron oxyhydroxide hybrid electrode with high capacity in lithium battery.

The preparation of graphene/iron oxyhydroxide hybrid electrode material with very homogeneous distribution and close contact of graphene and amorphous iron oxyhydroxide nanoparticles has been achieved by using high-intensity ultrasonication. Due to the negative charge of the graphene surface, iron ions are attracted toward the surface of dispersed graphene, according to the zeta potential measurements. The anchoring of the FeO(OH) particles to the graphene layers has been revealed by using mainly TEM, XPS and EPR. TEM observations show that the size of the iron oxide particles is about 4 nm. The ultrasonication treatment is the key parameter to achieve small particle size in these graphene/iron oxyhydroxide hybrid materials. The electrochemical behavior of composite graphene/amorphous iron oxyhydroxide prepared by using high-intensity ultrasonication is outstanding in terms of gravimetric capacity and cycling stability, particularly when metallic foam is used as both the substrate and current collector. The XRD-amorphous character of iron oxyhydroxide in the hybrid electrode material and the small particle size contribute to achieve the improved electrochemical performance.

Improving the performance of titania nanotube battery materials by surface modification with lithium phosphate.

Self-organized TiO2 nanotubes ranging from amorphous to anatase structures were obtained by anodization procedures and thermal treatments at 500°C. Then electrolytic Li3PO4 films were successfully deposited on the nanotube array by an electrochemical procedure consisting in proton reduction with subsequent increase in pH, hydrogen phosphate dissociation and Li3PO4 deposition on the surface of the cathode. The Li3PO4 polymorph (γ or ß) in the deposit could be tailored by modifying the electrodeposition parameters, such as time or current density, as determined by X-ray patterns. The morphological analysis evidenced the formation of a 3D nanostructure consisting of Li3PO4 coating the TiO2 nanotube array. The anode-solid electrolyte stacking was tested in lithium half cells. Interestingly, the electrochemical performances revealed a better cycling stability for samples containing low amount of lithium phosphate, which is deposited for short times and low current densities. These results suggested the possibility of fabricating 3D Li-ion batteries. nt-TiO2/γ-Li3PO4/LiFePO4 full cells were cycled at different rates in the C/5-5C range. This cathode-limited microbattery delivered a reversible gravimetric capacity of 110 mA h g(-1) and a capacity retention of 75 % after 190 cycles at 5C.