Structure, Composition, Transport Properties, and Electrochemical Performance of the Electrode‐Electrolyte Interphase in Non‐Aqueous Na‐Ion Batteries

Rechargeable Li-ion battery technology has progressed due to the development of a suitable combination of electroactive materials, binders, electrolytes, additives, and electrochemical cycling protocols that resulted in the formation of a stable electrode-electrolyte interphase. It is expected that Na-ion technology will attain a position comparable to Li-ion batteries dependent on advancements in establishing a stable electrode-electrolyte interphase. However, Li and Na are both alkali metals with similar characteristics, yet the physicochemical properties of these systems differ. For this reason, a detailed study on the electrode-electrolyte interphase properties, composition, and structure is required to understand the factors that influence the battery\u27s behavior. Herein, the research that has been performed on the electrode-electrolyte interphase for both anode and cathode in the most important families of electrode materials, including carbonate ester-based and advanced electrolytes such as ether-based carbonates and ionic liquids is presented

Influence of the Current Density on the Interfacial Reactivity of Layered Oxide Cathodes for Sodium‐Ion Batteries

The full commercialization of sodium-ion batteries (SIBs) is still hindered by their lower electrochemical performance and higher cost ($ W-1 h(-1)) with respect to lithium-ion batteries. Understanding the electrode-electrolyte interphase formation in both electrodes (anode and cathode) is crucial to increase the cell performance and, ultimately, reduce the cost. Herein, a step forward regarding the study of the cathode-electrolyte interphase (CEI) by means of X-ray photoelectron spectroscopy (XPS) has been carried out by correlating the formation of the CEI on the P2-Na0.67Mn0.8Ti0.2O2 layered oxide cathode with the cycling rate. The results reveal that the applied current density affects the concentration of the formed interphase species, as well as the thickness of CEI, but not its chemistry, indicating that the electrode-electrolyte interfacial reactivity is mainly driven by thermodynamic factors.The authors would like to thank B. Acebedo for her support with materials synthesis, characterization, and testing, and E. Gonzalo for the fruitful discussions. M.Z. thanks the Basque Government for her Post-doc fellowship (POS_2017_1_0006). HIU authors (M.Z and S.P.) acknowledge the Helmholtz Association Basic funding. Open Access Funding provided by Universita degli Studi di Camerino within the CRUI-CARE Agreement

Influence of Using Metallic Na on the Interfacial and Transport Properties of Na-Ion Batteries

Na2Ti3O7 is a promising negative electrode for rechargeable Na-ion batteries; however, its good properties in terms of insertion voltage and specific capacity are hampered by the poor capacity retention reported in the past. The interfacial and ionic/electronic properties are key factors to understanding the electrochemical performance of Na2Ti3O7. Therefore, its study is of utmost importance. In addition, although rather unexplored, the use of metallic Na in half-cell studies is another important issue due to the fact that side-reactions will be induced when metallic Na is in contact with the electrolyte. Hence, in this work the interfacial and transport properties of full Na-ion cells have been investigated and compared with half-cells upon electrochemical cycling by means of X-ray photoelectron spectroscopy (conventional XPS and Auger parameter analysis) and electrochemical impedance spectroscopy. The half-cell has been assembled with C-coated Na2Ti3O7 against metallic Na whilst the full-cell uses C-coated Na2Ti3O7 as negative electrode and NaFePO4 as positive electrode, delivering 112 Wh/kganode+cathode in the 2nd cycle. When comparing both types of cells, it has been found that the interfacial properties, the OCV (open circuit voltage) and the electrode—electrolyte interphase behavior are more stable in the full-cell than in the half-cell. The electronic transition from insulator to conductor previously observed in a half-cell for Na2Ti3O7 has also been detected in the full-cell impedance analysis

Work Function Evolution in Li Anode Processing

Toward improved understanding and control of the interactions of Li metal anodes with their processing environments, a combined X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and density functional theory (DFT) characterization of the effects that O-2, CO2, and N-2, the main gases in dry-atmosphere battery production lines, induced on a reproducibly clean Li surface at room temperature is presented here. XPS measurements demonstrate that O-2 is ten times more effective than CO2 at oxidizing metal Li. Notably, pure N-2 is shown to not dissociate on clean metal Li. UPS results indicate that decomposition of O-2 (CO2) reduces the work function of the Li surface by almost 1 eV, therefore increasing the reduction energy drive for the treated substrate by comparison to bare metallic Li. DFT simulations semiquantitatively account for these results on the basis of the effects of dissociative gas adsorption on the surface dipole density of the Li surface

Role of the voltage window on the capacity retention of P2-Na2_{2}/3_{3}[Fe1_{1}/2_{2}Mn1_{1}/2_{2}]O2_{2} cathode material for rechargeable sodium-ion batteries

P2-Na$_{2}$/$_{3}$[Fe$_{1}$/$_{2}$Mn$_{1}$/$_{2}$]O$_{2}$ layered oxide is a promising high energy density cathode material for sodium-ion batteries. However, one of its drawbacks is the poor long-term stability in the operating voltage window of 1.5–4.25 V vs Na$^{+}$/Na that prevents its commercialization. In this work, additional light is shed on the origin of capacity fading, which has been analyzed using a combination of experimental techniques and theoretical methods. Electrochemical impedance spectroscopy has been performed on P2-Na$_{2}$/$_{3}$[Fe$_{1}$/$_{2}$Mn$_{1}$/$_{2}$]O$_{2}$ half-cells operating in two different working voltage windows, one allowing and one preventing the high voltage phase transition occurring in P2-Na$_{2}$/$_{3}$[Fe$_{1}$/$_{2}$Mn$_{1}$/$_{2}$]O$_{2}$ above 4.0 V vs Na+/Na; so as to unveil the transport properties at different states of charge and correlate them with the existing phases in P2-Na$_{2}$/$_{3}$[Fe$_{1}$/$_{2}$Mn$_{1}$/$_{2}$]O$_{2}$. Supporting X-ray photoelectron spectroscopy experiments to elucidate the surface properties along with theoretical calculations have concluded that the formed electrode-electrolyte interphase is very thin and stable, mainly composed by inorganic species, and reveal that the structural phase transition at high voltage from P2- to “Z”/OP4-oxygen stacking is associated with a drastic increased in the bulk electronic resistance of P2-Na$_{2}$/$_{3}$[Fe$_{1}$/$_{2}$Mn$_{1}$/$_{2}$]O$_{2}$ electrodes which is one of the causes of the observed capacity fading

Evolution of the microstructure, chemical composition and magnetic behaviour during the synthesis of alkanethiol-capped gold nanoparticles

In the present paper, we show an exhaustive microstructural characterization of thiol-capped gold nanoparticles (NPs) with two different average particle sizes. These samples are compared with the polymer-like Au(I) phase formed as a precursor during the synthesis of the thiol-capped gold NPs. The set of analysed samples shows different microstructures at the nanoscale with different proportions of Au atoms bonded either to S or to Au atoms. It has been experimentally shown that the presence of a ferromagnetic-like behaviour is associated to the formation of NPs with simultaneous presence of Au–Au and Au–S bonds. In order to explain such magnetic behaviour a possible model is proposed based on the spin–orbit coupling so that localized charges and/or spins (Au–S bonds) can trap conduction electrons (Au–Au bonds) in orbits.XAS facilities at BM29 in ESRF and the technical support from G.L. Ciatto are acknowledged. Financial support from the Spanish MEC (NAN2004-09125-C07) and “Junta de Andalucía” is also acknowledged. E. Guerrero thanks the Spanish MEC for financial support.Peer reviewe

Thickening of the pituitary stalk in children and adolescents with central diabetes insipidus: Causes and consequences

Background: Central diabetes insipidus (CDI) is a rare disorder in children. The aetiology of CDI in childhood is heterogeneous. The aim of this study is to illustrate the importance of a careful clinical and neuro-radiological follow-up of the pituitary and hypothalamus region in order to identify the aetiology and the development of associated hormonal deficiencies. Methods: Clinical and auxological variables of 15 children diagnosed with CDI were retrospectively analysed in a paediatric hospital. Evaluations of adenohypophyseal function and cranial MRI were performed periodically. Results: The mean age at diagnosis of CDI was 9.6 years (range: 1.32-15.9). The aetiological diagnosis could be established initially in 9 of the 15 patients, as 7 with a germinoma and 2 with a histiocytosis. After a mean follow-up of 5.5 years (range: 1.6-11.8), the number of idiopathic cases was reduced by half. At the end of the follow-up, the aetiological diagnoses were: 9 germinoma (60%), 3 histiocytosis (20%), and 3 idiopathic CDI (20%). There is a statistically significant association between stalk thickening and tumour aetiology. At least one adenohypophyseal hormonal deficiency was found in 67% of cases, with the majority developing in the first two years of follow-up. Growth hormone deficiency (60%) was the most prevalent. Conclusion: The follow-up of CDI should include hormone evaluation with special attention, due to its frequency, to GH deficiency. In addition, a biannual MRI in an idiopathic CDI should be performed, at least during the first 2-3 years after diagnosis, as 50% of them were diagnosed with a germinoma or histiocytosis during this period.Introducción: La diabetes insípida central (DIC) es una entidad poco frecuente en la edad pediátrica, siendo su etiología heterogénea. El objetivo de nuestro trabajo es demostrar que el seguimiento clínico y neurorradiológico de la región hipotálamo-hipofisaria, puede ayudar a establecer el diagnóstico etiológico de DIC y la presencia de otros déficits hormonales. Métodos: Se revisaron de forma retrospectiva 15 pacientes diagnosticados de DIC en un hospital pediátrico. Se analizaron las características clínicas y auxológicas; así como la valoración de la función adenohipofisaria junto con RM craneal de manera periódica. Resultados: La mediana de edad al diagnóstico fue de 9,6 a˜nos (rango: 1,3-15,9). El diagnóstico etiológico pudo establecerse en 9 de los 15 pacientes (germinomas: 7 e histiocitosis: 2). Tras una mediana de seguimiento de 5,5 a˜nos (rango: 1,6-11,8), los casos idiopáticos se redujeron a la mitad. Finalmente, los diagnósticos etiológicos fueron: germinoma 9 (60%), histiocitosis 3 (20%) y DIC idiopática 3 (20%). Existe una asociación estadísticamente significativa entre el engrosamiento del tallo y la etiología tumoral. El 67% desarrolló, al menos, una deficiencia hormonal adenohipofisaria, la mayoría en los dos primeros a˜nos de seguimiento. El déficit más prevalente fue el de hormona de crecimiento (60%). Conclusiones: En todos los pacientes con DIC se deberá realizar un control auxológico y hormonal, con especial atención, por su frecuencia, a la deficiencia de GH, y en aquellos con DIC idiopática se debería incluir una RM semestral, al menos durante los 2-3 primeros a˜nos después del diagnóstico, pues en nuestro estudio el 50% fueron diagnosticados de germinomas o histiocitosis en este period

Monolithic All-Solid-State High-Voltage Li-Metal Thin-Film Rechargeable Battery

The substitution of an organic liquid electrolyte with lithium-conducting solid materials is a promising approach to overcome the limitations associated with conventional lithium-ion batteries. These constraints include a reduced electrochemical stability window, high toxicity, flammability, and the formation of lithium dendrites. In this way, all-solid-state batteries present themselves as ideal candidates for improving energy density, environmental friendliness, and safety. In particular, all-solid-state configurations allow the introduction of compact, lightweight, high-energy-density batteries, suitable for low-power applications, known as thin-film batteries. Moreover, solid electrolytes typically offer wide electrochemical stability windows, enabling the integration of high-voltage cathodes and permitting the fabrication of higher-energy-density batteries. A high-voltage, all-solid-state lithium-ion thin-film battery composed of LiNi0.5Mn1.5O4 cathode, a LiPON solid electrolyte, and a lithium metal anode has been deposited layer by layer on low-cost stainless-steel current collector substrates. The structural and electrochemical properties of each electroactive component of the battery had been analyzed separately prior to the full cell implementation. In addition to a study of the internal solid–solid interface, comparing them was done with two similar cells assembled using conventional lithium foil, one with thin-film solid electrolyte and another one with thin-film solid electrolyte plus a droplet of LP30 liquid electrolyte. The thin-film all-solid state cell developed in this work delivered 80.5 mAh g–1 in the first cycle at C/20 and after a C-rate test of 25 cycles at C/10, C/5, C/2, and 1C and stabilized its capacity at around 70 mAh g–1 for another 12 cycles prior to the start of its degradation. This cell reached gravimetric and volumetric energy densities of 333 Wh kg–1 and 1,212 Wh l–1, respectively. Overall, this cell showed a better performance than its counterparts assembled with Li foil, highlighting the importance of the battery interface control.The authors acknowledge the financial support from European H2020 project MONBASA (Monolithic Batteries for Spaceship Applications, grant no. 687561) and Basque Government through Elkartek 2017 program with the project Elkartek CICe2017-L4