Combined Effect of Halogenation and SiO2 Addition on the Li-Ion Conductivity of LiBH4

In this work, the combined effects of anion substitution (with Br− and I−) and SiO2 addition on the Li-ion conductivity in LiBH4 have been investigated. Hexagonal solid solutions with different compositions, h-Li(BH4)1−α(X)α (X = Br, I), were prepared by ball milling and fully characterized. The most conductive composition for each system was then mixed with different amounts of SiO2 nanoparticles. If the amount of added complex hydride fully fills the original pore volume of the added silica, in both LiBH4-LiBr/SiO2 and LiBH4-LiI/SiO2 systems, the Li-ion conductivity was further increased compared to the h-Li(BH4)1−α(X)α solid solutions alone. The use of LiBH4-LiX instead of LiBH4 in composites with SiO2 enabled the development of an optimal conductive pathway for the Li ions, since the h-Li(BH4)1−α(X)α possesses a higher conductivity than LiBH4. In fact, the Li conductivity of the silica containing h-Li(BH4)1−α(X)α is higher than the maximum reached in LiBH4-SiO2 alone. Therefore, a synergetic effect of combining halogenation and interface engineering is demonstrated in this work

Effects of LiBF4 Addition on the Lithium-Ion Conductivity of LiBH4

Complex hydrides, such as LiBH4, are a promising class of ion conductors for all-solid-state batteries, but their application is constrained by low ion mobility at room temperature. Mixing with halides or complex hydride anions, i.e., other complex hydrides, is an effective approach to improving the ionic conductivity. In the present study, we report on the reaction of LiBH4 with LiBF4, resulting in the formation of conductive composites consisting of LiBH4, LiF and lithium closo-borates. It is believed that the in-situ formation of closo-borate related species gives rise to highly conductive interfaces in the decomposed LiBH4 matrix. As a result, the ionic conductivity is improved by orders of magnitude with respect to the Li-ion conductivity of the LiBH4, up to 0.9 × 10−5 S cm−1 at 30◦C. The insights gained in this work show that the incorporation of a second compound is a versatile method to improve the ionic conductivity of complex metal hydrides, opening novel synthesis pathways not limited to conventional substituents

Ionic conductivity in complex metal hydride-based nanocomposite materials: The impact of nanostructuring and nanocomposite formation

Complex metal hydrides have recently gained interest as solid electrolytes for all-solid-state batteries due to their light weight, easy deformability, and fast ion mobility at elevated temperatures. However, increasing their low conductivity at room temperature is a prerequisite for application. In this review, two strategies to enhance room temperature conductivity in complex metal hydrides, nanostructuring and nanocomposite formation, are highlighted. First, the recent achievements in nanostructured complex metal hydride-based ion conductors and complex metal hydride/metal oxide nanocomposite ion conductors are summarized, and the trends and challenges in their preparation are discussed. Then, the reported all-solid-state batteries based on complex metal hydride nanocomposite electrolytes are highlighted. Finally, future research directions and perspectives are proposed, both for the preparation of improved metal hydride ion conductors, as well as metal hydride-based all-solid-state batteries

Improving the Cycle Life of Solid-State Batteries by Addition of Oxide Nanoparticles to a Complex Hydride Solid Electrolyte

We report that the addition of silica nanoparticles to the iodide-substituted LiBH4 (h-Li(BH4)0.8(I)0.2) improves the ion conductivity and, remarkably, the cycle life of the all-solid state batteries. The h-Li(BH4)0.8(I)0.2-SiO2 was synthesized by mechanochemical treatment and possesses a Li+ conductivity of 9.3 × 10-5 S cm-1 at RT. It has an electrochemical stability window of about 2.5 V vs Li+/Li and an improved stability against Li-metal, compared to h-Li(BH4)0.8(I)0.2, owing to the addition of oxide nanoparticles, which we ascribed to a greater mechanical stability of the solid-state electrolyte. The all-solid state battery Li|h-Li(BH4)0.8(I)0.2-SiO2|TiS2 demonstrated a good long-term cyclability, i.e., over 200 cycles at C/20 and even including a C-rate of C/5, demonstrating that the addition of oxide nanoparticles improves the cycling stability of the electrolyte

Designing Highly Conductive Sodium-Based Metal Hydride Nanocomposites: Interplay between Hydride and Oxide Properties

Sodium-based complex hydrides have recently gained interest as electrolytes for all-solid-state batteries due to their light weight and high electrochemical stability. Although their room temperature conductivities are not sufficiently high for battery application, nanocomposite formation with metal oxides has emerged as a promising approach to enhance the ionic conductivity of complex hydrides. This enhancement is generally attributed to the formation of a space charge layer at the hydride-oxide interface. However, in this study it is found that the conductivity enhancement results from interface reactions between the metal hydride and the oxide. Highly conductive NaBH4 and NaNH2/oxide nanocomposites are obtained by optimizing the interface reaction, which strongly depends on the interplay between the surface chemistry of the oxides and the reactivity of the metal hydrides. Notably, for NaBH4, the best performance is obtained with Al2O3, while NaNH2/SiO2 is the most conductive NaNH2/oxide nanocomposite with conductivities of, respectively, 4.7 × 10−5 and 2.1 × 10−5 S cm−1 at 80 °C. Detailed structural characterization reveals that this disparity originates from the formation of different tertiary interfacial compounds, and is not only a space charge effect. These results provide useful insights for the preparation of highly conductive nanocomposite electrolytes by optimizing interface interactions

Anomalous Impact of Mechanochemical Treatment on the Na-ion Conductivity of Sodium Closo-Carbadodecaborate Probed by X-Ray Raman Scattering Spectroscopy

Solid-state sodium ion conductors are crucial for the next generation of all-solid-state sodium batteries with high capacity, low cost, and improved safety. Sodium closo-carbadodecaborate (NaCB11H12) is an attractive Na-ion conductor owing to its high thermal, electrochemical, and interfacial stability. Mechanical milling has recently been shown to increase conductivity by five orders of magnitude at room temperature, making it appealing for application in all-solid-state sodium batteries. Intriguingly, milling longer than 2 h led to a significant decrease in conductivity. In this study, X-ray Raman scattering (XRS) spectroscopy is used to probe the origin of the anomalous impact of mechanical treatment on the ionic conductivity of NaCB11H12. The B, C, and Na K-edge XRS spectra are successfully measured for the first time, and ab initio calculations are employed to interpret the results. The experimental and computational results reveal that the decrease in ionic conductivity upon prolonged milling is due to the increased proximity of Na to the CB11H12 cage, caused by severe distortion of the long-range structure. Overall, this work demonstrates how the XRS technique, allowing investigation of low Z elements such as C and B in the bulk, can be used to acquire valuable information on the electronic structure of solid electrolytes and battery materials in general

Deciphering the Origin of Interface-Induced High Li and Na Ion Conductivity in Nanocomposite Solid Electrolytes Using X-Ray Raman Spectroscopy

Solid-state electrolytes (SSEs) with high ionic conductivities are crucial for safer and high-capacity batteries. Interface effects in nanocomposites of SSEs and insulators can lead to profound increases in conductivity. Understanding the composition of the interface is crucial for tuning the conductivity of composite solid electrolytes. Herein, X-ray Raman Scattering (XRS) spectroscopy is used for the first time to unravel the nature of the interface effects responsible for conductivity enhancements in nanocomposites of complex hydride-based electrolytes (LiBH4, NaBH4, and NaNH2) and oxides. XRS probe of the Li, Na, and B local environments reveals that the interface consists of highly distorted/defected and structurally distinct phase(s) compared to the original compounds. Interestingly, nanocomposites with higher concentrations of the interface compounds exhibit higher conductivities. Clear differences are observed in the interface composition of SiO2- and Al2O3-based nanocomposites, attributed to differences in the reactivity of their surface groups. These results demonstrate that interfacial reactions play a dominant role in conductivity enhancement in composite solid electrolytes. This work showcases the potential of XRS in investigating interface interactions, providing valuable insights into the often complex ion conductor/insulator interfaces, especially for systems containing light elements such as Li, B, and Na present in most SSEs and batteries

Characterizing light-dark cycles in the Neonatal Intensive Care Unit: a retrospective observational study

Objectives: To characterize bedside 24-h patterns in light exposure in the Neonatal Intensive Care Unit (NICU) and to explore the environmental and individual patient characteristics that influence these patterns in this clinical setting.Methods: We conducted a retrospective cohort study that included 79 very preterm infants who stayed in an incubator with a built-in light sensor. Bedside light exposure was measured continuously (one value per minute). Based on these data, various metrics (including relative amplitude, intradaily variability, and interdaily stability) were calculated to characterize the 24-h patterns of light exposure. Next, we determined the association between these metrics and various environmental and individual patient characteristics.Results: A 24-h light-dark cycle was apparent in the NICU with significant differences in light exposure between the three nurse shifts (p < 0.001), with the highest values in the morning and the lowest values at night. Light exposure was generally low, with illuminances rarely surpassing 75 lux, and highly variable between patients and across days within a single patient. Furthermore, the season of birth and phototherapy had a significant effect on 24-h light-dark cycles, whereas no effect of bed location and illness severity were observed.Conclusion: Even without an official lighting regime set, a 24-h light-dark cycle was observed in the NICU. Various rhythmicity metrics can be used to characterize 24-h light-dark cycles in a clinical setting and to study the relationship between light patterns and health outcomes

Characterizing light-dark cycles in the Neonatal Intensive Care Unit: a retrospective observational study

Objectives: To characterize bedside 24-h patterns in light exposure in the Neonatal Intensive Care Unit (NICU) and to explore the environmental and individual patient characteristics that influence these patterns in this clinical setting. Methods: We conducted a retrospective cohort study that included 79 very preterm infants who stayed in an incubator with a built-in light sensor. Bedside light exposure was measured continuously (one value per minute). Based on these data, various metrics (including relative amplitude, intradaily variability, and interdaily stability) were calculated to characterize the 24-h patterns of light exposure. Next, we determined the association between these metrics and various environmental and individual patient characteristics. Results: A 24-h light-dark cycle was apparent in the NICU with significant differences in light exposure between the three nurse shifts ( p < 0.001), with the highest values in the morning and the lowest values at night. Light exposure was generally low, with illuminances rarely surpassing 75 lux, and highly variable between patients and across days within a single patient. Furthermore, the season of birth and phototherapy had a significant effect on 24-h light-dark cycles, whereas no effect of bed location and illness severity were observed. Conclusion: Even without an official lighting regime set, a 24-h light-dark cycle was observed in the NICU. Various rhythmicity metrics can be used to characterize 24-h light-dark cycles in a clinical setting and to study the relationship between light patterns and health outcomes

Metallic and complex hydride-based electrochemical storage of energy

The development of efficient storage systems is one of the keys to the success of the energy transition. There are many ways to store energy, but among them, electrochemical storage is particularly valuable because it can store electrons produced by renewable energies with a very good efficiency. However, the solutions currently available on the market remain unsuitable in terms of storage capacity, recharging kinetics, durability, and cost. Technological breakthroughs are therefore expected to meet the growing need for energy storage. Within the framework of the Hydrogen Technology Collaboration Program—H2TCP Task-40, IEA\u27s expert researchers have developed innovative materials based on hydrides (metallic or complex) offering new solutions in the field of solid electrolytes and anodes for alkaline and ionic batteries. This review presents the state of the art of research in this field, from the most fundamental aspects to the applications in battery prototypes