Borohydride and halide dual-substituted lithium argyrodites.

Solid electrolyte is a crucial component of all-solid-state batteries, with sulphide solid electrolytes such as lithium argyrodite being closest to commercialization due to their high ionic conductivity and formability. In this study, borohydride/halide dual-substituted argyrodite-type electrolytes, Li7-α-ßPS6-α-ß(BH4)αXß (X = Cl, Br, I; α + ß ≤ 1.8), have been synthesized using a two-step ball-milling method without post-annealing. Among the various compositions, Li5.35PS4.35(BH4)1.15Cl0.5 exhibits the highest ionic conductivity of 16.4 mS cm-1 at 25 °C when cold-pressed, which further improves to 26.1 mS cm-1 after low temperature sintering. The enhanced conductivity can be attributed to the increased number of Li vacancies resulting from increased BH4 and halide occupancy and site disorder. Li symmetric cells with Li5.35PS4.35(BH4)1.15Cl0.5 demonstrate stable Li plating and stripping cycling for over 2,000 hours at 1 mA cm-2, along with a high critical current density of 2.1 mA cm-2. An all-solid-state battery prepared using Li5.35PS4.35(BH4)1.15Cl0.5 as the electrolyte and pure Li as the anode exhibits an initial coulombic efficiency of 86.4%. Although these electrolytes have limited thermal stability, it shows a wide compositional range while maintaining high ionic conductivity.

A Methodology for Predicting the Phase Fraction and Microhardness of Welded Joints Using Integrated Models.

Understanding the phase transformation and fraction affected by thermal changes is imperative for ensuring the safety of a welded joint. This study proposes a methodology for predicting the phase transformation and fraction of a welded joint using an integrated model. The integrated model includes a heat transfer model and procedures for predicting phase fraction and microhardness. The heat transfer model was developed to simulate the heat transfer in a welded joint and obtain the thermal cycles. The procedure consists of obtaining the peak temperature, austenite fraction, prior austenite grain size (PAGS), and t8/5 (the cooling time between 800 and 500 °C). A database was constructed based on the continuous cooling transformation (CCT) diagram using PAGS and t8/5 as the variables. The phase fraction was then predicted by considering the PAGS with t8/5 from the database. The predicted phase fraction and microhardness were in good agreement with those determined experimentally, demonstrating the reliability of the methodology. This methodology provides a more realistic understanding of phase transformation and facilitates the prediction of the phase fraction and microhardness under various welding conditions that have experimental limitations.

Molecularly Tailored Lithium-Arene Complex Enables Chemical Prelithiation of High-Capacity Lithium-Ion Battery Anodes.

Prelithiation is of great interest to Li-ion battery manufacturers as a strategy for compensating for the loss of active Li during initial cycling of a battery, which would otherwise degrade its available energy density. Solution-based chemical prelithiation using a reductive chemical promises unparalleled reaction homogeneity and simplicity. However, the chemicals applied so far cannot dope active Li in Si-based high-capacity anodes but merely form solid-electrolyte interphases, leading to only partial mitigation of the cycle irreversibility. Herein, we show that a molecularly engineered Li-arene complex with a sufficiently low redox potential drives active Li accommodation in Si-based anodes to provide an ideal Li content in a full cell. Fine control over the prelithiation degree and spatial uniformity of active Li throughout the electrodes are achieved by managing time and temperature during immersion, promising both fidelity and low cost of the process for large-scale integration.

Gaseous Nanocarving-Mediated Carbon Framework with Spontaneous Metal Assembly for Structure-Tunable Metal/Carbon Nanofibers.

Vapor phase carbon (C)-reduction-based syntheses of C nanotubes and graphene, which are highly functional solid C nanomaterials, have received extensive attention in the field of materials science. This study suggests a revolutionary method for precisely controlling the C structures by oxidizing solid C nanomaterials into gaseous products in the opposite manner of the conventional approach. This gaseous nanocarving enables the modulation of inherent metal assembly in metal/C hybrid nanomaterials because of the promoted C oxidation at the metal/C interface, which produces inner pores inside C nanomaterials. This phenomenon is revealed by investigating the aspects of structure formation with selective C oxidation in the metal/C nanofibers, and density functional theory calculation. Interestingly, the tendency of C oxidation and calculated oxygen binding energy at the metal surface plane is coincident with the order Co > Ni > Cu > Pt. The customizable control of the structural factors of metal/C nanomaterials through thermodynamic-calculation-derived processing parameters is reported for the first time in this work. This approach can open a new class of gas-solid reaction-based synthetic routes that dramatically broaden the structure-design range of metal/C hybrid nanomaterials. It represents an advancement toward overcoming the limitations of intrinsic activities in various applications.

Controlled Molybdenum Disulfide Assembly inside Carbon Nanofiber by Boudouard Reaction Inspired Selective Carbon Oxidation.

Vertical stacking and lateral growth of molybdenum disulfide (MoS2 ) are controlled with remarkable precision, and MoS2 nanotubes are directly converted from nanofibers. Predictive synthesis is enabled by identifying the specific thermodynamic region where the Boudouard reaction becomes favored. It reveals how the chemical potential of each species in the MoSCO system can predict phase behaviors.

Measurement and estimation of temperature rise in TEM sample during ion milling.

The actual temperature rise was measured during ion-milling process used in the transmission electron microscopy (TEM) sample preparation. Special probes were fabricated for the measurements, one with shielded, floating thermocouple mounted onto a 3mm grid to compute the thermal load at the sample, and the other, a bare probe with a polymer coating to measure the maximum temperature attained. The temperature measured in the most commonly used ion-milling system reached up to 295 degrees C when the typical milling conditions, 6keV ion-energy and an incident angle of 80 degrees, were used. Based on the temperature profiles that were obtained by the shielded probe, two unknown parameters, the amount of heat deposited by the energetic ions/neutrals to the sample and the thermal conductivities between the materials, were estimated and used to compute the temperature rise in commonly adopted materials. The calculation showed that the temperature of the glass sample reached more than 300 degrees C under typical ion-milling conditions. The calculated value was confirmed with the experimental result of the crystallization of an amorphous Si on the glass under the typical ion-milling condition, which gave the same extent as annealing at 350 degrees C.