This study reports a facile and reliable operando X-ray photoelectron spectroscopy (XPS) system for the characterization of the chemical state and electronic structure during Li-plating/stripping in all-solid-state batteries (ASSBs). The measurement conditions (including manufacturing an in situ sample holder) and experimental parameters have been optimized through experimentation. The proposed system accurately defines the status of every metal interlayer component during real-time battery operation (with simultaneous Li+-ion in/out migration) under a repeating Li-plating/stripping process. Moreover, it enables elucidation of ambiguous reaction mechanisms depending on the battery performance, such as the interlayer-material effect on the efficiency and reversibility of the Li-plating/stripping process, and changes in the oxygen-containing bonds due to reaction with Li. The significance of the developed system is further validated by the usefulness and reliability of the valence band structure as a criterion for the analysis of lithium-metal alloy formation and the progress of de-alloying reactions. A unique X-ray photoelectron spectroscopy (XPS) system has been built and validated to characterize the chemical state and electronic structure of the metal interlayer, a critical factor in the performance of all-solid-state batteries (ASSBs). image

Solid electrolytes are revolutionizing the field of lithium-metal batteries; however, their practical implementa-tion has been impeded by the interfacial instability between lithium metal electrodes and solid electrolytes. While various interlayers have been suggested to address this issue in recent years, long-term stability with repeated lithium deposition/ stripping has been challenging to attain. Herein, we successfully operate a high-power lithium-metal battery by inducing the preferred directional lithium growth with a rationally designed interlayer, which employs (i) crystalline-direction-controlled carbon material providing isotropic lithium transports, with (ii) prelithium deposits that guide the lithium nucleation direction toward the current collector. This combination ensures that the morphology of the interlayer is mechanically robust while regulating the preferred lithium growth underneath the interlayer without disrupting the initial interlayer/electrolyte interface, enhancing the durability of the interface. We illustrate how these material/geometric optimizations are conducted from the thermodynamic considerations, and its applicability is demonstrated for the garnet-type Li7-xLa3-aZr2-bO12 (LLZO) solid electrolytes paired with the capacity cathode. It is shown that a lithium-metal cell with the optimized amorphous carbon interlayer with prelithium deposits exhibits outstanding room-temperature cycling performance (99. 6% capacity retention after 250 cycles), delivering 4.0 mAh cm-2 at 2.5 mA cm-2 without significant degradation of the capacity. The successful long-term operation of the hybrid solid-state cell at room temperature (approximately a cumulative deliverable capacity of over 1000 mAh cm-2) is unprecedented and records the highest performance reported for lithium-metal batteries with LLZO electrolytes until date.

To achieve a high thermal conductivity, thermally conductive polymer composites have been recently exploited, focusing on connecting a 3D network of thermally conductive fillers by applying external pressure or constructing a pre-made 3D filler framework to reduce phonon scattering within the polymer matrix. However, these approaches severely restrict the use of polymers, particularly epoxy composites, in many commercial applications such as the thermal management of electronic device packaging. In this study, a high-thermal-conductivity epoxy composite is fabricated by incorporating hexagonal boron nitride (h-BN) decorated with tin nanoparticles (Sn NPs). Under a hybrid filler (Sn NPs on h-BN) loading (68 wt %), the composite exhibits a high thermal conductivity of 11.9 +/- 0.29 W m-1 K-1 while maintaining a relatively low dielectric constant (Dk - 7.52) and loss (Df - 0.023) at 1 MHz with a coefficient of thermal expansion of 34 ppm degrees C- 1. The Sn NPs on h-BN in the epoxy resin matrix are thermally percolated by the in-situ growth of Sn NPs under carefully controlled curing temperature and time, resulting in significantly improved thermal conductivity of the epoxy composite under pressure-less curing conditions.

HfO2-based ferroelectrics are highly expected to lead the new paradigm of nanoelectronic devices owing to their unexpected ability to enhance ferroelectricity in the ultimate thickness scaling limit (≤2 nm). However, an understanding of its physical origin remains uncertain because its direct microstructural and chemical characterization in such a thickness regime is extremely challenging. Herein, we solve the mystery for the continuous retention of high ferroelectricity in an ultrathin hafnium zirconium oxide (HZO) film (∼2 nm) by unveiling the evolution of microstructures and crystallographic orientations using a combination of state-of-the-art structural analysis techniques beyond analytical limits and theoretical approaches. We demonstrate that the enhancement of ferroelectricity in ultrathin HZO films originates from textured grains with a preferred orientation along an unusual out-of-plane direction of (112). In principle, (112)-oriented grains can exhibit 62% greater net polarization than the randomly oriented grains observed in thicker samples (>4 nm). Our first-principles calculations prove that the hydroxyl adsorption during the deposition process can significantly reduce the surface energy of (112)-oriented films, thereby stabilizing the high-index facet of (112). This work provides new insights into the ultimate scaling of HfO2-based ferroelectrics, which may facilitate the design of future extremely small-scale logic and memory devices.

Li7La3Zr2O12 (LLZO) is well received as a solid electrolyte for batteries. Its excellent properties render the implementation of lithium (Li) metal batteries, leading to the improvement of the performances of the batteries. However, a short-circuit failure by Li propagation through the LLZO is a crucial issue and major obstacle for Li-based batteries to overcome. Here, we investigate various growth mechanism of Li penetration through the LLZO. Because of cracks on the surface, the electric field inside the batteries becomes inhomogeneous. Li ions gather near cracks to form lithium dendrites or they also get together along the grain boundaries of LLZO to form the dendrites. Thus, some dendrites grow through grain boundaries once the cracks propagate. If electric field becomes uniform at the interfaces by surface etching or laser treatment, Li dendrite propagation on cracks and/or grain boundaries can be avoided.