The large interfacial resistance between electrolyte and electrodes poses a significant roadblock for the application of all‐solid‐state batteries. The formation of interfacial phases (interphases) has been identified as one of the most significant sources for such high resistance. Therefore, studying the mechanism of interphase formation, along with investigating its effect on ionic conductivity, could lead to the discovery of avenues towards designing high‐performance all‐solid‐state batteries. In this work, we studied the interphase formation in the perovskite electrolyte Li0.33La0.57TiO3 (LLTO) and spinel cathode LiMn2O4 (LMO) pair by co‐sintering experiments via spark plasma sintering (SPS), as well as conventional sintering. Although the processing method has an influence on the electrode/electrolyte contact, the formation of an interphase could not be avoided. At the LLTO/ LMO interface, we observed both an interphase formed by interdiffusion, as well as a complexion‐like amorphous layer. We directly characterized the complexion layer morphology by using HRTEM. Analytical TEM and SEM were used to reveal the elemental composition of the interphase and the interdiffusion layer. Furthermore, we used impedance spectroscopy to measure the electrical properties of the LLTO/LMO interphase and identified the interfacial resistance from the interdiffusion induced interphase to be larger than the individual phases by a factor of 40, whereas the amorphous layer was not visible in the impedance.
Recently, nonvolatile resistive switching memory effects have been actively studied in two-dimensional (2D) transition metal dichalcogenides and boron nitrides to advance future memory and neuromorphic computing applications. Here, we report on radiofrequency (RF) switches utilizing hexagonal boron nitride (h-BN) memristors that afford operation in the millimeter-wave (mmWave) range. Notably, silver (Ag) electrodes to h-BN offer outstanding nonvolatile bipolar resistive switching characteristics with a high ON/OFF switching ratio of 1011 and low switching voltage below 0.34 V. In addition, the switch exhibits a low insertion loss of 0.50 dB and high isolation of 23 dB across the D-band spectrum (110 to 170 GHz). Furthermore, the S 21 insertion loss can be tuned through five orders of current compliance magnitude, which increases the application prospects for atomic switches. These results can enable the switch to become a key component for future reconfigurable wireless and 6G communication systems.
The discovery of ferroelectric doped HfO 2 enabled the emergence of scalable and CMOS-compatible ferroelectric field-effect transistor (FeFET) technology which has the potential to meet the growing need for fast, low-power, low-cost, and high-density nonvolatile memory, and neuromorphic devices. Although HfO 2 FeFETs have been widely studied in the past few years, their fundamental switching speed is yet to be explored. Importantly, the shortest polarization time demonstrated to date in HfO 2 -based FeFET was ∼10 ns. Here, we report that a single subnanosecond pulse can fully switch HfO 2based FeFET. We also study the polarization switching kinetics across 11 orders of magnitude in time (300 ps to 8 s) and find a remarkably steep time-voltage relation, which is captured by the classical nucleation theory across this wide range of pulse widths. These results demonstrate the high-speed capabilities of FeFETs and help better understand their fundamental polarization switching speed limits and switching kinetics.
In this study, fabrication processes of solid electrolyte/cathode interfaces for their use in next‐generation all‐solid‐state lithium‐ion battery (LIB) applications are described. Standard lithium–aluminum–titanium–phosphate (LATP) solid electrolyte and lithium–manganese oxide (LMO) spinel cathode ceramic half cells are assembled using two all‐solid‐state methods: a) co‐sintering the cathode and electrolyte materials via field‐assisted sintering and b) field‐assisted high‐temperature bonding. The morphology and composition of the interfaces are analyzed by scanning electron microscopy (SEM) and energy‐dispersive X‐ray spectroscopy (EDS). This study reveals that the formation of interphases can be significantly decreased by separately performing the densification and joining procedures. Electrochemical impedance spectroscopy (EIS) is applied to understand and determine the effect of the manufactured interfaces on the system conductivity. Based on the results, it is concluded that the high‐temperature bonding technique appears to be a suitable technique for future production of all‐solid‐state LIBs.
We report the thermal conductivity of amorphous, cubic, and hexagonal Ge2Sb2Te5 using time-domain thermoreflectance from 80 to 500 K. The measured thermal conductivities are 0.20 W m−1 K−1 for amorphous Ge2Sb2Te5, 0.63 W m−1 K−1 for the cubic phase, and 1.45 W m−1 K−1 for the hexagonal phase at room temperature. For amorphous Ge2Sb2Te5, the thermal conductivity increases monotonically with temperature when T < 300 K, showing a typical glass-like temperature dependence, and increases dramatically after heating up to 435 K due to partial crystallization to the cubic phase. For hexagonal Ge2Sb2Te5, electronic contribution to thermal conductivity is significant. The lattice thermal conductivity of the hexagonal phase shows a relatively low value of 0.47 W m−1 K−1 at room temperature and has a temperature dependence of T−1 when T > 100 K, suggesting that phonon–phonon scattering dominates its lattice thermal conductivity. Although cubic Ge2Sb2Te5 has a similar grain size to hexagonal Ge2Sb2Te5, its thermal conductivity shows a glass-like trend like that of the amorphous phase, indicating a high concentration of vacancies that strongly scatter heat-carrying phonons. These thermal transport mechanisms of Ge2Sb2Te5 polymorphs help improve the thermal design of phase change memory devices for more energy-efficient non-volatile memory.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.