Atomic Interdiffusion and Diffusive Stabilization of Cobalt by Copper During Atomic Layer Deposition from Bis(<i>N</i>-<i>tert</i>-butyl‑<i>N</i>′‑ethylpropionamidinato) Cobalt(II)

Electromigration of copper in integrated circuits leads to device failure. Potential solutions involve capping the copper with ultrathin cobalt films. We report the properties of cobalt films after deposition on polycrystalline Cu at 265 °C by atomic layer deposition from H₂ and bis­(<i>N</i>-<i>tert</i>-butyl-<i>N</i>′-ethylpropionamidinato) cobalt­(II) (CoAMD). We find intermixing of Co and Cu producing a transition layer on the Cu nearly as thick as the Co-rich overlayer. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry depth profiling reveal that a finite amount of Cu continuously segregates to the progressing Co surface, minimizing the free surface energy, throughout deposition up to at least 16 nm. The Cu-stabilized Co film initially follows 2D growth and strain-relieving 3D crystal formation is apparent beyond 2 nm of film growth. Depth profiling indicates that Cu likely diffuses within the Co film and along the polycrystalline Co grain boundaries

High-Stability Lithium Metal Batteries Enabled by a Tetrahydrofuran-Based Electrolyte Mixture

There has been significant interest from academic and industrial sectors to use lithium metal anodes in energy storage devices due to their much higher energy density (3860 mAh/g) compared with their conventional, graphite-based counterparts. However, the safety and inefficiency concerns arising from lithium dendrite formation on these anodes during operation have prohibited their widespread adoption. This study focuses on reducing the dendritic tendencies of lithium anodes by forming a LiF-rich surface layer in situ on the lithium metal, designed specifically to facilitate uniform lithium diffusion and nucleation. The LiF-rich solid electrolyte interphase (SEI) results from the employment of a tetrahydrofuran-based electrolyte mixture (1.0 M LiFSI-THFMix). Li||Li symmetric cells with this type of electrolyte show remarkable performance, cycling stably for over 1700+ h at a current density of 0.5 mA cm–2. To elucidate the influence of the electrolyte on the resulting chemical composition of the SEI, a combination of time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) was applied. Through the systematic analysis of the electrolyte’s ionic properties, the resulting SEIs’ chemical properties, and their combinative electrochemical properties, this study aims to demonstrate the merit of tetrahydrofuran-based electrolytes for lithium metal batteries

Interfacial Chemistry in Solid-State Batteries: Formation of Interphase and Its Consequences

Benefiting from extremely high shear modulus and high ionic transference number, solid electrolytes are promising candidates to address both the dendrite-growth and electrolyte-consumption problems inherent to the widely adopted liquid-phase electrolyte batteries. However, solid electrolyte/electrode interfaces present high resistance and complicated morphology, hampering the development of solid-state battery systems, while requiring advanced analysis for rational improvement. Here, we employ an ultrasensitive three-dimensional (3D) chemical analysis to uncover the dynamic formation of interphases at the solid electrolyte/electrode interface. While the formation of interphases widens the electrochemical window, their electronic and ionic conductivities determine the electrochemical performance and have a large influence on dendrite growth. Our results suggest that, contrary to the general understanding, highly stable solid electrolytes with metal anodes in fact promote fast dendritic formation, as a result of less Li consumption and much larger curvature of dendrite tips that leads to an enhanced electric driving force. Detailed thermodynamic analysis shows an interphase with low electronic conductivity, high ionic conductivity, and chemical stability, yet having a dynamic thickness and uniform coverage is needed to prevent dendrite growth. This work provides a paradigm for interphase design to address the dendrite challenge, paving the way for the development of robust, fully operational solid-state batteries

Alloying Indium Additive Enables Fast-Charging Lithium Metal Batteries

Energy-dense lithium metal batteries (LMBs) are limited by safety risks and electrode degradation from dendritic lithium plating. To reap the benefits of lithium metal’s high theoretical capacity (3780 mAh g–1), forming an ionically conductive and electronically insulating protective layer that prevents dendritic lithium plating is crucial. Here, we investigate the synergistic combination of a Li–In alloy and a nitrate-derived protective layer resulting from an In(NO3)3 electrolyte additive. The protective layer was chemically characterized with time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS), revealing the composition of the mechanically stable and ionically conductive Li–In alloy, LiNxOy, Li2O, and Li3N. Protected Li||Li cells exhibit dendrite-free cycling at 2 mA cm–2 for 495 cycles and 10 mA cm–2 for 175 cycles. Li||LiFePO4 (LFP) cells retain a stable capacity of ∼130 mAh g–1 at C/2 for 250 cycles while achieving an average Coulombic efficiency of >99.97%

Probing the Degradation Chemistry and Enhanced Stability of 2D Organolead Halide Perovskites

Recent work on quasi-2D Ruddlesden–Popper phase organolead halide perovskites has shown that they possess many interesting optical and physical properties. Most notably, they are significantly more stable when exposed to moisture when compared to the typical 3D perovskite methylammonium lead iodide (MAPI); direct evidence for the chemical source of this stability remains elusive, however. Here, we present a detailed study of the superior moisture stability of a quasi-2D Ruddlesden–Popper perovskite, n-butylammonium methylammonium lead iodide (nBA-MAPI), compared to that of MAPI, and examine a simple, yet efficient, methodology to improve the stability of MAPI devices through the application of a thin layer of nBA-MAPI to the surface. By employing a variety of analytical techniques (photoluminescence, time-of-flight secondary ion mass spectrometry, cyclic voltammetry, X-ray diffraction) we determine that the improved stability of Ruddlesden–Popper perovskites is a consequence of a unique degradation pathway which produces a passivating surface layer, composed of increasingly stable phases of the 2D perovskite, via disproportionation. Our work establishes that this protective material isolates the bulk of the perovskite from a newly identified hydration layer which is found to accumulate at the C60/perovskite interface of full devices, slowing further hydrolysis reactions that would damage the device. As MAPI devices degrade quickly without any protection, a surface treatment of nBA-MAPI is an efficient way to delay device deterioration by creating an artificial 2D surface layer that similarly inhibits interaction with the hydration layer

p‑Si/W₂C and p‑Si/W₂C/Pt Photocathodes for the Hydrogen Evolution Reaction

p-Si/W2C photocathodes are synthesized by evaporating tungsten metal in an ambient of ethylene gas to form tungsten semicarbide (W2C) thin films on top of p-type silicon (p-Si) substrates. As deposited the thin films contain crystalline W2C with a bulk W:C atomic ratio of approximately 2:1. The W2C films demonstrate catalytic activity for the hydrogen evolution reaction (HER), and p-Si/W2C photocathodes produce cathodic photocurrent at potentials more positive than 0.0 V vs RHE while bare p-Si photocathodes do not. The W2C films are an effective support for Pt nanoparticles allowing for a considerable reduction in Pt loading. p-Si/W2C/Pt photocathodes with Pt nanoparticles achieve photocurrent onset potentials and limiting photocurrent densities that are comparable to p-Si/Pt photocathodes with Pt loading nine times higher. This makes W2C an earth abundant alternative to pure Pt for use as an electrocatalyst on photocathodes for the HER

Character descriptions

Descriptions of characters from the phylogenetic analysi