Graphite anodes offer low volumetric capacity in lithium‐ion batteries. By contrast, tellurene is expected to alloy with alkali metals with high volumetric capacity (≈2620 mAh cm−3), but to date there is no detailed study on its alloying behavior. In this work, the alloying response of a range of alkali metals (A = Li, Na, or K) with few‐layer Te is investigated. In situ transmission electron microscopy and density functional theory both indicate that Te alloys with alkali metals forming A2Te. However, the crystalline order of alloyed products varies significantly from single‐crystal (for Li2Te) to polycrystalline (for Na2Te and K2Te). Typical alloying materials lose their crystallinity when reacted with Li—the ability of Te to retain its crystallinity is therefore surprising. Simulations reveal that compared to Na or K, the migration of Li is highly “isotropic” in Te, enabling its crystallinity to be preserved. Such isotropic Li transport is made possible by Te's peculiar structure comprising chiral‐chains bound by van der Waals forces. While alloying with Na and K show poor performance, with Li, Te exhibits a stable volumetric capacity of ≈700 mAh cm−3, which is about twice the practical capacity of commercial graphite.

Incorporating molecular nanolayers (MNLs) at inorganic interfaces offers promise for reaping unusual enhancements in fracture energy, thermal and electrical transport. Here, we reveal that multilayering MNL-bonded inorganic interfaces can result in viscoelastic damping bandgaps. Molecular dynamics simulations of Au/octanedithiol MNL/Au multilayers reveal high-damping-loss frequency bands at 33 ≤ ν ≤ 77 GHz and 278 ≤ ν ≤ 833 GHz separated by a low-loss bandgap 77 ≤ ν ≤ 278 GHz region. The viscoelastic bandgap scales with the Au/MNL interface bonding strength and density, and MNL coverage. These results and the analyses of interfacial vibrations indicate that the viscoelastic bandgap is an interface effect that cannot be explained by weighted averages of bulk responses. These findings prognosticate a variety of possibilities for accessing and tuning novel dynamic mechanical responses in materials systems and devices with significant inorganic–organic interface fractions for many applications, e.g., smart composites and sensors with self-healing/-destructing mechanical responses.

Graphite is ubiquitous as the anode material in lithium-ion batteries, but offers relatively low volumetric capacity (330 to 430 mAh cm-3). By contrast, Tellurene (Te) is expected to alloy with alkali metals with high volumetric capacity (~2620 mAh cm-3), but to date there is no detailed study on its alloying behavior. In this work, we have investigated the alloying response of a range of alkali metals (A = Li, Na or K) with few-layer Te. In-situ transmission electron microscopy and density functional theory both indicate that Te alloys with alkali metals forming A2Te. However, the crystalline order of alloyed products varied significantly from single-crystal (for Li2Te) to polycrystalline (for Na2Te and K2Te). It is well established that typical alloying materials (e.g., silicon, tin, black phosphorous) lose their crystallinity when reacted with Li. The ability of Te to retain its crystallinity is therefore surprising. Nudged elastic band calculations and ab-initio molecular dynamics simulations reveal that compared to Na or K, the migration of Li is highly “isotropic” in Te, enabling its crystallinity to be preserved. Such isotropic Li transport is made possible by Te’s peculiar structure comprised of chiral chains bound by van der Waals forces. To evaluate the electrochemical performance of Te, we tested Te electrodes in half-cells vs Li/Na/K metal. While alloying with Na and K showed poor performance, with Li, the Te electrode exhibited a volumetric capacity of ~700 mAh cm-3, which is about two-times the practical capacity of commercial graphite. Such Te based batteries could play an important role in applications where high volumetric energy and power density are of paramount importance.

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In article number 2003248, Nikhil Koratkar and co‐workers work to better understand the electrochemical performance of Tellurene, a process akin to climbing a mountain. While the mountaineer uses specialized equipment such as ropes, crampons and ice axes to perform the perilous ascent, the electrochemist uses a suite of advanced microscopy and spectroscopy tools including in‐situ characterization to reveal the fundamental electrochemical behavior of new materials.