Wideband Absorbers in the Visible with Ultrathin Plasmonic-Phase Change Material Nanogratings

The narrowband surface plasmon resonance of metallic nanostructures was once thought to limit the bandwidth of absorptance, yet recent demonstrations show that it can be harnessed using mechanisms such as multiple resonances, impedance matching, and slow-light modes to create broadband absorptance. However, in the visible spectrum, realization of absorbers based on patterned plasmonic nanostructures is challenging due to strict fabrication tolerances. Here we experimentally compare two different candidates for visible light broadband high absorptance. The first candidate is planar thin film dual layers of Ge₂Sb₂Te₅ and aluminum (Al), while the second structure employs ultrathin Al grating/Ge₂Sb₂Te₅ dual layers. In both cases, the absorbers yield a measured absorptance greater than 78% in the visible. A remarkably high-absorptance bandwidth of 120 nm was measured and associated with the large imaginary part of Ge₂Sb₂Te₅ dielectric function. We find that the simple dual-layer planar structure is an effective absorber in the near-infrared, but its absorptance is less effective in the visible. However, for visible wavelengths the grating structure can blue-shift the absorptance peak to 422 nm. The simple geometries of the plasmonic absorbers facilitate fabrication over large areas. It has practical applications in light harvesting, sensing, and high-resolution color printing

Monodispersed Sulfur Nanoparticles for Lithium–Sulfur Batteries with Theoretical Performance

While Li–S batteries are poised to be the next generation high-density energy storage devices, low sulfur utilization and slow rate performance have limited their practical applications. Here, we report the synthesis of monodispersed S₈ nanoparticles (NPs) with different diameter and the nanosize dependent kinetic characteristics of the corresponding Li–S batteries. Most remarkably, 5 nm S NPs display the theoretical discharging/charging capacity of 1672 mAh g^–1 at 0.1 C rate and a discharge capacity of 1089 mAh g^–1 at 4 C

Influences of Additives on the Formation of a Solid Electrolyte Interphase on MnO Electrode Studied by Atomic Force Microscopy and Force Spectroscopy

The solid electrolyte interphase (SEI) that forms on electrodes largely defines the performances of lithium ion batteries (LIBs), such as cycling performance, shelf life, and safety. Additives in the electrolyte can modify the properties of the SEI and thus efficiently improve the performances of LIBs. However, the effects of additives on the mechanical properties, structure, and stability of the SEI have rarely been studied directly. In this paper, we report the influence of vinylene carbonate (VC) and lithium bis­(oxalate)­borate (LiBOB) additives on the mechanical properties of SEI films formed on MnO electrodes using atomic force microscopy (AFM) and force spectroscopy. The results show that the SEI formed from VC additive is thick and soft and partially decomposes upon charging. LiBOB forms thin, stiff, and electrochemically stable SEI films, but the stiff SEI may not be favorable for adapting the volume change of the electrodes. The VC and LiBOB mixed additive combines the advantages of the two components and produces stable SEI with moderate thickness and stiffness. This work also demonstrates that the AFM–force spectroscopy method is effective in investigating the structure and mechanical properties of SEI films