The altering of electronic states of metal oxides offers a promising opportunity to realize high‐efficiency surface catalysis, which play a key role in regulating polysulfides (PS) redox in lithium–sulfur (Li–S) batteries. However, little effort has been devoted to understanding the relationship between the electronic state of metal oxides and a catalyst's properties in Li–S cells. Herein, defect‐rich heterojunction electrocatalysts composed of ultrathin TiO2‐x nanosheets and carbon nanotubes (CNTs) for Li–S batteries are reported. Theoretical simulations indicate that oxygen vacancies and heterojunction can enhance electronic conductivity and chemical adsorption. Spectroscopy and electrochemical techniques further indicate that the rich surface vacancies in TiO2‐x nanosheets result in highly activated trapping sites for LiPS and lower energy barriers for fast Li ion mobility. Meanwhile, the redistribution of electrons at the heterojunction interfaces realizes accelerated surface electron exchange. Coupled with a polyacrylate terpolymer (LA132) binder, the CNT@TiO2‐x–S electrodes exhibit a long cycle life of more than 300 cycles at 1 C and a high area capacity of 5.4 mAh cm−2. This work offers a new perspective on understanding catalyst design in energy storage devices through band engineering.

A host of new low-frequency radio telescopes seek to measure the 21-cm transition of neutral hydrogen from the early universe. These telescopes have the potential to directly probe star and galaxy formation at redshifts 20 z 7, but are limited by the dynamic range they can achieve against foreground sources of low-frequency radio emission. Consequently, there is a growing demand for modern, high-fidelity maps of the sky at frequencies below 200 MHz for use in foreground modeling and removal. We describe a new widefield imaging technique for drift-scanning interferometers, Tikhonov-regularized m-mode analysis imaging. This technique constructs images of the entire sky in a single synthesis imaging step with exact treatment of widefield effects. We describe how the CLEAN algorithm can be adapted to deconvolve maps generated by m-mode analysis imaging. We demonstrate Tikhonov-regularized m-mode analysis imaging using the Owens Valley Long Wavelength Array (OVRO-LWA) by generating 8 new maps of the sky north of δ = −30 • with 15 arcmin angular resolution, at frequencies evenly spaced between 36.528 MHz and 73.152 MHz, and ∼800 mJy/beam thermal noise. These maps are a 10-fold improvement in angular resolution over existing full-sky maps at comparable frequencies, which have angular resolutions ≥ 2 • . Each map is constructed exclusively from interferometric observations and does not represent the globally averaged sky brightness. Future improvements will incorporate total power radiometry, improved thermal noise, and improved angular resolution -due to the planned expansion of the OVRO-LWA to 2.6 km baselines. These maps serve as a first step on the path to the use of more sophisticated foreground filters in 21-cm cosmology incorporating the measured angular and frequency structure of all foreground contaminants.

Construction of ultrafine ZnSe nanoparticles on/in amorphous carbon hollow nanospheres with high-power-density sodium storage, Nano Energy (2019), doi:

Lithium–sulfur batteries are currently being explored as promising advanced energy storage systems due to the high theoretical specific capacity of sulfur. However, achieving a scalable synthesis for the sulfur electrode material whilst maintaining a high volumetric energy density remains a serious challenge. Here, a continuous ball‐milling route is devised for synthesizing multifunctional FeS 2 /FeS/S composites for use as high tap density electrodes. These composites demonstrate a maximum reversible capacity of 1044.7 mAh g −1 and a peak volumetric capacity of 2131.1 Ah L −1 after 30 cycles. The binding direction is also considered here for the first time between dissolved lithium polysulfides (LiPSs) and host materials (FeS 2 and FeS in this work) as determined by density functional theory calculations. It is concluded that if only one lithium atom of the polysulfide bonds with the sulfur atoms of FeS 2 or FeS, then any chemical interaction between these species is weak or negligible. In addition, FeS 2 is shown to have a strong catalytic effect on the reduction reactions of LiPSs. This work demonstrates the limitations of a strategy based on chemical interactions to improve cycling stability and offers new insights into the development of high tap density and high‐performance sulfur‐based electrodes.

The mechanical properties and electrochemical stability of a PEO based composite solid polymer electrolyte are enhanced by adding MnO2 nanosheets.