Incorporating Diamondoids as Electrolyte Additive in the Sodium Metal Anode to Mitigate Dendrite Growth.

Owing to the high abundance and gravimetric capacity (1165.78 mAh g-1 ) of pure sodium, it is considered as a promising candidate for the anode of next-generation batteries. However, one major challenge needs to be solved before commercializing the sodium metal anode: The growth of dendrites during metal plating. One possibility to address this challenge is to use additives in the electrolyte to form a protective solid electrolyte interphase on the anode surface. In this work, we introduce a diamondoid-based additive, which is incorporated into the anode to target this problem. Combining operando and ex situ experiments (electrochemical impedance spectroscopy, optical characterization, and cycling experiments), we show that molecular diamondoids are incorporated into the anode during cycling and successfully mitigate the growth of dendrites. Furthermore, we demonstrate the positive effect of the additive on the operation of sodium-oxygen batteries by means of increased energy density.

Design Strategies to Enable the Efficient Use of Sodium Metal Anodes in High-Energy Batteries.

Sodium-based batteries have attracted considerable attention and are recognized as ideal candidates for large-scale and low-cost energy storage. Sodium (Na) metal anodes are considered as one of the most promising anodes for next-generation, high-energy, Na-based batteries owing to their high theoretical specific capacity (1166 mA h g-1 ) and low standard electrode potential. Herein, an overview of the recent developments in Na metal anodes for high-energy batteries is provided. The high reactivity and large volume expansion of Na metal anodes during charge and discharge make the electrode/electrolyte interphase unstable, leading to the formation of Na dendrites, short cycle life, and safety issues. Design strategies to enable the efficient use of Na metal anodes are elucidated, including liquid electrolyte engineering, electrode/electrolyte interface optimization, sophisticated electrode construction, and solid electrolyte engineering. Finally, the remaining challenges and future research directions are identified. It is hoped that this progress report will shape a consistent view of this field and provide inspiration for future research to improve Na metal anodes and enable the development of high-energy sodium batteries.

Oxygen-Driven Porous Film Formation of Single-Crystalline Ru Deposited on Au(111).

We examined the interaction of oxygen with ultrathin Ru layers deposited on a Au(111) substrate using scanning tunneling microscopy, X-ray photoelectron spectroscopy, and low-energy electron diffraction. The deposition of pure Ru below one monolayer (ML) at room temperature leads to the formation of clusters on the Au(111) surface, preferentially located at the elbow sites of the herringbone reconstruction. Subsequent exposure of molecular oxygen to such a Ru-covered Au(111) surface at 680 K results in the growth of two-layer-thick Ru islands that are embedded in the top Au(111) layer. This structural reorganization of Ru is driven by the minimization of surface energy and mediated by a mobile RuOx species. Deposition of an increasing amount of Ru at 620 K (0.5-10 ML, ML = monolayer) leads to a rough Ru film on Au(111). Subsequent oxygen treatment (10(-5) mbar) at 680 K creates either a porous Ru film (<4 ML) or a flat RuO2(110) film (>6 ML) depending on the thickness of the Ru film.