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Single-atom catalysts based on metal−N 4 moieties and anchored on carbon supports (defined as M−N−C) are promising for oxygen reduction reaction (ORR). Among those, M−N−C catalysts with 4d and 5d transition metal (TM 4d,5d ) centers are much more durable and not susceptible to the undesirable Fenton reaction, especially compared with 3d transition metal based ones. However, the ORR activity of these TM 4d,5d −N− C catalysts is still far from satisfactory; thus far, there are few discussions about how to accurately tune the ligand fields of singleatom TM 4d,5d sites in order to improve their catalytic properties. Herein, we leverage single-atom Ru−N−C as a model system and report an S-anion coordination strategy to modulate the catalyst's structure and ORR performance. The S anions are identified to bond with N atoms in the second coordination shell of Ru centers, which allows us to manipulate the electronic configuration of central Ru sites. The S-anion-coordinated Ru−N−C catalyst delivers not only promising ORR activity but also outstanding longterm durability, superior to those of commercial Pt/C and most of the near-term single-atom catalysts. DFT calculations reveal that the high ORR activity is attributed to the lower adsorption energy of ORR intermediates at Ru sites. Metal−air batteries using this catalyst in the cathode side also exhibit fast kinetics and excellent stability.

Lithium (Li) metal, a typical alkaline metal, has been hailed as the "holy grail" anode material for next generation batteries owing to its high theoretical capacity and low redox reaction potential. However, the uncontrolled Li plating/stripping issue of Li metal anodes, associated with polymorphous Li formation, "dead Li" accumulation, poor Coulombic efficiency, inferior cyclic stability, and hazardous safety risks (such as explosion), remains as one major roadblock for their practical applications. In principle, polymorphous Li deposits on Li metal anodes includes smooth Li (film-like Li) and a group of irregularly patterned Li (e.g., whisker-like Li (Li whiskers), moss-like Li (Li mosses), tree-like Li (Li dendrites), and their combinations). The nucleation and growth of these Li polymorphs are dominantly dependent on multiphysical fields, involving the ionic concentration field, electric field, stress field, and temperature field, etc. This review provides a clear picture and in-depth discussion on the classification and initiation/growth mechanisms of polymorphous Li from the new perspective of multiphysical fields, particularly for irregular Li patterns. Specifically, we discuss the impact of multiphysical fields' distribution and intensity on Li plating behavior as well as their connection with the electrochemical and metallurgical properties of Li metal and some other factors (e.g., electrolyte composition, solid electrolyte interphase (SEI) layer, and initial nuclei states). Accordingly, the studies on the progress for delaying/suppressing/ redirecting irregular Li evolution to enhance the stability and safety performance of Li metal batteries are reviewed, which are also categorized based on the multiphysical fields. Finally, an overview of the existing challenges and the future development directions of metal anodes are summarized and prospected.

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Using a collaborated in silico and experimental approach, we designed Sb-doped LiNiO2 with improved surface oxygen retention and electrochemical performance.