Activating the MnS0.5 Se0.5 Microspheres as High-Performance Cathode Materials for Aqueous Zinc-Ion Batteries: Insight into In Situ Electrooxidation Behavior and Energy Storage Mechanisms.

Manganese-based materials are regarded as the most prospective cathode materials because of their high natural abundance, low toxicity, and high specific capacity. Nevertheless, the low conductivity, poor cycling performance, and controversial energy storage mechanisms hinder their practical application. Here, the MnS0.5 Se0.5 microspheres are synthesized by a two-step hydrothermal approach and employed as cathode materials for aqueous zinc-ion batteries (AZIBs) for the first time. Interestingly, in-depth ex situ tests and electrochemical kinetic analyses reveal that MnS0.5 Se0.5 is first irreversibly converted into low-crystallinity ZnMnO3 and MnOx by in situ electrooxidation (MnS0.5 Se0.5 -EOP) during the first charging process, and then a reversible co-insertion/extraction of H+ /Zn2+ occurs in the as-obtained MnS0.5 Se0.5 -EOP electrode during the subsequent discharging and charging processes. Benefiting from the increased surface area, shortened ion transport path, and stable lamellar microsphere structure, the MnS0.5 Se0.5 -EOP electrodes deliver high reversible capacity (272.8 mAh g-1 at 0.1 A g-1 ), excellent rate capability (91.8 mAh g-1 at 2 A g-1 ), and satisfactory cyclic stability (82.1% capacity retention after 500 cycles at 1 A g-1 ). This study not only provides a powerful impetus for developing new types of manganese-based chalcogenides, but also puts forward a novel perspective for exploring the intrinsic mechanisms of in situ electrooxidation behavior.