Amorphous Heterostructure Derived from Divalent Manganese Borate for Ultrastable and Ultrafast Aqueous Zinc Ion Storage

Abstract

Abstract Aqueous zinc‐manganese (Zn–Mn) batteries have promising potential in large‐scale energy storage applications since they are highly safe, environment‐friendly, and low‐cost. However, the practicality of Mn‐based materials is plagued by their structural collapse and uncertain energy storage mechanism upon cycling. Herein, this work designs an amorphous manganese borate (a‐MnBOx) material via disordered coordination to alleviate the above issues and improve the electrochemical performance of Zn–Mn batteries. The unique physicochemical characteristic of a‐MnBOx enables the inner a‐MnBOx to serve as a robust framework in the initial energy storage process. Additionally, the amorphous manganese dioxide, amorphous ZnxMnO(OH)2, and Zn4SO4(OH)6·4H2O active components form on the surface of a‐MnBOx during the charge/discharge process. The detailed in situ/ex situ characterization demonstrates that the heterostructure of the inner a‐MnBOx and surface multicomponent phases endows two energy storage modes (Zn2+/H+ intercalation/deintercalation process and reversible conversion mechanism between the ZnxMnO(OH)2 and Zn4SO4(OH)6·4H2O) phases). Therefore, the obtained Zn//a‐MnBOx battery exhibits a high specific capacity of 360.4 mAh g−1, a high energy density of 484.2 Wh kg−1, and impressive cycling stability (97.0% capacity retention after 10 000 cycles). This finding on a‐MnBOx with a dual‐energy storage mechanism provides new opportunities for developing high‐performance aqueous Zn–Mn batteries.

Keywords

• aqueous Zn‐ion batteries
• charge storage mechanism
• high energy density
• long lifespan
• manganese borate