Layered Birnessite Cathode with a Displacement/Intercalation Mechanism for High-Performance Aqueous Zinc-Ion Batteries

A layered sodium-ion/crystal water co-intercalated Na 0.55 Mn 2 O 4 ·0.57H 2 O (NMOH) cathode is synthesized successfully with a selectively etching method for zinc-ion batteries. A displacement/intercalation mechanism is confirmed in the Mn-based cathode for the first time. The NMOH cathode delivers a competitive reversible capacity of 201.6 mA h g −1 at 500 mA g −1 after 400 cycles.