Ultrasmall Mn3O4 nanocrystalline@three-dimensional macroporous honeycomb-like hollow carbon matrix for high-rate and long-lifetime zinc-ion storage

Low specific capacity and poor cycling performance are two main problems of Mn-based oxides that hinder their application in aqueous zinc-ion batteries (ZIBs). Herein, we design a facile sacrificial template method to construct a unique three-dimensional macroporous honeycomb-like hollow carbon matrix, and then grow ultrasmall Mn 3 O 4 nanocrystalline with the diameter of 5 nm inside the hollow carbon matrix. The composite has large surface area (56.9 m 2 g −1 ) and high Mn 3 O 4 content (about 47.1%). When the composite is used as the cathode material of ZIBs, it exhibits extraordinary discharge capacity of 845 mAh g −1 at 1 A g −1 , impressive rate capability with average discharge capacity of 46 mAh g −1 at 10 A g −1 , and superior long-term cycling performance with discharge capacity of 123 mAh g −1 at 5 A g −1 after 800 cycles. Electrochemical kinetics measurements and ex-situ XRD, SEM and TEM further demonstrate that the macroporous honeycomb-like hollow carbon matrix significantly increases electronic conductivity and structural stability of Mn 3 O 4 . Besides, electrochemical activity and surface capacitive effect of Mn 3 O 4 are also greatly enhanced by its ultrasmall size.