Dynamic heterostructure design of MnO2 for high-performance aqueous zinc-ion batteries

Manganese oxide (MnO2) has attracted significant attention for aqueous zinc-ion batteries (ZIBs) due to its excellent theoretical capacity and high output voltage. However, irreversible phase transitions, manganese dissolution and low electrical conductivity of MnO2 lead to poor electrochemical performance. Herein, we proposed a novel Mn-based heterostructure, Bi12.53Mn0.47O19.85/R-MnO2 (BiO/MnO2), as the cathode for ZIBs. BiO, acting as a metal ion reservoir, can supply Bi3+ to R-MnO2in situ to form Bi2Mn4O10 (BMO), resulting in the continuous conversion from BiO/MnO2 to BMO/MnO2 during cycling. The formation of the dynamic BMO/MnO2 heterostructure can effectively reduce the formation of irreversible product ZnMn2O4, suppress Mn dissolution, and improve electrical conductivity. More importantly, the dynamic transformation can create more heterointerfaces, resulting in abundant active sites and built-in electric fields (BEFs), which enhances the capacity and accelerates the reaction kinetics. Accordingly, the highest specific capacity of the BiO/MnO2 heterostructure cathode reaches 720.6 mA h g−1 at 0.1 A g−1. Moreover, the BiO/MnO2 heterostructure cathode exhibits a high specific capacity of 474.4 mA h g−1 at 0.3 A g−1 and an excellent cycle life of over 160 cycles. This work provides new insights into the design of in situ metal ion reservoirs to stabilize the MnO2 structure at low current densities for Zn//MnO2 batteries.