In situ nitrogen-doped into MnO2/carbon derived from manganese (II) - triazole framework to achieve superior zinc ions storage

The widespread application of MnO2 as cathodes for aqueous zinc ions batteries (AZIBs) suffers from challenging issues of inferior ion storage capability, poor intrinsic electronic conduction and undesirable Mn dissolution. Herein, we demonstrate that the nitrogen can be successfully in situ doped into both the MnO2 and carbon lattice to form N-doped MnO2/C (NMC) by pyrolyzing the Mn based metal-triazole (Mn-MET) framework. The generation of oxygen vacancies in MnO2 and the presence of N-doped carbon in the composite not only increase the electronic conductivity to accelerate charges transfer in MnO2, but also relieve the Mn dissolution to stabilize the MnO2 structure. As a result, the NMC cathode based AZIB is able to display high discharge capacity of 339.3 mAh g-1, much higher than the bare Mn2O3 cathode (147.8 mAh g-1). The excellent long-term cycling life with a capacity retention of 82.8% can be also achieved after 1000 cycles under 3Ag-1. The energy storage mechanism of the NMC cathode related to the reversible H+ and Zn2+ interaction/extraction are systematically investigated through multiple ex situ characterizations. Thus, these inspiring results in our work are expected to stimulate the exploitation of MOFs derived cathode materials for high-performance AZIBs.