Metal–Organic Framework-Derived NiO@C as a Host for MnO2 Cathode of Stable Zinc-Ion Batteries

MnO2 has been regarded as one of the most promising cathode materials for safe and inexpensive aqueous Zn-ion batteries (AZIBs). However, the severe Mn dissolution upon cycling is a major challenge for their practical application. Herein, we prepared a flexible and carbonaceous host for the MnO2 cathode in the form of metal–organic framework-derived nanoporous carbon decorated with NiO nanoparticles. The NiO nanoparticle-encapsulated carbon as a helpful additive led to a synergistic effect with MnO2. The MnO2 hosted on the flexible support allowed the construction of AZIB with a high capacity (330 mAh/g after 250 cycles at 0.625 A/g) and good cyclic performance (74.4% retention after 1500 cycles at 3.75 A/g). It is believed that the structural transformation of β-MnO2 (MnO2 → Mn2+ → birnessite MnOx) and the reversible (de)insertion of Zn2+ into NiO (NiO ↔ ZnxNiO) play a key role in the high capacity and cyclic stability of the prepared AZIBs. Our approach holds great promise to design various hosts for MnO2-based cathodes of AZIBs.