MnO nanoparticles with cationic defects encapsulated in nitrogen-doped porous carbon for high-performance aqueous zinc-ion batteries

Manganese oxides are admittedly one of the most promising cathode materials in aqueous zinc-ion batteries (ZIBs) because of high operating voltage and economic benefit. However, the design of manganese oxides with high capacity and excellent cycling stability remains challenging. Herein, MnO nanoparticles with cationic defects encapsulated into nitrogen-doped porous carbon (MnO-NC) are synthesized as cathode material for aqueous ZIBs. Benefiting from nitrogen-doping porous carbon improving the electrical conductivity of MnO nanoparticles, MnO-NC exhibits high specific capacity of 402.4 mA h g−1 at 100 mA g−1 and long-term cyclic stability up to 1000 cycles at 1000 mA g−1. The cationic defects in the MnO-NC nanoparticles are also confirmed by XPS analysis, which will facilitate the reversible phase change during cycling. In addition, the ion storage mechanism of MnO-NC cathode is revealed by using XRD, SEM, XPS and in situ Raman spectroscopy, suggesting that the excellent electrochemical behavior of MnO-NC is attributed to the irreversible phase transformation of partial MnO into a layered-type MnO2. These findings demonstrate that porous MnO-NC nanoparticle is a promising cathode material for aqueous ZIBs.