Manganese octacyanomolybdate/carbon nanotube hybrids as novel cathode materials for aqueous zinc-ion batteries

Prussian blue analogues (PBAs) exhibit strong competitiveness as cathode materials in aqueous zinc-ion batteries (AZIBs) due to their ideal three-dimensional open framework structure based on hexacyanometallate building blocks. However, the intriguing open frameworks based on octacyanometallates have not been explored for AZIBs cathodes to date. In this paper, we demonstrate that manganese octacyanomolybdate (Mn₂Mo(CN)₈·nH₂O), a typical octacyanometallate-based complex, is also a feasible cathode material for AZIBs. Compared with the micron-sized particles, the nano-sized Mn₂Mo(CN)₈·nH₂O are more conducive to the electrochemical zinc storage, and the introduction of carbon nanotubes (CNTs) can further boost the zinc storage performance of the nanoscale Mn₂Mo(CN)₈·nH₂O. The resulted n-Mn₂Mo(CN)₈/CNTs-20 hybrid exhibits excellent zinc storage performance, with a high discharge specific capacity of 289 mAh/g at 200 mA g^-1 and capacity retention close to 100 % after 2000 cycles at 2000 mA g^-1, which are much superior to those of the previously reported PBAs-based cathodes. The work paves a new way for the development of advanced cathode materials for aqueous zinc-ion batteries.