In-situ coupling of N-doped carbon dots with manganese hexacyanoferrate as a cathode material for aqueous zinc-ion batteries

Prussian blue analogs (PBAs) are a competitive class of aqueous Zn-ion batteries (AZIBs) cathode materials with an ideal three-dimensional open structure for rapid insertion and removal of Zn2+. Meanwhile, PBAs have the advantages of high working voltage and a simple synthesis process. However, these materials are inherently poor in electrical conductivity and are susceptible to structural collapse during cycling. These defects affect the performance of zinc storage in this type of material. Here, the integration of zero-dimensional nitrogen-doped carbon dots (NCDs) and in-situ grown manganese hexacyanoferrate (MnHCF) affords the MnHCF/NCDs cathode materials, which are applied to AZIBs. The introduction of NCDs modifies the active component of MnHCF effectively. Meanwhile, NCDs significantly enhance the overall electrical conductivity and structural stability of the composites and also provide abundant active sites for electrochemical reactions. Benefiting from these merits, the MnHCF/NCDs composite exhibits an excellent electrochemical zinc storage performance. It has a high discharge-specific capacity of 131.2 mAh g-1 at 50 mA g-1 and has outstanding cycling stability of 91% capacity retention after 1000 cycles at 1000 mA g-1. The electrochemical performance of PBAs-based cathodes for AZIBs may be improved using the straightforward and efficient method presented in this work.