Synergistically coupling of graphene quantum dots with Zn-intercalated MnO₂ cathode for high-performance aqueous Zn-ion batteries

Cost-effective, safe, and highly performing energy storage devices require rechargeable batteries, and among various options, aqueous zinc-ion batteries (ZIBs) have shown high promise in this regard. As a cathode material for the aqueous ZIBs, manganese dioxide (MnO₂) has been found to be promising, but certain drawbacks of this cathode material are slow charge-transfer capability and poor cycling performance. Herein, a novel design of graphene quantum dots (GQDs) integrated with Zn-intercalated MnO₂ nanosheets is put forward to construct a 3D nanoflower-like GQDs@Zn_xMnO₂ composite cathode for aqueous ZIBs. The synergistic coupling of GQDs modification with Zn intercalation provides abundant active sites and conductive medium to facilitate the ion/electron transmission, as well as ensure the GQDs@Zn_xMnO₂ composite cathode with enhanced charge-transfer capability and high electrochemical reversibility, which are elucidated by experiment results and in-situ Raman investigation. These impressive properties endow the GQDs@Zn_xMnO₂ composite cathode with superior aqueous Zn²⁺ storage capacity (~403.6 mAh·g⁻¹), excellent electrochemical kinetics, and good structural stability. For actual applications, the fabricated aqueous ZIBs can deliver a substantial energy density (226.8 W·h·kg⁻¹), a remarkable power density (650 W·kg⁻¹), and long-term cycle performance, further stimulating their potential application as efficient electrochemical storage devices for various energy-related fields.