MnO₂ Nanowires Anchored with Graphene Quantum Dots for Stable Aqueous Zinc-Ion Batteries

Rechargeable aqueous zinc-ion batteries (ZIBs) hold tremendous potential for large-scale energy storage applications due to the natural abundance, low cost, and high ambient safety of Zn. Also, manganese oxides are the most representative cathode materials with the appropriate voltage platform and high specific theoretical capacity at present. However, the rapid capacity fading and sluggish transport kinetics are urgent issues waiting to be solved effectively. Thus, MnO2 nanowires anchored with graphene quantum dots (GQDs) are designed and studied as cathode materials for ZIBs. The GQDs can accelerate the transport kinetics as well as inhibit the dissolution of manganese during cycling. As a result, the MnO2-40GQD electrode can exhibit a high reversible specific capacity of 295.7 mA h g–1 at 0.1 A g–1 and a superior capacity retention of 88.99% with the excellent Coulombic efficiency of almost 100% after 100 cycles, which is more than 4 times that of pure MnO2 (the capacity retention of 22.90%).