Toward highly reversible aqueous zinc-ion batteries: nanoscale-regulated zinc nucleation via graphene quantum dots functionalized with multiple functional groups

Rechargeable aqueous Zn-ion batteries have a promising application potential and represent competitive candidates in the field of large-scale energy storage. However, Zn metal is prone to uncontrolled dendrite formation, hydrogen evolution, and corrosion, all of which limit the reversibility of the corresponding batteries. Herein, a novel kind of nanosized and functionalized graphene quantum dots (F-GQDs) is decorated on a Zn anode via in situ electrochemical induction. These quantum dots (∼5 nm) can regulate Zn plating/stripping at the nanoscale. Furthermore, the high electronegativity of polar functional groups (–OH, –COOH, –NH2, and -SCN) on the GQDs results in strong Zn2+ affinity and the F-GQDs endow the Zn anode with high hydrophilicity, low nucleation energy barrier, and an evenly distributed electrical field. As a result, the F-GQDs-decorated Zn anode achieves superior Zn plating/stripping for greater than 450 h at 10 mA cm−2 and 5 mAh cm−2, with a low voltage hysteresis of 81 mV. Moreover, when coupled with MnO2 cathodes, the F-GQDs-decorated Zn enables the fabrication of Zn||MnO2 full batteries with significantly enhanced rate capability and long-term cycling performance (capacity retention of 78.6 % at 1 A/g after 500 cycles).