Redistributing Zn ion flux by bifunctional graphitic carbon nitride nanosheets for dendrite-free zinc metal anodes

Zn metal with high chemical stability and low cost enables aqueous zinc ion batteries (ZIBs) to show promising applications in large-scale energy storage. However, the unlimited growth of Zn dendrites is the Achilles’ heel of ZIBs due to the nonuniform Zn nucleation and deposition. Herein, two-dimensional graphitic carbon nitride (g-C3N4) nanosheets are for the first time employed to modify glass fiber (GF) separators for highly-stable dendrite-free zinc anodes, in which g-C3N4 layers act as a bifunctional Zn ion distributor to physically force the diffusion of Zn2+ through the pores of hybrid separators and chemically guide Zn2+ ion flux via coordination effects between Zn2+ and abundant nitrogen species in g-C3N4 nanosheets. Furthermore, the g-C3N4 layers can efficiently avoid piercing through the hybrid separators and suppress self-discharging of ZIBs. As a result, the g-C3N4 nanosheets modified GF (g-C3N4/GF) separators endow Zn//Zn symmetrical batteries with a long lifespan over 700 h at 2 mA cm−2 and 2 mAh cm−2, superior to the counterpart with g-C3N4-free separators (64 h). In addition, the Zn//MnO2 batteries with g-C3N4/GF separators deliver an enhanced capacity of 280 mAh g−1 at 1 C after 400 cycles. Therefore, our work will pave a reliable strategy to design 2D nanosheets modified separators for high-performance ZIBs.