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

Abstract

Zinc (Zn) metal with a high chemical stability and low cost has enabled aqueous zinc ion batteries (ZIBs) to show promise for use 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 (2D) graphitic carbon nitride (g-C₃N₄) nanosheets are employed for the first time to modify glass fibre (GF) separators for highly-stable dendrite-free zinc anodes, in which the g-C₃N₄ layers act as a bifunctional Zn ion distributor to physically force the diffusion of Zn²⁺ through the pores of the hybrid separators and chemically guide the Zn²⁺ ion flux via coordination effects between Zn²⁺ and the abundant nitrogen species in the g-C₃N₄ nanosheets. Furthermore, the g-C₃N₄ layers can efficiently avoid piercing through the hybrid separators and suppress the self-discharging of the ZIBs. As a result, the g-C₃N₄ nanosheet-modified GF (g-C₃N₄/GF) separators endow the Zn//Zn symmetrical batteries with a long lifespan of 700 h at 2 mA cm⁻² and 2 mA h cm⁻², which is 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 mA h g⁻¹ at 1C after 400 cycles. Therefore, this work may pave the way to a reliable strategy to design 2D nanosheet-modified separators for high-performance ZIBs.