Towards a high-performance anode for zinc metal batteries: A tri-functional nitrogen-defective graphitic carbon nitride material for anode protection.

As an important potential candidate for large-scale energy storage, rechargeable zinc metal batteries have become a research hotspot. Zn metal anodes are an extremely crucial component of rechargeable Zn metal batteries. However, the Zn dendrites, the evolution of hydrogen and side reactions on the surface of the Zn metal anodes severely hinder its commercial use. Here, we report a modified Zn metal anode with a layer of nitrogen-defective graphitic carbon nitride (NDCN) nanosheets coated onto a commercial Zn foil by a simple spraying method. The NDCN coating on the anode's surface not only provides zincophilic sites, but also drives the deposition of zinc with a particular crystallographic orientation. At the same time, the formation of zinc dendrites and the evolution of hydrogen were suppressed, which enhanced the reversibility of the anode. Thus, the symmetric cells with the NDCN-protected zinc foil (NDCN@Zn) electrodes remained stable for 2000 h at a current density of 5 mA cm. More importantly, the long-term cycling performance of the full cell tested at 1 A g retained approximately 88 % of its capacity even after 2300 cycles. This simple but effective method will provide a reference for future studies on protecting the anodes of zinc metal batteries.