Artificial N-doped Graphene Protective Layer Enables Stable Zn Anode for Aqueous Zn-ion Batteries

Zinc (Zn) metal anode is one of the promising aqueous anodes due to its lower reduction potential and high capacity; however, the unstable interface during cycling severely inhibits the development of aqueous Zn-ion batteries (ZIBs). Here, we constructed a protective layer of nitrogen (N)-doped graphene (NGO) on Zn foil using a simple squeegee coating process. In situ optical microscopy and mass spectrometry analyses further demonstrated that this graphene protective layer alleviates the release of hydrogen as well as the hydrolysis of Zn. Meanwhile, the abundant N-doped functional groups modulate the deposition morphology of the Zn metal and inhibit the growth of porous dendrites. Based on this, the NGO@Zn||NGO@Zn symmetric cell presents a stable cycling performance over 500 h with a low overpotential (19 mV). Meanwhile, the full cell of the LiMn2O4 (LMO)||NGO@Zn battery delivers a capacity of 89.1 mAh g-1 after 600 cycles at the rate of 1C and a high specific capacity at the rate of 5C. Moreover, the LMO||NGO@Zn pouch cell (1.32 mAh cm-2) exhibits a capacity of up to 124.7 mAh g-1 at 0.5C and retains a capacity of 72.9 mAh g-1 after 90 cycles under no stress test conditions. This work offers a feasible synthesis approach and promising performance to accelerate the industrial application of aqueous ZIBs.