Optimized Nitrogen Sites in Yolk-Shell ZnNCN/Nitrogen-Doped Carbon Composite Interfacial Layer for Dendrite-Free and Highly Reversible Zn Anodes

Achieving stable zinc plating/stripping in zinc anodes is crucial for the development of high-performance aqueous Zn-ion batteries, but dendrite growth and side reactions severely limit their lifespan. Herein, a hydrophobic and zincophilic ZnNCN/nitrogen-doped carbon composite (ZNC800) with a hollow yolk-shell structure is designed for interfacial engineering. The ZNC800 interfacial layer incorporates optimized nitrogen sites with abundant Zn─N bonds, pyridinic nitrogen species, and π-conjugated NCN groups, which synergistically enhance Zn adsorption energy, lower ion diffusion barriers, and promote efficient Zn²⁺ desolvation. Simultaneously, the hydrophobic interfacial layer helps reduce side reactions such as hydrogen evolution and corrosion, while the yolk-shell architecture buffers volume changes. Consequently, the ZNC800-Zn electrode exhibits highly reversible Zn plating/stripping with extended cycling lifespan exceeding 2100 h at 1 mA cm⁻² and 1 mAh cm⁻² and maintains stability under extremely deep discharge conditions (DOD ≈ 95.7% over 228 h). It also delivers up to 2400 cycles with an average Coulombic efficiency of 99.65%, and the ZNC800-Zn||NaV₃O₈·1.5H₂O full cell exhibits a capacity retention of 76.93% after 7850 cycles at 10 A g⁻¹. These findings underscore the promising potential of nitrogen site optimization and yolk-shell structure in interfacial engineering for dendrite-free and highly reversible metal electrodes in aqueous systems.