Tunable N-doped Carbon Dots/SnO2 Interface as a Stable Artificial Solid Electrolyte Interphase for High-Performance Aqueous Zinc-Ion Batteries

Abstract

Poor stability of zinc (Zn) anode hinders the use of aqueous zinc-ion batteries (AZIBs) for large-scale energy storage. Here, we report an effective artificial solid electrolyte interphase (ASEI) using N-doped carbon dots (CDs) and SnO₂ to stabilize Zn anodes. By optimizing the CDs/SnO₂ ratio, we can synthesize porous composites to construct "bayberry" and flower-like morphologies. The N-doped CDs/SnO₂ anode creates surface dipoles and changes in charge distribution, allowing Zn ions to move to nitrogen functionalized sites with reduced adsorption barriers. Furthermore, hydroxyl oxygen boosts the surface's hydrophilicity, resulting in stronger adhesion to the Zn anode and better ion accessibility. This generates dense nucleation sites for uniform Zn deposition. The CDs/SnO₂@Zn electrode achieves a low nucleation potential of 47 mV and maintains 99.6% coulombic efficiency (CE) over 1000 cycles at 2 mA cm^-2. In the symmetrical cells, the modified Zn anode exhibits stable cycling for 1,200 h at 1 mAh cm^-2. A full cell with CDs/SnO₂@Zn anode and MnO₂ cathode retains 96.6% capacity after 800 h. This study introduces a promising strategy for stabilizing Zn anodes and offers valuable insights for designing dendrite-free electrodes in next-generation AZIBs.