Engineering hydrophobic protective layers on zinc anodes for enhanced performance in aqueous zinc-ion batteries

Abstract

Aqueous zinc-ion batteries possess substantial potential for energy storage applications; however, they are hampered by challenges such as dendrite formation and uncontrolled side reactions occurring at the zinc anode. In our investigation, we sought to mitigate these issues through the utilization of in situ zinc complex formation reactions to engineer hydrophobic protective layers on the zinc anode surface. These robust interfacial layers serve as effective barriers, isolating the zinc anode from the electrolyte and active water molecules and thereby preventing hydrogen evolution and the generation of undesirable byproducts. Additionally, the presence of numerous zincophilic sites within these protective layers facilitates uniform zinc deposition while concurrently inhibiting dendrite growth. Through comprehensive evaluation of functional anodes featuring diverse functional groups and alkyl chain lengths, we meticulously scrutinized the underlying mechanisms influencing performance variations. This analysis involved precise modulation of interfacial hydrophobicity, rapid Zn2+ ion transport, and ordered deposition of Zn2+ ions. Notably, the optimized anode, fabricated with octadecylphosphate (OPA), demonstrated exceptional performance characteristics. The Zn//Zn symmetric cell exhibited remarkable longevity, exceeding 4000 h under a current density of 2 mA cm−2 and a capacity density of 2 mA h cm−2. Furthermore, when integrated with a VOH cathode, the complete cell exhibited superior capacity retention compared to anodes modified with alternative organic molecules.