Enhancing Zn2+ diffusion for dendrite-free zinc anodes via a robust zincophilic clay mineral coating

Abstract

Clay minerals as artificial solid electrolyte interphase (SEI) layers have played a crucial role in protecting zinc metal anodes for aqueous Zn-ion batteries (AZIBs) due to their unique layered structure, negatively charged lamellas, ion exchange ability, and electronic insulation. However, the clay mineral layers exhibit limited ability to suppress dendrites and side reactions on the Zn anode in the water-based working environment. This limitation is attributed to the severe volumetric expansion, poor mechanical performance, and inferior zinc ion conductivity. To address these issues, montmorillonite (MMT) is intercalated with urea in this study. The resulting dense and robust UMMT coating layer enhances the diffusion of Zn2+ and increases the Zn2+ concentration at the Zn deposition surface through strong absorption of Zn2+ at −C=O and −NH2 active sites. As a result, it facilitates the uniform deposition of Zn2+ and inhibits dendrite growth. Additionally, the UMMT coating layer acts as a desolvation layer, mitigating parasitic reactions originated from active water. Consequently, the UMMT coating layer enables stable Zn plating/stripping compared to MMT layer. In symmetric cells, MMT@Zn electrode exhibits a significantly longer lifespan of over 1300 h at 6 mA cm−2 with a capacity of 3 mAh cm−2. Furthermore, it demonstrates enhanced cyclic performance of 254 mAh g−1 at 10 A g−1 after 4000 cycles in Zn//V2O5 full cells. This present work presents a strategy to intercalate small-molecule organics into clay minerals, enhancing their protective capacity and expanding their application as SEI layers in AZIBs.