An amine electrolyte additive with claw structure promoting the stability of a Zn anode in aqueous batteries

Abstract

The Zn metal anode in aqueous Zn batteries suffers a number of challenges, including dendritic deposition and parasitic reactions. Here, we present a facile interface regulation strategy using a low concentration of electrolyte additive of 0.5 wt% tris(3-aminopropyl)amine (TAA). The TAA molecule exhibits a claw structure with an electronegative amino site at each end. It allows a strong anchorage on the surface of Zn and regulation of Zn²⁺ solvation structures near the interface. This allows easier removal of solvated water, but makes final TAA removal more difficult, thereby suppressing side reactions and controlling deposition kinetics. Furthermore, the TAA molecule exhibits strong affinity on the (100) plane of Zn which is twice of the one on (002). It promotes a preferred growth orientation and generates uniform deposits. Benefitting from the above positive effects of the TAA additive, the cycle life of a Zn symmetric cell extends to 8.6 times that in the baseline electrolyte. The cycle life of a full battery using a commercial V₂O₅ cathode is also effectively increased.