Densely packed spherical zinc deposition by cation buffer strategy enabled high-rate alkaline zinc batteries with lean electrolyte

Abstract

Zinc (Zn) anode stability poses a critical challenge in alkaline electrolytes due to the unstable electrode/electrolyte interface. In particular, Zn dendrite growth is induced by uneven nucleation and fast diffusion of zincates ([Zn(OH)4]2-), which leads to severe passivation and spontaneous hydrogen evolution reaction (HER). To tackle these problems, a cation buffer strategy is designed to realize the unique dendrite-free spherical Zn deposition by initiating a new ‘fast nucleation-slow growth’ mode, which separates the Zn nucleation and growth process using poly-(dimethyl diallyl ammonium chloride) (PDDA) additive. The cation-rich chains with strong affinity at the electrode/electrolyte interface, can effectively concentrate the near-electrode [Zn(OH)4]2- and slow down the migration of bulk phase [Zn(OH)4]2-. Moreover, preferentially adsorbed PDDA also suppresses HER, and reduces corrosion and electrically inert ZnO by-products. The PDDA-modified electrolyte improves the durability of Zn anode in long-term plating/stripping cycles with higher utilization of both Zn and electrolyte. The symmetric cell with PDDA sustains over 450 hours at 20 mA cm-2 and 10 mAh cm-2. Finally, we demonstrate the practical implications of our findings through aqueous alkaline Zn-Air and Zn-Nickel batteries with extremely stable performance at high-rate and lean electrolyte conditions.