Densely packed spherical zinc deposition by a cation buffer strategy led to high-rate alkaline zinc batteries with lean electrolytes

Zinc (Zn) anode stability poses a critical challenge in alkaline electrolytes due to an 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 a spontaneous hydrogen evolution reaction (HER). To tackle these problems, a cation buffer strategy is designed to realize unique dendrite-free spherical Zn deposition by initiating a new ‘fast nucleation-slow growth’ mode, which separates the Zn nucleation and growth process using the poly(dimethyl diallyl ammonium chloride) (PDDA) additive. The cation-rich chains with strong affinity at the electrode/electrolyte interface can effectively concentrate at 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 the HER and reduces corrosion and electrically inert ZnO by-products. The PDDA-modified electrolyte improves the durability of the Zn anode in long-term plating/stripping cycles with higher utilization of both Zn and the electrolyte. The symmetric cell with PDDA sustains over 450 hours at 20 mA cm⁻² and 10 mA h cm⁻². Finally, we demonstrate the practical implications of our findings through aqueous alkaline Zn-air and Zn-nickel batteries with extremely stable performance under high-rate and lean electrolyte conditions.