Geometry-independent uniform zinc deposition in sustainable aqueous zinc-ion batteries

To address challenges such as dendrite growth, hydrogen evolution, and corrosion that degrade the reversibility and uniform zinc deposition in aqueous zinc-ion batteries, extensive research has focused on developing inorganic co-solvent systems. However, many of the co-solvents under investigation are highly toxic. Herein, to overcome these limitations, we employed provitamin B5, an eco-friendly and biocompatible co-solvent commonly used in skin moisturizers. The formation of a unique provitamin B5–zinc ion complex in the electrolyte was confirmed through heteronuclear multiple bond correlation (HMBC), indicating strong interactions between provitamin B5 molecules and zinc ions. This complex significantly enhanced zinc ion diffusion, enabling uniform zinc deposition up to 3.2 cm in a capillary cell without dendritic growth and hydrogen evolution. As a result, these effects of provitamin B5 co-solvent exhibited outstanding cycling stability for 3500 hours at 1 mA cm⁻² under 1 mAh cm⁻² conditions, and even under a harsh 35% depth-of-discharge condition, it maintained stable operation for 600 hours. Moreover, the full cell under pouch cell conditions revealed a remarkable cycle retention of 90% with a Coulombic efficiency of 99.75% over 1000 cycles. This study offers a new platform to co-solvent engineering for highly reversible and sustainable aqueous-ion batteries.