Multifunctional hydroxyurea additive enhances high stability and reversibility of zinc anodes

Abstract

The performance of aqueous zinc-ion batteries (AZIBs) is greatly influenced by both the electric double layer (EDL) at the Zn electrode/electrolyte interface and the solvation structure of Zn²⁺. In this study, hydroxyurea (HU), a widely used and low-cost polar molecule in the medical field, is innovatively introduced as an additive to optimize both the EDL and the solvation structure of Zn²⁺, thereby enhancing the stability and reversibility of the zinc anode. HU coordinates with Zn²⁺ through its polar functional groups, altering the solvation structure and reshaping the intrinsic hydrogen bonding network. Additionally, due to HU's strong adsorption capabilities, it forms a water-poor inner Helmholtz plane (IHP), effectively suppressing parasitic reactions and dendrite growth, while promoting uniform zinc deposition on the (002) crystal plane. The Zn//Zn symmetric cells with HU-modified electrolyte exhibit outstanding cycling stability, cycling over 2600 hours at 1 mA cm⁻² at room temperature, and over 1700 hours at 1 mA cm⁻² under low-temperature conditions (−25 °C). The Zn//MnO₂ full cell retains 86.88% of its initial capacity after 1400 cycles, with ultra-high coulombic efficiency (99.8%). Furthermore, the Zn//MnO₂ pouch cell assembled with HU-modified electrolyte demonstrates a high-capacity retention rate of 83.7% after 300 cycles, showing excellent commercial potential. These results indicate that as an effective additive, HU provides a promising route for high-performance and scalable AZIBs.