High-Entropy Second Solvation Shell by Anion Diversity for Aqueous Zinc-Ion Electrolytes

Our study introduces a novel electrolyte design strategy for aqueous zinc-ion batteries (AZIBs), leveraging high-entropy concepts specifically within the second solvation shell rather than the commonly targeted first shell. By combining multiple zinc salts to achieve controlled entropy enhancement, we demonstrated significantly improved zinc-ion transport kinetics, ionic conductivity, and suppression of the hydrogen evolution reactions (HER). Molecular dynamics simulations and spectroscopic analyses revealed that increased second-shell entropy weakened the hydrogen-bonding network, disrupting proton transfer pathways responsible for HER. Consequently, this high-entropy electrolyte substantially extended cycle life in symmetric cells and improved Coulombic efficiency in asymmetric configurations, outperforming conventional single-salt systems by up to 4-fold. In practical dual-electrode-free Zn–MnO2 and Zn–NVO full cell setups, our electrolytes showed enhanced cycling stability, rate capability, and capacity retention. This work presents a transformative electrolyte approach, highlighting second-shell entropy manipulation as an effective avenue for advancing performance and sustainability in aqueous zinc-ion battery technology and beyond.