Bifunctional Oxide Additive Enabling High‐Voltage Aqueous Zn/LiCoO2 Hybrid Batteries

Abstract The development of aqueous Zn/LiCoO 2 hybrid batteries faces challenges such as poor reversibility, rapid capacity degradation, and severe side reactions in base electrolytes. Herein, this study proposes Al 2 O 3 nanoparticles as a bifunctional additive in the base electrolyte, leading to a novel electrolyte that enhances the interfacial stability between electrolyte and electrode and improves the electrochemical performance. Al 2 O 3 reduces water molecules activity, inhibits the interfacial side reactions, and enhances the reversibility and stability of redox reactions. Molecular dynamics (MD) simulations reveal that Al 2 O 3 modifies the solvation structures of both Li + and Zn 2+ , lowers their de‐solvation energies, thereby improving ionic diffusion coefficients and reaction kinetics. Consequently, symmetric cells achieve a prolonged cycle life with uniform zinc deposition. Zn/LiCoO 2 hybrid cells exhibit excellent rate performance, maintaining 81 mAh g −1 at 0.8 A g −1 and stable cycling over 300 cycles at 0.4 A g −1 within a broadened voltage range of 1.5–2.15 V versus Zn/Zn 2+ . Additionally, these cells demonstrate ultrahigh capacity retention of 98.2% at 0 °C and 87% at a high mass loading of 5 mg cm −2 at 0.4 A g −1 . This study presents a promising additive strategy for enhancing the stability and performance of high‐voltage aqueous hybrid batteries, paving the way for their practical application.