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

Abstract

The development of aqueous Zn/LiCoO₂ hybrid batteries faces challenges such as poor reversibility, rapid capacity degradation, and severe side reactions in base electrolytes. Herein, this study proposes Al₂O₃ 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. Al₂O₃ reduces water molecules activity, inhibits the interfacial side reactions, and enhances the reversibility and stability of redox reactions. Molecular dynamics (MD) simulations reveal that Al₂O₃ modifies the solvation structures of both Li⁺ and Zn²⁺, 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/LiCoO₂ 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/Zn²⁺. 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.