Isoquinoline as an Electrolyte Additive for Electrolytic Zn-MnO₂ Batteries: Superior Cycling Stability and Areal Capacity.

Abstract

Aqueous electrolytic Zn-MnO₂ batteries hold great promise for energy storage applications owing to their high theoretical electromotive force and energy density. However, the zinc anode suffers from severe corrosion in strongly acidic electrolytes, leading to hydrogen evolution, low zinc utilization, and premature battery failure. To address these challenges, isoquinoline is introduced as an additive in a chloride-based acidic electrolyte. Isoquinoline molecules preferentially adsorb on the Zn surface and incorporate into the Zn²⁺ solvation sheath, thereby effectively suppressing zinc corrosion and enhancing Zn plating/stripping reversibility in both half-cell and full-cell configurations. At an optimized concentration of 500 mg L^-1 isoquinoline, the modified electrolyte enables the electrolytic Zn-MnO₂ battery to achieve outstanding cycling stability, delivering 3650 cycles with an average coulombic efficiency of 98%, demonstrating highly competitive cycling performance among reported electrolytic Zn-MnO₂ systems. Furthermore, this electrolyte modulation supports the development of a zinc metal anode-free full cell, which delivers a high areal discharge capacity of ≈8 mAh cm^-2 and maintains a stable discharge voltage plateau of ≈1.9 V. These findings underscore the pivotal role of isoquinoline in stabilizing the zinc interface and advancing the performance of electrolytic Zn-MnO₂ batteries.