Suppressing Spontaneous Acidic Corrosion and Hydrogen Evolution for Stable Zn//MnO₂ Batteries

Rechargeable aqueous Zn//MnO₂ batteries have attracted significant attention due to their high safety and cost-effective for potential large-scale energy storage. However, the severe acidic corrosion and hydrogen evolution reaction (HER) on Zn anodes in acidic electrolytes pose critical challenges to their practical application. Here, we introduce trace amounts of p-hydroxybenzaldehyde (M4) into the electrolyte to address the above anode issues. Leveraging its strong affinity for Zn²⁺ and H₂O, M4 molecules reconstruct the Zn(H₂O)₆ ²⁺ solvation sheath and adsorb onto the anode surface, effectively blocking direct contact between H⁺ and Zn. This dual action significantly mitigates acidic corrosion and HER, enhancing Zn anode reversibility and stability. Benefiting from these merits, symmetric cells exhibit exceptional cycling stability of over 2000 h at 5 mA cm^-2 and 1 mAh cm^-2, delivering a fivefold increase in lifespan compared to conventional electrolytic cells. Moreover, Zn//MnO₂ batteries demonstrate stable operation for more than 3000 cycles in acidic electrolyte with an average Coulombic efficiency (CE) exceeding 97.3%. The assembled pouch cell delivers a high capacity of 1.68 Ah, maintaining stable operation for over 100 cycles. This work presents unique perspectives and offers promising avenues to improve the stability and efficiency of aqueous battery systems.