Enhancing Electrochemical Performance of Alkaline Zn-MnO2 Batteries through Mannitol Electrolyte Additive

The zinc anode in alkaline Zn-MnO 2 primary batteries suffers from high reactivity causing passivation, corrosion and low active-material utilization, affecting performance and durability. Herein, we introduce mannitol, a hydroxyl-rich organic molecule, as a dual-functional electrolyte additive to simultaneously optimize the solvation structure and suppress zinc corrosion in alkaline Zn-MnO 2 batteries. Theoretical calculations and experimental analyses reveal that the hydroxyl moieties in mannitol disrupt the original hydrogen-bond network, elevate the energy barrier of the hydrogen evolution reaction (HER), and mitigate parasitic water splitting. Concurrently, mannitol enhances interfacial corrosion resistance via chemisorption on the zinc anode surface and promotes the formation of a complex and dense passivation layer. The optimized electrolyte delivers a 12.3% increase in discharge capacity at 10 mA (25°C), with a corresponding rise in Zn utilization from 55.6% to 62.5%. Furthermore, significantly greater capacity improvements are observed under extreme temperatures: 17.4% at 80°C and 44.4% at -10°C. Additionally, the corrosion efficiency is reduced by 29.6% compared to the blank sample. This study deciphers the mechanism by which polyhydroxy organic molecules optimize the performance of alkaline aqueous batteries through modulating solvation structures and the electrode/electrolyte interface, offering a scalable strategy toward high-performance alkaline Zn-MnO 2 batteries.