An effective and accessible cell configuration for testing rechargeable zinc-based alkaline batteries

Rechargeable aqueous zinc-air batteries have received much attention due to their intrinsic safety, high theoretical volumetric energy density (6134 Wh/L), and low cost. However, zinc anodes suffer from severe hydrogen evolution reaction (HER) in alkaline electrolytes, which are kinetically favorable for air cathodes. Through an electrochemical cell-gas chromatography setup, we quantitatively identified that 99% of the capacity loss on the zinc anode was caused by HER. Most previous research has focused on material design to suppress HER, while less attention has been paid to the device. Here we demonstrate that the testing device has an apparent effect on the HER in alkaline electrolytes. Stainless-steel coin cells, as common devices used in research laboratories, accelerate HER due to synergistic effects of galvanic corrosion and a high HER activity. We designed an effective and accessible cell configuration for testing zinc-based alkaline batteries, which minimizes HER and demonstrates a higher Coulombic efficiency and longer cycling life than stainless-steel coin cells. Minimized HER and self-discharge of Zn were visualized through the operando optical microscopy. Specifically, the Ni?Zn battery with our cell configuration achieved stable long-term cycling for 816 cycles compared with similar to 100 cycles for the stainless-steel cell. The cell configuration shown here can be directly used or modified for future research on zinc based aqueous batteries.