Enabling Acidic Oxygen Reduction Reaction in a Zinc-Air Battery with Bipolar Membrane.

Zinc-air batteries are a promising alternative to lithium ion batteries due to their large energy density, safety, and low production cost. However, the stability of the zinc-air battery is often low due to the formation of dendrite which causes short circuiting and the CO 2 adsorption from the air which causes carbonate formation on the air electrode. In this work, we demonstrate a zinc-air battery design with acidic oxygen reduction reaction for the first time via the incorporation of a bipolar membrane. The bipolar membrane creates a locally acidic environment in the air cathode which could lead to a higher oxygen reduction reaction activity and a better 4-electron selectivity toward water instead of the 2-electron pathway toward peroxide. Locally acidic air cathode is also effective at improving the cell's durability by preventing carbonate formation. Gas chromatography confirms that CO 2 adsorption is 7 times lower in the bipolar membrane compared to a conventional battery separator. A stable cycling of 300+ hours is achieved at 5 mA/cm 2 . Dendrite formation is also mitigated due to the mechanical strength of the membrane. The insights from this work could be leveraged to develop a better zinc-air battery design for long-term energy storage applications.