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 CO2 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 CO2 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/cm2. 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.