Enhancement of Oxygen Transfer by Design Nickel Foam Electrode for Zinc−Air Battery

To develop a long-lifetime metal-air battery, oxygen reduction electrodes with improved mass-transfer routes are designed by adjusting the mass ratio of the hydrophobic polytetrafluoroethylene (PTFE) to carbon nanotubes (CNTs) in nickel foam. The oxygen reduction catalyst MnO 2 is grown on the nickel foam using a hydrothermal method. Scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller analysis are employed to characterize the morphology, crystal structure, chemical composition, and pore structure of the electrodes, respectively. The air electrodes are evaluated using constant-current tests and electrochemical impedance spectroscopy. A PTFE:CNT mass ratio of 1:4–2:1 with 3-mm-thick nickel foam yields the optimal performance due to the balance of hydrophilicity and hydrophobicity. When the electrodes are applied in primary zinc–air batteries, the electrode with a PTFE:CNT mass ratio of 1:4 achieves the maximum power density of 95.7 mW cm −2 with a discharge voltage of 0.8 V at 100 mA cm −2 , and completes stable discharge for over 14400 s at 20 mA cm −2 .