Performance of Carbon/Polytetrafluoroethylene (PTFE) Air Cathodes from pH 0 to 14 for Li-Air Batteries

Report No. ARL-TR-4334
Authors: Michelle B. Marx and Jeffrey A. Read
Date/Pages: December 2007; 18 pages
Abstract: The performance of an uncatalyzed air cathode for use in a Li-Air battery was evaluated over the pH range from 0 to 14. This study was undertaken to determine if air cathodes constructed solely from carbon black and polytetrafluoroethylene (PTFE) can function at a sufficient rate in sulfate based electrolytes to be useful in Li-Air batteries. Layered cathodes were constructed with a hydrophobic wet-proofing layer and an active hydrophilic layer that utilizes a high surface area carbon black. Electrolytes were formulated using H2SO4, Na2SO4, and NaOH in various combinations giving pH values ranging from 0 to 14. Electrolytes were also formulated using H2SO4, Li2SO4, and LiOH in combination, and HCl, LiCl, and LiOH in combination giving electrolytes with pH values ranging from 0 to 14. The cathodes were discharged in a three electrode cell from 0.0 V to -0.6 V vs. a Ag/AgCl reference electrode. The cathode performed well and met the requirement that a current density of at least 1-2 mA/cm2 was maintained at -0.3 V vs. Ag/AgCl.
Distribution: Approved for public release
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Last Update / Reviewed: December 1, 2007