Fe/N/C Composite in Li-O2 Battery: Studies of Catalytic Structure and Activity toward Oxygen Evolution Reaction

Atomically dispersed Fe/N/C composite was synthesized and its role in controlling the oxygen evolution reaction during Li-O-2 battery charging was studied by use of a tetra(ethylene glycol) dimethyl ether-based electrolyte. Li-O-2 cells using Fe/N/C as the cathode catalyst showed lower overpotentials than alpha-MnO2/carbon catalyst and carbon-only material. Gases evolved during the charge step contained only oxygen for Fe/N/C cathode catalyst, whereas CO2 was also detected in the case of alpha-MnO2/C or carbon-only material; this CO2 was presumably generated from electrolyte decomposition. Our results reiterate the catalytic effect in reducing overpotentials, which not only enhances battery efficiency but also improves its lifespan by reducing or eliminating electrolyte decomposition. The structure of the Fe/N/C catalyst was characterized by transmission electron microscopy, scanning transmission electron microscopy, inductively coupled plasma optical emission spectroscopy, and X-ray absorption spectroscopy. Iron was found to be uniformly distributed within the carbon matrix, and on average, Fe was coordinated by 3.3 +/- 0.6 and 2.2 +/- 0.3 low Z elements (C/N/O) at bond distances of similar to 1.92 and similar to 2.09 angstrom, respectively.