Hybridization of Carbon Nanotube Tissue, MnO2 Catalyst and CFx as an Advanced Air Cathode in Metal–Air Batteries

Abstract

We first present the utilization of hybrid carbon nano-tube (CNT) – manganese dioxide (MnO2) tissues as air electrodes in nonaqueous aluminum- and lithium-based battery systems. The CNT tissues are impregnated with α-manganese dioxide nanoparticles via a straightforward binder-free ultrasonic treatment, thereby enabling an improved oxygen reduction reaction (ORR) catalytic activity. Half-cell potentiodynamic measurements along with full-cell discharge evaluations of Li- and Al-based battery systems are reported. Higher discharge potentials and capacities were obtained from generic and advanced hybrid CNT–MnO2 air cathodes. The discharge products obtained on the air cathode surface were studied using high-resolution scanning electron microscopy. Their chemical compositions were evaluated using elemental mapping energy-dispersive X-ray spectroscopy. The stability of the α-MnO2 catalyst was studied using X-ray photoelectron spectroscopy and electron paramagnetic resonance spectroscopy, thereby indicating the ongoing formation of an outer MnF2 shell layer, which affected the α-MnO2 functionality, as an efficient ORR catalyst. We conclude this part of the talk by showing that the function of the metal–air battery is enabled by using porous carbon nanotube (CNT)-based tissue substrates loaded with MnO2 catalyst.In contrast, fluorinated graphite (CFx) coating on the CNT substrate provides an additional discharge process, enhancing discharge capacity. Two CFx loadings are investigated, and their performances are compared with that of a pristine CNT tissue. Electrochemical evaluations, including half- and full-cell measurements, are performed to examine the effect of the coating layer thickness on the ability of the cell to function at high discharge rates.