Meso-pores carbon nano-tubes (CNTs) tissues-perfluorocarbons (PFCs) hybrid air-electrodes for Li-O_2 battery

摘要

Adding immiscible perfiuorocarbons (PFCs), possessing superior oxygen solubility and diffusivity, to a freestanding (metal-free and binder-free) CNTs air-electrode tissues with a meso-pore structure, fully maximized the advantages of PFCs as oxygenated-species' channels-providers. The discharge behavior of hybrid PFCs-CNT Li-O-2 systems demonstrated a drastic increase in cell capacity at high current density (0.2 mA cm(-2)), where oxygen transport limitations are best illustrated. The results of this research revealed several key factors affecting PFCs-Li-O-2 systems. The incorporation of PFCs with higher superoxide solubility and oxygen diffusivity, but more importantly higher PFCs/electrolyte miscibility, in a meso-pore air-electrode enabled better exploitation of PFCs potential. Consequently, the utilization of the air-electrode surface area was enhanced via the formation of artificial three phase reaction zones with additional oxygen transportation routes, leading to uniform and intimate Li-2-O-2 deposit at areas further away from the oxygen reservoir. Associated mechanisms are discussed along with insights into an improved Li-O-2 battery system.