The Role of Air–Electrode Structure on the Incorporation of Immiscible PFCs in Nonaqueous Li–O₂ Battery

Abstract

Perfluorocarbons (PFCs) are considered advantageous additives to nonaqueous Li-O battery due to their superior oxygen solubility and diffusivity compared to common battery electrolytes. Up to now, the main focus was concentrated on PFCs-electrolyte investigation; however, no special attention was granted to the role of carbon structure in the PFCs-Li-O system. In our current research, immiscible PFCs, rather than miscible fluorinated ethers, were added to activated carbon class air electrode due to their higher susceptibility toward O attack and to their ability to shift the reaction from two-phase to an artificial three-phase reaction zone. The results showed superior battery performance upon PFCs addition at lower current density (0.05 mA cm) but unexpectedly failed to do so at higher current density (0.1 and 0.2 mA cm), where oxygen transport limitation is best illustrated. The last was a direct result of liquid-liquid displacement phenomenon occurring when the two immiscible liquids were introduced into the porous carbon medium. The investigation and role of carbon structure on the mechanism upon PFCs addition to Li-O system are suggested based on electrochemical characterization, wettability behavior studies, and the physical adsorption technique. Finally, we suggest an optimum air-electrode structure enabling the incorporation of immiscible PFCs in a nonaqueous Li-O battery.

A Critical Review on Functionalization of Air‐Cathodes for Nonaqueous Li–O2 Batteries

“…Furthermore, one should consider combining Li–air cathode electrode technologies that would hold a synergistic effect. Hybridization and combination of functional materials, alongside with new and advanced materials and methods of applying these, calls for a close collaboration between researchers and the establishment of large consortia with the involvement of the battery industry. The role of the battery industry is crucial and of high importance, as the battery industry is emerging to take the role of a “locomotive growth engine,” similar to the semiconductor industry, which is the engine and the key player of R&D in the field.…”

Enhanced Li‐O2 Battery Performance in a Binary “Liquid Teflon” and Dual Redox Mediators

“…PFCs are organofluorine compounds, containing only carbon and fluorine bonded together, that is, C x F y , with high oxygen dissolving capacity, extreme inertness, and are hydrophobic with a lipophobic character . Introducing PFC additive, which possess ≈5 times higher oxygen solubility than tetraethylene glycol dimethyl ether (TEGDME), was reported to form a uniform and intimate Li 2 O 2 deposit, being evident at areas further away from the electrode/gas interface . Here, we present that improved oxygen availability and a better surface area utilization demonstrated extensively higher discharge capacity in TEGDME electrolytes containing both dual RMs and PFC.…”

Review and Recent Advances of Oxygen Transfer in Li‐air Batteries

“…In recent years, researchers added different kinds of oxygen enriched additives into the porous electrodes to improve the diffusion and transport performance of oxygen of Li‐air electrode. Balaish et al [113–115] . created an artificial three phase reaction zone, meanwhile added the perfluorocarbons (PFC) with excellent oxygen solubility and diffusivity properties into the porous electrode (as shown in figure 24), which improved the oxygen delivery capacity of the Li‐air battery.…”