Optimized Bicompartment Two Solution Cells for Effective and Stable Operation of Li-O-2 Batteries

Abstract

Lithium-oxygen batteries are in fact the only rechargeable batteries that can rival internal combustion engines, in terms of high energy density. However, they are still under development due to low-efficiency and short lifetime issues. There are problems of side reactions on the cathode side, high reactivity of the Li anode with solution species, and consumption of redox mediators via reactions with metallic lithium. Therefore, efforts are made to protect/block the lithium metal anode in these cells, in order to mitigate side reactions. However, new approach is required in order to solve the problems mentioned above, especially the irreversible reactions of the redox mediators which are mandatory to these systems with the Li anode. Here, optimized bicompartment two solution cells are proposed, in which detrimental crossover between the cathode and anode is completely avoided. The Li metal anode is cycled in electrolyte solution containing fluorinated ethylene carbonate, in which its cycling efficiency is excellent. The cathode compartment contains ethereal solution with redox mediator that enables oxidation of Li2O2 at low potentials. The electrodes are separated by a solid electrolyte membrane, allowing free transport of Li ions. This approach increases cycle life of lithium oxygen cells and their energy efficiency.