Potassium Salts as Electrolyte Additives in Lithium-Oxygen Batteries

The stabilization of the intermediates formed during oxygen reduction reaction and their efficient solubilization and diffusion is a crucial issue that needs to be improved in nonaqueous lithium oxygen batteries. By adding 0.1 M K+(as KOTf salt) to the electrolyte, we have observed remarkable improvements in the rate capability of the discharge process. The K+ cation facilitates a more homogeneous discharge product deposition in the porous cathode. Instead, as evidenced by synchrotron measurements, we find that K+ does not influence the cell chemistry, suggesting that it rather assists the superoxide solvation, thus enhancing the solution-based growth of the discharge products. In addition, if iodide (I-) is added as redox mediator, we find an extended cycle life when K+ instead of Li+ is used as cation. This finding remarks the benefits of stabilizing the oxygen reduction products in the electrolyte leading to a solution-based mechanism.