Metal air batteries have been pursued as a successor to lithium-ion batteries because of their distinctive gravimetric energy densities. They may probably allow electric cars to move thousands of miles or more on a single charge.
A promising new member of the alkali metal air battery family is the potassium air battery, which has greater than thrice the theoretical gravimetric energy density of lithium-ion batteries. A key problem in designing potassium-air batteries is selecting the best electrolyte, the liquid which facilitates the switch of ions between the cathode and anode.
Sometimes, electrolytes are chosen utilizing a trial-and-error method based on rules of thumb correlating a number of electrolyte properties, adopted by exhaustive (and time-consuming) testing of a number of electrolyte candidates to see if the specified efficiency is obtained.
Experts from Washington University in St. Louis, directed by the Roma B., Vijay Ramani, and Distinguished Professor of Environment & Energy Raymond H. Wittcoff at the McKelvey School of Engineering, have now revealed how electrolytes for alkali metal air batteries can be chosen utilizing a single, simple-to-measure parameter.
Ramani’s staff studied the elemental interactions between the salt and solvent in the electrolyte and present how these interactions can affect total battery performance. They developed a novel parameter, particularly the “Electrochemical” Thiele Modulus, a measure of the benefit of ion transport to &reaction at an electrode surface.
This Thiele Modulus was proven to exponentially lower with growing solvent reorganization energy—a measure of the energy wanted to change the solvation sphere of a dissolved species. Thus, the solvent reorganization power could possibly be used to rationally choose electrolytes for high-efficiency metal-air batteries. No more trial-and-error.