Transport of Li+ and O2 in glymes in relation to lithium-air batteries

HORACIO CORTI; GABRIELA HORWITZ; MATIAS FACTOROVICH; HENRY ANDRES CORTES PÁEZ; M. PAULA LONGINOTTI

Simposio; Hyceltec 2017 - VI Symposium on Hydrogen, Fuel Cells and Advanced Batteries; 2017

Lithium air batteries (LAB) promises higher energy density than available commercial advanced batteries, but their development is hindered by the lack of a suitable electrolyte. Recent interest in glymes (glycol ethers) as electrolytes for LAB is based in their relatively low volatility and the fact that the main discharge product is Li2O2 . Pure mono-, di-, tri-, and tetra-glyme are sufficiently stable against superoxide attack. The dissociation level of the lithium salt used in a LAB plays a significant role in the oxygen reduction reaction (ORR). The ion clustering of lithium salts in solvents of low dielectric constant, like glymes, could be very large and have a huge influence on the ohmic overpotentials during charge/discharge of LABs. Moreover, the solubility and diffusivity of oxygen in the electrolyte determine the efficiency of the cathodic process in LABs In this work we study the conductivity and speciation of lithium trifuorosulfonate (Li Triflate) and lithium bis(tri- fluoromethylsulfone)imide (LiTFSI) in two glymes: 1,2-di- methoxyethane (DME or monoglyme), and bis(2-methoxy- ethyl)ether (diglyme). We also analyze the diffusion of oxygen in glymes by resorting to semiempirical models.