Solvation structure of potassium bis(trifluoromethylsulfonyl)imide-glyme highly concentrated electrolytes and cycling on organic cathodes

Abstract

The physicochemical properties of highly concentrated electrolytes consisting of potassium bis(trifluoromethylsulfonyl)imide in oligo(ethyleneglycol) dimethyl ethers (glymes) are reported. The solvation structures were analyzed by Raman spectroscopy, single crystal X-ray diffraction, and theoretical calculations revealing significant ion-pairing at high concentrations for the shorter glymes. To assess the viability of these electrolytes in next-generation potassium-ion batteries, they were subjected to galvanostatic cycling on the new organic cathode material K2-Co-PTtSA, wherein PTtSA = benzene-1,2,4,5-tetra-methylsulfonamide. The results point to a better capacity retention with these electrolytes compared to a benchmark electrolyte consisting of 1 mol L 1 KPF6 in a mixture of ethylene carbonate and propylene carbonate, but a worse performance at high C-rates due to the high viscosities.