Solvated Structure of Hybrid Tetraglyme‐Aqueous Electrolyte Dissolving High‐Concentration LiTFSI‐LiFSI for Dual‐Ion Battery
Dengyao Yang, Huan Li, Xiaofeng Shen, Motonori Watanabe, Tatsumi Ishihara
Abstract
Abstract The solvated structure of a highly concentrated hybrid tetraglyme (G4)‐water electrolyte was studied for an increasing cycle stability and performance of a KS6 used dual‐ion battery. Hybrid solvent of G4 and water with a weight ratio of 2 to 8 was able to dissolve 9LiFSI‐1LiTFSI supporting salts up to 37 mol kg −1 (37 mol kg −1 G2W8). In spite of such high concentration of supporting salts, reasonable charge and discharge performance of dual‐ion battery (discharge capacity of ≈40 mAh g −1 and coulombic efficiency of 90 %) were exhibited over 300 cycles. This was attributed to the decreased hydrogen evolution reaction (HER) potential to −1.05 V vs. Ag/AgCl by addition of G4. From Fourier‐transform infrared, nuclear magnetic resonance, and Raman spectroscopies, G4 molecules were more strongly coordinated to Li + to form ion pairs of [Li(G4) x (H 2 O) y ] + complex in hybrid G4‐water electrolyte. Co‐intercalation of bis(trifluoromethanesulfonyl)imide (TFSI − ) and bis(fluorosulfonyl)imide (FSI − ) into graphitic carbon KS6 cathode was confirmed in hybrid aqueous electrolyte.