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

doi:10.1002/cssc.202201805

Solvated Structure of Hybrid Tetraglyme-Aqueous Electrolyte Dissolving High-Concentration LiTFSI-LiFSI for Dual-Ion Battery

ChemSusChem. 2023 Feb 20;16(4):e202201805. doi: 10.1002/cssc.202201805. Epub 2022 Dec 8.

Authors

Dengyao Yang^{1

2}, Huan Li², Xiaofeng Shen^{1

2}, Motonori Watanabe^{1

2

3}, Tatsumi Ishihara^{1

2

3}

Affiliations

¹ Graduates School of Integrated Frontier Sciences, Kyushu University, 744 Motooka Nishi-ku, Fukuoka, 819-0395, Japan.
² International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka Nishi-ku, Fukuoka, 819-0395, Japan.
³ Department of Applied Chemistry, Faculty of Engineering, Kyushu University, 744 Motooka Nishi-ku, Fukuoka, 819-0395, Japan.

PMID: 36354218
DOI: 10.1002/cssc.202201805

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 (H₂ 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.

Keywords: dual-ion battery; electrolytes; energy storage; hybrid aqueous electrolyte; tetraglyme.

Abstract

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