Deep Eutectic Solvent Based on Lithium Bis[(trifluoromethyl)sulfonyl] Imide (LiTFSI) and 2,2,2-Trifluoroacetamide (TFA) as a Promising Electrolyte for a High Voltage Lithium-Ion Battery with a LiMn2O4 Cathode

Thai T A Dinh; Tuyen T K Huynh; Linh T M Le; Tuyen T T Truong; Oanh H Nguyen; Kieu T T Tran; Man V Tran; Phuong Hoang Tran; Watchareeya Kaveevivitchai; Phung M L Le

doi:10.1021/acsomega.0c03099

Deep Eutectic Solvent Based on Lithium Bis[(trifluoromethyl)sulfonyl] Imide (LiTFSI) and 2,2,2-Trifluoroacetamide (TFA) as a Promising Electrolyte for a High Voltage Lithium-Ion Battery with a LiMn₂O₄ Cathode

ACS Omega. 2020 Sep 7;5(37):23843-23853. doi: 10.1021/acsomega.0c03099. eCollection 2020 Sep 22.

Authors

Thai T A Dinh^{1

2}, Tuyen T K Huynh^{1

2}, Linh T M Le^{1

2}, Tuyen T T Truong^{3

2}, Oanh H Nguyen^{3

2}, Kieu T T Tran^{3

2}, Man V Tran^{1

3

2}, Phuong Hoang Tran^{4

2}, Watchareeya Kaveevivitchai^{5

6}, Phung M L Le^{1

3

2}

Affiliations

¹ Applied Physical Chemistry Laboratory (APCLAB), University of Science, Ho Chi Minh City 700000, Viet Nam.
² Viet Nam National University-Ho Chi Minh (VNU HCM), Ho Chi Minh City 70000, Viet Nam.
³ Department of Physical Chemistry, Faculty of Chemistry, University of Science, Ho Chi Minh City 721337, Viet Nam.
⁴ Department of Organic Chemistry, Faculty of Chemistry, University of Science, Ho Chi Minh City 721337, Viet Nam.
⁵ Department of Chemical Engineering, National Cheng Kung University, Tainan City 701, Taiwan.
⁶ Hierarchical Green-Energy Materials Research Center, National Cheng Kung University, Tainan City 701, Taiwan.

Abstract

To design safe and electrochemically stable electrolytes for lithium-ion batteries, this study describes the synthesis and the utilization of new deep eutectic solvents (DESs) based on the mixture of 2,2,2-trifluoroacetamide (TFA) with a lithium salt (LiTFSI, lithium bis[(trifluoromethane)sulfonyl]imide). These prepared DESs were characterized in terms of thermal properties, ionic conductivity, viscosity, and electrochemical properties. Based on the appearance of the product and DSC measurements, it appears that this system is liquid at room temperature for LiTFSI mole fraction ranging from 0.25 to 0.5. At χ_LiTFSI = 0.25, DESs exhibited favorable electrolyte properties, such as thermal stability (up to 148 °C), relatively low viscosity (42.2 mPa.s at 30 °C), high ionic conductivity (1.5 mS.cm^-1 at 30 °C), and quite large electrochemical stability window up to 4.9-5.3 V. With these interesting properties, selected DES was diluted with slight amount of ethylene carbonate (EC). Different amounts of EC (x = 0-30 %wt) were used to form hybrid electrolytes for battery testing with high voltage LiMn₂O₄ cathode and Li anode. The addition of the EC solvent into DES expectedly aims at enhancing the battery cycling performance at room temperature due to reducing the viscosity. Preliminary results tests clearly show that LiTFSI-based DES can be successfully introduced as an electrolyte in the lithium-ion batteries cell with a LiMn₂O₄ cathode material. Among all of the studied electrolytes, DES (LiTFSI: TFA = 4:1 + 10 %wt EC) is the most promising. The EC-based system exhibited a good specific capacity of 102 mAh.g^-1 at C/10 with the theoretical capacity of 148 mAh.g^-1 and a good cycling behavior maintaining at 84% after 50 cycles.