Thermal Stability Analysis of Lithium-Ion Battery Electrolytes Based on Lithium Bis(trifluoromethanesulfonyl)imide-Lithium Difluoro(oxalato)Borate Dual-Salt

• Main Authors: Ya-Ping Yang, An-Chi Huang, Yan Tang, Ye-Cheng Liu, Zhi-Hao Wu, Hai-Lin Zhou, Zhi-Ping Li, Chi-Min Shu, Jun-Cheng Jiang, Zhi-Xiang Xing
• Format: Article
• Language: English
• Published: MDPI AG 2021-02-01
• Series: Polymers
• Subjects: LiTFSI-LiODFB dual-salt carbonate electrolyte; thermal analysis; accelerated rate calorimetry; differential scanning calorimetry; autocatalytic models; apparent activation energy
• Online Access: https://www.mdpi.com/2073-4360/13/5/707

Lithium-ion batteries with conventional LiPF₆ carbonate electrolytes are prone to failure at high temperature. In this work, the thermal stability of a dual-salt electrolyte of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium difluoro(oxalato)borate (LiODFB) in carbonate solvents was analyzed by accelerated rate calorimetry (ARC) and differential scanning calorimetry (DSC). LiTFSI-LiODFB dual-salt carbonate electrolyte decomposed when the temperature exceeded 138.5 °C in the DSC test and decomposed at 271.0 °C in the ARC test. The former is the onset decomposition temperature of the solvents in the electrolyte, and the latter is the LiTFSI-LiODFB dual salts. Flynn-Wall-Ozawa, Starink, and autocatalytic models were applied to determine pyrolysis kinetic parameters. The average apparent activation energy of the dual-salt electrolyte was 53.25 kJ/mol. According to the various model fitting, the thermal decomposition process of the dual-salt electrolyte followed the autocatalytic model. The results showed that the LiTFSI-LiODFB dual-salt electrolyte is significantly better than the LiPF₆ electrolyte in terms of thermal stability.