A Competitive Solvation of Ternary Eutectic Electrolytes Tailoring the Electrode/Electrolyte Interphase for Lithium Metal Batteries.

Wu, Wanbao; Liang, Yihong; Li, Deping; Bo, Yiyang; Wu, Dong; Ci, Lijie; Li, Mingyu; Zhang, Jiaheng · ACS Nano · 2022

basic_science · Level V

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Abstract

The development of electrolytes with high safety, high ionic conductivity, and the ability to inhibit lithium dendrites growth is crucial for the fabrication of high-energy-density lithium metal batteries. In this study, a ternary eutectic electrolyte is designed with LiTFSI (TFSI = bis(trifluoromethanesulfonyl)imide), butyrolactam (BL), and succinonitrile (SN). This electrolyte exhibits a high ion conductivity, nonflammability, and a wide electrochemical window. The competitive solvation effect among SN, BL, and Li<sup>+</sup> reduces the viscosity and improves the stability of the eutectic electrolyte. The preferential coordination of BL toward Li<sup>+</sup> facilitates the formation of stable solid electrolyte interphase films, leading to homogeneous and dendrite-free Li plating. As expected, the LiFePO<sub>4</sub>/Li cell with this ternary eutectic electrolyte delivers a high capacity retention of 90% after 500 cycles at 2 C and an average Coulombic efficiency of 99.8%. Moreover, Ni-rich LiNi<sub>0.8</sub>Co<sub>0.1</sub>Al<sub>0.1</sub>O<sub>2</sub>/Li and LiNi<sub>0.8</sub>Co<sub>0.1</sub>Mn<sub>0.1</sub>O<sub>2</sub>/Li cells based on the modified ternary eutectic electrolyte achieve an outstanding cycling performance. This study provides insights for understanding and designing better electrolytes for lithium metal batteries and analogous sodium/potassium metal batteries.