A Safe Electrolyte Enriched with Flame-Retardant Solvents for High-Voltage LiCoO<sub>2</sub>||Graphite Pouch Cells
Chao Yang, Xing Zhou, Ruitao Sun, Wenxi Hu, Meilong Wang, Xiaoli Dong, Nan Piao, Jin Han, Wen Chen, Ya You
Abstract
High Resolution Image Download MS PowerPoint Slide Employing a flame-retardant solvent (FRS) in the electrolyte has shown great potential for improving the safety of lithium-ion batteries (LIBs). Nevertheless, their poor compatibility with salts and commonly used solvents leads to the formation of a heterogeneous system, which drastically limits their concentration in the electrolyte and consequently deteriorates the safety performance. In this work, we employ a bridging solvent diethyl carbonate to raise the solubility of a highly effective FRS, ethoxy pentafluorocyclotriphosphonitrile (PFPN), to a concentration as high as 75 vol % in the electrolyte. The target electrolyte forms a stable N/P-rich cathode–electrolyte interface to protect the electrode from oxygen evolution and transition-metal ion dissolution, thereby enabling the LiCoO 2 cathode to preserve 72% capacity retention over 500 cycles at 4.62 V. Moreover, this electrolyte can effectively delay occurrence time and improve the critical temperature of thermal runaway of 1 Ah LiCoO 2 ||graphite pouch cells. Our work proposes a new direction for nonflammable electrolytes toward safe and high-energy LIBs.