High-voltage and intrinsically safe electrolytes for Li metal batteries

Current electrolytes of mixing different functional solvents inherit both merits and weaknesses of each solvent, thus cannot simultaneously meet all the requirements of high energy, long cycle life, and high safety for Li metal batteries (LMBs). Here, we design a high voltage and safe electrolyte (VSE) by integrating different functional groups into one molecule. The VSE electrolyte has a wide electrochemical stability window of ~5.6 V enabling a Li anode to achieve high Coulombic efficiency of >99.3%, Li | |LiNi0.8Co0.1Mn0.1O2 coin cell to maintain capacity retention of 92% after 500 cycles, and the 3.5-Ah-grade Li | |LiNi0.8Co0.1Mn0.1O2 pouch cell to deliver a high energy density of 531 Wh kg−1 without any flame and expansion after cycled under extreme conditions. The VSE electrolyte even enables 5.0 V Li | |LiNi0.5Mn1.5O4 cells to charge/discharge for 200 cycles without capacity decay. This work provides a promising direction for the rational design of high-voltage and intrinsically safe electrolytes for LMBs. This work provides a high voltage and intrinsically safe electrolyte (VSE) designed by integrating different functional groups into one molecule that enables Li metal batteries to safely operate at high temperatures and achieve a high energy density.