Intrinsic Nonflammable Ether Electrolytes for Ultrahigh‐Voltage Lithium Metal Batteries Enabled by Chlorine Functionality

Abstract The issues of inherent low anodic stability and high flammability hinder the deployment of the ether‐based electrolytes in practical high‐voltage lithium metal batteries. Here, we report a rationally designed ether‐based electrolyte with chlorine functionality on ether molecular structure to address these critical challenges. The chloroether‐based electrolyte demonstrates a high Li Coulombic efficiency of 99.2 % and a high capacity retention >88 % over 200 cycles for Ni‐rich cathodes at an ultrahigh cut‐off voltage of 4.6 V (stable even up to 4.7 V). The chloroether‐based electrolyte not only greatly improves electrochemical stabilities of Ni‐rich cathodes under ultrahigh voltages with interphases riched in LiF and LiCl, but possesses the intrinsic nonflammable safety feature owing to the flame‐retarding ability of chlorine functional groups. This study offers a new approach to enable ether‐based electrolytes for high energy density, long‐life and safe Li metal batteries.