Micelle-Like Electrolyte Design for 4.6 V Li||NCM811 Cells Workable at 70 °C.

Abstract

Localized high-concentration electrolytes (LHCE) feature satisfactory anode compatibility for lithium (Li)-metal batteries (LMBs). However, their application under high charging cut-off voltages and elevated temperatures still remains limited due to the electrochemical and thermal instabilities of solvents within the solvation sheath. Herein, we design a micelle-like electrolyte (QMLE) with a low anion-to-solvent ratio (0.3) and diluent-to-solvent ratio (1.3), achieved by regulating the length and type of non-solvating alkyl and fluorinated segments grafted onto polar ethyltrimethoxysilane (ETMOS) solvents, pushing the performance boundaries of LHCE. In this electrolyte, strong intramolecular interactions from the -CF₃ anchoring segments not only markedly whittle the solvation ability of the ETMOS but also elevate its flash point, thereby facilitating the formation of the anion-dominated solvation sheaths and the improvement of high-temperature tolerance of the QMLE. With the help of the QMLE, Li||Cu cell delivers a high coulombic efficiency of 98.5% at 3 mA cm^-2 and 3 mAh cm^-2. The newly assembled Li||NCM811 (11.5 mg cm^-2) cell achieves stable operation under a high charging cut-off voltage of 4.6 V and a high-temperature range from 30 °C to 70 °C. This study presents a versatile and scalable electrolyte design strategy for high-voltage and high-temperature LMBs.