Fluorinated electrolyte formulations design enabling high-voltage and long-life lithium metal batteries

Abstract

The poor compatibility of carbonate-based electrolytes with lithium metal anodes results in unstable solid electrolyte interphase, leading to lithium dendrite formation, low Coulombic efficiency, and short cycle life. To address this issue, we propose a novel fluorinated electrolyte that leverages lithium bis(fluorosulfonyl)imide (LiFSI), along with fluorinated solvents. An extremely low concentration of lithium nitrate exerts a substantial impact on the Li ion solvation structure, inducing an anions-rich solvation structure, results in an inorganic-rich electrolyte interphase layer mainly composed of Li3N and LiF, which effectively inhibits lithium dendrite formation, enhances the interfacial stability between the electrode and electrolyte, and yields excellent cycling performance in lithium metal batteries. When coupled with a high nickel content cathode (LiNi0.8Co0.1Mn0.1O2), the cells exhibit impressive cycling performance with 1000 cycles at 4 C, retaining 68.6 % capacity (with charge times under 15 min). Despite the relatively low oxidation stability of Dimethoxyethane in the electrolyte, the cell demonstrates exceptional high-voltage electrochemical performance, even up to 4.5 V, the cells do not show extensive electrolyte decomposition and structural changes, preserving 79.2 % capacity retention after 300 cycles. Using 50 µm lithium foil in the cells, remarkable capacity retention of 89.5 % is achieved after 400 cycles at 1 C. This remarkable compatibility between the anode and cathode represents a significant breakthrough in enhancing the reliability and performance of lithium metal batteries.