Cyano and Fluorine-Enhanced\nCopolymer Electrolytes:\nSynergistically Boosting High-Voltage Lithium Metal Batteries

In high-voltage lithium metal batteries, designing electrolytes\nwith low salt concentrations to achieve stable electrode interfaces\npresents a formidable challenge. High-concentration electrolytes stabilize\nthe interface through an anion-derived LiF-rich interphase; however,\ntheir anion-rich solvation structures compromise the ionic conductivity.\nThis study introduces a polymer-derived interphase that maintains\ninterface stability at low lithium salt concentrations (∼1\nM). This strategy enables copolymer electrolytes to sustain the Li|Li\ncell for over 2500 h at 0.1 mA/cm<sup>2</sup>, even with a water content\nof 1000 ppm. Moreover, this research addresses the weak solvation\neffects in fluorinated polymer electrolytes by modulating the strongly\nsolvating cyano groups, resulting in electrolytes with a high ionic\nconductivity of 4 × 10<sup>–5</sup> S/cm at 30 °C.\nA 143.8 Wh/kg Li|LiNi<sub>0.8</sub>Co<sub>0.1</sub>Mn<sub>0.1</sub>O<sub>2</sub> pouch cell, with a lean electrolyte ratio of 5 g/Ah\nand a low negative/positive capacity ratio of 4, maintains a capacity\nretention of 90.5% after 29 cycles.