Enhancing lithium-metal battery longevity through minimized coordinating diluent

Extending the lifespan of lithium (Li) batteries involves managing reactions at the Li anode and stabilizing the solid–electrolyte interphase (SEI) through strategic regulation of the electrolyte composition. Here we synthesized a fluorinated cyclic ether with minimized Li-ion coordination capability and enhanced electrochemical stability. We demonstrated its crucial role in manipulating the SEI formation process by differentiating the contribution of dual anions to the SEI layer. Consequently, a bilayer SEI is formed, featuring a Li2O-rich inner layer and a LiF-rich outer layer, enabling improved stability and reversibility of Li-metal anodes. The developed electrolyte shows remarkable improvement in calendar life and cycling stability of Li (50 µm)||NMC811 (4 mAh cm−2) cells, maintaining 80% capacity after 568 and 218 cycles at room temperature and 60 °C, respectively. Furthermore, our 410 Wh kg−1 prototype pouch cells demonstrate 80% capacity retention for 470 cycles. Lithium battery performance hinges significantly on the solvation structure of the electrolyte and the resulting interphase. Here the authors introduce a fluorinated ether with minimal lithium-ion coordination and enhanced electrochemical stability, thus improving both cyclability and calendar life.