A Nonflammable Electrolyte for High-Voltage Lithium Metal Batteries

The electrochemical instability of the polar solventsin electrolytesoften causes reduction/oxidation at the surface of both Li anodesand nickel-rich cathodes in high-voltage lithium metal batteries (LMBs).Here, we design a bipolar molecule-regulated electrolyte with a capsule-likesolvation structure and nonflammability to stabilize high-voltageLMBs. The key enabler is to design and synthesize a nonflammable bipolarmolecule with a ion-dissociative polar head and a perfluorinated nonpolartail. The bipolar solvent promotes the formation of capsule-like solvationsheaths via weak coordination and encapsulates the polar moleculesinside the primary solvation shell, drastically reducing the detrimentaldecomposition of solvents. Finally, the assembled high-voltage cellprovides high capacity retention (Li||LiNi0.8Co0.1Mn0.1O2: >90%) during 200 charge/dischargecycles under strict conditions. The capsule-like electrolyte alsoenables a 420 mAh pouch cell with a cell-level energy density of 440Wh kg(-1) along with long cycling stability over 150cycles (retention: 92%).