A Nonflammable Electrolyte for High-Voltage Lithium Metal Batteries

Abstract

The electrochemical instability of the polar solvents in electrolytes often causes reduction/oxidation at the surface of both Li anodes and nickel-rich cathodes in high-voltage lithium metal batteries (LMBs). Here, we design a bipolar molecule-regulated electrolyte with a capsule-like solvation structure and nonflammability to stabilize high-voltage LMBs. The key enabler is to design and synthesize a nonflammable bipolar molecule with a ion-dissociative polar head and a perfluorinated nonpolar tail. The bipolar solvent promotes the formation of capsule-like solvation sheaths via weak coordination and encapsulates the polar molecules inside the primary solvation shell, drastically reducing the detrimental decomposition of solvents. Finally, the assembled high-voltage cell provides high capacity retention (Li||LiNi0.8Co0.1Mn0.1O2: >90%) during 200 charge/discharge cycles under strict conditions. The capsule-like electrolyte also enables a 420 mAh pouch cell with a cell-level energy density of 440 Wh kg–1 along with long cycling stability over 150 cycles (retention: 92%).