A Nonflammable Electrolyte for High-Voltage Lithium Metal Batteries
Guangzhao Zhang, Jiawei Li, Qingrong Wang, Hui Wang, Jun Wang, Kai Yu, Jian Chang, Chaoyang Wang, Xiang Hong, Qiang Ma, Yonghong Deng
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||LiNi 0.8 Co 0.1 Mn 0.1 O 2: >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%).