High-safety and high-voltage lithium metal batteries enabled by nonflammable diluted highly concentrated electrolyte
Han Zhang, Ziqi Zeng, Shuping Wang, Yuanke Wu, Changhao Li, Mengchuang Liu, Xinlan Wang, Shijie Cheng, Jia Xie
Abstract
Lithium metal batteries (LMBs) show great promise for achieving energy densities over 400 Wh·kg−1. However, highly flammable organic electrolytes are a long-lasting problem that triggers safety hazards and hinders the commercial application of LMBs. Here, a nonflammable diluted highly concentrated electrolyte (DHCE) with ethoxy(pentafluoro)cyclotriphosphazene (PFPN) as a diluent is developed to simultaneously achieve high safety and cycling stability of high-voltage LMBs. The optimal DHCE not only ensures reversible Li deposition/dissolution behavior with a superior average Coulombic efficiency (CE) over 99.1% on lithium metal anode (LMA), but also suppresses side reactions and stress crack on the LiCoO2 (LCO) under high cut-off voltage. The newly developed DHCE exhibits high thermal stability, showing complete nonflammability and reduced heat generation between the electrolyte and delithiated LCO/cycled LMA. This work offers an opportunity for rational designing nonflammable electrolytes toward high-voltage and safe LMBs.