Anion-Diluent Pairing for Stable High-Energy Li Metal Batteries

Rechargeable Li metal batteries (LMBs) have attractedwide attention as promising candidates for the next generation of energy-storage systems. However, limited Coulombic efficiency and unregulateddendrite growth restrict its application. Here, we report a kind ofelectrolyte by introducingfluorinated aromatic diluents into high-concentration electrolytes (HCEs). Unlike other localized HCEs, thefluorinated aromatic diluents pairing with anions promote the formation of a homogeneous and robust solid-electrolyteinterphase (SEI), which endows Li metal with an ultrahigh Coulombic efficiency of similar to 99.8%. The Li||LiNi0.8Co0.1Mn0.1O2battery holds a capacity retention of >80% over 260 cycles even with a thin Li anode (20 mu m) and a high cathode loading (3.5mAh cm-2). A 1.8 Ah Li||NMC811 pouch cell with a lean electrolyte delivers an energy density of 340 Wh kg-1and a stablecycling life over 200 cycles. The designed electrolytes, which benefit from the synergetic effects of anions and diluents on theSEI, pave the way for the next-generation LMBs.

Automated summary

This research reports a new method to improve the Coulombic efficiency and inhibit dendritic growth in rechargeable Li metal batteries by introducing fluorinated aromatic diluents into high-concentration electrolytes. The use of this electrolyte provides higher energy density and cycling life without compromising the performance of the battery.