Synergy of an In Situ-Polymerized Electrolyte and a Li3N-LiF- Reinforced Interface Enables Long-Term Operation of Li-Metal Batteries

The long-term operation of a Li-metal anode remains a great challenge due to the severe dendrite growth in an organic liquid electrolyte. To protect a Li-anode surface from continuous corrosion by an electrolyte, a consistent and robust solid electrolyte interface (SEI) is an essential prerequisite. This work proposes a secure gel polymer electrolyte, which is in situ constructed via a facile polymerization process of vinylidene carbonate inside Li-metal batteries. The liquid components that are not involved in polymerization are well entrapped in the poly(vinyl carbonate) framework, leading to a high oxidative stability of up to 4.5 V (vs Li/Li+). A Li3N-LiF-reinforced SEI resulting from the reduction of fluoroethylene carbonate and lithium nitrate additives has a synergistic effect on the suppression of Li -dendrite growth. The densely packed Li deposition behavior is revealed by in situ/ex situ microscopic observations. Steady cycling of over 2500 h with a relatively low voltage hysteresis is achieved by the Li||Li symmetric cells. A Coulombic efficiency above 96% upon long-term cycling is available for the asymmetric Li||Cu cells. The smooth operation of batteries with commercial LiFePO4 cathodes further indicates that the SEI with homogeneity in composition and structure prompts Li deposition with alleviative dendrites.

Automated summary

This study proposes a secure gel polymer electrolyte that exhibits high oxidative stability and suppresses Li dendrite growth. By constructing a robust solid electrolyte interface (SEI) in Li-metal batteries, stable cycling and high Coulombic efficiency are achieved.