Covalent Organic Frameworks with Low Surface Work Function Enabled Stable Lithium Anode

Uniform deposition and distribution of lithium ion (Li+) on the surface of lithium metal anode is crucial for long-life and high-safety lithium metal batteries. However, the preparation of stable solid-electrolyte interphase (SEI) is mostly based on trial and error in the absence of guideline. Herein, covalent organic framework (COF) with high Young's modulus and low surface work function is in situ synthesized on Li anode to stabilize Li|electrolyte interface. Notably, Young's modulus, mechanical index for Li dendrite resistance, and surface work function, electrical index for Li+ distribution, can be regarded as macroscopically detectable indicators to evaluate the artificial SEI before battery assembly. The COFTpPa modified Li metal anodes delivered stable cycling over 1000 (2000) h at high current density of 5 (2) mA cm(-2) in the ether-based electrolyte, and the full cells with commercial LiFePO4 electrode (mass loading of 16.5 mg cm(-2)) demonstrate remarkably enhanced cycling performance with a high reversible capacity of 152.3 mAh g(-1) (retention of 96.8%) after 300 cycles.

Automated summary

The study found that in lithium metal batteries, stabilizing the Li|electrolyte interface can be achieved by in-situ synthesizing COF on the Li anode, leading to longer cycle life and higher safety. By measuring indicators such as Young's modulus and surface work function of the COF-modified Li metal anode, the performance of the artificial SEI can be evaluated before battery assembly.