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

Abstract

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 COF_TpPa 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.