Redox-Active Metal-Covalent Organic Frameworks for Dendrite-Free Lithium Metal Batteries.

Abstract

Lithium (Li) metal has gained attention as an anode material for lithium-metal batteries (LMBs) owing to its low electrochemical potential, high specific capacity, and low density. However, the accumulation of Li dendrites and unstable solid electrolyte interphases, caused by sluggish Li⁺ migration and uneven Li deposition, limit practical LMB applications. This study presents the first report on redox-active metal-covalent organic frameworks (MCOFs) with dual-active centers as functional separators for LMBs. These MCOFs facilitate homogeneous Li nucleation and accelerate Li⁺ ion transport. The synergistic effects of redox-active diarylamine units and trinuclear copper clusters modulate local electron-cloud density, regulating microenvironment of Li⁺ ions and ensuring homogeneous Li nucleation. The MCOF-based separator's well-defined 1D channels in MCOF-based separator enable uniform Li⁺ flux, and promote homogeneous Li deposition, resulting in high Li⁺ transference number of 0.93 and an ionic conductivity of 2.01 mS cm^-1 at room temperature. The Li|Cu cell demonstrates a low Li nucleation barrier of 16 mV, while the Li symmetric cell exhibits stable Li plating/stripping for over 1600 h at 0.5 mA cm^-2. When coupled with LiFePO₄ cathodes, the assembled LMB exhibits stable capacity retention of ≈98%. This work paves the way for dendrite-free Li metal anodes in high-performance LMBs.