Highly stable lithium metal anode enabled by lithiophilic and spatial-confined spherical-covalent organic framework

Li metal anode (LMA) has been considered as the most gifted anode material endowed with unprecedented theoretical specific capacity and ultralow redox potential. Nevertheless, the inevitable Li dendrite growth and frangible solid electrolyte interphase (SEI) severely impede its commercial application. Herein, a facile strategy via constructing an artificial SEI configured with highly-crystalline spherical covalent organic framework (S-COF) was applied to regulate the interfacial stability of LMA. Benefiting from the well balance of precise geometric symmetry and methodical morphology within S-COF, the regular 3D-spherical spreading with ordered 1D channels can effectively promote homogeneous distribution of Li+ flux. Meanwhile, the functional lithiophilic coordination has been identified by solid-state nuclear magnetic resonance, Fourier-transform infrared spectra and density functional theory calculations. The energetical Li+ affinity towards S-COF skeleton is prone to facilitate ion-pair dissociation and Li+ uniform transfer. Furthermore, the rigid nanochannels with space-confinement effect can also retard the large-scale lithium nucleation and dendrite formation. Consequently, the derived LiF and Li2S2/Li2S-riched S-COF@Li layer exhibits extraordinary cycling stability in Li|Li symmetrical cell, Li|LiFePO4, and Li|S full cells operated at higher current densities. The aforementioned experimental and theoretical evidences provide a viable guidance for further design and implementation of 2D COF in high energy density batteries.