Guiding Uniformly Distributed Li-Ion Flux by Lithiophilic Covalent Organic Framework Interlayers for High-Performance Lithium Metal Anodes.

Abstract

Lithium (Li) metal anodes are regarded as prospective anode materials in next-generation secondary lithium batteries due to their ultrahigh theoretical capacities and ultralow potentials. However, inhomogeneous lithium deposition and uncontrollable growth of lithium dendrites always give rise to the low lithium utilization, rapid capacity fading, and poor cycling performance. Herein, we design the lithiophilic covalent organic frameworks (COFs) containing preorganized triazine rings and carbonyl groups as the multifunctional interlayer in lithium metal batteries (LMBs). Triazine rings rich in lone pair electrons can act as the donor attracting Li ions, and carbonyl groups serve as Li-anchoring sites effectively coordinating Li ions. These periodic arranged subunits significantly guide uniform Li ion flux distribution, guarantee smooth Li deposition and less lithium dendrite formation. Consequently, the symmetric batteries with COF interlayers exhibit an extraordinary cycling stability for more than 2450 and 1000 h with ultralow polarization voltage of about 12 and 14 mV at 0.5 and 1.0 mA cm-1. Coupling with sulfur (S) cathodes and LiFePO4 (LFP) cathodes, the full cells also demonstrate superb energy density achievement and rate performance. With introducing lithiophilic COFs interlayers, the Li-LFP batteries exhibit high capacity of 150 mAh g-1 and 86% capacity retention after 450 cycles at 0.5 C.