Aligned artificial solid electrolyte interphase layers as versatile interfacial stabilizers on lithium metal anodes

Abstract

Lithium (Li) metal batteries (LMBs) have been recognized as ideal energy storage devices of the next generation because of the ultrahigh theoretical capacity of lithium metal anodes. However, lithium metal anodes suffer from inhomogeneous Li deposition and consequent serious Li dendritic problems, resulting in the fast fade of capacity and in potential safety hazard. Solid electrolyte interphase (SEI) is one of the most crucial factors in the regulation of Li deposition. An ideal SEI layer with remarkable Li affinity is conducive to homogeneous Li deposition. Therefore, precise regulation of the components of the SEI layer is the key strategy to stabilize the Li plating process. In this work, we designed a novel porous artificial SEI layer with electrochemically active sulfuryl fluoride (–SO₂F) groups grafted onto an aligned polymeric skeleton. The –SO₂F groups can in situ react with Li to generate –SO₂Li groups and lithium fluoride (LiF). The formed LiF-dominating SEI layer on the Li surfaces with high interfacial energy can passivate the Li metal electrode and stabilize the Li electrodeposition process. Moreover, –SO₂Li groups with ordered arrangement in hexagonal pores would effectively serve as ionic conductive sites to increase the Li affinity of the SEI layer and realize the satisfactory ionic redistribution at the interface. In addition, –SO₂Li groups grafted onto the pore walls in covalent organic framework can also facilitate the rapid ion transport along one-dimensional channels. The synergistic effect of –SO₂Li groups and LiF makes this artificial SEI layer a versatile interfacial stabilizer on lithium metal anodes. As a result, symmetric batteries exhibit superior cycling stability over 3530 h under 2 mA cm⁻². The exceptional electrochemical cycling stability demonstrates the effectiveness in addressing the disordered metallic Li electrodeposition in LMBs.