In situ formation of bifunctional interlayer on 3D conductive scaffold for dendrite-free Li metal batteries

Abstract

Regulating lithium (Li) plating/stripping behavior in three-dimensional (3D) conductive scaffolds is critical to stabilizing Li metal batteries (LMBs). Surface protrusions and roughness in these scaffolds can induce uneven distributions of the electric fields and ionic concentrations, forming “hot spots.” Hot spots may cause uncontrollable Li dendrites growth, presenting significant challenges to the cycle stability and safety of LMBs. To address these issues, we construct a Li ionic conductive-dielectric gradient bifunctional interlayer (ICDL) onto a 3D Li-injected graphene/carbon nanotube scaffold (LGCF) via in situ reaction of exfoliated hexagonal boron nitride (fhBN) and molten Li. Microscopic and spectroscopic analyses reveal that ICDL consists of fhBN-rich outer layer and inner layer enriched with Li3N and Li-boron composites (Li-B). The outer layer utilizes dielectric properties to effectively homogenize the electric field, while the inner layer ensures high Li ion conductivity. Moreover, DFT calculations indicate that ICDL can effectively adsorb Li and decrease the Li diffusion barrier, promoting enhanced Li ion transport. The modulation of Li kinetics by ICDL increases the critical length of the Li nucleus, enabling suppression of Li dendrite growth. Attributing to these advantages, the ICDL-coated LGCF (ICDL@LGCF) demonstrates impressive long-term cycle performances in both symmetric cells and full cells.