High lithiophilicity and Li diffusion rate on 1T phase transition metal dichalcogenides as effective Li regulating materials for dendrite-free metal anodes

Abstract

Effective lithium regulating materials (LRMs) that enable fast Li diffusion, as well as regulate Li nucleation to avoid its aggregation, are promising to eliminate the uncontrolled dendrite formation at the metal anode. Herein, we find that the 1T phase transition metal sulfides and selenides are a good LRM for Li metal anode via systematic investigation on Li binding strength and diffusion barrier, experimentally and computationally, among a series of 2D materials, including graphene, h-BN and 20 transition metal sulfides/selenides. The high Li binding strength arises from the high and concentrated charge transfer to Li due to the high electronegativity and local dipole of metal sulfides and selenides. To validate the result, 2D VS₂ flakes were synthesized on nitrogen-doped CNT (NCNT) using the chemical vapor deposition (CVD) method. The symmetric Li/Li cells using VS₂-LRM exhibited excellent cyclic stability over 1000 cycles with low overpotentials of 75 and 12 mV at 0.5 and 2 mA cm⁻², respectively, with uniform and compact Li deposition. This work provides a fundamental understanding of designing efficient LRMs for a dendrite-free metal anode and uncovers the lithiophilicity chemistry of 2D metal sulfides/selenides for safe rechargeable metal batteries.