Atomic Editing of the First‐Shell to Modulate the d‐Electron State of Transition Metal Sites for Accelerated Redox Kinetics in Lithium−Sulfur Batteries

Abstract

ABSTRACT Organometallic macrocyclic molecules have shown great potential to accelerate the reaction kinetics in Li−S batteries. However, it is still challenging to precisely tailor the microenvironment of metal sites and enhance its intrinsic reactivity. Herein, inspired by single‐atom editing in organic chemistry, we prepared a series of isolobal nickel‐based organometallic macrocyclic molecules (denoted as Ni−N x C y ) to optimize the steric configuration and d‐orbital states of Ni sites by tuning the first coordination shell at atom‐level. In situ x‐ray absorption spectroscopy revealed the dynamic evolution of nickel sites, while in situ Raman spectra demonstrated the accelerated sulfur conversion kinetics for Ni−N 2 C 2 in Li−S batteries. Theoretical calculations confirmed that the geometric configuration of Ni−N x C y can be modulated by first‐shell atoms, when the d xy and d x 2 − y 2 orbitals of nickel can be activated for N 2 C 2 ‐coordinated Ni site. In addition, the up‐shift of d‐band center for Ni−N 2 C 2 further facilitates its hybridization with sulfur species. Consequently, cells with Ni−N 2 C 2 deliver 1277 mA h g −1 at 0.5 C, while showing a decay rate of 0.04% at 2 C. Furthermore, an Ah‐level pouch cell with energy density of 393 W h kg −1 can be achieved based on the total mass of cell. This work provides mechanistic insights into the microenvironment regulation of single‐metal‐site and structure–activity relationships in Li−S batteries.