Exploiting the Coordination Effect in Fe-Phenanthroline Complex for the Catalytic Carbonization of Phenanthroline toward the High Capacity Anode Grade Carbon

Abstract

Aromatic organic molecules (AOMs) present an appealing precursor option for anode-grade hard carbon for sodium-ion batteries (SIBs) because of their prevalence, diverse chemical functionalities, and huge scope for nanostructure engineering at the molecular level. However, most small organic molecules decompose before actual carbonization is initiated unless reactions are carried out under high pressures or in the presence of catalysts. Herein, we report a facile carbonization of aromatic monomeric phenanthroline (phen) by exploiting the strong molecule-level coordination effect of the Fe-phen complex and in situ catalysis affected by Fe. With this carbonization strategy, we achieve better scalability with appreciable carbon yield, while carbonization of simple phen molecule returns zero carbon yields. The as-prepared N-doped microporous carbon (NMC) possesses desirable microstructural features with optimum nitrogen content to be employed as an anode for SIB. As an anode, the NMC delivers a high reversible capacity of 271 mAh g–1 at 100 mA g–1, an ultrahigh rate capability of 101 mAh g–1 at 1 A g–1, and a stable cycle life. The galvanostatic intermittent titration technique (GITT) depicts sodium ion diffusion coefficients of the order of ∼10–13 (cm2 s–1) in the intercalation region, which implies a faster sodium ion diffusion rate compared to most of the reported hard carbons. Given the vast diversity of AOMs, this work encourages new research interests to produce advanced carbon materials with nanostructure engineering at the molecular level for sodium-ion battery applications.