Longitudinally grown pyrolyzed quinacridones for sodium-ion battery anode

Abstract

Carbonaceous materials have been actively investigated as anode materials for sodium-ion batteries (SIBs). However, the development of carbonaceous materials that can effectively accommodate large sodium ions within carbon microstructures is highly challenging. In this study, quinacridones (QAs) are used to prepare SIB anode materials via pyrolysis. Among QAs, 2,9-dimethylquinacridone (2,9-DMQA) exhibits prominent morphological development with a high char yield of 61 % at 600 °C. Additionally, we reveal that the pyrolysis mechanism and microstructure are significantly affected by the crystal orientation of the precursor. As the 2,9-DMQA has a parallel-oriented crystal structure, the pyrolyzed 2,9-DMQAs grow polycyclic aromatic hydrocarbons with longitudinal microstructures through thermal polymerization initiated by methyl substituents. In addition, the evolution of gas from the 2,9-DMQA precursor induces the reorganization of the carbon framework to form a disordered structure. The anodes fabricated with the 2,9-DMQA pyrolyzed at 600 °C (2,9-DMQA-600) show sodium-ion storage performance with a high rate capability (290 mAh/g at a current density of 0.05 A/g) and excellent cycle stability (247 mAh/g at 0.1 A/g after 200 cycles and 134 mAh/g at 5 A/g after 1000 cycles). The well-developed carbon microstructures and surface-confined sodium-ion storage derived from the remaining N-containing and O-containing functional groups provide superior electrochemical performance.