Carbonaceous anodes based on organic pigments exhibit a high sodium-ion storage performance and excellent cycle stability, finds a new study.
Lithium is expensive and limited, necessitating the development of efficient energy storage systems beyond lithium-ion batteries. Sodium is a promising candidate. However, sodium ions, being large and sluggish, hamper sodium-ion battery (SIB) anode performance. Researchers from Korea and USA have recently developed pyrolyzed quinacridones, new carbonaceous SIB anode materials, that are efficient, easily prepared, and exhibit excellent electrochemical properties, including high sodium-ion storage performance and cycling stability.
Climate change is a major global concern of the present century. It is necessary to reduce carbon emissions by utilizing renewable energy sources and developing efficient energy storage systems. Lithium-ion batteries have high energy density and a long cycle life, making them indispensable in portable electronics as well as electric vehicles. However, the high cost and limited supply of lithium necessitate the development of alternative energy storage systems. To this end, researchers have suggested sodium-ion batteries (SIBs) as a possible candidate.
Besides having physicochemical properties similar to that of lithium, sodium is both sustainable and cost-effective. However, its ions are large with sluggish diffusion kinetics, hindering their accommodation within the carbon microstructures of the commercialized graphite anodes. Consequently, SIB anodes suffer from structural instability and poor storage performance. In this regard, carbonaceous materials doped with heteroatoms are showing promise. However, their preparation is complicated, expensive, and time-consuming.
Recently, a team of researchers, led by Professor Seung Geol Lee from Pusan National University in Korea, used quinacridones as precursors to prepare carbonaceous SIB anodes. “Organic pigments such as quinacridones have a variety of structures and functional groups. As a result, they develop different thermal decomposition behaviors and microstructures. When used as a precursor for energy storage materials, pyrolyzed quinacridones can greatly vary the performance of secondary batteries. Therefore, it is possible to implement a highly efficient battery by controlling the structure of organic pigments precursor,” explains Prof. Lee. Their study was made available online on 17 October 2022 and will be published in Volume 453, Part 1 of the Chemical Engineering Journal on 1 February 2023.
The researchers focused on 2,9-dimethylquinacridone (2,9-DMQA) in their study. 2,9-DMQA has a parallel molecular packing configuration. Upon pyrolysis (thermal decomposition) at 600°C, 2,9-DMQA turned from reddish to black with a high char yield of 61%. The researchers next performed a comprehensive experimental analysis to describe the underlying pyrolysis mechanism.
They proposed that the decomposition of methyl substituents generates free radicals at 450°C, which form polycyclic aromatic hydrocarbons with a longitudinally grown microstructure resulting from bond bridging along the parallel packing direction. Further, nitrogen- and oxygen-containing functional groups in 2,9-DMQA released gases, creating disordered domains in the microstructure. In contrast, pyrolyzed unsubstituted quinacridone developed highly aggregated structures. This suggested that the morphological development was significantly affected by the crystal orientation of the precursor.
In addition, 2,9-DMQA pyrolyzed at 600°C exhibited a high rate capability (290 mAh/g at 0.05 A/g ) and excellent cycle stability (134 mAh/g at 5 A/g for 1000 cycles) as an SIB anode. The nitrogen- and oxygen-containing groups further enhanced battery storage via surface confinement and interlayer distance increment.
“Organic pigments such as quinacridones can be used as anode materials in sodium-ion batteries. Given the high efficiency, they will provide an effective strategy for mass production of large-scale energy storage systems,” concludes Prof. Lee.
We sure hope his vision comes true soon!
Title of original paper: Longitudinally grown pyrolyzed quinacridones for sodium-ion battery anode
Journal: Chemical Engineering Journal
About Pusan National University
Pusan National University, located in Busan, South Korea, was founded in 1946, and is now the no. 1 national university of South Korea in research and educational competency. The multi-campus university also has other smaller campuses in Yangsan, Miryang, and Ami. The university prides itself on the principles of truth, freedom, and service, and has approximately 30,000 students, 1200 professors, and 750 faculty members. The university is composed of 14 colleges (schools) and one independent division, with 103 departments in all.
About the author
Seung Geol Lee is a Professor of Organic Material Science & Engineering at Pusan National University, Korea. In 2011, he received a Ph.D. in Materials Science and Engineering from Georgia Institute of Technology, USA. He has published 155 papers with 336 co-authors during the last 15 years. His work has been cited 3270 times. His research interests include electrode materials for energy storage in fuel cells and secondary