Pusan Researchers Develop Sodium-Ion Battery Anode to End Lithium Dependence

Pusan National University, South Korea, has come up with an interesting research wherein researchers have developed sodium-ion battery anode that is being claimed as highly efficient for the storage of power.

Pusan said that lithium is expensive and limited, necessitating the development of efficient energy storage systems beyond lithium-ion batteries and 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.

Pusan said that in view of climate change, it is necessary to reduce carbon emissions by utilizing renewable energy sources and developing efficient energy storage systems. Lithium-ion batteries are attached with high cost and limited supply of lithium. To this end, researchers have suggested sodium-ion batteries (SIBs) as a possible candidate.

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Pusan mentioned that 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.

A team of researchers, led by Professor Seung Geol Lee from Pusan, used quinacridones as precursors to prepare carbonaceous SIB anodes. Professor Geol said, “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 the professor.

The study will be published in the Chemical Engineering Journal in February. The researchers focused on 2,9-dimethylquinacridone (2,9-DMQA) in their study that 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.

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Technological breakthrough

Pusan researchers 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, said the Pusan research. The nitrogen- and oxygen-containing groups further enhanced battery storage via surface confinement and interlayer distance increment.

Prof. Lee said, “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.”