• Resources Recycling
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• v.25 no.3
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• pp.82-87
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• 2016

The discharged products of Li-$O_2$ and Na-$O_2$ batteries using ether-based electrolyte as next-generation battery system were analyzed. The morphology of the discharged products showed millet-like shape in the both battery systems by FESEM. However, the discharged product, $Li_2O_2$ showed amorphous-like form in the Li-$O_2$ cell while crystalline $NaO_2$ is formed in the Na-$O_2$ cell when confirmed by X-ray diffraction. In this work, we comprehended a principle operating mechanism of Li-$O_2$ and Na-$O_2$ battery.

• Clean Technology
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• v.29 no.3
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• pp.178-184
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• 2023

Transition metal chalcogenides have garnered significant attention as anode materials for sodium-ion batteries due to their high theoretical capacity. Nevertheless, their practical application is impeded by their limited lifespan resulting from substantial volume expansion during cycling and their low electrical conductivity. To tackle these issues, this study devised a solution by synthesizing a nanostructured anode material composed of porous CNT (carbon nanotube) spheres and (Ni,Co)Se₂ nanocrystals. By employing spray pyrolysis and subsequent heat treatments, a porous-structured (Ni,Co)Se₂-CNT composite microsphere was successfully synthesized, and its electrochemical properties as an anode for sodium-ion batteries were evaluated. The synthesized (Ni,Co)Se₂-CNT microsphere possesses a porous structure due to the nanovoids that formed as a result of the decomposition of the polystyrene (PS) nanobeads during spray pyrolysis. This porous structure can effectively accommodate the volume expansion that occurs during repeated cycling, while the CNT scaffold enhances electronic conductivity. Consequently, the (Ni,Co)Se₂-CNT anode exhibited an initial discharge capacity of 698 mA h g^-1 and maintained a high discharge capacity of 400 mA h g^-1 after 100 cycles at a current density of 0.2 A g^-1.

• Journal of the Korean Electrochemical Society
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• v.23 no.1
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• pp.11-17
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• 2020

The Prussian blue analogues of Fe₂(CN)₆ and Na_xFe₂(CN)₆ are prepared by precipitation method and evaluated the electrochemical characteristics as positive electrode materials for lithium-ion batteries (LIBs) because of their low cost. Fe₂(CN)₆ shows a low reversible capacity of 34.6 mAh g^-1, whereas sodium-containing Na_xFe₂(CN)₆ exhibits a reversible capacity of 107.5 mAh g^-1 when the discharge process proceeds first. When charging is first carried out to remove sodium in the structure, the reversible capacity of 114.1 mAh g^-1 is achieved and the cycle performance is further improved. In addition, Na_x-Fe₂(CN)₆ is synthesized at 0℃, room temperature (RT), and 60℃, respectively. Regardless of the synthesis temperature, Na_xFe₂(CN)₆ shows similar initial reversible capacity, but the crystallite size is formed smaller and improved cycle performance when synthetic temperature is lower. The sample synthesized at 0℃ shows a reversible capacity of 86.4 mAh g^-1 at the 120^th cycle and maintains 76.8% of the initial capacity.