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Jong Chan Hyun(Advisor: Prof. Young Soo Yun), Revisiting Lithium- and Sodium-Ion storage in Hard Car
2023.03.08 Views 379
Jong Chan Hyun(Advisor: Prof. Young Soo Yun), Revisiting Lithium- and Sodium-Ion storage in Hard Carbon Anodes
From left, KU-KIST Graduate School of Converging Science and Technology Ph. D. corse Jong Chan Hyun and Prof. Young Soo Yun
A comprehensive comparative study elucidated the lithium/sodium-ion storage sites and mechanisms of hard carbon anodes for both sloping and plateau voltage sections and confirmed two important correlations between: i) the bulk chemisorption and intercalation capacities and ii) the closed pore volume and plateau capacities. These findings suggest that improved hard carbon anodes can be manufactured by designing optimal primary and secondary graphitic microstructures with well-developed bulk-chemisorption sites, poor intercalation characteristics, and an increased available closed pore volume.
The galvanostatic lithiation/sodiation voltage profiles of hard carbon anodes are simple, with a sloping drop followed by a plateau. However, a precise understanding of the corresponding redox sites and storage mechanisms is still elusive, which hinders further development in commercial applications. Here, a comprehensive comparison of the lithium- and sodium-ion storage behaviors of hard carbon is conducted, yielding the following key findings: 1) the sloping voltage section is presented by the lithium-ion intercalation in the graphitic lattices of hard carbons, whereas it mainly arises from the chemisorption of sodium ions on their inner surfaces constituting closed pores, even if the graphitic lattices are unoccupied; 2) the redox sites for the plateau capacities are the same as those for the closed pores regardless of the alkali ions; 3) the sodiation plateau capacities are mostly determined by the volume of the available closed pore, whereas the lithiation plateau capacities are primarily affected by the intercalation propensity; and 4) the intercalation preference and the plateau capacity have an inverse correlation. These findings from extensive characterizations and theoretical investigations provide a relatively clear elucidation of the electrochemical footprint of hard carbon anodes in relation to the redox mechanisms and storage sites for lithium and sodium ions, thereby providing a more rational design strategy for constructing better hard carbon anodes.
This research was published in Advanced Materials under the title of “Revisiting lithium- and sodium-ion storage in hard carbon anode”
Figure 1. Schematic image of lithium and sodium ion storage mechanism in hard carbon anode
The galvanostatic lithiation/sodiation voltage profiles of hard carbon anodes are simple, with a sloping drop followed by a plateau. However, a precise understanding of the corresponding redox sites and storage mechanisms is still elusive, which hinders further development in commercial applications. Here, a comprehensive comparison of the lithium- and sodium-ion storage behaviors of hard carbon is conducted, yielding the following key findings: 1) the sloping voltage section is presented by the lithium-ion intercalation in the graphitic lattices of hard carbons, whereas it mainly arises from the chemisorption of sodium ions on their inner surfaces constituting closed pores, even if the graphitic lattices are unoccupied; 2) the redox sites for the plateau capacities are the same as those for the closed pores regardless of the alkali ions; 3) the sodiation plateau capacities are mostly determined by the volume of the available closed pore, whereas the lithiation plateau capacities are primarily affected by the intercalation propensity; and 4) the intercalation preference and the plateau capacity have an inverse correlation. These findings from extensive characterizations and theoretical investigations provide a relatively clear elucidation of the electrochemical footprint of hard carbon anodes in relation to the redox mechanisms and storage sites for lithium and sodium ions, thereby providing a more rational design strategy for constructing better hard carbon anodes.
This research was published in Advanced Materials under the title of “Revisiting lithium- and sodium-ion storage in hard carbon anode”
Figure 1. Schematic image of lithium and sodium ion storage mechanism in hard carbon anode
