Nanographenes with Fully-Substituted Group 7A Elements: The Chemistry in Lithium-ion Battery Anodes

Graphene has received intensive scientific attentions as an electrode material for lithium-ion batteries because of its extraordinary physical and electrical properties. However, the lacking of structural control and restacking issues have hindered its application as carbon-based anode materials for next generation lithium-ion batteries. To tackle these problems and improve its performance, several modification approaches such as edge-functionalization and electron-donating/withdrawing substitution have been considered as promising strategies. In addition, group 7A elements have been known as critical elements due to their electronegativity and electron withdrawing character, which can regulate the electronic and structural properties of materials. Herein we elucidated the chemistry of nanographenes with fully-substituted group 7A elements as lithium-ion battery anodes. The nanographenes have been synthesized via bottom-up organic synthesis to ensure the structural control. Our study reveals that the present of halogen atoms on the edge not only tuned their structural and electronic properties, but also impacted material stability and reactivity as well as Li⁺ storage capability. Further systematically spectroscopic study indicates that the charge polarization caused by halogen atoms could also regulate the Li⁺ transport, charge transfer energy, and charge storage behavior of nanographenes. This study provides a deep understanding on the molecular design of nanographene anodes for next-generation lithium-ion batteries.