Understanding an Exceptionally Fast and Stable Li-Ion Charging of Highly Fluorinated Graphene with Fine-Controlled C–F Configuration

Fluorine (F) atoms with the highest electronegativity and low polarizability can easily modify the surface and composition of carbon-based electrode materials. However, this is accompanied by complete irreversibility and uncontrolled reactivity, thus hindering their use in rechargeable electronic devices. Therefore, understanding the electrochemical effects of the C–F configuration might lead to achieving superior electrochemical properties. Here, we demonstrate that the fluorinated and simultaneously reduced graphene oxide (FrGO) was easily synthesized through direct gas fluorination. The as-prepared 11%-FrGO electrode exhibited a high capacity (1365 mAh g^–1 at 0.1 A g^–1), remarkable rate capability, and good stability (64% retention after 1000 cycles at 5 A g^–1). Furthermore, the annealed FrGO (11%-FrGO­(A)) electrode in which the C–F bond configurations were controlled by facile thermal treatment shows long-term stability (80% retention after 1000 cycles at 5 A g^–1). Above a certain content, F atoms enhance Li-ion adsorption and electron transfer, accelerate Li-ion diffusion, and facilitate the formation of a solid electrolyte interphase layer. In particular, the C–F configuration plays a significant role in retaining the capacity under harsh recharging conditions. The results in this study could provide valuable insights into the field of rechargeable devices.