Functionalization Mechanism of Reduced Graphene Oxide Flakes with BF3·THF and Its Influence on Interaction with Li+ Ions in Lithium-Ion Batteries

Abstract

Doping of graphene and a controlled induction of disturbances in the graphene lattice allows the production of numerous active sites for lithium ions on the surface and edges of graphene nanolayers and improvement of the functionality of the material in lithium-ion batteries (LIBs). This work presents the process of introducing boron and fluorine atoms into the structure of the reduced graphene during hydrothermal reaction with boron fluoride tetrahydrofuran (BF3·THF). The described process is a simple, one-step synthesis with little to no side products. The synthesized materials showed an irregular, porous structure, with an average pore size of 3.44–3.61 nm (total pore volume (BJH)) and a multi-layer structure and a developed specific surface area at the level of 586–660 m2/g (analysis of specific surface Area (BET)). On the external surfaces, the occurrence of irregular particles with a size of 0.5 to 10 µm was observed, most probably the effect of doping the graphene structure and the formation of sp3 hybridization defects. The obtained materials show the ability to store electric charge due to the development of the specific surface area. Based on cyclic voltammetry, the tested material showed a capacity of 450–550 mAh/g (charged up to 2.5 V).