Strong anchoring effect of ferric chloride-graphite intercalation compounds (FeCl3-GICs) with tailored epoxy groups for high-capacity and stable lithium storage

FeCl3-intercalated graphite intercalation compounds (GICs) show fascinating potential as anodes for high-performance lithium ion batteries (LIBs) due to their excellent reaction reversibility, low volume change and high volumetric energy density. Despite the recent success in the application of FeCl3-GICs in LIBs, the issue of dissolution of chlorides and the relevant Li-ion storage mechanism have not been well handled. Herein, we have designed and developed a type of FeCl3-intercalated GIC with abundant epoxy functional groups, which provide a strong chemical anchoring effect for effectively immobilizing chlorides in the interlayer space of graphite layers. By combining the first-principles calculations and experimental studies, it is discovered that the electronic decoupling effect of the adjacent graphite layers due to the intercalation of FeCl3 at a molecular level will significantly promote the amount of Li-ions stored in graphite accompanied by the formation of a stable discharge product of CLi. Benefiting from the strong chemical binding strength and the change of electronic characteristics, reversible capacities up to 1371 mA h g(-1) with a capacity retention of 98% after 50 cycles are attained. Our study provides a new route to restrict the dissolution of chlorides and may open the gate for metal chloride-based materials as high-capacity electrochemical energy storage systems.