Synthesis and characterization of a new lithium-rich graphite intercalation compound: Li2C6Oy (y≈0.5)

Abstract

The electrochemical reduction of the blue, second-stage NaC₆O_0.5 graphite intercalation compound (GIC) in LiClO₄–ethylene carbonate electrolyte results in the formation of the new yellow quasi-stage 1 GIC, of biintercalation type and ideally formulated as Li₂C₆O_0.5. Such a high lithium concentration has never been observed in GICs synthesized in ambient conditions. The identity period along the c axis is equal to 1035 pm and results, as in biintercalation compounds, in the addition of two interplanar spacings of different values: one equal to 370 pm as in LiC₆ and the other equal to 665 pm, resulting from the intercalation of five alternating layers, three of lithium and two of oxygen. Sodium is present in this material in the form of regularly distributed metallic clusters.