X-ray diffraction analysis of the structure of the new lithium rich graphite intercalation compound Li2C6O0.5

A new yellow lithium-rich graphite intercalation compound formulated Li2C6O 0.5 has been synthesized in ambient conditions by electrochemical intercala tion of lithium into the blue stage two NaC6O0.5 compound in LiClO4-ethylen e carbonate electrolyte. This new compound is a quasi stage 1 compound of b iintercalation type characterized by an identity period along c-axis (I-c) equal to 1035 pm. Such a value is the sum of an interplanar distance of 370 pm resulting in lithium intercalation in the Van der Waals gap of NaC6O0.5 and of another one of 665 pm related both to the intercalation of lithium and to the concomitant exchange of sodium by lithium in the five intercalat ed layers of the pristine stage two compound. Preliminary studies of the st ructural 2D-organization give evidence for lithium species arranged in a cl assical hexal structure as in LiC6 or LiC12 compounds. Sodium resulting fro m sodium ion reduction appears in the form of clusters distributed in the n ew material. (C) 1999 Elsevier Science Ltd. All rights reserved.