Superfine Expanded Graphite with Large Capacity for Lithium Storage

A superfine expanded graphite (s-EG) fiber material was investigated as an anode material for lithium-based batteries. The fibers were prepared by decomposition of dicarbon monofluoride-intercalated graphite. The high resolution transmission electron microscopy (HRTEM) images showed the fiber thickness in range of 2-3 nm with several microns in length. Lithium storage capacity in this material was measured in lithium half cells. High lithium storage capacity of about 1000 mAh.g(-1) at a rate of C/10, corresponding to Li3C6 composition was obtained. The material showed fairly good rate capability exhibiting lithium storage capabilities even at 60C. As a effect of ball milling, the s-EG showed crystallographic ordering in the sample with reduced the lithium storage capacity corresponding to composition of LiC6. A simple mathematical relation to account for the excess lithium storage capacity in this material is put forward.