CORRELATION BETWEEN LITHIUM INTERCALATION CAPACITY AND MICROSTRUCTUREIN HARD CARBONS

Hard carbons prepared from organic precursors by pyrolysis near 1000 d egrees C generally have poorly developed (002) Bragg peaks and also sh ow evidence for microporosity in small angle x-ray scattering experime nts. When the peak-to-background ratio of the (002) peak is small, it indicates that hard carbons contain significant amounts of single, bil ayer, or trilayer graphene sheets which are arranged at arbitrary angl es. These carbons also contain the micropores implied by such a stacki ng arrangement. With electrochemical measurements on Li/carbon electro chemical cells, we show that those carbons with the largest capacity f or lithium are those with the largest fraction of single graphene shee ts and with the smallest average micropore size. Over 80 samples prepa red from a variety of precursors at a selection of temperatures have b een studied. The trends observed may help point the way to better anod e materials for advanced Li-ion batteries.