Lithium Insertion in Carbons Containing Nanodispersed Silicon

Graphite and pregraphitic carbons are intercalation hosts commonly used in Li ion cells. Using chemical vapor deposition of benzene and of silicon‐containing precursors, we have prepared carbons containing nanodispersed silicon. The silicon resides within the unorganized regions in the pregraphitic carbons. Materials with up to 11% atomic silicon have been prepared. These materials reversibly react with lithium in electrochemical cells and the reversible specific capacity increases from , in the absence of silicon, to near as silicon is added. For silicon content <6 atomic percent, the reversible capacity increases linearly with a slope of approximately per percentage point silicon. This suggests that each silicon atom can reversibly bond with ∼1.5 lithium atoms. The increased capacity due to the silicon appears as a broad feature in the differential capacity between 0.1 and 0.6 V vs. Li metal. The large reversible capacities are maintained over many charge/discharge cycles. It is our view that the carbonaceous matrix provides a pathway for diffusion of Li to the nanodispersed silicon atoms, while it can still intercalate a substantial amount of lithium. Nanodispersions of other lithium alloying atoms in carbon probably can be prepared.