Oxide-modified carbon was prepared by adding boron acid in the precursor using the wet chemical method. The modification effect on the electrochemical performance of the hard carbon is then evaluated. It is found that the capacity of the hard carbon can be enhanced by more than 50% of the original sample cycling between 0.0 and 3.0 V after 10.52 wt % O is introduced. This enhancement originates from the up-shift effect of the insertion potential during the discharge process. The modification of the electron structure of the host material by oxide in the carbon matrix is supposed to be responsible for the enhanced lithium storage capacity. (C) 2004 The Electrochemical Society.