The surface of pyrolyzed sugar carbons (PSCs) was treated with H2O2, HNO3, or H2SO4 reagents. Surface modification of these materials improved their electrode performance. FTIR, Raman, C-13 NMR, and X-ray diffraction (XRD) spectroscopic techniques were used to characterize structures of the treated and untreated carbons. The charge/discharge capacity, potential profile, and irreversible capacity loss have been investigated. The correlations between cell capacities, H/C ratios, and Raman vibrational modes are discussed. (C) 2002 Elsevier Science B.V. All rights reserved.