In order to investigate the influence of the dispersion state of electro-conductive additives on the properties of lithium ion batteries, we examined the charge-discharge properties of cathodes prepared with suspensions of ketjen black (KB) dispersed in an organic solvent with different particle sizes. Discharge capacity, durability and resistance to high-current discharge of the cathode prepared from a well-dispersed suspension was higher than those of the cathode prepared with ketjen black powder. Because ketjen black particles in the cathode prepared from a well-dispersed suspension formed a conductive dense-network uniformly, despite the low amount of additive, we concluded that an electro-conductive network made of ketjen black, which can transmit electrons smoothly from active materials to the collector, formed in the cathode when the cathode was prepared from a well-dispersed suspension. (C) 2003 Elsevier Science B.V. All rights reserved.