In our previous work. we found that the LiCoO2/graphite-coke hybrid carbon system had less initial discharge capacity but better cycle performance than the LiCoO2/pure graphite system, which is the most commonly used lithium secondary battery system. In this report, we examine the effects of a better graphite-coke hybrid carbon mixing ratio for long-life use. We have found that the feature of the curve of the carbon negative electrode material influences the feature of the discharge curve of the battery, and graphite-coke hybrid carbons with a mixing ratio of 4/1 enable better cycle performance. We compared the initial discharge characteristics and cycle performance of batteries with LiCoxNi1-xO2,/graphite-coke hybrid carbon systems with those of a LiCoxNi1-xO2/pure graphite system for x = 0.3 and 0.7. Moreover, we examined the cycle performance of 10-Wh class cells using some of these systems under load-levelling imitation conditions. (c) 2004 Elsevier B.V. All rights reserved.