Despite the advantageous characteristics of a carbon nanotube (CNT), commercially reliable Si-CNT nanocomposites have not yet been developed due to the difficulties in effective dispersion of CNTs and low initial coulombic efficiency arising from the high surface area of CNTs. In this study, we present a facile wet-type milling process, providing Si-CNT nanocomposites with excellent electrochemical performances (initial capacity > 2000 mAh g(-1), initial coulombic efficiency similar to 80%, and improved lifetime) through a proper selection of a liquid medium and a post-thermal treatment. The improved performance is largely contributed from a suppressed oxidation of silicon nanograins as well as a stronger linkage between silicon and CNTs. The comparison of a series of Si-carbon nanocomposites prepared by an identical method but using different types of carbons indicates that only the one-dimensional CNT achieved effective percolation through the randomly networked electrical conduction in silicon nanograin aggregates. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3223963] All rights reserved.