The reactions between lithiated Sn30Co30C40, LiSi, or Li0.81C6 and 1 M LiPF6 ethylene carbonate: diethyl carbonate (EC:DEC) electrolyte were compared using accelerating rate calorimetry (ARC). Both lithiated Sn30Co30C40 and LiSi showed less reactivity than Li0.81C6 over the entire ARC test temperature range. For both lithiated Sn30Co30C40 and LiSi, the self-heating rates were very similar in the low-temperature range (below 225 degrees C). However, lithiated Sn30Co30C40 was less reactive than LiSi at higher temperatures primarily because the formed Si reacted with the electrolyte itself, while the formed Sn-Co-C nanocomposite apparently does not. The attractive thermal stability of lithiated Sn30Co30C40 suggests that it could be a good alternative to currently used carbonaceous negative electrode materials for lithium-ion batteries where increased safety is desired. (c) 2008 The Electrochemical Society. [DOI: 10.1149/1.2988060] All rights reserved.