Novel tin-graphite composites as negative electrodes of Li-ion batteries

For the purpose of obtaining an improved performance of the graphite negative electrode of Li-ion batteries, a novel graphite tin composite has been synthesized by reduction of tin chloride (SnCl2) with KC8 in THF medium. This composite contains nano-sized tin particles dispersed on the graphite surface and free tin aggregates. Lithium electrochemical insertion occurs both in graphite and in tin. An experimental reversible specific charge of 489 mA It g(-1) is found stable upon cycling. Such a value is lower than the maximum theoretical one of 609 mA h g(-1) suggesting that only a part of tin is involved in the lithium insertion/extraction process. This part of active tin responsible for the stable capacity could be that bound to graphite. To the contrary, free tin aggregates could contribute to an extra capacity that decreases upon cycling in relation with the volume changes that occurs during alloying/dealloying. (C) 2005 Elsevier Ltd. All rights reserved.