Electrochemical lithiation of new graphite-nanosized tin particle materials obtained by SnCl2 reduction in organic medium

SnCl2 was reduced in the presence of graphite by t-BuONa-activated NaH. The resulting (tin/graphite)-based system was composed of nanosized tin particles deposited on the graphite surface and of free tin aggregates. Lithium electrochemical insertion occurs in graphite and in tin. A reversible specific charge of 500 mAh/g is found stable upon cycling. This value is lower than the maximum theoretical one (650 mAh/g) assuming a Sn/12C molar composition and the formation of the highest lithium content alloy Li22Sn5. It is suggested that the part of tin responsible for the stable reversible capacity is the one bound to graphite. To the contrary, free tin aggregates could contribute to a capacity which decreases upon cycling in connection with the volume changes accompanying lithium insertion/extraction in/out of these aggregates. (c) 2005 Elsevier Ltd. All rights reserved.