Dispersion of Sn and SnO on carbon anodes

Sn and SnO were supported on large surface-area synthetic graphite (KS6) to obtain composite materials with improved electrochemical performance relat ive to bulk Sn and SnO. in general the composites are superior to the mecha nical mixtures of KS6 and Sn (or SnO) of similar overall compositions in ma ny performance areas. The Sn-KS6 composites increase the reversible capacit y of graphite at some expense of the cyclability. It was observed that Sn c ould also contribute to the irreversible capacity loss in the first cycle, probably through a mechanism similar to solid electrolyte interface (SEI) f ormation on carbonaceous surfaces. The KS6-SnO composites have good reversi ble capacities, rate capability and cycle life, although their irreversible capacity losses in the first cycles are necessarily higher because of the requisite electro-reduction reaction to convert the oxide precursor into Sn -based Li storage compounds. The observation of specific capacities that ar e larger than the weighted sums of the capacities of SnO and graphite sugge sts the presence of synergistic interaction between the two constituents. ( C) 2000 Elsevier Science S.A. All rights reserved.