Tin-transition metal-carbon systems for lithium-ion battery negative electrodes

Magnetron cosputter deposited ternary libraries of Sn1-x-yMxCy (M=Ti, V and Co) (0 < x < 0.5 and 0 < y < 0.5) have been studied structurally and electrochemically using combinatorial and high-throughput methods. Each of the sputtered Sn1-xMx binary systems shows an amorphous composition range where the specific capacity for lithium decreases with M content. Adding carbon to the amorphous binaries, to make ternaries, causes the precipitation of crystalline Sn in the cases when M=Ti or V, but not when M=Co. We believe this is because stable carbides of Ti and V exist but stable Co carbides do not. The sputtered Sn-Co-C system was found to have a large amorphous range and the initial amorphous atomic arrangement in certain compositions are stable over at least 27 charge-discharge cycles of 600 mAh/g. Crystalline Sn was found to precipitate in composition ranges having competitive specific capacity in the Sn-Ti-C and Sn-V-C libraries causing rearrangement of the atoms during cycling leading to poor capacity retention. (c) 2007 The Electrochemical Society.