Effects of heteroatoms and nanosize on tin-based electrodes

Tin-based intermetallic compounds of different compositions and with micro and nano-sized particles are studied as electrodes for lithium ion batteries. Crystalline microsized particles of CoSnx are obtained at high temperatures, while crystalline nano-sized particles are obtained at low-temperature following a one-pot method which is based on TEG solvent and reduction with NaBH4. The observed capacities of CoSnx compounds in lithium test cells depend on the tin content, electrochemical cycling conditions and crystallite size. The change of the 119Sn Mössbauer isomer shift upon the electrochemical reaction with lithium is more limited for the intermetallic compounds CoSnx than for pure Sn. Nano-sized CoSnx materials show superior specific capacity than microsized CoSnx powders. The maximum observed reversible capacity of nano-Co3Sn2 is equal to 544 m Ah g−1 in the first cycle, while 413 m Ah g−1 were observed for nano-CoSn.